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Re: LTO question


On Thu, Apr 29, 2010 at 9:28 AM, Bingfeng Mei <bmei@broadcom.com> wrote:
> I turned on -ffunction-sections and compiled with -Os.
> The size gain at -O2 is less though.

Interesting.

Thanks,

David
>
> Bingfeng
>
>> -----Original Message-----
>> From: Xinliang David Li [mailto:davidxl@google.com]
>> Sent: 29 April 2010 17:17
>> To: Bingfeng Mei
>> Cc: Richard Guenther; gcc@gcc.gnu.org
>> Subject: 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)?
>>
>> David
>>
>> On Wed, Apr 28, 2010 at 2:44 AM, Bingfeng Mei
>> <bmei@broadcom.com> 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.
>> >
>> > 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
>> >> >
>> >>
>> >>
>> >
>>
>>
>


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