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[AsmParser][SystemZ][z/OS] Introducing HLASM Comment Syntax

Authored by anirudhp on Mar 12 2021, 8:39 AM.

Description

[AsmParser][SystemZ][z/OS] Introducing HLASM Comment Syntax

  • This patch adds in support for the ordinary HLASM comment syntax asm statements (Reference - Chapter 7, Comment Statements, Ordinary Comment Statements)
  • In brief, the ordinary comment syntax if used, must begin with the "*" character
  • To achieve this, this patch makes use of the CommentString attribute provided in the base MCAsmInfo class
  • In the SystemZMCAsmInfo class, the CommentString attribute was set to "*" based on the assembler dialect
  • Furthermore, a new attribute RestrictCommentString, is provided to only treat a string as a comment if it appears at the start of the asm statement. Example: "jo *-4" is valid in HLASM (jump back 4 bytes from current point - similar to jo -4 in gnu asm) and we don't want "*-4" to be treated as a comment.
  • RFC for HLASM Parser support implementation: https://lists.llvm.org/pipermail/llvm-dev/2021-January/147686.html

Reviewed By: scott.linder, Kai

Differential Revision: https://reviews.llvm.org/D97703