ports/sysdeps/ia64/strlen.S

   1 /* Optimized version of the standard strlen() function.
   2    This file is part of the GNU C Library.
   3    Copyright (C) 2000-2014 Free Software Foundation, Inc.
   4    Contributed by Dan Pop <Dan.Pop@cern.ch>.
   5
   6    The GNU C Library is free software; you can redistribute it and/or
   7    modify it under the terms of the GNU Lesser General Public
   8    License as published by the Free Software Foundation; either
   9    version 2.1 of the License, or (at your option) any later version.
  10
  11    The GNU C Library is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14    Lesser General Public License for more details.
  15
  16    You should have received a copy of the GNU Lesser General Public
  17    License along with the GNU C Library; if not, see
  18    <http://www.gnu.org/licenses/>.  */
  19
  20 /* Return: the length of the input string
  21
  22    Input:
  23         in0:    str
  24
  25    Look for the null character byte by byte, until we reach a word aligned
  26    address, then search word by word, using the czx instruction.  We're
  27    also doing one word of read ahead, which could cause problems if the
  28    null character is on the last word of a page and the next page is not
  29    mapped in the process address space.  Hence the use of the speculative
  30    load.
  31
  32    This implementation assumes little endian mode.  For big endian mode,
  33    the instruction czx1.r should be replaced by czx1.l.  */
  34
  35 #include <sysdep.h>
  36 #undef ret
  37
  38 #define saved_lc        r18
  39 #define str             r19
  40 #define pos0            r20
  41 #define val1            r21
  42 #define val2            r22
  43 #define origadd         r23
  44 #define tmp             r24
  45 #define loopcnt         r30
  46 #define len             ret0
  47
  48 ENTRY(strlen)
  49         .prologue
  50         alloc r2 = ar.pfs, 1, 0, 0, 0
  51         .save ar.lc, saved_lc
  52         mov     saved_lc = ar.lc        // save the loop counter
  53         .body
  54         mov     str = in0
  55         mov     len = r0                // len = 0
  56         and     tmp = 7, in0            // tmp = str % 8
  57         ;;
  58         sub     loopcnt = 8, tmp        // loopcnt = 8 - tmp
  59         cmp.eq  p6, p0 = tmp, r0
  60 (p6)    br.cond.sptk    .str_aligned;;
  61         adds    loopcnt = -1, loopcnt;;
  62         mov     ar.lc = loopcnt
  63 .l1:
  64         ld1     val2 = [str], 1
  65         ;;
  66         cmp.eq  p6, p0 = val2, r0
  67 (p6)    br.cond.spnt    .restore_and_exit
  68         adds    len = 1, len
  69         br.cloop.dptk   .l1
  70 .str_aligned:
  71         mov     origadd = str           // origadd = orig
  72         ld8     val1 = [str], 8;;
  73         nop.b   0
  74         nop.b   0
  75 .l2:    ld8.s   val2 = [str], 8         // don't bomb out here
  76         czx1.r  pos0 = val1
  77         ;;
  78         cmp.ne  p6, p0 = 8, pos0
  79 (p6)    br.cond.spnt .foundit
  80         chk.s   val2, .recovery
  81 .back:
  82         mov     val1 = val2
  83         br.cond.dptk    .l2
  84 .foundit:
  85         sub     tmp = str, origadd      // tmp = crt address - orig
  86         add     len = len, pos0;;
  87         add     len = len, tmp;;
  88         adds    len = -16, len
  89 .restore_and_exit:
  90         mov ar.lc = saved_lc            // restore the loop counter
  91         br.ret.sptk.many b0
  92 .recovery:
  93         adds    str = -8, str;;
  94         ld8     val2 = [str], 8         // bomb out here
  95         br.cond.sptk    .back
  96 END(strlen)
  97 libc_hidden_builtin_def (strlen)