Update contrib/libs/cxxsupp/libcxxabi to 14.0.4

ref:9027119e143437bfa6df5c013a9b754905669a23

5 files changed, 343 insertions, 207 deletions

diff --git a/contrib/libs/cxxsupp/libcxxabi/src/cxa_guard_impl.h b/contrib/libs/cxxsupp/libcxxabi/src/cxa_guard_impl.h
index df3f4a48bb..5a7cbfd5cd 100644
--- a/contrib/libs/cxxsupp/libcxxabi/src/cxa_guard_impl.h
+++ b/contrib/libs/cxxsupp/libcxxabi/src/cxa_guard_impl.h
@@ -23,9 +23,15 @@
  * the thread currently performing initialization is stored in the second word.
  *
  *  Guard Object Layout:
- * -------------------------------------------------------------------------
- * |a: guard byte | a+1: init byte | a+2 : unused ... | a+4: thread-id ... |
- * -------------------------------------------------------------------------
+ * ---------------------------------------------------------------------------
+ * | a+0: guard byte | a+1: init byte | a+2: unused ... | a+4: thread-id ... |
+ * ---------------------------------------------------------------------------
+ *
+ * Note that we don't do what the ABI docs suggest (put a mutex in the guard
+ * object which we acquire in cxa_guard_acquire and release in
+ * cxa_guard_release). Instead we use the init byte to imitate that behaviour,
+ * but without actually holding anything mutex related between aquire and
+ * release/abort.
  *
  *  Access Protocol:
  *    For each implementation the guard byte is checked and set before accessing
@@ -48,6 +54,7 @@
 #  endif
 #endif
 
+#include <limits.h>
 #include <stdlib.h>
 #include <__threading_support>
 #ifndef _LIBCXXABI_HAS_NO_THREADS
@@ -156,92 +163,107 @@ uint32_t PlatformThreadID() {
 constexpr uint32_t (*PlatformThreadID)() = nullptr;
 #endif
 
-constexpr bool PlatformSupportsThreadID() { return +PlatformThreadID != nullptr; }
-
 //===----------------------------------------------------------------------===//
-//                          GuardBase
+//                          GuardByte
 //===----------------------------------------------------------------------===//
 
-enum class AcquireResult {
-  INIT_IS_DONE,
-  INIT_IS_PENDING,
-};
-constexpr AcquireResult INIT_IS_DONE = AcquireResult::INIT_IS_DONE;
-constexpr AcquireResult INIT_IS_PENDING = AcquireResult::INIT_IS_PENDING;
-
 static constexpr uint8_t UNSET = 0;
 static constexpr uint8_t COMPLETE_BIT = (1 << 0);
 static constexpr uint8_t PENDING_BIT = (1 << 1);
 static constexpr uint8_t WAITING_BIT = (1 << 2);
 
-template <class Derived>
-struct GuardObject {
-  GuardObject() = delete;
-  GuardObject(GuardObject const&) = delete;
-  GuardObject& operator=(GuardObject const&) = delete;
-
-  explicit GuardObject(uint32_t* g)
-      : base_address(g), guard_byte_address(reinterpret_cast<uint8_t*>(g)),
-        init_byte_address(reinterpret_cast<uint8_t*>(g) + 1), thread_id_address(nullptr) {}
+/// Manages reads and writes to the guard byte.
+struct GuardByte {
+  GuardByte() = delete;
+  GuardByte(GuardByte const&) = delete;
+  GuardByte& operator=(GuardByte const&) = delete;
 
-  explicit GuardObject(uint64_t* g)
-      : base_address(g), guard_byte_address(reinterpret_cast<uint8_t*>(g)),
-        init_byte_address(reinterpret_cast<uint8_t*>(g) + 1), thread_id_address(reinterpret_cast<uint32_t*>(g) + 1) {}
+  explicit GuardByte(uint8_t* const guard_byte_address) : guard_byte(guard_byte_address) {}
 
 public:
-  /// Implements __cxa_guard_acquire
-  AcquireResult cxa_guard_acquire() {
-    AtomicInt<uint8_t> guard_byte(guard_byte_address);
-    if (guard_byte.load(std::_AO_Acquire) != UNSET)
-      return INIT_IS_DONE;
-    return derived()->acquire_init_byte();
-  }
-
-  /// Implements __cxa_guard_release
-  void cxa_guard_release() {
-    AtomicInt<uint8_t> guard_byte(guard_byte_address);
-    // Store complete first, so that when release wakes other folks, they see
-    // it as having been completed.
-    guard_byte.store(COMPLETE_BIT, std::_AO_Release);
-    derived()->release_init_byte();
+  /// The guard byte portion of cxa_guard_acquire. Returns true if
+  /// initialization has already been completed.
+  bool acquire() {
+    // if guard_byte is non-zero, we have already completed initialization
+    // (i.e. release has been called)
+    return guard_byte.load(std::_AO_Acquire) != UNSET;
   }
 
