lib/msun/src/e_hypotf.c

   1 /* e_hypotf.c -- float version of e_hypot.c.
   2  * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
   3  *
   4  * $FreeBSD: src/lib/msun/src/e_hypotf.c,v 1.7 1999/08/28 00:06:32 peter Exp $
   5  * $DragonFly: src/lib/msun/src/Attic/e_hypotf.c,v 1.3 2004/12/29 15:22:57 asmodai Exp $
   6  */
   7
   8 /*
   9  * ====================================================
  10  * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
  11  *
  12  * Developed at SunPro, a Sun Microsystems, Inc. business.
  13  * Permission to use, copy, modify, and distribute this
  14  * software is freely granted, provided that this notice
  15  * is preserved.
  16  * ====================================================
  17  */
  18
  19 #include "math.h"
  20 #include "math_private.h"
  21
  22 float
  23 __ieee754_hypotf(float x, float y)
  24 {
  25         float a=x,b=y,t1,t2,y1,y2,w;
  26         int32_t j,k,ha,hb;
  27
  28         GET_FLOAT_WORD(ha,x);
  29         ha &= 0x7fffffff;
  30         GET_FLOAT_WORD(hb,y);
  31         hb &= 0x7fffffff;
  32         if(hb > ha) {a=y;b=x;j=ha; ha=hb;hb=j;} else {a=x;b=y;}
  33         SET_FLOAT_WORD(a,ha);   /* a <- |a| */
  34         SET_FLOAT_WORD(b,hb);   /* b <- |b| */
  35         if((ha-hb)>0xf000000) {return a+b;} /* x/y > 2**30 */
  36         k=0;
  37         if(ha > 0x58800000) {   /* a>2**50 */
  38            if(ha >= 0x7f800000) {       /* Inf or NaN */
  39                w = a+b;                 /* for sNaN */
  40                if(ha == 0x7f800000) w = a;
  41                if(hb == 0x7f800000) w = b;
  42                return w;
  43            }
  44            /* scale a and b by 2**-68 */
  45            ha -= 0x22000000; hb -= 0x22000000;  k += 68;
  46            SET_FLOAT_WORD(a,ha);
  47            SET_FLOAT_WORD(b,hb);
  48         }
  49         if(hb < 0x26800000) {   /* b < 2**-50 */
  50             if(hb <= 0x007fffff) {      /* subnormal b or 0 */
  51                 if(hb==0) return a;
  52                 SET_FLOAT_WORD(t1,0x7e800000);  /* t1=2^126 */
  53                 b *= t1;
  54                 a *= t1;
  55                 k -= 126;
  56             } else {            /* scale a and b by 2^68 */
  57                 ha += 0x22000000;       /* a *= 2^68 */
  58                 hb += 0x22000000;       /* b *= 2^68 */
  59                 k -= 68;
  60                 SET_FLOAT_WORD(a,ha);
  61                 SET_FLOAT_WORD(b,hb);
  62             }
  63         }
  64     /* medium size a and b */
  65         w = a-b;
  66         if (w>b) {
  67             SET_FLOAT_WORD(t1,ha&0xfffff000);
  68             t2 = a-t1;
  69             w  = __ieee754_sqrtf(t1*t1-(b*(-b)-t2*(a+t1)));
  70         } else {
  71             a  = a+a;
  72             SET_FLOAT_WORD(y1,hb&0xfffff000);
  73             y2 = b - y1;
  74             SET_FLOAT_WORD(t1,ha+0x00800000);
  75             t2 = a - t1;
  76             w  = __ieee754_sqrtf(t1*y1-(w*(-w)-(t1*y2+t2*b)));
  77         }
  78         if(k!=0) {
  79             SET_FLOAT_WORD(t1,0x3f800000+(k<<23));
  80             return t1*w;
  81         } else return w;
  82 }