[PATCH] D76674: [Attributor] Derive better alignment for accessed pointers

Thu Mar 26 11:25:37 PDT 2020

uenoku added a comment.

In D76674#1944353 <https://reviews.llvm.org/D76674#1944353>, @lebedev.ri wrote:

> In D76674#1944250 <https://reviews.llvm.org/D76674#1944250>, @uenoku wrote:
>
> > Why can't we use ABI info without known access?
> >  I mean, is it possible to use ABI info in initialize?
>
>
> See my previous comment.
>  If we decide that pointer has ABI alignment from the get go,
>  then we will immediately update every underaligned load/store to no longer be underaligned,
>  which makes no sense. Unless i'm horribly mistaken, just because we said that %z is `i32*` or `i512*`,
>  it doesn't mean it is UB for it to be aligned to a single byte (`& 0b1 == 1`),
>  it is the access to such misaligned pointer that is UB.

I got it. This makes sense. Thank you.

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https://reviews.llvm.org/D76674