[cairo] [Pixman] help building cairo on windows

[Siarhei Siamashka]

On Thu, 13 Sep 2012 09:08:59 +0200
Andrea Canciani <ranma42 at gmail.com> wrote:

> On Thu, Sep 13, 2012 at 2:08 AM, Siarhei Siamashka
> <siarhei.siamashka at gmail.com> wrote:
> > On Tue, 11 Sep 2012 23:45:47 +0200
> > Andrea Canciani <ranma42 at gmail.com> wrote:
> >
> >> On Tue, Sep 11, 2012 at 10:44 PM, Siarhei Siamashka
> >> <siarhei.siamashka at gmail.com> wrote:
> >> > On Tue, 11 Sep 2012 22:25:15 +0200
> >> > Andrea Canciani <ranma42 at gmail.com> wrote:
> >> >
> >> >> On Tue, Sep 11, 2012 at 7:34 PM, Søren Sandmann
> >> >> <sandmann at cs.au.dk> wrote:
> >> >> > Andrea Canciani <ranma42 at gmail.com> writes:
> >> >> >
> >> >> >> This reminds me that I have some patches to improve building
> >> >> >> pixman on win32:
> >> >> >> http://cgit.freedesktop.org/~ranma42/pixman/commit/?h=wip/simpleops-to-master
> >> >> >>
> >> >> >> Soren, is it ok if I push the attached patches?
> >> >> >
> >> >> > No objections from me if the test suite still passes with
> >> >> > PIXMAN_DISABLE=sse2 set.
> >> >>
> >> >> On MacOS X the testsuite shows no regression with that variable
> >> >> in the env. On win32, pixman did not compile without the first
> >> >> of those patches. After it, the testsuite fails with:
> >> >>
> >> >> $ PIXMAN_DISABLE=sse2 ./scaling-test.exe
> >> >> Assertion failed: frcd_canary_variable1 ==
> >> >> frcd_volatile_constant1, file scaling-test.c, line 356
> >> >> pixman: Disabled sse2 implementation
> >> >>
> >> >> The failing testcase is:
> >> >> $ PIXMAN_DISABLE=sse2 ./scaling-test.exe 3348
> >> >> Assertion failed: frcd_canary_variable1 ==
> >> >> frcd_volatile_constant1, file scaling-test.c, line 356
> >> >> src_fmt=20028888, dst_fmt=20028888
> >> >> op=3, scale_x=27881, scale_y=-65000, repeat=0
> >> >> translate_x=55344, translate_y=56484
> >> >> src_width=11, src_height=8, dst_width=24, dst_height=7
> >> >> src_x=0, src_y=4, dst_x=4, dst_y=3
> >> >> w=20, h=2
> >> >> destination clip box: [16,6-20,6]
> >> >> destination clip box: [3,2-18,6]
> >> >> pixman: Disabled sse2 implementation
> >> >> ...
> >> >>
> >> >> This seems to be consistent with the compiler warnings:
> >> >> pixman-mmx.c
> >> >> c:\cygwin\home\ranma42\code\fdo\pixman\pixman\pixman-mmx.c(286) :
> >> >> warning C4799: function 'to_uint64' has no EMMS instruction
> >> >> c:\cygwin\home\ranma42\code\fdo\pixman\pixman\pixman-mmx.c(469) :
> >> >> warning C4799: function 'store8888' has no EMMS instruction
> >> >> c:\cygwin\home\ranma42\code\fdo\pixman\pixman\pixman-mmx.c(480) :
> >> >> warning C4799: function 'is_equal' has no EMMS instruction
> >> >> c:\cygwin\home\ranma42\code\fdo\pixman\pixman\pixman-mmx.c(491) :
> >> >> warning C4799: function 'is_opaque' has no EMMS instruction
> >> >> c:\cygwin\home\ranma42\code\fdo\pixman\pixman\pixman-mmx.c(497) :
> >> >> warning C4799: function 'is_zero' has no EMMS instruction
> >> >> c:\cygwin\home\ranma42\code\fdo\pixman\pixman\pixman-mmx.c(565) :
> >> >> warning C4799: function 'expand_4xpacked565' has no EMMS
> >> >> instruction
> >> >> c:\cygwin\home\ranma42\code\fdo\pixman\pixman\pixman-mmx.c(591) :
> >> >> warning C4799: function 'expand_4x565' has no EMMS instruction
> >> >> c:\cygwin\home\ranma42\code\fdo\pixman\pixman\pixman-mmx.c(3760) :
> >> >> warning C4799: function
> >> >> 'fast_composite_scaled_bilinear_mmx_8888_8_8888_pad_OVER' has no
> >> >> EMMS instruction
> >> >> c:\cygwin\home\ranma42\code\fdo\pixman\pixman\pixman-mmx.c(3764) :
> >> >> warning C4799: function
> >> >> 'fast_composite_scaled_bilinear_mmx_8888_8_8888_none_OVER' has
> >> >> no EMMS instruction
> >> >>
> >> >> I was unable to find out why MSVC thinks that
> >> >> fast_composite_scaled_bilinear_mmx_8888_8_8888_{pad,none}_OVER
> >> >> are missing an EMMS instruction, but cover/normal are ok.
> >> >
> >> > Does MSVC respect 'force_inline' and actually inline all of these
> >> > functions ('to_uint64', 'store8888', ...)?
> >>
> >> The compiler does not report inline warnings in pixman-mmx.c, so I
> >> would expect that it respects force_inline.
> >> I'm attaching the build log, in case it is of any help.
> >
> > I'm not sure if I can provide much help with MSVC. The _mm_empty()
> > intrinsic is also not totally problem free even when using gcc:
> >     http://gcc.gnu.org/bugzilla/show_bug.cgi?id=47759
> >
> > But some kind of workaround is still needed. Can you try to
> > confirm which pixman fast paths are triggering this problem?
> 
> It looks like the compiler warning match the issue:
> fast_composite_scaled_bilinear_mmx_8888_8_8888_pad_OVER
> fast_composite_scaled_bilinear_mmx_8888_8_8888_none_OVER
> 
> >
> > If the problem is related to incorrect EMMS instruction reordering,
> > then maybe moving EMMS into a non-inlinable function and calling it
> > instead of _mm_empty() can help? Just as an experiment for getting
> > a bit better understanding about what is going on.
> 
> I confirm that it is likely to be an optimization bug (disabling the
> optimizations fixes it).
> The attached patch is another possible workaround to the issue.
> It causes a lot of warnings about missing EMMS, because the compiler
> does not find any EMMS instruction after the MMX instructions), but
> the whole testsuite succeeds.
> Marking the function as noinline (without disabling the optimizations
> on it) does not fix the issue.
> 
> What would be the best way to work around this issue both in gcc and
> in msvc? Would it be ok to create a "pixman_mm_empty()" function (to
> be used everywhere instead of mm_empty) and disable the optimizations
> on it?

Looks like this issue has slipped through the cracks. What about
just adding something like this to pixman-mmx.c ?

#ifdef _MSC_VER
#error Sorry, MMX can't be safely used with MSVC. Please consider
#error building pixman without MMX support as a workaround.
#error More details can be found at
#error     https://bugs.freedesktop.org/show_bug.cgi?id=NNNNN
#endif

If it's some specific version of MSVC failing, a precise version
check can be used.

-- 
Best regards,
Siarhei Siamashka