a70aa7bb0d
This has been a major TODO for a very long time, and is necessary for establishing a proper dialect-free dependency layering for the Transforms library. Code was moved to effectively two main locations: * Affine/ There was quite a bit of affine dialect related code in Transforms/ do to historical reasons (of a time way into MLIR's past). The following headers were moved to: Transforms/LoopFusionUtils.h -> Dialect/Affine/LoopFusionUtils.h Transforms/LoopUtils.h -> Dialect/Affine/LoopUtils.h Transforms/Utils.h -> Dialect/Affine/Utils.h The following transforms were also moved: AffineLoopFusion, AffinePipelineDataTransfer, LoopCoalescing * SCF/ Only one SCF pass was in Transforms/ (likely accidentally placed here): ParallelLoopCollapsing The SCF specific utilities in LoopUtils have been moved to SCF/Utils.h * Misc: mlir::moveLoopInvariantCode was also moved to LoopLikeInterface.h given that it is a simple utility defined in terms of LoopLikeOpInterface. Differential Revision: https://reviews.llvm.org/D117848
73 lines
2.6 KiB
C++
73 lines
2.6 KiB
C++
//===- ControlFlowSink.cpp - Code to perform control-flow sinking ---------===//
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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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//
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// This file implements a basic control-flow sink pass. Control-flow sinking
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// moves operations whose only uses are in conditionally-executed blocks in to
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// those blocks so that they aren't executed on paths where their results are
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// not needed.
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//
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//===----------------------------------------------------------------------===//
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#include "PassDetail.h"
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#include "mlir/IR/Dominance.h"
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#include "mlir/Interfaces/ControlFlowInterfaces.h"
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#include "mlir/Transforms/ControlFlowSinkUtils.h"
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#include "mlir/Transforms/Passes.h"
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using namespace mlir;
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namespace {
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/// A control-flow sink pass.
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struct ControlFlowSink : public ControlFlowSinkBase<ControlFlowSink> {
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void runOnOperation() override;
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};
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} // end anonymous namespace
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/// Returns true if the given operation is side-effect free as are all of its
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/// nested operations.
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static bool isSideEffectFree(Operation *op) {
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if (auto memInterface = dyn_cast<MemoryEffectOpInterface>(op)) {
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// If the op has side-effects, it cannot be moved.
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if (!memInterface.hasNoEffect())
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return false;
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// If the op does not have recursive side effects, then it can be moved.
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if (!op->hasTrait<OpTrait::HasRecursiveSideEffects>())
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return true;
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} else if (!op->hasTrait<OpTrait::HasRecursiveSideEffects>()) {
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// Otherwise, if the op does not implement the memory effect interface and
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// it does not have recursive side effects, then it cannot be known that the
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// op is moveable.
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return false;
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}
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// Recurse into the regions and ensure that all nested ops can also be moved.
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for (Region ®ion : op->getRegions())
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for (Operation &op : region.getOps())
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if (!isSideEffectFree(&op))
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return false;
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return true;
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}
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void ControlFlowSink::runOnOperation() {
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auto &domInfo = getAnalysis<DominanceInfo>();
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getOperation()->walk([&](RegionBranchOpInterface branch) {
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SmallVector<Region *> regionsToSink;
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// Get the regions are that known to be executed at most once.
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getSinglyExecutedRegionsToSink(branch, regionsToSink);
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// Sink side-effect free operations.
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numSunk =
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controlFlowSink(regionsToSink, domInfo, [](Operation *op, Region *) {
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return isSideEffectFree(op);
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});
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});
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}
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std::unique_ptr<Pass> mlir::createControlFlowSinkPass() {
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return std::make_unique<ControlFlowSink>();
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}
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