If the input quotation is a literal, or built up from curry and compose with terminal quotations literal, it is inlined at the call site.
For dynamic call sites, call( uses the following strategy:
Inline caching. If the quotation is the same as last time, just call it unsafely
Effect inference. Infer quotation's effect, caching it in the cached-effect slot, and compare it with declaration. If matches, call it unsafely.
Fallback. If the above doesn't work, call it and compare the datastack before and after to make sure it didn't mess anything up.
Inline caches and cached effects are invalidated whenever a macro is redefined, or a word's effect changes, by comparing a global counter against the counter value last observed. The counter is incremented by compiler.units.