ProfileSummaryInfo improvements

[eraman]

Summary

• Add is{Hot|Cold}CallSite methods
• Fix a bug in isHotBB where it was looking for MD_prof on a return instruction
• Use MD_prof data only if sample profiling was used to collect profiles.
• Add an unit test to ProfileSummaryInfo

[davidxl]

lib/Analysis/ProfileSummaryInfo.cpp

140

is this a separate fix?

163

should the order of check swapped? BFI check first and then meta data ?

[eraman]

lib/Analysis/ProfileSummaryInfo.cpp

140

yes, that part was never exercised before.

163

I discussed this with Dehao and he said it is possible that block's hotness got messed up in the upward direction (higher than what it should be) in sample profiling. If there is annotation, it is better to treat it as the ground truth.

[davidxl]

lib/Analysis/ProfileSummaryInfo.cpp

163

This is not good for instrumentation based PGO.

1. meta data is not updated during cloning so it can get wrong for instrumentation based pgo
2. it is slightly slower for instrumentation based PGO.

In fact, we should probably never need to check weight data for instPGO.

[eraman]

lib/Analysis/ProfileSummaryInfo.cpp

163

Agreed that we should check which mode we're in, but it is not a problem now because the annotations happen only in Sample PGO.

[davidxl]

lib/Analysis/ProfileSummaryInfo.cpp

163

ok. A comment there is good for clarification.

[eraman]

Check MD_prof metadata on calls and branches to determine hotness only when it is sample profile and fix the unittest.

[eraman]

lib/Analysis/ProfileSummaryInfo.cpp

163

I have added the check for profile type instead.

[davidxl]

looks fine to me. Dehao, do you have any comments?

[danielcdh]

In D28584#644323, @davidxl wrote:

looks fine to me. Dehao, do you have any comments?

The current changes LGTM.

Thanks,
Dehao

[davidxl]

lgtm

include/llvm/Analysis/ProfileSummaryInfo.h

 #include "llvm/IR/ProfileSummary.h"
 #include "llvm/IR/ValueHandle.h"
 #include "llvm/Pass.h"
 #include <memory>
 
 namespace llvm {
 class BasicBlock;
 class BlockFrequencyInfo;
+class CallSite;
 class ProfileSummary;
 /// \brief Analysis providing profile information.
 ///
 /// This is an immutable analysis pass that provides ability to query global
 /// (program-level) profile information. The main APIs are isHotCount and
 /// isColdCount that tells whether a given profile count is considered hot/cold
 /// based on the profile summary. This also provides convenience methods to
 /// check whether a function is hot or cold.
public:
   /// \brief Returns true if \p F has cold function entry.
   bool isFunctionEntryCold(const Function *F);
   /// \brief Returns true if \p F is a hot function.
   bool isHotCount(uint64_t C);
   /// \brief Returns true if count \p C is considered cold.
   bool isColdCount(uint64_t C);
   /// \brief Returns true if BasicBlock \p B is considered hot.
   bool isHotBB(const BasicBlock *B, BlockFrequencyInfo *BFI);
+  /// \brief Returns true if BasicBlock \p B is considered cold.
+  bool isColdBB(const BasicBlock *B, BlockFrequencyInfo *BFI);
+  /// \brief Returns true if CallSite \p CS is considered hot.
+  bool isHotCallSite(const CallSite &CS, BlockFrequencyInfo *BFI);
+  /// \brief Returns true if Callsite \p CS is considered cold.
+  bool isColdCallSite(const CallSite &CS, BlockFrequencyInfo *BFI);
 };
 
 /// An analysis pass based on legacy pass manager to deliver ProfileSummaryInfo.
 class ProfileSummaryInfoWrapperPass : public ImmutablePass {
   std::unique_ptr<ProfileSummaryInfo> PSI;
 
 public:
   static char ID;

lib/Analysis/ProfileSummaryInfo.cpp

 //===- ProfileSummaryInfo.cpp - Global profile summary information --------===//
 //
 //                     The LLVM Compiler Infrastructure
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 //
 // This file contains a pass that provides access to the global profile summary
 // information.
 //
 //===----------------------------------------------------------------------===//
 
-#include "llvm/Analysis/BlockFrequencyInfo.h"
 #include "llvm/Analysis/ProfileSummaryInfo.h"
+#include "llvm/Analysis/BlockFrequencyInfo.h"
 #include "llvm/IR/BasicBlock.h"
+#include "llvm/IR/CallSite.h"
 #include "llvm/IR/Metadata.h"
 #include "llvm/IR/Module.h"
 #include "llvm/IR/ProfileSummary.h"
 using namespace llvm;
 
