LTO question

Richard Guenther richard.guenther@gmail.com
Thu Apr 29 08:57:00 GMT 2010


2010/4/29 Jan Hubicka <hubicka@ucw.cz>:
>> > On 4/28/10 10:26 , Manuel López-Ibá?ez wrote:
>> > >>>> Not yet, I mistakenly thought -fwhole-program is the same as -fwhopr
>> > >>>> and it is just for solving scaling issue of large program.(These two
>> > >>>> options do look similar :-). I shall try next.
>> > >>>
>> > >>> Yep, -fwhopr is not ideal name, but I guess there is not much
>> > >>> to do about it.
>> > >
>> > > It is marked as experimental, so if it is going to stay for GCC 4.6,
>> > > then we should change the name. I think one possibility discussed
>> > > somewhere is that LTO scales back automatically, so the option would
>> > > be not necessary.
>> >
>> > Yes.  I think we should just keep -flto and make it use split
>> > compilation if needed.  -fwhopr is only needed to explicitly enable it.
>> >  My suggestion is to just keep -flto and invoke whopr with -flto=split
>> > or -flto=big (until the automatic threshold is added).
>>
>> Yep, I like this idea too.  I hope to be able to drop "experimental" status
>> from mainline whopr soonish (basically I need to implement references and then
>> I will burn a lot of time fixing how clones are streamed to enable ipa-cp).
>
> And do something about paralelizing the whopr build.  I guess it means storing
> ltrans partition list into file and making collect2 to execute compilation
> and re-invent the Makefile code?
> It would be great if someone took look at this, I am not at all familiar with that
> code and in a way I would preffer it to stay that way ;))

I will look at moving the LTRANS driving to the driver, it should be
easy to do parallel execs from it and hopefully make debugging
WPA/LTRANS less of a headache.

Richard.

> Honza
>



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