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

[Shilei Tian 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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shiltian wrote:

However, s30-s31 are for return address. [A patch](https://reviews.llvm.org/D114652) made them callee saved years ago. I can start from s40 though. However, s32, s33, as well as s34 are used for stack pointer, frame pointer, and base pointer, respectively. Is it a good idea to make them caller saved?

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