[all-commits] [llvm/llvm-project] a45e58: [mlir][bufferization] Add `BufferViewFlowOpInterfa...

[Matthias Springer via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: a45e58af1b381cf3c0374332386b8291ec5310f4
      https://github.com/llvm/llvm-project/commit/a45e58af1b381cf3c0374332386b8291ec5310f4
  Author: Matthias Springer <me at m-sp.org>
  Date:   2024-03-24 (Sun, 24 Mar 2024)

  Changed paths:
    A mlir/include/mlir/Dialect/Arith/Transforms/BufferViewFlowOpInterfaceImpl.h
    A mlir/include/mlir/Dialect/Bufferization/IR/BufferViewFlowOpInterface.h
    A mlir/include/mlir/Dialect/Bufferization/IR/BufferViewFlowOpInterface.td
    M mlir/include/mlir/Dialect/Bufferization/IR/CMakeLists.txt
    M mlir/include/mlir/Dialect/Bufferization/Transforms/BufferViewFlowAnalysis.h
    A mlir/include/mlir/Dialect/MemRef/Transforms/BufferViewFlowOpInterfaceImpl.h
    M mlir/include/mlir/InitAllDialects.h
    A mlir/lib/Dialect/Arith/Transforms/BufferViewFlowOpInterfaceImpl.cpp
    M mlir/lib/Dialect/Arith/Transforms/CMakeLists.txt
    A mlir/lib/Dialect/Bufferization/IR/BufferViewFlowOpInterface.cpp
    M mlir/lib/Dialect/Bufferization/IR/CMakeLists.txt
    M mlir/lib/Dialect/Bufferization/Transforms/BufferViewFlowAnalysis.cpp
    A mlir/lib/Dialect/MemRef/Transforms/BufferViewFlowOpInterfaceImpl.cpp
    M mlir/lib/Dialect/MemRef/Transforms/CMakeLists.txt
    M utils/bazel/llvm-project-overlay/mlir/BUILD.bazel

  Log Message:
  -----------
  [mlir][bufferization] Add `BufferViewFlowOpInterface` (#78718)

This commit adds the `BufferViewFlowOpInterface` to the bufferization
dialect. This interface can be implemented by ops that operate on
buffers to indicate that a buffer op result and/or region entry block
argument may be the same buffer as a buffer operand (or a view thereof).
This interface is queried by the `BufferViewFlowAnalysis`.

The new interface has two interface methods:
* `populateDependencies`: Implementations use the provided callback to
declare dependencies between operands and op results/region entry block
arguments. E.g., for `%r = arith.select %c, %m1, %m2 : memref<5xf32>`,
the interface implementation should declare two dependencies: %m1 -> %r
and %m2 -> %r.
* `mayBeTerminalBuffer`: An SSA value is a terminal buffer if the buffer
view flow analysis stops at the specified value. E.g., because the value
is a newly allocated buffer or because no further information is
available about the origin of the buffer.

Ops that implement the `RegionBranchOpInterface` or `BranchOpInterface`
do not have to implement the `BufferViewFlowOpInterface`. The buffer
dependencies can be inferred from those two interfaces.

This commit makes the `BufferViewFlowAnalysis` more accurate. For
unknown ops, it conservatively used to declare all combinations of
operands and op results/region entry block arguments as dependencies
(false positives). This is no longer the case. While the analysis is
still a "maybe" analysis with false positives (e.g., when analyzing ops
such as `arith.select` or `scf.if` where the taken branch is not known
at compile time), results and region entry block arguments of unknown
ops are now marked as terminal buffers.

This commit addresses a TODO in `BufferViewFlowAnalysis.cpp`:
```
// TODO: We should have an op interface instead of a hard-coded list of
// interfaces/ops.
```
It is no longer needed to hard-code ops.



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