memcpy_P函数是AVR吗? [英] memcpy_P function AVR?
问题描述
void * memcpy_P(void * dest,PGM_VOID_P src,size_t n)
void * memcpy_P( void * dest, PGM_VOID_P src, size_t n )
有人可以告诉我上述功能在avr libc库中的何处实现吗?
Could someone please tell me where the above function is implemented in the avr libc library?
我似乎只能在几个头文件中找到该函数的定义,而不是实际的实现.
I can only seem to find a definition for the function in a few header files, not the actual implementation.
我要执行此操作的原因是因为目前正在对AVRAtmega128rfa1进行性能测试,并且我还需要查看该功能的AVR汇编代码,以及执行所需的时间.
The reason I want to do this is because at the moment I am doing so performance testing on the AVRAtmega128rfa1 and I need see the AVR assembly code for the function too see how long it takes to execute.
谢谢.
推荐答案
在avr-libc-1.8.0中,该函数在avr-libc-1.8.0/libc/pmstring/memcpy_P.S中定义
In avr-libc-1.8.0, the function is defined in avr-libc-1.8.0/libc/pmstring/memcpy_P.S
/* Copyright (c) 2002, 2005, 2006, 2007 Marek Michalkiewicz
All rights reserved.
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are met:
* Redistributions of source code must retain the above copyright
notice, this list of conditions and the following disclaimer.
* Redistributions in binary form must reproduce the above copyright
notice, this list of conditions and the following disclaimer in
the documentation and/or other materials provided with the
distribution.
* Neither the name of the copyright holders nor the names of
contributors may be used to endorse or promote products derived
from this software without specific prior written permission.
THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
POSSIBILITY OF SUCH DAMAGE. */
/* $Id: memcpy_P.S 2191 2010-11-05 13:45:57Z arcanum $ */
/** \file */
/** \ingroup avr_pgmspace
\fn void *memcpy_P(void *dest, PGM_VOID_P src, size_t n)
The memcpy_P() function is similar to memcpy(), except the src string
resides in program space.
\returns The memcpy_P() function returns a pointer to dest. */
#if !defined(__AVR_TINY__)
#if !defined(__DOXYGEN__)
#include "macros.inc"
#define dest_hi r25
#define dest_lo r24
#define src_hi r23
#define src_lo r22
#define len_hi r21
#define len_lo r20
ASSEMBLY_CLIB_SECTION
.global _U(memcpy_P)
.type _U(memcpy_P), @function
_U(memcpy_P):
X_movw ZL, src_lo
X_movw XL, dest_lo
#if OPTIMIZE_SPEED
; 17 words, (14 + len * 9 - (len & 1)) cycles
sbrs len_lo, 0
rjmp .L_memcpy_P_start
rjmp .L_memcpy_P_odd
.L_memcpy_P_loop:
X_lpm r0, Z+
st X+, r0
.L_memcpy_P_odd:
X_lpm r0, Z+
st X+, r0
.L_memcpy_P_start:
subi len_lo, lo8(2)
sbci len_hi, hi8(2)
#else
; 12 words, (13 + len * 11) cycles
rjmp .L_memcpy_P_start
.L_memcpy_P_loop:
X_lpm r0, Z+
st X+, r0
.L_memcpy_P_start:
subi len_lo, lo8(1)
sbci len_hi, hi8(1)
#endif
brcc .L_memcpy_P_loop
; return dest (unchanged)
ret
.L_memcpy_P_end:
.size _U(memcpy_P), .L_memcpy_P_end - _U(memcpy_P)
#endif /* not __DOXYGEN__ */
#endif /* !defined(__AVR_TINY__) */
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