[mlir][SCF] Allow using a custom operation to generate loops with `mlir::tileUsingSCF`. (#159506)

This change adds an option to use a custom operation to generate the
inter-tile loops during tiling. When the loop type is set to
`scf::SCFTilingOptions::LoopType::CustomOp`, the method
`mlir::tileUsingSCF` provides two callback functions

1. First one to generate the header of the loop.
2. Second one to generate the terminator of the loop.

These methods receive the information needed to generate the
loops/terminator and expect to return information needed to generate
the code for the intra-tile computation. See comments for more
details.

Presently this is adds support only for tiling. Subsequent commits
will update this to add support for fusion as well.

The PR is split into two commits.
1) The first commit is an NFC that just refactors the code (and cleans
up some naming) to make it easier to add the support for custom loop
operations.
2) The second commit adds the support for using a custom loop operation,
as well as a test to exercise this path.

Signed-off-by: MaheshRavishankar <mahesh.ravishankar@gmail.com>

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Signed-off-by: MaheshRavishankar <mahesh.ravishankar@gmail.com>

0 files changed, 0 insertions, 0 deletions