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vm: speed up bignum log2.

db4
John Benediktsson 2013-12-06 14:40:22 -08:00
parent 1acf307e15
commit 0dda4fc812
1 changed files with 17 additions and 15 deletions
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32
vm/bignum.cpp
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@ -419,9 +419,7 @@ bignum* factor_vm::bignum_add_unsigned(bignum* x, bignum* y, int negative_p) {
GC_BIGNUM(y);
if ((BIGNUM_LENGTH(y)) > (BIGNUM_LENGTH(x))) {
bignum* z = x;
x = y;
y = z;
std::swap(x, y);
}
{
bignum_length_type x_length = (BIGNUM_LENGTH(x));
@ -481,9 +479,7 @@ bignum* factor_vm::bignum_subtract_unsigned(bignum* x, bignum* y) {
case bignum_comparison_equal:
return (BIGNUM_ZERO());
case bignum_comparison_less: {
bignum* z = x;
x = y;
y = z;
std::swap(x, y);
}
negative_p = 1;
break;
@ -548,9 +544,7 @@ bignum* factor_vm::bignum_multiply_unsigned(bignum* x, bignum* y,
GC_BIGNUM(y);
if ((BIGNUM_LENGTH(y)) > (BIGNUM_LENGTH(x))) {
bignum* z = x;
x = y;
y = z;
std::swap(x, y);
}
{
bignum_digit_type carry;
@ -1578,16 +1572,24 @@ bignum* factor_vm::bignum_integer_length(bignum* x) {
bignum_length_type index = ((BIGNUM_LENGTH(x)) - 1);
bignum_digit_type digit = (BIGNUM_REF(x, index));
bignum_digit_type carry = 0;
bignum* result;
bignum* result = (allot_bignum(2, 0));
(BIGNUM_REF(result, 0)) = index;
(BIGNUM_REF(result, 1)) = 0;
bignum_destructive_scale_up(result, BIGNUM_DIGIT_LENGTH);
while (digit > 1) {
bignum_destructive_add(result, ((bignum_digit_type) 1));
carry += 1;
digit >>= 1;
}
if (index < BIGNUM_RADIX_ROOT) {
result = allot_bignum(1, 0);
(BIGNUM_REF(result, 0)) = (index * BIGNUM_DIGIT_LENGTH) + carry;
} else {
result = allot_bignum(2, 0);
(BIGNUM_REF(result, 0)) = index;
(BIGNUM_REF(result, 1)) = 0;
bignum_destructive_scale_up(result, BIGNUM_DIGIT_LENGTH);
bignum_destructive_add(result, carry);
}
return (bignum_trim(result));
}