Infrastructure to allow use of PGO in inliner

[eraman]

Summary

This patch provides the following infrastructure to enable the use of PGO in inliner:

• Enable the use of block level profile information in inliner
• Incremental update of block frequency information during inlining
• Update the function entry counts of callees when they get inlined into callers.

[davidxl]

The subject of the patch is misleading -- it should really be 'Make block/callsite level profile data available for inliner'

[zzheng]

A few suggestions to make code more easy to read. This patch of course needs a PGO expert to review.

include/llvm/Transforms/IPO/InlinerPass.h

110

Where's these two being used?

lib/Analysis/InlineCost.cpp

622

Unused variable: CallerEntryCount

627

Caller->getEntryCount() called twice, this looks simpler:

Optional<uint64_t> CallerEntryCount = Caller->getEntryCount();
if (CallerEntryCount.hasValue()) {
  uint64_t CallSiteCount =
          CallerEntryCount.getValue() * CallSiteFreq / CallerEntryFreq;
}

1577

Empty comment line, I think it can be removed.

[eraman]

Address comments by zzheng

[eraman]

Thanks for the comments.

include/llvm/Transforms/IPO/InlinerPass.h

106

Removed them. I had initially used them and later replaced them by getXXXFunctor methods but forgot to remove those fields.

[junbuml]

lib/Analysis/InlineCost.cpp

1465

I cannot see any use of this function. Are you planing to hook this function in heuristic in this patch ?

1583

You can call LoopInfo LI(DT) instead of LoopInfo LI; LI.analyze(DT);

1586

BranchProbabilityInfo BPI(*F, LI); will call calculate(F, LI);

1589

You can also call BlockFrequencyInfo(*F, BPI, LI), which call calculate(*F, BPI, LI); inside.

[davidxl]

include/llvm/Transforms/IPO/InlinerPass.h

103

Can they be made pure virtual -- probably not if the derived class is not required to override it.

include/llvm/Transforms/Utils/Cloning.h

51

Is there a common header to put this decl in?

lib/Analysis/InlineCost.cpp

75

Remove this -- it can be folded in the threshold adjusting method tuned in the future.

81

I suggest removing these two parameters in these patch, as they are for not irrelevant and confusing (and subject to change in the very near future when summary data is available to be used here).

The objective of this patch is to provide infrastructure hooks to feed profile data to the inliner, not to tune/or change the current inline behavior/decision -- as that needs more design and experiment. To accomplish that goal, I suggest simply add a dummy wrapper function to do this:

int getAdjustedThreshold(int current_threshold, uint64_t callsite_count attribute((unused))) {

// just return the input threshold for now
return current_threshold;

}

In the future, I expect the threshold is different based on callsite_count and summary cutoffs.

623

Define a helper method to get callsite profile count.

629

call the proposed 'getAdjustedThreshold(Threshold, CallSiteCount);

1465

Remove unused function.

[davidxl]

When the invalidation happens, the updated entry count information gets discarded it seems. This is wrong. The data should be propagated back to the IR. The information can be useful later for decisions such as function layout and optimize for size etc.

Some test case is also needed to test that the entry counts can be properly updated during inlining.

lib/Transforms/IPO/InlineSimple.cpp

108

\p OrigBB \p NewBB

123

Freq --> OrigBBFreq with comment it is OrigBB's frequency in callee

128

\p Callee ... after it got inlined at callsite in block \p CallBB

143

computing callsite count belongs to a common helper function -- which can be used elsewhere too.

146

It is an estimate because the limitation of frequency propagation algorithm (unable to handle zero BP etc).

It is helpful to add a debug message here to indicate this condition.

[eraman]

Address review comments and add a test case to function entry counts are correctly updated.

[eraman]

In D16381#334500, @davidxl wrote:

When the invalidation happens, the updated entry count information gets discarded it seems. This is wrong. The data should be propagated back to the IR. The information can be useful later for decisions such as function layout and optimize for size etc.

UpdateEntryCount in InlineSimple.cpp calls setEntryCount and hence the counts are not lost.

Some test case is also needed to test that the entry counts can be properly updated during inlining.

Added a test case.

lib/Transforms/IPO/InlineSimple.cpp

143

I have placed this helper in Inlinecost.cpp.

[eraman]

include/llvm/Transforms/IPO/InlinerPass.h

103

AlwaysInliner then has to implement this method to return nullptr. I don't see any advantage in making it pyure virtual.

include/llvm/Transforms/Utils/Cloning.h

51

I could leave it in Cloning.h and include it in InlineSimple.cpp and get rid of it in InlinerPass.h, but this adds an unnecessary dependence to InlineSimple.cpp. There is no other header file common to the inliner proper and CloneFunction.cpp where it is appropriate to add this.

lib/Analysis/InlineCost.cpp

1465

Yes, I was planning to use this as part of tuning, but I've now removed it from this patch.

[davidxl]

We need to add more test cases. For instance

1. two callsites to one callee all get inlined -- the callee should have zero count left
2. scaling testing -- especially interesting in the context of top-down inlining (in the future we may have more heuristics to enable more top down inining, there are existing heuristics that can be used to trigger the case):

a ---> (200) ---> c
b ---> (300) ---> c
where c has entry count of 500

c-->(200) --> e
d -->(300) --> e
where e has entry count of 500.

Suppose there are two inlines in the following order: a->c, and a->e

After inlining, testing e's entry count is properly updated.

include/llvm/Analysis/InlineCost.h

44

suggested comment change: ... on demand, cached (for callees), and incrementally updated (for callers). The caller BFI is invalidated after inlining is done for (the caller).

53

Typo -- frequency

lib/Analysis/InlineCost.cpp

620

This guard is wrong :1) it should check caller entry count, not callee entry count. 2) hasPGOCounts also depends on other conditions.

In fact, this condition can be removed.

1564

Add a comment for the function.

1577

Irrelevant comment line?

[eraman]

Address David's review comments.

[eraman]

I've added two more test cases.

include/llvm/Analysis/InlineCost.h

44

This class itself is agnostic about callers and callees. All it does is cache the BFI and invalidate them when required - and that's what the comment says.

lib/Analysis/InlineCost.cpp

620

Yes, this check is not needed and I've removed it.

[eraman]

Chandler and Hal, could you please give your feedback on this patch? Even if you can not give detailed comments right now, any high level comments will be very useful and I can iterate on this patch based on them.

[davidxl]

Nice test case.

Dehao mentioned there is a problem with BB splitting when a basic block has two callsites -- after the first call gets inlined, the newly split block with the second callsite does not have updated profile data. Please handle that (with a proper test case).

[junbuml]

lib/Analysis/InlineCost.cpp

618–619

Call and CallBB seems to be used only in llvm::getBlockCount(CallBB, BFA);

1574

Can we guarantee FunctionEntryFreq is always non-zero if EntryCount is non-zero ?

lib/Transforms/IPO/InlineSimple.cpp

125

Should we have (double) here ?

126

why not checking CalleeEntryFreq * CallSiteFreq is non-zero.

162

No need to have braces.

[eraman]

In D16381#341243, @davidxl wrote:

Nice test case.

Dehao mentioned there is a problem with BB splitting when a basic block has two callsites -- after the first call gets inlined, the newly split block with the second callsite does not have updated profile data. Please handle that (with a proper test case).

I am working on the fix. I am also going to refactor the code a bit to do all updates in the base Inliner class rather than SimpleInliner. My original reasoning was that we don't have to do the updates for AlwaysInliner, but that is not true. With PGO, if always inline pass inlines a hot callsite, the callee will not be updated with the right entruy count. Besides using callbacks between the base and derived class looks ugly. I am going to move all the updates to the base class (there will still be a callback passed to the cloning methods) and guard the updates with a check for PGO. Later, we can refine this to support updates for non-PGO cases as well.

[eraman]

This fixes a bug (BB containing call's successor didn't have the right BFI), addresses reviewer comments and has been rebased to a recent head.

lib/Analysis/InlineCost.cpp

1574

FunctionEntryFreq is always non-zero and that doesn't depend on entry count.

lib/Transforms/IPO/InlineSimple.cpp

125

Not sure why that is needed.

126

It is dividing by CalleeEntryFreq and multiplying by CallSiteFreq, so this is a problem only when CalleeEntryFreq is 0. As I wrote in a previous comment, that is not possible.

[davidxl]

include/llvm/Transforms/IPO/InlinerPass.h

80

--> hasProfileData

lib/Transforms/IPO/Inliner.cpp

433

hasProfileData

583

add a comment here.

test/Transforms/Inline/function-count-update.ll

5

into two callsites in the same block.

21

Can you make these two calls in a block that is not the entry block?

[davidxl]

Please also add a test case that covers proper profile update with always inline as intended for the refactoring.

[davidxl]

include/llvm/Analysis/InlineCost.h

152

I suggest making this a member method of BFA. Also provide a wrapper method -- this will be the primary API used by other clients for callsite hotness:

Optional<uint64_t> getCallsiteCount(CallSite CS);

[eraman]

In D16381#342401, @davidxl wrote:

Please also add a test case that covers proper profile update with always inline as intended for the refactoring.

Done. I have added the alwaysinline attribute to the callee in the first test case and have run it with -always-inline alone.

include/llvm/Analysis/InlineCost.h

152

I agree that this needs to be moved somewhere else, but I am not convinced BFA is that place. In the other profile refactoring patch, I have created a ProfileCommon.h. Perhaps that is a good place for profile related urility methods like this?

test/Transforms/Inline/function-count-update.ll

21

That does not matter for the purposes of this test case.

