Wwise SDK 2018.1.11

Moves the lower two single-precision, floating-point values of b to the upper two single-precision, floating-point values of the result. The lower two single-precision, floating-point values of a are passed through to the result. r3 := b1 ; r2 := b0 ; r1 := a1 ; r0 := a0 (see _mm_movelh_ps)

AkSimd.h の 146 行目に定義があります。