"Implement" codegen support for __noop().

Eli discovered that __noop's sema behavior also needs some love. I filed
PR14081 for that and intend to improve it.



git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@165886 91177308-0d34-0410-b5e6-96231b3b80d8

lib/CodeGen/CGBuiltin.cpp

@@ -1321,6 +1321,8 @@ RValue CodeGenFunction::EmitBuiltinExpr(const FunctionDecl *FD,
     llvm::StringRef Str = cast<StringLiteral>(AnnotationStrExpr)->getString();
     return RValue::get(EmitAnnotationCall(F, AnnVal, Str, E->getExprLoc()));
   }
+  case Builtin::BI__noop:
+    return RValue::get(0);
   }
 
   // If this is an alias for a lib function (e.g. __builtin_sin), emit

test/CodeGen/builtin-ms-noop.cpp

@@ -0,0 +1,14 @@
+// RUN: %clang_cc1 -triple i686-pc-win32 -emit-llvm %s -o - | FileCheck %s
+
+class A {
+ public:
+  ~A() {}
+};
+
+void f() {
+// CHECK: @_Z1fv
+// CHECK-NOT: call void @_ZN1AD1Ev
+// CHECK: ret void
+  __noop(A());
+};
+