2 ms·

I would be interested in the impact of just replacing every fixed size integer with variable length ones. Plain integer array - gone. Single cycle math operatio

• dezgeg 12y ago
  A sane implementation of bigints uses pointer tagging such that arithmetic on sufficiently small numbers (e.g. two 63-bit operands on a 64-bit machine) is still just a couple of cycles, with just an extra comparison and a (most likely optimally predicted) branch in the hot path. Then, assuming the bigints are implemented in the core language, we could make the compiler optimize the bigint checks away when possible. For example, consider this hypothetical function: void memzero_range(char* array, int start, int end) { for(int i = start; i < end; i++) array[i] = 0; } Now, what can we infer from the 'array[i] = 0;' in the body of the loop? Certainly, on a 64-bit machine it's not possible for i to go over 2^64 without experiencing undefined behaviour. So a smart (and conforming) compiler could just do if (is_bigint(start) || is_bigint(end)) abort(); once, and then execute the loop itself without any overhead from bigints. Or well, that's at least my personal dream of what should happen.