Make some key functions elidable

Taken from krono/PySOM@9ae38c02b87c20e5e3df865be4d542238d95f335 and krono/PySOM@9af3f0be15d662c80c9f20a6ab337c669ec0d677
Signed-off-by: Stefan Marr <git@stefan-marr.de>

src/som/interpreter/bytecodes.py

 from rpython.rlib.unroll import unrolling_iterable
+from rpython.rlib import jit
 
 class Bytecodes(object):
     
@@ -58,12 +59,15 @@ class Bytecodes(object):
                               0,                                # return_local    
                               0 ]                               # return_non_local
 
-    
+@jit.elidable
 def bytecode_length(bytecode):
+    assert bytecode >= 0 and bytecode <= len(Bytecodes._bytecode_length)
     return Bytecodes._bytecode_length[bytecode]
 
 
+@jit.elidable
 def bytecode_stack_effect(bytecode, number_of_arguments_of_message_send = 0):
+    assert bytecode >= 0 and bytecode < len(Bytecodes._bytecode_stack_effect)
     if bytecode_stack_effect_depends_on_send(bytecode):
         return -number_of_arguments_of_message_send + 1 # +1 in order to account for the return value
     else:
@@ -71,17 +75,13 @@ def bytecode_stack_effect(bytecode, number_of_arguments_of_message_send = 0):
 
 
 def bytecode_stack_effect_depends_on_send(bytecode):
-    assert bytecode >= 0 and bytecode <= Bytecodes._num_bytecodes
+    assert bytecode >= 0 and bytecode < len(Bytecodes._bytecode_stack_effect)
     return Bytecodes._bytecode_stack_effect[bytecode] == Bytecodes._stack_effect_depends_on_message
 
 
+@jit.elidable
 def bytecode_as_str(bytecode):
-    if not isinstance(bytecode, int):
-        raise ValueError('bytecode is expected to be an integer.')
-
-    if bytecode > len(_bytecode_names):
-        raise ValueError('No Bytecode defined for the value %d.' % bytecode)
-    else:
+    assert bytecode >= 0 and bytecode < len(_bytecode_names)
     return _bytecode_names[bytecode]
 
 def _sorted_bytecode_names(cls):

src/som/vmobjects/method.py

 from __future__ import absolute_import
 
+from rpython.rlib import jit
+
 from som.vmobjects.array import Array
 
 class Method(Array):
@@ -40,7 +42,7 @@ class Method(Array):
         return True
   
     def get_number_of_locals(self):
-        # Get the number of locals (converted to a Java integer)
+        # Get the number of locals
         return self._number_of_locals
 
     def get_maximum_number_of_stack_elements(self):
@@ -86,8 +88,10 @@ class Method(Array):
         # Get the number of bytecodes in this method
         return len(self._bytecodes)
 
+    @jit.elidable
     def get_bytecode(self, index):
         # Get the bytecode at the given index
+        assert 0 <= index and index < len(self._bytecodes)
         return ord(self._bytecodes[index])
 
     def set_bytecode(self, index, value):
@@ -104,10 +108,14 @@ class Method(Array):
     def __str__(self):
         return "Method(" + self.get_holder().get_name().get_string() + ">>" + str(self.get_signature()) + ")"
 
+    @jit.elidable
     def get_inline_cache_class(self, bytecode_index):
+        assert 0 <= bytecode_index and bytecode_index < len(self._inline_cache_class)
         return self._inline_cache_class[bytecode_index]
 
+    @jit.elidable
     def get_inline_cache_invokable(self, bytecode_index):
+        assert 0 <= bytecode_index and bytecode_index < len(self._inline_cache_invokable)
         return self._inline_cache_invokable[bytecode_index]
 
     def set_inline_cache(self, bytecode_index, receiver_class, invokable):