eliminate pnnx tail reshape permute

tools/pnnx/src/CMakeLists.txt

@@ -234,6 +234,7 @@ set(pnnx_pass_ncnn_SRCS
     pass_ncnn/solve_batch_index.cpp
 
     pass_ncnn/eliminate_noop.cpp
+    pass_ncnn/eliminate_tail_reshape_permute.cpp
     pass_ncnn/fuse_convolution_activation.cpp
     pass_ncnn/fuse_convolution1d_activation.cpp
     pass_ncnn/fuse_convolutiondepthwise_activation.cpp

tools/pnnx/src/pass_ncnn.cpp

@@ -27,6 +27,7 @@
 #include "pass_ncnn/solve_batch_index.h"
 
 #include "pass_ncnn/eliminate_noop.h"
+#include "pass_ncnn/eliminate_tail_reshape_permute.h"
 #include "pass_ncnn/fuse_convolution_activation.h"
 #include "pass_ncnn/fuse_convolution1d_activation.h"
 #include "pass_ncnn/fuse_convolutiondepthwise_activation.h"
@@ -95,6 +96,7 @@ void pass_ncnn(Graph& g)
     ncnn::fuse_deconvolution_activation(g);
     ncnn::fuse_deconvolutiondepthwise_activation(g);
     ncnn::fuse_innerproduct_activation(g);
+    ncnn::eliminate_tail_reshape_permute(g);
 
     dead_code_elimination(g);
 

tools/pnnx/src/pass_ncnn/eliminate_tail_reshape_permute.cpp

@@ -0,0 +1,82 @@
+// Tencent is pleased to support the open source community by making ncnn available.
+//
+// Copyright (C) 2021 THL A29 Limited, a Tencent company. All rights reserved.
+//
+// Licensed under the BSD 3-Clause License (the "License"); you may not use this file except
+// in compliance with the License. You may obtain a copy of the License at
+//
+// https://opensource.org/licenses/BSD-3-Clause
+//
+// Unless required by applicable law or agreed to in writing, software distributed
+// under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR
+// CONDITIONS OF ANY KIND, either express or implied. See the License for the
+// specific language governing permissions and limitations under the License.
+
+#include "eliminate_tail_reshape_permute.h"
+
+#include <algorithm>
+
+namespace pnnx {
+
+namespace ncnn {
+
+void eliminate_tail_reshape_permute(Graph& graph)
+{
+    for (;;)
+    {
+        bool need_eliminate = false;
+
+        for (int i = (int)graph.ops.size() - 1; i >= 0; i--)
+        {
+            Operator* op = graph.ops[i];
+
+            if (op->type != "Reshape" && op->type != "Permute")
+                continue;
+
+            Operand* op_out = op->outputs[0];
+
+            if (op_out->consumers.size() != 1)
+                continue;
+
+            Operator* op2 = op_out->consumers[0];
+
+            if (op2->type != "pnnx.Output")
+                continue;
+
+            need_eliminate = true;
+
+            op->inputs[0]->remove_consumer(op);
+
+            op->inputs[0]->params = op_out->params;
+
+            for (size_t j = 0; j < op2->inputs.size(); j++)
+            {
+                if (op2->inputs[j] == op_out)
+                    op2->inputs[j] = op->inputs[0];
+            }
+
+            op->inputs[0]->consumers.push_back(op2);
+
+            op_out->producer = 0;
+            op_out->consumers.clear();
+
+            graph.operands.erase(std::find(graph.operands.begin(), graph.operands.end(), op_out));
+            delete op_out;
+
+            op->inputs.clear();
+            op->outputs.clear();
+
+            graph.ops.erase(graph.ops.begin() + i);
+            delete op;
+
+            break;
+        }
+
+        if (!need_eliminate)
+            break;
+    }
+}
+
+} // namespace ncnn
+
+} // namespace pnnx

tools/pnnx/src/pass_ncnn/eliminate_tail_reshape_permute.h

@@ -0,0 +1,26 @@
+// Tencent is pleased to support the open source community by making ncnn available.
+//
+// Copyright (C) 2021 THL A29 Limited, a Tencent company. All rights reserved.
+//
+// Licensed under the BSD 3-Clause License (the "License"); you may not use this file except
+// in compliance with the License. You may obtain a copy of the License at
+//
+// https://opensource.org/licenses/BSD-3-Clause
+//
+// Unless required by applicable law or agreed to in writing, software distributed
+// under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR
+// CONDITIONS OF ANY KIND, either express or implied. See the License for the
+// specific language governing permissions and limitations under the License.
+
+#include "pass_ncnn.h"
+
+namespace pnnx {
+
+namespace ncnn {
+
+void eliminate_tail_reshape_permute(Graph& graph);
+
+} // namespace ncnn
+
+} // namespace pnnx
+