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 #include "math.h" 17 #include "math_private.h" 18 19 #ifdef USE_BUILTIN_SQRTF 20 float 21 sqrtf(float x) 22 { 23 return (__builtin_sqrtf(x)); 24 } 25 #else 26 static const float one = 1.0, tiny=1.0e-30; 27 28 float 29 sqrtf(float x) 30 { 31 float z; 32 int32_t sign = (int)0x80000000; 33 int32_t ix,s,q,m,t,i; 34 u_int32_t r; 35 36 GET_FLOAT_WORD(ix,x); 37 38 /* take care of Inf and NaN */ 39 if((ix&0x7f800000)==0x7f800000) { 40 return x*x+x; /* sqrt(NaN)=NaN, sqrt(+inf)=+inf 41 sqrt(-inf)=sNaN */ 42 } 43 /* take care of zero */ 44 if(ix<=0) { 45 if((ix&(~sign))==0) return x;/* sqrt(+-0) = +-0 */ 46 else if(ix<0) 47 return (x-x)/(x-x); /* sqrt(-ve) = sNaN */ 48 } 49 /* normalize x */ 50 m = (ix>>23); 51 if(m==0) { /* subnormal x */ 52 for(i=0;(ix&0x00800000)==0;i++) ix<<=1; 53 m -= i-1; 54 } 55 m -= 127; /* unbias exponent */ 56 ix = (ix&0x007fffff)|0x00800000; 57 if(m&1) /* odd m, double x to make it even */ 58 ix += ix; 59 m >>= 1; /* m = [m/2] */ 60 61 /* generate sqrt(x) bit by bit */ 62 ix += ix; 63 q = s = 0; /* q = sqrt(x) */ 64 r = 0x01000000; /* r = moving bit from right to left */ 65 66 while(r!=0) { 67 t = s+r; 68 if(t<=ix) { 69 s = t+r; 70 ix -= t; 71 q += r; 72 } 73 ix += ix; 74 r>>=1; 75 } 76 77 /* use floating add to find out rounding direction */ 78 if(ix!=0) { 79 z = one-tiny; /* trigger inexact flag */ 80 if (z>=one) { 81 z = one+tiny; 82 if (z>one) 83 q += 2; 84 else 85 q += (q&1); 86 } 87 } 88 ix = (q>>1)+0x3f000000; 89 ix += (m <<23); 90 SET_FLOAT_WORD(z,ix); 91 return z; 92 } 93 #endif 94