Move STLFunctionalExtras out of STLExtras

Only using that change in StringRef already decreases the number of
preoprocessed lines from 7837621 to 7776151 for LLVMSupport

Perhaps more interestingly, it shows that many files were relying on the
inclusion of StringRef.h to have the declaration from STLExtras.h. This
patch tries hard to patch relevant part of llvm-project impacted by this
hidden dependency removal.

Potential impact:
- "llvm/ADT/StringRef.h" no longer includes <memory>,
  "llvm/ADT/Optional.h" nor "llvm/ADT/STLExtras.h"

Related Discourse thread:
https://llvm.discourse.group/t/include-what-you-use-include-cleanup/5831

clang/include/clang/Basic/DirectoryEntry.h

@@ -19,6 +19,7 @@
 #include "llvm/ADT/Hashing.h"
 #include "llvm/ADT/StringMap.h"
 #include "llvm/ADT/StringRef.h"
+#include "llvm/ADT/STLExtras.h"
 #include "llvm/Support/ErrorOr.h"
 
 namespace clang {

clang/tools/diagtool/DiagTool.cpp

@@ -12,6 +12,7 @@
 
 #include "DiagTool.h"
 #include "llvm/ADT/StringMap.h"
+#include "llvm/ADT/STLExtras.h"
 #include <vector>
 
 using namespace diagtool;

lld/ELF/Relocations.h

@@ -11,6 +11,7 @@
 
 #include "lld/Common/LLVM.h"
 #include "llvm/ADT/DenseMap.h"
+#include "llvm/ADT/STLExtras.h"
 #include <map>
 #include <vector>
 

lldb/include/lldb/Utility/UserIDResolver.h

@@ -10,6 +10,7 @@
 #define LLDB_UTILITY_USERIDRESOLVER_H
 
 #include "llvm/ADT/DenseMap.h"
+#include "llvm/ADT/Optional.h"
 #include "llvm/ADT/StringRef.h"
 #include <mutex>
 

llvm/include/llvm/ADT/CombinationGenerator.h

@@ -28,7 +28,7 @@
 #define LLVM_ADT_COMBINATIONGENERATOR_H
 
 #include "llvm/ADT/ArrayRef.h"
-#include "llvm/ADT/STLExtras.h"
+#include "llvm/ADT/STLFunctionalExtras.h"
 #include "llvm/ADT/SmallVector.h"
 #include <cassert>
 #include <cstring>

llvm/include/llvm/ADT/STLExtras.h

@@ -16,8 +16,10 @@
 #ifndef LLVM_ADT_STLEXTRAS_H
 #define LLVM_ADT_STLEXTRAS_H
 
+#include "llvm/ADT/identity.h"
 #include "llvm/ADT/Optional.h"
 #include "llvm/ADT/STLForwardCompat.h"
+#include "llvm/ADT/STLFunctionalExtras.h"
 #include "llvm/ADT/iterator.h"
 #include "llvm/ADT/iterator_range.h"
 #include "llvm/Config/abi-breaking.h"
@@ -199,65 +201,6 @@ struct FirstIndexOfType<T, T, Us...> : std::integral_constant<size_t, 0> {};
 template <size_t I, typename... Ts>
 using TypeAtIndex = std::tuple_element_t<I, std::tuple<Ts...>>;
 
