patch-2.4.22 linux-2.4.22/arch/sh64/lib/page_clear.S

• Lines: 47
• Date: 2003-08-25 04:44:40.000000000 -0700
• Orig file: linux-2.4.21/arch/sh64/lib/page_clear.S
• Orig date: 1969-12-31 16:00:00.000000000 -0800

diff -urN linux-2.4.21/arch/sh64/lib/page_clear.S linux-2.4.22/arch/sh64/lib/page_clear.S
@@ -0,0 +1,46 @@
+/* Written by Richard P. Curnow, SuperH (UK) Ltd.
+
+   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
+
+