[eraman]

Address David's comments.

[davidxl]

include/llvm/Analysis/InlineCost.h

152

ok -- ProfileCommon.h will be a better place in the future. For now let's keep it here -- but I think we should have a top level wrapper to get count for callsite here.

test/Transforms/Inline/function-count-update.ll

6

in a single callee or in a single BB?

The test intends to verify that the profile update of the second inlined callsite is correct after block split -- so having the callee identical in the two sites are not essential to the test.

22

The purpose is to verify that copyBlockFrequency after bb split works in general not just the entry block.

[eraman]

include/llvm/Analysis/InlineCost.h

152

Do you want the wrapper in InlineCost.cpp or in ProfileCommon.h (later)? As of now, there are two calls to this and one of them can not pass CS (this is in Inliner.cpp during BFI updates) since the call instruction in CS has been removed.

I agree that getProfileCount(CS) is a useful API, but I think that should be somewhere like ProfileCommon

test/Transforms/Inline/function-count-update.ll

6

This is a typo - I meant to write "in the same caller". I have fixed the comments. Yes, for the purpose of this test, we don't need the callee to be the same. I have made the caller call 2 different functions. I also don't think making the calls in a block other than the entry makes any difference, but since it doesn't hurt, I've made that change as well.

[eraman]

Tweaks to a test case based on David's feedback.

[eraman]

Ping.

[davidxl]

This is a very important enhancement that many people and tuning work are waiting for. It is IMO very clean, solid and non-intrusive. Before we move on, I'd like to see more testings on large apps for sanity.

[eraman]

Ping. I would like to move forward on this to enable PGO improvements in
inliner and function layout (separating cold functions becomes effective if
we have their entry counts after inlining). Specifically, I think the code
that computes BFA is isolated enough that ripping it out when inliner is
ported to the new pass manager is not very intrusive.

I did more testing as asked by David. Specifically,

1. Turn on the updates by default (instead of inly in PGO) and ran llvm

testsuite

2. Turn on the updates by default and build clang.
3. Build Google internal compiler benchmark suite in PGO mode with this

patch enabled.

These tests above didn't reveal any issues.

Thanks,
Easwaran

[davidxl]

Thanks for collecting the data!

I have a couple of more comments below:

lib/Analysis/InlineCost.cpp

618

This call has the side effect of force computing BFI even when it is disabled (with option). I think CallAnalyzer needs to have a wrapper to this function and check the settings before this is called.

lib/Transforms/IPO/Inliner.cpp

428

Needs to be guarded with EnableProfile?

446

I think we should introduce a more general flag here EnableProfile. This flag's value is determined by an internal option:

--enable-profile-in-inliner=default|yes|no

With yes and no can be used to force turning on|off while default is subject to compiler: for now if hasProfile is true, turn it on otherwise off.

587

Should this be guarded with EnableProfile too?

[eraman]

lib/Analysis/InlineCost.cpp

618

I have guarded the computation in getBlockCount by a check to see if BFA is nullptr. Also made sure getInlineCost gets a non-null BFA only when HasProfileData is true.

lib/Transforms/IPO/Inliner.cpp

446

I don't prefer to add a new flag for that. I think the current solution of checking if profile is turned on is sufficient for now.

587

The callee copyBlockFrequency has the guard, so it is not necessary at the callsite.

[davidxl]

LGTM.

This looks really great, so let's move on with this long waited missing feature.

1. watch for sanitizer build results
2. there are more tuning opportunities that can be done in the future -- e.g, if all incoming callgraph edges of a node have been analyzed and marked as non-inlinable, the node's prof data can be evicted from the cache. Maybe useful for LTO.

[chandlerc]

In D16381#367348, @davidxl wrote:

LGTM.

This looks really great, so let's move on with this long waited missing feature.

David, this is not an area of LLVM you have done substantial work on, and this is a very significant feature.

I'm sorry that I have not had time to review this yet, but the correct response is not for you to make a patch as LGTM. Please revert this and let's actually get it reviewed before it goes into the project.

[chandlerc]

First and foremost, sorry about snapping earlier. I shouldn't have done that, I was frustrated and not communicating very effectively. Thanks to Sean and Hal and others who wrote constructive and helpful emails to get this back on the rails. Secondly, sorry that I've neglected this patch for so long. I kept prioritizing working on the actual pass manager stuff over it, and I should have at least written this up.

So I do have some serious concerns with the approach. I think it is probably a nice way to prototype things and understand their impact (which is very important!) but there are several aspects of the design that seem to be the wrong approach. I've detailed them below.

I've said a few times before, but I continue to think that while some of the issues I've raised below could be addressed, that may not be the best use of time. I think it would probably be more effective to work on helping with the pass manager effort in order to make that effort finish more rapidly. There is a large amount of work that is essentially unblocked right now to help port function passes over. All of this is very easily parallelized.

Once that is done, I would work on designing a good interprocedural profile analysis interface with a good update API, and then teach the inliner to use that. I think that the process of porting the inliner to the new pass manager will end up being a fairly substantial change (essentially a re-write) which will make integrating this much cleaner and easier.

I'm somewhat worried that in its current form, this change would actually make it *harder* to port the inliner and more work to introduce the correct long-term design.

Below are detailed comments about the design issues, but also quite a few comments about serious API, code, and implementation issues with the patch as it currently stands. I think it still needs substantial work to go into the tree, even if the high level design concern above is addressed.

llvm/trunk/include/llvm/Analysis/InlineCost.h

42–55 ↗

(On Diff #49755)

This is pretty much re-implementing a tiny part of the new pass manager inside the inline cost analysis. That really feels like the wrong approach to me. Notably, this is even named exactly the same as we would want to name a port of BlockFrequencyInfo to the new pass manager.

I don't agree with this approach. Fundamentally, this is not the right long-term design for how the inliner should access profile information, and it actually obstructs getting the right design in place.

151–152 ↗

(On Diff #49755)

This seems like a surprising API to expose at the top level from the inline cost analysis.

llvm/trunk/include/llvm/Transforms/IPO/InlinerPass.h

30–37 ↗

(On Diff #49755)

These functor typedefs are a bit confusing. First off, std::function is very slow. Is this overhead going to cause a compile time issue?

The second two of these typedefs aren't used, please don't leave dead code in the patch.

Lastly, having them at the global scope seems like a bad design. It seems like they should be part of some API instead of just being global?

82 ↗

(On Diff #49755)

I would keep vertical space between declarations. It makes the comments much easier to read.

102 ↗

(On Diff #49755)

I would say "Indicates whether we are using profile guided optimization." in the comment.

However, I'm surprised we need both a bool and a unique_ptr -- wouldn't the nullness of the pointer indicate the same thing as the bool?

llvm/trunk/include/llvm/Transforms/Utils/Cloning.h

51–52 ↗

(On Diff #49755)

This is in essence an ODR violation -- two headers are defining the same typedef.

164 ↗

(On Diff #49755)

Initializing a functor from nullptr is pretty surprising. I would just use BlockCloningFunctor Ftor = BlockCloningFunctor() instead.

However, I think this is an indication of a larger design issue. I think the fact that you need to thread this cloning functor between very disparate layers of the code isn't good. I feel like the cloning layer should really be taught to directly support updating profile information when cloning. This of course may not be terrible reasonable to implement currently, as you have the inliner essentially maintaining a mini form of the pass manager internally and need to thread some way to update it through these layers. If that's the problem, I think it really is indicating that this needs to wait until we have the pass manager fixed so that we can layer this logic more cleanly.

llvm/trunk/lib/Analysis/InlineCost.cpp

585–588 ↗

(On Diff #49755)

It's a bit odd that this isn't a doxygen comment. Also that this is marked as "unused". What's the plan here?

618–620 ↗

(On Diff #49755)

Separating this out into two functions doesn't make a lot of sense here. You now have two parts of the code handling profile based inlining adjustments.

I think you should keep all of the profile based adjustments inline here, and integrate it with the function count logic above.

1570–1576 ↗

(On Diff #49755)

So, inside this routine, you're actually implementing a proper interprocedural profile analysis. I really think this needs to be extracted to provide a high level analysis API around interprocedurally weighted profile information.

1591–1595 ↗

(On Diff #49755)

While it happens that BPI doesn't keep any references or pointers back into the dominator tree or loop info, the APIs of these analyses actually would make that OK to do... Which makes this code a rather subtle mini implementation of the core logic of the pass manager but inside the inline cost analysis. That worries me some. At the very least it would need a lot of documentation to make it clear exactly what was going on and why this was a safe thing to do.

llvm/trunk/lib/Transforms/IPO/Inliner.cpp

376–380 ↗

(On Diff #49755)

You're dividing by CalleeEntryFreq because the original value was scaled up by that. This essentially strips some precision off. It would seem better to instead directly access the unscaled block frequency for the old BB, and then scale it correctly for the post-inlined state.

383–384 ↗

(On Diff #49755)

We have worked very hard throughout the PGO analysis infrastructure to not rely on actual hardware floating point. We have a broad collection of carefully written math utilities for this. One part of factoring this logic into a real IPO profile update routine would be to use the same facilities and infrastructure that the existing profile (and profile update) analyses use for this purpose.

570 ↗

(On Diff #49755)

Please use lambdas instead of std::bind -- they make the code much more readable as it is easier to understand how they behave. It also avoids the pain of using placeholder values.

759 ↗

(On Diff #49755)

I'm really concerned by the need to manually invalidate BFI in so many places. I think this is going to prove to be a very error prone pattern to maintain long term.

