Enable userdata derivatives for interpolated parameters on the GPU.
When generating calls to osl_bind_interpolated_param in llvm_instance.cpp, the userdata_has_derivs field is set to true if the parameter's derivatives are needed, but the code does not take into account that on gpu there is no space allocated for these derivatives.
This leads to an incorrect derivatives pointer getting passed into the renderer, which the renderer will use to write into unrelated groupdata fields.
For our renders, getting the correct image was worth the 1-2% inflation of groupdata struct size that we observed by simply re-enabling gpu userdata derivatives. If desired, adding an option to turn them on/off is straightforward, but I didn't want to preemptively bloat the code if it's not necessary.
Description
Enable userdata derivatives for interpolated parameters on the GPU.
When generating calls to
osl_bind_interpolated_paramin llvm_instance.cpp, theuserdata_has_derivsfield is set to true if the parameter's derivatives are needed, but the code does not take into account that on gpu there is no space allocated for these derivatives.This leads to an incorrect derivatives pointer getting passed into the renderer, which the renderer will use to write into unrelated groupdata fields.
For our renders, getting the correct image was worth the 1-2% inflation of groupdata struct size that we observed by simply re-enabling gpu userdata derivatives. If desired, adding an option to turn them on/off is straightforward, but I didn't want to preemptively bloat the code if it's not necessary.
Tests
Checklist: