[cairo] [cairo-announce] [ANNOUNCE] Stable pixman release 0.16.0 now available

Siarhei Siamashka siarhei.siamashka at gmail.com
Wed Sep 2 03:49:22 PDT 2009

On Wednesday 02 September 2009, Koen Kooi wrote:
> On 02-09-09 00:49, Siarhei Siamashka wrote:
> > On Monday 31 August 2009, Koen Kooi wrote:
> >> And I still hate that pixman puts in it's own -march and -mcpu, but
> >> that's a discussion for another day.
> >
> > Pixman puts -mcpu only into the flags for compiling some selected files,
> > *after* configure script has already verified that gcc can accept this
> > set of flags. If gcc would reject this combination of flags, it would not
> > try to compile these sources at all. Still a missing part here is
> > -mfloat-abi=softfp option for the source file with NEON optimizations.
> >
> > This behavior is consistent with the rest of pixman, except that gcc
> > behaves a lot more ugly on ARM than on other platforms.
> This is an excerpt of the gcc commandline from pixman:
> arm-angstrom-linux-gnueabi-gcc \
> -march=armv7-a -mtune=cortex-a8 -mfpu=neon -mfloat-abi=softfp \
> -mcpu=arm1136j-s
> I split it between what I'm using when building for armv7a and what
> pixman adds.

You omitted the most important detail: the file for which this 
additional -mcpu=arm1136j-s option is added.

The fact is that it is enabled for 'pixman-arm-simd.c' exclusively, which
contains nothing more, but ARMv6 specific optimizations.

> So pixman adds too little to be usefull and what it adds is 
> not right for the target I'm targetting.

This file with overridden cpu type contains the code, which is only important
for the ARM cores which support ARMv6 but not ARMv7 instructions, it is not
supposed to be used on your target at all (or at least it is not optimal
for it anyway).

You can actually reduce the size of compiled binaries a bit by
adding --disable-arm-simd configure option, so this file will not
be compiled in for your target.

> Can we please add a 
> --I'm-using-ARM-but-actually-know-what-I'm-doing configure switch to
> disable this behaviour?

Yes. Can you propose some patch?

Best regards,
Siarhei Siamashka
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