[FFmpeg-devel] [RFC] insufficient VFP check?

Reimar Döffinger Reimar.Doeffinger
Sun Jan 17 09:43:20 CET 2010

On Sun, Jan 17, 2010 at 12:31:02AM +0000, M?ns Rullg?rd wrote:
> M?ns Rullg?rd <mans at mansr.com> writes:
> > Reimar D?ffinger <Reimar.Doeffinger at gmx.de> writes:
> >> Uh, can the -unknown- variant compile vfp/neon?
> >> I came to the conclusion, idiotic as it is (not commenting on the technical
> >> point, but from a usability one), that softfloat is necessary
> >> to have neon/vfp support.
> >
> > Hmm, I didn't read carefully enough first time, and missed the
> > softfloat part.  You definitely do *not* want to mess with softfloat
> > on A8.  The softfloat compilers are configured to emulate FP, and the
> > -mfloat-abi=softfp flag contradicts that.  No idea what that might
> > lead to.
> >
> > With a softfloat compiler I get the same error.
> Mystery solved: running gcc with -v reveals the assembler invocation
> to be this:
> /usr/libexec/gcc/arm-softfloat-linux-gnueabi/as --gdwarf2 -mcpu=cortex-a8 -mfpu=softvfp -meabi=4 -o libavcodec/arm/dsputil_vfp.o /tmp/ccsHJvmR.s
> The -mfpu=softvfp there means all manner of FP is out of the question.
> Oddly enough, non-softfloat compilers will happily compile to
> softfloat if only given the -msoft-float flag.

Well, in my previous try with non-softfloat toolchain it couldn't compile since it
could not find -lfloat (which it wanted to use even with -mfloat-abi=softfp -mfpu=neon).
Someone really did make a royal mess with that softfloat stuff.

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