parse_slice.cpp

#include <migraphx/onnx/op_parser.hpp>
#include <migraphx/onnx/checks.hpp>
#include <migraphx/op/slice.hpp>
#include <migraphx/ranges.hpp>
#include <migraphx/instruction.hpp>
#include <migraphx/make_op.hpp>

namespace migraphx {
inline namespace MIGRAPHX_INLINE_NS {
namespace onnx {

struct parse_slice : op_parser<parse_slice>
{
    std::vector<op_desc> operators() const { return {{"Slice"}}; }

    instruction_ref parse(const op_desc& /*opd*/,
                          const onnx_parser& parser,
                          onnx_parser::node_info info,
                          std::vector<instruction_ref> args) const
    {
        op::slice op;

        std::vector<int64_t> steps;

        // slice can have up to 5 inputs, we first check the 5th one
        // to decide whether MIGRAPHX can handle this slice
        if(args.size() == 5)
        {
            migraphx::argument step_arg = args.back()->eval();
            check_arg_empty(step_arg, "PARSE_SLICE: cannot handle variable steps for slice");
            step_arg.visit([&](auto s) { steps.assign(s.begin(), s.end()); });
        }

        if(args.size() >= 4)
        {
            migraphx::argument axes_arg = args.at(3)->eval();
            check_arg_empty(axes_arg, "PARSE_SLICE: cannot handle variable axes for slice");
            axes_arg.visit([&](auto s) { op.axes.assign(s.begin(), s.end()); });
        }
        else if(contains(info.attributes, "axes"))
        {
            literal s = parser.parse_value(info.attributes.at("axes"));
            s.visit([&](auto v) { copy(v, std::back_inserter(op.axes)); });
        }

        if(args.size() >= 3)
        {
            migraphx::argument end_arg = args.at(2)->eval();
            check_arg_empty(end_arg, "PARSE_SLICE: cannot handle variable ends for slice");
            end_arg.visit([&](auto s) { op.ends.assign(s.begin(), s.end()); });
        }
        else if(contains(info.attributes, "ends"))
        {
            literal s = parser.parse_value(info.attributes.at("ends"));
            s.visit([&](auto v) { copy(v, std::back_inserter(op.ends)); });
        }

        if(args.size() >= 2)
        {
            migraphx::argument start_arg = args.at(1)->eval();
            check_arg_empty(start_arg, "PARSE_SLICE: cannot handle variable starts for slice");
            start_arg.visit([&](auto s) { op.starts.assign(s.begin(), s.end()); });
        }
        else if(contains(info.attributes, "starts"))
        {
            literal s = parser.parse_value(info.attributes.at("starts"));
            s.visit([&](auto v) { copy(v, std::back_inserter(op.starts)); });
        }

        if(op.axes.empty())
        {
            std::vector<int64_t> axes(args[0]->get_shape().lens().size());
            std::iota(axes.begin(), axes.end(), int64_t{0});
            op.axes = axes;
        }

        std::vector<int64_t> raxes;

        assert(steps.empty() or steps.size() == op.axes.size());
        assert(op.axes.size() == op.starts.size());
        assert(op.axes.size() == op.ends.size());

        for(auto i : range(steps.size()))
        {
            if(steps[i] >= 0)
                continue;
            op.starts[i] += 1;
            if(op.starts[i] == 0)
                op.starts[i] = INT_MAX;
            op.ends[i] += 1;
            raxes.push_back(op.axes[i]);
            std::swap(op.starts[i], op.ends[i]);
        }

        auto ins = info.add_instruction(op, args[0]);
        if(not raxes.empty())
            ins = info.add_instruction(make_op("reverse", {{"axes", raxes}}), ins);
        if(std::any_of(steps.begin(), steps.end(), [](auto s) { return std::abs(s) != 1; }))
        {
            std::vector<int64_t> nsteps;
            std::transform(steps.begin(), steps.end(), std::back_inserter(nsteps), [](auto s) {
                return std::abs(s);
            });
            return ins = info.add_instruction(
                       make_op("step", {{"axes", op.axes}, {"steps", nsteps}}), ins);
        }
        else
            return ins;
    }
};

} // namespace onnx
} // namespace MIGRAPHX_INLINE_NS
} // namespace migraphx