bunch of method extraction on instructions

lib/arm/instructions/stack_instruction.rb

@@ -12,45 +12,21 @@ module Arm
       @attributes[:update_status] = 0 if @attributes[:update_status] == nil
       @attributes[:condition_code] = :al if @attributes[:condition_code] == nil
       @attributes[:opcode] = attributes[:opcode]
-      @operand = 0
-
-#      @attributes[:update_status]= 0
-      @rn = :r0 # register zero = zero bit pattern
-      # downward growing, decrement before memory access
-      # official ARM style stack as used by gas
+      @rn = :sp # sp register
     end
 
+    # don't overwrite instance variables, to make assembly repeatable
     def assemble(io)
-      # don't overwrite instance variables, to make assembly repeatable
-      operand = @operand
-
-      if (@first.is_a?(Array))
-        operand = 0
-        @first.each do |r|
-          raise "nil register in push, index #{r}- #{inspect}" if r.nil?
-          operand = operand | (1 << reg_code(r))
-        end
-      else
-        raise "invalid operand argument #{inspect}"
+      operand = 0
+      raise "invalid operand argument #{inspect}" unless (@first.is_a?(Array))
+      @first.each do |r|
+        raise "nil register in push, index #{r}- #{inspect}" if r.nil?
+        operand = operand | (1 << reg_code(r))
       end
-      write_base = 1
-      if (opcode == :push)
-        pre_post_index = 1
-        up_down = 0
-        is_pop = 0
-      else  #pop
-        pre_post_index = 0
-        up_down = 1
-        is_pop = 1
-      end
-      instuction_class = 0b10 # OPC_STACK
-      cond = @attributes[:condition_code].is_a?(Symbol) ?  COND_CODES[@attributes[:condition_code]]   : @attributes[:condition_code]
-      @rn = :sp # sp register
-      #assemble of old
       val = operand
       val = val | (reg_code(@rn) <<             16)
       val = val | (is_pop <<              16 + 4) #20
-      val = val | (write_base <<          16 + 4 + 1)
+      val = val | (1          <<          16 + 4 + 1)
       val = val | (@attributes[:update_status] <<  16 + 4 + 1 + 1)
       val = val | (up_down <<             16 + 4 + 1 + 1 + 1)
       val = val | (pre_post_index <<      16 + 4 + 1 + 1 + 1 + 1)#24
@@ -59,9 +35,29 @@ module Arm
       io.write_uint32 val
     end
 
+    def cond
+      if @attributes[:condition_code].is_a?(Symbol)
+        COND_CODES[@attributes[:condition_code]]
+      else
+        @attributes[:condition_code]
+      end
+    end
+    def instuction_class
+      0b10 # OPC_STACK
+    end
+    def up_down
+      (opcode == :push) ?  0 :  1
+    end
+    alias :is_pop :up_down
+
+    def pre_post_index
+      (opcode == :push) ?  1 :  0
+    end
+
     def regs
       @first
     end
+
     def to_s
       "#{opcode} [#{@first.join(',') }] #{super}"
     end