Iniital work to add in splitToSequence operator for onnx

Basing this around the split operator. Need to add in other tests

src/onnx/parse_splitToSequence.cpp

+/*
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2015-2022 Advanced Micro Devices, Inc. All rights reserved.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+#include <migraphx/onnx/op_parser.hpp>
+#include <migraphx/instruction.hpp>
+#include <migraphx/ranges.hpp>
+#include <migraphx/make_op.hpp>
+#include <migraphx/tune_axis.hpp>
+
+namespace migraphx {
+inline namespace MIGRAPHX_INLINE_NS {
+namespace onnx {
+
+struct parse_splitToSequence : op_parser<parse_splitToSequence>
+{
+    std::vector<op_desc> operators() const { return {{"SplitToSequence"}}; }
+
+    std::vector<instruction_ref> parse(const op_desc& opd,
+                                       const onnx_parser& parser,
+                                       onnx_parser::node_info info,
+                                       std::vector<instruction_ref> args) const
+    {
+        int64_t axis = 0;
+
+        if(contains(info.attributes, "axis"))
+        {
+            axis = parser.parse_value(info.attributes.at("axis")).at<int>();
+        }
+
+        auto lens          = args[0]->get_shape().lens();
+        int64_t n_rank     = lens.size();
+        int64_t tuned_axis = tune_axis(n_rank, axis, opd.op_name);
+
+        std::vector<int64_t> vec_splits;
+        if(contains(info.attributes, "split"))
+        {
+            literal s = parser.parse_value(info.attributes.at("split"));
+            s.visit([&](auto v) { vec_splits.assign(v.begin(), v.end()); });
+
+            if(std::accumulate(vec_splits.begin(), vec_splits.end(), int64_t(0)) !=
+               static_cast<int64_t>(lens[tuned_axis]))
+            {
+                MIGRAPHX_THROW("PARSE_SPLIT_TO_SEQ: sum of split attribute unequal to dim size of axis!");
+            }
+        }
+        // no split attribute, use other paremters to determine splits
+        else
+        {
+            int64_t keepdims = 1;
+
+            if(contains(info.attributes, "keepdims"))
+            {
+                keepdims = parser.parse_value(info.attributes.at("keepdims")).at<int>();
+            }
+
+            if((lens[tuned_axis] % info.num_outputs) != 0)
+            {
+                MIGRAPHX_THROW("PARSE_SPLIT_TO_SEQ: input cannot be equally divided into " +
+                               std::to_string(info.num_outputs) + " splits!");
+            }
+            auto dl = lens[tuned_axis] / info.num_outputs;
+            vec_splits.resize(info.num_outputs, dl);
+        }
+
+        std::vector<instruction_ref> ret_ins;
+        int64_t start = 0;
+        for(auto sl : vec_splits)
+        {
+            ret_ins.push_back(info.add_instruction(
+                make_op("slice", {{"axes", {axis}}, {"starts", {start}}, {"ends", {start + sl}}}),
+                args[0]));
+            start += sl;
+        }
+
+        return ret_ins;
+    }
+};
+
+} // namespace onnx
+} // namespace MIGRAPHX_INLINE_NS
+} // namespace migraphx