Form a CallExpr from __noop without parens

MSVC accepts __noop without any trailing parens and treats it like a
literal zero.  We don't treat __noop as an integer literal, but now at
least we can parse a naked __noop expression.

Reviewers: rsmith

Differential Revision: http://reviews.llvm.org/D4476

llvm-svn: 212860

1 files changed, 14 insertions, 1 deletions

diff --git a/clang/lib/Sema/SemaExpr.cpp b/clang/lib/Sema/SemaExpr.cpp
index 67e839c7e59..8db782a7e20 100644
--- a/clang/lib/Sema/SemaExpr.cpp
+++ b/clang/lib/Sema/SemaExpr.cpp
@@ -13477,9 +13477,22 @@ ExprResult Sema::CheckPlaceholderExpr(Expr *E) {
   case BuiltinType::PseudoObject:
     return checkPseudoObjectRValue(E);
 
-  case BuiltinType::BuiltinFn:
+  case BuiltinType::BuiltinFn: {
+    // Accept __noop without parens by implicitly converting it to a call expr.
+    auto *DRE = dyn_cast<DeclRefExpr>(E->IgnoreParenImpCasts());
+    if (DRE) {
+      auto *FD = cast<FunctionDecl>(DRE->getDecl());
+      if (FD->getBuiltinID() == Builtin::BI__noop) {
+        E = ImpCastExprToType(E, Context.getPointerType(FD->getType()),
+                              CK_BuiltinFnToFnPtr).get();
+        return new (Context) CallExpr(Context, E, None, Context.IntTy,
+                                      VK_RValue, SourceLocation());
+      }
+    }
+
     Diag(E->getLocStart(), diag::err_builtin_fn_use);
     return ExprError();
+  }
 
   // Everything else should be impossible.
 #define BUILTIN_TYPE(Id, SingletonId) \