On 27.02.19 17:20, Richard Henderson wrote:
> On 2/26/19 3:39 AM, David Hildenbrand wrote:
>> + for (dst_idx = 0; dst_idx < NUM_VEC_ELEMENTS(es); dst_idx++) {
>> + src_idx = dst_idx / 2;
>> + if (!high) {
>> + src_idx += NUM_VEC_ELEMENTS(es) / 2;
>> + }
>> + if (dst_idx % 2 == 0) {
>> + read_vec_element_i64(tmp, v2, src_idx, es);
>> + } else {
>> + read_vec_element_i64(tmp, v3, src_idx, es);
>> + }
>> + write_vec_element_i64(tmp, dst_v, dst_idx, es);
>> + }
>
> TODO: Note that you do not need a vector temporary here, so long as you load
> both source elements before writing, and you iterate in the proper direction.
>
> For VMRL, iterate forward as you do now. The element access order for MO_32:
>
> read v2: 2 3
> read v3: 2 3
> write v1: 0 1 2 3
>
> For VMRH, iterate backward:
>
> read v2: 1 0
> read v3: 1 0
> write v1: 3 2 1 0
>
>
> r~
>
Let's have a look for VMRH when iterating forward (My brain is a little
slow in the morning):
v1[0] = v2[0]
v1[1] = v3[0]
v1[2] = v2[1]
v1[3] = v3[1]
If all would overlap
v1[0] = v1[0]
v1[1] = v1[0] -> v1[0] already modified
v1[2] = v1[1] -> v1[1] already modified
v1[3] = v1[1] -> v1[1] already modified
When iterating backwards:
v1[3] = v3[1]
v1[2] = v2[1]
v1[1] = v3[0]
v1[0] = v2[0]
If all would overlap
v1[3] = v1[1]
v1[2] = v1[1]
v1[1] = v1[0]
v1[0] = v1[0]
VMRH when iterating forward:
v1[0] = v2[2]
v1[1] = v3[2]
v1[2] = v2[3]
v1[3] = v3[3]
If all would overlap
v1[0] = v1[2]
v1[1] = v1[2]
v1[2] = v1[3]
v1[3] = v1[3]
Perfect :) I'll split up the two cases! Thanks!
--
Thanks,
David / dhildenb
