[all-commits] [llvm/llvm-project] f9e2fb: [InstCombine] combine intersection for inequality ...

[Yingchi Long via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: f9e2fb9d8e59e5a6428727d984c95753d57c3bb8
      https://github.com/llvm/llvm-project/commit/f9e2fb9d8e59e5a6428727d984c95753d57c3bb8
  Author: Yingchi Long <i at lyc.dev>
  Date:   2023-02-10 (Fri, 10 Feb 2023)

  Changed paths:
    M llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
    M llvm/test/Transforms/InstCombine/icmp-logical.ll

  Log Message:
  -----------
  [InstCombine] combine intersection for inequality icmps

```
define i1 @src(i32 %A) {
  %mask1 = and i32 %A, 15 ; 0x0f
  %tst1 = icmp eq i32 %mask1, 3 ; 0x03
  %mask2 = and i32 %A, 255 ; 0xff
  %tst2 = icmp eq i32 %mask2, 243; 0xf3
  %res = or i1 %tst1, %tst2
  ret i1 %res
}
```

->

```
define i1 @tgt(i32 %A) {
  %1 = and i32 %A, 15
  %res = icmp eq i32 %1, 3
  ret i1 %res
}
```

Proof: https://alive2.llvm.org/ce/z/4AyvcE

Assume that `(B & D) & (C ^ E) == 0`, and `(B & D) == D || (B & D) == B`,
transforms:

```
(icmp ne (A & B), C) & (icmp ne (A & D), E)
-> (icmp ne (A & (B&D)), (C&E))
```

Fixes: https://github.com/llvm/llvm-project/issues/59680

Reviewed By: spatel, bcl5980

Differential Revision: https://reviews.llvm.org/D140666