-  /// Implements __cxa_guard_abort
-  void cxa_guard_abort() { derived()->abort_init_byte(); }
+  /// The guard byte portion of cxa_guard_release.
+  void release() { guard_byte.store(COMPLETE_BIT, std::_AO_Release); }
 
-public:
-  /// base_address - the address of the original guard object.
-  void* const base_address;
-  /// The address of the guard byte at offset 0.
-  uint8_t* const guard_byte_address;
-  /// The address of the byte used by the implementation during initialization.
-  uint8_t* const init_byte_address;
-  /// An optional address storing an identifier for the thread performing initialization.
-  /// It's used to detect recursive initialization.
-  uint32_t* const thread_id_address;
+  /// The guard byte portion of cxa_guard_abort.
+  void abort() {} // Nothing to do
 
 private:
-  Derived* derived() { return static_cast<Derived*>(this); }
+  AtomicInt<uint8_t> guard_byte;
 };
 
 //===----------------------------------------------------------------------===//
+//                       InitByte Implementations
+//===----------------------------------------------------------------------===//
+//
+// Each initialization byte implementation supports the following methods:
+//
+//  InitByte(uint8_t* _init_byte_address, uint32_t* _thread_id_address)
+//    Construct the InitByte object, initializing our member variables
+//
+//  bool acquire()
+//    Called before we start the initialization. Check if someone else has already started, and if
+//    not to signal our intent to start it ourselves. We determine the current status from the init
+//    byte, which is one of 4 possible values:
+//      COMPLETE:           Initialization was finished by somebody else. Return true.
+//      PENDING:            Somebody has started the initialization already, set the WAITING bit,
+//                          then wait for the init byte to get updated with a new value.
+//      (PENDING|WAITING):  Somebody has started the initialization already, and we're not the
+//                          first one waiting. Wait for the init byte to get updated.
+//      UNSET:              Initialization hasn't successfully completed, and nobody is currently
+//                          performing the initialization. Set the PENDING bit to indicate our
+//                          intention to start the initialization, and return false.
+//    The return value indicates whether initialization has already been completed.
+//
+//  void release()
+//    Called after successfully completing the initialization. Update the init byte to reflect
+//    that, then if anybody else is waiting, wake them up.
+//
+//  void abort()
+//    Called after an error is thrown during the initialization. Reset the init byte to UNSET to
+//    indicate that we're no longer performing the initialization, then if anybody is waiting, wake
+//    them up so they can try performing the initialization.
+//
+
+//===----------------------------------------------------------------------===//
 //                    Single Threaded Implementation
 //===----------------------------------------------------------------------===//
 
-struct InitByteNoThreads : GuardObject<InitByteNoThreads> {
-  using GuardObject::GuardObject;
+/// InitByteNoThreads - Doesn't use any inter-thread synchronization when
+/// managing reads and writes to the init byte.
+struct InitByteNoThreads {
+  InitByteNoThreads() = delete;
+  InitByteNoThreads(InitByteNoThreads const&) = delete;
+  InitByteNoThreads& operator=(InitByteNoThreads const&) = delete;
 
-  AcquireResult acquire_init_byte() {
+  explicit InitByteNoThreads(uint8_t* _init_byte_address, uint32_t*) : init_byte_address(_init_byte_address) {}
+
+  /// The init byte portion of cxa_guard_acquire. Returns true if
+  /// initialization has already been completed.
+  bool acquire() {
     if (*init_byte_address == COMPLETE_BIT)
-      return INIT_IS_DONE;
+      return true;
     if (*init_byte_address & PENDING_BIT)
       ABORT_WITH_MESSAGE("__cxa_guard_acquire detected recursive initialization");
     *init_byte_address = PENDING_BIT;
-    return INIT_IS_PENDING;
+    return false;
   }
 
-  void release_init_byte() { *init_byte_address = COMPLETE_BIT; }
-  void abort_init_byte() { *init_byte_address = UNSET; }
+  /// The init byte portion of cxa_guard_release.
+  void release() { *init_byte_address = COMPLETE_BIT; }
+  /// The init byte portion of cxa_guard_abort.
+  void abort() { *init_byte_address = UNSET; }
+
+private:
+  /// The address of the byte used during initialization.
+  uint8_t* const init_byte_address;
 };
 
