[llvm] [X86][FixupSetCC] Substitute setcc + zext pair with setzucc if possible (PR #96594)

[Phoebe Wang via llvm-commits]

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@@ -0,0 +1,49 @@
+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
+; RUN: llc < %s -mtriple=x86_64 -mattr=+zu | FileCheck %s
+
+define i16 @i8(i8 %x) nounwind {
+; CHECK-LABEL: i8:
+; CHECK:       # %bb.0:
+; CHECK-NEXT:    cmpb $3, %dil
+; CHECK-NEXT:    setzuae %al
+; CHECK-NEXT:    # kill: def $ax killed $ax killed $eax
+; CHECK-NEXT:    retq
+  %t0 = icmp ugt i8 %x, 2
+  %if = select i1 %t0, i8 1, i8 0
+  %zext = zext i8 %if to i16
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phoebewang wrote:

How about `zext i1 %t0` to i16?

https://github.com/llvm/llvm-project/pull/96594