I just tried -fwhole-program. It can achieve extra 3%-4% saving. That is brilliant. Thanks.
Bingfeng > -----Original Message----- > From: Jan Hubicka [mailto:hubi...@ucw.cz] > Sent: 28 April 2010 13:59 > To: Bingfeng Mei > Subject: Re: LTO question > > > 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. > With -fwhole-program LTO should be a lot more effective. > > Honza > > > > Bingfeng > > > > > -----Original Message----- > > > From: Jan Hubicka [mailto:hubi...@ucw.cz] > > > Sent: 28 April 2010 12:21 > > > To: Bingfeng Mei > > > Subject: Re: LTO question > > > > > > > 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. > > > Did you also tested with -fwhole-program? :) > > > > > > Honza > > > > > > > > Bingfeng > > > > > > > > > -----Original Message----- > > > > > From: Richard Guenther [mailto:richard.guent...@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 > > > > > <b...@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 archiv...@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 > > > > > > > > > > > > > > > > > > > > > > > >
