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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/WalkPatternRewriteDriver.h"
namespace fir {
#define GEN_PASS_DEF_FIRTOSCFPASS
#include "flang/Optimizer/Transforms/Passes.h.inc"
} // namespace fir
namespace {
class FIRToSCFPass : public fir::impl::FIRToSCFPassBase<FIRToSCFPass> {
public:
void runOnOperation() override;
};
struct DoLoopConversion : public mlir::OpRewritePattern<fir::DoLoopOp> {
using OpRewritePattern<fir::DoLoopOp>::OpRewritePattern;
mlir::LogicalResult
matchAndRewrite(fir::DoLoopOp doLoopOp,
mlir::PatternRewriter &rewriter) const override {
mlir::Location loc = doLoopOp.getLoc();
bool hasFinalValue = doLoopOp.getFinalValue().has_value();
// Get loop values from the DoLoopOp
mlir::Value low = doLoopOp.getLowerBound();
mlir::Value high = doLoopOp.getUpperBound();
assert(low && high && "must be a Value");
mlir::Value step = doLoopOp.getStep();
mlir::SmallVector<mlir::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 = mlir::arith::SubIOp::create(rewriter, loc, high, low);
auto distance = mlir::arith::AddIOp::create(rewriter, loc, diff, step);
auto tripCount =
mlir::arith::DivSIOp::create(rewriter, loc, distance, step);
auto zero = mlir::arith::ConstantIndexOp::create(rewriter, loc, 0);
auto one = mlir::arith::ConstantIndexOp::create(rewriter, loc, 1);
auto scfForOp =
mlir::scf::ForOp::create(rewriter, loc, zero, tripCount, one, iterArgs);
auto &loopOps = doLoopOp.getBody()->getOperations();
auto resultOp =
mlir::cast<fir::ResultOp>(doLoopOp.getBody()->getTerminator());
auto results = resultOp.getOperands();
mlir::Block *loweredBody = scfForOp.getBody();
loweredBody->getOperations().splice(loweredBody->begin(), loopOps,
loopOps.begin(),
std::prev(loopOps.end()));
rewriter.setInsertionPointToStart(loweredBody);
mlir::Value iv = mlir::arith::MulIOp::create(
rewriter, loc, scfForOp.getInductionVar(), step);
iv = mlir::arith::AddIOp::create(rewriter, loc, low, iv);
if (!results.empty()) {
rewriter.setInsertionPointToEnd(loweredBody);
mlir::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 mlir::success();
}
};
struct IterWhileConversion : public mlir::OpRewritePattern<fir::IterWhileOp> {
using OpRewritePattern<fir::IterWhileOp>::OpRewritePattern;
mlir::LogicalResult
matchAndRewrite(fir::IterWhileOp iterWhileOp,
mlir::PatternRewriter &rewriter) const override {
mlir::Location loc = iterWhileOp.getLoc();
mlir::Value lowerBound = iterWhileOp.getLowerBound();
mlir::Value upperBound = iterWhileOp.getUpperBound();
mlir::Value step = iterWhileOp.getStep();
mlir::Value okInit = iterWhileOp.getIterateIn();
mlir::ValueRange iterArgs = iterWhileOp.getInitArgs();
mlir::SmallVector<mlir::Value> initVals;
initVals.push_back(lowerBound);
initVals.push_back(okInit);
initVals.append(iterArgs.begin(), iterArgs.end());
mlir::SmallVector<mlir::Type> loopTypes;
loopTypes.push_back(lowerBound.getType());
loopTypes.push_back(okInit.getType());
for (auto val : iterArgs)
loopTypes.push_back(val.getType());
auto scfWhileOp =
mlir::scf::WhileOp::create(rewriter, loc, loopTypes, initVals);
auto &beforeBlock = *rewriter.createBlock(
&scfWhileOp.getBefore(), scfWhileOp.getBefore().end(), loopTypes,
mlir::SmallVector<mlir::Location>(loopTypes.size(), loc));
mlir::Region::BlockArgListType argsInBefore =
scfWhileOp.getBefore().getArguments();
auto ivInBefore = argsInBefore[0];
auto earlyExitInBefore = argsInBefore[1];
rewriter.setInsertionPointToStart(&beforeBlock);
mlir::Value inductionCmp = mlir::arith::CmpIOp::create(
rewriter, loc, mlir::arith::CmpIPredicate::sle, ivInBefore, upperBound);
mlir::Value cond = mlir::arith::AndIOp::create(rewriter, loc, inductionCmp,
earlyExitInBefore);
mlir::scf::ConditionOp::create(rewriter, loc, cond, argsInBefore);
rewriter.moveBlockBefore(iterWhileOp.getBody(), &scfWhileOp.getAfter(),
scfWhileOp.getAfter().begin());
auto *afterBody = scfWhileOp.getAfterBody();
auto resultOp = mlir::cast<fir::ResultOp>(afterBody->getTerminator());
mlir::SmallVector<mlir::Value> results(resultOp->getOperands());
mlir::Value ivInAfter = scfWhileOp.getAfterArguments()[0];
rewriter.setInsertionPointToStart(afterBody);
results[0] = mlir::arith::AddIOp::create(rewriter, loc, ivInAfter, step);
rewriter.setInsertionPointToEnd(afterBody);
rewriter.replaceOpWithNewOp<mlir::scf::YieldOp>(resultOp, results);
scfWhileOp->setAttrs(iterWhileOp->getAttrs());
rewriter.replaceOp(iterWhileOp, scfWhileOp);
return mlir::success();
}
};
void copyBlockAndTransformResult(mlir::PatternRewriter &rewriter,
mlir::Block &srcBlock, mlir::Block &dstBlock) {
mlir::Operation *srcTerminator = srcBlock.getTerminator();
auto resultOp = mlir::cast<fir::ResultOp>(srcTerminator);
dstBlock.getOperations().splice(dstBlock.begin(), srcBlock.getOperations(),
srcBlock.begin(), std::prev(srcBlock.end()));
if (!resultOp->getOperands().empty()) {
rewriter.setInsertionPointToEnd(&dstBlock);
mlir::scf::YieldOp::create(rewriter, resultOp->getLoc(),
resultOp->getOperands());
}
rewriter.eraseOp(srcTerminator);
}
struct IfConversion : public mlir::OpRewritePattern<fir::IfOp> {
using OpRewritePattern<fir::IfOp>::OpRewritePattern;
mlir::LogicalResult
matchAndRewrite(fir::IfOp ifOp,
mlir::PatternRewriter &rewriter) const override {
bool hasElse = !ifOp.getElseRegion().empty();
auto scfIfOp =
mlir::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 mlir::success();
}
};
} // namespace
void FIRToSCFPass::runOnOperation() {
mlir::RewritePatternSet patterns(&getContext());
patterns.add<DoLoopConversion, IterWhileConversion, IfConversion>(
patterns.getContext());
walkAndApplyPatterns(getOperation(), std::move(patterns));
}
std::unique_ptr<mlir::Pass> fir::createFIRToSCFPass() {
return std::make_unique<FIRToSCFPass>();
}
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