AVX512CD contains the intrinsic _mm512_conflict_epi32(__m512i a) it returns a vector where for every element in a a bit is set if it has the same value. Is there a way to do something similar in AVX2?
I'm not interested in the extact bits I just need to know which elements are duplicates of the elements to their left (or right). I simply need to know if a scatter would conflict.
Basically I need an AVX2 equivalent for
__mm256i detect_conflict(__mm256i a) {
__mm256i cd = _mm256_conflict_epi32(a);
return _mm256_cmpgt_epi32(cd, _mm256_set1_epi32(0));
}
The only way I could think of is to use _mm256_permutevar8x32_epi32() shift each value right by 1 (across the lanes) and than do seven compares, mask out the unsed bits and than _mm256_or_si256() them together which is horribly slow.