 // The following two parameters determine the threshold for a count to be
 // considered hot/cold. These two parameters are percentile values (multiplied
 // by 10000). If the counts are sorted in descending order, the minimum count to
bool ProfileSummaryInfo::isHotBB(const BasicBlock *B, BlockFrequencyInfo *BFI) {
   // Use extractProfTotalWeight to get BB count.
   // For Sample PGO, BFI may not provide accurate BB count due to errors
   // magnified during sample count propagation. This serves as a backup plan
   // to ensure all hot BB will not be missed.
   // The query currently has false positives as branch instruction cloning does
   // not update/scale branch weights. Unlike false negatives, this will not cause
   // performance problem.
   uint64_t TotalCount;
-  if (B->getTerminator()->extractProfTotalWeight(TotalCount) &&
-      isHotCount(TotalCount))
+  auto *TI = B->getTerminator();
+  if (isa<ReturnInst>(TI))
+    return false;
+  if (TI->extractProfTotalWeight(TotalCount) && isHotCount(TotalCount))
     return true;
   return false;
 }
 
+bool ProfileSummaryInfo::isColdBB(const BasicBlock *B,
+                                  BlockFrequencyInfo *BFI) {
+  auto Count = BFI->getBlockProfileCount(B);
+  return Count && isColdCount(*Count);
+}
+
+bool ProfileSummaryInfo::isHotCallSite(const CallSite &CS,
+                                       BlockFrequencyInfo *BFI) {
+  auto *CallInst = CS.getInstruction();
+  if (!CS)
+    return false;
+  // Check if there is a profile metadata on the instruction. If it is present,
+  // determine hotness solely based on that.
+  uint64_t TotalCount;
+  if (CallInst->extractProfTotalWeight(TotalCount))
+    return isHotCount(TotalCount);
+  return BFI && isHotBB(CallInst->getParent(), BFI);
+}
+
+bool ProfileSummaryInfo::isColdCallSite(const CallSite &CS,
+                                        BlockFrequencyInfo *BFI) {
+  auto *CallInst = CS.getInstruction();
+  if (!CS)
+    return false;
+  // Check if there is a profile metadata on the instruction. If it is present,
+  // and tells that the callsite is not cold, then return false;
+  uint64_t TotalCount;
+  if (CallInst->extractProfTotalWeight(TotalCount) && !isColdCount(TotalCount))
+    return false;
+  return BFI && isColdBB(CallInst->getParent(), BFI);
+}
+
 INITIALIZE_PASS(ProfileSummaryInfoWrapperPass, "profile-summary-info",
                 "Profile summary info", false, true)
 
 ProfileSummaryInfoWrapperPass::ProfileSummaryInfoWrapperPass()
     : ImmutablePass(ID) {
   initializeProfileSummaryInfoWrapperPassPass(*PassRegistry::getPassRegistry());
 }
 

unittests/Analysis/CMakeLists.txt

add_llvm_unittest(AnalysisTests
   BlockFrequencyInfoTest.cpp
   BranchProbabilityInfoTest.cpp
   CallGraphTest.cpp
   CFGTest.cpp
   CGSCCPassManagerTest.cpp
   LazyCallGraphTest.cpp
   LoopPassManagerTest.cpp
   MemoryBuiltinsTest.cpp
+  ProfileSummaryInfoTest.cpp
   ScalarEvolutionTest.cpp
   TBAATest.cpp
   ValueTrackingTest.cpp
   UnrollAnalyzer.cpp
   )

