[Unroll/UnrollAndJam/Vectorizer/Distribute] Add followup loop attributes.

[Meinersbur]

Summary

When multiple loop transformation are defined in a loop's metadata, their order of execution is defined by the order of their respective passes in the pass pipeline. For instance, e.g.

#pragma clang loop unroll_and_jam(enable)
#pragma clang loop distribute(enable)

is the same as

#pragma clang loop distribute(enable)
#pragma clang loop unroll_and_jam(enable)

and will try to loop-distribute before Unroll-And-Jam because the LoopDistribute pass is scheduled after UnrollAndJam pass. UnrollAndJamPass only supports one inner loop, i.e. it will necessarily fail after loop distribution. It is not possible to specify another execution order. Also,t the order of passes in the pipeline is subject to change between versions of LLVM, optimization options and which pass manager is used.

This patch adds 'followup' attributes to various loop transformation passes. These attributes define which attributes the resulting loop of a transformation should have. For instance,

!0 = !{!0, !1, !2}
!1 = !{!"llvm.loop.unroll_and_jam.enable"}
!2 = !{!"llvm.loop.unroll_and_jam.followup_inner", !3}
!3 = !{!"llvm.loop.distribute.enable"}

defines a loop ID (!0) to be unrolled-and-jammed (!1) and then the attribute !3 to be added to the jammed inner loop, which contains the instruction to distribute the inner loop.

Currently, in both pass managers, pass execution is in a fixed order and UnrollAndJamPass will not execute again after LoopDistribute. We hope to fix this in the future by allowing pass managers to run passes until a fixpoint is reached, use Polly to perform these transformations, or add a loop transformation pass which takes the order issue into account.

For mandatory/forced transformations (e.g. by having been declared by #pragma omp simd), the user must be notified when a transformation could not be performed. It is not possible that the responsible pass emits such a warning because the transformation might be 'hidden' in a followup attribute when it is executed, or it is not present in the pipeline at all. For this reason, this patche introduces a WarnMissedTransformations pass, to warn about orphaned transformations.

To ensure that no other transformation is executed before the intended one, the attribute llvm.loop.transformations.disable_nonforced can be added which should disable transformation heuristics before the intended transformation is applied. E.g. it would be surprising if a loop is distributed before a #pragma unroll_and_jam is applied.

With more supported code transformations (loop fusion, interchange, stripmining, offloading, etc.), transformations can be used as building blocks for more complex transformations (e.g. stripmining+stripmining+interchange -> tiling).

This approach deviates from proposal in the RFC at http://lists.llvm.org/pipermail/llvm-dev/2018-May/123690.html. There are three reasons:

• In the RFC approach, when a pass wants to determine whether it should perform a transformation, it must search the list of transformations for the first transformation on its loop. When inlining, the two transformation list must be combined.
• For compatibility, the current approach using loop IDs must still be supported, either each pass looks up both metadata formats, or using the AutoUpgrade mechanism. This patch's approach keeps the current mechanism.
• The "loop IDs" can change. When a attribute is added/removed from the Loop ID metata (e.g. adding "llvm.loop.isvectorized" after vectorizing), the loop is assigned a new, distrinct MDNode. Every reference to these nodes needs to be updated as well, and metadata nodes do not support RAUW. Some of the current passes (e.g. LoopDistribution) keep the same loop ID for multiple output loops such that the loop ID is not uniquely identifying loops anymore. This patch's approach does not reference loop IDs in the attribute values.

[dmgreen]

I like the idea of this, giving control to the user to figure out the best way to manipulate loops (even if they end up shooting themselves in the foot with it :) )

What does this mean for the clang side of this patch? Has the user-visible loop-naming scheme changed, or will it be mapped to these matadatas?

What follows is mostly a number of small Nits:

docs/TransformMetadata.rst

24

Nit: from the emitted IR

54

Nit: transformation

83

Nit: transformed

88

Nit: occur

253

Nit: have

344

Should we fix this? Will it work as expected with nonforced, if it was enabled?

include/llvm/LinkAllPasses.h

223

Nit: Space I guess? I think this file could do with a clang-formatting

include/llvm/Transforms/Scalar/WarnMissedTransforms.h

36

Are these two needed here, if they are declared in other places?

lib/Transforms/Scalar/LoopUnrollAndJamPass.cpp

361

This is called SubLoop here

[Meinersbur]

Thanks for the review.

In D49281#1162931, @dmgreen wrote:

What does this mean for the clang side of this patch? Has the user-visible loop-naming scheme changed, or will it be mapped to these matadatas?

I also have a patch for clang in mind to make the order defined by the frontend, not the pass pipeline. However, for compatibility it will have to put them in the order of the current pass order e.g.

#pragma unroll_and_jam
#pragma clang loop vectorize(enable)

and

#pragma clang loop vectorize(enable)
#pragma unroll_and_jam

both have to emit

!0 = !{!0, 
    !{!"llvm.loop.vectorize.enable"},
    !{!"llvm.loop.vectorize.followup_all", 
        !{!"llvm.loop.unrollandjam.enable"}}}}

A different syntax is needed that the user can use if they want to define the transformation order.

Also for compatibility we cannot error-out if transformation undefined (at least for any combination of currently supported transformations), but could use the Auto-Upgrader.

[Meinersbur]

ping

[Meinersbur]

docs/TransformMetadata.rst

344

Yes, but in a separate patch that adds interchange-specific metadata. LoopInterchange currently is not enabled by default and does not modify metadata so its interaction with other transformation is less significant.

include/llvm/LinkAllPasses.h

223

I used git clang-format origin/master which only applies to changed lines like this one.

include/llvm/Transforms/Scalar/WarnMissedTransforms.h

36

Depends on which headers are included when using this pass.

WarnMissingTransforms.cpp itself does not include include/llvm/InitializePasses.h or include/llvm/Transforms/Scalar.h. Having the forward declarations here matches the translation unit header idiom an the compiler checks that the definition matches the declaration here.

[Meinersbur]

• Address @dmgreen's remarks

[dmgreen]

Some extra tests for nonforced + a pragma would be good to see.

I'm not much of an expert on the vectoriser changes here.

docs/LangRef.rst

5296

These can now move down with the other unroll_and_jam metadata

5314

Nit: This loop

docs/TransformMetadata.rst

72

Nit: Maybe change the second "for instance"

164

Do you think it's worth mentioning unroll.count and unroll.disable etc, before jumping into the followup metadata?

207

Again, could mention unroll_and_jam.count and enable/disable.

265

Again, maybe describe other metadata first?

344

Yep. Certainly a separate patch.

396

Nit: pass pass

lib/Transforms/Scalar/LoopUnrollAndJamPass.cpp

206

Same as unroll. What if PragmaCount and hasDisableAllTransformsHint?

lib/Transforms/Scalar/LoopUnrollPass.cpp

755

What if it has PragmaCount and hasDisableAllTransformsHint? Should that not enable too?

test/Transforms/LoopUnroll/unroll-pragmas_transform.ll

1 ↗

(On Diff #157638)

This file look sensible on it's own and I think looks OK to be committed separately. (Apart from the nit below)

5 ↗

(On Diff #157638)

Nit: Is this sentence still true?

[hsaito]

In D49281#1187583, @dmgreen wrote:

I'm not much of an expert on the vectoriser changes here.

There is a call for a vectorizer person, and here I am, but before going there, ever since this patch was uploaded, I've been thinking whether the original intent of this patch can be really accomplished ---- especially so with the set of "hints" being used here. So, I'd like to go back and start there if that's okay. I think this patch is in some sense based on the optimism of "programmer won't abuse this and transformation will happen". Reality is more like programmer will try using those pragmas to arm-twist the compiler to get the set of transformations he/she wants w/o thinking deep enough about what happens at each step of the way. As such, how to fall back when the transformation doesn't happen is almost equally important as what to do next when the transformation happens. From what I've read --- granted that I haven't gone through this very deep, the fall back aspect isn't handled well. If we don't start from "programmer specified transformation may fail to kick-in", providing this feature to the programmers would quickly backfire and we'll get tons of this doesn't work that doesn't work problem reports ---- which is a big mess/disaster. If we are doing this for research purposes, that may be fine. I'm looking at this from a production compiler development perspective.

There are two different approaches we can think of.

1. Start from defining the transformation directives that actually transforms in most cases. For example, Intel compiler's implementation of OpenMP SIMD is in this position, and we are trying to bring the same position to LLVM LV. Then, failing to transform is a compiler bug (or a programmer has a bug in the source code to fix). OpenMP SIMD is defined in such a way for compilers to be able to take this positioning. In this approach, we can stop processing transformation directives after the first failed transformation. Even in this case, for example, programmer probably won't know under certain circumstances, vectorizer won't produce remainder loop, or under certain cases, vectorizer completely unrolls the loop so that there aren't any loops left after vectorization. So, controlling a single transformation in a programmer predictable manner --- enough to describe what should happen next --- is a big task.
2. Based on transformation hint directives. Since what the programmer is using is a hint, for each transformation, programmer needs to tell the next step 1) if the transformation kicks in and also 2) if the transformation does not kick-in. This will be very messy and I'm not sure how practical it would be for the programmer to specify the behaviors for all situations.

If these kinds of stuff have been already discussed, please give me the pointers and I'll try to digest. Else, we can talk about this in this review or in llvm-dev. Hope my argument makes sense to you/others, but please feel free to ask for clarification. I've been working on making SIMD directive programmer predictable for many years. So, I may be skipping some explanations that became natural enough to me over the years.

In short, doing this even for one transformation (in my case SIMD) is difficult enough. If we are trying to expand to multiple transformations, we should try doing so in baby steps.

The idea behind this is so powerful such that even if we start from "best effort basis", programmers will quickly jump on and say make this more robust/predictable. We'd rather spend time to design this as a robust/predictable feature from the beginning than having to work on it under the customer pressure.

Thanks,
Hideki

[hfinkel]

... As such, how to fall back when the transformation doesn't happen is almost equally important as what to do next when the transformation happens.

Hideki, I think that LLVM does the right thing here: We provide a separation between the hint and the mandate (i.e., using assume_safety or not). By default, the compiler should still provide safety conditions. The alternative to providing the functionality proposed here is, in reality, source-to-source code generators (which often do semantically-incorrect things and are hard to use in production for a large number of reasons). Also, the client for this functionality is not just programmers directly, but other tools (e.g., autotuners and other higher-level languages), which is also why generating safety predicates, or at least having that option, is important. I think that LLVM also currently does the right thing regarding transformations that don't apply: we issue a warning (which bubbles up from the optimizer via the optimization-remark interface). We should certainly continue to do that (and I know that Michael has experimented with ways of making this continue to happen reliably).

The idea behind this is so powerful such that even if we start from "best effort basis", programmers will quickly jump on and say make this more robust/predictable. We'd rather spend time to design this as a robust/predictable feature from the beginning than having to work on it under the customer pressure.

I don't think that we can ever really having something in this space which isn't best effort, but, I think that providing a warning is both necessary (because silent failure is poor user experience) and sufficient (it's not clear to me what kind of fallback we could provide that would be more robust in practice). If people start providing us with bug reports about loops that we couldn't transform, but should have transformed, that will be great data on what to improve. That having been said, if you can suggest pragmas that have semantics that allow us to control loop transformations in a way that's more robust than the current ones, then please, of course, suggest them.

I feel obligated to note, however, that the motivation for this work comes entirely from our experience supporting HPC users. I'm convinced that it will provide a significantly better user experience over the current state of the art. I'm sure that you've seen code that comes out of higher-level code generators and the like. These tend to be hard to maintain, inflexible, and buggy, and the code produced is difficult for both humans and compilers to understand. I'm sure you've also seen cases where people implement these transformations by hand (do I need to go on?). The compiler can perform these transformations and having the user able to direct the compiler to do so if a much better option. To some extent, a compiler can have cost models and heuristics to apply these automatically, but only occasionally do we actually have enough static information to do so (even with some PGO capabilities).

[Meinersbur]

In D49281#1187583, @dmgreen wrote:

Some extra tests for nonforced + a pragma would be good to see.

Any transformations in particular?

In D49281#1188026, @hsaito wrote:

In D49281#1187583, @dmgreen wrote:

I'm not much of an expert on the vectoriser changes here.

There is a call for a vectorizer person, and here I am,

Thank you!!!

but before going there, ever since this patch was uploaded, I've been thinking whether the original intent of this patch can be really accomplished ---- especially so with the set of "hints" being used here. So, I'd like to go back and start there if that's okay. I think this patch is in some sense based on the optimism of "programmer won't abuse this and transformation will happen". Reality is more like programmer will try using those pragmas to arm-twist the compiler to get the set of transformations he/she wants w/o thinking deep enough about what happens at each step of the way. As such, how to fall back when the transformation doesn't happen is almost equally important as what to do next when the transformation happens. From what I've read --- granted that I haven't gone through this very deep, the fall back aspect isn't handled well. If we don't start from "programmer specified transformation may fail to kick-in", providing this feature to the programmers would quickly backfire and we'll get tons of this doesn't work that doesn't work problem reports ---- which is a big mess/disaster. If we are doing this for research purposes, that may be fine. I'm looking at this from a production compiler development perspective.

There are two different approaches we can think of.

1. Start from defining the transformation directives that actually transforms in most cases. For example, Intel compiler's implementation of OpenMP SIMD is in this position, and we are trying to bring the same position to LLVM LV. Then, failing to transform is a compiler bug (or a programmer has a bug in the source code to fix). OpenMP SIMD is defined in such a way for compilers to be able to take this positioning. In this approach, we can stop processing transformation directives after the first failed transformation. Even in this case, for example, programmer probably won't know under certain circumstances, vectorizer won't produce remainder loop, or under certain cases, vectorizer completely unrolls the loop so that there aren't any loops left after vectorization. So, controlling a single transformation in a programmer predictable manner --- enough to describe what should happen next --- is a big task.
2. Based on transformation hint directives. Since what the programmer is using is a hint, for each transformation, programmer needs to tell the next step 1) if the transformation kicks in and also 2) if the transformation does not kick-in. This will be very messy and I'm not sure how practical it would be for the programmer to specify the behaviors for all situations.

If these kinds of stuff have been already discussed, please give me the pointers and I'll try to digest. Else, we can talk about this in this review or in llvm-dev. Hope my argument makes sense to you/others, but please feel free to ask for clarification. I've been working on making SIMD directive programmer predictable for many years. So, I may be skipping some explanations that became natural enough to me over the years.

All these issues apply to the current loop metadata/#pragma clang loop as well. A user can specify #pragma clang loop distribute(enable) vectorize_width(4) with the expectation that these will be carried out. If not, this can be a bug (or semantically incorrect) just as if the distribution/vecorization was explicitly orderder using followup-attributes.
In contrast, currently there is no way to even express that the transformations should be carried out in there reverse order (first vectorization, then distribution; let's ignore for the moment whether this makes sense, it definitely makes sense with loop transformations other than those for which LLVM currently has metadata). Our longer-term plans are to support this in LLVM and the first step is to make sequences of transformations expressible in IR. Of course our goal is also to make transformations more applicable/robust. I see these as two orthogonal problems.

I don't think we need a fallback loop transformation. If a transformation cannot be applied, the user's reactions is probably not "let's do a different transformation then" (which will in most cases also fail for the same reasons the primary transformation failed), but "unfortunately the compiler cannot do my transformation I need to get the best performance, will implement it by hand then." Even if the first option is what the programmer wantsm they will implement it using preprocessor switches as it is common today with different compilers that support/do not support specific pragmas.

I had already some discussions on the reliability of transformations in the compiler. Some groups do not want to rely at all on the compiler being able to do a specific optimization and user libraries instead. Those libraries will 'miscompile' the input if certain preconditions are not met which is the desired outcome where slow execution just is no option. With incorrect results it at least becomes obvious that there is a problem. However, this is not an option for a compiler where correctness is the most important aspect (and only relaxed by attributes such as assume_safety). For some use cases, such as autotuning, being able to rely on the compiler producing correct output makes it possible in first place.
We could argue about whether we want high-level transformations in a low-level compiler in the first place. I think this has been answered a long time ago: LoopVectorizer, LoopUnroll, LoopInterchange, LoopDistribution, LoopUnswitch, etc. Since we have this kind of transformation, why not mkaing them as good as possible?

In short, doing this even for one transformation (in my case SIMD) is difficult enough.

I'd be happy to extract-out attributes for specific transformations in separate reviews. However, to be come useful, I think we need the entire set.

If we are trying to expand to multiple transformations, we should try doing so in baby steps.

I understood that you are working on making the loop vectorizer predictable, i.e. we are working towards the same goal.

The idea behind this is so powerful such that even if we start from "best effort basis", programmers will quickly jump on and say make this more robust/predictable. We'd rather spend time to design this as a robust/predictable feature from the beginning than having to work on it under the customer pressure.

I think the current one-pass-per-transformation is indeed very fragile and I am working on something that should be more robust.

lib/Transforms/Scalar/LoopUnrollPass.cpp

755

If llvm.loop.unroll.enable is not set, interpretation here is that the transformation is 'non-forced', that is, llvm.loop.unroll.count is a hint to the compiler that if it unrolls, then it should unroll by that amount. llvm.loop.disable_nonforced overrride the decision whether to unroll, i.e. the unroll factor does not matter.

I am aware that the concept of 'forced' transformations is not consistent between passes, but I am trying to give it some consistency. Passes could query shared code such as hasUnrollTransformation in LoopUtils. hasUnrollTransformation currently follows your interpretation of llvm.loop.unroll.count / llvm.loop.disable_nonforced. I am happy to implement either definition, as long as we find a consistent rule.

test/Transforms/LoopUnroll/unroll-pragmas_transform.ll

1 ↗

(On Diff #157638)

This is a copy of unroll-pragmas.ll and any ambiguous metadata replaced by follow-up attributes.

An hope is to generally make 'multiple transformation attributes on the same loop' illegal and rejected by the IR verifier (since the result depends on an implementation detail: the order in the pass manager). In this case this file would replace unroll-pragmas.ll.

But my expectation is that we cannot break backwards-compatibility this way.

5 ↗

(On Diff #157638)

Yes: When no follow-up attributes are specified, the default ones are added (here: llvm.loop.unroll.disable to disable further unrolling). In case there are follow-up attribute lists, there is no default and the transformation-disabling must be added explicitly (MDNode !18) and of course added after unrolling and recognized by the second LoopUnroll.

[dmgreen]

I agree that this is a very powerful idea (something I wish I'd had back when I was writing psuedo-hpc applications). I think it's well worth having, but equally worth making sure we get it right. The clang side is very important for that.

In D49281#1188441, @Meinersbur wrote:

In D49281#1187583, @dmgreen wrote:

Some extra tests for nonforced + a pragma would be good to see.

Any transformations in particular?

There seem to be tests that nonforced disables things, but not that nonforced + an attribute keeps it enabled. e.g. the unroll.count metadata.

lib/Transforms/Scalar/LoopUnrollPass.cpp

755

I would expect that if a loop has any metadata for a pass, that would mean disable_nonforced doesn't apply. As if the user has specified some metadata, it likely wants something to happen.

I think in this specific case llvm.loop.unroll.count implies llvm.loop.unroll.enable, and we wouldn't put both on a loop for "#pragma unroll(4)" or "#pragma clang loop unroll_count(4)"

test/Transforms/LoopUnroll/unroll-pragmas_transform.ll

1 ↗

(On Diff #157638)

Ah, I missed the "followup" here. Is it worth replicating this entire file, or should it just be an extra test in the old file.
The "followup" on unroll_1 seems to be the only test changed here? To add unroll.disable as a followup attribute? I'm not sure I see why. Would we expect "#pragma unroll(1)" to not work as it did before? (disable unroll)

[hsaito]

In D49281#1188249, @hfinkel wrote:

... As such, how to fall back when the transformation doesn't happen is almost equally important as what to do next when the transformation happens.

Hideki, I think that LLVM does the right thing here: We provide a separation between the hint and the mandate (i.e., using assume_safety or not).

That, I know. I wasn't questioning about that.

What I'm not seeing from this RFC/patch is that, if the programmer specifies transformation behavior A -> B -> C, what happens if transformation A does not kick-in? Should we just warn that "A did not happen" and stop processing the request B and C?
Also, if the programmer requests that the loop to be distribute in three ways and specify different transformations for each, what should the latter transformation do if the loop is distributed in two ways or four ways? If we are serious about introducing this kind of features, we should clearly define what should happen when the programmer intention cannot be satisfied well enough ---- when we should continue honoring and when we should stop honoring. If we say "we should stop in all those circumstances", that should simplify the problem a lot. If we say "we should allow to continue on subset of those cases", we should clearly state which subset and why. If there are any prior discussions (or descriptions within this patch) along this lines, please point me to that.

[hfinkel]

In D49281#1189643, @hsaito wrote:

In D49281#1188249, @hfinkel wrote:

... As such, how to fall back when the transformation doesn't happen is almost equally important as what to do next when the transformation happens.

Hideki, I think that LLVM does the right thing here: We provide a separation between the hint and the mandate (i.e., using assume_safety or not).

That, I know. I wasn't questioning about that.

What I'm not seeing from this RFC/patch is that, if the programmer specifies transformation behavior A -> B -> C, what happens if transformation A does not kick-in? Should we just warn that "A did not happen" and stop processing the request B and C?
Also, if the programmer requests that the loop to be distribute in three ways and specify different transformations for each, what should the latter transformation do if the loop is distributed in two ways or four ways? If we are serious about introducing this kind of features, we should clearly define what should happen when the programmer intention cannot be satisfied well enough ---- when we should continue honoring and when we should stop honoring. If we say "we should stop in all those circumstances", that should simplify the problem a lot. If we say "we should allow to continue on subset of those cases", we should clearly state which subset and why. If there are any prior discussions (or descriptions within this patch) along this lines, please point me to that.

I certainly agree that we should document this.

[Meinersbur]

In D49281#1189643, @hsaito wrote:

What I'm not seeing from this RFC/patch is that, if the programmer specifies transformation behavior A -> B -> C, what happens if transformation A does not kick-in? Should we just warn that "A did not happen" and stop processing the request B and C?

Yes. A warning will be emitted by the -transform-warning pass (Please see Passes.rst). B and C cannot apply on a loop that does not exist.

Also, if the programmer requests that the loop to be distribute in three ways and specify different transformations for each, what should the latter transformation do if the loop is distributed in two ways or four ways?

The current LoopDistribution pass unfortunately does not support this, by a goal is to make the user able to define what code should become their own loop. See [[ A Proposal for Loop-Transformation Pragmas | https://arxiv.org/abs/1805.03374 ]].
For the current LoopDistribution pass, only two categories of followup-attributes can be defined noncyclic and cyclic. The noncyclic category can be added to multiple loops.

If we are serious about introducing this kind of features, we should clearly define what should happen when the programmer intention cannot be satisfied well enough ---- when we should continue honoring and when we should stop honoring. If we say "we should stop in all those circumstances", that should simplify the problem a lot. If we say "we should allow to continue on subset of those cases", we should clearly state which subset and why. If there are any prior discussions (or descriptions within this patch) along this lines, please point me to that.

Documented in TransformMetadata.rst line 57ff.

docs/TransformMetadata.rst

164

Yes, maybe, but they are also already documented in the LangRef.rst. Please understand that the goal in this patch is to define a transformation model for each pass such that it is clear what are those followup-loops, not to write an exhaustive documentation.

[hsaito]

In D49281#1189737, @Meinersbur wrote:

In D49281#1189643, @hsaito wrote:

What I'm not seeing from this RFC/patch is that, if the programmer specifies transformation behavior A -> B -> C, what happens if transformation A does not kick-in? Should we just warn that "A did not happen" and stop processing the request B and C?

Yes. A warning will be emitted by the -transform-warning pass (Please see Passes.rst).

This part, I know you did.

B and C cannot apply on a loop that does not exist.

I don't think this is explicitly written. Here's an example. Suppose A is vectorization and B is unroll. If a loop is somehow not vectorized. Unrolling can still happen to the non-vectorized loop. Whether we stop unrolling in this situation is what I'd like to see us being explicit about.

Also, if the programmer requests that the loop to be distribute in three ways and specify different transformations for each, what should the latter transformation do if the loop is distributed in two ways or four ways?

The current LoopDistribution pass unfortunately does not support this, by a goal is to make the user able to define what code should become their own loop. See [[ A Proposal for Loop-Transformation Pragmas | https://arxiv.org/abs/1805.03374 ]].
For the current LoopDistribution pass, only two categories of followup-attributes can be defined noncyclic and cyclic. The noncyclic category can be added to multiple loops.

Whether distribution currently supports that is a different issue. I'm sure we will be expanding the features in the futures. This composability discussion should encapsulate the baseline behaviors for enough of possible future situations ---- else we have to keep revising baseline behaviors, which is very bad.

If we are serious about introducing this kind of features, we should clearly define what should happen when the programmer intention cannot be satisfied well enough ---- when we should continue honoring and when we should stop honoring. If we say "we should stop in all those circumstances", that should simplify the problem a lot. If we say "we should allow to continue on subset of those cases", we should clearly state which subset and why. If there are any prior discussions (or descriptions within this patch) along this lines, please point me to that.

Documented in TransformMetadata.rst line 57ff.

I only see the warning behavior there. I'd like to see us explicitly saying that any subsequent explicit transformation metadata will be ignored for the given loop ---- if that's what we'll agree on, or be explicit about something else we'll agree on in the terms that can be clearly explainable to the programmers. "Compiler will skip all remaining transformations after the first failed transform" is pretty straightforward to the programmers. If anyone is proposing other behaviors, I'd like to also see how to explain those behaviors to the programmers.

[Meinersbur]

• Explicitly document followup of not applied transformations to be ignored
• Unroll/UnrollAndJam: Interpret enable/count/full as forced
• Unroll/UnrollAndJam: Add tests for disable_nonforced combined with enable/count/full
• Reduce size of unroll-pragmas_transform.ll

[Meinersbur]

In D49281#1189774, @hsaito wrote:

I'd like to see us explicitly saying that any subsequent explicit transformation metadata will be ignored for the given loop ---- if that's what we'll agree on, or be explicit about something else we'll agree on in the terms that can be clearly explainable to the programmers. "Compiler will skip all remaining transformations after the first failed transform" is pretty straightforward to the programmers. If anyone is proposing other behaviors, I'd like to also see how to explain those behaviors to the programmers.

I added a paragraph to TransformMetadata.rst. (I was assuming it was obvious from the definition: A transformation in a followup-attribute only becomes assigned to a loop by the loop transformation pass. Before that, it is not associated with any loop)

[hsaito]

In D49281#1194814, @Meinersbur wrote:

In D49281#1189774, @hsaito wrote:

I'd like to see us explicitly saying that any subsequent explicit transformation metadata will be ignored for the given loop ---- if that's what we'll agree on, or be explicit about something else we'll agree on in the terms that can be clearly explainable to the programmers. "Compiler will skip all remaining transformations after the first failed transform" is pretty straightforward to the programmers. If anyone is proposing other behaviors, I'd like to also see how to explain those behaviors to the programmers.

I added a paragraph to TransformMetadata.rst. (I was assuming it was obvious from the definition: A transformation in a followup-attribute only becomes assigned to a loop by the loop transformation pass. Before that, it is not associated with any loop)

The added paragraph looks good to me on the implementation side specification. Looking forward to see the programmers (i.e., compiler users, not compiler writers) side pragma description, but that will not gate my review of this patch. There is a difference between specification forcing one behavior versus implementation choice ends up in the same behavior. I wanted the former, not the latter. With this specification, we can have another implementation choice ---- attaching all those metadata to the loop, to be updated by the successful transformation, and let failed transform drop subsequent ones. I'm not saying it's better to go that way. What I'm saying is that if, for some reason, we later choose to implement this differently, there is a specification to guide how to implement the feature correctly. Hope I don't sound too picky. I just want to provide consistent experiences to the programmers.

[Meinersbur]

In D49281#1196034, @hsaito wrote:

The added paragraph looks good to me on the implementation side specification. Looking forward to see the programmers (i.e., compiler users, not compiler writers) side pragma description, but that will not gate my review of this patch. There is a difference between specification forcing one behavior versus implementation choice ends up in the same behavior. I wanted the former, not the latter.

Different behavior of different implementations is also a serious concern for me. I have three different implementations in mind (the current loop transformations, an extension to Polly to use this metadata, and an idealized loop-transformation pass; the latter two being more powerful is one of the motivtions for this path). Given the prototypical transformations in TransformMetadata.rst, I think the model is applicable to other implementations as well.

With this specification, we can have another implementation choice ---- attaching all those metadata to the loop, to be updated by the successful transformation, and let failed transform drop subsequent ones. I'm not saying it's better to go that way. What I'm saying is that if, for some reason, we later choose to implement this differently, there is a specification to guide how to implement the feature correctly.

This would unfortunately break existing behavior. E.g. llvm.loop.distribute.enable and llvm.loop.vectorize,enable can both be specified in the same loop attributes. Currently, if LoopDistribution fails, the attribute llvm.loop.vectorize.enable will be left untouched. If we change LoopDistribution to remove it, the loop would not be vectorized anymore (assuming the heuristic does not deem it profitable).
It also does do what motivates this patch: Neither the order of transformations be specified, nor can the same transformation be applied multiple times.

[dmgreen]

I was testing the code and ran into some problems with debug metadata on the loop nodes (actually using -Rpass=unroll in that case). Can you make sure that works as expected?

docs/TransformMetadata.rst

111

Nit: never be added

include/llvm/Transforms/Utils/LoopUtils.h

177

Nit: transformations->transformation

185

Nit: inherit

197

Nit: choose

227

Nit: warning

lib/Transforms/Scalar/LoopUnrollAndJamPass.cpp

205

This code will need rebasing. There is a check earlier that looks for disable metadata that could be replaced by this. Look for HasUnrollDisablePragma/HasUnrollAndJamDisablePragma. If the same was done for unrolling, I think that would remove the need for the IgnoreUser (although your comment about it is probably still true).

lib/Transforms/Utils/LoopUtils.cpp

287

Maybe InheritSomeAttrs -> InheritNonExceptAttrs?

[hiraditya]

lib/Transforms/Scalar/LoopUnrollPass.cpp

1085

nit: maybe put the string literals as a separate declaration?

lib/Transforms/Utils/LoopUnrollRuntime.cpp

542

What is the rationale of using pointer to a pointer here? If we want to assign to ResultLoop, then maybe we can just return ResultLoop and bool as a pair.

925

nit: space

[Meinersbur]

I am thinking about adding a LoopMetadataTacker (sort of a combination of LoopVectorizeHints and AssumptionTracker) analysis pass which would centralize the interpretation of that metadata and avoid the linear search through the metadata list when looking up a specific attribute.

lib/Transforms/Scalar/LoopUnrollAndJamPass.cpp

205

I'd push towards refectoring-out the common parts of computeUnrollCount used by LoopUnroll and LoopUnrollAndJam. Currently computeUnrollCount uses lots of settings meant for LoopUnroll (llvm.loop.unroll. metadata which should not exist anymore, OptimizationRemarkMissed specific to LoopUnroll, -unroll-count, PartialThreshold, handling of full unroll, loop peeling that UnrollAndJam does not support, being used in a single call by UnrollAndJam for two different things: determining ExplicitUnroll (i.e. is normal unroll is forced) and the unroll-and-jam count). It's hard to understand the subtleties between those codes.

