--- /dev/null
+/* origin: FreeBSD /usr/src/lib/msun/src/e_acoshf.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
+one = 1.0,
+ln2 = 6.9314718246e-01; /* 0x3f317218 */
+
+float acoshf(float x)
+{
+ float t;
+ int32_t hx;
+
+ GET_FLOAT_WORD(hx, x);
+ if (hx < 0x3f800000) { /* x < 1 */
+ return (x-x)/(x-x);
+ } else if (hx >= 0x4d800000) { /* x > 2**28 */
+ if (hx >= 0x7f800000) /* x is inf of NaN */
+ return x + x;
+ return logf(x) + ln2; /* acosh(huge)=log(2x) */
+ } else if (hx == 0x3f800000) {
+ return 0.0; /* acosh(1) = 0 */
+ } else if (hx > 0x40000000) { /* 2**28 > x > 2 */
+ t = x*x;
+ return logf((float)2.0*x - one/(x+sqrtf(t-one)));
+ } else { /* 1 < x < 2 */
+ t = x-one;
+ return log1pf(t + sqrtf((float)2.0*t+t*t));
+ }
+}