sysdeps/alpha/stpncpy.S

   1 /* Copyright (C) 1996-2021 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3    Contributed by Richard Henderson (rth@tamu.edu)
   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    <https://www.gnu.org/licenses/>.  */
  18
  19 /* Copy no more than COUNT bytes of the null-terminated string from
  20    SRC to DST.  If SRC does not cover all of COUNT, the balance is
  21    zeroed.  Return the address of the terminating null in DEST, if
  22    any, else DEST + COUNT.  */
  23
  24 #include <sysdep.h>
  25
  26         .set noat
  27         .set noreorder
  28
  29         .text
  30
  31 ENTRY(__stpncpy)
  32         ldgp    gp, 0(pv)
  33 #ifdef PROF
  34         lda     AT, _mcount
  35         jsr     AT, (AT), _mcount
  36 #endif
  37         .prologue 1
  38
  39         beq     a2, $zerocount
  40         jsr     t9, __stxncpy   # do the work of the copy
  41
  42         and     t8, 0xf0, t3    # binary search for byte offset of the
  43         and     t8, 0xcc, t2    # last byte written.
  44         and     t8, 0xaa, t1
  45         andnot  a0, 7, v0
  46         cmovne  t3, 4, t3
  47         cmovne  t2, 2, t2
  48         cmovne  t1, 1, t1
  49         addq    v0, t3, v0
  50         addq    t1, t2, t1
  51         addq    v0, t1, v0
  52
  53         bne     a2, $multiword  # do we have full words left?
  54
  55         .align 3
  56         zapnot  t0, t8, t4      # e0    : was last byte a null?
  57         subq    t8, 1, t2       # .. e1 :
  58         addq    v0, 1, t5       # e0    :
  59         subq    t10, 1, t3      # .. e1 :
  60         or      t2, t8, t2      # e0    : clear the bits between the last
  61         or      t3, t10, t3     # .. e1 : written byte and the last byte in
  62         andnot  t3, t2, t3      # e0    : COUNT
  63         cmovne  t4, t5, v0      # .. e1 : if last written wasnt null, inc v0
  64         zap     t0, t3, t0      # e0    :
  65         stq_u   t0, 0(a0)       # e1    :
  66         ret                     # .. e1 :
  67
  68         .align 3
  69 $multiword:
  70         subq    t8, 1, t7       # e0    : clear the final bits in the prev
  71         or      t7, t8, t7      # e1    : word
  72         zapnot  t0, t7, t0      # e0    :
  73         subq    a2, 1, a2       # .. e1 :
  74         stq_u   t0, 0(a0)       # e0    :
  75         addq    a0, 8, a0       # .. e1 :
  76
  77         beq     a2, 1f          # e1    :
  78         blbc    a2, 0f          # e1    :
  79
  80         stq_u   zero, 0(a0)     # e0    : zero one word
  81         subq    a2, 1, a2       # .. e1 :
  82         addq    a0, 8, a0       # e0    :
  83         beq     a2, 1f          # .. e1 :
  84
  85 0:      stq_u   zero, 0(a0)     # e0    : zero two words
  86         subq    a2, 2, a2       # .. e1 :
  87         stq_u   zero, 8(a0)     # e0    :
  88         addq    a0, 16, a0      # .. e1 :
  89         bne     a2, 0b          # e1    :
  90         unop
  91
  92 1:      ldq_u   t0, 0(a0)       # e0    : clear the leading bits in the final
  93         subq    t10, 1, t7      # .. e1 : word
  94         or      t7, t10, t7     # e0    :
  95         zap     t0, t7, t0      # e1 (stall)
  96         stq_u   t0, 0(a0)       # e0    :
  97         ret                     # .. e1 :
  98
  99 $zerocount:
 100         mov     a0, v0
 101         ret
 102
 103         END(__stpncpy)
 104
 105 libc_hidden_def (__stpncpy)
 106 weak_alias (__stpncpy, stpncpy)