71 lines
2.1 KiB
Ruby
71 lines
2.1 KiB
Ruby
require "vm/instruction"
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require_relative "constants"
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module Arm
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# ADDRESSING MODE 4
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class StackInstruction < Vm::StackInstruction
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include Arm::Constants
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# arm intrucioons are pretty sensible, and always 4 bytes (thumb not supported)
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def length
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4
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end
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def initialize(first , attributes)
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super(first , attributes)
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@attributes[:update_status] = 0 if @attributes[:update_status] == nil
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@attributes[:condition_code] = :al if @attributes[:condition_code] == nil
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@attributes[:opcode] = attributes[:opcode]
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@operand = 0
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@attributes[:update_status]= 0
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@rn = :r0 # register zero = zero bit pattern
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# downward growing, decrement before memory access
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# official ARM style stack as used by gas
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end
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def assemble(io)
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build
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write_base = 1
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if (opcode == :push)
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pre_post_index = 1
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up_down = 0
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is_pop = 0
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else #pop
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pre_post_index = 0
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up_down = 1
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is_pop = 1
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end
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instuction_class = 0b10 # OPC_STACK
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cond = @attributes[:condition_code].is_a?(Symbol) ? COND_CODES[@attributes[:condition_code]] : @attributes[:condition_code]
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@rn = :sp # sp register
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#assemble of old
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val = @operand
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val |= (reg_code(@rn) << 16)
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val |= (is_pop << 16+4) #20
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val |= (write_base << 16+4+ 1)
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val |= (@attributes[:update_status] << 16+4+ 1+1)
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val |= (up_down << 16+4+ 1+1+1)
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val |= (pre_post_index << 16+4+ 1+1+1+1)#24
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val |= (instuction_class << 16+4+ 1+1+1+1 +2)
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val |= (cond << 16+4+ 1+1+1+1 +2+2)
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io.write_uint32 val
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end
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private
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# Build representation for source value
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def build
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regs = @first
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if (regs.is_a?(Array))
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@operand = 0
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regs.each_with_index do |reg , index|
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raise "nil register in push, index #{index}" if reg == nil
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@operand |= (1 << reg_code(reg))
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end
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else
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raise "invalid operand argument #{regs.inspect} #{inspect}"
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end
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end
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end
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end
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