mirror of https://github.com/acidanthera/audk.git
81 lines
2.8 KiB
NASM
81 lines
2.8 KiB
NASM
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;------------------------------------------------------------------------------
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;
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; Copyright (c) 2007, Intel Corporation
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; All rights reserved. This program and the accompanying materials
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; are licensed and made available under the terms and conditions of the BSD License
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; which accompanies this distribution. The full text of the license may be found at
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; http://opensource.org/licenses/bsd-license.php
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;
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; THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
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; WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
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;
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; Module Name:
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;
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; CopyMem.asm
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;
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; Abstract:
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;
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; memcpy function
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;
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; Notes:
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;
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;------------------------------------------------------------------------------
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.code
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;------------------------------------------------------------------------------
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; VOID *
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; memcpy (
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; OUT VOID *DestinationBuffer,
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; IN CONST VOID *SourceBuffer,
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; IN UINTN Length
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; );
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;------------------------------------------------------------------------------
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memcpy PROC USES rsi rdi
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mov rax, rcx ; rax <- Destination as return value
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cmp rdx, rcx ; if Source == Destination, do nothing
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je @CopyMemDone
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cmp r8, 0 ; if Count == 0, do nothing
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je @CopyMemDone
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mov rsi, rdx ; rsi <- Source
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mov rdi, rcx ; rdi <- Destination
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lea r9, [rsi + r8 - 1] ; r9 <- Last byte of Source
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cmp rsi, rdi
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jae @F ; Copy forward if Source > Destination
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cmp r9, rdi ; Overlapped?
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jae @CopyBackward ; Copy backward if overlapped
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@@:
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xor rcx, rcx
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sub rcx, rdi ; rcx <- -rdi
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and rcx, 15 ; rcx + rsi should be 16 bytes aligned
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jz @F ; skip if rcx == 0
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cmp rcx, r8
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cmova rcx, r8
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sub r8, rcx
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rep movsb
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@@:
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mov rcx, r8
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and r8, 15
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shr rcx, 4 ; rcx <- # of DQwords to copy
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jz @CopyBytes
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@@:
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movdqu xmm0, [rsi] ; rsi may not be 16-byte aligned
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movdqa [rdi], xmm0 ; rdi should be 16-byte aligned
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add rsi, 16
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add rdi, 16
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loop @B
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jmp @CopyBytes ; copy remaining bytes
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@CopyBackward:
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mov rsi, r9 ; rsi <- Last byte of Source
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lea rdi, [rdi + r8 - 1] ; rdi <- Last byte of Destination
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std
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@CopyBytes:
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mov rcx, r8
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rep movsb
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cld
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@CopyMemDone:
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ret
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memcpy ENDP
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END
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