From 2cdafcbbe0ec40481d8a5abb4b2f3eb1072db03a Mon Sep 17 00:00:00 2001
From: Alan Cox <alc@FreeBSD.org>
Date: Sat, 3 Apr 2004 05:33:10 +0000
Subject: [PATCH] Microoptimize pagezero() based upon something that I learned
 writing the optimized pagecopy().  This also has the virtual of making these
 two functions more similar in style.

---
 sys/amd64/amd64/support.S | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/sys/amd64/amd64/support.S b/sys/amd64/amd64/support.S
index 633f7b1c052..7fcb4b9d07f 100644
--- a/sys/amd64/amd64/support.S
+++ b/sys/amd64/amd64/support.S
@@ -76,15 +76,15 @@ ENTRY(bzero)
 
 /* Address: %rdi */
 ENTRY(pagezero)
-	lea	4096(%rdi),%rsi
+	movq	$-PAGE_SIZE,%rdx
+	subq	%rdx,%rdi
 	xorq	%rax,%rax
 1:
-	movnti	%rax,(%rdi)
-	movnti	%rax,8(%rdi)
-	movnti	%rax,16(%rdi)
-	movnti	%rax,24(%rdi)
-	addq	$32,%rdi
-	cmpq	%rsi,%rdi
+	movnti	%rax,(%rdi,%rdx)
+	movnti	%rax,8(%rdi,%rdx)
+	movnti	%rax,16(%rdi,%rdx)
+	movnti	%rax,24(%rdi,%rdx)
+	addq	$32,%rdx
 	jne	1b
 	sfence
 	retq