Constant core::arch::x86_64::_MM_FROUND_NEARBYINT

pub const _MM_FROUND_NEARBYINT: i32 = _MM_FROUND_NO_EXC | _MM_FROUND_CUR_DIRECTION; // 12i32

This is supported on x86-64 only.

use MXCSR.RC and suppress exceptions; see vendor::_MM_SET_ROUNDING_MODE