| Message ID | 20180512004311.9299-7-richard.henderson@linaro.org |
|---|---|
| State | New |
| Headers | show |
| Series | softfloat patch roundup | expand |
On 12 May 2018 at 01:42, Richard Henderson <richard.henderson@linaro.org> wrote: > 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 <richard.henderson@linaro.org> The commit message says it simplifies the float-to-float codepath, but the patch doesn't touch that: it's missing the part that was in v1 of the series that removed the a.frac = a.frac << (64 - srcf->frac_size) >> (64 - dstf->frac_size); line and updated the associated comment. Isn't that change necessary in this patch if we're changing the canonical representation of NaNs ? > --- > fpu/softfloat.c | 7 ++++++- > 1 file changed, 6 insertions(+), 1 deletion(-) > > diff --git a/fpu/softfloat.c b/fpu/softfloat.c > index 353893aaea..a56d3d975b 100644 > --- a/fpu/softfloat.c > +++ b/fpu/softfloat.c > @@ -330,10 +330,11 @@ 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 { > @@ -480,6 +481,7 @@ static FloatParts round_canonical(FloatParts p, float_status *s, > case float_class_qnan: > case float_class_snan: > exp = exp_max; > + frac >>= parm->frac_shift; > break; > > default: > @@ -503,6 +505,7 @@ static float16 float16_round_pack_canonical(FloatParts p, float_status *s) > case float_class_dnan: > return float16_default_nan(s); > case float_class_msnan: > + p.frac >>= float16_params.frac_shift; > return float16_maybe_silence_nan(float16_pack_raw(p), s); > default: > p = round_canonical(p, s, &float16_params); > @@ -521,6 +524,7 @@ 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); > @@ -539,6 +543,7 @@ 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); > -- > 2.17.0 > thanks -- PMM
On 05/14/2018 03:29 AM, Peter Maydell wrote: > On 12 May 2018 at 01:42, Richard Henderson <richard.henderson@linaro.org> wrote: >> 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 <richard.henderson@linaro.org> > > The commit message says it simplifies the float-to-float codepath, > but the patch doesn't touch that: it's missing the part that was in > v1 of the series that removed the > a.frac = a.frac << (64 - srcf->frac_size) >> (64 - dstf->frac_size); > line and updated the associated comment. > > Isn't that change necessary in this patch if we're changing the > canonical representation of NaNs ? With the reordering of the patches, the offending line never gets added. So, yeah, the text should be re-worded here. r~
diff --git a/fpu/softfloat.c b/fpu/softfloat.c index 353893aaea..a56d3d975b 100644 --- a/fpu/softfloat.c +++ b/fpu/softfloat.c @@ -330,10 +330,11 @@ 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 { @@ -480,6 +481,7 @@ static FloatParts round_canonical(FloatParts p, float_status *s, case float_class_qnan: case float_class_snan: exp = exp_max; + frac >>= parm->frac_shift; break; default: @@ -503,6 +505,7 @@ static float16 float16_round_pack_canonical(FloatParts p, float_status *s) case float_class_dnan: return float16_default_nan(s); case float_class_msnan: + p.frac >>= float16_params.frac_shift; return float16_maybe_silence_nan(float16_pack_raw(p), s); default: p = round_canonical(p, s, &float16_params); @@ -521,6 +524,7 @@ 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); @@ -539,6 +543,7 @@ 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);
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 <richard.henderson@linaro.org> --- fpu/softfloat.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-)