[llvm-profgen] Trim cold function profiles for non-CS AutoFDO

[wlei]

Summary

This change allows to trim the profile if it's considered to be cold for baseline AutoFDO. We reuse the cold threshold from ProfileSummaryBuilder::getColdCountThreshold(..) which can be set by percent(--profile-summary-cutoff-cold) or by value(--profile-summary-cold-count).

[hoy]

llvm/tools/llvm-profgen/ProfileGenerator.cpp

63

How about merge the new switch with this one?

[wenlei]

llvm/tools/llvm-profgen/ProfileGenerator.cpp

63

Yeah, let's merge them. And this may also mean we need to put it on afdo-specific path, instead having it in ProfileGenerator::postProcessProfiles.

[wlei]

merge TrimColdProfile and CSProfTrimColdContext

[hoy]

lgtm, thanks.

llvm/test/tools/llvm-profgen/merge-cold-profile.test

9 ↗

(On Diff #387374)

nit: this should not change?

[wlei]

Updating D113785: [llvm-profgen] Trim cold function profiles for non-CS AutoFDO

[wenlei]

None of the tests cover trim vs no-trim difference, it'd be good to have one, so we check trimming is actually making a difference.

[wenlei]

lgtm with a comment on test.

[wlei]

llvm/test/tools/llvm-profgen/inline-noprobe2.test

111

None of the tests cover trim vs no-trim difference, it'd be good to have one, so we check trimming is actually making a difference.

@wenlei We do have a test case for the trimming here which checked the function won't appear if its total sample is smaller than --profile-summary-cold-count=100

[wenlei]

llvm/test/tools/llvm-profgen/inline-noprobe2.test

111

But we don't have a check to make sure main/quick_sort actually appears without trimming, right? If for whatever reason these two never appears even without trimming (--trim-cold-profile=0), this test could be doing nothing.

[wlei]

llvm/test/tools/llvm-profgen/inline-noprobe2.test

89

Here

111

Oh, I got your meaning. In the test above, there is a CHECK for main/quick_sort, but I realize it's mixed with other test and not visible. I will add a separate test case for cold trimming.Thanks for the clarification.

[wlei]

add a separated test case for trimming, added no trim case

[wenlei]

llvm/test/tools/llvm-profgen/inline-noprobe2.test

111

Thanks, looks good now.

llvm/test/tools/llvm-profgen/inline-noprobe2.test

 ; RUN: llvm-profgen --format=text --perfscript=%S/Inputs/artificial-branch.perfscript --binary=%S/Inputs/inline-noprobe2.perfbin --output=%t  --skip-symbolization --use-offset=0
 ; RUN: FileCheck %s --input-file %t --check-prefix=CHECK-ARTIFICIAL-BRANCH
 ; RUN: llvm-profgen --format=text --perfscript=%S/Inputs/inline-noprobe2.perfscript --binary=%S/Inputs/inline-noprobe2.perfbin --output=%t  --skip-symbolization --use-offset=0
 ; RUN: FileCheck %s --input-file %t --check-prefix=CHECK-RAW-PROFILE
 ; RUN: llvm-profgen --format=text --unsymbolized-profile=%t --binary=%S/Inputs/inline-noprobe2.perfbin --output=%t1 --use-offset=0 --show-density -hot-function-density-threshold=1 &> %t2
 ; RUN: FileCheck %s --input-file %t1 --check-prefix=CHECK
 ; RUN: FileCheck %s --input-file %t2 --check-prefix=CHECK-DENSITY
 
+; RUN: llvm-profgen --format=text --unsymbolized-profile=%t --binary=%S/Inputs/inline-noprobe2.perfbin --output=%t1 --use-offset=0 --trim-cold-profile --profile-summary-cold-count=100
+; RUN: FileCheck %s --input-file %t1 --check-prefix=CHECK-TRIM-COLD
+
 ; RUN: llvm-profgen --format=extbinary --perfscript=%S/Inputs/inline-noprobe2.perfscript --binary=%S/Inputs/inline-noprobe2.perfbin --output=%t --populate-profile-symbol-list=1
 ; RUN: llvm-profdata show -show-prof-sym-list -sample %t | FileCheck %s --check-prefix=CHECK-SYM-LIST
 
 ; CHECK-ARTIFICIAL-BRANCH: 3
 ; CHECK-ARTIFICIAL-BRANCH: 400540-400540:1
 ; CHECK-ARTIFICIAL-BRANCH: 400870-400870:2
 ; CHECK-ARTIFICIAL-BRANCH: 400875-4008bf:1
 ; CHECK-ARTIFICIAL-BRANCH: 2

 ;CHECK-NEXT:   2: 5
 ;CHECK-NEXT:   3: 5
 ;CHECK-NEXT: quick_sort:83:25
 ;CHECK-NEXT:  1: 24
 ;CHECK-NEXT:  2: 12 partition_pivot_last:7 partition_pivot_first:5
 ;CHECK-NEXT:  3: 11 quick_sort:12
 ;CHECK-NEXT:  4: 12 quick_sort:12
 ;CHECK-NEXT:  6: 24
 ;CHECK-NEXT: main:52:0
 ;CHECK-NEXT:  0: 0
 ;CHECK-NEXT:  3: 0
 ;CHECK-NEXT:  4.1: 0
 ;CHECK-NEXT:  4.3: 0
 ;CHECK-NEXT:  5.1: 10
 ;CHECK-NEXT:  5.3: 10
 ;CHECK-NEXT:  6: 10
 ;CHECK-NEXT:  6.1: 12
 ;CHECK-NEXT:  6.3: 10
 ;CHECK-NEXT:  7: 0
 ;CHECK-NEXT:  8: 0 quick_sort:1
 ;CHECK-NEXT:  9: 0
 ;CHECK-NEXT:  11: 0
 ;CHECK-NEXT:  14: 0
 
