## _mm256_castpd128_pd256

# Function _mm256_castpd128_pd256

1.27.0 (const: unstable) · Source

    pub fn _mm256_castpd128_pd256(a: __m128d) -> __m256d

Available on x86 and target feature `avx` only.
Expand description

Casts vector of type __m128d to type __m256d; the upper 128 bits of the result are indeterminate.

In the Intel documentation, the upper bits are declared to be “undefined”. This is not equivalent to `mem::MaybeUninit`; instead, these bits are non-deterministically set to some valid value. In practice, this is typically equivalent to `mem::zeroed`.

Intel’s documentation