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//===- SimplifyAffineStructures.cpp ---------------------------------------===//
//
// Part of the MLIR 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
//
//===----------------------------------------------------------------------===//
//
// This file implements a pass to simplify affine structures.
//
//===----------------------------------------------------------------------===//
#include "mlir/Analysis/AffineStructures.h"
#include "mlir/IR/IntegerSet.h"
#include "mlir/Pass/Pass.h"
#include "mlir/Transforms/Passes.h"
#include "mlir/Transforms/Utils.h"
#define DEBUG_TYPE "simplify-affine-structure"
using namespace mlir;
namespace {
/// Simplifies affine maps and sets appearing in the operations of the Function.
/// This part is mainly to test the simplifyAffineExpr method. In addition,
/// all memrefs with non-trivial layout maps are converted to ones with trivial
/// identity layout ones.
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<OpPassBase<FuncOp>> mlir::createSimplifyAffineStructuresPass() {
return std::make_unique<SimplifyAffineStructures>();
}
void SimplifyAffineStructures::runOnFunction() {
auto func = getFunction();
simplifiedAttributes.clear();
func.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);
}
});
// Turn memrefs' non-identity layouts maps into ones with identity. Collect
// alloc ops first and then process since normalizeMemRef replaces/erases ops
// during memref rewriting.
SmallVector<AllocOp, 4> allocOps;
func.walk([&](AllocOp op) { allocOps.push_back(op); });
for (auto allocOp : allocOps) {
normalizeMemRef(allocOp);
}
}
static PassRegistration<SimplifyAffineStructures>
pass("simplify-affine-structures",
"Simplify affine expressions in maps/sets and normalize memrefs");
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