Saves an intermediate temporary. See !3818 (merged)
Unfortunately, the win doesn't seem to be as big as I had hoped, or at least I'm not looking at the right benchmarks ... it doesn't appear that the x11perf benchmark used for Iris in the linked MR is even using tiled textures at all, so there's that. If there's a good benchmark that would hit this path, I'd be curious (Weston performance should theoretically be helped.)
If nothing else, this is negative knowledge?