On Thu, Apr 29, 2010 at 9:28 AM, Bingfeng Mei <b...@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:davi...@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 >> <b...@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.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 >> >> > >> >> >> >> >> > >> >> >
