| 1 | //===- LoopUnrollAndJam.cpp - Code to perform loop unroll and jam ---------===// |
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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 loop unroll and jam. Unroll and jam is a transformation |
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| 10 | // that improves locality, in particular, register reuse, while also improving |
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| 11 | // operation level parallelism. The example below shows what it does in nearly |
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| 12 | // the general case. Loop unroll and jam currently works if the bounds of the |
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| 13 | // loops inner to the loop being unroll-jammed do not depend on the latter. |
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| 14 | // |
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| 15 | // Before After unroll and jam of i by factor 2: |
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| 16 | // |
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| 17 | // for i, step = 2 |
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| 18 | // for i S1(i); |
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| 19 | // S1; S2(i); |
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| 20 | // S2; S1(i+1); |
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| 21 | // for j S2(i+1); |
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| 22 | // S3; for j |
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| 23 | // S4; S3(i, j); |
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| 24 | // S5; S4(i, j); |
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| 25 | // S6; S3(i+1, j) |
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| 26 | // S4(i+1, j) |
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| 27 | // S5(i); |
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| 28 | // S6(i); |
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| 29 | // S5(i+1); |
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| 30 | // S6(i+1); |
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| 31 | // |
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| 32 | // Note: 'if/else' blocks are not jammed. So, if there are loops inside if |
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| 33 | // op's, bodies of those loops will not be jammed. |
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| 34 | //===----------------------------------------------------------------------===// |
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| 35 | |
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| 36 | #include "mlir/Dialect/Affine/Passes.h" |
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| 37 | |
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| 38 | #include "mlir/Dialect/Affine/Analysis/AffineAnalysis.h" |
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| 39 | #include "mlir/Dialect/Affine/Analysis/LoopAnalysis.h" |
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| 40 | #include "mlir/Dialect/Affine/IR/AffineOps.h" |
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| 41 | #include "mlir/Dialect/Affine/LoopUtils.h" |
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| 42 | #include "mlir/Dialect/Func/IR/FuncOps.h" |
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| 43 | #include "mlir/IR/AffineExpr.h" |
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| 44 | #include "mlir/IR/AffineMap.h" |
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| 45 | #include "mlir/IR/Builders.h" |
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| 46 | #include "mlir/IR/IRMapping.h" |
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| 47 | #include "llvm/ADT/DenseMap.h" |
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| 48 | #include "llvm/Support/CommandLine.h" |
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| 49 | #include <optional> |
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| 50 | |
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| 51 | namespace mlir { |
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| 52 | namespace affine { |
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| 53 | #define GEN_PASS_DEF_AFFINELOOPUNROLLANDJAM |
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| 54 | #include "mlir/Dialect/Affine/Passes.h.inc" |
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| 55 | } // namespace affine |
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| 56 | } // namespace mlir |
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| 57 | |
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| 58 | #define DEBUG_TYPE "affine-loop-unroll-jam" |
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| 59 | |
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| 60 | using namespace mlir; |
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| 61 | using namespace mlir::affine; |
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| 62 | |
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| 63 | namespace { |
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| 64 | /// Loop unroll jam pass. Currently, this just unroll jams the first |
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| 65 | /// outer loop in a Function. |
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| 66 | struct LoopUnrollAndJam |
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| 67 | : public affine::impl::AffineLoopUnrollAndJamBase<LoopUnrollAndJam> { |
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| 68 | explicit LoopUnrollAndJam( |
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| 69 | std::optional<unsigned> unrollJamFactor = std::nullopt) { |
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| 70 | if (unrollJamFactor) |
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| 71 | this->unrollJamFactor = *unrollJamFactor; |
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| 72 | } |
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| 73 | |
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| 74 | void runOnOperation() override; |
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| 75 | }; |
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| 76 | } // namespace |
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| 77 | |
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| 78 | std::unique_ptr<OperationPass<func::FuncOp>> |
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| 79 | mlir::affine::createLoopUnrollAndJamPass(int unrollJamFactor) { |
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| 80 | return std::make_unique<LoopUnrollAndJam>( |
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| 81 | args: unrollJamFactor == -1 ? std::nullopt |
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| 82 | : std::optional<unsigned>(unrollJamFactor)); |
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| 83 | } |
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| 84 | |
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| 85 | void LoopUnrollAndJam::runOnOperation() { |
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| 86 | if (getOperation().isExternal()) |
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| 87 | return; |
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| 88 | |
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| 89 | // Currently, just the outermost loop from the first loop nest is |
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| 90 | // unroll-and-jammed by this pass. However, runOnAffineForOp can be called on |
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| 91 | // any for operation. |
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| 92 | auto &entryBlock = getOperation().front(); |
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| 93 | if (auto forOp = dyn_cast<AffineForOp>(entryBlock.front())) |
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| 94 | (void)loopUnrollJamByFactor(forOp, unrollJamFactor); |
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| 95 | } |
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| 96 | |
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