s_cbrtf.c - vx32 - Local 9vx git repository for patches.
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       ---
       s_cbrtf.c (1851B)
       ---
            1 /* s_cbrtf.c -- float version of s_cbrt.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: src/lib/msun/src/s_cbrtf.c,v 1.7 2002/05/28 18:15:04 alfred Exp $";
           18 #endif
           19 
           20 #include "math.h"
           21 #include "math_private.h"
           22 
           23 /* cbrtf(x)
           24  * Return cube root of x
           25  */
           26 static const unsigned
           27         B1 = 709958130, /* B1 = (84+2/3-0.03306235651)*2**23 */
           28         B2 = 642849266; /* B2 = (76+2/3-0.03306235651)*2**23 */
           29 
           30 static const float
           31 C =  5.4285717010e-01, /* 19/35     = 0x3f0af8b0 */
           32 D = -7.0530611277e-01, /* -864/1225 = 0xbf348ef1 */
           33 E =  1.4142856598e+00, /* 99/70     = 0x3fb50750 */
           34 F =  1.6071428061e+00, /* 45/28     = 0x3fcdb6db */
           35 G =  3.5714286566e-01; /* 5/14      = 0x3eb6db6e */
           36 
           37 float
           38 cbrtf(float x)
           39 {
           40         float r,s,t;
           41         int32_t hx;
           42         u_int32_t sign;
           43         u_int32_t high;
           44 
           45         GET_FLOAT_WORD(hx,x);
           46         sign=hx&0x80000000;                 /* sign= sign(x) */
           47         hx  ^=sign;
           48         if(hx>=0x7f800000) return(x+x); /* cbrt(NaN,INF) is itself */
           49         if(hx==0)
           50             return(x);                /* cbrt(0) is itself */
           51 
           52         SET_FLOAT_WORD(x,hx);        /* x <- |x| */
           53     /* rough cbrt to 5 bits */
           54         if(hx<0x00800000)                 /* subnormal number */
           55           {SET_FLOAT_WORD(t,0x4b800000); /* set t= 2**24 */
           56            t*=x; GET_FLOAT_WORD(high,t); SET_FLOAT_WORD(t,high/3+B2);
           57           }
           58         else
           59           SET_FLOAT_WORD(t,hx/3+B1);
           60 
           61 
           62     /* new cbrt to 23 bits */
           63         r=t*t/x;
           64         s=C+r*t;
           65         t*=G+F/(s+E+D/s);
           66 
           67     /* retore the sign bit */
           68         GET_FLOAT_WORD(high,t);
           69         SET_FLOAT_WORD(t,high|sign);
           70         return(t);
           71 }