On Wed, 4 Jul 2018, Kugan Vivekanandarajah wrote: > We noticed a difference in the code generated for aarch64 gcc 7.2 > hosted in Linux vs mingw. AFIK, we are supposed to produce the same > output. > > For the testacse we have (quite large and I am trying to reduce), the > difference comes from sched1 pass. If I disable sched1 the difference > is going away. > > Is this a known issue? Attached is the sched1 dump snippet where there > is the difference.
The rank_for_schedule comparator used for qsort in the scheduler is known to be invalid; some issues have been fixed in gcc-8, but some remain (you can search the bugzilla for qsort_chk issues). Since the comparator is invalid, different qsort implementations reorder the ready list differently. In gcc-9 qsort calls use gcc_qsort instead and thus wouldn't diverge. Alexander
