Nikita Popov 47255834e7 [ValueTracking] A and (B & ~A) have no common bits set ...

This extends haveNoCommonBitsSet() to two additional cases, allowing
the following folds:

 * `A + (B & ~A)` --> `A | (B & ~A)`
    (https://alive2.llvm.org/ce/z/crxxhN)
 * `A + ((A & B) ^ B)` --> `A | ((A & B) ^ B)`
    (https://alive2.llvm.org/ce/z/A_wsH_)

These should further fold to just `A | B`, though this currently
only works in the first case.

The reason why the second fold is necessary is that we consider
this to be the canonical form if B is a constant. (I did check
whether we can change that, but it looks like a number of folds
depend on the current canonicalization, so I ended up adding both
patterns here.)

Differential Revision: https://reviews.llvm.org/D124763

2022-05-03 11:33:27 +02:00

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