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cosmopolitan/libc/tinymath/powl.c
Justine Tunney 592f6ebc20
Make quality improvements 
- Write some more unit tests
- memcpy() on ARM is now faster
- Address the Musl complex math FIXME comments
- Some libm funcs like pow() now support setting errno
- Import the latest and greatest math functions from ARM
- Use more accurate atan2f() and log1pf() implementations
- atoi() and atol() will no longer saturate or clobber errno
2024-02-25 19:08:43 -08:00

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/*-*- mode:c;indent-tabs-mode:t;c-basic-offset:8;tab-width:8;coding:utf-8 -*-│
│ vi: set noet ft=c ts=8 sw=8 fenc=utf-8 :vi │
╚──────────────────────────────────────────────────────────────────────────────╝
│ │
│ OpenBSD /usr/src/lib/libm/src/ld80/e_powl.c │
│ /usr/src/lib/libm/src/ld128/e_powl.c │
│ │
│ Copyright (c) 2008 Stephen L. Moshier <steve@moshier.net> │
│ │
│ Permission to use, copy, modify, and distribute this software for any │
│ purpose with or without fee is hereby granted, provided that the above │
│ copyright notice and this permission notice appear in all copies. │
│ │
│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES │
│ WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF │
│ MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR │
│ ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES │
│ WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN │
│ ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF │
│ │
│ Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. │
│ │
│ Developed at SunPro, a Sun Microsystems, Inc. business. │
│ Permission to use, copy, modify, and distribute this │
│ software is freely granted, provided that this notice │
│ is preserved. │
│ │
╚─────────────────────────────────────────────────────────────────────────────*/
#include "libc/errno.h"
#include "libc/math.h"
#include "libc/tinymath/internal.h"
#include "libc/tinymath/freebsd.internal.h"
__static_yoink("openbsd_libm_notice");
__static_yoink("musl_libc_notice");
__static_yoink("fdlibm_notice");
#if LDBL_MANT_DIG == 64 && LDBL_MAX_EXP == 16384
/* powl.c
*
* Power function, long double precision
*
*
* SYNOPSIS:
*
* long double x, y, z, powl();
*
* z = powl( x, y );
*
*
* DESCRIPTION:
*
* Computes x raised to the yth power. Analytically,
*
* x**y = exp( y log(x) ).
*
* Following Cody and Waite, this program uses a lookup table
* of 2**-i/32 and pseudo extended precision arithmetic to
* obtain several extra bits of accuracy in both the logarithm
* and the exponential.
*
*
* ACCURACY:
*
* The relative error of pow(x,y) can be estimated
* by y dl ln(2), where dl is the absolute error of
* the internally computed base 2 logarithm. At the ends
* of the approximation interval the logarithm equal 1/32
* and its relative error is about 1 lsb = 1.1e-19. Hence
* the predicted relative error in the result is 2.3e-21 y .
*
* Relative error:
* arithmetic domain # trials peak rms
*
* IEEE +-1000 40000 2.8e-18 3.7e-19
* .001 < x < 1000, with log(x) uniformly distributed.
* -1000 < y < 1000, y uniformly distributed.
*
* IEEE 0,8700 60000 6.5e-18 1.0e-18
* 0.99 < x < 1.01, 0 < y < 8700, uniformly distributed.
*
*
* ERROR MESSAGES:
*
* message condition value returned
* pow overflow x**y > MAXNUM INFINITY
* pow underflow x**y < 1/MAXNUM 0.0
* pow domain x<0 and y noninteger 0.0
*
*/
/* Table size */
#define NXT 32
/* log(1+x) = x - .5x^2 + x^3 * P(z)/Q(z)
* on the domain 2^(-1/32) - 1 <= x <= 2^(1/32) - 1
*/
static const long double P[] = {
8.3319510773868690346226E-4L,
4.9000050881978028599627E-1L,
1.7500123722550302671919E0L,
1.4000100839971580279335E0L,
};
static const long double Q[] = {
/* 1.0000000000000000000000E0L,*/
5.2500282295834889175431E0L,
8.4000598057587009834666E0L,
4.2000302519914740834728E0L,
};
/* A[i] = 2^(-i/32), rounded to IEEE long double precision.
* If i is even, A[i] + B[i/2] gives additional accuracy.
