[PATCH] D75138: [WIP][AMDGPU] Eliminate the ScratchWaveOffset register from the calling convention

[Matt Arsenault via Phabricator via llvm-commits]

arsenm added a comment.

In D75138#1892192 <https://reviews.llvm.org/D75138#1892192>, @scott.linder wrote:

> I'm having trouble working out the best way forward on this patch, with the core issue relating to the fact that we no longer need anything equivalent to a frame pointer in the entry function when there is no stack usage. This is complicated by the fact that `hasFP` is broken in some of the places it is called, including `reservePrivateMemoryRegs`. I'm not sure I completely understand where the best place to handle this is, but without addressing it I can't avoid gratuitously initializing the SP and/or FP in many cases, including a trivial kernel with no body.


Why is this a problem exactly? I only vaguely remember what kind of problems this would cause. hasFP has always been broken depending on what time it's called, so in some places we do have to guess if it's needed


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