Re: debug-early branch merged into mainline

[Richard Biener <richard dot guenther at gmail dot com>]

On June 8, 2015 7:14:19 PM GMT+02:00, Aldy Hernandez <aldyh@redhat.com> wrote:
>On 06/08/2015 09:30 AM, Richard Biener wrote:
>> On Mon, Jun 8, 2015 at 2:05 PM, Aldy Hernandez <aldyh@redhat.com>
>wrote:
>>> On 06/08/2015 04:26 AM, Richard Biener wrote:
>>>>
>>>> On Mon, Jun 8, 2015 at 3:23 AM, Aldy Hernandez <aldyh@redhat.com>
>wrote:
>>>>>
>>>>> On 06/07/2015 02:33 PM, Richard Biener wrote:
>>>>>>
>>>>>>
>>>>>> On June 7, 2015 6:00:05 PM GMT+02:00, Aldy Hernandez
><aldyh@redhat.com>
>>>>>> wrote:
>>>>>>>
>>>>>>>
>>>>>>> On 06/07/2015 11:25 AM, Richard Biener wrote:
>>>>>>>>
>>>>>>>>
>>>>>>>> On June 7, 2015 5:03:30 PM GMT+02:00, Aldy Hernandez
>>>>>>>
>>>>>>>
>>>>>>> <aldyh@redhat.com> wrote:
>>>>>>>>>
>>>>>>>>>
>>>>>>>>> On 06/06/2015 05:49 AM, Andreas Schwab wrote:
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>> Bootstrap fails on aarch64:
>>>>>>>>>>
>>>>>>>>>> Comparing stages 2 and 3
>>>>>>>>>> warning: gcc/cc1objplus-checksum.o differs
>>>>>>>>>> warning: gcc/cc1obj-checksum.o differs
>>>>>>>>>> warning: gcc/cc1plus-checksum.o differs
>>>>>>>>>> warning: gcc/cc1-checksum.o differs
>>>>>>>>>> Bootstrap comparison failure!
>>>>>>>>>> gcc/ira-costs.o differs
>>>>>>>>>> gcc/tree-sra.o differs
>>>>>>>>>> gcc/tree-parloops.o differs
>>>>>>>>>> gcc/tree-vect-data-refs.o differs
>>>>>>>>>> gcc/java/jcf-io.o differs
>>>>>>>>>> gcc/ipa-inline-analysis.o differs
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>> The bootstrap comparison failure on ppc64le, aarch64, and
>possibly
>>>>>>>>> others is due to the order of some sections being in a
>different
>>>>>>>
>>>>>>>
>>>>>>> order
>>>>>>>>>
>>>>>>>>>
>>>>>>>>> with and without debugging.
>>>>>>>>>
>>>>>>>>> Stage2 is being compiled with no debugging due to -gtoggle,
>and
>>>>>>>
>>>>>>>
>>>>>>> stage3
>>>>>>>>>
>>>>>>>>>
>>>>>>>>> is being compiled with debugging.
>>>>>>>>>
>>>>>>>>> For ira-costs.o on ppc64le we have:
>>>>>>>>>
>>>>>>>>> -Disassembly of section
>>>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>.rodata._ZN10hash_tableI19cost_classes_hasher11xcallocatorE6expandEv.str1.8:
>>>>>>>>>
>>>>>>>>>
>>>>>>>>> +Disassembly of section
>>>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>.rodata._ZN10hash_tableI19cost_classes_hasher11xcallocatorE26find_empty_slot_for_expandEj.str1.8:
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>> ...
>>>>>>>>>
>>>>>>>>> -Disassembly of section
>>>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>.rodata._ZN10hash_tableI19cost_classes_hasher11xcallocatorE26find_empty_slot_for_expandEj.str1.8:
>>>>>>>>>
>>>>>>>>>
>>>>>>>>> +Disassembly of section
>>>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>.rodata._ZN10hash_tableI19cost_classes_hasher11xcallocatorE6expandEv.str1.8:
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>> There is no semantic difference between the objects, just the
>>>>>>>
>>>>>>>
>>>>>>> ordering.
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>> I assume it's the same problem for the rest of the objects and
>>>>>>>>> architectures.
>>>>>>>>>
>>>>>>>>> I will look into this, unless someone beats me to it, or has
>an idea
>>>>>>>>> right off the bat.
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>> Check whether the symbol table walkers are walking hash tables.
> I
>>>>>>>
>>>>>>>
>>>>>>> assume the above are emitted via the symbol removal handling for
>debug
>>>>>>> stuff?
>>>>>>>
>>>>>>> Ughh, indeed.  These sections are being outputted from
>>>>>>> output_object_blocks which traverses a hash table:
>>>>>>>
>>>>>>> void
>>>>>>> output_object_blocks (void)
>>>>>>> {
>>>>>>>     object_block_htab->traverse<void *,
>output_object_block_htab>
>>>>>>> (NULL);
>>>>>>> }
>>>>>>>
>>>>>>> Perhaps we should sort them by some deterministic field and then
>call
>>>>>>> output_object_block() on each member of the resulting list?
>>>>>>
>>>>>>
>>>>>>
>>>>>> Yes, that would be the usual fix. Maybe sth has an UID already,
>is the
>>>>>> 'object' a decl by chance?
>>>>>
>>>>>
>>>>>
>>>>> The attached patch fixes the bootstrap failure on ppc64le, and
>>>>> theoretically
>>>>> the aarch64 problem as well, but I haven't checked.
>>>>>
>>>>> Tested on ppc64le linux by bootstrapping, and regtesting C/C++
>against
>>>>> pre
>>>>> debug-early merge sources.  Also tested by a full bootstrap and
>regtest
>>>>> on
>>>>> x86-64 Linux.
>>>>>
>>>>> OK for mainline?
>>>>
>>>>
>>>> Please use FOR_EACH_HASH_TABLE_ELEMENT to put elements on the
>>>> vector instead of the htab traversal.
>>>>
>>>> The compare function looks like we will end up having many equal
>elements
>>>> (and thus random ordering on hosts where qsort doesn't behave
>"sane"
>>>> here, like Solaris IIRC).  Unless all sections are named (which it
>looks
>>>> like)
>>>
>>>
>>> Some sections are not named.
>>>
>>> How about we sort the named sections and output them, but call
>>> output_object_block() on the rest of the sections on whatever order
>they
>>> were in?  This solves the bootstrap problem as well.
>>>
>>> Attached patch tested on x86-64 and ppc64le Linux.
>>>
>>> OK?
>>
>> No, but hash_section suggests to sort after sect->common.flags if
>> the section is not named.  Conveniently flags is just an 'int' ...
>
>What about if the comparison routine gets a named section and an
>unnamed 
>section?  How to compare?  That's why I was giving priority to one over
>
>the other originally, but I didn't know about problematic qsort 
>implementations.

Obviously unnamed and a named section can be sorted like you did in the original patch.

Richard.

>Aldy