sysdeps/ieee754/flt-32/s_tanf.c

   1 /* s_tanf.c -- float version of s_tan.c.
   2  */
   3
   4 /*
   5  * ====================================================
   6  * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
   7  *
   8  * Developed at SunPro, a Sun Microsystems, Inc. business.
   9  * Permission to use, copy, modify, and distribute this
  10  * software is freely granted, provided that this notice
  11  * is preserved.
  12  * ====================================================
  13  */
  14
  15 #if defined(LIBM_SCCS) && !defined(lint)
  16 static char rcsid[] = "$NetBSD: s_tanf.c,v 1.4 1995/05/10 20:48:20 jtc Exp $";
  17 #endif
  18
  19 #include <errno.h>
  20 #include <math.h>
  21 #include <math_private.h>
  22 #include <libm-alias-float.h>
  23 #include "s_sincosf.h"
  24
  25 /* Reduce range of X to a multiple of PI/2.  The modulo result is between
  26    -PI/4 and PI/4 and returned as a high part y[0] and a low part y[1].
  27    The low bit in the return value indicates the first or 2nd half of tanf.  */
  28 static inline int32_t
  29 rem_pio2f (float x, float *y)
  30 {
  31   double dx = x;
  32   int n;
  33   const sincos_t *p = &__sincosf_table[0];
  34
  35   if (__glibc_likely (abstop12 (x) < abstop12 (120.0f)))
  36     dx = reduce_fast (dx, p, &n);
  37   else
  38     {
  39       uint32_t xi = asuint (x);
  40       int sign = xi >> 31;
  41
  42       dx = reduce_large (xi, &n);
  43       dx = sign ? -dx : dx;
  44     }
  45
  46   y[0] = dx;
  47   y[1] = dx - y[0];
  48   return n;
  49 }
  50
  51 float __tanf(float x)
  52 {
  53         float y[2],z=0.0;
  54         int32_t n, ix;
  55
  56         GET_FLOAT_WORD(ix,x);
  57
  58     /* |x| ~< pi/4 */
  59         ix &= 0x7fffffff;
  60         if(ix <= 0x3f490fda) return __kernel_tanf(x,z,1);
  61
  62     /* tan(Inf or NaN) is NaN */
  63         else if (ix>=0x7f800000) {
  64           if (ix==0x7f800000)
  65             __set_errno (EDOM);
  66           return x-x;           /* NaN */
  67         }
  68
  69     /* argument reduction needed */
  70         else {
  71             n = rem_pio2f(x,y);
  72             return __kernel_tanf(y[0],y[1],1-((n&1)<<1)); /*   1 -- n even
  73                                                               -1 -- n odd */
  74         }
  75 }
  76 libm_alias_float (__tan, tan)