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

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Date:	Thu, 12 Mar 2009 10:47:13 +0000
From:	"Jan Beulich" <jbeulich@...ell.com>
To:	<mingo@...e.hu>, <tglx@...utronix.de>, <hpa@...or.com>
Cc:	<linux-kernel@...r.kernel.org>
Subject: [PATCH] x86-64: remove unnecessary spill/reload of rbx from
	 memcpy

This should slightly improve its performance.

Signed-off-by: Jan Beulich <jbeulich@...ell.com>

---
 arch/x86/lib/memcpy_64.S |    7 -------
 1 file changed, 7 deletions(-)

--- linux-2.6.29-rc7/arch/x86/lib/memcpy_64.S	2008-01-24 23:58:37.000000000 +0100
+++ 2.6.29-rc7-x86_64-memcpy-rbx/arch/x86/lib/memcpy_64.S	2008-12-18 10:58:11.000000000 +0100
@@ -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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