I gave up at some point and added the IgnoreUser flag to make test cases pass.

lib/Transforms/Utils/LoopUnrollRuntime.cpp

542

If the Result loop is not needed, one can pass nullptr (which is the default argument). Returning std::pair will require more changes.

925

This is done by clang-format. It try not to fight its decisions and hope for future improvement.

lib/Transforms/Utils/LoopUtils.cpp

287

Avoiding double negation here.

[Meinersbur]

lib/Transforms/Utils/LoopUnrollRuntime.cpp

925

I will try to remove the space in patch updates, but may sneak in again when I re-run clang-format and forget about it before submission.

[hsaito]

docs/LangRef.rst

5192

I understand that the RST file update should talk about what happens today, but for the sake of code review, it's good to discuss what could happen in reasonably foreseeable future so that we don't under-design things.

I think we should be thinking ahead about

1. vectorizer peeling the loop, for example, for alignment optimization. Such peeled loop could be fully unrolled if the trip count is known, or vectorized with mask.
2. main vector loop could be fully unrolled
3. there may be more than one remainder loop, e.g., vectorized remainder followed by scalar remainder.
4. remainder loop may be fully unrolled.

All those situations could happen w/o programmer knowing it'll happen that way.

Some of the questions we want to think before the real need arises:

Will the loop attribute get dropped if the "loop" is fully unrolled?
How do we designate more than one remainder loop?
Will the loop attribute applicable for vectorized peel/remainder?
Should we have a way to designate runtime-DD non-vectorizable loop separately from remainder?

5289

Remainder here may be unrolled again or fully unrolled (see the comments on vectorize metadata). What do we do for that?

5349

Is there an assumption of unroll_and_jam operating only on a double loop and/or a perfect loop? Technically speaking, we can unroll_and_jam a loop if we can legally outerloop-vectorize. So, there can be multiple inner loops.

5418

Looks rather centric to distribute-for-vectorization.

Loop distribution can happen for many reasons (and it may be more than one reasons). Are we going to define followup_ Metadata for each of those reasons? What'll happen if a loop matches the characteristics of more than one Metadata?

[Meinersbur]

• Report unroll-and-jam as not applied even if unroll is present as well.
  • rename followup_cyclic/followup_noncyclic to followup_sequential/followup_coincident
  • Move hasUnrollAndJamTransformation in LoopUnrollAndJamPass to different place
  • Remove some unrelated whitespace changes made by clang-format
  • Extract followup attribute names into constant

docs/LangRef.rst

5192

1. I think a prologue/peel is analogous to epilogue/remainder. That is, a new llvm.loop.vectorize.followup_peel can be added.
2. Should be handled as two separate transformations (such as vectorize/interleave). That is llvm.loop.disable_nonforced would ensure that a loop does not unexpectedly disappear
3. llvm.loop.followup_remainder should apply on any of the remainder loops. If a finer distinction is required, we can add more specific attributes.
4. This can already happen, at least with LoopUnroll/LoopUnrollandJam. The docs mentions that in this case the followup_remainder is dropped.

However, changing the model a transformation transform to can indeed raise some backward-compatibility issues. This also applies to the user-interface. If a programmer added

#pragma clang loop vectorize(enable)

do they expect it to be unrolled as well? Loop peeling? D50480 is interesting here: At -Os, it uses masking instead of an epilogue to avoid a code copy. In this case followup_remainder explicitly states that there's not necessarily a remainder loop, so I don't see a problem here. But a programmer might expect more control over what the output structure is.

We can add more attributes to control this behaviour, such as llvm.loop.vectorize.peel.enable, llvm.loop.vectorize.remainder.enable, llvm.loop.vectorize.allow_versioning. The interesting question is, what is the default setting?
If we go by the current behavior to maximize backwards-compatibility, remainder and versioning would be enabled by default (if not in -Os), peeling disabled because it is not yet implemented.

On the other side we probably do not want frontends to emit the most recent enable-metadata to get the best vectorization. So we would enable all features by default, but the output loops might be different from what the programmer intended before the feature is introduced.

We can enable all features unless the transformation is forced, in which case all deviations from the current transformation model needs to be explicitly enabled.

IMHO, we can decide this case-by-case, weighting compatibility concerns and optimization levels. Then again, such transformations does not influence the correctness of the output.

To be less concerned about compatibility issues, I could for now remove all followup-attributes except those that are 'central' to the transformation, and followup_all. For vectorization, there will always be the performance-critical vectorized loop (i.e. followup_vectorized), independent of whether there is a prologue, epilogue or fallback. For partial unrolling, it is always a unrolled loop.

• Will the loop attribute get dropped if the "loop" is fully unrolled?

Yes. But it should not happen if llvm.loop.disable_nonforced is used and the unroll is not explicitly specified.

• How do we designate more than one remainder loop?

Using different attributes. Like followup_all it is possibly to address a group of loops.

• Will the loop attribute applicable for vectorized peel/remainder?

Only for the followup that addresses them

• Should we have a way to designate runtime-DD non-vectorizable loop separately from remainder?

As mentioned sometime before, the typical reaction to 'loop not vectorized' is not 'ok, let's unroll it instead', but 'how can I make it vectorize'. So I don't think fallbacks are necessary (unless we can apply a sequence of transformation to multiple loop), but I am open if you think there is a need for such.

5289

followup_remainder is ignored. If this it is not clear from the section in TransformMetadata.rst, please tell me.

[Meinersbur]

docs/LangRef.rst

5303–5304

@dmgreen This directly contradicts the nounroll_plus_unroll_and_jam test case in Transforms/LoopUnrollAndJam/pragma.ll

5349

There's still an outermost (unrolled) loop and an innermost (jammed) loop. We could also adds followups for middle loops.

If it is the naming that concerns you: Would you prefer followup_unrolled and followup_jammed?

5418

There is no overlap between cyclic and noncyclic. For the extended loop-transformations, the user would name the loops they want distributed.

Indeed, these followup are are specific to the current distribution pass. However, I think it is easy for any distribution to determine whether a loop has cyclic dependences and and those attributes to any output loop that matches.

makeFollowupLoopID can already combine attributes from multiple followups.

lib/Transforms/Scalar/LoopUnrollAndJamPass.cpp

205

IgnoreUser exists for the nounroll_plus_unroll_and_jam in LoopUnrollAndJam\pragma.ll.

llvm.loop.unroll.disable causeshasUnrollTransformation` in computeUnrollCount to return TM_Disable. Unrolling inside computeUnrollCount is disabled setting the unroll factor to 0. UnrollAndJam then tries to use the that unroll factor.

[dmgreen]

docs/LangRef.rst

5303–5304

The way this should be working at the moment is:

If there is any unroll_and_jam metadata
  do that thing             (the user explicitly asked for a thing -> do it)
if there is any unroll metadata
  disable unrollandjam      (leave the loop to the unroller)
normal heiristics

I think with "but no `llvm.loop.unroll_and_jam` metadata", that is what this is saying. Correct me if I'm wrong and it's not working like this. Or feel free to update it if it's unclear. Or if you think this should work another way...? ;)

I originally invisioned unrollandjam as an extension to the unroll pass, so I sometimes see the two things as interrelated. If a user specifies loop.unroll.disable, they almost certainly wanted to disable all unrolling, not just that in the unroll pass.

5349

I believe he meant this being unrolled and jammed:

for i {
  for j
    A(i,j)
  for k
    B(i,k)
}

This is not something we currently support as I didn't think it would ever be likely to be profitable. Users specifying metadata might change that. The pass could be able to be expanded to work on this (I think), but it's not something that it currently does.

lib/Transforms/Scalar/LoopUnrollAndJamPass.cpp

205

Have you considered moving the "disable" check out of computeUnrollCount and into tryUnrollLoop, where the existing "HasUnrollDisablePragma" check is? Hopefully that could be replaced with the new method, much like HasUnrollAndJamDisablePragma has been, and would mean this computeUnrollCount function would just work as it used to.

[Meinersbur]

docs/LangRef.rst

5303–5304

If there is any unroll_and_jam metadata
  do that thing             (the user explicitly asked for a thing -> do it)

There is a comment in LoopUnrollAndJamPass.cpp:

// We have already checked that the loop has no unroll.* pragmas.

According to this, this is not true (since only checked afterwards) and computeUnrollCount will consider e.g. llvm.loop.unroll.count even when used for unroll-and-jam.

I was concerned about the last phrase plus llvm.loop.unroll.disable metadata will disable unroll and jam too., but it might be a misinterpretation in that it will disable unroll-and-jam, but only if unroll-and-jam is not explicitly enabled.

5349

The j- and k-loops are both inner loops, so followup_inner should apply to both of them.
distinguishing them might be possible when introducing a mechanism like for naming the output loops of loop distribution.

lib/Transforms/Scalar/LoopUnrollAndJamPass.cpp

205

There are multiple mechanisms in computeUnrollCount that disable unrolling (such as UnrollCountPragmaValue returning zero).

If I was to fix this method, I'd do it cleanly by refactoring-out the mechanism that computes the unroll factor when pragmas/options are absent (and not emit any LoopUnroll-specific diagnostics).

[hfinkel]

docs/LangRef.rst

5117

This is too strong (see comment below).

5203

preserving -> preserve

5203

e.g., because two ...

5205

vector lane -> set of vector lanes

5211

added to both the vectorized and remainder loop

docs/TransformMetadata.rst

15

By default, transformation passes use heuristics to determine whether or not to perform transformations, and when doing so, other details of how the transformations are applied (e.g., which vectorization factor to select).

18

As stated, this is untrue (for -O3). For -O3, we only require a likely speedup across many workloads (and slowdowns be unlikely). This is why, for example, under -O3, we can vectorize with runtime checks. How about this wording:

Unless the optimizer is otherwise directed, transformations are applied conservatively. This conservatism generally allows the optimizer to avoid unprofitable transformations, but in practice, this results in the optimizer not applying transformations that would be highly profitable.

23

it -> they

25

for -> of

52

Unrolling, etc. - no need to capitalize.

55

We should be careful with the language here. As any of these can be dropped without changing the semantics of the code, nothing here is "mandatory". How about saying, ", or convey a specific request from the user"

59

optimization-missed warning

61

I know what you mean by "separate", but I think it's better to say:

is separate. -> can be unused by the optimizer without generating a warning.

69

This wording is too strong. I think that we need to draw a distinction here between (at least) three classes of transformations:

1. canonicalizing transformations
2. (cost-model-driven) restructuring transformations
3. low-level (target-specific) transformations (e.g., using ctr-register-based loops on PowerPC)

I believe that this pragma should only affect those in class (2). Canonizalizing transformations are always performed (when optimizing at all), and low-level transformations are beyond the reach of this kind of metadata.

I'd recommend using the wording that this metadata disables, "optional, high-level, restructuring transformations."

71

avoids that the loop is altered -> avoids the loop being altered

88

Why is this a useful feature? Should we allow only one transformation per node?

91

loop being vectorized -> loop to be vectorized

104

This leaves open the question of whether the vectorizer adds the 'isvectorized' attribute when a follow-up is specific. It should, right?

121

for -> to

122

comma after following

153

Why would isvectorized not always be provided?

301

where 'rtc' is the generated runtime safety check.

391

must be -> should be

392

responsible for this reporting

393

they might -> there might

393

being able - > able

395

is -> may be

(keep the entire list in the hypothetical)

411

in a fixedpoint loop -> using a dynamic ordering

(not to be too prescriptive)

include/llvm/Transforms/Utils/LoopUtils.h

224

We can't have metadata necessary for correctness. 'ForcedByUser' is fine to indicate that the user should receive a warning if the transformation cannot be performed.

lib/Transforms/Scalar/LoopUnrollAndJamPass.cpp

364

So each inner loop gets the same id? That doesn't sound right.

[Meinersbur]

docs/TransformMetadata.rst

88

It's not a new feature, but effectively the current behavior. ("is possible for compatibility
reasons"). I'd indeed prefer to crash if multiple transformations are applied to avoid undefined behavior, which unfortunately is a breaking change.

104

I think it should not, but the metadata gives complete control over which attributes will be in the new loop to the metadata. If a frontend wants to apply a transformation twice, it should be able to do so.

I think the paragraph says that no such additional implicit attributes are added when a followup is specified:

If no followup is specified, ...

I added "If, and only if," to make it even clearer.

153

I don't know how LoopVectorize behaves when encountering vector instructions, but I want to avoid the vagueness of some passes adding implicit metadata in some situation. The IR should have the control over whether a transformation is applied multiple times.

include/llvm/Transforms/Utils/LoopUtils.h

224

[comment] This indicates that using metadata for user-directed loop-transformation #pragmas is a leaky abstraction.

lib/Transforms/Scalar/LoopUnrollAndJamPass.cpp

364

LoopID is a misnomer. A LoopID is neither unique (multiple loops having the same LoopID, e.g. because LoopVersioning of any pass not aware of loops copied the BBs of a loop; there is even a regression test for the behaviour with non-unique LoopID) nor identifying (adding/removing attributes in the LoopID MDNode will create a new MDNode; see D52116 for a fix for llvm.loop.parallel_accesses assuming this property).

Fixing LoopID to be identifier-like is not possible with the current MDNode structure and would require to make any pass that copies code to be aware of LoopIDs. It would be easier to not assume that LoopID has any identifying properties. I am open to rename 'LoopID' to something else.

[Meinersbur]

• Rebase
• Address @hfinkel's remarks

[Meinersbur]

ping

[dmgreen]

docs/TransformMetadata.rst

18

(Space in howthe)

lib/Transforms/Scalar/LoopUnrollPass.cpp

753

This shouldn't be needed here. Before this patch, there was a single place that checked if the loop had unroll disable pragma (HasUnrollDisablePragma at the start of tryToUnrollLoop). It seems best to keep that as-is in this patch (it's already long enough!) and remove HasUnrollDisablePragma, replacing it with the new hasUnrollTransformation & TM_Disable check. Then we won't need this IgnoreUser.

lib/Transforms/Utils/LoopUtils.cpp

299

Would this fall over if the metadata was not a string? Such as debug metadata.

[Meinersbur]

lib/Transforms/Scalar/LoopUnrollPass.cpp

753

This is here because if the unfortunate interaction between LoopUnroll and LoopUnrollAndJam. computeUnrollAndJamCount uses the result of this function to itself determine whether it should unroll-and-jam.

HasUnrollDisablePragma checks for the llvm.loop.unroll.enable property. hasUnrollTransformation returns whether LoopUnroll should do something which is not interchangeable. For some reason, llvm.loop.unroll.enable is handled here, but llvm.loop.unroll.count and llvm.loop.unroll.full are handled here and therefore have in influence on LoopUnrollAndJam.

I would be glad if you, the author of LoopUnrollAndJam, could untangle this.

lib/Transforms/Utils/LoopUtils.cpp

299

This was previously checked to be in a LoopID, therefore cannot be debug metadata.

This assumes that the metadata is not malformed. However, this is nowhere handled gracefully in LLVM. For instance, UnrollAndJamCountPragmaValue will trigger an assertion if the MDNode has not exactly 2 items, or the second item is something else than a positive integer. In the case here, an assertion in cast<T> will trigger.

I added extra checks at this location, but there are many others.

[Meinersbur]

• Address dmgreen's comments
• Rebase

[dmgreen]

lib/Transforms/Scalar/LoopUnrollPass.cpp

753

Sometimes it's easier to show with code :-) so this is what I was thinking of:
https://reviews.llvm.org/P8121
Unless you think that will not work for some reason? It passes all the tests you have here, and removes HasUnrollDisablePragma and the IgnoreUser, so seems cleaner. It also has the advantage of keeping unrelated changes to a minimum and not introducing a second place for llvm.loop.unroll.disable to be checked.

[dmgreen]

lib/Transforms/Utils/LoopUtils.cpp

299

Yeah, malformed input would be fine to not handle, as far as I understand (or perhaps is just QOI). But I was testing something like this (hope I still have it correct):

void c(int n, int* w, int* x, int *y, int* z, int *a) {
#pragma clang loop distribute(enable)  vectorize(disable)
    for (int i=0; i < n; i++) {
        x[i] = y[i] + z[i]*w[i];
        a[i+1] = (a[i-1] + a[i] + a[i+1])/3.0;
        y[i] = z[i] - x[i];
    }
}

Ran with "clang -O3 distribute.c -S -g" would crash with the previous patch. Now I think it doesn't drop the distribute metadata? I believe the llvm.loop metedata will looks something like !58 in:

!58 = distinct !{!58, !30, !59, !60, !61, !62}
!59 = !DILocation(line: 8, column: 5, scope: !20)
!60 = !{!"llvm.loop.vectorize.width", i32 1}
!61 = !{!"llvm.loop.unroll.disable"}
!62 = !{!"llvm.loop.distribute.enable", i1 true}

!30 is a DILocation too, which I think are the parts causing the problems.

[Meinersbur]

lib/Transforms/Scalar/LoopUnrollPass.cpp

753

Thank you for the patch. I am not 100% sure whether this does not change LoopUnroll's behavior. That is, with !{!"llvm.loop.unroll.count", i32 1} it currently executes

UP.Count = PragmaCount;
UP.Runtime = true;
UP.AllowExpensiveTripCount = true;
UP.Force = true;
if ((UP.AllowRemainder || (TripMultiple % PragmaCount == 0)) &&
    getUnrolledLoopSize(LoopSize, UP) < PragmaUnrollThreshold)
  return true;

where as with your patch it bails out early (it might still do peeling even if UP.Count is 1). Also, the -unroll-count command-line option would be evaluated first before your patch.

unroll-pragmas_contradiction.ll950 BDownload

fails with your patch.

However, I like that it indeed makes the unroll decision simpler and goes in the direction of separating LoopUnroll and LoopUnrollAndJam's decision logic.

lib/Transforms/Utils/LoopUtils.cpp

299

I may not have considered that CGLoopInfo.cpp also adds debug locations to LoopIDs. Should be fixed with the previous update. Thanks for noticing.

I also made a mistake in that update which dropped all non-distribute metadata instead of the distribute metadata. It made one regression test fail.

[Meinersbur]

• Rebress
• Fix drop metadata regression
• Apply dmgreen's patch suggestion

[hfinkel]

A few additional comments. Otherwise, this LGTM. When @dmgreen is happy with the unrolling changes, I think you're good to go.

docs/LangRef.rst

5124

Maybe add, "It is recommended to use this metadata when using any of the other llvm.loop.* metadata to direct specific transformations."

docs/TransformMetadata.rst

401

there -> they

lib/Transforms/Scalar/LoopDistribute.cpp

87

This should say Followup, not Followu, I suppose.

lib/Transforms/Scalar/WarnMissedTransforms.cpp

33

Here and below, explicitly specified should have a hyphen (it is a compound adjective):

explicitly-specified loop unrolling

that having been said, I'd prefer a different phrasing all together. These are end-user visible messages, and I think that we can make these slightly more user friendly. How about this:

"loop not unrolled: the optimizer was unable to perform the requested transformation"

(and similar for the others)

[Meinersbur]

• Add transformation order notice to llvm.loop.disable_nonforced.
• Typos

[Meinersbur]

lib/Transforms/Scalar/WarnMissedTransforms.cpp

33

I think that "the optimizer was unable to perform" is less accurate: it gives the impression that the optimizer actually tried to perform the transformation, but one of the reasons the metadata is still present is that the corresponding pass is not in the pipeline (e.g. because of -fno-vectorize or -mllvm -enable-unroll-and-jam is missing). That is, the user should modify the compiler flags instead of tweaking the source code.

That being said, "failed to ..." is not much better. Any better suggestions?

[hfinkel]

lib/Transforms/Scalar/WarnMissedTransforms.cpp

33

I think that "the optimizer was unable to perform" is less accurate: ... but one of the reasons the metadata is still present is that the corresponding pass is not in the pipeline...

I disagree that it is less accurate, and the optimizer might be unable to perform an optimization for structural reasons, and to say that something "failed" clearly implies to me that it was explicitly attempted (which in this case it was not). Nevertheless, this is a good point, and we could provide a more-useful message. How about this:

loop not unrolled: the optimizer was unable to perform the requested transformation; the transformation might be disabled or specified as part of an unsupported transformation ordering

[Meinersbur]

• Clear-up leftover transformation warning messages

This change requires a patch to Clang: D55288

[dmgreen]

When @dmgreen is happy with the unrolling changes, I think you're good to go.

Certainly. If you are happy, I am happy. Thanks.

[Meinersbur]

• [test] Revise tests
  • Consistent disable_nonforced testing
  • Unify followup-attribute testing. The previous approach was to copy existing test cases and emulate the behavior of the loop transformation passes using followup attributes. This had the disadvantage that the pass would pass even if the followup-attribute was ignored (indeed, some were misspelled) since the result is the same. Instead, use a new "followup.ll" test per loop pass that checks the presence of new attributes specific for each followup.
• [docs] Add followup attribute recommendations

docs/LangRef.rst

 
 ``unpredictable`` metadata may be attached to any branch or switch
 instruction. It can be used to express the unpredictability of control
 flow. Similar to the llvm.expect intrinsic, it may be used to alter
 optimizations related to compare and branch instructions. The metadata
 is treated as a boolean value; if it exists, it signals that the branch
 or switch that it is attached to is completely unpredictable.
 
+.. _llvm.loop:
+
 '``llvm.loop``'
 ^^^^^^^^^^^^^^^
 
 It is sometimes useful to attach information to loop constructs. Currently,
 loop metadata is implemented as metadata attached to the branch instruction
 in the loop latch block. This type of metadata refer to a metadata node that is
 guaranteed to be separate for each loop. The loop identifier metadata is
 specified with the name ``llvm.loop``.

 
 .. code-block:: llvm
 
       br i1 %exitcond, label %._crit_edge, label %.lr.ph, !llvm.loop !0
     ...
     !0 = !{!0, !1}
     !1 = !{!"llvm.loop.unroll.count", i32 4}
 
+'``llvm.loop.disable_nonforced``'
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+This metadata disables all optional loop transformations unless
+explicitly instructed using other transformation metdata such as
+``llvm.loop.unroll.enable''. That is, no heuristic will try to determine
+whether a transformation is profitable. The purpose is to avoid that the
+loop is transformed to a different loop before an explicitly requested
+(forced) transformation is applied. For instance, loop fusion can make
+other transformations impossible. Mandatory loop canonicalizations such
+as loop rotation are still applied.
+
+It is recommended to use this metadata in addition to any llvm.loop.*
+transformation directive. Also, any loop should have at most one
+directive applied to it (and a sequence of transformations built using
+followup-attributes). Otherwise, which transformation will be applied
+depends on implementation details such as the pass pipeline order.
+
+See :ref:`transformation-metadata` for details.
+
 '``llvm.loop.vectorize``' and '``llvm.loop.interleave``'
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 Metadata prefixed with ``llvm.loop.vectorize`` or ``llvm.loop.interleave`` are
 used to control per-loop vectorization and interleaving parameters such as
 vectorization width and interleave count. These metadata should be used in
 conjunction with ``llvm.loop`` loop identification metadata. The
 ``llvm.loop.vectorize`` and ``llvm.loop.interleave`` metadata are only
.. code-block:: llvm
 
    !0 = !{!"llvm.loop.vectorize.width", i32 4}
 
 Note that setting ``llvm.loop.vectorize.width`` to 1 disables
 vectorization of the loop. If ``llvm.loop.vectorize.width`` is set to
 0 or if the loop does not have this metadata the width will be
 determined automatically.
 
+'``llvm.loop.vectorize.followup_vectorized``' Metadata
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+This metadata defines which loop attributes the vectorized loop will
+have. See :ref:`transformation-metadata` for details.
+
+'``llvm.loop.vectorize.followup_epilogue``' Metadata
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+This metadata defines which loop attributes the epilogue will have. The
+epilogue is not vectorized and is executed when either the vectorized
+loop is not known to preserve semantics (because e.g., it processes two
+arrays that are found to alias by a runtime check) or for the last
+iterations that do not fill a complete set of vector lanes. See
+:ref:`Transformation Metadata <transformation-metadata>` for details.
+
+'``llvm.loop.vectorize.followup_all``' Metadata
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Attributes in the metadata will be added to both the vectorized and
+epilogue loop.
+See :ref:`Transformation Metadata <transformation-metadata>` for details.
+
 '``llvm.loop.unroll``'
 ^^^^^^^^^^^^^^^^^^^^^^
 
 Metadata prefixed with ``llvm.loop.unroll`` are loop unrolling
 optimization hints such as the unroll factor. ``llvm.loop.unroll``
 metadata should be used in conjunction with ``llvm.loop`` loop
 identification metadata. The ``llvm.loop.unroll`` metadata are only
 optimization hints and the unrolling will only be performed if the

 This metadata suggests that the loop should be unrolled fully. The
 metadata has a single operand which is the string ``llvm.loop.unroll.full``.
 For example:
 
 .. code-block:: llvm
 
    !0 = !{!"llvm.loop.unroll.full"}
 
+'``llvm.loop.unroll.followup``' Metadata
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+This metadata defines which loop attributes the unrolled loop will have.
+See :ref:`Transformation Metadata <transformation-metadata>` for details.
+
+'``llvm.loop.unroll.followup_remainder``' Metadata
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+This metadata defines which loop attributes the remainder loop after
+partial/runtime unrolling will have. See
+:ref:`Transformation Metadata <transformation-metadata>` for details.
+
 '``llvm.loop.unroll_and_jam``'
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 This metadata is treated very similarly to the ``llvm.loop.unroll`` metadata
 above, but affect the unroll and jam pass. In addition any loop with
 ``llvm.loop.unroll`` metadata but no ``llvm.loop.unroll_and_jam`` metadata will
 disable unroll and jam (so ``llvm.loop.unroll`` metadata will be left to the
 unroller, plus ``llvm.loop.unroll.disable`` metadata will disable unroll and jam
 too.)
 
 The metadata for unroll and jam otherwise is the same as for ``unroll``.
 ``llvm.loop.unroll_and_jam.enable``, ``llvm.loop.unroll_and_jam.disable`` and
 ``llvm.loop.unroll_and_jam.count`` do the same as for unroll.
 ``llvm.loop.unroll_and_jam.full`` is not supported. Again these are only hints
 and the normal safety checks will still be performed.
 
 '``llvm.loop.unroll_and_jam.count``' Metadata
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 This metadata suggests an unroll and jam factor to use, similarly to
 ``llvm.loop.unroll.count``. The first operand is the string
 ``llvm.loop.unroll_and_jam.count`` and the second operand is a positive integer
 specifying the unroll factor. For example:
 
 .. code-block:: llvm
 
    !0 = !{!"llvm.loop.unroll_and_jam.count", i32 4}

 trip count is known at compile time and partially unrolled if the trip count is
 not known at compile time. The metadata has a single operand which is the
 string ``llvm.loop.unroll_and_jam.enable``.  For example:
 
 .. code-block:: llvm
 
    !0 = !{!"llvm.loop.unroll_and_jam.enable"}
 
+'``llvm.loop.unroll_and_jam.followup_outer``' Metadata
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+This metadata defines which loop attributes the outer unrolled loop will
+have. See :ref:`Transformation Metadata <transformation-metadata>` for
+details.
+
+'``llvm.loop.unroll_and_jam.followup_inner``' Metadata
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+This metadata defines which loop attributes the inner jammed loop will
+have. See :ref:`Transformation Metadata <transformation-metadata>` for
+details.
+
+'``llvm.loop.unroll_and_jam.followup_remainder_outer``' Metadata
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+This metadata defines which attributes the epilogue of the outer loop
+will have. This loop is usually unrolled, meaning there is no such
+loop. This attribute will be ignored in this case. See
+:ref:`Transformation Metadata <transformation-metadata>` for details.
+
+'``llvm.loop.unroll_and_jam.followup_remainder_inner``' Metadata
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+This metadata defines which attributes the inner loop of the epilogue
+will have. The outer epilogue will usually be unrolled, meaning there
+can be multiple inner remainder loops. See
+:ref:`Transformation Metadata <transformation-metadata>` for details.
+
+'``llvm.loop.unroll_and_jam.followup_all``' Metadata
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Attributes specified in the metadata is added to all
+``llvm.loop.unroll_and_jam.*`` loops. See
+:ref:`Transformation Metadata <transformation-metadata>` for details.
+
 '``llvm.loop.licm_versioning.disable``' Metadata
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 This metadata indicates that the loop should not be versioned for the purpose
 of enabling loop-invariant code motion (LICM). The metadata has a single operand
 which is the string ``llvm.loop.licm_versioning.disable``. For example:
 
 .. code-block:: llvm

 .. code-block:: llvm
 
    !0 = !{!"llvm.loop.distribute.enable", i1 0}
    !1 = !{!"llvm.loop.distribute.enable", i1 1}
 
 This metadata should be used in conjunction with ``llvm.loop`` loop
 identification metadata.
 
+'``llvm.loop.distribute.followup_coincident``' Metadata
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+This metadata defines which attributes extracted loops with no cyclic
+dependencies will have (i.e. can be vectorized). See
+:ref:`Transformation Metadata <transformation-metadata>` for details.
+
+'``llvm.loop.distribute.followup_sequential``' Metadata
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+This metadata defines which attributes the isolated loops with unsafe
+memory dependencies will have. See
+:ref:`Transformation Metadata <transformation-metadata>` for details.
+
+'``llvm.loop.distribute.followup_fallback``' Metadata
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+If loop versioning is necessary, this metadata defined the attributes
+the non-distributed fallback version will have. See
+:ref:`Transformation Metadata <transformation-metadata>` for details.
+
+'``llvm.loop.distribute.followup_all``' Metadata
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Thes attributes in this metdata is added to all followup loops of the
+loop distribution pass. See
+:ref:`Transformation Metadata <transformation-metadata>` for details.
+
 '``llvm.mem``'
 ^^^^^^^^^^^^^^^
 
 Metadata types used to annotate memory accesses with information helpful
 for optimizations are prefixed with ``llvm.mem``.
 
 '``llvm.mem.parallel_loop_access``' Metadata
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

docs/Passes.rst

 Displays the post dominator tree using the GraphViz tool.
 
 ``-view-postdom-only``: View postdominance tree of function (with no function bodies)
 -------------------------------------------------------------------------------------
 
 Displays the post dominator tree using the GraphViz tool, but omitting function
 bodies.
 
