[Mesa-dev] Accelerated meta CopyTexSubImage

[Eric Anholt]

Here's a rework of the series for meta CopyTexSubImage (required for
i965's gen8 support, since we're probably going to avoid doing blorp at
all for it).  Ken had almost-reviewed a previous version of the patch, but
I went back and did some refactors before it that bring this feature
improvement to a net lines of code reduction while hopefully improving
performance on older drivers at the same time.