linux/arch/sh64/lib/page_clear.S
Linus Torvalds 1da177e4c3 Linux-2.6.12-rc2
Initial git repository build. I'm not bothering with the full history,
even though we have it. We can create a separate "historical" git
archive of that later if we want to, and in the meantime it's about
3.2GB when imported into git - space that would just make the early
git days unnecessarily complicated, when we don't have a lot of good
infrastructure for it.

Let it rip!
2005-04-16 15:20:36 -07:00

54 lines
1.2 KiB
ArmAsm

/*
Copyright 2003 Richard Curnow, SuperH (UK) Ltd.
This file is subject to the terms and conditions of the GNU General Public
License. See the file "COPYING" in the main directory of this archive
for more details.
Tight version of memset for the case of just clearing a page. It turns out
that having the alloco's spaced out slightly due to the increment/branch
pair causes them to contend less for access to the cache. Similarly,
keeping the stores apart from the allocos causes less contention. => Do two
separate loops. Do multiple stores per loop to amortise the
increment/branch cost a little.
Parameters:
r2 : source effective address (start of page)
Always clears 4096 bytes.
Note : alloco guarded by synco to avoid TAKum03020 erratum
*/
.section .text..SHmedia32,"ax"
.little
.balign 8
.global sh64_page_clear
sh64_page_clear:
pta/l 1f, tr1
pta/l 2f, tr2
ptabs/l r18, tr0
movi 4096, r7
add r2, r7, r7
add r2, r63, r6
1:
alloco r6, 0
synco ! TAKum03020
addi r6, 32, r6
bgt/l r7, r6, tr1
add r2, r63, r6
2:
st.q r6, 0, r63
st.q r6, 8, r63
st.q r6, 16, r63
st.q r6, 24, r63
addi r6, 32, r6
bgt/l r7, r6, tr2
blink tr0, r63