sdk/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/amd64/rtlmem.S
   6  * PROGRAMER:         Timo Kreuzer (timo.kreuzer@reactos.org)
   7  */
   8
   9 /* INCLUDES ******************************************************************/
  10
  11 #include <asm.inc>
  12
  13 /* FUNCTIONS *****************************************************************/
  14
  15 .code64
  16
  17 /* SIZE_T
  18  * RtlCompareMemory(
  19  *   IN CONST VOID *Source1, <rcx>
  20  *   IN CONST VOID *Source2, <rdx>
  21  *   IN SIZE_T  Length <r8>
  22  * );
  23  */
  24 .proc RtlCompareMemory
  25
  26     /* Save registers */
  27     push rsi
  28     .pushreg rsi
  29     push rdi
  30     .pushreg rdi
  31     .ENDPROLOG
  32
  33     /* Setup registers for compare */
  34     mov rsi, rcx
  35     mov rdi, rdx
  36
  37     /* Clear direction flag */
  38     cli
  39
  40     /* Get number of qwords */
  41     mov rcx, r8
  42     shr rcx, 3
  43     jz RtlCompareMemory2
  44
  45     /* Compare qwords */
  46     repe cmpsq
  47     jnz RtlCompareMemory4
  48
  49 RtlCompareMemory2:
  50     /* Compare rest */
  51     mov rcx, r8
  52     and rcx, 7
  53     jz RtlCompareMemory3
  54
  55     repe cmpsb
  56     jnz RtlCompareMemory5
  57
  58 RtlCompareMemory3:
  59     /* All equal */
  60     /* Return the full count */
  61     mov rax, rcx
  62     jmp RtlCompareMemory6
  63
  64 RtlCompareMemory4:
  65     /* Not equal after comparing qwords */
  66     /* Compare the last qword */
  67     sub rsi, 8
  68     sub rdi, 8
  69     mov rcx, 8
  70     repe cmpsb
  71
  72 RtlCompareMemory5:
  73     /* Not equal after comparing bytes */
  74     /* Return difference */
  75     sub rdi, rdx
  76     dec rdi
  77     mov rax, rdi
  78
  79 RtlCompareMemory6:
  80    /* Cleanup and return */
  81     pop rdi
  82     pop rsi
  83     ret
  84 .endp
  85
  86 END
  87