llvm-project

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//===- 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 "mlir/Transforms/Passes.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/Interfaces/SideEffectInterfaces.h"
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#include "mlir/Transforms/ControlFlowSinkUtils.h"
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namespace mlir {
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#define GEN_PASS_DEF_CONTROLFLOWSINK
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#include "mlir/Transforms/Passes.h.inc"
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} // namespace mlir
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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 impl::ControlFlowSinkBase<ControlFlowSink> {
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  void runOnOperation() override;
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};
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} // end anonymous namespace
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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 = controlFlowSink(
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        regionsToSink, domInfo,
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        [](Operation *op, Region *) { return isMemoryEffectFree(op); },
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        [](Operation *op, Region *region) {
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          // Move the operation to the beginning of the region's entry block.
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          // This guarantees the preservation of SSA dominance of all of the
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          // operation's uses are in the region.
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          op->moveBefore(&region->front(), region->front().begin());
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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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