Always emit Atomics for now for their side effects, even if they're known to act on thread-local objects. TODO: improve this to reduce such atomics into their component parts.
Add -O option to LTO, so I can use ld for convenience without always implying -O3
Don't synth pointers based on pseudo-locations!
Don't mark a yield point when an atomic acts on a known-thread-local object
Don't depend on an empty filename, which always fails stat()
Move test for command-line disabled critical edge splitting after the expensive test, so it can be used to improve link performance