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[/] [openrisc/] [trunk/] [gnu-src/] [newlib-1.18.0/] [newlib/] [libc/] [machine/] [hppa/] [strlen.S] - Blame information for rev 207

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1 207 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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