[PATCH] D116053: [MachineSink] Allow sinking of constant or ignorable physreg uses

[ChenZheng via Phabricator via llvm-commits]

shchenz added a comment.

In D116053#3203538 <https://reviews.llvm.org/D116053#3203538>, @rampitec wrote:

> I am not sure I can prove to myself this is legal. For example you are sinking a def into a loop with divergent condition and this def is used after the loop. Can this happen?

If `SuccToSinkTo` exists, all uses of the def must be dominated by block `SuccToSinkTo`. So I think it is ok to do the sinking.

`isConstantPhysReg()` seems ok as any def to such register has no meaning.

Better let an AMDGPU expert have a look especially at the code gen changes.


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https://reviews.llvm.org/D116053