Nate Chandler ae6868a296 [DCE] Process instructions added during deletion. ...

In cea0f00598, `InstructionDeleter` began
deleting `load [take]` instructions.  Analogous to how it creates a
`destroy_value` when deleting an instruction which consumes a value, in
the case of deleting a `load [take]` the `InstructionDeleter` inserts a
compensating `destroy_addr`.

Previously, `DeadCodeElimination` did not observe the creation of any
instructions created by the `InstructionDeleter`.  In the case of the
newly created `destroy_addr`, DCE didn't mark that the `destroy_addr`
was live and so deleted it.  The result was a leak.

Here, this is fixed by passing an `InstModCallbacks`--with an
`onCreateNewInst` implementation--down into `erasePhiArgument` that
eventually invokes the `InstructionDeleter`.  When the
`InstructionDeleter` creates a new instruction, DCE marks it live.

2023-11-15 15:03:24 -08:00

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