arch/sh64/lib/page_clear.S

   1 /*
   2    Copyright 2003 Richard Curnow, SuperH (UK) Ltd.
   3
   4    This file is subject to the terms and conditions of the GNU General Public
   5    License.  See the file "COPYING" in the main directory of this archive
   6    for more details.
   7
   8    Tight version of memset for the case of just clearing a page.  It turns out
   9    that having the alloco's spaced out slightly due to the increment/branch
  10    pair causes them to contend less for access to the cache.  Similarly,
  11    keeping the stores apart from the allocos causes less contention.  => Do two
  12    separate loops.  Do multiple stores per loop to amortise the
  13    increment/branch cost a little.
  14
  15    Parameters:
  16    r2 : source effective address (start of page)
  17
  18    Always clears 4096 bytes.
  19
  20    Note : alloco guarded by synco to avoid TAKum03020 erratum
  21
  22 */
  23
  24         .section .text..SHmedia32,"ax"
  25         .little
  26
  27         .balign 8
  28         .global sh64_page_clear
  29 sh64_page_clear:
  30         pta/l 1f, tr1
  31         pta/l 2f, tr2
  32         ptabs/l r18, tr0
  33
  34         movi 4096, r7
  35         add  r2, r7, r7
  36         add  r2, r63, r6
  37 1:
  38         alloco r6, 0
  39         synco   ! TAKum03020
  40         addi    r6, 32, r6
  41         bgt/l   r7, r6, tr1
  42
  43         add  r2, r63, r6
  44 2:
  45         st.q  r6,   0, r63
  46         st.q  r6,   8, r63
  47         st.q  r6,  16, r63
  48         st.q  r6,  24, r63
  49         addi r6, 32, r6
  50         bgt/l r7, r6, tr2
  51
  52         blink tr0, r63
  53
  54