Re: [Qemu-devel] [PATCH 02/14] Add various NaN-handling macros

[Aurelien Jarno <aurelien@aurel32.net>]

On Thu, Jan 22, 2009 at 12:44:02PM -0800, Nathan Froyd wrote:
> These simplify the implementation of the floating-point Altivec
> instructions and reduce clutter.
> 
> Signed-off-by: Nathan Froyd <froydnj@codesourcery.com>
> ---
>  target-ppc/op_helper.c |   21 +++++++++++++++++++++
>  1 files changed, 21 insertions(+), 0 deletions(-)
> 
> diff --git a/target-ppc/op_helper.c b/target-ppc/op_helper.c
> index d531dd8..9820040 100644
> --- a/target-ppc/op_helper.c
> +++ b/target-ppc/op_helper.c
> @@ -1965,6 +1965,23 @@ target_ulong helper_dlmzb (target_ulong high, target_ulong low, uint32_t update_
>    for (index = ARRAY_SIZE(r->element)-1; index >= 0; index--)
>  #endif
>  
> +/* If X is a NaN, store the corresponding QNaN into RESULT.  Otherwise,
> + * execute the following block.  */
> +#define DO_HANDLE_NAN(result, x)                \
> +    if (float32_is_nan(x) || float32_is_signaling_nan(x)) {     \
> +        CPU_FloatU __f;                                         \
> +        __f.f = x;                                              \
> +        __f.l = __f.l | (1 << 22);  /* Set QNaN bit. */         \
> +        result = __f.f;                                         \
> +    } else
> +
> +#define HANDLE_NAN1(result, x)                  \
> +    DO_HANDLE_NAN(result, x)
> +#define HANDLE_NAN2(result, x, y)               \
> +    DO_HANDLE_NAN(result, x) DO_HANDLE_NAN(result, y)
> +#define HANDLE_NAN3(result, x, y, z)            \
> +    DO_HANDLE_NAN(result, x) DO_HANDLE_NAN(result, y) DO_HANDLE_NAN(result, z)
> +
>  /* Saturating arithmetic helpers.  */
>  #define SATCVT(from, to, from_type, to_type, min, max, use_min, use_max) \
>      static always_inline to_type cvt##from##to (from_type x, int *sat)  \
> @@ -2808,6 +2825,10 @@ VUPK(lsh, s32, s16, UPKLO)
>  #undef UPKHI
>  #undef UPKLO
>  
> +#undef DO_HANDLE_NAN
> +#undef HANDLE_NAN1
> +#undef HANDLE_NAN2
> +#undef HANDLE_NAN3
>  #undef VECTOR_FOR_INORDER_I
>  #undef HI_IDX
>  #undef LO_IDX

This is something already handled by the softfloat code. You should use
set_default_nan_mode(1, &env->vec_status) to get this behavior. This
could probably done directly in the init code.

-- 
Aurelien Jarno	                        GPG: 1024D/F1BCDB73
aurelien@aurel32.net                 http://www.aurel32.net