Use 64-bit GMP limbs on wasm32
This is a rather low priority feature request, filed since I noticed a fact in GMP configure system: it's possible to forcibly use 64-bit limbs on 32-bit host archs. Our ghc-bignum
has the assumption that limb size must equals word size, though I think it's possible to relax that restriction.
Using 64-bit GMP limbs likely improves performance on wasm32 when dealing with large Integer
s, since wasm32 supports i64 arithmetic perfectly, and in general the same amount of computation can be achieved by less i64 instructions than their i32 equivalents.