1;------------------------------------------------------------------------------
2;
3; Copyright (c) 2016, Intel Corporation. All rights reserved.<BR>
4; SPDX-License-Identifier: BSD-2-Clause-Patent
5;
6; Module Name:
7;
8;   IsZeroBuffer.nasm
9;
10; Abstract:
11;
12;   IsZeroBuffer function
13;
14; Notes:
15;
16;------------------------------------------------------------------------------
17
18    DEFAULT REL
19    SECTION .text
20
21;------------------------------------------------------------------------------
22;  BOOLEAN
23;  EFIAPI
24;  InternalMemIsZeroBuffer (
25;    IN CONST VOID  *Buffer,
26;    IN UINTN       Length
27;    );
28;------------------------------------------------------------------------------
29global ASM_PFX(InternalMemIsZeroBuffer)
30ASM_PFX(InternalMemIsZeroBuffer):
31    push    rdi
32    mov     rdi, rcx                   ; rdi <- Buffer
33    mov     rcx, rdx                   ; rcx <- Length
34    shr     rcx, 3                     ; rcx <- number of qwords
35    and     rdx, 7                     ; rdx <- number of trailing bytes
36    xor     rax, rax                   ; rax <- 0, also set ZF
37    repe    scasq
38    jnz     @ReturnFalse               ; ZF=0 means non-zero element found
39    mov     rcx, rdx
40    repe    scasb
41    jnz     @ReturnFalse
42    pop     rdi
43    mov     rax, 1                     ; return TRUE
44    ret
45@ReturnFalse:
46    pop     rdi
47    xor     rax, rax
48    ret                                ; return FALSE
49
50