ports/sysdeps/powerpc/powerpc32/405/strlen.S

   1 /* Optimized strlen implementation for PowerPC476.
   2    Copyright (C) 2010-2013 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library.  If not, see
  17    <http://www.gnu.org/licenses/>.  */
  18
  19 #include <sysdep.h>
  20 #include <bp-sym.h>
  21 #include <bp-asm.h>
  22
  23 /* strlen
  24
  25        Register Use
  26        r3:source address and return length of string
  27        r4:byte counter
  28
  29        Implementation description
  30        Load 2 words at a time and count bytes, if we find null we subtract one from
  31        the count and return the count value. We need to subtract one because
  32        we don't count the null character as a byte. */
  33
  34 EALIGN (BP_SYM (strlen),5,0)
  35        neg     r7,r3
  36        clrlwi. r8,r7,29
  37        addi    r4,0,0
  38        beq     L(byte_count_loop)
  39        mtctr   r8
  40
  41 L(loop):
  42        lbz     r5,0(r3)
  43        cmpi    cr5,r5,0x0
  44        addi    r3,r3,0x1
  45        addi    r4,r4,0x1
  46        beq     cr5,L(end_strlen)
  47        bdnz    L(loop)
  48
  49 L(byte_count_loop):
  50        lwz     r5,0(r3)
  51        lwz     r6,4(r3)
  52        dlmzb.  r12,r5,r6
  53        add     r4,r4,r12
  54        bne     L(end_strlen)
  55        lwz     r5,8(r3)
  56        lwz     r6,12(r3)
  57        dlmzb.  r12,r5,r6
  58        add     r4,r4,r12
  59        bne     L(end_strlen)
  60        lwz     r5,16(r3)
  61        lwz     r6,20(r3)
  62        dlmzb.  r12,r5,r6
  63        add     r4,r4,r12
  64        bne     L(end_strlen)
  65        lwz     r5,24(r3)
  66        lwz     r6,28(r3)
  67        addi    r3,r3,0x20
  68        dlmzb.  r12,r5,r6
  69        add     r4,r4,r12
  70        bne     L(end_strlen)
  71        b       L(byte_count_loop)
  72
  73 L(end_strlen):
  74        addi    r3,r4,-1
  75        blr
  76 END (BP_SYM (strlen))
  77 libc_hidden_builtin_def (strlen)