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SubjectRe: [PATCH] fixing sendfile on 64bit architectures
>>>>> On Thu, 20 May 2004 15:25:10 -0700, Andrew Morton <akpm@osdl.org> said:

Andrew> Jesse Barnes <jbarnes@engr.sgi.com> wrote:
>> On Thursday, May 20, 2004 5:56 pm, Andrew Morton wrote: > An
>> alternative might be to remove all the ifdefs, build with >
>> -ffunction-sections and let the linker drop any unreferenced
>> code...

>> That would probably be even more confusing than the #ifdefs. At
>> least with those you know that you need to check whether the
>> current code will be called...

Andrew> Me no understand Jesse.

Andrew> Removing the ifdefs and letting the linker do the job has
Andrew> the advantage that the compiler gets to check more code for
Andrew> you.

I think he meant that it's easier to see who (what platform) is
relying on the code.

Another disadvantage of -ffunction-sections is that the compiler won't
be able to do proper inlining. There are several cases where you
have:

static
do_the_work ()
{
...
}

asmlinkage long
sys_one_variant ()
{
do_the_work(some args...);
}

asmlinkage long
sys_other_variant ()
{
do_the_work(other args...);
}

If only one variant is needed, GCC 3.4 will automatically inline
"do_the_work()" (since there is only one call-site), which is exactly
what you want. You won't get that with -ffunction-sections.

--david
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