[PATCH] D87585: [AMDGPU] Dynamically clear renamable to avoid constant bus errors

[Carl Ritson via Phabricator via llvm-commits]

critson added a comment.

In D87585#2276142 <https://reviews.llvm.org/D87585#2276142>, @foad wrote:

> In D87585#2276099 <https://reviews.llvm.org/D87585#2276099>, @critson wrote:
>
>> I will review shader changes; however, I do not think Machine Copy Propagation propagates constants.
>
> True. But this can also help with stalls:
>
>   v_mov v0, s0
>   v_mov v1, v0
>
> ->
>
>   v_mov v0, s0
>   v_mov v1, s0

I looked over all the GFX10 diffs and could not find anything useful happening except a handful of rewrites of v_cndmask to use an additional SGPR argument; however, in practice none these would affect stalls.  This is not too surprising v_cndmask was the made target of this when I wrote it, but for the specific code generation use case (moving WQM) I will take care of these at code generation time instead.


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