[InstCombine] Simplify select using KnownBits of condition (#95923)

Simplify the arms of a select based on the KnownBits implied by its condition.
For now this only handles the case where the select arm folds to a constant,
but this can be generalized to handle other patterns by using
SimplifyDemandedBits instead (in that case we would also have to limit to
non-undef conditions).

This is implemented by adding a new member to SimplifyQuery that can be used
to inject an additional condition. The affected values are pre-computed and
we don't call computeKnownBits() if the select arms don't contain affected
values. This reduces the cost in some pathological cases.

0 files changed, 0 insertions, 0 deletions