From cbfb7d182a4e90e4e263696d1fca35e47d3eabb4 Mon Sep 17 00:00:00 2001
From: ReinUsesLisp <reinuseslisp@airmail.cc>
Date: Sun, 14 Feb 2021 20:15:42 -0300
Subject: shader: Support SSA loops on IR

---
 src/shader_recompiler/frontend/ir/function.h     |  1 +
 src/shader_recompiler/frontend/ir/post_order.cpp | 48 ++++++++++++++++++++++++
 src/shader_recompiler/frontend/ir/post_order.h   | 13 +++++++
 3 files changed, 62 insertions(+)
 create mode 100644 src/shader_recompiler/frontend/ir/post_order.cpp
 create mode 100644 src/shader_recompiler/frontend/ir/post_order.h

(limited to 'src/shader_recompiler/frontend/ir')

diff --git a/src/shader_recompiler/frontend/ir/function.h b/src/shader_recompiler/frontend/ir/function.h
index fd7d56419..d1f061146 100644
--- a/src/shader_recompiler/frontend/ir/function.h
+++ b/src/shader_recompiler/frontend/ir/function.h
@@ -12,6 +12,7 @@ namespace Shader::IR {
 
 struct Function {
     BlockList blocks;
+    BlockList post_order_blocks;
 };
 
 } // namespace Shader::IR
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
diff --git a/src/shader_recompiler/frontend/ir/post_order.h b/src/shader_recompiler/frontend/ir/post_order.h
new file mode 100644
index 000000000..30137ff57
--- /dev/null
+++ b/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
-- 
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