Integrated assembler incorrectly lexes ARM-style comments

The integrated assembler fails to properly lex arm comments when
they are adjacent to an identifier in the input stream. The reason
is that the arm comment symbol '@' is also used as symbol variant in
other assembly languages so when lexing an identifier it allows the
'@' symbol as part of the identifier.

Example:
  $ cat comment.s
  foo:
    add r0, r0@got to parse this as a comment

  $ llvm-mc -triple armv7 comment.s
  comment.s:4:18: error: unexpected token in argument list
    add r0, r0@got to parse this as a comment
                   ^
This should be parsed as correctly as `add r0, r0`.

This commit modifes the assembly lexer to not include the '@' symbol
in identifiers when lexing for targets that use '@' for comments.

llvm-svn: 196607

llvm/lib/MC/MCParser/AsmLexer.cpp

@@ -139,20 +139,23 @@ AsmToken AsmLexer::LexHexFloatLiteral(bool NoIntDigits) {
 }
 
 /// LexIdentifier: [a-zA-Z_.][a-zA-Z0-9_$.@?]*
-static bool IsIdentifierChar(char c) {
-  return isalnum(c) || c == '_' || c == '$' || c == '.' || c == '@' || c == '?';
+static bool IsIdentifierChar(char c, bool AllowAt) {
+  return isalnum(c) || c == '_' || c == '$' || c == '.' ||
+         (c == '@' && AllowAt) || c == '?';
 }
 AsmToken AsmLexer::LexIdentifier() {
+  bool AllowAtInIdentifier = !StringRef(MAI.getCommentString()).startswith("@");
   // Check for floating point literals.
   if (CurPtr[-1] == '.' && isdigit(*CurPtr)) {
     // Disambiguate a .1243foo identifier from a floating literal.
     while (isdigit(*CurPtr))
       ++CurPtr;
-    if (*CurPtr == 'e' || *CurPtr == 'E' || !IsIdentifierChar(*CurPtr))
+    if (*CurPtr == 'e' || *CurPtr == 'E' ||
+        !IsIdentifierChar(*CurPtr, AllowAtInIdentifier))
       return LexFloatLiteral();
   }
 
-  while (IsIdentifierChar(*CurPtr))
+  while (IsIdentifierChar(*CurPtr, AllowAtInIdentifier))
     ++CurPtr;
 
   // Handle . as a special case.

llvm/test/MC/ARM/comment.s

@@ -0,0 +1,24 @@
+@ Tests to check that '@' does not get lexed as an identifier for arm
+@ RUN: llvm-mc %s -triple=armv7-linux-gnueabi  | FileCheck %s
+@ RUN: llvm-mc %s -triple=armv7-linux-gnueabi 2>&1 | FileCheck %s --check-prefix=ERROR
+
+foo:
+  bl boo@plt should be ignored
+  bl goo@plt
+  .long bar@got to parse this as a comment
+  .long baz@got
+  add r0, r0@ignore this extra junk
+
+@CHECK-LABEL: foo:
+@CHECK: bl boo
+@CHECK-NOT: @
+@CHECK: bl goo
+@CHECK-NOT: @
+@CHECK: .long bar
+@CHECK-NOT: @
+@CHECK: .long baz
+@CHECK-NOT: @
+@CHECK: add r0, r0
+@CHECK-NOT: @
+
+@ERROR-NOT: error: