[Mesa-dev] i965: Improving FS register spilling performance.

[Eric Anholt]

In the process of trying to work around the spilling in the huge unigine
soft shadowing shaders, I got to wondering if we couldn't just reduce the
cost of spilling to the point of "I don't care".  Notably, there is this
nice message for doing unspills on gen7 where you don't need to set up the
message beyond passing in g0.

It turns out to be a slight win.  Unfortunately, the complementary spill
message was a loss.  You can find the code in this submission on
gen7-scratch-read of my tree, and the code I'm not trying to push is on
gen7-scratch-write.