Update clang to r339409.
Change-Id: I800772d2d838223be1f6b40d490c4591b937fca2
diff --git a/linux-x64/clang/include/llvm/ADT/FunctionExtras.h b/linux-x64/clang/include/llvm/ADT/FunctionExtras.h
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+++ b/linux-x64/clang/include/llvm/ADT/FunctionExtras.h
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+//===- FunctionExtras.h - Function type erasure utilities -------*- C++ -*-===//
+//
+// The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+/// \file
+/// This file provides a collection of function (or more generally, callable)
+/// type erasure utilities supplementing those provided by the standard library
+/// in `<function>`.
+///
+/// It provides `unique_function`, which works like `std::function` but supports
+/// move-only callable objects.
+///
+/// Future plans:
+/// - Add a `function` that provides const, volatile, and ref-qualified support,
+/// which doesn't work with `std::function`.
+/// - Provide support for specifying multiple signatures to type erase callable
+/// objects with an overload set, such as those produced by generic lambdas.
+/// - Expand to include a copyable utility that directly replaces std::function
+/// but brings the above improvements.
+///
+/// Note that LLVM's utilities are greatly simplified by not supporting
+/// allocators.
+///
+/// If the standard library ever begins to provide comparable facilities we can
+/// consider switching to those.
+///
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_ADT_FUNCTION_EXTRAS_H
+#define LLVM_ADT_FUNCTION_EXTRAS_H
+
+#include "llvm/ADT/PointerIntPair.h"
+#include "llvm/ADT/PointerUnion.h"
+#include "llvm/Support/type_traits.h"
+#include <memory>
+
+namespace llvm {
+
+template <typename FunctionT> class unique_function;
+
+template <typename ReturnT, typename... ParamTs>
+class unique_function<ReturnT(ParamTs...)> {
+ static constexpr size_t InlineStorageSize = sizeof(void *) * 3;
+
+ // MSVC has a bug and ICEs if we give it a particular dependent value
+ // expression as part of the `std::conditional` below. To work around this,
+ // we build that into a template struct's constexpr bool.
+ template <typename T> struct IsSizeLessThanThresholdT {
+ static constexpr bool value = sizeof(T) <= (2 * sizeof(void *));
+ };
+
+ // Provide a type function to map parameters that won't observe extra copies
+ // or moves and which are small enough to likely pass in register to values
+ // and all other types to l-value reference types. We use this to compute the
+ // types used in our erased call utility to minimize copies and moves unless
+ // doing so would force things unnecessarily into memory.
+ //
+ // The heuristic used is related to common ABI register passing conventions.
+ // It doesn't have to be exact though, and in one way it is more strict
+ // because we want to still be able to observe either moves *or* copies.
+ template <typename T>
+ using AdjustedParamT = typename std::conditional<
+ !std::is_reference<T>::value &&
+ llvm::is_trivially_copy_constructible<T>::value &&
+ llvm::is_trivially_move_constructible<T>::value &&
+ IsSizeLessThanThresholdT<T>::value,
+ T, T &>::type;
+
+ // The type of the erased function pointer we use as a callback to dispatch to
+ // the stored callable when it is trivial to move and destroy.
+ using CallPtrT = ReturnT (*)(void *CallableAddr,
+ AdjustedParamT<ParamTs>... Params);
+ using MovePtrT = void (*)(void *LHSCallableAddr, void *RHSCallableAddr);
+ using DestroyPtrT = void (*)(void *CallableAddr);
+
+ /// A struct to hold a single trivial callback with sufficient alignment for
+ /// our bitpacking.
+ struct alignas(8) TrivialCallback {
+ CallPtrT CallPtr;
+ };
+
+ /// A struct we use to aggregate three callbacks when we need full set of
+ /// operations.
+ struct alignas(8) NonTrivialCallbacks {
+ CallPtrT CallPtr;
+ MovePtrT MovePtr;
+ DestroyPtrT DestroyPtr;
+ };
+
+ // Create a pointer union between either a pointer to a static trivial call
+ // pointer in a struct or a pointer to a static struct of the call, move, and
+ // destroy pointers.
