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

[Thorsten Schütt via llvm-commits]

================
@@ -375,60 +393,38 @@ body: |
   bb.0:
 
     ; SI-LABEL: name: test_ffloor_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: [[DEF:%[0-9]+]]:_(s16) = G_IMPLICIT_DEF
+    ; SI-NEXT: [[FPEXT:%[0-9]+]]:_(s32) = G_FPEXT [[DEF]](s16)
     ; SI-NEXT: [[FFLOOR:%[0-9]+]]:_(s32) = G_FFLOOR [[FPEXT]]
     ; SI-NEXT: [[FPTRUNC:%[0-9]+]]:_(s16) = G_FPTRUNC [[FFLOOR]](s32)
-    ; SI-NEXT: [[FPEXT1:%[0-9]+]]:_(s32) = G_FPEXT [[TRUNC1]](s16)
+    ; SI-NEXT: [[FPEXT1:%[0-9]+]]:_(s32) = G_FPEXT [[DEF]](s16)
     ; SI-NEXT: [[FFLOOR1:%[0-9]+]]:_(s32) = G_FFLOOR [[FPEXT1]]
     ; SI-NEXT: [[FPTRUNC1:%[0-9]+]]:_(s16) = G_FPTRUNC [[FFLOOR1]](s32)
-    ; SI-NEXT: [[FPEXT2:%[0-9]+]]:_(s32) = G_FPEXT [[TRUNC2]](s16)
+    ; SI-NEXT: [[FPEXT2:%[0-9]+]]:_(s32) = G_FPEXT [[DEF]](s16)
     ; SI-NEXT: [[FFLOOR2:%[0-9]+]]:_(s32) = G_FFLOOR [[FPEXT2]]
     ; SI-NEXT: [[FPTRUNC2:%[0-9]+]]:_(s16) = G_FPTRUNC [[FFLOOR2]](s32)
     ; SI-NEXT: [[ANYEXT:%[0-9]+]]:_(s32) = G_ANYEXT [[FPTRUNC]](s16)
     ; SI-NEXT: [[ANYEXT1:%[0-9]+]]:_(s32) = G_ANYEXT [[FPTRUNC1]](s16)
     ; SI-NEXT: [[ANYEXT2:%[0-9]+]]:_(s32) = G_ANYEXT [[FPTRUNC2]](s16)
     ; SI-NEXT: [[BUILD_VECTOR:%[0-9]+]]:_(<3 x s32>) = G_BUILD_VECTOR [[ANYEXT]](s32), [[ANYEXT1]](s32), [[ANYEXT2]](s32)
     ; SI-NEXT: S_NOP 0, implicit [[BUILD_VECTOR]](<3 x s32>)
+    ;
     ; VI-LABEL: name: test_ffloor_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: [[FFLOOR:%[0-9]+]]:_(s16) = G_FFLOOR [[TRUNC]]
-    ; VI-NEXT: [[FFLOOR1:%[0-9]+]]:_(s16) = G_FFLOOR [[TRUNC1]]
-    ; VI-NEXT: [[FFLOOR2:%[0-9]+]]:_(s16) = G_FFLOOR [[TRUNC2]]
+    ; VI: [[DEF:%[0-9]+]]:_(s16) = G_IMPLICIT_DEF
+    ; VI-NEXT: [[FFLOOR:%[0-9]+]]:_(s16) = G_FFLOOR [[DEF]]
----------------
tschuett wrote:

G_FFLOOR of undef.

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