[FFmpeg-devel] [PATCH 2/3] arm: vp9mc: Load only 12 pixels in the 4 pixel wide horizontal filter

[Janne Grunau]

On Fri, Dec 20, 2024 at 07:53:33PM +0100, Michael Niedermayer wrote:
> Hi Janne
> 
> On Thu, Dec 19, 2024 at 10:12:22PM +0100, Janne Grunau wrote:
> > This reduces the amount the horizontal filters read beyond the filter
> > width to a consistent 1 pixel. The data is not used so this is usually
> > not noticeable. It becomes a problem when the application allocates
> > frame buffers only for the aligned picture size and the end of it is at
> > a page boundary. This happens for picture sizes which are a multiple of
> > the page size like 1280x640. The frame buffer allocation is based on
> > its most likely done via mmap + MAP_ANONYMOUS so start and end of the
> > buffer are page aligned and the previous and next page are not
> > necessarily mapped.
> > This mirrors the aarch64 change.
> > 
> > Signed-off-by: Janne Grunau <janne-ffmpeg at jannau.net>
> > ---
> >  libavcodec/arm/vp9mc_neon.S | 13 ++++++++++---
> >  1 file changed, 10 insertions(+), 3 deletions(-)
> 
> tested on qemu-arm (assuming the standard fate and qemu covers this)

the asm is covered by checkasm and intentionally breaking the functions
was detected

Janne