[Pixman] pixman general_composite_rect

[kb pachauri]

Hi,

I am working for developing pixman with OpenCL (only compositing function),
and made it working, but performance is very very very slow..

Main reason for slow performance is basically doing compositing line by
line..
1) i think launching kernel per scan-line is too much overhead,
2) i think copying memory in scaline ways is also overhead.. (from host to
device) [general recommendation in gpgpu computing is copy all the data once
do the the task..]
3) also kernel are not optimized much (kernels are just combine function
which are there in pixman_composite_32.c)

after that i changed to launch the kernel for whole rectangle
(width*height), basically remove the height for loop in
general_composite_rect.. .
(i.e. get all the src, dest, mask data for widht & height (whole rectangular
area),  do the compositing)

now performance is much better than my last attempt.. (still not very
promising though)

how can i handle case where store var is not null i.e fetc dest, composite
line & store dest?


Thanks & Regards,
Pachauri
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