shader: Use shared_ptr to store nodes and move initialization to file

Instead of having a vector of unique_ptr stored in a vector and
returning star pointers to this, use shared_ptr. While changing
initialization code, move it to a separate file when possible.

This is a first step to allow code analysis and node generation beyond
the ShaderIR class.

src/video_core/shader/node_helper.h

@@ -0,0 +1,60 @@
+// Copyright 2019 yuzu Emulator Project
+// Licensed under GPLv2 or any later version
+// Refer to the license.txt file included.
+
+#pragma once
+
+#include <memory>
+#include <string>
+#include <tuple>
+#include <type_traits>
+#include <utility>
+#include <vector>
+
+#include "common/common_types.h"
+#include "video_core/shader/shader_ir.h"
+
+namespace VideoCommon::Shader {
+
+/// Creates a conditional node
+Node Conditional(Node condition, std::vector<Node> code);
+
+/// Creates a commentary node
+Node Comment(std::string text);
+
+/// Creates an u32 immediate
+Node Immediate(u32 value);
+
+/// Creates a s32 immediate
+Node Immediate(s32 value);
+
+/// Creates a f32 immediate
+Node Immediate(f32 value);
+
+/// Converts an signed operation code to an unsigned operation code
+OperationCode SignedToUnsignedCode(OperationCode operation_code, bool is_signed);
+
+template <typename T, typename... Args>
+Node MakeNode(Args&&... args) {
+    static_assert(std::is_convertible_v<T, NodeData>);
+    return std::make_shared<NodeData>(T(std::forward<Args>(args)...));
+}
+
+template <typename... Args>
+Node Operation(OperationCode code, Args&&... args) {
+    if constexpr (sizeof...(args) == 0) {
+        return MakeNode<OperationNode>(code);
+    } else if constexpr (std::is_convertible_v<std::tuple_element_t<0, std::tuple<Args...>>,
+                                               Meta>) {
+        return MakeNode<OperationNode>(code, std::forward<Args>(args)...);
+    } else {
+        return MakeNode<OperationNode>(code, Meta{}, std::forward<Args>(args)...);
+    }
+}
+
+template <typename... Args>
+Node SignedOperation(OperationCode code, bool is_signed, Args&&... args) {
+    return Operation(SignedToUnsignedCode(code, is_signed), std::forward<Args>(args)...);
+}
+
+} // namespace VideoCommon::Shader