[FFmpeg-devel] [RFC] insufficient VFP check?
Sun Jan 17 13:12:16 CET 2010
On Sun, Jan 17, 2010 at 11:53:15AM +0000, M?ns Rullg?rd wrote:
> Reimar D?ffinger <Reimar.Doeffinger at gmx.de> writes:
> > 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).
> Never seen anything like that. Where do you get your compilers?
> Perhaps you should consider another vendor.
I simply compiled for a target like arm-unknown-linux or so.
That whole --target stuff is just a huge mess, about 90% of combinations
result in a gcc/binutils combination that doesn't actually produce
anything working but without any clear hint.
Yes, I understand it's my fault for actually expecting compiling yourself
not to need special secret magic, I guess I am quite spoilt in that regard
due to MPlayer/FFmpeg and some other projects.
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