On Sat, Aug 26, 2023 at 09:55:05PM -0700, Richard Henderson wrote:
> On 8/26/23 09:02, Bastian Koppelmann wrote:
> > +uint32_t helper_ftohp(CPUTriCoreState *env, uint32_t arg)
> > +{
> > + float32 f_arg = make_float32(arg);
> > + uint32_t result = 0;
> > + int32_t flags = 0;
> > +
> > + if (float32_is_infinity(f_arg)) {
> > + if (float32_is_neg(f_arg)) {
> > + return HP_NEG_INFINITY;
> > + } else {
> > + return HP_POS_INFINITY;
> > + }
> > + } else if (float32_is_any_nan(f_arg)) {
> > + if (float32_is_signaling_nan(f_arg, &env->fp_status)) {
> > + flags |= float_flag_invalid;
> > + }
> > + result = float16_set_sign(result, arg >> 31);
> > + result = deposit32(result, 10, 5, 0x1f);
> > + result = deposit32(result, 8, 2, extract32(arg, 21, 2));
> > + result = deposit32(result, 0, 8, extract32(arg, 0, 8));
> > + if (extract32(result, 0, 10) == 0) {
> > + result |= (1 << 8);
> > + }
> > + } else {
> > + set_flush_to_zero(0, &env->fp_status);
> > + result = float32_to_float16(f_arg, true, &env->fp_status);
> > + set_flush_to_zero(1, &env->fp_status);
> > + flags = f_get_excp_flags(env);
> > + }
>
> All of this is standard behaviour. All you need is the final else case.
Unfortunately not quite. For NANs the top 2 and lower 8 output mantissa bits
need to be
set to the top 2 and lower 8 input mantissa bits respectively. This behaviour is
unique to ftohp and hptof, so I don't think we should specialize it in
parts64_default_nan().
Cheers,
Bastian
