MdePkg/Library/BaseMemoryLibOptPei/X64/IsZeroBuffer.nasm

   1 ;------------------------------------------------------------------------------
   2 ;
   3 ; Copyright (c) 2016, Intel Corporation. All rights reserved.<BR>
   4 ; This program and the accompanying materials
   5 ; are licensed and made available under the terms and conditions of the BSD License
   6 ; which accompanies this distribution.  The full text of the license may be found at
   7 ; http://opensource.org/licenses/bsd-license.php.
   8 ;
   9 ; THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
  10 ; WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
  11 ;
  12 ; Module Name:
  13 ;
  14 ;   IsZeroBuffer.nasm
  15 ;
  16 ; Abstract:
  17 ;
  18 ;   IsZeroBuffer function
  19 ;
  20 ; Notes:
  21 ;
  22 ;------------------------------------------------------------------------------
  23
  24     DEFAULT REL
  25     SECTION .text
  26
  27 ;------------------------------------------------------------------------------
  28 ;  BOOLEAN
  29 ;  EFIAPI
  30 ;  InternalMemIsZeroBuffer (
  31 ;    IN CONST VOID  *Buffer,
  32 ;    IN UINTN       Length
  33 ;    );
  34 ;------------------------------------------------------------------------------
  35 global ASM_PFX(InternalMemIsZeroBuffer)
  36 ASM_PFX(InternalMemIsZeroBuffer):
  37     push    rdi
  38     mov     rdi, rcx                   ; rdi <- Buffer
  39     mov     rcx, rdx                   ; rcx <- Length
  40     shr     rcx, 3                     ; rcx <- number of qwords
  41     and     rdx, 7                     ; rdx <- number of trailing bytes
  42     xor     rax, rax                   ; rax <- 0, also set ZF
  43     repe    scasq
  44     jnz     @ReturnFalse               ; ZF=0 means non-zero element found
  45     mov     rcx, rdx
  46     repe    scasb
  47     jnz     @ReturnFalse
  48     pop     rdi
  49     mov     rax, 1                     ; return TRUE
  50     ret
  51 @ReturnFalse:
  52     pop     rdi
  53     xor     rax, rax
  54     ret                                ; return FALSE
  55