From 057e05c1d6440117875f455e59da8691e08f65d5 Mon Sep 17 00:00:00 2001 From: Fenghua Yu Date: Tue, 17 May 2011 15:29:17 -0700 Subject: [PATCH] x86, mem: memmove_64.S: Optimize memmove by enhanced REP MOVSB/STOSB Support memmove() by enhanced rep movsb. On processors supporting enhanced REP MOVSB/STOSB, the alternative memmove() function using enhanced rep movsb overrides the original function. The patch doesn't change the backward memmove case to use enhanced rep movsb. Signed-off-by: Fenghua Yu Link: http://lkml.kernel.org/r/1305671358-14478-9-git-send-email-fenghua.yu@intel.com Signed-off-by: H. Peter Anvin --- arch/x86/lib/memmove_64.S | 29 ++++++++++++++++++++++++++++- 1 file changed, 28 insertions(+), 1 deletion(-) diff --git a/arch/x86/lib/memmove_64.S b/arch/x86/lib/memmove_64.S index 0ecb8433e5a8..d0ec9c2936d7 100644 --- a/arch/x86/lib/memmove_64.S +++ b/arch/x86/lib/memmove_64.S @@ -8,6 +8,7 @@ #define _STRING_C #include #include +#include #undef memmove @@ -24,6 +25,7 @@ */ ENTRY(memmove) CFI_STARTPROC + /* Handle more 32bytes in loop */ mov %rdi, %rax cmp $0x20, %rdx @@ -31,8 +33,13 @@ ENTRY(memmove) /* Decide forward/backward copy mode */ cmp %rdi, %rsi - jb 2f + jge .Lmemmove_begin_forward + mov %rsi, %r8 + add %rdx, %r8 + cmp %rdi, %r8 + jg 2f +.Lmemmove_begin_forward: /* * movsq instruction have many startup latency * so we handle small size by general register. @@ -78,6 +85,8 @@ ENTRY(memmove) rep movsq movq %r11, (%r10) jmp 13f +.Lmemmove_end_forward: + /* * Handle data backward by movsq. */ @@ -194,4 +203,22 @@ ENTRY(memmove) 13: retq CFI_ENDPROC + + .section .altinstr_replacement,"ax" +.Lmemmove_begin_forward_efs: + /* Forward moving data. */ + movq %rdx, %rcx + rep movsb + retq +.Lmemmove_end_forward_efs: + .previous + + .section .altinstructions,"a" + .align 8 + .quad .Lmemmove_begin_forward + .quad .Lmemmove_begin_forward_efs + .word X86_FEATURE_ERMS + .byte .Lmemmove_end_forward-.Lmemmove_begin_forward + .byte .Lmemmove_end_forward_efs-.Lmemmove_begin_forward_efs + .previous ENDPROC(memmove)