Commit-ID: 1153933703d927b3d4874c0bc801de32b1b58be9 Gitweb: https://git.kernel.org/tip/1153933703d927b3d4874c0bc801de32b1b58be9 Author: Alexey Dobriyan <[email protected]> AuthorDate: Tue, 8 May 2018 00:39:37 +0300 Committer: Ingo Molnar <[email protected]> CommitDate: Mon, 14 May 2018 11:38:51 +0200
x86/asm/64: Micro-optimize __clear_user() - Use immediate constants Save two registers. Adding constants should be just as fast as adding registers. Signed-off-by: Alexey Dobriyan <[email protected]> Cc: Linus Torvalds <[email protected]> Cc: Peter Zijlstra <[email protected]> Cc: Thomas Gleixner <[email protected]> Link: http://lkml.kernel.org/r/20180507213937.GB32406@avx2 Signed-off-by: Ingo Molnar <[email protected]> --- arch/x86/lib/usercopy_64.c | 9 ++++----- 1 file changed, 4 insertions(+), 5 deletions(-) diff --git a/arch/x86/lib/usercopy_64.c b/arch/x86/lib/usercopy_64.c index 75d3776123cc..a624dcc4de10 100644 --- a/arch/x86/lib/usercopy_64.c +++ b/arch/x86/lib/usercopy_64.c @@ -23,13 +23,13 @@ unsigned long __clear_user(void __user *addr, unsigned long size) asm volatile( " testq %[size8],%[size8]\n" " jz 4f\n" - "0: movq %[zero],(%[dst])\n" - " addq %[eight],%[dst]\n" + "0: movq $0,(%[dst])\n" + " addq $8,%[dst]\n" " decl %%ecx ; jnz 0b\n" "4: movq %[size1],%%rcx\n" " testl %%ecx,%%ecx\n" " jz 2f\n" - "1: movb %b[zero],(%[dst])\n" + "1: movb $0,(%[dst])\n" " incq %[dst]\n" " decl %%ecx ; jnz 1b\n" "2:\n" @@ -40,8 +40,7 @@ unsigned long __clear_user(void __user *addr, unsigned long size) _ASM_EXTABLE(0b,3b) _ASM_EXTABLE(1b,2b) : [size8] "=&c"(size), [dst] "=&D" (__d0) - : [size1] "r"(size & 7), "[size8]" (size / 8), "[dst]"(addr), - [zero] "r" (0UL), [eight] "r" (8UL)); + : [size1] "r"(size & 7), "[size8]" (size / 8), "[dst]"(addr)); clac(); return size; }
