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