[PATCH] D86294: [RFC] AMDGPU/GlobalISel: Look through copies in GIM_CheckOpcode

[Matt Arsenault via Phabricator via llvm-commits]

arsenm added a comment.

In D86294#2262832 <https://reviews.llvm.org/D86294#2262832>, @foad wrote:

> In D86294#2261887 <https://reviews.llvm.org/D86294#2261887>, @arsenm wrote:
>
>> I think copies that can be ignored should be taken care of by a combiner pass, and the selector should not have to do this
>
> Can you explain how you think this should work for selecting e.g. v_add_lshl where some of the operands can be sgprs? A combiner pass can't remove cross-register-bank copies, can it?

A combiner could, but under the current scheme it should not. I want to minimize the amount of places/code that need to worry about the constant bus restriction. The pattern for these instructions should search through the copies if it can. We may need a new tablegen operator or something to look through copies


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