Michael Gottesman 8f7620f627 [semantic-arc-opts] Implement a simple load [copy] -> load_borrow optimization for arguments to create optimization scaffolding. ...

This is the first in a sequence of patches that implement various optimizations
to transform load [copy] into load_borrow.

The optimization works by looking for a load [copy] that:

1. Only has destroy_value as consuming users. This implies that we do not need
to pass off the in memory value at +1 and that we can use a +0 value.

2. Is loading from a memory location that is never written to or only written to
after all uses of the load [copy].

and then RAUW the load [copy] with a load_borrow and convertes the destroy_value
to end_borrow.

NOTE: I also a .def file for AccessedStorage so we can do visitors over the
kinds. The reason I want to do this is to ensure that people update these
optimizations if we add new storage kinds.

2018-12-16 12:32:46 -08:00

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