Retry: [profiling] Fix profile counter increment when emitting selects (PR32019)

2nd attempt: the first was in r296231, but it had a use after lifetime
bug.

Clang has logic to lower certain conditional expressions directly into llvm
select instructions. However, it does not emit the correct profile counter
increment as it does this: it emits an unconditional increment of the counter
for the 'then branch', even if the value selected is from the 'else branch'
(this is PR32019).

That means, given the following snippet, we would report that "0" is selected
twice, and that "1" is never selected:

  int f1(int x) {
    return x ? 0 : 1;
               ^2  ^0
  }

  f1(0);
  f1(1);

Fix the problem by using the instrprof_increment_step intrinsic to do the
proper increment.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@296245 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/CodeGen/CGExprScalar.cpp b/lib/CodeGen/CGExprScalar.cpp
index 529642cb83e6daf3db230a82bba1926949ea8ce5..43267833821e7137547dbacfb69f3e8b0735c0eb 100644 (file)
--- a/lib/CodeGen/CGExprScalar.cpp
+++ b/lib/CodeGen/CGExprScalar.cpp
@@ -3414,9 +3414,11 @@ VisitAbstractConditionalOperator(const AbstractConditionalOperator *E) {
   // safe to evaluate the LHS and RHS unconditionally.
   if (isCheapEnoughToEvaluateUnconditionally(lhsExpr, CGF) &&
       isCheapEnoughToEvaluateUnconditionally(rhsExpr, CGF)) {
-    CGF.incrementProfileCounter(E);
-
     llvm::Value *CondV = CGF.EvaluateExprAsBool(condExpr);
+    llvm::Value *StepV = Builder.CreateZExtOrBitCast(CondV, CGF.Int64Ty);
+
+    CGF.incrementProfileCounter(E, StepV);
+
     llvm::Value *LHS = Visit(lhsExpr);
     llvm::Value *RHS = Visit(rhsExpr);
     if (!LHS) {

diff --git a/lib/CodeGen/CodeGenFunction.h b/lib/CodeGen/CodeGenFunction.h
index 72105802b45a9407a4c85ea5a60cc5b59f2f3965..e011c1167fd31a9505ba449d5823a904cbe00ed8 100644 (file)
--- a/lib/CodeGen/CodeGenFunction.h
+++ b/lib/CodeGen/CodeGenFunction.h
@@ -1127,10 +1127,11 @@ private:
                                             uint64_t LoopCount);
 
 public:
-  /// Increment the profiler's counter for the given statement.
-  void incrementProfileCounter(const Stmt *S) {
+  /// Increment the profiler's counter for the given statement by \p StepV.
+  /// If \p StepV is null, the default increment is 1.
+  void incrementProfileCounter(const Stmt *S, llvm::Value *StepV = nullptr) {
     if (CGM.getCodeGenOpts().hasProfileClangInstr())
-      PGO.emitCounterIncrement(Builder, S);
+      PGO.emitCounterIncrement(Builder, S, StepV);
     PGO.setCurrentStmt(S);
   }
 

diff --git a/lib/CodeGen/CodeGenPGO.cpp b/lib/CodeGen/CodeGenPGO.cpp
index 530ee9b4e9e266a1aa587f6fc8e74c66833d0bb8..90711b5479408948ce6d7162d5eba83385fd2802 100644 (file)
--- a/lib/CodeGen/CodeGenPGO.cpp
+++ b/lib/CodeGen/CodeGenPGO.cpp
@@ -739,7 +739,8 @@ CodeGenPGO::applyFunctionAttributes(llvm::IndexedInstrProfReader *PGOReader,
   Fn->setEntryCount(FunctionCount);
 }
 
-void CodeGenPGO::emitCounterIncrement(CGBuilderTy &Builder, const Stmt *S) {
+void CodeGenPGO::emitCounterIncrement(CGBuilderTy &Builder, const Stmt *S,
+                                      llvm::Value *StepV) {
   if (!CGM.getCodeGenOpts().hasProfileClangInstr() || !RegionCounterMap)
     return;
   if (!Builder.GetInsertBlock())
@@ -747,11 +748,18 @@ void CodeGenPGO::emitCounterIncrement(CGBuilderTy &Builder, const Stmt *S) {
 
   unsigned Counter = (*RegionCounterMap)[S];
   auto *I8PtrTy = llvm::Type::getInt8PtrTy(CGM.getLLVMContext());
-  Builder.CreateCall(CGM.getIntrinsic(llvm::Intrinsic::instrprof_increment),
-                     {llvm::ConstantExpr::getBitCast(FuncNameVar, I8PtrTy),
-                      Builder.getInt64(FunctionHash),
-                      Builder.getInt32(NumRegionCounters),
-                      Builder.getInt32(Counter)});
+
+  llvm::Value *Args[] = {llvm::ConstantExpr::getBitCast(FuncNameVar, I8PtrTy),
+                         Builder.getInt64(FunctionHash),
+                         Builder.getInt32(NumRegionCounters),
+                         Builder.getInt32(Counter), StepV};
+  if (!StepV)
+    Builder.CreateCall(CGM.getIntrinsic(llvm::Intrinsic::instrprof_increment),
+                       makeArrayRef(Args, 4));
+  else
+    Builder.CreateCall(
+        CGM.getIntrinsic(llvm::Intrinsic::instrprof_increment_step),
+        makeArrayRef(Args));
 }
 
 // This method either inserts a call to the profile run-time during

diff --git a/lib/CodeGen/CodeGenPGO.h b/lib/CodeGen/CodeGenPGO.h
index 4f229cde63b03426ae7f74b7a110422e4882b60c..0026df570bce0617034fef73833b71e9ad4f972d 100644 (file)
--- a/lib/CodeGen/CodeGenPGO.h
+++ b/lib/CodeGen/CodeGenPGO.h
@@ -105,7 +105,8 @@ private:
   void emitCounterRegionMapping(const Decl *D);
 
 public:
-  void emitCounterIncrement(CGBuilderTy &Builder, const Stmt *S);
+  void emitCounterIncrement(CGBuilderTy &Builder, const Stmt *S,
+                            llvm::Value *StepV);
 
   /// Return the region count for the counter at the given index.
   uint64_t getRegionCount(const Stmt *S) {

diff --git a/test/Profile/c-ternary.c b/test/Profile/c-ternary.c
new file mode 100644 (file)
index 0000000..09e8329
--- /dev/null
+++ b/test/Profile/c-ternary.c
@@ -0,0 +1,15 @@
+// RUN: %clang_cc1 -triple x86_64-apple-macosx10.11.0 -x c %s -o - -emit-llvm -fprofile-instrument=clang | FileCheck %s
+
+// PR32019: Clang can lower some ternary operator expressions to select
+// instructions. Make sure we only increment the profile counter for the
+// condition when the condition evaluates to true.
+// CHECK-LABEL: define i32 @f1
+int f1(int x) {
+// CHECK: [[TOBOOL:%.*]] = icmp ne i32 %1, 0
+// CHECK-NEXT: [[STEP:%.*]] = zext i1 [[TOBOOL]] to i64
+// CHECK-NEXT: [[COUNTER:%.*]] = load i64, i64* getelementptr inbounds ([2 x i64], [2 x i64]* @__profc_f1, i64 0, i64 1)
+// CHECK-NEXT: add i64 [[COUNTER]], [[STEP]]
+// CHECK: [[COND:%.*]] = select i1 [[TOBOOL]], i32 0, i32 1
+  return x ? 0 : 1;
+// CHECK: ret i32 [[COND]]
+}