Register allocation

class X86RegisterAllocator(BlockNaiveAllocator):
    def __init__(self, available_registers: RegisterStack) -> None:
        super().__init__(available_registers, registers.X86RegisterType)

    def allocate_func(self, func: x86_func.FuncOp) -> None:
        """
        Allocates values in function passed in to registers.
        The whole function must have been lowered to the relevant x86 dialects
        and it must contain no unrealized casts.
        """
        if not func.body.blocks:
            # External function declaration
            return

        if len(func.body.blocks) != 1:
            raise NotImplementedError(
                f"Cannot register allocate func with {len(func.body.blocks)} blocks."
            )

        preallocated = RegisterAllocatableOperation.all_used_registers(func.body)
        excluded = RegisterAllocatableOperation.all_excluded_registers(func.body)

        for pa_reg in preallocated | excluded:
            self.available_registers.exclude_register(pa_reg)

        block = func.body.block

        self.live_ins_per_block = live_ins_per_block(block)
        assert not self.live_ins_per_block[block]

        self.allocate_block(block)