[PATCH] D65402: [Attributor][MustExec] Deduce dereferenceable and nonnull attribute using MustBeExecutedContextExplorer

[Hideto Ueno via Phabricator via llvm-commits]

uenoku added a comment.

In D65402#1701550 <https://reviews.llvm.org/D65402#1701550>, @xbolva00 wrote:

> dereferenceable attribute is not added to the arguments?
>
> define dso_local void @_Z3fooPaS_S_ii(i8* noalias nocapture writeonly %0, i8* noalias nocapture readnone %1, i8* noalias nocapture readonly %2, i32 %3, i32 %4) local_unnamed_addr #0 {
>
>   tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* noalias nocapture nonnull writeonly align 1 dereferenceable(16) %0, i8* noalias nocapture nonnull readonly align 1 dereferenceable(16) %2, i64 16, i1 false) #2
>   ret void
>
> }
>
> I would expect
>
> define dso_local void @_Z3fooPaS_S_ii(i8* noalias nocapture writeonly dereferenceable(16) %0, i8* noalias nocapture readnone %1, i8* noalias nocapture readonly dereferenceable(16) %2, i32 %3, i32 %4) local_unnamed_addr #0 {
>
>   tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* noalias nocapture nonnull writeonly align 1 dereferenceable(16) %0, i8* noalias nocapture nonnull readonly align 1 dereferenceable(16) %2, i64 16, i1 false) #2
>   ret void
>
> }
>
> https://godbolt.org/z/if9rle


Actually, dereferenceable is added to the arguments if opt is executed for the above IR. https://godbolt.org/z/CItEJG

As far as I see the log, the problem is that InstCombine is located after Attributor Pass in -O3. Therefore, dereferenceable is not propagated.
Please take a look at the stderr output in https://godbolt.org/z/l_6aVE.

Solutions are to change the order or to run the Attributor several times.


Repository:
  rG LLVM Github Monorepo

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  https://reviews.llvm.org/D65402/new/

https://reviews.llvm.org/D65402