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Re: Enable FTZ/DAZ for SSE?
On Tue, Aug 09, 2005 at 02:01:08PM -0700, H. J. Lu wrote:
> On Tue, Aug 09, 2005 at 01:35:11PM -0700, Richard Henderson wrote:
> > On Tue, Aug 09, 2005 at 11:02:22AM -0700, H. J. Lu wrote:
> > > I have a small testcase to show that enable FTZ/DAZ makes a huge (>160
> > > times faster) difference on SSE floating point code. Icc enables it by
> > > defailt for -ON (N>=1). Should gcc do the same?
> >
> > This is the flush-denormals-to-zero bit?
> >
>
> Yes, FTZ stands for flush to zero and DAZ stands for denormals are
> zero.
>
> > See config/{alpha,ia64,sparc}/crtfastmath.c, and how that gets used.
> >
>
> The one for x86 may be very similar to alpha's crtfastmath.c. It can
> be used for fast math on SSE targets.
There is a minor problem. How can I add crtfastmath.o for SSE targets
only? Can I add a new macro, TARGET_EXPAND_MAIN_FUNCTION, to
expand_main_function to generate those instructions directly?
H.J.