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The Android Open Source Project1dc9e472009-03-03 19:28:35 -08001/* 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
Elliott Hughesa0ee0782013-01-30 19:06:37 -080017static char rcsid[] = "$FreeBSD$";
The Android Open Source Project1dc9e472009-03-03 19:28:35 -080018#endif
19
20#include "math.h"
21#include "math_private.h"
22
Elliott Hughes99ef4472022-01-12 17:51:20 -080023#ifdef USE_BUILTIN_SQRTF
24float
25__ieee754_sqrtf(float x)
26{
27 return (__builtin_sqrtf(x));
28}
29#else
The Android Open Source Project1dc9e472009-03-03 19:28:35 -080030static const float one = 1.0, tiny=1.0e-30;
31
32float
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}
Elliott Hughes99ef4472022-01-12 17:51:20 -080097#endif