unittests/Analysis/ProfileSummaryInfoTest.cpp

+//===- ProfileSummaryInfoTest.cpp - ProfileSummaryInfo unit tests ---------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Analysis/ProfileSummaryInfo.h"
+#include "llvm/Analysis/BlockFrequencyInfo.h"
+#include "llvm/Analysis/BlockFrequencyInfoImpl.h"
+#include "llvm/Analysis/BranchProbabilityInfo.h"
+#include "llvm/Analysis/LoopInfo.h"
+#include "llvm/AsmParser/Parser.h"
+#include "llvm/IR/BasicBlock.h"
+#include "llvm/IR/CallSite.h"
+#include "llvm/IR/Dominators.h"
+#include "llvm/IR/Function.h"
+#include "llvm/IR/LLVMContext.h"
+#include "llvm/IR/MDBuilder.h"
+#include "llvm/IR/Module.h"
+#include "llvm/Support/DataTypes.h"
+#include "llvm/Support/SourceMgr.h"
+#include "llvm/Support/raw_ostream.h"
+#include "gtest/gtest.h"
+
+namespace llvm {
+namespace {
+
+class ProfileSummaryInfoTest : public testing::Test {
+protected:
+  LLVMContext C;
+  std::unique_ptr<BranchProbabilityInfo> BPI;
+  std::unique_ptr<DominatorTree> DT;
+  std::unique_ptr<LoopInfo> LI;
+
+  ProfileSummaryInfo buildPSI(Module *M) {
+    return ProfileSummaryInfo(*M);
+  }
+  BlockFrequencyInfo buildBFI(Function &F) {
+    DT.reset(new DominatorTree(F));
+    LI.reset(new LoopInfo(*DT));
+    BPI.reset(new BranchProbabilityInfo(F, *LI));
+    return BlockFrequencyInfo(F, *BPI, *LI);
+  }
+  std::unique_ptr<Module> makeLLVMModule() {
+    const char *ModuleStrig = "define i32 @g(i32 %x) !prof !21 {\n"
+                              "  ret i32 0\n"
+                              "}\n"
+                              "define i32 @h(i32 %x) !prof !22 {\n"
+                              "  ret i32 0\n"
+                              "}\n"
+                              "define i32 @f(i32 %x) !prof !20 {\n"
+                              "bb0:\n"
+                              "  %y1 = icmp eq i32 %x, 0 \n"
+                              "  br i1 %y1, label %bb1, label %bb2, !prof !23 \n"
+                              "bb1:\n"
+                              "  %z1 = call i32 @g(i32 %x)\n"
+                              "  br label %bb3\n"
+                              "bb2:\n"
+                              "  %z2 = call i32 @h(i32 %x)\n"
+                              "  br label %bb3\n"
+                              "bb3:\n"
+                              "  %y2 = phi i32 [0, %bb1], [1, %bb2] \n"
+                              "  ret i32 %y2\n"
+                              "}\n"
+                              "!llvm.module.flags = !{!1}"
+                              "!20 = !{!\"function_entry_count\", i64 400}"
+                              "!21 = !{!\"function_entry_count\", i64 1}"
+                              "!22 = !{!\"function_entry_count\", i64 100}"
+                              "!23 = !{!\"branch_weights\", i32 64, i32 4}"
+                              "!1 = !{i32 1, !\"ProfileSummary\", !2}"
+                              "!2 = !{!3, !4, !5, !6, !7, !8, !9, !10}"
+                              "!3 = !{!\"ProfileFormat\", !\"InstrProf\"}"
+                              "!4 = !{!\"TotalCount\", i64 10000}"
+                              "!5 = !{!\"MaxCount\", i64 10}"
+                              "!6 = !{!\"MaxInternalCount\", i64 1}"
+                              "!7 = !{!\"MaxFunctionCount\", i64 1000}"
+                              "!8 = !{!\"NumCounts\", i64 3}"
+                              "!9 = !{!\"NumFunctions\", i64 3}"
+                              "!10 = !{!\"DetailedSummary\", !11}"
+                              "!11 = !{!12, !13, !14}"
+                              "!12 = !{i32 10000, i64 1000, i32 1}"
+                              "!13 = !{i32 999000, i64 300, i32 3}"
+                              "!14 = !{i32 999999, i64 5, i32 10}";
+    SMDiagnostic Err;
+    return parseAssemblyString(ModuleStrig, Err, C);
+  }
+};
+
+TEST_F(ProfileSummaryInfoTest, Basic) {
+  auto M = makeLLVMModule();
+  Function *F = M->getFunction("f");
+  Function *G = M->getFunction("g");
+  Function *H = M->getFunction("h");
+
+  ProfileSummaryInfo PSI = buildPSI(M.get());
+  EXPECT_TRUE(PSI.isHotCount(400));
+  EXPECT_TRUE(PSI.isColdCount(2));
+  EXPECT_FALSE(PSI.isColdCount(100));
+  EXPECT_FALSE(PSI.isHotCount(100));
+
+  EXPECT_TRUE(PSI.isFunctionEntryHot(F));
+  EXPECT_FALSE(PSI.isFunctionEntryHot(G));
+  EXPECT_FALSE(PSI.isFunctionEntryHot(H));
+
+  BasicBlock &BB0 = F->getEntryBlock();
+  BasicBlock *BB1 = BB0.getTerminator()->getSuccessor(0);
+  BasicBlock *BB2 = BB0.getTerminator()->getSuccessor(1);
+  BasicBlock *BB3 = BB1->getSingleSuccessor();
+
+  BlockFrequencyInfo BFI = buildBFI(*F);
+  EXPECT_TRUE(PSI.isHotBB(&BB0, &BFI));
+  EXPECT_TRUE(PSI.isHotBB(BB1, &BFI));
+  EXPECT_FALSE(PSI.isHotBB(BB2, &BFI));
+  EXPECT_TRUE(PSI.isHotBB(BB3, &BFI));
+
+  CallSite CS1(BB1->getFirstNonPHI());
+  auto *CI2 = BB2->getFirstNonPHI();
+  CallSite CS2(CI2);
+
+  EXPECT_TRUE(PSI.isHotCallSite(CS1, &BFI));
+  EXPECT_FALSE(PSI.isHotCallSite(CS2, &BFI));
+
+  // Test that CS2 is considered hot when it gets an MD_prof metadata with
+  // weights that exceed the hot count threshold.
+  MDBuilder MDB(M->getContext());
+  CI2->setMetadata(llvm::LLVMContext::MD_prof, MDB.createBranchWeights({300}));
+  EXPECT_TRUE(PSI.isHotCallSite(CS2, &BFI));
+
+}
+
+} // end anonymous namespace
+} // end namespace llvm