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

[Thorsten Schütt via llvm-commits]

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@@ -465,37 +457,21 @@ body: |
     ; SI-NEXT: S_NOP 0, implicit [[BUILD_VECTOR]](<3 x s32>)
     ;
     ; VI-LABEL: name: test_fsqrt_v3s16
-    ; VI: [[DEF:%[0-9]+]]:_(<4 x s16>) = G_IMPLICIT_DEF
-    ; VI-NEXT: [[UV:%[0-9]+]]:_(<2 x s16>), [[UV1:%[0-9]+]]:_(<2 x s16>) = G_UNMERGE_VALUES [[DEF]](<4 x s16>)
-    ; VI-NEXT: [[BITCAST:%[0-9]+]]:_(s32) = G_BITCAST [[UV]](<2 x s16>)
-    ; VI-NEXT: [[TRUNC:%[0-9]+]]:_(s16) = G_TRUNC [[BITCAST]](s32)
-    ; VI-NEXT: [[C:%[0-9]+]]:_(s32) = G_CONSTANT i32 16
-    ; VI-NEXT: [[LSHR:%[0-9]+]]:_(s32) = G_LSHR [[BITCAST]], [[C]](s32)
-    ; VI-NEXT: [[TRUNC1:%[0-9]+]]:_(s16) = G_TRUNC [[LSHR]](s32)
-    ; VI-NEXT: [[BITCAST1:%[0-9]+]]:_(s32) = G_BITCAST [[UV1]](<2 x s16>)
-    ; VI-NEXT: [[TRUNC2:%[0-9]+]]:_(s16) = G_TRUNC [[BITCAST1]](s32)
-    ; VI-NEXT: [[FSQRT:%[0-9]+]]:_(s16) = G_FSQRT [[TRUNC]]
-    ; VI-NEXT: [[FSQRT1:%[0-9]+]]:_(s16) = G_FSQRT [[TRUNC1]]
-    ; VI-NEXT: [[FSQRT2:%[0-9]+]]:_(s16) = G_FSQRT [[TRUNC2]]
+    ; VI: [[DEF:%[0-9]+]]:_(s16) = G_IMPLICIT_DEF
+    ; VI-NEXT: [[FSQRT:%[0-9]+]]:_(s16) = G_FSQRT [[DEF]]
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tschuett wrote:

G_FSQRT of undef.

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