[PATCH] D87882: [AMDGPU] Fix merging m0 inits

[Stanislav Mekhanoshin via Phabricator via llvm-commits]

rampitec added a comment.

In D87882#2282818 <https://reviews.llvm.org/D87882#2282818>, @piotr wrote:

> In D87882#2282278 <https://reviews.llvm.org/D87882#2282278>, @rampitec wrote:
>
>> Doesn't loop block self dominate?
>
> You mean, why the condition "MDT.dominates(From, To)" returns false if From and To are in the same BB? Inside that function there is a bb dominance check if the instructions are in different blocks, but if the instructions are in the same block the code checks whether From comes before To.
>
> The bug I am trying to fix is simplified in the test m0-in-loop-0 where before my patch SI_INIT from line 333 was incorrectly removed. Although "m0 = COPY" comes after SI_INIT in that bb, this is a loop and in the second iteration DS_WRITE would see a clobbered m0, so SI_INIT has to be preserved.

That sounds like a bug in the dominate() to me.


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https://reviews.llvm.org/D87882