[Torch] Upsampling op support and enable registering a user defined o…

…p conversion map (apache#4961)

* add custom conversion map

* add roi align test using custom convert map

* refactor test

* add support for upsampling op and test on segmentation models

* remove redundant no_grad

* add upsampling test case

* make the default custom map None, instead of empty dict

* updated tests, remove packaging and drop PT 1.2 support

* add better support for aten::to and tests

* add a note on dilation in x86

python/tvm/relay/frontend/pytorch.py

@@ -19,7 +19,6 @@
 # pylint: disable=import-outside-toplevel, simplifiable-if-expression, unnecessary-comprehension
 """PT: PyTorch frontend."""
 import itertools
-from packaging import version
 
 import numpy as np
 
@@ -31,6 +30,7 @@
 from .. import op as _op
 from .common import get_relay_op
 from .common import infer_shape as _infer_shape
+from .common import infer_value as _infer_value
 
 __all__ = ["from_pytorch"]
 
@@ -614,6 +614,61 @@ def _impl(inputs, input_types):
         return _op.tensor.sqrt(data)
     return _impl
 
+def _floor():
+    def _impl(inputs, input_types):
+        data = inputs[0]
+        return _op.floor(data)
+    return _impl
+
+def _to():
+    def _impl(inputs, input_types):
+        data = inputs[0]
+        if inputs[3] in ["cpu", "cuda"]:
+            return data
+        # special handling for aten::to(data, 6, _, _, _) case
+        # 6 means dtype = float
+        # this happens when converting upsampling with scale factor
+        cast_func = {
+            6: float,
+            3: int,
+        }
+        cast_func_expr = {
+            6: lambda x: _op.cast(x, "float32"),
+            3: lambda x: _op.cast(x, "int32"),
+        }
+        if inputs[1] in cast_func and not isinstance(data, _expr.Expr):
+            return cast_func[inputs[1]](data)
+        elif inputs[1] in cast_func and isinstance(data, _expr.Expr):
+            return cast_func_expr[inputs[1]](data)
+        return data
+
+    return _impl
+
+def _upsample(method):
+    def _impl(inputs, input_types):
+        if isinstance(inputs[1], _expr.Var):
+            out_size = _infer_shape(inputs[1])
+        elif isinstance(inputs[1], list):
+            infer_res = [_infer_value(size, {}) for size in inputs[1]]
+            out_size = [np.asscalar(res.asnumpy().astype(np.int))
+                        for res in infer_res]
+
+        data = inputs[0]
+
+        if len(inputs) > 2:
+            align_corners = inputs[2]
+        else:
+            align_corners = False
+
+        if align_corners:
+            coord_trans = "align_corners"
+        else:
+            coord_trans = "half_pixel"
+
+        return _op.image.resize(data, out_size, "NCHW", method, coord_trans)
+
+    return _impl
+
 # Helper functions for operator implementation
 
 def _convert_data_type(input_type):
@@ -686,7 +741,7 @@ def _convert_elemwise_input(data, input_type):
     "aten::div_"                            : _elemwise("divide"),
     "aten::ones"                            : _ones(),
     "aten::zeros"                           : _zeros(),
-    "aten::to"                              : _identity(),
+    "aten::to"                              : _to(),
     "aten::unsqueeze"                       : _unsqueeze(),
     "aten::cat"                             : _concatenate(),
     "aten::slice"                           : _slice(),
@@ -729,15 +784,18 @@ def _convert_elemwise_input(data, input_type):
     "aten::permute"                         : _transpose(),
     "aten::sum"                             : _reduce("sum"),
     "aten::prod"                            : _reduce("prod"),
-    "aten::sqrt"                            : _sqrt()
+    "aten::sqrt"                            : _sqrt(),
+    'aten::floor'                           : _floor(),
+    "aten::detach"                          : _identity(),
+    "aten::upsample_bilinear2d"             : _upsample("bilinear"),
+    "aten::upsample_nearest2d"              : _upsample("nearest_neighbor"),
 }
 
 
 def _run_jit_passes(graph):
     """ The inline pass is necessary to unwrap prim::CallMethod """
     import torch
-    if version.parse(torch.__version__) >= version.parse("1.4.0"):
-        torch._C._jit_pass_inline(graph)
+    torch._C._jit_pass_inline(graph)
 
 
 def _is_int_seq(seq):
@@ -985,8 +1043,7 @@ def parse_operators(operators, outputs, output_index_map, ret_name):
 
 def get_all_op_names(graph):
     """ Return all operator names in the input graph """
-    nodes = list(graph.nodes())
-    return set(node.kind() for node in nodes)
+    return set(node.kind() for node in graph.nodes())
 
 
 def get_graph_input_names(script_module):
@@ -997,7 +1054,7 @@ def get_graph_input_names(script_module):
     return ir_inputs[1:]  # remove self at the 0th arg
 
 
-def from_pytorch(script_module, input_shapes):
+def from_pytorch(script_module, input_shapes, custom_convert_map=None):
     """ Load PyTorch model in the form of a scripted PyTorch model and convert into relay.
     The companion parameters will be handled automatically.
 
@@ -1011,6 +1068,9 @@ def from_pytorch(script_module, input_shapes):
         Graph level input shape dictionary
         The keys should be the same one returned by get_graph_input_names(...) above
 
+    custom_convert_map: Dictionary of str to Relay op
+        A custom op conversion map in the same format as _convert_map above
+
     Returns
     -------
     mod : tvm.relay.Module
@@ -1021,6 +1081,10 @@ def from_pytorch(script_module, input_shapes):
     """
     graph = script_module.graph.copy()
     _run_jit_passes(graph)
+
+    if custom_convert_map:
+        _convert_map.update(custom_convert_map)
+
     op_names = get_all_op_names(graph)
     _report_missing_conversion(op_names)