57 lines
2.4 KiB
Ruby
57 lines
2.4 KiB
Ruby
module SlotMachine
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# SlotLoad is for moving data into a slot, either from another slot, or constant
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# A Slot is basically an instance variable, but it must be of known type
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#
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# The value loaded (the right hand side) can be a constant (SlotMachine::Constant) or come from
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# another Slot (Slot)
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#
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# The Slot on the left hand side is always a Slot.
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# The only known object (*) for the left side is the current message, which is a bit like
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# the oo version of a Stack (Stack Register, Frame Pointer, ..)
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# (* off course all class objects are global, and so they are allowed too)
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#
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# A maybe not immediately obvious corrolar of this design is the total absence of
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# general external instance variable accessors. Ie only inside an object's functions
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# can a method access instance variables, because only inside the method is the type
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# guaranteed.
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# From the outside a send is neccessary, both for get and set, (which goes through the method
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# resolution and guarantees the correct method for a type), in other words perfect data hiding.
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#
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# @left: A Slot, or an array that can be passed to the constructor of the
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# Slot (see there)
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#
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# @right: A Slot with slots or a SlotMachine::Constant
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# original_source: optinally another slot_machine instruction that will be passed down
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# to created risc instructions. (Because SlotLoad is often used internally)
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class SlotLoad < Instruction
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attr_reader :left , :right , :original_source
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def initialize(source , left , right, original_source = nil)
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super(source)
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@left , @right = left , right
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@left = Slotted.for(@left.shift , @left) if @left.is_a? Array
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@right = Slotted.for(@right.shift , @right) if @right.is_a? Array
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raise "right not SlotMachine, #{@right.to_s}" unless @right.is_a?( Slotted )
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raise "left not SlotMachine, #{@left.to_s}" unless @left.is_a?( Slotted )
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@original_source = original_source || self
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end
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def to_s
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"SlotLoad #{right} -> #{left}"
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end
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# resolve the SlotLoad to the respective risc Instructions.
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# calls sym_to_risc for most (symbols), and ConstantLoad for CacheEntry
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# after loading the right into register
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def to_risc(compiler)
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const_reg = @right.to_register(compiler , original_source)
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@left.reduce_and_load(const_reg , compiler , original_source )
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compiler.reset_regs
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end
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end
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end
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