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.
I think your patch loses transitivity in autopref_rank_for_schedule, see Wilco's
response.
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;
}
