mirror of
https://sourceware.org/git/glibc.git
synced 2024-11-22 21:10:07 +00:00
94 lines
2.1 KiB
C
94 lines
2.1 KiB
C
/* e_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 <math.h>
|
|
#include <math_private.h>
|
|
#include <libm-alias-finite.h>
|
|
#include <math-use-builtins.h>
|
|
|
|
float
|
|
__ieee754_sqrtf(float x)
|
|
{
|
|
#if USE_SQRTF_BUILTIN
|
|
return __builtin_sqrtf (x);
|
|
#else
|
|
/* Use generic implementation. */
|
|
float z;
|
|
int32_t sign = (int)0x80000000;
|
|
int32_t ix,s,q,m,t,i;
|
|
uint32_t r;
|
|
|
|
GET_FLOAT_WORD(ix,x);
|
|
|
|
/* take care of Inf and NaN */
|
|
if((ix&0x7f800000)==0x7f800000) {
|
|
return x*x+x; /* sqrt(NaN)=NaN, sqrt(+inf)=+inf
|
|
sqrt(-inf)=sNaN */
|
|
}
|
|
/* take care of zero */
|
|
if(ix<=0) {
|
|
if((ix&(~sign))==0) return x;/* sqrt(+-0) = +-0 */
|
|
else if(ix<0)
|
|
return (x-x)/(x-x); /* sqrt(-ve) = sNaN */
|
|
}
|
|
/* normalize x */
|
|
m = (ix>>23);
|
|
if(m==0) { /* subnormal x */
|
|
for(i=0;(ix&0x00800000)==0;i++) ix<<=1;
|
|
m -= i-1;
|
|
}
|
|
m -= 127; /* unbias exponent */
|
|
ix = (ix&0x007fffff)|0x00800000;
|
|
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 = 0x01000000; /* 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 = 0x1p0 - 0x1.4484cp-100; /* trigger inexact flag. */
|
|
if (z >= 0x1p0) {
|
|
z = 0x1p0 + 0x1.4484cp-100;
|
|
if (z > 0x1p0)
|
|
q += 2;
|
|
else
|
|
q += (q&1);
|
|
}
|
|
}
|
|
ix = (q>>1)+0x3f000000;
|
|
ix += (m <<23);
|
|
SET_FLOAT_WORD(z,ix);
|
|
return z;
|
|
#endif /* ! USE_SQRTF_BUILTIN */
|
|
}
|
|
#ifndef __ieee754_sqrtf
|
|
libm_alias_finite (__ieee754_sqrtf, __sqrtf)
|
|
#endif
|