sum pairs in an AVX register

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intrinsics

AVX

i have an _m256 with 8 floats in it:



i want to add pairs of values : (0+4, 1+5, 2+6, 3+7)

__m256 i;

... i gets some values...
 and then...
i = {
   i.m256_f32[0] + i.m256_f32[4], 
   i.m256_f32[1] + i.m256_f32[5], 
   i.m256_f32[2] + i.m256_f32[6], 
   i.m256_f32[3] + i.m256_f32[7], 
   x, x, x, x
};

x = don't care

in SSE, i would shuffle the 4,5,6,7 into a new register then add the two, but i can't find any good docs for _mm256_shuffle_ps.

anyone know how to do this?