knc.h
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

1. pmulus_vi64.ispc (-O2)
The root of the broblem is in the code generator - it assumes __vec16_i64 stores its elements sequentually in memory,
not high and low parts separately as we do. Consequently, this construction works incorrectly

```
__vec16_i64 (((uint64_t *)(&tmp__2_))[0], ((uint64_t *)(&tmp__2_))[0], ((uint64_t *)(&tmp__2_))[0], ((uint64_t
*)(&tmp__2_))[0], ((uint64_t *)(&tmp__2_))[0], ((uint64_t *)(&tmp__2_))[0], ((uint64_t *)(&tmp__2_))[0], ((uint64_t
*)(&tmp__2_))[0], ((uint64_t *)(&tmp__2_))[0], ((uint64_t *)(&tmp__2_))[0], ((uint64_t *)(&tmp__2_))[0], ((uint64_t
*)(&tmp__2_))[0], ((uint64_t *)(&tmp__2_))[0], ((uint64_t *)(&tmp__2_))[0], ((uint64_t *)(&tmp__2_))[0], ((uint64_t
*)(&tmp__2_))[0]
```
where 'tmp__2_' is of  __vec16_i64 data type.

2. soa-18.ispc (-O0)
The same as (1). The generator uses the structure of a kind
```
struct l_unnamed_0 {
  __vec16_i64 field0;
  __vec16_i32 field1;
} ptr_;
```
and a function
```
  __masked_store_i64(((&ptr_.field0)), _slice_ptr7_slice_offset_extract_0_, internal_mask_26_function_mask9_);
```

where '_slice_ptr7_slice_offset_extract_0_' is of type __vec16_i64. The
problem is, we store 64 bit ints in memory sequentually and in vectors
separately (hi and lo parts). This way, the '.field0' has wrong layout