[llvm] r252825 - [ARM] Enable shrink-wrapping by default.

[Evgenii Stepanov via llvm-commits]

Looks like debug location for prologue code could be broken or
missing. See EntryDebugLocation in
FunctionStackPoisoner::poisonStack() in AddressSanitizer.cpp.

On Thu, Nov 12, 2015 at 12:32 PM, Quentin Colombet <qcolombet at apple.com> wrote:
> Hi,
>
> I’ve had a quick look and the generated code looks good to me.
> The prologue code in the failing example is needed only just before the call to the asan function (see attached assembly for x86).
>
> I am guessing that ASAN has some heuristics to find the prologue code in the disassembly and that fails for the new code.
> Note that the debugger just get it right!
>
> Could you advise on what to do?
>
> Thanks,
> Q
>
>
>
>> On Nov 12, 2015, at 9:45 AM, Quentin Colombet <qcolombet at apple.com> wrote:
>>
>> Hi Renato,
>>
>> Thanks for the follow-up.
>>
>> I’ll try to have a look as well, unless you beat me at it :).
>>
>> Cheers,
>> -Quentin
>>> On Nov 12, 2015, at 5:35 AM, Renato Golin <renato.golin at linaro.org> wrote:
>>>
>>> On 11 November 2015 at 23:31, Quentin Colombet via llvm-commits
>>> <llvm-commits at lists.llvm.org> wrote:
>>>> Author: qcolombet
>>>> Date: Wed Nov 11 17:31:46 2015
>>>> New Revision: 252825
>>>>
>>>> URL: http://llvm.org/viewvc/llvm-project?rev=252825&view=rev
>>>> Log:
>>>> [ARM] Enable shrink-wrapping by default.
>>>>
>>>> Differential Revision: http://reviews.llvm.org/D14357
>>>>
>>>> rdar://problem/21942589
>>>
>>> Quentin,
>>>
>>> After bisecting, this seems to have caused:
>>>
>>> http://lab.llvm.org:8011/builders/clang-cmake-armv7-a15-full/builds/9014
>>>
>>> http://lab.llvm.org:8011/builders/clang-cmake-armv7-a15-full/builds/9014/steps/ninja%20check%201/logs/FAIL%3A%20AddressSanitizer-armhf-linux%3A%3Anull_deref.cc
>>>
>>> I'm copying sanitizer folks to understand what's the change here, but
>>> I'm guessing the sanitizer instrumentation didn't get inserted right,
>>> with the prologue changed.
>>>
>>> I'll revert for now...
>>>
>>> cheers,
>>> --renato
>>
>
>