Assume MMX/SSE/SSE2 if targeting x64 on MSVC
MSVC doesn't define _M_IX86_FP when targeting x64.
# if (_M_IX86_FP >= 2)
# define SIMDE_ARCH_X86_SSE2 1
# endif
+# elif defined(_M_X64)
+# define SIMDE_ARCH_X86_MMX 1
+# define SIMDE_ARCH_X86_SSE 1
+# define SIMDE_ARCH_X86_SSE2 1
# else
# if defined(__MMX__)
# define SIMDE_ARCH_X86_MMX 1
