1 files changed, 33 insertions, 0 deletions
diff --git a/winsup/cygwin/math/asinhl.c b/winsup/cygwin/math/asinhl.c
new file mode 100644
index 000000000..bb2ca97b2
--- /dev/null
+++ b/winsup/cygwin/math/asinhl.c
@@ -0,0 +1,33 @@
+/**
+ * This file has no copyright assigned and is placed in the Public Domain.
+ * This file is part of the mingw-w64 runtime package.
+ * No warranty is given; refer to the file DISCLAIMER.PD within this package.
+ */
+#include <math.h>
+#include <errno.h>
+#include "fastmath.h"
+
+ /* asinh(x) = copysign(log(fabs(x) + sqrt(x * x + 1.0)), x) */
+long double asinhl(long double x)
+{
+  long double z;
+  if (!isfinite (x))
+    return x;
+
+  z = fabsl (x);
+
+  /* Avoid setting FPU underflow exception flag in x * x. */
+#if 0
+  if ( z < 0x1p-32)
+    return x;
+#endif
+
+  /* Use log1p to avoid cancellation with small x. Put
+     x * x in denom, so overflow is harmless. 
+     asinh(x) = log1p (x + sqrt (x * x + 1.0) - 1.0)
+              = log1p (x + x * x / (sqrt (x * x + 1.0) + 1.0))  */
+
+  z = __fast_log1pl (z + z * z / (__fast_sqrtl (z * z + 1.0L) + 1.0L));
+
+  return ( x > 0.0 ? z : -z);
+}