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#/*++
#
#Copyright (c) 2006, Intel Corporation
#All rights reserved. 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:
#
# EfiZeroMem.c
#
#Abstract:
#
# This is the code that supports IA32-optimized ZeroMem service
#
#--*/
#include "EfiBind.h"
#---------------------------------------------------------------------------
.686:
#.MODEL flat,C
.mmx:
.code:
#---------------------------------------------------------------------------
.globl ASM_PFX(EfiCommonLibZeroMem)
#VOID
#EfiCommonLibZeroMem (
# IN VOID *Buffer,
# IN UINTN Count
# )
#/*++
#
#Input: VOID *Buffer - Pointer to buffer to clear
# UINTN Count - Number of bytes to clear
#
#Output: None.
#
#Saves:
#
#Modifies:
#
#Description: This function is an optimized zero-memory function.
#
#Notes: This function tries to zero memory 8 bytes at a time. As a result,
# it first picks up any misaligned bytes, then words, before getting
# in the main loop that does the 8-byte clears.
#
#--*/
ASM_PFX(EfiCommonLibZeroMem):
# UINT64 MmxSave;
pushl %ebp
movl %esp, %ebp
pushl %ecx # Reserve space for local variable MmxSave
pushl %ecx
pushl %edi
movl 0xC(%ebp), %ecx # Count
movl 8(%ebp), %edi # Buffer
# Pick up misaligned start bytes (get pointer 4-byte aligned)
_StartByteZero:
movl %edi, %eax
andb $3, %al # check lower 2 bits of address
testb %al, %al
je _ZeroBlocks # already aligned?
cmpl $0, %ecx
je _ZeroMemDone
# Clear the byte memory location
movb $0, (%edi)
incl %edi
# Decrement our count
decl %ecx
jmp _StartByteZero # back to top of loop
_ZeroBlocks:
# Compute how many 64-byte blocks we can clear
movl %ecx, %edx
shrl $6, %ecx # convert to 64-byte count
shll $6, %ecx # convert back to bytes
subl %ecx, %edx # subtract from the original count
shrl $6, %ecx # and this is how many 64-byte blocks
# If no 64-byte blocks, then skip
cmpl $0, %ecx
je _ZeroRemaining
# Save mm0
movq %mm0, -8(%ebp) # Save mm0 to MmxSave
pxor %mm0, %mm0 # Clear mm0
_B:
movq %mm0, %ds:(%edi)
movq %mm0, %ds:8(%edi)
movq %mm0, %ds:16(%edi)
movq %mm0, %ds:24(%edi)
movq %mm0, %ds:32(%edi)
movq %mm0, %ds:40(%edi)
movq %mm0, %ds:48(%edi)
movq %mm0, %ds:56(%edi)
addl $64, %edi
decl %ecx
jnz _B
# Restore mm0
movq -8(%ebp), %mm0 # Restore mm0 from MmxSave
emms # Exit MMX Instruction
_ZeroRemaining:
# Zero out as many DWORDS as possible
movl %edx, %ecx
shrl $2, %ecx
xorl %eax, %eax
rep
stosl
# Zero out remaining as bytes
movl %edx, %ecx
andl $03, %ecx
rep
stosb
_ZeroMemDone:
popl %edi
leave
ret
#EfiCommonLibZeroMem ENDP
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