[all-commits] [llvm/llvm-project] 6fd229: [X86] Invert (and X, ~(and ~Y, Z)) back into (and ...

[Miguel Saldivar via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 6fd229a655f521a9f58d40c671e5cab4ea3ea87b
      https://github.com/llvm/llvm-project/commit/6fd229a655f521a9f58d40c671e5cab4ea3ea87b
  Author: Miguel Saldivar <miguel.saldivar at hpe.com>
  Date:   2024-10-12 (Sat, 12 Oct 2024)

  Changed paths:
    M llvm/lib/Target/X86/X86ISelLowering.cpp
    A llvm/test/CodeGen/X86/pr108731.ll

  Log Message:
  -----------
  [X86] Invert (and X, ~(and ~Y, Z)) back into (and X, (or Y, ~Z)) (#109215)

When `andn` is available, we should avoid switching `s &= ~(z & ~y);` into `s &= ~z | y;`

This patch turns this assembly from:
```
foo:
        not     rcx
        and     rsi, rdx
        andn    rax, rsi, rdi
        or      rcx, rdx
        and     rax, rcx
        ret
```
into:
```
foo:
        and     rsi, rdx
        andn    rcx, rdx, rcx
        andn    rax, rsi, rdi
        andn    rax, rcx, rax
        ret
```
Fixes #108731



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