The test drivers can stop calling comp_ctx.verify because legalize() and
regalloc() do it themselves now.
This also makes it possible for those two passes to return other
CtonError codes in the future, not just verifier errors.
Run the verify_contexti() function after invoking the legalize() and
regalloc() context functions. This will help catch bad code produced by
these passes.
Legalizing some instructions may require modifications to the control
flow graph, and some operations need to use the CFG analysis.
The CFG reference is threaded through all the legalization functions to
reach the generated expansion functions as well as the legalizer::split
module where it will be used first.
Move the flow graph computation into a compute method which can be
called with multiple functions.
This allows us to reuse the ControlFlowGraph memory and keep an instance
in the Context.
This will provide main entry points for compiling functions, and it
serves as a place for keeping data structures that should be preserved
between function compilations to reduce allocator thrashing.
So far, Context is just basic scaffolding. More to be added.