+ using CallbackPointerUnionT =
+ PointerUnion<TrivialCallback *, NonTrivialCallbacks *>;
+
+ // The main storage buffer. This will either have a pointer to out-of-line
+ // storage or an inline buffer storing the callable.
+ union StorageUnionT {
+ // For out-of-line storage we keep a pointer to the underlying storage and
+ // the size. This is enough to deallocate the memory.
+ struct OutOfLineStorageT {
+ void *StoragePtr;
+ size_t Size;
+ size_t Alignment;
+ } OutOfLineStorage;
+ static_assert(
+ sizeof(OutOfLineStorageT) <= InlineStorageSize,
+ "Should always use all of the out-of-line storage for inline storage!");
+
+ // For in-line storage, we just provide an aligned character buffer. We
+ // provide three pointers worth of storage here.
+ typename std::aligned_storage<InlineStorageSize, alignof(void *)>::type
+ InlineStorage;
+ } StorageUnion;
+
+ // A compressed pointer to either our dispatching callback or our table of
+ // dispatching callbacks and the flag for whether the callable itself is
+ // stored inline or not.
+ PointerIntPair<CallbackPointerUnionT, 1, bool> CallbackAndInlineFlag;
+
+ bool isInlineStorage() const { return CallbackAndInlineFlag.getInt(); }
+
+ bool isTrivialCallback() const {
+ return CallbackAndInlineFlag.getPointer().template is<TrivialCallback *>();
+ }
+
+ CallPtrT getTrivialCallback() const {
+ return CallbackAndInlineFlag.getPointer().template get<TrivialCallback *>()->CallPtr;
+ }
+
+ NonTrivialCallbacks *getNonTrivialCallbacks() const {
+ return CallbackAndInlineFlag.getPointer()
+ .template get<NonTrivialCallbacks *>();
+ }
+
+ void *getInlineStorage() { return &StorageUnion.InlineStorage; }
+
+ void *getOutOfLineStorage() {
+ return StorageUnion.OutOfLineStorage.StoragePtr;
+ }
+ size_t getOutOfLineStorageSize() const {
+ return StorageUnion.OutOfLineStorage.Size;
+ }
+ size_t getOutOfLineStorageAlignment() const {
+ return StorageUnion.OutOfLineStorage.Alignment;
+ }
+
+ void setOutOfLineStorage(void *Ptr, size_t Size, size_t Alignment) {
+ StorageUnion.OutOfLineStorage = {Ptr, Size, Alignment};
+ }
+
+ template <typename CallableT>
+ static ReturnT CallImpl(void *CallableAddr, AdjustedParamT<ParamTs>... Params) {
+ return (*reinterpret_cast<CallableT *>(CallableAddr))(
+ std::forward<ParamTs>(Params)...);
+ }
+
+ template <typename CallableT>
+ static void MoveImpl(void *LHSCallableAddr, void *RHSCallableAddr) noexcept {
+ new (LHSCallableAddr)
+ CallableT(std::move(*reinterpret_cast<CallableT *>(RHSCallableAddr)));
+ }
+
+ template <typename CallableT>
+ static void DestroyImpl(void *CallableAddr) noexcept {
+ reinterpret_cast<CallableT *>(CallableAddr)->~CallableT();
+ }
+
+public:
+ unique_function() = default;
+ unique_function(std::nullptr_t /*null_callable*/) {}
+
+ ~unique_function() {
+ if (!CallbackAndInlineFlag.getPointer())
+ return;
+
+ // Cache this value so we don't re-check it after type-erased operations.
+ bool IsInlineStorage = isInlineStorage();
+
+ if (!isTrivialCallback())
+ getNonTrivialCallbacks()->DestroyPtr(
+ IsInlineStorage ? getInlineStorage() : getOutOfLineStorage());
+
+ if (!IsInlineStorage)
+ deallocate_buffer(getOutOfLineStorage(), getOutOfLineStorageSize(),
+ getOutOfLineStorageAlignment());
+ }
+
+ unique_function(unique_function &&RHS) noexcept {
+ // Copy the callback and inline flag.
