Re: [PATCH v2 for-10.0 00/54] fpu: Remove pickNaNMulAdd, default-NaN ifdefs

[Richard Henderson]

On 12/2/24 07:12, Peter Maydell wrote:
> (Apologies for this patchset being both big and having a wide CC list;
> the good news is that this is the last lot of fpu ifdef cleanup that
> needs to touch all the targets.)
>
> This patchset does the same thing we already did for pickNaN() to
> pickNaNMulAdd() -- it replaces the compile-time ifdef ladder that
> selected target-specific NaN propagation behaviour with checking some
> runtime selectable settings in the float_status.  The motivation is:
>   * this will let us have multiple targets in one QEMU binary
>   * the Arm FEAT_AFP architectural feature includes letting
>     the guest select a NaN propagation rule at runtime
> This is patches 1-26 (which were in the v1 of this series).
>
> It then does a similar thing for making targets select the default
> NaN value at runtime rather than relying on a compile-time ifdef.
> This is patches 34-54, which are new in v2.

Update needed for is_ebf in target/arm/tcg/vec_helper.c.

I think the best choice is to reverse the copy and test, e.g.

    *statusp = env->vfp.fp_status;
    set_default_nan_mode(true, statusp);

    if (ebf) {
        /* EBF=1 needs to do a step with round-to-odd semantics */
        *oddstatusp = *statusp;
        set_float_rounding_mode(float_round_to_odd, oddstatusp);
    } else {
        set_flush_to_zero(true, statusp);
        set_flush_inputs_to_zero(true, statusp);
        set_float_rounding_mode(float_round_to_odd_inf, statusp);
    }


r~