+``-transform-warning``: Report missed forced transformations
+------------------------------------------------------------
+
+Emits warnings about not yet applied forced transformations (e.g. from
+``#pragma omp simd``).

docs/TransformMetadata.rst

+.. _transformation-metadata:
+
+============================
+Code Transformation Metadata
+============================
+
+.. contents::
+   :local:
+
+Overview
+========
+
+LLVM transformation passes can be controlled by attaching metadata to
+the code to transform. By default, transformation passes use heuristics
+to determine whether or not to perform transformations, and when doing
+so, other details of how the transformations are applied (e.g., which
+vectorization factor to select).
+Unless the optimizer is otherwise directed, transformations are applied
+conservatively. This conservatism generally allows the optimizer to
+avoid unprofitable transformations, but in practice, this results in the
+optimizer not applying transformations that would be highly profitable.
+
+Frontends can give additional hints to LLVM passes on which
+transformations they should apply. This can be additional knowledge that
+cannot be derived from the emitted IR, or directives passed from the
+user/programmer. OpenMP pragmas are an example of the latter.
+
+If any such metadata is dropped from the program, the code's semantics
+must not change.
+
+Metadata on Loops
+=================
+
+Attributes can be attached to loops as described in :ref:`llvm.loop`.
+Attributes can describe properties of the loop, disable transformations,
+force specific transformations and set transformation options.
+
+Because metadata nodes are immutable (with the exception of
+``MDNode::replaceOperandWith`` which is dangerous to use on uniqued
+metadata), in order to add or remove a loop attributes, a new ``MDNode``
+must be created and assigned as the new ``llvm.loop`` metadata. Any
+connection between the old ``MDNode`` and the loop is lost. The
+``llvm.loop`` node is also used as LoopID (``Loop::getLoopID()``), i.e.
+the loop effectively gets a new identifier. For instance,
+``llvm.mem.parallel_loop_access`` references the LoopID. Therefore, if
+the parallel access property is to be preserved after adding/removing
+loop attributes, any ``llvm.mem.parallel_loop_access`` reference must be
+updated to the new LoopID.
+
+Transformation Metadata Structure
+=================================
+
+Some attributes describe code transformations (unrolling, vectorizing,
+loop distribution, etc.). They can either be a hint to the optimizer
+that a transformation might be beneficial, instruction to use a specific
+option, , or convey a specific request from the user (such as
+``#pragma clang loop`` or ``#pragma omp simd``).
+
+If a transformation is forced but cannot be carried-out for any reason,
+an optimization-missed warning must be emitted. Semantic information
+such as a transformation being safe (e.g.
+``llvm.mem.parallel_loop_access``) can be unused by the optimizer
+without generating a warning.
+
+Unless explicitly disabled, any optimization pass may heuristically
+determine whether a transformation is beneficial and apply it. If
+metadata for another transformation was specified, applying a different
+transformation before it might be inadvertent due to being applied on a
+different loop or the loop not existing anymore. To avoid having to
+explicitly disable an unknown number of passes, the attribute
+``llvm.loop.disable_nonforced`` disables all optional, high-level,
+restructuring transformations.
+
+The following example avoids the loop being altered before being
+vectorized, for instance being unrolled.
+
+.. code-block:: llvm
+
+      br i1 %exitcond, label %for.exit, label %for.header, !llvm.loop !0
+    ...
+    !0 = distinct !{!0, !1, !2}
+    !1 = !{!"llvm.loop.vectorize.enable", i1 true}
+    !2 = !{!"llvm.loop.disable_nonforced"}
+
+After a transformation is applied, follow-up attributes are set on the
+transformed and/or new loop(s). This allows additional attributes
+including followup-transformations to be specified. Specifying multiple
+transformations in the same metadata node is possible for compatibility
+reasons, but their execution order is undefined. For instance, when
+``llvm.loop.vectorize.enable`` and ``llvm.loop.unroll.enable`` are
+specified at the same time, unrolling may occur either before or after
+vectorization.
+
+As an example, the following instructs a loop to be vectorized and only
+then unrolled.
+
+.. code-block:: llvm
+
+    !0 = distinct !{!0, !1, !2, !3}
+    !1 = !{!"llvm.loop.vectorize.enable", i1 true}
+    !2 = !{!"llvm.loop.disable_nonforced"}
+    !3 = !{!"llvm.loop.vectorize.followup_vectorized", !{"llvm.loop.unroll.enable"}}
+
+If, and only if, no followup is specified, the pass may add attributes itself.
+For instance, the vectorizer adds a ``llvm.loop.isvectorized`` attribute and
+all attributes from the original loop excluding its loop vectorizer
+attributes. To avoid this, an empty followup attribute can be used, e.g.
+
+.. code-block:: llvm
+
+    !3 = !{!"llvm.loop.vectorize.followup_vectorized"}
+
+The followup attributes of a transformation that cannot be applied will
+never be added to a loop and are therefore effectively ignored. This means
+that any followup-transformation in such attributes requires that its
+prior transformations are applied before the followup-transformation.
+The user should receive a warning about the first transformation in the
+transformation chain that could not be applied if it a forced
+transformation. All following transformations are skipped.
+
+Pass-Specific Transformation Metadata
+=====================================
+
+Transformation options are specific to each transformation. In the
+following, we present the model for each LLVM loop optimization pass and
+the metadata to influence them.
+
+Loop Vectorization and Interleaving
+-----------------------------------
+
+Loop vectorization and interleaving is interpreted as a single
+transformation. It is interpreted as forced if
+``!{"llvm.loop.vectorize.enable", i1 true}`` is set.
+
+Assuming the pre-vectorization loop is
+
+.. code-block:: c
+
+    for (int i = 0; i < n; i+=1) // original loop
+      Stmt(i);
+
+then the code after vectorization will be approximately (assuming an
+SIMD width of 4):
+
+.. code-block:: c
+
+    int i = 0;
+    if (rtc) {
+      for (; i + 3 < n; i+=4) // vectorized/interleaved loop
+        Stmt(i:i+3);
+    }
+    for (; i < n; i+=1) // epilogue loop
+      Stmt(i);
+
+where ``rtc`` is a generated runtime check.
+
+``llvm.loop.vectorize.followup_vectorized`` will set the attributes for
+the vectorized loop. If not specified, ``llvm.loop.isvectorized`` is
+combined with the original loop's attributes to avoid it being
+vectorized multiple times.
+
+``llvm.loop.vectorize.followup_epilogue`` will set the attributes for
+the remainder loop. If not specified, it will have the original loop's
+attributes combined with ``llvm.loop.isvectorized`` and
+``llvm.loop.unroll.runtime.disable`` (unless the original loop already
+has unroll metadata).
+
+The attributes specified by ``llvm.loop.vectorize.followup_all`` are
+added to both loops.
+
+When using a follow-up attribute, it replaces any automatically deduced
+attributes for the generated loop in question. Therefore it is
+recommended to add ``llvm.loop.isvectorized`` to
+``llvm.loop.vectorize.followup_all`` which avoids that the loop
+vectorizer tries to optimize the loops again.
+
+Loop Unrolling
+--------------
+
+Unrolling is interpreted as forced any ``!{!"llvm.loop.unroll.enable"}``
+metadata or option (``llvm.loop.unroll.count``, ``llvm.loop.unroll.full``)
+is present. Unrolling can be full unrolling, partial unrolling of a loop
+with constant trip count or runtime unrolling of a loop with a trip
+count unknown at compile-time.
+
+If the loop has been unrolled fully, there is no followup-loop. For
+partial/runtime unrolling, the original loop of
+
+.. code-block:: c
+
+    for (int i = 0; i < n; i+=1) // original loop
+      Stmt(i);
+
+is transformed into (using an unroll factor of 4):
+
+.. code-block:: c
+
+    int i = 0;
+    for (; i + 3 < n; i+=4) // unrolled loop
+      Stmt(i);
+      Stmt(i+1);
+      Stmt(i+2);
+      Stmt(i+3);
+    }
+    for (; i < n; i+=1) // remainder loop
+      Stmt(i);
+
+``llvm.loop.unroll.followup_unrolled`` will set the loop attributes of
+the unrolled loop. If not specified, the attributes of the original loop
+without the ``llvm.loop.unroll.*`` attributes are copied and
+``llvm.loop.unroll.disable`` added to it.
+
+``llvm.loop.unroll.followup_remainder`` defines the attributes of the
+remainder loop. If not specified the remainder loop will have no
+attributes. The remainder loop might not be present due to being fully
+unrolled in which case this attribute has no effect.
+
+Attributes defined in ``llvm.loop.unroll.followup_all`` are added to the
+unrolled and remainder loops.
+
+To avoid that the partially unrolled loop is unrolled again, it is
+recommended to add ``llvm.loop.unroll.disable`` to
+``llvm.loop.unroll.followup_all``. If no follow-up attribute specified
+for a generated loop, it is added automatically.
+
+Unroll-And-Jam
+--------------
+
+Unroll-and-jam uses the following transformation model (here with an
+unroll factor if 2). Currently, it does not support a fallback version
+when the transformation is unsafe.
+
+.. code-block:: c
+
+    for (int i = 0; i < n; i+=1) { // original outer loop
+      Fore(i);
+      for (int j = 0; j < m; j+=1) // original inner loop
+        SubLoop(i, j);
+      Aft(i);
+    }
+
+.. code-block:: c
+
+    int i = 0;
+    for (; i + 1 < n; i+=2) { // unrolled outer loop
+      Fore(i);
+      Fore(i+1);
+      for (int j = 0; j < m; j+=1) { // unrolled inner loop
+        SubLoop(i, j);
+        SubLoop(i+1, j);
+      }
+      Aft(i);
+      Aft(i+1);
+    }
+    for (; i < n; i+=1) { // remainder outer loop
+      Fore(i);
+      for (int j = 0; j < m; j+=1) // remainder inner loop
+        SubLoop(i, j);
+      Aft(i);
+    }
+
+``llvm.loop.unroll_and_jam.followup_outer`` will set the loop attributes
+of the unrolled outer loop. If not specified, the attributes of the
+original outer loop without the ``llvm.loop.unroll.*`` attributes are
+copied and ``llvm.loop.unroll.disable`` added to it.
+
+``llvm.loop.unroll_and_jam.followup_inner`` will set the loop attributes
+of the unrolled inner loop. If not specified, the attributes of the
+original inner loop are used unchanged.
+
+``llvm.loop.unroll_and_jam.followup_remainder_outer`` sets the loop
+attributes of the outer remainder loop. If not specified it will not
+have any attributes. The remainder loop might not be present due to
+being fully unrolled.
+
+``llvm.loop.unroll_and_jam.followup_remainder_inner`` sets the loop
+attributes of the inner remainder loop. If not specified it will have
+the attributes of the original inner loop. It the outer remainder loop
+is unrolled, the inner remainder loop might be present multiple times.
+
+Attributes defined in ``llvm.loop.unroll_and_jam.followup_all`` are
+added to all of the aforementioned output loops.
+
+To avoid that the unrolled loop is unrolled again, it is
+recommended to add ``llvm.loop.unroll.disable`` to
+``llvm.loop.unroll_and_jam.followup_all``. It suppresses unroll-and-jam
+as well as an additional inner loop unrolling. If no follow-up
+attribute specified for a generated loop, it is added automatically.
+
+Loop Distribution
+-----------------
+
+The LoopDistribution pass tries to separate vectorizable parts of a loop
+from the non-vectorizable part (which otherwise would make the entire
+loop non-vectorizable). Conceptually, it transforms a loop such as
+
+.. code-block:: c
+
+    for (int i = 1; i < n; i+=1) { // original loop
+      A[i] = i;
+      B[i] = 2 + B[i];
+      C[i] = 3 + C[i - 1];
+    }
+
+into the following code:
+
+.. code-block:: c
+
+    if (rtc) {
+      for (int i = 1; i < n; i+=1) // coincident loop
+        A[i] = i;
+      for (int i = 1; i < n; i+=1) // coincident loop
+        B[i] = 2 + B[i];
+      for (int i = 1; i < n; i+=1) // sequential loop
+        C[i] = 3 + C[i - 1];
+    } else {
+      for (int i = 1; i < n; i+=1) { // fallback loop
+        A[i] = i;
+        B[i] = 2 + B[i];
+        C[i] = 3 + C[i - 1];
+      }
+    }
+
+where ``rtc`` is a generated runtime check.
+
+``llvm.loop.distribute.followup_coincident`` sets the loop attributes of
+all loops without loop-carried dependencies (i.e. vectorizable loops).
+There might be more than one such loops. If not defined, the loops will
+inherit the original loop's attributes.
+
+``llvm.loop.distribute.followup_sequential`` sets the loop attributes of the
+loop with potentially unsafe dependencies. There should be at most one
+such loop. If not defined, the loop will inherit the original loop's
+attributes.
+
+``llvm.loop.distribute.followup_fallback`` defines the loop attributes
+for the fallback loop, which is a copy of the original loop for when
+loop versioning is required. If undefined, the fallback loop inherits
+all attributes from the original loop.
+
+Attributes defined in ``llvm.loop.distribute.followup_all`` are added to
+all of the aforementioned output loops.
+
+It is recommended to add ``llvm.loop.disable_nonforced`` to
+``llvm.loop.distribute.followup_fallback``. This avoids that the
+fallback version (which is likely never executed) is further optimzed
+which would increase the code size.
+
+Versioning LICM
+---------------
+
+The pass hoists code out of loops that are only loop-invariant when
+dynamic conditions apply. For instance, it transforms the loop
+
+.. code-block:: c
+
+    for (int i = 0; i < n; i+=1) // original loop
+      A[i] = B[0];
+
+into:
+
+.. code-block:: c
+
+    if (rtc) {
+      auto b = B[0];
+      for (int i = 0; i < n; i+=1) // versioned loop
+        A[i] = b;
+    } else {
+      for (int i = 0; i < n; i+=1) // unversioned loop
+        A[i] = B[0];
+    }
+
+The runtime condition (``rtc``) checks that the array ``A`` and the
+element `B[0]` do not alias.
+
+Currently, this transformation does not support followup-attributes.
+
+Loop Interchange
+----------------
+
+Currently, the ``LoopInterchange`` pass does not use any metadata.
+
+Ambiguous Transformation Order
+==============================
+
+If there multiple transformations defined, the order in which they are
+executed depends on the order in LLVM's pass pipeline, which is subject
+to change. The default optimization pipeline (anything higher than
+``-O0``) has the following order.
+
+When using the legacy pass manager:
+
+ - LoopInterchange (if enabled)
+ - SimpleLoopUnroll/LoopFullUnroll (only performs full unrolling)
+ - VersioningLICM (if enabled)
+ - LoopDistribute
+ - LoopVectorizer
+ - LoopUnrollAndJam (if enabled)
+ - LoopUnroll (partial and runtime unrolling)
+
+When using the legacy pass manager with LTO:
+
+ - LoopInterchange (if enabled)
+ - SimpleLoopUnroll/LoopFullUnroll (only performs full unrolling)
+ - LoopVectorizer
+ - LoopUnroll (partial and runtime unrolling)
+
+When using the new pass manager:
+
+ - SimpleLoopUnroll/LoopFullUnroll (only performs full unrolling)
+ - LoopDistribute
+ - LoopVectorizer
+ - LoopUnrollAndJam (if enabled)
+ - LoopUnroll (partial and runtime unrolling)
+
+Leftover Transformations
+========================
+
+Forced transformations that have not been applied after the last
+transformation pass should be reported to the user. The transformation
+passes themselves cannot be responsible for this reporting because they
+might not be in the pipeline, there might be multiple passes able to
+apply a transformation (e.g. ``LoopInterchange`` and Polly) or a
+transformation attribute may be 'hidden' inside another passes' followup
+attribute.
+
+The pass ``-transform-warning`` (``WarnMissedTransformationsPass``)
+emits such warnings. It should be placed after the last transformation
+pass.
+
+The current pass pipeline has a fixed order in which transformations
+passes are executed. A transformation can be in the followup of a pass
+that is executed later and thus leftover. For instance, a loop nest
+cannot be distributed and then interchanged with the current pass
+pipeline. The loop distribution will execute, but there is no loop
+interchange pass following such that any loop interchange metadata will
+be ignored. The ``-transform-warning`` should emit a warning in this
+case.
+
+Future versions of LLVM may fix this by executing transformations using
+a dynamic ordering.

docs/index.rst

.. toctree::
    AMDGPUUsage
    StackMaps
    InAlloca
    BigEndianNEON
    CoverageMappingFormat
    Statepoints
    MergeFunctions
    TypeMetadata
+   TransformMetadata
    FaultMaps
    MIRLangRef
    Coroutines
    GlobalISel
    XRay
    XRayExample
    XRayFDRFormat
    PDB/index

include/llvm/InitializePasses.h

 void initializeTypeBasedAAWrapperPassPass(PassRegistry&);
 void initializeUnifyFunctionExitNodesPass(PassRegistry&);
 void initializeUnpackMachineBundlesPass(PassRegistry&);
 void initializeUnreachableBlockElimLegacyPassPass(PassRegistry&);
 void initializeUnreachableMachineBlockElimPass(PassRegistry&);
 void initializeVerifierLegacyPassPass(PassRegistry&);
 void initializeVirtRegMapPass(PassRegistry&);
 void initializeVirtRegRewriterPass(PassRegistry&);
+void initializeWarnMissedTransformationsLegacyPass(PassRegistry &);
 void initializeWasmEHPreparePass(PassRegistry&);
 void initializeWholeProgramDevirtPass(PassRegistry&);
 void initializeWinEHPreparePass(PassRegistry&);
 void initializeWriteBitcodePassPass(PassRegistry&);
 void initializeWriteThinLTOBitcodePass(PassRegistry&);
 void initializeXRayInstrumentationPass(PassRegistry&);
 
 } // end namespace llvm
 
 #endif // LLVM_INITIALIZEPASSES_H

include/llvm/LinkAllPasses.h

ForcePassLinking() {
       (void) llvm::createSpeculativeExecutionIfHasBranchDivergencePass();
       (void) llvm::createRewriteSymbolsPass();
       (void) llvm::createStraightLineStrengthReducePass();
       (void) llvm::createMemDerefPrinter();
       (void) llvm::createMustExecutePrinter();
       (void) llvm::createFloat2IntPass();
       (void) llvm::createEliminateAvailableExternallyPass();
       (void) llvm::createScalarizeMaskedMemIntrinPass();
+      (void) llvm::createWarnMissedTransformationsPass();
 
       (void)new llvm::IntervalPartition();
       (void)new llvm::ScalarEvolutionWrapperPass();
       llvm::Function::Create(nullptr, llvm::GlobalValue::ExternalLinkage)->viewCFGOnly();
       llvm::RGPassManager RGM;
       llvm::TargetLibraryInfoImpl TLII;
       llvm::TargetLibraryInfo TLI(TLII);
       llvm::AliasAnalysis AA(TLI);

include/llvm/Transforms/Scalar.h

 FunctionPass *createLibCallsShrinkWrapPass();
 
 //===----------------------------------------------------------------------===//
 //
 // LoopSimplifyCFG - This pass performs basic CFG simplification on loops,
 // primarily to help other loop passes.
 //
 Pass *createLoopSimplifyCFGPass();
+
+//===----------------------------------------------------------------------===//
+//
+// WarnMissedTransformations - This pass emits warnings for leftover forced
+// transformations.
+//
+Pass *createWarnMissedTransformationsPass();
 } // End llvm namespace
 
 #endif

include/llvm/Transforms/Scalar/WarnMissedTransforms.h

+//===- WarnMissedTransforms.h -----------------------------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// Emit warnings if forced code transformations have not been performed.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_TRANSFORMS_SCALAR_WARNMISSEDTRANSFORMS_H
+#define LLVM_TRANSFORMS_SCALAR_WARNMISSEDTRANSFORMS_H
+
+#include "llvm/IR/PassManager.h"
+
+namespace llvm {
+class Function;
+class Loop;
+class LPMUpdater;
+
+// New pass manager boilerplate.
+class WarnMissedTransformationsPass
+    : public PassInfoMixin<WarnMissedTransformationsPass> {
+public:
+  explicit WarnMissedTransformationsPass() {}
+
+  PreservedAnalyses run(Function &F, FunctionAnalysisManager &AM);
+};
+
+// Legacy pass manager boilerplate.
+Pass *createWarnMissedTransformationsPass();
+void initializeWarnMissedTransformationsLegacyPass(PassRegistry &);
+} // end namespace llvm
+
+#endif // LLVM_TRANSFORMS_SCALAR_WARNMISSEDTRANSFORMS_H

include/llvm/Transforms/Utils/LoopUtils.h

 /// Find string metadata for loop
 ///
 /// If it has a value (e.g. {"llvm.distribute", 1} return the value as an
 /// operand or null otherwise.  If the string metadata is not found return
 /// Optional's not-a-value.
 Optional<const MDOperand *> findStringMetadataForLoop(Loop *TheLoop,
                                                       StringRef Name);
 
+/// Find named metadata for a loop with an integer value.
+llvm::Optional<int> getOptionalIntLoopAttribute(Loop *TheLoop, StringRef Name);
+
+/// Create a new loop identifier for a loop created from a loop transformation.
+///
+/// @param OrigLoopID The loop ID of the loop before the transformation.
+/// @param FollowupAttrs List of attribute names that contain attributes to be
+///                      added to the new loop ID.
+/// @param InheritAttrsExceptPrefix Selects which attributes should be inherited
+///                                 from the original loop. The following values
+///                                 are considered:
+///        nullptr   : Inherit all attributes from @p OrigLoopID.
+///        ""        : Do not inherit any attribute from @p OrigLoopID; only use
+///                    those specified by a followup attribute.
+///        "<prefix>": Inherit all attributes except those which start with
+///                    <prefix>; commonly used to remove metadata for the
+///                    applied transformation.
+/// @param AlwaysNew If true, do not try to reuse OrigLoopID and never return
+///                  None.
+///
+/// @return The loop ID for the after-transformation loop. The following values
+///         can be returned:
+///         None         : No followup attribute was found; it is up to the
+///                        transformation to choose attributes that make sense.
+///         @p OrigLoopID: The original identifier can be reused.
+///         nullptr      : The new loop has no attributes.
+///         MDNode*      : A new unique loop identifier.
+Optional<MDNode *>
+makeFollowupLoopID(MDNode *OrigLoopID, ArrayRef<StringRef> FollowupAttrs,
+                   const char *InheritOptionsAttrsPrefix = "",
+                   bool AlwaysNew = false);
+
+/// Look for the loop attribute that disables all transformation heuristic.
+bool hasDisableAllTransformsHint(const Loop *L);
+
+/// The mode sets how eager a transformation should be applied.
+enum TransformationMode {
+  /// The pass can use heuristics to determine whether a transformation should
+  /// be applied.
+  TM_Unspecified,
+
+  /// The transformation should be applied without considering a cost model.
+  TM_Enable,
+
+  /// The transformation should not be applied.
+  TM_Disable,
+
+  /// Force is a flag and should not be used alone.
+  TM_Force = 0x04,
+
+  /// The transformation was directed by the user, e.g. by a #pragma in
+  /// the source code. If the transformation could not be applied, a
+  /// warning should be emitted.
+  TM_ForcedByUser = TM_Enable | TM_Force,
+
+  /// The transformation must not be applied. For instance, `#pragma clang loop
+  /// unroll(disable)` explicitly forbids any unrolling to take place. Unlike
+  /// general loop metadata, it must not be dropped. Most passes should not
+  /// behave differently under TM_Disable and TM_SuppressedByUser.
+  TM_SuppressedByUser = TM_Disable | TM_Force
+};
+
+/// @{
+/// Get the mode for LLVM's supported loop transformations.
+TransformationMode hasUnrollTransformation(Loop *L);
+TransformationMode hasUnrollAndJamTransformation(Loop *L);
+TransformationMode hasVectorizeTransformation(Loop *L);
+TransformationMode hasDistributeTransformation(Loop *L);
+TransformationMode hasLICMVersioningTransformation(Loop *L);
+/// @}
+
 /// Set input string into loop metadata by keeping other values intact.
 void addStringMetadataToLoop(Loop *TheLoop, const char *MDString,
                              unsigned V = 0);
 
 /// Get a loop's estimated trip count based on branch weight metadata.
 /// Returns 0 when the count is estimated to be 0, or None when a meaningful
 /// estimate can not be made.
 Optional<unsigned> getLoopEstimatedTripCount(Loop *L);

include/llvm/Transforms/Utils/UnrollLoop.h

 class Loop;
 class LoopInfo;
 class MDNode;
 class OptimizationRemarkEmitter;
 class ScalarEvolution;
 
 using NewLoopsMap = SmallDenseMap<const Loop *, Loop *, 4>;
 
+/// @{
+/// Metadata attribute names
+const char *const LLVMLoopUnrollFollowupAll = "llvm.loop.unroll.followup_all";
+const char *const LLVMLoopUnrollFollowupUnrolled =
+    "llvm.loop.unroll.followup_unrolled";
+const char *const LLVMLoopUnrollFollowupRemainder =
+    "llvm.loop.unroll.followup_remainder";
+/// @}
+
 const Loop* addClonedBlockToLoopInfo(BasicBlock *OriginalBB,
                                      BasicBlock *ClonedBB, LoopInfo *LI,
                                      NewLoopsMap &NewLoops);
 
 /// Represents the result of a \c UnrollLoop invocation.
 enum class LoopUnrollResult {
   /// The loop was not modified.
   Unmodified,

 
 LoopUnrollResult UnrollLoop(Loop *L, unsigned Count, unsigned TripCount,
                             bool Force, bool AllowRuntime,
                             bool AllowExpensiveTripCount, bool PreserveCondBr,
                             bool PreserveOnlyFirst, unsigned TripMultiple,
                             unsigned PeelCount, bool UnrollRemainder,
                             LoopInfo *LI, ScalarEvolution *SE,
                             DominatorTree *DT, AssumptionCache *AC,
-                            OptimizationRemarkEmitter *ORE, bool PreserveLCSSA);
+                            OptimizationRemarkEmitter *ORE, bool PreserveLCSSA,
+                            Loop **RemainderLoop = nullptr);
 
 bool UnrollRuntimeLoopRemainder(Loop *L, unsigned Count,
                                 bool AllowExpensiveTripCount,
                                 bool UseEpilogRemainder, bool UnrollRemainder,
-                                LoopInfo *LI,
-                                ScalarEvolution *SE, DominatorTree *DT,
-                                AssumptionCache *AC,
-                                bool PreserveLCSSA);
+                                LoopInfo *LI, ScalarEvolution *SE,
+                                DominatorTree *DT, AssumptionCache *AC,
+                                bool PreserveLCSSA,
+                                Loop **ResultLoop = nullptr);
 
 void computePeelCount(Loop *L, unsigned LoopSize,
                       TargetTransformInfo::UnrollingPreferences &UP,
                       unsigned &TripCount, ScalarEvolution &SE);
 
 bool canPeel(Loop *L);
 
 bool peelLoop(Loop *L, unsigned PeelCount, LoopInfo *LI, ScalarEvolution *SE,
               DominatorTree *DT, AssumptionCache *AC, bool PreserveLCSSA);
 
 LoopUnrollResult UnrollAndJamLoop(Loop *L, unsigned Count, unsigned TripCount,
                                   unsigned TripMultiple, bool UnrollRemainder,
                                   LoopInfo *LI, ScalarEvolution *SE,
                                   DominatorTree *DT, AssumptionCache *AC,
-                                  OptimizationRemarkEmitter *ORE);
+                                  OptimizationRemarkEmitter *ORE,
+                                  Loop **EpilogueLoop = nullptr);
 
 bool isSafeToUnrollAndJam(Loop *L, ScalarEvolution &SE, DominatorTree &DT,
                           DependenceInfo &DI);
 
 bool computeUnrollCount(Loop *L, const TargetTransformInfo &TTI,
                         DominatorTree &DT, LoopInfo *LI, ScalarEvolution &SE,
                         const SmallPtrSetImpl<const Value *> &EphValues,
                         OptimizationRemarkEmitter *ORE, unsigned &TripCount,

include/llvm/Transforms/Vectorize/LoopVectorizationLegality.h

public:
   bool allowVectorization(Function *F, Loop *L, bool AlwaysVectorize) const;
 
   /// Dumps all the hint information.
   void emitRemarkWithHints() const;
 
   unsigned getWidth() const { return Width.Value; }
   unsigned getInterleave() const { return Interleave.Value; }
   unsigned getIsVectorized() const { return IsVectorized.Value; }
-  enum ForceKind getForce() const { return (ForceKind)Force.Value; }
+  enum ForceKind getForce() const {
+    if (Force.Value == FK_Undefined && hasDisableAllTransformsHint(TheLoop))
+      return FK_Disabled;
+    return (ForceKind)Force.Value;
+  }
 
   /// If hints are provided that force vectorization, use the AlwaysPrint
   /// pass name to force the frontend to print the diagnostic.
   const char *vectorizeAnalysisPassName() const;
 
   bool allowReordering() const {
     // When enabling loop hints are provided we allow the vectorizer to change
     // the order of operations that is given by the scalar loop. This is not

lib/Analysis/LoopInfo.cpp

MDNode *Loop::getLoopID() const {
   }
   if (!LoopID || LoopID->getNumOperands() == 0 ||
       LoopID->getOperand(0) != LoopID)
     return nullptr;
   return LoopID;
 }
 
 void Loop::setLoopID(MDNode *LoopID) const {
-  assert(LoopID && "Loop ID should not be null");
-  assert(LoopID->getNumOperands() > 0 && "Loop ID needs at least one operand");
-  assert(LoopID->getOperand(0) == LoopID && "Loop ID should refer to itself");
+  assert((!LoopID || LoopID->getNumOperands() > 0) &&
+         "Loop ID needs at least one operand");
+  assert((!LoopID || LoopID->getOperand(0) == LoopID) &&
+         "Loop ID should refer to itself");
 
