[Frontend][PyTorch] support for quantized conv_transpose2d op

PyTorch uses the same underlying function to pack and
unpack the params for conv2d and conv_transpose2d ops.

This change adds support for quantized conv_transpose2d op
by reusing the ConvPackedParam and adding the
output_padding param to it.
This output_padding param will remain unused in case of conv2d.

Also added test for above with specific condition for
torch v1.7.1 and below.

python/tvm/relay/frontend/qnn_torch.py

@@ -56,13 +56,25 @@ class ConvPackedParam(QNNParam):
     """
 
     def __init__(
-        self, weight_np, bias, scale, zero_point, param_name, stride, padding, dilation, groups
+        self,
+        weight_np,
+        bias,
+        scale,
+        zero_point,
+        param_name,
+        stride,
+        padding,
+        dilation,
+        groups,
+        output_padding,
     ):
         super().__init__(weight_np, bias, scale, zero_point, param_name)
         self.stride = stride
         self.padding = padding
         self.dilation = dilation
         self.groups = groups
+        # Used only for conv_transpose2d
+        self.output_padding = output_padding
 
 
 def _get_quant_params(qweight):
@@ -92,8 +104,18 @@ def make_conv_packed_param(param_name, qweight, bias, packed_params):
     padding = packed_params.padding()
     dilation = packed_params.dilation()
     groups = packed_params.groups()
+    output_padding = packed_params.output_padding()
     return ConvPackedParam(
-        weight_np, bias, scale, zero_point, param_name, stride, padding, dilation, groups
+        weight_np,
+        bias,
+        scale,
+        zero_point,
+        param_name,
+        stride,
+        padding,
+        dilation,
+        groups,
+        output_padding,
     )
 
 
@@ -154,7 +176,13 @@ def add_quant_params_to_outputs(outputs, packed_param_map, quant_params):
         params = [qweight, qparam.scale, qparam.zero_point, qparam.bias_var]
 
         if isinstance(quant_params[packed_param_name], ConvPackedParam):
-            params += [qparam.stride, qparam.padding, qparam.dilation, qparam.groups]
+            params += [
+                qparam.stride,
+                qparam.padding,
+                qparam.dilation,
+                qparam.groups,
+                qparam.output_padding,
+            ]
 
         outputs[node_name] = params
 
@@ -192,6 +220,7 @@ def _get_quant_param_for_input(input_value):
         "quantized::mul_scalar": (2, 3),
         "quantized::add_scalar": (2, 3),
         "quantized::hardswish": (1, 2),
+        "quantized::conv_transpose2d": qconv_indices,
     }
 
     def dfs(current_node):
@@ -362,6 +391,7 @@ def add_input_quant_params_to_op_inputs(graph):
         "quantized::relu6": 1,
         "quantized::hardswish": 1,
         "aten::hardsigmoid": 1,
+        "quantized::conv_transpose2d": 1,
     }
 
     need_input_quant_param = set(num_quantized_inputs.keys())
@@ -924,6 +954,65 @@ def _impl(inputs, _):
     return _impl
 
