Cherry-pick upstream r237073

lib/Parse/Parser.cpp

Index: lib/Parse/Parser.cpp
diff --git a/lib/Parse/Parser.cpp b/lib/Parse/Parser.cpp
index 3b56102dcfad045b36288dc0ac5a35692460aa42..697fda9215df3f423c74b9e4b4e208e37e0413a2 100644
--- a/lib/Parse/Parser.cpp
+++ b/lib/Parse/Parser.cpp
@@ -669,8 +669,18 @@ Parser::ParseExternalDeclaration(ParsedAttributesWithRange &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");