-  if (BasicBlock *Latch = getLoopLatch()) {
-    Latch->getTerminator()->setMetadata(LLVMContext::MD_loop, LoopID);
-    return;
-  }
-
-  assert(!getLoopLatch() &&
-         "The loop should have no single latch at this point");
   BasicBlock *H = getHeader();
   for (BasicBlock *BB : this->blocks()) {
     Instruction *TI = BB->getTerminator();
     for (BasicBlock *Successor : successors(TI)) {
-      if (Successor == H)
+      if (Successor == H) {
         TI->setMetadata(LLVMContext::MD_loop, LoopID);
+        break;
+      }
     }
   }
 }
 
 void Loop::setLoopAlreadyUnrolled() {
   MDNode *LoopID = getLoopID();
   // First remove any existing loop unrolling metadata.
   SmallVector<Metadata *, 4> MDs;

lib/Passes/PassBuilder.cpp

 #include "llvm/Transforms/Scalar/SROA.h"
 #include "llvm/Transforms/Scalar/Scalarizer.h"
 #include "llvm/Transforms/Scalar/SimpleLoopUnswitch.h"
 #include "llvm/Transforms/Scalar/SimplifyCFG.h"
 #include "llvm/Transforms/Scalar/Sink.h"
 #include "llvm/Transforms/Scalar/SpeculateAroundPHIs.h"
 #include "llvm/Transforms/Scalar/SpeculativeExecution.h"
 #include "llvm/Transforms/Scalar/TailRecursionElimination.h"
+#include "llvm/Transforms/Scalar/WarnMissedTransforms.h"
 #include "llvm/Transforms/Utils/AddDiscriminators.h"
 #include "llvm/Transforms/Utils/BreakCriticalEdges.h"
 #include "llvm/Transforms/Utils/EntryExitInstrumenter.h"
 #include "llvm/Transforms/Utils/LCSSA.h"
 #include "llvm/Transforms/Utils/LibCallsShrinkWrap.h"
 #include "llvm/Transforms/Utils/LoopSimplify.h"
 #include "llvm/Transforms/Utils/LowerInvoke.h"
 #include "llvm/Transforms/Utils/Mem2Reg.h"
PassBuilder::buildModuleOptimizationPipeline(OptimizationLevel Level,
   // combiner for cleanup here so that the unrolling and LICM can be pipelined
   // across the loop nests.
   // We do UnrollAndJam in a separate LPM to ensure it happens before unroll
   if (EnableUnrollAndJam) {
     OptimizePM.addPass(
         createFunctionToLoopPassAdaptor(LoopUnrollAndJamPass(Level)));
   }
   OptimizePM.addPass(LoopUnrollPass(LoopUnrollOptions(Level)));
+  OptimizePM.addPass(WarnMissedTransformationsPass());
   OptimizePM.addPass(InstCombinePass());
   OptimizePM.addPass(RequireAnalysisPass<OptimizationRemarkEmitterAnalysis, Function>());
   OptimizePM.addPass(createFunctionToLoopPassAdaptor(LICMPass(), DebugLogging));
 
   // Now that we've vectorized and unrolled loops, we may have more refined
   // alignment information, try to re-derive it here.
   OptimizePM.addPass(AlignmentFromAssumptionsPass());
 

lib/Passes/PassRegistry.def

 FUNCTION_PASS("unroll<peeling;no-runtime>",LoopUnrollPass(LoopUnrollOptions().setPeeling(true).setRuntime(false)))
 FUNCTION_PASS("verify", VerifierPass())
 FUNCTION_PASS("verify<domtree>", DominatorTreeVerifierPass())
 FUNCTION_PASS("verify<loops>", LoopVerifierPass())
 FUNCTION_PASS("verify<memoryssa>", MemorySSAVerifierPass())
 FUNCTION_PASS("verify<regions>", RegionInfoVerifierPass())
 FUNCTION_PASS("view-cfg", CFGViewerPass())
 FUNCTION_PASS("view-cfg-only", CFGOnlyViewerPass())
+FUNCTION_PASS("transform-warning", WarnMissedTransformationsPass())
 #undef FUNCTION_PASS
 
 #ifndef LOOP_ANALYSIS
 #define LOOP_ANALYSIS(NAME, CREATE_PASS)
 #endif
 LOOP_ANALYSIS("no-op-loop", NoOpLoopAnalysis())
 LOOP_ANALYSIS("access-info", LoopAccessAnalysis())
 LOOP_ANALYSIS("ivusers", IVUsersAnalysis())

lib/Transforms/IPO/PassManagerBuilder.cpp

if (!DisableUnrollLoops) {
 
     // Runtime unrolling will introduce runtime check in loop prologue. If the
     // unrolled loop is a inner loop, then the prologue will be inside the
     // outer loop. LICM pass can help to promote the runtime check out if the
     // checked value is loop invariant.
     MPM.add(createLICMPass());
  }
 
+  MPM.add(createWarnMissedTransformationsPass());
+
   // After vectorization and unrolling, assume intrinsics may tell us more
   // about pointer alignments.
   MPM.add(createAlignmentFromAssumptionsPass());
 
   // FIXME: We shouldn't bother with this anymore.
   MPM.add(createStripDeadPrototypesPass()); // Get rid of dead prototypes
 
   // GlobalOpt already deletes dead functions and globals, at -O2 try a
void PassManagerBuilder::addLTOOptimizationPasses(legacy::PassManagerBase &PM) {
 
   if (!DisableUnrollLoops)
     PM.add(createSimpleLoopUnrollPass(OptLevel));   // Unroll small loops
   PM.add(createLoopVectorizePass(true, LoopVectorize));
   // The vectorizer may have significantly shortened a loop body; unroll again.
   if (!DisableUnrollLoops)
     PM.add(createLoopUnrollPass(OptLevel));
 
+  PM.add(createWarnMissedTransformationsPass());
+
   // Now that we've optimized loops (in particular loop induction variables),
   // we may have exposed more scalar opportunities. Run parts of the scalar
   // optimizer again at this point.
   addInstructionCombiningPass(PM); // Initial cleanup
   PM.add(createCFGSimplificationPass()); // if-convert
   PM.add(createSCCPPass()); // Propagate exposed constants
   addInstructionCombiningPass(PM); // Clean up again
   PM.add(createBitTrackingDCEPass());

lib/Transforms/Scalar/CMakeLists.txt

add_llvm_library(LLVMScalarOpts
   SimpleLoopUnswitch.cpp
   SimplifyCFGPass.cpp
   Sink.cpp
   SpeculativeExecution.cpp
   SpeculateAroundPHIs.cpp
   StraightLineStrengthReduce.cpp
   StructurizeCFG.cpp
   TailRecursionElimination.cpp
+  WarnMissedTransforms.cpp
 
   ADDITIONAL_HEADER_DIRS
   ${LLVM_MAIN_INCLUDE_DIR}/llvm/Transforms
   ${LLVM_MAIN_INCLUDE_DIR}/llvm/Transforms/Scalar
 
   DEPENDS
   intrinsics_gen
   )

lib/Transforms/Scalar/LoopDistribute.cpp

 #include <tuple>
 #include <utility>
 
 using namespace llvm;
 
 #define LDIST_NAME "loop-distribute"
 #define DEBUG_TYPE LDIST_NAME
 
+/// @{
+/// Metadata attribute names
+static const char *const LLVMLoopDistributeFollowupAll =
+    "llvm.loop.distribute.followup_all";
+static const char *const LLVMLoopDistributeFollowupCoincident =
+    "llvm.loop.distribute.followup_coincident";
+static const char *const LLVMLoopDistributeFollowupSequential =
+    "llvm.loop.distribute.followup_sequential";
+static const char *const LLVMLoopDistributeFollowupFallback =
+    "llvm.loop.distribute.followup_fallback";
+/// @}
+
 static cl::opt<bool>
     LDistVerify("loop-distribute-verify", cl::Hidden,
                 cl::desc("Turn on DominatorTree and LoopInfo verification "
                          "after Loop Distribution"),
                 cl::init(false));
 
 static cl::opt<bool> DistributeNonIfConvertible(
     "loop-distribute-non-if-convertible", cl::Hidden,
public:
 
   /// The cloned loop.  If this partition is mapped to the original loop,
   /// this is null.
   const Loop *getClonedLoop() const { return ClonedLoop; }
 
   /// Returns the loop where this partition ends up after distribution.
   /// If this partition is mapped to the original loop then use the block from
   /// the loop.
-  const Loop *getDistributedLoop() const {
+  Loop *getDistributedLoop() const {
     return ClonedLoop ? ClonedLoop : OrigLoop;
   }
 
   /// The VMap that is populated by cloning and then used in
   /// remapinstruction to remap the cloned instructions.
   ValueToValueMapTy &getVMap() { return VMap; }
 
   /// Remaps the cloned instructions using VMap.
void cloneLoops() {
     Loop *NewLoop;
 
     assert(!PartitionContainer.empty() && "at least two partitions expected");
     // We're cloning the preheader along with the loop so we already made sure
     // it was empty.
     assert(&*OrigPH->begin() == OrigPH->getTerminator() &&
            "preheader not empty");
 
+    // Preserve the original loop ID for use after the transformation.
+    MDNode *OrigLoopID = L->getLoopID();
+
     // Create a loop for each partition except the last.  Clone the original
     // loop before PH along with adding a preheader for the cloned loop.  Then
     // update PH to point to the newly added preheader.
     BasicBlock *TopPH = OrigPH;
     unsigned Index = getSize() - 1;
     for (auto I = std::next(PartitionContainer.rbegin()),
               E = PartitionContainer.rend();
          I != E; ++I, --Index, TopPH = NewLoop->getLoopPreheader()) {
       auto *Part = &*I;
 
       NewLoop = Part->cloneLoopWithPreheader(TopPH, Pred, Index, LI, DT);
 
       Part->getVMap()[ExitBlock] = TopPH;
       Part->remapInstructions();
+      setNewLoopID(OrigLoopID, Part);
     }
     Pred->getTerminator()->replaceUsesOfWith(OrigPH, TopPH);
 
+    // Also set a new loop ID for the last loop.
+    setNewLoopID(OrigLoopID, &PartitionContainer.back());
+
     // Now go in forward order and update the immediate dominator for the
     // preheaders with the exiting block of the previous loop.  Dominance
     // within the loop is updated in cloneLoopWithPreheader.
     for (auto Curr = PartitionContainer.cbegin(),
               Next = std::next(PartitionContainer.cbegin()),
               E = PartitionContainer.cend();
          Next != E; ++Curr, ++Next)
       DT->changeImmediateDominator(
for (auto I = PartitionContainer.begin(); I != PartitionContainer.end();) {
         I->moveTo(*PrevMatch);
         I = PartitionContainer.erase(I);
       } else {
         PrevMatch = nullptr;
         ++I;
       }
     }
   }
+
+  /// Assign new LoopIDs for the partition's cloned loop.
+  void setNewLoopID(MDNode *OrigLoopID, InstPartition *Part) {
+    Optional<MDNode *> PartitionID = makeFollowupLoopID(
+        OrigLoopID,
+        {LLVMLoopDistributeFollowupAll,
+         Part->hasDepCycle() ? LLVMLoopDistributeFollowupSequential
+                             : LLVMLoopDistributeFollowupCoincident});
+    if (PartitionID.hasValue()) {
+      Loop *NewLoop = Part->getDistributedLoop();
+      NewLoop->setLoopID(PartitionID.getValue());
+    }
+  }
 };
 
 /// For each memory instruction, this class maintains difference of the
 /// number of unsafe dependences that start out from this instruction minus
 /// those that end here.
 ///
 /// By traversing the memory instructions in program order and accumulating this
 /// number, we know whether any unsafe dependence crosses over a program point.
bool processLoop(std::function<const LoopAccessInfo &(Loop &)> &GetLAA) {
     // Don't distribute the loop if we need too many SCEV run-time checks.
     const SCEVUnionPredicate &Pred = LAI->getPSE().getUnionPredicate();
     if (Pred.getComplexity() > (IsForced.getValueOr(false)
                                     ? PragmaDistributeSCEVCheckThreshold
                                     : DistributeSCEVCheckThreshold))
       return fail("TooManySCEVRuntimeChecks",
                   "too many SCEV run-time checks needed.\n");
 
+    if (!IsForced.getValueOr(false) && hasDisableAllTransformsHint(L))
+      return fail("HeuristicDisabled", "distribution heuristic disabled");
+
     LLVM_DEBUG(dbgs() << "\nDistributing loop: " << *L << "\n");
     // We're done forming the partitions set up the reverse mapping from
     // instructions to partitions.
     Partitions.setupPartitionIdOnInstructions();
 
     // To keep things simple have an empty preheader before we version or clone
     // the loop.  (Also split if this has no predecessor, i.e. entry, because we
     // rely on PH having a predecessor.)
     if (!PH->getSinglePredecessor() || &*PH->begin() != PH->getTerminator())
       SplitBlock(PH, PH->getTerminator(), DT, LI);
 
     // If we need run-time checks, version the loop now.
     auto PtrToPartition = Partitions.computePartitionSetForPointers(*LAI);
     const auto *RtPtrChecking = LAI->getRuntimePointerChecking();
     const auto &AllChecks = RtPtrChecking->getChecks();
     auto Checks = includeOnlyCrossPartitionChecks(AllChecks, PtrToPartition,
                                                   RtPtrChecking);
 
     if (!Pred.isAlwaysTrue() || !Checks.empty()) {
+      MDNode *OrigLoopID = L->getLoopID();
+
       LLVM_DEBUG(dbgs() << "\nPointers:\n");
       LLVM_DEBUG(LAI->getRuntimePointerChecking()->printChecks(dbgs(), Checks));
       LoopVersioning LVer(*LAI, L, LI, DT, SE, false);
       LVer.setAliasChecks(std::move(Checks));
       LVer.setSCEVChecks(LAI->getPSE().getUnionPredicate());
       LVer.versionLoop(DefsUsedOutside);
       LVer.annotateLoopWithNoAlias();
+
+      // The unversioned loop will not be changed, so we inherit all attributes
+      // from the original loop, but remove the loop distribution metadata to
+      // avoid to distribute it again.
+      MDNode *UnversionedLoopID =
+          makeFollowupLoopID(OrigLoopID,
+                             {LLVMLoopDistributeFollowupAll,
+                              LLVMLoopDistributeFollowupFallback},
+                             "llvm.loop.distribute.", true)
+              .getValue();
+      LVer.getNonVersionedLoop()->setLoopID(UnversionedLoopID);
     }
 
     // Create identical copies of the original loop for each partition and hook
     // them up sequentially.
     Partitions.cloneLoops();
 
     // Now, we remove the instruction from each loop that don't belong to that
     // partition.

lib/Transforms/Scalar/LoopUnrollAndJamPass.cpp

 #include <cassert>
 #include <cstdint>
 #include <string>
 
 using namespace llvm;
 
 #define DEBUG_TYPE "loop-unroll-and-jam"
 
+/// @{
+/// Metadata attribute names
+static const char *const LLVMLoopUnrollAndJamFollowupAll =
+    "llvm.loop.unroll_and_jam.followup_all";
+static const char *const LLVMLoopUnrollAndJamFollowupInner =
+    "llvm.loop.unroll_and_jam.followup_inner";
+static const char *const LLVMLoopUnrollAndJamFollowupOuter =
+    "llvm.loop.unroll_and_jam.followup_outer";
+static const char *const LLVMLoopUnrollAndJamFollowupRemainderInner =
+    "llvm.loop.unroll_and_jam.followup_remainder_inner";
+static const char *const LLVMLoopUnrollAndJamFollowupRemainderOuter =
+    "llvm.loop.unroll_and_jam.followup_remainder_outer";
+/// @}
+
 static cl::opt<bool>
     AllowUnrollAndJam("allow-unroll-and-jam", cl::Hidden,
                       cl::desc("Allows loops to be unroll-and-jammed."));
 
 static cl::opt<unsigned> UnrollAndJamCount(
     "unroll-and-jam-count", cl::Hidden,
     cl::desc("Use this unroll count for all loops including those with "
              "unroll_and_jam_count pragma values, for testing purposes"));
static bool HasAnyUnrollPragma(const Loop *L, StringRef Prefix) {
   return false;
 }
 
 // Returns true if the loop has an unroll_and_jam(enable) pragma.
 static bool HasUnrollAndJamEnablePragma(const Loop *L) {
   return GetUnrollMetadataForLoop(L, "llvm.loop.unroll_and_jam.enable");
 }
 
-// Returns true if the loop has an unroll_and_jam(disable) pragma.
-static bool HasUnrollAndJamDisablePragma(const Loop *L) {
-  return GetUnrollMetadataForLoop(L, "llvm.loop.unroll_and_jam.disable");
-}
-
 // If loop has an unroll_and_jam_count pragma return the (necessarily
 // positive) value from the pragma.  Otherwise return 0.
 static unsigned UnrollAndJamCountPragmaValue(const Loop *L) {
   MDNode *MD = GetUnrollMetadataForLoop(L, "llvm.loop.unroll_and_jam.count");
   if (MD) {
     assert(MD->getNumOperands() == 2 &&
            "Unroll count hint metadata should have two operands.");
     unsigned Count =
if (PragmaCount > 0) {
     UP.Force = true;
     if ((UP.AllowRemainder || (OuterTripMultiple % PragmaCount == 0)) &&
         getUnrollAndJammedLoopSize(OuterLoopSize, UP) < UP.Threshold &&
         getUnrollAndJammedLoopSize(InnerLoopSize, UP) <
             UP.UnrollAndJamInnerLoopThreshold)
       return true;
   }
 
   bool PragmaEnableUnroll = HasUnrollAndJamEnablePragma(L);
   bool ExplicitUnrollAndJamCount = PragmaCount > 0 || UserUnrollCount;
   bool ExplicitUnrollAndJam = PragmaEnableUnroll || ExplicitUnrollAndJamCount;
 
   // If the loop has an unrolling pragma, we want to be more aggressive with
   // unrolling limits.
   if (ExplicitUnrollAndJam)
     UP.UnrollAndJamInnerLoopThreshold = PragmaUnrollAndJamThreshold;
 
   if (!UP.AllowRemainder && getUnrollAndJammedLoopSize(InnerLoopSize, UP) >=
tryToUnrollAndJamLoop(Loop *L, DominatorTree &DT, LoopInfo *LI,
   // Exit early if unrolling is disabled.
   if (!UP.UnrollAndJam || UP.UnrollAndJamInnerLoopThreshold == 0)
     return LoopUnrollResult::Unmodified;
 
   LLVM_DEBUG(dbgs() << "Loop Unroll and Jam: F["
                     << L->getHeader()->getParent()->getName() << "] Loop %"
                     << L->getHeader()->getName() << "\n");
 
+  TransformationMode EnableMode = hasUnrollAndJamTransformation(L);
+  if (EnableMode & TM_Disable)
+    return LoopUnrollResult::Unmodified;
+
   // A loop with any unroll pragma (enabling/disabling/count/etc) is left for
   // the unroller, so long as it does not explicitly have unroll_and_jam
   // metadata. This means #pragma nounroll will disable unroll and jam as well
   // as unrolling
-  if (HasUnrollAndJamDisablePragma(L) ||
-      (HasAnyUnrollPragma(L, "llvm.loop.unroll.") &&
-       !HasAnyUnrollPragma(L, "llvm.loop.unroll_and_jam."))) {
+  if (HasAnyUnrollPragma(L, "llvm.loop.unroll.") &&
+      !HasAnyUnrollPragma(L, "llvm.loop.unroll_and_jam.")) {
     LLVM_DEBUG(dbgs() << "  Disabled due to pragma.\n");
     return LoopUnrollResult::Unmodified;
   }
 
   if (!isSafeToUnrollAndJam(L, SE, DT, DI)) {
     LLVM_DEBUG(dbgs() << "  Disabled due to not being safe.\n");
     return LoopUnrollResult::Unmodified;
   }
if (NumInlineCandidates != 0) {
     return LoopUnrollResult::Unmodified;
   }
   if (Convergent) {
     LLVM_DEBUG(
         dbgs() << "  Not unrolling loop with convergent instructions.\n");
     return LoopUnrollResult::Unmodified;
   }
 
+  // Save original loop IDs for after the transformation.
+  MDNode *OrigOuterLoopID = L->getLoopID();
+  MDNode *OrigSubLoopID = SubLoop->getLoopID();
+
+  // To assign the loop id of the epilogue, assign it before unrolling it so it
+  // is applied to every inner loop of the epilogue. We later apply the loop ID
+  // for the jammed inner loop.
+  Optional<MDNode *> NewInnerEpilogueLoopID = makeFollowupLoopID(
+      OrigOuterLoopID, {LLVMLoopUnrollAndJamFollowupAll,
+                        LLVMLoopUnrollAndJamFollowupRemainderInner});
+  if (NewInnerEpilogueLoopID.hasValue())
+    SubLoop->setLoopID(NewInnerEpilogueLoopID.getValue());
+
   // Find trip count and trip multiple
   unsigned OuterTripCount = SE.getSmallConstantTripCount(L, Latch);
   unsigned OuterTripMultiple = SE.getSmallConstantTripMultiple(L, Latch);
   unsigned InnerTripCount = SE.getSmallConstantTripCount(SubLoop, SubLoopLatch);
 
   // Decide if, and by how much, to unroll
   bool IsCountSetExplicitly = computeUnrollAndJamCount(
       L, SubLoop, TTI, DT, LI, SE, EphValues, &ORE, OuterTripCount,
       OuterTripMultiple, OuterLoopSize, InnerTripCount, InnerLoopSize, UP);
   if (UP.Count <= 1)
     return LoopUnrollResult::Unmodified;
   // Unroll factor (Count) must be less or equal to TripCount.
   if (OuterTripCount && UP.Count > OuterTripCount)
     UP.Count = OuterTripCount;
 
-  LoopUnrollResult UnrollResult =
-      UnrollAndJamLoop(L, UP.Count, OuterTripCount, OuterTripMultiple,
-                       UP.UnrollRemainder, LI, &SE, &DT, &AC, &ORE);
+  Loop *EpilogueOuterLoop = nullptr;
+  LoopUnrollResult UnrollResult = UnrollAndJamLoop(
+      L, UP.Count, OuterTripCount, OuterTripMultiple, UP.UnrollRemainder, LI,
+      &SE, &DT, &AC, &ORE, &EpilogueOuterLoop);
+
+  // Assign new loop attributes.
+  if (EpilogueOuterLoop) {
+    Optional<MDNode *> NewOuterEpilogueLoopID = makeFollowupLoopID(
+        OrigOuterLoopID, {LLVMLoopUnrollAndJamFollowupAll,
+                          LLVMLoopUnrollAndJamFollowupRemainderOuter});
+    if (NewOuterEpilogueLoopID.hasValue())
+      EpilogueOuterLoop->setLoopID(NewOuterEpilogueLoopID.getValue());
+  }
+
+  Optional<MDNode *> NewInnerLoopID =
+      makeFollowupLoopID(OrigOuterLoopID, {LLVMLoopUnrollAndJamFollowupAll,
+                                           LLVMLoopUnrollAndJamFollowupInner});
+  if (NewInnerLoopID.hasValue())
+    SubLoop->setLoopID(NewInnerLoopID.getValue());
+  else
+    SubLoop->setLoopID(OrigSubLoopID);
+
+  if (UnrollResult == LoopUnrollResult::PartiallyUnrolled) {
+    Optional<MDNode *> NewOuterLoopID = makeFollowupLoopID(
+        OrigOuterLoopID,
+        {LLVMLoopUnrollAndJamFollowupAll, LLVMLoopUnrollAndJamFollowupOuter});
+    if (NewOuterLoopID.hasValue()) {
+      L->setLoopID(NewOuterLoopID.getValue());
+
+      // Do not setLoopAlreadyUnrolled if a followup was given.
+      return UnrollResult;
+    }
+  }
 
   // If loop has an unroll count pragma or unrolled by explicitly set count
   // mark loop as unrolled to prevent unrolling beyond that requested.
   if (UnrollResult != LoopUnrollResult::FullyUnrolled && IsCountSetExplicitly)
     L->setLoopAlreadyUnrolled();
 
   return UnrollResult;
 }

lib/Transforms/Scalar/LoopUnrollPass.cpp

 }
 
 // Returns true if the loop has an unroll(enable) pragma. This metadata is used
 // for both "#pragma unroll" and "#pragma clang loop unroll(enable)" directives.
 static bool HasUnrollEnablePragma(const Loop *L) {
   return GetUnrollMetadataForLoop(L, "llvm.loop.unroll.enable");
 }
 
-// Returns true if the loop has an unroll(disable) pragma.
-static bool HasUnrollDisablePragma(const Loop *L) {
-  return GetUnrollMetadataForLoop(L, "llvm.loop.unroll.disable");
-}
-
 // Returns true if the loop has an runtime unroll(disable) pragma.
 static bool HasRuntimeUnrollDisablePragma(const Loop *L) {
   return GetUnrollMetadataForLoop(L, "llvm.loop.unroll.runtime.disable");
 }
 
 // If loop has an unroll_count pragma return the (necessarily
 // positive) value from the pragma.  Otherwise return 0.
 static unsigned UnrollCountPragmaValue(const Loop *L) {
static uint64_t getUnrolledLoopSize(
     unsigned LoopSize,
     TargetTransformInfo::UnrollingPreferences &UP) {
   assert(LoopSize >= UP.BEInsns && "LoopSize should not be less than BEInsns!");
   return (uint64_t)(LoopSize - UP.BEInsns) * UP.Count + UP.BEInsns;
 }
 
 // Returns true if unroll count was set explicitly.
 // Calculates unroll count and writes it to UP.Count.
+// Unless IgnoreUser is true, will also use metadata and command-line options
+// that are specific to to the LoopUnroll pass (which, for instance, are
+// irrelevant for the LoopUnrollAndJam pass).
+// FIXME: This function is used by LoopUnroll and LoopUnrollAndJam, but consumes
+// many LoopUnroll-specific options. The shared functionality should be
+// refactored into it own function.
 bool llvm::computeUnrollCount(
     Loop *L, const TargetTransformInfo &TTI, DominatorTree &DT, LoopInfo *LI,
     ScalarEvolution &SE, const SmallPtrSetImpl<const Value *> &EphValues,
     OptimizationRemarkEmitter *ORE, unsigned &TripCount, unsigned MaxTripCount,
     unsigned &TripMultiple, unsigned LoopSize,
     TargetTransformInfo::UnrollingPreferences &UP, bool &UseUpperBound) {
+
   // Check for explicit Count.
   // 1st priority is unroll count set by "unroll-count" option.
   bool UserUnrollCount = UnrollCount.getNumOccurrences() > 0;
   if (UserUnrollCount) {
     UP.Count = UnrollCount;
     UP.AllowExpensiveTripCount = true;
     UP.Force = true;
     if (UP.AllowRemainder && getUnrolledLoopSize(LoopSize, UP) < UP.Threshold)
bool llvm::computeUnrollCount(
   }
   bool PragmaFullUnroll = HasUnrollFullPragma(L);
   if (PragmaFullUnroll && TripCount != 0) {
     UP.Count = TripCount;
     if (getUnrolledLoopSize(LoopSize, UP) < PragmaUnrollThreshold)
       return false;
   }
 
   bool PragmaEnableUnroll = HasUnrollEnablePragma(L);
   bool ExplicitUnroll = PragmaCount > 0 || PragmaFullUnroll ||
                         PragmaEnableUnroll || UserUnrollCount;
 
   if (ExplicitUnroll && TripCount != 0) {
     // If the loop has an unrolling pragma, we want to be more aggressive with
     // unrolling limits. Set thresholds to at least the PragmaUnrollThreshold
     // value which is larger than the default limits.
     UP.Threshold = std::max<unsigned>(UP.Threshold, PragmaUnrollThreshold);
     UP.PartialThreshold =
         std::max<unsigned>(UP.PartialThreshold, PragmaUnrollThreshold);
static LoopUnrollResult tryToUnrollLoop(
     const TargetTransformInfo &TTI, AssumptionCache &AC,
     OptimizationRemarkEmitter &ORE, bool PreserveLCSSA, int OptLevel,
     Optional<unsigned> ProvidedCount, Optional<unsigned> ProvidedThreshold,
     Optional<bool> ProvidedAllowPartial, Optional<bool> ProvidedRuntime,
     Optional<bool> ProvidedUpperBound, Optional<bool> ProvidedAllowPeeling) {
   LLVM_DEBUG(dbgs() << "Loop Unroll: F["
                     << L->getHeader()->getParent()->getName() << "] Loop %"
                     << L->getHeader()->getName() << "\n");
-  if (HasUnrollDisablePragma(L))
+  if (hasUnrollTransformation(L) & TM_Disable)
     return LoopUnrollResult::Unmodified;
   if (!L->isLoopSimplifyForm()) {
     LLVM_DEBUG(
         dbgs() << "  Not unrolling loop which is not in loop-simplify form.\n");
     return LoopUnrollResult::Unmodified;
   }
 
   unsigned NumInlineCandidates;
bool IsCountSetExplicitly = computeUnrollCount(
       L, TTI, DT, LI, SE, EphValues, &ORE, TripCount, MaxTripCount,
       TripMultiple, LoopSize, UP, UseUpperBound);
   if (!UP.Count)
     return LoopUnrollResult::Unmodified;
   // Unroll factor (Count) must be less or equal to TripCount.
   if (TripCount && UP.Count > TripCount)
     UP.Count = TripCount;
 
+  // Save loop properties before it is transformed.
+  MDNode *OrigLoopID = L->getLoopID();
+
   // Unroll the loop.
+  Loop *RemainderLoop = nullptr;
   LoopUnrollResult UnrollResult = UnrollLoop(
       L, UP.Count, TripCount, UP.Force, UP.Runtime, UP.AllowExpensiveTripCount,
       UseUpperBound, MaxOrZero, TripMultiple, UP.PeelCount, UP.UnrollRemainder,
-      LI, &SE, &DT, &AC, &ORE, PreserveLCSSA);
+      LI, &SE, &DT, &AC, &ORE, PreserveLCSSA, &RemainderLoop);
   if (UnrollResult == LoopUnrollResult::Unmodified)
     return LoopUnrollResult::Unmodified;
 
