move message to stack_pointer

changing a bunch of register names
some of which get names now

lib/risc/interpreter.rb

@@ -47,6 +47,14 @@ module Risc
       trigger(:state_changed , old , state )
     end
 
+    # return the name of the register  that the argument is mapped to
+    # this info is in the Platform object in the linker instance
+    # eg: syscall_1 maps to :r0 , and :message to :r13
+    # So as not to hardcode values (as used to )
+    def std_reg(name)
+      @linker.platform.assign_reg?(name)
+    end
+
     # set all flags to false
     def reset_flags
       @flags = {  :zero => false , :plus => false ,
@@ -258,7 +266,7 @@ module Risc
         set_instruction(nil)
         return false
       when :died
-        raise "Method #{@registers[:r1]} not found for #{@registers[:r0].receiver}"
+        raise "Method #{@registers[std_reg(:syscall_2)]} not found for #{@registers[std_reg(:syscall_2)]}"
       else
         raise "un-implemented syscall #{name}"
       end

lib/risc/platform.rb

@@ -20,7 +20,7 @@ module Risc
     # does not include :message
     # could be in interpreter and arm, but here for now
     def register_names
-      (1 ... 16).collect{|i| "r#{i}".to_sym }
+      (0 .. 12).collect{|i| "r#{i}".to_sym }
     end
 
     # return the Allocator for the platform
@@ -35,13 +35,13 @@ module Risc
     def assign_reg?(name)
       case name
       when :message
-        :r0
+        :r13
       when :syscall_1
         :r0
       when :syscall_2
         :r1
       when :saved_message
-        :r15
+        :r14
       else
         nil
       end