[LAA] Analyze pointers forked by a select

[huntergr]

Summary

Given a function like the following:

void forked_ptrs_different_base_same_offset(float *Base1, float *Base2, float *Dest, int *Preds) {
  for (int i=0; i<100; i++) {
    if (Pred[i] != 0) {
      Dest[i] = Base1[i];
    } else {
      Dest[i] = Base2[i];
    }
  }
}

LLVM will optimize the IR to a single load using a pointer determined by a select instruction:

%spec.select = select i1 %cmp1.not, float* %Base2, float* %Base1
%.sink.in = getelementptr inbounds float, float* %spec.select, i64 %indvars.iv 
%.sink = load float, float* %.sink.in, align 4

LAA is currently unable to analyze such IR, since ScalarEvolution will return a SCEVUnknown for the pointer operand for the load.

This patch adds initial optional support for analyzing both possibilities for the pointer and allowing LAA to generate runtime checks for the bounds if required.

[huntergr]

Rebased, ran clang-format over the patch.

[david-arm]

Hi @huntergr, apologies for delay reviewing this patch! I've not finished reviewing it, but I've left some comments that I have so far. Thanks!

llvm/include/llvm/Analysis/LoopAccessAnalysis.h

355

If we're only ever going to support two forks couldn't we make this simpler by just having:

unsigned Members[2];

instead or is this a real pain to implement? Or is the idea that we may want to extend the fork to allow more than 2 in future?

378

Again, does this need to be a SmallVector and can it just be const SCEV *Starts[2];?

llvm/include/llvm/Analysis/ScalarEvolution.h

444 ↗

(On Diff #370905)

Hi Graham, it feels slightly awkward having to essentially redefine a ForkedPointer as a pair in the same way as ForkedPtrs in llvm/include/llvm/Analysis/LoopAccessAnalysis.h. Maybe we could define something like:

using ForkedPointer = std::pair<const SCEV *, const SCEV *>;

in llvm/include/llvm/Analysis/ScalarEvolution.h that can be used in LoopAccessAnalysis too?

llvm/lib/Analysis/LoopAccessAnalysis.cpp

176

nit: Perhaps you can just write assert(Fork <= 1 && ...) since it's unsigned anyway?

287

nit: Perhaps you can just write assert(Fork <= 1 && ...) since it's unsigned anyway?

412

Have you rewritten the logic here as a performance improvement, i.e. to avoid calling Group.addPointer() after it's already been merged?

652

nit: This is just a suggestion, but you could restructure this a little to remove the extra indentation I think here:

if (!AR) {
  if (!RtCheck.AllowForkedPtrs)
    return false;
  ...

Not sure if this is better?

668

Is it better to just make a recursive call to hasComputableBounds instead of calling isAffine here? We're potentially missing out on future improvements to hasComputableBounds here, and also we're ignoring the possibility of a forked pointer being loop invariant I think.

llvm/test/Transforms/LoopVectorize/forked-pointers.ll

1

Can we also have a test where at least one of the forked pointers is loop-invariant?

[huntergr]

llvm/include/llvm/Analysis/LoopAccessAnalysis.h

355

So this is for a RuntimeCheckingPtrGroup, which may have more than two members already; I've only changed it from a SmallVector to a SmallSetVector here in order to avoid duplicate members, since both sides of a forked pointer can be added to the same group.

378

I'll look into it, but it'll make other parts messier since I can't just iterate over the members of the SmallVectors and would need to perform null checks for all those places for the second element.

One solution I thought of (but didn't implement, since I wanted some community feedback on the overall work first) was to create a new SCEVForkedExpr so that we wouldn't need to store two SCEVs here and could just note which fork(s) was represented. It'll take a while to implement that, but might be cleaner. Thoughts?

llvm/lib/Analysis/LoopAccessAnalysis.cpp

412

Not intentionally, no -- I just replicated the behaviour of the original (break out of the loop if the pointer merged into a group) but considered both potential forks.

llvm/test/Transforms/LoopVectorize/forked-pointers.ll

1

We already do; see forked_ptrs_uniform_and_contiguous_forks

We could properly analyze and vectorize that case as well, but I haven't implemented that yet so I'm just testing that it gets rejected for now.

[david-arm]

llvm/test/Transforms/LoopVectorize/forked-pointers.ll

1

Ah ok, sorry I missed that. I guess what I meant was that this should be trivial to implement, particularly if we can find a way of making calls to hasComputableBounds recursive and re-use the existing code that checks for loop-invariants and affine pointers.

[huntergr]

Rebased, updated based on review comments.

[huntergr]

llvm/lib/Analysis/LoopAccessAnalysis.cpp

652

We still needed to bail out if AR was false and forked pointers weren't allowed... so I rewrote it to check for the positive case for AR first and then proceed with the forked pointers check and default false afterwards.

668

We can't do that right now -- hasComputableBounds takes a Value* rather than a SCEV* so it can (potentially) be added to the stride map in replaceSymbolicStrideSCEV. We'd just end up looking at the same Value and splitting again.

This is something the SCEVForkedExpr would make cleaner, since we would only need to evaluate a single SCEV. But it'll take a bit of refactoring to do that, which is why I wanted some feedback on the whole idea first.

We could also separate out parts of these functions to make it recursive, but I'll need to be careful since replaceSymbolicStrideSCEV has other users.

llvm/test/Transforms/LoopVectorize/forked-pointers.ll

1

Sadly, it'll require a bit more work to support invariant addresses. My original downstream code allowed them, but we ran into a bug with it and disabled them.

My plan is to get the base functionality committed, then go back and add an interface so that LoopVectorize (or other LAA consumers) can query the type of the forks in order to generate correct (and hopefully more optimal) IR for various cases -- the current contiguous-only SCEVs, strides of >1, loop-invariant but unknown strides, uniform/invariant addresses, indexed gather/scatter, etc.

If both forks have a stride of 1, or are invariant, then we could potentially plant two masked load instructions (or load + broadcast) instead of a gather, for instance. But that's future work until this part is completed.

[huntergr]

Ping.

[david-arm]

Thanks for making the changes @huntergr! I've got a few mostly minor comments so far, but still have to review findForkedSCEVs. :)

llvm/include/llvm/Analysis/LoopAccessAnalysis.h

404

Hi @huntergr, thanks for making the changes to Exprs. I just wonder if we should have an assert here that ScExprs.size() <= 2?

llvm/lib/Analysis/LoopAccessAnalysis.cpp

370

nit: Is it worth calling CheckingGroups.emplace_back(I, *this, /*Fork=0*/0) for clarity here?

664

nit: This is just a minor comment, but you could remove indentation further here by bailing out early, i.e.

if (!FPtr)
  return false;

const SCEV *A =

668

nit: Instead of writing:

LLVM_DEBUG(dbgs() << "LAA: SCEV1: " << *(FPtr->first) << "\n");

I think you can just write

LLVM_DEBUG(dbgs() << "LAA: SCEV1: " << *A << "\n");

and same for the second one.

[david-arm]

llvm/lib/Analysis/LoopAccessAnalysis.cpp

670

Is there any danger in setting this before we return true?

688

You're introducing a new implicit TypeSize -> uint64_t cast here. Could you rewrite this as:

int64_t Size = DL.getTypeAllocSize(PtrTy->getElementType()).getFixedSize();

[huntergr]

Rebased, minor fixes from review comments.

[david-arm]

Thanks for dealing with all the review comments @huntergr! I think the patch looks sensible to me, although I'm not as familiar with the SCEV code as others might be. I'm adding @lebedev.ri as a potential reviewer if that's ok?

llvm/test/Transforms/LoopVectorize/forked-pointers.ll

33

It would be good to show some distinction here between Check 1 and Check 2. I assume it's actually checking each of the forked pointers, but the output doesn't make that clear.

[huntergr]

Rebased, and changed the membership of a checking group to be a pair of PointerInfo index and fork so that printing can show which forks are present in a group.

[huntergr]

Rebased, disabled by default, added a couple of different instructions into the tests to ensure those paths are at least covered even if they aren't in a positive case right now; I'm still planning to leave those cases (known strides, g/s, uniform) for a followup patch; I suppose I could start a patch series if people want to see those earlier.

I've run the LNT nightly suite with this enabled, along with a few HPC benchmarks I have access to and they all pass.

[david-arm]

LGTM! Thanks for making all the changes @huntergr and adding the tests. This patch is low risk at the moment with the flag being disabled currently. At some point once there have been performance investigations to prove there are no regressions we can then enable this by default.

[fhahn]

In D108699#3148674, @david-arm wrote:

LGTM! Thanks for making all the changes @huntergr and adding the tests. This patch is low risk at the moment with the flag being disabled currently. At some point once there have been performance investigations to prove there are no regressions we can then enable this by default.

llvm/include/llvm/Analysis/LoopAccessAnalysis.h

19

Is this needed? Other SCEV types are forward-declared below, so ScalarEvolution.h doesn't need to be included.

329

Could we use a bool for Fork if it only has 2 possible values?

llvm/include/llvm/Analysis/ScalarEvolution.h

769 ↗

(On Diff #388889)

This is only used by LAA. Is there a reason this needs to be part of ScalarEvolution?

llvm/test/Transforms/LoopVectorize/forked-pointers.ll

1

the tests running -loop-accesses should be in llvm/test/Analysis/LoopAccessAnalysis.

Also, could you pre-commit the tests and update the diff here to show only the difference? That way it is a bit easier to see the impact in the diff.

[fhahn]

I just realized how this may be a bit similar to how we handle pointers that are phi nodes. Currently those are handled by adding accesses for both incoming values (see D109381). Unfortunately the same approach cannot be directly used for selects, because we need to create 2 pointers that do not exist in the IR.

But if MemAccessInfo/ would also carry the pointer SCEV directly, I think it would be possible to avoid adding another dimension to RuntimePointerChecking::PointerInfo. Instead we would add 2 PointerInfo entries with separate translated pointer SCEVs. I put up a rough sketch of what this may look like in D114480, D114479 to see how this may look like

[fhahn]

In D108699#3150041, @fhahn wrote:

I just realized how this may be a bit similar to how we handle pointers that are phi nodes. Currently those are handled by adding accesses for both incoming values (see D109381). Unfortunately the same approach cannot be directly used for selects, because we need to create 2 pointers that do not exist in the IR.

But if MemAccessInfo/ would also carry the pointer SCEV directly, I think it would be possible to avoid adding another dimension to RuntimePointerChecking::PointerInfo. Instead we would add 2 PointerInfo entries with separate translated pointer SCEVs. I put up a rough sketch of what this may look like in D114480, D114479 to see how this may look like

I also put up a sketch of a stripped down variant that only supports runtime check generation by adding multiple PointerInfos with different associated pointer SCEVs: D114487.

