CodeGen: Emit warnings for out of date profile data during PGO

This adds a warning that triggers when profile data doesn't match for
the source that's being compiled with -fprofile-instr-use=. This fires
only once per translation unit, as warning on every mismatched
function would be quite noisy.

llvm-svn: 206322

3 files changed, 25 insertions, 2 deletions

diff --git a/clang/lib/CodeGen/CodeGenModule.cpp b/clang/lib/CodeGen/CodeGenModule.cpp
index 6ea60ba1c0d..d4daaa55c79 100644
--- a/clang/lib/CodeGen/CodeGenModule.cpp
+++ b/clang/lib/CodeGen/CodeGenModule.cpp
@@ -286,6 +286,9 @@ void CodeGenModule::Release() {
   if (getCodeGenOpts().ProfileInstrGenerate)
     if (llvm::Function *PGOInit = CodeGenPGO::emitInitialization(*this))
       AddGlobalCtor(PGOInit, 0);
+  if (PGOData && PGOStats.isOutOfDate())
+    getDiags().Report(diag::warn_profile_data_out_of_date)
+        << PGOStats.Visited << PGOStats.Missing << PGOStats.Mismatched;
   EmitCtorList(GlobalCtors, "llvm.global_ctors");
   EmitCtorList(GlobalDtors, "llvm.global_dtors");
   EmitGlobalAnnotations();
diff --git a/clang/lib/CodeGen/CodeGenModule.h b/clang/lib/CodeGen/CodeGenModule.h
index 0d13bdcc2fa..f6614dd44bd 100644
--- a/clang/lib/CodeGen/CodeGenModule.h
+++ b/clang/lib/CodeGen/CodeGenModule.h
@@ -220,6 +220,15 @@ struct ARCEntrypoints {
   llvm::Constant *clang_arc_use;
 };
 
+/// This class records statistics on instrumentation based profiling.
+struct InstrProfStats {
+  InstrProfStats() : Visited(0), Missing(0), Mismatched(0) {}
+  bool isOutOfDate() { return Missing || Mismatched; }
+  uint32_t Visited;
+  uint32_t Missing;
+  uint32_t Mismatched;
+};
+
 /// CodeGenModule - This class organizes the cross-function state that is used
 /// while generating LLVM code.
 class CodeGenModule : public CodeGenTypeCache {
@@ -258,6 +267,7 @@ class CodeGenModule : public CodeGenTypeCache {
   llvm::MDNode *NoObjCARCExceptionsMetadata;
   RREntrypoints *RRData;
   PGOProfileData *PGOData;
+  InstrProfStats PGOStats;
 
   // WeakRefReferences - A set of references that have only been seen via
   // a weakref so far. This is used to remove the weak of the reference if we
@@ -483,6 +493,10 @@ public:
     return *RRData;
   }
 
+  InstrProfStats &getPGOStats() {
+    return PGOStats;
+  }
+
   PGOProfileData *getPGOData() const {
     return PGOData;
   }
diff --git a/clang/lib/CodeGen/CodeGenPGO.cpp b/clang/lib/CodeGen/CodeGenPGO.cpp
index 55a09e8db52..c451bef57c5 100644
--- a/clang/lib/CodeGen/CodeGenPGO.cpp
+++ b/clang/lib/CodeGen/CodeGenPGO.cpp
@@ -908,11 +908,17 @@ void CodeGenPGO::emitCounterIncrement(CGBuilderTy &Builder, unsigned Counter) {
 }
 
 void CodeGenPGO::loadRegionCounts(PGOProfileData *PGOData) {
+  CGM.getPGOStats().Visited++;
   RegionCounts.reset(new std::vector<uint64_t>);
   uint64_t Hash;
-  if (PGOData->getFunctionCounts(getFuncName(), Hash, *RegionCounts) ||
-      Hash != FunctionHash || RegionCounts->size() != NumRegionCounters)
+  if (PGOData->getFunctionCounts(getFuncName(), Hash, *RegionCounts)) {
+    CGM.getPGOStats().Missing++;
     RegionCounts.reset();
+  } else if (Hash != FunctionHash ||
+             RegionCounts->size() != NumRegionCounters) {
+    CGM.getPGOStats().Mismatched++;
+    RegionCounts.reset();
+  }
 }
 
 void CodeGenPGO::destroyRegionCounters() {