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vm: adding a fast path for bignum sq.

db4
John Benediktsson 2014-06-06 10:45:09 -07:00
parent a992963f44
commit 6c703bbd6c
2 changed files with 58 additions and 0 deletions
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57
vm/bignum.cpp
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@ -107,8 +107,65 @@ bignum* factor_vm::bignum_subtract(bignum* x, bignum* y) {
: (bignum_subtract_unsigned(x, y))))));
}
#ifdef _WIN64
bignum *factor_vm::bignum_square(bignum * x)
{
return bignum_multiply(x, x);
}
#else
/* Allocates memory */
bignum *factor_vm::bignum_square(bignum * x)
{
GC_BIGNUM(x);
bignum_length_type length = (BIGNUM_LENGTH (x));
bignum * z = (allot_bignum_zeroed ((length + length), 0));
bignum_digit_type * scan_z = BIGNUM_START_PTR (z);
bignum_digit_type * scan_x = BIGNUM_START_PTR (x);
bignum_digit_type * end_x = scan_x + length;
for (int i = 0; i < length; ++i) {
bignum_twodigit_type carry;
bignum_twodigit_type f = BIGNUM_REF (x, i);
bignum_digit_type *pz = scan_z + (i << 1);
bignum_digit_type *px = scan_x + i + 1;
carry = *pz + f * f;
*pz++ = carry & BIGNUM_DIGIT_MASK;
carry >>= BIGNUM_DIGIT_LENGTH;
BIGNUM_ASSERT (carry <= BIGNUM_DIGIT_MASK);
f <<= 1;
while (px < end_x)
{
carry += *pz + *px++ * f;
*pz++ = carry & BIGNUM_DIGIT_MASK;
carry >>= BIGNUM_DIGIT_LENGTH;
BIGNUM_ASSERT (carry <= (BIGNUM_DIGIT_MASK << 1));
}
if (carry) {
carry += *pz;
*pz++ = carry & BIGNUM_DIGIT_MASK;
carry >>= BIGNUM_DIGIT_LENGTH;
}
if (carry)
*pz += carry & BIGNUM_DIGIT_MASK;
BIGNUM_ASSERT ((carry >> BIGNUM_DIGIT_LENGTH) == 0);
}
return (bignum_trim (z));
}
#endif
/* Allocates memory */
bignum* factor_vm::bignum_multiply(bignum* x, bignum* y) {
#ifndef _WIN64
if (x == y) {
return bignum_square(x);
}
#endif
bignum_length_type x_length = (BIGNUM_LENGTH(x));
bignum_length_type y_length = (BIGNUM_LENGTH(y));
int negative_p = ((BIGNUM_NEGATIVE_P(x)) ? (!(BIGNUM_NEGATIVE_P(y)))

1
vm/vm.hpp
View File

@ -232,6 +232,7 @@ struct factor_vm {
enum bignum_comparison bignum_compare(bignum* x, bignum* y);
bignum* bignum_add(bignum* x, bignum* y);
bignum* bignum_subtract(bignum* x, bignum* y);
bignum* bignum_square(bignum* x);
bignum* bignum_multiply(bignum* x, bignum* y);
void bignum_divide(bignum* numerator, bignum* denominator, bignum** quotient,
bignum** remainder);