diff --git a/lib/floatundixf.c b/lib/floatundixf.c
new file mode 100644
index 0000000..6e8c483
--- /dev/null
+++ b/lib/floatundixf.c
@@ -0,0 +1,40 @@
+//===-- floatundixf.c - Implement __floatundixf ---------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file implements __floatundixf for the compiler_rt library.
+//
+//===----------------------------------------------------------------------===//
+
+#if !_ARCH_PPC
+
+#include "int_lib.h"
+
+// Returns: convert a to a long double, rounding toward even.
+
+// Assumption: long double is a IEEE 80 bit floating point type padded to 128 bits
+//             du_int is a 64 bit integral type
+
+// gggg gggg gggg gggg gggg gggg gggg gggg | gggg gggg gggg gggg seee eeee eeee eeee |
+// 1mmm mmmm mmmm mmmm mmmm mmmm mmmm mmmm | mmmm mmmm mmmm mmmm mmmm mmmm mmmm mmmm
+
+long double
+__floatundixf(du_int a)
+{
+    if (a == 0)
+        return 0.0;
+    const unsigned N = sizeof(du_int) * CHAR_BIT;
+    int clz = __builtin_clzll(a);
+    int e = (N - 1) - clz ;    // exponent
+    long_double_bits fb;
+    fb.u.high.low = (e + 16383);               // exponent
+    fb.u.low.all = a << clz;                   // mantissa
+    return fb.f;
+}
+
+#endif