Remove extra reshape

Development
#1

In current relay pass, we can merge two consecutive reshape op by SimplifyExpr pass. Sometimes, We may produce useless reshape op in the process of importing models. For example:

#[version = "0.0.5"]
def @main(%Placeholder: Tensor[(1, 3, 227, 227), float32], %conv1/weights: Tensor[(96, 3, 11, 11), float32], %conv1/biases: Tensor[(96), float32]) -> Tensor[(1, 96, 55, 55), float32] {
  %0 = nn.conv2d(%Placeholder, %conv1/weights, strides=[4, 4], padding=[0, 0, 0, 0], channels=96, kernel_size=[11, 11]) /* ty=Tensor[(1, 96, 55, 55), float32] */;
  %1 = nn.bias_add(%0, %conv1/biases) /* ty=Tensor[(1, 96, 55, 55), float32] */;
  %2 = reshape(%1, newshape=[1, 96, 55, 55]) /* ty=Tensor[(1, 96, 55, 55), float32] */;
  nn.relu(%2) /* ty=Tensor[(1, 96, 55, 55), float32] */
}

We can see that the output of %2 have the same shape with %1, then the reshape op is useless…

In order to deal with this problem, we have extended the functionality of SimplifyExpr pass, and now it will remove the useless reshape op. Do you think it is necessary for me to propose a pr? @haichen

#2

Sure, I think you can add this into the SimplifyExpr pass. I thought about this before, but I think that the reshape op might be inlined in the fused op.