/* ef_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. * ==================================================== */ #include "fdlibm.h" #ifdef __STDC__ static const volatile float one = 1.0, tiny=1.0e-30; #else static float volatile one = 1.0, tiny=1.0e-30; #endif #ifdef __STDC__ float __ieee754_sqrtf(float x) #else float __ieee754_sqrtf(x) float x; #endif { float z; __uint32_t r,hx; __int32_t ix,s,q,m,t,i; GET_FLOAT_WORD(ix,x); hx = ix&0x7fffffff; /* take care of Inf and NaN */ if(!FLT_UWORD_IS_FINITE(hx)) return x*x+x; /* sqrt(NaN)=NaN, sqrt(+inf)=+inf sqrt(-inf)=sNaN */ /* take care of zero and -ves */ if(FLT_UWORD_IS_ZERO(hx)) return x;/* sqrt(+-0) = +-0 */ if(ix<0) return (x-x)/(x-x); /* sqrt(-ve) = sNaN */ /* normalize x */ m = (ix>>23); if(FLT_UWORD_IS_SUBNORMAL(hx)) { /* subnormal x */ for(i=0;(ix&0x00800000L)==0;i++) ix<<=1; m -= i-1; } m -= 127; /* unbias exponent */ ix = (ix&0x007fffffL)|0x00800000L; 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 = 0x01000000L; /* 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)+0x3f000000L; ix += (m <<23); SET_FLOAT_WORD(z,ix); return z; }