Re: [PATCH v3 3/9] target/ppc: reduce usage of fpscr_set_rounding_mode

[David Gibson]

On Fri, May 21, 2021 at 05:17:53PM -0300, Bruno Larsen (billionai) wrote:
> It is preferable to store the current rounding mode and retore from that
> than recalculating from fpscr, so we changed the behavior of do_fri and
> VSX_ROUND to do it like that.
> 
> Suggested-by: Richard Henderson <richard.henderson@linaro.org>
> Signed-off-by: Bruno Larsen (billionai) <bruno.larsen@eldorado.org.br>
> Reviewed-by: Richard Henderson <richard.henderson@linaro.org>

Applied to ppc-for-6.1, thanks.

> ---
>  target/ppc/fpu_helper.c | 8 +++++---
>  1 file changed, 5 insertions(+), 3 deletions(-)
> 
> diff --git a/target/ppc/fpu_helper.c b/target/ppc/fpu_helper.c
> index 44315fca0b..a4a283df2b 100644
> --- a/target/ppc/fpu_helper.c
> +++ b/target/ppc/fpu_helper.c
> @@ -822,6 +822,7 @@ static inline uint64_t do_fri(CPUPPCState *env, uint64_t 
> arg,
>                                int rounding_mode)
>  {
>      CPU_DoubleU farg;
> +    FloatRoundMode old_rounding_mode = 
> get_float_rounding_mode(&env->fp_status);
>  
>      farg.ll = arg;
>  
> @@ -834,8 +835,7 @@ static inline uint64_t do_fri(CPUPPCState *env, uint64_t 
> arg,
>                        float_flag_inexact;
>          set_float_rounding_mode(rounding_mode, &env->fp_status);
>          farg.ll = float64_round_to_int(farg.d, &env->fp_status);
> -        /* Restore rounding mode from FPSCR */
> -        fpscr_set_rounding_mode(env);
> +        set_float_rounding_mode(old_rounding_mode, &env->fp_status);
>  
>          /* fri* does not set FPSCR[XX] */
>          if (!inexact) {
> @@ -3136,8 +3136,10 @@ void helper_##op(CPUPPCState *env, ppc_vsr_t *xt, 
> ppc_vsr_t *xb)       \
>  {                                                                      \
>      ppc_vsr_t t = *xt;                                                 \
>      int i;                                                             \
> +    FloatRoundMode curr_rounding_mode;                                 \
>                                                                         \
>      if (rmode != FLOAT_ROUND_CURRENT) {                                \
> +        curr_rounding_mode = get_float_rounding_mode(&env->fp_status); \
>          set_float_rounding_mode(rmode, &env->fp_status);               \
>      }                                                                  \
>                                                                         \
> @@ -3160,7 +3162,7 @@ void helper_##op(CPUPPCState *env, ppc_vsr_t *xt, 
> ppc_vsr_t *xb)       \
>       * mode from FPSCR                                                 \
>       */                                                                \
>      if (rmode != FLOAT_ROUND_CURRENT) {                                \
> -        fpscr_set_rounding_mode(env);                                  \
> +        set_float_rounding_mode(curr_rounding_mode, &env->fp_status);  \
>          env->fp_status.float_exception_flags &= ~float_flag_inexact;   \
>      }                                                                  \
>                                                                         \

-- 
David Gibson                    | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au  | minimalist, thank you.  NOT _the_ _other_
                                | _way_ _around_!
http://www.ozlabs.org/~dgibson

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