Use union for MSLFormatInfo

Author: etang-cw

spirv_msl.hpp

@@ -368,20 +368,44 @@ enum class MSLFormatPacking : uint16_t
 };
 
 /// Describes the details of an MSLFormat necessary for easily generating vertex loading code
-struct MSLFormatInfo
+union MSLFormatInfo
 {
-	uint16_t log2_align : 2; ///< log2(minimum msl alignment)
-	uint16_t num_elems : 3;
-	MSLFormatPacking packing : 3;
-	uint16_t is_float : 1;
-	uint16_t is_signed : 1;
-	uint16_t is_normalized : 1;
-	uint16_t is_packed : 1; ///< Is packed in MSL
-	uint16_t vk_packed : 1; ///< Is packed in Vulkan but not MSL
-	uint16_t is_bgr : 1;
-	uint16_t is_srgb : 1;
-	uint16_t _pad : 1;
-
+	struct
+	{
+		uint16_t log2_align : 2; ///< log2(minimum msl alignment)
+		uint16_t num_elems : 3;
+		MSLFormatPacking packing : 3;
+		uint16_t is_float : 1;
+		uint16_t is_signed : 1;
+		uint16_t is_normalized : 1;
+		uint16_t is_packed : 1; ///< Is packed in MSL
+		uint16_t vk_packed : 1; ///< Is packed in Vulkan but not MSL
+		uint16_t is_bgr : 1;
+		uint16_t is_srgb : 1;
+		uint16_t _pad : 1;
+	};
+	uint16_t bits;
+
+	constexpr MSLFormatInfo(uint16_t log2_align, uint16_t num_elems, MSLFormatPacking packing, bool is_float,
+	                        bool is_signed, bool is_normalized, bool is_packed, bool vk_packed, bool is_bgr,
+	                        bool is_srgb)
+	    : log2_align(log2_align)
+	    , num_elems(num_elems)
+	    , packing(packing)
+	    , is_float(is_float)
+	    , is_signed(is_signed)
+	    , is_normalized(is_normalized)
+	    , is_packed(is_packed)
+	    , vk_packed(vk_packed)
+	    , is_bgr(is_bgr)
+	    , is_srgb(is_srgb)
+	    , _pad(0)
+	{
+	}
+	constexpr MSLFormatInfo()
+	    : bits(0)
+	{
+	}
 	constexpr uint32_t align() const
 	{
 		return 1 << log2_align;
@@ -400,8 +424,8 @@ struct MSLFormatInfo
 	}
 	uint16_t raw_value() const
 	{
-		static_assert(sizeof(MSLFormatInfo) == sizeof(uint16_t), "Size check");
-		return *reinterpret_cast<const uint16_t *>(this);
+		static_assert(sizeof(MSLFormatInfo) == sizeof(bits), "Size check");
+		return bits;
 	}
 	bool operator==(const MSLFormatInfo &other) const
 	{

spirv_msl_vertex_loader.cpp

@@ -155,7 +155,7 @@ const MSLFormatInfo &CompilerMSL::get_format_info(MSLFormat format)
 	};
 	// clang-format off
 #define FORMAT(log2_align, elems, packing, type, packed, order, vk_packed) \
-	MSLFormatInfo{ \
+	MSLFormatInfo( \
 		/* log2_align = */ log2_align, \
 		/* num_elems = */ elems, \
 		/* packing = */ MSLFormatPacking::packing, \
@@ -165,9 +165,8 @@ const MSLFormatInfo &CompilerMSL::get_format_info(MSLFormat format)
 		/* is_packed = */ packed, \
 		/* vk_packed = */ vk_packed, \
 		/* is_bgr = */ (PixelOrder::order == PixelOrder::BGR), \
-		/* is_srgb = */ (Type::type == Type::SRGB), \
-		/* _pad = */ 0, \
-	}
+		/* is_srgb = */ (Type::type == Type::SRGB) \
+	)
 #define SIMPLE_FORMAT_VK_PACKED(log2_align, elems, type, order) FORMAT(log2_align, elems, EvenAHigh, type, false, order, true)
 #define SIMPLE_FORMAT(log2_align, elems, type, order) FORMAT(log2_align, elems, EvenAHigh, type, false, order, false)
 #define PACKED_FORMAT(log2_align, elems, packing, type, order) FORMAT(log2_align, elems, packing, type, true, order, false)