[PATCH] D93927: [ArgPromotion] Copy !range metadata for loads.

[Chenguang Wang via Phabricator via llvm-commits]

wecing added a comment.

> We were already transfering the AA metadata, which is also incorrect.

IIUC, lack of AA metadata wouldn't result in incorrect code, so that SGTM. But for this:

> And we were transferring the load alignment (this probably shouldn't be transferred at all but rather a precondition)

I have an counterexample:

  int func(int *p) {
      if (p % 4 != 0) {
          return load(p, align=1);
      }
      return 0;
  }

>From LLVM lang ref <https://llvm.org/docs/LangRef.html#load-instruction>:

> an omitted align argument means that the operation has the ABI alignment for the target... Overestimating the alignment results in undefined behavior... An alignment of 1 is always safe.

Not copying the `align` info should cause LLVM to fall back to `load align 4`, but since `p % 4 != 0`, it would produce undefined behavior.

So my guess is we should always copy `align` and `!align`; for the rest metadata items, as you suggested, only copy if they are guaranteed to be executed.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D93927/new/

https://reviews.llvm.org/D93927