Cherry-pick upstream r237073

lib/Parse/Parser.cpp

 //===--- Parser.cpp - C Language Family Parser ----------------------------===//
 //
 //                     The LLVM Compiler Infrastructure
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 //
 //  This file implements the Parser interfaces.
@@ skipping 651 matching lines @@
     // __extension__ silences extension warnings in the subexpression.
     ExtensionRAIIObject O(Diags);  // Use RAII to do this.
     ConsumeToken();
     return ParseExternalDeclaration(attrs);
   }
   case tok::kw_asm: {
     ProhibitAttributes(attrs);
 
     SourceLocation StartLoc = Tok.getLocation();
     SourceLocation EndLoc;
+
     ExprResult Result(ParseSimpleAsm(&EndLoc));
 
+    // Check if GNU-style InlineAsm is disabled.
+    // Empty asm string is allowed because it will not introduce
+    // any assembly code.
+    if (!(getLangOpts().GNUAsm || Result.isInvalid())) {
+      const auto *SL = cast<StringLiteral>(Result.get());
+      if (!SL->getString().trim().empty())
+        Diag(StartLoc, diag::err_gnu_inline_asm_disabled);
+    }
+
     ExpectAndConsume(tok::semi, diag::err_expected_after,
                      "top-level asm block");
 
     if (Result.isInvalid())
       return DeclGroupPtrTy();
     SingleDecl = Actions.ActOnFileScopeAsmDecl(Result.get(), StartLoc, EndLoc);
     break;
   }
   case tok::at:
     return ParseObjCAtDirectives();
@@ skipping 1269 matching lines @@
                   Parser::StopAtSemi | Parser::StopBeforeMatch) &&
       P.Tok.is(Close))
     LClose = P.ConsumeAnyToken();
   return true;
 }
 
 void BalancedDelimiterTracker::skipToEnd() {
   P.SkipUntil(Close, Parser::StopBeforeMatch);
   consumeClose();
 }