70 lines
2.2 KiB
Ruby
70 lines
2.2 KiB
Ruby
module Register
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# GetSlot moves data into a register from memory.
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# SetSlot moves data into memory from a register.
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# Both use a base memory (a register)
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# While the virtual machine has only one instruction (Set) to move data between slots,
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# the register has two, namely GetSlot and SetSlot
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#
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# This is because that is what cpu's can do. In programming terms this would be accessing
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# an element in an array, in the case of GetSlot setting the value in the array.
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# btw: to move data between registers, use RegisterTransfer
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class GetSlot < Instruction
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# If you had a c array and index offset
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# the instruction would do register = array[index]
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# The arguments are in the order that makes sense for the Instruciton name
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# So GetSlot means the slot (array and index) moves to the register (last argument)
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def initialize source , array , index , register
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super(source)
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@array = array
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@index = index
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@register = register
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raise "not integer #{index}" unless index.is_a? Numeric
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raise "Not register #{register}" unless Register::RegisterValue.look_like_reg(register)
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raise "Not register #{array}" unless Register::RegisterValue.look_like_reg(array)
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end
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attr_accessor :array , :index , :register
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def to_s
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"GetSlot: #{array} [#{index}] -> #{register}"
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end
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end
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# Produce a GetSlot instruction.
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# Array and to are registers or symbols that can be transformed to a register by resolve_to_register
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# index resolves with resolve_index.
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def self.get_slot source , array , index , to
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index = resolve_index( array , index)
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array = resolve_to_register array
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to = resolve_to_register to
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GetSlot.new( source , array , index , to)
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end
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def self.get_slot_to source , slot , to
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array = nil
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index = nil
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case slot
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when Virtual::Self
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array = :message
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index = :receiver
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when Virtual::Return
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array = :message
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index = :return_value
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when Virtual::FrameSlot
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array = :frame
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index = slot.index
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when Virtual::ArgSlot
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array = :message
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index = slot.index
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else
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raise "not done #{slot}"
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end
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get_slot( source , array , index , to)
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end
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end
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