forked from OSchip/llvm-project
79 lines
2.8 KiB
C++
79 lines
2.8 KiB
C++
//===- LoopUnrollAndJam.cpp - Code to perform loop unroll and jam ---------===//
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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 loop unroll and jam. Unroll and jam is a transformation
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// that improves locality, in particular, register reuse, while also improving
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// operation level parallelism. The example below shows what it does in nearly
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// the general case. Loop unroll and jam currently works if the bounds of the
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// loops inner to the loop being unroll-jammed do not depend on the latter.
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//
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// Before After unroll and jam of i by factor 2:
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//
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// for i, step = 2
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// for i S1(i);
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// S1; S2(i);
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// S2; S1(i+1);
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// for j S2(i+1);
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// S3; for j
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// S4; S3(i, j);
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// S5; S4(i, j);
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// S6; S3(i+1, j)
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// S4(i+1, j)
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// S5(i);
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// S6(i);
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// S5(i+1);
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// S6(i+1);
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//
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// Note: 'if/else' blocks are not jammed. So, if there are loops inside if
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// op's, bodies of those loops will not be jammed.
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//===----------------------------------------------------------------------===//
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#include "PassDetail.h"
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#include "mlir/Analysis/LoopAnalysis.h"
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#include "mlir/Dialect/Affine/IR/AffineOps.h"
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#include "mlir/Dialect/Affine/Passes.h"
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#include "mlir/IR/AffineExpr.h"
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#include "mlir/IR/AffineMap.h"
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#include "mlir/IR/BlockAndValueMapping.h"
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#include "mlir/IR/Builders.h"
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#include "mlir/Transforms/LoopUtils.h"
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#include "llvm/ADT/DenseMap.h"
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#include "llvm/Support/CommandLine.h"
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using namespace mlir;
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#define DEBUG_TYPE "affine-loop-unroll-jam"
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namespace {
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/// Loop unroll jam pass. Currently, this just unroll jams the first
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/// outer loop in a Function.
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struct LoopUnrollAndJam : public AffineLoopUnrollAndJamBase<LoopUnrollAndJam> {
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explicit LoopUnrollAndJam(Optional<unsigned> unrollJamFactor = None) {
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if (unrollJamFactor)
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this->unrollJamFactor = *unrollJamFactor;
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}
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void runOnFunction() override;
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};
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} // end anonymous namespace
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std::unique_ptr<OperationPass<FuncOp>>
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mlir::createLoopUnrollAndJamPass(int unrollJamFactor) {
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return std::make_unique<LoopUnrollAndJam>(
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unrollJamFactor == -1 ? None : Optional<unsigned>(unrollJamFactor));
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}
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void LoopUnrollAndJam::runOnFunction() {
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// Currently, just the outermost loop from the first loop nest is
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// unroll-and-jammed by this pass. However, runOnAffineForOp can be called on
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// any for operation.
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auto &entryBlock = getFunction().front();
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if (auto forOp = dyn_cast<AffineForOp>(entryBlock.front()))
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(void)loopUnrollJamByFactor(forOp, unrollJamFactor);
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}
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