hypotl.c raw

   1  #include "libm.h"
   2  
   3  #if LDBL_MANT_DIG == 53 && LDBL_MAX_EXP == 1024
   4  long double hypotl(long double x, long double y)
   5  {
   6  	return hypot(x, y);
   7  }
   8  #elif (LDBL_MANT_DIG == 64 || LDBL_MANT_DIG == 113) && LDBL_MAX_EXP == 16384
   9  #if LDBL_MANT_DIG == 64
  10  #define SPLIT (0x1p32L+1)
  11  #elif LDBL_MANT_DIG == 113
  12  #define SPLIT (0x1p57L+1)
  13  #endif
  14  
  15  static void sq(long double *hi, long double *lo, long double x)
  16  {
  17  	long double xh, xl, xc;
  18  	xc = x*SPLIT;
  19  	xh = x - xc + xc;
  20  	xl = x - xh;
  21  	*hi = x*x;
  22  	*lo = xh*xh - *hi + 2*xh*xl + xl*xl;
  23  }
  24  
  25  long double hypotl(long double x, long double y)
  26  {
  27  	union ldshape ux = {x}, uy = {y};
  28  	int ex, ey;
  29  	long double hx, lx, hy, ly, z;
  30  
  31  	ux.i.se &= 0x7fff;
  32  	uy.i.se &= 0x7fff;
  33  	if (ux.i.se < uy.i.se) {
  34  		ex = uy.i.se;
  35  		ey = ux.i.se;
  36  		x = uy.f;
  37  		y = ux.f;
  38  	} else {
  39  		ex = ux.i.se;
  40  		ey = uy.i.se;
  41  		x = ux.f;
  42  		y = uy.f;
  43  	}
  44  
  45  	if (ex == 0x7fff && isinf(y))
  46  		return y;
  47  	if (ex == 0x7fff || y == 0)
  48  		return x;
  49  	if (ex - ey > LDBL_MANT_DIG)
  50  		return x + y;
  51  
  52  	z = 1;
  53  	if (ex > 0x3fff+8000) {
  54  		z = 0x1p10000L;
  55  		x *= 0x1p-10000L;
  56  		y *= 0x1p-10000L;
  57  	} else if (ey < 0x3fff-8000) {
  58  		z = 0x1p-10000L;
  59  		x *= 0x1p10000L;
  60  		y *= 0x1p10000L;
  61  	}
  62  	sq(&hx, &lx, x);
  63  	sq(&hy, &ly, y);
  64  	return z*sqrtl(ly+lx+hy+hx);
  65  }
  66  #endif
  67