Re: Can LTO minor version be updated in backward compatible way ?

["Martin Liška" <mliska@suse.cz>]

On 7/22/19 4:31 PM, Jeff Law wrote:
> On 7/22/19 8:25 AM, Martin Liška wrote:
>> On 7/17/19 8:10 PM, Jeff Law wrote:
>>> On 7/17/19 11:29 AM, Andi Kleen wrote:
>>>> Romain Geissler <romain.geissler@amadeus.com> writes:
>>>>>
>>>>> I have no idea of the LTO format and if indeed it can easily be updated
>>>>> in a backward compatible way. But I would say it would be nice if it
>>>>> could, and would allow adoption for projects spread on many teams
>>>>> depending on each others and unable to re-build everything at each
>>>>> toolchain update.
>>>>
>>>> Right now any change to an compiler option breaks the LTO format
>>>> in subtle ways. In fact even the minor changes that are currently
>>>> done are not frequent enough to catch all such cases.
>>>>
>>>> So it's unlikely to really work.
>>> Right and stable LTO bytecode really isn't on the radar at this time.
>>>
>>> IMHO it's more important right now to start pushing LTO into the
>>> mainstream for the binaries shipped by the vendors (and stripping the
>>> LTO bits out of any static libraries/.o's shipped by the vendors).
>>>
>>>
>>> SuSE's announcement today is quite ironic. 
>>
>> Why and what is ironic about it?
> Sorry, you'd have to have internal context -- we'd been discussing it
> within the Red Hat team for Fedora 32 the previous day.  One of the
> questions that came up was whether or not any other major distributor
> was shipping with LTO enabled :-)

According to what I know, OpenMandriva should be using LTO:
https://www.openmandriva.org/en/news/article/openmandriva-lx-4-0-rc-released
but the package building machinery is closed, so I can't confirm that.

One another example is Gentoo:
https://github.com/InBetweenNames/gentooLTO
but it's up to users preferences.

So that I consider openSUSE Tumbleweed as a first one :P

Martin


> 
> 
> Jeff
>