[MPlayer-dev-eng] [PATCH] Fix for ARM compilation failure?when?IWMMXT support is disabled

[Diego Biurrun]

On Mon, Apr 28, 2008 at 06:06:18PM +0300, Siarhei Siamashka wrote:
> On Monday 28 April 2008, Diego Biurrun wrote:
> > On Mon, Apr 28, 2008 at 02:03:35AM +0300, Siarhei Siamashka wrote:
> > > On Monday 28 April 2008, Diego Biurrun wrote:
> > > > On Mon, Apr 28, 2008 at 12:44:42AM +0300, Siarhei Siamashka wrote:
> > > > > --- libmpeg2/motion_comp.c	(revision 26548)
> > > > > +++ libmpeg2/motion_comp.c	(working copy)
> > > > > @@ -62,9 +62,12 @@
> > > > >  #ifdef ARCH_ARM
> > > > > +#ifdef HAVE_IWMMXT
> > > > >      if (accel & MPEG2_ACCEL_ARM_IWMMXT)
> > > > >  	mpeg2_mc = mpeg2_mc_iwmmxt;
> > > > > -    else if (accel & MPEG2_ACCEL_ARM)
> > > > > +    else
> > > > > +#endif
> > > > > +    if (accel & MPEG2_ACCEL_ARM)
> > > > >  	mpeg2_mc = mpeg2_mc_arm;
> > > > >      else
> > > > >  #endif
> > > >
> > > > Hmm, I think this is wrong.  Why is MPEG2_ACCEL_ARM_IWMMXT defined if
> > > > IWMMXT is not available?
> > >
> > > It is not defined, but we just get linking error:
> > > [...]
> > > libmpeg2/libmpeg2.a(motion_comp.o): In function
> > > `mpeg2_mc_init':/home/serge/mplayer-svn/libmpeg2/motion_comp.c:68:
> > > undefined reference to `mpeg2_mc_iwmmxt'
> > > collect2: ld returned 1 exit status
> >
> > The bug must be elsewhere.  Where is mpeg2_mc_iwmmxt declared?  And why
> > is it declared on your machine?
> 
> This code refers to 'mpeg2_mc_iwmmxt' symbol, which is defined
> in 'motion_comp_iwmmxt.c' when HAVE_IWMMXT macro is enabled.
> 
> So either the code which refers to 'mpeg2_mc_iwmmxt' in 'motion_comp.c' should
> be hidden under conditional compilation too, or something more cluttered
> should be introduced.
> 
> Well, having one more look, turns out that now neither MPEG2_ACCEL_ARM nor
> MPEG2_ACCEL_ARM_IWMMXT flags get ever set in 'accel' variable, so these
> optimizations can not be activated. Looks like a lot has changed since I 
> looked at this code last time.

This sounds more as if the HAVE_IWMMXT ifdef should be removed from
motion_comp_iwmmxt.c.  mpeg2_mc_init works fine on other platforms.

I suspect that some optimizations are not set on ARM.  Please try the
attached patch.

Also, isn't libavcodec faster for MPEG-1/2 decoding on ARM?

> > > PS. You can try installing ARM crosscompiler for testing when doing major
> > > build system changes. No ARM hardware is required for this and the
> > > problems would be spotted right away :)
> >
> > Nah, I prefer to wait for bug reports to trickle in :)
> 
> Well, you will have to deal with a number of reports from me then :)

Just keep them coming...

Diego
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