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| ;------------------------------------------------------------------------------
| ;
| ; Copyright (c) 2016, Intel Corporation. All rights reserved.<BR>
| ; SPDX-License-Identifier: BSD-2-Clause-Patent
| ;
| ; Module Name:
| ;
| ; IsZeroBuffer.nasm
| ;
| ; Abstract:
| ;
| ; IsZeroBuffer function
| ;
| ; Notes:
| ;
| ;------------------------------------------------------------------------------
|
| DEFAULT REL
| SECTION .text
|
| ;------------------------------------------------------------------------------
| ; BOOLEAN
| ; EFIAPI
| ; InternalMemIsZeroBuffer (
| ; IN CONST VOID *Buffer,
| ; IN UINTN Length
| ; );
| ;------------------------------------------------------------------------------
| global ASM_PFX(InternalMemIsZeroBuffer)
| ASM_PFX(InternalMemIsZeroBuffer):
| push rdi
| mov rdi, rcx ; rdi <- Buffer
| xor rcx, rcx ; rcx <- 0
| sub rcx, rdi
| and rcx, 15 ; rcx + rdi aligns on 16-byte boundary
| jz @Is16BytesZero
| cmp rcx, rdx ; Length already in rdx
| cmova rcx, rdx ; bytes before the 16-byte boundary
| sub rdx, rcx
| xor rax, rax ; rax <- 0, also set ZF
| repe scasb
| jnz @ReturnFalse ; ZF=0 means non-zero element found
| @Is16BytesZero:
| mov rcx, rdx
| and rdx, 15
| shr rcx, 4
| jz @IsBytesZero
| .0:
| pxor xmm0, xmm0 ; xmm0 <- 0
| pcmpeqb xmm0, [rdi] ; check zero for 16 bytes
| pmovmskb eax, xmm0 ; eax <- compare results
| ; nasm doesn't support 64-bit destination
| ; for pmovmskb
| cmp eax, 0xffff
| jnz @ReturnFalse
| add rdi, 16
| loop .0
| @IsBytesZero:
| mov rcx, rdx
| xor rax, rax ; rax <- 0, also set ZF
| repe scasb
| jnz @ReturnFalse ; ZF=0 means non-zero element found
| pop rdi
| mov rax, 1 ; return TRUE
| ret
| @ReturnFalse:
| pop rdi
| xor rax, rax
| ret ; return FALSE
|
|
|
