b6cbf7203b
This patch imports the unmodified current version of NetBSD libc. The NetBSD includes are in /nbsd_include, while the libc code itself is split between lib/nbsd_libc and common/lib/libc.
166 lines
4.5 KiB
ArmAsm
166 lines
4.5 KiB
ArmAsm
/* $NetBSD: strlen.S,v 1.1 2005/12/20 19:28:50 christos Exp $ */
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/*
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* Copyright 2002 Wasabi Systems, Inc.
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* All rights reserved.
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*
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* Written by Eduardo Horvath for Wasabi Systems, Inc.
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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 for the NetBSD Project by
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* Wasabi Systems, Inc.
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* 4. The name of Wasabi Systems, Inc. may not be used to endorse
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* or promote products derived from this software without specific prior
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* written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY WASABI SYSTEMS, INC. ``AS IS'' AND
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* 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 WASABI SYSTEMS, INC
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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(LIBC_SCCS) && !defined(lint)
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RCSID("$NetBSD: strlen.S,v 1.1 2005/12/20 19:28:50 christos Exp $")
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#endif /* LIBC_SCCS and not lint */
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/* The algorithm here uses the following techniques:
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*
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* 1) Given a word 'x', we can test to see if it contains any 0 bytes
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* by subtracting 0x01010101, and seeing if any of the high bits of each
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* byte changed from 0 to 1. This works because the least significant
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* 0 byte must have had no incoming carry (otherwise it's not the least
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* significant), so it is 0x00 - 0x01 == 0xff. For all other
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* byte values, either they have the high bit set initially, or when
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* 1 is subtracted you get a value in the range 0x00-0x7f, none of which
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* have their high bit set. The expression here is
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* (x + 0xfefefeff) & ~(x | 0x7f7f7f7f), which gives 0x00000000 when
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* there were no 0x00 bytes in the word.
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*
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* 2) Now just hunt for the first byte that's 0x00 in 'x'.
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*
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* This is from the book 'The PowerPC Compiler Writer's Guide',
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* by Steve Hoxey, Faraydon Karim, Bill Hay and Hank Warren.
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*/
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ENTRY(strlen)
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/*
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* Calculate address for and load the first xword.
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*/
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andn %o0, 0x7, %o1
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ldx [%o1], %g1
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/*
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* Now prepare some constants while the data arrives...
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*/
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sethi %hi(0xfefefefe), %o3
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sethi %hi(0x7f7f7f7f), %o2
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or %o3, %lo(0xfefefefe), %o3
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or %o2, %lo(0x7f7f7f7f), %o2
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sllx %o3, 32, %o5
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andcc %o0, 0x7, %g5 ! Hoisted from below to fill a slot
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sllx %o2, 32, %o4
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or %o3, %o5, %o3
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sll %g5, 3, %g5 ! Convert to bytes. hoisted
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or %o2, %o4, %o2
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inc %o3
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neg %g5 ! hoisted
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/*
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* Mask off the leading bits:
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*
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* if (ptr & 0x7)
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* mask = -1 << (64 - ((ptr & 0x7) << 3));
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*/
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! andcc %o0, 0x7, %g5 ! Hoisted above
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bz,pt %icc, 0f
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! sll %g5, 3, %g5 ! Convert to bytes. Also hoisted
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! neg %g5 ! Hoisted
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add %g5, 64, %g5
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mov -1, %o4
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sllx %o4, %g5, %o4
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or %o4, %g1, %g1 ! Make leading bytes != 0
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0:
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or %g1, %o2, %o5 ! Do step 1 -- use or/andn instead of nor/and
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add %g1, %o3, %g5
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inc 8, %o1 ! Point to next word
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andncc %g5, %o5, %g0
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bz,a,pt %xcc, 0b
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ldx [%o1], %g1
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mov -1, %o4
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dec 8, %o1
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sllx %o4, 64-8, %o5
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btst %g1, %o5 ! Check high byte
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bz %xcc,0f
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srlx %o5, 8, %o5
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inc %o1
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btst %g1, %o5 ! Check 2nd byte
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bz %xcc,0f
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srlx %o5, 8, %o5
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inc %o1
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btst %g1, %o5 ! Check 3rd byte
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bz %xcc,0f
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srlx %o5, 8, %o5
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inc %o1
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btst %g1, %o5 ! Check 4th byte
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bz %xcc,0f
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srlx %o5, 8, %o5
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inc %o1
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btst %g1, %o5 ! Check 5th byte
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bz %xcc,0f
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srlx %o5, 8, %o5
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inc %o1
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btst %g1, %o5 ! Check 6th byte
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bz %xcc,0f
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srlx %o5, 8, %o5
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inc %o1
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btst %g1, %o5 ! Check 7th byte
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bz %xcc,0f
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nop
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inc %o1
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0:
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retl
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sub %o1, %o0, %o0 ! return length (ptr - (origptr+1))
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