[PATCH] x86_64: Small assembly improvements
Save a byte here and there. Ultimatively useless, but these things always
catch my eyes when reading the code so just fix them for now.
Also I got at least one patch fixing of them already, which gives a good
excuse.
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/arch/x86_64/kernel/entry.S b/arch/x86_64/kernel/entry.S
index 2881749..0696e02 100644
--- a/arch/x86_64/kernel/entry.S
+++ b/arch/x86_64/kernel/entry.S
@@ -76,7 +76,7 @@
.macro FAKE_STACK_FRAME child_rip
/* push in order ss, rsp, eflags, cs, rip */
- xorq %rax, %rax
+ xorl %eax, %eax
pushq %rax /* ss */
CFI_ADJUST_CFA_OFFSET 8
pushq %rax /* rsp */
@@ -423,7 +423,7 @@
testl $3,CS(%rdi)
je 1f
swapgs
-1: addl $1,%gs:pda_irqcount # RED-PEN should check preempt count
+1: incl %gs:pda_irqcount # RED-PEN should check preempt count
movq %gs:pda_irqstackptr,%rax
cmoveq %rax,%rsp
pushq %rdi # save old stack
@@ -436,7 +436,7 @@
ret_from_intr:
popq %rdi
cli
- subl $1,%gs:pda_irqcount
+ decl %gs:pda_irqcount
#ifdef CONFIG_DEBUG_INFO
movq RBP(%rdi),%rbp
#endif
@@ -494,7 +494,7 @@
sti
SAVE_REST
movq $-1,ORIG_RAX(%rsp)
- xorq %rsi,%rsi # oldset
+ xorl %esi,%esi # oldset
movq %rsp,%rdi # &pt_regs
call do_notify_resume
RESTORE_REST
@@ -752,7 +752,7 @@
movq %rsi, %rdi
call *%rax
# exit
- xorq %rdi, %rdi
+ xorl %edi, %edi
call do_exit
/*
diff --git a/arch/x86_64/kernel/head.S b/arch/x86_64/kernel/head.S
index 8d765aa..98ff5eb 100644
--- a/arch/x86_64/kernel/head.S
+++ b/arch/x86_64/kernel/head.S
@@ -137,14 +137,14 @@
wrmsr
/* Setup cr0 */
- xorq %rax, %rax
- btsq $31, %rax /* Enable paging */
- btsq $0, %rax /* Enable protected mode */
- btsq $1, %rax /* Enable MP */
- btsq $4, %rax /* Enable ET */
- btsq $5, %rax /* Enable NE */
- btsq $16, %rax /* Enable WP */
- btsq $18, %rax /* Enable AM */
+#define CR0_PM 1 /* protected mode */
+#define CR0_MP (1<<1)
+#define CR0_ET (1<<4)
+#define CR0_NE (1<<5)
+#define CR0_WP (1<<16)
+#define CR0_AM (1<<18)
+#define CR0_PAGING (1<<31)
+ movl $CR0_PM|CR0_MP|CR0_ET|CR0_NE|CR0_WP|CR0_AM|CR0_PAGING,%eax
/* Make changes effective */
movq %rax, %cr0
