[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 (file)
--- 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 @@ ENTRY(stub_rt_sigreturn)
        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 @@ ENTRY(common_interrupt)
 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 @@ retint_signal:
        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 @@ child_rip:
        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 (file)
--- a/arch/x86_64/kernel/head.S
+++ b/arch/x86_64/kernel/head.S
@@ -137,14 +137,14 @@ startup_64:
        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