[PATCH] D109300: [AMDGPU] Make vector superclasses allocatable

Fri Sep 24 13:32:56 PDT 2021

arsenm added a comment.

In D109300#3019936 <https://reviews.llvm.org/D109300#3019936>, @cdevadas wrote:

> In D109300#3018937 <https://reviews.llvm.org/D109300#3018937>, @rampitec wrote:
>
>> Thanks. FoldImmediate() and Global ISel seems to be last issue to me.
>
> The MAIInst uses AVSrc_32 for src0 & src1 operands.
> https://github.com/llvm/llvm-project/blob/main/llvm/lib/Target/AMDGPU/VOP3PInstructions.td#L378
>
> I am not sure we can do something to prevent GIsel from choosing AV classes here.
> Yes, the w/a in FoldImmediate was done to adjust the register class as per the opcode we choose.

Regbankselect is only implemented in a way that should just work and is probably not optimal. In the future we could improve the selector to take the hint of the incoming bank to select the specific A/V class

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https://reviews.llvm.org/D109300