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Re: [patches] Re: SSE min/max instruction support
On Sat, Feb 24, 2001 at 04:20:34PM -0800, Richard Henderson wrote:
> On Sun, Feb 25, 2001 at 12:25:24AM +0100, Jan Hubicka wrote:
> > Whats also about explicitly documenting the i386 behaviour for smin/smax
> > FP, so we can use them in IEEE compilation?
>
> Not possible. Naturally the ia64 definition is the same
> as the i386 definition. But rs6000 uses
>
> tmp = a - b;
> result = (tmp >= 0 ? a : b);
>
> where the >= is hardcoded in "fsel %0,%1,%2,%3".
Actually, I take this back. It is possible for us to define an order
for this. If, for instance, we choose the Intel definition, then an
implementation that breaks ties with the first argument merely needs
to swap the arguments as present in the rtl. For rs6000 this becomes:
tmp = b - a;
result = (tmp >= 0 ? b : a);
Everyone's happy.
r~