*/
static const long double A[33] = {
1.0000000000000000000000E0L,
9.7857206208770013448287E-1L,
9.5760328069857364691013E-1L,
9.3708381705514995065011E-1L,
9.1700404320467123175367E-1L,
8.9735453750155359320742E-1L,
8.7812608018664974155474E-1L,
8.5930964906123895780165E-1L,
8.4089641525371454301892E-1L,
8.2287773907698242225554E-1L,
8.0524516597462715409607E-1L,
7.8799042255394324325455E-1L,
7.7110541270397041179298E-1L,
7.5458221379671136985669E-1L,
7.3841307296974965571198E-1L,
7.2259040348852331001267E-1L,
7.0710678118654752438189E-1L,
6.9195494098191597746178E-1L,
6.7712777346844636413344E-1L,
6.6261832157987064729696E-1L,
6.4841977732550483296079E-1L,
6.3452547859586661129850E-1L,
6.2092890603674202431705E-1L,
6.0762367999023443907803E-1L,
5.9460355750136053334378E-1L,
5.8186242938878875689693E-1L,
5.6939431737834582684856E-1L,
5.5719337129794626814472E-1L,
5.4525386633262882960438E-1L,
5.3357020033841180906486E-1L,
5.2213689121370692017331E-1L,
5.1094857432705833910408E-1L,
5.0000000000000000000000E-1L,
};
static const long double B[17] = {
0.0000000000000000000000E0L,
2.6176170809902549338711E-20L,
-1.0126791927256478897086E-20L,
1.3438228172316276937655E-21L,
1.2207982955417546912101E-20L,
-6.3084814358060867200133E-21L,
1.3164426894366316434230E-20L,
-1.8527916071632873716786E-20L,
1.8950325588932570796551E-20L,
1.5564775779538780478155E-20L,
6.0859793637556860974380E-21L,
-2.0208749253662532228949E-20L,
1.4966292219224761844552E-20L,
3.3540909728056476875639E-21L,
-8.6987564101742849540743E-22L,
-1.2327176863327626135542E-20L,
0.0000000000000000000000E0L,
};
/* 2^x = 1 + x P(x),
* on the interval -1/32 <= x <= 0
*/
static const long double R[] = {
1.5089970579127659901157E-5L,
1.5402715328927013076125E-4L,
1.3333556028915671091390E-3L,
9.6181291046036762031786E-3L,
5.5504108664798463044015E-2L,
2.4022650695910062854352E-1L,
6.9314718055994530931447E-1L,
};
#define MEXP (NXT*16384.0L)
/* The following if denormal numbers are supported, else -MEXP: */
#define MNEXP (-NXT*(16384.0L+64.0L))
/* log2(e) - 1 */
#define LOG2EA 0.44269504088896340735992L
#define F W
#define Fa Wa
#define Fb Wb
#define G W
#define Ga Wa
#define Gb u
#define H W
#define Ha Wb
#define Hb Wb
static const long double MAXLOGL = 1.1356523406294143949492E4L;
static const long double MINLOGL = -1.13994985314888605586758E4L;
static const long double LOGE2L = 6.9314718055994530941723E-1L;
static const long double huge = 0x1p10000L;
/* XXX Prevent gcc from erroneously constant folding this. */
static const volatile long double twom10000 = 0x1p-10000L;
static long double reducl(long double);
static long double powil(long double, int);
long double powl(long double x, long double y)
{
/* double F, Fa, Fb, G, Ga, Gb, H, Ha, Hb */
int i, nflg, iyflg, yoddint;
long e;
volatile long double z=0;
long double w=0, W=0, Wa=0, Wb=0, ya=0, yb=0, u=0;
/* make sure no invalid exception is raised by nan comparision */
if (isnan(x)) {
if (!isnan(y) && y == 0.0)
return 1.0;
return x;
}
if (isnan(y)) {
if (x == 1.0)
return 1.0;
return y;
}
if (x == 1.0)
