1 files changed, 6 insertions, 1 deletions
diff --git a/clang/lib/CodeGen/CGBuiltin.cpp b/clang/lib/CodeGen/CGBuiltin.cpp
index 8f320d1d776..ee8aa12b680 100644
--- a/clang/lib/CodeGen/CGBuiltin.cpp
+++ b/clang/lib/CodeGen/CGBuiltin.cpp
@@ -389,9 +389,14 @@ RValue CodeGenFunction::EmitBuiltinExpr(const FunctionDecl *FD,
     Value *ArgValue = EmitScalarExpr(E->getArg(0));
     llvm::Type *ArgType = ArgValue->getType();
 
-    Value *FnExpect = CGM.getIntrinsic(Intrinsic::expect, ArgType);
     Value *ExpectedValue = EmitScalarExpr(E->getArg(1));
+    // Don't generate llvm.expect on -O0 as the backend won't use it for
+    // anything.
+    // Note, we still IRGen ExpectedValue because it could have side-effects.
+    if (CGM.getCodeGenOpts().OptimizationLevel == 0)
+      return RValue::get(ArgValue);
 
+    Value *FnExpect = CGM.getIntrinsic(Intrinsic::expect, ArgType);
     Value *Result = Builder.CreateCall2(FnExpect, ArgValue, ExpectedValue,
                                         "expval");
     return RValue::get(Result);