a45e58af1b
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.
49 lines
1.6 KiB
C++
49 lines
1.6 KiB
C++
//===- BufferViewFlowOpInterfaceImpl.cpp - Buffer View Flow Analysis ------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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#include "mlir/Dialect/MemRef/Transforms/BufferViewFlowOpInterfaceImpl.h"
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#include "mlir/Dialect/Bufferization/IR/BufferViewFlowOpInterface.h"
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#include "mlir/Dialect/MemRef/IR/MemRef.h"
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using namespace mlir;
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using namespace mlir::bufferization;
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namespace mlir {
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namespace memref {
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namespace {
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struct ReallocOpInterface
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: public BufferViewFlowOpInterface::ExternalModel<ReallocOpInterface,
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ReallocOp> {
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void
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populateDependencies(Operation *op,
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RegisterDependenciesFn registerDependenciesFn) const {
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auto reallocOp = cast<ReallocOp>(op);
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// memref.realloc may return the source operand.
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registerDependenciesFn(reallocOp.getSource(), reallocOp.getResult());
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}
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bool mayBeTerminalBuffer(Operation *op, Value value) const {
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// The return value of memref.realloc is a terminal buffer because the op
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// may return a newly allocated buffer.
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return true;
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}
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};
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} // namespace
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} // namespace memref
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} // namespace mlir
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void memref::registerBufferViewFlowOpInterfaceExternalModels(
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DialectRegistry ®istry) {
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registry.addExtension(+[](MLIRContext *ctx, memref::MemRefDialect *dialect) {
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ReallocOp::attachInterface<ReallocOpInterface>(*ctx);
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});
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}
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