split create_binary into two phases

Which gives instructions a chance to check everything
and in Arms case check the constant loads/ instruction adding
So that during assembly no more change happens (and we don't have to reassemble)

lib/arm/instructions/instruction.rb

@@ -1,4 +1,6 @@
 require "util/list"
+require "util/dev_null"
+
 module Arm
   # Arm instruction base class
   # Mostly linked list functionality that all instructions have
@@ -21,6 +23,13 @@ module Arm
       ret
     end
 
+    # precheck that everything is ok, before asembly
+    # in arm, we use the oppertunity to assemble to dev_null, so any
+    # additions are done _before_ assemnly
+    def precheck
+      assemble(Util::DevNull.new)
+    end
+
     def insert(instruction)
       ret = super
       Risc::Position.get(self).trigger_inserted if Risc::Position.set?(self)

lib/risc/instruction.rb

@@ -37,6 +37,10 @@ module Risc
       ret
     end
 
+    # just part of the protocol, noop in this case
+    def precheck
+    end
+
     def to_cpu( translator )
       translator.translate( self )
     end

lib/risc/machine.rb

@@ -22,6 +22,7 @@ module Risc
       @constants = []
       @next_address = nil
     end
+    
     attr_reader  :constants , :cpu_init
     attr_reader  :booted , :translated
     attr_reader  :platform
@@ -143,12 +144,23 @@ module Risc
     # constant loads into one instruction.
     #
     def create_binary
-      object_positions.keys.each do |method|
-        next unless method.is_a? Parfait::TypedMethod
+      methods = object_positions.keys.find_all{|obj| obj.is_a? Parfait::TypedMethod}
+      prerun(methods)
+      assemble(methods)
+      log.debug "BinaryInit #{cpu_init.object_id.to_s(16)}"
+    end
+
+    def prerun(methods)
+      methods.each do |method|
+        method.cpu_instructions.each {|i| i.precheck }
+      end
+    end
+
+    def assemble(methods)
+      methods.each do |method|
         writer = BinaryWriter.new(method.binary)
         writer.assemble(method.cpu_instructions)
       end
-      log.debug "BinaryInit #{cpu_init.object_id.to_s(16)}"
     end
 
     def boot

lib/util/dev_null.rb

@@ -0,0 +1,7 @@
+module Util
+  # A class that does not write, or swallows all incoming data
+  # Used in Arm to do a dry run (and in testing, where it was born)
+  class DevNull
+    def write_unsigned_int_32( _ );end
+  end
+end

test/risc/helper.rb

@@ -1,4 +1 @@
 require_relative "../helper"
-class DevNull
-  def write_unsigned_int_32( _ );end
-end

test/risc/test_interpreter_platform.rb

@@ -57,7 +57,7 @@ module Risc
       @machine.object_positions.each do | method , position|
         next unless method.is_a? Parfait::TypedMethod
         method.cpu_instructions.each do |ins|
-          ins.assemble(DevNull.new)
+          ins.assemble(Util::DevNull.new)
         end
       end
     end

test/risc/test_translator.rb

@@ -33,7 +33,7 @@ module Risc
       @machine.object_positions.keys.each do |method|
         next unless method.is_a? Parfait::TypedMethod
         method.cpu_instructions.each do |ins|
-          ins.assemble(DevNull.new)
+          ins.assemble(Util::DevNull.new)
         end
       end
     end