[Mesa-dev] V5 Loop unrolling in NIR

[Timothy Arceri]

Again thanks to Jason and Connor for their feedback, and to 
Thomas for getting this work started.

V5: Has been updated to reflect Jasons feedback and also some
changes from self review after not looking at this for a few weeks.

total instructions in shared programs: 8530600 -> 8530365 (-0.00%)
instructions in affected programs: 46967 -> 46732 (-0.50%)
helped: 62
HURT: 92

total cycles in shared programs: 67279552 -> 67251326 (-0.04%)
cycles in affected programs: 2548608 -> 2520382 (-1.11%)
helped: 925
HURT: 909

total loops in shared programs: 1868 -> 1214 (-35.01%)
loops in affected programs: 687 -> 33 (-95.20%)
helped: 655
HURT: 17

LOST:   5
GAINED: 0

Most of the HURT instruction count is caused by patch 1. See the
commit message for more details.

The HURT loops are caused by a couple of different things that can be
addressed in a follow up series. For example handling if statements
that contain a break but also other instructions.