shader: Support SSA loops on IR

1 files changed, 48 insertions, 0 deletions

diff --git a/src/shader_recompiler/frontend/ir/post_order.cpp b/src/shader_recompiler/frontend/ir/post_order.cpp
new file mode 100644
index 000000000..a48b8dec5
--- /dev/null
+++ b/src/shader_recompiler/frontend/ir/post_order.cpp
@@ -0,0 +1,48 @@
+// Copyright 2021 yuzu Emulator Project
+// Licensed under GPLv2 or any later version
+// Refer to the license.txt file included.
+
+#include <boost/container/flat_set.hpp>
+#include <boost/container/small_vector.hpp>
+
+#include "shader_recompiler/frontend/ir/basic_block.h"
+#include "shader_recompiler/frontend/ir/post_order.h"
+
+namespace Shader::IR {
+
+BlockList PostOrder(const BlockList& blocks) {
+    boost::container::small_vector<Block*, 16> block_stack;
+    boost::container::flat_set<Block*> visited;
+
+    BlockList post_order_blocks;
+    post_order_blocks.reserve(blocks.size());
+
+    Block* const first_block{blocks.front()};
+    visited.insert(first_block);
+    block_stack.push_back(first_block);
+
+    const auto visit_branch = [&](Block* block, Block* branch) {
+        if (!branch) {
+            return false;
+        }
+        if (!visited.insert(branch).second) {
+            return false;
+        }
+        // Calling push_back twice is faster than insert on msvc
+        block_stack.push_back(block);
+        block_stack.push_back(branch);
+        return true;
+    };
+    while (!block_stack.empty()) {
+        Block* const block{block_stack.back()};
+        block_stack.pop_back();
+
+        if (!visit_branch(block, block->TrueBranch()) &&
+            !visit_branch(block, block->FalseBranch())) {
+            post_order_blocks.push_back(block);
+        }
+    }
+    return post_order_blocks;
+}
+
+} // namespace Shader::IR