RE: LTO question

["Bingfeng Mei" <bmei at broadcom dot com>]

Thanks, I will check what I can do with collect2. LTO
seems to save 6-9% code size for applications I tested
and should be very useful for us.

Bingfeng 

> -----Original Message-----
> From: Richard Guenther [mailto:richard.guenther@gmail.com] 
> Sent: 28 April 2010 10:33
> To: Bingfeng Mei
> Cc: gcc@gcc.gnu.org
> Subject: Re: LTO question
> 
> On Tue, Apr 27, 2010 at 6:30 PM, Bingfeng Mei 
> <bmei@broadcom.com> wrote:
> > Hello,
> > I have been playing with LTO. I notice that LTO doesn't work when
> > object files are achived into static library files and the final
> > binary is linked against them, although these object files 
> are compiled
> > with -flto and I can see all the lto related sections in .a files.
> > Is this what is described in LTO Wiki page?
> >
> > "As an added feature, LTO will take advantage of the plugin feature
> > in gold. This allows the compiler to pick up object files that may
> > have been stored in library archives. "
> >
> > So do I have to use gold to solve this issue?
> 
> Yes.  Or you fix collect2 to do processing of archives and hand
> lto1 the required information (it expects archive components
> with LTO bytecode like archive.a@offset with offset being the
> offset of the .o file with LTO bytecode inside the archive).  See
> lto/lto-elf.c:lto_obj_file_open for "details".
> 
> Richard.
> 
> > Many thanks,
> > Bingfeng
> >
> 
>