+  if (RemainderLoop) {
+    Optional<MDNode *> RemainderLoopID =
+        makeFollowupLoopID(OrigLoopID, {LLVMLoopUnrollFollowupAll,
+                                        LLVMLoopUnrollFollowupRemainder});
+    if (RemainderLoopID.hasValue())
+      RemainderLoop->setLoopID(RemainderLoopID.getValue());
+  }
+
+  if (UnrollResult != LoopUnrollResult::FullyUnrolled) {
+    Optional<MDNode *> NewLoopID =
+        makeFollowupLoopID(OrigLoopID, {LLVMLoopUnrollFollowupAll,
+                                        LLVMLoopUnrollFollowupUnrolled});
+    if (NewLoopID.hasValue()) {
+      L->setLoopID(NewLoopID.getValue());
+
+      // Do not setLoopAlreadyUnrolled if loop attributes have been specified
+      // explicitly.
+      return UnrollResult;
+    }
+  }
+
   // If loop has an unroll count pragma or unrolled by explicitly set count
   // mark loop as unrolled to prevent unrolling beyond that requested.
   // If the loop was peeled, we already "used up" the profile information
   // we had, so we don't want to unroll or peel again.
   if (UnrollResult != LoopUnrollResult::FullyUnrolled &&
       (IsCountSetExplicitly || UP.PeelCount))
     L->setLoopAlreadyUnrolled();
 

lib/Transforms/Scalar/LoopVersioningLICM.cpp

 
 bool LoopVersioningLICM::runOnLoop(Loop *L, LPPassManager &LPM) {
   // This will automatically release all resources hold by the current
   // LoopVersioningLICM object.
   AutoResetter Resetter(*this);
 
   if (skipLoop(L))
     return false;
+
+  // Do not do the transformation if disabled by metadata.
+  if (hasLICMVersioningTransformation(L) & TM_Disable)
+    return false;
+
   // Get Analysis information.
   AA = &getAnalysis<AAResultsWrapperPass>().getAAResults();
   SE = &getAnalysis<ScalarEvolutionWrapperPass>().getSE();
   LAA = &getAnalysis<LoopAccessLegacyAnalysis>();
   ORE = &getAnalysis<OptimizationRemarkEmitterWrapperPass>().getORE();
   LAI = nullptr;
   // Set Current Loop
   CurLoop = L;

lib/Transforms/Scalar/Scalar.cpp

void llvm::initializeScalarOpts(PassRegistry &Registry) {
   initializeLoopInterchangePass(Registry);
   initializeLoopPredicationLegacyPassPass(Registry);
   initializeLoopRotateLegacyPassPass(Registry);
   initializeLoopStrengthReducePass(Registry);
   initializeLoopRerollPass(Registry);
   initializeLoopUnrollPass(Registry);
   initializeLoopUnrollAndJamPass(Registry);
   initializeLoopUnswitchPass(Registry);
+  initializeWarnMissedTransformationsLegacyPass(Registry);
   initializeLoopVersioningLICMPass(Registry);
   initializeLoopIdiomRecognizeLegacyPassPass(Registry);
   initializeLowerAtomicLegacyPassPass(Registry);
   initializeLowerExpectIntrinsicPass(Registry);
   initializeLowerGuardIntrinsicLegacyPassPass(Registry);
   initializeMemCpyOptLegacyPassPass(Registry);
   initializeMergeICmpsPass(Registry);
   initializeMergedLoadStoreMotionLegacyPassPass(Registry);

lib/Transforms/Scalar/WarnMissedTransforms.cpp

+//===- LoopTransformWarning.cpp -  ----------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// Emit warnings if forced code transformations have not been performed.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Transforms/Scalar/WarnMissedTransforms.h"
+#include "llvm/Analysis/OptimizationRemarkEmitter.h"
+#include "llvm/Transforms/Utils/LoopUtils.h"
+
+using namespace llvm;
+
+#define DEBUG_TYPE "transform-warning"
+
+/// Emit warnings for forced (i.e. user-defined) loop transformations which have
+/// still not been performed.
+static void warnAboutLeftoverTransformations(Loop *L,
+                                             OptimizationRemarkEmitter *ORE) {
+  if (hasUnrollTransformation(L) == TM_ForcedByUser) {
+    LLVM_DEBUG(dbgs() << "Leftover unroll transformation\n");
+    ORE->emit(
+        DiagnosticInfoOptimizationFailure(DEBUG_TYPE,
+                                          "FailedRequestedUnrolling",
+                                          L->getStartLoc(), L->getHeader())
+        << "loop not unrolled: the optimizer was unable to perform the "
+           "requested transformation; the transformation might be disabled or "
+           "specified as part of an unsupported transformation ordering");
+  }
+
+  if (hasUnrollAndJamTransformation(L) == TM_ForcedByUser) {
+    LLVM_DEBUG(dbgs() << "Leftover unroll-and-jam transformation\n");
+    ORE->emit(
+        DiagnosticInfoOptimizationFailure(DEBUG_TYPE,
+                                          "FailedRequestedUnrollAndJamming",
+                                          L->getStartLoc(), L->getHeader())
+        << "loop not unroll-and-jammed: the optimizer was unable to perform "
+           "the requested transformation; the transformation might be disabled "
+           "or specified as part of an unsupported transformation ordering");
+  }
+
+  if (hasVectorizeTransformation(L) == TM_ForcedByUser) {
+    LLVM_DEBUG(dbgs() << "Leftover vectorization transformation\n");
+    Optional<int> VectorizeWidth =
+        getOptionalIntLoopAttribute(L, "llvm.loop.vectorize.width");
+    Optional<int> InterleaveCount =
+        getOptionalIntLoopAttribute(L, "llvm.loop.interleave.count");
+
+    if (VectorizeWidth.getValueOr(0) != 1)
+      ORE->emit(
+          DiagnosticInfoOptimizationFailure(DEBUG_TYPE,
+                                            "FailedRequestedVectorization",
+                                            L->getStartLoc(), L->getHeader())
+          << "loop not vectorized: the optimizer was unable to perform the "
+             "requested transformation; the transformation might be disabled "
+             "or specified as part of an unsupported transformation ordering");
+    else if (InterleaveCount.getValueOr(0) != 1)
+      ORE->emit(
+          DiagnosticInfoOptimizationFailure(DEBUG_TYPE,
+                                            "FailedRequestedInterleaving",
+                                            L->getStartLoc(), L->getHeader())
+          << "loop not interleaved: the optimizer was unable to perform the "
+             "requested transformation; the transformation might be disabled "
+             "or specified as part of an unsupported transformation ordering");
+  }
+
+  if (hasDistributeTransformation(L) == TM_ForcedByUser) {
+    LLVM_DEBUG(dbgs() << "Leftover distribute transformation\n");
+    ORE->emit(
+        DiagnosticInfoOptimizationFailure(DEBUG_TYPE,
+                                          "FailedRequestedDistribution",
+                                          L->getStartLoc(), L->getHeader())
+        << "loop not distributed: the optimizer was unable to perform the "
+           "requested transformation; the transformation might be disabled or "
+           "specified as part of an unsupported transformation ordering");
+  }
+}
+
+static void warnAboutLeftoverTransformations(Function *F, LoopInfo *LI,
+                                             OptimizationRemarkEmitter *ORE) {
+  for (auto *L : LI->getLoopsInPreorder())
+    warnAboutLeftoverTransformations(L, ORE);
+}
+
+// New pass manager boilerplate
+PreservedAnalyses
+WarnMissedTransformationsPass::run(Function &F, FunctionAnalysisManager &AM) {
+  auto &ORE = AM.getResult<OptimizationRemarkEmitterAnalysis>(F);
+  auto &LI = AM.getResult<LoopAnalysis>(F);
+
+  warnAboutLeftoverTransformations(&F, &LI, &ORE);
+
+  return PreservedAnalyses::all();
+}
+
+// Legacy pass manager boilerplate
+namespace {
+class WarnMissedTransformationsLegacy : public FunctionPass {
+public:
+  static char ID;
+
+  explicit WarnMissedTransformationsLegacy() : FunctionPass(ID) {
+    initializeWarnMissedTransformationsLegacyPass(
+        *PassRegistry::getPassRegistry());
+  }
+
+  bool runOnFunction(Function &F) override {
+    if (skipFunction(F))
+      return false;
+
+    auto &ORE = getAnalysis<OptimizationRemarkEmitterWrapperPass>().getORE();
+    auto &LI = getAnalysis<LoopInfoWrapperPass>().getLoopInfo();
+
+    warnAboutLeftoverTransformations(&F, &LI, &ORE);
+    return false;
+  }
+
+  void getAnalysisUsage(AnalysisUsage &AU) const override {
+    AU.addRequired<OptimizationRemarkEmitterWrapperPass>();
+    AU.addRequired<LoopInfoWrapperPass>();
+
+    AU.setPreservesAll();
+  }
+};
+} // end anonymous namespace
+
+char WarnMissedTransformationsLegacy::ID = 0;
+
+INITIALIZE_PASS_BEGIN(WarnMissedTransformationsLegacy, "transform-warning",
+                      "Warn about non-applied transformations", false, false)
+INITIALIZE_PASS_DEPENDENCY(LoopInfoWrapperPass)
+INITIALIZE_PASS_DEPENDENCY(OptimizationRemarkEmitterWrapperPass)
+INITIALIZE_PASS_END(WarnMissedTransformationsLegacy, "transform-warning",
+                    "Warn about non-applied transformations", false, false)
+
+Pass *llvm::createWarnMissedTransformationsPass() {
+  return new WarnMissedTransformationsLegacy();
+}

lib/Transforms/Utils/LoopUnroll.cpp

 ///
 /// If we want to perform PGO-based loop peeling, PeelCount is set to the
 /// number of iterations we want to peel off.
 ///
 /// The LoopInfo Analysis that is passed will be kept consistent.
 ///
 /// This utility preserves LoopInfo. It will also preserve ScalarEvolution and
 /// DominatorTree if they are non-null.
+///
+/// If RemainderLoop is non-null, it will receive the remainder loop (if
+/// required and not fully unrolled).
 LoopUnrollResult llvm::UnrollLoop(
     Loop *L, unsigned Count, unsigned TripCount, bool Force, bool AllowRuntime,
     bool AllowExpensiveTripCount, bool PreserveCondBr, bool PreserveOnlyFirst,
     unsigned TripMultiple, unsigned PeelCount, bool UnrollRemainder,
     LoopInfo *LI, ScalarEvolution *SE, DominatorTree *DT, AssumptionCache *AC,
-    OptimizationRemarkEmitter *ORE, bool PreserveLCSSA) {
+    OptimizationRemarkEmitter *ORE, bool PreserveLCSSA, Loop **RemainderLoop) {
 
   BasicBlock *Preheader = L->getLoopPreheader();
   if (!Preheader) {
     LLVM_DEBUG(dbgs() << "  Can't unroll; loop preheader-insertion failed.\n");
     return LoopUnrollResult::Unmodified;
   }
 
   BasicBlock *LatchBlock = L->getLoopLatch();
LoopUnrollResult llvm::UnrollLoop(
 
   bool EpilogProfitability =
       UnrollRuntimeEpilog.getNumOccurrences() ? UnrollRuntimeEpilog
                                               : isEpilogProfitable(L);
 
   if (RuntimeTripCount && TripMultiple % Count != 0 &&
       !UnrollRuntimeLoopRemainder(L, Count, AllowExpensiveTripCount,
                                   EpilogProfitability, UnrollRemainder, LI, SE,
-                                  DT, AC, PreserveLCSSA)) {
+                                  DT, AC, PreserveLCSSA, RemainderLoop)) {
     if (Force)
       RuntimeTripCount = false;
     else {
       LLVM_DEBUG(dbgs() << "Won't unroll; remainder loop could not be "
                            "generated when assuming runtime trip count\n");
       return LoopUnrollResult::Unmodified;
     }
   }

lib/Transforms/Utils/LoopUnrollAndJam.cpp

/*
 
   We do this by spliting the blocks in the loop into Fore, Subloop and Aft.
   Fore blocks are those before the inner loop, Aft are those after. Normal
   Unroll code is used to copy each of these sets of blocks and the results are
   combined together into the final form above.
 
   isSafeToUnrollAndJam should be used prior to calling this to make sure the
   unrolling will be valid. Checking profitablility is also advisable.
+
+  If EpilogueLoop is non-null, it receives the epilogue loop (if it was
+  necessary to create one and not fully unrolled).
 */
-LoopUnrollResult
-llvm::UnrollAndJamLoop(Loop *L, unsigned Count, unsigned TripCount,
-                       unsigned TripMultiple, bool UnrollRemainder,
-                       LoopInfo *LI, ScalarEvolution *SE, DominatorTree *DT,
-                       AssumptionCache *AC, OptimizationRemarkEmitter *ORE) {
+LoopUnrollResult llvm::UnrollAndJamLoop(
+    Loop *L, unsigned Count, unsigned TripCount, unsigned TripMultiple,
+    bool UnrollRemainder, LoopInfo *LI, ScalarEvolution *SE, DominatorTree *DT,
+    AssumptionCache *AC, OptimizationRemarkEmitter *ORE, Loop **EpilogueLoop) {
 
   // When we enter here we should have already checked that it is safe
   BasicBlock *Header = L->getHeader();
   assert(L->getSubLoops().size() == 1);
   Loop *SubLoop = *L->begin();
 
   // Don't enter the unroll code if there is nothing to do.
   if (TripCount == 0 && Count < 2) {
     LLVM_DEBUG(dbgs() << "Won't unroll-and-jam; almost nothing to do\n");
     return LoopUnrollResult::Unmodified;
   }
 
   assert(Count > 0);
   assert(TripMultiple > 0);
   assert(TripCount == 0 || TripCount % TripMultiple == 0);
 
   // Are we eliminating the loop control altogether?
   bool CompletelyUnroll = (Count == TripCount);
 
   // We use the runtime remainder in cases where we don't know trip multiple
   if (TripMultiple == 1 || TripMultiple % Count != 0) {
     if (!UnrollRuntimeLoopRemainder(L, Count, /*AllowExpensiveTripCount*/ false,
                                     /*UseEpilogRemainder*/ true,
-                                    UnrollRemainder, LI, SE, DT, AC, true)) {
+                                    UnrollRemainder, LI, SE, DT, AC, true,
+                                    EpilogueLoop)) {
       LLVM_DEBUG(dbgs() << "Won't unroll-and-jam; remainder loop could not be "
                            "generated when assuming runtime trip count\n");
       return LoopUnrollResult::Unmodified;
     }
   }
 
   // Notify ScalarEvolution that the loop will be substantially changed,
   // if not outright eliminated.

lib/Transforms/Utils/LoopUnrollRuntime.cpp

if (!CreateRemainderLoop) {
       Value *InVal = NewPHI->getIncomingValue(idx);
       NewPHI->setIncomingBlock(idx, NewLatch);
       if (Value *V = VMap.lookup(InVal))
         NewPHI->setIncomingValue(idx, V);
     }
   }
   if (CreateRemainderLoop) {
     Loop *NewLoop = NewLoops[L];
+    MDNode *LoopID = NewLoop->getLoopID();
     assert(NewLoop && "L should have been cloned");
 
     // Only add loop metadata if the loop is not going to be completely
     // unrolled.
     if (UnrollRemainder)
       return NewLoop;
 
+    Optional<MDNode *> NewLoopID = makeFollowupLoopID(
+        LoopID, {LLVMLoopUnrollFollowupAll, LLVMLoopUnrollFollowupRemainder});
+    if (NewLoopID.hasValue()) {
+      NewLoop->setLoopID(NewLoopID.getValue());
+
+      // Do not setLoopAlreadyUnrolled if loop attributes have been defined
+      // explicitly.
+      return NewLoop;
+    }
+
     // Add unroll disable metadata to disable future unrolling for this loop.
     NewLoop->setLoopAlreadyUnrolled();
     return NewLoop;
   }
   else
     return nullptr;
 }
 

 /// Epil:  LoopBody; (executes extraiters times)
 ///        extraiters -= 1                 // Omitted if unroll factor is 2.
 ///        if (extraiters != 0) jump Epil: // Omitted if unroll factor is 2.
 /// EpilExit:
 
 bool llvm::UnrollRuntimeLoopRemainder(Loop *L, unsigned Count,
                                       bool AllowExpensiveTripCount,
                                       bool UseEpilogRemainder,
-                                      bool UnrollRemainder,
-                                      LoopInfo *LI, ScalarEvolution *SE,
-                                      DominatorTree *DT, AssumptionCache *AC,
-                                      bool PreserveLCSSA) {
+                                      bool UnrollRemainder, LoopInfo *LI,
+                                      ScalarEvolution *SE, DominatorTree *DT,
+                                      AssumptionCache *AC, bool PreserveLCSSA,
+                                      Loop **ResultLoop) {
   LLVM_DEBUG(dbgs() << "Trying runtime unrolling on Loop: \n");
   LLVM_DEBUG(L->dump());
   LLVM_DEBUG(UseEpilogRemainder ? dbgs() << "Using epilog remainder.\n"
                                 : dbgs() << "Using prolog remainder.\n");
 
   // Make sure the loop is in canonical form.
   if (!L->isLoopSimplifyForm()) {
     LLVM_DEBUG(dbgs() << "Not in simplify form!\n");
if (OtherExits.size() > 0) {
     // LoopSimplifyForm.
     formDedicatedExitBlocks(L, DT, LI, PreserveLCSSA);
     // Generate dedicated exit blocks for the remainder loop if one exists, to
     // preserve LoopSimplifyForm.
     if (remainderLoop)
       formDedicatedExitBlocks(remainderLoop, DT, LI, PreserveLCSSA);
   }
 
+  auto UnrollResult = LoopUnrollResult::Unmodified;
   if (remainderLoop && UnrollRemainder) {
     LLVM_DEBUG(dbgs() << "Unrolling remainder loop\n");
+    UnrollResult =
         UnrollLoop(remainderLoop, /*Count*/ Count - 1, /*TripCount*/ Count - 1,
                    /*Force*/ false, /*AllowRuntime*/ false,
                    /*AllowExpensiveTripCount*/ false, /*PreserveCondBr*/ true,
                    /*PreserveOnlyFirst*/ false, /*TripMultiple*/ 1,
                    /*PeelCount*/ 0, /*UnrollRemainder*/ false, LI, SE, DT, AC,
                    /*ORE*/ nullptr, PreserveLCSSA);
   }
 
+  if (ResultLoop && UnrollResult != LoopUnrollResult::FullyUnrolled)
+    *ResultLoop = remainderLoop;
   NumRuntimeUnrolled++;
   return true;
 }

lib/Transforms/Utils/LoopUtils.cpp

 #include "llvm/Support/KnownBits.h"
 #include "llvm/Transforms/Utils/BasicBlockUtils.h"
 
 using namespace llvm;
 using namespace llvm::PatternMatch;
 
 #define DEBUG_TYPE "loop-utils"
 
+static const char *LLVMLoopDisableNonforced = "llvm.loop.disable_nonforced";
+
 bool llvm::formDedicatedExitBlocks(Loop *L, DominatorTree *DT, LoopInfo *LI,
                                    bool PreserveLCSSA) {
   bool Changed = false;
 
   // We re-use a vector for the in-loop predecesosrs.
   SmallVector<BasicBlock *, 4> InLoopPredecessors;
 
   auto RewriteExit = [&](BasicBlock *BB) {
void llvm::initializeLoopPassPass(PassRegistry &Registry) {
   INITIALIZE_PASS_DEPENDENCY(LCSSAWrapperPass)
   INITIALIZE_PASS_DEPENDENCY(AAResultsWrapperPass)
   INITIALIZE_PASS_DEPENDENCY(BasicAAWrapperPass)
   INITIALIZE_PASS_DEPENDENCY(GlobalsAAWrapperPass)
   INITIALIZE_PASS_DEPENDENCY(SCEVAAWrapperPass)
   INITIALIZE_PASS_DEPENDENCY(ScalarEvolutionWrapperPass)
 }
 
-/// Find string metadata for loop
-///
-/// If it has a value (e.g. {"llvm.distribute", 1} return the value as an
-/// operand or null otherwise.  If the string metadata is not found return
-/// Optional's not-a-value.
-Optional<const MDOperand *> llvm::findStringMetadataForLoop(Loop *TheLoop,
-                                                            StringRef Name) {
-  MDNode *LoopID = TheLoop->getLoopID();
+static Optional<MDNode *> findOptionMDForLoopID(MDNode *LoopID,
   // Return none if LoopID is false.
   if (!LoopID)
     return None;
 
   // First operand should refer to the loop id itself.
   assert(LoopID->getNumOperands() > 0 && "requires at least one operand");
   assert(LoopID->getOperand(0) == LoopID && "invalid loop id");
 
   // Iterate over LoopID operands and look for MDString Metadata
   for (unsigned i = 1, e = LoopID->getNumOperands(); i < e; ++i) {
     MDNode *MD = dyn_cast<MDNode>(LoopID->getOperand(i));
     if (!MD)
       continue;
     MDString *S = dyn_cast<MDString>(MD->getOperand(0));
     if (!S)
       continue;
     // Return true if MDString holds expected MetaData.
     if (Name.equals(S->getString()))
-      switch (MD->getNumOperands()) {
-      case 1:
-        return nullptr;
-      case 2:
-        return &MD->getOperand(1);
-      default:
-        llvm_unreachable("loop metadata has 0 or 1 operand");
-      }
-  }
+      return MD;
+  }
+  return None;
+}
+
+static Optional<MDNode *> findOptionMDForLoop(const Loop *TheLoop,
+                                              StringRef Name) {
+  return findOptionMDForLoopID(TheLoop->getLoopID(), Name);
+}
+
+/// Find string metadata for loop
+///
+/// If it has a value (e.g. {"llvm.distribute", 1} return the value as an
+/// operand or null otherwise.  If the string metadata is not found return
+/// Optional's not-a-value.
+Optional<const MDOperand *> llvm::findStringMetadataForLoop(Loop *TheLoop,
+                                                            StringRef Name) {
+  auto MD = findOptionMDForLoop(TheLoop, Name).getValueOr(nullptr);
+  if (!MD)
+    return None;
+
+static Optional<bool> getOptionalBoolLoopAttribute(const Loop *TheLoop,
+                                                   StringRef Name) {
+  Optional<MDNode *> MD = findOptionMDForLoop(TheLoop, Name);
+  if (!MD.hasValue())
+    return None;
+  MDNode *OptionNode = MD.getValue();
+  if (OptionNode == nullptr)
+    return None;
+  switch (OptionNode->getNumOperands()) {
+  case 1:
+    // When the value is absent it is interpreted as 'attribute set'.
+    return true;
+  case 2:
+    return mdconst::extract_or_null<ConstantInt>(
+        OptionNode->getOperand(1).get());
+  }
+  llvm_unreachable("unexpected number of options");
+}
+
+static bool getBooleanLoopAttribute(const Loop *TheLoop, StringRef Name) {
+  return getOptionalBoolLoopAttribute(TheLoop, Name).getValueOr(false);
+}
+
+llvm::Optional<int> llvm::getOptionalIntLoopAttribute(Loop *TheLoop,
+                                                      StringRef Name) {
+  const MDOperand *AttrMD =
+      findStringMetadataForLoop(TheLoop, Name).getValueOr(nullptr);
+  if (!AttrMD)
+    return None;
+
+  ConstantInt *IntMD = mdconst::extract_or_null<ConstantInt>(AttrMD->get());
+  if (!IntMD)
+    return None;
+
+  return IntMD->getSExtValue();
+}
+
+Optional<MDNode *> llvm::makeFollowupLoopID(
+    MDNode *OrigLoopID, ArrayRef<StringRef> FollowupOptions,
+    const char *InheritOptionsExceptPrefix, bool AlwaysNew) {
+  if (!OrigLoopID) {
+    if (AlwaysNew)
+      return nullptr;
+    return None;
+  }
+
+  assert(OrigLoopID->getOperand(0) == OrigLoopID);
+
+  bool InheritAllAttrs = !InheritOptionsExceptPrefix;
+  bool InheritSomeAttrs =
+      InheritOptionsExceptPrefix && InheritOptionsExceptPrefix[0] != '\0';
+  SmallVector<Metadata *, 8> MDs;
+  MDs.push_back(nullptr);
+
+  bool Changed = false;
+  if (InheritAllAttrs || InheritSomeAttrs) {
+    for (const MDOperand &Existing : drop_begin(OrigLoopID->operands(), 1)) {
+      MDNode *Op = cast<MDNode>(Existing.get());
+
+      auto InheritThisAttribute = [InheritSomeAttrs,
+                                   InheritOptionsExceptPrefix](MDNode *Op) {
+        if (!InheritSomeAttrs)
+          return false;
+
+        // Skip malformatted attribute metadata nodes.
+        if (Op->getNumOperands() == 0)
+          return true;
+        Metadata *NameMD = Op->getOperand(0).get();
+        if (!isa<MDString>(NameMD))
+          return true;
+        StringRef AttrName = cast<MDString>(NameMD)->getString();
+
+        // Do not inherit excluded attributes.
+        return !AttrName.startswith(InheritOptionsExceptPrefix);
+      };
+
+      if (InheritThisAttribute(Op))
+        MDs.push_back(Op);
+      else
+        Changed = true;
+    }
+  } else {
+    // Modified if we dropped at least one attribute.
+    Changed = OrigLoopID->getNumOperands() > 1;
+  }
+
+  bool HasAnyFollowup = false;
+  for (StringRef OptionName : FollowupOptions) {
+    MDNode *FollowupNode =
+        findOptionMDForLoopID(OrigLoopID, OptionName).getValueOr(nullptr);
+    if (!FollowupNode)
+      continue;
+
+    HasAnyFollowup = true;
+    for (const MDOperand &Option : drop_begin(FollowupNode->operands(), 1)) {
+      MDs.push_back(Option.get());
+      Changed = true;
+    }
+  }
+
+  // Attributes of the followup loop not specified explicity, so signal to the
+  // transformation pass to add suitable attributes.
+  if (!AlwaysNew && !HasAnyFollowup)
     return None;
+
+  // If no attributes were added or remove, the previous loop Id can be reused.
+  if (!AlwaysNew && !Changed)
+    return OrigLoopID;
+
+  // No attributes is equivalent to having no !llvm.loop metadata at all.
+  if (MDs.size() == 1)
+    return nullptr;
+
+  // Build the new loop ID.
+  MDTuple *FollowupLoopID = MDNode::get(OrigLoopID->getContext(), MDs);
+  FollowupLoopID->replaceOperandWith(0, FollowupLoopID);
+  return FollowupLoopID;
+}
+
+bool llvm::hasDisableAllTransformsHint(const Loop *L) {
+  return getBooleanLoopAttribute(L, LLVMLoopDisableNonforced);
+}
+
+TransformationMode llvm::hasUnrollTransformation(Loop *L) {
+  if (getBooleanLoopAttribute(L, "llvm.loop.unroll.disable"))
+    return TM_SuppressedByUser;
+
+  Optional<int> Count =
+      getOptionalIntLoopAttribute(L, "llvm.loop.unroll.count");
+  if (Count.hasValue())
+    return Count.getValue() == 1 ? TM_SuppressedByUser : TM_ForcedByUser;
+
+  if (getBooleanLoopAttribute(L, "llvm.loop.unroll.enable"))
+    return TM_ForcedByUser;
+
+  if (getBooleanLoopAttribute(L, "llvm.loop.unroll.full"))
+    return TM_ForcedByUser;
+
+  if (hasDisableAllTransformsHint(L))
+    return TM_Disable;
+
+  return TM_Unspecified;
+}
+
+TransformationMode llvm::hasUnrollAndJamTransformation(Loop *L) {
+  if (getBooleanLoopAttribute(L, "llvm.loop.unroll_and_jam.disable"))
+    return TM_SuppressedByUser;
+
+  Optional<int> Count =
+      getOptionalIntLoopAttribute(L, "llvm.loop.unroll_and_jam.count");
+  if (Count.hasValue())
+    return Count.getValue() == 1 ? TM_SuppressedByUser : TM_ForcedByUser;
+
+  if (getBooleanLoopAttribute(L, "llvm.loop.unroll_and_jam.enable"))
+    return TM_ForcedByUser;
+
+  if (hasDisableAllTransformsHint(L))
+    return TM_Disable;
+
+  return TM_Unspecified;
+}
+
+TransformationMode llvm::hasVectorizeTransformation(Loop *L) {
+  Optional<bool> Enable =
+      getOptionalBoolLoopAttribute(L, "llvm.loop.vectorize.enable");
+
+  if (Enable == false)
+    return TM_SuppressedByUser;
+
+  Optional<int> VectorizeWidth =
+      getOptionalIntLoopAttribute(L, "llvm.loop.vectorize.width");
+  Optional<int> InterleaveCount =
+      getOptionalIntLoopAttribute(L, "llvm.loop.interleave.count");
+
+  if (Enable == true) {
+    // 'Forcing' vector width and interleave count to one effectively disables
+    // this tranformation.
+    if (VectorizeWidth == 1 && InterleaveCount == 1)
+      return TM_SuppressedByUser;
+    return TM_ForcedByUser;
+  }
+
+  if (getBooleanLoopAttribute(L, "llvm.loop.isvectorized"))
+    return TM_Disable;
+
+  if (VectorizeWidth == 1 && InterleaveCount == 1)
+    return TM_Disable;
+
+  if (VectorizeWidth > 1 || InterleaveCount > 1)
+    return TM_Enable;
+
+  if (hasDisableAllTransformsHint(L))
+    return TM_Disable;
+
+  return TM_Unspecified;
+}
+
+TransformationMode llvm::hasDistributeTransformation(Loop *L) {
+  if (getBooleanLoopAttribute(L, "llvm.loop.distribute.enable"))
+    return TM_ForcedByUser;
+
+  if (hasDisableAllTransformsHint(L))
+    return TM_Disable;
+
+  return TM_Unspecified;
+}
+
+TransformationMode llvm::hasLICMVersioningTransformation(Loop *L) {
+  if (getBooleanLoopAttribute(L, "llvm.loop.licm_versioning.disable"))
+    return TM_SuppressedByUser;
+
+  if (hasDisableAllTransformsHint(L))
+    return TM_Disable;
+
+  return TM_Unspecified;
 }
 
 /// Does a BFS from a given node to all of its children inside a given loop.
 /// The returned vector of nodes includes the starting point.
 SmallVector<DomTreeNode *, 16>
 llvm::collectChildrenInLoop(DomTreeNode *N, const Loop *CurLoop) {
   SmallVector<DomTreeNode *, 16> Worklist;
   auto AddRegionToWorklist = [&](DomTreeNode *DTN) {

lib/Transforms/Vectorize/LoopVectorize.cpp

 #include <utility>
 #include <vector>
 
 using namespace llvm;
 
 #define LV_NAME "loop-vectorize"
 #define DEBUG_TYPE LV_NAME
 
+/// @{
+/// Metadata attribute names
+static const char *const LLVMLoopVectorizeFollowupAll =
+    "llvm.loop.vectorize.followup_all";
+static const char *const LLVMLoopVectorizeFollowupVectorized =
+    "llvm.loop.vectorize.followup_vectorized";
+static const char *const LLVMLoopVectorizeFollowupEpilogue =
+    "llvm.loop.vectorize.followup_epilogue";
+/// @}
+
 STATISTIC(LoopsVectorized, "Number of loops vectorized");
 STATISTIC(LoopsAnalyzed, "Number of loops analyzed for vectorization");
 
 /// Loops with a known constant trip count below this number are vectorized only
 /// if no scalar iteration overheads are incurred.
 static cl::opt<unsigned> TinyTripCountVectorThreshold(
     "vectorizer-min-trip-count", cl::init(16), cl::Hidden,
     cl::desc("Loops with a constant trip count that is smaller than this "

 void InnerLoopVectorizer::addMetadata(ArrayRef<Value *> To,
                                       Instruction *From) {
   for (Value *V : To) {
     if (Instruction *I = dyn_cast<Instruction>(V))
       addMetadata(I, From);
   }
 }
 
-static void emitMissedWarning(Function *F, Loop *L,
-                              const LoopVectorizeHints &LH,
-                              OptimizationRemarkEmitter *ORE) {
-  LH.emitRemarkWithHints();
-
-  if (LH.getForce() == LoopVectorizeHints::FK_Enabled) {
-    if (LH.getWidth() != 1)
-      ORE->emit(DiagnosticInfoOptimizationFailure(
-                    DEBUG_TYPE, "FailedRequestedVectorization",
-                    L->getStartLoc(), L->getHeader())
-                << "loop not vectorized: "
-                << "failed explicitly specified loop vectorization");
-    else if (LH.getInterleave() != 1)
-      ORE->emit(DiagnosticInfoOptimizationFailure(
-                    DEBUG_TYPE, "FailedRequestedInterleaving", L->getStartLoc(),
-                    L->getHeader())
-                << "loop not interleaved: "
-                << "failed explicitly specified loop interleaving");
-  }
-}
-
 namespace llvm {
 
