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RandomizeBranchHints.cpp
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73 lines (61 loc) · 1.85 KB
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/*
* Copyright 2025 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.
*/
//
// Apply random branch hints. This is really only useful for fuzzing. The
// randomness here is deterministic, so that reducing can work.
//
#include "pass.h"
#include "support/hash.h"
#include "wasm-builder.h"
#include "wasm.h"
namespace wasm {
struct RandomizeBranchHints
: public WalkerPass<
PostWalker<RandomizeBranchHints,
UnifiedExpressionVisitor<RandomizeBranchHints>>> {
uint64_t hash = 42;
void visitExpression(Expression* curr) {
// Add some deterministic randomness as we go.
deterministic_hash_combine(hash, curr->_id);
}
void visitIf(If* curr) {
deterministic_hash_combine(hash, 1337);
processCondition(curr);
}
void visitBreak(Break* curr) {
deterministic_hash_combine(hash, 99999);
if (curr->condition) {
processCondition(curr);
}
}
// TODO: BrOn
template<typename T> void processCondition(T* curr) {
auto& likely = getFunction()->codeAnnotations[curr].branchLikely;
switch (hash % 3) {
case 0:
likely = true;
break;
case 1:
likely = false;
break;
case 2:
likely = {};
break;
}
}
};
Pass* createRandomizeBranchHintsPass() { return new RandomizeBranchHints(); }
} // namespace wasm