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/*
* Simple O(N^2) Multiplication and Squaring
* (C) 1999-2008 Jack Lloyd
*
* Distributed under the terms of the Botan license
*/
#include <botan/internal/mp_asm.h>
#include <botan/internal/mp_asmi.h>
#include <botan/internal/mp_core.h>
#include <botan/mem_ops.h>
namespace Botan {
extern "C" {
/*
* Simple O(N^2) Multiplication
*/
void bigint_simple_mul(word z[], const word x[], u32bit x_size,
const word y[], u32bit y_size)
{
const u32bit blocks = x_size - (x_size % 8);
clear_mem(z, x_size + y_size);
for(u32bit i = 0; i != y_size; ++i)
{
word carry = 0;
for(u32bit j = 0; j != blocks; j += 8)
carry = word8_madd3(z + i + j, x + j, y[i], carry);
for(u32bit j = blocks; j != x_size; ++j)
z[i+j] = word_madd3(x[j], y[i], z[i+j], &carry);
z[x_size+i] = carry;
}
}
inline word word_sqr(word x,
/*
* Simple O(N^2) Squaring
This is exactly the same algorithm as bigint_simple_mul,
however because C/C++ compilers suck at alias analysis it
is good to have the version where the compiler knows
that x == y
*/
void bigint_simple_sqr(word z[], const word x[], u32bit x_size)
{
clear_mem(z, 2*x_size);
for(u32bit i = 0; i != x_size; ++i)
{
const word x_i = x[i];
word carry = z[2*i];
z[2*i] = word_madd2(x_i, x_i, z[2*i], &carry);
for(u32bit j = i; j != x_size; ++j)
{
// z[i+j] = z[i+j] + 2 * x[j] * x_i + carry;
/*
load z[i+j] into register
load x[j] into %hi
mulq %[x_i] -> x[i] * x[j] -> %lo:%hi
shlq %lo, $1
// put carry bit (cf) from %lo into %temp
xorl %temp
adcq $0, %temp
// high bit of lo now in cf
shl %hi, $1
// add in lowest bid from %lo
orl %temp, %hi
addq %[c], %[lo]
adcq $0, %[hi]
addq %[z_ij], %[lo]
adcq $0, %[hi]
*/
}
z[x_size+i] = carry;
}
}
}
}
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