Introduce simd32_t type.

Discontinue use of disagreeable __SIMD #define.

firmware/common/simd.hpp

@@ -28,6 +28,30 @@
 
 #include <cstdint>
 
+template<typename T>
+struct simd32_t {
+	union {
+		uint32_t raw;
+		T vec;
+	};
+
+	operator uint32_t() const {
+		return raw;
+	}
+
+	simd32_t& operator=(uint32_t v) {
+		raw = v;
+		return *this;
+	}
+
+	static_assert(sizeof(raw) == sizeof(vec), "simd32_t types are not the same size.");
+};
+
+template<typename T>
+simd32_t<T>* simd32_ptr(T* const p) {
+	return reinterpret_cast<simd32_t<T>*>(p);
+}
+
 struct vec4_s8 {
 	union {
 		int8_t v[4];