The variant that also extends MemAccessInfo should also be able to determine that certain loops are safe without runtime checks, e.g. like the one below I think:

%s1 = type { [32000 x float], [32000 x float], [32000 x float] }
define dso_local void @foo(%s1 * nocapture readonly %Base, i32* nocapture readonly %Preds) {
entry:
  br label %for.body

for.cond.cleanup:
  ret void

for.body:
  %indvars.iv = phi i64 [ 0, %entry ], [ %indvars.iv.next, %for.body ]
  %arrayidx = getelementptr inbounds i32, i32* %Preds, i64 %indvars.iv
  %0 = load i32, i32* %arrayidx, align 4
  %cmp1.not = icmp eq i32 %0, 0
  %gep.1 = getelementptr inbounds %s1, %s1* %Base, i64 0, i32 1, i32 0
  %gep.2 = getelementptr inbounds %s1, %s1* %Base, i64 0, i32 2, i32 0
  %spec.select = select i1 %cmp1.not, float* %gep.1, float* %gep.2
  %.sink.in = getelementptr inbounds float, float* %spec.select, i64 %indvars.iv
  %.sink = load float, float* %.sink.in, align 4
  %1= getelementptr inbounds %s1, %s1 * %Base, i64 0, i32 0, i64 %indvars.iv
  store float %.sink, float* %1, align 4
  %indvars.iv.next = add nuw nsw i64 %indvars.iv, 1
  %exitcond.not = icmp eq i64 %indvars.iv.next, 100
  br i1 %exitcond.not, label %for.cond.cleanup, label %for.body
}

[huntergr]

Revised based on @fhahn 's initial suggestions, rebased.

I'll look into the MemAccessInfo approach.

[huntergr]

llvm/include/llvm/Analysis/LoopAccessAnalysis.h

19

It was there to include the 'using ForkedPointer =' definition, but moving it out of ScalarEvolution means we can just define it here.

I had hoped that we could maybe integrate it further into ScalarEvolution as a new type of SCEV, but maybe this isn't the right time -- you're correct, this will be the only user for now, so we can just keep it here until we find a case where it would be useful to have it more widely available.

[david-arm]

LGTM!

Hi @huntergr, thanks for making all the changes. I think the patch looks good to
go for now. It's still worth looking into the MemAccessInfo approach as a follow-up,
but the patch has been sat in review for long enough (3 months) without any
fundamental objections so I'd prefer we got something merged now to get the
functionality defended and unblock future work. This is currently only enabled
under an option, so any refactoring for the MemAccessInfo approach can be
done safely under another patch.

[fhahn]

In D108699#3158014, @david-arm wrote:

LGTM!

Hi @huntergr, thanks for making all the changes. I think the patch looks good to
go for now. It's still worth looking into the MemAccessInfo approach as a follow-up,
but the patch has been sat in review for long enough (3 months) without any
fundamental objections so I'd prefer we got something merged now to get the
functionality defended and unblock future work.

I agree it is not ideal that there's been not much feedback so far, but now that there is some additional feedback/suggestion, I think it would be good to hear additional opinions on the preferred direction here or at least discuss concrete potential alternatives; D114487 in particular which should have similar effects, but with less invasive changes, i.e. there's no need to adjust isNoWrap, hasComputableBounds, RuntimePointerChecking::insert or add additional state.

You mention future work blocked by this as a reason for landing this now, however I cannot find any references to patches depending on this work.

This is currently only enabled
under an option, so any refactoring for the MemAccessInfo approach can be
done safely under another patch.

While it is true that it is off by default, it adds substantial complexity to LAA which is already quite complex and the changes are quite spread out. One concern is that it adds an additional way to model 'forked pointers'; we already handle 'forked pointers' via phi nodes (by adding multiple PointerInfos). I am also not sure it should be off by default, once it lands. IMO better analysis should be the right thing to do and should be quite safe from a performance regression perspective. I don't see a strong reason for not enabling this by default and having wide testing surface potential issues early.

[huntergr]

Rebased and changed to use @fhahn 's lighter-weight approach from D114487 combined with my recursive function to find the SCEVs. Although the simplified tests are handled with a couple levels of checking, the real applications I was working on had additional operations between the ptr value for the load or store and a select.

It might be best to introduce a limit to recursion though, any thoughts?

[huntergr]

Rebased, added a recursion limit to the SCEV building function.

[huntergr]

Rebased. Ping?

[fhahn]

Thanks for the update!

I think it would be good to split this up to have a first patch that just adds very limited support in findForkedSCEVs and then gradually add support for more cases separately. This also makes it easier to make sure all code paths in findForkedSCEVs are covered by the unit tests.

I went ahead and rebased D114487 and stripped the fork analysis to the bare minimum. I'd be happy to land the scaffolding in D114487 separately and this patch and following could add the sophisticated fork analysis.

llvm/lib/Analysis/LoopAccessAnalysis.cpp

133

It would be good to add a test for the option, e.g. a case that requires 2 or 3 recursions and set test with max-forked-scev-depth=2/3

375–380

This scheme would need documenting, i.e. why we can have multiple expressions for a pointer.

380

should be removed?

640

should be removed?

745

missing test for this?

763

It looks like tests for those conditions are missing?

776

I don't think we can use the inbounds info here, unless we prove that the program is undefined if GEP is poison.

Consider something like below. If %c is always false, the GEP index could be out-of-bounds (and the GEP poison). Adding a runtime check based on the SCEV expression may introduce a branch on poison unconditionally.

define dso_local void @forked_ptrs_different_base_same_offset(float* nocapture readonly %Base1, float* nocapture readonly %Base2, float* nocapture %Dest, i32* nocapture readonly %Preds, i1 %c) {
entry:
  br label %for.body

for.cond.cleanup:
  ret void

for.body:
  %indvars.iv = phi i64 [ 0, %entry ], [ %indvars.iv.next, %latch ]
  %arrayidx = getelementptr inbounds i32, i32* %Preds, i64 %indvars.iv
  %0 = load i32, i32* %arrayidx, align 4
  %cmp1.not = icmp eq i32 %0, 0
  %spec.select = select i1 %cmp1.not, float* %Base2, float* %Base1
  %.sink.in = getelementptr inbounds float, float* %spec.select, i64 %indvars.iv
  %.sink = load float, float* %.sink.in, align 4
  %1 = getelementptr inbounds float, float* %Dest, i64 %indvars.iv
  br i1 %c, label %then, label %latch

then:
  store float %.sink, float* %1, align 4
  br label %latch

latch:
  %indvars.iv.next = add nuw nsw i64 %indvars.iv, 1
  %exitcond.not = icmp eq i64 %indvars.iv.next, 100
  br i1 %exitcond.not, label %for.cond.cleanup, label %for.body
}

783

It might be a bit simpler to just add a duplicate to BaseScevs/OffsetScevs and have one common code path to compute the SCEVs to add

891

Needs resolving.

It should be needed, because the above code may have added assumptions, which make Ptr an AddRec, See comment in D114487.

[huntergr]

In D108699#3441724, @fhahn wrote:

Thanks for the update!

I think it would be good to split this up to have a first patch that just adds very limited support in findForkedSCEVs and then gradually add support for more cases separately. This also makes it easier to make sure all code paths in findForkedSCEVs are covered by the unit tests.

I went ahead and rebased D114487 and stripped the fork analysis to the bare minimum. I'd be happy to land the scaffolding in D114487 separately and this patch and following could add the sophisticated fork analysis.

Sure, that sounds like a good plan. I'll try and review your patch this week.

[fhahn]

In D108699#3445309, @huntergr wrote:

In D108699#3441724, @fhahn wrote:

Thanks for the update!

I think it would be good to split this up to have a first patch that just adds very limited support in findForkedSCEVs and then gradually add support for more cases separately. This also makes it easier to make sure all code paths in findForkedSCEVs are covered by the unit tests.

I went ahead and rebased D114487 and stripped the fork analysis to the bare minimum. I'd be happy to land the scaffolding in D114487 separately and this patch and following could add the sophisticated fork analysis.

Sure, that sounds like a good plan. I'll try and review your patch this week.

Sounds great, thanks!

[huntergr]

Rebased on top of Florian's patch from https://reviews.llvm.org/D114487

That patch has been reverted for now so builds will fail, but this should be pretty close to what we want once the base feature is back in.

I've cut the walker function down to only handle GEPs and selects for now; we can add more cases (and more tests) later.

I've added tests to exercise the checks that exclude a given select or GEP from processing, as well as one for the recursion limit.

I'll precommit the new tests before the next update on this patch.

[fhahn]

In D108699#3591443, @huntergr wrote:

Rebased on top of Florian's patch from https://reviews.llvm.org/D114487

That patch has been reverted for now so builds will fail, but this should be pretty close to what we want once the base feature is back in.

Thanks, the patch has been relanded a while ago.

I've cut the walker function down to only handle GEPs and selects for now; we can add more cases (and more tests) later.

I've added tests to exercise the checks that exclude a given select or GEP from processing, as well as one for the recursion limit.

I'll precommit the new tests before the next update on this patch.

Sounds good! I skimmed the current version and it looks like most comments should be addressed in the latest update. It might be good to mark them as done. One thing I couldn't spot in the latest version is a test for the potential inbounds issue mentioned inline.

llvm/test/Analysis/LoopAccessAnalysis/forked-pointers.ll

2

It would be probably be good to convert the IR to use opaque pointers in a pre-commit, so -opaque-pointers is not needed.

[huntergr]

Rebased on top of @fhahn 's fixed patch, including changes to detect possible undef/poison.

New tests were precommitted in rGa19cf47da095.

[huntergr]

llvm/lib/Analysis/LoopAccessAnalysis.cpp

776

I removed the code to add no-wrap flags to the SCEV based on 'inbounds', then added your test.

[fhahn]

LGTM, thanks!

llvm/lib/Analysis/LoopAccessAnalysis.cpp

825

nit: unnecessary move?

llvm/test/Analysis/LoopAccessAnalysis/forked-pointers.ll

72

nit: it would probably be good to also have a few tests that access different sizes, including odd ones like i23 or something like that, to ensure the right size expressions are used.

[ro]

This patch broke the Solaris/amd64 and Solaris/sparcv9 builds:

/vol/llvm/src/llvm-project/dist/llvm/lib/Analysis/LoopAccessAnalysis.cpp: In function ‘llvm::SmallVector<std::pair<const llvm::SCEV*, bool> > findForkedPointer(llvm::PredicatedScalarEvolution&, const ValueToValueMap&, llvm::Value*, const llvm::Loop*)’:
/vol/llvm/src/llvm-project/dist/llvm/lib/Analysis/LoopAccessAnalysis.cpp:916:12: error: could not convert ‘Scevs’ from ‘SmallVector<[...],2>’ to ‘SmallVector<[...],3>’
  916 |     return Scevs;
      |            ^~~~~
      |            |
      |            SmallVector<[...],2>

[huntergr]

In D108699#3659633, @ro wrote:

This patch broke the Solaris/amd64 and Solaris/sparcv9 builds:

/vol/llvm/src/llvm-project/dist/llvm/lib/Analysis/LoopAccessAnalysis.cpp: In function ‘llvm::SmallVector<std::pair<const llvm::SCEV*, bool> > findForkedPointer(llvm::PredicatedScalarEvolution&, const ValueToValueMap&, llvm::Value*, const llvm::Loop*)’:
/vol/llvm/src/llvm-project/dist/llvm/lib/Analysis/LoopAccessAnalysis.cpp:916:12: error: could not convert ‘Scevs’ from ‘SmallVector<[...],2>’ to ‘SmallVector<[...],3>’
  916 |     return Scevs;
      |            ^~~~~
      |            |
      |            SmallVector<[...],2>

Does rG4bd072c56b87 fix this for you?

