sysdeps/alpha/alphaev67/strlen.S

   1 /* Copyright (C) 2000-2017 Free Software Foundation, Inc.
   2    Contributed by David Mosberger (davidm@cs.arizona.edu).
   3    EV67 optimized by Rick Gorton <rick.gorton@alpha-processor.com>.
   4    This file is part of the GNU C Library.
   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 /* Finds length of a 0-terminated string.  */
  21
  22 #include <sysdep.h>
  23
  24         .arch ev6
  25         .set noreorder
  26         .set noat
  27
  28 ENTRY(strlen)
  29 #ifdef PROF
  30         ldgp    gp, 0(pv)
  31         lda     AT, _mcount
  32         jsr     AT, (AT), _mcount
  33         .prologue 1
  34 #else
  35         .prologue 0
  36 #endif
  37
  38         ldq_u   $1, 0($16)      # L : load first quadword ($16 may be misaligned)
  39         lda     $2, -1($31)     # E :
  40         insqh   $2, $16, $2     # U :
  41         andnot  $16, 7, $0      # E :
  42
  43         or      $2, $1, $1      # E :
  44         cmpbge  $31, $1, $2     # E : $2  <- bitmask: bit i == 1 <==> i-th byte == 0
  45         nop                     # E :
  46         bne     $2, $found      # U :
  47
  48 $loop:  ldq     $1, 8($0)       # L :
  49         addq    $0, 8, $0       # E : addr += 8
  50         cmpbge  $31, $1, $2     # E :
  51         beq     $2, $loop       # U :
  52
  53 $found:
  54         cttz    $2, $3          # U0 :
  55         addq    $0, $3, $0      # E :
  56         subq    $0, $16, $0     # E :
  57         ret     $31, ($26)      # L0 :
  58
  59         END(strlen)
  60 libc_hidden_builtin_def (strlen)