1 /* e_rem_pio2f.c -- float version of e_rem_pio2.c
2 * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
3 * Debugged and optimized by Bruce D. Evans.
4 */
5
6 /*
7 * ====================================================
8 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
9 *
10 * Developed at SunPro, a Sun Microsystems, Inc. business.
11 * Permission to use, copy, modify, and distribute this
12 * software is freely granted, provided that this notice
13 * is preserved.
14 * ====================================================
15 */
16
17 #include <sys/cdefs.h>
18 __FBSDID("$FreeBSD$");
19
20 /* __ieee754_rem_pio2f(x,y)
21 *
22 * return the remainder of x rem pi/2 in *y
23 * use double precision for everything except passing x
24 * use __kernel_rem_pio2() for large x
25 */
26
27 #include <float.h>
28
29 #include "math.h"
30 #include "math_private.h"
31
32 /*
33 * invpio2: 53 bits of 2/pi
34 * pio2_1: first 25 bits of pi/2
35 * pio2_1t: pi/2 - pio2_1
36 */
37
38 static const double
39 invpio2 = 6.36619772367581382433e-01, /* 0x3FE45F30, 0x6DC9C883 */
40 pio2_1 = 1.57079631090164184570e+00, /* 0x3FF921FB, 0x50000000 */
41 pio2_1t = 1.58932547735281966916e-08; /* 0x3E5110b4, 0x611A6263 */
42
43 #ifdef INLINE_REM_PIO2F
44 static __inline __always_inline
45 #endif
46 int
__ieee754_rem_pio2f(float x,double * y)47 __ieee754_rem_pio2f(float x, double *y)
48 {
49 double w,r,fn;
50 double tx[1],ty[1];
51 float z;
52 int32_t e0,n,ix,hx;
53
54 GET_FLOAT_WORD(hx,x);
55 ix = hx&0x7fffffff;
56 /* 33+53 bit pi is good enough for medium size */
57 if(ix<0x4dc90fdb) { /* |x| ~< 2^28*(pi/2), medium size */
58 /* Use a specialized rint() to get fn. Assume round-to-nearest. */
59 STRICT_ASSIGN(double,fn,x*invpio2+0x1.8p52);
60 fn = fn-0x1.8p52;
61 #ifdef HAVE_EFFICIENT_IRINT
62 n = irint(fn);
63 #else
64 n = (int32_t)fn;
65 #endif
66 r = x-fn*pio2_1;
67 w = fn*pio2_1t;
68 *y = r-w;
69 return n;
70 }
71 /*
72 * all other (large) arguments
73 */
74 if(ix>=0x7f800000) { /* x is inf or NaN */
75 *y=x-x; return 0;
76 }
77 /* set z = scalbn(|x|,ilogb(|x|)-23) */
78 e0 = (ix>>23)-150; /* e0 = ilogb(|x|)-23; */
79 SET_FLOAT_WORD(z, ix - ((int32_t)(e0<<23)));
80 tx[0] = z;
81 n = __kernel_rem_pio2(tx,ty,e0,1,0);
82 if(hx<0) {*y = -ty[0]; return -n;}
83 *y = ty[0]; return n;
84 }
85