| 1 | //===- ControlFlowSink.cpp - Code to perform control-flow sinking ---------===// |
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| 2 | // |
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| 3 | // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. |
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| 4 | // See https://llvm.org/LICENSE.txt for license information. |
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| 5 | // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception |
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| 6 | // |
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| 7 | //===----------------------------------------------------------------------===// |
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| 8 | // |
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| 9 | // This file implements a basic control-flow sink pass. Control-flow sinking |
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| 10 | // moves operations whose only uses are in conditionally-executed blocks in to |
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| 11 | // those blocks so that they aren't executed on paths where their results are |
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| 12 | // not needed. |
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| 13 | // |
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| 14 | //===----------------------------------------------------------------------===// |
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| 15 | |
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| 16 | #include "mlir/Transforms/Passes.h" |
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| 17 | |
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| 18 | #include "mlir/IR/Dominance.h" |
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| 19 | #include "mlir/Interfaces/ControlFlowInterfaces.h" |
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| 20 | #include "mlir/Interfaces/SideEffectInterfaces.h" |
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| 21 | #include "mlir/Transforms/ControlFlowSinkUtils.h" |
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| 22 | |
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| 23 | namespace mlir { |
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| 24 | #define GEN_PASS_DEF_CONTROLFLOWSINK |
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| 25 | #include "mlir/Transforms/Passes.h.inc" |
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| 26 | } // namespace mlir |
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| 27 | |
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| 28 | using namespace mlir; |
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| 29 | |
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| 30 | namespace { |
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| 31 | /// A control-flow sink pass. |
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| 32 | struct ControlFlowSink : public impl::ControlFlowSinkBase<ControlFlowSink> { |
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| 33 | void runOnOperation() override; |
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| 34 | }; |
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| 35 | } // end anonymous namespace |
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| 36 | |
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| 37 | void ControlFlowSink::runOnOperation() { |
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| 38 | auto &domInfo = getAnalysis<DominanceInfo>(); |
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| 39 | getOperation()->walk([&](RegionBranchOpInterface branch) { |
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| 40 | SmallVector<Region *> regionsToSink; |
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| 41 | // Get the regions are that known to be executed at most once. |
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| 42 | getSinglyExecutedRegionsToSink(branch, regionsToSink); |
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| 43 | // Sink side-effect free operations. |
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| 44 | numSunk = controlFlowSink( |
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| 45 | regionsToSink, domInfo, |
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| 46 | [](Operation *op, Region *) { return isMemoryEffectFree(op); }, |
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| 47 | [](Operation *op, Region *region) { |
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| 48 | // Move the operation to the beginning of the region's entry block. |
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| 49 | // This guarantees the preservation of SSA dominance of all of the |
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| 50 | // operation's uses are in the region. |
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| 51 | op->moveBefore(®ion->front(), region->front().begin()); |
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| 52 | }); |
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| 53 | }); |
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| 54 | } |
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| 55 | |
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| 56 | std::unique_ptr<Pass> mlir::createControlFlowSinkPass() { |
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| 57 | return std::make_unique<ControlFlowSink>(); |
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| 58 | } |
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| 59 | |
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