110 lines
3.0 KiB
Ruby
110 lines
3.0 KiB
Ruby
require_relative "values"
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module Vm
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# Think flowcharts: blocks are the boxes. The smallest unit of linear code
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# Blocks must end in control instructions (jump/call/return).
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# And the only valid argument for a jump is a Block
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# Blocks form a linked list
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# There are four ways for a block to get data (to work on)
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# - hard coded constants (embedded in code)
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# - memory move
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# - values passed in (from previous blocks. ie local variables)
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# See Value description on how to create code/instructions
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# Codes then get assembled into bytes (after linking)
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class Block < Code
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def initialize(name , function , next_block )
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super()
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@function = function
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@name = name.to_sym
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@next = next_block
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@branch = nil
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@codes = []
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# keeping track of register usage, left (assigns) or right (uses)
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@assigns = []
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@uses = []
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end
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attr_reader :name , :next , :codes , :function , :assigns , :uses
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attr_accessor :branch
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def reachable ret = []
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add_next ret
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add_branch ret
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ret
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end
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def do_add kode
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kode.assigns.each { |a| (@assigns << a) unless @assigns.include?(a) }
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kode.uses.each { |use| (@uses << use) unless (@assigns.include?(use) or @uses.include?(use)) }
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#puts "IN ADD #{name}#{uses}"
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@codes << kode
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end
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def set_next next_b
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@next = next_b
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end
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# returns if this is a block that ends in a call (and thus needs local variable handling)
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def call_block?
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return false unless codes.last.is_a?(CallInstruction)
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return false unless codes.last.opcode == :call
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codes.dup.reverse.find{ |c| c.is_a? StackInstruction }
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end
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# Code interface follows. Note position is inheitted as is from Code
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# length of the block is the length of it's codes, plus any next block (ie no branch follower)
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# Note, the next is in effect a linked list and as such may have many blocks behind it.
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def length
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cods = @codes.inject(0) {| sum , item | sum + item.length}
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cods += @next.length if @next
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cods
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end
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# to link we link the codes (instructions), plus any next in line block (non- branched)
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def link_at pos , context
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super(pos , context)
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@codes.each do |code|
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code.link_at(pos , context)
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pos += code.length
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end
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if @next
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@next.link_at pos , context
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pos += @next.length
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end
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pos
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end
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# assemble the codes (instructions) and any next in line block
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def assemble(io)
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@codes.each do |obj|
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obj.assemble io
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end
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@next.assemble(io) if @next
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end
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private
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# helper for determining reachable blocks
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def add_next ret
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return if @next.nil?
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return if ret.include? @next
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ret << @next
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@next.reachable ret
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end
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# helper for determining reachable blocks
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def add_branch ret
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return if @branch.nil?
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return if ret.include? @branch
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ret << @branch
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@branch.reachable ret
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end
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end
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end |