;------------------------------------------------------------------------------ ; ; 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: ; ;------------------------------------------------------------------------------ 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