[ORC-RT] Add MethodWrapperHandler utility for WrapperFunction.

This is an ORC runtime counterpart to a01f772d19, which introduced the same
functionality into LLVM.

compiler-rt/lib/orc/wrapper_function_utils.h

@@ -16,6 +16,7 @@
 #include "c_api.h"
 #include "common.h"
 #include "error.h"
+#include "executor_address.h"
 #include "simple_packed_serialization.h"
 #include <type_traits>
 
@@ -321,8 +322,8 @@ public:
   static WrapperFunctionResult handle(const char *ArgData, size_t ArgSize,
                                       HandlerT &&Handler) {
     using WFHH =
-        detail::WrapperFunctionHandlerHelper<HandlerT, ResultSerializer,
-                                             SPSTagTs...>;
+        detail::WrapperFunctionHandlerHelper<std::remove_reference_t<HandlerT>,
+                                             ResultSerializer, SPSTagTs...>;
     return WFHH::apply(std::forward<HandlerT>(Handler), ArgData, ArgSize);
   }
 
@@ -354,6 +355,48 @@ public:
   using WrapperFunction<SPSEmpty(SPSTagTs...)>::handle;
 };
 
+/// A function object that takes an ExecutorAddr as its first argument,
+/// casts that address to a ClassT*, then calls the given method on that
+/// pointer passing in the remaining function arguments. This utility
+/// removes some of the boilerplate from writing wrappers for method calls.
+///
+///   @code{.cpp}
+///   class MyClass {
+///   public:
+///     void myMethod(uint32_t, bool) { ... }
+///   };
+///
+///   // SPS Method signature -- note MyClass object address as first argument.
+///   using SPSMyMethodWrapperSignature =
+///     SPSTuple<SPSExecutorAddr, uint32_t, bool>;
+///
+///   WrapperFunctionResult
+///   myMethodCallWrapper(const char *ArgData, size_t ArgSize) {
+///     return WrapperFunction<SPSMyMethodWrapperSignature>::handle(
+///        ArgData, ArgSize, makeMethodWrapperHandler(&MyClass::myMethod));
+///   }
+///   @endcode
+///
+template <typename RetT, typename ClassT, typename... ArgTs>
+class MethodWrapperHandler {
+public:
+  using MethodT = RetT (ClassT::*)(ArgTs...);
+  MethodWrapperHandler(MethodT M) : M(M) {}
+  RetT operator()(ExecutorAddr ObjAddr, ArgTs &...Args) {
+    return (ObjAddr.toPtr<ClassT *>()->*M)(std::forward<ArgTs>(Args)...);
+  }
+
+private:
+  MethodT M;
+};
+
+/// Create a MethodWrapperHandler object from the given method pointer.
+template <typename RetT, typename ClassT, typename... ArgTs>
+MethodWrapperHandler<RetT, ClassT, ArgTs...>
+makeMethodWrapperHandler(RetT (ClassT::*Method)(ArgTs...)) {
+  return MethodWrapperHandler<RetT, ClassT, ArgTs...>(Method);
+}
+
 } // end namespace __orc_rt
 
 #endif // ORC_RT_WRAPPER_FUNCTION_UTILS_H