arch/x86/lib/memset_64.S

   1 /* Copyright 2002 Andi Kleen, SuSE Labs */
   2
   3 #include <linux/linkage.h>
   4 #include <asm/dwarf2.h>
   5
   6 /*
   7  * ISO C memset - set a memory block to a byte value.
   8  *
   9  * rdi   destination
  10  * rsi   value (char)
  11  * rdx   count (bytes)
  12  *
  13  * rax   original destination
  14  */
  15         .section .altinstr_replacement, "ax", @progbits
  16 .Lmemset_c:
  17         movq %rdi,%r9
  18         movl %edx,%r8d
  19         andl $7,%r8d
  20         movl %edx,%ecx
  21         shrl $3,%ecx
  22         /* expand byte value  */
  23         movzbl %sil,%esi
  24         movabs $0x0101010101010101,%rax
  25         mulq %rsi               /* with rax, clobbers rdx */
  26         rep stosq
  27         movl %r8d,%ecx
  28         rep stosb
  29         movq %r9,%rax
  30         ret
  31 .Lmemset_e:
  32         .previous
  33
  34 ENTRY(memset)
  35 ENTRY(__memset)
  36         CFI_STARTPROC
  37         movq %rdi,%r10
  38         movq %rdx,%r11
  39
  40         /* expand byte value  */
  41         movzbl %sil,%ecx
  42         movabs $0x0101010101010101,%rax
  43         mul    %rcx             /* with rax, clobbers rdx */
  44
  45         /* align dst */
  46         movl  %edi,%r9d
  47         andl  $7,%r9d
  48         jnz  .Lbad_alignment
  49         CFI_REMEMBER_STATE
  50 .Lafter_bad_alignment:
  51
  52         movl %r11d,%ecx
  53         shrl $6,%ecx
  54         jz       .Lhandle_tail
  55
  56         .p2align 4
  57 .Lloop_64:
  58         decl   %ecx
  59         movq  %rax,(%rdi)
  60         movq  %rax,8(%rdi)
  61         movq  %rax,16(%rdi)
  62         movq  %rax,24(%rdi)
  63         movq  %rax,32(%rdi)
  64         movq  %rax,40(%rdi)
  65         movq  %rax,48(%rdi)
  66         movq  %rax,56(%rdi)
  67         leaq  64(%rdi),%rdi
  68         jnz    .Lloop_64
  69
  70         /* Handle tail in loops. The loops should be faster than hard
  71            to predict jump tables. */
  72         .p2align 4
  73 .Lhandle_tail:
  74         movl    %r11d,%ecx
  75         andl    $63&(~7),%ecx
  76         jz              .Lhandle_7
  77         shrl    $3,%ecx
  78         .p2align 4
  79 .Lloop_8:
  80         decl   %ecx
  81         movq  %rax,(%rdi)
  82         leaq  8(%rdi),%rdi
  83         jnz    .Lloop_8
  84
  85 .Lhandle_7:
  86         movl    %r11d,%ecx
  87         andl    $7,%ecx
  88         jz      .Lende
  89         .p2align 4
  90 .Lloop_1:
  91         decl    %ecx
  92         movb    %al,(%rdi)
  93         leaq    1(%rdi),%rdi
  94         jnz     .Lloop_1
  95
  96 .Lende:
  97         movq    %r10,%rax
  98         ret
  99
 100         CFI_RESTORE_STATE
 101 .Lbad_alignment:
 102         cmpq $7,%r11
 103         jbe     .Lhandle_7
 104         movq %rax,(%rdi)        /* unaligned store */
 105         movq $8,%r8
 106         subq %r9,%r8
 107         addq %r8,%rdi
 108         subq %r8,%r11
 109         jmp .Lafter_bad_alignment
 110 .Lfinal:
 111         CFI_ENDPROC
 112 ENDPROC(memset)
 113 ENDPROC(__memset)
 114
 115         /* Some CPUs run faster using the string instructions.
 116            It is also a lot simpler. Use this when possible */
 117
 118 #include <asm/cpufeature.h>
 119
 120         .section .altinstructions,"a"
 121         .align 8
 122         .quad memset
 123         .quad .Lmemset_c
 124         .word X86_FEATURE_REP_GOOD
 125         .byte .Lfinal - memset
 126         .byte .Lmemset_e - .Lmemset_c
 127         .previous