[mlir][bufferization] Remove allow-return-allocs and create-deallocs pass options, remove bufferization.escape attribute (#66619)

This commit removes the deallocation capabilities of
one-shot-buffe

[mlir][bufferization] Remove allow-return-allocs and create-deallocs pass options, remove bufferization.escape attribute (#66619)

This commit removes the deallocation capabilities of
one-shot-bufferization. One-shot-bufferization should never deallocate
any memrefs as this should be entirely handled by the
ownership-based-buffer-deallocation pass going forward. This means the
`allow-return-allocs` pass option will default to true now,
`create-deallocs` defaults to false and they, as well as the escape
attribute indicating whether a memref escapes the current region, will
be removed. A new `allow-return-allocs-from-loops` option is added as a
temporary workaround for some bufferization limitations.

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Revert "[mlir][bufferization] Remove allow-return-allocs and create-deallocs pass options, remove bufferization.escape attribute"

This reverts commit 6a91dfedeb956dfa092a6a3f411e8b02f0d5d289.

This

Revert "[mlir][bufferization] Remove allow-return-allocs and create-deallocs pass options, remove bufferization.escape attribute"

This reverts commit 6a91dfedeb956dfa092a6a3f411e8b02f0d5d289.

This caused problems in downstream projects. We are reverting to give
them more time for integration.

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[mlir][bufferization] Remove allow-return-allocs and create-deallocs pass options, remove bufferization.escape attribute

This is the first commit in a series with the goal to rework the
BufferDeallo

[mlir][bufferization] Remove allow-return-allocs and create-deallocs pass options, remove bufferization.escape attribute

This is the first commit in a series with the goal to rework the
BufferDeallocation pass. Currently, this pass heavily relies on copies
to perform correct deallocations, which leads to very slow code and
potentially high memory usage. Additionally, there are unsupported cases
such as returning memrefs which this series of commits aims to add
support for as well.

This first commit removes the deallocation capabilities of
one-shot-bufferization.One-shot-bufferization should never deallocate any
memrefs as this should be entirely handled by the buffer-deallocation pass
going forward. This means the allow-return-allocs pass option will
default to true now, create-deallocs defaults to false and they, as well
as the escape attribute indicating whether a memref escapes the current region,
will be removed.

The documentation should w.r.t. these pass option changes should also be
updated in this commit.

Reviewed By: springerm

Differential Revision: https://reviews.llvm.org/D156662

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[mlir][bufferization] Support unstructured control flow

This revision adds support for unstructured control flow to the bufferization infrastructure. In particular: regions with multiple blocks, `cf

[mlir][bufferization] Support unstructured control flow

This revision adds support for unstructured control flow to the bufferization infrastructure. In particular: regions with multiple blocks, `cf.br`, `cf.cond_br`.

Two helper templates are added to `BufferizableOpInterface.h`, which can be implemented by ops that supported unstructured control flow in their regions (e.g., `func.func`) and ops that branch to another block (e.g., `cf.br`).

A block signature is always bufferized together with the op that owns the block.

Differential Revision: https://reviews.llvm.org/D158094

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