Shader: Add constant cast optimization

src/Nazara/Shader/Ast/ConstantValue.cpp

@@ -0,0 +1,40 @@
+// Copyright (C) 2020 Jérôme Leclercq
+// This file is part of the "Nazara Engine - Shader generator"
+// For conditions of distribution and use, see copyright notice in Config.hpp
+
+#include <Nazara/Shader/Ast/ConstantValue.hpp>
+#include <Nazara/Shader/Debug.hpp>
+
+namespace Nz::ShaderAst
+{
+	ExpressionType GetExpressionType(const ConstantValue& constant)
+	{
+		return std::visit([&](auto&& arg) -> ShaderAst::ExpressionType
+		{
+			using T = std::decay_t<decltype(arg)>;
+
+			if constexpr (std::is_same_v<T, bool>)
+				return PrimitiveType::Boolean;
+			else if constexpr (std::is_same_v<T, float>)
+				return PrimitiveType::Float32;
+			else if constexpr (std::is_same_v<T, Int32>)
+				return PrimitiveType::Int32;
+			else if constexpr (std::is_same_v<T, UInt32>)
+				return PrimitiveType::UInt32;
+			else if constexpr (std::is_same_v<T, Vector2f>)
+				return VectorType{ 2, PrimitiveType::Float32 };
+			else if constexpr (std::is_same_v<T, Vector3f>)
+				return VectorType{ 3, PrimitiveType::Float32 };
+			else if constexpr (std::is_same_v<T, Vector4f>)
+				return VectorType{ 4, PrimitiveType::Float32 };
+			else if constexpr (std::is_same_v<T, Vector2i32>)
+				return VectorType{ 2, PrimitiveType::Int32 };
+			else if constexpr (std::is_same_v<T, Vector3i32>)
+				return VectorType{ 3, PrimitiveType::Int32 };
+			else if constexpr (std::is_same_v<T, Vector4i32>)
+				return VectorType{ 4, PrimitiveType::Int32 };
+			else
+				static_assert(AlwaysFalse<T>::value, "non-exhaustive visitor");
+		}, constant);
+	}
+}