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//===- DuplicateFunctionElimination.cpp - Duplicate function elimination --===//
//
// 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/Func/IR/FuncOps.h"
#include "mlir/Dialect/Func/Transforms/Passes.h"
namespace mlir {
namespace {
#define GEN_PASS_DEF_DUPLICATEFUNCTIONELIMINATIONPASS
#include "mlir/Dialect/Func/Transforms/Passes.h.inc"
// Define a notion of function equivalence that allows for reuse. Ignore the
// symbol name for this purpose.
struct DuplicateFuncOpEquivalenceInfo
: public llvm::DenseMapInfo<func::FuncOp> {
static unsigned getHashValue(const func::FuncOp cFunc) {
if (!cFunc) {
return DenseMapInfo<func::FuncOp>::getHashValue(cFunc);
}
// Aggregate attributes, ignoring the symbol name.
llvm::hash_code hash = {};
func::FuncOp func = const_cast<func::FuncOp &>(cFunc);
StringAttr symNameAttrName = func.getSymNameAttrName();
for (NamedAttribute namedAttr : cFunc->getAttrs()) {
StringAttr attrName = namedAttr.getName();
if (attrName == symNameAttrName)
continue;
hash = llvm::hash_combine(hash, namedAttr);
}
// Also hash the func body.
func.getBody().walk([&](Operation *op) {
hash = llvm::hash_combine(
hash, OperationEquivalence::computeHash(
op, /*hashOperands=*/OperationEquivalence::ignoreHashValue,
/*hashResults=*/OperationEquivalence::ignoreHashValue,
OperationEquivalence::IgnoreLocations));
});
return hash;
}
static bool isEqual(func::FuncOp lhs, func::FuncOp rhs) {
if (lhs == rhs)
return true;
if (lhs == getTombstoneKey() || lhs == getEmptyKey() ||
rhs == getTombstoneKey() || rhs == getEmptyKey())
return false;
// Check discardable attributes equivalence
if (lhs->getDiscardableAttrDictionary() !=
rhs->getDiscardableAttrDictionary())
return false;
// Check properties equivalence, ignoring the symbol name.
// Make a copy, so that we can erase the symbol name and perform the
// comparison.
auto pLhs = lhs.getProperties();
auto pRhs = rhs.getProperties();
pLhs.sym_name = nullptr;
pRhs.sym_name = nullptr;
if (pLhs != pRhs)
return false;
// Compare inner workings.
return OperationEquivalence::isRegionEquivalentTo(
&lhs.getBody(), &rhs.getBody(), OperationEquivalence::IgnoreLocations);
}
};
struct DuplicateFunctionEliminationPass
: public impl::DuplicateFunctionEliminationPassBase<
DuplicateFunctionEliminationPass> {
using DuplicateFunctionEliminationPassBase<
DuplicateFunctionEliminationPass>::DuplicateFunctionEliminationPassBase;
void runOnOperation() override {
auto module = getOperation();
// Find unique representant per equivalent func ops.
DenseSet<func::FuncOp, DuplicateFuncOpEquivalenceInfo> uniqueFuncOps;
DenseMap<StringAttr, func::FuncOp> getRepresentant;
DenseSet<func::FuncOp> toBeErased;
module.walk([&](func::FuncOp f) {
auto [repr, inserted] = uniqueFuncOps.insert(f);
getRepresentant[f.getSymNameAttr()] = *repr;
if (!inserted) {
toBeErased.insert(f);
}
});
// Update call ops to call unique func op representants.
module.walk([&](func::CallOp callOp) {
func::FuncOp callee = getRepresentant[callOp.getCalleeAttr().getAttr()];
callOp.setCallee(callee.getSymName());
});
// Erase redundant func ops.
for (auto it : toBeErased) {
it.erase();
}
}
};
} // namespace
std::unique_ptr<Pass> mlir::func::createDuplicateFunctionEliminationPass() {
return std::make_unique<DuplicateFunctionEliminationPass>();
}
} // namespace mlir
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