[PATCH] D109301: [AMDGPU] Enable copy between VGPR and AGPR classes during regalloc

[Christudasan Devadasan via Phabricator via llvm-commits]

cdevadas added a comment.

> In fact restoring into av superclass also seems problematic. I believe we have agreed all the code here only work correctly if we have no actual av registers past selection.

The function `getLargestLegalSuperClass` is used mainly during Greedy, coalescer, and spiller.
Restore to AV class is part of the Spiller during regalloc. In this patch, I made a fix in `storeRegToStackSlot` to convert superclass spills into VGPR spills by introducing a copy.
AV classes appear only in COPY instances and they all become either VGPRs or AGPRs after `virtregrewriter`.


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https://reviews.llvm.org/D109301