[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 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.


-- 
Zuxy
Beauty is truth,
While truth is beauty.
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