[FFmpeg-devel] [PATCH v6 1/3] mips: improve detection of ISAs, FPU and ASEs (DSP, MSA)
Michael Niedermayer
michael at niedermayer.cc
Fri Jan 22 00:17:33 CET 2016
On Wed, Jan 20, 2016 at 02:33:21PM +0000, Vicente Olivert Riera wrote:
> On 20/01/16 13:15, Michael Niedermayer wrote:
> > On Wed, Jan 20, 2016 at 12:21:37PM +0000, Vicente Olivert Riera wrote:
> >> On 20/01/16 12:05, Michael Niedermayer wrote:
> >>> On Wed, Jan 20, 2016 at 11:37:52AM +0000, Vicente Olivert Riera wrote:
> >>>> Hello Michael,
> >>>>
> >>>> On 19/01/16 22:11, Michael Niedermayer wrote:
> >>>>> On Thu, Jan 14, 2016 at 02:59:03PM +0000, Vicente Olivert Riera wrote:
> >>>>>> Signed-off-by: Vicente Olivert Riera <Vincent.Riera at imgtec.com>
> >>>>>> ---
> >>>>>> Changes v5 -> v6:
> >>>>>> - Multiple changes:
> >>>>>> - Use separate if blocks when detecting the MIPS ISA, this way when a block
> >>>>>> disables one ISA it will be detected by the next one. Before the elif was
> >>>>>> preventing this to be done.
> >>>>>> - Don't use check_cflags and use only check_ldflags instead, which will
> >>>>>> check if that flag is valid for compiling and linking. The compiler may
> >>>>>> accept some cflags for compiling but not for linking, so if we check first
> >>>>>> for the cflags it will succeed, and the cflags will be added to the CFLAGS
> >>>>>> variable despite of the check_ldflags failing after that. This can cause
> >>>>>> problems because of having multiple incompatible cflags enabled at the same
> >>>>>> time.
> >>>>>> - Check if mipsfpu has been disabled, and if so, then use -msoft-float. This
> >>>>>> way we override the compiler default behavious which can be building for
> >>>>>> hard-float.
> >>>>>> - Explicitly disable the features that fail any check by adding "|| disable
> >>>>>> $feature" at the end of the checks chain.
> >>>>>>
> >>>>>> Changes v4 -> v5:
> >>>>>> - Check for msa.h and disable msa if not found.
> >>>>>>
> >>>>>> Changes v3 -> v4:
> >>>>>> - Nothing.
> >>>>>>
> >>>>>> Changes v2 -> v3:
> >>>>>> - Nothing.
> >>>>>>
> >>>>>> Changes v1 -> v2:
> >>>>>> - Add a block of code for mipsdspr2 which was previously placed in the
> >>>>>> first patch of this series causing a syntax error in the configure
> >>>>>> script.
> >>>>>> https://lists.ffmpeg.org/pipermail/ffmpeg-devel/2015-November/183444.html
> >>>>>
> >>>>> make distclean ; ../configure --cross-prefix=/usr/mips-linux-gnu/bin/ --cc='ccache mips-linux-gnu-gcc-4.4' --arch=mips --target-os=linux --enable-cross-compile --disable-mipsfpu && make -j12
> >>>>> results in pages of:
> >>>>>
> >>>>> /usr/lib/gcc/mips-linux-gnu/4.4.5/../../../../mips-linux-gnu/bin/ld: Warning: libavfilter/filtfmts-test uses hard float, libswresample/libswresample.a(dither.o) uses soft float
> >>>>> /usr/lib/gcc/mips-linux-gnu/4.4.5/../../../../mips-linux-gnu/bin/ld: Warning: libavfilter/filtfmts-test uses hard float, libswresample/libswresample.a(resample.o) uses soft float
> >>>>> /usr/lib/gcc/mips-linux-gnu/4.4.5/../../../../mips-linux-gnu/bin/ld: Warning: libavfilter/filtfmts-test uses hard float, libswresample/libswresample.a(resample_dsp.o) uses soft float
> >>>>> /usr/lib/gcc/mips-linux-gnu/4.4.5/../../../../mips-linux-gnu/bin/ld: Warning: libavfilter/filtfmts-test uses hard float, libavutil/libavutil.a(adler32.o) uses soft float
> >>>>> /usr/lib/gcc/mips-linux-gnu/4.4.5/../../../../mips-linux-gnu/bin/ld: Warning: libavfilter/filtfmts-test uses hard float, libavutil/libavutil.a(aes.o) uses soft float
> >>>>> /usr/lib/gcc/mips-linux-gnu/4.4.5/../../../../mips-linux-gnu/bin/ld: Warning: libavfilter/filtfmts-test uses hard float, libavutil/libavutil.a(aes_ctr.o) uses soft float
> >>>>> /usr/lib/gcc/mips-linux-gnu/4.4.5/../../../../mips-linux-gnu/bin/ld: Warning: libavfilter/filtfmts-test uses hard float, libavutil/libavutil.a(audio_fifo.o) uses soft float
> >>>>>
> >>>>>
> >>>>> [...]
