[llvm] [AMDGPU] SIFixSgprCopies should not process twice VGPR to SGPR copies inserted by PHI preprocessing. (PR #134153)

[Matt Arsenault via llvm-commits]

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@@ -0,0 +1,43 @@
+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py UTC_ARGS: --version 5
+; RUN: llc -mtriple=amdgcn -mcpu=gfx942 -o - %s | FileCheck --check-prefix=GCN %s
+
+target triple = "amdgcn-amd-amdhsa"
+
+define amdgpu_kernel void @test_should_convert_to_v_readfirstlane_b32(float %fval, i32 %arg1, i32 %arg2) {
+; GCN-LABEL: test_should_convert_to_v_readfirstlane_b32:
+; GCN:       ; %bb.0: ; %entry
+; GCN-NEXT:    s_load_dwordx4 s[0:3], s[4:5], 0x24
+; GCN-NEXT:    s_waitcnt lgkmcnt(0)
+; GCN-NEXT:    v_cvt_u32_f32_e32 v0, s0
+; GCN-NEXT:    s_nop 0
+; GCN-NEXT:    v_readfirstlane_b32 s0, v0
+; GCN-NEXT:    s_lshl_b32 s0, s0, 16
+; GCN-NEXT:    s_or_b32 s5, s0, s1
+; GCN-NEXT:    s_and_b32 s6, s5, s2
+; GCN-NEXT:    s_lshr_b32 s4, s6, 2
+; GCN-NEXT:    s_mov_b32 s7, s4
+; GCN-NEXT:    v_mov_b32_e32 v0, s1
+; GCN-NEXT:    buffer_store_dword v0, off, s[4:7], 0 nt
+; GCN-NEXT:    s_endpgm
+entry:
+  %conv = fptoui float %fval to i32
+
+  %shl = shl i32 %conv, 16
+  %or = or i32 %shl, %arg1
+  %and = and i32 %or, %arg2
+  %shr = lshr i32 %and, 2
+
+  %sgpr128_0 = insertelement <4 x i32> undef, i32 %shr, i32 0
----------------
arsenm wrote:

```suggestion
  %sgpr128_0 = insertelement <4 x i32> poison, i32 %shr, i32 0
```

https://github.com/llvm/llvm-project/pull/134153