PR #106760 aligned the handling of dropped block arguments and dropped
op results. The two helper functions that insert source materializations
for uses of replaced block arguments / op results that survived the
conversion are now almost identical (`legalizeConvertedArgumentTypes`
and `legalizeConvertedOpResultTypes`). This PR merges the two functions
and moves the implementation directly into `finalize`.
This PR simplifies the code base and improves the efficiency a bit:
previously, `finalize` iterated over
`ConversionPatternRewriterImpl::rewrites` twice. Now, only one iteration
is needed.
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Co-authored-by: Jakub Kuderski <jakub@nod-labs.com>
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