Compute summary before calling extractProfTotalWeight

[eraman]

Summary

extractProfTotalWeight checks if the profile type is sample profile, but before that we have to ensure that summary is available. Also expanded the unittest to test the case where there is no summary.

[davidxl]

lgtm

unittests/Analysis/ProfileSummaryInfoTest.cpp

101

It is slightly more readable to do:

const char *ProfKind = nullptr;
auto M = makeLLVMModule(ProfKind);

include/llvm/Analysis/ProfileSummaryInfo.h

 /// check whether a function is hot or cold.
 
 // FIXME: Provide convenience methods to determine hotness/coldness of other IR
 // units. This would require making this depend on BFI.
 class ProfileSummaryInfo {
 private:
   Module &M;
   std::unique_ptr<ProfileSummary> Summary;
-  void computeSummary();
+  bool computeSummary();
   void computeThresholds();
   // Count thresholds to answer isHotCount and isColdCount queries.
   Optional<uint64_t> HotCountThreshold, ColdCountThreshold;
   bool extractProfTotalWeight(const Instruction *TI, uint64_t &TotalCount);
 
 public:
   ProfileSummaryInfo(Module &M) : M(M) {}
   ProfileSummaryInfo(ProfileSummaryInfo &&Arg)

lib/Analysis/ProfileSummaryInfo.cpp

static uint64_t getMinCountForPercentile(SummaryEntryVector &DS,
   if (It == DS.end())
     report_fatal_error("Desired percentile exceeds the maximum cutoff");
   return It->MinCount;
 }
 
 // The profile summary metadata may be attached either by the frontend or by
 // any backend passes (IR level instrumentation, for example). This method
 // checks if the Summary is null and if so checks if the summary metadata is now
-// available in the module and parses it to get the Summary object.
-void ProfileSummaryInfo::computeSummary() {
+// available in the module and parses it to get the Summary object. Returns true
+// if a valid Summary is available.
+bool ProfileSummaryInfo::computeSummary() {
   if (Summary)
-    return;
+    return true;
   auto *SummaryMD = M.getProfileSummary();
   if (!SummaryMD)
-    return;
+    return false;
   Summary.reset(ProfileSummary::getFromMD(SummaryMD));
+  return true;
 }
 
 /// Returns true if the function's entry is hot. If it returns false, it
 /// either means it is not hot or it is unknown whether it is hot or not (for
 /// example, no profile data is available).
 bool ProfileSummaryInfo::isFunctionEntryHot(const Function *F) {
-  computeSummary();
-  if (!F || !Summary)
+  if (!F || !computeSummary())
     return false;
   auto FunctionCount = F->getEntryCount();
   // FIXME: The heuristic used below for determining hotness is based on
   // preliminary SPEC tuning for inliner. This will eventually be a
   // convenience method that calls isHotCount.
   return FunctionCount && isHotCount(FunctionCount.getValue());
 }
 
 /// Returns true if the function's entry is a cold. If it returns false, it
 /// either means it is not cold or it is unknown whether it is cold or not (for
 /// example, no profile data is available).
 bool ProfileSummaryInfo::isFunctionEntryCold(const Function *F) {
-  computeSummary();
   if (!F)
     return false;
   if (F->hasFnAttribute(Attribute::Cold)) {
     return true;
   }
-  if (!Summary)
+  if (!computeSummary())
     return false;
   auto FunctionCount = F->getEntryCount();
   // FIXME: The heuristic used below for determining coldness is based on
   // preliminary SPEC tuning for inliner. This will eventually be a
   // convenience method that calls isHotCount.
   return FunctionCount && isColdCount(FunctionCount.getValue());
 }
 
 /// Compute the hot and cold thresholds.
 void ProfileSummaryInfo::computeThresholds() {
-  if (!Summary)
-    computeSummary();
-  if (!Summary)
+  if (!computeSummary())
     return;
   auto &DetailedSummary = Summary->getDetailedSummary();
   HotCountThreshold =
       getMinCountForPercentile(DetailedSummary, ProfileSummaryCutoffHot);
   ColdCountThreshold =
       getMinCountForPercentile(DetailedSummary, ProfileSummaryCutoffCold);
 }
 

 bool ProfileSummaryInfo::isColdBB(const BasicBlock *B,
                                   BlockFrequencyInfo *BFI) {
   auto Count = BFI->getBlockProfileCount(B);
   return Count && isColdCount(*Count);
 }
 
 bool ProfileSummaryInfo::extractProfTotalWeight(const Instruction *I,
                                                 uint64_t &TotalCount) {
+  if (!computeSummary())
+    return false;
   // Use profile weight on metadata only for sample profiling where block counts
   // could differ from the count of an instruction within the block.
   if (Summary.get()->getKind() != ProfileSummary::PSK_Sample)
     return false;
 
