334 lines
9.6 KiB
Ruby
334 lines
9.6 KiB
Ruby
module Risc
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# An interpreter for the register level. As the register machine is a simple model,
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# interpreting it is not so terribly difficult.
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#
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# There is a certain amount of basic machinery to fetch and execute the next instruction
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# (as a cpu would), and then there is a method for each instruction. Eg an instruction SlotToReg
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# will be executed by method execute_SlotToReg
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#
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# The Interpreter (a bit like a cpu) has a state flag, a current instruction and registers
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# We collect the stdout (as a hack not to interpret the OS)
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#
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class Interpreter
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# fire events for changed pc and register contents
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include Util::Eventable
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include Util::Logging
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log_level :debug
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attr_reader :instruction , :clock # current instruction or pc
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attr_reader :registers # the registers, 16 (a hash, sym -> contents)
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attr_reader :stdout, :state , :flags # somewhat like the lags on a cpu, hash sym => bool (zero .. . )
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#start in state :stopped and set registers to unknown
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def initialize()
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@stdout , @clock , @state = "", 0 , :stopped
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@registers = {}
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@flags = { :zero => false , :plus => false ,
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:minus => false , :overflow => false }
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(0...12).each do |reg|
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set_register "r#{reg}".to_sym , "r#{reg}:unknown"
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end
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end
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def start_machine
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initialize
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init = Risc.machine.cpu_init
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set_state(:running)
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set_pc( Position.get(init).at )
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end
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def set_state( state )
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old = @state
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return if state == old
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@state = state
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trigger(:state_changed , old , state )
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end
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def set_pc( pos )
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raise "Not int #{pos}" unless pos.is_a? Numeric
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position = Position.at(pos)
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log.debug "Setting Position #{pos}"
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if position.is_a?(Position::CodePosition)
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return set_pc(position.at + 12)
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end
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raise "not instruction position #{position}-#{position.class}-#{position.object.class}" unless position.is_a?(Position::InstructionPosition)
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set_instruction( position.instruction)
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@clock = position.at
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end
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def set_instruction( instruction )
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raise "set to same instruction #{instruction}:#{instruction.class}" if @instruction == instruction
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log.debug "Setting Instruction #{instruction}"
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old = @instruction
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@instruction = instruction
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trigger(:instruction_changed, old , instruction)
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set_state( :exited ) unless instruction
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end
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def get_register( reg )
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reg = reg.symbol if reg.is_a? Risc::RiscValue
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raise "Not a register #{reg}" unless Risc::RiscValue.look_like_reg(reg)
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@registers[reg]
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end
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def set_register( reg , val )
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old = get_register( reg ) # also ensures format
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if val.is_a? Fixnum
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@flags[:zero] = (val == 0)
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@flags[:plus] = (val >= 0)
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@flags[:minus] = (val < 0)
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log.debug "Set_flags #{val} :#{@flags.inspect}"
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else
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@flags[:zero] = @flags[:plus] = true
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@flags[:minus] = false
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end
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return if old === val
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reg = reg.symbol if reg.is_a? Risc::RiscValue
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val = Parfait.object_space.nil_object if val.nil? #because that's what real code has
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@registers[reg] = val
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trigger(:register_changed, reg , old , val)
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end
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def tick
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unless @instruction
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log.debug "No Instruction , No Tick"
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return @clock
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end
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name = @instruction.class.name.split("::").last
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log.debug "#{@clock.to_s}: #{@instruction.to_s}"
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fetch = send "execute_#{name}"
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log.debug register_dump
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if fetch
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clock = @clock + @instruction.byte_length
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set_pc(clock)
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else
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log.debug "No Fetch"
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end
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@clock
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end
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# Instruction interpretation starts here
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def execute_DynamicJump
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method = get_register(@instruction.register)
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set_instruction( method.risc_instructions )
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false
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end
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def execute_Branch
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label = @instruction.label
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set_pc Position.get(label).at
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false
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end
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def execute_IsZero
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@flags[:zero] ? execute_Branch : true
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end
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def execute_IsNotZero
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@flags[:zero] ? true : execute_Branch
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end
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def execute_IsPlus
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@flags[:plus] ? execute_Branch : true
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end
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def execute_IsMinus
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@flags[:minus] ? execute_Branch : true
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end
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def execute_LoadConstant
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to = @instruction.register
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value = @instruction.constant
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value = value.value if value.is_a?(Mom::Constant)
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set_register( to , value )
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true
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end
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alias :execute_LoadData :execute_LoadConstant
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def execute_SlotToReg
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object = get_register( @instruction.array )
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if( @instruction.index.is_a?(Numeric) )
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index = @instruction.index
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else
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index = get_register(@instruction.index)
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end
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case object
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when Symbol
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raise "Must convert symbol to word:#{object}" unless( index == 2 )
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value = object.to_s.length
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when nil
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raise "error #{@instruction} retrieves nil"
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else
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value = object.get_internal_word( index )
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end
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log.debug "#{@instruction} == #{object}(#{object.class}) (#{value}|#{index})"
