[PATCH] x86-64: improve cmpxchg16b_emu.S

[PATCH] x86-64: improve cmpxchg16b_emu.S

[Jan Beulich]

- don't include unneeded headers
- don't open-code PER_CPU_VAR()
- drop redundant entry point label
- complete unwind annotations
- use .L prefix on local label to not clutter the symbol table

Signed-off-by: Jan Beulich <jbeulich@suse.com>
---
 arch/x86/lib/cmpxchg16b_emu.S |   32 +++++++++++++-------------------
 1 file changed, 13 insertions(+), 19 deletions(-)

--- 3.17-rc6/arch/x86/lib/cmpxchg16b_emu.S
+++ 3.17-rc6-x86_64-improve-cmpxchg16b_emu/arch/x86/lib/cmpxchg16b_emu.S
@@ -6,15 +6,8 @@
  *
  */
 #include <linux/linkage.h>
-#include <asm/alternative-asm.h>
-#include <asm/frame.h>
 #include <asm/dwarf2.h>
-
-#ifdef CONFIG_SMP
-#define SEG_PREFIX %gs:
-#else
-#define SEG_PREFIX
-#endif
+#include <asm/percpu.h>
 
 .text
 
@@ -39,24 +32,25 @@ CFI_STARTPROC
 # *atomic* on a single cpu (as provided by the this_cpu_xx class of
 # macros).
 #
-this_cpu_cmpxchg16b_emu:
-	pushf
+	pushfq_cfi
 	cli
 
-	cmpq SEG_PREFIX(%rsi), %rax
-	jne not_same
-	cmpq SEG_PREFIX 8(%rsi), %rdx
-	jne not_same
+	cmpq PER_CPU_VAR((%rsi)), %rax
+	jne .Lnot_same
+	cmpq PER_CPU_VAR(8(%rsi)), %rdx
+	jne .Lnot_same
 
-	movq %rbx, SEG_PREFIX(%rsi)
-	movq %rcx, SEG_PREFIX 8(%rsi)
+	movq %rbx, PER_CPU_VAR((%rsi))
+	movq %rcx, PER_CPU_VAR(8(%rsi))
 
-	popf
+	CFI_REMEMBER_STATE
+	popfq_cfi
 	mov $1, %al
 	ret
 
- not_same:
-	popf
+	CFI_RESTORE_STATE
+.Lnot_same:
+	popfq_cfi
 	xor %al,%al
 	ret
 

[tip:x86/asm] x86: Improve cmpxchg16b_emu.S

[tip-bot for Jan Beulich]

Commit-ID:  3f63572187f5ae6a0a9e5ebee88b57e6f71c3cd4
Gitweb:     http://git.kernel.org/tip/3f63572187f5ae6a0a9e5ebee88b57e6f71c3cd4
Author:     Jan Beulich <JBeulich@suse.com>
AuthorDate: Wed, 24 Sep 2014 08:37:00 +0100
Committer:  Thomas Gleixner <tglx@linutronix.de>
CommitDate: Wed, 8 Oct 2014 10:05:49 +0200

x86: Improve cmpxchg16b_emu.S

- don't include unneeded headers
- don't open-code PER_CPU_VAR()
- drop redundant entry point label
- complete unwind annotations
- use .L prefix on local label to not clutter the symbol table

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Link: http://lkml.kernel.org/r/542290BC020000780003807D@mail.emea.novell.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
 arch/x86/lib/cmpxchg16b_emu.S | 32 +++++++++++++-------------------
 1 file changed, 13 insertions(+), 19 deletions(-)

diff --git a/arch/x86/lib/cmpxchg16b_emu.S b/arch/x86/lib/cmpxchg16b_emu.S
index 1e572c5..40a1725 100644
--- a/arch/x86/lib/cmpxchg16b_emu.S
+++ b/arch/x86/lib/cmpxchg16b_emu.S
@@ -6,15 +6,8 @@
  *
  */
 #include <linux/linkage.h>
-#include <asm/alternative-asm.h>
-#include <asm/frame.h>
 #include <asm/dwarf2.h>
-
-#ifdef CONFIG_SMP
-#define SEG_PREFIX %gs:
-#else
-#define SEG_PREFIX
-#endif
+#include <asm/percpu.h>
 
 .text
 
@@ -39,24 +32,25 @@ CFI_STARTPROC
 # *atomic* on a single cpu (as provided by the this_cpu_xx class of
 # macros).
 #
-this_cpu_cmpxchg16b_emu:
-	pushf
+	pushfq_cfi
 	cli
 
-	cmpq SEG_PREFIX(%rsi), %rax
-	jne not_same
-	cmpq SEG_PREFIX 8(%rsi), %rdx
-	jne not_same
+	cmpq PER_CPU_VAR((%rsi)), %rax
+	jne .Lnot_same
+	cmpq PER_CPU_VAR(8(%rsi)), %rdx
+	jne .Lnot_same
 
-	movq %rbx, SEG_PREFIX(%rsi)
-	movq %rcx, SEG_PREFIX 8(%rsi)
+	movq %rbx, PER_CPU_VAR((%rsi))
+	movq %rcx, PER_CPU_VAR(8(%rsi))
 
-	popf
+	CFI_REMEMBER_STATE
+	popfq_cfi
 	mov $1, %al
 	ret
 
- not_same:
-	popf
+	CFI_RESTORE_STATE
+.Lnot_same:
+	popfq_cfi
 	xor %al,%al
 	ret