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Re: [Qemu-devel] [PATCH 04/19] fpu/softfloat: Canonicalize NaN fraction
From: |
Alex Bennée |
Subject: |
Re: [Qemu-devel] [PATCH 04/19] fpu/softfloat: Canonicalize NaN fraction |
Date: |
Fri, 11 May 2018 17:26:58 +0100 |
User-agent: |
mu4e 1.1.0; emacs 26.1 |
Richard Henderson <address@hidden> writes:
> Shift the NaN fraction to a canonical position, much like we do
> for the fraction of normal numbers. Immediately, this simplifies
> the float-to-float conversion. Later, this will facilitate
> manipulation of NaNs within the shared code paths.
>
> Signed-off-by: Richard Henderson <address@hidden>
> ---
> fpu/softfloat.c | 13 ++++++-------
> 1 file changed, 6 insertions(+), 7 deletions(-)
>
> diff --git a/fpu/softfloat.c b/fpu/softfloat.c
> index 5e4982b035..df377b6314 100644
> --- a/fpu/softfloat.c
> +++ b/fpu/softfloat.c
> @@ -329,10 +329,11 @@ static FloatParts canonicalize(FloatParts part, const
> FloatFmt *parm,
> if (part.frac == 0) {
> part.cls = float_class_inf;
> } else {
> + part.frac <<= parm->frac_shift;
> #ifdef NO_SIGNALING_NANS
> part.cls = float_class_qnan;
> #else
> - int64_t msb = part.frac << (parm->frac_shift + 2);
> + int64_t msb = part.frac << 2;
> if ((msb < 0) == status->snan_bit_is_one) {
> part.cls = float_class_snan;
> } else {
> @@ -498,6 +499,7 @@ static FloatParts round_canonical(FloatParts p,
> float_status *s,
> case float_class_qnan:
> case float_class_snan:
> exp = exp_max;
> + frac >>= parm->frac_shift;
Unfortunately we now miss this step when we handle:
case float_class_msnan:
return float64_maybe_silence_nan(float64_pack_raw(p), s);
This seems to fix that:
recanonicalise frac before packing and sending
1 file changed, 3 insertions(+)
fpu/softfloat.c | 3 +++
modified fpu/softfloat.c
@@ -532,6 +532,7 @@ static float16 float16a_round_pack_canonical(const FloatFmt
*params,
case float_class_dnan:
return float16_default_nan(s);
case float_class_msnan:
+ p.frac >>= params->frac_shift;
return float16_maybe_silence_nan(float16_pack_raw(p), s);
default:
p = round_canonical(p, s, params);
@@ -555,6 +556,7 @@ static float32 float32_round_pack_canonical(FloatParts p,
float_status *s)
case float_class_dnan:
return float32_default_nan(s);
case float_class_msnan:
+ p.frac >>= float32_params.frac_shift;
return float32_maybe_silence_nan(float32_pack_raw(p), s);
default:
p = round_canonical(p, s, &float32_params);
@@ -573,6 +575,7 @@ static float64 float64_round_pack_canonical(FloatParts p,
float_status *s)
case float_class_dnan:
return float64_default_nan(s);
case float_class_msnan:
+ p.frac >>= float64_params.frac_shift;
return float64_maybe_silence_nan(float64_pack_raw(p), s);
default:
p = round_canonical(p, s, &float64_params);
--
Alex Bennée
- [Qemu-devel] [PATCH 00/19] softfloat: Clean up NaN handling, Richard Henderson, 2018/05/10
- [Qemu-devel] [PATCH 04/19] fpu/softfloat: Canonicalize NaN fraction, Richard Henderson, 2018/05/10
- Re: [Qemu-devel] [PATCH 04/19] fpu/softfloat: Canonicalize NaN fraction,
Alex Bennée <=
- [Qemu-devel] [PATCH 03/19] fpu/softfloat: Move softfloat-specialize.h below FloatParts definition, Richard Henderson, 2018/05/10
- [Qemu-devel] [PATCH 05/19] fpu/softfloat: Introduce parts_is_snan_frac, Richard Henderson, 2018/05/10
- [Qemu-devel] [PATCH 06/19] fpu/softfloat: Replace float_class_dnan with parts_default_nan, Richard Henderson, 2018/05/10
- [Qemu-devel] [PATCH 08/19] target/arm: Use floatX_silence_nan when we have already checked for SNaN, Richard Henderson, 2018/05/10
- [Qemu-devel] [PATCH 09/19] target/arm: Remove floatX_maybe_silence_nan from conversions, Richard Henderson, 2018/05/10
- [Qemu-devel] [PATCH 07/19] fpu/softfloat: Replace float_class_msnan with parts_silence_nan, Richard Henderson, 2018/05/10
- [Qemu-devel] [PATCH 11/19] target/m68k: Use floatX_silence_nan when we have already checked for SNaN, Richard Henderson, 2018/05/10