[llvm] [AMDGPU] Simplify and improve codegen for llvm.amdgcn.set.inactive (PR #107889)

[Jay Foad via llvm-commits]

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@@ -178,6 +177,9 @@ define amdgpu_cs void @cfg(ptr addrspace(8) inreg %tmp14, i32 %arg) {
 ; GFX9-O0-NEXT:    v_mov_b32_e32 v0, v4
 ; GFX9-O0-NEXT:    s_or_saveexec_b64 s[0:1], -1
 ; GFX9-O0-NEXT:    v_mov_b32_e32 v1, 0
+; GFX9-O0-NEXT:    s_mov_b64 exec, s[0:1]
+; GFX9-O0-NEXT:    ; implicit-def: $sgpr0_sgpr1
+; GFX9-O0-NEXT:    s_or_saveexec_b64 s[0:1], -1
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jayfoad wrote:

Unfortunate regression here. I'm not sure how to fix it. Maybe we need some peephole for redundant exec mask changes.

https://github.com/llvm/llvm-project/pull/107889