[llvm] [AArch64] Convert UADDV(add(zext, zext)) into UADDLV(concat). (PR #78301)

[David Green via llvm-commits]

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@@ -5416,12 +5394,20 @@ entry:
 }
 
 define i32 @extract_hi_hi(<8 x i16> %a) {
-; CHECK-LABEL: extract_hi_hi:
-; CHECK:       // %bb.0: // %entry
-; CHECK-NEXT:    uaddl2 v0.4s, v0.8h, v0.8h
-; CHECK-NEXT:    addv s0, v0.4s
-; CHECK-NEXT:    fmov w0, s0
-; CHECK-NEXT:    ret
+; CHECK-SD-LABEL: extract_hi_hi:
+; CHECK-SD:       // %bb.0: // %entry
+; CHECK-SD-NEXT:    ext v0.16b, v0.16b, v0.16b, #8
+; CHECK-SD-NEXT:    mov v0.d[1], v0.d[0]
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davemgreen wrote:

We'll have to try and improve this a bit, but that can be done separately.

https://github.com/llvm/llvm-project/pull/78301