put the constant folding optimization into fast_compile

theano/compile/mode.py

@@ -130,7 +130,7 @@ optdb = gof.SequenceDB()
 optdb.register('merge1', gof.MergeOptimizer(), 
         0, 'fast_run', 'fast_compile')
 optdb.register('canonicalize', gof.EquilibriumDB(),         # rearranges elemwise expressions
-        1, 'fast_run')
+        1, 'fast_run', 'fast_compile')
 optdb.register('merge1.2', gof.MergeOptimizer(skip_const_merge=False),
         1.2, 'fast_run', 'fast_compile')
 optdb.register('stabilize', gof.EquilibriumDB(),            # replace unstable subgraphs

theano/tensor/opt.py

@@ -2017,7 +2017,7 @@ def constant_folding(node):
         msg += [constant(output.type, s[0])]
     return msg
 
-register_canonicalize(constant_folding)
+register_canonicalize(constant_folding, 'fast_compile')
 register_stabilize(constant_folding) # because 
 register_specialize(constant_folding)