return 1.0; /* 1**y = 1, even if y is nan */
if (x == -1.0 && !isfinite(y))
return 1.0; /* -1**inf = 1 */
if (y == 0.0)
return 1.0; /* x**0 = 1, even if x is nan */
if (y == 1.0)
return x;
if (y >= LDBL_MAX) {
if (x > 1.0 || x < -1.0)
return INFINITY;
if (x != 0.0)
return 0.0;
}
if (y <= -LDBL_MAX) {
if (x > 1.0 || x < -1.0)
return 0.0;
if (x != 0.0 || y == -INFINITY)
return INFINITY;
}
if (x >= LDBL_MAX) {
if (y > 0.0)
return INFINITY;
return 0.0;
}
w = floorl(y);
/* Set iyflg to 1 if y is an integer. */
iyflg = 0;
if (w == y)
iyflg = 1;
/* Test for odd integer y. */
yoddint = 0;
if (iyflg) {
ya = fabsl(y);
ya = floorl(0.5 * ya);
yb = 0.5 * fabsl(w);
if( ya != yb )
yoddint = 1;
}
if (x <= -LDBL_MAX) {
if (y > 0.0) {
if (yoddint)
return -INFINITY;
return INFINITY;
}
if (y < 0.0) {
if (yoddint)
return -0.0;
return 0.0;
}
}
nflg = 0; /* (x<0)**(odd int) */
if (x <= 0.0) {
if (x == 0.0) {
if (y < 0.0) {
if (signbit(x) && yoddint)
/* (-0.0)**(-odd int) = -inf, divbyzero */
return -1.0/0.0;
/* (+-0.0)**(negative) = inf, divbyzero */
return 1.0/0.0;
}
if (signbit(x) && yoddint)
return -0.0;
return 0.0;
}
if (iyflg == 0)
return (x - x) / (x - x); /* (x<0)**(non-int) is NaN */
/* (x<0)**(integer) */
if (yoddint)
nflg = 1; /* negate result */
x = -x;
}
/* (+integer)**(integer) */
if (iyflg && floorl(x) == x && fabsl(y) < 32768.0) {
w = powil(x, (int)y);
return nflg ? -w : w;
}
/* separate significand from exponent */
x = frexpl(x, &i);
e = i;
/* find significand in antilog table A[] */
i = 1;
if (x <= A[17])
i = 17;
if (x <= A[i+8])
i += 8;
if (x <= A[i+4])
i += 4;
if (x <= A[i+2])
i += 2;
if (x >= A[1])
i = -1;
i += 1;
/* Find (x - A[i])/A[i]
* in order to compute log(x/A[i]):
*
* log(x) = log( a x/a ) = log(a) + log(x/a)
*
* log(x/a) = log(1+v), v = x/a - 1 = (x-a)/a
*/
x -= A[i];
x -= B[i/2];
x /= A[i];
/* rational approximation for log(1+v):
*
* log(1+v) = v - v**2/2 + v**3 P(v) / Q(v)
*/
z = x*x;
w = x * (z * __polevll(x, P, 3) / __p1evll(x, Q, 3));
w = w - 0.5*z;
/* Convert to base 2 logarithm:
* multiply by log2(e) = 1 + LOG2EA
*/
z = LOG2EA * w;
z += w;
z += LOG2EA * x;
z += x;
/* Compute exponent term of the base 2 logarithm. */
w = -i;
w /= NXT;
w += e;
/* Now base 2 log of x is w + z. */
/* Multiply base 2 log by y, in extended precision. */
/* separate y into large part ya
* and small part yb less than 1/NXT
*/
ya = reducl(y);
yb = y - ya;
/* (w+z)(ya+yb)
* = w*ya + w*yb + z*y
*/
F = z * y + w * yb;
Fa = reducl(F);
Fb = F - Fa;
G = Fa + w * ya;
Ga = reducl(G);
Gb = G - Ga;
H = Fb + Gb;
Ha = reducl(H);
w = (Ga + Ha) * NXT;
/* Test the power of 2 for overflow */
if (w > MEXP)
return huge * huge; /* overflow */
if (w < MNEXP)
return twom10000 * twom10000; /* underflow */
e = w;
Hb = H - Ha;
if (Hb > 0.0) {
e += 1;
Hb -= 1.0/NXT; /*0.0625L;*/
}
/* Now the product y * log2(x) = Hb + e/NXT.
*
* Compute base 2 exponential of Hb,
* where -0.0625 <= Hb <= 0.
*/
z = Hb * __polevll(Hb, R, 6); /* z = 2**Hb - 1 */
/* Express e/NXT as an integer plus a negative number of (1/NXT)ths.
* Find lookup table entry for the fractional power of 2.
