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jeremybenn |
/*
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* (c) Copyright 1986 HEWLETT-PACKARD COMPANY
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*
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* To anyone who acknowledges that this file is provided "AS IS"
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* without any express or implied warranty:
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* permission to use, copy, modify, and distribute this file
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* for any purpose is hereby granted without fee, provided that
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* the above copyright notice and this notice appears in all
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* copies, and that the name of Hewlett-Packard Company not be
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* used in advertising or publicity pertaining to distribution
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* of the software without specific, written prior permission.
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* Hewlett-Packard Company makes no representations about the
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* suitability of this software for any purpose.
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*/
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/* HPUX_ID = "@(#) $Revision: 1.1 $" */
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/* strlen(s): Return length of string s */
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#define start arg0
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#define end ret0
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#define tmp1 arg1
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#define tmp2 arg2
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#include "DEFS.h"
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ENTRY(strlen)
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movb,=,n start,end,$null_ptr
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depi 0,31,2,end
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comb,<> start,end,$not_aligned
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ldws,ma 4(end),tmp1
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comib,tr 0,0,$loop /* avoid INDIGO two register interlock */
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uxor,nbz 0,tmp1,0
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$not_aligned:
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/*
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; Tricky code. The problem is that the value of of the word
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; including the start of the string has some garbage bytes that
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; may be 0. We don't want them to stop the string scan. So
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; we make those bytes non-zero (and any old non-zero value
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; will do). Notice that the end pointer has been rounded
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; down to a word boundary, and then incremented to the next
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; word by the time we get here. Therefore, (start-end) has
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; one of the values (-3, -2, or -1). Use uaddcm to do the
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; subtraction (instead of sub), and the result will be
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; (-4, -3, or -2). Multiply this by 8, and put into the
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; shift register (which truncates to the last 5 bits) and
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; the value will be (0, 8, or 16). Use this as a bit position,
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; and drop a mask down into tmp1. All the garbage bytes will
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; have at least 1 bit affected by the vdepi, so all the garbage
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; in this first word will be non-zero garbage.
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*/
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uaddcm start,end,tmp2 /* tmp2 <- { -4, -3, -2 } */
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sh3add tmp2,0,tmp2 /* tmp2 <- { -32, -24, -16 } */
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mtsar tmp2 /* sar <- { 0, 8, 16 } */
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vdepi -1,32,tmp1
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uxor,nbz 0,tmp1,0
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$loop:
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b,n $end_loop
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ldws,ma 4(end),tmp1
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comib,tr 0,0,$loop /* avoid INDIGO two register interlock */
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uxor,nbz 0,tmp1,0
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$end_loop:
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/* adjust the end pointer to one past the end of the string */
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extru,<> tmp1,7,8,0
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addib,tr,n -3,end,$out
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extru,<> tmp1,15,8,0
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addib,tr,n -2,end,$out
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extru,<> tmp1,23,8,0
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addi -1,end,end
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$out:
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bv 0(rp)
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/*
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; tricky code. the end pointer is just beyond the terminating
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; null byte, so the length is (end-start-1). use uaddcm
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; to do this in 1 instruction
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*/
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uaddcm end,start,ret0
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$null_ptr:
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EXIT(strlen)
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