[eraman]

Thanks for the detailed comments Chandler. The comments related to problems around API, code and implementation are very helpful and I'll address them.

Your main concern is that this patch tries to provide the functionality of pass manager inside inline cost analysis. The intention is indeed to provide a restricted subset of pass manager's functionality for the inliner to use, but with the understanding that this is a temporary fix for inliner that should be easily replaceable when this functionality is available in PM. If this doesn't meet those goals (restricted to inliner and takes minimal effort to replace it by the new PM), I'll happily iterate on this patch to address that concern. I have responded inline to the comments related to this aspect.

Thanks,
Easwaran

llvm/trunk/include/llvm/Analysis/InlineCost.h

42–55 ↗

(On Diff #49755)

This is not *intended* to be a long term solution. The idea is to provide an interface similar to what the new pass manager provides so that when it lands, this code can be ripped off. I can rename it and/or move this code to a separate file if that will make the migration smoother.

151–152 ↗

(On Diff #49755)

I'll move it to ProfileCommon.h. I left it here because I don't want to make anything outside of inliner to use BlockFrequencyAnalysis

llvm/trunk/include/llvm/Transforms/Utils/Cloning.h

164 ↗

(On Diff #49755)

I think clients that invoke the cloning code might want to update different analyses or choose to not update at all. IMO, sinking all that into the cloning code doesn't seem a good idea,

llvm/trunk/lib/Analysis/InlineCost.cpp

1570–1576 ↗

(On Diff #49755)

Ok.

1591–1595 ↗

(On Diff #49755)

To reiterate, the intention is to *temporarily* provide the functionality that will be provided by the PM in a way that will make the transition easier. Agreed that this is not documented at all. Will fix that.

llvm/trunk/lib/Transforms/IPO/Inliner.cpp

376–380 ↗

(On Diff #49755)

The unscaled block frequency is meant to be used only for the initial BFI computation right? Moreover as we incrementally update the block frequency using setBlockFrequency interface of BFI, there may be blocks that do not have an unscaled value associated with them,

759 ↗

(On Diff #49755)

The alternative is to conservatively invalidate BFI at the beginning of the inliner loop. That is fine with me if the increase in compilation time is ok.

include/llvm/Analysis/InlineCost.h

 #define LLVM_ANALYSIS_INLINECOST_H
 
 #include "llvm/Analysis/CallGraphSCCPass.h"
 #include <cassert>
 #include <climits>
 
 namespace llvm {
 class AssumptionCacheTracker;
+class BlockFrequencyInfo;
 class CallSite;
 class DataLayout;
 class Function;
 class TargetTransformInfo;
 
 namespace InlineConstants {
   // Various magic constants used to adjust heuristics.
   const int InstrCost = 5;
   const int IndirectCallThreshold = 100;
   const int CallPenalty = 25;
   const int LastCallToStaticBonus = -15000;
   const int ColdccPenalty = 2000;
   const int NoreturnPenalty = 10000;
   /// Do not inline functions which allocate this many bytes on the stack
   /// when the caller is recursive.
   const unsigned TotalAllocaSizeRecursiveCaller = 1024;
 }
 
+/// \brief Block frequency analysis for multiple functions.
+/// This class mimics block frequency analysis on CGSCC level. Block frequency
+/// info is computed on demand and cached unless they are invalidated.
+class BlockFrequencyAnalysis {
+private:
+  DenseMap<Function *, BlockFrequencyInfo *> BFM;
+
+public:
+  ~BlockFrequencyAnalysis();
+  /// \brief Returns BlockFrequencyInfo for a function.
+  BlockFrequencyInfo *getBlockFrequencyInfo(Function *);
+  /// \brief Invalidates block frequency info for a function.
+  void invalidateBlockFrequencyInfo(Function *);
+};
+
 /// \brief Represents the cost of inlining a function.
 ///
 /// This supports special values for functions which should "always" or
 /// "never" be inlined. Otherwise, the cost represents a unitless amount;
 /// smaller values increase the likelihood of the function being inlined.
 ///
 /// Objects of this type also provide the adjusted threshold for inlining
 /// based on the information available for a particular callsite. They can be

 /// new threshold are computed with any accuracy. The new threshold can be
 /// used to bound the computation necessary to determine whether the cost is
 /// sufficiently low to warrant inlining.
 ///
 /// Also note that calling this function *dynamically* computes the cost of
 /// inlining the callsite. It is an expensive, heavyweight call.
 InlineCost getInlineCost(CallSite CS, int DefaultThreshold,
                          TargetTransformInfo &CalleeTTI,
-                         AssumptionCacheTracker *ACT);
+                         AssumptionCacheTracker *ACT,
+                         BlockFrequencyAnalysis *BFA);
 
 /// \brief Get an InlineCost with the callee explicitly specified.
 /// This allows you to calculate the cost of inlining a function via a
 /// pointer. This behaves exactly as the version with no explicit callee
 /// parameter in all other respects.
 //
 InlineCost getInlineCost(CallSite CS, Function *Callee, int DefaultThreshold,
                          TargetTransformInfo &CalleeTTI,
-                         AssumptionCacheTracker *ACT);
+                         AssumptionCacheTracker *ACT,
+                         BlockFrequencyAnalysis *BFA);
 
 int computeThresholdFromOptLevels(unsigned OptLevel, unsigned SizeOptLevel);
 
 /// \brief Return the default value of -inline-threshold.
 int getDefaultInlineThreshold();
 
 /// \brief Minimal filter to detect invalid constructs for inlining.
 bool isInlineViable(Function &Callee);
+
+/// \brief Return estimated count of the block \p BB.
+Optional<uint64_t> getBlockCount(BasicBlock *BB, BlockFrequencyAnalysis *BFA);
 }
 
 #endif

include/llvm/Transforms/IPO/InlinerPass.h

 
 #include "llvm/Analysis/CallGraphSCCPass.h"
 
 namespace llvm {
 class AssumptionCacheTracker;
 class CallSite;
 class DataLayout;
 class InlineCost;
+class BlockFrequencyAnalysis;
 template <class PtrType, unsigned SmallSize> class SmallPtrSet;
 
+// Functor invoked when a block is cloned during inlining.
+typedef std::function<void(const BasicBlock *, const BasicBlock *)>
+    BlockCloningFunctor;
+// Functor invoked when a function is inlined inside the basic block
+// containing the call.
+typedef std::function<void(BasicBlock *, Function *)> FunctionCloningFunctor;
+// Functor invoked when a function gets deleted during inlining.
+typedef std::function<void(Function *)> FunctionDeletedFunctor;
+
 /// Inliner - This class contains all of the helper code which is used to
 /// perform the inlining operations that do not depend on the policy.
 ///
 struct Inliner : public CallGraphSCCPass {
   explicit Inliner(char &ID);
   explicit Inliner(char &ID, bool InsertLifetime);
 
   /// getAnalysisUsage - For this class, we declare that we require and preserve
struct Inliner : public CallGraphSCCPass {
   /// deal with that subset of the functions.
   bool removeDeadFunctions(CallGraph &CG, bool AlwaysInlineOnly = false);
 
 private:
   // InsertLifetime - Insert @llvm.lifetime intrinsics.
   bool InsertLifetime;
 
   /// shouldInline - Return true if the inliner should attempt to
   /// inline at the given CallSite.
   bool shouldInline(CallSite CS);
+  /// Set the BFI of \p Dst to be the same as \p Src.
+  void copyBlockFrequency(BasicBlock *Src, BasicBlock *Dst);
+  /// Invalidates BFI for function \p F.
+  void invalidateBFI(Function *F);
+  /// Invalidates BFI for all functions in  \p SCC.
+  void invalidateBFI(CallGraphSCC &SCC);
+  /// Update function entry count for \p Callee which has been inlined into
+  /// \p CallBB.
+  void updateEntryCount(BasicBlock *CallBB, Function *Callee);
+  /// \brief Update block frequency of an inlined block.
+  /// This method updates the block frequency of \p NewBB which is a clone of
+  /// \p OrigBB when the callsite \p CS gets inlined. The frequency of \p NewBB
+  /// is computed as follows:
+  /// Freq(NewBB) = Freq(OrigBB) * CallSiteFreq / CalleeEntryFreq.
+  void updateBlockFreq(CallSite &CS, const BasicBlock *OrigBB,
+                       const BasicBlock *NewBB);
 
 protected:
   AssumptionCacheTracker *ACT;
+  std::unique_ptr<BlockFrequencyAnalysis> BFA;
+  /// Are we using profile guided optimization?
+  bool HasProfileData;
 };
 
 } // End llvm namespace
 
 #endif

include/llvm/Transforms/Utils/Cloning.h

 class CallGraph;
 class DataLayout;
 class Loop;
 class LoopInfo;
 class AllocaInst;
 class AssumptionCacheTracker;
 class DominatorTree;
 
+typedef std::function<void(const BasicBlock *, const BasicBlock *)>
+    BlockCloningFunctor;
+
 /// Return an exact copy of the specified module
 ///
 std::unique_ptr<Module> CloneModule(const Module *M);
 std::unique_ptr<Module> CloneModule(const Module *M, ValueToValueMapTy &VMap);
 
