[llvm] [PowerPC] Combine sub within setcc back to sext (PR #66978)

[Qiu Chaofan via llvm-commits]

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@@ -171,12 +164,13 @@ entry:
 define zeroext i1 @test10(i16 %a) {
 ; CHECK-LABEL: test10:
 ; CHECK:       # %bb.0: # %entry
-; CHECK-NEXT:    addi 3, 3, -128
-; CHECK-NEXT:    lis 4, -1
+; CHECK-NEXT:    clrlwi 4, 3, 16
+; CHECK-NEXT:    extsb 3, 3
 ; CHECK-NEXT:    clrlwi 3, 3, 16
-; CHECK-NEXT:    ori 4, 4, 256
-; CHECK-NEXT:    add 3, 3, 4
-; CHECK-NEXT:    rldicl 3, 3, 1, 63
+; CHECK-NEXT:    xor 3, 4, 3
+; CHECK-NEXT:    cntlzw 3, 3
+; CHECK-NEXT:    srwi 3, 3, 5
+; CHECK-NEXT:    xori 3, 3, 1
 ; CHECK-NEXT:    blr
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ecnelises wrote:

This should not be regression. Parameter should have `signext`.

https://github.com/llvm/llvm-project/pull/66978