src/libm/s_sin.c
author Ryan C. Gordon <icculus@icculus.org>
Mon, 21 May 2018 12:00:21 -0400
changeset 11994 8e094f91ddab
parent 11683 48bcba563d9c
permissions -rw-r--r--
thread: fixed compiler warnings on non-Linux systems that use pthread.

(static function rtkit_setpriority was unused, moved it in with rest of
__LINUX__ section.)
     1 /*
     2  * ====================================================
     3  * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
     4  *
     5  * Developed at SunPro, a Sun Microsystems, Inc. business.
     6  * Permission to use, copy, modify, and distribute this
     7  * software is freely granted, provided that this notice
     8  * is preserved.
     9  * ====================================================
    10  */
    11 
    12 /* sin(x)
    13  * Return sine function of x.
    14  *
    15  * kernel function:
    16  *	__kernel_sin		... sine function on [-pi/4,pi/4]
    17  *	__kernel_cos		... cose function on [-pi/4,pi/4]
    18  *	__ieee754_rem_pio2	... argument reduction routine
    19  *
    20  * Method.
    21  *      Let S,C and T denote the sin, cos and tan respectively on
    22  *	[-PI/4, +PI/4]. Reduce the argument x to y1+y2 = x-k*pi/2
    23  *	in [-pi/4 , +pi/4], and let n = k mod 4.
    24  *	We have
    25  *
    26  *          n        sin(x)      cos(x)        tan(x)
    27  *     ----------------------------------------------------------
    28  *	    0	       S	   C		 T
    29  *	    1	       C	  -S		-1/T
    30  *	    2	      -S	  -C		 T
    31  *	    3	      -C	   S		-1/T
    32  *     ----------------------------------------------------------
    33  *
    34  * Special cases:
    35  *      Let trig be any of sin, cos, or tan.
    36  *      trig(+-INF)  is NaN, with signals;
    37  *      trig(NaN)    is that NaN;
    38  *
    39  * Accuracy:
    40  *	TRIG(x) returns trig(x) nearly rounded
    41  */
    42 
    43 #include "math_libm.h"
    44 #include "math_private.h"
    45 
    46 double sin(double x)
    47 {
    48 	double y[2],z=0.0;
    49 	int32_t n, ix;
    50 
    51     /* High word of x. */
    52 	GET_HIGH_WORD(ix,x);
    53 
    54     /* |x| ~< pi/4 */
    55 	ix &= 0x7fffffff;
    56 	if(ix <= 0x3fe921fb) return __kernel_sin(x,z,0);
    57 
    58     /* sin(Inf or NaN) is NaN */
    59 	else if (ix>=0x7ff00000) return x-x;
    60 
    61     /* argument reduction needed */
    62 	else {
    63 	    n = __ieee754_rem_pio2(x,y);
    64 	    switch(n&3) {
    65 		case 0: return  __kernel_sin(y[0],y[1],1);
    66 		case 1: return  __kernel_cos(y[0],y[1]);
    67 		case 2: return -__kernel_sin(y[0],y[1],1);
    68 		default:
    69 			return -__kernel_cos(y[0],y[1]);
    70 	    }
    71 	}
    72 }
    73 libm_hidden_def(sin)