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fmaq.c (fmaq): Merge from GLIBC.

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2012-11-01  Tobias Burnus  <burnus@net-b.de>
            Joseph Myers  <joseph@codesourcery.com>

        * math/fmaq.c (fmaq): Merge from GLIBC. Handle cases
        with small x * y using scaling, not as x * y + z.
        * math/lgammaq.c (lgammaq): Fix signgam handling.


Co-Authored-By: Joseph Myers <joseph@codesourcery.com>

From-SVN: r193099
This commit is contained in:
Tobias Burnus 2012-11-02 17:59:30 +01:00 committed by Tobias Burnus
parent f2a1b46987
commit e4320d7da0
3 changed files with 56 additions and 21 deletions
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7
libquadmath/ChangeLog
View File

@ -1,3 +1,10 @@
2012-11-01 Tobias Burnus <burnus@net-b.de>
Joseph Myers <joseph@codesourcery.com>
* math/fmaq.c (fmaq): Merge from GLIBC. Handle cases
with small x * y using scaling, not as x * y + z.
* math/lgammaq.c (lgammaq): Fix signgam handling.
2012-11-01 Tobias Burnus <burnus@net-b.de>
* Makefile.am (libquadmath_la_SOURCES): Add new math/* files.

53
libquadmath/math/fmaq.c
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@ -73,6 +73,37 @@ fmaq (__float128 x, __float128 y, __float128 z)
|| u.ieee.exponent + v.ieee.exponent
< IEEE854_FLOAT128_BIAS - FLT128_MANT_DIG - 2)
return x * y + z;
/* If x * y is less than 1/4 of FLT128_DENORM_MIN, neither the
result nor whether there is underflow depends on its exact
value, only on its sign. */
if (u.ieee.exponent + v.ieee.exponent
< IEEE854_FLT128_DOUBLE_BIAS - FLT128_MANT_DIG - 2)
{
int neg = u.ieee.negative ^ v.ieee.negative;
__float128 tiny = neg ? -0x1p-16494L : 0x1p-16494L;
if (w.ieee.exponent >= 3)
return tiny + z;
/* Scaling up, adding TINY and scaling down produces the
correct result, because in round-to-nearest mode adding
TINY has no effect and in other modes double rounding is
harmless. But it may not produce required underflow
exceptions. */
v.value = z * 0x1p114L + tiny;
if (TININESS_AFTER_ROUNDING
? v.ieee.exponent < 115
: (w.ieee.exponent == 0
|| (w.ieee.exponent == 1
&& w.ieee.negative != neg
&& w.ieee.mantissa3 == 0
&& w.ieee.mantissa2 == 0
&& w.ieee.mantissa1 == 0
&& w.ieee.mantissa0 == 0)))
{
volatile __float128 force_underflow = x * y;
(void) force_underflow;
}
return v.value * 0x1p-114L;
}
if (u.ieee.exponent + v.ieee.exponent
>= 0x7fff + IEEE854_FLOAT128_BIAS - FLT128_MANT_DIG)
{
@ -228,17 +259,17 @@ fmaq (__float128 x, __float128 y, __float128 z)
for proper rounding. */
if (v.ieee.exponent == 226)
{
/* If the exponent would be in the normal range when
rounding to normal precision with unbounded exponent
range, the exact result is known and spurious underflows
must be avoided on systems detecting tininess after
rounding. */
if (TININESS_AFTER_ROUNDING)
{
w.value = a1 + u.value;
if (w.ieee.exponent == 227)
return w.value * 0x1p-226L;
}
/* If the exponent would be in the normal range when
rounding to normal precision with unbounded exponent
range, the exact result is known and spurious underflows
must be avoided on systems detecting tininess after
rounding. */
if (TININESS_AFTER_ROUNDING)
{
w.value = a1 + u.value;
if (w.ieee.exponent == 227)
return w.value * 0x1p-226L;
}
/* v.ieee.mant_low & 2 is LSB bit of the result before rounding,
v.ieee.mant_low & 1 is the round bit and j is our sticky
bit. */

17
libquadmath/math/lgammaq.c
View File

@ -759,7 +759,8 @@ lgammaq (__float128 x)
{
__float128 p, q, w, z, nx;
int i, nn;
int sign;
signgam = 1;
if (! finiteq (x))
return x * x;
@ -767,11 +768,9 @@ lgammaq (__float128 x)
if (x == 0.0Q)
{
if (signbitq (x))
sign = -1;
signgam = -1;
}
signgam = sign;
if (x < 0.0Q)
{
q = -x;
@ -780,9 +779,9 @@ lgammaq (__float128 x)
return (one / (p - p));
i = p;
if ((i & 1) == 0)
sign = -1;
signgam = -1;
else
sign = 1;
signgam = 1;
z = q - p;
if (z > 0.5Q)
{
@ -790,10 +789,8 @@ lgammaq (__float128 x)
z = p - q;
}
z = q * sinq (PIQ * z);
signgam = sign;
if (z == 0.0Q)
return (sign * huge * huge);
return (signgam * huge * huge);
w = lgammaq (q);
z = logq (PIQ / z) - w;
return (z);
@ -1025,7 +1022,7 @@ lgammaq (__float128 x)
}
if (x > MAXLGM)
return (sign * huge * huge);
return (signgam * huge * huge);
q = ls2pi - x;
q = (x - 0.5Q) * logq (x) + q;