SPIM machine description level 1
--------------------------------

These  machine descriptions  have  been prepared  by Sameera  Deshpande 
(sameera@cse.iitb.ac.in)   for   the    Workshop   on   GCC   Internals 
(www.cse.iitb.ac.in/~uday/gcc-workshop) conducted by CFDVS and Dept. of 
CSE, IIT Bombay, during 18,19, and 20 June 2007.                        


Level 1  allows supports integer  variables (both local and  global) and
assignment  statements.  The  expression can  have  addition  operation.
Functions may return an integer value.

We  list the  changes required  in  the machine  descriptions along  the
following headINGS. Many of the changes involve replacing function stubs
more complete function.

A. Memory Layout

       No changes.

B. Supported Instructions

        Now we need to support:

  	. loads and stores
  	. addition

C. Registers

  Now we need to ensure that if constant 0 appears on the right hand side,
  register $zero is used for the purpose.

D. Addressing Modes

        All  possible  addressing  modes  are supported  for  the  above
        instruction. This  does not require  any change because  it gets
        specified as a part of the instructions.

E. Activation Record Conventions

       No change.

F. Assembly output format

       Here we need to output global declarations. Since a variable name
       may conflict with  a reserved word in the assembly,  we prefix an
       "_" to each variable name.