[X86][MC] Fix bracket expression parsing in intel-style assembly.

[niravd]

Summary

Only perform struct field check on Identifier tokens.

Fixes PR28547.

[rnk]

Why are we calling ParseIntelBracExpression in a comment in the first place?

[niravd]

We're not. We're dealing with the next token after a bracket expression may be a struct field accessor. If it didn't exist, we should get an EndOfStatement with a string of "" or "\n" and so skipping the Token Kind check was okay. But now that end of line comments are embedded in the EndOfStatement token there we can potentially have '.' characters we erroneously fail.

[rnk]

makes sense, lgtm

lib/Target/X86/AsmParser/X86AsmParser.cpp

X86AsmParser::ParseIntelBracExpression(unsigned SegReg, SMLoc Start,
                                        int64_t ImmDisp, unsigned Size) {
   MCAsmParser &Parser = getParser();
   const AsmToken &Tok = Parser.getTok();
   SMLoc BracLoc = Tok.getLoc(), End = Tok.getEndLoc();
   if (getLexer().isNot(AsmToken::LBrac))
     return ErrorOperand(BracLoc, "Expected '[' token!");
   Parser.Lex(); // Eat '['
 
-  SMLoc StartInBrac = Tok.getLoc();
+  SMLoc StartInBrac = Parser.getTok().getLoc();
   // Parse [ Symbol + ImmDisp ] and [ BaseReg + Scale*IndexReg + ImmDisp ].  We
   // may have already parsed an immediate displacement before the bracketed
   // expression.
   IntelExprStateMachine SM(ImmDisp, /*StopOnLBrac=*/false, /*AddImmPrefix=*/true);
   if (ParseIntelExpression(SM, End))
     return nullptr;
 
   const MCExpr *Disp = nullptr;
if (Disp)
       Disp = MCBinaryExpr::createAdd(Disp, Imm, getContext());
     else
       Disp = Imm;  // An immediate displacement only.
   }
 
   // Parse struct field access.  Intel requires a dot, but MSVC doesn't.  MSVC
   // will in fact do global lookup the field name inside all global typedefs,
   // but we don't emulate that.
-  if (Tok.getString().find('.') != StringRef::npos) {
+  if (Parser.getTok().getKind() == AsmToken::Identifier &&
+      Parser.getTok().getString().find('.') != StringRef::npos) {
     const MCExpr *NewDisp;
     if (ParseIntelDotOperator(Disp, NewDisp))
       return nullptr;
 
     End = Tok.getEndLoc();
     Parser.Lex();  // Eat the field.
     Disp = NewDisp;
   }

test/MC/X86/pr28547.s

+// RUN: llvm-mc -triple x86_64-unknown-unknown %s
+  .intel_syntax
+ones:
+  .float +1.0, +1.0, +1.0, +1.0
+  vmovaps xmm15, xmmword ptr [rip+ones] # +1.0, +1.0, +1.0, +1.0