[REFACTOR][PY][API-CHANGE] establish tvm.ir, migrate corresponding fi…

…les (apache#4862)

* [REFACTOR][PY][API-CHANGE] establish tvm.ir, migrate corresponding relay files.

This PR establishes tvm.ir and migrates the corresponding relay
files into the new folder.

API Change:
- relay.Module -> tvm.IRModule

* Update with ADT

* Migrate transform

* address comments

* Migrate module

* Migrate json_compact

* Migrate attrs

* Move LoweredFunc to stmt temporarily

* temp migrate container

* Finish migrate container

python/vta/build_module.py

@@ -33,7 +33,7 @@ def early_rewrite(stmt):
     """Try to do storage rewrite in early pass."""
     try:
         return tvm.ir_pass.StorageRewrite(stmt)
-    except tvm.TVMError:
+    except tvm.error.TVMError:
         return stmt
 
 

python/vta/top/graphpack.py

@@ -17,14 +17,15 @@
 # pylint: disable=unused-argument
 """A Relay implementation of graph packing."""
 
+import tvm
 from tvm import relay
 from tvm.relay import op, transform
 from tvm.relay import ExprMutator
 
 def run_opt_pass(expr, opt_pass):
     """Exectue a relay pass."""
     assert isinstance(opt_pass, transform.Pass)
-    mod = relay.Module.from_expr(expr)
+    mod = tvm.IRModule.from_expr(expr)
     mod = opt_pass(mod)
     entry = mod["main"]
     return entry if isinstance(expr, relay.Function) else entry.body

tutorials/autotvm/tune_relay_vta.py

@@ -353,7 +353,7 @@ def tune_and_evaluate(tuning_opt):
     # Perform task extraction on Relay program
     print("Extract tasks...")
     relay_prog, params = compile_network(env, target, network, start_pack, stop_pack)
-    mod = relay.Module.from_expr(relay_prog)
+    mod = tvm.IRModule.from_expr(relay_prog)
     tasks = autotvm.task.extract_from_program(mod,
                                               params=params,
                                               ops=(tvm.relay.op.nn.conv2d, ),