mirror of https://github.com/acidanthera/audk.git
112 lines
2.8 KiB
C
112 lines
2.8 KiB
C
/*++
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Copyright (c) 2006, 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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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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Module Name:
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EfiZeroMemSSE2.c
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Abstract:
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This is the code that supports IA32-optimized ZeroMem service
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--*/
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#include "Tiano.h"
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VOID
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EfiCommonLibZeroMem (
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IN VOID *Buffer,
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IN UINTN Count
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)
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/*++
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Input: VOID *Buffer - Pointer to buffer to clear
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UINTN Count - Number of bytes to clear
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Output: None.
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Saves:
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Modifies:
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Description: This function is an optimized zero-memory function.
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Notes: This function tries to zero memory 8 bytes at a time. As a result,
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it first picks up any misaligned bytes, then words, before getting
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in the main loop that does the 8-byte clears.
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--*/
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{
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__asm {
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mov ecx, Count
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mov edi, Buffer
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; Pick up misaligned start bytes (get pointer 4-byte aligned)
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_StartByteZero:
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mov eax, edi
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and al, 3 ; check lower 2 bits of address
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test al, al
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je _ZeroBlocks ; already aligned?
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cmp ecx, 0
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je _ZeroMemDone
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; Clear the byte memory location
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mov BYTE PTR [edi], 0
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inc edi
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; Decrement our count
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dec ecx
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jmp _StartByteZero ; back to top of loop
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_ZeroBlocks:
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; Compute how many 64-byte blocks we can clear
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mov edx, ecx
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shr ecx, 6 ; convert to 64-byte count
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shl ecx, 6 ; convert back to bytes
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sub edx, ecx ; subtract from the original count
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shr ecx, 6 ; and this is how many 64-byte blocks
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; If no 64-byte blocks, then skip
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cmp ecx, 0
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je _ZeroRemaining
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xorps xmm1, xmm1
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_B:
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movdqu OWORD PTR ds:[edi], xmm1
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movdqu OWORD PTR ds:[edi+16], xmm1
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movdqu OWORD PTR ds:[edi+32], xmm1
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movdqu OWORD PTR ds:[edi+48], xmm1
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add edi, 64
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dec ecx
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jnz _B
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_ZeroRemaining:
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; Zero out as many DWORDS as possible
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mov ecx, edx
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shr ecx, 2
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xor eax, eax
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rep stosd
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; Zero out remaining as bytes
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mov ecx, edx
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and ecx, 03
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rep stosb
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_ZeroMemDone:
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}
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}
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