99 lines
2.4 KiB
Ruby
99 lines
2.4 KiB
Ruby
module Vm
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# Values represent the information as it is processed. Different subclasses for different types,
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# each type with different operations.
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# The oprerations on values is what makes a machine do things.
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# For compilation, values are moved to the machines registers and the methods (on values) map
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# to machine instructions
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# Values are immutable! (that's why they are called values)
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# Operations on values _always_ produce new values (conceptionally)
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# Values are a way to reason about (create/validate) instructions.
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# In fact a linked lists of values is created by invoking instructions
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# the linked list goes from value to instruction to value, backwards
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# Word Values are what fits in a register. Derived classes
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# Float, Reference , Integer(s) must fit the same registers
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class Value
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def bit_size
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8 * byte_size
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end
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def byte_size
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raise "abstract method called #{self.inspect}"
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end
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# since we convert ast to values in conversion, value itself is responsible for compiling itself
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# Compile must return a value, usually used in the next level up
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def compile(context)
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raise "abstract method called #{self.inspect}"
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end
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end
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class Word < Value
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def load reg
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Machine.instance.word_load self , reg
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end
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def compile context
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#nothing to do here
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end
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end
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class Unsigned < Word
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def plus unsigned
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Machine.instance.unsigned_plus self , unsigned
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end
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end
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class Signed < Word
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def plus signed
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Machine.instance.signed_plus self , signed
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end
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end
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class Float < Word
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end
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class Reference < Word
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end
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class StringValue < Value
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def initialize string
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@string = string
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end
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def at pos
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@pos = pos
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end
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def length
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@string.length + 3
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end
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def compile context
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#nothing to do here
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end
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attr_reader :string
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end
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class MemoryReference < Reference
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end
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class ObjectReference < Reference
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def initialize obj
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@object = obj
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end
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attr_reader :object
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def compile context
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if object.is_a? StringValue
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context.program.add_object object
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else
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#TODO define object layout more generally and let objects lay themselves out
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# as it is the program does this (in the objectwriter/stringtable)
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un.done
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end
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end
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end
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end
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