 /// Return a copy of the specified module. The ShouldCloneDefinition function
 /// controls whether a specific GlobalValue's definition is cloned. If the
 /// function returns false, the module copy will contain an external reference
void CloneFunctionInto(Function *NewFunc, const Function *OldFunc,
                        ValueMapTypeRemapper *TypeMapper = nullptr,
                        ValueMaterializer *Materializer = nullptr);
 
 void CloneAndPruneIntoFromInst(Function *NewFunc, const Function *OldFunc,
                                const Instruction *StartingInst,
                                ValueToValueMapTy &VMap, bool ModuleLevelChanges,
                                SmallVectorImpl<ReturnInst *> &Returns,
                                const char *NameSuffix = "",
-                               ClonedCodeInfo *CodeInfo = nullptr);
+                               ClonedCodeInfo *CodeInfo = nullptr,
+                               BlockCloningFunctor Ftor = nullptr);
 
 /// CloneAndPruneFunctionInto - This works exactly like CloneFunctionInto,
 /// except that it does some simple constant prop and DCE on the fly.  The
 /// effect of this is to copy significantly less code in cases where (for
 /// example) a function call with constant arguments is inlined, and those
 /// constant arguments cause a significant amount of code in the callee to be
 /// dead.  Since this doesn't produce an exactly copy of the input, it can't be
 /// used for things like CloneFunction or CloneModule.
 ///
 /// If ModuleLevelChanges is false, VMap contains no non-identity GlobalValue
 /// mappings.
 ///
 void CloneAndPruneFunctionInto(Function *NewFunc, const Function *OldFunc,
                                ValueToValueMapTy &VMap, bool ModuleLevelChanges,
-                               SmallVectorImpl<ReturnInst*> &Returns,
+                               SmallVectorImpl<ReturnInst *> &Returns,
                                const char *NameSuffix = "",
                                ClonedCodeInfo *CodeInfo = nullptr,
-                               Instruction *TheCall = nullptr);
+                               Instruction *TheCall = nullptr,
+                               BlockCloningFunctor Ftor = nullptr);
 
 /// InlineFunctionInfo - This class captures the data input to the
 /// InlineFunction call, and records the auxiliary results produced by it.
 class InlineFunctionInfo {
 public:
   explicit InlineFunctionInfo(CallGraph *cg = nullptr,
-                              AssumptionCacheTracker *ACT = nullptr)
-      : CG(cg), ACT(ACT) {}
+                              AssumptionCacheTracker *ACT = nullptr,
+                              BlockCloningFunctor Ftor = nullptr)
+      : CG(cg), ACT(ACT), Ftor(Ftor) {}
 
   /// CG - If non-null, InlineFunction will update the callgraph to reflect the
   /// changes it makes.
   CallGraph *CG;
   AssumptionCacheTracker *ACT;
+  // Functor that is invoked when a block is cloned into the new function.
+  BlockCloningFunctor Ftor;
 
   /// StaticAllocas - InlineFunction fills this in with all static allocas that
   /// get copied into the caller.
   SmallVector<AllocaInst *, 4> StaticAllocas;
 
   /// InlinedCalls - InlineFunction fills this in with callsites that were
   /// inlined from the callee.  This is only filled in if CG is non-null.
   SmallVector<WeakVH, 8> InlinedCalls;

lib/Analysis/InlineCost.cpp

 
 #include "llvm/Analysis/InlineCost.h"
 #include "llvm/ADT/STLExtras.h"
 #include "llvm/ADT/SetVector.h"
 #include "llvm/ADT/SmallPtrSet.h"
 #include "llvm/ADT/SmallVector.h"
 #include "llvm/ADT/Statistic.h"
 #include "llvm/Analysis/AssumptionCache.h"
+#include "llvm/Analysis/BlockFrequencyInfo.h"
+#include "llvm/Analysis/BlockFrequencyInfoImpl.h"
+#include "llvm/Analysis/BranchProbabilityInfo.h"
 #include "llvm/Analysis/CodeMetrics.h"
 #include "llvm/Analysis/ConstantFolding.h"
 #include "llvm/Analysis/InstructionSimplify.h"
+#include "llvm/Analysis/LoopInfo.h"
 #include "llvm/Analysis/TargetTransformInfo.h"
 #include "llvm/IR/CallSite.h"
 #include "llvm/IR/CallingConv.h"
 #include "llvm/IR/DataLayout.h"
+#include "llvm/IR/Dominators.h"
 #include "llvm/IR/GetElementPtrTypeIterator.h"
 #include "llvm/IR/GlobalAlias.h"
 #include "llvm/IR/InstVisitor.h"
 #include "llvm/IR/IntrinsicInst.h"
 #include "llvm/IR/Operator.h"
 #include "llvm/Support/Debug.h"
 #include "llvm/Support/raw_ostream.h"
 

 // PGO before we actually hook up inliner with analysis passes such as BPI and
 // BFI.
 static cl::opt<int> ColdThreshold(
     "inlinecold-threshold", cl::Hidden, cl::init(225),
     cl::desc("Threshold for inlining functions with cold attribute"));
 
 namespace {
 
 class CallAnalyzer : public InstVisitor<CallAnalyzer, bool> {
   typedef InstVisitor<CallAnalyzer, bool> Base;
   friend class InstVisitor<CallAnalyzer, bool>;
 
   /// The TargetTransformInfo available for this compilation.
   const TargetTransformInfo &TTI;
 
   /// The cache of @llvm.assume intrinsics.
   AssumptionCacheTracker *ACT;
 
   // The called function.
   Function &F;
 
   // The candidate callsite being analyzed. Please do not use this to do
   // analysis in the caller function; we want the inline cost query to be
   // easily cacheable. Instead, use the cover function paramHasAttr.
   CallSite CandidateCS;
 
+  BlockFrequencyAnalysis *BFA;
   int Threshold;
   int Cost;
 
   bool IsCallerRecursive;
   bool IsRecursiveCall;
   bool ExposesReturnsTwice;
   bool HasDynamicAlloca;
   bool ContainsNoDuplicateCall;
class CallAnalyzer : public InstVisitor<CallAnalyzer, bool> {
   /// inlined through this particular callsite.
   bool isKnownNonNullInCallee(Value *V);
 
   /// Update Threshold based on callsite properties such as callee
   /// attributes and callee hotness for PGO builds. The Callee is explicitly
   /// passed to support analyzing indirect calls whose target is inferred by
   /// analysis.
   void updateThreshold(CallSite CS, Function &Callee);
+  /// Adjust Threshold based on CallSiteCount and return the adjusted threshold.
+  int getAdjustedThreshold(int Threshold, Optional<uint64_t> CallSiteCount);
 
   // Custom analysis routines.
   bool analyzeBlock(BasicBlock *BB, SmallPtrSetImpl<const Value *> &EphValues);
 
   // Disable several entry points to the visitor so we don't accidentally use
   // them by declaring but not defining them here.
   void visit(Module *);     void visit(Module &);
   void visit(Function *);   void visit(Function &);
class CallAnalyzer : public InstVisitor<CallAnalyzer, bool> {
   bool visitIndirectBrInst(IndirectBrInst &IBI);
   bool visitResumeInst(ResumeInst &RI);
   bool visitCleanupReturnInst(CleanupReturnInst &RI);
   bool visitCatchReturnInst(CatchReturnInst &RI);
   bool visitUnreachableInst(UnreachableInst &I);
 
 public:
   CallAnalyzer(const TargetTransformInfo &TTI, AssumptionCacheTracker *ACT,
-               Function &Callee, int Threshold, CallSite CSArg)
-    : TTI(TTI), ACT(ACT), F(Callee), CandidateCS(CSArg), Threshold(Threshold),
-        Cost(0), IsCallerRecursive(false), IsRecursiveCall(false),
-        ExposesReturnsTwice(false), HasDynamicAlloca(false),
-        ContainsNoDuplicateCall(false), HasReturn(false), HasIndirectBr(false),
-        HasFrameEscape(false), AllocatedSize(0), NumInstructions(0),
-        NumVectorInstructions(0), FiftyPercentVectorBonus(0),
-        TenPercentVectorBonus(0), VectorBonus(0), NumConstantArgs(0),
-        NumConstantOffsetPtrArgs(0), NumAllocaArgs(0), NumConstantPtrCmps(0),
-        NumConstantPtrDiffs(0), NumInstructionsSimplified(0),
-        SROACostSavings(0), SROACostSavingsLost(0) {}
+               Function &Callee, int Threshold, CallSite CSArg,
+               BlockFrequencyAnalysis *BFA)
+      : TTI(TTI), ACT(ACT), F(Callee), CandidateCS(CSArg), BFA(BFA),
+        Threshold(Threshold), Cost(0), IsCallerRecursive(false),
+        IsRecursiveCall(false), ExposesReturnsTwice(false),
+        HasDynamicAlloca(false), ContainsNoDuplicateCall(false),
+        HasReturn(false), HasIndirectBr(false), HasFrameEscape(false),
+        AllocatedSize(0), NumInstructions(0), NumVectorInstructions(0),
+        FiftyPercentVectorBonus(0), TenPercentVectorBonus(0), VectorBonus(0),
+        NumConstantArgs(0), NumConstantOffsetPtrArgs(0), NumAllocaArgs(0),
+        NumConstantPtrCmps(0), NumConstantPtrDiffs(0),
+        NumInstructionsSimplified(0), SROACostSavings(0),
+        SROACostSavingsLost(0) {}
 
   bool analyzeCall(CallSite CS);
 
   int getThreshold() { return Threshold; }
   int getCost() { return Cost; }
 
   // Keep a bunch of stats about the cost savings found so we can print them
   // out when debugging.
if (isAllocaDerivedArg(V))
     // We can actually predict the result of comparisons between an
     // alloca-derived value and null. Note that this fires regardless of
     // SROA firing.
     return true;
   
   return false;
 }
 
+// Adjust the threshold based on callsite hotness. Currently this is a nop.
+int CallAnalyzer::getAdjustedThreshold(int Threshold,
+                                       Optional<uint64_t> CallSiteCount
+                                       __attribute__((unused))) {
+  // FIXME: The new threshold should be computed from the given Threshold and
+  // the callsite hotness.
+  return Threshold;
+}
+
 void CallAnalyzer::updateThreshold(CallSite CS, Function &Callee) {
   // If -inline-threshold is not given, listen to the optsize and minsize
   // attributes when they would decrease the threshold.
   Function *Caller = CS.getCaller();
 
   if (!(DefaultInlineThreshold.getNumOccurrences() > 0)) {
     if (Caller->optForMinSize() && OptMinSizeThreshold < Threshold)
       Threshold = OptMinSizeThreshold;
     else if (Caller->optForSize() && OptSizeThreshold < Threshold)
       Threshold = OptSizeThreshold;
   }
 