 ;CHECK-DENSITY: AutoFDO is estimated to optimize better with 4.9x more samples. Please consider increasing sampling rate or profiling for longer duration to get more samples.
 ;CHECK-DENSITY: Minimum profile density for hot functions with top 99.00% total samples: 0.2
 
+;CHECK-TRIM-COLD: partition_pivot_first:367:5
+;CHECK-TRIM-COLD: partition_pivot_last:225:7
+;CHECK-TRIM-COLD-NOT: quick_sort:83:25
+;CHECK-TRIM-COLD-NOT: main:52:0
+
 ; original code:
 ; clang -O3 -g -fno-optimize-sibling-calls -fdebug-info-for-profiling qsort.c -o a.out
 #include <stdio.h>
 #include <stdlib.h>
 
 void swap(int *a, int *b) {
   int t = *a;
   *a = *b;

llvm/tools/llvm-profgen/ProfileGenerator.h

private:
   // inline stack and meanwhile it adds the total samples for each frame's
   // function profile.
   FunctionSamples &
   getLeafFrameProfile(const SampleContextFrameVector &FrameVec);
   void populateBodySamplesForAllFunctions(const RangeSample &RangeCounter);
   void
   populateBoundarySamplesForAllFunctions(const BranchSample &BranchCounters);
   void postProcessProfiles();
+  void trimColdProfiles(const SampleProfileMap &Profiles,
+                        uint64_t ColdCntThreshold);
   void calculateAndShowDensity(const SampleProfileMap &Profiles) override;
 };
 
 using ProbeCounterMap =
     std::unordered_map<const MCDecodedPseudoProbe *, uint64_t>;
 
 class CSProfileGenerator : public ProfileGeneratorBase {
 public:

llvm/tools/llvm-profgen/ProfileGenerator.cpp

 
 static cl::opt<int32_t, true> RecursionCompression(
     "compress-recursion",
     cl::desc("Compressing recursion by deduplicating adjacent frame "
              "sequences up to the specified size. -1 means no size limit."),
     cl::Hidden,
     cl::location(llvm::sampleprof::CSProfileGenerator::MaxCompressionSize));
 
+static cl::opt<bool>
+    TrimColdProfile("trim-cold-profile", cl::init(false), cl::ZeroOrMore,
+                    cl::desc("If the total count of the profile is smaller "
+                             "than threshold, it will be trimmed."));
+
 static cl::opt<bool> CSProfMergeColdContext(
     "csprof-merge-cold-context", cl::init(true), cl::ZeroOrMore,
     cl::desc("If the total count of context profile is smaller than "
              "the threshold, it will be merged into context-less base "
              "profile."));
 
 static cl::opt<bool> CSProfTrimColdContext(
     "csprof-trim-cold-context", cl::init(false), cl::ZeroOrMore,
     cl::desc("If the total count of the profile after all merge is done "
              "is still smaller than threshold, it will be trimmed."));
 
 static cl::opt<uint32_t> CSProfMaxColdContextDepth(
     "csprof-max-cold-context-depth", cl::init(1), cl::ZeroOrMore,
     cl::desc("Keep the last K contexts while merging cold profile. 1 means the "
              "context-less base profile"));
void ProfileGenerator::generateProfile() {
   } else {
     generateLineNumBasedProfile();
   }
   postProcessProfiles();
 }
 
 void ProfileGenerator::postProcessProfiles() {
   computeSummaryAndThreshold();
+  trimColdProfiles(ProfileMap, ColdCountThreshold);
   calculateAndShowDensity(ProfileMap);
 }
 
+void ProfileGenerator::trimColdProfiles(const SampleProfileMap &Profiles,
+                                        uint64_t ColdCntThreshold) {
+  if (!TrimColdProfile)
+    return;
+
+  // Move cold profiles into a tmp container.
+  std::vector<SampleContext> ColdProfiles;
+  for (const auto &I : ProfileMap) {
+    if (I.second.getTotalSamples() < ColdCntThreshold)
+      ColdProfiles.emplace_back(I.first);
+  }
+
+  // Remove the cold profile from ProfileMap.
+  for (const auto &I : ColdProfiles)
+    ProfileMap.erase(I);
+}
+
 void ProfileGenerator::generateLineNumBasedProfile() {
   assert(SampleCounters.size() == 1 &&
          "Must have one entry for profile generation.");
   const SampleCounter &SC = SampleCounters.begin()->second;
   // Fill in function body samples
   populateBodySamplesForAllFunctions(SC.RangeCounter);
   // Fill in boundary sample counts as well as call site samples for calls
   populateBoundarySamplesForAllFunctions(SC.BranchCounter);