Assembly version of ffs(3).
Confirmed to return the same value as that of the C version. The results of a simple benchmark on SH-4 200MHz, is shown below. I think this shows acceptable performance. return value C version this version speed of ffs() (ns/call) (ns/call) ratio ------------ --------- ------------ ----- 0 86 86 1.00 1 110 86 1.27 2 132 86 1.53 3 165 105 1.57 4 201 104 1.93 5 237 111 2.13 6 271 111 2.44 7 307 126 2.43 8 342 125 2.73 9 376 122 3.08 10 410 121 3.38 11 446 139 3.20 12 483 140 3.45 13 518 146 3.54 14 551 146 3.77 15 587 161 3.64 16 624 162 3.85 17 658 141 4.66 18 694 142 4.88 19 727 160 4.54 20 764 161 4.74 21 799 167 4.78 22 834 167 4.99 23 868 181 4.79 24 903 181 4.98 25 939 146 6.43 26 974 146 6.67 27 1009 166 6.07 28 1044 165 6.32 29 1080 171 6.31 30 1115 171 6.52 31 1151 185 6.22 32 1185 186 6.37
This commit is contained in:
itohy
parent
41c25cb648
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70b5675025
111
lib/libc/arch/sh3/string/ffs.S
Normal file
111
lib/libc/arch/sh3/string/ffs.S
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@ -0,0 +1,111 @@
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/* $NetBSD: ffs.S,v 1.1 2002/08/24 06:30:34 itohy Exp $ */
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/*-
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* Copyright (c) 2002 The NetBSD Foundation, Inc.
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* All rights reserved.
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*
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* This code is derived from software contributed to The NetBSD Foundation
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* by ITOH Yasufumi.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. All advertising materials mentioning features or use of this software
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* must display the following acknowledgement:
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* This product includes software developed by the NetBSD
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* Foundation, Inc. and its contributors.
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* 4. Neither the name of The NetBSD Foundation nor the names of its
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* contributors may be used to endorse or promote products derived
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* from this software without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
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* ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
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* TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
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* BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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* POSSIBILITY OF SUCH DAMAGE.
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*/
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#include <machine/asm.h>
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#if defined(SYSLIBC_SCCS) && !defined(lint)
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RCSID("$NetBSD: ffs.S,v 1.1 2002/08/24 06:30:34 itohy Exp $")
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#endif
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/*
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* ffs - find first bit set
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*
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* This code makes use of ``test 8bit'' and ``shift 8bit'' instructions.
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* The remaining 8bit is tested in every 2bit.
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*/
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ENTRY(ffs)
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mov r4,r0 ! using r0 specific instructions
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tst #0xff,r0
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bt Lshift8
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mov #0+2,r1 ! ret = 1..8
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L8bit:
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tst #0x0f,r0
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bt 4f
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tst #0x03,r0
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bt 2f
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and #1,r0
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sub r0,r1
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rts
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mov r1,r0
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2: shlr2 r0
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add #2,r1
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and #1,r0
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sub r0,r1
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rts
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mov r1,r0
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4: shlr2 r0
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shlr2 r0
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tst #0x03,r0
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bt 6f
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add #4,r1
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and #1,r0
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sub r0,r1
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rts
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mov r1,r0
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6: shlr2 r0
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add #6,r1
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and #1,r0
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sub r0,r1
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rts
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mov r1,r0
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Lzero: rts
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Lshift8:
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tst r0,r0 ! ffs(0) is 0
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bt Lzero ! testing here to accelerate ret=1..8 cases
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shlr8 r0
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tst #0xff,r0
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bt Lshift16
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bra L8bit
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mov #8+2,r1 ! ret = 9..16
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Lshift16:
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shlr8 r0
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tst #0xff,r0
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bt Lshift24
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bra L8bit
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mov #16+2,r1 ! ret = 17..24
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Lshift24:
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shlr8 r0
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bra L8bit
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mov #24+2,r1 ! ret = 25..32
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111
sys/lib/libkern/arch/sh3/ffs.S
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111
sys/lib/libkern/arch/sh3/ffs.S
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@ -0,0 +1,111 @@
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/* $NetBSD: ffs.S,v 1.1 2002/08/24 06:30:36 itohy Exp $ */
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/*-
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* Copyright (c) 2002 The NetBSD Foundation, Inc.
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* All rights reserved.
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*
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* This code is derived from software contributed to The NetBSD Foundation
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* by ITOH Yasufumi.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
|
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* 1. Redistributions of source code must retain the above copyright
|
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* notice, this list of conditions and the following disclaimer.
|
||||
* 2. Redistributions in binary form must reproduce the above copyright
|
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* notice, this list of conditions and the following disclaimer in the
|
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* documentation and/or other materials provided with the distribution.
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* 3. All advertising materials mentioning features or use of this software
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* must display the following acknowledgement:
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* This product includes software developed by the NetBSD
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* Foundation, Inc. and its contributors.
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* 4. Neither the name of The NetBSD Foundation nor the names of its
|
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* contributors may be used to endorse or promote products derived
|
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* from this software without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
|
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* ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
|
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* TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
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* BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
|
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* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
|
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* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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* POSSIBILITY OF SUCH DAMAGE.
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*/
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#include <machine/asm.h>
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#if defined(SYSLIBC_SCCS) && !defined(lint)
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RCSID("$NetBSD: ffs.S,v 1.1 2002/08/24 06:30:36 itohy Exp $")
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#endif
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/*
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* ffs - find first bit set
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*
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* This code makes use of ``test 8bit'' and ``shift 8bit'' instructions.
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* The remaining 8bit is tested in every 2bit.
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*/
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ENTRY(ffs)
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mov r4,r0 ! using r0 specific instructions
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tst #0xff,r0
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bt Lshift8
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mov #0+2,r1 ! ret = 1..8
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L8bit:
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tst #0x0f,r0
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bt 4f
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tst #0x03,r0
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bt 2f
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and #1,r0
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sub r0,r1
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rts
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mov r1,r0
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2: shlr2 r0
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add #2,r1
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and #1,r0
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sub r0,r1
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rts
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mov r1,r0
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4: shlr2 r0
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shlr2 r0
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tst #0x03,r0
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bt 6f
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add #4,r1
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and #1,r0
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sub r0,r1
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rts
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mov r1,r0
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6: shlr2 r0
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add #6,r1
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and #1,r0
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sub r0,r1
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rts
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mov r1,r0
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Lzero: rts
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Lshift8:
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tst r0,r0 ! ffs(0) is 0
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bt Lzero ! testing here to accelerate ret=1..8 cases
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shlr8 r0
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tst #0xff,r0
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bt Lshift16
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bra L8bit
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mov #8+2,r1 ! ret = 9..16
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Lshift16:
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shlr8 r0
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tst #0xff,r0
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bt Lshift24
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bra L8bit
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mov #16+2,r1 ! ret = 17..24
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Lshift24:
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shlr8 r0
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bra L8bit
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mov #24+2,r1 ! ret = 25..32
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