Index: head/contrib/compiler-rt/lib/builtins/README.txt
===================================================================
--- head/contrib/compiler-rt/lib/builtins/README.txt
+++ head/contrib/compiler-rt/lib/builtins/README.txt
@@ -45,6 +45,7 @@
 si_int __ctzdi2(di_int a);  // count trailing zeros
 si_int __ctzti2(ti_int a);  // count trailing zeros
 
+si_int __ffssi2(si_int a);  // find least significant 1 bit
 si_int __ffsdi2(di_int a);  // find least significant 1 bit
 si_int __ffsti2(ti_int a);  // find least significant 1 bit
 
Index: head/contrib/compiler-rt/lib/builtins/ffssi2.c
===================================================================
--- head/contrib/compiler-rt/lib/builtins/ffssi2.c
+++ head/contrib/compiler-rt/lib/builtins/ffssi2.c
@@ -0,0 +1,29 @@
+/* ===-- ffssi2.c - Implement __ffssi2 -------------------------------------===
+ *
+ *                     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 __ffssi2 for the compiler_rt library.
+ *
+ * ===----------------------------------------------------------------------===
+ */
+
+#include "int_lib.h"
+
+/* Returns: the index of the least significant 1-bit in a, or
+ * the value zero if a is zero. The least significant bit is index one.
+ */
+
+COMPILER_RT_ABI si_int
+__ffssi2(si_int a)
+{
+    if (a == 0)
+    {
+        return 0;
+    }
+    return __builtin_ctz(a) + 1;
+}
Index: head/lib/libcompiler_rt/Makefile.inc
===================================================================
--- head/lib/libcompiler_rt/Makefile.inc
+++ head/lib/libcompiler_rt/Makefile.inc
@@ -38,6 +38,7 @@
 SRCF+=		enable_execute_stack
 SRCF+=		eprintf
 SRCF+=		extendhfsf2
+SRCF+=		ffssi2
 SRCF+=		ffsdi2
 SRCF+=		ffsti2
 SRCF+=		fixdfdi