[ro]

In D108699#3659641, @huntergr wrote:

In D108699#3659633, @ro wrote:

This patch broke the Solaris/amd64 and Solaris/sparcv9 builds:

[...]

Does rG4bd072c56b87 fix this for you?

It does indeed, thanks. FWIW, this is with g++ 11.3.0.

[efriedma]

https://github.com/llvm/llvm-project/issues/57368 is an open bug report describing a regression from this patch.

[huntergr]

In D108699#3756189, @efriedma wrote:

https://github.com/llvm/llvm-project/issues/57368 is an open bug report describing a regression from this patch.

Thanks for the report and reproducer, I'll look into it.

llvm/include/llvm/Analysis/LoopAccessAnalysis.h

 //
 //===----------------------------------------------------------------------===//
 
 #ifndef LLVM_ANALYSIS_LOOPACCESSANALYSIS_H
 #define LLVM_ANALYSIS_LOOPACCESSANALYSIS_H
 
 #include "llvm/ADT/EquivalenceClasses.h"
 #include "llvm/Analysis/LoopAnalysisManager.h"
 #include "llvm/Analysis/ScalarEvolutionExpressions.h"
 #include "llvm/IR/DiagnosticInfo.h"
 #include "llvm/Pass.h"
 
 namespace llvm {
 
 class AAResults;
 class DataLayout;
 class Loop;

 
 class RuntimePointerChecking;
 /// A grouping of pointers. A single memcheck is required between
 /// two groups.
 struct RuntimeCheckingPtrGroup {
   /// Create a new pointer checking group containing a single
   /// pointer, with index \p Index in RtCheck.
   RuntimeCheckingPtrGroup(unsigned Index, RuntimePointerChecking &RtCheck);
 
   RuntimeCheckingPtrGroup(unsigned Index, const SCEV *Start, const SCEV *End,
                           unsigned AS)
       : High(End), Low(Start), AddressSpace(AS) {
     Members.push_back(Index);
   }
 
   /// Tries to add the pointer recorded in RtCheck at index
   /// \p Index to this pointer checking group. We can only add a pointer
struct RuntimeCheckingPtrGroup {
   const SCEV *High;
   /// The SCEV expression which represents the lower bound of all the
   /// pointers in this group.
   const SCEV *Low;
   /// Indices of all the pointers that constitute this grouping.
   SmallVector<unsigned, 2> Members;
   /// Address space of the involved pointers.
   unsigned AddressSpace;
 };
 
 /// A memcheck which made up of a pair of grouped pointers.
 typedef std::pair<const RuntimeCheckingPtrGroup *,
                   const RuntimeCheckingPtrGroup *>
     RuntimePointerCheck;
 
 /// Holds information about the memory runtime legality checks to verify
 /// that a group of pointers do not overlap.
 class RuntimePointerChecking {
   friend struct RuntimeCheckingPtrGroup;
 
 public:
   struct PointerInfo {
     /// Holds the pointer value that we need to check.
     TrackingVH<Value> PointerValue;
     /// Holds the smallest byte address accessed by the pointer throughout all
     /// iterations of the loop.
     const SCEV *Start;
     /// Holds the largest byte address accessed by the pointer throughout all
     /// iterations of the loop, plus 1.
     const SCEV *End;
     /// Holds the information if this pointer is used for writing to memory.
     bool IsWritePtr;
     /// Holds the id of the set of pointers that could be dependent because of a
     /// shared underlying object.
     unsigned DependencySetId;
     /// Holds the id of the disjoint alias set to which this pointer belongs.
     unsigned AliasSetId;
     /// SCEV for the access.
     const SCEV *Expr;
 
public:
 
   /// Reset the state of the pointer runtime information.
   void reset() {
     Need = false;
     Pointers.clear();
     Checks.clear();
   }
 
   /// Insert a pointer and calculate the start and end SCEVs.
   /// We need \p PSE in order to compute the SCEV expression of the pointer
   /// according to the assumptions that we've made during the analysis.
   /// The method might also version the pointer stride according to \p Strides,
   /// and add new predicates to \p PSE.
-  void insert(Loop *Lp, Value *Ptr, bool WritePtr, unsigned DepSetId,
-              unsigned ASId, const ValueToValueMap &Strides,
+  void insert(Loop *Lp, Value *Ptr, const SCEV *PtrExpr, bool WritePtr,
+              unsigned DepSetId, unsigned ASId, const ValueToValueMap &Strides,
               PredicatedScalarEvolution &PSE);
 
   /// No run-time memory checking is necessary.
   bool empty() const { return Pointers.empty(); }
 
   /// Generate the checks and store it.  This also performs the grouping
   /// of pointers to reduce the number of memchecks necessary.
   void generateChecks(MemoryDepChecker::DepCandidates &DepCands,

llvm/lib/Analysis/LoopAccessAnalysis.cpp

 /// Enable store-to-load forwarding conflict detection. This option can
 /// be disabled for correctness testing.
 static cl::opt<bool> EnableForwardingConflictDetection(
     "store-to-load-forwarding-conflict-detection", cl::Hidden,
     cl::desc("Enable conflict detection in loop-access analysis"),
     cl::init(true));
 
 bool VectorizerParams::isInterleaveForced() {
   return ::VectorizationInterleave.getNumOccurrences() > 0;
 }
 
 Value *llvm::stripIntegerCast(Value *V) {
   if (auto *CI = dyn_cast<CastInst>(V))
     if (CI->getOperand(0)->getType()->isIntegerTy())
       return CI->getOperand(0);
   return V;
 }

 }
 
 RuntimeCheckingPtrGroup::RuntimeCheckingPtrGroup(
     unsigned Index, RuntimePointerChecking &RtCheck)
     : High(RtCheck.Pointers[Index].End), Low(RtCheck.Pointers[Index].Start),
       AddressSpace(RtCheck.Pointers[Index]
                        .PointerValue->getType()
                        ->getPointerAddressSpace()) {
   Members.push_back(Index);
 }
 
 /// Calculate Start and End points of memory access.
 /// Let's assume A is the first access and B is a memory access on N-th loop
 /// iteration. Then B is calculated as:
 ///   B = A + Step*N .
 /// Step value may be positive or negative.
 /// N is a calculated back-edge taken count:
 ///     N = (TripCount > 0) ? RoundDown(TripCount -1 , VF) : 0
 /// Start and End points are calculated in the following way:
 /// Start = UMIN(A, B) ; End = UMAX(A, B) + SizeOfElt,
 /// where SizeOfElt is the size of single memory access in bytes.
 ///
 /// There is no conflict when the intervals are disjoint:
 /// NoConflict = (P2.Start >= P1.End) || (P1.Start >= P2.End)
-void RuntimePointerChecking::insert(Loop *Lp, Value *Ptr, bool WritePtr,
-                                    unsigned DepSetId, unsigned ASId,
+void RuntimePointerChecking::insert(Loop *Lp, Value *Ptr, const SCEV *PtrExpr,
+                                    bool WritePtr, unsigned DepSetId,
+                                    unsigned ASId,
                                     const ValueToValueMap &Strides,
                                     PredicatedScalarEvolution &PSE) {
   // Get the stride replaced scev.
-  const SCEV *Sc = replaceSymbolicStrideSCEV(PSE, Strides, Ptr);
+  const SCEV *Sc = PtrExpr; // replaceSymbolicStrideSCEV(PSE, Strides, Ptr);
   ScalarEvolution *SE = PSE.getSE();
 
   const SCEV *ScStart;
   const SCEV *ScEnd;
 
   if (SE->isLoopInvariant(Sc, Lp)) {
     ScStart = ScEnd = Sc;
   } else {
static const SCEV *getMinFromExprs(const SCEV *I, const SCEV *J,
   if (C->getValue()->isNegative())
     return J;
   return I;
 }
 
 bool RuntimeCheckingPtrGroup::addPointer(unsigned Index,
                                          RuntimePointerChecking &RtCheck) {
   return addPointer(
       Index, RtCheck.Pointers[Index].Start, RtCheck.Pointers[Index].End,
       RtCheck.Pointers[Index].PointerValue->getType()->getPointerAddressSpace(),
       *RtCheck.SE);
 }
 
 bool RuntimeCheckingPtrGroup::addPointer(unsigned Index, const SCEV *Start,
                                          const SCEV *End, unsigned AS,
                                          ScalarEvolution &SE) {
   assert(AddressSpace == AS &&
void RuntimePointerChecking::groupChecks(
 
   // If we don't have the dependency partitions, construct a new
   // checking pointer group for each pointer. This is also required
   // for correctness, because in this case we can have checking between
   // pointers to the same underlying object.
   if (!UseDependencies) {
     for (unsigned I = 0; I < Pointers.size(); ++I)
       CheckingGroups.push_back(RuntimeCheckingPtrGroup(I, *this));
     return;
   }
 
   unsigned TotalComparisons = 0;
 
-  DenseMap<Value *, unsigned> PositionMap;
-  for (unsigned Index = 0; Index < Pointers.size(); ++Index)
-    PositionMap[Pointers[Index].PointerValue] = Index;
+  DenseMap<Value *, SmallVector<unsigned, 2>> PositionMap;
+  for (unsigned Index = 0; Index < Pointers.size(); ++Index) {
+    auto Iter = PositionMap.insert({Pointers[Index].PointerValue, {}});
+    Iter.first->second.push_back(Index);
+  }
+  // PositionMap[Pointers[Index].PointerValue] = Index;
 
   // We need to keep track of what pointers we've already seen so we
   // don't process them twice.
   SmallSet<unsigned, 2> Seen;
 
   // Go through all equivalence classes, get the "pointer check groups"
   // and add them to the overall solution. We use the order in which accesses
   // appear in 'Pointers' to enforce determinism.
for (unsigned I = 0; I < Pointers.size(); ++I) {
     // iteration order within an equivalence class member is only dependent on
     // the order in which unions and insertions are performed on the
     // equivalence class, the iteration order is deterministic.
     for (auto MI = DepCands.member_begin(LeaderI), ME = DepCands.member_end();
          MI != ME; ++MI) {
       auto PointerI = PositionMap.find(MI->getPointer());
       assert(PointerI != PositionMap.end() &&
              "pointer in equivalence class not found in PositionMap");
-      unsigned Pointer = PointerI->second;
+      for (unsigned Pointer : PointerI->second) {
         bool Merged = false;
         // Mark this pointer as seen.
         Seen.insert(Pointer);
 