+ CallbackAndInlineFlag = RHS.CallbackAndInlineFlag;
+
+ // If the RHS is empty, just copying the above is sufficient.
+ if (!RHS)
+ return;
+
+ if (!isInlineStorage()) {
+ // The out-of-line case is easiest to move.
+ StorageUnion.OutOfLineStorage = RHS.StorageUnion.OutOfLineStorage;
+ } else if (isTrivialCallback()) {
+ // Move is trivial, just memcpy the bytes across.
+ memcpy(getInlineStorage(), RHS.getInlineStorage(), InlineStorageSize);
+ } else {
+ // Non-trivial move, so dispatch to a type-erased implementation.
+ getNonTrivialCallbacks()->MovePtr(getInlineStorage(),
+ RHS.getInlineStorage());
+ }
+
+ // Clear the old callback and inline flag to get back to as-if-null.
+ RHS.CallbackAndInlineFlag = {};
+
+#ifndef NDEBUG
+ // In debug builds, we also scribble across the rest of the storage.
+ memset(RHS.getInlineStorage(), 0xAD, InlineStorageSize);
+#endif
+ }
+
+ unique_function &operator=(unique_function &&RHS) noexcept {
+ if (this == &RHS)
+ return *this;
+
+ // Because we don't try to provide any exception safety guarantees we can
+ // implement move assignment very simply by first destroying the current
+ // object and then move-constructing over top of it.
+ this->~unique_function();
+ new (this) unique_function(std::move(RHS));
+ return *this;
+ }
+
+ template <typename CallableT> unique_function(CallableT Callable) {
+ bool IsInlineStorage = true;
+ void *CallableAddr = getInlineStorage();
+ if (sizeof(CallableT) > InlineStorageSize ||
+ alignof(CallableT) > alignof(decltype(StorageUnion.InlineStorage))) {
+ IsInlineStorage = false;
+ // Allocate out-of-line storage. FIXME: Use an explicit alignment
+ // parameter in C++17 mode.
+ auto Size = sizeof(CallableT);
+ auto Alignment = alignof(CallableT);
+ CallableAddr = allocate_buffer(Size, Alignment);
+ setOutOfLineStorage(CallableAddr, Size, Alignment);
+ }
+
+ // Now move into the storage.
+ new (CallableAddr) CallableT(std::move(Callable));
+
+ // See if we can create a trivial callback. We need the callable to be
+ // trivially moved and trivially destroyed so that we don't have to store
+ // type erased callbacks for those operations.
+ //
+ // FIXME: We should use constexpr if here and below to avoid instantiating
+ // the non-trivial static objects when unnecessary. While the linker should
+ // remove them, it is still wasteful.
+ if (llvm::is_trivially_move_constructible<CallableT>::value &&
+ std::is_trivially_destructible<CallableT>::value) {
+ // We need to create a nicely aligned object. We use a static variable
+ // for this because it is a trivial struct.
+ static TrivialCallback Callback = { &CallImpl<CallableT> };
+
+ CallbackAndInlineFlag = {&Callback, IsInlineStorage};
+ return;
+ }
+
+ // Otherwise, we need to point at an object that contains all the different
+ // type erased behaviors needed. Create a static instance of the struct type
+ // here and then use a pointer to that.
+ static NonTrivialCallbacks Callbacks = {
+ &CallImpl<CallableT>, &MoveImpl<CallableT>, &DestroyImpl<CallableT>};
+
+ CallbackAndInlineFlag = {&Callbacks, IsInlineStorage};
+ }
+
+ ReturnT operator()(ParamTs... Params) {
+ void *CallableAddr =
+ isInlineStorage() ? getInlineStorage() : getOutOfLineStorage();
+
+ return (isTrivialCallback()
+ ? getTrivialCallback()
+ : getNonTrivialCallbacks()->CallPtr)(CallableAddr, Params...);
+ }
+
+ explicit operator bool() const {
+ return (bool)CallbackAndInlineFlag.getPointer();
+ }
+};
+
+} // end namespace llvm
+
+#endif // LLVM_ADT_FUNCTION_H