[llvm] [InstCombine] Canoncalize complex boolean expressions into ~((y | z) ^ x) (PR #149530)

[Yingwei Zheng via llvm-commits]

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

We don't accept complex patterns without real-world usefulness: https://llvm.org/docs/InstCombineContributorGuide.html#real-world-usefulness

Currently, the original case can be simplified into a smaller expression: https://godbolt.org/z/En3za8Gjz. Please check if we can fold it into the target pattern through a simpler transformation (2-3 instructions). Then you need to demonstrate its real-world usefulness.

Reducing the size of an expression is not the business of optimizing compilers. Instead, it is widely used by decompilers. See also https://docs.hex-rays.com/user-guide/decompiler/goomba.


https://github.com/llvm/llvm-project/pull/149530