[llvm] [GlobalISel] Combine G_MERGE_VALUES of x and undef (PR #113616)

[Thorsten Schütt via llvm-commits]

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@@ -115,9 +115,11 @@ body:             |
   bb.1:
     ; CHECK-LABEL: name: test_combine_unmerge_bitcast_merge
     ; CHECK: [[DEF:%[0-9]+]]:_(s32) = G_IMPLICIT_DEF
-    ; CHECK-NEXT: [[DEF1:%[0-9]+]]:_(s32) = G_IMPLICIT_DEF
-    ; CHECK-NEXT: $w0 = COPY [[DEF]](s32)
-    ; CHECK-NEXT: $w1 = COPY [[DEF1]](s32)
+    ; CHECK-NEXT: [[ZEXT:%[0-9]+]]:_(s64) = G_ZEXT [[DEF]](s32)
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tschuett wrote:

The test case is G_MERGE_VALUES of undef, undef, which can become undef. We decided it will become zero in the future.

https://github.com/llvm/llvm-project/pull/113616