-//===----------------------------------------------------------------------===//
-//     Extra additions to <functional>
-//===----------------------------------------------------------------------===//
-
-template <class Ty> struct identity {
-  using argument_type = Ty;
-
-  Ty &operator()(Ty &self) const {
-    return self;
-  }
-  const Ty &operator()(const Ty &self) const {
-    return self;
-  }
-};
-
-/// An efficient, type-erasing, non-owning reference to a callable. This is
-/// intended for use as the type of a function parameter that is not used
-/// after the function in question returns.
-///
-/// This class does not own the callable, so it is not in general safe to store
-/// a function_ref.
-template<typename Fn> class function_ref;
-
-template<typename Ret, typename ...Params>
-class function_ref<Ret(Params...)> {
-  Ret (*callback)(intptr_t callable, Params ...params) = nullptr;
-  intptr_t callable;
-
-  template<typename Callable>
-  static Ret callback_fn(intptr_t callable, Params ...params) {
-    return (*reinterpret_cast<Callable*>(callable))(
-        std::forward<Params>(params)...);
-  }
-
-public:
-  function_ref() = default;
-  function_ref(std::nullptr_t) {}
-
-  template <typename Callable>
-  function_ref(
-      Callable &&callable,
-      // This is not the copy-constructor.
-      std::enable_if_t<!std::is_same<remove_cvref_t<Callable>,
-                                     function_ref>::value> * = nullptr,
-      // Functor must be callable and return a suitable type.
-      std::enable_if_t<std::is_void<Ret>::value ||
-                       std::is_convertible<decltype(std::declval<Callable>()(
-                                               std::declval<Params>()...)),
-                                           Ret>::value> * = nullptr)
-      : callback(callback_fn<typename std::remove_reference<Callable>::type>),
-        callable(reinterpret_cast<intptr_t>(&callable)) {}
-
-  Ret operator()(Params ...params) const {
-    return callback(callable, std::forward<Params>(params)...);
-  }
-
-  explicit operator bool() const { return callback; }
-};
-
 //===----------------------------------------------------------------------===//
 //     Extra additions to <iterator>
 //===----------------------------------------------------------------------===//

llvm/include/llvm/ADT/STLFunctionalExtras.h

@@ -0,0 +1,76 @@
+//===- llvm/ADT/STLFunctionalExtras.h - Extras for <functional> -*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// This file contains some extension to <functional>.
+//
+// No library is required when using these functions.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_ADT_STLFUNCTIONALEXTRAS_H
+#define LLVM_ADT_STLFUNCTIONALEXTRAS_H
+
+#include "llvm/ADT/STLForwardCompat.h"
+
+#include <type_traits>
+#include <utility>
+#include <cstdint>
+
+namespace llvm {
+
+//===----------------------------------------------------------------------===//
+//     Extra additions to <functional>
+//===----------------------------------------------------------------------===//
+
+/// An efficient, type-erasing, non-owning reference to a callable. This is
+/// intended for use as the type of a function parameter that is not used
+/// after the function in question returns.
+///
+/// This class does not own the callable, so it is not in general safe to store
+/// a function_ref.
+template<typename Fn> class function_ref;
+
+template<typename Ret, typename ...Params>
+class function_ref<Ret(Params...)> {
+  Ret (*callback)(intptr_t callable, Params ...params) = nullptr;
+  intptr_t callable;
+
+  template<typename Callable>
+  static Ret callback_fn(intptr_t callable, Params ...params) {
+    return (*reinterpret_cast<Callable*>(callable))(
+        std::forward<Params>(params)...);
+  }
+
+public:
+  function_ref() = default;
+  function_ref(std::nullptr_t) {}
+
+  template <typename Callable>
+  function_ref(
+      Callable &&callable,
+      // This is not the copy-constructor.
+      std::enable_if_t<!std::is_same<remove_cvref_t<Callable>,
+                                     function_ref>::value> * = nullptr,
+      // Functor must be callable and return a suitable type.
+      std::enable_if_t<std::is_void<Ret>::value ||
+                       std::is_convertible<decltype(std::declval<Callable>()(
+                                               std::declval<Params>()...)),
+                                           Ret>::value> * = nullptr)
+      : callback(callback_fn<typename std::remove_reference<Callable>::type>),
+        callable(reinterpret_cast<intptr_t>(&callable)) {}
+
+  Ret operator()(Params ...params) const {
+    return callback(callable, std::forward<Params>(params)...);
+  }
+
+  explicit operator bool() const { return callback; }
+};
+
+} // end namespace llvm
+
+#endif // LLVM_ADT_STLFUNCTIONALEXTRAS_H

llvm/include/llvm/ADT/SmallSet.h

@@ -16,6 +16,7 @@
 #include "llvm/ADT/None.h"
 #include "llvm/ADT/SmallPtrSet.h"
 #include "llvm/ADT/SmallVector.h"
+#include "llvm/ADT/STLExtras.h"
 #include "llvm/ADT/iterator.h"
 #include "llvm/Support/Compiler.h"
 #include "llvm/Support/type_traits.h"

llvm/include/llvm/ADT/SparseMultiSet.h

@@ -20,7 +20,7 @@
 #ifndef LLVM_ADT_SPARSEMULTISET_H
 #define LLVM_ADT_SPARSEMULTISET_H
 
