clean up Get/SetSlot

document and make arguments consistent

lib/register/instructions/get_slot.rb

@@ -1,16 +1,28 @@
 module Register
-  # offset memory get access
-  # so the value to be set must be given as the first register
-  # the second argument holds the base address
-  # and the third a possible (small) offset into the "object"
+
+  # GetSlot moves data into a register from memory.
+  # SetSlot moves data into memory from a register.
+  # Both use a base memory (a register)
+
+  # While the virtual machine has only one instruction (Set) to move data between slots,
+  # the register has two, namely GetSlot and SetSlot
   #
-  # if for example the value is pointed to by a register, a VariableGet (load) is needed first
+  # This is because that is what cpu's can do. In programming terms this would be accessing
+  #  an element in an array, in the case of GetSlot setting the value in the array.
+
+  # btw: to move data between registers, use RegisterTransfer
+
   class GetSlot < Instruction
-    def initialize value , reference , index = 0
-      @value = value
-      @reference = reference
+
+    # If you had a c array and index offset
+    # the instruction would do register = array[index]
+    # The arguments are in the order that makes sense for the Instruciton name
+    # So GetSlot means the slot (array and index) moves to the register (last argument)
+    def initialize array , index , register
+      @register = register
+      @array = array
       @index = index
     end
-    attr_accessor :value , :reference , :index
+    attr_accessor :register , :array , :index
   end
 end

lib/register/instructions/register_transfer.rb

@@ -1,6 +1,13 @@
 module Register
 
-  #transfer the constents of one register to another. possibly called move in some cpus
+  # transfer the constents of one register to another.
+  # possibly called move in some cpus
+
+  # There are other instructions to move data from / to memory, namely GetSlot and SetSlot
+
+  # Get/Set Slot move data around in vm objects, but transfer moves the objects (in the machine)
+  #
+  # Also it is used for moving temorary data
   
   class RegisterTransfer < Instruction
     def initialize from , to

lib/register/instructions/set_slot.rb

@@ -1,16 +1,27 @@
 module Register
-  # offset memory set access
-  # so the value must be given as the first register
-  # the second argument holds the base address
-  # and the third a possible (small) offset into the "object"
+
+  # SetSlot moves data into memory from a register.
+  # GetSlot moves data into a register from memory.
+  # Both use a base memory (a register)
+
+  # While the virtual machine has only one instruction (Set) to move data between slots,
+  # the register has two, namely GetSlot and SetSlot
   #
-  # if for example the value is pointed to by a register, a VariableGet (load) is needed first
+  # This is because that is what cpu's can do. In programming terms this would be accessing
+  #  an element in an array, in the case of SetSlot setting the register in the array.
+
+  # btw: to move data between registers, use RegisterTransfer
+
   class SetSlot < Instruction
-    def initialize value , reference , index = 0
-      @value = value
-      @reference = reference
+
+    # If you had a c array and index offset
+    # the instruction would do array[index] = register
+    # So SGetSlot means the register (first argument) moves to the slot (array and index)
+    def initialize register , array , index
+      @register = register
+      @array = array
       @index = index
     end
-    attr_accessor :value , :reference , :index
+    attr_accessor :register , :array , :index
   end
 end

lib/register/passes/frame_implementation.rb

@@ -39,11 +39,11 @@ module Register
         ind = Parfait::Space.object_space.get_layout().index_of( kind )
         raise "index not found for #{kind}.#{kind.class}" unless ind
         # load the frame/message from space by index
-        new_codes << GetSlot.new( frame_tmp , space_tmp , 5 )
+        new_codes << GetSlot.new( space_tmp , 5 , frame_tmp )
         # save the frame in real frame register
         new_codes << RegisterTransfer.new( RegisterReference.frame_reg , frame_tmp )
         # get the next_frame
-        new_codes << GetSlot.new( frame_tmp , frame_tmp , 2 ) # 2 index of next_frame
+        new_codes << GetSlot.new( frame_tmp , 2 , frame_tmp) # 2 index of next_frame
         # save next frame into space
         new_codes << SetSlot.new( frame_tmp , space_tmp , ind)
         block.replace(code , new_codes )

lib/register/passes/return_implementation.rb

@@ -8,10 +8,10 @@ module Register
         # move the current message to new_message
         new_codes << RegisterTransfer.new( slot::MESSAGE_REGISTER , slot::NEW_MESSAGE_REGISTER )
         # and restore the message from saved value in new_message
-        new_codes << GetSlot.new( slot::MESSAGE_REGISTER , slot::NEW_MESSAGE_REGISTER , Virtual::MESSAGE_CALLER )
+        new_codes << GetSlot.new( slot::NEW_MESSAGE_REGISTER , Virtual::MESSAGE_CALLER , slot::MESSAGE_REGISTER)
         # "roll out" self and frame into their registers
-        new_codes << GetSlot.new( slot::SELF_REGISTER ,slot::MESSAGE_REGISTER , Virtual::MESSAGE_SELF )
-        new_codes << GetSlot.new( slot::FRAME_REGISTER ,slot::MESSAGE_REGISTER , Virtual::MESSAGE_FRAME )
+        new_codes << GetSlot.new( slot::MESSAGE_REGISTER , Virtual::MESSAGE_SELF , slot::SELF_REGISTER )
+        new_codes << GetSlot.new( slot::MESSAGE_REGISTER , Virtual::MESSAGE_FRAME , slot::FRAME_REGISTER )
         #load the return address into pc, affecting return. (other cpus have commands for this, but not arm)
         new_codes << FunctionReturn.new( slot::MESSAGE_REGISTER , Virtual::MESSAGE_RETURN_ADDRESS )
         block.replace(code , new_codes )

lib/register/passes/set_implementation.rb

@@ -35,7 +35,7 @@ module Register
         if( code.from.is_a?(Parfait::Value) or code.from.is_a?(Symbol))
           move1 = LoadConstant.new( tmp , code.from )
         else # while otherwise we "load"
-          move1 = GetSlot.new( tmp , code.from.reg , code.from.index )
+          move1 = GetSlot.new( code.from.reg , code.from.index , tmp )
         end
         move2 = SetSlot.new( tmp , to , code.to.index )
         block.replace(code , [move1,move2] )