| /* e_sqrtf.c -- float version of e_sqrt.c. |
| * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com. |
| */ |
| |
| /* |
| * ==================================================== |
| * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. |
| * |
| * Developed at SunPro, a Sun Microsystems, Inc. business. |
| * Permission to use, copy, modify, and distribute this |
| * software is freely granted, provided that this notice |
| * is preserved. |
| * ==================================================== |
| */ |
| |
| #ifndef lint |
| static char rcsid[] = "$FreeBSD$"; |
| #endif |
| |
| #include "math.h" |
| #include "math_private.h" |
| |
| static const float one = 1.0, tiny=1.0e-30; |
| |
| float |
| __ieee754_sqrtf(float x) |
| { |
| float z; |
| int32_t sign = (int)0x80000000; |
| int32_t ix,s,q,m,t,i; |
| u_int32_t r; |
| |
| GET_FLOAT_WORD(ix,x); |
| |
| /* take care of Inf and NaN */ |
| if((ix&0x7f800000)==0x7f800000) { |
| return x*x+x; /* sqrt(NaN)=NaN, sqrt(+inf)=+inf |
| sqrt(-inf)=sNaN */ |
| } |
| /* take care of zero */ |
| if(ix<=0) { |
| if((ix&(~sign))==0) return x;/* sqrt(+-0) = +-0 */ |
| else if(ix<0) |
| return (x-x)/(x-x); /* sqrt(-ve) = sNaN */ |
| } |
| /* normalize x */ |
| m = (ix>>23); |
| if(m==0) { /* subnormal x */ |
| for(i=0;(ix&0x00800000)==0;i++) ix<<=1; |
| m -= i-1; |
| } |
| m -= 127; /* unbias exponent */ |
| ix = (ix&0x007fffff)|0x00800000; |
| if(m&1) /* odd m, double x to make it even */ |
| ix += ix; |
| m >>= 1; /* m = [m/2] */ |
| |
| /* generate sqrt(x) bit by bit */ |
| ix += ix; |
| q = s = 0; /* q = sqrt(x) */ |
| r = 0x01000000; /* r = moving bit from right to left */ |
| |
| while(r!=0) { |
| t = s+r; |
| if(t<=ix) { |
| s = t+r; |
| ix -= t; |
| q += r; |
| } |
| ix += ix; |
| r>>=1; |
| } |
| |
| /* use floating add to find out rounding direction */ |
| if(ix!=0) { |
| z = one-tiny; /* trigger inexact flag */ |
| if (z>=one) { |
| z = one+tiny; |
| if (z>one) |
| q += 2; |
| else |
| q += (q&1); |
| } |
| } |
| ix = (q>>1)+0x3f000000; |
| ix += (m <<23); |
| SET_FLOAT_WORD(z,ix); |
| return z; |
| } |
