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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;
namespace mlir {
namespace scf {
namespace {
struct ForOpInterface
: public ValueBoundsOpInterface::ExternalModel<ForOpInterface, ForOp> {
/// Populate bounds of values/dimensions for iter_args/OpResults. If the
/// value/dimension size does not change in an iteration, we can deduce that
/// it the same as the initial value/dimension.
///
/// Example 1:
/// %0 = scf.for ... iter_args(%arg0 = %t) -> tensor<?xf32> {
/// ...
/// %1 = tensor.insert %f into %arg0[...] : tensor<?xf32>
/// scf.yield %1 : tensor<?xf32>
/// }
/// --> bound(%0)[0] == bound(%t)[0]
/// --> bound(%arg0)[0] == bound(%t)[0]
///
/// Example 2:
/// %0 = scf.for ... iter_args(%arg0 = %t) -> tensor<?xf32> {
/// %sz = tensor.dim %arg0 : tensor<?xf32>
/// %incr = arith.addi %sz, %c1 : index
/// %1 = tensor.empty(%incr) : tensor<?xf32>
/// scf.yield %1 : tensor<?xf32>
/// }
/// --> The yielded tensor dimension size changes with each iteration. Such
/// loops are not supported and no constraints are added.
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();
}
Value yieldedValue = cast<scf::YieldOp>(forOp.getBody()->getTerminator())
.getOperand(iterArgIdx);
Value iterArg = forOp.getRegionIterArg(iterArgIdx);
Value initArg = forOp.getInitArgs()[iterArgIdx];
// An EQ constraint can be added if the yielded value (dimension size)
// equals the corresponding block argument (dimension size).
if (cstr.populateAndCompare(
/*lhs=*/{yieldedValue, dim},
ValueBoundsConstraintSet::ComparisonOperator::EQ,
/*rhs=*/{iterArg, dim})) {
if (dim.has_value()) {
cstr.bound(value)[*dim] == cstr.getExpr(initArg, dim);
} else {
cstr.bound(value) == cstr.getExpr(initArg);
}
}
}
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);
}
};
struct IfOpInterface
: public ValueBoundsOpInterface::ExternalModel<IfOpInterface, IfOp> {
static void populateBounds(scf::IfOp ifOp, Value value,
std::optional<int64_t> dim,
ValueBoundsConstraintSet &cstr) {
unsigned int resultNum = cast<OpResult>(value).getResultNumber();
Value thenValue = ifOp.thenYield().getResults()[resultNum];
Value elseValue = ifOp.elseYield().getResults()[resultNum];
auto boundsBuilder = cstr.bound(value);
if (dim)
boundsBuilder[*dim];
// Compare yielded values.
// If thenValue <= elseValue:
// * result <= elseValue
// * result >= thenValue
if (cstr.populateAndCompare(
/*lhs=*/{thenValue, dim},
ValueBoundsConstraintSet::ComparisonOperator::LE,
/*rhs=*/{elseValue, dim})) {
if (dim) {
cstr.bound(value)[*dim] >= cstr.getExpr(thenValue, dim);
cstr.bound(value)[*dim] <= cstr.getExpr(elseValue, dim);
} else {
cstr.bound(value) >= thenValue;
cstr.bound(value) <= elseValue;
}
}
// If elseValue <= thenValue:
// * result <= thenValue
// * result >= elseValue
if (cstr.populateAndCompare(
/*lhs=*/{elseValue, dim},
ValueBoundsConstraintSet::ComparisonOperator::LE,
/*rhs=*/{thenValue, dim})) {
if (dim) {
cstr.bound(value)[*dim] >= cstr.getExpr(elseValue, dim);
cstr.bound(value)[*dim] <= cstr.getExpr(thenValue, dim);
} else {
cstr.bound(value) >= elseValue;
cstr.bound(value) <= thenValue;
}
}
}
void populateBoundsForIndexValue(Operation *op, Value value,
ValueBoundsConstraintSet &cstr) const {
populateBounds(cast<IfOp>(op), value, /*dim=*/std::nullopt, cstr);
}
void populateBoundsForShapedValueDim(Operation *op, Value value, int64_t dim,
ValueBoundsConstraintSet &cstr) const {
populateBounds(cast<IfOp>(op), 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);
scf::IfOp::attachInterface<scf::IfOpInterface>(*ctx);
});
}
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