[all-commits] [llvm/llvm-project] 6d3db2: [InstCombine] Generalize complex OR patterns to AND

[Stanislav Mekhanoshin via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 6d3db28088267203ab4a42c5da0d53c0a259f316
      https://github.com/llvm/llvm-project/commit/6d3db28088267203ab4a42c5da0d53c0a259f316
  Author: Stanislav Mekhanoshin <Stanislav.Mekhanoshin at amd.com>
  Date:   2021-11-17 (Wed, 17 Nov 2021)

  Changed paths:
    M llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
    M llvm/test/Transforms/InstCombine/and-xor-or.ll

  Log Message:
  -----------
  [InstCombine] Generalize complex OR patterns to AND

For every pattern with only NOT, OR, and AND operations there is
always a symmetrical attern with AND and OR swapped.

This adds 2 transformations: https://reviews.llvm.org/D113526

```
(~(a & b) | c) & (~(a & c) | b) --> ~((b ^ c) & a)
(~(a & b) | c) & ~(a & c) --> ~((b | c) & a)
```

```
----------------------------------------
define i4 @src(i4 %a, i4 %b, i4 %c) {
%0:
  %and1 = and i4 %b, %a
  %not1 = xor i4 %and1, 15
  %and2 = and i4 %a, %c
  %not2 = xor i4 %and2, 15
  %or = or i4 %not2, %b
  %r = and i4 %or, %not1
  ret i4 %r
}
=>
define i4 @tgt(i4 %a, i4 %b, i4 %c) {
%0:
  %or = or i4 %b, %c
  %and = and i4 %or, %a
  %r = xor i4 %and, 15
  ret i4 %r
}
Transformation seems to be correct!

----------------------------------------
define i4 @src(i4 %a, i4 %b, i4 %c) {
%0:
  %and1 = and i4 %a, %b
  %not1 = xor i4 %and1, 15
  %or1 = or i4 %not1, %c
  %and2 = and i4 %a, %c
  %not2 = xor i4 %and2, 15
  %or2 = or i4 %not2, %b
  %and3 = and i4 %or1, %or2
  ret i4 %and3
}
=>
define i4 @tgt(i4 %a, i4 %b, i4 %c) {
%0:
  %xor = xor i4 %b, %c
  %and = and i4 %xor, %a
  %not = xor i4 %and, 15
  ret i4 %not
}
Transformation seems to be correct!
```

Differential Revision: https://reviews.llvm.org/D113526