lift more of Core to CoreBase

Summary: Reduces the sizes of function template instantiations. Reviewed By: Gownta Differential Revision: D55427323 fbshipit-source-id: 2e21c81d6ad354e22000f37fc4ceaeed5a147d45
facebook · Mar 31, 2024 · ff659d3 · ff659d3
1 parent e887076
commit ff659d3
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Showing 2 changed files with 47 additions and 34 deletions.
diff --git a/folly/futures/detail/Core.cpp b/folly/futures/detail/Core.cpp
@@ -670,6 +670,31 @@ void CoreBase::derefCallback() noexcept {
   }
 }
 
+bool CoreBase::destroyDerived() noexcept {
+  DCHECK(attached_ == 0);
+  auto state = state_.load(std::memory_order_relaxed);
+  switch (state) {
+    case State::OnlyResult:
+      [[fallthrough]];
+
+    case State::Done:
+      return true;
+
+    case State::Proxy:
+      proxy_->detachFuture();
+      [[fallthrough]];
+
+    case State::Empty:
+      return false;
+
+    case State::Start:
+    case State::OnlyCallback:
+    case State::OnlyCallbackAllowInline:
+    default:
+      terminate_with<std::logic_error>("~Core unexpected state");
+  }
+}
+
 #if FOLLY_USE_EXTERN_FUTURE_UNIT
 template class Core<folly::Unit>;
 #endif

diff --git a/folly/futures/detail/Core.h b/folly/futures/detail/Core.h
@@ -524,6 +524,24 @@ class CoreBase {
 
   void derefCallback() noexcept;
 
+  template <typename Self>
+  FOLLY_ERASE static Self& walkProxyChainImpl(Self& self) noexcept {
+    DCHECK(self.hasResult());
+    auto core = &self;
+    while (core->state_.load(std::memory_order_relaxed) == State::Proxy) {
+      core = core->proxy_;
+    }
+    return *core;
+  }
+  FOLLY_ERASE CoreBase& walkProxyChain() noexcept {
+    return walkProxyChainImpl(*this);
+  }
+  FOLLY_ERASE CoreBase const& walkProxyChain() const noexcept {
+    return walkProxyChainImpl(*this);
+  }
+
+  bool destroyDerived() noexcept;
+
   Callback callback_;
   std::atomic<State> state_;
   std::atomic<unsigned char> attached_;
@@ -590,20 +608,10 @@ class Core final : private ResultHolder<T>, public CoreBase {
   ///   possibly moved-out, depending on what the callback did; some but not
   ///   all callbacks modify (possibly move-out) the result.)
   Try<T>& getTry() {
-    DCHECK(hasResult());
-    auto core = this;
-    while (core->state_.load(std::memory_order_relaxed) == State::Proxy) {
-      core = static_cast<Core*>(core->proxy_);
-    }
-    return core->result_;
+    return static_cast<decltype(*this)&>(walkProxyChain()).result_;
   }
   Try<T> const& getTry() const {
-    DCHECK(hasResult());
-    auto core = this;
-    while (core->state_.load(std::memory_order_relaxed) == State::Proxy) {
-      core = static_cast<Core const*>(core->proxy_);
-    }
-    return core->result_;
+    return static_cast<decltype(*this)&>(walkProxyChain()).result_;
   }
 
   /// Call only from consumer thread.
@@ -682,28 +690,8 @@ class Core final : private ResultHolder<T>, public CoreBase {
   }
 
   ~Core() override {
-    DCHECK(attached_ == 0);
-    auto state = state_.load(std::memory_order_relaxed);
-    switch (state) {
-      case State::OnlyResult:
-        [[fallthrough]];
-
-      case State::Done:
-        this->result_.~Result();
-        break;
-
-      case State::Proxy:
-        proxy_->detachFuture();
-        break;
-
-      case State::Empty:
-        break;
-
-      case State::Start:
-      case State::OnlyCallback:
-      case State::OnlyCallbackAllowInline:
-      default:
-        terminate_with<std::logic_error>("~Core unexpected state");
+    if (destroyDerived()) {
+      this->result_.~Result();
     }
   }