[MPlayer-dev-eng] [PATCH] Enable FTZ and DAZ w/ -ffast-math

[Zuxy Meng]

2009/2/10 Diego Biurrun <diego at biurrun.de>:
> On Tue, Feb 10, 2009 at 08:10:06PM +0800, Zuxy Meng wrote:
>> 2009/2/10 Diego Biurrun <diego at biurrun.de>:
>> > On Tue, Feb 10, 2009 at 12:12:23AM +0800, Zuxy Meng wrote:
>> >> 2009/2/10 Diego Biurrun <diego at biurrun.de>:
>> >> > On Sun, Feb 08, 2009 at 02:02:20PM +0800, Zuxy Meng wrote:
>> >> >>
>> >> >> 2009/2/8 Diego Biurrun <diego at biurrun.de>:
>> >> >> > On Mon, Feb 02, 2009 at 09:33:08PM +0800, Zuxy Meng wrote:
>> >> >> >>
>> >> >> >> GCC does a trick to enable FTZ (flush to zero) and DAZ (denormals are
>> >> >> >> zeroes) when either -ffast-math or -funsafe-math-optimizations is used
>> >> >> >> by linking crtfastmath.o into the executive. It requires the presence
>> >> >> >> of one of the options in the final linking stage.
>> >> >> >
>> >> >> > I don't like CFLAGS being used during the linking stage.  Add those
>> >> >> > options to the linker flags instead.
>> >> >>
>> >> >> Something like COMMON_LDFLAGS += $(findstr, -ffast-math, $CFLAGS)?
>> >> >
>> >> > No, add it to LDFLAGS in configure in the same place where fast-math is
>> >> > added to CFLAGS.
>> >>
>> >> Do we check user specified CFLAGS?
>> >
>> > Somewhat.  But IMO users have to make sure they add it to LDFLAGS as
>> > well then.
>>
>> Actually gcc may pay attention to other CFLAGS during linking. For
>> example, if one wants to generate coverage info s/he must pass "-pg"
>> to gcc both during compilation and linking. IMHO it's cleaner to just
>> pass the whole CFLAGS in makefile. Anyway it doesn't do anything bad.
>
> I don't like it and still think that those flags should then appear in
> both CFLAGS and LDFLAGS.

Well...I guess I'll just drop it :-)

-- 
Zuxy
Beauty is truth,
While truth is beauty.
PGP KeyID: E8555ED6