page_clear.s

来自「优龙2410linux2.6.8内核源代码」· S 代码 · 共 52 行

/*
   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.

*/

	.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
	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