         // Go through all the existing sets and see if we can find one
         // which can include this pointer.
         for (RuntimeCheckingPtrGroup &Group : Groups) {
           // Don't perform more than a certain amount of comparisons.
           // This should limit the cost of grouping the pointers to something
           // reasonable.  If we do end up hitting this threshold, the algorithm
           // will create separate groups for all remaining pointers.
           if (TotalComparisons > MemoryCheckMergeThreshold)
             break;
 
           TotalComparisons++;
 
           if (Group.addPointer(Pointer, *this)) {
             Merged = true;
             break;
           }
         }
 
         if (!Merged)
           // We couldn't add this pointer to any existing set or the threshold
           // for the number of comparisons has been reached. Create a new group
           // to hold the current pointer.
           Groups.push_back(RuntimeCheckingPtrGroup(Pointer, *this));
       }
+    }
 
     // We've computed the grouped checks for this partition.
     // Save the results and continue with the next one.
     llvm::copy(Groups, std::back_inserter(CheckingGroups));
   }
 }
 
 bool RuntimePointerChecking::arePointersInSamePartition(
private:
   PredicatedScalarEvolution &PSE;
 };
 
 } // end anonymous namespace
 
 /// Check whether a pointer can participate in a runtime bounds check.
 /// If \p Assume, try harder to prove that we can compute the bounds of \p Ptr
 /// by adding run-time checks (overflow checks) if necessary.
-static bool hasComputableBounds(PredicatedScalarEvolution &PSE,
-                                const ValueToValueMap &Strides, Value *Ptr,
-                                Loop *L, bool Assume) {
-  const SCEV *PtrScev = replaceSymbolicStrideSCEV(PSE, Strides, Ptr);
+static bool hasComputableBounds(PredicatedScalarEvolution &PSE, Value *Ptr,
+                                const SCEV *PtrScev, Loop *L, bool Assume) {
+  //  const SCEV *PtrScev = replaceSymbolicStrideSCEV(PSE, Strides, Ptr);
 
   // The bounds for loop-invariant pointer is trivial.
   if (PSE.getSE()->isLoopInvariant(PtrScev, L))
     return true;
 
   const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(PtrScev);
 
   if (!AR && Assume)
     AR = PSE.getAsAddRec(Ptr);
 
   if (!AR)
     return false;
 
   return AR->isAffine();
 }
 
 /// Check whether a pointer address cannot wrap.
 static bool isNoWrap(PredicatedScalarEvolution &PSE,
                      const ValueToValueMap &Strides, Value *Ptr, Loop *L) {
   const SCEV *PtrScev = PSE.getSCEV(Ptr);
   if (PSE.getSE()->isLoopInvariant(PtrScev, L))
     return true;
 
   Type *AccessTy = Ptr->getType()->getPointerElementType();
   int64_t Stride = getPtrStride(PSE, AccessTy, Ptr, L, Strides);
   if (Stride == 1 || PSE.hasNoOverflow(Ptr, SCEVWrapPredicate::IncrementNUSW))
     return true;
 
   return false;
 }
 
 static void visitPointers(Value *StartPtr, const Loop &InnermostLoop,
                           function_ref<void(Value *)> AddPointer) {
   SmallPtrSet<Value *, 8> Visited;
   SmallVector<Value *> WorkList;
   WorkList.push_back(StartPtr);
 
   while (!WorkList.empty()) {
     Value *Ptr = WorkList.pop_back_val();
     if (!Visited.insert(Ptr).second)
       continue;
     auto *PN = dyn_cast<PHINode>(Ptr);
     // SCEV does not look through non-header PHIs inside the loop. Such phis
     // can be analyzed by adding separate accesses for each incoming pointer
     // value.
     if (PN && InnermostLoop.contains(PN->getParent()) &&
         PN->getParent() != InnermostLoop.getHeader()) {
       for (const Use &Inc : PN->incoming_values())
         WorkList.push_back(Inc);
     } else
       AddPointer(Ptr);
   }
 }
 
+// Walk back through the IR for a pointer, looking for a select like the
+// following:
+//
+//  %offset = select i1 %cmp, i64 %a, i64 %b
+//  %addr = getelementptr double, double* %base, i64 %offset
+//  %ld = load double, double* %addr, align 8
+//
+// We won't be able to form a single SCEVAddRecExpr from this since the
+// address for each loop iteration depends on %cmp. We could potentially
+// produce multiple valid SCEVAddRecExprs, though, and check all of them for
+// memory safety/aliasing if needed.
+//
+// If we encounter some IR we don't yet handle, or something obviously fine
+// like a constant, then we just add the SCEV for that term to the list passed
+// in by the caller. If we have a node that may potentially yield a valid
+// SCEVAddRecExpr then we decompose it into parts and build the SCEV terms
+// ourselves before adding to the list.
+static void findForkedSCEVs(ScalarEvolution *SE, const Loop *L, Value *Ptr,
+                            SmallVectorImpl<const SCEV *> &ScevList) {
+  const SCEV *Scev = SE->getSCEV(Ptr);
+  if (SE->isLoopInvariant(Scev, L) || isa<SCEVAddRecExpr>(Scev) ||
+      !isa<Instruction>(Ptr)) {
+    ScevList.push_back(Scev);
+    return;
+  }
+
+  auto GetBinOpExpr = [&SE](unsigned Opcode, const SCEV *L, const SCEV *R) {
+    switch (Opcode) {
+    case Instruction::Add:
+      return SE->getAddExpr(L, R);
+    case Instruction::Sub:
+      return SE->getMinusSCEV(L, R);
+    case Instruction::Mul:
+      return SE->getMulExpr(L, R);
+    default:
+      llvm_unreachable("Unexpected binary operator when walking ForkedPtrs");
+    }
+  };
+
+  Instruction *I = cast<Instruction>(Ptr);
+  unsigned Opcode = I->getOpcode();
+  switch (Opcode) {
+  case Instruction::BitCast:
+    findForkedSCEVs(SE, L, I->getOperand(0), ScevList);
+    break;
+  case Instruction::SExt:
+  case Instruction::ZExt: {
+    SmallVector<const SCEV *, 2> ExtScevs;
+    findForkedSCEVs(SE, L, I->getOperand(0), ExtScevs);
+    for (const SCEV *Scev : ExtScevs)
+      if (Opcode == Instruction::SExt)
+        ScevList.push_back(SE->getSignExtendExpr(Scev, I->getType()));
+      else
+        ScevList.push_back(SE->getZeroExtendExpr(Scev, I->getType()));
+    break;
+  }
+  case Instruction::GetElementPtr: {
+    GetElementPtrInst *GEP = cast<GetElementPtrInst>(I);
+    Type *SourceTy = GEP->getSourceElementType();
+    // We only handle base + single offset GEPs here for now.
+    // Not dealing with preexisting gathers yet, so no vectors.
+    if (I->getNumOperands() != 2 || SourceTy->isVectorTy()) {
+      ScevList.push_back(Scev);
+      break;
+    }
+    SmallVector<const SCEV *, 2> BaseScevs;
+    SmallVector<const SCEV *, 2> OffsetScevs;
+    findForkedSCEVs(SE, L, I->getOperand(0), BaseScevs);
+    findForkedSCEVs(SE, L, I->getOperand(1), OffsetScevs);
+
+    // Make sure we get the correct pointer type to extend to, including the
+    // address space.
+    const SCEV *BaseExpr = SE->getSCEV(GEP->getPointerOperand());
+    Type *IntPtrTy = SE->getEffectiveSCEVType(BaseExpr->getType());
+    SCEV::NoWrapFlags Wrap =
+        GEP->isInBounds() ? SCEV::FlagNSW : SCEV::FlagAnyWrap;
+    // Find the size of the type being pointed to. We only have a single
+    // index term (guarded above) so we don't need to index into arrays or
+    // structures, just get the size of the scalar value.
+    const SCEV *Size = SE->getSizeOfExpr(IntPtrTy, SourceTy);
+
+    if (OffsetScevs.size() == 2 && BaseScevs.size() == 1) {
+      const SCEV *Off1 = SE->getTruncateOrSignExtend(OffsetScevs[0], IntPtrTy);
+      const SCEV *Off2 = SE->getTruncateOrSignExtend(OffsetScevs[1], IntPtrTy);
+      const SCEV *Mul1 = SE->getMulExpr(Size, Off1, Wrap);
+      const SCEV *Mul2 = SE->getMulExpr(Size, Off2, Wrap);
+      const SCEV *Add1 = SE->getAddExpr(BaseScevs[0], Mul1, Wrap);
+      const SCEV *Add2 = SE->getAddExpr(BaseScevs[0], Mul2, Wrap);
+      ScevList.push_back(Add1);
+      ScevList.push_back(Add2);
+    } else if (BaseScevs.size() == 2 && OffsetScevs.size() == 1) {
+      const SCEV *Off = SE->getTruncateOrSignExtend(OffsetScevs[0], IntPtrTy);
+      const SCEV *Mul = SE->getMulExpr(Size, Off, Wrap);
+      const SCEV *Add1 = SE->getAddExpr(BaseScevs[0], Mul, Wrap);
+      const SCEV *Add2 = SE->getAddExpr(BaseScevs[1], Mul, Wrap);
+      ScevList.push_back(Add1);
+      ScevList.push_back(Add2);
+    } else
+      ScevList.push_back(Scev);
+    break;
+  }
+  case Instruction::Select: {
+    SmallVector<const SCEV *, 2> ChildScevs;
+    // A select means we've found a forked pointer, but we currently only
+    // support a single select per pointer so if there's another behind this
+    // then we just bail out and return the generic SCEV.
+    findForkedSCEVs(SE, L, I->getOperand(1), ChildScevs);
+    findForkedSCEVs(SE, L, I->getOperand(2), ChildScevs);
+    if (ChildScevs.size() == 2) {
+      ScevList.push_back(ChildScevs[0]);
+      ScevList.push_back(ChildScevs[1]);
+    } else
+      ScevList.push_back(Scev);
+    break;
+  }
+  // If adding another binop to this list, update GetBinOpExpr above
+  case Instruction::Add:
+  case Instruction::Sub:
+  case Instruction::Mul: {
+    SmallVector<const SCEV *, 2> LScevs;
+    SmallVector<const SCEV *, 2> RScevs;
+    findForkedSCEVs(SE, L, I->getOperand(0), LScevs);
+    findForkedSCEVs(SE, L, I->getOperand(1), RScevs);
+    if (LScevs.size() == 2 && RScevs.size() == 1) {
+      const SCEV *Op1 = GetBinOpExpr(Opcode, LScevs[0], RScevs[0]);
+      const SCEV *Op2 = GetBinOpExpr(Opcode, LScevs[1], RScevs[0]);
+      ScevList.push_back(Op1);
+      ScevList.push_back(Op2);
+    } else if (LScevs.size() == 1 && RScevs.size() == 2) {
+      const SCEV *Op1 = GetBinOpExpr(Opcode, LScevs[0], RScevs[0]);
+      const SCEV *Op2 = GetBinOpExpr(Opcode, LScevs[0], RScevs[1]);
+      ScevList.push_back(Op1);
+      ScevList.push_back(Op2);
+    } else
+      ScevList.push_back(Scev);
+    break;
+  }
+  default:
+    // Just return the current SCEV if we haven't handled the instruction yet.
+    LLVM_DEBUG(dbgs() << "ForkedPtr unhandled instruction: " << *I << "\n");
+    ScevList.push_back(Scev);
+    break;
+  }
+
+  return;
+}
+
+static SmallVector<const SCEV *>
+findForkedPointer(PredicatedScalarEvolution &PSE,
+                  const ValueToValueMap &StridesMap, Value *Ptr,
+                  const Loop *L) {
+  ScalarEvolution *SE = PSE.getSE();
+  assert(SE->isSCEVable(Ptr->getType()) && "Value is not SCEVable!");
+  SmallVector<const SCEV *, 2> Scevs;
+  findForkedSCEVs(SE, L, Ptr, Scevs);
+
+  // For now, we will only accept a forked pointer with two options.
+  if (Scevs.size() == 2)
+    return std::move(Scevs);
+
+  return {replaceSymbolicStrideSCEV(PSE, StridesMap, Ptr)};
+}
+
 bool AccessAnalysis::createCheckForAccess(RuntimePointerChecking &RtCheck,
                                           MemAccessInfo Access,
                                           const ValueToValueMap &StridesMap,
                                           DenseMap<Value *, unsigned> &DepSetId,
                                           Loop *TheLoop, unsigned &RunningDepId,
                                           unsigned ASId, bool ShouldCheckWrap,
                                           bool Assume) {
   Value *Ptr = Access.getPointer();
 