   // If profile information is available, use that to adjust threshold of hot
   // and cold functions.
   // FIXME: The heuristic used below for determining hotness and coldness are
   // based on preliminary SPEC tuning and may not be optimal. Replace this with
   // a well-tuned heuristic based on *callsite* hotness and not callee hotness.
   uint64_t FunctionCount = 0, MaxFunctionCount = 0;
   bool HasPGOCounts = false;
   if (Callee.getEntryCount() && Callee.getParent()->getMaximumFunctionCount()) {
     HasPGOCounts = true;
     FunctionCount = Callee.getEntryCount().getValue();
     MaxFunctionCount = Callee.getParent()->getMaximumFunctionCount().getValue();
   }
+  Optional<uint64_t> CallSiteCount =
+      llvm::getBlockCount(CS.getInstruction()->getParent(), BFA);
+  Threshold = getAdjustedThreshold(Threshold, CallSiteCount);
 
   // Listen to the inlinehint attribute or profile based hotness information
   // when it would increase the threshold and the caller does not need to
   // minimize its size.
   bool InlineHint =
       Callee.hasFnAttribute(Attribute::InlineHint) ||
       (HasPGOCounts &&
        FunctionCount >= (uint64_t)(0.3 * (double)MaxFunctionCount));
   if (InlineHint && HintThreshold > Threshold && !Caller->optForMinSize())
     Threshold = HintThreshold;
 
   // Listen to the cold attribute or profile based coldness information
   // when it would decrease the threshold.
   bool ColdCallee =
       Callee.hasFnAttribute(Attribute::Cold) ||
       (HasPGOCounts &&
        FunctionCount <= (uint64_t)(0.01 * (double)MaxFunctionCount));
bool CallAnalyzer::visitCallSite(CallSite CS) {
   if (!F)
     return Base::visitCallSite(CS);
 
   // If we have a constant that we are calling as a function, we can peer
   // through it and see the function target. This happens not infrequently
   // during devirtualization and so we want to give it a hefty bonus for
   // inlining, but cap that bonus in the event that inlining wouldn't pan
   // out. Pretend to inline the function, with a custom threshold.
-  CallAnalyzer CA(TTI, ACT, *F, InlineConstants::IndirectCallThreshold, CS);
+  CallAnalyzer CA(TTI, ACT, *F, InlineConstants::IndirectCallThreshold, CS,
+                  BFA);
   if (CA.analyzeCall(CS)) {
     // We were able to inline the indirect call! Subtract the cost from the
     // threshold to get the bonus we want to apply, but don't go below zero.
     Cost -= std::max(0, CA.getThreshold() - CA.getCost());
   }
 
   return Base::visitCallSite(CS);
 }
static bool functionsHaveCompatibleAttributes(Function *Caller,
                                               Function *Callee,
                                               TargetTransformInfo &TTI) {
   return TTI.areInlineCompatible(Caller, Callee) &&
          AttributeFuncs::areInlineCompatible(*Caller, *Callee);
 }
 
 InlineCost llvm::getInlineCost(CallSite CS, int DefaultThreshold,
                                TargetTransformInfo &CalleeTTI,
-                               AssumptionCacheTracker *ACT) {
+                               AssumptionCacheTracker *ACT,
+                               BlockFrequencyAnalysis *BFA) {
   return getInlineCost(CS, CS.getCalledFunction(), DefaultThreshold, CalleeTTI,
-                       ACT);
+                       ACT, BFA);
 }
 
 int llvm::computeThresholdFromOptLevels(unsigned OptLevel,
                                         unsigned SizeOptLevel) {
   if (OptLevel > 2)
     return OptAggressiveThreshold;
   if (SizeOptLevel == 1) // -Os
     return OptSizeThreshold;
   if (SizeOptLevel == 2) // -Oz
     return OptMinSizeThreshold;
   return DefaultInlineThreshold;
 }
 
 int llvm::getDefaultInlineThreshold() { return DefaultInlineThreshold; }
 
 InlineCost llvm::getInlineCost(CallSite CS, Function *Callee,
                                int DefaultThreshold,
                                TargetTransformInfo &CalleeTTI,
-                               AssumptionCacheTracker *ACT) {
+                               AssumptionCacheTracker *ACT,
+                               BlockFrequencyAnalysis *BFA) {
 
   // Cannot inline indirect calls.
   if (!Callee)
     return llvm::InlineCost::getNever();
 
   // Calls to functions with always-inline attributes should be inlined
   // whenever possible.
   if (CS.hasFnAttr(Attribute::AlwaysInline)) {
InlineCost llvm::getInlineCost(CallSite CS, Function *Callee,
   // marked noinline.
   if (Callee->mayBeOverridden() ||
       Callee->hasFnAttribute(Attribute::NoInline) || CS.isNoInline())
     return llvm::InlineCost::getNever();
 
   DEBUG(llvm::dbgs() << "      Analyzing call of " << Callee->getName()
         << "...\n");
 
-  CallAnalyzer CA(CalleeTTI, ACT, *Callee, DefaultThreshold, CS);
+  CallAnalyzer CA(CalleeTTI, ACT, *Callee, DefaultThreshold, CS, BFA);
   bool ShouldInline = CA.analyzeCall(CS);
 
   DEBUG(CA.dump());
 
   // Check if there was a reason to force inlining or no inlining.
   if (!ShouldInline && CA.getCost() < CA.getThreshold())
     return InlineCost::getNever();
   if (ShouldInline && CA.getCost() >= CA.getThreshold())
for (auto &II : *BI) {
           CS.getCalledFunction()->getIntrinsicID() ==
               llvm::Intrinsic::localescape)
         return false;
     }
   }
 
   return true;
 }
+
+/// \brief Get estimated execution count for \p BB.
+Optional<uint64_t> llvm::getBlockCount(BasicBlock *BB,
+                                       BlockFrequencyAnalysis *BFA) {
+  if (!BFA)
+    return None;
+  Function *F = BB->getParent();
+  Optional<uint64_t> EntryCount = F->getEntryCount();
+  if (!EntryCount)
+    return None;
+  BlockFrequencyInfo *BFI = BFA->getBlockFrequencyInfo(F);
+  uint64_t BBFreq = BFI->getBlockFreq(BB).getFrequency();
+  uint64_t FunctionEntryFreq = BFI->getEntryFreq();
+  uint64_t BBCount = EntryCount.getValue() * BBFreq / FunctionEntryFreq;
+  return BBCount;
+}
+
+BlockFrequencyAnalysis::~BlockFrequencyAnalysis() {
+  for (auto &Entry : BFM) {
+    delete Entry.second;
+  }
+}
+
+/// \brief Get BlockFrequencyInfo for a function.
+BlockFrequencyInfo *BlockFrequencyAnalysis::getBlockFrequencyInfo(Function *F) {
+  auto Iter = BFM.find(F);
+  if (Iter != BFM.end())
+    return Iter->second;
+  // We need to create a BlockFrequencyInfo object for F and store it.
+  DominatorTree DT;
+  DT.recalculate(*F);
+  LoopInfo LI(DT);
+  BranchProbabilityInfo BPI(*F, LI);
+  BlockFrequencyInfo *BFI = new BlockFrequencyInfo(*F, BPI, LI);
+  BFM[F] = BFI;
+  return BFI;
+}
+
+/// \brief Invalidate BlockFrequencyInfo for a function.
+void BlockFrequencyAnalysis::invalidateBlockFrequencyInfo(Function *F) {
+  BFM.erase(F);
+}

lib/Transforms/IPO/InlineSimple.cpp

SimpleInliner(int Threshold) : Inliner(ID), DefaultThreshold(Threshold) {
     initializeSimpleInlinerPass(*PassRegistry::getPassRegistry());
   }
 
   static char ID; // Pass identification, replacement for typeid
 
   InlineCost getInlineCost(CallSite CS) override {
     Function *Callee = CS.getCalledFunction();
     TargetTransformInfo &TTI = TTIWP->getTTI(*Callee);
-    return llvm::getInlineCost(CS, DefaultThreshold, TTI, ACT);
+    return llvm::getInlineCost(CS, DefaultThreshold, TTI, ACT,
+                               HasProfileData ? BFA.get() : nullptr);
   }
 
   bool runOnSCC(CallGraphSCC &SCC) override;
   void getAnalysisUsage(AnalysisUsage &AU) const override;
 
 private:
   TargetTransformInfoWrapperPass *TTIWP;
 };

 bool SimpleInliner::runOnSCC(CallGraphSCC &SCC) {
   TTIWP = &getAnalysis<TargetTransformInfoWrapperPass>();
   return Inliner::runOnSCC(SCC);
 }
 
 void SimpleInliner::getAnalysisUsage(AnalysisUsage &AU) const {
   AU.addRequired<TargetTransformInfoWrapperPass>();
   Inliner::getAnalysisUsage(AU);
 }

lib/Transforms/IPO/Inliner.cpp

 //===----------------------------------------------------------------------===//
 
 #include "llvm/Transforms/IPO/InlinerPass.h"
 #include "llvm/ADT/SmallPtrSet.h"
 #include "llvm/ADT/Statistic.h"
 #include "llvm/Analysis/AliasAnalysis.h"
 #include "llvm/Analysis/AssumptionCache.h"
 #include "llvm/Analysis/BasicAliasAnalysis.h"
+#include "llvm/Analysis/BlockFrequencyInfo.h"
 #include "llvm/Analysis/CallGraph.h"
 #include "llvm/Analysis/InlineCost.h"
 #include "llvm/Analysis/TargetLibraryInfo.h"
 #include "llvm/IR/CallSite.h"
 #include "llvm/IR/DataLayout.h"
 #include "llvm/IR/DiagnosticInfo.h"
 #include "llvm/IR/Instructions.h"
 #include "llvm/IR/IntrinsicInst.h"

