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

[Matt Arsenault 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))
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arsenm wrote:

This isn't quite 8, maybe adjust the description to be more specific? Also should comment the scheme here. Also, I can never remember what level of SGPRs corresponds to what occupancy 

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