On 1/7/23 15:00, Mark Cave-Ayland wrote:
void HELPER(frem)(CPUM68KState *env, FPReg *res, FPReg *val0, FPReg *val1)
{
+ float_status fp_status;
+ FPReg fp_quot;
uint32_t quotient;
int sign;
+ /* Calculate quotient directly using round to nearest mode */
+ set_float_rounding_mode(float_round_nearest_even, &fp_status);
+ set_floatx80_rounding_precision(
+ get_floatx80_rounding_precision(&env->fp_status), &fp_status);
+ fp_quot.d = floatx80_div(val1->d, val0->d, &fp_status);
+
res->d = floatx80_rem(val1->d, val0->d, &env->fp_status);
- if (floatx80_is_any_nan(res->d)) {
+ if (floatx80_is_any_nan(fp_quot.d)) {
I think you should leave this line unchanged, and move the div afterward.
I also think you should completely initialize the local fp_status = { }.
With that,
Reviewed-by: Richard Henderson <richard.hender...@linaro.org>
I can leave the floatx80_is_any_nan() line above unchanged and also initialise the local
fp_status, however the floatx80_div() has to happen before floatx80_rem() function is
called. This is because the fmod and frem instructions write the result back to one of the
input registers, which then causes the subsequent floatx80_div() to return an incorrect
result.
Would just these 2 changes be enough to keep your R-B tag for a v3?
Mm. I suppose so. Otherwise, compute into a local variable:
floatx80 fp_rem = floatx80_rem(val1->d, val0->d, &env->fp_status);
if (!floatx80_is_any_nan(fp_rem)) {
float_status scratch = env->fp_status;
floatx80 fp_quot;
uint32_t int_quot;
int sign;
set_float_rounding_mode(float_round_nearest_even, &scratch);
fp_quot = floatx80_div(val1->d, val0->d, &scratch);
sign = ...
int_quot = ...
...
}
res->d = fp_rem;
?
r~
