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//===- ValueBoundsOpInterfaceImpl.cpp - Impl. of ValueBoundsOpInterface ---===//
//
// 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 "mlir/Dialect/SCF/IR/ValueBoundsOpInterfaceImpl.h"
#include "mlir/Dialect/SCF/IR/SCF.h"
#include "mlir/Interfaces/ValueBoundsOpInterface.h"
using namespace mlir;
using presburger::BoundType;
namespace mlir {
namespace scf {
namespace {
struct ForOpInterface
: public ValueBoundsOpInterface::ExternalModel<ForOpInterface, ForOp> {
/// Populate bounds of values/dimensions for iter_args/OpResults.
static void populateIterArgBounds(scf::ForOp forOp, Value value,
std::optional<int64_t> dim,
ValueBoundsConstraintSet &cstr) {
// `value` is an iter_arg or an OpResult.
int64_t iterArgIdx;
if (auto iterArg = llvm::dyn_cast<BlockArgument>(value)) {
iterArgIdx = iterArg.getArgNumber() - forOp.getNumInductionVars();
} else {
iterArgIdx = llvm::cast<OpResult>(value).getResultNumber();
}
// An EQ constraint can be added if the yielded value (dimension size)
// equals the corresponding block argument (dimension size).
Value yieldedValue = cast<scf::YieldOp>(forOp.getBody()->getTerminator())
.getOperand(iterArgIdx);
Value iterArg = forOp.getRegionIterArg(iterArgIdx);
Value initArg = forOp.getInitArgs()[iterArgIdx];
auto addEqBound = [&]() {
if (dim.has_value()) {
cstr.bound(value)[*dim] == cstr.getExpr(initArg, dim);
} else {
cstr.bound(value) == initArg;
}
};
if (yieldedValue == iterArg) {
addEqBound();
return;
}
// Compute EQ bound for yielded value.
AffineMap bound;
ValueDimList boundOperands;
LogicalResult status = ValueBoundsConstraintSet::computeBound(
bound, boundOperands, BoundType::EQ, yieldedValue, dim,
[&](Value v, std::optional<int64_t> d, ValueBoundsConstraintSet &cstr) {
// Stop when reaching a block argument of the loop body.
if (auto bbArg = llvm::dyn_cast<BlockArgument>(v))
return bbArg.getOwner()->getParentOp() == forOp;
// Stop when reaching a value that is defined outside of the loop. It
// is impossible to reach an iter_arg from there.
Operation *op = v.getDefiningOp();
return forOp.getRegion().findAncestorOpInRegion(*op) == nullptr;
});
if (failed(status))
return;
if (bound.getNumResults() != 1)
return;
// Check if computed bound equals the corresponding iter_arg.
Value singleValue = nullptr;
std::optional<int64_t> singleDim;
if (auto dimExpr = dyn_cast<AffineDimExpr>(bound.getResult(0))) {
int64_t idx = dimExpr.getPosition();
singleValue = boundOperands[idx].first;
singleDim = boundOperands[idx].second;
} else if (auto symExpr = dyn_cast<AffineSymbolExpr>(bound.getResult(0))) {
int64_t idx = symExpr.getPosition() + bound.getNumDims();
singleValue = boundOperands[idx].first;
singleDim = boundOperands[idx].second;
}
if (singleValue == iterArg && singleDim == dim)
addEqBound();
}
void populateBoundsForIndexValue(Operation *op, Value value,
ValueBoundsConstraintSet &cstr) const {
auto forOp = cast<ForOp>(op);
if (value == forOp.getInductionVar()) {
// TODO: Take into account step size.
cstr.bound(value) >= forOp.getLowerBound();
cstr.bound(value) < forOp.getUpperBound();
return;
}
// Handle iter_args and OpResults.
populateIterArgBounds(forOp, value, std::nullopt, cstr);
}
void populateBoundsForShapedValueDim(Operation *op, Value value, int64_t dim,
ValueBoundsConstraintSet &cstr) const {
auto forOp = cast<ForOp>(op);
// Handle iter_args and OpResults.
populateIterArgBounds(forOp, value, dim, cstr);
}
};
} // namespace
} // namespace scf
} // namespace mlir
void mlir::scf::registerValueBoundsOpInterfaceExternalModels(
DialectRegistry ®istry) {
registry.addExtension(+[](MLIRContext *ctx, scf::SCFDialect *dialect) {
scf::ForOp::attachInterface<scf::ForOpInterface>(*ctx);
});
}
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