-#include "llvm/ADT/STLExtras.h"
+#include "llvm/ADT/identity.h"
 #include "llvm/ADT/SmallVector.h"
 #include "llvm/ADT/SparseSet.h"
 #include <cassert>

llvm/include/llvm/ADT/SparseSet.h

@@ -19,7 +19,7 @@
 #ifndef LLVM_ADT_SPARSESET_H
 #define LLVM_ADT_SPARSESET_H
 
-#include "llvm/ADT/STLExtras.h"
+#include "llvm/ADT/identity.h"
 #include "llvm/ADT/SmallVector.h"
 #include "llvm/Support/AllocatorBase.h"
 #include <cassert>

llvm/include/llvm/ADT/StringMap.h

@@ -14,6 +14,7 @@
 #define LLVM_ADT_STRINGMAP_H
 
 #include "llvm/ADT/StringMapEntry.h"
+#include "llvm/ADT/iterator.h"
 #include "llvm/Support/AllocatorBase.h"
 #include "llvm/Support/PointerLikeTypeTraits.h"
 #include <initializer_list>

llvm/include/llvm/ADT/StringMapEntry.h

@@ -15,7 +15,9 @@
 #ifndef LLVM_ADT_STRINGMAPENTRY_H
 #define LLVM_ADT_STRINGMAPENTRY_H
 
+#include "llvm/ADT/None.h"
 #include "llvm/ADT/StringRef.h"
+#include "llvm/ADT/STLFunctionalExtras.h"
 
 namespace llvm {
 

llvm/include/llvm/ADT/StringRef.h

@@ -9,7 +9,8 @@
 #ifndef LLVM_ADT_STRINGREF_H
 #define LLVM_ADT_STRINGREF_H
 
-#include "llvm/ADT/STLExtras.h"
+#include "llvm/ADT/DenseMapInfo.h"
+#include "llvm/ADT/STLFunctionalExtras.h"
 #include "llvm/ADT/iterator_range.h"
 #include "llvm/Support/Compiler.h"
 #include <algorithm>
@@ -978,13 +979,7 @@ namespace llvm {
           reinterpret_cast<const char *>(~static_cast<uintptr_t>(1)), 0);
     }
 
-    static unsigned getHashValue(StringRef Val) {
-      assert(Val.data() != getEmptyKey().data() &&
-             "Cannot hash the empty key!");
-      assert(Val.data() != getTombstoneKey().data() &&
-             "Cannot hash the tombstone key!");
-      return (unsigned)(hash_value(Val));
-    }
+    static unsigned getHashValue(StringRef Val);
 
     static bool isEqual(StringRef LHS, StringRef RHS) {
       if (RHS.data() == getEmptyKey().data())

llvm/include/llvm/ADT/StringSwitch.h

@@ -12,6 +12,7 @@
 #ifndef LLVM_ADT_STRINGSWITCH_H
 #define LLVM_ADT_STRINGSWITCH_H
 
+#include "llvm/ADT/Optional.h"
 #include "llvm/ADT/StringRef.h"
 #include "llvm/Support/Compiler.h"
 #include <cassert>

llvm/include/llvm/ADT/identity.h

@@ -0,0 +1,34 @@
+//===- llvm/ADT/Identity.h - Provide std::identity from C++20 ---*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// This file provides an implementation of std::identity from C++20.
+//
+// No library is required when using these functions.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_ADT_IDENTITY_H
+#define LLVM_ADT_IDENTITY_H
+
+
+namespace llvm {
+
+template <class Ty> struct identity {
+  using argument_type = Ty;
+
+  Ty &operator()(Ty &self) const {
+    return self;
+  }
+  const Ty &operator()(const Ty &self) const {
+    return self;
+  }
+};
+
+} // end namespace llvm
+
+#endif // LLVM_ADT_IDENTITY_H

llvm/include/llvm/ExecutionEngine/JITLink/MemoryFlags.h

@@ -16,6 +16,7 @@
 
 #include "llvm/ADT/BitmaskEnum.h"
 #include "llvm/ADT/DenseMapInfo.h"
+#include "llvm/ADT/STLExtras.h"
 #include "llvm/Support/Memory.h"
 #include "llvm/Support/raw_ostream.h"
 

