> On Oct 5, 2017, at 11:28 PM, Alexander Monakov <amona...@ispras.ru> wrote: > > On Thu, 5 Oct 2017, Maxim Kuvyrkov wrote: >> I'm still working on analysis, but it appears to me that Alexander's patch >> (current state of trunk) fails qsort check due to not being symmetric for >> load/store analysis (write == 0 or write == 1) in comparisons with >> "irrelevant" instructions. Wilco's patch does not seem to address that, and, >> possibly, makes the failure latent (I may be wrong here, it's late and I >> didn't finish analysis yet). > > Yes, your analysis is incomplete, it should be easy to see that for > always-false > multi_mem_insn_p, autopref_rank_for_schedule implements lexicographical order. > The problem is that when multi_mem_insn_p may be true, autopref_rank_data is > not guaranteed to be transitive.
Agree. > > I think your patch loses transitivity in autopref_rank_for_schedule, see > Wilco's > response. Agree. > > FWIW, this hunk from my patch posted back on Friday is sufficient to restore > bootstrap as confirmed (again, back on Friday) by Steve. It avoids the fancy > non-transitive comparison for qsort (but autopref_rank_data is still used in > multipref_dfa_lookahead_guard). > > (I'm surprised Kyrill wasn't Cc'ed - adding him now) > > Alexander > > * haifa-sched.c (autopref_rank_for_schedule): Do not invoke > autopref_rank_data, order by min_offset. > > diff --git a/gcc/haifa-sched.c b/gcc/haifa-sched.c > index 549e8961411..cea1242e1f1 100644 > --- a/gcc/haifa-sched.c > +++ b/gcc/haifa-sched.c > @@ -5725,7 +5669,7 @@ autopref_rank_for_schedule (const rtx_insn *insn1, > const rtx_insn *insn2) > int irrel2 = data2->status == AUTOPREF_MULTIPASS_DATA_IRRELEVANT; > > if (!irrel1 && !irrel2) > - r = autopref_rank_data (data1, data2); > + r = data1->min_offset - data2->min_offset; > else > r = irrel2 - irrel1; > } I think that this is the best solution so far. Could you add a comment like the following? == Ideally, we would call autopref_rank_data() here, but we can't since it is not guaranteed to return transitive results fro multi_mem_insns. We use an approximation here and rely on lookahead_guard below to force instruction order according to autopref_rank_data(). == I think that the above patch qualifies as obvious to unbreak the bootstrap. Wilco, any objection to the above fix? Regards, -- Maxim Kuvyrkov www.linaro.org
