With floatx80_precision_x, the rounding happens across
the break between words. Notice this case with
frac_lsb = round_mask + 1 -> 0
and check the bits in frac_hi as needed.
In addition, since frac_shift == 0, we won't implicitly clear
round_mask via the right-shift, so explicitly clear those bits.
This fixes rounding for floatx80_precision_[sd].
Signed-off-by: Richard Henderson <richard.hender...@linaro.org>
---
fpu/softfloat-parts.c.inc | 36 ++++++++++++++++++++++++++++++------
1 file changed, 30 insertions(+), 6 deletions(-)
diff --git a/fpu/softfloat-parts.c.inc b/fpu/softfloat-parts.c.inc
index b456c1c30c..8a7f22d6b5 100644
--- a/fpu/softfloat-parts.c.inc
+++ b/fpu/softfloat-parts.c.inc
@@ -156,7 +156,13 @@ static void partsN(uncanon_normal)(FloatPartsN *p,
float_status *s,
switch (s->float_rounding_mode) {
case float_round_nearest_even:
overflow_norm = false;
- inc = ((p->frac_lo & roundeven_mask) != frac_lsbm1 ? frac_lsbm1 : 0);
+ if (N > 64 && frac_lsb == 0) {
+ inc = ((p->frac_hi & 1) || (p->frac_lo & round_mask) != frac_lsbm1
+ ? frac_lsbm1 : 0);
+ } else {
+ inc = ((p->frac_lo & roundeven_mask) != frac_lsbm1
+ ? frac_lsbm1 : 0);
+ }
break;
case float_round_ties_away:
overflow_norm = false;
@@ -176,7 +182,11 @@ static void partsN(uncanon_normal)(FloatPartsN *p,
float_status *s,
break;
case float_round_to_odd:
overflow_norm = true;
- inc = p->frac_lo & frac_lsb ? 0 : round_mask;
+ if (N > 64 && frac_lsb == 0) {
+ inc = p->frac_hi & 1 ? 0 : round_mask;
+ } else {
+ inc = p->frac_lo & frac_lsb ? 0 : round_mask;
+ }
break;
default:
g_assert_not_reached();
@@ -191,8 +201,8 @@ static void partsN(uncanon_normal)(FloatPartsN *p,
float_status *s,
p->frac_hi |= DECOMPOSED_IMPLICIT_BIT;
exp++;
}
+ p->frac_lo &= ~round_mask;
}
- frac_shr(p, frac_shift);
if (fmt->arm_althp) {
/* ARM Alt HP eschews Inf and NaN for a wider exponent. */
@@ -201,18 +211,21 @@ static void partsN(uncanon_normal)(FloatPartsN *p,
float_status *s,
flags = float_flag_invalid;
exp = exp_max;
frac_allones(p);
+ p->frac_lo &= ~round_mask;
}
} else if (unlikely(exp >= exp_max)) {
flags |= float_flag_overflow | float_flag_inexact;
if (overflow_norm) {
exp = exp_max - 1;
frac_allones(p);
+ p->frac_lo &= ~round_mask;
} else {
p->cls = float_class_inf;
exp = exp_max;
frac_clear(p);
}
}
+ frac_shr(p, frac_shift);
} else if (s->flush_to_zero) {
flags |= float_flag_output_denormal;
p->cls = float_class_zero;
@@ -232,17 +245,28 @@ static void partsN(uncanon_normal)(FloatPartsN *p,
float_status *s,
/* Need to recompute round-to-even/round-to-odd. */
switch (s->float_rounding_mode) {
case float_round_nearest_even:
- inc = ((p->frac_lo & roundeven_mask) != frac_lsbm1
- ? frac_lsbm1 : 0);
+ if (N > 64 && frac_lsb == 0) {
+ inc = ((p->frac_hi & 1) ||
+ (p->frac_lo & round_mask) != frac_lsbm1
+ ? frac_lsbm1 : 0);
+ } else {
+ inc = ((p->frac_lo & roundeven_mask) != frac_lsbm1
+ ? frac_lsbm1 : 0);
+ }
break;
case float_round_to_odd:
- inc = p->frac_lo & frac_lsb ? 0 : round_mask;
+ if (N > 64 && frac_lsb == 0) {
+ inc = p->frac_hi & 1 ? 0 : round_mask;
+ } else {
+ inc = p->frac_lo & frac_lsb ? 0 : round_mask;
+ }
break;
default:
break;
}
flags |= float_flag_inexact;
frac_addi(p, p, inc);
+ p->frac_lo &= ~round_mask;
}
exp = (p->frac_hi & DECOMPOSED_IMPLICIT_BIT) != 0;
--
2.25.1
