[PGO] Fix select instruction annotation

Summary:
Select instruction annotation in IR PGO uses the edge count to infer the
branch count. It's currently placed in setInstrumentedCounts() where
no all the BB counts have been computed. This leads to wrong branch weights.
Move the annotation after all BB counts are populated.

Reviewers: davidxl

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D25961

llvm-svn: 285128

1 files changed, 13 insertions, 4 deletions

diff --git a/llvm/lib/Transforms/Instrumentation/PGOInstrumentation.cpp b/llvm/lib/Transforms/Instrumentation/PGOInstrumentation.cpp
index c2e42177661..833a8d8536f 100644
--- a/llvm/lib/Transforms/Instrumentation/PGOInstrumentation.cpp
+++ b/llvm/lib/Transforms/Instrumentation/PGOInstrumentation.cpp
@@ -642,7 +642,7 @@ public:
              BranchProbabilityInfo *BPI = nullptr,
              BlockFrequencyInfo *BFI = nullptr)
       : F(Func), M(Modu), FuncInfo(Func, ComdatMembers, false, BPI, BFI),
-        FreqAttr(FFA_Normal) {}
+        CountPosition(0), ProfileCountSize(0), FreqAttr(FFA_Normal) {}
 
   // Read counts for the instrumented BB from profile.
   bool readCounters(IndexedInstrProfReader *PGOReader);
@@ -682,6 +682,12 @@ private:
   // compilation.
   uint64_t ProgramMaxCount;
 
+  // Position of counter that remains to be read.
+  uint32_t CountPosition;
+
+  // Total size of the profile count for this function.
+  uint32_t ProfileCountSize;
+
   // ProfileRecord for this function.
   InstrProfRecord ProfileRecord;
 
@@ -750,9 +756,8 @@ void PGOUseFunc::setInstrumentedCounts(
     NewEdge1.InMST = true;
     getBBInfo(InstrBB).setBBInfoCount(CountValue);
   }
-  // Now annotate select instructions
-  FuncInfo.SIVisitor.annotateSelects(F, this, &I);
-  assert(I == CountFromProfile.size());
+  ProfileCountSize =  CountFromProfile.size();
+  CountPosition = I;
 }
 
 // Set the count value for the unknown edge. There should be one and only one
@@ -892,6 +897,10 @@ void PGOUseFunc::populateCounters() {
     FuncMaxCount = std::max(FuncMaxCount, getBBInfo(&BB).CountValue);
   markFunctionAttributes(FuncEntryCount, FuncMaxCount);
 
+  // Now annotate select instructions
+  FuncInfo.SIVisitor.annotateSelects(F, this, &CountPosition);
+  assert(CountPosition == ProfileCountSize);
+
   DEBUG(FuncInfo.dumpInfo("after reading profile."));
 }