shader: Support SSA loops on IR

src/shader_recompiler/frontend/ir/post_order.h

@@ -0,0 +1,13 @@
+// Copyright 2021 yuzu Emulator Project
+// Licensed under GPLv2 or any later version
+// Refer to the license.txt file included.
+
+#pragma once
+
+#include "shader_recompiler/frontend/ir/basic_block.h"
+
+namespace Shader::IR {
+
+BlockList PostOrder(const BlockList& blocks);
+
+} // namespace Shader::IR