auto import from //depot/cupcake/@135843
diff --git a/libc/arch-arm/bionic/ffs.S b/libc/arch-arm/bionic/ffs.S
new file mode 100644
index 0000000..f11141c
--- /dev/null
+++ b/libc/arch-arm/bionic/ffs.S
@@ -0,0 +1,82 @@
+/* $NetBSD: ffs.S,v 1.5 2003/04/05 23:08:52 bjh21 Exp $ */
+/*
+ * Copyright (c) 2001 Christopher Gilbert
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the distribution.
+ * 3. The name of the company nor the name of the author may be used to
+ * endorse or promote products derived from this software without specific
+ * prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
+ * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
+ * IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
+ * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+ * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <machine/asm.h>
+
+/*
+ * ffs - find first set bit, this algorithm isolates the first set
+ * bit, then multiplies the number by 0x0450fbaf which leaves the top
+ * 6 bits as an index into the table. This algorithm should be a win
+ * over the checking each bit in turn as per the C compiled version.
+ *
+ * under ARMv5 there's an instruction called CLZ (count leading Zero's) that
+ * could be used
+ *
+ * This is the ffs algorithm devised by d.seal and posted to comp.sys.arm on
+ * 16 Feb 1994.
+ */
+
+ENTRY(ffs)
+ /* Standard trick to isolate bottom bit in r0 or 0 if r0 = 0 on entry */
+ rsb r1, r0, #0
+ ands r0, r0, r1
+#ifndef __ARM_ARCH_5__
+ /*
+ * now r0 has at most one set bit, call this X
+ * if X = 0, all further instructions are skipped
+ */
+ adrne r2, .L_ffs_table
+ orrne r0, r0, r0, lsl #4 /* r0 = X * 0x11 */
+ orrne r0, r0, r0, lsl #6 /* r0 = X * 0x451 */
+ rsbne r0, r0, r0, lsl #16 /* r0 = X * 0x0450fbaf */
+
+ /* now lookup in table indexed on top 6 bits of r0 */
+ ldrneb r0, [ r2, r0, lsr #26 ]
+
+ bx lr
+
+.text;
+.type .L_ffs_table, _ASM_TYPE_OBJECT;
+.L_ffs_table:
+/* 0 1 2 3 4 5 6 7 */
+ .byte 0, 1, 2, 13, 3, 7, 0, 14 /* 0- 7 */
+ .byte 4, 0, 8, 0, 0, 0, 0, 15 /* 8-15 */
+ .byte 11, 5, 0, 0, 9, 0, 0, 26 /* 16-23 */
+ .byte 0, 0, 0, 0, 0, 22, 28, 16 /* 24-31 */
+ .byte 32, 12, 6, 0, 0, 0, 0, 0 /* 32-39 */
+ .byte 10, 0, 0, 25, 0, 0, 21, 27 /* 40-47 */
+ .byte 31, 0, 0, 0, 0, 24, 0, 20 /* 48-55 */
+ .byte 30, 0, 23, 19, 29, 18, 17, 0 /* 56-63 */
+#else
+ clzne r0, r0
+ rsbne r0, r0, #32
+ bx lr
+#endif
+