 STATISTIC(NumDeleted, "Number of functions deleted because all callers found");
 STATISTIC(NumMergedAllocas, "Number of allocas merged together");
 
 // This weirdly named statistic tracks the number of times that, when attempting
 // to inline a function A into B, we analyze the callers of B in order to see
 // if those would be more profitable and blocked inline steps.
 STATISTIC(NumCallerCallersAnalyzed, "Number of caller-callers analyzed");
 
-Inliner::Inliner(char &ID) : CallGraphSCCPass(ID), InsertLifetime(true) {}
+Inliner::Inliner(char &ID)
+    : CallGraphSCCPass(ID), InsertLifetime(true),
+      BFA(new BlockFrequencyAnalysis()) {}
 
 Inliner::Inliner(char &ID, bool InsertLifetime)
-    : CallGraphSCCPass(ID), InsertLifetime(InsertLifetime) {}
+    : CallGraphSCCPass(ID), InsertLifetime(InsertLifetime),
+      BFA(new BlockFrequencyAnalysis()) {}
 
 /// For this class, we declare that we require and preserve the call graph.
 /// If the derived class implements this method, it should
 /// always explicitly call the implementation here.
 void Inliner::getAnalysisUsage(AnalysisUsage &AU) const {
   AU.addRequired<AssumptionCacheTracker>();
   AU.addRequired<TargetLibraryInfoWrapperPass>();
   addUsedAAAnalyses(AU);
DEBUG(dbgs() << "    NOT Inlining: cost=" << IC.getCost()
           << ", thres=" << (IC.getCostDelta() + IC.getCost())
           << ", Call: " << *CS.getInstruction() << "\n");
     emitAnalysis(CS, Twine(CS.getCalledFunction()->getName() +
                            " too costly to inline (cost=") +
                          Twine(IC.getCost()) + ", threshold=" +
                          Twine(IC.getCostDelta() + IC.getCost()) + ")");
     return false;
   }
-  
   // Try to detect the case where the current inlining candidate caller (call
   // it B) is a static or linkonce-ODR function and is an inlining candidate
   // elsewhere, and the current candidate callee (call it C) is large enough
   // that inlining it into B would make B too big to inline later. In these
   // circumstances it may be best not to inline C into B, but to inline B into
   // its callers.
   //
   // This only applies to static and linkonce-ODR functions because those are
assert(unsigned(InlineHistoryID) < InlineHistory.size() &&
            "Invalid inline history ID");
     if (InlineHistory[InlineHistoryID].first == F)
       return true;
     InlineHistoryID = InlineHistory[InlineHistoryID].second;
   }
   return false;
 }
 
+/// \brief Update the frequency of a block that is cloned into the caller.
+/// This is invoked when \p OrigBB from the callee is cloned into \p NewBB in
+/// the caller.
+void Inliner::updateBlockFreq(CallSite &CS, const BasicBlock *OrigBB,
+                              const BasicBlock *NewBB) {
+  if (!HasProfileData)
+    return;
+  Instruction *Call = CS.getInstruction();
+  BasicBlock *CallBB = Call->getParent();
+  BlockFrequencyInfo *CalleeBFI =
+      BFA->getBlockFrequencyInfo(CS.getCalledFunction());
+  BlockFrequencyInfo *CallerBFI =
+      BFA->getBlockFrequencyInfo(CallBB->getParent());
+  // Find the number of times OrigBB is executed per invocation of the callee
+  // and multiply by the number of times callee is executed in the caller.
+  // Freq(NewBB) = Freq(OrigBB) * CallSiteFreq / CalleeEntryFreq.
+  uint64_t CallSiteFreq = CallerBFI->getBlockFreq(CallBB).getFrequency();
+  uint64_t CalleeEntryFreq = CalleeBFI->getEntryFreq();
+  // Frequency of OrigBB in the callee.
+  BlockFrequency OrigBBFreq = CalleeBFI->getBlockFreq(OrigBB);
+  CallerBFI->setBlockFreq(NewBB, (double)(OrigBBFreq.getFrequency()) /
+                                     CalleeEntryFreq * CallSiteFreq);
+}
+
+/// \brief Update entry count of \p Callee after it got inlined at a callsite
+/// in block \p CallBB.
+void Inliner::updateEntryCount(BasicBlock *CallBB, Function *Callee) {
+  if (!HasProfileData)
+    return;
+  // If the callee has a original count of N, and the estimated count of
+  // callsite is M, the new callee count is set to N - M. M is estimated from
+  // the caller's entry count, its entry block frequency and the block frequency
+  // of the callsite.
+  Optional<uint64_t> CalleeCount = Callee->getEntryCount();
+  if (!CalleeCount)
+    return;
+  Optional<uint64_t> CallSiteCount = llvm::getBlockCount(CallBB, BFA.get());
+  if (!CallSiteCount)
+    return;
+  // Since CallSiteCount is an estimate, it could exceed the original callee
+  // count and has to be set to 0.
+  if (CallSiteCount.getValue() > CalleeCount.getValue()) {
+    Callee->setEntryCount(0);
+    DEBUG(llvm::dbgs() << "Estimated count of block " << CallBB->getName()
+                       << " is " << CallSiteCount.getValue()
+                       << " which exceeds the entry count "
+                       << CalleeCount.getValue() << " of the callee "
+                       << Callee->getName() << "\n");
+  } else
+    Callee->setEntryCount(CalleeCount.getValue() - CallSiteCount.getValue());
+}
+
+void Inliner::invalidateBFI(Function *F) {
+  if (!HasProfileData)
+    return;
+  if (F)
+    BFA->invalidateBlockFrequencyInfo(F);
+}
+void Inliner::invalidateBFI(CallGraphSCC &SCC) {
+  if (!HasProfileData)
+    return;
+  for (CallGraphNode *Node : SCC) {
+    Function *F = Node->getFunction();
+    invalidateBFI(F);
+  }
+}
+void Inliner::copyBlockFrequency(BasicBlock *Src, BasicBlock *Dst) {
+  if (!HasProfileData)
+    return;
+  Function *F = Src->getParent();
+  BlockFrequencyInfo *BFI = BFA->getBlockFrequencyInfo(F);
+  BFI->setBlockFreq(Dst, BFI->getBlockFreq(Src).getFrequency());
+}
+
+static bool hasProfileData(Module &M) {
+  // We check for the presence of MaxFunctionCount in the module.
+  // FIXME: This now only works for frontend based instrumentation.
+  return M.getMaximumFunctionCount().hasValue();
+}
+
 bool Inliner::runOnSCC(CallGraphSCC &SCC) {
+  using namespace std::placeholders;
   CallGraph &CG = getAnalysis<CallGraphWrapperPass>().getCallGraph();
+  HasProfileData = hasProfileData(CG.getModule());
   ACT = &getAnalysis<AssumptionCacheTracker>();
   auto &TLI = getAnalysis<TargetLibraryInfoWrapperPass>().getTLI();
 
   SmallPtrSet<Function*, 8> SCCFunctions;
   DEBUG(dbgs() << "Inliner visiting SCC:");
   for (CallGraphNode *Node : SCC) {
     Function *F = Node->getFunction();
     if (F) SCCFunctions.insert(F);
bool Inliner::runOnSCC(CallGraphSCC &SCC) {
   unsigned FirstCallInSCC = CallSites.size();
   for (unsigned i = 0; i < FirstCallInSCC; ++i)
     if (Function *F = CallSites[i].first.getCalledFunction())
       if (SCCFunctions.count(F))
         std::swap(CallSites[i--], CallSites[--FirstCallInSCC]);
 
   
   InlinedArrayAllocasTy InlinedArrayAllocas;
-  InlineFunctionInfo InlineInfo(&CG, ACT);
 
