[LEDE-DEV] [PATCH] gcc: 7.2: remove mips patch causing broken code

[Hauke Mehrtens]

On 12/19/2017 12:01 AM, Hauke Mehrtens wrote:
> On 12/18/2017 11:38 PM, Hauke Mehrtens wrote:
>> On 12/18/2017 03:07 PM, Kevin Darbyshire-Bryant wrote:
>>>
>>>
>>>> On 18 Dec 2017, at 10:12, Felix Fietkau <nbd at nbd.name> wrote:
>>>>
>>>> On 2017-12-18 11:07, Kevin Darbyshire-Bryant wrote:
>>>>> Hi Felix,
>>>>>
>>>>> Thanks for explaining that.  I suspect you’re right that there’s an underlying bug in gcc mips.  So ideally we need some code that exposes the bug when using -O2 (or even just -funroll_loops) Looking at FS 814 there’s a hint in there that uhttpd was similarly affected…and not solved by the patch drop.  So what to do if there’s a bug just lurking to bite us?
>>>>
>>>> If possible, reproduce it on uhttpd with an unmodified upstream version
>>>> of GCC and open up a bug report.
>>>>
>>>> - Felix
>>>
>>> Sadly I’m unable to reproduce the uhttpd issue - frustrating.
>>>
>>> Cheers,
>>>
>>> Kevin D-B
>>
>> Hi,
>>
>> The attached patch also made the problem disappear.
>> This patch builds the code with -funroll-loops in addition, otherwise
>> only the default settings are used.
>>
>> Hauke
> 
> I can reproduce this problem also without Felix's gcc patch.
> When I compile libtommath from dropbear with "-mbranch-cost=1" I get the
> same broken code. This is one of the changes Felix's patch does.
> 
> Hauke

I am able to reproduce this problem with the free electrons toolchain
for MIPS 32 BE and created a bug report for GCC:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83496

Hauke

-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 858 bytes
Desc: OpenPGP digital signature
URL: <http://lists.infradead.org/pipermail/lede-dev/attachments/20171219/9d94530f/attachment.sig>