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+/* Copyright (C) 1996 Free Software Foundation, Inc.
+ Contributed by David Mosberger (davidm@cs.arizona.edu).
+
+This file is part of the GNU C Library.
+
+The GNU C Library is free software; you can redistribute it and/or
+modify it under the terms of the GNU Library General Public License as
+published by the Free Software Foundation; either version 2 of the
+License, or (at your option) any later version.
+
+The GNU C Library is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+Library General Public License for more details.
+
+You should have received a copy of the GNU Library General Public
+License along with the GNU C Library; see the file COPYING.LIB. If
+not, write to the Free Software Foundation, Inc., 675 Mass Ave,
+Cambridge, MA 02139, USA. */
+
+/* Finds the first bit set in an integer. Optimized for the Alpha
+architecture. */
+
+#include <sysdep.h>
+#ifdef __linux__
+# include <alpha/regdef.h>
+#else
+#include <regdef.h>
+#endif
+
+ .set noreorder
+ .set noat
+
+ENTRY(ffs)
+ .prologue 0
+
+ ldq_u zero, 0(sp) # on the 21064, this helps dual-issuing
+ addl a0, zero, a0 # the last insn and reduces the stall
+ negq a0, t0 # due to the srl instruction
+ and a0, t0, t0
+ clr v0
+ beq a0, done
+
+ # now do binary search for first non-zero bit
+
+ zapnot t0, 0x03, t2
+ addq v0, 16, t3
+ cmoveq t2, t3, v0
+
+ zapnot t0, 0x05, t2
+ addq v0, 8, t3
+ cmoveq t2, t3, v0
+
+ srl t0, v0, t0
+ addq v0, 1, v0
+
+ and t0, 0x0f, t2
+ addq v0, 4, t3
+ cmoveq t2, t3, v0
+
+ and t0, 0x33, t2
+ addq v0, 2, t3
+ cmoveq t2, t3, v0
+
+ and t0, 0x55, t2
+ addq v0, 1, t3
+ cmoveq t2, t3, v0
+
+done: ret
+
+ .end ffs