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|
;------------------------------------------------------------------------------
;
; CopyMem() worker for ARM
;
; This file started out as C code that did 64 bit moves if the buffer was
; 32-bit aligned, else it does a byte copy. It also does a byte copy for
; any trailing bytes. It was updated to do 32-byte copies using stm/ldm.
;
; Copyright (c) 2008 - 2010, Apple Inc. 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.
;
;------------------------------------------------------------------------------
/**
Copy Length bytes from Source to Destination. Overlap is OK.
This implementation
@param Destination Target of copy
@param Source Place to copy from
@param Length Number of bytes to copy
@return Destination
VOID *
EFIAPI
InternalMemCopyMem (
OUT VOID *DestinationBuffer,
IN CONST VOID *SourceBuffer,
IN UINTN Length
)
**/
EXPORT InternalMemCopyMem
AREA AsmMemStuff, CODE, READONLY
InternalMemCopyMem
stmfd sp!, {r4-r11, lr}
// Save the input parameters in extra registers (r11 = destination, r14 = source, r12 = length)
mov r11, r0
mov r10, r0
mov r12, r2
mov r14, r1
memcopy_check_overlapped
cmp r11, r1
// If (dest < source)
bcc memcopy_check_optim_default
// If (dest <= source). But with the previous condition -> If (dest == source)
bls memcopy_end
// If (source + length < dest)
rsb r3, r1, r11
cmp r12, r3
bcc memcopy_check_optim_default
// If (length == 0)
cmp r12, #0
beq memcopy_end
b memcopy_check_optim_overlap
memcopy_check_optim_default
// Check if we can use an optimized path ((length >= 32) && destination word-aligned && source word-aligned) for the memcopy (optimized path if r0 == 1)
tst r0, #0xF
movne r0, #0
bne memcopy_default
tst r1, #0xF
movne r3, #0
moveq r3, #1
cmp r2, #31
movls r0, #0
andhi r0, r3, #1
b memcopy_default
memcopy_check_optim_overlap
// r10 = dest_end, r14 = source_end
add r10, r11, r12
add r14, r12, r1
// Are we in the optimized case ((length >= 32) && dest_end word-aligned && source_end word-aligned)
cmp r2, #31
movls r0, #0
movhi r0, #1
tst r10, #0xF
movne r0, #0
tst r14, #0xF
movne r0, #0
b memcopy_overlapped
memcopy_overlapped_non_optim
// We read 1 byte from the end of the source buffer
sub r3, r14, #1
sub r12, r12, #1
ldrb r3, [r3, #0]
sub r2, r10, #1
cmp r12, #0
// We write 1 byte at the end of the dest buffer
sub r10, r10, #1
sub r14, r14, #1
strb r3, [r2, #0]
bne memcopy_overlapped_non_optim
b memcopy_end
// r10 = dest_end, r14 = source_end
memcopy_overlapped
// Are we in the optimized case ?
cmp r0, #0
beq memcopy_overlapped_non_optim
// Optimized Overlapped - Read 32 bytes
sub r14, r14, #32
sub r12, r12, #32
cmp r12, #31
ldmia r14, {r2-r9}
// If length is less than 32 then disable optim
movls r0, #0
cmp r12, #0
// Optimized Overlapped - Write 32 bytes
sub r10, r10, #32
stmia r10, {r2-r9}
// while (length != 0)
bne memcopy_overlapped
b memcopy_end
memcopy_default_non_optim
// Byte copy
ldrb r3, [r14], #1
sub r12, r12, #1
strb r3, [r10], #1
memcopy_default
cmp r12, #0
beq memcopy_end
// r10 = dest, r14 = source
memcopy_default_loop
cmp r0, #0
beq memcopy_default_non_optim
// Optimized memcopy - Read 32 Bytes
sub r12, r12, #32
cmp r12, #31
ldmia r14!, {r2-r9}
// If length is less than 32 then disable optim
movls r0, #0
cmp r12, #0
// Optimized memcopy - Write 32 Bytes
stmia r10!, {r2-r9}
// while (length != 0)
bne memcopy_default_loop
memcopy_end
mov r0, r11
ldmfd sp!, {r4-r11, pc}
END
|
