[llvm] [SDAG] (setcc (sub nsw a, b), zero, s??) -> (setcc a, b, s??) (PR #175459)

[Simon Pilgrim via llvm-commits]

https://github.com/RKSimon requested changes to this pull request.

```
Failed Tests (8):
  LLVM :: CodeGen/AArch64/cond-br-tuning.ll
  LLVM :: CodeGen/AArch64/selectcc-to-shiftand.ll
  LLVM :: CodeGen/AArch64/sub1.ll
  LLVM :: CodeGen/RISCV/selectcc-to-shiftand.ll
  LLVM :: CodeGen/SystemZ/int-cmp-44.ll
  LLVM :: CodeGen/SystemZ/int-cmp-56.ll
  LLVM :: CodeGen/Thumb2/mve-vabdus.ll
  LLVM :: CodeGen/X86/jump_sign.ll
```

https://github.com/llvm/llvm-project/pull/175459