This is supported on

**WebAssembly and target feature**only.`simd128`

## Expand description

Saturating conversion of the two double-precision floating point lanes to
two lower integer lanes using the IEEE `convertToIntegerTowardZero`

function.

The two higher lanes of the result are initialized to zero. If any input lane is a NaN, the resulting lane is 0. If the rounded integer value of a lane is outside the range of the destination type, the result is saturated to the nearest representable integer value.