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authorRichard Henderson <richard.henderson@linaro.org>2020-11-21 16:35:54 -0800
committerRichard Henderson <richard.henderson@linaro.org>2021-06-03 14:09:02 -0700
commit98b3cff7537ad2a9ce0faa6ad0af4191bd066916 (patch)
tree1268113bf435285c52033e27e75224f3ba155ce4 /fpu
parent8da5f1dbb0d7b97686d54584c70b55cb05f89007 (diff)
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softfloat: Adjust parts_uncanon_normal for floatx80
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]. Reviewed-by: Alex Bennée <alex.bennee@linaro.org> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Diffstat (limited to 'fpu')
-rw-r--r--fpu/softfloat-parts.c.inc36
1 files changed, 30 insertions, 6 deletions
diff --git a/fpu/softfloat-parts.c.inc b/fpu/softfloat-parts.c.inc
index a026581..efb81bb 100644
--- a/fpu/softfloat-parts.c.inc
+++ b/fpu/softfloat-parts.c.inc
@@ -155,7 +155,13 @@ static void partsN(uncanon_normal)(FloatPartsN *p, float_status *s,
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_ties_away:
inc = frac_lsbm1;
@@ -176,7 +182,11 @@ static void partsN(uncanon_normal)(FloatPartsN *p, float_status *s,
overflow_norm = true;
/* fall through */
case float_round_to_odd_inf:
- 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;
@@ -232,18 +245,29 @@ 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:
case float_round_to_odd_inf:
- 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;