Re: [Qemu-devel] [PATCH 1/1] target/ppc: Fix do_float_check_status vs inexact

[Paul Clarke]

On 8/26/19 11:54 AM, Richard Henderson wrote:
> The underflow and inexact exceptions are not mutually exclusive.
> Check for both of them.  Tidy the reset of FPSCR[FI].
> 
> Fixes: https://bugs.launchpad.net/bugs/1841442
> Reported-by: Paul Clarke <address@hidden>
> Signed-off-by: Richard Henderson <address@hidden>

Tested-by: Paul Clarke <address@hidden>

Thanks, Richard!

There seems to be a similar problem with underflow.  I'll narrow down a test 
case, and I guess I'll just open a new bug report.

PC
> ---
>  target/ppc/fpu_helper.c | 10 +++-------
>  1 file changed, 3 insertions(+), 7 deletions(-)
> 
> diff --git a/target/ppc/fpu_helper.c b/target/ppc/fpu_helper.c
> index 07bc9051b0..2e023c5204 100644
> --- a/target/ppc/fpu_helper.c
> +++ b/target/ppc/fpu_helper.c
> @@ -630,19 +630,15 @@ static void do_float_check_status(CPUPPCState *env, 
> uintptr_t raddr)
>  {
>      CPUState *cs = env_cpu(env);
>      int status = get_float_exception_flags(&env->fp_status);
> -    bool inexact_happened = false;
>  
>      if (status & float_flag_overflow) {
>          float_overflow_excp(env);
>      } else if (status & float_flag_underflow) {
>          float_underflow_excp(env);
> -    } else if (status & float_flag_inexact) {
> -        float_inexact_excp(env);
> -        inexact_happened = true;
>      }
> -
> -    /* if the inexact flag was not set */
> -    if (inexact_happened == false) {
> +    if (status & float_flag_inexact) {
> +        float_inexact_excp(env);
> +    } else {
>          env->fpscr &= ~(1 << FPSCR_FI); /* clear the FPSCR[FI] bit */
>      }
>  
>