[Mesa-dev] Loop unrolling and if statement opts

[Timothy Arceri]

This series started out as me trying to unrolls some useless loops I
spotted in some shaders from DXVK games (see patch 10), but I found
some other issues and improvements along the way.

The biggest winner seem like it could be the dolphin uber shaders on
i965 (on radeonsi the shaders don't seem to have spilling issues).
The loops in the uber shaders that are unrolled are those used as
wrappers around switchs by GLSL IR.

shader-db results for the series on IVB (note as the loops that are
unrolled only have a single iteration I enabled shader-db reporting
on shaders where loops are unrolled):

total instructions in shared programs: 10018187 -> 10016468 (-0.02%)
instructions in affected programs: 104080 -> 102361 (-1.65%)
helped: 36
HURT: 15

total cycles in shared programs: 220065064 -> 154529655 (-29.78%)
cycles in affected programs: 126063017 -> 60527608 (-51.99%)
helped: 51
HURT: 0

total loops in shared programs: 2515 -> 2308 (-8.23%)
loops in affected programs: 903 -> 696 (-22.92%)
helped: 51
HURT: 0

total spills in shared programs: 4370 -> 4124 (-5.63%)
spills in affected programs: 1397 -> 1151 (-17.61%)
helped: 9
HURT: 12

total fills in shared programs: 4581 -> 4419 (-3.54%)
fills in affected programs: 2201 -> 2039 (-7.36%)
helped: 9
HURT: 15