> >>>>>
> >>>>
> >>>> I can't reproduce your issue. Look:
> >>>>
> >>>> $ make distclean ; ./configure --cross-prefix=mips-linux-gnu-
> >>>> --arch=mips --target-os=linux --enable-cross-compile --disable-mipsfpu
> >>>>
> >>>> And then:
> >>>>
> >>>> $ make -j1 V=1 2>&1 | tee build.log
> >>>>
> >>>> And then:
> >>>>
> >>>> $ grep "uses soft float" build.log
> >>>> $ grep "filtfmts-test" build.log
> >>>>
> >>>> It gives me nothing.
> >>>>
> >>>> Also I try to find for that filtfmts-test file which your logs say that
> >>>> is using hard-float, and I cannot find it:
> >>>>
> >>>
> >>>> $ find . -name "filtfmts-test*"
> >>>> $
> >>>
> >>> see libavfilter/filtfmts.c
> >>
> >> But do you have a generated filtfmts-test binary or a filtfmts.o file?
> >> Because when my build is finished I don't any anything of that.
> >
> > make libavfilter/filtfmts-test
> > CC libavfilter/filtfmts-test.o
> > libavfilter/filtfmts.c:141:9: warning: ignoring return value of function declared with warn_unused_result attribute [-Wunused-result]
> > ff_default_query_formats(filter_ctx);
> > ^~~~~~~~~~~~~~~~~~~~~~~~ ~~~~~~~~~~
> > 1 warning generated.
> > LD libavfilter/filtfmts-test
> >
> > the source and object files differ in their names
> >
>
> I see. Ok, look at this:
>
> $ make libavfilter/filtfmts-test
> CC libavfilter/filtfmts-test.o
> libavfilter/filtfmts.c: In function 'main':
> libavfilter/filtfmts.c:141:9: warning: ignoring return value of
> 'ff_default_query_formats', declared with attribute warn_unused_result
> [-Wunused-result]
> ff_default_query_formats(filter_ctx);
> ^
> LD libavfilter/filtfmts-test
>
> $ mips-linux-gnu-objdump -x libavfilter/filtfmts-test | grep "FP ABI"
> FP ABI: Soft float
>
> It shows to me that it has been for soft-float.
>
> >>
> >>> our compilers differ
> >>> the one i have here is a binary from emdebian
> >>> are you droping support for that ?
> >>> if so that should be clearly stated in the commit message, and the
> >>> compiler cleanly detected and a clear warning given to the user why
> >>> his/her compiler isnt supported and what is supported
> >>
> >> Well, my intention isn't dropping support for anything, although this is
> >> what the emdebian website says:
> >>
> >> "Status of Emdebian distributions
> >>
> >> As of July 2014, updates to the Emdebian distributions ceased. There
> >> will be no further updates and no further stable releases."
> >
> > i know, the problem is not me, i can update, IIRC you guys posted a
> > binary already
> > but others might use similarly build or old compilers
> > so keeping this one here gives some wider coverage ... and its less
> > work
>
> I also want to keep it.
>
> >>
> >> Anyway, how can I obtain the same compiler as you have in order to try
> >> reproducing the bug?
> >
> > i dont know, if they arent on emdian anymore
> > i dont seem to have the deb files in var/cache/apt/archive anymore
> >
> > Package: gcc-4.4-mips-linux-gnu
> > Status: install ok installed
> > Priority: extra
> > Section: devel
> > Installed-Size: 3088
> > Maintainer: Debian GCC Maintainers <debian-gcc at lists.debian.org>
> > Architecture: amd64
> > Source: gcc-4.4
> > Version: 4.4.5-8
> > Provides: c-compiler-mips-linux-gnu
> > Depends: gcc-4.4-mips-linux-gnu-base (= 4.4.5-8), cpp-4.4-mips-linux-gnu (= 4.4.5-8), binutils-mips-linux-gnu (>= 2.20.1-15~), libgcc1-mips-cross (>= 1:4.4.5-8), libgomp1-mips-cross (>= 4.4.5-8), libc6 (>= 2.11)
> > Recommends: libc6-dev-mips-cross (>= 2.5)
> > Suggests: gcc-4.4-multilib-mips-linux-gnu, libmudflap0-4.4-dev-mips-cross (>= 4.4.5-8), gcc-4.4-doc (>= 4.4.4-17), gcc-4.4-locales (>= 4.4.4-17), libgcc1-dbg-mips-cross, libgomp1-dbg-mips-cross, libmudflap0-dbg-mips-cross, libcloog-ppl0 (>= 0.15.9-2~), libppl-c2, libppl7
> > Description: The GNU C compiler
> > This is the GNU C compiler, a fairly portable optimizing compiler for C.
> > .
> > This package contains C cross-compiler for mips architecture.
> > Homepage: http://gcc.gnu.org/
> >
>
> Ok then.
