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Subject[tip:x86/asm] x86: Optimize loadsegment()
Commit-ID:  79b0379cee09b00ef309384aff652e328e438c79
Gitweb: http://git.kernel.org/tip/79b0379cee09b00ef309384aff652e328e438c79
Author: Brian Gerst <brgerst@gmail.com>
AuthorDate: Wed, 25 Nov 2009 14:18:26 -0500
Committer: Ingo Molnar <mingo@elte.hu>
CommitDate: Thu, 26 Nov 2009 10:33:58 +0100

x86: Optimize loadsegment()

Zero the input register in the exception handler instead of
using an extra register to pass in a zero value.

Signed-off-by: Brian Gerst <brgerst@gmail.com>
LKML-Reference: <1259176706-5908-1-git-send-email-brgerst@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
---
arch/x86/include/asm/system.h | 15 ++++++++-------
1 files changed, 8 insertions(+), 7 deletions(-)

diff --git a/arch/x86/include/asm/system.h b/arch/x86/include/asm/system.h
index 1a953e2..537395a 100644
--- a/arch/x86/include/asm/system.h
+++ b/arch/x86/include/asm/system.h
@@ -156,18 +156,19 @@ extern void native_load_gs_index(unsigned);
* segment if something goes wrong..
*/
#define loadsegment(seg, value) \
+do { \
+ unsigned short __val = value; \
asm volatile("\n" \
"1:\t" \
"movl %k0,%%" #seg "\n" \
- "2:\n" \
".section .fixup,\"ax\"\n" \
- "3:\t" \
- "movl %k1, %%" #seg "\n\t" \
- "jmp 2b\n" \
+ "2:\t" \
+ "xorl %k0,%k0\n\t" \
+ "jmp 1b\n" \
".previous\n" \
- _ASM_EXTABLE(1b,3b) \
- : :"r" (value), "r" (0) : "memory")
-
+ _ASM_EXTABLE(1b, 2b) \
+ : "+r" (__val) : : "memory"); \
+} while (0)

/*
* Save a segment register away

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