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//===- DIExpressionRewriter.cpp - Rewriter for DIExpression operators -----===//
//
// 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/LLVMIR/Transforms/DIExpressionRewriter.h"
#include "llvm/Support/DebugLog.h"
using namespace mlir;
using namespace LLVM;
#define DEBUG_TYPE "llvm-di-expression-simplifier"
//===----------------------------------------------------------------------===//
// DIExpressionRewriter
//===----------------------------------------------------------------------===//
void DIExpressionRewriter::addPattern(
std::unique_ptr<ExprRewritePattern> pattern) {
patterns.emplace_back(std::move(pattern));
}
DIExpressionAttr
DIExpressionRewriter::simplify(DIExpressionAttr expr,
std::optional<uint64_t> maxNumRewrites) const {
ArrayRef<OperatorT> operators = expr.getOperations();
// `inputs` contains the unprocessed postfix of operators.
// `result` contains the already finalized prefix of operators.
// Invariant: concat(result, inputs) is equivalent to `operators` after some
// application of the rewrite patterns.
// Using a deque for inputs so that we have efficient front insertion and
// removal. Random access is not necessary for patterns.
std::deque<OperatorT> inputs(operators.begin(), operators.end());
SmallVector<OperatorT> result;
uint64_t numRewrites = 0;
while (!inputs.empty() &&
(!maxNumRewrites || numRewrites < *maxNumRewrites)) {
bool foundMatch = false;
for (const std::unique_ptr<ExprRewritePattern> &pattern : patterns) {
ExprRewritePattern::OpIterT matchEnd = pattern->match(inputs);
if (matchEnd == inputs.begin())
continue;
foundMatch = true;
SmallVector<OperatorT> replacement =
pattern->replace(llvm::make_range(inputs.cbegin(), matchEnd));
inputs.erase(inputs.begin(), matchEnd);
inputs.insert(inputs.begin(), replacement.begin(), replacement.end());
++numRewrites;
break;
}
if (!foundMatch) {
// If no match, pass along the current operator.
result.push_back(inputs.front());
inputs.pop_front();
}
}
if (maxNumRewrites && numRewrites >= *maxNumRewrites) {
LDBG() << "LLVMDIExpressionSimplifier exceeded max num rewrites ("
<< maxNumRewrites << ")";
// Skip rewriting the rest.
result.append(inputs.begin(), inputs.end());
}
return LLVM::DIExpressionAttr::get(expr.getContext(), result);
}
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