[llvm] AMDGPU: Delete spills of undef values (PR #119684)

[Paul Kirth via llvm-commits]

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@@ -54,3 +54,45 @@ body:             |
     SI_SPILL_S64_SAVE renamable $sgpr4_sgpr5, %stack.0, implicit $exec, implicit $sgpr96_sgpr97_sgpr98_sgpr99, implicit $sgpr32 :: (store (s64) into %stack.0, align 4, addrspace 5)
 
 ...
+
+---
+name:  sgpr_spill_s32_undef
+tracksRegLiveness: true
+machineFunctionInfo:
+  isEntryFunction: true
+  hasSpilledSGPRs:     true
+  scratchRSrcReg:  '$sgpr96_sgpr97_sgpr98_sgpr99'
+  stackPtrOffsetReg: '$sgpr32'
+stack:
+  - { id: 0, type: spill-slot, size: 4, alignment: 4, stack-id: sgpr-spill }
+body:             |
+  bb.0:
+    ; CHECK-LABEL: name: sgpr_spill_s32_undef
+    ; CHECK: body:
+    ; CHECK-NEXT: bb.0:
+    ; CHECK-NOT: {{.+}}
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ilovepi wrote:

I think we have `CHECK-EMPTY:` for blank lines. And yeah, I agree, the tool can probably be better.

https://github.com/llvm/llvm-project/pull/119684