Honza,
Thanks a lot for your information.
> On Mar 8, 2023, at 8:19 AM, Jan Hubicka <hubi...@ucw.cz> wrote:
>
>> Hi, Jan,
>>
>> I am studying one profiling feedback ICE bug with GCC8 recently.
>> It’s an assertion failure inside the routine “compute_working_sets”of
>> gcov-io.c:
>>
>> gcov_nonruntime_assert (ws_ix == NUM_GCOV_WORKING_SETS);
>>
>> After some debugging and study, I found that the corresponding .gcda file
>> has two PROGRAM_SUMMARY sections:
>>
>> foo.gcda: a3000000: 202:PROGRAM_SUMMARY checksum=0x91f3e3ae
>> foo.gcda: counts=10831, runs=0, sum_all=478965,
>> run_max=125615, sum_max=201126
>> foo.gcda: counter histogram:
>> foo.gcda: 0: num counts=10187, min counter=0, cum_counter=0
>> …
>> foo.gcda: 51: num counts=1, min counter=14524,
>> cum_counter=14524
>> foo.gcda: 63: num counts=1, min counter=125615,
>> cum_counter=125615
>> foo.gcda: a3000000: 137:PROGRAM_SUMMARY checksum=0xcf9f0896
>> foo.gcda: counts=10502, runs=1, sum_all=48618, run_max=13999,
>> sum_max=14046
>> foo.gcda: counter histogram:
>> foo.gcda: 0: num counts=9821, min counter=0, cum_counter=0
>> …
>> foo.gcda: 43: num counts=1, min counter=3830,
>> cum_counter=3830
>> foo.gcda: 50: num counts=1, min counter=13999,
>> cum_counter=13999
>>
>> Looks like the 2nd PROGRAM_SUMMARY has some issue. If I manually change
>> gcc/coverage.c
>> to ignore the 2nd PROGRAM_SUMMARY section, the ICE disappears.
>>
>> I have several questions for the profiling feedback data file:
>>
>> 1. Under what situation, there will be multiple PROGRAM_SUMMARY sections for
>> one module?
>
> This is itended to resolve situations where one object file is linked
> into multiple final binaries (just like libbackend is linked into
> multiple FEs).
Okay, I see. (That was my guess too. -:)
> The overall binary checksum is known to
> the runtime and it creates entry for each checksum.
Okay.
>> 2. How to check whether one of the PROGRAM_SUMMARY has issue?
>
> The histograms was added by google to get better threshold for hot/cold
> partitioning. They never worked too well, because it is hard to merge
> histograms from multipe runs meaningfully, so we dropped them some time
> ago.
Just checked, the PROGRAM_SUMMARY has been removed completely since GCC9 with
the following commit:
commit 512cc0151207de4c7ff3a84f040f730fe0d52458
Author: Martin Liska <mli...@suse.cz>
Date: Fri Sep 21 10:41:17 2018 +0200
Remove arc profile histogram in non-LTO mode.
2018-09-21 Martin Liska <mli...@suse.cz>
> With LTO it is easier to produce the histogram after reading all
> profiles together and without LTO we use easier heuristics that only
> computes constant fraction of maximum number of iterations.
Okay.
>
> What confuses me is the first summary having runs=0. I wonder how with
> zero runs it even has an entry?
I was surprised by this too. Don’t know the reason yet.
The application that has this problem is huge. I don’t have the complete source
codes and make files.
The thing that is even more strange is, there are multiple files have the same
ICE during profiling use phase, and as I checked today, all the corresponding
.gcda files have
the exactly same PROGRAM_SUMMARY sections, i.e.
foo.gcda:
foo.gcda: a3000000: 202:PROGRAM_SUMMARY checksum=0x91f3e3ae
foo.gcda: counts=10831, runs=0, sum_all=478965, run_max=125615,
sum_max=201126
foo.gcda: counter histogram:
foo.gcda: 0: num counts=10187, min counter=0, cum_counter=0
…
foo.gcda: 51: num counts=1, min counter=14524, cum_counter=14524
foo.gcda: 63: num counts=1, min counter=125615,
cum_counter=125615
foo.gcda: a3000000: 137:PROGRAM_SUMMARY checksum=0xcf9f0896
foo.gcda: counts=10502, runs=1, sum_all=48618, run_max=13999,
sum_max=14046
foo.gcda: counter histogram:
foo.gcda: 0: num counts=9821, min counter=0, cum_counter=0
…
foo.gcda: 43: num counts=1, min counter=3830, cum_counter=3830
foo.gcda: 50: num counts=1, min counter=13999, cum_counter=13999
foo_1.gcda:
foo_1.gcda: a3000000: 202:PROGRAM_SUMMARY checksum=0x91f3e3ae
foo_1.gcda: counts=10831, runs=0, sum_all=478965,
run_max=125615, sum_max=201126
foo_1.gcda: counter histogram:
foo_1.gcda: 0: num counts=10187, min counter=0, cum_counter=0
…
foo_1.gcda: 51: num counts=1, min counter=14524,
cum_counter=14524
foo_1.gcda: 63: num counts=1, min counter=125615,
cum_counter=125615
foo_1.gcda: a3000000: 137:PROGRAM_SUMMARY checksum=0xcf9f0896
foo_1.gcda: counts=10502, runs=1, sum_all=48618, run_max=13999,
sum_max=14046
foo_1.gcda: counter histogram:
foo_1.gcda: 0: num counts=9821, min counter=0, cum_counter=0
…
foo_1.gcda: 43: num counts=1, min counter=3830, cum_counter=3830
foo_1.gcda: 50: num counts=1, min counter=13999,
cum_counter=13999
Exactly the same. Really don’t understand what’s going on.
>
> What is the assert that fials in gcov-io.c?
during IPA pass: profile
foo.c: In function ‘foo_print’:
foo.c:509:1: internal compiler error: in compute_working_sets, at gcov-io.c:1066
(NOTE, I changed the names of the file and the function).
For GCC8, what should we do to work around this issue? Do you have any
suggestions?
Thanks.
Qing
>
> Honza
>
>>
>> Thanks a lot for any help.
>>
>> Qing