   return (isa<CallInst>(I) ||
           (isa<TerminatorInst>(I) && !isa<ReturnInst>(I))) &&
          I->extractProfTotalWeight(TotalCount);

unittests/Analysis/ProfileSummaryInfoTest.cpp

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(StringRef ProfKind) {
-    const char *ModuleStrig =
+  std::unique_ptr<Module> makeLLVMModule(const char *ProfKind = nullptr) {
+    const char *ModuleString =
         "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}"
+        "!20 = !{{!\"function_entry_count\", i64 400}\n"
+        "!21 = !{{!\"function_entry_count\", i64 1}\n"
+        "!22 = !{{!\"function_entry_count\", i64 100}\n"
+        "!23 = !{{!\"branch_weights\", i32 64, i32 4}\n"
+        "{0}";
+    const char *SummaryString = "!llvm.module.flags = !{{!1}"
                                 "!1 = !{{i32 1, !\"ProfileSummary\", !2}"
                                 "!2 = !{{!3, !4, !5, !6, !7, !8, !9, !10}"
                                 "!3 = !{{!\"ProfileFormat\", !\"{0}\"}"
                                 "!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(StringRef(formatv(ModuleStrig, ProfKind)), Err,
-                               C);
+    if (ProfKind)
+      return parseAssemblyString(
+          formatv(ModuleString, formatv(SummaryString, ProfKind).str()).str(),
+          Err, C);
+    else
+      return parseAssemblyString(formatv(ModuleString, "").str(), Err, C);
   }
 };
 
+TEST_F(ProfileSummaryInfoTest, TestNoProfile) {
+  auto M = makeLLVMModule();
+  Function *F = M->getFunction("f");
+
+  ProfileSummaryInfo PSI = buildPSI(M.get());
+  // In the absence of profiles, is{Hot|Cold}X methods should always return
+  // false.
+  EXPECT_FALSE(PSI.isHotCount(1000));
+  EXPECT_FALSE(PSI.isHotCount(0));
+  EXPECT_FALSE(PSI.isColdCount(1000));
+  EXPECT_FALSE(PSI.isColdCount(0));
+
+  EXPECT_FALSE(PSI.isFunctionEntryHot(F));
+  EXPECT_FALSE(PSI.isFunctionEntryCold(F));
+
+  BasicBlock &BB0 = F->getEntryBlock();
+  BasicBlock *BB1 = BB0.getTerminator()->getSuccessor(0);
+
+  BlockFrequencyInfo BFI = buildBFI(*F);
+  EXPECT_FALSE(PSI.isHotBB(&BB0, &BFI));
+  EXPECT_FALSE(PSI.isColdBB(&BB0, &BFI));
+
+  CallSite CS1(BB1->getFirstNonPHI());
+  EXPECT_FALSE(PSI.isHotCallSite(CS1, &BFI));
+  EXPECT_FALSE(PSI.isColdCallSite(CS1, &BFI));
+}
 TEST_F(ProfileSummaryInfoTest, TestCommon) {
   auto M = makeLLVMModule("InstrProf");
   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));
TEST_F(ProfileSummaryInfoTest, InstrProf) {
   CallSite CS2(CI2);
 
   EXPECT_TRUE(PSI.isHotCallSite(CS1, &BFI));
   EXPECT_FALSE(PSI.isHotCallSite(CS2, &BFI));
 
   // Test that adding an MD_prof metadata with a hot count on CS2 does not
   // change itas hotness as it has no effect in instrumented profiling.
   MDBuilder MDB(M->getContext());
-  CI2->setMetadata(llvm::LLVMContext::MD_prof, MDB.createBranchWeights({200}));
+  CI2->setMetadata(llvm::LLVMContext::MD_prof, MDB.createBranchWeights({400}));
   EXPECT_FALSE(PSI.isHotCallSite(CS2, &BFI));
 }
 
 TEST_F(ProfileSummaryInfoTest, SampleProf) {
   auto M = makeLLVMModule("SampleProfile");
   Function *F = M->getFunction("f");
   ProfileSummaryInfo PSI = buildPSI(M.get());
 
TEST_F(ProfileSummaryInfoTest, SampleProf) {
   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}));
+  CI2->setMetadata(llvm::LLVMContext::MD_prof, MDB.createBranchWeights({400}));
   EXPECT_TRUE(PSI.isHotCallSite(CS2, &BFI));
 }
 
 } // end anonymous namespace
 } // end namespace llvm