blob: 7740f1aefce402160778e42c77c1d7058540e118 [file] [log] [blame]
/*
* Copyright (C) 2016 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_LICENCE ( GPL2_OR_LATER_OR_UBDL );
#include <stdint.h>
#include <string.h>
#include <ipxe/bigint.h>
/** @file
*
* Big integer support
*/
/**
* Multiply big integers
*
* @v multiplicand0 Element 0 of big integer to be multiplied
* @v multiplicand_size Number of elements in multiplicand
* @v multiplier0 Element 0 of big integer to be multiplied
* @v multiplier_size Number of elements in multiplier
* @v result0 Element 0 of big integer to hold result
*/
void bigint_multiply_raw ( const uint64_t *multiplicand0,
unsigned int multiplicand_size,
const uint64_t *multiplier0,
unsigned int multiplier_size,
uint64_t *result0 ) {
unsigned int result_size = ( multiplicand_size + multiplier_size );
const bigint_t ( multiplicand_size ) __attribute__ (( may_alias ))
*multiplicand = ( ( const void * ) multiplicand0 );
const bigint_t ( multiplier_size ) __attribute__ (( may_alias ))
*multiplier = ( ( const void * ) multiplier0 );
bigint_t ( result_size ) __attribute__ (( may_alias ))
*result = ( ( void * ) result0 );
unsigned int i;
unsigned int j;
uint64_t multiplicand_element;
uint64_t multiplier_element;
uint64_t *result_elements;
uint64_t discard_low;
uint64_t discard_high;
uint64_t discard_temp_low;
uint64_t discard_temp_high;
/* Zero result */
memset ( result, 0, sizeof ( *result ) );
/* Multiply integers one element at a time */
for ( i = 0 ; i < multiplicand_size ; i++ ) {
multiplicand_element = multiplicand->element[i];
for ( j = 0 ; j < multiplier_size ; j++ ) {
multiplier_element = multiplier->element[j];
result_elements = &result->element[ i + j ];
/* Perform a single multiply, and add the
* resulting double-element into the result,
* carrying as necessary. The carry can
* never overflow beyond the end of the
* result, since:
*
* a < 2^{n}, b < 2^{m} => ab < 2^{n+m}
*/
__asm__ __volatile__ ( "mul %1, %6, %7\n\t"
"umulh %2, %6, %7\n\t"
"ldp %3, %4, [%0]\n\t"
"adds %3, %3, %1\n\t"
"adcs %4, %4, %2\n\t"
"stp %3, %4, [%0], #16\n\t"
"bcc 2f\n\t"
"\n1:\n\t"
"ldr %3, [%0]\n\t"
"adcs %3, %3, xzr\n\t"
"str %3, [%0], #8\n\t"
"bcs 1b\n\t"
"\n2:\n\t"
: "+r" ( result_elements ),
"=&r" ( discard_low ),
"=&r" ( discard_high ),
"=r" ( discard_temp_low ),
"=r" ( discard_temp_high ),
"+m" ( *result )
: "r" ( multiplicand_element ),
"r" ( multiplier_element )
: "cc" );
}
}
}