diff --git a/lib/subsf3.c b/lib/subsf3.c
new file mode 100644
index 0000000..9ce14d7
--- /dev/null
+++ b/lib/subsf3.c
@@ -0,0 +1,23 @@
+//===-- lib/subsf3.c - Single-precision subtraction ---------------*- C -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file implements single-precision soft-float subtraction with the
+// IEEE-754 default rounding (to nearest, ties to even).
+//
+//===----------------------------------------------------------------------===//
+
+#define SINGLE_PRECISION
+#include "fp_lib.h"
+
+fp_t __addsf3(fp_t a, fp_t b);
+
+// Subtraction; flip the sign bit of b and add.
+fp_t __subsf3(fp_t a, fp_t b) {
+    return __addsf3(a, fromRep(toRep(b) ^ signBit));
+}