chore: import upstream snapshot with attribution

tools/converter/source/optimizer/merge/RemoveDuplicatedTensorConvert.cpp

@@ -0,0 +1,66 @@
+//
+//  RemoveDuplicatedTensorConvert.cpp
+//  MNNConverter
+//
+//  Created by MNN on 2020/07/09.
+//  Copyright © 2018, Alibaba Group Holding Limited
+//
+
+#include "../TemplateMerge.hpp"
+#include "MNN/expr/ExprCreator.hpp"
+#include "MNN_generated.h"
+#include "MergeHelpers.hpp"
+
+namespace MNN {
+namespace Express {
+
+class RemoveDuplicatedTensorConvert {
+public:
+    RemoveDuplicatedTensorConvert();
+};
+
+RemoveDuplicatedTensorConvert::RemoveDuplicatedTensorConvert() {
+    auto match = [this](EXPRP expr) -> bool {
+        if (!expr->get() || expr->get()->type() != OpType_ConvertTensor) {
+            return false;
+        }
+        VARP input       = expr->inputs().at(0);
+        EXPRP input_expr = input->expr().first;
+        if (!input_expr->get() || input_expr->get()->type() != OpType_ConvertTensor) {
+            return false;
+        }
+
+        const auto* convert1_params = input_expr->get()->main_as_TensorConvertInfo();
+        const auto* convert2_params = expr->get()->main_as_TensorConvertInfo();
+        if (convert1_params->source() != convert2_params->source()) {
+            return false;
+        }
+        if (convert1_params->dest() != convert2_params->dest()) {
+            return false;
+        }
+
+        return true;
+    };
+
+    auto fold = [this](EXPRP expr) -> bool {
+        VARP input      = expr->inputs().at(0);
+        auto input_expr = input->expr().first;
+
+        const auto* convert1_params = input_expr->get()->main_as_TensorConvertInfo();
+        const auto* convert2_params = expr->get()->main_as_TensorConvertInfo();
+        EXPRP new_expr;
+        
+        VARP x   = input_expr->inputs().at(0);
+        new_expr = Expr::create(expr->extra(), {x});
+        new_expr->setName(expr->name());
+
+        Expr::replace(expr, new_expr);
+        return true /*modified*/;
+    };
+    TemplateMerge::getInstance("Merge").insertTemplate("RemoveDuplicatedTensorConvert", match, fold, PASS_PRIORITY_LOW);
+}
+
+static RemoveDuplicatedTensorConvert g_remove_duplicated_tensor_convert;
+
+} // namespace Express
+} // namespace MNN