Peter Maydell <[email protected]> writes:
> On 9 January 2018 at 12:22, Alex Bennée <[email protected]> wrote:
>> We can now add float16_mul and use the common decompose and
>> canonicalize functions to have a single implementation for
>> float16/32/64 versions.
>>
>> Signed-off-by: Alex Bennée <[email protected]>
>> Signed-off-by: Richard Henderson <[email protected]>
>> Signed-off-by: Richard Henderson <[email protected]>
>> ---
>> fpu/softfloat.c | 207
>> ++++++++++++++++++------------------------------
>> include/fpu/softfloat.h | 1 +
>> 2 files changed, 80 insertions(+), 128 deletions(-)
>>
>> diff --git a/fpu/softfloat.c b/fpu/softfloat.c
>> index f89e47e3ef..6e9d4c172c 100644
>> --- a/fpu/softfloat.c
>> +++ b/fpu/softfloat.c
>> @@ -730,6 +730,85 @@ float64 float64_sub(float64 a, float64 b, float_status
>> *status)
>> return float64_round_pack_canonical(pr, status);
>> }
>>
>> +/*
>> + * Returns the result of multiplying the floating-point values `a' and
>> + * `b'. The operation is performed according to the IEC/IEEE Standard
>> + * for Binary Floating-Point Arithmetic.
>> + */
>> +
>> +static decomposed_parts mul_decomposed(decomposed_parts a, decomposed_parts
>> b,
>> + float_status *s)
>> +{
>> + bool sign = a.sign ^ b.sign;
>> +
>> + if (a.cls == float_class_normal && b.cls == float_class_normal) {
>> + uint64_t hi, lo;
>> + int exp = a.exp + b.exp;
>> +
>> + mul64To128(a.frac, b.frac, &hi, &lo);
>> + shift128RightJamming(hi, lo, DECOMPOSED_BINARY_POINT, &hi, &lo);
>> + if (lo & DECOMPOSED_OVERFLOW_BIT) {
>> + shift64RightJamming(lo, 1, &lo);
>> + exp += 1;
>> + }
>> +
>> + /* Re-use a */
>> + a.exp = exp;
>> + a.sign = sign;
>> + a.frac = lo;
>> + return a;
>> + }
>> + /* handle all the NaN cases */
>> + if (a.cls >= float_class_qnan || b.cls >= float_class_qnan) {
>> + return pick_nan_parts(a, b, s);
>> + }
>> + /* Inf * Zero == NaN */
>> + if (((1 << a.cls) | (1 << b.cls)) ==
>> + ((1 << float_class_inf) | (1 << float_class_zero))) {
>
> This is kinda confusing...
Yeah it's a bit of a shortcut to:
if ((a.cls == float_class_inf && b.cls == float_class_zero)
||
(a.cls == float_class_zero && b.cls == float_class_inf))
Would you prefer it long hand or tidied away to a helper?
if (cls_combination(a, b, float_class_inf, float_class_zero))
?
>
>> + s->float_exception_flags |= float_flag_invalid;
>> + a.cls = float_class_dnan;
>> + a.sign = sign;
>> + return a;
>> + }
>> + /* Multiply by 0 or Inf */
>> + if (a.cls == float_class_inf || a.cls == float_class_zero) {
>> + a.sign = sign;
>> + return a;
>> + }
>> + if (b.cls == float_class_inf || b.cls == float_class_zero) {
>> + b.sign = sign;
>> + return b;
>> + }
>> + g_assert_not_reached();
>> +}
>
> thanks
> -- PMM
--
Alex Bennée
