Nikita Popov 77eb056830 [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.

2024-07-01 09:26:01 +02:00

158 KiB

Raw Blame History

View Raw