1 files changed, 94 insertions, 0 deletions

diff --git a/arch/x86_64/lib/memset.S b/arch/x86_64/lib/memset.S
index 2aa48f24ed1e..ad397f2c7de8 100644
--- a/arch/x86_64/lib/memset.S
+++ b/arch/x86_64/lib/memset.S
@@ -13,6 +13,98 @@
         .p2align 4
 memset: 
 __memset:
+        movq %rdi,%r10
+        movq %rdx,%r11
+
+        /* expand byte value  */
+        movzbl %sil,%ecx
+        movabs $0x0101010101010101,%rax
+        mul    %rcx             /* with rax, clobbers rdx */
+
+        /* align dst */
+        movl  %edi,%r9d
+        andl  $7,%r9d
+        jnz  .Lbad_alignment
+.Lafter_bad_alignment:
+
+        movl %r11d,%ecx
+        shrl $6,%ecx
+        jz       .Lhandle_tail
+
+        .p2align 4
+.Lloop_64:
+        decl   %ecx
+        movq  %rax,(%rdi)
+        movq  %rax,8(%rdi)
+        movq  %rax,16(%rdi)
+        movq  %rax,24(%rdi)
+        movq  %rax,32(%rdi)
+        movq  %rax,40(%rdi)
+        movq  %rax,48(%rdi)
+        movq  %rax,56(%rdi)
+        leaq  64(%rdi),%rdi
+        jnz    .Lloop_64
+
+        /* Handle tail in loops. The loops should be faster than hard
+           to predict jump tables. */
+        .p2align 4
+.Lhandle_tail:
+        movl    %r11d,%ecx
+        andl    $63&(~7),%ecx
+        jz              .Lhandle_7
+        shrl    $3,%ecx
+        .p2align 4
+.Lloop_8:
+        decl   %ecx
+        movq  %rax,(%rdi)
+        leaq  8(%rdi),%rdi
+        jnz    .Lloop_8
+
+.Lhandle_7:
+        movl    %r11d,%ecx
+        andl    $7,%ecx
+        jz      .Lende
+        .p2align 4
+.Lloop_1:
+        decl    %ecx
+        movb    %al,(%rdi)
+        leaq    1(%rdi),%rdi
+        jnz     .Lloop_1
+
+.Lende:
+        movq    %r10,%rax
+        ret
+
+.Lbad_alignment:
+        cmpq $7,%r11
+        jbe     .Lhandle_7
+        movq %rax,(%rdi)        /* unaligned store */
+        movq $8,%r8
+        subq %r9,%r8
+        addq %r8,%rdi
+        subq %r8,%r11
+        jmp .Lafter_bad_alignment
+
+        /* Some CPUs run faster using the string instructions.
+           It is also a lot simpler. Use this when possible */
+
+#include <asm/cpufeature.h>
+
+        .section .altinstructions,"a"
+        .align 8
+        .quad  memset
+        .quad  memset_c
+        .byte  X86_FEATURE_REP_GOOD
+        .byte  memset_c_end-memset_c
+        .byte  memset_c_end-memset_c
+        .previous
+
+        .section .altinstr_replacement,"ax"
+ /* rdi destination
+  * rsi value
+  * rdx count
+  */
+memset_c:
         movq %rdi,%r9
         movl %edx,%r8d
         andl $7,%r8d            
@@ -29,3 +121,5 @@ __memset:
         stosb
         movq %r9,%rax
         ret
+memset_c_end:
+        .previous