[llvm] [AArch64] Use isKnownNonZero to optimize eligible compares to cmn and ccmn (PR #96349)

[David Green via llvm-commits]

https://github.com/davemgreen commented:

This case is now transforming, but I don't believe that is valid:
```
define i32 @and_ult_eq_s0s1_or(i32 %s0a, i32 %s1a, i32 %s2, i32 %s3) {
; CHECK-LABEL: and_ult_eq_s0s1_or:
; CHECK:       // %bb.0: // %entry
; CHECK-NEXT:    orr w8, w1, #0x1
; CHECK-NEXT:    orr w9, w0, #0x1
; CHECK-NEXT:    cmp w2, w3
; CHECK-NEXT:    ccmn w8, w9, #2, eq
; CHECK-NEXT:    mov w8, #20 // =0x14
; CHECK-NEXT:    mov w9, #10 // =0xa
; CHECK-NEXT:    csel w0, w9, w8, lo
; CHECK-NEXT:    ret
entry:
  %a1 = or i32 %s0a, 1
  %s1 = or i32 %s1a, 1
  %s0 = sub i32 0, %a1
  %c0 = icmp ult i32 %s0, %s1
  %c1 = icmp eq i32 %s2, %s3
  %a = and i1 %c0, %c1
  %r = select i1 %a, i32 10, i32 20
  ret i32 %r
}
```

https://github.com/llvm/llvm-project/pull/96349