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| 1 | +//===-- FIRToSCF.cpp ------------------------------------------------------===// |
| 2 | +// |
| 3 | +// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. |
| 4 | +// See https://llvm.org/LICENSE.txt for license information. |
| 5 | +// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception |
| 6 | +// |
| 7 | +//===----------------------------------------------------------------------===// |
| 8 | + |
| 9 | +#include "flang/Optimizer/Dialect/FIRDialect.h" |
| 10 | +#include "flang/Optimizer/Transforms/Passes.h" |
| 11 | +#include "mlir/Dialect/SCF/IR/SCF.h" |
| 12 | +#include "mlir/Transforms/DialectConversion.h" |
| 13 | + |
| 14 | +namespace fir { |
| 15 | +#define GEN_PASS_DEF_FIRTOSCFPASS |
| 16 | +#include "flang/Optimizer/Transforms/Passes.h.inc" |
| 17 | +} // namespace fir |
| 18 | + |
| 19 | +using namespace fir; |
| 20 | +using namespace mlir; |
| 21 | + |
| 22 | +namespace { |
| 23 | +class FIRToSCFPass : public fir::impl::FIRToSCFPassBase<FIRToSCFPass> { |
| 24 | +public: |
| 25 | + void runOnOperation() override; |
| 26 | +}; |
| 27 | + |
| 28 | +struct DoLoopConversion : public OpRewritePattern<fir::DoLoopOp> { |
| 29 | + using OpRewritePattern<fir::DoLoopOp>::OpRewritePattern; |
| 30 | + |
| 31 | + LogicalResult matchAndRewrite(fir::DoLoopOp doLoopOp, |
| 32 | + PatternRewriter &rewriter) const override { |
| 33 | + auto loc = doLoopOp.getLoc(); |
| 34 | + bool hasFinalValue = doLoopOp.getFinalValue().has_value(); |
| 35 | + |
| 36 | + // Get loop values from the DoLoopOp |
| 37 | + auto low = doLoopOp.getLowerBound(); |
| 38 | + auto high = doLoopOp.getUpperBound(); |
| 39 | + assert(low && high && "must be a Value"); |
| 40 | + auto step = doLoopOp.getStep(); |
| 41 | + llvm::SmallVector<Value> iterArgs; |
| 42 | + if (hasFinalValue) |
| 43 | + iterArgs.push_back(low); |
| 44 | + iterArgs.append(doLoopOp.getIterOperands().begin(), |
| 45 | + doLoopOp.getIterOperands().end()); |
| 46 | + |
| 47 | + // fir.do_loop iterates over the interval [%l, %u], and the step may be |
| 48 | + // negative. But scf.for iterates over the interval [%l, %u), and the step |
| 49 | + // must be a positive value. |
| 50 | + // For easier conversion, we calculate the trip count and use a canonical |
| 51 | + // induction variable. |
| 52 | + auto diff = rewriter. create<arith::SubIOp>(loc, high, low); |
| 53 | + auto distance = rewriter. create<arith::AddIOp>(loc, diff, step); |
| 54 | + auto tripCount = rewriter. create<arith::DivSIOp>(loc, distance, step); |
| 55 | + auto zero = rewriter. create<arith::ConstantIndexOp>(loc, 0); |
| 56 | + auto one = rewriter. create<arith::ConstantIndexOp>(loc, 1); |
| 57 | + auto scfForOp = |
| 58 | + rewriter.create<scf::ForOp>(loc, zero, tripCount, one, iterArgs); |
| 59 | + |
| 60 | + auto &loopOps = doLoopOp.getBody()->getOperations(); |
| 61 | + auto resultOp = cast<fir::ResultOp>(doLoopOp.getBody()->getTerminator()); |
| 62 | + auto results = resultOp.getOperands(); |
| 63 | + Block *loweredBody = scfForOp.getBody(); |
| 64 | + |
| 65 | + loweredBody->getOperations().splice(loweredBody->begin(), loopOps, |
| 66 | + loopOps.begin(), |
| 67 | + std::prev(loopOps.end())); |
| 68 | + |
| 69 | + rewriter.setInsertionPointToStart(loweredBody); |
| 70 | + Value iv = |
| 71 | + rewriter. create<arith::MulIOp>(loc, scfForOp. getInductionVar(), step); |
| 72 | + iv = rewriter. create<arith::AddIOp>(loc, low, iv); |
| 73 | + |
| 74 | + if (!results.empty()) { |
| 75 | + rewriter.setInsertionPointToEnd(loweredBody); |
| 76 | + rewriter.create<scf::YieldOp>(resultOp->getLoc(), results); |
| 77 | + } |
| 78 | + doLoopOp.getInductionVar().replaceAllUsesWith(iv); |
| 79 | + rewriter.replaceAllUsesWith(doLoopOp.getRegionIterArgs(), |
| 80 | + hasFinalValue |
| 81 | + ? scfForOp.getRegionIterArgs().drop_front() |
| 82 | + : scfForOp.getRegionIterArgs()); |
| 83 | + |
| 84 | + // Copy all the attributes from the old to new op. |
| 85 | + scfForOp->setAttrs(doLoopOp->getAttrs()); |
| 86 | + rewriter.replaceOp(doLoopOp, scfForOp); |
| 87 | + return success(); |
| 88 | + } |
| 89 | +}; |
| 90 | +} // namespace |
| 91 | + |
| 92 | +void FIRToSCFPass::runOnOperation() { |
| 93 | + RewritePatternSet patterns(&getContext()); |
| 94 | + patterns.add<DoLoopConversion>(patterns.getContext()); |
| 95 | + ConversionTarget target(getContext()); |
| 96 | + target.addIllegalOp<fir::DoLoopOp>(); |
| 97 | + target.markUnknownOpDynamicallyLegal([](Operation *) { return true; }); |
| 98 | + if (failed( |
| 99 | + applyPartialConversion(getOperation(), target, std::move(patterns)))) |
| 100 | + signalPassFailure(); |
| 101 | +} |
| 102 | + |
| 103 | +std::unique_ptr<Pass> fir::createFIRToSCFPass() { |
| 104 | + return std::make_unique<FIRToSCFPass>(); |
| 105 | +} |
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