[PATCH] D97244: [SimplifyCFG] Update passingValueIsAlwaysUndefined to check more attributes

Tue Feb 23 09:41:41 PST 2021

spatel added a comment.

In D97244#2581118 <https://reviews.llvm.org/D97244#2581118>, @aqjune wrote:

> @spatel Now I fully got what https://reviews.llvm.org/D96663#2578814 meant. This change is introducing assume because it introduces unreachable which finally turns into assume.
>
> But, an ongoing clang frontend patch will introduce many more noundefs, and this will anyway create assumes;
> If the assumes inserted by this patch cause problems, it is likely that the problems will happen with the noundef patch as well. I think it is about facing the problem earlier or not.
>
> If we decide to be lightweight (and not to insert assume), I'll move towards SimplifyCFG to simply swap the phi's operand with undef if nonnull without noundef is met.

Another idea - proposal to limit the creation of assumes from simplifycfg:
D97306 <https://reviews.llvm.org/D97306>

Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D97244/new/

https://reviews.llvm.org/D97244