compiler/stdc/math/e_rem_pio2f.c

   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 #ifndef lint
  18 static char rcsid[] = "$FreeBSD: src/lib/msun/src/e_rem_pio2f.c,v 1.32 2009/06/03 08:16:34 ed Exp $";
  19 #endif
  20
  21 /* __ieee754_rem_pio2f(x,y)
  22  *
  23  * return the remainder of x rem pi/2 in *y
  24  * use double precision for everything except passing x
  25  * use __kernel_rem_pio2() for large x
  26  */
  27
  28 #include <float.h>
  29
  30 #include "math.h"
  31 #include "math_private.h"
  32
  33 /*
  34  * invpio2:  53 bits of 2/pi
  35  * pio2_1:   first 25 bits of pi/2
  36  * pio2_1t:  pi/2 - pio2_1
  37  */
  38
  39 static const double
  40 invpio2 =  6.36619772367581382433e-01, /* 0x3FE45F30, 0x6DC9C883 */
  41 pio2_1  =  1.57079631090164184570e+00, /* 0x3FF921FB, 0x50000000 */
  42 pio2_1t =  1.58932547735281966916e-08; /* 0x3E5110b4, 0x611A6263 */
  43
  44 #ifdef INLINE_REM_PIO2F
  45 static __inline
  46 #endif
  47 int32_t
  48 __ieee754_rem_pio2f(float x, double *y)
  49 {
  50         double w,r,fn;
  51         double tx[1],ty[1];
  52         float z;
  53         int32_t e0,n,ix,hx;
  54
  55         GET_FLOAT_WORD(hx,x);
  56         ix = hx&0x7fffffff;
  57     /* 33+53 bit pi is good enough for medium size */
  58         if(ix<0x4dc90fdb) {             /* |x| ~< 2^28*(pi/2), medium size */
  59             /* Use a specialized rint() to get fn.  Assume round-to-nearest. */
  60             STRICT_ASSIGN(double,fn,x*invpio2+0x1.8p52);
  61             fn = fn-0x1.8p52;
  62 #ifdef HAVE_EFFICIENT_IRINT
  63             n  = irint(fn);
  64 #else
  65             n  = (int32_t)fn;
  66 #endif
  67             r  = x-fn*pio2_1;
  68             w  = fn*pio2_1t;
  69             *y = r-w;
  70             return n;
  71         }
  72     /*
  73      * all other (large) arguments
  74      */
  75         if(ix>=0x7f800000) {            /* x is inf or NaN */
  76             *y=x-x; return 0;
  77         }
  78     /* set z = scalbn(|x|,ilogb(|x|)-23) */
  79         e0 = (ix>>23)-150;              /* e0 = ilogb(|x|)-23; */
  80         SET_FLOAT_WORD(z, ix - ((int32_t)(e0<<23)));
  81         tx[0] = z;
  82         n  =  __kernel_rem_pio2(tx,ty,e0,1,0);
  83         if(hx<0) {*y = -ty[0]; return -n;}
  84         *y = ty[0]; return n;
  85 }