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Re: LTO question
Just curious, what is the base line size of your comparison? Did you
turn on GC (-ffunction-sections -fdata-sections -Wl,--gc-sections)?
On Wed, Apr 28, 2010 at 2:44 AM, Bingfeng Mei <firstname.lastname@example.org> wrote:
> 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.
>> -----Original Message-----
>> From: Richard Guenther [mailto:email@example.com]
>> Sent: 28 April 2010 10:33
>> To: Bingfeng Mei
>> Cc: firstname.lastname@example.org
>> Subject: Re: LTO question
>> On Tue, Apr 27, 2010 at 6:30 PM, Bingfeng Mei
>> <email@example.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".
>> > Many thanks,
>> > Bingfeng