gallium/u_simple_shaders: Optimize out ffloors
What does this MR do and why?
gallium/u_simple_shaders: Optimize out ffloors
ffloor(f2i(x)) can't be optimized to f2i(x) due to differing behaviour for negative x, but u_blitter only uses this with nonnegative x so we can instead use ftrunc(f2i(x)) which NIR will optimize to f2i(x) for us. This gets rid of the silly ffloor instructions in blit shaders.
Signed-off-by: Alyssa Rosenzweig alyssa@rosenzweig.io