[FFmpeg-devel] [PATCH] split-radix FFT

Uoti Urpala uoti.urpala
Tue Jul 29 20:21:32 CEST 2008

On Tue, 2008-07-29 at 19:38 +0200, Michael Niedermayer wrote:
> On Tue, Jul 29, 2008 at 06:57:21PM +0300, Uoti Urpala wrote:
> > On Tue, 2008-07-29 at 17:41 +0200, Michael Niedermayer wrote:
> > > x86-64 shared libs require -fPIC, unless that has been fixed.
> > > so the user does not always have the option to omit -fPIC
> > 
> > I didn't mean to include AMD64 in x86. -fPIC does not cause that much
> > slowdown on it. And anyway what shared libs on AMD64 require is *no
> > textrels* - generating them by some other method wouldn't work any
> > better. So you don't need MANGLE to force creating textrels, and if it
> > did that the result in fact wouldn't work. You can avoid GOT lookup by
> > adding visibility information (and then the compiler will avoid it for
> > ALL uses, not just those inside asm).
> We dont have visibility attributes in svn,

I'm not aware of any significant difficulties with adding them, less
still for the subset of symbols that are candidates for MANGLE.

> they are a gcc only feature and

No more so than inline asm which can use MANGLE. The __attribute__
syntax for declaring them is specific to GCC/ICC but if you use macros
there are more compilers that support some visibility syntax than
compilers that support MANGLE.

> I think noone came up with a clean way to add visibility attributes,
> that is a way that does not require adding them to a significant
> portion of the globals one by one.

I've explained that before. I don't think adding them per global is a
particular problem (though somewhat more work); they're conceptually
similar to "static" which is also used per symbol. You can also set the
default visibility for a portion of the file so it will be used for all
symbols defined/declared there.

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