Re: [PATCH] fpu/softfloat: set invalid excp flag for RISC-V muladd instructions

[Richard Henderson]

On 4/18/21 10:56 PM, frank.chang@sifive.com wrote:
> +#elif defined(TARGET_RISCV)
> +    /*
> +     * For RISC-V, InvalidOp is set when multiplicands are Inf and zero
> +     * and returns default NaN.
> +     */
> +    if (infzero) {
> +        float_raise(float_flag_invalid, status);
> +        return 3;
> +    }
> +
> +    if (is_nan(a_cls)) {
> +        return 0;
> +    } else if (is_nan(b_cls)) {
> +        return 1;
> +    } else {
> +        return 2;
> +    }

This second half of the function made me go look into the spec to make sure you 
had got that selection right.  But RISCV is always in default_nan mode, so all 
this is unused (and overridden in pick_nan_muladd).

I think for avoidance of confusion, you should use

    if (infzero) {
        float_raise(float_flag_invalid, status);
    }
    return 3; /* default nan */


r~