59 lines
1.6 KiB
Ruby
59 lines
1.6 KiB
Ruby
require "asm/instruction"
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module Asm
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# ADDRESSING MODE 4
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class StackInstruction < Instruction
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def initialize(opcode , args)
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super(opcode,args)
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@update_status_flag= 0
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@rn = reg "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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@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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end
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attr_accessor :pre_post_index, :up_down,
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:update_status_flag, :write_base, :is_pop, :rn
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def assemble(io)
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build
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instuction_class = 0b10 # OPC_STACK
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cond = @cond.is_a?(Symbol) ? COND_CODES[@cond] : @cond
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rn = reg "sp" # sp register
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#assemble of old
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val = operand
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val |= (rn.bits << 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 |= (update_status_flag << 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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if (args.is_a?(Array))
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@operand = 0
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args.each do |reg |
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@operand |= (1 << reg.bits)
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end
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else
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raise Asm::AssemblyError.new("invalid operand argument #{args.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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