54998986c3
Seems to have been an accident of history and none of these had any reason to be restricted to FuncOp. Differential Revision: https://reviews.llvm.org/D128614
115 lines
4.6 KiB
C++
115 lines
4.6 KiB
C++
//===- ForToWhile.cpp - scf.for to scf.while loop conversion --------------===//
|
|
//
|
|
// 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
|
|
//
|
|
//===----------------------------------------------------------------------===//
|
|
//
|
|
// Transforms SCF.ForOp's into SCF.WhileOp's.
|
|
//
|
|
//===----------------------------------------------------------------------===//
|
|
|
|
#include "PassDetail.h"
|
|
#include "mlir/Dialect/Arithmetic/IR/Arithmetic.h"
|
|
#include "mlir/Dialect/SCF/IR/SCF.h"
|
|
#include "mlir/Dialect/SCF/Transforms/Passes.h"
|
|
#include "mlir/Dialect/SCF/Transforms/Transforms.h"
|
|
#include "mlir/IR/PatternMatch.h"
|
|
#include "mlir/Transforms/GreedyPatternRewriteDriver.h"
|
|
|
|
using namespace llvm;
|
|
using namespace mlir;
|
|
using scf::ForOp;
|
|
using scf::WhileOp;
|
|
|
|
namespace {
|
|
|
|
struct ForLoopLoweringPattern : public OpRewritePattern<ForOp> {
|
|
using OpRewritePattern<ForOp>::OpRewritePattern;
|
|
|
|
LogicalResult matchAndRewrite(ForOp forOp,
|
|
PatternRewriter &rewriter) const override {
|
|
// Generate type signature for the loop-carried values. The induction
|
|
// variable is placed first, followed by the forOp.iterArgs.
|
|
SmallVector<Type> lcvTypes;
|
|
SmallVector<Location> lcvLocs;
|
|
lcvTypes.push_back(forOp.getInductionVar().getType());
|
|
lcvLocs.push_back(forOp.getInductionVar().getLoc());
|
|
for (Value value : forOp.getInitArgs()) {
|
|
lcvTypes.push_back(value.getType());
|
|
lcvLocs.push_back(value.getLoc());
|
|
}
|
|
|
|
// Build scf.WhileOp
|
|
SmallVector<Value> initArgs;
|
|
initArgs.push_back(forOp.getLowerBound());
|
|
llvm::append_range(initArgs, forOp.getInitArgs());
|
|
auto whileOp = rewriter.create<WhileOp>(forOp.getLoc(), lcvTypes, initArgs,
|
|
forOp->getAttrs());
|
|
|
|
// 'before' region contains the loop condition and forwarding of iteration
|
|
// arguments to the 'after' region.
|
|
auto *beforeBlock = rewriter.createBlock(
|
|
&whileOp.getBefore(), whileOp.getBefore().begin(), lcvTypes, lcvLocs);
|
|
rewriter.setInsertionPointToStart(&whileOp.getBefore().front());
|
|
auto cmpOp = rewriter.create<arith::CmpIOp>(
|
|
whileOp.getLoc(), arith::CmpIPredicate::slt,
|
|
beforeBlock->getArgument(0), forOp.getUpperBound());
|
|
rewriter.create<scf::ConditionOp>(whileOp.getLoc(), cmpOp.getResult(),
|
|
beforeBlock->getArguments());
|
|
|
|
// Inline for-loop body into an executeRegion operation in the "after"
|
|
// region. The return type of the execRegionOp does not contain the
|
|
// iv - yields in the source for-loop contain only iterArgs.
|
|
auto *afterBlock = rewriter.createBlock(
|
|
&whileOp.getAfter(), whileOp.getAfter().begin(), lcvTypes, lcvLocs);
|
|
|
|
// Add induction variable incrementation
|
|
rewriter.setInsertionPointToEnd(afterBlock);
|
|
auto ivIncOp = rewriter.create<arith::AddIOp>(
|
|
whileOp.getLoc(), afterBlock->getArgument(0), forOp.getStep());
|
|
|
|
// Rewrite uses of the for-loop block arguments to the new while-loop
|
|
// "after" arguments
|
|
for (const auto &barg : enumerate(forOp.getBody(0)->getArguments()))
|
|
barg.value().replaceAllUsesWith(afterBlock->getArgument(barg.index()));
|
|
|
|
// Inline for-loop body operations into 'after' region.
|
|
for (auto &arg : llvm::make_early_inc_range(*forOp.getBody()))
|
|
arg.moveBefore(afterBlock, afterBlock->end());
|
|
|
|
// Add incremented IV to yield operations
|
|
for (auto yieldOp : afterBlock->getOps<scf::YieldOp>()) {
|
|
SmallVector<Value> yieldOperands = yieldOp.getOperands();
|
|
yieldOperands.insert(yieldOperands.begin(), ivIncOp.getResult());
|
|
yieldOp->setOperands(yieldOperands);
|
|
}
|
|
|
|
// We cannot do a direct replacement of the forOp since the while op returns
|
|
// an extra value (the induction variable escapes the loop through being
|
|
// carried in the set of iterargs). Instead, rewrite uses of the forOp
|
|
// results.
|
|
for (const auto &arg : llvm::enumerate(forOp.getResults()))
|
|
arg.value().replaceAllUsesWith(whileOp.getResult(arg.index() + 1));
|
|
|
|
rewriter.eraseOp(forOp);
|
|
return success();
|
|
}
|
|
};
|
|
|
|
struct ForToWhileLoop : public SCFForToWhileLoopBase<ForToWhileLoop> {
|
|
void runOnOperation() override {
|
|
auto *parentOp = getOperation();
|
|
MLIRContext *ctx = parentOp->getContext();
|
|
RewritePatternSet patterns(ctx);
|
|
patterns.add<ForLoopLoweringPattern>(ctx);
|
|
(void)applyPatternsAndFoldGreedily(parentOp, std::move(patterns));
|
|
}
|
|
};
|
|
} // namespace
|
|
|
|
std::unique_ptr<Pass> mlir::createForToWhileLoopPass() {
|
|
return std::make_unique<ForToWhileLoop>();
|
|
}
|