   // Now that we have all of the call sites, loop over them and inline them if
   // it looks profitable to do so.
   bool Changed = false;
   bool LocalChange;
   do {
     LocalChange = false;
     // Iterate over the outer loop because inlining functions can cause indirect
for (unsigned CSi = 0; CSi != CallSites.size(); ++CSi) {
       if (isInstructionTriviallyDead(CS.getInstruction(), &TLI)) {
         DEBUG(dbgs() << "    -> Deleting dead call: "
                      << *CS.getInstruction() << "\n");
         // Update the call graph by deleting the edge from Callee to Caller.
         CG[Caller]->removeCallEdgeFor(CS);
         CS.getInstruction()->eraseFromParent();
         ++NumCallsDeleted;
       } else {
+        Instruction *TheCall = CS.getInstruction();
+        BasicBlock *CallSiteBlock = TheCall->getParent();
+        Instruction *CallSuccessor = &*(++BasicBlock::iterator(TheCall));
+
         // We can only inline direct calls to non-declarations.
         if (!Callee || Callee->isDeclaration()) continue;
       
         // If this call site was obtained by inlining another function, verify
         // that the include path for the function did not include the callee
         // itself.  If so, we'd be recursively inlining the same function,
         // which would provide the same callsites, which would cause us to
         // infinitely inline.
for (unsigned CSi = 0; CSi != CallSites.size(); ++CSi) {
         if (!shouldInline(CS)) {
           emitOptimizationRemarkMissed(CallerCtx, DEBUG_TYPE, *Caller, DLoc,
                                        Twine(Callee->getName() +
                                              " will not be inlined into " +
                                              Caller->getName()));
           continue;
         }
 
+        BlockCloningFunctor BCF = nullptr;
+        if (HasProfileData)
+          BCF = std::bind(&Inliner::updateBlockFreq, this, CS, _1, _2);
+        InlineFunctionInfo InlineInfo(&CG, ACT, BCF);
+
         // Attempt to inline the function.
         if (!InlineCallIfPossible(*this, CS, InlineInfo, InlinedArrayAllocas,
                                   InlineHistoryID, InsertLifetime)) {
           emitOptimizationRemarkMissed(CallerCtx, DEBUG_TYPE, *Caller, DLoc,
                                        Twine(Callee->getName() +
                                              " will not be inlined into " +
                                              Caller->getName()));
           continue;
         }
+        updateEntryCount(CallSiteBlock, Callee);
+        // The instruction following the call is part of a new basic block
+        // created during the inlining process. This does not have an entry in
+        // the BFI. We create an entry by copying the frequency of the original
+        // block containing the call.
+        copyBlockFrequency(CallSiteBlock, CallSuccessor->getParent());
+
         ++NumInlined;
 
         // Report the inline decision.
         emitOptimizationRemark(
             CallerCtx, DEBUG_TYPE, *Caller, DLoc,
             Twine(Callee->getName() + " inlined into " + Caller->getName()));
 
         // If inlining this function gave us any new call sites, throw them
for (unsigned CSi = 0; CSi != CallSites.size(); ++CSi) {
         DEBUG(dbgs() << "    -> Deleting dead function: "
               << Callee->getName() << "\n");
         CallGraphNode *CalleeNode = CG[Callee];
 
         // Remove any call graph edges from the callee to its callees.
         CalleeNode->removeAllCalledFunctions();
         
         // Removing the node for callee from the call graph and delete it.
-        delete CG.removeFunctionFromModule(CalleeNode);
+        Function *F = CG.removeFunctionFromModule(CalleeNode);
+        invalidateBFI(F);
+        delete F;
         ++NumDeleted;
       }
 
       // Remove this call site from the list.  If possible, use 
       // swap/pop_back for efficiency, but do not use it if doing so would
       // move a call site to a function in this SCC before the
       // 'FirstCallInSCC' barrier.
       if (SCC.isSingular()) {
         CallSites[CSi] = CallSites.back();
         CallSites.pop_back();
       } else {
         CallSites.erase(CallSites.begin()+CSi);
       }
       --CSi;
 
       Changed = true;
       LocalChange = true;
     }
   } while (LocalChange);
 
+  invalidateBFI(SCC);
   return Changed;
 }
 
 /// Remove now-dead linkonce functions at the end of
 /// processing to avoid breaking the SCC traversal.
 bool Inliner::doFinalization(CallGraph &CG) {
   return removeDeadFunctions(CG);
 }
bool Inliner::removeDeadFunctions(CallGraph &CG, bool AlwaysInlineOnly) {
   // Note that it doesn't matter that we are iterating over a non-stable order
   // here to do this, it doesn't matter which order the functions are deleted
   // in.
   array_pod_sort(FunctionsToRemove.begin(), FunctionsToRemove.end());
   FunctionsToRemove.erase(std::unique(FunctionsToRemove.begin(),
                                       FunctionsToRemove.end()),
                           FunctionsToRemove.end());
   for (CallGraphNode *CGN : FunctionsToRemove) {
-    delete CG.removeFunctionFromModule(CGN);
+    Function *F = CG.removeFunctionFromModule(CGN);
+    invalidateBFI(F);
+    delete F;
     ++NumDeleted;
   }
   return true;
 }

lib/Transforms/Utils/CloneFunction.cpp

PruningFunctionCloner(Function *newFunc, const Function *oldFunc,
                           ValueToValueMapTy &valueMap, bool moduleLevelChanges,
                           const char *nameSuffix, ClonedCodeInfo *codeInfo)
         : NewFunc(newFunc), OldFunc(oldFunc), VMap(valueMap),
           ModuleLevelChanges(moduleLevelChanges), NameSuffix(nameSuffix),
           CodeInfo(codeInfo) {}
 
     /// The specified block is found to be reachable, clone it and
     /// anything that it can reach.
-    void CloneBlock(const BasicBlock *BB, 
+    void CloneBlock(const BasicBlock *BB,
                     BasicBlock::const_iterator StartingInst,
-                    std::vector<const BasicBlock*> &ToClone);
+                    std::vector<const BasicBlock *> &ToClone,
+                    BlockCloningFunctor Ftor = nullptr);
   };
 }
 
 /// The specified block is found to be reachable, clone it and
 /// anything that it can reach.
 void PruningFunctionCloner::CloneBlock(const BasicBlock *BB,
                                        BasicBlock::const_iterator StartingInst,
-                                       std::vector<const BasicBlock*> &ToClone){
+                                       std::vector<const BasicBlock *> &ToClone,
+                                       BlockCloningFunctor Ftor) {
   WeakVH &BBEntry = VMap[BB];
 
   // Have we already cloned this block?
   if (BBEntry) return;
   
   // Nope, clone it now.
   BasicBlock *NewBB;
   BBEntry = NewBB = BasicBlock::Create(BB->getContext());
void PruningFunctionCloner::CloneBlock(const BasicBlock *BB,
   }
   
   if (CodeInfo) {
     CodeInfo->ContainsCalls          |= hasCalls;
     CodeInfo->ContainsDynamicAllocas |= hasDynamicAllocas;
     CodeInfo->ContainsDynamicAllocas |= hasStaticAllocas && 
       BB != &BB->getParent()->front();
   }
+  // Call Ftor to tell BB has been cloned to NewBB
+  if (Ftor)
+    Ftor(BB, NewBB);
 }
 
 /// This works like CloneAndPruneFunctionInto, except that it does not clone the
 /// entire function. Instead it starts at an instruction provided by the caller
 /// and copies (and prunes) only the code reachable from that instruction.
-void llvm::CloneAndPruneIntoFromInst(Function *NewFunc, const Function *OldFunc,
-                                     const Instruction *StartingInst,
-                                     ValueToValueMapTy &VMap,
-                                     bool ModuleLevelChanges,
-                                     SmallVectorImpl<ReturnInst *> &Returns,
-                                     const char *NameSuffix,
-                                     ClonedCodeInfo *CodeInfo) {
+void llvm::CloneAndPruneIntoFromInst(
+    Function *NewFunc, const Function *OldFunc, const Instruction *StartingInst,
+    ValueToValueMapTy &VMap, bool ModuleLevelChanges,
+    SmallVectorImpl<ReturnInst *> &Returns, const char *NameSuffix,
+    ClonedCodeInfo *CodeInfo, BlockCloningFunctor Ftor) {
   assert(NameSuffix && "NameSuffix cannot be null!");
 
   ValueMapTypeRemapper *TypeMapper = nullptr;
   ValueMaterializer *Materializer = nullptr;
 
 #ifndef NDEBUG
   // If the cloning starts at the beginning of the function, verify that
   // the function arguments are mapped.
if (StartingInst)
     StartingBB = StartingInst->getParent();
   else {
     StartingBB = &OldFunc->getEntryBlock();
     StartingInst = &StartingBB->front();
   }
 
   // Clone the entry block, and anything recursively reachable from it.
   std::vector<const BasicBlock*> CloneWorklist;
-  PFC.CloneBlock(StartingBB, StartingInst->getIterator(), CloneWorklist);
+  PFC.CloneBlock(StartingBB, StartingInst->getIterator(), CloneWorklist, Ftor);
   while (!CloneWorklist.empty()) {
     const BasicBlock *BB = CloneWorklist.back();
     CloneWorklist.pop_back();
-    PFC.CloneBlock(BB, BB->begin(), CloneWorklist);
+    PFC.CloneBlock(BB, BB->begin(), CloneWorklist, Ftor);
   }
   
   // Loop over all of the basic blocks in the old function.  If the block was
   // reachable, we have cloned it and the old block is now in the value map:
   // insert it into the new function in the right order.  If not, ignore it.
   //
   // Defer PHI resolution until rest of function is resolved.
   SmallVector<const PHINode*, 16> PHIToResolve;

