[llvm] r211639 - Print a=b as an assignment.

[Jim Grosbach]

The symbols need to be in the same atom, not just in the same section. When there’s no subsections-via-symbols being done, the two are roughly synonymous, but not in the general case.

-Jim

> On Jul 2, 2014, at 12:58 PM, Daniel Sanders <Daniel.Sanders at imgtec.com> wrote:
> 
> Yes, I think I was fairly close to finding the real bug but I need to move on to some other work before I can dig any deeper. I believe the lurking bug is in MCAssembler::evaluateFixup() or somewhere nearby. I saw this function successfully evaluate 'SymA - SymB' but return false (meaning it could not evaluate the fixup) because Target.isAbsolute() was false. I think it should have returned true when SymA and SymB were known and in the same section.
> 
>> -----Original Message-----
>> From: Rafael Avila de Espindola [mailto:rafael.espindola at gmail.com]
>> Sent: 02 July 2014 17:30
>> To: Daniel Sanders
>> Cc: Doug Gilmore; llvm-commits
>> Subject: Re: [llvm] r211639 - Print a=b as an assignment.
>> 
>> 
>> 
>> Sent from my iPhone
>> 
>>> On Jul 2, 2014, at 11:46, Daniel Sanders <Daniel.Sanders at imgtec.com>
>> wrote:
>>> 
>>> All the SingleSource/Regression/C++/EH tests pass on MIPS32r6 with that
>> commit. They also passed the most recent integrated assembler builds on
>> our buildbots.
>>> 
>> 
>> Ok. Do note that that revision just made us compute more fixups at assembly
>> time. This means it is very likely hiding a bug somewhere else as the
>> relocations should have been producing an equivalent result. One possibility
>> is that we write bad relocation info for a valid fixup. Another is that we hit a
>> bug in ld.
>> 
>> 
>>> Thanks.
>>> 
>>>> -----Original Message-----
>>>> From: Rafael Espíndola [mailto:rafael.espindola at gmail.com]
>>>> Sent: 02 July 2014 15:51
>>>> To: Daniel Sanders
>>>> Cc: Doug Gilmore; llvm-commits
>>>> Subject: Re: [llvm] r211639 - Print a=b as an assignment.
>>>> 
>>>> The extra relocations seem to be avoided by r212101. Can you check if
>>>> that makes a difference?
>>>> 
>>>>> On 2 July 2014 10:29, Daniel Sanders <Daniel.Sanders at imgtec.com>
>> wrote:
>>>>> The problem appears to the contents of .gcc_except_table after
>>>>> relocations are applied in the final link. I haven't figured out why
>>>>> yet, but the integrated assembler is emitting five R_MIPS_32
>>>>> relocations with a value of '.text' to offsets 0x7, 0xb, 0x14, 0x1c,
>>>>> and 0x21. Binutils doesn't emit any relocations. Obviously these
>>>>> should either be label differences or they should be resolved by the
>>>>> integrated assembler but also I believe the last four ought to be at
>>>>> offsets
>>>> 0xc, 0x15, 0x1d, and 0x22.
>>>>> 
>>>>> 
>>>>> 
>>>>> From: llvm-commits-bounces at cs.uiuc.edu
>>>>> [mailto:llvm-commits-bounces at cs.uiuc.edu] On Behalf Of Daniel
>>>>> Sanders
>>>>> Sent: 02 July 2014 12:49
>>>>> To: Doug Gilmore; Rafael Espíndola
>>>>> 
>>>>> 
>>>>> Cc: llvm-commits
>>>>> Subject: RE: [llvm] r211639 - Print a=b as an assignment.
>>>>> 
>>>>> 
>>>>> 
>>>>> I had a look yesterday afternoon and I have an assembly file
>>>>> (attached) that when used in the link for the simple_throw test,
>>>>> works with binutils and crashes with '–fintegrated-as
>>>>> –via-file-asm'. There seem to be a few differences between the two
>>>>> objects but the assignments seemed to be working fine. The most
>>>>> suspicious looking difference was the two bytes difference in the
>> .eh_frame section.
>>>>> Patching the .eh_frame section to match the binutils output with a
>>>>> hex editor doesn't seem to fix the problem though. That's as far as
>>>>> I've got at
>>>> the moment, I'll take another look when I get chance.
>>>>> 
>>>>> 
>>>>> 
>>>>>> -----Original Message-----
>>>>> 
>>>>>> From: llvm-commits-bounces at cs.uiuc.edu [mailto:llvm-commits-
>>>>> 
>>>>>> bounces at cs.uiuc.edu] On Behalf Of Doug Gilmore
>>>>> 
>>>>>> Sent: 29 June 2014 22:55
>>>>> 
>>>>>> To: Rafael Espíndola
>>>>> 
>>>>>> Cc: llvm-commits
>>>>> 
>>>>>> Subject: RE: [llvm] r211639 - Print a=b as an assignment.
>>>>> 
>>>>> 
>>>>>>> From: Rafael Espíndola [rafael.espindola at gmail.com]
>>>>> 
>>>>>>> Sent: Sunday, June 29, 2014 1:25 PM
>>>>> 
>>>>>>> To: Doug Gilmore
>>>>> 
>>>>>>> Cc: llvm-commits
>>>>> 
>>>>>>> Subject: Re: [llvm] r211639 - Print a=b as an assignment.
>>>>> 
>>>>> 
>>>>>>>>> Is this using mips16 or micromips? ".set mips16" in particular
>>>>> 
>>>>>>>>> doesn't seem to be implemented for example.
>>>>> 
>>>>>>>> It is just normal mips32.
>>>>> 
>>>>> 
>>>>>>> Interesting. The original message (r170279) made it look like a
>>>>>>> mip16  issue.
>>>>> 
>>>>> 
>>>>>>> Do you have a testcase where gas produces a working file but MC is
>>>>> 
>>>>>> broken?
>>>>> 
>>>>>> There doesn't appear to be.  Sorry for the lack of debugging input
>>>>>> on our
>>>>> 
>>>>>> end, we are a bit swamped at the moment.  In the next day or so we
>>>>>> should
>>>>> 
>>>>>> be in the position to put more resources on the problem so that we
>>>>>> can find
>>>>> 
>>>>>> the root cause.
>>>>> 
>>>>> 
>>>>>> Thanks,
>>>>> 
>>>>> 
>>>>>> Doug
>>>>> 
>>>>> 
>>>>>>> Cheers,
>>>>> 
>>>>>>> Rafael
>>>>> 
>>>>> 
>>>>>> _______________________________________________
>>>>> 
>>>>>> llvm-commits mailing list
>>>>> 
>>>>>> llvm-commits at cs.uiuc.edu
>>>>> 
>>>>>> http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits
> 
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