CodeGen: Avoid instrumenting implicit Decls more effectively

We don't assign counters for implicit Decls, but we were emitting code
to increment the (non-existent) counters and adding empty counter
lists in the output. This fixes the checks in assignRegionCounters and
emitInstrumentationData to do the right thing, and adds an assert for
the pathological case of emitting zero counters.

llvm-svn: 207203

2 files changed, 21 insertions, 2 deletions

diff --git a/clang/lib/CodeGen/CodeGenPGO.cpp b/clang/lib/CodeGen/CodeGenPGO.cpp
index 6991e40f97c..9d4aaff8888 100644
--- a/clang/lib/CodeGen/CodeGenPGO.cpp
+++ b/clang/lib/CodeGen/CodeGenPGO.cpp
@@ -146,7 +146,7 @@ llvm::GlobalVariable *CodeGenPGO::buildDataVar() {
 }
 
 void CodeGenPGO::emitInstrumentationData() {
-  if (!CGM.getCodeGenOpts().ProfileInstrGenerate)
+  if (!RegionCounters)
     return;
 
   // Build the data.
@@ -803,7 +803,7 @@ void CodeGenPGO::assignRegionCounters(const Decl *D, llvm::Function *Fn) {
   llvm::IndexedInstrProfReader *PGOReader = CGM.getPGOReader();
   if (!InstrumentRegions && !PGOReader)
     return;
-  if (!D)
+  if (D->isImplicit())
     return;
   setFuncName(Fn);
 
@@ -845,6 +845,7 @@ void CodeGenPGO::mapRegionCounters(const Decl *D) {
     Walker.TraverseDecl(const_cast<BlockDecl *>(BD));
   else if (const CapturedDecl *CD = dyn_cast_or_null<CapturedDecl>(D))
     Walker.TraverseDecl(const_cast<CapturedDecl *>(CD));
+  assert(Walker.NextCounter > 0 && "no entry counter mapped for decl");
   NumRegionCounters = Walker.NextCounter;
   FunctionHash = Walker.Hash.finalize();
 }
@@ -920,6 +921,7 @@ void CodeGenPGO::destroyRegionCounters() {
   RegionCounterMap.reset();
   StmtCountMap.reset();
   RegionCounts.reset();
+  RegionCounters = nullptr;
 }
 
 /// \brief Calculate what to divide by to scale weights.
diff --git a/clang/test/Profile/cxx-implicit.cpp b/clang/test/Profile/cxx-implicit.cpp
new file mode 100644
index 00000000000..79840ad9385
--- /dev/null
+++ b/clang/test/Profile/cxx-implicit.cpp
@@ -0,0 +1,17 @@
+// Ensure that implicit methods aren't instrumented.
+
+// RUN: %clang_cc1 -x c++ %s -triple %itanium_abi_triple -main-file-name cxx-implicit.cpp -o - -emit-llvm -fprofile-instr-generate | FileCheck %s
+
+// An implicit constructor is generated for Base. We should not emit counters
+// for it.
+// CHECK-NOT: @__llvm_profile_counters__ZN4BaseC2Ev =
+
+struct Base {
+  virtual void foo();
+};
+
+struct Derived : public Base {
+  Derived();
+};
+
+Derived::Derived() {}