1 files changed, 71 insertions, 0 deletions
diff --git a/src/math/log10f.c b/src/math/log10f.c
new file mode 100644
index 00000000..4175cce2
--- /dev/null
+++ b/src/math/log10f.c
@@ -0,0 +1,71 @@
+/* origin: FreeBSD /usr/src/lib/msun/src/e_log10f.c */
+/*
+ * ====================================================
+ * 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.
+ * ====================================================
+ */
+/*
+ * See comments in log10.c.
+ */
+
+#include "libm.h"
+#include "__log1pf.h"
+
+static const float
+two25     =  3.3554432000e+07, /* 0x4c000000 */
+ivln10hi  =  4.3432617188e-01, /* 0x3ede6000 */
+ivln10lo  = -3.1689971365e-05, /* 0xb804ead9 */
+log10_2hi =  3.0102920532e-01, /* 0x3e9a2080 */
+log10_2lo =  7.9034151668e-07; /* 0x355427db */
+
+static const float zero = 0.0;
+
+float log10f(float x)
+{
+	float f,hfsq,hi,lo,r,y;
+	int32_t i,k,hx;
+
+	GET_FLOAT_WORD(hx, x);
+
+	k = 0;
+	if (hx < 0x00800000) {  /* x < 2**-126  */
+		if ((hx&0x7fffffff) == 0)
+			return -two25/zero;  /* log(+-0)=-inf */
+		if (hx < 0)
+			return (x-x)/zero;   /* log(-#) = NaN */
+		/* subnormal number, scale up x */
+		k -= 25;
+		x *= two25;
+		GET_FLOAT_WORD(hx, x);
+	}
+	if (hx >= 0x7f800000)
+		return x+x;
+	if (hx == 0x3f800000)
+		return zero;  /* log(1) = +0 */
+	k += (hx>>23) - 127;
+	hx &= 0x007fffff;
+	i = (hx+(0x4afb0d))&0x800000;
+	SET_FLOAT_WORD(x, hx|(i^0x3f800000));  /* normalize x or x/2 */
+	k += i>>23;
+	y = (float)k;
+	f = x - (float)1.0;
+	hfsq = (float)0.5*f*f;
+	r = __log1pf(f);
+
+// FIXME
+//      /* See log2f.c and log2.c for details. */
+//      if (sizeof(float_t) > sizeof(float))
+//              return (r - hfsq + f) * ((float_t)ivln10lo + ivln10hi) +
+//                  y * ((float_t)log10_2lo + log10_2hi);
+	hi = f - hfsq;
+	GET_FLOAT_WORD(hx, hi);
+	SET_FLOAT_WORD(hi, hx&0xfffff000);
+	lo = (f - hi) - hfsq + r;
+	return y*log10_2lo + (lo+hi)*ivln10lo + lo*ivln10hi +
+	        hi*ivln10hi + y*log10_2hi;
+}