 /// LoopVectorizationCostModel - estimates the expected speedups due to
 /// vectorization.
 /// In many cases vectorization is not profitable. This can happen because of
 /// a number of reasons. In this class we mainly attempt to predict the
 /// expected speedup/slowdowns due to the supported instruction set. We use the
 /// TargetTransformInfo to query the different backends for the cost of
static bool isExplicitVecOuterLoop(Loop *OuterLp,
   Function *Fn = OuterLp->getHeader()->getParent();
   if (!Hints.allowVectorization(Fn, OuterLp, false /*AlwaysVectorize*/)) {
     LLVM_DEBUG(dbgs() << "LV: Loop hints prevent outer loop vectorization.\n");
     return false;
   }
 
   if (!Hints.getWidth()) {
     LLVM_DEBUG(dbgs() << "LV: Not vectorizing: No user vector width.\n");
-    emitMissedWarning(Fn, OuterLp, Hints, ORE);
+    Hints.emitRemarkWithHints();
     return false;
   }
 
   if (Hints.getInterleave() > 1) {
     // TODO: Interleave support is future work.
     LLVM_DEBUG(dbgs() << "LV: Not vectorizing: Interleave is not supported for "
                          "outer loops.\n");
-    emitMissedWarning(Fn, OuterLp, Hints, ORE);
+    Hints.emitRemarkWithHints();
     return false;
   }
 
   return true;
 }
 
 static void collectSupportedLoops(Loop &L, LoopInfo *LI,
                                   OptimizationRemarkEmitter *ORE,
|   [ ]_|   <-- old scalar loop to handle remainder.
      \  v
       >[ ]     <-- exit block.
    ...
    */
 
   BasicBlock *OldBasicBlock = OrigLoop->getHeader();
   BasicBlock *VectorPH = OrigLoop->getLoopPreheader();
   BasicBlock *ExitBlock = OrigLoop->getExitBlock();
+  MDNode *OrigLoopID = OrigLoop->getLoopID();
   assert(VectorPH && "Invalid loop structure");
   assert(ExitBlock && "Must have an exit block");
 
   // Some loops have a single integer induction variable, while other loops
   // don't. One example is c++ iterators that often have multiple pointer
   // induction variables. In the code below we also support a case where we
   // don't have a single induction variable.
   //
BasicBlock *InnerLoopVectorizer::createVectorizedLoopSkeleton() {
   // Save the state.
   LoopVectorPreHeader = Lp->getLoopPreheader();
   LoopScalarPreHeader = ScalarPH;
   LoopMiddleBlock = MiddleBlock;
   LoopExitBlock = ExitBlock;
   LoopVectorBody = VecBody;
   LoopScalarBody = OldBasicBlock;
 
+  Optional<MDNode *> VectorizedLoopID =
+      makeFollowupLoopID(OrigLoopID, {LLVMLoopVectorizeFollowupAll,
+                                      LLVMLoopVectorizeFollowupVectorized});
+  if (VectorizedLoopID.hasValue()) {
+    Lp->setLoopID(VectorizedLoopID.getValue());
+
+    // Do not setAlreadyVectorized if loop attributes have been defined
+    // explicitly.
+    return LoopVectorPreHeader;
+  }
+
   // Keep all loop hints from the original loop on the vector loop (we'll
   // replace the vectorizer-specific hints below).
   if (MDNode *LID = OrigLoop->getLoopID())
     Lp->setLoopID(LID);
 
   LoopVectorizeHints Hints(Lp, true, *ORE);
   Hints.setAlreadyVectorized();
 
#endif /* NDEBUG */
   PredicatedScalarEvolution PSE(*SE, *L);
 
   // Check if it is legal to vectorize the loop.
   LoopVectorizationRequirements Requirements(*ORE);
   LoopVectorizationLegality LVL(L, PSE, DT, TLI, AA, F, GetLAA, LI, ORE,
                                 &Requirements, &Hints, DB, AC);
   if (!LVL.canVectorize(EnableVPlanNativePath)) {
     LLVM_DEBUG(dbgs() << "LV: Not vectorizing: Cannot prove legality.\n");
-    emitMissedWarning(F, L, Hints, ORE);
+    Hints.emitRemarkWithHints();
     return false;
   }
 
   // Check the function attributes to find out if this function should be
   // optimized for size.
   bool OptForSize =
       Hints.getForce() != LoopVectorizeHints::FK_Enabled && F->optForSize();
 
#endif /* NDEBUG */
   // an integer loop and the vector instructions selected are purely integer
   // vector instructions?
   if (F->hasFnAttribute(Attribute::NoImplicitFloat)) {
     LLVM_DEBUG(dbgs() << "LV: Can't vectorize when the NoImplicitFloat"
                          "attribute is used.\n");
     ORE->emit(createLVMissedAnalysis(Hints.vectorizeAnalysisPassName(),
                                      "NoImplicitFloat", L)
               << "loop not vectorized due to NoImplicitFloat attribute");
-    emitMissedWarning(F, L, Hints, ORE);
+    Hints.emitRemarkWithHints();
     return false;
   }
 
   // Check if the target supports potentially unsafe FP vectorization.
   // FIXME: Add a check for the type of safety issue (denormal, signaling)
   // for the target we're vectorizing for, to make sure none of the
   // additional fp-math flags can help.
   if (Hints.isPotentiallyUnsafe() &&
       TTI->isFPVectorizationPotentiallyUnsafe()) {
     LLVM_DEBUG(
         dbgs() << "LV: Potentially unsafe FP op prevents vectorization.\n");
     ORE->emit(
         createLVMissedAnalysis(Hints.vectorizeAnalysisPassName(), "UnsafeFP", L)
         << "loop not vectorized due to unsafe FP support.");
-    emitMissedWarning(F, L, Hints, ORE);
+    Hints.emitRemarkWithHints();
     return false;
   }
 
   bool UseInterleaved = TTI->enableInterleavedAccessVectorization();
   InterleavedAccessInfo IAI(PSE, L, DT, LI, LVL.getLAI());
 
   // If an override option has been passed in for interleaved accesses, use it.
   if (EnableInterleavedMemAccesses.getNumOccurrences() > 0)
#endif /* NDEBUG */
   unsigned UserIC = Hints.getInterleave();
 
   // Identify the diagnostic messages that should be produced.
   std::pair<StringRef, std::string> VecDiagMsg, IntDiagMsg;
   bool VectorizeLoop = true, InterleaveLoop = true;
   if (Requirements.doesNotMeet(F, L, Hints)) {
     LLVM_DEBUG(dbgs() << "LV: Not vectorizing: loop did not meet vectorization "
                          "requirements.\n");
-    emitMissedWarning(F, L, Hints, ORE);
+    Hints.emitRemarkWithHints();
     return false;
   }
 
   if (VF.Width == 1) {
     LLVM_DEBUG(dbgs() << "LV: Vectorization is possible but not beneficial.\n");
     VecDiagMsg = std::make_pair(
         "VectorizationNotBeneficial",
         "the cost-model indicates that vectorization is not beneficial");
if (!VectorizeLoop && !InterleaveLoop) {
     LLVM_DEBUG(dbgs() << "LV: Found a vectorizable loop (" << VF.Width
                       << ") in " << DebugLocStr << '\n');
     LLVM_DEBUG(dbgs() << "LV: Interleave Count is " << IC << '\n');
   }
 
   LVP.setBestPlan(VF.Width, IC);
 
   using namespace ore;
+  bool DisableRuntimeUnroll = false;
+  MDNode *OrigLoopID = L->getLoopID();
 
   if (!VectorizeLoop) {
     assert(IC > 1 && "interleave count should not be 1 or 0");
     // If we decided that it is not legal to vectorize the loop, then
     // interleave it.
     InnerLoopUnroller Unroller(L, PSE, LI, DT, TLI, TTI, AC, ORE, IC, &LVL,
                                &CM);
     LVP.executePlan(Unroller, DT);
InnerLoopVectorizer LB(L, PSE, LI, DT, TLI, TTI, AC, ORE, VF.Width, IC,
                            &LVL, &CM);
     LVP.executePlan(LB, DT);
     ++LoopsVectorized;
 
     // Add metadata to disable runtime unrolling a scalar loop when there are
     // no runtime checks about strides and memory. A scalar loop that is
     // rarely used is not worth unrolling.
     if (!LB.areSafetyChecksAdded())
-      AddRuntimeUnrollDisableMetaData(L);
+      DisableRuntimeUnroll = true;
 
     // Report the vectorization decision.
     ORE->emit([&]() {
       return OptimizationRemark(LV_NAME, "Vectorized", L->getStartLoc(),
                                 L->getHeader())
              << "vectorized loop (vectorization width: "
              << NV("VectorizationFactor", VF.Width)
              << ", interleaved count: " << NV("InterleaveCount", IC) << ")";
     });
   }
 
+  Optional<MDNode *> RemainderLoopID =
+      makeFollowupLoopID(OrigLoopID, {LLVMLoopVectorizeFollowupAll,
+                                      LLVMLoopVectorizeFollowupEpilogue});
+  if (RemainderLoopID.hasValue()) {
+    L->setLoopID(RemainderLoopID.getValue());
+  } else {
+    if (DisableRuntimeUnroll)
+      AddRuntimeUnrollDisableMetaData(L);
+
     // Mark the loop as already vectorized to avoid vectorizing again.
     Hints.setAlreadyVectorized();
+  }
 
   LLVM_DEBUG(verifyFunction(*L->getHeader()->getParent()));
   return true;
 }
 
 bool LoopVectorizePass::runImpl(
     Function &F, ScalarEvolution &SE_, LoopInfo &LI_, TargetTransformInfo &TTI_,
     DominatorTree &DT_, BlockFrequencyInfo &BFI_, TargetLibraryInfo *TLI_,

test/Other/new-pm-defaults.ll

 ; CHECK-O-NEXT: Running pass: LoopLoadEliminationPass
 ; CHECK-O-NEXT: Running analysis: LoopAccessAnalysis
 ; CHECK-O-NEXT: Running pass: InstCombinePass
 ; CHECK-O-NEXT: Running pass: SimplifyCFGPass
 ; CHECK-O-NEXT: Running pass: SLPVectorizerPass
 ; CHECK-O-NEXT: Running pass: InstCombinePass
 ; CHECK-O-NEXT: Running pass: LoopUnrollPass
 ; CHECK-O-NEXT: Running analysis: OuterAnalysisManagerProxy
+; CHECK-O-NEXT: Running pass: WarnMissedTransformationsPass
 ; CHECK-O-NEXT: Running pass: InstCombinePass
 ; CHECK-O-NEXT: Running pass: RequireAnalysisPass<{{.*}}OptimizationRemarkEmitterAnalysis
 ; CHECK-O-NEXT: Running pass: FunctionToLoopPassAdaptor<{{.*}}LICMPass
 ; CHECK-O-NEXT: Starting llvm::Function pass manager run.
 ; CHECK-O-NEXT: Running pass: LoopSimplifyPass
 ; CHECK-O-NEXT: Running pass: LCSSAPass
 ; CHECK-O-NEXT: Finished llvm::Function pass manager run.
 ; CHECK-O-NEXT: Running pass: AlignmentFromAssumptionsPass

test/Other/new-pm-thinlto-defaults.ll

 ; CHECK-POSTLINK-O-NEXT: Running pass: LoopLoadEliminationPass
 ; CHECK-POSTLINK-O-NEXT: Running analysis: LoopAccessAnalysis
 ; CHECK-POSTLINK-O-NEXT: Running pass: InstCombinePass
 ; CHECK-POSTLINK-O-NEXT: Running pass: SimplifyCFGPass
 ; CHECK-POSTLINK-O-NEXT: Running pass: SLPVectorizerPass
 ; CHECK-POSTLINK-O-NEXT: Running pass: InstCombinePass
 ; CHECK-POSTLINK-O-NEXT: Running pass: LoopUnrollPass
 ; CHECK-POSTLINK-O-NEXT: Running analysis: OuterAnalysisManagerProxy
+; CHECK-POSTLINK-O-NEXT: Running pass: WarnMissedTransformationsPass
 ; CHECK-POSTLINK-O-NEXT: Running pass: InstCombinePass
 ; CHECK-POSTLINK-O-NEXT: Running pass: RequireAnalysisPass<{{.*}}OptimizationRemarkEmitterAnalysis
 ; CHECK-POSTLINK-O-NEXT: Running pass: FunctionToLoopPassAdaptor<{{.*}}LICMPass
 ; CHECK-POSTLINK-O-NEXT: Starting llvm::Function pass manager run
 ; CHECK-POSTLINK-O-NEXT: Running pass: LoopSimplifyPass
 ; CHECK-POSTLINK-O-NEXT: Running pass: LCSSAPass
 ; CHECK-POSTLINK-O-NEXT: Finished llvm::Function pass manager run
 ; CHECK-POSTLINK-O-NEXT: Running pass: AlignmentFromAssumptionsPass

test/Other/opt-O2-pipeline.ll

 ; CHECK-NEXT:       Optimization Remark Emitter
 ; CHECK-NEXT:       Combine redundant instructions
 ; CHECK-NEXT:       Canonicalize natural loops
 ; CHECK-NEXT:       LCSSA Verifier
 ; CHECK-NEXT:       Loop-Closed SSA Form Pass
 ; CHECK-NEXT:       Scalar Evolution Analysis
 ; CHECK-NEXT:       Loop Pass Manager
 ; CHECK-NEXT:         Loop Invariant Code Motion
+; CHECK-NEXT:       Lazy Branch Probability Analysis
+; CHECK-NEXT:       Lazy Block Frequency Analysis
+; CHECK-NEXT:       Optimization Remark Emitter
+; CHECK-NEXT:       Warn about non-applied transformations
 ; CHECK-NEXT:       Alignment from assumptions
 ; CHECK-NEXT:     Strip Unused Function Prototypes
 ; CHECK-NEXT:     Dead Global Elimination
 ; CHECK-NEXT:     Merge Duplicate Global Constants
 ; CHECK-NEXT:     FunctionPass Manager
 ; CHECK-NEXT:       Dominator Tree Construction
 ; CHECK-NEXT:       Natural Loop Information
 ; CHECK-NEXT:       Branch Probability Analysis

test/Other/opt-O3-pipeline.ll

 ; CHECK-NEXT:       Optimization Remark Emitter
 ; CHECK-NEXT:       Combine redundant instructions
 ; CHECK-NEXT:       Canonicalize natural loops
 ; CHECK-NEXT:       LCSSA Verifier
 ; CHECK-NEXT:       Loop-Closed SSA Form Pass
 ; CHECK-NEXT:       Scalar Evolution Analysis
 ; CHECK-NEXT:       Loop Pass Manager
 ; CHECK-NEXT:         Loop Invariant Code Motion
+; CHECK-NEXT:       Lazy Branch Probability Analysis
+; CHECK-NEXT:       Lazy Block Frequency Analysis
+; CHECK-NEXT:       Optimization Remark Emitter
+; CHECK-NEXT:       Warn about non-applied transformations
 ; CHECK-NEXT:       Alignment from assumptions
 ; CHECK-NEXT:     Strip Unused Function Prototypes
 ; CHECK-NEXT:     Dead Global Elimination
 ; CHECK-NEXT:     Merge Duplicate Global Constants
 ; CHECK-NEXT:     FunctionPass Manager
 ; CHECK-NEXT:       Dominator Tree Construction
 ; CHECK-NEXT:       Natural Loop Information
 ; CHECK-NEXT:       Branch Probability Analysis

test/Other/opt-Os-pipeline.ll

 ; CHECK-NEXT:       Optimization Remark Emitter
 ; CHECK-NEXT:       Combine redundant instructions
 ; CHECK-NEXT:       Canonicalize natural loops
 ; CHECK-NEXT:       LCSSA Verifier
 ; CHECK-NEXT:       Loop-Closed SSA Form Pass
 ; CHECK-NEXT:       Scalar Evolution Analysis
 ; CHECK-NEXT:       Loop Pass Manager
 ; CHECK-NEXT:         Loop Invariant Code Motion
+; CHECK-NEXT:       Lazy Branch Probability Analysis
+; CHECK-NEXT:       Lazy Block Frequency Analysis
+; CHECK-NEXT:       Optimization Remark Emitter
+; CHECK-NEXT:       Warn about non-applied transformations
 ; CHECK-NEXT:       Alignment from assumptions
 ; CHECK-NEXT:     Strip Unused Function Prototypes
 ; CHECK-NEXT:     Dead Global Elimination
 ; CHECK-NEXT:     Merge Duplicate Global Constants
 ; CHECK-NEXT:     FunctionPass Manager
 ; CHECK-NEXT:       Dominator Tree Construction
 ; CHECK-NEXT:       Natural Loop Information
 ; CHECK-NEXT:       Branch Probability Analysis

test/Other/opt-hot-cold-split.ll

 ; CHECK-NEXT:       Optimization Remark Emitter
 ; CHECK-NEXT:       Combine redundant instructions
 ; CHECK-NEXT:       Canonicalize natural loops
 ; CHECK-NEXT:       LCSSA Verifier
 ; CHECK-NEXT:       Loop-Closed SSA Form Pass
 ; CHECK-NEXT:       Scalar Evolution Analysis
 ; CHECK-NEXT:       Loop Pass Manager
 ; CHECK-NEXT:         Loop Invariant Code Motion
+; CHECK-NEXT:       Lazy Branch Probability Analysis
+; CHECK-NEXT:       Lazy Block Frequency Analysis
+; CHECK-NEXT:       Optimization Remark Emitter
+; CHECK-NEXT:       Warn about non-applied transformations
 ; CHECK-NEXT:       Alignment from assumptions
 ; CHECK-NEXT:     Strip Unused Function Prototypes
 ; CHECK-NEXT:     Dead Global Elimination
 ; CHECK-NEXT:     Merge Duplicate Global Constants
 ; CHECK-NEXT:     FunctionPass Manager
 ; CHECK-NEXT:       Dominator Tree Construction
 ; CHECK-NEXT:       Natural Loop Information
 ; CHECK-NEXT:       Branch Probability Analysis

test/Transforms/LoopDistribute/disable_nonforced.ll

+; RUN: opt -loop-distribute -enable-loop-distribute=1 -S < %s | FileCheck %s
+;
+; Check that the disable_nonforced is honored by loop distribution.
+;
+target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
+
+; CHECK-LABEL: @disable_nonforced(
+; CHECK-NOT: for.body.ldist1:
+define void @disable_nonforced(i32* noalias %a,
+                         i32* noalias %b,
+                         i32* noalias %c,
+                         i32* noalias %d,
+                         i32* noalias %e) {
+entry:
+  br label %for.body
+
+for.body:
+  %ind = phi i64 [ 0, %entry ], [ %add, %for.body ]
+
+  %arrayidxA = getelementptr inbounds i32, i32* %a, i64 %ind
+  %loadA = load i32, i32* %arrayidxA, align 4
+
+  %arrayidxB = getelementptr inbounds i32, i32* %b, i64 %ind
+  %loadB = load i32, i32* %arrayidxB, align 4
+
+  %mulA = mul i32 %loadB, %loadA
+
+  %add = add nuw nsw i64 %ind, 1
+  %arrayidxA_plus_4 = getelementptr inbounds i32, i32* %a, i64 %add
+  store i32 %mulA, i32* %arrayidxA_plus_4, align 4
+
+  %arrayidxD = getelementptr inbounds i32, i32* %d, i64 %ind
+  %loadD = load i32, i32* %arrayidxD, align 4
+
+  %arrayidxE = getelementptr inbounds i32, i32* %e, i64 %ind
+  %loadE = load i32, i32* %arrayidxE, align 4
+
+  %mulC = mul i32 %loadD, %loadE
+
+  %arrayidxC = getelementptr inbounds i32, i32* %c, i64 %ind
+  store i32 %mulC, i32* %arrayidxC, align 4
+
+  %exitcond = icmp eq i64 %add, 20
+  br i1 %exitcond, label %for.end, label %for.body, !llvm.loop !0
+
+for.end:
+  ret void
+}
+
+!0 = distinct !{!0, !{!"llvm.loop.disable_nonforced"}}

test/Transforms/LoopDistribute/disable_nonforced_enable.ll

+; RUN: opt -loop-distribute -S < %s | FileCheck %s
+;
+; Check that llvm.loop.distribute.enable overrides
+; llvm.loop.disable_nonforced.
+;
+target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
+
+; CHECK-LABEL: @disable_nonforced(
+; CHECK: for.body.ldist1:
+define void @disable_nonforced(i32* noalias %a,
+                         i32* noalias %b,
+                         i32* noalias %c,
+                         i32* noalias %d,
+                         i32* noalias %e) {
+entry:
+  br label %for.body
+
+for.body:
+  %ind = phi i64 [ 0, %entry ], [ %add, %for.body ]
+
+  %arrayidxA = getelementptr inbounds i32, i32* %a, i64 %ind
+  %loadA = load i32, i32* %arrayidxA, align 4
+
+  %arrayidxB = getelementptr inbounds i32, i32* %b, i64 %ind
+  %loadB = load i32, i32* %arrayidxB, align 4
+
+  %mulA = mul i32 %loadB, %loadA
+
+  %add = add nuw nsw i64 %ind, 1
+  %arrayidxA_plus_4 = getelementptr inbounds i32, i32* %a, i64 %add
+  store i32 %mulA, i32* %arrayidxA_plus_4, align 4
+
+  %arrayidxD = getelementptr inbounds i32, i32* %d, i64 %ind
+  %loadD = load i32, i32* %arrayidxD, align 4
+
+  %arrayidxE = getelementptr inbounds i32, i32* %e, i64 %ind
+  %loadE = load i32, i32* %arrayidxE, align 4
+
+  %mulC = mul i32 %loadD, %loadE
+
+  %arrayidxC = getelementptr inbounds i32, i32* %c, i64 %ind
+  store i32 %mulC, i32* %arrayidxC, align 4
+
+  %exitcond = icmp eq i64 %add, 20
+  br i1 %exitcond, label %for.end, label %for.body, !llvm.loop !0
+
+for.end:
+  ret void
+}
+
+!0 = distinct !{!0, !{!"llvm.loop.disable_nonforced"}, !{!"llvm.loop.distribute.enable", i32 1}}

test/Transforms/LoopDistribute/followup.ll

+; RUN: opt -basicaa -loop-distribute -S < %s | FileCheck %s
+;
+; Check that followup loop-attributes are applied to the loops after
+; loop distribution.
+;
+target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
+
+define void @f(i32* %a, i32* %b, i32* %c, i32* %d, i32* %e) {
+entry:
+  br label %for.body
+
+for.body:
+  %ind = phi i64 [ 0, %entry ], [ %add, %for.body ]
+
+  %arrayidxA = getelementptr inbounds i32, i32* %a, i64 %ind
+  %loadA = load i32, i32* %arrayidxA, align 4
+
+  %arrayidxB = getelementptr inbounds i32, i32* %b, i64 %ind
+  %loadB = load i32, i32* %arrayidxB, align 4
+
+  %mulA = mul i32 %loadB, %loadA
+
+  %add = add nuw nsw i64 %ind, 1
+  %arrayidxA_plus_4 = getelementptr inbounds i32, i32* %a, i64 %add
+  store i32 %mulA, i32* %arrayidxA_plus_4, align 4
+
+  %arrayidxD = getelementptr inbounds i32, i32* %d, i64 %ind
+  %loadD = load i32, i32* %arrayidxD, align 4
+
+  %arrayidxE = getelementptr inbounds i32, i32* %e, i64 %ind
+  %loadE = load i32, i32* %arrayidxE, align 4
+
+  %mulC = mul i32 %loadD, %loadE
+
+  %arrayidxC = getelementptr inbounds i32, i32* %c, i64 %ind
+  store i32 %mulC, i32* %arrayidxC, align 4
+
+  %exitcond = icmp eq i64 %add, 20
+  br i1 %exitcond, label %for.end, label %for.body, !llvm.loop !0
+
+for.end:
+  ret void
+}
+
+!0 = distinct !{!0, !1, !2, !3, !4, !5}
+!1 = !{!"llvm.loop.distribute.enable", i1 true}
+!2 = !{!"llvm.loop.distribute.followup_all", !{!"FollowupAll"}}
+!3 = !{!"llvm.loop.distribute.followup_coincident", !{!"FollowupCoincident", i1 false}}
+!4 = !{!"llvm.loop.distribute.followup_sequential", !{!"FollowupSequential", i32 8}}
+!5 = !{!"llvm.loop.distribute.followup_fallback", !{!"FollowupFallback"}}
+
+
+; CHECK-LABEL: for.body.lver.orig:
+; CHECK: br i1 %exitcond.lver.orig, label %for.end, label %for.body.lver.orig, !llvm.loop ![[LOOP_ORIG:[0-9]+]]
+; CHECK-LABEL: for.body.ldist1:
+; CHECK: br i1 %exitcond.ldist1, label %for.body.ph, label %for.body.ldist1, !llvm.loop ![[LOOP_SEQUENTIAL:[0-9]+]]
+; CHECK-LABEL: for.body:
+; CHECK: br i1 %exitcond, label %for.end, label %for.body, !llvm.loop ![[LOOP_COINCIDENT:[0-9]+]]
+
+; CHECK: ![[LOOP_ORIG]] = distinct !{![[LOOP_ORIG]], ![[FOLLOWUP_ALL:[0-9]+]], ![[FOLLOUP_FALLBACK:[0-9]+]]}
+; CHECK: ![[FOLLOWUP_ALL]] = !{!"FollowupAll"}
+; CHECK: ![[FOLLOUP_FALLBACK]] = !{!"FollowupFallback"}
+; CHECK: ![[LOOP_SEQUENTIAL]] = distinct !{![[LOOP_SEQUENTIAL]], ![[FOLLOWUP_ALL]], ![[FOLLOWUP_SEQUENTIAL:[0-9]+]]}
+; CHECK: ![[FOLLOWUP_SEQUENTIAL]] = !{!"FollowupSequential", i32 8}
+; CHECK: ![[LOOP_COINCIDENT]] = distinct !{![[LOOP_COINCIDENT]], ![[FOLLOWUP_ALL]], ![[FOLLOWUP_COINCIDENT:[0-9]+]]}
+; CHECK: ![[FOLLOWUP_COINCIDENT]] = !{!"FollowupCoincident", i1 false}

test/Transforms/LoopTransformWarning/distribution-remarks-missed.ll

+; Legacy pass manager
+; RUN: opt < %s -transform-warning -disable-output -pass-remarks-missed=transform-warning -pass-remarks-analysis=transform-warning 2>&1 | FileCheck %s
+; RUN: opt < %s -transform-warning -disable-output -pass-remarks-output=%t.yaml
+; RUN: cat %t.yaml | FileCheck -check-prefix=YAML %s
+
+; New pass manager
+; RUN: opt < %s -passes=transform-warning -disable-output -pass-remarks-missed=transform-warning -pass-remarks-analysis=transform-warning 2>&1 | FileCheck %s
+; RUN: opt < %s -passes=transform-warning -disable-output -pass-remarks-output=%t.yaml
+; RUN: cat %t.yaml | FileCheck -check-prefix=YAML %s
+
+
+; CHECK: warning: source.cpp:19:5: loop not distributed: the optimizer was unable to perform the requested transformation; the transformation might be disabled or specified as part of an unsupported transformation ordering
+
+; YAML:     --- !Failure
+; YAML-NEXT: Pass:            transform-warning
+; YAML-NEXT: Name:            FailedRequestedDistribution
+; YAML-NEXT: DebugLoc:        { File: source.cpp, Line: 19, Column: 5 }
+; YAML-NEXT: Function:        _Z17test_array_boundsPiS_i
+; YAML-NEXT: Args:
+; YAML-NEXT:   - String:          'loop not distributed: the optimizer was unable to perform the requested transformation; the transformation might be disabled or specified as part of an unsupported transformation ordering'
+; YAML-NEXT: ...
+
+target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
+
+define void @_Z17test_array_boundsPiS_i(i32* nocapture %A, i32* nocapture readonly %B, i32 %Length) !dbg !8 {
+entry:
+  %cmp9 = icmp sgt i32 %Length, 0, !dbg !32
+  br i1 %cmp9, label %for.body.preheader, label %for.end, !dbg !32
+
+for.body.preheader:                          
+  br label %for.body, !dbg !35
+
+for.body:                                    
+  %indvars.iv = phi i64 [ %indvars.iv.next, %for.body ], [ 0, %for.body.preheader ]
+  %arrayidx = getelementptr inbounds i32, i32* %B, i64 %indvars.iv, !dbg !35
+  %0 = load i32, i32* %arrayidx, align 4, !dbg !35, !tbaa !18
+  %idxprom1 = sext i32 %0 to i64, !dbg !35
+  %arrayidx2 = getelementptr inbounds i32, i32* %A, i64 %idxprom1, !dbg !35
+  %1 = load i32, i32* %arrayidx2, align 4, !dbg !35, !tbaa !18
+  %arrayidx4 = getelementptr inbounds i32, i32* %A, i64 %indvars.iv, !dbg !35
+  store i32 %1, i32* %arrayidx4, align 4, !dbg !35, !tbaa !18
+  %indvars.iv.next = add nuw nsw i64 %indvars.iv, 1, !dbg !32
+  %lftr.wideiv = trunc i64 %indvars.iv.next to i32, !dbg !32
+  %exitcond = icmp eq i32 %lftr.wideiv, %Length, !dbg !32
+  br i1 %exitcond, label %for.end.loopexit, label %for.body, !dbg !32, !llvm.loop !50
+
+for.end.loopexit:                            
+  br label %for.end
+
+for.end:                                      
+  ret void, !dbg !36
+}
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!9, !10}
+!llvm.ident = !{!11}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus, producer: "clang version 3.5.0", isOptimized: true, runtimeVersion: 6, emissionKind: LineTablesOnly, file: !1, enums: !2, retainedTypes: !2, globals: !2, imports: !2)
+!1 = !DIFile(filename: "source.cpp", directory: ".")
+!2 = !{}
+!4 = distinct !DISubprogram(name: "test", line: 1, isLocal: false, isDefinition: true, virtualIndex: 6, flags: DIFlagPrototyped, isOptimized: true, unit: !0, scopeLine: 1, file: !1, scope: !5, type: !6, retainedNodes: !2)
+!5 = !DIFile(filename: "source.cpp", directory: ".")
+!6 = !DISubroutineType(types: !2)
+!7 = distinct !DISubprogram(name: "test_disabled", line: 10, isLocal: false, isDefinition: true, virtualIndex: 6, flags: DIFlagPrototyped, isOptimized: true, unit: !0, scopeLine: 10, file: !1, scope: !5, type: !6, retainedNodes: !2)
+!8 = distinct !DISubprogram(name: "test_array_bounds", line: 16, isLocal: false, isDefinition: true, virtualIndex: 6, flags: DIFlagPrototyped, isOptimized: true, unit: !0, scopeLine: 16, file: !1, scope: !5, type: !6, retainedNodes: !2)
+!9 = !{i32 2, !"Dwarf Version", i32 2}
+!10 = !{i32 2, !"Debug Info Version", i32 3}
+!11 = !{!"clang version 3.5.0"}
+!12 = !DILocation(line: 3, column: 8, scope: !13)
+!13 = distinct !DILexicalBlock(line: 3, column: 3, file: !1, scope: !4)
+!16 = !DILocation(line: 4, column: 5, scope: !17)
+!17 = distinct !DILexicalBlock(line: 3, column: 36, file: !1, scope: !13)
+!18 = !{!19, !19, i64 0}
+!19 = !{!"int", !20, i64 0}
+!20 = !{!"omnipotent char", !21, i64 0}
+!21 = !{!"Simple C/C++ TBAA"}
+!22 = !DILocation(line: 5, column: 9, scope: !23)
+!23 = distinct !DILexicalBlock(line: 5, column: 9, file: !1, scope: !17)
+!24 = !DILocation(line: 8, column: 1, scope: !4)
+!25 = !DILocation(line: 12, column: 8, scope: !26)
+!26 = distinct !DILexicalBlock(line: 12, column: 3, file: !1, scope: !7)
+!30 = !DILocation(line: 13, column: 5, scope: !26)
+!31 = !DILocation(line: 14, column: 1, scope: !7)
+!32 = !DILocation(line: 18, column: 8, scope: !33)
+!33 = distinct !DILexicalBlock(line: 18, column: 3, file: !1, scope: !8)
+!35 = !DILocation(line: 19, column: 5, scope: !33)
+!36 = !DILocation(line: 20, column: 1, scope: !8)
+!37 = distinct !DILexicalBlock(line: 24, column: 3, file: !1, scope: !46)
+!38 = !DILocation(line: 27, column: 3, scope: !37)
+!39 = !DILocation(line: 31, column: 3, scope: !37)
+!40 = !DILocation(line: 28, column: 9, scope: !37)
+!41 = !DILocation(line: 29, column: 11, scope: !37)
+!42 = !DILocation(line: 29, column: 7, scope: !37)
+!43 = !DILocation(line: 27, column: 32, scope: !37)
+!44 = !DILocation(line: 27, column: 30, scope: !37)
+!45 = !DILocation(line: 27, column: 21, scope: !37)
+!46 = distinct !DISubprogram(name: "test_multiple_failures", line: 26, isLocal: false, isDefinition: true, virtualIndex: 6, flags: DIFlagPrototyped, isOptimized: true, unit: !0, scopeLine: 26, file: !1, scope: !5, type: !6, retainedNodes: !2)
+
+!50 = !{!50, !{!"llvm.loop.distribute.enable"}}

