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//===- ControlFlowSink.cpp - Code to perform control-flow sinking ---------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This file implements a basic control-flow sink pass. Control-flow sinking
// moves operations whose only uses are in conditionally-executed blocks in to
// those blocks so that they aren't executed on paths where their results are
// not needed.
//
//===----------------------------------------------------------------------===//
#include "mlir/Transforms/Passes.h"
#include "mlir/IR/Dominance.h"
#include "mlir/Interfaces/ControlFlowInterfaces.h"
#include "mlir/Interfaces/SideEffectInterfaces.h"
#include "mlir/Transforms/ControlFlowSinkUtils.h"
namespace mlir {
#define GEN_PASS_DEF_CONTROLFLOWSINK
#include "mlir/Transforms/Passes.h.inc"
} // namespace mlir
using namespace mlir;
namespace {
/// A control-flow sink pass.
struct ControlFlowSink : public impl::ControlFlowSinkBase<ControlFlowSink> {
void runOnOperation() override;
};
} // end anonymous namespace
void ControlFlowSink::runOnOperation() {
auto &domInfo = getAnalysis<DominanceInfo>();
getOperation()->walk([&](RegionBranchOpInterface branch) {
SmallVector<Region *> regionsToSink;
// Get the regions are that known to be executed at most once.
getSinglyExecutedRegionsToSink(branch, regionsToSink);
// Sink side-effect free operations.
numSunk = controlFlowSink(
regionsToSink, domInfo,
[](Operation *op, Region *) { return isMemoryEffectFree(op); },
[](Operation *op, Region *region) {
// Move the operation to the beginning of the region's entry block.
// This guarantees the preservation of SSA dominance of all of the
// operation's uses are in the region.
op->moveBefore(®ion->front(), region->front().begin());
});
});
}
std::unique_ptr<Pass> mlir::createControlFlowSinkPass() {
return std::make_unique<ControlFlowSink>();
}
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