Re: [PATCH 45/76] target/arm: Implement FPCR.AH semantics for scalar FMIN/FMAX

[Richard Henderson]

On 1/31/25 05:09, Peter Maydell wrote:
> > > +/*
> > > + * AH=1 min/max have some odd special cases:
> > > + * comparing two zeroes (even of different sign), (NaN, anything),
> > > + * or (anything, NaN) should return the second argument (possibly
> > > + * squashed to zero).
> > > + * Also, denormal outputs are not squashed to zero regardless of FZ or FZ16.
> > > + */
> > > +#define AH_MINMAX_HELPER(NAME, CTYPE, FLOATTYPE, MINMAX)                \
> > > +    CTYPE HELPER(NAME)(CTYPE a, CTYPE b, float_status *fpst)            \
> > > +    {                                                                   \
> > > +        bool save;                                                      \
> > > +        CTYPE r;                                                        \
> > > +        a = FLOATTYPE ## _squash_input_denormal(a, fpst);               \
> > > +        b = FLOATTYPE ## _squash_input_denormal(b, fpst);               \
> > > +        if (FLOATTYPE ## _is_zero(a) && FLOATTYPE ## _is_zero(b)) {     \
> >
> > The comment says "even of different sign", the pseudocode explicitly checks 
> > different
> > sign.  But of course if they're the same sign a and b are indistinguishable.  
> > Perhaps
> > slightly different wording?
>
> Sure. I changed from "(even of different sign)" to
> "(regardless of sign)". Let me know if you have a
> more specific tweak you'd like.

Sounds good.


r~