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//===-- FIRToSCF.cpp ------------------------------------------------------===//
//
// 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
//
//===----------------------------------------------------------------------===//
#include "flang/Optimizer/Dialect/FIRDialect.h"
#include "flang/Optimizer/Transforms/Passes.h"
#include "mlir/Dialect/SCF/IR/SCF.h"
#include "mlir/Transforms/DialectConversion.h"
namespace fir {
#define GEN_PASS_DEF_FIRTOSCFPASS
#include "flang/Optimizer/Transforms/Passes.h.inc"
} // namespace fir
using namespace fir;
using namespace mlir;
namespace {
class FIRToSCFPass : public fir::impl::FIRToSCFPassBase<FIRToSCFPass> {
public:
void runOnOperation() override;
};
struct DoLoopConversion : public OpRewritePattern<fir::DoLoopOp> {
using OpRewritePattern<fir::DoLoopOp>::OpRewritePattern;
LogicalResult matchAndRewrite(fir::DoLoopOp doLoopOp,
PatternRewriter &rewriter) const override {
auto loc = doLoopOp.getLoc();
bool hasFinalValue = doLoopOp.getFinalValue().has_value();
// Get loop values from the DoLoopOp
auto low = doLoopOp.getLowerBound();
auto high = doLoopOp.getUpperBound();
assert(low && high && "must be a Value");
auto step = doLoopOp.getStep();
llvm::SmallVector<Value> iterArgs;
if (hasFinalValue)
iterArgs.push_back(low);
iterArgs.append(doLoopOp.getIterOperands().begin(),
doLoopOp.getIterOperands().end());
// fir.do_loop iterates over the interval [%l, %u], and the step may be
// negative. But scf.for iterates over the interval [%l, %u), and the step
// must be a positive value.
// For easier conversion, we calculate the trip count and use a canonical
// induction variable.
auto diff = arith::SubIOp::create(rewriter, loc, high, low);
auto distance = arith::AddIOp::create(rewriter, loc, diff, step);
auto tripCount = arith::DivSIOp::create(rewriter, loc, distance, step);
auto zero = arith::ConstantIndexOp::create(rewriter, loc, 0);
auto one = arith::ConstantIndexOp::create(rewriter, loc, 1);
auto scfForOp =
scf::ForOp::create(rewriter, loc, zero, tripCount, one, iterArgs);
auto &loopOps = doLoopOp.getBody()->getOperations();
auto resultOp = cast<fir::ResultOp>(doLoopOp.getBody()->getTerminator());
auto results = resultOp.getOperands();
Block *loweredBody = scfForOp.getBody();
loweredBody->getOperations().splice(loweredBody->begin(), loopOps,
loopOps.begin(),
std::prev(loopOps.end()));
rewriter.setInsertionPointToStart(loweredBody);
Value iv =
arith::MulIOp::create(rewriter, loc, scfForOp.getInductionVar(), step);
iv = arith::AddIOp::create(rewriter, loc, low, iv);
if (!results.empty()) {
rewriter.setInsertionPointToEnd(loweredBody);
scf::YieldOp::create(rewriter, resultOp->getLoc(), results);
}
doLoopOp.getInductionVar().replaceAllUsesWith(iv);
rewriter.replaceAllUsesWith(doLoopOp.getRegionIterArgs(),
hasFinalValue
? scfForOp.getRegionIterArgs().drop_front()
: scfForOp.getRegionIterArgs());
// Copy all the attributes from the old to new op.
scfForOp->setAttrs(doLoopOp->getAttrs());
rewriter.replaceOp(doLoopOp, scfForOp);
return success();
}
};
void copyBlockAndTransformResult(PatternRewriter &rewriter, Block &srcBlock,
Block &dstBlock) {
Operation *srcTerminator = srcBlock.getTerminator();
auto resultOp = cast<fir::ResultOp>(srcTerminator);
dstBlock.getOperations().splice(dstBlock.begin(), srcBlock.getOperations(),
srcBlock.begin(), std::prev(srcBlock.end()));
if (!resultOp->getOperands().empty()) {
rewriter.setInsertionPointToEnd(&dstBlock);
scf::YieldOp::create(rewriter, resultOp->getLoc(), resultOp->getOperands());
}
rewriter.eraseOp(srcTerminator);
}
struct IfConversion : public OpRewritePattern<fir::IfOp> {
using OpRewritePattern<fir::IfOp>::OpRewritePattern;
LogicalResult matchAndRewrite(fir::IfOp ifOp,
PatternRewriter &rewriter) const override {
bool hasElse = !ifOp.getElseRegion().empty();
auto scfIfOp =
scf::IfOp::create(rewriter, ifOp.getLoc(), ifOp.getResultTypes(),
ifOp.getCondition(), hasElse);
copyBlockAndTransformResult(rewriter, ifOp.getThenRegion().front(),
scfIfOp.getThenRegion().front());
if (hasElse) {
copyBlockAndTransformResult(rewriter, ifOp.getElseRegion().front(),
scfIfOp.getElseRegion().front());
}
scfIfOp->setAttrs(ifOp->getAttrs());
rewriter.replaceOp(ifOp, scfIfOp);
return success();
}
};
} // namespace
void FIRToSCFPass::runOnOperation() {
RewritePatternSet patterns(&getContext());
patterns.add<DoLoopConversion, IfConversion>(patterns.getContext());
ConversionTarget target(getContext());
target.addIllegalOp<fir::DoLoopOp, fir::IfOp>();
target.markUnknownOpDynamicallyLegal([](Operation *) { return true; });
if (failed(
applyPartialConversion(getOperation(), target, std::move(patterns))))
signalPassFailure();
}
std::unique_ptr<Pass> fir::createFIRToSCFPass() {
return std::make_unique<FIRToSCFPass>();
}
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