[Mesa-dev] i965: tiled-memcpy + subimages

[Chris Wilson]

I noticed when enabling "accelerated readback" with userptr enabling
writes directly into client memory was that we often missed the
tiled-memcpy fastpaths; in particular it did not handle subimages. Since
I was relying on the tiled-memcpy fastpath to avoid using the GPU for
readback where unnecessary, this is unfortunate! ;)

Quickly checking with x11perf on glamor (bdw) shows a slight benefit:

       1                 2                 Operation
------------   -------------------------   -------------------------
    587000.0       628000.0 (     1.070)   ShmPutImage 10x10 square 
     12100.0        13300.0 (     1.099)   ShmPutImage 500x500 square 
    114000.0       117000.0 (     1.026)   ShmGetImage 10x10 square 
     10700.0         9930.0 (     0.928)   ShmGetImage 500x500 square