Code cleanup.

src/optimizer.py

-def equal_mov(statement):
+def equal_mov(s):
     '''Check for useless move operations.'''
-    stype, name, args = statement
-    return stype == 'command' and name == 'move' \
-        and args['args'][0] == args['args'][1]
-    
-def empty_shift(statement):
+    return s.is_command() and s.name == 'move' and s[0] == s[1]
+
+def empty_shift(s):
     '''Check for useless shift operations.'''
-    shift_types = ['sll', 'sla', 'srl', 'sra']
-    stype, name, args = statement
-    return stype == 'command' and name in shift_types and \
-        args['args'][0] == args['args'][1] and args['args'][2] == 0
-        
+    return s.is_shift() and s[0] == s[1] and s[2] == 0
+
 def optimize_branch_jump_label(statements):
     '''Optimize jumps after branches.'''
     out_statements = []
-    
+
     for i in xrange(len(statements)):
         if i + 3 > len(statements):
             out_statements.append(statements[i])
             continue
-        
+
         stype, name, args = statements[i]
         stype2, name2, args2 = statements[i + 1]
         stype3, name3, args3 = statements[i + 2]
-        
+
         if stype == 'command' and name == 'beq' and \
            stype2 == 'command' and name2 in ['j', 'jal'] and \
            stype3 == 'label' and name3 == args['args'][2]:
@@ -33,45 +28,43 @@ def optimize_branch_jump_label(statements):
             i += 3
         else:
             out_statements.append(statements[i])
-            
+
     return out_statements
-            
-    
 
 def optimize_global(statements):
     '''Optimize one-line statements in entire code.'''
     statements = optimize_branch_jump_label(statements)
-    
+
     return filter(lambda s: not equal_mov(s) and not empty_shift(s), statements)
 
 def optimize_blocks(blocks):
     '''Call the optimizer for each basic block. Do this several times until
     no more optimizations are achieved.'''
     changed = True
-    
+
     while changed:
         changed = False
         optimized = []
-        
+
         for block in blocks:
             block_changed, b = optimize_block(block)
             optimized.append(b)
-            
+
             if block_changed:
                 changed = True
-            
+
         blocks = optimized
-    
+
     return reduce(lambda a, b: a + b, blocks, [])
 
 def optimize_block(statements):
     '''Optimize a basic block.'''
     changed = False
     output_statements = []
-    
+
     for statement in statements:
         new_statement = statement
-        
+
         output_statements.append(new_statement)
 
     return changed, output_statements