>
> >>
> >>> make distclean ; ../configure --cross-prefix=/usr/mips-linux-gnu/bin/ --cc='mips-linux-gnu-gcc-4.4' --arch=mips --target-os=linux --enable-cross-compile --disable-mipsfpu && make -j12 >& build
> >>>
> >>> grep 'uses soft float' build | wc
> >>> 2327 24879 389225
> >>>
> >>> echo 'int main(void){ return 0; }' | mips-linux-gnu-gcc-4.4 -x c - -o out.o
> >>> echo 'int main(void){ return 0; }' | mips-linux-gnu-gcc-4.4 -x c - -o out.o -msoft-float
> >>> /usr/lib/gcc/mips-linux-gnu/4.4.5/../../../../mips-linux-gnu/bin/ld: Warning: out.o uses hard float, /tmp/ccFlutMG.o uses soft float
> >>>
> >>>
> >>
> >> But I don't understand how your compiler built something for hard-float
> >> when the -msoft-float option should be used instead. This is what I have
> >> (note that I passed V=1 to the make command):
> >>
> >> $ grep '\-mhard-float' build.log | wc -l
> >> 0
> >> $ grep '\-msoft-float' build.log | wc -l
> >> 1411
> >> $ grep "mips-linux-gnu-gcc" build.log | wc -l
> >> 1411
> >>
> >> So the -mhard-float option wasn't used at all, and the -msoft-float one
> >> was used every time the compiler was called.
> >>
> >> I'm curious, can you show me your output for those same commands, please?
> >
> > before the patch:
> > grep '\-mhard-float' build.log-V1-disable-mipsfpu | wc -l
> > 0
> >
> > grep '\-msoft-float' build.log-V1-disable-mipsfpu | wc -l
> > 0
>
> So, before the patch when you pass the --disable-mipsfpu option, what
> configure does is not adding the -mhard-float option to the CFLAGS. But
> also it doesn't add -msoft-float. So no float option is passed to the
> compiler at all.
>
> Given that you don't pass any of those two options to the compiler, the
> default one will be used, which I think it will be -mhard-float.
>
> Look at this simple test:
>
> $ cat test.c
> int main(){return 0;}
> $ # USING -mhard-float
> $ mips-linux-gnu-gcc -mhard-float test.c
> $ mips-linux-gnu-objdump -x a.out | grep "FP ABI"
> FP ABI: Hard float (double precision)
> $ # USING -msoft-float
> $ mips-linux-gnu-gcc -msoft-float test.c
> $ mips-linux-gnu-objdump -x a.out | grep "FP ABI"
> FP ABI: Soft float
> $ # USING COMPILER'S DEFAULT
> $ mips-linux-gnu-gcc test.c
> $ mips-linux-gnu-objdump -x a.out | grep "FP ABI"
> FP ABI: Hard float (double precision)
>
> So, as you can see, before that patch, when we were passing
> --disable-mipsfpu to the configure script, we weren't building ffmpeg
> for soft-float. We were actually building it for the compiler's default
> floatness, which could be either soft-float or (more likely) hard-float.
>
> That's why you didn't see those warnings, because everything was being
> built for hard-float.
>
> > after the patch:
> > grep '\-mhard-float' build.log-V1-disable-mipsfpu-with-patch | wc -l
> > 0
> > grep '\-msoft-float' build.log-V1-disable-mipsfpu-with-patch | wc -l
> > 1428
> > grep "mips-linux-gnu-gcc" build.log-V1-disable-mipsfpu-with-patch | wc -l
> > 1428
>
> This is what doesn't make sense to me. Every time your compiler is
> called it has the -msoft-float option with it, so everything it has
> built was built for soft-float.
>
> > also forget about filtfmts, its not specifici to that
> > /usr/lib/gcc/mips-linux-gnu/4.4.5/../../../../mips-linux-gnu/bin/ld: Warning: ffprobe_g uses hard float, libavutil/libavutil.a(samplefmt.o) uses soft float
> > /usr/lib/gcc/mips-linux-gnu/4.4.5/../../../../mips-linux-gnu/bin/ld: Warning: ffprobe_g uses hard float, libavutil/libavutil.a(sha.o) uses soft float
> > /usr/lib/gcc/mips-linux-gnu/4.4.5/../../../../mips-linux-gnu/bin/ld: Warning: ffprobe_g uses hard float, libavutil/libavutil.a(sha512.o) uses soft float
> > /usr/lib/gcc/mips-linux-gnu/4.4.5/../../../../mips-linux-gnu/bin/ld: Warning: ffprobe_g uses hard float, libavutil/libavutil.a(stereo3d.o) uses soft float
>
> Can you grep the output of "mips-linux-gnu-objdump -x ffprobe_g" and
> search for "FP ABI" in order to see if it actually uses hard float?
before and after the patch there is no match, greping for ABI
1 .note.ABI-tag 00000020 004001a4 004001a4 000001a4 2**2
004001a4 l d .note.ABI-tag 00000000 .note.ABI-tag
mips-linux-gnu-objdump -x ffprobe_g | grep 'ABI'
1 .note.ABI-tag 00000020 004001a4 004001a4 000001a4 2**2
004001a4 l d .note.ABI-tag 00000000 .note.ABI-tag
also both mips-linux-gnu-objdump and the normal hosts objdump give the
same result
[...]
--
Michael GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB
Those who are best at talking, realize last or never when they are wrong.
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