1 files changed, 43 insertions, 0 deletions
diff --git a/src/math/acoshf.c b/src/math/acoshf.c
new file mode 100644
index 00000000..30a3a943
--- /dev/null
+++ b/src/math/acoshf.c
@@ -0,0 +1,43 @@
+/* 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));
+	}
+}