[opus] Opus floating-point NEON jump table question

[Linfeng Zhang]

Thank Jean-Mark and Jonathan!

I tested current OPUS encoder in floating-point with Complexity 8. Hacking
using the attached patch (which will generate "#define
OPUS_ARM_MAY_HAVE_NEON 1" in config.h) will speed up about 14.7% on my
Chromebook. Probably it's because many NEON intrinsics optimizations can
benefit both fixed-point and floating-point encoder.

So if it's safe enough to enable MAY_HAVE_NEON in floating-point by
default, it could speed up floating-point NEON encoder a little bit.

Thanks,
Linfeng

On Thu, Jun 1, 2017 at 2:22 PM, Jonathan Lennox <jonathan at vidyo.com> wrote:

>
> On May 31, 2017, at 12:47 PM, Linfeng Zhang <linfengz at google.com> wrote:
>
> Hi,
>
> ./configure --build x86_64-unknown-linux-gnu --host arm-linux-gnueabihf
> --disable-assertions --disable-check-asm --enable-intrinsics CFLAGS=-O3
> --disable-shared
>
> When configuring with floating-point and intrinsics enabled as above, the
> generated config.h only has OPUS_ARM_MAY_HAVE_NEON_INTR defined (to 1),
> with
> /* #undef OPUS_ARM_ASM */
> /* #undef OPUS_ARM_INLINE_ASM */
> /* #undef OPUS_ARM_INLINE_EDSP */
> /* #undef OPUS_ARM_INLINE_MEDIA */
> /* #undef OPUS_ARM_INLINE_NEON */
> /* #undef OPUS_ARM_MAY_HAVE_EDSP */
> /* #undef OPUS_ARM_MAY_HAVE_MEDIA */
> /* #undef OPUS_ARM_MAY_HAVE_NEON */
> /* #undef OPUS_ARM_PRESUME_AARCH64_NEON_INTR */
> /* #undef OPUS_ARM_PRESUME_EDSP */
> /* #undef OPUS_ARM_PRESUME_MEDIA */
> /* #undef OPUS_ARM_PRESUME_NEON */
> /* #undef OPUS_ARM_PRESUME_NEON_INTR */
>
> So MAY_HAVE_NEON will be defined to MEDIA version, which will eventually
> fall down to C functions in the jump table:
> #  define MAY_HAVE_NEON(name) MAY_HAVE_MEDIA(name)
>
> Therefore all NEON intrinsics optimizations in their jump tables won't get
> called for floating-point.
>
> Am I missing some options in my configure command, or the config is intend
> to do so in floating-point?
>
> Thanks,
> Linfeng
>
>
> The structure of this is pretty tangled and confusing, but what you’ll
> find is that the MAY_HAVE_NEON macro isn’t used in the jump tables for the
> two Neon intrinsics functions (silk_NSQ_noise_shape_feedback_loop_neon
> and celt_pitch_xcorr_float_neon) which are used in a floating-point neon
> build.  See silk/arm/arm_silk_map.c and celt/arm/arm_celt_map.c.
>
> So long as OPUS_ARM_MAY_HAVE_NEON_INTR and OPUS_HAVE_RTCD are set in
> config.h, it’ll pick up those functions, and check for them using RTCD.
>
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