 
+def _quantized_conv_transpose2d(with_relu=False):
+    def _impl(inputs, _):
+        # Refer to aten/src/ATen/native/quantized/cpu/qconv.cpp
+        # Supported in Torch 1.7 or newer
+        conv_params = inputs[1]
+        weight = conv_params[0]
+        weight_scale = conv_params[1]
+        weight_zero_point = conv_params[2]
+        bias = conv_params[3]
+
+        strides = conv_params[4]
+        padding = conv_params[5]
+        dilation = conv_params[6]
+        groups = conv_params[7]
+        output_padding = conv_params[8]
+
+        output_scale = _expr.const(inputs[2])
+        output_zero_point = _expr.const(inputs[3])
+
+        assert len(inputs) == 6, "Input quant params not found in op inputs"
+
+        # These are manually added by add_input_quant_params_to_op_inputs above
+        # In torch, they are retrieved from QTensor data structure at runtime
+        input_scale = _expr.const(inputs[4])
+        input_zero_point = _expr.const(inputs[5])
+
+        weight_shape = list(infer_shape(weight))
+
+        # Swap I and O dims to match shape relay expects for OIHW
+        weight_shape[0], weight_shape[1] = weight_shape[1], weight_shape[0]
+
+        kernel_size = (weight_shape[2], weight_shape[3])
+        out_channels = weight_shape[0]
+
+        conv_out = relay.qnn.op.conv2d_transpose(
+            inputs[0],
+            weight,
+            input_zero_point,
+            weight_zero_point,
+            input_scale,
+            weight_scale,
+            kernel_size=kernel_size,
+            dilation=dilation,
+            strides=strides,
+            padding=padding,
+            groups=groups,
+            channels=out_channels,
+            output_padding=output_padding,
+            out_dtype="int32",
+            kernel_layout="OIHW",
+        )
+
+        return _do_bias_and_requantize(
+            conv_out, bias, input_scale, weight_scale, output_scale, output_zero_point, with_relu
+        )
+
+    return _impl
+
+
 convert_map = {
     "aten::quantize_per_tensor": _quantize_per_tensor(),
     "quantized::conv2d_relu": _quantized_conv2d(with_relu=True),
@@ -941,4 +1030,5 @@ def _impl(inputs, _):
     "quantized::relu6": _relu6(),
     "quantized::linear_dynamic": _linear_dynamic(),
     "quantized::hardswish": _hswish(),
+    "quantized::conv_transpose2d": _quantized_conv_transpose2d(),
 }

tests/python/frontend/pytorch/qnn_test.py

@@ -92,6 +92,20 @@ def fuse_model(self):
         fuse_modules(self.conv, indices, inplace=True)
 
 
+class ConvTranspose(nn.Module):
+    def __init__(self):
+        super().__init__()
+        layers = [nn.ConvTranspose2d(3, 32, 3, bias=True)]
+        self.conv = nn.Sequential(*layers)
+        self.quant_wrap = QuantWrapper(self.conv)
+
+    def forward(self, x):
+        return self.quant_wrap(x)
+
+    def fuse_model(self):
+        pass
+
+
 class Linear(nn.Module):
     def __init__(self, with_relu=False):
         super().__init__()
@@ -270,6 +284,7 @@ def test_quantized_modules():
             ("conv_bn_relu" + postfix, imagenet_ishape, ConvBn(with_relu=True), per_channel),
             ("linear" + postfix, (16, 16), Linear(), per_channel),
             ("linear_relu" + postfix, (16, 16), Linear(with_relu=True), per_channel),
+            ("conv_transpose", imagenet_ishape, ConvTranspose(), False),
             ("hsigmoid", imagenet_ishape, Hsigmoid(add_stub=True), False),
             ("hswish", imagenet_ishape, Hswish(add_stub=True), False),
             ("semodule", (1, 16, 64, 64), SqueezeExcite(16, add_stub=True), False),
@@ -281,7 +296,15 @@ def test_quantized_modules():
         raw_module.eval()
         inp = torch.rand(ishape)
 
-        quantize_model(raw_module, inp, per_channel=per_channel)
+        # quantized conv_transpose2d is supported only with qnnpack engine before torch v1.8.0.
+        if module_name == "conv_transpose" and not is_version_greater_than("1.7.1"):
+            prev_engine = torch.backends.quantized.engine
+            torch.backends.quantized.engine = "qnnpack"
+            quantize_model(raw_module, inp, per_channel=per_channel)
+            torch.backends.quantized.engine = prev_engine
+        else:
+            quantize_model(raw_module, inp, per_channel=per_channel)
+
         script_module = torch.jit.trace(raw_module, inp).eval()
 
         with torch.no_grad():
@@ -308,6 +331,7 @@ def test_quantized_modules():
         conv_bn_relu 0.3700896 0.010921672 0.7489366477964451
         linear 0.15987062 0.009231662 0.794921875
         linear_relu 0.14180502 0.0053220326 0.8828125
+        conv_transpose 0.0033792555 4.4658788e-07 0.9998678439971806
         conv_bn, per_channel 0.01654929 2.9486866e-06 0.9998218235127019
         conv_bn_relu, per_channel 0.009089053 1.4926576e-06 0.9998357732732732
         linear, per_channel 0.0 0.0 1.0