A function that returns a record its caller only projects fills the
caller's frame storage through a %into.<name> entry. These entries are
small and called once per use, but LLVM kept them out of line in loops:
record-boundaries' pathLength called %into.pointAt twice per iteration.
They now carry inlinehint, like the indexed-read and interface-dispatch
helpers.
Once inlined, the scalar array reads in them still blocked hoisting the
arrays' header loads: the slow path's scr_arr_state and getter calls had
no memory attributes. They are now read-only cold calls, as the dense
read fallbacks already are (the getter runs only for a present element,
so it does not trap).