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set_register( @instruction.register , value )
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true
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end
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def execute_RegToSlot
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value = get_register( @instruction.register )
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object = get_register( @instruction.array )
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if( @instruction.index.is_a?(Numeric) )
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index = @instruction.index
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else
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index = get_register(@instruction.index)
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end
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object.set_internal_word( index , value )
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trigger(:object_changed, @instruction.array , index)
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true
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end
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def execute_ByteToReg
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object = get_register( @instruction.array )
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if( @instruction.index.is_a?(Numeric) )
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index = @instruction.index
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else
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index = get_register(@instruction.index)
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end
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raise "Unsupported action, must convert symbol to word:#{object}" if object.is_a?(Symbol)
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value = object.get_char( index )
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#value = value.object_id unless value.is_a? Fixnum
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set_register( @instruction.register , value )
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true
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end
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def execute_RegToByte
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value = get_register( @instruction.register )
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object = get_register( @instruction.array )
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if( @instruction.index.is_a?(Numeric) )
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index = @instruction.index
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else
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index = get_register(@instruction.index)
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end
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object.set_char( index , value )
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trigger(:object_changed, @instruction.array , index / 4 )
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true
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end
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def execute_Transfer
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value = get_register @instruction.from
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set_register @instruction.to , value
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true
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end
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def execute_FunctionCall
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meth = @instruction.method
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at = Position.get(meth.binary).at
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log.debug "Call to #{meth.name} at:#{at}"
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set_pc(at + 12)
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#set_instruction @instruction.method.risc_instructions
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false
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end
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def execute_FunctionReturn
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link = get_register( @instruction.register )
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log.debug "Return to #{link}"
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@instruction = link
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# we jump back to the call instruction. so it is as if the call never happened and we continue
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true
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end
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def execute_Syscall
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name = @instruction.name
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ret_value = 0
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case name
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when :putstring
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ret_value = handle_putstring
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when :exit
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set_instruction(nil)
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return false
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else
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raise "un-implemented syscall #{name}"
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end
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set_register( :r0 , ret_value ) # syscalls return into r0 , usually some int
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true
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end
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def handle_putstring
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str = get_register( :r1 ) # should test length, ie r2
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case str
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when Symbol
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@stdout += str.to_s
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return str.to_s.length
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when Parfait::Word
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@stdout += str.to_string
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return str.char_length
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else
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raise "NO string for putstring #{str.class}:#{str.object_id}" unless str.is_a?(Symbol)
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end
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end
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def execute_OperatorInstruction
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left = get_register(@instruction.left) || 0
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rr = @instruction.right
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right = get_register(rr) || 0
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@flags[:overflow] = false
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result = handle_operator(left,right)
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if( result > 2**32 )
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@flags[:overflow] = true
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result = result % 2**32
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else
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result = result.to_i
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end
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log.debug "#{@instruction} == #{result}(#{result.class}) (#{left}|#{right})"
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right = set_register(@instruction.left , result)
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true
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end
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def make_op_arg(arg)
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case arg
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when Integer
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arg
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when Parfait::Word
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arg.to_string.to_sym.object_id
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when String
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arg.to_sym.object_id
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when Symbol
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arg.object_id
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when Parfait::Object
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arg.object_id
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else
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raise "Op arg #{arg}:#{arg.class}"
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end
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end
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def handle_operator(left, right)
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left = make_op_arg(left)
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right = make_op_arg(right)
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case @instruction.operator
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when :+
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left + right
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when :-
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if( left.is_a?(String) or right.is_a?(String))
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left == right ? 0 : 1 #for opal, and exception
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else
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left - right
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end
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when :>>
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left / (2**right)
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when :<<
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left * (2**right)
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when :*
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left * right
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when :&
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left & right
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when :|
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left | right
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else
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raise "unimplemented '#{@instruction.operator}' #{@instruction}"
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end
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end
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def register_dump
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(0..7).collect do |reg|
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value = @registers["r#{reg}".to_sym]
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"#{reg}-" +
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case value
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when String
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value[0..10]
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else
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value.class.name.split("::").last
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end
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end.join("|")
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end
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end
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end
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