dump lowered IR when debug logging (#292)

* dump lowered ir when debug log

* avoid calling tvm.lower() twice when not debug

nnvm/python/nnvm/compiler/build_module.py

@@ -101,6 +101,7 @@ def _lower(sch, inputs, func_name, graph):
     try:
         f = tvm.lower(sch, inputs, name=func_name)
         logging.debug("lower function %s", func_name)
+        logging.debug("%s", tvm.lower(sch, inputs, simple_mode=True))
     except Exception:
         msg = traceback.format_exc()
         msg += "Error during compile graph\n"

nnvm/python/nnvm/testing/vgg.py

@@ -68,7 +68,7 @@ def get_symbol(num_classes, num_layers=11, batch_norm=False, dtype='float32'):
                 13: ([2, 2, 2, 2, 2], [64, 128, 256, 512, 512]),
                 16: ([2, 2, 3, 3, 3], [64, 128, 256, 512, 512]),
                 19: ([2, 2, 4, 4, 4], [64, 128, 256, 512, 512])}
-    if not vgg_spec.has_key(num_layers):
+    if num_layers not in vgg_spec:
         raise ValueError("Invalide num_layers {}. Choices are 11,13,16,19.".format(num_layers))
     layers, filters = vgg_spec[num_layers]
     data = sym.Variable(name="data")