Committed r128 Composite acceleration support for blending with no mask, no transform, and no repeat. It was a diff bounced around between myself and andersca, with andersca having written some of the most important bits. Unfortunately this doesn't cover any of what xcompmgr wants to do.
Took a look at whether xvideo could be done using the scaler like the Composite accel is. Although the scaling parts should be OK, it looks like the formats supported by the hardware don't match the formats desired by Xv. Or I'm failing to understand YUV formats, which is quite likely.
Spent a solid chunk of the day working on Radeon Render acceleration. I think I do have enough information in the end to do Composite cleanly on Radeon in Xati. The code is written, but nothing's being rendered yet. Not sure what's going on.