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-rw-r--r--src/shader_recompiler/frontend/ir/breadth_first_search.h57
1 files changed, 57 insertions, 0 deletions
diff --git a/src/shader_recompiler/frontend/ir/breadth_first_search.h b/src/shader_recompiler/frontend/ir/breadth_first_search.h
new file mode 100644
index 000000000..b35f062d4
--- /dev/null
+++ b/src/shader_recompiler/frontend/ir/breadth_first_search.h
@@ -0,0 +1,57 @@
+// 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