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
sqrtf(float x)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
sqrtf(float x)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