1  /* s_tanl.c -- long double version of s_tan.c.
       2   * Conversion to IEEE quad long double by Jakub Jelinek, jj@ultra.linux.cz.
       3   */
       4  
       5  /* @(#)s_tan.c 5.1 93/09/24 */
       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  /* tanq(x)
      18   * Return tangent function of x.
      19   *
      20   * kernel function:
      21   *	__quadmath_kernel_tanq		... tangent 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 tanq(__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) return __quadmath_kernel_tanq(x,z,1);
      60  
      61      /* tanq(Inf or NaN) is NaN */
      62  	else if (ix>=0x7fff000000000000LL) {
      63  	    if (ix == 0x7fff000000000000LL) {
      64  		GET_FLT128_LSW64(n,x);
      65  		if (n == 0)
      66  		    errno = EDOM;
      67  	    }
      68  	    return x-x;		/* NaN */
      69  	}
      70  
      71      /* argument reduction needed */
      72  	else {
      73  	    n = __quadmath_rem_pio2q(x,y);
      74  	    return __quadmath_kernel_tanq(y[0],y[1],1-((n&1)<<1)); /*   1 -- n even
      75  							-1 -- n odd */
      76  	}
      77  }