Check in LLVM r95781.
diff --git a/lib/Support/IsInf.cpp b/lib/Support/IsInf.cpp
new file mode 100644
index 0000000..d6da0c9
--- /dev/null
+++ b/lib/Support/IsInf.cpp
@@ -0,0 +1,49 @@
+//===-- IsInf.cpp - Platform-independent wrapper around C99 isinf() -------===//
+//
+// The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// Platform-independent wrapper around C99 isinf()
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Config/config.h"
+
+#if HAVE_ISINF_IN_MATH_H
+# include <math.h>
+#elif HAVE_ISINF_IN_CMATH
+# include <cmath>
+#elif HAVE_STD_ISINF_IN_CMATH
+# include <cmath>
+using std::isinf;
+#elif HAVE_FINITE_IN_IEEEFP_H
+// A handy workaround I found at http://www.unixguide.net/sun/faq ...
+// apparently this has been a problem with Solaris for years.
+# include <ieeefp.h>
+static int isinf(double x) { return !finite(x) && x==x; }
+#elif defined(_MSC_VER)
+#include <float.h>
+#define isinf(X) (!_finite(X))
+#elif defined(_AIX) && defined(__GNUC__)
+// GCC's fixincludes seems to be removing the isinf() declaration from the
+// system header /usr/include/math.h
+# include <math.h>
+static int isinf(double x) { return !finite(x) && x==x; }
+#elif defined(__hpux)
+// HP-UX is "special"
+#include <math.h>
+static int isinf(double x) { return ((x) == INFINITY) || ((x) == -INFINITY); }
+#else
+# error "Don't know how to get isinf()"
+#endif
+
+namespace llvm {
+
+int IsInf(float f) { return isinf(f); }
+int IsInf(double d) { return isinf(d); }
+
+} // end namespace llvm;