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// Copyright 2021 yuzu Emulator Project
// Licensed under GPLv2 or any later version
// Refer to the license.txt file included.
#pragma once
#include <optional>
#include <type_traits>
#include <queue>
#include <boost/container/small_vector.hpp>
#include "shader_recompiler/frontend/ir/microinstruction.h"
#include "shader_recompiler/frontend/ir/value.h"
namespace Shader::IR {
template <typename Pred>
auto BreadthFirstSearch(const Value& value, Pred&& pred)
-> std::invoke_result_t<Pred, const Inst*> {
if (value.IsImmediate()) {
// Nothing to do with immediates
return std::nullopt;
}
// Breadth-first search visiting the right most arguments first
// Small vector has been determined from shaders in Super Smash Bros. Ultimate
boost::container::small_vector<const Inst*, 2> visited;
std::queue<const Inst*> queue;
queue.push(value.InstRecursive());
while (!queue.empty()) {
// Pop one instruction from the queue
const Inst* const inst{queue.front()};
queue.pop();
if (const std::optional result = pred(inst)) {
// This is the instruction we were looking for
return result;
}
// Visit the right most arguments first
for (size_t arg = inst->NumArgs(); arg--;) {
const Value arg_value{inst->Arg(arg)};
if (arg_value.IsImmediate()) {
continue;
}
// Queue instruction if it hasn't been visited
const Inst* const arg_inst{arg_value.InstRecursive()};
if (std::ranges::find(visited, arg_inst) == visited.end()) {
visited.push_back(arg_inst);
queue.push(arg_inst);
}
}
}
// SSA tree has been traversed and the result hasn't been found
return std::nullopt;
}
} // namespace Shader::IR
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