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Commit 48b5259c authored by Linus Torvalds's avatar Linus Torvalds
Browse files

Merge branch 'x86-asm-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 

Pull x86 asm updates from Ingo Molnar:
 "A single commit micro-optimizing short user copies on certain Intel
  CPUs"

* 'x86-asm-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/uaccess: Optimize copy_user_enhanced_fast_string() for short strings
parents 2a275382 236222d3

arch/x86/lib/copy_user_64.S

+5 −2
Original line number Diff line number Diff line
@@ -37,7 +37,7 @@ ENTRY(copy_user_generic_unrolled) 
	movl %edx,%ecx

	andl $63,%edx

	shrl $6,%ecx

	jz 17f

	jz .L_copy_short_string

1:	movq (%rsi),%r8

2:	movq 1*8(%rsi),%r9

3:	movq 2*8(%rsi),%r10
@@ -58,7 +58,8 @@ ENTRY(copy_user_generic_unrolled) 
	leaq 64(%rdi),%rdi

	decl %ecx

	jnz 1b

17:	movl %edx,%ecx

.L_copy_short_string:

	movl %edx,%ecx

	andl $7,%edx

	shrl $3,%ecx

	jz 20f
@@ -174,6 +175,8 @@ EXPORT_SYMBOL(copy_user_generic_string) 
 */

ENTRY(copy_user_enhanced_fast_string)

	ASM_STAC

	cmpl $64,%edx

	jb .L_copy_short_string	/* less then 64 bytes, avoid the costly 'rep' */

	movl %edx,%ecx

1:	rep

	movsb