[PATCH] D70157: Align branches within 32-Byte boundary(NOP padding)

[annita.zhang via Phabricator via llvm-commits]

annita.zhang added a comment.

> To be concrete, I propose:
>  ".autopad", ".noautopad": allow/disallow the assembler to emit padding via inserting a nop or prefix before any instruction, as needed.
>  ".align_branch_boundary [N,] [instruction,]": Enable branch-boundary padding (per previous description).

I had thought I sent the comments yesterday, but I didn't. :( I think my comments are aligned with the conclusion that Philip and Jame got. Wait for Jame's summary.

In general, I think it's a good idea to have generic directives to control the padding behavior in assembler. ".autopad", ".noautopad", ".align_branch_boundary" looks good except it can't handle the nested scenarios. I can imagine the nested cases in assembly file which includes another assembly file. If we want to handle it, we need to have a pair of directives for each above. It will make the semantics complicated. We need elaborately design it.
I'd echo what Philip said. We want a more focused and basic implementation here. We're very open to have more discussion on generic directives. However, I'd prefer it's a separate topic from this one.


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D70157/new/

https://reviews.llvm.org/D70157