-  if (!hasComputableBounds(PSE, StridesMap, Ptr, TheLoop, Assume))
+  SmallVector<const SCEV *> TranslatedPtrs =
+      findForkedPointer(PSE, StridesMap, Ptr, TheLoop);
+
+  for (const SCEV *PtrExpr : TranslatedPtrs) {
+    if (!hasComputableBounds(PSE, Ptr, PtrExpr, TheLoop, Assume))
       return false;
 
     // When we run after a failing dependency check we have to make sure
     // we don't have wrapping pointers.
-  if (ShouldCheckWrap && !isNoWrap(PSE, StridesMap, Ptr, TheLoop)) {
+    if (ShouldCheckWrap) {
+      // If we forked a pointer via a select, don't check for wrapping
+      // behaviour.
+      // TODO: Implement this; requires checking the SCEVs individually
+      // instead of the overall ptr, since that just resolves to a SCEVUnknown.
+      if (TranslatedPtrs.size() > 1)
+        return false;
+
+      if (!isNoWrap(PSE, StridesMap, Ptr, TheLoop)) {
         auto *Expr = PSE.getSCEV(Ptr);
         if (!Assume || !isa<SCEVAddRecExpr>(Expr))
           return false;
         PSE.setNoOverflow(Ptr, SCEVWrapPredicate::IncrementNUSW);
       }
+    }
+    // Is this needed? I think the method above forced it, so can be skipped?
+    if (TranslatedPtrs.size() == 1)
+      TranslatedPtrs[0] = replaceSymbolicStrideSCEV(PSE, StridesMap, Ptr);
+  }
 
+  for (const SCEV *PtrExpr : TranslatedPtrs) {
     // The id of the dependence set.
     unsigned DepId;
 
     if (isDependencyCheckNeeded()) {
       Value *Leader = DepCands.getLeaderValue(Access).getPointer();
       unsigned &LeaderId = DepSetId[Leader];
       if (!LeaderId)
         LeaderId = RunningDepId++;
       DepId = LeaderId;
     } else
       // Each access has its own dependence set.
       DepId = RunningDepId++;
 
     bool IsWrite = Access.getInt();
-  RtCheck.insert(TheLoop, Ptr, IsWrite, DepId, ASId, StridesMap, PSE);
+    RtCheck.insert(TheLoop, Ptr, PtrExpr, IsWrite, DepId, ASId, StridesMap,
+                   PSE);
     LLVM_DEBUG(dbgs() << "LAA: Found a runtime check ptr:" << *Ptr << '\n');
+  }
 
   return true;
  }
 
 bool AccessAnalysis::canCheckPtrAtRT(RuntimePointerChecking &RtCheck,
                                      ScalarEvolution *SE, Loop *TheLoop,
                                      const ValueToValueMap &StridesMap,
                                      bool ShouldCheckWrap) {

llvm/test/Analysis/LoopAccessAnalysis/forked-pointers.ll

 ; RUN: opt -loop-accesses -analyze -enable-new-pm=0 %s 2>&1 | FileCheck %s
 ; RUN: opt -disable-output -passes='print-access-info' %s 2>&1 | FileCheck %s
 
 target datalayout = "e-m:e-i8:8:32-i16:16:32-i64:64-i128:128-n32:64-S128"
 
 ; CHECK-LABEL: function 'forked_ptrs_different_base_same_offset':
-; CHECK-NEXT:  for.body:
-; CHECK-NEXT:    Report: cannot identify array bounds
-; CHECK-NEXT:    Dependences:
-; CHECK-NEXT:    Run-time memory checks:
-; CHECK-NEXT:    Grouped accesses:
+; CHECK-NEXT: for.body:
+; CHECK-NEXT:   Memory dependences are safe with run-time checks
+; CHECK-NEXT:   Dependences:
+; CHECK-NEXT:   Run-time memory checks:
+; CHECK-NEXT:   Check 0:
+; CHECK-NEXT:     Comparing group
+; CHECK-NEXT:       %1 = getelementptr inbounds float, float* %Dest, i64 %indvars.iv
+; CHECK-NEXT:     Against group
+; CHECK-NEXT:       %arrayidx = getelementptr inbounds i32, i32* %Preds, i64 %indvars.iv
+; CHECK-NEXT:   Check 1:
+; CHECK-NEXT:     Comparing group
+; CHECK-NEXT:       %1 = getelementptr inbounds float, float* %Dest, i64 %indvars.iv
+; CHECK-NEXT:     Against group
+; CHECK-NEXT:       %.sink.in = getelementptr inbounds float, float* %spec.select, i64 %indvars.iv
+; CHECK-NEXT:   Check 2:
+; CHECK-NEXT:     Comparing group
+; CHECK-NEXT:       %1 = getelementptr inbounds float, float* %Dest, i64 %indvars.iv
+; CHECK-NEXT:     Against group
+; CHECK-NEXT:       %.sink.in = getelementptr inbounds float, float* %spec.select, i64 %indvars.iv
+; CHECK-NEXT:   Grouped accesses:
+; CHECK-NEXT:     Group
+; CHECK-NEXT:       (Low: %Dest High: (400 + %Dest))
+; CHECK-NEXT:         Member: {%Dest,+,4}<nuw><%for.body>
+; CHECK-NEXT:     Group
+; CHECK-NEXT:       (Low: %Preds High: (400 + %Preds))
+; CHECK-NEXT:         Member: {%Preds,+,4}<nuw><%for.body>
+; CHECK-NEXT:     Group
+; CHECK-NEXT:       (Low: %Base2 High: (400 + %Base2))
+; CHECK-NEXT:         Member: {%Base2,+,4}<nsw><%for.body>
+; CHECK-NEXT:     Group
+; CHECK-NEXT:       (Low: %Base1 High: (400 + %Base1))
+; CHECK-NEXT:         Member: {%Base1,+,4}<nsw><%for.body>
 ; CHECK-EMPTY:
-; CHECK-NEXT:    Non vectorizable stores to invariant address were not found in loop.
-; CHECK-NEXT:    SCEV assumptions:
+; CHECK-NEXT:   Non vectorizable stores to invariant address were not found in loop.
+; CHECK-NEXT:   SCEV assumptions:
 ; CHECK-EMPTY:
-; CHECK-NEXT:    Expressions re-written:
+; CHECK-NEXT:   Expressions re-written:
 
 ;;;; Derived from the following C code
 ;; void forked_ptrs_different_base_same_offset(float *A, float *B, float *C, int *D) {
 ;;   for (int i=0; i<100; i++) {
 ;;     if (D[i] != 0) {
 ;;       C[i] = A[i];
 ;;     } else {
 ;;       C[i] = B[i];
for.body:
   %indvars.iv = phi i64 [ 0, %entry ], [ %indvars.iv.next, %for.body ]
   %arrayidx = getelementptr inbounds i32, i32* %Preds, i64 %indvars.iv
   %0 = load i32, i32* %arrayidx, align 4
   %cmp1.not = icmp eq i32 %0, 0
   %spec.select = select i1 %cmp1.not, float* %Base2, float* %Base1
   %.sink.in = getelementptr inbounds float, float* %spec.select, i64 %indvars.iv
   %.sink = load float, float* %.sink.in, align 4
   %1 = getelementptr inbounds float, float* %Dest, i64 %indvars.iv
   store float %.sink, float* %1, align 4
   %indvars.iv.next = add nuw nsw i64 %indvars.iv, 1
   %exitcond.not = icmp eq i64 %indvars.iv.next, 100
   br i1 %exitcond.not, label %for.cond.cleanup, label %for.body
 }
 
