Re: [Qemu-devel] [PATCH 3/7] target-tricore: add add.f/sub.f instructions

[Richard Henderson <rth@twiddle.net>]

> +    f_set_flags(env);                                                          \

You shouldn't need to set the flags every instruction.
You ought to be able to limit the changes to reset and
stores to the PSW.

> +    arg1 = float32_squash_input_denormal(arg1, &env->fp_status);               \
> +    arg2 = float32_squash_input_denormal(arg2, &env->fp_status);               \
> +                                                                               \
> +    if (float32_is_any_nan(arg1) || float32_is_any_nan(arg2)) {                \
> +        f_result = QUIET_NAN;                                                  \
> +        if (float32_is_signaling_nan(arg1) ||                                  \
> +            float32_is_signaling_nan(arg2)) {                                  \
> +            env->fp_status.float_exception_flags |= float_flag_invalid;        \
> +        }                                                                      \
> +    } else if (f_is_pos_inf(arg1) && f_is_neg_inf(arg2)) {                     \
> +        f_result = ADD_NAN;                                                    \
> +    } else if (f_is_pos_inf(arg2) && f_is_neg_inf(arg1)) {                     \
> +        f_result = ADD_NAN;                                                    \
> +    } else {                                                                   \
> +        f_result = float32_##name(arg1, arg2 , &env->fp_status);               \
> +    }                                                                          \

If we assume that exceptional situations are, well, exceptional, then we can
re-order this to

  f_result = float32_op(arg1, arg2, &env->fp_status);
  flags = env->fp_status.float_exception_flags;
  if (flags) {
      /* If the output is a NaN, but the inputs aren't,
         we return a unique value.  */
      if ((flags & float_flag_invalid)
          && !float32_is_any_nan(arg1)
          && !float32_is_any_nan(arg2)) {
          f_result = ADD_NAN;
      }
      f_update_psw_flags(env, flags, false);
  }

This does assume that fp_status.default_nan_mode = 1, so that
float32_default_nan is returned.  Which means that first patch should touch
fpu/softfloat-specialize.h to add tricore to the list of those defaulting to
0x7fc00000.


r~