Cherry-pick upstream r237073

lib/Parse/ParseStmtAsm.cpp

 //===---- ParseStmtAsm.cpp - Assembly Statement 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 parsing for GCC and Microsoft inline assembly. 
@@ skipping 598 matching lines @@
 StmtResult Parser::ParseAsmStatement(bool &msAsm) {
   assert(Tok.is(tok::kw_asm) && "Not an asm stmt");
   SourceLocation AsmLoc = ConsumeToken();
 
   if (getLangOpts().AsmBlocks && Tok.isNot(tok::l_paren) &&
       !isTypeQualifier()) {
     msAsm = true;
     return ParseMicrosoftAsmStatement(AsmLoc);
   }
 
-  // Check if GNU-style inline Asm is disabled.
-  if (!getLangOpts().GNUAsm)
-    Diag(AsmLoc, diag::err_gnu_inline_asm_disabled);
-
   DeclSpec DS(AttrFactory);
   SourceLocation Loc = Tok.getLocation();
   ParseTypeQualifierListOpt(DS, AR_VendorAttributesParsed);
 
   // GNU asms accept, but warn, about type-qualifiers other than volatile.
   if (DS.getTypeQualifiers() & DeclSpec::TQ_const)
     Diag(Loc, diag::w_asm_qualifier_ignored) << "const";
   if (DS.getTypeQualifiers() & DeclSpec::TQ_restrict)
     Diag(Loc, diag::w_asm_qualifier_ignored) << "restrict";
   // FIXME: Once GCC supports _Atomic, check whether it permits it here.
   if (DS.getTypeQualifiers() & DeclSpec::TQ_atomic)
     Diag(Loc, diag::w_asm_qualifier_ignored) << "_Atomic";
 
   // Remember if this was a volatile asm.
   bool isVolatile = DS.getTypeQualifiers() & DeclSpec::TQ_volatile;
   if (Tok.isNot(tok::l_paren)) {
     Diag(Tok, diag::err_expected_lparen_after) << "asm";
     SkipUntil(tok::r_paren, StopAtSemi);
     return StmtError();
   }
   BalancedDelimiterTracker T(*this, tok::l_paren);
   T.consumeOpen();
 
   ExprResult AsmString(ParseAsmStringLiteral());
+
+  // Check if GNU-style InlineAsm is disabled.
+  // Error on anything other than empty string.
+  if (!(getLangOpts().GNUAsm || AsmString.isInvalid())) {
+    const auto *SL = cast<StringLiteral>(AsmString.get());
+    if (!SL->getString().trim().empty())
+      Diag(Loc, diag::err_gnu_inline_asm_disabled);
+  }
+
   if (AsmString.isInvalid()) {
     // Consume up to and including the closing paren.
     T.skipToEnd();
     return StmtError();
   }
 
   SmallVector<IdentifierInfo *, 4> Names;
   ExprVector Constraints;
   ExprVector Exprs;
   ExprVector Clobbers;
@@ skipping 127 matching lines @@
     if (Res.isInvalid()) {
       SkipUntil(tok::r_paren, StopAtSemi);
       return true;
     }
     Exprs.push_back(Res.get());
     // Eat the comma and continue parsing if it exists.
     if (!TryConsumeToken(tok::comma))
       return false;
   }
 }