 ; CHECK-LABEL: function 'forked_ptrs_same_base_different_offset':
-; CHECK-NEXT:   for.body:
-; CHECK-NEXT:     Report: cannot identify array bounds
-; CHECK-NEXT:     Dependences:
-; CHECK-NEXT:     Run-time memory checks:
-; CHECK-NEXT:     Grouped accesses:
+; CHECK-NEXT: for.body:
+; CHECK-NEXT:   Memory dependences are safe with run-time checks
+; CHECK-NEXT:   Dependences:
+; CHECK-NEXT:   Run-time memory checks:
+; CHECK-NEXT:   Check 0:
+; CHECK-NEXT:     Comparing group
+; CHECK-NEXT:       %arrayidx5 = getelementptr inbounds float, float* %Dest, i64 %indvars.iv
+; CHECK-NEXT:     Against group
+; CHECK-NEXT:       %arrayidx = getelementptr inbounds i32, i32* %Preds, i64 %indvars.iv
+; CHECK-NEXT:   Check 1:
+; CHECK-NEXT:     Comparing group
+; CHECK-NEXT:       %arrayidx5 = getelementptr inbounds float, float* %Dest, i64 %indvars.iv
+; CHECK-NEXT:     Against group
+; CHECK-NEXT:       %arrayidx3 = getelementptr inbounds float, float* %Base, i64 %idxprom213
+; CHECK-NEXT:       %arrayidx3 = getelementptr inbounds float, float* %Base, i64 %idxprom213
+; CHECK-NEXT:   Grouped accesses:
+; CHECK-NEXT:     Group
+; CHECK-NEXT:       (Low: %Dest High: (400 + %Dest))
+; CHECK-NEXT:         Member: {%Dest,+,4}<nuw><%for.body>
+; CHECK-NEXT:     Group
+; CHECK-NEXT:       (Low: %Preds High: (400 + %Preds))
+; CHECK-NEXT:         Member: {%Preds,+,4}<nuw><%for.body>
+; CHECK-NEXT:     Group
+; CHECK-NEXT:       (Low: %Base High: (404 + %Base))
+; CHECK-NEXT:         Member: {(4 + %Base)<nsw>,+,4}<nsw><%for.body>
+; CHECK-NEXT:         Member: {%Base,+,4}<nsw><%for.body>
 ; CHECK-EMPTY:
-; CHECK-NEXT:     Non vectorizable stores to invariant address were not found in loop.
-; CHECK-NEXT:     SCEV assumptions:
+; CHECK-NEXT:   Non vectorizable stores to invariant address were not found in loop.
+; CHECK-NEXT:   SCEV assumptions:
 ; CHECK-EMPTY:
-; CHECK-NEXT:     Expressions re-written:
+; CHECK-NEXT:   Expressions re-written:
 
 ;;;; Derived from the following C code
 ;; void forked_ptrs_same_base_different_offset(float *A, float *B, int *C) {
 ;;   int offset;
 ;;   for (int i = 0; i < 100; i++) {
 ;;     if (C[i] != 0)
 ;;       offset = i;
 ;;     else
for.body:                                         ; preds = %entry, %for.body
   %arrayidx3 = getelementptr inbounds float, float* %Base, i64 %idxprom213
   %2 = load float, float* %arrayidx3, align 4
   %arrayidx5 = getelementptr inbounds float, float* %Dest, i64 %indvars.iv
   store float %2, float* %arrayidx5, align 4
   %exitcond.not = icmp eq i64 %indvars.iv.next, 100
   br i1 %exitcond.not, label %for.cond.cleanup, label %for.body
 }
 
-;;;; Cases that can be handled by a forked pointer but are not currently allowed.
-
 ; CHECK-LABEL: function 'forked_ptrs_uniform_and_strided_forks':
-; CHECK-NEXT:  for.body:
-; CHECK-NEXT:    Report: cannot identify array bounds
-; CHECK-NEXT:    Dependences:
-; CHECK-NEXT:    Run-time memory checks:
-; CHECK-NEXT:    Grouped accesses:
+; CHECK-NEXT: for.body:
+; CHECK-NEXT:   Memory dependences are safe with run-time checks
+; CHECK-NEXT:   Dependences:
+; CHECK-NEXT:   Run-time memory checks:
+; CHECK-NEXT:   Check 0:
+; CHECK-NEXT:     Comparing group
+; CHECK-NEXT:       %arrayidx5 = getelementptr inbounds float, float* %Dest, i64 %indvars.iv
+; CHECK-NEXT:     Against group
+; CHECK-NEXT:       %arrayidx = getelementptr inbounds i32, i32* %Preds, i64 %indvars.iv
+; CHECK-NEXT:   Check 1:
+; CHECK-NEXT:     Comparing group
+; CHECK-NEXT:       %arrayidx5 = getelementptr inbounds float, float* %Dest, i64 %indvars.iv
+; CHECK-NEXT:     Against group
+; CHECK-NEXT:       %arrayidx3 = getelementptr inbounds float, float* %Base, i64 %idxprom213
+; CHECK-NEXT:       %arrayidx3 = getelementptr inbounds float, float* %Base, i64 %idxprom213
+; CHECK-NEXT:   Grouped accesses:
+; CHECK-NEXT:     Group
+; CHECK-NEXT:       (Low: %Dest High: (400 + %Dest))
+; CHECK-NEXT:         Member: {%Dest,+,4}<nuw><%for.body>
+; CHECK-NEXT:     Group
+; CHECK-NEXT:       (Low: %Preds High: (400 + %Preds))
+; CHECK-NEXT:         Member: {%Preds,+,4}<nuw><%for.body>
+; CHECK-NEXT:     Group
+; CHECK-NEXT:       (Low: %Base High: (1192 + %Base))
+; CHECK-NEXT:         Member: (16 + %Base)<nsw>
+; CHECK-NEXT:         Member: {%Base,+,12}<nsw><%for.body>
 ; CHECK-EMPTY:
-; CHECK-NEXT:    Non vectorizable stores to invariant address were not found in loop.
-; CHECK-NEXT:    SCEV assumptions:
+; CHECK-NEXT:   Non vectorizable stores to invariant address were not found in loop.
+; CHECK-NEXT:   SCEV assumptions:
 ; CHECK-EMPTY:
-; CHECK-NEXT:    Expressions re-written:
+; CHECK-NEXT:   Expressions re-written:
 
 ;;;; Derived from forked_ptrs_same_base_different_offset with a manually
 ;;;; added uniform offset and a mul to provide a stride
 
 define dso_local void @forked_ptrs_uniform_and_strided_forks(float* nocapture readonly %Base, float* nocapture %Dest, i32* nocapture readonly %Preds) {
 entry:
   br label %for.body
 
for.body:                                         ; preds = %entry, %for.body
   %arrayidx3 = getelementptr inbounds float, float* %Base, i64 %idxprom213
   %2 = load float, float* %arrayidx3, align 4
   %arrayidx5 = getelementptr inbounds float, float* %Dest, i64 %indvars.iv
   store float %2, float* %arrayidx5, align 4
   %exitcond.not = icmp eq i64 %indvars.iv.next, 100
   br i1 %exitcond.not, label %for.cond.cleanup, label %for.body
 }
 
+;;;; Cases that can be handled by a forked pointer but are not currently allowed.
+
 ; CHECK-LABEL:  function 'forked_ptrs_gather_and_contiguous_forks':
 ; CHECK-NEXT:   for.body:
 ; CHECK-NEXT:     Report: cannot identify array bounds
 ; CHECK-NEXT:     Dependences:
 ; CHECK-NEXT:     Run-time memory checks:
 ; CHECK-NEXT:     Grouped accesses:
 ; CHECK-EMPTY:
 ; CHECK-NEXT:     Non vectorizable stores to invariant address were not found in loop.

llvm/test/Transforms/LoopVectorize/forked-pointers.ll

 ; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
 ; RUN: opt -loop-vectorize -instcombine -force-vector-width=4 -S < %s 2>&1 | FileCheck %s
 
 target datalayout = "e-m:e-i8:8:32-i16:16:32-i64:64-i128:128-n32:64-S128"
 
 ;;;; Derived from the following C code
 ;; void forked_ptrs_different_base_same_offset(float *A, float *B, float *C, int *D) {
 ;;   for (int i=0; i<100; i++) {
 ;;     if (D[i] != 0) {
 ;;       C[i] = A[i];
 ;;     } else {
 ;;       C[i] = B[i];
 ;;     }
 ;;   }
 ;; }
 