test/Transforms/LoopTransformWarning/unrollandjam-remarks-missed.ll

+; Legacy pass manager
+; RUN: opt < %s -transform-warning -disable-output -pass-remarks-missed=transform-warning -pass-remarks-analysis=transform-warning 2>&1 | FileCheck %s
+; RUN: opt < %s -transform-warning -disable-output -pass-remarks-output=%t.yaml
+; RUN: cat %t.yaml | FileCheck -check-prefix=YAML %s
+
+; New pass manager
+; RUN: opt < %s -passes=transform-warning -disable-output -pass-remarks-missed=transform-warning -pass-remarks-analysis=transform-warning 2>&1 | FileCheck %s
+; RUN: opt < %s -passes=transform-warning -disable-output -pass-remarks-output=%t.yaml
+; RUN: cat %t.yaml | FileCheck -check-prefix=YAML %s
+
+
+; CHECK: warning: source.cpp:19:5: loop not unroll-and-jammed: the optimizer was unable to perform the requested transformation; the transformation might be disabled or specified as part of an unsupported transformation ordering
+
+; YAML:     --- !Failure
+; YAML-NEXT: Pass:            transform-warning
+; YAML-NEXT: Name:            FailedRequestedUnrollAndJamming
+; YAML-NEXT: DebugLoc:        { File: source.cpp, Line: 19, Column: 5 }
+; YAML-NEXT: Function:        _Z17test_array_boundsPiS_i
+; YAML-NEXT: Args:
+; YAML-NEXT:   - String:          'loop not unroll-and-jammed: the optimizer was unable to perform the requested transformation; the transformation might be disabled or specified as part of an unsupported transformation ordering'
+; YAML-NEXT: ...
+
+target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
+
+define void @_Z17test_array_boundsPiS_i(i32* nocapture %A, i32* nocapture readonly %B, i32 %Length) !dbg !8 {
+entry:
+  %cmp9 = icmp sgt i32 %Length, 0, !dbg !32
+  br i1 %cmp9, label %for.body.preheader, label %for.end, !dbg !32
+
+for.body.preheader:                          
+  br label %for.body, !dbg !35
+
+for.body:                                    
+  %indvars.iv = phi i64 [ %indvars.iv.next, %for.body ], [ 0, %for.body.preheader ]
+  %arrayidx = getelementptr inbounds i32, i32* %B, i64 %indvars.iv, !dbg !35
+  %0 = load i32, i32* %arrayidx, align 4, !dbg !35, !tbaa !18
+  %idxprom1 = sext i32 %0 to i64, !dbg !35
+  %arrayidx2 = getelementptr inbounds i32, i32* %A, i64 %idxprom1, !dbg !35
+  %1 = load i32, i32* %arrayidx2, align 4, !dbg !35, !tbaa !18
+  %arrayidx4 = getelementptr inbounds i32, i32* %A, i64 %indvars.iv, !dbg !35
+  store i32 %1, i32* %arrayidx4, align 4, !dbg !35, !tbaa !18
+  %indvars.iv.next = add nuw nsw i64 %indvars.iv, 1, !dbg !32
+  %lftr.wideiv = trunc i64 %indvars.iv.next to i32, !dbg !32
+  %exitcond = icmp eq i32 %lftr.wideiv, %Length, !dbg !32
+  br i1 %exitcond, label %for.end.loopexit, label %for.body, !dbg !32, !llvm.loop !50
+
+for.end.loopexit:                            
+  br label %for.end
+
+for.end:                                      
+  ret void, !dbg !36
+}
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!9, !10}
+!llvm.ident = !{!11}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus, producer: "clang version 3.5.0", isOptimized: true, runtimeVersion: 6, emissionKind: LineTablesOnly, file: !1, enums: !2, retainedTypes: !2, globals: !2, imports: !2)
+!1 = !DIFile(filename: "source.cpp", directory: ".")
+!2 = !{}
+!4 = distinct !DISubprogram(name: "test", line: 1, isLocal: false, isDefinition: true, virtualIndex: 6, flags: DIFlagPrototyped, isOptimized: true, unit: !0, scopeLine: 1, file: !1, scope: !5, type: !6, retainedNodes: !2)
+!5 = !DIFile(filename: "source.cpp", directory: ".")
+!6 = !DISubroutineType(types: !2)
+!7 = distinct !DISubprogram(name: "test_disabled", line: 10, isLocal: false, isDefinition: true, virtualIndex: 6, flags: DIFlagPrototyped, isOptimized: true, unit: !0, scopeLine: 10, file: !1, scope: !5, type: !6, retainedNodes: !2)
+!8 = distinct !DISubprogram(name: "test_array_bounds", line: 16, isLocal: false, isDefinition: true, virtualIndex: 6, flags: DIFlagPrototyped, isOptimized: true, unit: !0, scopeLine: 16, file: !1, scope: !5, type: !6, retainedNodes: !2)
+!9 = !{i32 2, !"Dwarf Version", i32 2}
+!10 = !{i32 2, !"Debug Info Version", i32 3}
+!11 = !{!"clang version 3.5.0"}
+!12 = !DILocation(line: 3, column: 8, scope: !13)
+!13 = distinct !DILexicalBlock(line: 3, column: 3, file: !1, scope: !4)
+!16 = !DILocation(line: 4, column: 5, scope: !17)
+!17 = distinct !DILexicalBlock(line: 3, column: 36, file: !1, scope: !13)
+!18 = !{!19, !19, i64 0}
+!19 = !{!"int", !20, i64 0}
+!20 = !{!"omnipotent char", !21, i64 0}
+!21 = !{!"Simple C/C++ TBAA"}
+!22 = !DILocation(line: 5, column: 9, scope: !23)
+!23 = distinct !DILexicalBlock(line: 5, column: 9, file: !1, scope: !17)
+!24 = !DILocation(line: 8, column: 1, scope: !4)
+!25 = !DILocation(line: 12, column: 8, scope: !26)
+!26 = distinct !DILexicalBlock(line: 12, column: 3, file: !1, scope: !7)
+!30 = !DILocation(line: 13, column: 5, scope: !26)
+!31 = !DILocation(line: 14, column: 1, scope: !7)
+!32 = !DILocation(line: 18, column: 8, scope: !33)
+!33 = distinct !DILexicalBlock(line: 18, column: 3, file: !1, scope: !8)
+!35 = !DILocation(line: 19, column: 5, scope: !33)
+!36 = !DILocation(line: 20, column: 1, scope: !8)
+!37 = distinct !DILexicalBlock(line: 24, column: 3, file: !1, scope: !46)
+!38 = !DILocation(line: 27, column: 3, scope: !37)
+!39 = !DILocation(line: 31, column: 3, scope: !37)
+!40 = !DILocation(line: 28, column: 9, scope: !37)
+!41 = !DILocation(line: 29, column: 11, scope: !37)
+!42 = !DILocation(line: 29, column: 7, scope: !37)
+!43 = !DILocation(line: 27, column: 32, scope: !37)
+!44 = !DILocation(line: 27, column: 30, scope: !37)
+!45 = !DILocation(line: 27, column: 21, scope: !37)
+!46 = distinct !DISubprogram(name: "test_multiple_failures", line: 26, isLocal: false, isDefinition: true, virtualIndex: 6, flags: DIFlagPrototyped, isOptimized: true, unit: !0, scopeLine: 26, file: !1, scope: !5, type: !6, retainedNodes: !2)
+
+!50 = !{!50, !{!"llvm.loop.unroll_and_jam.enable"}}

test/Transforms/LoopTransformWarning/unrolling-remarks-missed.ll

+; Legacy pass manager
+; RUN: opt < %s -transform-warning -disable-output -pass-remarks-missed=transform-warning -pass-remarks-analysis=transform-warning 2>&1 | FileCheck %s
+; RUN: opt < %s -transform-warning -disable-output -pass-remarks-output=%t.yaml
+; RUN: cat %t.yaml | FileCheck -check-prefix=YAML %s
+
+; New pass manager
+; RUN: opt < %s -passes=transform-warning -disable-output -pass-remarks-missed=transform-warning -pass-remarks-analysis=transform-warning 2>&1 | FileCheck %s
+; RUN: opt < %s -passes=transform-warning -disable-output -pass-remarks-output=%t.yaml
+; RUN: cat %t.yaml | FileCheck -check-prefix=YAML %s
+
+
+; CHECK: warning: source.cpp:19:5: loop not unrolled: the optimizer was unable to perform the requested transformation; the transformation might be disabled or specified as part of an unsupported transformation ordering
+
+; YAML:     --- !Failure
+; YAML-NEXT: Pass:            transform-warning
+; YAML-NEXT: Name:            FailedRequestedUnrolling
+; YAML-NEXT: DebugLoc:        { File: source.cpp, Line: 19, Column: 5 }
+; YAML-NEXT: Function:        _Z17test_array_boundsPiS_i
+; YAML-NEXT: Args:
+; YAML-NEXT:   - String:          'loop not unrolled: the optimizer was unable to perform the requested transformation; the transformation might be disabled or specified as part of an unsupported transformation ordering'
+; YAML-NEXT: ...
+
+target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
+
+define void @_Z17test_array_boundsPiS_i(i32* nocapture %A, i32* nocapture readonly %B, i32 %Length) !dbg !8 {
+entry:
+  %cmp9 = icmp sgt i32 %Length, 0, !dbg !32
+  br i1 %cmp9, label %for.body.preheader, label %for.end, !dbg !32
+
+for.body.preheader:                          
+  br label %for.body, !dbg !35
+
+for.body:                                    
+  %indvars.iv = phi i64 [ %indvars.iv.next, %for.body ], [ 0, %for.body.preheader ]
+  %arrayidx = getelementptr inbounds i32, i32* %B, i64 %indvars.iv, !dbg !35
+  %0 = load i32, i32* %arrayidx, align 4, !dbg !35, !tbaa !18
+  %idxprom1 = sext i32 %0 to i64, !dbg !35
+  %arrayidx2 = getelementptr inbounds i32, i32* %A, i64 %idxprom1, !dbg !35
+  %1 = load i32, i32* %arrayidx2, align 4, !dbg !35, !tbaa !18
+  %arrayidx4 = getelementptr inbounds i32, i32* %A, i64 %indvars.iv, !dbg !35
+  store i32 %1, i32* %arrayidx4, align 4, !dbg !35, !tbaa !18
+  %indvars.iv.next = add nuw nsw i64 %indvars.iv, 1, !dbg !32
+  %lftr.wideiv = trunc i64 %indvars.iv.next to i32, !dbg !32
+  %exitcond = icmp eq i32 %lftr.wideiv, %Length, !dbg !32
+  br i1 %exitcond, label %for.end.loopexit, label %for.body, !dbg !32, !llvm.loop !50
+
+for.end.loopexit:                            
+  br label %for.end
+
+for.end:                                      
+  ret void, !dbg !36
+}
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!9, !10}
+!llvm.ident = !{!11}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus, producer: "clang version 3.5.0", isOptimized: true, runtimeVersion: 6, emissionKind: LineTablesOnly, file: !1, enums: !2, retainedTypes: !2, globals: !2, imports: !2)
+!1 = !DIFile(filename: "source.cpp", directory: ".")
+!2 = !{}
+!4 = distinct !DISubprogram(name: "test", line: 1, isLocal: false, isDefinition: true, virtualIndex: 6, flags: DIFlagPrototyped, isOptimized: true, unit: !0, scopeLine: 1, file: !1, scope: !5, type: !6, retainedNodes: !2)
+!5 = !DIFile(filename: "source.cpp", directory: ".")
+!6 = !DISubroutineType(types: !2)
+!7 = distinct !DISubprogram(name: "test_disabled", line: 10, isLocal: false, isDefinition: true, virtualIndex: 6, flags: DIFlagPrototyped, isOptimized: true, unit: !0, scopeLine: 10, file: !1, scope: !5, type: !6, retainedNodes: !2)
+!8 = distinct !DISubprogram(name: "test_array_bounds", line: 16, isLocal: false, isDefinition: true, virtualIndex: 6, flags: DIFlagPrototyped, isOptimized: true, unit: !0, scopeLine: 16, file: !1, scope: !5, type: !6, retainedNodes: !2)
+!9 = !{i32 2, !"Dwarf Version", i32 2}
+!10 = !{i32 2, !"Debug Info Version", i32 3}
+!11 = !{!"clang version 3.5.0"}
+!12 = !DILocation(line: 3, column: 8, scope: !13)
+!13 = distinct !DILexicalBlock(line: 3, column: 3, file: !1, scope: !4)
+!16 = !DILocation(line: 4, column: 5, scope: !17)
+!17 = distinct !DILexicalBlock(line: 3, column: 36, file: !1, scope: !13)
+!18 = !{!19, !19, i64 0}
+!19 = !{!"int", !20, i64 0}
+!20 = !{!"omnipotent char", !21, i64 0}
+!21 = !{!"Simple C/C++ TBAA"}
+!22 = !DILocation(line: 5, column: 9, scope: !23)
+!23 = distinct !DILexicalBlock(line: 5, column: 9, file: !1, scope: !17)
+!24 = !DILocation(line: 8, column: 1, scope: !4)
+!25 = !DILocation(line: 12, column: 8, scope: !26)
+!26 = distinct !DILexicalBlock(line: 12, column: 3, file: !1, scope: !7)
+!30 = !DILocation(line: 13, column: 5, scope: !26)
+!31 = !DILocation(line: 14, column: 1, scope: !7)
+!32 = !DILocation(line: 18, column: 8, scope: !33)
+!33 = distinct !DILexicalBlock(line: 18, column: 3, file: !1, scope: !8)
+!35 = !DILocation(line: 19, column: 5, scope: !33)
+!36 = !DILocation(line: 20, column: 1, scope: !8)
+!37 = distinct !DILexicalBlock(line: 24, column: 3, file: !1, scope: !46)
+!38 = !DILocation(line: 27, column: 3, scope: !37)
+!39 = !DILocation(line: 31, column: 3, scope: !37)
+!40 = !DILocation(line: 28, column: 9, scope: !37)
+!41 = !DILocation(line: 29, column: 11, scope: !37)
+!42 = !DILocation(line: 29, column: 7, scope: !37)
+!43 = !DILocation(line: 27, column: 32, scope: !37)
+!44 = !DILocation(line: 27, column: 30, scope: !37)
+!45 = !DILocation(line: 27, column: 21, scope: !37)
+!46 = distinct !DISubprogram(name: "test_multiple_failures", line: 26, isLocal: false, isDefinition: true, virtualIndex: 6, flags: DIFlagPrototyped, isOptimized: true, unit: !0, scopeLine: 26, file: !1, scope: !5, type: !6, retainedNodes: !2)
+
+!50 = !{!50, !{!"llvm.loop.unroll.enable"}}

test/Transforms/LoopTransformWarning/vectorization-remarks-missed.ll

+; Legacy pass manager
+; RUN: opt < %s -transform-warning -disable-output -pass-remarks-missed=transform-warning -pass-remarks-analysis=transform-warning 2>&1 | FileCheck %s
+; RUN: opt < %s -transform-warning -disable-output -pass-remarks-output=%t.yaml
+; RUN: cat %t.yaml | FileCheck -check-prefix=YAML %s
+
+; New pass manager
+; RUN: opt < %s -passes=transform-warning -disable-output -pass-remarks-missed=transform-warning -pass-remarks-analysis=transform-warning 2>&1 | FileCheck %s
+; RUN: opt < %s -passes=transform-warning -disable-output -pass-remarks-output=%t.yaml
+; RUN: cat %t.yaml | FileCheck -check-prefix=YAML %s
+
+
+; C/C++ code for tests
+; void test(int *A, int Length) {
+; #pragma clang loop vectorize(enable) interleave(enable)
+;   for (int i = 0; i < Length; i++) {
+;     A[i] = i;
+;     if (A[i] > Length)
+;       break;
+;   }
+; }
+; File, line, and column should match those specified in the metadata
+; CHECK: warning: source.cpp:19:5: loop not vectorized: the optimizer was unable to perform the requested transformation; the transformation might be disabled or specified as part of an unsupported transformation ordering
+
+; YAML:     --- !Failure
+; YAML-NEXT: Pass:            transform-warning
+; YAML-NEXT: Name:            FailedRequestedVectorization
+; YAML-NEXT: DebugLoc:        { File: source.cpp, Line: 19, Column: 5 }
+; YAML-NEXT: Function:        _Z17test_array_boundsPiS_i
+; YAML-NEXT: Args:
+; YAML-NEXT:   - String:          'loop not vectorized: the optimizer was unable to perform the requested transformation; the transformation might be disabled or specified as part of an unsupported transformation ordering'
+; YAML-NEXT: ...
+
+target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
+
+define void @_Z17test_array_boundsPiS_i(i32* nocapture %A, i32* nocapture readonly %B, i32 %Length) !dbg !8 {
+entry:
+  %cmp9 = icmp sgt i32 %Length, 0, !dbg !32
+  br i1 %cmp9, label %for.body.preheader, label %for.end, !dbg !32, !llvm.loop !34
+
+for.body.preheader:                          
+  br label %for.body, !dbg !35
+
+for.body:                                    
+  %indvars.iv = phi i64 [ %indvars.iv.next, %for.body ], [ 0, %for.body.preheader ]
+  %arrayidx = getelementptr inbounds i32, i32* %B, i64 %indvars.iv, !dbg !35
+  %0 = load i32, i32* %arrayidx, align 4, !dbg !35, !tbaa !18
+  %idxprom1 = sext i32 %0 to i64, !dbg !35
+  %arrayidx2 = getelementptr inbounds i32, i32* %A, i64 %idxprom1, !dbg !35
+  %1 = load i32, i32* %arrayidx2, align 4, !dbg !35, !tbaa !18
+  %arrayidx4 = getelementptr inbounds i32, i32* %A, i64 %indvars.iv, !dbg !35
+  store i32 %1, i32* %arrayidx4, align 4, !dbg !35, !tbaa !18
+  %indvars.iv.next = add nuw nsw i64 %indvars.iv, 1, !dbg !32
+  %lftr.wideiv = trunc i64 %indvars.iv.next to i32, !dbg !32
+  %exitcond = icmp eq i32 %lftr.wideiv, %Length, !dbg !32
+  br i1 %exitcond, label %for.end.loopexit, label %for.body, !dbg !32, !llvm.loop !34
+
+for.end.loopexit:                            
+  br label %for.end
+
+for.end:                                      
+  ret void, !dbg !36
+}
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!9, !10}
+!llvm.ident = !{!11}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus, producer: "clang version 3.5.0", isOptimized: true, runtimeVersion: 6, emissionKind: LineTablesOnly, file: !1, enums: !2, retainedTypes: !2, globals: !2, imports: !2)
+!1 = !DIFile(filename: "source.cpp", directory: ".")
+!2 = !{}
+!4 = distinct !DISubprogram(name: "test", line: 1, isLocal: false, isDefinition: true, virtualIndex: 6, flags: DIFlagPrototyped, isOptimized: true, unit: !0, scopeLine: 1, file: !1, scope: !5, type: !6, retainedNodes: !2)
+!5 = !DIFile(filename: "source.cpp", directory: ".")
+!6 = !DISubroutineType(types: !2)
+!7 = distinct !DISubprogram(name: "test_disabled", line: 10, isLocal: false, isDefinition: true, virtualIndex: 6, flags: DIFlagPrototyped, isOptimized: true, unit: !0, scopeLine: 10, file: !1, scope: !5, type: !6, retainedNodes: !2)
+!8 = distinct !DISubprogram(name: "test_array_bounds", line: 16, isLocal: false, isDefinition: true, virtualIndex: 6, flags: DIFlagPrototyped, isOptimized: true, unit: !0, scopeLine: 16, file: !1, scope: !5, type: !6, retainedNodes: !2)
+!9 = !{i32 2, !"Dwarf Version", i32 2}
+!10 = !{i32 2, !"Debug Info Version", i32 3}
+!11 = !{!"clang version 3.5.0"}
+!12 = !DILocation(line: 3, column: 8, scope: !13)
+!13 = distinct !DILexicalBlock(line: 3, column: 3, file: !1, scope: !4)
+!14 = !{!14, !15, !15}
+!15 = !{!"llvm.loop.vectorize.enable", i1 true}
+!16 = !DILocation(line: 4, column: 5, scope: !17)
+!17 = distinct !DILexicalBlock(line: 3, column: 36, file: !1, scope: !13)
+!18 = !{!19, !19, i64 0}
+!19 = !{!"int", !20, i64 0}
+!20 = !{!"omnipotent char", !21, i64 0}
+!21 = !{!"Simple C/C++ TBAA"}
+!22 = !DILocation(line: 5, column: 9, scope: !23)
+!23 = distinct !DILexicalBlock(line: 5, column: 9, file: !1, scope: !17)
+!24 = !DILocation(line: 8, column: 1, scope: !4)
+!25 = !DILocation(line: 12, column: 8, scope: !26)
+!26 = distinct !DILexicalBlock(line: 12, column: 3, file: !1, scope: !7)
+!27 = !{!27, !28, !29}
+!28 = !{!"llvm.loop.interleave.count", i32 1}
+!29 = !{!"llvm.loop.vectorize.width", i32 1}
+!30 = !DILocation(line: 13, column: 5, scope: !26)
+!31 = !DILocation(line: 14, column: 1, scope: !7)
+!32 = !DILocation(line: 18, column: 8, scope: !33)
+!33 = distinct !DILexicalBlock(line: 18, column: 3, file: !1, scope: !8)
+!34 = !{!34, !15}
+!35 = !DILocation(line: 19, column: 5, scope: !33)
+!36 = !DILocation(line: 20, column: 1, scope: !8)
+!37 = distinct !DILexicalBlock(line: 24, column: 3, file: !1, scope: !46)
+!38 = !DILocation(line: 27, column: 3, scope: !37)
+!39 = !DILocation(line: 31, column: 3, scope: !37)
+!40 = !DILocation(line: 28, column: 9, scope: !37)
+!41 = !DILocation(line: 29, column: 11, scope: !37)
+!42 = !DILocation(line: 29, column: 7, scope: !37)
+!43 = !DILocation(line: 27, column: 32, scope: !37)
+!44 = !DILocation(line: 27, column: 30, scope: !37)
+!45 = !DILocation(line: 27, column: 21, scope: !37)
+!46 = distinct !DISubprogram(name: "test_multiple_failures", line: 26, isLocal: false, isDefinition: true, virtualIndex: 6, flags: DIFlagPrototyped, isOptimized: true, unit: !0, scopeLine: 26, file: !1, scope: !5, type: !6, retainedNodes: !2)

test/Transforms/LoopUnroll/disable_nonforced.ll

+; RUN: opt -loop-unroll -unroll-count=2 -S < %s | FileCheck %s
+;
+; Check that the disable_nonforced loop property is honored by
+; loop unroll.
+;
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+
+; CHECK-LABEL: @disable_nonforced(
+; CHECK: load
+; CHECK-NOT: load
+define void @disable_nonforced(i32* nocapture %a) {
+entry:
+  br label %for.body
+
+for.body:
+  %indvars.iv = phi i64 [ 0, %entry ], [ %indvars.iv.next, %for.body ]
+  %arrayidx = getelementptr inbounds i32, i32* %a, i64 %indvars.iv
+  %0 = load i32, i32* %arrayidx, align 4
+  %inc = add nsw i32 %0, 1
+  store i32 %inc, i32* %arrayidx, align 4
+  %indvars.iv.next = add nuw nsw i64 %indvars.iv, 1
+  %exitcond = icmp eq i64 %indvars.iv.next, 64
+  br i1 %exitcond, label %for.end, label %for.body, !llvm.loop !0
+
+for.end:
+  ret void
+}
+
+!0 = !{!0, !{!"llvm.loop.disable_nonforced"}}

test/Transforms/LoopUnroll/disable_nonforced_count.ll

+; RUN: opt -loop-unroll -unroll-count=2 -S < %s | FileCheck %s
+;
+; Check whether the llvm.loop.unroll.count loop property overrides
+; llvm.loop.disable_nonforced.
+;
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+
+; CHECK-LABEL: @disable_nonforced_count(
+; CHECK: store
+; CHECK: store
+; CHECK-NOT: store
+define void @disable_nonforced_count(i32* nocapture %a) {
+entry:
+  br label %for.body
+
+for.body:
+  %indvars.iv = phi i64 [ 0, %entry ], [ %indvars.iv.next, %for.body ]
+  %arrayidx = getelementptr inbounds i32, i32* %a, i64 %indvars.iv
+  %0 = load i32, i32* %arrayidx, align 4
+  %inc = add nsw i32 %0, 1
+  store i32 %inc, i32* %arrayidx, align 4
+  %indvars.iv.next = add nuw nsw i64 %indvars.iv, 1
+  %exitcond = icmp eq i64 %indvars.iv.next, 64
+  br i1 %exitcond, label %for.end, label %for.body, !llvm.loop !0
+
+for.end:
+  ret void
+}
+
+!0 = !{!0, !{!"llvm.loop.disable_nonforced"}, !{!"llvm.loop.unroll.count", i32 2}}

test/Transforms/LoopUnroll/disable_nonforced_enable.ll

+; RUN: opt -loop-unroll -unroll-count=2 -S < %s | FileCheck %s
+;
+; Check that the llvm.loop.unroll.enable loop property overrides
+; llvm.loop.disable_nonforced.
+;
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+
+; CHECK-LABEL: @disable_nonforced_enable(
+; CHECK: store
+; CHECK: store
+; CHECK-NOT: store
+define void @disable_nonforced_enable(i32* nocapture %a) {
+entry:
+  br label %for.body
+
+for.body:
+  %indvars.iv = phi i64 [ 0, %entry ], [ %indvars.iv.next, %for.body ]
+  %arrayidx = getelementptr inbounds i32, i32* %a, i64 %indvars.iv
+  %0 = load i32, i32* %arrayidx, align 4
+  %inc = add nsw i32 %0, 1
+  store i32 %inc, i32* %arrayidx, align 4
+  %indvars.iv.next = add nuw nsw i64 %indvars.iv, 1
+  %exitcond = icmp eq i64 %indvars.iv.next, 64
+  br i1 %exitcond, label %for.end, label %for.body, !llvm.loop !0
+
+for.end:
+  ret void
+}
+
+!0 = !{!0, !{!"llvm.loop.disable_nonforced"}, !{!"llvm.loop.unroll.enable"}}

test/Transforms/LoopUnroll/disable_nonforced_full.ll

+; RUN: opt -loop-unroll -S < %s | FileCheck %s
+;
+; Check that the llvm.loop.unroll.full loop property overrides
+; llvm.loop.disable_nonforced.
+;
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+
+; CHECK-LABEL: @disable_nonforced_full(
+; CHECK: store
+; CHECK: store
+; CHECK: store
+; CHECK: store
+; CHECK-NOT: store
+define void @disable_nonforced_full(i32* nocapture %a) {
+entry:
+  br label %for.body
+
+for.body:
+  %indvars.iv = phi i64 [ 0, %entry ], [ %indvars.iv.next, %for.body ]
+  %arrayidx = getelementptr inbounds i32, i32* %a, i64 %indvars.iv
+  %0 = load i32, i32* %arrayidx, align 4
+  %inc = add nsw i32 %0, 1
+  store i32 %inc, i32* %arrayidx, align 4
+  %indvars.iv.next = add nuw nsw i64 %indvars.iv, 1
+  %exitcond = icmp eq i64 %indvars.iv.next, 4
+  br i1 %exitcond, label %for.end, label %for.body, !llvm.loop !0
+
+for.end:
+  ret void
+}
+
+!0 = !{!0, !{!"llvm.loop.disable_nonforced"}, !{!"llvm.loop.unroll.full"}}

