[PATCH] D63709: [AMDGPU] Add peephole to optimize MOV

Tue Jun 25 08:51:45 PDT 2019

arsenm added a comment.

In D63709#1557626 <https://reviews.llvm.org/D63709#1557626>, @arsenm wrote:

> In D63709#1557605 <https://reviews.llvm.org/D63709#1557605>, @arsenm wrote:
>
> > In D63709#1557592 <https://reviews.llvm.org/D63709#1557592>, @arsenm wrote:
> >
> > > Reduced further: https://paste.debian.net/1089194
> >
> >
> > Other targets seem to not have this problem with a slightly generalized version, so I would look into how this is cleaned up there
>
>
> It seems we're missing a simplifycfg run somewhere, so maybe we're thinking of this on the wrong level entirely.. If I run simplify cfg on any of the testcase variants, this problem disappears

Other targets seem to run SimiplifyCFG after AtomicExpand, which we are missing. Even with that disabled and the phi survives to machineinstrs, aarch64 and hexagon both avoid this

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  rL LLVM

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  https://reviews.llvm.org/D63709/new/

https://reviews.llvm.org/D63709