llvm/include/llvm/IR/LLVMContext.h

@@ -15,6 +15,7 @@
 #define LLVM_IR_LLVMCONTEXT_H
 
 #include "llvm-c/Types.h"
+#include "llvm/ADT/Optional.h"
 #include "llvm/IR/DiagnosticHandler.h"
 #include "llvm/Support/CBindingWrapping.h"
 #include <cstdint>

llvm/include/llvm/MC/SubtargetFeature.h

@@ -18,6 +18,7 @@
 #define LLVM_MC_SUBTARGETFEATURE_H
 
 #include "llvm/ADT/StringRef.h"
+#include "llvm/ADT/STLExtras.h"
 #include "llvm/Support/MathExtras.h"
 #include <array>
 #include <bitset>

llvm/include/llvm/Support/CrashRecoveryContext.h

@@ -9,7 +9,7 @@
 #ifndef LLVM_SUPPORT_CRASHRECOVERYCONTEXT_H
 #define LLVM_SUPPORT_CRASHRECOVERYCONTEXT_H
 
-#include "llvm/ADT/STLExtras.h"
+#include "llvm/ADT/STLFunctionalExtras.h"
 
 namespace llvm {
 class CrashRecoveryContextCleanup;

llvm/include/llvm/Support/JSON.h

@@ -49,6 +49,7 @@
 #include "llvm/ADT/DenseMap.h"
 #include "llvm/ADT/SmallVector.h"
 #include "llvm/ADT/StringRef.h"
+#include "llvm/ADT/STLFunctionalExtras.h"
 #include "llvm/Support/Error.h"
 #include "llvm/Support/FormatVariadic.h"
 #include "llvm/Support/raw_ostream.h"

llvm/include/llvm/Support/TimeProfiler.h

@@ -10,6 +10,7 @@
 #define LLVM_SUPPORT_TIMEPROFILER_H
 
 #include "llvm/Support/Error.h"
+#include "llvm/ADT/STLFunctionalExtras.h"
 
 namespace llvm {
 

llvm/include/llvm/Support/Timer.h

@@ -13,6 +13,7 @@
 #include "llvm/ADT/StringRef.h"
 #include "llvm/Support/DataTypes.h"
 #include <cassert>
+#include <memory>
 #include <string>
 #include <vector>
 

llvm/include/llvm/Support/VirtualFileSystem.h

@@ -19,6 +19,7 @@
 #include "llvm/ADT/Optional.h"
 #include "llvm/ADT/SmallVector.h"
 #include "llvm/ADT/StringRef.h"
+#include "llvm/ADT/STLFunctionalExtras.h"
 #include "llvm/Support/Chrono.h"
 #include "llvm/Support/ErrorOr.h"
 #include "llvm/Support/FileSystem.h"

llvm/include/llvm/Support/raw_ostream.h

@@ -15,6 +15,7 @@
 
 #include "llvm/ADT/SmallVector.h"
 #include "llvm/ADT/StringRef.h"
+#include "llvm/ADT/Optional.h"
 #include "llvm/Support/DataTypes.h"
 #include <cassert>
 #include <cstddef>

llvm/include/llvm/Testing/Support/Annotations.h

@@ -16,6 +16,8 @@
 
 namespace llvm {
 
+class raw_ostream;
+
 /// Annotations lets you mark points and ranges inside source code, for tests:
 ///
 ///    Annotations Example(R"cpp(

llvm/lib/CodeGen/NonRelocatableStringpool.cpp

@@ -7,6 +7,7 @@
 //===----------------------------------------------------------------------===//
 
