109 lines
3.7 KiB
Ruby
109 lines
3.7 KiB
Ruby
require_relative "block"
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module Vm
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# Functions are similar to Blocks. Where Blocks can be jumped to, Functions can be called.
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# Functions also have arguments and a return. These are Value subclass instances, ie specify
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# type (by class type) and register by instance
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# They also have local variables. Args take up the first n regs, then locals the rest. No
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# direct manipulating of registers (ie specifying the number) should be done.
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# Code-wise Functions are made up from a list of Blocks, in a similar way blocks are made up of codes
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# Four of the block have a special role:
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# - entry/exit: are usually system specific
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# - body: the logical start of the function
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# - return: the logical end, where ALL blocks must end
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# Blocks can be linked in two ways:
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# -linear: flow continues from one to the next as they are sequential both logically and "physically"
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# use the block set_next for this.
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# This "the straight line", there must be a continuous sequence from body to return
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# Linear blocks may be created from an existing block with new_block
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# - branched: You create new blocks using function.new_block which gets added "after" return
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# These (eg if/while) blocks may themselves have linear blocks ,but the last of these
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# MUST have an uncoditional branch. And remember, all roads lead to return.
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class Function < Code
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def initialize(name , args = [] , return_type = nil)
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super()
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@name = name
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@args = Array.new(args.length)
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args.each_with_index do |arg , i|
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if arg.is_a?(Value)
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@args[i] = arg
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raise "arg in non std register #{arg.inspect}" unless i == arg.register
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else
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@args[i] = arg.new(i)
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end
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end
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@return_type = return_type || Vm::Integer
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if @return_type.is_a?(Value)
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raise "return in non std register #{@return_type.inspect}" unless 0 == @return_type.register
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else
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@return_type = @return_type.new(0)
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end
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@exit = Core::Kernel::function_exit( Vm::Block.new("#{name}_exit" , self) , name )
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@return = Block.new("#{name}_return", self , @exit)
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@body = Block.new("#{name}_body", self , @return)
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@entry = Core::Kernel::function_entry( Vm::Block.new("#{name}_entry" , self , @body) ,name )
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@locals = []
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@blocks = []
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end
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attr_reader :args , :entry , :exit , :body , :name
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attr_accessor :return_type
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def arity
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@args.length
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end
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def new_local type = Vm::Integer
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register = args.length + @locals.length
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l = type.new(register)
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@locals << l
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l
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end
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def new_block name
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block = Block.new(name , self)
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@blocks << block
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block
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end
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# following id the Code interface
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# to link we link the entry and then any blocks. The entry links the straight line
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def link_at address , context
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super #just sets the position
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@entry.link_at address , context
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address += @entry.length
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@blocks.each do |block|
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block.link_at(pos , context)
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pos += block.length
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end
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end
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# position of the function is the position of the entry block
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def position
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@entry.position
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end
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# length of a function is the entry block length (includes the straight line behind it)
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# plus any out of line blocks that have been added
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def length
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@blocks.inject(@entry.length) {| sum , item | sum + item.length}
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end
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# assembling assembles the entry (straight line/ no branch line) + any additional branches
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def assemble io
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@entry.assemble(io)
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@blocks.each do |block|
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block.assemble io
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end
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end
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end
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end |