Re: [PATCH 07/13] target/hexagon: add v68 HVX IEEE float conversion insns

[Taylor Simpson <ltaylorsimpson@gmail.com>]

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On Tue, Mar 24, 2026 at 3:04 PM Matheus Bernardino <
matheus.bernardino@oss.qualcomm.com> wrote:

> On Mon, Mar 23, 2026 at 6:26 PM Taylor Simpson <ltaylorsimpson@gmail.com>
> wrote:
> >
> >
> >
> > On Mon, Mar 23, 2026 at 7:16 AM Matheus Tavares Bernardino <
> matheus.bernardino@oss.qualcomm.com> wrote:
> >>
> >>
> >> diff --git a/target/hexagon/mmvec/kvx_ieee.c
> b/target/hexagon/mmvec/kvx_ieee.c
> >> index 33621a15f3..bbeec09707 100644
> >> --- a/target/hexagon/mmvec/kvx_ieee.c
> >> +++ b/target/hexagon/mmvec/kvx_ieee.c
> >> @@ -131,3 +131,101 @@ uint16_t qf_min_hf(uint16_t a1, uint16_t a2,
> float_status *fp_status)
> >>      if (float16_is_pos_nan(f2) || float16_is_neg_nan(f1)) return a1;
> >>      return fp_min_hf(a1, a2, fp_status);
> >>  }
> >> +
> >> +uint16_t f16_to_uh(uint16_t op1, float_status *fp_status)
> >> +{
> >> +    return float16_to_uint16_scalbn(make_float16(op1),
> >> +                                    float_round_nearest_even,
> >
> >
> > Does HVX always use this rounding mode?  The scalar core uses the
> rounding mode in USR.
>
> Yeah, almost always this mode, with the exception of some
> instructions. It's not configurable via USR (or anything else).
>

You can set that in the hvx_fp_status, and the softfloat lib will handle it
from there.


>
> >> +
> >> +int32_t conv_w_sf(uint32_t a, float_status *fp_status)
> >> +{
> >> +    float_status scratch_fpst = {};
> >> +    const float32 W_MAX = int32_to_float32(INT32_MAX, &scratch_fpst);
> >> +    const float32 W_MIN = int32_to_float32(INT32_MIN, &scratch_fpst);
> >> +    float32 f1 = make_float32(a);
> >> +
> >> +    if (float32_is_any_nan(f1) || float32_is_infinity(f1) ||
> >> +        float32_le_quiet(W_MAX, f1, fp_status) ||
> >> +        float32_le_quiet(f1, W_MIN, fp_status)) {
> >> +        return float32_is_neg(f1) ? INT32_MIN : INT32_MAX;
> >> +    }
> >
> >
> > Does float32_to_int32 handle these checks?
>
> Hmm, I don't think they are exactly the same. For example,
> float32_to_int32 will return INT32_MAX for any NAN. But the hexagon
> implementation here returns INT32_MIN for negative NAN.
>

Look around in the softfloat code - especially fields in float_status.  Ths
scalar core has a few exceptions, but not alot.

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