mirror of
git://sourceware.org/git/glibc.git
synced 2024-12-21 04:31:04 +08:00
67 lines
1.7 KiB
ArmAsm
67 lines
1.7 KiB
ArmAsm
/* 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>
|
|
|
|
.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)
|