Tune Swing Modulo Scheduling or Selective Scheduling for ARM

[Yao Qi]

GCC has two scheduling algorithms that support fancy loop optimizations: -fmodulo-sched and -fselective-scheduling / -fsel-sched-pipelining. When I tried them on FSF GCC mainline (2010-10-17), neither was super helpful for ARM.
Performance number can be found here https://wiki.linaro.org/YaoQi/Sandbox/Thumb2SpeedOptimization

They should be helpful on A-family processors where you have a lot of cache and pipeline to work with.

[codesourcery #6873]

[Yao Qi (yao-codesourcery)]

It is hard. If we can do it, we could improve a lot. The goal is to get the performance we get from loop unrolling with smaller code size.

[Michael Hope (michaelh1)]

Pulled SMS out into a blueprint:
 https://blueprints.launchpad.net/gcc-linaro/+spec/add-sms-support

[Michael Hope (michaelh1)]

Closed out as Revital is tracking this via blueprints.