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//===- SimplifyAffineStructures.cpp ---------------------------------------===//
//
// Copyright 2019 The MLIR Authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
// =============================================================================
//
// This file implements a pass to simplify affine structures.
//
//===----------------------------------------------------------------------===//
#include "mlir/Analysis/AffineStructures.h"
#include "mlir/IR/AffineMap.h"
#include "mlir/IR/Function.h"
#include "mlir/IR/IntegerSet.h"
#include "mlir/IR/Operation.h"
#include "mlir/Pass/Pass.h"
#include "mlir/Transforms/Passes.h"
#define DEBUG_TYPE "simplify-affine-structure"
using namespace mlir;
namespace {
/// Simplifies all affine expressions appearing in the operations of
/// the Function. This is mainly to test the simplifyAffineExpr method.
/// TODO(someone): This should just be defined as a canonicalization pattern
/// on AffineMap and driven from the existing canonicalization pass.
struct SimplifyAffineStructures
: public FunctionPass<SimplifyAffineStructures> {
void runOnFunction() override;
/// Utility to simplify an affine attribute and update its entry in the parent
/// operation if necessary.
template <typename AttributeT>
void simplifyAndUpdateAttribute(Operation *op, Identifier name,
AttributeT attr) {
auto &simplified = simplifiedAttributes[attr];
if (simplified == attr)
return;
// This is a newly encountered attribute.
if (!simplified) {
// Try to simplify the value of the attribute.
auto value = attr.getValue();
auto simplifiedValue = simplify(value);
if (simplifiedValue == value) {
simplified = attr;
return;
}
simplified = AttributeT::get(simplifiedValue);
}
// Simplification was successful, so update the attribute.
op->setAttr(name, simplified);
}
/// Performs basic integer set simplifications. Checks if it's empty, and
/// replaces it with the canonical empty set if it is.
IntegerSet simplify(IntegerSet set) {
FlatAffineConstraints fac(set);
if (fac.isEmpty())
return IntegerSet::getEmptySet(set.getNumDims(), set.getNumSymbols(),
&getContext());
return set;
}
/// Performs basic affine map simplifications.
AffineMap simplify(AffineMap map) {
MutableAffineMap mMap(map);
mMap.simplify();
return mMap.getAffineMap();
}
DenseMap<Attribute, Attribute> simplifiedAttributes;
};
} // end anonymous namespace
std::unique_ptr<FunctionPassBase> mlir::createSimplifyAffineStructuresPass() {
return std::make_unique<SimplifyAffineStructures>();
}
void SimplifyAffineStructures::runOnFunction() {
simplifiedAttributes.clear();
getFunction().walk([&](Operation *opInst) {
for (auto attr : opInst->getAttrs()) {
if (auto mapAttr = attr.second.dyn_cast<AffineMapAttr>())
simplifyAndUpdateAttribute(opInst, attr.first, mapAttr);
else if (auto setAttr = attr.second.dyn_cast<IntegerSetAttr>())
simplifyAndUpdateAttribute(opInst, attr.first, setAttr);
}
});
}
static PassRegistration<SimplifyAffineStructures>
pass("simplify-affine-structures", "Simplify affine expressions");
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