[llvm] [AMDGPU] Change SGPR layout to striped caller/callee saved (PR #127353)

[Sebastian Neubauer via llvm-commits]

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@@ -91,7 +91,11 @@ def CSR_AMDGPU_AGPRs : CalleeSavedRegs<
 >;
 
 def CSR_AMDGPU_SGPRs : CalleeSavedRegs<
-  (sequence "SGPR%u", 30, 105)
+  (add (sequence "SGPR%u", 30, 37),
+       (sequence "SGPR%u", 46, 53),
+       (sequence "SGPR%u", 62, 69),
+       (sequence "SGPR%u", 78, 85),
+       (sequence "SGPR%u", 94, 105))
 >;
 
 def CSR_AMDGPU_SI_Gfx_SGPRs : CalleeSavedRegs<
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Flakebi wrote:

I think both is fine (changing it or leaving it for now). amdgpu_gfx already has caller-saves that are not used for arguments, so it’s not hit by this bug.

The important part is that amdgpu_gfx wants the SGPR arguments to be in callee-save registers. I assume compute would likely benefit from having SGPR args in callee-saves as well, as they usually contain constant data, but it’s not there yet.
Once the C calling convention does that, we can probably ditch amdgpu_gfx and switch to the C calling conv for graphics.

https://github.com/llvm/llvm-project/pull/127353