1 files changed, 79 insertions, 0 deletions
diff --git a/libm/src/s_cbrtf.c b/libm/src/s_cbrtf.c
new file mode 100644
index 0000000..75569a2
--- /dev/null
+++ b/libm/src/s_cbrtf.c
@@ -0,0 +1,79 @@
+/* s_cbrtf.c -- float version of s_cbrt.c.
+ * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
+ * Debugged and optimized by Bruce D. Evans.
+ */
+
+/*
+ * ====================================================
+ * 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.
+ * ====================================================
+ */
+
+#ifndef lint
+static char rcsid[] = "$FreeBSD: src/lib/msun/src/s_cbrtf.c,v 1.12 2005/12/13 20:17:23 bde Exp $";
+#endif
+
+#include "math.h"
+#include "math_private.h"
+
+/* cbrtf(x)
+ * Return cube root of x
+ */
+static const unsigned
+	B1 = 709958130, /* B1 = (127-127.0/3-0.03306235651)*2**23 */
+	B2 = 642849266; /* B2 = (127-127.0/3-24/3-0.03306235651)*2**23 */
+
+static const float
+C =  5.4285717010e-01, /* 19/35     = 0x3f0af8b0 */
+D = -7.0530611277e-01, /* -864/1225 = 0xbf348ef1 */
+E =  1.4142856598e+00, /* 99/70     = 0x3fb50750 */
+F =  1.6071428061e+00, /* 45/28     = 0x3fcdb6db */
+G =  3.5714286566e-01; /* 5/14      = 0x3eb6db6e */
+
+float
+cbrtf(float x)
+{
+	float r,s,t,w;
+	int32_t hx;
+	u_int32_t sign;
+	u_int32_t high;
+
+	GET_FLOAT_WORD(hx,x);
+	sign=hx&0x80000000; 		/* sign= sign(x) */
+	hx  ^=sign;
+	if(hx>=0x7f800000) return(x+x); /* cbrt(NaN,INF) is itself */
+	if(hx==0)
+	    return(x);		/* cbrt(0) is itself */
+
+    /* rough cbrt to 5 bits */
+	if(hx<0x00800000) { 		/* subnormal number */
+	    SET_FLOAT_WORD(t,0x4b800000); /* set t= 2**24 */
+	    t*=x;
+	    GET_FLOAT_WORD(high,t);
+	    SET_FLOAT_WORD(t,sign|((high&0x7fffffff)/3+B2));
+	} else
+	    SET_FLOAT_WORD(t,sign|(hx/3+B1));
+
+    /* new cbrt to 23 bits */
+	r=t*t/x;
+	s=C+r*t;
+	t*=G+F/(s+E+D/s);
+
+    /* chop t to 12 bits and make it larger in magnitude than cbrt(x) */
+	GET_FLOAT_WORD(high,t);
+	SET_FLOAT_WORD(t,(high&0xfffff000)+0x00001000);
+
+    /* one step Newton iteration to 24 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);
+}