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/*
* Copyright 2023 WebAssembly Community Group participants
*
* 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.
*/
#include "stringify-walker.h"
namespace wasm {
size_t StringifyHasher::operator()(Expression* curr) const {
if (Properties::isControlFlowStructure(curr)) {
if (auto* iff = curr->dynCast<If>()) {
size_t digest = wasm::hash(iff->_id);
rehash(digest, ExpressionAnalyzer::hash(iff->ifTrue));
if (iff->ifFalse) {
rehash(digest, ExpressionAnalyzer::hash(iff->ifFalse));
}
return digest;
}
return ExpressionAnalyzer::hash(curr);
}
return ExpressionAnalyzer::shallowHash(curr);
}
bool StringifyEquator::operator()(Expression* lhs, Expression* rhs) const {
if (Properties::isControlFlowStructure(lhs) &&
Properties::isControlFlowStructure(rhs)) {
auto* iffl = lhs->dynCast<If>();
auto* iffr = rhs->dynCast<If>();
if (iffl && iffr) {
return ExpressionAnalyzer::equal(iffl->ifTrue, iffr->ifTrue) &&
ExpressionAnalyzer::equal(iffl->ifFalse, iffr->ifFalse);
}
return ExpressionAnalyzer::equal(lhs, rhs);
}
return ExpressionAnalyzer::shallowEqual(lhs, rhs);
}
void HashStringifyWalker::addUniqueSymbol() {
// Use a negative value to distinguish symbols for separators from symbols
// for Expressions
assert((uint32_t)nextSeparatorVal >= nextVal);
hashString.push_back((uint32_t)nextSeparatorVal);
nextSeparatorVal--;
}
void HashStringifyWalker::visitExpression(Expression* curr) {
auto [it, inserted] = exprToCounter.insert({curr, nextVal});
hashString.push_back(it->second);
if (inserted) {
nextVal++;
}
}
// Deduplicate substrings by iterating through the list of substrings, keeping
// only those whose list of end indices is disjoint from the set of end indices
// for all substrings kept so far. Substrings that are contained within other
// substrings will always share an end index with those other substrings. Note
// that this deduplication may be over-aggressive, since it will remove
// substrings that are contained within any previous substring, even if they
// have many other occurrences that are not inside other substrings. Part of the
// reason dedupe can be so aggressive is an assumption 1) that the input
// substrings have been sorted so that the longest substrings with the most
// repeats come first and 2) these are more worthwhile to keep than subsequent
// substrings of substrings, even if they appear more times.
std::vector<SuffixTree::RepeatedSubstring> StringifyProcessor::dedupe(
const std::vector<SuffixTree::RepeatedSubstring> substrings) {
std::unordered_set<uint32_t> seen;
std::vector<SuffixTree::RepeatedSubstring> result;
for (auto substring : substrings) {
std::vector<uint32_t> idxToInsert;
bool seenEndIdx = false;
for (auto startIdx : substring.StartIndices) {
// We are using the end index to ensure that each repeated substring
// reported by the SuffixTree is unique. This is because LLVM's SuffixTree
// reports back repeat sequences that are substrings of longer repeat
// sequences with the same endIdx, and we generally prefer to outline
// longer repeat sequences.
uint32_t endIdx = substring.Length + startIdx;
if (seen.count(endIdx)) {
seenEndIdx = true;
break;
}
idxToInsert.push_back(endIdx);
}
if (!seenEndIdx) {
seen.insert(idxToInsert.begin(), idxToInsert.end());
result.push_back(substring);
}
}
return result;
}
} // namespace wasm
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