[ms-inline asm] Avoid a false positive assertion

Assertion failed: (Start.isValid() == End.isValid() && "Start and end should 
either both be valid or both be invalid!")

when parsing inline asm.  SMLoc assumes that the first char * in the source is
invalid.  However, when parsing an inline asm the mnemonic is at this location.
I don't want to change SMLoc, so use a trivial workaround.

llvm-svn: 162381

lib/Target/X86/AsmParser/X86AsmParser.cpp

@@ -1677,8 +1677,10 @@ MatchInstruction(SMLoc IDLoc,
   if ((Match1 == Match_MnemonicFail) && (Match2 == Match_MnemonicFail) &&
       (Match3 == Match_MnemonicFail) && (Match4 == Match_MnemonicFail)) {
     if (!WasOriginallyInvalidOperand) {
+      ArrayRef<SMRange> Ranges = matchingInlineAsm ? EmptyRanges :
+        Op->getLocRange();
       return Error(IDLoc, "invalid instruction mnemonic '" + Base + "'",
-                   Op->getLocRange(), matchingInlineAsm);
+                   Ranges, matchingInlineAsm);
     }
 
     // Recover location info for the operand if we know which was the problem.