X86 target does not provide any target specific cost calculation for interleave patterns. It uses the common target-independent calculation, which gives very high numbers.
As a result, the scalar version is chosen in many cases. The situation on AVX-512 is even worse, since we have 3-src shuffles that significantly reduce the cost.
In this patch I calculate the cost on AVX-512. It will allow to compare interleave pattern with gather/scatter and choose a better solution (PR31426).