[SeparateConstOffsetFromGEP] Avoid miscompiles related to trunc nuw/nsw (#154582) Drop poison generating flags on trunc when distributing trunc over add/sub/or. We need to do this since for example (add (trunc nuw A), (trunc nuw B)) is more poisonous than (trunc nuw (add A, B))). In some situations it is pessimistic to drop the flags. Such as if the add in the example above also has the nuw flag. For now we keep it simple and always drop the flags. Worth mentioning is that we drop the flags when cloning instructions and rebuilding the chain. This is done after the "allowsPreservingNUW" checks in ConstantOffsetExtractor::Extract. So we still take the "trunc nuw" into consideration when determining if nuw can be preserved in the gep (which should be ok since that check also require that all the involved binary operations has nuw). Fixes #154116
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