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

[Evgenii Stepanov via llvm-commits]

I'm not sure without taking a closer look. Maybe next week.

On Fri, Nov 13, 2015 at 6:03 PM, Quentin Colombet <qcolombet at apple.com> wrote:
> Hi Evgenii,
>
> Thanks for the inputs.
>
> I’ve disabled shrink-wrapping for functions with the sanitize like
> attributes in Committed revision 253116.
> My understanding is that the frame information must be correct at the
> location of the crash, which can happen anywhere, not just at what
> shrink-wrapping considers as needing the frame to be lowered.
>
> Does that make sense or did I just create a workaround for something I
> didn’t understand?
>
> Thanks,
> -Quentin
>
> On Nov 12, 2015, at 12:59 PM, Evgenii Stepanov <eugenis at google.com> wrote:
>
> 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
>
>
>
>
>