Jeffrey Byrnes b761137049 [AMDGPU] Use correct VGPR threshold for flagging ExcessRP regions in unified register file case (#85860) ...

`ST.getMaxNumVGPRs(MF)` lowers to `AMDGPUBaseInfo.cpp:getTotalNumVGPRs`
which returns 512 for gfx90a. This is subsequently limited by
`AMDGPUBaseInfo:getAddressableNumVGPRs()`, which also returns 512 for
gfx90a. The ISA states we can have a total of 512 registers, but a
maximum of only 256 of each of AGPR and VGPR (gfx90a 3.6.4).

Therefore, in unified register file case, `ST.getMaxNumVGPRs(MF)`
calculates the maximum number of combined VGPR + AGPR. But, it is
currently used as the limit for accvgpr and as the limit for archvgpr.

This patch uses it as the combined limit, and accounts for the maximum addressable arch/acc VGPRs when calculating the per RegClass limits.

It is not unreasonable to think other clients of getTotalNumVGPRs are
using it in the wrong way.

2024-03-25 13:11:58 -07:00

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