*/
if (e < 0)
i = 0;
else
i = 1;
i = e/NXT + i;
e = NXT*i - e;
w = A[e];
z = w * z; /* 2**-e * ( 1 + (2**Hb-1) ) */
z = z + w;
z = scalbnl(z, i); /* multiply by integer power of 2 */
if (nflg)
z = -z;
return z;
}
/* Find a multiple of 1/NXT that is within 1/NXT of x. */
static long double reducl(long double x)
{
long double t;
t = x * NXT;
t = floorl(t);
t = t / NXT;
return t;
}
/*
* Positive real raised to integer power, long double precision
*
*
* SYNOPSIS:
*
* long double x, y, powil();
* int n;
*
* y = powil( x, n );
*
*
* DESCRIPTION:
*
* Returns argument x>0 raised to the nth power.
* The routine efficiently decomposes n as a sum of powers of
* two. The desired power is a product of two-to-the-kth
* powers of x. Thus to compute the 32767 power of x requires
* 28 multiplications instead of 32767 multiplications.
*
*
* ACCURACY:
*
* Relative error:
* arithmetic x domain n domain # trials peak rms
* IEEE .001,1000 -1022,1023 50000 4.3e-17 7.8e-18
* IEEE 1,2 -1022,1023 20000 3.9e-17 7.6e-18
* IEEE .99,1.01 0,8700 10000 3.6e-16 7.2e-17
*
* Returns MAXNUM on overflow, zero on underflow.
*/
static long double powil(long double x, int nn)
{
long double ww, y;
long double s;
int n, e, sign, lx;
if (nn == 0)
return 1.0;
if (nn < 0) {
sign = -1;
n = -nn;
} else {
sign = 1;
n = nn;
}
/* Overflow detection */
/* Calculate approximate logarithm of answer */
s = x;
s = frexpl( s, &lx);
e = (lx - 1)*n;
if ((e == 0) || (e > 64) || (e < -64)) {
s = (s - 7.0710678118654752e-1L) / (s + 7.0710678118654752e-1L);
s = (2.9142135623730950L * s - 0.5 + lx) * nn * LOGE2L;
} else {
s = LOGE2L * e;
}
if (s > MAXLOGL)
return huge * huge; /* overflow */
if (s < MINLOGL)
return twom10000 * twom10000; /* underflow */
/* Handle tiny denormal answer, but with less accuracy
* since roundoff error in 1.0/x will be amplified.
* The precise demarcation should be the gradual underflow threshold.
*/
if (s < -MAXLOGL+2.0) {
x = 1.0/x;
sign = -sign;
}
/* First bit of the power */
if (n & 1)
y = x;
else
y = 1.0;
ww = x;
n >>= 1;
while (n) {
ww = ww * ww; /* arg to the 2-to-the-kth power */
if (n & 1) /* if that bit is set, then include in product */
y *= ww;
n >>= 1;
}
if (sign < 0)
y = 1.0/y;
return y;
}
__weak_reference(powl, __powl_finite);
#elif LDBL_MANT_DIG == 113 && LDBL_MAX_EXP == 16384
/* powl(x,y) return x**y
*
* n
* Method: Let x = 2 * (1+f)
* 1. Compute and return log2(x) in two pieces:
* log2(x) = w1 + w2,
* where w1 has 113-53 = 60 bit trailing zeros.
* 2. Perform y*log2(x) = n+y' by simulating multi-precision
* arithmetic, where |y'|<=0.5.