test/Transforms/LoopUnroll/followup.ll

+; RUN: opt < %s -S -loop-unroll -unroll-count=2 | FileCheck %s -check-prefixes=COUNT,COMMON
+; RUN: opt < %s -S -loop-unroll -unroll-runtime=true -unroll-runtime-epilog=true  | FileCheck %s -check-prefixes=EPILOG,COMMON
+; RUN: opt < %s -S -loop-unroll -unroll-runtime=true -unroll-runtime-epilog=false | FileCheck %s -check-prefixes=PROLOG,COMMON
+;
+; Check that followup-attributes are applied after LoopUnroll.
+;
+target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64-S128"
+
+define i32 @test(i32* nocapture %a, i32 %n) nounwind uwtable readonly {
+entry:
+  %cmp1 = icmp eq i32 %n, 0
+  br i1 %cmp1, label %for.end, label %for.body
+
+for.body:                                         ; preds = %for.body, %entry
+  %indvars.iv = phi i64 [ %indvars.iv.next, %for.body ], [ 0, %entry ]
+  %sum.02 = phi i32 [ %add, %for.body ], [ 0, %entry ]
+  %arrayidx = getelementptr inbounds i32, i32* %a, i64 %indvars.iv
+  %0 = load i32, i32* %arrayidx, align 4
+  %add = add nsw i32 %0, %sum.02
+  %indvars.iv.next = add i64 %indvars.iv, 1
+  %lftr.wideiv = trunc i64 %indvars.iv.next to i32
+  %exitcond = icmp eq i32 %lftr.wideiv, %n
+  br i1 %exitcond, label %for.end, label %for.body, !llvm.loop !4
+
+for.end:                                          ; preds = %for.body, %entry
+  %sum.0.lcssa = phi i32 [ 0, %entry ], [ %add, %for.body ]
+  ret i32 %sum.0.lcssa
+}
+
+!1 = !{!"llvm.loop.unroll.followup_all", !{!"FollowupAll"}}
+!2 = !{!"llvm.loop.unroll.followup_unrolled", !{!"FollowupUnrolled"}}
+!3 = !{!"llvm.loop.unroll.followup_remainder", !{!"FollowupRemainder"}}
+!4 = distinct !{!4, !1, !2, !3}
+
+
+; COMMON-LABEL: @test(
+
+
+; COUNT: br i1 %exitcond.1, label %for.end.loopexit, label %for.body, !llvm.loop ![[LOOP:[0-9]+]]
+
+; COUNT: ![[FOLLOWUP_ALL:[0-9]+]] = !{!"FollowupAll"}
+; COUNT: ![[FOLLOWUP_UNROLLED:[0-9]+]] = !{!"FollowupUnrolled"}
+; COUNT: ![[LOOP]] = distinct !{![[LOOP]], ![[FOLLOWUP_ALL]], ![[FOLLOWUP_UNROLLED]]}
+
+
+; EPILOG: br i1 %niter.ncmp.7, label %for.end.loopexit.unr-lcssa.loopexit, label %for.body, !llvm.loop ![[LOOP_0:[0-9]+]]
+; EPILOG: br i1 %epil.iter.cmp, label %for.body.epil, label %for.end.loopexit.epilog-lcssa, !llvm.loop ![[LOOP_2:[0-9]+]]
+
+; EPILOG: ![[LOOP_0]] = distinct !{![[LOOP_0]], ![[FOLLOWUP_ALL:[0-9]+]], ![[FOLLOWUP_UNROLLED:[0-9]+]]}
+; EPILOG: ![[FOLLOWUP_ALL]] = !{!"FollowupAll"}
+; EPILOG: ![[FOLLOWUP_UNROLLED]] = !{!"FollowupUnrolled"}
+; EPILOG: ![[LOOP_2]] = distinct !{![[LOOP_2]], ![[FOLLOWUP_ALL]], ![[FOLLOWUP_REMAINDER:[0-9]+]]}
+; EPILOG: ![[FOLLOWUP_REMAINDER]] = !{!"FollowupRemainder"}
+
+
+; PROLOG:  br i1 %prol.iter.cmp, label %for.body.prol, label %for.body.prol.loopexit.unr-lcssa, !llvm.loop ![[LOOP_0:[0-9]+]]
+; PROLOG:  br i1 %exitcond.7, label %for.end.loopexit.unr-lcssa, label %for.body, !llvm.loop ![[LOOP_2:[0-9]+]]
+
+; PROLOG: ![[LOOP_0]] = distinct !{![[LOOP_0]], ![[FOLLOWUP_ALL:[0-9]+]], ![[FOLLOWUP_REMAINDER:[0-9]+]]}
+; PROLOG: ![[FOLLOWUP_ALL]] = !{!"FollowupAll"}
+; PROLOG: ![[FOLLOWUP_REMAINDER]] = !{!"FollowupRemainder"}
+; PROLOG: ![[LOOP_2]] = distinct !{![[LOOP_2]], ![[FOLLOWUP_ALL]], ![[FOLLOWUP_UNROLLED:[0-9]+]]}
+; PROLOG: ![[FOLLOWUP_UNROLLED]] = !{!"FollowupUnrolled"}

test/Transforms/LoopUnrollAndJam/disable_nonforced.ll

+; RUN: opt -loop-unroll-and-jam -allow-unroll-and-jam -unroll-and-jam-count=2 -S < %s | FileCheck %s
+;
+; Check that the disable_nonforced loop property is honored by
+; loop unroll-and-jam.
+;
+target datalayout = "e-m:e-p:32:32-i64:64-v128:64:128-a:0:32-n32-S64"
+
+; CHECK-LABEL: disable_nonforced
+; CHECK: load
+; CHECK-NOT: load
+define void @disable_nonforced(i32 %I, i32 %J, i32* noalias nocapture %A, i32* noalias nocapture readonly %B) {
+entry:
+  %cmp = icmp ne i32 %J, 0
+  %cmp122 = icmp ne i32 %I, 0
+  %or.cond = and i1 %cmp, %cmp122
+  br i1 %or.cond, label %for.outer.preheader, label %for.end
+
+for.outer.preheader:
+  br label %for.outer
+
+for.outer:
+  %i.us = phi i32 [ %add8.us, %for.latch ], [ 0, %for.outer.preheader ]
+  br label %for.inner
+
+for.inner:
+  %j.us = phi i32 [ 0, %for.outer ], [ %inc.us, %for.inner ]
+  %sum1.us = phi i32 [ 0, %for.outer ], [ %add.us, %for.inner ]
+  %arrayidx.us = getelementptr inbounds i32, i32* %B, i32 %j.us
+  %0 = load i32, i32* %arrayidx.us, align 4
+  %add.us = add i32 %0, %sum1.us
+  %inc.us = add nuw i32 %j.us, 1
+  %exitcond = icmp eq i32 %inc.us, %J
+  br i1 %exitcond, label %for.latch, label %for.inner
+
+for.latch:
+  %add.us.lcssa = phi i32 [ %add.us, %for.inner ]
+  %arrayidx6.us = getelementptr inbounds i32, i32* %A, i32 %i.us
+  store i32 %add.us.lcssa, i32* %arrayidx6.us, align 4
+  %add8.us = add nuw i32 %i.us, 1
+  %exitcond25 = icmp eq i32 %add8.us, %I
+  br i1 %exitcond25, label %for.end.loopexit, label %for.outer, !llvm.loop !0
+
+for.end.loopexit:
+  br label %for.end
+
+for.end:
+  ret void
+}
+
+!0 = distinct !{!0, !{!"llvm.loop.disable_nonforced"}}

test/Transforms/LoopUnrollAndJam/disable_nonforced_count.ll

+; RUN: opt -loop-unroll-and-jam -allow-unroll-and-jam -S < %s | FileCheck %s
+;
+; Verify that the llvm.loop.unroll_and_jam.count loop property overrides
+; llvm.loop.disable_nonforced.
+;
+target datalayout = "e-m:e-p:32:32-i64:64-v128:64:128-a:0:32-n32-S64"
+
+; CHECK-LABEL: @disable_nonforced_enable(
+; CHECK: load
+; CHECK: load
+; CHECK-NOT: load
+; CHECK: br i1
+define void @disable_nonforced_enable(i32 %I, i32 %J, i32* noalias nocapture %A, i32* noalias nocapture readonly %B) {
+entry:
+  %cmp = icmp ne i32 %J, 0
+  %cmp122 = icmp ne i32 %I, 0
+  %or.cond = and i1 %cmp, %cmp122
+  br i1 %or.cond, label %for.outer.preheader, label %for.end
+
+for.outer.preheader:
+  br label %for.outer
+
+for.outer:
+  %i.us = phi i32 [ %add8.us, %for.latch ], [ 0, %for.outer.preheader ]
+  br label %for.inner
+
+for.inner:
+  %j.us = phi i32 [ 0, %for.outer ], [ %inc.us, %for.inner ]
+  %sum1.us = phi i32 [ 0, %for.outer ], [ %add.us, %for.inner ]
+  %arrayidx.us = getelementptr inbounds i32, i32* %B, i32 %j.us
+  %0 = load i32, i32* %arrayidx.us, align 4
+  %add.us = add i32 %0, %sum1.us
+  %inc.us = add nuw i32 %j.us, 1
+  %exitcond = icmp eq i32 %inc.us, %J
+  br i1 %exitcond, label %for.latch, label %for.inner
+
+for.latch:
+  %add.us.lcssa = phi i32 [ %add.us, %for.inner ]
+  %arrayidx6.us = getelementptr inbounds i32, i32* %A, i32 %i.us
+  store i32 %add.us.lcssa, i32* %arrayidx6.us, align 4
+  %add8.us = add nuw i32 %i.us, 1
+  %exitcond25 = icmp eq i32 %add8.us, %I
+  br i1 %exitcond25, label %for.end.loopexit, label %for.outer, !llvm.loop !0
+
+for.end.loopexit:
+  br label %for.end
+
+for.end:
+  ret void
+}
+
+!0 = distinct !{!0, !{!"llvm.loop.disable_nonforced"}, !{!"llvm.loop.unroll_and_jam.count", i32 2}}

test/Transforms/LoopUnrollAndJam/disable_nonforced_enable.ll

+; RUN: opt -loop-unroll-and-jam -allow-unroll-and-jam -unroll-and-jam-count=2 -S < %s | FileCheck %s
+;
+; Verify that the llvm.loop.unroll_and_jam.enable loop property
+; overrides llvm.loop.disable_nonforced.
+;
+target datalayout = "e-m:e-p:32:32-i64:64-v128:64:128-a:0:32-n32-S64"
+
+; CHECK-LABEL: disable_nonforced_enable
+; CHECK: load
+; CHECK: load
+; CHECK-NOT: load
+; CHECK: br i1
+define void @disable_nonforced_enable(i32 %I, i32 %J, i32* noalias nocapture %A, i32* noalias nocapture readonly %B) {
+entry:
+  %cmp = icmp ne i32 %J, 0
+  %cmp122 = icmp ne i32 %I, 0
+  %or.cond = and i1 %cmp, %cmp122
+  br i1 %or.cond, label %for.outer.preheader, label %for.end
+
+for.outer.preheader:
+  br label %for.outer
+
+for.outer:
+  %i.us = phi i32 [ %add8.us, %for.latch ], [ 0, %for.outer.preheader ]
+  br label %for.inner
+
+for.inner:
+  %j.us = phi i32 [ 0, %for.outer ], [ %inc.us, %for.inner ]
+  %sum1.us = phi i32 [ 0, %for.outer ], [ %add.us, %for.inner ]
+  %arrayidx.us = getelementptr inbounds i32, i32* %B, i32 %j.us
+  %0 = load i32, i32* %arrayidx.us, align 4
+  %add.us = add i32 %0, %sum1.us
+  %inc.us = add nuw i32 %j.us, 1
+  %exitcond = icmp eq i32 %inc.us, %J
+  br i1 %exitcond, label %for.latch, label %for.inner
+
+for.latch:
+  %add.us.lcssa = phi i32 [ %add.us, %for.inner ]
+  %arrayidx6.us = getelementptr inbounds i32, i32* %A, i32 %i.us
+  store i32 %add.us.lcssa, i32* %arrayidx6.us, align 4
+  %add8.us = add nuw i32 %i.us, 1
+  %exitcond25 = icmp eq i32 %add8.us, %I
+  br i1 %exitcond25, label %for.end.loopexit, label %for.outer, !llvm.loop !0
+
+for.end.loopexit:
+  br label %for.end
+
+for.end:
+  ret void
+}
+
+!0 = distinct !{!0, !{!"llvm.loop.disable_nonforced"}, !{!"llvm.loop.unroll_and_jam.enable"}}

test/Transforms/LoopUnrollAndJam/followup.ll

+; RUN: opt -basicaa -tbaa -loop-unroll-and-jam -allow-unroll-and-jam -unroll-and-jam-count=4 -unroll-remainder < %s -S | FileCheck %s
+;
+; Check that followup attributes are set in the new loops.
+;
+target datalayout = "e-m:e-p:32:32-i64:64-v128:64:128-a:0:32-n32-S64"
+
+define void @followup(i32 %I, i32 %J, i32* noalias nocapture %A, i32* noalias nocapture readonly %B) {
+entry:
+  %cmp = icmp ne i32 %J, 0
+  %cmp122 = icmp ne i32 %I, 0
+  %or.cond = and i1 %cmp, %cmp122
+  br i1 %or.cond, label %for.outer.preheader, label %for.end
+
+for.outer.preheader:
+  br label %for.outer
+
+for.outer:
+  %i.us = phi i32 [ %add8.us, %for.latch ], [ 0, %for.outer.preheader ]
+  br label %for.inner
+
+for.inner:
+  %j.us = phi i32 [ 0, %for.outer ], [ %inc.us, %for.inner ]
+  %sum1.us = phi i32 [ 0, %for.outer ], [ %add.us, %for.inner ]
+  %arrayidx.us = getelementptr inbounds i32, i32* %B, i32 %j.us
+  %0 = load i32, i32* %arrayidx.us, align 4
+  %add.us = add i32 %0, %sum1.us
+  %inc.us = add nuw i32 %j.us, 1
+  %exitcond = icmp eq i32 %inc.us, %J
+  br i1 %exitcond, label %for.latch, label %for.inner
+
+for.latch:
+  %add.us.lcssa = phi i32 [ %add.us, %for.inner ]
+  %arrayidx6.us = getelementptr inbounds i32, i32* %A, i32 %i.us
+  store i32 %add.us.lcssa, i32* %arrayidx6.us, align 4
+  %add8.us = add nuw i32 %i.us, 1
+  %exitcond25 = icmp eq i32 %add8.us, %I
+  br i1 %exitcond25, label %for.end.loopexit, label %for.outer, !llvm.loop !0
+
+for.end.loopexit:
+  br label %for.end
+
+for.end:
+  ret void
+}
+
+!0 = !{!0, !1, !2, !3, !4, !6}
+!1 = !{!"llvm.loop.unroll_and_jam.enable"}
+!2 = !{!"llvm.loop.unroll_and_jam.followup_outer", !{!"FollowupOuter"}}
+!3 = !{!"llvm.loop.unroll_and_jam.followup_inner", !{!"FollowupInner"}}
+!4 = !{!"llvm.loop.unroll_and_jam.followup_all", !{!"FollowupAll"}}
+!6 = !{!"llvm.loop.unroll_and_jam.followup_remainder_inner", !{!"FollowupRemainderInner"}}
+
+
+; CHECK: br i1 %exitcond.3, label %for.latch, label %for.inner, !llvm.loop ![[LOOP_INNER:[0-9]+]]
+; CHECK: br i1 %niter.ncmp.3, label %for.end.loopexit.unr-lcssa.loopexit, label %for.outer, !llvm.loop ![[LOOP_OUTER:[0-9]+]]
+; CHECK: br i1 %exitcond.epil, label %for.latch.epil, label %for.inner.epil, !llvm.loop ![[LOOP_REMAINDER_INNER:[0-9]+]]
+; CHECK: br i1 %exitcond.epil.1, label %for.latch.epil.1, label %for.inner.epil.1, !llvm.loop ![[LOOP_REMAINDER_INNER]]
+; CHECK: br i1 %exitcond.epil.2, label %for.latch.epil.2, label %for.inner.epil.2, !llvm.loop ![[LOOP_REMAINDER_INNER]]
+
+; CHECK: ![[LOOP_INNER]] = distinct !{![[LOOP_INNER]], ![[FOLLOWUP_ALL:[0-9]+]], ![[FOLLOWUP_INNER:[0-9]+]]}
+; CHECK: ![[FOLLOWUP_ALL]] = !{!"FollowupAll"}
+; CHECK: ![[FOLLOWUP_INNER]] = !{!"FollowupInner"}
+; CHECK: ![[LOOP_OUTER]] = distinct !{![[LOOP_OUTER]], ![[FOLLOWUP_ALL]], ![[FOLLOWUP_OUTER:[0-9]+]]}
+; CHECK: ![[FOLLOWUP_OUTER]] = !{!"FollowupOuter"}
+; CHECK: ![[LOOP_REMAINDER_INNER]] = distinct !{![[LOOP_REMAINDER_INNER]], ![[FOLLOWUP_ALL]], ![[FOLLOWUP_REMAINDER_INNER:[0-9]+]]}
+; CHECK: ![[FOLLOWUP_REMAINDER_INNER]] = !{!"FollowupRemainderInner"}

test/Transforms/LoopUnrollAndJam/pragma.ll

 !3 = distinct !{!3, !4}
 !4 = distinct !{!"llvm.loop.unroll_and_jam.count", i32 8}
 !5 = distinct !{!5, !6}
 !6 = distinct !{!"llvm.loop.unroll_and_jam.enable"}
 !7 = distinct !{!7, !8}
 !8 = distinct !{!"llvm.loop.unroll.disable"}
 !9 = distinct !{!9, !10}
 !10 = distinct !{!"llvm.loop.unroll.enable"}
-!11 = distinct !{!11, !8, !6}
+!11 = distinct !{!11, !8, !6}
 

test/Transforms/LoopVectorize/X86/vectorization-remarks-missed.ll

-; RUN: opt < %s -loop-vectorize -S -pass-remarks-missed='loop-vectorize' -pass-remarks-analysis='loop-vectorize' 2>&1 | FileCheck %s
-; RUN: opt < %s -loop-vectorize -o /dev/null -pass-remarks-output=%t.yaml
+; RUN: opt < %s -loop-vectorize -transform-warning -S -pass-remarks-missed='loop-vectorize' -pass-remarks-analysis='loop-vectorize' 2>&1 | FileCheck %s
+; RUN: opt < %s -loop-vectorize -transform-warning -o /dev/null -pass-remarks-output=%t.yaml
 ; RUN: cat %t.yaml | FileCheck -check-prefix=YAML %s
 
-; RUN: opt < %s -passes=loop-vectorize -S -pass-remarks-missed='loop-vectorize' -pass-remarks-analysis='loop-vectorize' 2>&1 | FileCheck %s
-; RUN: opt < %s -passes=loop-vectorize -o /dev/null -pass-remarks-output=%t.yaml
+; RUN: opt < %s -passes=loop-vectorize,transform-warning -S -pass-remarks-missed='loop-vectorize' -pass-remarks-analysis='loop-vectorize'  2>&1 | FileCheck %s
+; RUN: opt < %s -passes=loop-vectorize,transform-warning -o /dev/null -pass-remarks-output=%t.yaml
 ; RUN: cat %t.yaml | FileCheck -check-prefix=YAML %s
 
 ; C/C++ code for tests
 ; void test(int *A, int Length) {
 ; #pragma clang loop vectorize(enable) interleave(enable)
 ;   for (int i = 0; i < Length; i++) {
 ;     A[i] = i;
 ;     if (A[i] > Length)

 
 ; void test_array_bounds(int *A, int *B, int Length) {
 ; #pragma clang loop vectorize(enable)
 ;   for (int i = 0; i < Length; i++)
 ;     A[i] = A[B[i]];
 ; }
 ; CHECK: remark: source.cpp:19:5: loop not vectorized: cannot identify array bounds
 ; CHECK: remark: source.cpp:19:5: loop not vectorized
-; CHECK: warning: source.cpp:19:5: loop not vectorized: failed explicitly specified loop vectorization
+; CHECK: warning: source.cpp:19:5: loop not vectorized: the optimizer was unable to perform the requested transformation; the transformation might be disabled or specified as part of an unsupported transformation ordering
 
 ; int foo();
 ; void test_multiple_failures(int *A) {
 ;   int k = 0;
 ; #pragma clang loop vectorize(enable) interleave(enable)
 ;   for (int i = 0; i < 1000; i+=A[i]) {
 ;     if (A[i])
 ;       k = foo();

 ; YAML-NEXT: Function:        _Z17test_array_boundsPiS_i
 ; YAML-NEXT: Args:
 ; YAML-NEXT:   - String:          loop not vectorized
 ; YAML-NEXT:   - String:          ' (Force='
 ; YAML-NEXT:   - Force:           'true'
 ; YAML-NEXT:   - String:          ')'
 ; YAML-NEXT: ...
 ; YAML-NEXT: --- !Failure
-; YAML-NEXT: Pass:            loop-vectorize
+; YAML-NEXT: Pass:            transform-warning
 ; YAML-NEXT: Name:            FailedRequestedVectorization
 ; YAML-NEXT: DebugLoc:        { File: source.cpp, Line: 19, Column: 5 }
 ; YAML-NEXT: Function:        _Z17test_array_boundsPiS_i
 ; YAML-NEXT: Args:
-; YAML-NEXT:   - String:          'loop not vectorized: '
-; YAML-NEXT:   - String:          failed explicitly specified loop vectorization
+; YAML-NEXT:   - String:          'loop not vectorized: the optimizer was unable to perform the requested transformation; the transformation might be disabled or specified as part of an unsupported transformation ordering'
 ; YAML-NEXT: ...
 ; YAML-NEXT: --- !Analysis
 ; YAML-NEXT: Pass:            loop-vectorize
 ; YAML-NEXT: Name:            NoCFGForSelect
 ; YAML-NEXT: DebugLoc:        { File: source.cpp, Line: 29, Column: 7 }
 ; YAML-NEXT: Function:        test_multiple_failures
 ; YAML-NEXT: Args:
 ; YAML-NEXT:   - String:          'loop not vectorized: '

test/Transforms/LoopVectorize/disable_nonforced.ll

+; RUN: opt -loop-vectorize -force-vector-interleave=1 -force-vector-width=2 -S < %s | FileCheck %s
+;
+; Check that the disable_nonforced loop property is honored by the
+; loop vectorizer.
+;
+target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64-S128"
+
+; CHECK-LABEL: @disable_nonforced(
+; CHECK-NOT: x i32>
+define void @disable_nonforced(i32* nocapture %a, i32 %n) {
+entry:
+  %cmp4 = icmp sgt i32 %n, 0
+  br i1 %cmp4, label %for.body, label %for.end
+
+for.body:
+  %indvars.iv = phi i64 [ %indvars.iv.next, %for.body ], [ 0, %entry ]
+  %arrayidx = getelementptr inbounds i32, i32* %a, i64 %indvars.iv
+  %0 = trunc i64 %indvars.iv to i32
+  store i32 %0, i32* %arrayidx, align 4
+  %indvars.iv.next = add i64 %indvars.iv, 1
+  %lftr.wideiv = trunc i64 %indvars.iv.next to i32
+  %exitcond = icmp eq i32 %lftr.wideiv, %n
+  br i1 %exitcond, label %for.end, label %for.body, !llvm.loop !0
+
+for.end:
+  ret void
+}
+
+!0 = !{!0, !{!"llvm.loop.disable_nonforced"}}

test/Transforms/LoopVectorize/disable_nonforced_enable.ll

+; RUN: opt -loop-vectorize -force-vector-interleave=1 -force-vector-width=2 -S < %s | FileCheck %s
+;
+; Check whether the llvm.loop.vectorize.enable loop property overrides
+; llvm.loop.disable_nonforced.
+;
+target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64-S128"
+
+; CHECK-LABEL: @disable_nonforced_enable(
+; CHECK: store <2 x i32>
+define void @disable_nonforced_enable(i32* nocapture %a, i32 %n) {
+entry:
+  %cmp4 = icmp sgt i32 %n, 0
+  br i1 %cmp4, label %for.body, label %for.end
+
+for.body:
+  %indvars.iv = phi i64 [ %indvars.iv.next, %for.body ], [ 0, %entry ]
+  %arrayidx = getelementptr inbounds i32, i32* %a, i64 %indvars.iv
+  %0 = trunc i64 %indvars.iv to i32
+  store i32 %0, i32* %arrayidx, align 4
+  %indvars.iv.next = add i64 %indvars.iv, 1
+  %lftr.wideiv = trunc i64 %indvars.iv.next to i32
+  %exitcond = icmp eq i32 %lftr.wideiv, %n
+  br i1 %exitcond, label %for.end, label %for.body, !llvm.loop !0
+
+for.end:
+  ret void
+}
+
+!0 = !{!0, !{!"llvm.loop.disable_nonforced"}, !{!"llvm.loop.vectorize.enable", i32 1}}

test/Transforms/LoopVectorize/followup.ll

+; RUN: opt -loop-vectorize -force-vector-width=4 -force-vector-interleave=1 -S < %s | FileCheck %s
+;
+; Check that the followup loop attributes are applied.
+;
+target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64-S128"
+
+define void @followup(i32* nocapture %a, i32 %n) {
+entry:
+  %cmp4 = icmp sgt i32 %n, 0
+  br i1 %cmp4, label %for.body, label %for.end
+
+for.body:
+  %indvars.iv = phi i64 [ %indvars.iv.next, %for.body ], [ 0, %entry ]
+  %arrayidx = getelementptr inbounds i32, i32* %a, i64 %indvars.iv
+  %0 = trunc i64 %indvars.iv to i32
+  store i32 %0, i32* %arrayidx, align 4
+  %indvars.iv.next = add i64 %indvars.iv, 1
+  %lftr.wideiv = trunc i64 %indvars.iv.next to i32
+  %exitcond = icmp eq i32 %lftr.wideiv, %n
+  br i1 %exitcond, label %for.end, label %for.body, !llvm.loop !0
+
+for.end:
+  ret void
+}
+
+!0 = distinct !{!0, !3, !4, !5}
+!3 = !{!"llvm.loop.vectorize.followup_vectorized", !{!"FollowupVectorized"}}
+!4 = !{!"llvm.loop.vectorize.followup_epilogue", !{!"FollowupEpilogue"}}
+!5 = !{!"llvm.loop.vectorize.followup_all", !{!"FollowupAll"}}
+
+
+; CHECK-LABEL @followup(
+
+; CHECK-LABEL: vector.body:
+; CHECK: br i1 %13, label %middle.block, label %vector.body, !llvm.loop ![[LOOP_VECTOR:[0-9]+]]
+; CHECK-LABEL: for.body:
+; CHECK: br i1 %exitcond, label %for.end.loopexit, label %for.body, !llvm.loop ![[LOOP_EPILOGUE:[0-9]+]]
+
+; CHECK: ![[LOOP_VECTOR]] = distinct !{![[LOOP_VECTOR]], ![[FOLLOWUP_ALL:[0-9]+]], ![[FOLLOWUP_VECTORIZED:[0-9]+]]}
+; CHECK: ![[FOLLOWUP_ALL]] = !{!"FollowupAll"}
+; CHECK: ![[FOLLOWUP_VECTORIZED:[0-9]+]] = !{!"FollowupVectorized"}
+; CHECK: ![[LOOP_EPILOGUE]] = distinct !{![[LOOP_EPILOGUE]], ![[FOLLOWUP_ALL]], ![[FOLLOWUP_EPILOGUE:[0-9]+]]}
+; CHECK: ![[FOLLOWUP_EPILOGUE]] = !{!"FollowupEpilogue"}

test/Transforms/LoopVectorize/no_array_bounds.ll

-; RUN: opt < %s -loop-vectorize -S 2>&1 | FileCheck %s
+; RUN: opt < %s -loop-vectorize -transform-warning -S 2>&1 | FileCheck %s
 
 ; Verify warning is generated when vectorization/ interleaving is explicitly specified and fails to occur.
-; CHECK: warning: no_array_bounds.cpp:5:5: loop not vectorized: failed explicitly specified loop vectorization
-; CHECK: warning: no_array_bounds.cpp:10:5: loop not interleaved: failed explicitly specified loop interleaving
+; CHECK: warning: no_array_bounds.cpp:5:5: loop not vectorized: the optimizer was unable to perform the requested transformation; the transformation might be disabled or specified as part of an unsupported transformation ordering
+; CHECK: warning: no_array_bounds.cpp:10:5: loop not interleaved: the optimizer was unable to perform the requested transformation; the transformation might be disabled or specified as part of an unsupported transformation ordering
 
 ;  #pragma clang loop vectorize(enable)
 ;  for (int i = 0; i < number; i++) {
 ;    A[B[i]]++;
 ;  }
 
 ;  #pragma clang loop vectorize(disable) interleave(enable)
 ;  for (int i = 0; i < number; i++) {

test/Transforms/LoopVectorize/no_switch.ll

-; RUN: opt < %s -loop-vectorize -force-vector-width=4 -S 2>&1 | FileCheck %s
-; RUN: opt < %s -loop-vectorize -force-vector-width=1 -S 2>&1 | FileCheck %s -check-prefix=NOANALYSIS
-; RUN: opt < %s -loop-vectorize -force-vector-width=4 -pass-remarks-missed='loop-vectorize' -S 2>&1 | FileCheck %s -check-prefix=MOREINFO
+; RUN: opt < %s -loop-vectorize -force-vector-width=4 -transform-warning -S 2>&1 | FileCheck %s
+; RUN: opt < %s -loop-vectorize -force-vector-width=1 -transform-warning -S 2>&1 | FileCheck %s -check-prefix=NOANALYSIS
+; RUN: opt < %s -loop-vectorize -force-vector-width=4 -transform-warning -pass-remarks-missed='loop-vectorize' -S 2>&1 | FileCheck %s -check-prefix=MOREINFO
 
 ; CHECK: remark: source.cpp:4:5: loop not vectorized: loop contains a switch statement
-; CHECK: warning: source.cpp:4:5: loop not vectorized: failed explicitly specified loop vectorization
+; CHECK: warning: source.cpp:4:5: loop not vectorized: the optimizer was unable to perform the requested transformation; the transformation might be disabled or specified as part of an unsupported transformation ordering
 
 ; NOANALYSIS-NOT: remark: {{.*}}
-; NOANALYSIS: warning: source.cpp:4:5: loop not interleaved: failed explicitly specified loop interleaving
+; NOANALYSIS: warning: source.cpp:4:5: loop not vectorized: the optimizer was unable to perform the requested transformation; the transformation might be disabled or specified as part of an unsupported transformation ordering
 
 ; MOREINFO: remark: source.cpp:4:5: loop not vectorized: loop contains a switch statement
 ; MOREINFO: remark: source.cpp:4:5: loop not vectorized (Force=true, Vector Width=4)
-; MOREINFO: warning: source.cpp:4:5: loop not vectorized: failed explicitly specified loop vectorization
+; MOREINFO: warning: source.cpp:4:5: loop not vectorized: the optimizer was unable to perform the requested transformation; the transformation might be disabled or specified as part of an unsupported transformation ordering
 
 ; CHECK: _Z11test_switchPii
 ; CHECK-NOT: x i32>
 ; CHECK: ret
 
 target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
 
 ; Function Attrs: nounwind optsize ssp uwtable