[llvm] [GlobalISel] Combine into abd[su] and legalize abd[su] (PR #118865)

[Matt Arsenault via llvm-commits]

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In-Reply-To: <llvm.org/llvm/llvm-project/pull/118865 at github.com>


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@@ -93,9 +147,14 @@ define <8 x i16> @abdu_const_bothhigh() {
 }
 
 define <8 x i16> @abdu_undef(<8 x i16> %src1) {
-; CHECK-LABEL: abdu_undef:
-; CHECK:       // %bb.0:
-; CHECK-NEXT:    ret
+; CHECK-SD-LABEL: abdu_undef:
+; CHECK-SD:       // %bb.0:
+; CHECK-SD-NEXT:    ret
+;
+; CHECK-GI-LABEL: abdu_undef:
+; CHECK-GI:       // %bb.0:
+; CHECK-GI-NEXT:    uabd v0.8h, v0.8h, v0.8h
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arsenm wrote:

There's no problem. The undef should have already propagated to fold the whole result to undef in the original IR. You could fold undef inputs to the new node if you really wanted this to disappear

https://github.com/llvm/llvm-project/pull/118865