[PATCH] D80434: [AMDGPU] Reject moving PHI to VALU if the only VGPR input originated from move immediate

Fri May 22 12:52:45 PDT 2020

alex-t added a comment.

In D80434#2051336 <https://reviews.llvm.org/D80434#2051336>, @rampitec wrote:

> Every mov isMoveImmediate(), it is just a property on MCDesc.
>  I also assume it relies on the folding later. If that folding will not happen for whatever reason it will be a broken IR. Right?

I meant the move a constant value to VGPR. In this particular case it was moving 0. Then GVN force the VGPR to be reused multiple times along the basic block and it's successors.
The PHI in question just needed value 0. No other reasons to use VGPR.

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