Implicit sharing dramatically reduces the cost of coping geometry
which is extremely helpful for read-only and slight modification.
But case of Sort Elements node implies a total rewrite of whole domain,
so implicit sharing only adds redundant cost for write access. This fix
uses kernel API to create domains without attributes, manually forcing
implicit sharing for offset indices and uses kernel attribute copy
functions to force sharing for all attributes when this is possible.
In all other cases new attributes are created from scratch and copied
as re-ordered only once.
In attached example file shown the difference depend on the number of
attributes on the mesh, benchmark result:
| Attributes | Before | After |
| ---------- | ------ | ----- |
| 1 | 2 ms | 1.5 ms |
| 5 | 5 ms | 4 ms |
| 10 | 9 ms | 6 ms |
| 50 | 45 ms | 30 ms |
| 100 | 89 ms | 59 ms |
Pull Request: https://projects.blender.org/blender/blender/pulls/117910
9d13e39585