Re: [Qemu-devel] [PATCH v2] target/ppc: rewrite f[n]m[add, sub] using float64_muladd

[David Gibson]

On Fri, Mar 03, 2017 at 02:31:38PM +1100, Richard Henderson wrote:
> On 03/03/2017 01:10 AM, Nikunj A Dadhania wrote:
> > +static void float64_maddsub_update_excp(CPUPPCState *env, float64 arg1,
> > +                                        float64 arg2, float64 arg3,
> > +                                        unsigned int madd_flags)
> >  {
> > +    if (unlikely((float64_is_infinity(arg1) && float64_is_zero(arg2)) ||
> > +                 (float64_is_zero(arg1) && float64_is_infinity(arg2)))) {
> >          /* Multiplication of zero by infinity */
> > +        arg1 = float_invalid_op_excp(env, POWERPC_EXCP_FP_VXIMZ, 1);
> > +    } else if (unlikely(float64_is_signaling_nan(arg1, &env->fp_status) ||
> > +                        float64_is_signaling_nan(arg2, &env->fp_status) ||
> > +                        float64_is_signaling_nan(arg3, &env->fp_status))) {
> > +        /* sNaN operation */
> > +        float_invalid_op_excp(env, POWERPC_EXCP_FP_VXSNAN, 1);
> 
> Are you sure you shouldn't be testing for NaN first?
> Do you really get VXIMZ if arg3 (the addend) is (S)NaN?
> 
> You should probably eliminate QNaN as well, before the other checks.

Oh.. I've already merged and pull requested this.  I'm afraid any
further corrections will have to be done as followup patches.

-- 
David Gibson                    | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au  | minimalist, thank you.  NOT _the_ _other_
                                | _way_ _around_!
http://www.ozlabs.org/~dgibson

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