107 lines
3.4 KiB
Ruby
107 lines
3.4 KiB
Ruby
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require_relative "instruction"
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module Asm
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# ADDRESSING MODE 1
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# Logic ,Maths, Move and compare instructions (last three below)
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class LogicInstruction < Instruction
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def initialize(opcode , condition_code , update_status , args)
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super(opcode , condition_code , update_status , args)
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@rn = nil
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@i = 0
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@rd = args[0]
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end
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attr_accessor :i, :rn, :rd
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# Build representation for source value
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def build
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@rn = args[1]
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do_build args[2]
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end
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#(stays in subclases, while build is overriden to provide different arguments)
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def do_build(arg)
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if arg.is_a?(Asm::StringLiteral)
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# do pc relative addressing with the difference to the instuction
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# 8 is for the funny pipeline adjustment (ie oc pointing to fetch and not execute)
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arg = Asm::NumLiteral.new( arg.position - self.position - 8 )
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end
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if (arg.is_a?(Asm::NumLiteral))
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if (arg.value.fits_u8?)
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# no shifting needed
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@operand = arg.value
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@i = 1
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elsif (op_with_rot = calculate_u8_with_rr(arg))
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@operand = op_with_rot
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@i = 1
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else
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raise Asm::AssemblyError.new("cannot fit numeric literal argument in operand #{arg}")
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end
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elsif (arg.is_a?(Asm::Register))
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@operand = arg
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@i = 0
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elsif (arg.is_a?(Asm::Shift))
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rm_ref = arg.argument
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@i = 0
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shift_op = {'lsl' => 0b000, 'lsr' => 0b010, 'asr' => 0b100,
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'ror' => 0b110, 'rrx' => 0b110}[arg.type]
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if (arg.type == 'ror' and arg.value.nil?)
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# ror #0 == rrx
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raise Asm::AssemblyError.new('cannot rotate by zero', arg)
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end
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arg1 = arg.value
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if (arg1.is_a?(Asm::NumLiteral))
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if (arg1.value >= 32)
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raise Asm::AssemblyError.new('cannot shift by more than 31', arg1)
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end
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shift_imm = arg1.value
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elsif (arg1.is_a?(Asm::Register))
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shift_op val |= 0x1;
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shift_imm = arg1.number << 1
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elsif (arg.type == 'rrx')
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shift_imm = 0
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end
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@operand = rm_ref | (shift_op << 4) | (shift_imm << 4+3)
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else
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raise Asm::AssemblyError.new("invalid operand argument #{arg.inspect}")
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end
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end
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def assemble(io)
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build
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instuction_class = 0b00 # OPC_DATA_PROCESSING
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val = operand.is_a?(Register) ? operand.bits : operand
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val |= (rd.bits << 12)
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val |= (rn.bits << 12+4)
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val |= (update_status_flag << 12+4+4)#20
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val |= (op_bit_code << 12+4+4 +1)
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val |= (i << 12+4+4 +1+4)
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val |= (instuction_class << 12+4+4 +1+4+1)
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val |= (cond_bit_code << 12+4+4 +1+4+1+2)
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io.write_uint32 val
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end
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end
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class CompareInstruction < LogicInstruction
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def initialize(opcode , condition_code , update_status , args)
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super(opcode , condition_code , update_status , args)
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@update_status_flag = 1
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@rn = args[0]
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@rd = reg "r0"
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end
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def build
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do_build args[1]
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end
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end
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class MoveInstruction < LogicInstruction
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def initialize(opcode , condition_code , update_status , args)
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super(opcode , condition_code , update_status , args)
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@rn = reg "r0" # register zero = zero bit pattern
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end
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def build
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do_build args[1]
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end
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end
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end
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