fix the exit sequence

was returning wrong register (1, not 0)
also saving the message for test, which changes order as the return value destroys the message

lib/arm/translator.rb

@@ -146,15 +146,16 @@ module Arm
     end
 
     def exit( int_code )
-      codes =  ArmMachine.ldr( :r0 ,  :r0 , arm_index(Risc.resolve_to_index(:Message , :return_value)) )
-      syscall int_code , codes
+      codes = ArmMachine.mov( :r7 ,  int_code )
+      codes.append ArmMachine.swi( 0 )
+      codes
     end
 
     private
 
     # syscall is always triggered by swi(0)
     # The actual code (ie the index of the kernel function) is in r7
-    def syscall int_code , codes
+    def syscall( int_code , codes)
       codes.append ArmMachine.mov( :r7 ,  int_code )
       codes.append ArmMachine.swi( 0 )
       codes

lib/risc/builtin/object.rb

@@ -78,10 +78,10 @@ module Risc
         # a sort of inline version of exit method.
         # Used by exit and __init__ (so it doesn't have to call it)
         def exit_sequence(builder)
-          r1 = RiscValue.new( :r1 , :Integer )
-          builder.add_slot_to_reg "get return" , :message , :return_value , r1
-          builder.reduce_int( "reduce return" , r1)
-          emit_syscall( builder  , :exit )
+          save_message( builder )
+          builder.add_slot_to_reg "get return" , :message , :return_value , :message
+          builder.reduce_int( "reduce return" , :message)
+          builder.add_code Syscall.new("emit_syscall(exit)", :exit )
         end
 
         def exit( context )