I propose a new way to computing the float flags,
We preserve a float computing cash
typedef struct FpRecord {
uint8_t op;
float32 A;
float32 B;
} FpRecord;
FpRecord fp_cache[1024];
int fp_cache_length;
uint32_t fp_exceptions;
1. For each new fp operation we push it to the fp_cache,
2. Once we read the fp_exceptions , then we re-compute
the fp_exceptions by re-running the fp FpRecord sequence.
and clear fp_cache_length.
3. If we clear the fp_exceptions , then we set fp_cache_length to 0 and
clear fp_exceptions.
4. If the fp_cache are full, then we re-compute
the fp_exceptions by re-running the fp FpRecord sequence.
Would this be a general method to use hard-float?
The consued time should be 2*hard_float.
Considerating read fp_exceptions are rare, then the amortized time
complexity
would be 1 * hard_float.
On Thu, Apr 30, 2020 at 10:18 AM Richard Henderson <
richard.hender...@linaro.org> wrote:
> On 4/29/20 5:20 PM, 罗勇刚(Yonggang Luo) wrote:
> > Question, in hard-float, if we don't want to read the fp register.
> > for example: If we wanna compute c = a + b in fp32
> > if c = a + b In hard float
> > and if b1 = c - a in hard float
> > if b1 != b at bitwise level, the we se the inexat to 1, otherwsie
> > we set inexat bit to 0? are this valid?
> >
> > we can also do it for a * b, a - b, a / b.
> >
>
> That does seem plausible, for all of the normal values for which we would
> apply
> the hard-float optimization anyway. But we already check for the
> exceptional
> cases:
>
> if (unlikely(f32_is_inf(ur))) {
> s->float_exception_flags |= float_flag_overflow;
> } else if (unlikely(fabsf(ur.h) <= FLT_MIN)) {
> if (post == NULL || post(ua, ub)) {
> goto soft;
> }
> }
>
>
> r~
>
--
此致
礼
罗勇刚
Yours
sincerely,
Yonggang Luo
