+/*
+ * Determine whether SSE2 intrinsics are understood by the compiler.
+ * Right now, we restrict ourselves to compiler versions where things
+ * are documented to work well:
+ * -- GCC 4.4+ and Clang 3.7+ understand the function attribute "target"
+ * -- MS Visual Studio 2005 documents the existence of <emmintrin.h>
+ * SSE2-powered code _might_ work with older versions, but there is no
+ * pressing need to do so right now.
+ */
+#ifndef BR_SSE2
+#if (__i386__ || __x86_64__) \
+ && ((__GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 4)) \
+ || (__clang_major__ > 3 \
+ || (__clang_major__ == 3 && __clang_minor__ >= 7)))
+#define BR_SSE2 1
+#elif (_M_IX86 || _M_X64) && (_MSC_VER >= 1400)
+#define BR_SSE2 1
+#endif
+#endif
+
+/*
+ * If we use SSE2 intrinsics, determine the compiler brand.
+ */
+#if BR_SSE2
+#ifndef BR_SSE2_GCC
+#if __GNUC__
+#define BR_SSE2_GCC 1
+#endif
+#endif
+#ifndef BR_SSE2_MSC
+#if _MSC_VER >= 1400
+#define BR_SSE2_MSC 1
+#endif
+#endif
+#endif
+