linux-kernel - [tip:x86/asm] x86-64: remove unnecessary spill/reload of rbx from memcpy

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Date:	Thu, 12 Mar 2009 11:57:45 GMT
From:	Jan Beulich <jbeulich@...ell.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, hpa@...or.com, mingo@...hat.com,
	jbeulich@...ell.com, tglx@...utronix.de, mingo@...e.hu
Subject: [tip:x86/asm] x86-64: remove unnecessary spill/reload of rbx from memcpy

Commit-ID:  dd1ef4ec4721ddc0a1f2b73a4f67930cb320665c
Gitweb:     http://git.kernel.org/tip/dd1ef4ec4721ddc0a1f2b73a4f67930cb320665c
Author:     "Jan Beulich" <jbeulich@...ell.com>
AuthorDate: Thu, 12 Mar 2009 10:47:13 +0000
Commit:     Ingo Molnar <mingo@...e.hu>
CommitDate: Thu, 12 Mar 2009 12:04:47 +0100

x86-64: remove unnecessary spill/reload of rbx from memcpy

Impact: micro-optimization

This should slightly improve its performance.

Signed-off-by: Jan Beulich <jbeulich@...ell.com>
LKML-Reference: <49B8F641.76E4.0078.0@...ell.com>
Signed-off-by: Ingo Molnar <mingo@...e.hu>


---
 arch/x86/lib/memcpy_64.S |    7 -------
 1 files changed, 0 insertions(+), 7 deletions(-)

diff --git a/arch/x86/lib/memcpy_64.S b/arch/x86/lib/memcpy_64.S
index c22981f..10c0676 100644
--- a/arch/x86/lib/memcpy_64.S
+++ b/arch/x86/lib/memcpy_64.S
@@ -33,9 +33,6 @@ ENDPROC(memcpy_c)
 ENTRY(__memcpy)
 ENTRY(memcpy)
 	CFI_STARTPROC
-	pushq %rbx
-	CFI_ADJUST_CFA_OFFSET 8
-	CFI_REL_OFFSET rbx, 0
 	movq %rdi,%rax
 
 	movl %edx,%ecx
@@ -102,11 +99,7 @@ ENTRY(memcpy)
 	jnz .Lloop_1
 
 .Lende:
-	popq %rbx
-	CFI_ADJUST_CFA_OFFSET -8
-	CFI_RESTORE rbx
 	ret
-.Lfinal:
 	CFI_ENDPROC
 ENDPROC(memcpy)
 ENDPROC(__memcpy)
--
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