- RIP-relative LEA is now used to load program counter in prolog and tail calls; saves 3 bytes of code and 4 bytes of relocation information over an immediate MOV
- VM field accesses no longer involve a redundant addition
- change some primitives into sub-primitives: fixnum+ fixnum- fixnum* inline-cache-miss inline-cache-miss-tail
- rename some relocation types for clarity
- some other minor re-organizations and cleanups
- Move forward declarations of 'struct factor_vm' to one place
- Rename template parameters from T and TYPE to descriptive names. New convention: CamelCase for template parameters
- Change some higher-order functions taking function pointers into templates, and define classes overriding operator(). There's a bit of new boilerplate here but its more consistent than the old mish-mash approaches
- Put GC state into a gc_state struct
- Use exceptions instead of longjmp for non-local control transfer in GC
- In code GC, instead of interleaving code block tracing with copying, add code blocks which need to be revisited to an std::set stored in the gc_state