* 3. Return x**y = 2**n*exp(y'*log2)
*
* Special cases:
* 1. (anything) ** 0 is 1
* 2. (anything) ** 1 is itself
* 3. (anything) ** NAN is NAN
* 4. NAN ** (anything except 0) is NAN
* 5. +-(|x| > 1) ** +INF is +INF
* 6. +-(|x| > 1) ** -INF is +0
* 7. +-(|x| < 1) ** +INF is +0
* 8. +-(|x| < 1) ** -INF is +INF
* 9. +-1 ** +-INF is NAN
* 10. +0 ** (+anything except 0, NAN) is +0
* 11. -0 ** (+anything except 0, NAN, odd integer) is +0
* 12. +0 ** (-anything except 0, NAN) is +INF
* 13. -0 ** (-anything except 0, NAN, odd integer) is +INF
* 14. -0 ** (odd integer) = -( +0 ** (odd integer) )
* 15. +INF ** (+anything except 0,NAN) is +INF
* 16. +INF ** (-anything except 0,NAN) is +0
* 17. -INF ** (anything) = -0 ** (-anything)
* 18. (-anything) ** (integer) is (-1)**(integer)*(+anything**integer)
* 19. (-anything except 0 and inf) ** (non-integer) is NAN
*
*/
static const long double bp[] = {
1.0L,
1.5L,
};
/* log_2(1.5) */
static const long double dp_h[] = {
0.0,
5.8496250072115607565592654282227158546448E-1L
};
/* Low part of log_2(1.5) */
static const long double dp_l[] = {
0.0,
1.0579781240112554492329533686862998106046E-16L
};
static const long double zero = 0.0L,
one = 1.0L,
two = 2.0L,
two113 = 1.0384593717069655257060992658440192E34L,
huge = 1.0e3000L,
tiny = 1.0e-3000L;
/* 3/2 log x = 3 z + z^3 + z^3 (z^2 R(z^2))
z = (x-1)/(x+1)
1 <= x <= 1.25
Peak relative error 2.3e-37 */
static const long double LN[] =
{
-3.0779177200290054398792536829702930623200E1L,
6.5135778082209159921251824580292116201640E1L,
-4.6312921812152436921591152809994014413540E1L,
1.2510208195629420304615674658258363295208E1L,
-9.9266909031921425609179910128531667336670E-1L
};
static const long double LD[] =
{
-5.129862866715009066465422805058933131960E1L,
1.452015077564081884387441590064272782044E2L,
-1.524043275549860505277434040464085593165E2L,
7.236063513651544224319663428634139768808E1L,
-1.494198912340228235853027849917095580053E1L
/* 1.0E0 */
};
/* exp(x) = 1 + x - x / (1 - 2 / (x - x^2 R(x^2)))
0 <= x <= 0.5
Peak relative error 5.7e-38 */
static const long double PN[] =
{
5.081801691915377692446852383385968225675E8L,
9.360895299872484512023336636427675327355E6L,
4.213701282274196030811629773097579432957E4L,
5.201006511142748908655720086041570288182E1L,
9.088368420359444263703202925095675982530E-3L,
};
static const long double PD[] =
{
3.049081015149226615468111430031590411682E9L,
1.069833887183886839966085436512368982758E8L,
8.259257717868875207333991924545445705394E5L,
1.872583833284143212651746812884298360922E3L,
/* 1.0E0 */
};
static const long double
/* ln 2 */
lg2 = 6.9314718055994530941723212145817656807550E-1L,
lg2_h = 6.9314718055994528622676398299518041312695E-1L,
lg2_l = 2.3190468138462996154948554638754786504121E-17L,
ovt = 8.0085662595372944372e-0017L,
/* 2/(3*log(2)) */
cp = 9.6179669392597560490661645400126142495110E-1L,
cp_h = 9.6179669392597555432899980587535537779331E-1L,
cp_l = 5.0577616648125906047157785230014751039424E-17L;
long double
powl(long double x, long double y)
{
long double z, ax, z_h, z_l, p_h, p_l;
long double yy1, t1, t2, r, s, t, u, v, w;
long double s2, s_h, s_l, t_h, t_l;
