[llvm] [InstCombine] avoid extra instructions in foldSelectICmpAnd (PR #127398)

[Andreas Jonson via llvm-commits]

andjo403 wrote:

It is actually canonicalized the other way around see:
https://github.com/llvm/llvm-project/blob/5ecce45ea2980aff35d1283d4dd3feb8f74de16c/llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp#L835-L865

possible to add special case there for:
(icmp eq (X & C), 0) ? (X & ~C) : (X | C) -> X 
(icmp eq (X & C), 0) ? (X & ~C) : (X | C) -> X ^ C 
IFF C is a power of 2.

https://alive2.llvm.org/ce/z/dD3XTi

but is it common enough that special handling is wanted?

have added a test for the regression

https://github.com/llvm/llvm-project/pull/127398