Add reverse lookup of c++ class to c class (#1099)

Needed for custom_op so we can generically convert the C type back to the C++ type in the function pointer.

src/api/include/migraphx/migraphx.hpp

@@ -152,6 +152,35 @@ struct array_base
     }
 };
 
+#if defined(__GNUC__) && !defined(__clang__)
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wnon-template-friend"
+#endif
+
+template <class T>
+struct holder
+{
+    // Friend injection
+    friend auto migraphx_adl_handle_lookup(holder<T>);
+    // Function left unimplemented since its only used in non-evaluated
+    // context
+    T get() const;
+};
+
+template <class C, class T>
+struct handle_lookup
+{
+    friend auto migraphx_adl_handle_lookup(holder<T>) { return holder<C>{}; }
+};
+
+#if defined(__GNUC__) && !defined(__clang__)
+#pragma GCC diagnostic pop
+#endif
+
+template <class T>
+using as_handle = decltype(
+    migraphx_adl_handle_lookup(holder<std::remove_cv_t<std::remove_pointer_t<T>>>{}).get());
+
 struct own
 {
 };
@@ -159,8 +188,8 @@ struct borrow
 {
 };
 
-template <class T, class D, D Deleter, class A, A Assigner>
-struct handle_base
+template <class Derived, class T, class D, D Deleter, class A, A Assigner>
+struct handle_base : handle_lookup<Derived, std::remove_cv_t<T>>
 {
     handle_base() : m_handle(nullptr) {}
     template <class F, class... Ts>
@@ -204,7 +233,8 @@ struct handle_base
 #define MIGRAPHX_DETAIL_HANDLE_BASE(name, const_) handle_base<>
 #else
 #define MIGRAPHX_DETAIL_HANDLE_BASE(name, const_)       \
-    handle_base<const_ migraphx_##name,                 \
+    handle_base<name,                                   \
+                const_ migraphx_##name,                 \
                 decltype(&migraphx_##name##_destroy),   \
                 migraphx_##name##_destroy,              \
                 decltype(&migraphx_##name##_assign_to), \

test/api/CMakeLists.txt

@@ -12,6 +12,7 @@ endfunction()
 
 add_api_test(assign test_assign.cpp ${TEST_ONNX_DIR})
 add_api_test(compile_options test_compile_options.cpp ${TEST_ONNX_DIR})
+add_api_test(lookup test_lookup.cpp ${TEST_ONNX_DIR})
 add_api_test(ref test_cpu.cpp ${TEST_ONNX_DIR})
 add_api_test(save_load test_save_load.cpp ${TEST_ONNX_DIR})
 add_api_test(op test_op_construct.cpp ${TEST_ONNX_DIR})

test/api/test_lookup.cpp

+#include <migraphx/migraphx.hpp>
+#include <migraphx/rank.hpp>
+#include "test.hpp"
+
+template <class T>
+std::false_type has_handle(migraphx::rank<0>, T)
+{
+    return {};
+}
+
+template <class T>
+auto has_handle(migraphx::rank<1>, T*) -> decltype(migraphx::as_handle<T>{}, std::true_type{})
+{
+    return {};
+}
+
+TEST_CASE(shape)
+{
+    static_assert(std::is_same<migraphx::as_handle<migraphx_shape>, migraphx::shape>{}, "Failed");
+    static_assert(std::is_same<migraphx::as_handle<migraphx_shape_t>, migraphx::shape>{}, "Failed");
+    static_assert(std::is_same<migraphx::as_handle<const_migraphx_shape_t>, migraphx::shape>{},
+                  "Failed");
+}
+TEST_CASE(non_handle)
+{
+    int i = 0;
+    EXPECT(bool{has_handle(migraphx::rank<1>{}, migraphx_shape_t{})});
+    EXPECT(bool{not has_handle(migraphx::rank<1>{}, &i)});
+}
+
+int main(int argc, const char* argv[]) { test::run(argc, argv); }