[x264-devel] warning building in arm without neon and asm enabled

[Janne Grunau]

On 2015-11-16 16:13:50 +0000, Sérgio Basto wrote:
> On Seg, 2015-11-16 at 12:44 +0100, Janne Grunau wrote:
> > Hi,
> > 
> > On 2015-11-05 20:09:48 +0000, Sérgio Basto wrote:
> > > 
> > > Should I be concerned about this warning ? 
> > > 
> > > build common/arm/mc-c.c:75:5: warning: initialization from
> > > incompatible
> > > pointer type [-Wincompatible-pointer-types]
> > > x264_mc_weight_w4##func##_neon,\      ^ common/arm/mc-c.c:83:1:
> > > note: in
> > > expansion of macro 'MC_WEIGHT'  MC_WEIGHT()
> > 
> > That doesn't really match your config description in the topic. NEON 
> > seems to be enabled. It's probably nothing to be concerned about but
> > I 
> > can't reproduce it with current git master. Please post the revision
> > and 
> > your full configure command.
> 
> build.log in attach

thanks, it happens only with --bit-depth=9/10 and is completely benign.  
I'll sent patch to avoid the warnings. Thanks for the report.

> , what happens if x264 is build with neon flag and
> runs in a (compatible) arm but without neon ? x264 fallback to other
> thing and work or doesn't work ? 

In theory there is some sort of runtime detection but it is ugly. It 
tries to execute a neon instruction and uses a signal handler to 
continue after an illegal instruction on CPUs without neon.

> I was expect compile with neon was something like: gcc -mfpu=neon

Most of the functions were neon is helpful are handwritten assembler 
files using gnu as' '.mfpu' directive so the compiler/as flags are 
overriden.

Janne