reactos/lib/rtl/amd64/rtlmem.S

   1 /*
   2  * COPYRIGHT:         See COPYING in the top level directory
   3  * PROJECT:           ReactOS Run-Time Library
   4  * PURPOSE:           Memory functions for amd64
   5  * FILE:              lib/rtl/i386/rtlswap.S
   6  * PROGRAMER:         Timo Kreuzer (timo.kreuzer@reactos.org)
   7  */
   8
   9 /* INCLUDES ******************************************************************/
  10
  11 #include <ndk/amd64/asmmacro.S>
  12
  13 /* FUNCTIONS *****************************************************************/
  14 .intel_syntax noprefix
  15
  16 /* SIZE_T
  17  * RtlCompareMemory(
  18  *   IN CONST VOID *Source1, <rcx>
  19  *   IN CONST VOID *Source2, <rdx>
  20  *   IN SIZE_T  Length <r8>
  21  * );
  22  */
  23 .proc RtlCompareMemory
  24
  25     /* Save registers */
  26     push rsi
  27     .pushreg rsi
  28     push rdi
  29     .pushreg rdi
  30
  31     /* Setup registers for compare */
  32     mov rsi, rcx
  33     mov rdi, rdx
  34
  35     /* Clear direction flag */
  36     cli
  37
  38     /* Get number of qwords */
  39     mov rcx, r8
  40     shr rcx, 3
  41     jz 2f
  42
  43     /* Compare qwords */
  44     repe cmpsq
  45     jnz 4f
  46
  47 2:  /* Compare rest */
  48     mov rcx, r8
  49     and rcx, 7
  50     jz 3f
  51
  52     repe cmpsb
  53     jnz 5f
  54
  55 3:  /* All equal */
  56     /* Return the full count */
  57     mov rax, rcx
  58     jmp 6f
  59
  60 4:  /* Not equal after comparing qwords */
  61     /* Compare the last qword */
  62     sub rsi, 8
  63     sub rdi, 8
  64     mov rcx, 8
  65     repe cmpsb
  66
  67 5:  /* Not equal after comparing bytes */
  68     /* Return difference */
  69     sub rdi, rdx
  70     dec rdi
  71     mov rax, rdi
  72
  73 6:  /* Cleanup and return */
  74     pop rdi
  75     pop rsi
  76     ret
  77 .endproc
  78