[llvm] InstSimplify: lookthru casts, binops in folding shuffles (PR #92668)

[Matt Arsenault via llvm-commits]

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@@ -6,26 +6,11 @@ declare i32 @llvm.amdgcn.sffbh.i32(i32) nounwind readnone speculatable
 define amdgpu_kernel void @select_constant_cttz(ptr addrspace(1) noalias %out, ptr addrspace(1) nocapture readonly %arrayidx) nounwind {
 ; GCN-LABEL: select_constant_cttz:
 ; GCN:       ; %bb.0:
-; GCN-NEXT:    s_load_dwordx4 s[0:3], s[0:1], 0x9
-; GCN-NEXT:    s_waitcnt lgkmcnt(0)
-; GCN-NEXT:    s_load_dword s2, s[2:3], 0x0
+; GCN-NEXT:    s_load_dwordx2 s[0:1], s[0:1], 0x9
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arsenm wrote:

This looks like the point of the test was defeated, so should do something to keep the codegen similar 

https://github.com/llvm/llvm-project/pull/92668