[OE-core] why do we poison -Os?

[Kumar Gala]

On Aug 23, 2011, at 8:47 PM, Xu, Dongxiao wrote:

>> -----Original Message-----
>> From: Kumar Gala [mailto:galak at kernel.crashing.org]
>> 
>> If tinylogin is the only issue why modify/patch gcc?  I see we have
>> meta/recipes-core/tinylogin/tinylogin-1.4/use_O2_option.patch to deal with
>> this?
> 
> Yes, patch for tinylogin is to deal with the issue.
> Besides that, we added this poison detection mechanism and suppose it should not affect functionality.
> My understanding is that, if GCC is not configured with the ability of code space optimization, target recipes will not have code size benefit even if adding "-Os" option.
> 
>> 
>> Not allowing -Os at all, which is our current situation on PPC is problematic.
>> So trying to see if this issue is really limited to gcc 4.5 or not.  How can I
>> reproduce it with current poky.git?
> 
> Not allowing -Os for PPC is because --enable-target-optspace is not enabled for PPC GCC. This is a known issue for PPC GCC 4.5.x.
> 
> I wonder if GCC 4.6.x has fixed this issue. If so, we should add "--enable-target-optspace" for PPC GCC again, thus -Os will be allowed for recipes.

Thus my query on how to verify this and if it was limited to tinylogin.

- k

> 
> Thanks,
> Dongxiao
> 
>> 
>> - k
>> 
>> On Aug 23, 2011, at 8:16 PM, Xu, Dongxiao wrote:
>> 
>>> Hi Kumar,
>>> 
>>> The background of this commit is, when I upgraded PowerPC gcc to 4.5,
>> tinylogin would crash with certain GCC build parameters.
>>> 
>>> The root cause for that bug is, if enabled both "-frename-registers" and "-Os"
>> options to build tinylogin in powerpc architecture, the tinylogin/getty
>> application will encounter segmentation fault. Other combinations like
>> "-frename-registers and -O2" or only "-Os" will not trigger this issue.
>>> 
>>> Poky cross environment provides the "-frename-registers" parameter,
>> however it does not provide -Os option since "--enable-target-optspace" option
>> is disabled for powerpc gcc. The "-Os" option in tinylogin is added by its own
>> Makefile.
>>> 
>>> This commit is to prevent the above case. If --enable-target-optspace is
>> disabled for GCC, "-Os" should not be added by recipe.
>>> 
>>> Thanks,
>>> Dongxiao
>>> 
>>>> -----Original Message-----
>>>> From: Kumar Gala [mailto:galak at kernel.crashing.org]
>>>> Sent: Wednesday, August 24, 2011 8:53 AM
>>>> To: Xu, Dongxiao
>>>> Cc: Patches and discussions about the oe-core layer; Khem Raj
>>>> Subject: why do we poison -Os?
>>>> 
>>>> Dongxiao,
>>>> 
>>>> Can you explain why this was needed:
>>>> 
>>>> commit ce456306dad3fdf42494830011dacae213c48edf
>>>> Author: Dongxiao Xu <dongxiao.xu at intel.com>
>>>> Date:   Sat Sep 25 10:16:26 2010 +0800
>>>> 
>>>>   gcc: enable poison parameters detection
>>>> 
>>>>   If not configured with --enable-target-optspace, gcc will report
>>>>   errors if there is '-Os' optimization in parameters.
>>>> 
>>>>   This fixes [BUGID #342]
>>>> 
>>>>   Also add "--enable-target-optspace" option to arm gcc configuration.
>>>> 
>>>>   Signed-off-by: Dongxiao Xu <dongxiao.xu at intel.com>
>>>> 
>>>> 
>>>> - k