diff --git a/libm/src/s_cbrt.c b/libm/src/s_cbrt.c
new file mode 100644
index 0000000..b600677
--- /dev/null
+++ b/libm/src/s_cbrt.c
@@ -0,0 +1,92 @@
+/* @(#)s_cbrt.c 5.1 93/09/24 */
+/*
+ * ====================================================
+ * 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.
+ * ====================================================
+ *
+ * Optimized by Bruce D. Evans.
+ */
+
+#ifndef lint
+static char rcsid[] = "$FreeBSD: src/lib/msun/src/s_cbrt.c,v 1.10 2005/12/13 20:17:23 bde Exp $";
+#endif
+
+#include "math.h"
+#include "math_private.h"
+
+/* cbrt(x)
+ * Return cube root of x
+ */
+static const u_int32_t
+	B1 = 715094163, /* B1 = (1023-1023/3-0.03306235651)*2**20 */
+	B2 = 696219795; /* B2 = (1023-1023/3-54/3-0.03306235651)*2**20 */
+
+static const double
+C =  5.42857142857142815906e-01, /* 19/35     = 0x3FE15F15, 0xF15F15F1 */
+D = -7.05306122448979611050e-01, /* -864/1225 = 0xBFE691DE, 0x2532C834 */
+E =  1.41428571428571436819e+00, /* 99/70     = 0x3FF6A0EA, 0x0EA0EA0F */
+F =  1.60714285714285720630e+00, /* 45/28     = 0x3FF9B6DB, 0x6DB6DB6E */
+G =  3.57142857142857150787e-01; /* 5/14      = 0x3FD6DB6D, 0xB6DB6DB7 */
+
+double
+cbrt(double x)
+{
+	int32_t	hx;
+	double r,s,t=0.0,w;
+	u_int32_t sign;
+	u_int32_t high,low;
+
+	GET_HIGH_WORD(hx,x);
+	sign=hx&0x80000000; 		/* sign= sign(x) */
+	hx  ^=sign;
+	if(hx>=0x7ff00000) return(x+x); /* cbrt(NaN,INF) is itself */
+	GET_LOW_WORD(low,x);
+	if((hx|low)==0)
+	    return(x);		/* cbrt(0) is itself */
+
+    /*
+     * Rough cbrt to 5 bits:
+     *    cbrt(2**e*(1+m) ~= 2**(e/3)*(1+(e%3+m)/3)
+     * where e is integral and >= 0, m is real and in [0, 1), and "/" and
+     * "%" are integer division and modulus with rounding towards minus
+     * infinity.  The RHS is always >= the LHS and has a maximum relative
+     * error of about 1 in 16.  Adding a bias of -0.03306235651 to the
+     * (e%3+m)/3 term reduces the error to about 1 in 32. With the IEEE
+     * floating point representation, for finite positive normal values,
+     * ordinary integer divison of the value in bits magically gives
+     * almost exactly the RHS of the above provided we first subtract the
+     * exponent bias (1023 for doubles) and later add it back.  We do the
+     * subtraction virtually to keep e >= 0 so that ordinary integer
+     * division rounds towards minus infinity; this is also efficient.
+     */
+	if(hx<0x00100000) { 		/* subnormal number */
+	    SET_HIGH_WORD(t,0x43500000); /* set t= 2**54 */
+	    t*=x;
+	    GET_HIGH_WORD(high,t);
+	    SET_HIGH_WORD(t,sign|((high&0x7fffffff)/3+B2));
+	} else
+	    SET_HIGH_WORD(t,sign|(hx/3+B1));
+
+    /* new cbrt to 23 bits; may be implemented in single precision */
+	r=t*t/x;
+	s=C+r*t;
+	t*=G+F/(s+E+D/s);
+
+    /* chop t to 20 bits and make it larger in magnitude than cbrt(x) */
+	GET_HIGH_WORD(high,t);
+	INSERT_WORDS(t,high+0x00000001,0);
+
+    /* one step Newton iteration to 53 bits with error less than 0.667 ulps */
+	s=t*t;		/* t*t is exact */
+	r=x/s;
+	w=t+t;
+	r=(r-t)/(w+r);	/* r-t is exact */
+	t=t+t*r;
+
+	return(t);
+}