 
 /// This works exactly like CloneFunctionInto,
 /// except that it does some simple constant prop and DCE on the fly.  The
 /// effect of this is to copy significantly less code in cases where (for
 /// example) a function call with constant arguments is inlined, and those
 /// constant arguments cause a significant amount of code in the callee to be
 /// dead.  Since this doesn't produce an exact copy of the input, it can't be
 /// used for things like CloneFunction or CloneModule.
-void llvm::CloneAndPruneFunctionInto(Function *NewFunc, const Function *OldFunc,
-                                     ValueToValueMapTy &VMap,
-                                     bool ModuleLevelChanges,
-                                     SmallVectorImpl<ReturnInst*> &Returns,
-                                     const char *NameSuffix, 
-                                     ClonedCodeInfo *CodeInfo,
-                                     Instruction *TheCall) {
+void llvm::CloneAndPruneFunctionInto(
+    Function *NewFunc, const Function *OldFunc, ValueToValueMapTy &VMap,
+    bool ModuleLevelChanges, SmallVectorImpl<ReturnInst *> &Returns,
+    const char *NameSuffix, ClonedCodeInfo *CodeInfo, Instruction *TheCall,
+    BlockCloningFunctor Ftor) {
   CloneAndPruneIntoFromInst(NewFunc, OldFunc, &OldFunc->front().front(), VMap,
-                            ModuleLevelChanges, Returns, NameSuffix, CodeInfo);
+                            ModuleLevelChanges, Returns, NameSuffix, CodeInfo,
+                            Ftor);
 }
 
 /// \brief Remaps instructions in \p Blocks using the mapping in \p VMap.
 void llvm::remapInstructionsInBlocks(
     const SmallVectorImpl<BasicBlock *> &Blocks, ValueToValueMapTy &VMap) {
   // Rewrite the code to refer to itself.
   for (auto *BB : Blocks)
     for (auto &Inst : *BB)

lib/Transforms/Utils/InlineFunction.cpp

 bool llvm::InlineFunction(CallSite CS, InlineFunctionInfo &IFI,
                           AAResults *CalleeAAR, bool InsertLifetime) {
   Instruction *TheCall = CS.getInstruction();
   assert(TheCall->getParent() && TheCall->getParent()->getParent() &&
          "Instruction not in function!");
 
   // If IFI has any state in it, zap it before we fill it in.
   IFI.reset();
-  
   const Function *CalledFunc = CS.getCalledFunction();
   if (!CalledFunc ||              // Can't inline external function or indirect
       CalledFunc->isDeclaration() || // call, or call to a vararg function!
       CalledFunc->getFunctionType()->isVarArg()) return false;
 
   // The inliner does not know how to inline through calls with operand bundles
   // in general ...
   if (CS.hasOperandBundles()) {
Function::iterator FirstNewBlock;
     AddAlignmentAssumptions(CS, IFI);
 
     // We want the inliner to prune the code as it copies.  We would LOVE to
     // have no dead or constant instructions leftover after inlining occurs
     // (which can happen, e.g., because an argument was constant), but we'll be
     // happy with whatever the cloner can do.
     CloneAndPruneFunctionInto(Caller, CalledFunc, VMap,
                               /*ModuleLevelChanges=*/false, Returns, ".i",
-                              &InlinedFunctionInfo, TheCall);
+                              &InlinedFunctionInfo, TheCall, IFI.Ftor);
 
     // Remember the first block that is newly cloned over.
     FirstNewBlock = LastBlock; ++FirstNewBlock;
 
     // Inject byval arguments initialization.
     for (std::pair<Value*, Value*> &Init : ByValInit)
       HandleByValArgumentInit(Init.first, Init.second, Caller->getParent(),
                               &*FirstNewBlock, IFI);

test/Transforms/Inline/function-count-update-2.ll

+; RUN: opt < %s -inline -S | FileCheck %s
+
+; This tests that the function count of a callee gets correctly updated after it
+; has been inlined into a two callsites.
+
+; CHECK: @callee() !prof [[COUNT:![0-9]+]]
+define i32 @callee() !prof !1 {
+  ret i32 0
+}
+
+define i32 @caller1() !prof !2 {
+  %i = call i32 @callee()
+  ret i32 %i
+}
+
+define i32 @caller2() !prof !3 {
+  %i = call i32 @callee()
+  ret i32 %i
+}
+
+!llvm.module.flags = !{!0}
+; CHECK: [[COUNT]] = !{!"function_entry_count", i64 0}
+!0 = !{i32 1, !"MaxFunctionCount", i32 1000}
+!1 = !{!"function_entry_count", i64 1000}
+!2 = !{!"function_entry_count", i64 600}
+!3 = !{!"function_entry_count", i64 400}
+

test/Transforms/Inline/function-count-update-3.ll

+; RUN: opt < %s -inline -S -inline-threshold=50 | FileCheck %s
+
+; This tests that the function count of a function gets properly scaled after 
+; inlining a call chain leading to the function.
+; Function a calls c with count 200 (C1)
+; Function b calls c with count 300
+; Function c calls e with count 250 (C2)
+; Entry count of e is 500 (C3)
+; c->e inlining does not happen since the cost exceeds threshold.
+; c then inlined into a.
+; e now gets inlined into a (through c) since the branch condition in e is now
+; known and hence the cost gets reduced.
+; Estimated count of a->e callsite = C2 * (C1 / C3)
+; Estimated count of a->e callsite = 250 * (200 / 500) = 100
+; Remaining count of e = C3 - 100 = 500 - 100 = 400
+
+@data = external global i32
+
+define i32 @a(i32 %a1) !prof !1 {
+  %a2 = call i32 @c(i32 %a1, i32 1)
+  ret i32 %a2
+}
+
+define i32 @b(i32 %b1) !prof !2 {
+  %b2 = call i32 @c(i32 %b1, i32 %b1)
+  ret i32 %b2
+}
+
+define i32 @c(i32 %c1, i32 %c100) !prof !3 {
+  %cond = icmp sle i32 %c1, 1
+  br i1 %cond, label %cond_true, label %cond_false
+
+cond_false:
+  ret i32 0
+
+cond_true:
+  %c11 = call i32 @e(i32 %c100)
+  ret i32 %c11
+}
+
+; CHECK: @e(i32 %c1) !prof [[COUNT:![0-9]+]]
+define i32 @e(i32 %c1) !prof !4 {
+  %cond = icmp sle i32 %c1, 1
+  br i1 %cond, label %cond_true, label %cond_false
+
+cond_false:
+  %c2 = load i32, i32* @data, align 4
+  %c3 = add i32 %c1, %c2
+  %c4 = mul i32 %c3, %c2
+  %c5 = add i32 %c4, %c2
+  %c6 = mul i32 %c5, %c2
+  %c7 = add i32 %c6, %c2
+  %c8 = mul i32 %c7, %c2
+  %c9 = add i32 %c8, %c2
+  %c10 = mul i32 %c9, %c2
+  ret i32 %c10
+
+cond_true:
+  ret i32 0
+}
+
+!llvm.module.flags = !{!0}
+; CHECK: [[COUNT]] = !{!"function_entry_count", i64 400}
+!0 = !{i32 1, !"MaxFunctionCount", i32 5000}
+!1 = !{!"function_entry_count", i64 200}
+!2 = !{!"function_entry_count", i64 300}
+!3 = !{!"function_entry_count", i64 500}
+!4 = !{!"function_entry_count", i64 500}
+

test/Transforms/Inline/function-count-update.ll

+; RUN: opt < %s -inline -S | FileCheck %s
+; RUN: opt < %s -always-inline -S | FileCheck %s
+
+; This tests that the function count of two callees get correctly updated after
+; they have been inlined into two back-to-back callsites in a single basic block
+; in the caller. The callees have the alwaysinline attribute and so they get
+; inlined both with the regular inliner pass and the always inline pass. In
+; both cases, the new count of each callee is the original count minus callsite
+; count which is 200 (since the caller's entry count is 400 and the block
+; containing the calls have a relative block frequency of 0.5).
+
+; CHECK: @callee1(i32 %n) #0 !prof [[COUNT1:![0-9]+]]
+define i32 @callee1(i32 %n) #0 !prof !1 {
+  %cond = icmp sle i32 %n, 10
+  br i1 %cond, label %cond_true, label %cond_false
+
+cond_true:
+  %r1 = add i32 %n, 1
+  ret i32 %r1
+cond_false:
+  %r2 = add i32 %n, 2
+  ret i32 %r2
+}
+
+; CHECK: @callee2(i32 %n) #0 !prof [[COUNT2:![0-9]+]]
+define i32 @callee2(i32 %n) #0 !prof !2 {
+  %r1 = add i32 %n, 1
+  ret i32 %r1
+}
+
+define i32 @caller(i32 %n) !prof !3 {
+  %cond = icmp sle i32 %n, 100
+  br i1 %cond, label %cond_true, label %cond_false
+
+cond_true:
+  %i = call i32 @callee1(i32 %n)
+  %j = call i32 @callee2(i32 %i)
+  ret i32 %j
+cond_false:
+  ret i32 0
+}
+
+!llvm.module.flags = !{!0}
+; CHECK: [[COUNT1]] = !{!"function_entry_count", i64 800}
+; CHECK: [[COUNT2]] = !{!"function_entry_count", i64 1800}
+!0 = !{i32 1, !"MaxFunctionCount", i32 1000}
+!1 = !{!"function_entry_count", i64 1000}
+!2 = !{!"function_entry_count", i64 2000}
+!3 = !{!"function_entry_count", i64 400}
+attributes #0 = { alwaysinline }
+