[Python-Dev] Re: opcode performance measurements

[Skip Montanaro]

    SP> cases. How does it handle things like
    SP> import a.b
    SP> use a.b.x

    Jeremy> You're a smart guy, can you tell me?  :-).  Seriously, I haven't
    Jeremy> gotten that far.

My stuff does handle this, as long as the first name is global.  It just
gobbles up all LOAD_GLOBALS and any immediately following LOAD_ATTRs.  For
instance, this trivial function:

    def f():
       return distutils.core.setup

compiles to:

      0 LOAD_GLOBAL              0 (distutils)
      3 LOAD_ATTR                1 (core)
      6 LOAD_ATTR                2 (setup)
      9 RETURN_VALUE        
     10 LOAD_CONST               0 (None)
     13 RETURN_VALUE        

My TrackGlobalOptimizer class currently transforms this to

      0 SETUP_FINALLY           11 (to 14)
      3 TRACK_GLOBAL             3 (distutils.core.setup, distutils.core.setup)
      6 POP_BLOCK           
      7 LOAD_CONST               0 (None)
     10 LOAD_FAST                0 (distutils.core.setup)
     13 RETURN_VALUE        
>>   14 UNTRACK_GLOBAL           3 (distutils.core.setup, distutils.core.setup)
     17 END_FINALLY         
     18 LOAD_CONST               0 (None)
     21 RETURN_VALUE        

which is obviously not an improvement because distutils.core.setup is only
accessed once.  As people make more use of packages, such multiple attribute
loads might become more common.

Skip