Re: [PATCH 2/2] target/ppc: Bugfix FP when OE/UE are set

[Richard Henderson]

On 8/5/22 07:15, Lucas Mateus Castro(alqotel) wrote:
> From: "Lucas Mateus Castro (alqotel)" <lucas.araujo@eldorado.org.br>
>
> When an overflow exception occurs and OE is set the intermediate result
> should be adjusted (by subtracting from the exponent) to avoid rounding
> to inf. The same applies to an underflow exceptionion and UE (but adding
> to the exponent). To do this set the fp_status.rebias_overflow when OE
> is set and fp_status.rebias_underflow when UE is set as the FPU will
> recalculate in case of a overflow/underflow if the according rebias* is
> set.
>
> Signed-off-by: Lucas Mateus Castro (alqotel) <lucas.araujo@eldorado.org.br>
> ---
>   target/ppc/cpu.c        | 2 ++
>   target/ppc/fpu_helper.c | 2 --
>   2 files changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/target/ppc/cpu.c b/target/ppc/cpu.c
> index 401b6f9e63..0ebac04bc4 100644
> --- a/target/ppc/cpu.c
> +++ b/target/ppc/cpu.c
> @@ -120,6 +120,8 @@ void ppc_store_fpscr(CPUPPCState *env, target_ulong val)
>           val |= FP_FEX;
>       }
>       env->fpscr = val;
> +    env->fp_status.rebias_overflow  = (FP_OE & env->fpscr) ? true : false;
> +    env->fp_status.rebias_underflow = (FP_UE & env->fpscr) ? true : false;

No point in the ?: operator.

Otherwise,
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>


r~

>       if (tcg_enabled()) {
>           fpscr_set_rounding_mode(env);
>       }
> diff --git a/target/ppc/fpu_helper.c b/target/ppc/fpu_helper.c
> index 134804628b..c17575de5d 100644
> --- a/target/ppc/fpu_helper.c
> +++ b/target/ppc/fpu_helper.c
> @@ -344,7 +344,6 @@ static inline int float_overflow_excp(CPUPPCState *env)
>   
>       bool overflow_enabled = !!(env->fpscr & FP_OE);
>       if (overflow_enabled) {
> -        /* XXX: should adjust the result */
>           /* Update the floating-point enabled exception summary */
>           env->fpscr |= FP_FEX;
>           /* We must update the target FPR before raising the exception */
> @@ -363,7 +362,6 @@ static inline void float_underflow_excp(CPUPPCState *env)
>       /* Update the floating-point exception summary */
>       env->fpscr |= FP_FX;
>       if (env->fpscr & FP_UE) {
> -        /* XXX: should adjust the result */
>           /* Update the floating-point enabled exception summary */
>           env->fpscr |= FP_FEX;
>           /* We must update the target FPR before raising the exception */