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/*
* Copyright (C) 2024 Michael Brown <mbrown@fensystems.co.uk>.
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License as
* published by the Free Software Foundation; either version 2 of the
* License, or any later version.
*
* This program is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
* 02110-1301, USA.
*
* You can also choose to distribute this program under the terms of
* the Unmodified Binary Distribution Licence (as given in the file
* COPYING.UBDL), provided that you have satisfied its requirements.
*/
/** @file
*
* Optimised string operations
*
*/
FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
#include <string.h>
/**
* Copy memory area
*
* @v dest Destination address
* @v src Source address
* @v len Length
* @ret dest Destination address
*/
void riscv_memcpy ( void *dest, const void *src, size_t len ) {
size_t len_pre;
size_t len_mid;
size_t len_post;
unsigned long discard_data;
/* Calculate pre-aligned, aligned, and post-aligned lengths.
* (Align on the destination address, on the assumption that
* misaligned stores are likely to be more expensive than
* misaligned loads.)
*/
len_pre = ( ( sizeof ( unsigned long ) - ( ( intptr_t ) dest ) ) &
( sizeof ( unsigned long ) - 1 ) );
if ( len_pre > len )
len_pre = len;
len -= len_pre;
len_mid = ( len & ~( sizeof ( unsigned long ) - 1 ) );
len -= len_mid;
len_post = len;
/* Copy pre-aligned section */
__asm__ __volatile__ ( "j 2f\n\t"
"\n1:\n\t"
"lb %2, (%1)\n\t"
"sb %2, (%0)\n\t"
"addi %0, %0, 1\n\t"
"addi %1, %1, 1\n\t"
"\n2:\n\t"
"bne %0, %3, 1b\n\t"
: "+r" ( dest ), "+r" ( src ),
"=&r" ( discard_data )
: "r" ( dest + len_pre )
: "memory" );
/* Copy aligned section */
__asm__ __volatile__ ( "j 2f\n\t"
"\n1:\n\t"
LOADN " %2, (%1)\n\t"
STOREN " %2, (%0)\n\t"
"addi %0, %0, %4\n\t"
"addi %1, %1, %4\n\t"
"\n2:\n\t"
"bne %0, %3, 1b\n\t"
: "+r" ( dest ), "+r" ( src ),
"=&r" ( discard_data )
: "r" ( dest + len_mid ),
"i" ( sizeof ( unsigned long ) )
: "memory" );
/* Copy post-aligned section */
__asm__ __volatile__ ( "j 2f\n\t"
"\n1:\n\t"
"lb %2, (%1)\n\t"
"sb %2, (%0)\n\t"
"addi %0, %0, 1\n\t"
"addi %1, %1, 1\n\t"
"\n2:\n\t"
"bne %0, %3, 1b\n\t"
: "+r" ( dest ), "+r" ( src ),
"=&r" ( discard_data )
: "r" ( dest + len_post )
: "memory" );
}
/**
* Zero memory region
*
* @v dest Destination region
* @v len Length
*/
void riscv_bzero ( void *dest, size_t len ) {
size_t len_pre;
size_t len_mid;
size_t len_post;
/* Calculate pre-aligned, aligned, and post-aligned lengths */
len_pre = ( ( sizeof ( unsigned long ) - ( ( intptr_t ) dest ) ) &
( sizeof ( unsigned long ) - 1 ) );
if ( len_pre > len )
len_pre = len;
len -= len_pre;
len_mid = ( len & ~( sizeof ( unsigned long ) - 1 ) );
len -= len_mid;
len_post = len;
/* Zero pre-aligned section */
__asm__ __volatile__ ( "j 2f\n\t"
"\n1:\n\t"
"sb zero, (%0)\n\t"
"addi %0, %0, 1\n\t"
"\n2:\n\t"
"bne %0, %1, 1b\n\t"
: "+r" ( dest )
: "r" ( dest + len_pre )
: "memory" );
/* Zero aligned section */
__asm__ __volatile__ ( "j 2f\n\t"
"\n1:\n\t"
STOREN " zero, (%0)\n\t"
"addi %0, %0, %2\n\t"
"\n2:\n\t"
"bne %0, %1, 1b\n\t"
: "+r" ( dest )
: "r" ( dest + len_mid ),
"i" ( sizeof ( unsigned long ) )
: "memory" );
/* Zero post-aligned section */
__asm__ __volatile__ ( "j 2f\n\t"
"\n1:\n\t"
"sb zero, (%0)\n\t"
"addi %0, %0, 1\n\t"
"\n2:\n\t"
"bne %0, %1, 1b\n\t"
: "+r" ( dest )
: "r" ( dest + len_post )
: "memory" );
}
/**
* Fill memory region
*
* @v dest Destination region
* @v len Length
* @v character Fill character
*
* The unusual parameter order is to allow for more efficient
* tail-calling to riscv_bzero() when zeroing a region.
*/
void riscv_memset ( void *dest, size_t len, int character ) {
/* Do nothing if length is zero */
if ( ! len )
return;
/* Use optimised zeroing code if applicable */
if ( character == 0 ) {
riscv_bzero ( dest, len );
return;
}
/* Fill one byte at a time. Calling memset() with a non-zero
* value is relatively rare and unlikely to be
* performance-critical.
*/
__asm__ __volatile__ ( "\n1:\n\t"
"sb %2, (%0)\n\t"
"addi %0, %0, 1\n\t"
"bne %0, %1, 1b\n\t"
: "+r" ( dest )
: "r" ( dest + len ), "r" ( character )
: "memory" );
}
/**
* Copy (possibly overlapping) memory region
*
* @v dest Destination region
* @v src Source region
* @v len Length
*/
void riscv_memmove ( void *dest, const void *src, size_t len ) {
void *orig_dest = dest;
unsigned long discard_data;
/* Do nothing if length is zero */
if ( ! len )
return;
/* Use memcpy() if copy direction is forwards */
if ( dest <= src ) {
memcpy ( dest, src, len );
return;
}
/* Assume memmove() is not performance-critical, and perform a
* bytewise copy backwards for simplicity.
*/
dest += len;
src += len;
__asm__ __volatile__ ( "\n1:\n\t"
"addi %1, %1, -1\n\t"
"addi %0, %0, -1\n\t"
"lb %2, (%1)\n\t"
"sb %2, (%0)\n\t"
"bne %0, %3, 1b\n\t"
: "+r" ( dest ), "+r" ( src ),
"=&r" ( discard_data )
: "r" ( orig_dest )
: "memory" );
}
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