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/* From: @(#)e_rem_pio2.c 1.4 95/01/18 */
/*
* ====================================================
* Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
* Copyright (c) 2008 Steven G. Kargl, David Schultz, Bruce D. Evans.
*
* Developed at SunSoft, a Sun Microsystems, Inc. business.
* Permission to use, copy, modify, and distribute this
* software is freely granted, provided that this notice
* is preserved.
* ====================================================
*
* Optimized by Bruce D. Evans.
*/
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
/* ld128 version of __ieee754_rem_pio2l(x,y)
*
* return the remainder of x rem pi/2 in y[0]+y[1]
* use __kernel_rem_pio2()
*/
#include <float.h>
#include "math.h"
#include "math_private.h"
#include "fpmath.h"
#define BIAS (LDBL_MAX_EXP - 1)
/*
* XXX need to verify that nonzero integer multiples of pi/2 within the
* range get no closer to a long double than 2**-140, or that
* ilogb(x) + ilogb(min_delta) < 45 - -140.
*/
/*
* invpio2: 113 bits of 2/pi
* pio2_1: first 68 bits of pi/2
* pio2_1t: pi/2 - pio2_1
* pio2_2: second 68 bits of pi/2
* pio2_2t: pi/2 - (pio2_1+pio2_2)
* pio2_3: third 68 bits of pi/2
* pio2_3t: pi/2 - (pio2_1+pio2_2+pio2_3)
*/
static const double
zero = 0.00000000000000000000e+00, /* 0x00000000, 0x00000000 */
two24 = 1.67772160000000000000e+07; /* 0x41700000, 0x00000000 */
static const long double
invpio2 = 6.3661977236758134307553505349005747e-01L, /* 0x145f306dc9c882a53f84eafa3ea6a.0p-113 */
pio2_1 = 1.5707963267948966192292994253909555e+00L, /* 0x1921fb54442d18469800000000000.0p-112 */
pio2_1t = 2.0222662487959507323996846200947577e-21L, /* 0x13198a2e03707344a4093822299f3.0p-181 */
pio2_2 = 2.0222662487959507323994779168837751e-21L, /* 0x13198a2e03707344a400000000000.0p-181 */
pio2_2t = 2.0670321098263988236496903051604844e-43L, /* 0x127044533e63a0105df531d89cd91.0p-254 */
pio2_3 = 2.0670321098263988236499468110329591e-43L, /* 0x127044533e63a0105e00000000000.0p-254 */
pio2_3t = -2.5650587247459238361625433492959285e-65L; /* -0x159c4ec64ddaeb5f78671cbfb2210.0p-327 */
static inline __always_inline int
__ieee754_rem_pio2l(long double x, long double *y)
{
union IEEEl2bits u,u1;
long double z,w,t,r,fn;
double tx[5],ty[3];
int64_t n;
int e0,ex,i,j,nx;
int16_t expsign;
u.e = x;
expsign = u.xbits.expsign;
ex = expsign & 0x7fff;
if (ex < BIAS + 45 || ex == BIAS + 45 &&
u.bits.manh < 0x921fb54442d1LL) {
/* |x| ~< 2^45*(pi/2), medium size */
/* Use a specialized rint() to get fn. Assume round-to-nearest. */
fn = x*invpio2+0x1.8p112;
fn = fn-0x1.8p112;
#ifdef HAVE_EFFICIENT_I64RINT
n = i64rint(fn);
#else
n = fn;
#endif
r = x-fn*pio2_1;
w = fn*pio2_1t; /* 1st round good to 180 bit */
{
union IEEEl2bits u2;
int ex1;
j = ex;
y[0] = r-w;
u2.e = y[0];
ex1 = u2.xbits.expsign & 0x7fff;
i = j-ex1;
if(i>51) { /* 2nd iteration needed, good to 248 */
t = r;
w = fn*pio2_2;
r = t-w;
w = fn*pio2_2t-((t-r)-w);
y[0] = r-w;
u2.e = y[0];
ex1 = u2.xbits.expsign & 0x7fff;
i = j-ex1;
if(i>119) { /* 3rd iteration need, 316 bits acc */
t = r; /* will cover all possible cases */
w = fn*pio2_3;
r = t-w;
w = fn*pio2_3t-((t-r)-w);
y[0] = r-w;
}
}
}
y[1] = (r-y[0])-w;
return n;
}
/*
* all other (large) arguments
*/
if(ex==0x7fff) { /* x is inf or NaN */
y[0]=y[1]=x-x; return 0;
}
/* set z = scalbn(|x|,ilogb(x)-23) */
u1.e = x;
e0 = ex - BIAS - 23; /* e0 = ilogb(|x|)-23; */
u1.xbits.expsign = ex - e0;
z = u1.e;
for(i=0;i<4;i++) {
tx[i] = (double)((int32_t)(z));
z = (z-tx[i])*two24;
}
tx[4] = z;
nx = 5;
while(tx[nx-1]==zero) nx--; /* skip zero term */
n = __kernel_rem_pio2(tx,ty,e0,nx,3);
t = (long double)ty[2] + ty[1];
r = t + ty[0];
w = ty[0] - (r - t);
if(expsign<0) {y[0] = -r; y[1] = -w; return -n;}
y[0] = r; y[1] = w; return n;
}
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