 define dso_local void @forked_ptrs_different_base_same_offset(float* nocapture readonly %Base1, float* nocapture readonly %Base2, float* nocapture %Dest, i32* nocapture readonly %Preds) {
 ; CHECK-LABEL: @forked_ptrs_different_base_same_offset(
 ; CHECK-NEXT:  entry:
+; CHECK-NEXT:    br i1 false, label [[SCALAR_PH:%.*]], label [[VECTOR_MEMCHECK:%.*]]
+; CHECK:       vector.memcheck:
+; CHECK-NEXT:    [[SCEVGEP:%.*]] = getelementptr float, float* [[DEST:%.*]], i64 100
+; CHECK-NEXT:    [[SCEVGEP4:%.*]] = getelementptr i32, i32* [[PREDS:%.*]], i64 100
+; CHECK-NEXT:    [[SCEVGEP7:%.*]] = getelementptr float, float* [[BASE2:%.*]], i64 100
+; CHECK-NEXT:    [[SCEVGEP10:%.*]] = getelementptr float, float* [[BASE1:%.*]], i64 100
+; CHECK-NEXT:    [[TMP0:%.*]] = bitcast i32* [[SCEVGEP4]] to float*
+; CHECK-NEXT:    [[BOUND0:%.*]] = icmp ugt float* [[TMP0]], [[DEST]]
+; CHECK-NEXT:    [[TMP1:%.*]] = bitcast float* [[SCEVGEP]] to i32*
+; CHECK-NEXT:    [[BOUND1:%.*]] = icmp ugt i32* [[TMP1]], [[PREDS]]
+; CHECK-NEXT:    [[FOUND_CONFLICT:%.*]] = and i1 [[BOUND0]], [[BOUND1]]
+; CHECK-NEXT:    [[BOUND012:%.*]] = icmp ugt float* [[SCEVGEP7]], [[DEST]]
+; CHECK-NEXT:    [[BOUND113:%.*]] = icmp ugt float* [[SCEVGEP]], [[BASE2]]
+; CHECK-NEXT:    [[FOUND_CONFLICT14:%.*]] = and i1 [[BOUND012]], [[BOUND113]]
+; CHECK-NEXT:    [[CONFLICT_RDX:%.*]] = or i1 [[FOUND_CONFLICT]], [[FOUND_CONFLICT14]]
+; CHECK-NEXT:    [[BOUND015:%.*]] = icmp ugt float* [[SCEVGEP10]], [[DEST]]
+; CHECK-NEXT:    [[BOUND116:%.*]] = icmp ugt float* [[SCEVGEP]], [[BASE1]]
+; CHECK-NEXT:    [[FOUND_CONFLICT17:%.*]] = and i1 [[BOUND015]], [[BOUND116]]
+; CHECK-NEXT:    [[CONFLICT_RDX18:%.*]] = or i1 [[CONFLICT_RDX]], [[FOUND_CONFLICT17]]
+; CHECK-NEXT:    br i1 [[CONFLICT_RDX18]], label [[SCALAR_PH]], label [[VECTOR_PH:%.*]]
+; CHECK:       vector.ph:
+; CHECK-NEXT:    [[BROADCAST_SPLATINSERT:%.*]] = insertelement <4 x float*> poison, float* [[BASE2]], i64 0
+; CHECK-NEXT:    [[BROADCAST_SPLAT:%.*]] = shufflevector <4 x float*> [[BROADCAST_SPLATINSERT]], <4 x float*> poison, <4 x i32> zeroinitializer
+; CHECK-NEXT:    [[BROADCAST_SPLATINSERT19:%.*]] = insertelement <4 x float*> poison, float* [[BASE1]], i64 0
+; CHECK-NEXT:    [[BROADCAST_SPLAT20:%.*]] = shufflevector <4 x float*> [[BROADCAST_SPLATINSERT19]], <4 x float*> poison, <4 x i32> zeroinitializer
+; CHECK-NEXT:    br label [[VECTOR_BODY:%.*]]
+; CHECK:       vector.body:
+; CHECK-NEXT:    [[INDEX:%.*]] = phi i64 [ 0, [[VECTOR_PH]] ], [ [[INDEX_NEXT:%.*]], [[VECTOR_BODY]] ]
+; CHECK-NEXT:    [[TMP2:%.*]] = or i64 [[INDEX]], 1
+; CHECK-NEXT:    [[TMP3:%.*]] = or i64 [[INDEX]], 2
+; CHECK-NEXT:    [[TMP4:%.*]] = or i64 [[INDEX]], 3
+; CHECK-NEXT:    [[TMP5:%.*]] = getelementptr inbounds i32, i32* [[PREDS]], i64 [[INDEX]]
+; CHECK-NEXT:    [[TMP6:%.*]] = bitcast i32* [[TMP5]] to <4 x i32>*
+; CHECK-NEXT:    [[WIDE_LOAD:%.*]] = load <4 x i32>, <4 x i32>* [[TMP6]], align 4, !alias.scope !0
+; CHECK-NEXT:    [[TMP7:%.*]] = icmp eq <4 x i32> [[WIDE_LOAD]], zeroinitializer
+; CHECK-NEXT:    [[TMP8:%.*]] = select <4 x i1> [[TMP7]], <4 x float*> [[BROADCAST_SPLAT]], <4 x float*> [[BROADCAST_SPLAT20]]
+; CHECK-NEXT:    [[TMP9:%.*]] = extractelement <4 x float*> [[TMP8]], i64 0
+; CHECK-NEXT:    [[TMP10:%.*]] = getelementptr inbounds float, float* [[TMP9]], i64 [[INDEX]]
+; CHECK-NEXT:    [[TMP11:%.*]] = extractelement <4 x float*> [[TMP8]], i64 1
+; CHECK-NEXT:    [[TMP12:%.*]] = getelementptr inbounds float, float* [[TMP11]], i64 [[TMP2]]
+; CHECK-NEXT:    [[TMP13:%.*]] = extractelement <4 x float*> [[TMP8]], i64 2
+; CHECK-NEXT:    [[TMP14:%.*]] = getelementptr inbounds float, float* [[TMP13]], i64 [[TMP3]]
+; CHECK-NEXT:    [[TMP15:%.*]] = extractelement <4 x float*> [[TMP8]], i64 3
+; CHECK-NEXT:    [[TMP16:%.*]] = getelementptr inbounds float, float* [[TMP15]], i64 [[TMP4]]
+; CHECK-NEXT:    [[TMP17:%.*]] = load float, float* [[TMP10]], align 4, !alias.scope !3
+; CHECK-NEXT:    [[TMP18:%.*]] = load float, float* [[TMP12]], align 4, !alias.scope !3
+; CHECK-NEXT:    [[TMP19:%.*]] = load float, float* [[TMP14]], align 4, !alias.scope !3
+; CHECK-NEXT:    [[TMP20:%.*]] = load float, float* [[TMP16]], align 4, !alias.scope !3
+; CHECK-NEXT:    [[TMP21:%.*]] = insertelement <4 x float> poison, float [[TMP17]], i64 0
+; CHECK-NEXT:    [[TMP22:%.*]] = insertelement <4 x float> [[TMP21]], float [[TMP18]], i64 1
+; CHECK-NEXT:    [[TMP23:%.*]] = insertelement <4 x float> [[TMP22]], float [[TMP19]], i64 2
+; CHECK-NEXT:    [[TMP24:%.*]] = insertelement <4 x float> [[TMP23]], float [[TMP20]], i64 3
+; CHECK-NEXT:    [[TMP25:%.*]] = getelementptr inbounds float, float* [[DEST]], i64 [[INDEX]]
+; CHECK-NEXT:    [[TMP26:%.*]] = bitcast float* [[TMP25]] to <4 x float>*
+; CHECK-NEXT:    store <4 x float> [[TMP24]], <4 x float>* [[TMP26]], align 4, !alias.scope !5, !noalias !7
+; CHECK-NEXT:    [[INDEX_NEXT]] = add nuw i64 [[INDEX]], 4
+; CHECK-NEXT:    [[TMP27:%.*]] = icmp eq i64 [[INDEX_NEXT]], 100
+; CHECK-NEXT:    br i1 [[TMP27]], label [[MIDDLE_BLOCK:%.*]], label [[VECTOR_BODY]], !llvm.loop [[LOOP9:![0-9]+]]
+; CHECK:       middle.block:
+; CHECK-NEXT:    br i1 true, label [[FOR_COND_CLEANUP:%.*]], label [[SCALAR_PH]]
+; CHECK:       scalar.ph:
+; CHECK-NEXT:    [[BC_RESUME_VAL:%.*]] = phi i64 [ 100, [[MIDDLE_BLOCK]] ], [ 0, [[ENTRY:%.*]] ], [ 0, [[VECTOR_MEMCHECK]] ]
 ; CHECK-NEXT:    br label [[FOR_BODY:%.*]]
 ; CHECK:       for.cond.cleanup:
 ; CHECK-NEXT:    ret void
 ; CHECK:       for.body:
-; CHECK-NEXT:    [[INDVARS_IV:%.*]] = phi i64 [ 0, [[ENTRY:%.*]] ], [ [[INDVARS_IV_NEXT:%.*]], [[FOR_BODY]] ]
-; CHECK-NEXT:    [[ARRAYIDX:%.*]] = getelementptr inbounds i32, i32* [[PREDS:%.*]], i64 [[INDVARS_IV]]
-; CHECK-NEXT:    [[TMP0:%.*]] = load i32, i32* [[ARRAYIDX]], align 4
-; CHECK-NEXT:    [[CMP1_NOT:%.*]] = icmp eq i32 [[TMP0]], 0
-; CHECK-NEXT:    [[SPEC_SELECT:%.*]] = select i1 [[CMP1_NOT]], float* [[BASE2:%.*]], float* [[BASE1:%.*]]
+; CHECK-NEXT:    [[INDVARS_IV:%.*]] = phi i64 [ [[BC_RESUME_VAL]], [[SCALAR_PH]] ], [ [[INDVARS_IV_NEXT:%.*]], [[FOR_BODY]] ]
+; CHECK-NEXT:    [[ARRAYIDX:%.*]] = getelementptr inbounds i32, i32* [[PREDS]], i64 [[INDVARS_IV]]
+; CHECK-NEXT:    [[TMP28:%.*]] = load i32, i32* [[ARRAYIDX]], align 4
+; CHECK-NEXT:    [[CMP1_NOT:%.*]] = icmp eq i32 [[TMP28]], 0
+; CHECK-NEXT:    [[SPEC_SELECT:%.*]] = select i1 [[CMP1_NOT]], float* [[BASE2]], float* [[BASE1]]
 ; CHECK-NEXT:    [[DOTSINK_IN:%.*]] = getelementptr inbounds float, float* [[SPEC_SELECT]], i64 [[INDVARS_IV]]
 ; CHECK-NEXT:    [[DOTSINK:%.*]] = load float, float* [[DOTSINK_IN]], align 4
-; CHECK-NEXT:    [[TMP1:%.*]] = getelementptr inbounds float, float* [[DEST:%.*]], i64 [[INDVARS_IV]]
-; CHECK-NEXT:    store float [[DOTSINK]], float* [[TMP1]], align 4
+; CHECK-NEXT:    [[TMP29:%.*]] = getelementptr inbounds float, float* [[DEST]], i64 [[INDVARS_IV]]
+; CHECK-NEXT:    store float [[DOTSINK]], float* [[TMP29]], align 4
 ; CHECK-NEXT:    [[INDVARS_IV_NEXT]] = add nuw nsw i64 [[INDVARS_IV]], 1
 ; CHECK-NEXT:    [[EXITCOND_NOT:%.*]] = icmp eq i64 [[INDVARS_IV_NEXT]], 100
-; CHECK-NEXT:    br i1 [[EXITCOND_NOT]], label [[FOR_COND_CLEANUP:%.*]], label [[FOR_BODY]]
+; CHECK-NEXT:    br i1 [[EXITCOND_NOT]], label [[FOR_COND_CLEANUP]], label [[FOR_BODY]], !llvm.loop [[LOOP11:![0-9]+]]
 ;
 entry:
   br label %for.body
 
 for.cond.cleanup:
   ret void
 
 for.body:

