2nd argument of __builtin_expect must be evaluated

if it hs side-effect to matchgcc's behaviour.
Addresses radar 8172109.

llvm-svn: 109467

2 files changed, 15 insertions, 1 deletions

diff --git a/clang/lib/CodeGen/CGBuiltin.cpp b/clang/lib/CodeGen/CGBuiltin.cpp
index 06140119321..f3346e7bd71 100644
--- a/clang/lib/CodeGen/CGBuiltin.cpp
+++ b/clang/lib/CodeGen/CGBuiltin.cpp
@@ -284,9 +284,12 @@ RValue CodeGenFunction::EmitBuiltinExpr(const FunctionDecl *FD,
                                      "cast");
     return RValue::get(Result);
   }
-  case Builtin::BI__builtin_expect:
+  case Builtin::BI__builtin_expect: {
     // FIXME: pass expect through to LLVM
+    if (E->getArg(1)->HasSideEffects(getContext()))
+      (void)EmitScalarExpr(E->getArg(1));
     return RValue::get(EmitScalarExpr(E->getArg(0)));
+  }
   case Builtin::BI__builtin_bswap32:
   case Builtin::BI__builtin_bswap64: {
     Value *ArgValue = EmitScalarExpr(E->getArg(0));
diff --git a/clang/test/CodeGen/builtin-expect.c b/clang/test/CodeGen/builtin-expect.c
new file mode 100644
index 00000000000..8f02c4da78a
--- /dev/null
+++ b/clang/test/CodeGen/builtin-expect.c
@@ -0,0 +1,11 @@
+// RUN: %clang_cc1 -emit-llvm -o - %s | FileCheck %s
+
+int x;
+int y(void);
+void foo();
+void FUNC() {
+// CHECK: [[call:%.*]] = call i32 @y
+  if (__builtin_expect (x, y()))
+    foo ();
+}
+