1 /* e_sqrtf.c -- float version of e_sqrt.c. 2 * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com. 3 */ 4 5 /* 6 * ==================================================== 7 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. 8 * 9 * Developed at SunPro, a Sun Microsystems, Inc. business. 10 * Permission to use, copy, modify, and distribute this 11 * software is freely granted, provided that this notice 12 * is preserved. 13 * ==================================================== 14 */ 15 16 #ifndef lint 17 static char rcsid[] = "$FreeBSD$"; 18 #endif 19 20 #include "math.h" 21 #include "math_private.h" 22 23 #ifdef USE_BUILTIN_SQRTF 24 float 25 __ieee754_sqrtf(float x) 26 { 27 return (__builtin_sqrtf(x)); 28 } 29 #else 30 static const float one = 1.0, tiny=1.0e-30; 31 32 float 33 __ieee754_sqrtf(float x) 34 { 35 float z; 36 int32_t sign = (int)0x80000000; 37 int32_t ix,s,q,m,t,i; 38 u_int32_t r; 39 40 GET_FLOAT_WORD(ix,x); 41 42 /* take care of Inf and NaN */ 43 if((ix&0x7f800000)==0x7f800000) { 44 return x*x+x; /* sqrt(NaN)=NaN, sqrt(+inf)=+inf 45 sqrt(-inf)=sNaN */ 46 } 47 /* take care of zero */ 48 if(ix<=0) { 49 if((ix&(~sign))==0) return x;/* sqrt(+-0) = +-0 */ 50 else if(ix<0) 51 return (x-x)/(x-x); /* sqrt(-ve) = sNaN */ 52 } 53 /* normalize x */ 54 m = (ix>>23); 55 if(m==0) { /* subnormal x */ 56 for(i=0;(ix&0x00800000)==0;i++) ix<<=1; 57 m -= i-1; 58 } 59 m -= 127; /* unbias exponent */ 60 ix = (ix&0x007fffff)|0x00800000; 61 if(m&1) /* odd m, double x to make it even */ 62 ix += ix; 63 m >>= 1; /* m = [m/2] */ 64 65 /* generate sqrt(x) bit by bit */ 66 ix += ix; 67 q = s = 0; /* q = sqrt(x) */ 68 r = 0x01000000; /* r = moving bit from right to left */ 69 70 while(r!=0) { 71 t = s+r; 72 if(t<=ix) { 73 s = t+r; 74 ix -= t; 75 q += r; 76 } 77 ix += ix; 78 r>>=1; 79 } 80 81 /* use floating add to find out rounding direction */ 82 if(ix!=0) { 83 z = one-tiny; /* trigger inexact flag */ 84 if (z>=one) { 85 z = one+tiny; 86 if (z>one) 87 q += 2; 88 else 89 q += (q&1); 90 } 91 } 92 ix = (q>>1)+0x3f000000; 93 ix += (m <<23); 94 SET_FLOAT_WORD(z,ix); 95 return z; 96 } 97 #endif 98