int32_t i, j, k, yisint, n;
uint32_t ix, iy;
int32_t hx, hy;
ieee_quad_shape_type o, p, q;
p.value = x;
hx = p.parts32.mswhi;
ix = hx & 0x7fffffff;
q.value = y;
hy = q.parts32.mswhi;
iy = hy & 0x7fffffff;
/* y==zero: x**0 = 1 */
if ((iy | q.parts32.mswlo | q.parts32.lswhi | q.parts32.lswlo) == 0)
return one;
/* 1.0**y = 1; -1.0**+-Inf = 1 */
if (x == one)
return one;
if (x == -1.0L && iy == 0x7fff0000
&& (q.parts32.mswlo | q.parts32.lswhi | q.parts32.lswlo) == 0)
return one;
/* +-NaN return x+y */
if ((ix > 0x7fff0000)
|| ((ix == 0x7fff0000)
&& ((p.parts32.mswlo | p.parts32.lswhi | p.parts32.lswlo) != 0))
|| (iy > 0x7fff0000)
|| ((iy == 0x7fff0000)
&& ((q.parts32.mswlo | q.parts32.lswhi | q.parts32.lswlo) != 0)))
return nan_mix(x, y);
/* determine if y is an odd int when x < 0
* yisint = 0 ... y is not an integer
* yisint = 1 ... y is an odd int
* yisint = 2 ... y is an even int
*/
yisint = 0;
if (hx < 0)
{
if (iy >= 0x40700000) /* 2^113 */
yisint = 2; /* even integer y */
else if (iy >= 0x3fff0000) /* 1.0 */
{
if (floorl (y) == y)
{
z = 0.5 * y;
if (floorl (z) == z)
yisint = 2;
else
yisint = 1;
}
}
}
/* special value of y */
if ((q.parts32.mswlo | q.parts32.lswhi | q.parts32.lswlo) == 0)
{
if (iy == 0x7fff0000) /* y is +-inf */
{
if (((ix - 0x3fff0000) | p.parts32.mswlo | p.parts32.lswhi |
p.parts32.lswlo) == 0)
return y - y; /* +-1**inf is NaN */
else if (ix >= 0x3fff0000) /* (|x|>1)**+-inf = inf,0 */
return (hy >= 0) ? y : zero;
else /* (|x|<1)**-,+inf = inf,0 */
return (hy < 0) ? -y : zero;
}
if (iy == 0x3fff0000)
{ /* y is +-1 */
if (hy < 0)
return one / x;
else
return x;
}
if (hy == 0x40000000)
return x * x; /* y is 2 */
if (hy == 0x3ffe0000)
{ /* y is 0.5 */
if (hx >= 0) /* x >= +0 */
return sqrtl (x);
}
}
ax = fabsl (x);
/* special value of x */
if ((p.parts32.mswlo | p.parts32.lswhi | p.parts32.lswlo) == 0)
{
if (ix == 0x7fff0000 || ix == 0 || ix == 0x3fff0000)
{
z = ax; /*x is +-0,+-inf,+-1 */
if (hy < 0)
z = one / z; /* z = (1/|x|) */
if (hx < 0)
{
if (((ix - 0x3fff0000) | yisint) == 0)
{
z = (z - z) / (z - z); /* (-1)**non-int is NaN */
}
else if (yisint == 1)
z = -z; /* (x<0)**odd = -(|x|**odd) */
}
return z;
}
}
/* (x<0)**(non-int) is NaN */
if (((((uint32_t) hx >> 31) - 1) | yisint) == 0)
return (x - x) / (x - x);
/* |y| is huge.
2^-16495 = 1/2 of smallest representable value.
If (1 - 1/131072)^y underflows, y > 1.4986e9 */
if (iy > 0x401d654b)
{
/* if (1 - 2^-113)^y underflows, y > 1.1873e38 */
if (iy > 0x407d654b)
{
if (ix <= 0x3ffeffff)
return (hy < 0) ? huge * huge : tiny * tiny;
if (ix >= 0x3fff0000)
return (hy > 0) ? huge * huge : tiny * tiny;
}
/* over/underflow if x is not close to one */
if (ix < 0x3ffeffff)
return (hy < 0) ? huge * huge : tiny * tiny;
if (ix > 0x3fff0000)
return (hy > 0) ? huge * huge : tiny * tiny;
}
n = 0;
/* take care subnormal number */
if (ix < 0x00010000)
{
ax *= two113;
n -= 113;
o.value = ax;
ix = o.parts32.mswhi;
}
n += ((ix) >> 16) - 0x3fff;
j = ix & 0x0000ffff;
/* determine interval */
ix = j | 0x3fff0000; /* normalize ix */
if (j <= 0x3988)
k = 0; /* |x|<sqrt(3/2) */
else if (j < 0xbb67)
k = 1; /* |x|<sqrt(3) */
else
{
k = 0;
n += 1;
ix -= 0x00010000;
