Linux/ARM: Bus error with -O3 flag of clang/llvm-3.6 while running unit-test of .NET Core

Wed Jul 13 21:14:55 PDT 2016

>>I'm not sure which emulator is this, but it's clear that it doesn't
>>care much for unaligned access, whereas your hardware does.
>
>>RPi2 is a Cortex-A7, the Chromebooks are Cortex-A15, both should
>>handle unaligned access, but they can still be se to crash via flags.

Dear Renato Golin,

Do you mean that we don't face "bus error" cases because Linux ARM Emulator
doesn't  handle (or proceed) unaligned access? Could you tell me more
technical opinion?

* Downloading Linux ARM Emulator:
https://github.com/dotnet/coreclr/issues/3805

Below is CPU information while running our Linux ARM Emulator.
arm-emulator# cat /proc/cpuinfo
processor : 0
model name : ARMv7 Processor rev 0 (v7l)
BogoMIPS : 806.91
Features : half thumb fastmult vfp edsp neon vfpv3 tls vfpd32
CPU implementer : 0x41
CPU architecture: 7
CPU variant : 0x0
CPU part : 0xc09
CPU revision : 0

processor : 1
model name : ARMv7 Processor rev 0 (v7l)
BogoMIPS : 801.17
Features : half thumb fastmult vfp edsp neon vfpv3 tls vfpd32
CPU implementer : 0x41
CPU architecture: 7
CPU variant : 0x0
CPU part : 0xc09
CPU revision : 0

Hardware : ARM-Versatile Express
Revision : 0000
Serial : 0000000000000000

BRs,
Geunsik Lim.

On Thu, Jul 14, 2016 at 1:14 PM, Geunsik Lim <leemgs at gmail.com> wrote:

> > I don't think there is any. The closest I could find is the FreeBSD
> > manpage: https://www.freebsd.org/cgi/man.cgi?query=clang, which at
> > least mentions all of them
>
> Thank you for sharing the FreeBSD manpage. BTW, Is O4 flag available now?
> * -O4 and higher: Currently equivalent to -O3
>
> BRs,
> Geunsik Lim.
>
> On Wed, Jul 13, 2016 at 10:59 PM, Tim Northover <t.p.northover at gmail.com>
> wrote:
>
>> On 13 July 2016 at 00:22, Geunsik Lim <leemgs at gmail.com> wrote:
>> > BTW, Where can we find an official documentation of the optimization
>> levels
>> > (e.g., O0, O1, O2, O3, Ofast, and so on)  of clang like GCC online
>> manual?
>>
>> I don't think there is any. The closest I could find is the FreeBSD
>> manpage: https://www.freebsd.org/cgi/man.cgi?query=clang, which at
>> least mentions all of them.
>>
>> Tim.
>>
>
>
>
> --
> http://leemgs.fedorapeople.org
> Don't try to avoid pain if you fail.
> If you decided to face the challenges in life,
> you can gain a lot by giving your best.
> Cheolsang Jeong's Book & life
> --
>

-- 
http://leemgs.fedorapeople.org
Don't try to avoid pain if you fail.
If you decided to face the challenges in life,
you can gain a lot by giving your best.
Cheolsang Jeong's Book & life
--
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