Re: debug-early branch merged into mainline

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

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' ...

Can you adjust again?

Thanks,
Richard.

> Aldy