Re: [PATCH] target/ppc: Replicate double->int32 result for some vector insns

[Cédric Le Goater]

On 3/15/22 06:39, Richard Henderson wrote:
> Power ISA v3.1 formalizes the previously undefined result in
> words 1 and 3 to be a copy of the result in words 0 and 2.
>
> This affects: xscvdpsxws, xscvdpuxws, xvcvdpsxws, xvcvdpuxws.
>
> Resolves: https://gitlab.com/qemu-project/qemu/-/issues/852
> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

Reviewed-by: Cédric Le Goater <clg@kaod.org>
Tested-by: Cédric Le Goater <clg@kaod.org>

Thanks,

C.


> ---
>   target/ppc/fpu_helper.c | 43 +++++++++++++++++++++++++++++++++++------
>   1 file changed, 37 insertions(+), 6 deletions(-)
>
> diff --git a/target/ppc/fpu_helper.c b/target/ppc/fpu_helper.c
> index bd12db960a..e76d2ae83a 100644
> --- a/target/ppc/fpu_helper.c
> +++ b/target/ppc/fpu_helper.c
> @@ -2891,22 +2891,53 @@ void helper_##op(CPUPPCState *env, ppc_vsr_t *xt, 
> ppc_vsr_t *xb)             \
>   
>   VSX_CVT_FP_TO_INT(xscvdpsxds, 1, float64, int64, VsrD(0), VsrD(0), \
>                     0x8000000000000000ULL)
> -VSX_CVT_FP_TO_INT(xscvdpsxws, 1, float64, int32, VsrD(0), VsrW(1), \
> -                  0x80000000U)
>   VSX_CVT_FP_TO_INT(xscvdpuxds, 1, float64, uint64, VsrD(0), VsrD(0), 0ULL)
> -VSX_CVT_FP_TO_INT(xscvdpuxws, 1, float64, uint32, VsrD(0), VsrW(1), 0U)
>   VSX_CVT_FP_TO_INT(xvcvdpsxds, 2, float64, int64, VsrD(i), VsrD(i), \
>                     0x8000000000000000ULL)
> -VSX_CVT_FP_TO_INT(xvcvdpsxws, 2, float64, int32, VsrD(i), VsrW(2 * i), \
> -                  0x80000000U)
>   VSX_CVT_FP_TO_INT(xvcvdpuxds, 2, float64, uint64, VsrD(i), VsrD(i), 0ULL)
> -VSX_CVT_FP_TO_INT(xvcvdpuxws, 2, float64, uint32, VsrD(i), VsrW(2 * i), 0U)
>   VSX_CVT_FP_TO_INT(xvcvspsxds, 2, float32, int64, VsrW(2 * i), VsrD(i), \
>                     0x8000000000000000ULL)
>   VSX_CVT_FP_TO_INT(xvcvspsxws, 4, float32, int32, VsrW(i), VsrW(i), 
> 0x80000000U)
>   VSX_CVT_FP_TO_INT(xvcvspuxds, 2, float32, uint64, VsrW(2 * i), VsrD(i), 0ULL)
>   VSX_CVT_FP_TO_INT(xvcvspuxws, 4, float32, uint32, VsrW(i), VsrW(i), 0U)
>   
> +/*
> + * Likewise, except that the result is duplicated into both subwords.
> + * Power ISA v3.1 has Programming Notes for these insns:
> + *     Previous versions of the architecture allowed the contents of
> + *     word 0 of the result register to be undefined. However, all
> + *     processors that support this instruction write the result into
> + *     words 0 and 1 (and words 2 and 3) of the result register, as
> + *     is required by this version of the architecture.
> + */
> +#define VSX_CVT_FP_TO_INT2(op, nels, stp, ttp, rnan)                         \
> +void helper_##op(CPUPPCState *env, ppc_vsr_t *xt, ppc_vsr_t *xb)             \
> +{                                                                            \
> +    int all_flags = env->fp_status.float_exception_flags, flags;             \
> +    ppc_vsr_t t = { };                                                       \
> +    int i;                                                                   \
> +                                                                             \
> +    for (i = 0; i < nels; i++) {                                             \
> +        env->fp_status.float_exception_flags = 0;                            \
> +        t.VsrW(2 * i) = stp##_to_##ttp##_round_to_zero(xb->VsrD(i), 
> &env->fp_status);  \
> +        flags = env->fp_status.float_exception_flags;                        \
> +        if (unlikely(flags & float_flag_invalid)) {                          \
> +            t.VsrW(2 * i) = float_invalid_cvt(env, flags, t.VsrW(2 * i), rnan, 
> 0, GETPC()); \
> +        }                                                                    \
> +        t.VsrW(2 * i + 1) = t.VsrW(2 * i);                                   \
> +        all_flags |= flags;                                                  \
> +    }                                                                        \
> +                                                                             \
> +    *xt = t;                                                                 \
> +    env->fp_status.float_exception_flags = all_flags;                        \
> +    do_float_check_status(env, GETPC());                                     \
> +}
> +
> +VSX_CVT_FP_TO_INT2(xscvdpsxws, 1, float64, int32, 0x80000000U)
> +VSX_CVT_FP_TO_INT2(xscvdpuxws, 1, float64, uint32, 0U)
> +VSX_CVT_FP_TO_INT2(xvcvdpsxws, 2, float64, int32, 0x80000000U)
> +VSX_CVT_FP_TO_INT2(xvcvdpuxws, 2, float64, uint32, 0U)
> +
>   /*
>    * VSX_CVT_FP_TO_INT_VECTOR - VSX floating point to integer conversion
>    *   op    - instruction mnemonic