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

[Diego Biurrun]

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.

Diego