 #include "llvm/CodeGen/NonRelocatableStringpool.h"
+#include "llvm/ADT/STLExtras.h"
 
 namespace llvm {
 

llvm/lib/Support/CommandLine.cpp

@@ -22,7 +22,7 @@
 #include "llvm-c/Support.h"
 #include "llvm/ADT/ArrayRef.h"
 #include "llvm/ADT/Optional.h"
-#include "llvm/ADT/STLExtras.h"
+#include "llvm/ADT/STLFunctionalExtras.h"
 #include "llvm/ADT/SmallPtrSet.h"
 #include "llvm/ADT/SmallString.h"
 #include "llvm/ADT/StringExtras.h"

llvm/lib/Support/StringRef.cpp

@@ -597,3 +597,11 @@ bool StringRef::getAsDouble(double &Result, bool AllowInexact) const {
 hash_code llvm::hash_value(StringRef S) {
   return hash_combine_range(S.begin(), S.end());
 }
+
+unsigned DenseMapInfo<StringRef, void>::getHashValue(StringRef Val) {
+  assert(Val.data() != getEmptyKey().data() &&
+         "Cannot hash the empty key!");
+  assert(Val.data() != getTombstoneKey().data() &&
+         "Cannot hash the tombstone key!");
+  return (unsigned)(hash_value(Val));
+}

llvm/lib/Support/TimeProfiler.cpp

@@ -11,7 +11,7 @@
 //===----------------------------------------------------------------------===//
 
 #include "llvm/Support/TimeProfiler.h"
-#include "llvm/ADT/STLExtras.h"
+#include "llvm/ADT/STLFunctionalExtras.h"
 #include "llvm/ADT/StringMap.h"
 #include "llvm/Support/JSON.h"
 #include "llvm/Support/ManagedStatic.h"

llvm/lib/Target/AMDGPU/AMDGPULibFunc.h

@@ -10,6 +10,7 @@
 #define _AMDGPU_LIBFUNC_H_
 
 #include "llvm/ADT/StringRef.h"
+#include <memory>
 
 namespace llvm {
 

llvm/unittests/ADT/SequenceTest.cpp

@@ -7,6 +7,7 @@
 //===----------------------------------------------------------------------===//
 
 #include "llvm/ADT/Sequence.h"
+#include "llvm/ADT/STLExtras.h"
 #include "gmock/gmock.h"
 #include "gtest/gtest.h"
 

llvm/unittests/ADT/SimpleIListTest.cpp

@@ -7,6 +7,7 @@
 //===----------------------------------------------------------------------===//
 
 #include "llvm/ADT/simple_ilist.h"
+#include "llvm/ADT/STLExtras.h"
 #include "gtest/gtest.h"
 
 using namespace llvm;

llvm/unittests/ADT/SmallPtrSetTest.cpp

@@ -12,6 +12,7 @@
 
 #include "llvm/ADT/SmallPtrSet.h"
 #include "llvm/ADT/PointerIntPair.h"
+#include "llvm/ADT/STLExtras.h"
 #include "llvm/Support/PointerLikeTypeTraits.h"
 #include "gtest/gtest.h"
 

llvm/unittests/ADT/StringMapTest.cpp

@@ -7,6 +7,7 @@
 //===----------------------------------------------------------------------===//
 
 #include "llvm/ADT/StringMap.h"
+#include "llvm/ADT/STLExtras.h"
 #include "llvm/ADT/Twine.h"
 #include "llvm/Support/DataTypes.h"
 #include "gtest/gtest.h"

llvm/unittests/ADT/StringSetTest.cpp

@@ -7,6 +7,7 @@
 //===----------------------------------------------------------------------===//
 
 #include "llvm/ADT/StringSet.h"
+#include "llvm/ADT/STLExtras.h"
 #include "gtest/gtest.h"
 using namespace llvm;
 

llvm/unittests/Support/ReverseIterationTest.cpp

@@ -13,6 +13,7 @@
 #include "llvm/Support/ReverseIteration.h"
 #include "llvm/ADT/DenseMap.h"
 #include "llvm/ADT/DenseMapInfo.h"
+#include "llvm/ADT/STLExtras.h"
 #include "gtest/gtest.h"
 
 using namespace llvm;

mlir/include/mlir/Conversion/GPUCommon/GPUCommonPass.h

@@ -10,6 +10,7 @@
 
 #include "mlir/Support/LLVM.h"
 #include "llvm/ADT/StringRef.h"
+#include <functional>
 #include <vector>
 
 namespace llvm {

mlir/lib/Parser/Token.h

@@ -10,6 +10,7 @@
 #define MLIR_LIB_PARSER_TOKEN_H
 
 #include "mlir/Support/LLVM.h"
+#include "llvm/ADT/Optional.h"
 #include "llvm/ADT/StringRef.h"
 #include "llvm/Support/SMLoc.h"