[Torch, QNN] Add support for quantized models via QNN (apache#4977)

* qnn support initial import

* fix upsampling num input

* imagenet tests added

* add qunatized module tests

* quantized module tests working

* imagenet test working

* fix lint

* remove top level torch import to fix ci error

* disable lint warning on outside toplevel import

* revert parse -> convert change

* add comments to qnn translation

* address comments, add sample outputs

* add more comments

* refactor bias add and requantize step

python/tvm/relay/frontend/pytorch.py

@@ -19,6 +19,7 @@
 # pylint: disable=import-outside-toplevel, simplifiable-if-expression, unnecessary-comprehension
 """PT: PyTorch frontend."""
 import itertools
+import logging
 
 import numpy as np
 
@@ -32,6 +33,8 @@
 from .common import infer_shape as _infer_shape
 from .common import infer_value as _infer_value
 
+from . import qnn_torch
+
 __all__ = ["from_pytorch"]
 
 # operator implementation
@@ -146,6 +149,10 @@ def _impl(inputs, input_types):
 def _relu():
     def _impl(inputs, input_types):
         data = inputs[0]
+        if input_types[0] == "quint8":
+            assert len(inputs) == 3, "Input quant param not found in op inputs"
+            input_zero_point = _expr.const(inputs[2], dtype="int32")
+            return qnn_torch.quantized_relu(data, input_zero_point)
         return _op.nn.relu(data)
     return _impl
 
@@ -154,9 +161,14 @@ def _impl(inputs, input_types):
         data = inputs[0]
         output_size = _infer_shape(inputs[1])
 
-        return _op.nn.adaptive_avg_pool2d(
-            data,
-            output_size=output_size)
+        def func(x):
+            return _op.nn.adaptive_avg_pool2d(x, output_size=output_size)
+
+        if input_types[0] == "quint8":
+            return qnn_torch.quantized_adaptive_avg_2d(data, func)
+
+        return func(data)
+
     return _impl
 
 def _adaptive_max_2d():
@@ -503,7 +515,18 @@ def _impl(inputs, input_types):
         else:
             exclude = False
 
-        return _op.mean(data, axis, keepdims, exclude)
+        def func(x):
+            return _op.mean(x, axis, keepdims, exclude)
+
+        if input_types[0] == "quint8":
+            assert len(inputs) == 6, "Input quant param not found in op inputs"
+            input_scale = _expr.const(inputs[4])
+            input_zero_point = _expr.const(inputs[5])
+            return qnn_torch.quantized_mean(data, input_scale,
+                                            input_zero_point, func)
+
+        return func(data)
+
     return _impl
 
 def _chunk():
@@ -665,10 +688,40 @@ def _impl(inputs, input_types):
         else:
             coord_trans = "half_pixel"
 
-        return _op.image.resize(data, out_size, "NCHW", method, coord_trans)
+        def func(x):
+            return _op.image.resize(x, out_size, "NCHW", method, coord_trans)
+
+        if input_types[0] == "quint8":
+            import torch
+            from packaging import version
+
+            # Torch version > 1.4 changed upsampling API
+            if version.parse(torch.__version__) > version.parse("1.4.0"):
+                num_inputs = 7
+            else:
+                num_inputs = 5
+
+            assert len(inputs) == num_inputs, "Input quant param not found in op inputs"
+
+            input_scale = _expr.const(inputs[-2])
+            input_zero_point = _expr.const(inputs[-1])
+            return qnn_torch.quantized_upsample(data, input_scale,
+                                                input_zero_point, func)
+        return func(data)
 
     return _impl
 
+
+def _expand_as():
+    def _impl(inputs, input_types):
+        # TODO: maybe fix this
+        # This assumes expand_as can be removed because TVM has broadcast op
+        msg = "aten::expand_as(...) found, assume it is part of broadcast op"
+        logging.warning(msg)
+        return inputs[0]
+    return _impl
+
+
 # Helper functions for operator implementation
 
 def _convert_data_type(input_type):
@@ -789,6 +842,7 @@ def _convert_elemwise_input(data, input_type):
     "aten::detach"                          : _identity(),
     "aten::upsample_bilinear2d"             : _upsample("bilinear"),
     "aten::upsample_nearest2d"              : _upsample("nearest_neighbor"),
+    "aten::expand_as"                       : _expand_as()
 }
 
 
@@ -839,6 +893,7 @@ def _report_missing_conversion(op_names):
                  "prim::ListConstruct", "prim::ListUnpack",
                  "prim::TupleConstruct", "prim::TupleUnpack"]
     known_ops += list(_convert_map.keys())
+    known_ops += list(qnn_torch.convert_map.keys())
 
     missing = [op_name for op_name in op_names
                if op_name not in known_ops]
@@ -991,6 +1046,7 @@ def parse_params(graph, state_dict):
     getattr_nodes = graph.findAllNodes("prim::GetAttr", recurse=True)
     params = {}
     param_tensors = {}
+    packed_param_map = {}
     seen = set()
 
     for node in getattr_nodes:
@@ -1003,14 +1059,18 @@ def parse_params(graph, state_dict):
             full_attr = _getattr_full_name(getattrs)
             full_attr_node_name = _get_output_name(getattrs[-1])
 
-            if full_attr in state_dict:
+            if full_attr.endswith("_packed_params"):  # for quantized models
+                err_msg = "parameter %s not found in state dict" % full_attr
+                assert full_attr in state_dict, err_msg
+                packed_param_map[full_attr_node_name] = full_attr
+            elif full_attr in state_dict:
                 torch_tensor = state_dict[full_attr]
                 tensor, var = _get_tensor_and_var(torch_tensor,
                                                   full_attr_node_name)
                 param_tensors[full_attr_node_name] = tensor
                 params[full_attr_node_name] = var
 
-    return params, param_tensors
+    return params, param_tensors, packed_param_map
 
 
 def parse_operators(operators, outputs, output_index_map, ret_name):
@@ -1090,16 +1150,26 @@ def from_pytorch(script_module, input_shapes, custom_convert_map=None):
 
     params = script_module.state_dict()
     input_vars = parse_inputs(graph.inputs(), input_shapes)
-    param_vars, tensors = parse_params(graph, params)
+    param_vars, tensors, packed_param_map = parse_params(graph, params)
+    tvm_params = {k: tvm.nd.array(v) for k, v in tensors.items()}
 
     input_vars.update(param_vars)
     outputs = list(input_vars.values())
     output_index_map = dict(zip(input_vars.keys(), range(len(outputs))))
     ret_name = _get_input_names(graph.return_node())[0]
 
+    # For quantized models
+    if "aten::quantize_per_tensor" in op_names:
+        weight_quant_params = qnn_torch.get_weight_quant_params(script_module)
+        qnn_torch.add_input_quant_params_to_op_inputs(graph)
+        qnn_torch.add_quant_params_to_outputs(outputs, output_index_map,
+                                              packed_param_map,
+                                              weight_quant_params)
+        qnn_torch.add_quant_params(tvm_params, weight_quant_params)
+        _convert_map.update(qnn_torch.convert_map)
+
     body = parse_operators(_get_operator_nodes(graph.nodes()), outputs,
                            output_index_map, ret_name)
     func = tvm.relay.Function(_analysis.free_vars(body), body)
-    tvm_params = {k: tvm.nd.array(v) for k, v in tensors.items()}
 
     return _module.IRModule.from_expr(func), tvm_params