When `replaceExtractSliceWithTiledProducer `creates a rank-reducing
slice to handle type mismatches, it should be tracked in
`generatedSlices `so downstream cleanup patterns (like IREE's
FoldExtractSliceOfBroadcast) can process it.
This PR also fixes an infinite loop in getUntiledProducerFromSliceSource
where adding the slice to generatedSlices caused the fusion worklist to
repeatedly try to re-fuse producers already inside the innermost loop;
the fix skips producers that are already inside the innermost loop via
an isProperAncestor check.
Added a lit test (@fuse_through_rank_reducing_slice) demonstrating
correct fusion through rank-reducing slices. Note that demonstrating the
generatedSlices tracking benefit requires a cleanup pattern
(SwapExtractSliceWithFillPatterns) to consume the slice; IREE's full CI
suite (iree-org/iree#23012) validates this works correctly in practice
with patterns like FoldExtractSliceOfBroadcast.
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Signed-off-by: Bangtian Liu <liubangtian@gmail.com>
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