Re: [Qemu-devel] [PATCH v4 2/4] target-tilegx: Add single floating point implementation

[Richard Henderson <rth@twiddle.net>]

On 12/23/2015 01:48 PM, chengang@emindsoft.com.cn wrote:
> +static float32 sfmt_to_float32(uint64_t sfmt)
> +{
> +    uint32_t sign = get_fsingle_sign(sfmt);
> +    uint32_t man = get_fsingle_man(sfmt);
> +    uint32_t exp = get_fsingle_exp(sfmt);
> +    float32 f;
> +
> +    if (get_fsingle_calc(sfmt) == TILEGX_F_CALC_CVT) {
> +        if (sign) {
> +            f = int32_to_float32(0 - man, &fp_status);
> +        } else {
> +            f = uint32_to_float32(man, &fp_status);
> +        }
> +        exp += get_f32_exp(f) - 0x9e;
> +        if ((int32_t) exp < 0) {
> +            return float32_infinity | float32_set_sign(float32_zero, sign);
> +        } else if (exp >= 0xff) {
> +            return float32_zero | float32_set_sign(float32_zero, sign);
> +        } else {
> +            set_f32_exp(&f, exp);
> +        }


What in the world are you attempting to do here?
This is not normalization.  This is not even remotely
correct with respect to zero or infinity.

Moreover, I thought we agreed to do away with that CALC bit.


r~

> +    } else {
> +        f = create_f32_man(man >> 8);
> +        set_f32_exp(&f, exp);
> +    }
> +
> +    f = float32_set_sign(f, sign);
> +    return f;
> +}
> +
> +uint64_t helper_fsingle_pack2(uint64_t srca)
> +{
> +    return float32_val(sfmt_to_float32(srca));
> +}
> +
> +static uint64_t main_calc(float32 fsrca, float32 fsrcb,
> +                          float32 (*calc)(float32, float32, float_status *))
> +{
> +    uint64_t sfmt = float32_to_sfmt(calc(fsrca, fsrcb, &fp_status));
> +
> +    if (float32_eq(fsrca, fsrcb, &fp_status)) {
> +        sfmt |= create_fsfd_flag_eq();
> +    } else {
> +        sfmt |= create_fsfd_flag_ne();
> +    }
> +
> +    if (float32_lt(fsrca, fsrcb, &fp_status)) {
> +        sfmt |= create_fsfd_flag_lt();
> +    }
> +    if (float32_le(fsrca, fsrcb, &fp_status)) {
> +        sfmt |= create_fsfd_flag_le();
> +    }
> +
> +    if (float32_lt(fsrcb, fsrca, &fp_status)) {
> +        sfmt |= create_fsfd_flag_gt();
> +    }
> +    if (float32_le(fsrcb, fsrca, &fp_status)) {
> +        sfmt |= create_fsfd_flag_ge();
> +    }
> +
> +    if (float32_unordered(fsrca, fsrcb, &fp_status)) {
> +        sfmt |= create_fsfd_flag_un();
> +    }
> +
> +    set_fsingle_calc(&sfmt, TILEGX_F_CALC_NCVT);
> +    return sfmt;
> +}
> +
> +uint64_t helper_fsingle_add1(uint64_t srca, uint64_t srcb)
> +{
> +    return main_calc(make_float32(srca), make_float32(srcb), float32_add);
> +}
> +
> +uint64_t helper_fsingle_sub1(uint64_t srca, uint64_t srcb)
> +{
> +    return main_calc(make_float32(srca), make_float32(srcb), float32_sub);
> +}
> +
> +uint64_t helper_fsingle_mul1(uint64_t srca, uint64_t srcb)
> +{
> +    return main_calc(make_float32(srca), make_float32(srcb), float32_mul);
> +}
>