GCC 10 Switches Arm's Scheduling-Pressure Algorithm For Better Performance

[phoronix]

Phoronix: GCC 10 Switches Arm's Scheduling-Pressure Algorithm For Better Performance

A minor optimization was merged into GCC 10 last week for benefiting those on Arm compiling their code with the GNU Compiler Collection...

http://www.phoronix.com/scan.php?page=news_item&px=GCC-10-Arm-Pressure-Sched-Algo

[hotaru]

why were they using the alternate algorithm in the first place if the default one is so much better?

[trubicoid2]

From man gcc:

--param sched-pressure-algorithm

Choose between the two available implementations of -fsched-pressure. Algorithm 1 is the original implementation and is the more likely to prevent instructions from being reordered. Algorithm 2 was designed to be a compromise between the relatively conservative approach taken by algorithm 1 and the rather aggressive approach taken by the default scheduler. It relies more heavily on having a regular register file and accurate register pressure classes. See haifa-sched.c in the GCC sources for more details.

The default choice depends on the target.