[llvm-ml] Disallow '{' and '}' at the start of a statement

[barannikov88]

Summary

'{', '}' and (conditionally) '*' were allowed at the start of a
statement. This behavior was copied from AsmParser, where they were
added to support Hexagon bundles (braces) and BFP memory instructions
(the star).
MASM dialect is x86-specific and does not allow these symbols to be
used at the beginning of an instruction.

Worth noting that '{' is a valid first character in AT&T syntax
(e.g. "{vex} vpmadd52huq ..."); MASM variant is to omit the braces.

[barannikov88]

Fix FileCheck directives in the test

[barannikov88]

Rebase

llvm/lib/MC/MCParser/MasmParser.cpp

bool MasmParser::parseStatement(ParseStatementInfo &Info,
   SMLoc IDLoc = ID.getLoc();
   StringRef IDVal;
   if (Lexer.is(AsmToken::HashDirective))
     return parseCppHashLineFilenameComment(IDLoc);
   if (Lexer.is(AsmToken::Dot)) {
     // Treat '.' as a valid identifier in this context.
     Lex();
     IDVal = ".";
-  } else if (Lexer.is(AsmToken::LCurly)) {
-    // Treat '{' as a valid identifier in this context.
-    Lex();
-    IDVal = "{";
-
-  } else if (Lexer.is(AsmToken::RCurly)) {
-    // Treat '}' as a valid identifier in this context.
-    Lex();
-    IDVal = "}";
-  } else if (Lexer.is(AsmToken::Star) &&
-             getTargetParser().starIsStartOfStatement()) {
-    // Accept '*' as a valid start of statement.
-    Lex();
-    IDVal = "*";
   } else if (Lexer.is(AsmToken::Real)) {
     // Treat ".<number>" as a valid identifier in this context.
     IDVal = getTok().getString();
     Lex(); // always eat a token
     if (!IDVal.startswith("."))
       return Error(IDLoc, "unexpected token at start of statement");
   } else if (parseIdentifier(IDVal, StartOfStatement)) {
     if (!TheCondState.Ignore) {

llvm/test/tools/llvm-ml/label_errors.asm

+; RUN: not llvm-ml -filetype=s %s /Fo - 2>&1 \
+; RUN:   | FileCheck %s --implicit-check-not="{{[0-9]+:[0-9]+: error:}}"
+
+.code
+
+; These used to be valid label names.
+{: ; CHECK: [[@LINE]]:1: error: unexpected token at start of statement
+}: ; CHECK: [[@LINE]]:1: error: unexpected token at start of statement