From: Brian Dessent <brian@dessent.net>
To: gcc-help@gcc.gnu.org
Subject: Re: --gc-sections on x86
Date: Tue, 05 Dec 2006 09:57:00 -0000 [thread overview]
Message-ID: <45754266.671DDF7E@dessent.net> (raw)
In-Reply-To: <45753BC9.4030306@jeuxvideo.com>
Gabriel Linder wrote:
> I am trying to remove some unused functions from our programs, with gcc
> flag -ffunction-sections and ld flag --gc-sections, but it doesn't seem
> to work at all :-(
>
> I use gcc 3.2.2, and I get the following (sample source attached, 18
> lines) :
> 2828 bytes with gcc -march=i686 -O2 -ffunction-sections
> -Wl,--gc-sections oblivion.c -o oblivion && strip -s oblivion
> 2812 bytes with gcc -DNOTHING -march=i686 -O2 -ffunction-sections
> -Wl,--gc-sections oblivion.c -o oblivion && strip -s oblivion
>
> Is this a known problem ? Is a workaround available ?
This testcase may not be actually showing you what you want. You have
to balance the extra overhead of having a section for each function
against the savings, and in this case the function being removed is
completely trivial. When you're looking at a 2800 byte ELF file the
noise (headers, padding, etc) is going to overwhelm everything. Try a
more realistic testcase.
Brian
next prev parent reply other threads:[~2006-12-05 9:57 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-12-05 9:28 Gabriel Linder
2006-12-05 9:57 ` Brian Dessent [this message]
2006-12-05 10:13 ` Gabriel Linder
2006-12-05 14:27 ` Perry Smith
2006-12-05 13:04 ` John Love-Jensen
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