 ;;       offset = i+1;
 ;;     B[i] = A[offset];
 ;;   }
 ;; }
 
 define dso_local void @forked_ptrs_same_base_different_offset(float* nocapture readonly %Base, float* nocapture %Dest, i32* nocapture readonly %Preds) {
 ; CHECK-LABEL: @forked_ptrs_same_base_different_offset(
 ; CHECK-NEXT:  entry:
+; CHECK-NEXT:    br i1 false, label [[SCALAR_PH:%.*]], label [[VECTOR_MEMCHECK:%.*]]
+; CHECK:       vector.memcheck:
+; CHECK-NEXT:    [[SCEVGEP:%.*]] = getelementptr float, float* [[DEST:%.*]], i64 100
+; CHECK-NEXT:    [[SCEVGEP4:%.*]] = getelementptr i32, i32* [[PREDS:%.*]], i64 100
+; CHECK-NEXT:    [[SCEVGEP7:%.*]] = getelementptr float, float* [[BASE:%.*]], i64 101
+; CHECK-NEXT:    [[TMP0:%.*]] = bitcast i32* [[SCEVGEP4]] to float*
+; CHECK-NEXT:    [[BOUND0:%.*]] = icmp ugt float* [[TMP0]], [[DEST]]
+; CHECK-NEXT:    [[TMP1:%.*]] = bitcast float* [[SCEVGEP]] to i32*
+; CHECK-NEXT:    [[BOUND1:%.*]] = icmp ugt i32* [[TMP1]], [[PREDS]]
+; CHECK-NEXT:    [[FOUND_CONFLICT:%.*]] = and i1 [[BOUND0]], [[BOUND1]]
+; CHECK-NEXT:    [[BOUND09:%.*]] = icmp ugt float* [[SCEVGEP7]], [[DEST]]
+; CHECK-NEXT:    [[BOUND110:%.*]] = icmp ugt float* [[SCEVGEP]], [[BASE]]
+; CHECK-NEXT:    [[FOUND_CONFLICT11:%.*]] = and i1 [[BOUND09]], [[BOUND110]]
+; CHECK-NEXT:    [[CONFLICT_RDX:%.*]] = or i1 [[FOUND_CONFLICT]], [[FOUND_CONFLICT11]]
+; CHECK-NEXT:    br i1 [[CONFLICT_RDX]], label [[SCALAR_PH]], label [[VECTOR_PH:%.*]]
+; CHECK:       vector.ph:
+; CHECK-NEXT:    br label [[VECTOR_BODY:%.*]]
+; CHECK:       vector.body:
+; CHECK-NEXT:    [[INDEX:%.*]] = phi i64 [ 0, [[VECTOR_PH]] ], [ [[INDEX_NEXT:%.*]], [[VECTOR_BODY]] ]
+; CHECK-NEXT:    [[VEC_IND13:%.*]] = phi <4 x i32> [ <i32 0, i32 1, i32 2, i32 3>, [[VECTOR_PH]] ], [ [[VEC_IND_NEXT14:%.*]], [[VECTOR_BODY]] ]
+; CHECK-NEXT:    [[VEC_IND15:%.*]] = phi <4 x i32> [ <i32 0, i32 1, i32 2, i32 3>, [[VECTOR_PH]] ], [ [[VEC_IND_NEXT16:%.*]], [[VECTOR_BODY]] ]
+; CHECK-NEXT:    [[TMP2:%.*]] = getelementptr inbounds i32, i32* [[PREDS]], i64 [[INDEX]]
+; CHECK-NEXT:    [[TMP3:%.*]] = bitcast i32* [[TMP2]] to <4 x i32>*
+; CHECK-NEXT:    [[WIDE_LOAD:%.*]] = load <4 x i32>, <4 x i32>* [[TMP3]], align 4, !alias.scope !12
+; CHECK-NEXT:    [[TMP4:%.*]] = icmp eq <4 x i32> [[WIDE_LOAD]], zeroinitializer
+; CHECK-NEXT:    [[TMP5:%.*]] = add nuw nsw <4 x i32> [[VEC_IND13]], <i32 1, i32 1, i32 1, i32 1>
+; CHECK-NEXT:    [[TMP6:%.*]] = select <4 x i1> [[TMP4]], <4 x i32> [[TMP5]], <4 x i32> [[VEC_IND15]]
+; CHECK-NEXT:    [[TMP7:%.*]] = zext <4 x i32> [[TMP6]] to <4 x i64>
+; CHECK-NEXT:    [[TMP8:%.*]] = extractelement <4 x i64> [[TMP7]], i64 0
+; CHECK-NEXT:    [[TMP9:%.*]] = getelementptr inbounds float, float* [[BASE]], i64 [[TMP8]]
+; CHECK-NEXT:    [[TMP10:%.*]] = extractelement <4 x i64> [[TMP7]], i64 1
+; CHECK-NEXT:    [[TMP11:%.*]] = getelementptr inbounds float, float* [[BASE]], i64 [[TMP10]]
+; CHECK-NEXT:    [[TMP12:%.*]] = extractelement <4 x i64> [[TMP7]], i64 2
+; CHECK-NEXT:    [[TMP13:%.*]] = getelementptr inbounds float, float* [[BASE]], i64 [[TMP12]]
+; CHECK-NEXT:    [[TMP14:%.*]] = extractelement <4 x i64> [[TMP7]], i64 3
+; CHECK-NEXT:    [[TMP15:%.*]] = getelementptr inbounds float, float* [[BASE]], i64 [[TMP14]]
+; CHECK-NEXT:    [[TMP16:%.*]] = load float, float* [[TMP9]], align 4, !alias.scope !15
+; CHECK-NEXT:    [[TMP17:%.*]] = load float, float* [[TMP11]], align 4, !alias.scope !15
+; CHECK-NEXT:    [[TMP18:%.*]] = load float, float* [[TMP13]], align 4, !alias.scope !15
+; CHECK-NEXT:    [[TMP19:%.*]] = load float, float* [[TMP15]], align 4, !alias.scope !15
+; CHECK-NEXT:    [[TMP20:%.*]] = insertelement <4 x float> poison, float [[TMP16]], i64 0
+; CHECK-NEXT:    [[TMP21:%.*]] = insertelement <4 x float> [[TMP20]], float [[TMP17]], i64 1
+; CHECK-NEXT:    [[TMP22:%.*]] = insertelement <4 x float> [[TMP21]], float [[TMP18]], i64 2
+; CHECK-NEXT:    [[TMP23:%.*]] = insertelement <4 x float> [[TMP22]], float [[TMP19]], i64 3
+; CHECK-NEXT:    [[TMP24:%.*]] = getelementptr inbounds float, float* [[DEST]], i64 [[INDEX]]
+; CHECK-NEXT:    [[TMP25:%.*]] = bitcast float* [[TMP24]] to <4 x float>*
+; CHECK-NEXT:    store <4 x float> [[TMP23]], <4 x float>* [[TMP25]], align 4, !alias.scope !17, !noalias !19
+; CHECK-NEXT:    [[INDEX_NEXT]] = add nuw i64 [[INDEX]], 4
+; CHECK-NEXT:    [[VEC_IND_NEXT14]] = add <4 x i32> [[VEC_IND13]], <i32 4, i32 4, i32 4, i32 4>
+; CHECK-NEXT:    [[VEC_IND_NEXT16]] = add <4 x i32> [[VEC_IND15]], <i32 4, i32 4, i32 4, i32 4>
+; CHECK-NEXT:    [[TMP26:%.*]] = icmp eq i64 [[INDEX_NEXT]], 100
+; CHECK-NEXT:    br i1 [[TMP26]], label [[MIDDLE_BLOCK:%.*]], label [[VECTOR_BODY]], !llvm.loop [[LOOP20:![0-9]+]]
+; CHECK:       middle.block:
+; CHECK-NEXT:    br i1 true, label [[FOR_COND_CLEANUP:%.*]], label [[SCALAR_PH]]
+; CHECK:       scalar.ph:
+; CHECK-NEXT:    [[BC_RESUME_VAL:%.*]] = phi i64 [ 100, [[MIDDLE_BLOCK]] ], [ 0, [[ENTRY:%.*]] ], [ 0, [[VECTOR_MEMCHECK]] ]
+; CHECK-NEXT:    [[BC_RESUME_VAL12:%.*]] = phi i32 [ 100, [[MIDDLE_BLOCK]] ], [ 0, [[ENTRY]] ], [ 0, [[VECTOR_MEMCHECK]] ]
 ; CHECK-NEXT:    br label [[FOR_BODY:%.*]]
 ; CHECK:       for.cond.cleanup:
 ; CHECK-NEXT:    ret void
 ; CHECK:       for.body:
-; CHECK-NEXT:    [[INDVARS_IV:%.*]] = phi i64 [ 0, [[ENTRY:%.*]] ], [ [[INDVARS_IV_NEXT:%.*]], [[FOR_BODY]] ]
-; CHECK-NEXT:    [[I_014:%.*]] = phi i32 [ 0, [[ENTRY]] ], [ [[ADD:%.*]], [[FOR_BODY]] ]
-; CHECK-NEXT:    [[ARRAYIDX:%.*]] = getelementptr inbounds i32, i32* [[PREDS:%.*]], i64 [[INDVARS_IV]]
-; CHECK-NEXT:    [[TMP0:%.*]] = load i32, i32* [[ARRAYIDX]], align 4
-; CHECK-NEXT:    [[CMP1_NOT:%.*]] = icmp eq i32 [[TMP0]], 0
+; CHECK-NEXT:    [[INDVARS_IV:%.*]] = phi i64 [ [[BC_RESUME_VAL]], [[SCALAR_PH]] ], [ [[INDVARS_IV_NEXT:%.*]], [[FOR_BODY]] ]
+; CHECK-NEXT:    [[I_014:%.*]] = phi i32 [ [[BC_RESUME_VAL12]], [[SCALAR_PH]] ], [ [[ADD:%.*]], [[FOR_BODY]] ]
+; CHECK-NEXT:    [[ARRAYIDX:%.*]] = getelementptr inbounds i32, i32* [[PREDS]], i64 [[INDVARS_IV]]
+; CHECK-NEXT:    [[TMP27:%.*]] = load i32, i32* [[ARRAYIDX]], align 4
+; CHECK-NEXT:    [[CMP1_NOT:%.*]] = icmp eq i32 [[TMP27]], 0
 ; CHECK-NEXT:    [[INDVARS_IV_NEXT]] = add nuw nsw i64 [[INDVARS_IV]], 1
 ; CHECK-NEXT:    [[ADD]] = add nuw nsw i32 [[I_014]], 1
-; CHECK-NEXT:    [[TMP1:%.*]] = trunc i64 [[INDVARS_IV]] to i32
-; CHECK-NEXT:    [[OFFSET_0:%.*]] = select i1 [[CMP1_NOT]], i32 [[ADD]], i32 [[TMP1]]
+; CHECK-NEXT:    [[TMP28:%.*]] = trunc i64 [[INDVARS_IV]] to i32
+; CHECK-NEXT:    [[OFFSET_0:%.*]] = select i1 [[CMP1_NOT]], i32 [[ADD]], i32 [[TMP28]]
 ; CHECK-NEXT:    [[IDXPROM213:%.*]] = zext i32 [[OFFSET_0]] to i64
-; CHECK-NEXT:    [[ARRAYIDX3:%.*]] = getelementptr inbounds float, float* [[BASE:%.*]], i64 [[IDXPROM213]]
-; CHECK-NEXT:    [[TMP2:%.*]] = load float, float* [[ARRAYIDX3]], align 4
-; CHECK-NEXT:    [[ARRAYIDX5:%.*]] = getelementptr inbounds float, float* [[DEST:%.*]], i64 [[INDVARS_IV]]
-; CHECK-NEXT:    store float [[TMP2]], float* [[ARRAYIDX5]], align 4
+; CHECK-NEXT:    [[ARRAYIDX3:%.*]] = getelementptr inbounds float, float* [[BASE]], i64 [[IDXPROM213]]
+; CHECK-NEXT:    [[TMP29:%.*]] = load float, float* [[ARRAYIDX3]], align 4
+; CHECK-NEXT:    [[ARRAYIDX5:%.*]] = getelementptr inbounds float, float* [[DEST]], i64 [[INDVARS_IV]]
+; CHECK-NEXT:    store float [[TMP29]], float* [[ARRAYIDX5]], align 4
 ; CHECK-NEXT:    [[EXITCOND_NOT:%.*]] = icmp eq i64 [[INDVARS_IV_NEXT]], 100
-; CHECK-NEXT:    br i1 [[EXITCOND_NOT]], label [[FOR_COND_CLEANUP:%.*]], label [[FOR_BODY]]
+; CHECK-NEXT:    br i1 [[EXITCOND_NOT]], label [[FOR_COND_CLEANUP]], label [[FOR_BODY]], !llvm.loop [[LOOP21:![0-9]+]]
 ;
 entry:
   br label %for.body
 
 for.cond.cleanup:                                 ; preds = %for.body
   ret void
 
 for.body:                                         ; preds = %entry, %for.body