[all-commits] [llvm/llvm-project] 703401: [InstCombine] Combine or-disjoint (and->mul), (and...

[Jeffrey Byrnes via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 7034014d08249a1e159a668a71e96a0b78636a39
      https://github.com/llvm/llvm-project/commit/7034014d08249a1e159a668a71e96a0b78636a39
  Author: Jeffrey Byrnes <jeffrey.byrnes at amd.com>
  Date:   2025-06-11 (Wed, 11 Jun 2025)

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

  Log Message:
  -----------
  [InstCombine] Combine or-disjoint (and->mul), (and->mul) to and->mul (#136013)

The canonical pattern for bitmasked mul is currently

```
%val = and %x, %bitMask // where %bitMask is some constant
%cmp = icmp eq %val, 0
%sel = select %cmp, 0, %C // where %C is some constant = C' * %bitMask
```

In certain cases, where we are combining multiple of these bitmasked
muls with common factors, we are able to optimize into and->mul (see
https://github.com/llvm/llvm-project/pull/135274 )

This optimization lends itself to further optimizations. This PR
addresses one of such optimizations.

In cases where we have

`or-disjoint ( mul(and (X, C1), D) , mul (and (X, C2), D))`

we can combine into

`mul( and (X, (C1 + C2)), D) `

provided C1 and C2 are disjoint.

Generalized proof: https://alive2.llvm.org/ce/z/MQYMui



To unsubscribe from these emails, change your notification settings at https://github.com/llvm/llvm-project/settings/notifications