1  /* s_cosl.c -- long double version of s_cos.c.
       2   * Conversion to long double by Jakub Jelinek, jj@ultra.linux.cz.
       3   */
       4  
       5  /*
       6   * ====================================================
       7   * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
       8   *
       9   * Developed at SunPro, a Sun Microsystems, Inc. business.
      10   * Permission to use, copy, modify, and distribute this
      11   * software is freely granted, provided that this notice
      12   * is preserved.
      13   * ====================================================
      14   */
      15  
      16  /* cosq(x)
      17   * Return cosine function of x.
      18   *
      19   * kernel function:
      20   *	__quadmath_kernel_sinq		... sine function on [-pi/4,pi/4]
      21   *	__quadmath_kernel_cosq		... cosine function on [-pi/4,pi/4]
      22   *	__quadmath_rem_pio2q	... argument reduction routine
      23   *
      24   * Method.
      25   *      Let S,C and T denote the sin, cos and tan respectively on
      26   *	[-PI/4, +PI/4]. Reduce the argument x to y1+y2 = x-k*pi/2
      27   *	in [-pi/4 , +pi/4], and let n = k mod 4.
      28   *	We have
      29   *
      30   *          n        sin(x)      cos(x)        tan(x)
      31   *     ----------------------------------------------------------
      32   *	    0	       S	   C		 T
      33   *	    1	       C	  -S		-1/T
      34   *	    2	      -S	  -C		 T
      35   *	    3	      -C	   S		-1/T
      36   *     ----------------------------------------------------------
      37   *
      38   * Special cases:
      39   *      Let trig be any of sin, cos, or tan.
      40   *      trig(+-INF)  is NaN, with signals;
      41   *      trig(NaN)    is that NaN;
      42   *
      43   * Accuracy:
      44   *	TRIG(x) returns trig(x) nearly rounded
      45   */
      46  
      47  #include "quadmath-imp.h"
      48  
      49  __float128 cosq(__float128 x)
      50  {
      51  	__float128 y[2],z=0;
      52  	int64_t n, ix;
      53  
      54      /* High word of x. */
      55  	GET_FLT128_MSW64(ix,x);
      56  
      57      /* |x| ~< pi/4 */
      58  	ix &= 0x7fffffffffffffffLL;
      59  	if(ix <= 0x3ffe921fb54442d1LL)
      60  	  return __quadmath_kernel_cosq(x,z);
      61  
      62      /* cos(Inf or NaN) is NaN */
      63  	else if (ix>=0x7fff000000000000LL) {
      64  	    if (ix == 0x7fff000000000000LL) {
      65  		GET_FLT128_LSW64(n,x);
      66  		if (n == 0)
      67  		    errno = EDOM;
      68  	    }
      69  	    return x-x;
      70  	}
      71  
      72      /* argument reduction needed */
      73  	else {
      74  	    n = __quadmath_rem_pio2q(x,y);
      75  	    switch(n&3) {
      76  		case 0: return  __quadmath_kernel_cosq(y[0],y[1]);
      77  		case 1: return -__quadmath_kernel_sinq(y[0],y[1],1);
      78  		case 2: return -__quadmath_kernel_cosq(y[0],y[1]);
      79  		default:
      80  		        return  __quadmath_kernel_sinq(y[0],y[1],1);
      81  	    }
      82  	}
      83  }