}
o.value = ax;
o.parts32.mswhi = ix;
ax = o.value;
/* compute s = s_h+s_l = (x-1)/(x+1) or (x-1.5)/(x+1.5) */
u = ax - bp[k]; /* bp[0]=1.0, bp[1]=1.5 */
v = one / (ax + bp[k]);
s = u * v;
s_h = s;
o.value = s_h;
o.parts32.lswlo = 0;
o.parts32.lswhi &= 0xf8000000;
s_h = o.value;
/* t_h=ax+bp[k] High */
t_h = ax + bp[k];
o.value = t_h;
o.parts32.lswlo = 0;
o.parts32.lswhi &= 0xf8000000;
t_h = o.value;
t_l = ax - (t_h - bp[k]);
s_l = v * ((u - s_h * t_h) - s_h * t_l);
/* compute log(ax) */
s2 = s * s;
u = LN[0] + s2 * (LN[1] + s2 * (LN[2] + s2 * (LN[3] + s2 * LN[4])));
v = LD[0] + s2 * (LD[1] + s2 * (LD[2] + s2 * (LD[3] + s2 * (LD[4] + s2))));
r = s2 * s2 * u / v;
r += s_l * (s_h + s);
s2 = s_h * s_h;
t_h = 3.0 + s2 + r;
o.value = t_h;
o.parts32.lswlo = 0;
o.parts32.lswhi &= 0xf8000000;
t_h = o.value;
t_l = r - ((t_h - 3.0) - s2);
/* u+v = s*(1+...) */
u = s_h * t_h;
v = s_l * t_h + t_l * s;
/* 2/(3log2)*(s+...) */
p_h = u + v;
o.value = p_h;
o.parts32.lswlo = 0;
o.parts32.lswhi &= 0xf8000000;
p_h = o.value;
p_l = v - (p_h - u);
z_h = cp_h * p_h; /* cp_h+cp_l = 2/(3*log2) */
z_l = cp_l * p_h + p_l * cp + dp_l[k];
/* log2(ax) = (s+..)*2/(3*log2) = n + dp_h + z_h + z_l */
t = (long double) n;
t1 = (((z_h + z_l) + dp_h[k]) + t);
o.value = t1;
o.parts32.lswlo = 0;
o.parts32.lswhi &= 0xf8000000;
t1 = o.value;
t2 = z_l - (((t1 - t) - dp_h[k]) - z_h);
/* s (sign of result -ve**odd) = -1 else = 1 */
s = one;
if (((((uint32_t) hx >> 31) - 1) | (yisint - 1)) == 0)
s = -one; /* (-ve)**(odd int) */
/* split up y into yy1+y2 and compute (yy1+y2)*(t1+t2) */
yy1 = y;
o.value = yy1;
o.parts32.lswlo = 0;
o.parts32.lswhi &= 0xf8000000;
yy1 = o.value;
p_l = (y - yy1) * t1 + y * t2;
p_h = yy1 * t1;
z = p_l + p_h;
o.value = z;
j = o.parts32.mswhi;
if (j >= 0x400d0000) /* z >= 16384 */
{
/* if z > 16384 */
if (((j - 0x400d0000) | o.parts32.mswlo | o.parts32.lswhi |
o.parts32.lswlo) != 0)
return s * huge * huge; /* overflow */
else
{
if (p_l + ovt > z - p_h)
return s * huge * huge; /* overflow */
}
}
else if ((j & 0x7fffffff) >= 0x400d01b9) /* z <= -16495 */
{
/* z < -16495 */
if (((j - 0xc00d01bc) | o.parts32.mswlo | o.parts32.lswhi |
o.parts32.lswlo)
!= 0)
return s * tiny * tiny; /* underflow */
else
{
if (p_l <= z - p_h)
return s * tiny * tiny; /* underflow */
}
}
/* compute 2**(p_h+p_l) */
i = j & 0x7fffffff;
k = (i >> 16) - 0x3fff;
n = 0;
if (i > 0x3ffe0000)
{ /* if |z| > 0.5, set n = [z+0.5] */
n = floorl (z + 0.5L);
t = n;
p_h -= t;
}
t = p_l + p_h;
o.value = t;
o.parts32.lswlo = 0;
o.parts32.lswhi &= 0xf8000000;
t = o.value;
u = t * lg2_h;
v = (p_l - (t - p_h)) * lg2 + t * lg2_l;
z = u + v;
w = v - (z - u);
/* exp(z) */
t = z * z;
u = PN[0] + t * (PN[1] + t * (PN[2] + t * (PN[3] + t * PN[4])));
v = PD[0] + t * (PD[1] + t * (PD[2] + t * (PD[3] + t)));
t1 = z - t * u / v;
r = (z * t1) / (t1 - two) - (w + z * w);
z = one - (r - z);
o.value = z;
j = o.parts32.mswhi;
j += (n << 16);
if ((j >> 16) <= 0)
z = scalbnl (z, n); /* subnormal output */
else
{
o.parts32.mswhi = j;
z = o.value;
}
return s * z;
}
__weak_reference(powl, __powl_finite);
#endif /* __x86_64__ */
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