From 804db2dde3f13834891d11b47dc0f0e18b9d6320 Mon Sep 17 00:00:00 2001
From: Karl Wiberg <kwiberg@webrtc.org>
Date: Tue, 15 Sep 2020 11:07:10 +0200
Subject: [PATCH] UntypedFunction: Eliminate an unnecessary indirection in the
 implementation

Bug: webrtc:11943
Change-Id: Ib57b13977910ede430e4228a9d382fb765bf1d84
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/184261
Commit-Queue: Karl Wiberg <kwiberg@webrtc.org>
Reviewed-by: Mirko Bonadei <mbonadei@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#32120}
---
 rtc_base/function.h | 15 +++++++++------
 1 file changed, 9 insertions(+), 6 deletions(-)

diff --git a/rtc_base/function.h b/rtc_base/function.h
index cbc5f7dabd..005c360e9e 100644
--- a/rtc_base/function.h
+++ b/rtc_base/function.h
@@ -32,24 +32,26 @@ template <typename T>
 struct CallHelpers;
 template <typename RetT, typename... ArgT>
 struct CallHelpers<RetT(ArgT...)> {
+  // Return type of the three helpers below.
   using return_type = RetT;
+  // Complete function type of the three helpers below.
+  using function_type = RetT(VoidUnion*, ArgT...);
+  // Helper for calling the `void_ptr` case of VoidUnion.
   template <typename F>
   static RetT CallVoidPtr(VoidUnion* vu, ArgT... args) {
     return (*static_cast<F*>(vu->void_ptr))(std::forward<ArgT>(args)...);
   }
+  // Helper for calling the `fun_ptr` case of VoidUnion.
   static RetT CallFunPtr(VoidUnion* vu, ArgT... args) {
     return (reinterpret_cast<RetT (*)(ArgT...)>(vu->fun_ptr))(
         std::forward<ArgT>(args)...);
   }
+  // Helper for calling the `inline_storage` case of VoidUnion.
   template <typename F>
   static RetT CallInlineStorage(VoidUnion* vu, ArgT... args) {
     return (*reinterpret_cast<F*>(&vu->inline_storage))(
         std::forward<ArgT>(args)...);
   }
-  static RetT DoCall(FunVoid* f, VoidUnion* vu, ArgT... args) {
-    return reinterpret_cast<RetT (*)(VoidUnion*, ArgT...)>(f)(
-        vu, std::forward<ArgT>(args)...);
-  }
 };
 
 }  // namespace webrtc_function_impl
@@ -188,8 +190,9 @@ class UntypedFunction final {
   template <typename Signature, typename... ArgT>
   typename webrtc_function_impl::CallHelpers<Signature>::return_type Call(
       ArgT&&... args) {
-    return webrtc_function_impl::CallHelpers<Signature>::DoCall(
-        call_, &f_, std::forward<ArgT>(args)...);
+    return reinterpret_cast<
+        typename webrtc_function_impl::CallHelpers<Signature>::function_type*>(
+        call_)(&f_, std::forward<ArgT>(args)...);
   }
 
   // Returns true iff we don't need to call a destructor. This is guaranteed