Function _mm_round_sd

pub unsafe fn _mm_round_sd(
    a: __m128d,
    b: __m128d,
    const ROUNDING: i32,
) -> __m128d

Available on (x86 or x86-64) and target feature sse4.1 and x86 only.

Round the lower double-precision (64-bit) floating-point element in b using the ROUNDING parameter, store the result as a double-precision floating-point element in the lower element of the intrinsic result, and copies the upper element from a to the upper element of the intrinsic result. Rounding is done according to the rounding parameter, which can be one of:

#[cfg(target_arch = "x86")]
use std::arch::x86::*;
#[cfg(target_arch = "x86_64")]
use std::arch::x86_64::*;

// round to nearest, and suppress exceptions:
_MM_FROUND_TO_NEAREST_INT | _MM_FROUND_NO_EXC;
// round down, and suppress exceptions:
_MM_FROUND_TO_NEG_INF | _MM_FROUND_NO_EXC;
// round up, and suppress exceptions:
_MM_FROUND_TO_POS_INF | _MM_FROUND_NO_EXC;
// truncate, and suppress exceptions:
_MM_FROUND_TO_ZERO | _MM_FROUND_NO_EXC;
// use MXCSR.RC; see `_MM_SET_ROUNDING_MODE`:
_MM_FROUND_CUR_DIRECTION;

Intel’s documentation