43 lines
1.2 KiB
Ruby
43 lines
1.2 KiB
Ruby
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module Asm
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# ADDRESSING MODE 4 , Calling
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class CallInstruction < Instruction
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include Asm::InstructionTools
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def initialize(opcode , args)
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super(opcode,args)
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end
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def assemble(io, as)
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s = @update_status_flag? 1 : 0
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case opcode
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when :b, :bl
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arg = args[0]
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if arg.is_a? Label
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diff = arg.position - self.position - 8
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arg = NumLiteral.new(diff)
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end
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if (arg.is_a?(Asm::NumLiteral))
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jmp_val = arg.value >> 2
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packed = [jmp_val].pack('l')
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# signed 32-bit, condense to 24-bit
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# TODO add check that the value fits into 24 bits
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io << packed[0,3]
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else
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raise "else not coded #{arg.inspect}"
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end
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io.write_uint8 OPCODES[opcode] | (COND_CODES[@cond] << 4)
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when :swi
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arg = args[0]
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if (arg.is_a?(Asm::NumLiteral))
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packed = [arg.value].pack('L')[0,3]
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io << packed
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io.write_uint8 0b1111 | (COND_CODES[@cond] << 4)
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else
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raise Asm::AssemblyError.new("invalid operand argument expected literal not #{arg}")
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end
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end
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end
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end#class
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end
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