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;------------------------------------------------------------------------------
;
; Copyright (c) 2016, Intel Corporation. All rights reserved.<BR>
; This program and the accompanying materials
; are licensed and made available under the terms and conditions of the BSD License
; which accompanies this distribution. The full text of the license may be found at
; http://opensource.org/licenses/bsd-license.php.
;
; THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
; WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
;
; Module Name:
;
; IsZeroBuffer.nasm
;
; Abstract:
;
; IsZeroBuffer function
;
; Notes:
;
;------------------------------------------------------------------------------
SECTION .text
;------------------------------------------------------------------------------
; BOOLEAN
; EFIAPI
; InternalMemIsZeroBuffer (
; IN CONST VOID *Buffer,
; IN UINTN Length
; );
;------------------------------------------------------------------------------
global ASM_PFX(InternalMemIsZeroBuffer)
ASM_PFX(InternalMemIsZeroBuffer):
push edi
mov edi, [esp + 8] ; edi <- Buffer
mov edx, [esp + 12] ; edx <- Length
xor ecx, ecx ; ecx <- 0
sub ecx, edi
and ecx, 15 ; ecx + edi aligns on 16-byte boundary
jz @Is16BytesZero
cmp ecx, edx
cmova ecx, edx ; bytes before the 16-byte boundary
sub edx, ecx
xor eax, eax ; eax <- 0, also set ZF
repe scasb
jnz @ReturnFalse ; ZF=0 means non-zero element found
@Is16BytesZero:
mov ecx, edx
and edx, 15
shr ecx, 4
jz @IsBytesZero
.0:
pxor xmm0, xmm0 ; xmm0 <- 0
pcmpeqb xmm0, [edi] ; check zero for 16 bytes
pmovmskb eax, xmm0 ; eax <- compare results
cmp eax, 0xffff
jnz @ReturnFalse
add edi, 16
loop .0
@IsBytesZero:
mov ecx, edx
xor eax, eax ; eax <- 0, also set ZF
repe scasb
jnz @ReturnFalse ; ZF=0 means non-zero element found
pop edi
mov eax, 1 ; return TRUE
ret
@ReturnFalse:
pop edi
xor eax, eax
ret ; return FALSE
|
