On Tue, Dec 20, 2016 at 11:27:18AM -0600, Pat Haugen wrote:
> This patch attempts to fix problems with the first scheduling pass creating
> too much register pressure. It does this by enabling the target hook to
> compute the pressure classes for rs6000 target since the first thing I
> observed while investigating the testcase in the subject PR is that IRA was
> picking NON_SPECIAL_REGS as a pressure class which led to the sched-pressure
> code computing too high of a value for number of regs available for pseudos
> preferring GENERAL_REGS. It also enables -fsched-pressure by default, using
> the 'model' algorithm.
>
> I ran various runs of cpu20006 to determine the set of pressure classes and
> which sched-pressure algorithm to use. Net result is that with these patches
> I see 6 benchmarks improve in the 2.4-6% range but there are also a couple 2%
> degradations which will need follow up in GCC 8. There was also one benchmark
> that showed a much bigger improvement with the 'weighted' sched-pressure
> algorithm that also needs follow up ('weighted' was not chosen as default
> since it showed more degradations).
>
> Bootstrap/regtest on powerpc64/powerpc64le. There were 2 testcases that
> failed (sms-3.c/sms-6.c) but I have submitted a separate patch to fix those.
> Ok for trunk?
Okay. Thanks!
Segher
> 2016-12-20 Pat Haugen <pthau...@us.ibm.com>
>
> PR rtl-optimization/11488
> * common/config/rs6000/rs6000-common.c
> (rs6000_option_optimization_table): Enable -fsched-pressure.
> * config/rs6000/rs6000.c (TARGET_COMPUTE_PRESSURE_CLASSES): Define
> target hook.
> (rs6000_option_override_internal): Set default -fsched-pressure
> algorithm.
> (rs6000_compute_pressure_classes): Implement target hook.
