This structure records a sequence of operations.
`ops' is the number of operations recorded.
`cost' is their total cost.
The operations are stored in `op' and the corresponding
logarithms of the integer coefficients in `log'.
These are the operations:
alg_zero total := 0;
alg_m total := multiplicand;
alg_shift total := total * coeff
alg_add_t_m2 total := total + multiplicand * coeff;
alg_sub_t_m2 total := total - multiplicand * coeff;
alg_add_factor total := total * coeff + total;
alg_sub_factor total := total * coeff - total;
alg_add_t2_m total := total * coeff + multiplicand;
alg_sub_t2_m total := total * coeff - multiplicand;
The first operand must be either alg_zero or alg_m.

enum alg_code algorithm::op[MAX_BITS_PER_WORD] |

The size of the OP and LOG fields are not directly related to the
word size, but the worst-case algorithms will be if we have few
consecutive ones or zeros, i.e., a multiplicand like 10101010101...
In that case we will generate shift-by-2, add, shift-by-2, add,...,
in total wordsize operations.