1 files changed, 89 insertions, 0 deletions
diff --git a/src/math/logf.c b/src/math/logf.c
new file mode 100644
index 00000000..285ee615
--- /dev/null
+++ b/src/math/logf.c
@@ -0,0 +1,89 @@
+/* origin: FreeBSD /usr/src/lib/msun/src/e_logf.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 "libm.h"
+
+static const float
+ln2_hi = 6.9313812256e-01, /* 0x3f317180 */
+ln2_lo = 9.0580006145e-06, /* 0x3717f7d1 */
+two25  = 3.355443200e+07,  /* 0x4c000000 */
+/* |(log(1+s)-log(1-s))/s - Lg(s)| < 2**-34.24 (~[-4.95e-11, 4.97e-11]). */
+Lg1 = 0xaaaaaa.0p-24, /* 0.66666662693 */
+Lg2 = 0xccce13.0p-25, /* 0.40000972152 */
+Lg3 = 0x91e9ee.0p-25, /* 0.28498786688 */
+Lg4 = 0xf89e26.0p-26; /* 0.24279078841 */
+
+static const float zero = 0.0;
+
+float logf(float x)
+{
+	float hfsq,f,s,z,R,w,t1,t2,dk;
+	int32_t k,ix,i,j;
+
+	GET_FLOAT_WORD(ix, x);
+
+	k = 0;
+	if (ix < 0x00800000) {  /* x < 2**-126  */
+		if ((ix & 0x7fffffff) == 0)
+			return -two25/zero;  /* log(+-0)=-inf */
+		if (ix < 0)
+			return (x-x)/zero;   /* log(-#) = NaN */
+		/* subnormal number, scale up x */
+		k -= 25;
+		x *= two25;
+		GET_FLOAT_WORD(ix, x);
+	}
+	if (ix >= 0x7f800000)
+		return x+x;
+	k += (ix>>23) - 127;
+	ix &= 0x007fffff;
+	i = (ix + (0x95f64<<3)) & 0x800000;
+	SET_FLOAT_WORD(x, ix|(i^0x3f800000));  /* normalize x or x/2 */
+	k += i>>23;
+	f = x - (float)1.0;
+	if ((0x007fffff & (0x8000 + ix)) < 0xc000) {  /* -2**-9 <= f < 2**-9 */
+		if (f == zero) {
+			if (k == 0)
+				return zero;
+			dk = (float)k;
+			return dk*ln2_hi + dk*ln2_lo;
+		}
+		R = f*f*((float)0.5 - (float)0.33333333333333333*f);
+		if (k == 0)
+			return f-R;
+		dk = (float)k;
+		return dk*ln2_hi - ((R-dk*ln2_lo)-f);
+	}
+	s = f/((float)2.0+f);
+	dk = (float)k;
+	z = s*s;
+	i = ix-(0x6147a<<3);
+	w = z*z;
+	j = (0x6b851<<3)-ix;
+	t1= w*(Lg2+w*Lg4);
+	t2= z*(Lg1+w*Lg3);
+	i |= j;
+	R = t2 + t1;
+	if (i > 0) {
+		hfsq = (float)0.5*f*f;
+		if (k == 0)
+			return f - (hfsq-s*(hfsq+R));
+		return dk*ln2_hi - ((hfsq-(s*(hfsq+R)+dk*ln2_lo))-f);
+	} else {
+		if (k == 0)
+			return f - s*(f-R);
+		return dk*ln2_hi - ((s*(f-R)-dk*ln2_lo)-f);
+	}
+}