[llvm] [GlobalISel] Combine away G_UNMERGE(G_IMPLICITDEF). (PR #119183)

[Thorsten Schütt via llvm-commits]

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@@ -367,28 +381,20 @@ body: |
   bb.0:
 
     ; SI-LABEL: name: test_fcos_v3s16
-    ; SI: [[DEF:%[0-9]+]]:_(<4 x s16>) = G_IMPLICIT_DEF
-    ; SI-NEXT: [[UV:%[0-9]+]]:_(<2 x s16>), [[UV1:%[0-9]+]]:_(<2 x s16>) = G_UNMERGE_VALUES [[DEF]](<4 x s16>)
-    ; SI-NEXT: [[BITCAST:%[0-9]+]]:_(s32) = G_BITCAST [[UV]](<2 x s16>)
-    ; SI-NEXT: [[TRUNC:%[0-9]+]]:_(s16) = G_TRUNC [[BITCAST]](s32)
-    ; SI-NEXT: [[C:%[0-9]+]]:_(s32) = G_CONSTANT i32 16
-    ; SI-NEXT: [[LSHR:%[0-9]+]]:_(s32) = G_LSHR [[BITCAST]], [[C]](s32)
-    ; SI-NEXT: [[TRUNC1:%[0-9]+]]:_(s16) = G_TRUNC [[LSHR]](s32)
-    ; SI-NEXT: [[BITCAST1:%[0-9]+]]:_(s32) = G_BITCAST [[UV1]](<2 x s16>)
-    ; SI-NEXT: [[TRUNC2:%[0-9]+]]:_(s16) = G_TRUNC [[BITCAST1]](s32)
-    ; SI-NEXT: [[FPEXT:%[0-9]+]]:_(s32) = G_FPEXT [[TRUNC]](s16)
-    ; SI-NEXT: [[C1:%[0-9]+]]:_(s32) = G_FCONSTANT float 0x3FC45F3060000000
-    ; SI-NEXT: [[FMUL:%[0-9]+]]:_(s32) = G_FMUL [[FPEXT]], [[C1]]
+    ; SI: [[DEF:%[0-9]+]]:_(s16) = G_IMPLICIT_DEF
+    ; SI-NEXT: [[FPEXT:%[0-9]+]]:_(s32) = G_FPEXT [[DEF]](s16)
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tschuett wrote:

G_FPEXT of undef.

https://github.com/llvm/llvm-project/pull/119183