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

[Thorsten Schütt via llvm-commits]

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@@ -350,36 +350,22 @@ body: |
     ; SI-LABEL: name: test_abs_v3s16
     ; SI: liveins: $vgpr0
     ; SI-NEXT: {{  $}}
-    ; SI-NEXT: [[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: [[C:%[0-9]+]]:_(s32) = G_CONSTANT i32 16
-    ; SI-NEXT: [[LSHR:%[0-9]+]]:_(s32) = G_LSHR [[BITCAST]], [[C]](s32)
-    ; SI-NEXT: [[BITCAST1:%[0-9]+]]:_(s32) = G_BITCAST [[UV1]](<2 x s16>)
-    ; SI-NEXT: [[SEXT_INREG:%[0-9]+]]:_(s32) = G_SEXT_INREG [[BITCAST]], 16
-    ; SI-NEXT: [[ABS:%[0-9]+]]:_(s32) = G_ABS [[SEXT_INREG]]
-    ; SI-NEXT: [[SEXT_INREG1:%[0-9]+]]:_(s32) = G_SEXT_INREG [[LSHR]], 16
-    ; SI-NEXT: [[ABS1:%[0-9]+]]:_(s32) = G_ABS [[SEXT_INREG1]]
-    ; SI-NEXT: [[SEXT_INREG2:%[0-9]+]]:_(s32) = G_SEXT_INREG [[BITCAST1]], 16
-    ; SI-NEXT: [[ABS2:%[0-9]+]]:_(s32) = G_ABS [[SEXT_INREG2]]
+    ; SI-NEXT: [[C:%[0-9]+]]:_(s32) = G_CONSTANT i32 0
+    ; SI-NEXT: [[COPY:%[0-9]+]]:_(s32) = COPY [[C]](s32)
+    ; SI-NEXT: [[ABS:%[0-9]+]]:_(s32) = G_ABS [[COPY]]
+    ; SI-NEXT: [[COPY1:%[0-9]+]]:_(s32) = COPY [[C]](s32)
+    ; SI-NEXT: [[ABS1:%[0-9]+]]:_(s32) = G_ABS [[COPY1]]
+    ; SI-NEXT: [[ABS2:%[0-9]+]]:_(s32) = G_ABS [[C]]
     ; SI-NEXT: [[BUILD_VECTOR:%[0-9]+]]:_(<3 x s32>) = G_BUILD_VECTOR [[ABS]](s32), [[ABS1]](s32), [[ABS2]](s32)
     ; SI-NEXT: S_NOP 0, implicit [[BUILD_VECTOR]](<3 x s32>)
     ;
     ; VI-LABEL: name: test_abs_v3s16
     ; VI: liveins: $vgpr0
     ; VI-NEXT: {{  $}}
-    ; VI-NEXT: [[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: [[ABS:%[0-9]+]]:_(s16) = G_ABS [[TRUNC]]
-    ; VI-NEXT: [[ABS1:%[0-9]+]]:_(s16) = G_ABS [[TRUNC1]]
-    ; VI-NEXT: [[ABS2:%[0-9]+]]:_(s16) = G_ABS [[TRUNC2]]
+    ; VI-NEXT: [[DEF:%[0-9]+]]:_(s16) = G_IMPLICIT_DEF
+    ; VI-NEXT: [[ABS:%[0-9]+]]:_(s16) = G_ABS [[DEF]]
----------------
tschuett wrote:

G_ABS of undef.

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