Most strings used as keys are either small or not shared, where the
data pointers cannot be equal. Of the rest (shared), most could have
been small.
This diff copies small SharedVariant strings, so they don't refer
back to the SharedVariant, and don't need to be enlisted. Then,
this changes hitStringKey() to not check data pointers, making it
equivalent to StringData::same(). Lastly, hand-write the comparison
loop in StringData::same() so we compare words at a time, and the
loop can be inlined.
Differential Revision: D937233
Enable guarding tracelets on ArrayKind when we can generate
better code for a specific kind.
Added specialized helpers for CGetM, FPassM, and IssetM of
vector-shaped arrays. This eliminates an indirect call and allows the
entire array-access call stack to be inlined into the helper
Differential Revision: D873631
Edwin Smith