 //===----------------------------------------------------------------------===//
@@ -281,18 +303,20 @@ struct LibcppMutex {};
 struct LibcppCondVar {};
 #endif // !defined(_LIBCXXABI_HAS_NO_THREADS)
 
+/// InitByteGlobalMutex - Uses a global mutex and condition variable (common to
+/// all static local variables) to manage reads and writes to the init byte.
 template <class Mutex, class CondVar, Mutex& global_mutex, CondVar& global_cond,
           uint32_t (*GetThreadID)() = PlatformThreadID>
-struct InitByteGlobalMutex : GuardObject<InitByteGlobalMutex<Mutex, CondVar, global_mutex, global_cond, GetThreadID>> {
+struct InitByteGlobalMutex {
 
-  using BaseT = typename InitByteGlobalMutex::GuardObject;
-  using BaseT::BaseT;
-
-  explicit InitByteGlobalMutex(uint32_t* g) : BaseT(g), has_thread_id_support(false) {}
-  explicit InitByteGlobalMutex(uint64_t* g) : BaseT(g), has_thread_id_support(PlatformSupportsThreadID()) {}
+  explicit InitByteGlobalMutex(uint8_t* _init_byte_address, uint32_t* _thread_id_address)
+      : init_byte_address(_init_byte_address), thread_id_address(_thread_id_address),
+        has_thread_id_support(_thread_id_address != nullptr && GetThreadID != nullptr) {}
 
 public:
-  AcquireResult acquire_init_byte() {
+  /// The init byte portion of cxa_guard_acquire. Returns true if
+  /// initialization has already been completed.
+  bool acquire() {
     LockGuard g("__cxa_guard_acquire");
     // Check for possible recursive initialization.
     if (has_thread_id_support && (*init_byte_address & PENDING_BIT)) {
@@ -307,16 +331,17 @@ public:
     }
 
     if (*init_byte_address == COMPLETE_BIT)
-      return INIT_IS_DONE;
+      return true;
 
     if (has_thread_id_support)
       *thread_id_address = current_thread_id.get();
 
     *init_byte_address = PENDING_BIT;
-    return INIT_IS_PENDING;
+    return false;
   }
 
-  void release_init_byte() {
+  /// The init byte portion of cxa_guard_release.
+  void release() {
     bool has_waiting;
     {
       LockGuard g("__cxa_guard_release");
@@ -330,7 +355,8 @@ public:
     }
   }
 
-  void abort_init_byte() {
+  /// The init byte portion of cxa_guard_abort.
+  void abort() {
     bool has_waiting;
     {
       LockGuard g("__cxa_guard_abort");
@@ -347,8 +373,12 @@ public:
   }
 
 private:
-  using BaseT::init_byte_address;
-  using BaseT::thread_id_address;
+  /// The address of the byte used during initialization.
+  uint8_t* const init_byte_address;
+  /// An optional address storing an identifier for the thread performing initialization.
+  /// It's used to detect recursive initialization.
+  uint32_t* const thread_id_address;
+
   const bool has_thread_id_support;
   LazyValue<uint32_t, GetThreadID> current_thread_id;
 
@@ -395,36 +425,32 @@ constexpr void (*PlatformFutexWake)(int*) = nullptr;
 
 constexpr bool PlatformSupportsFutex() { return +PlatformFutexWait != nullptr; }
 
-/// InitByteFutex - Manages initialization using atomics and the futex syscall
-/// for waiting and waking.
+/// InitByteFutex - Uses a futex to manage reads and writes to the init byte.
 template <void (*Wait)(int*, int) = PlatformFutexWait, void (*Wake)(int*) = PlatformFutexWake,
           uint32_t (*GetThreadIDArg)() = PlatformThreadID>
-struct InitByteFutex : GuardObject<InitByteFutex<Wait, Wake, GetThreadIDArg>> {
-  using BaseT = typename InitByteFutex::GuardObject;
-
-  /// ARM Constructor
-  explicit InitByteFutex(uint32_t* g)
-      : BaseT(g), init_byte(this->init_byte_address), has_thread_id_support(this->thread_id_address && GetThreadIDArg),
-        thread_id(this->thread_id_address) {}
+struct InitByteFutex {
 
-  /// Itanium Constructor
-  explicit InitByteFutex(uint64_t* g)
-      : BaseT(g), init_byte(this->init_byte_address), has_thread_id_support(this->thread_id_address && GetThreadIDArg),
-        thread_id(this->thread_id_address) {}
+  explicit InitByteFutex(uint8_t* _init_byte_address, uint32_t* _thread_id_address)
+      : init_byte(_init_byte_address),
+        has_thread_id_support(_thread_id_address != nullptr && GetThreadIDArg != nullptr),
+        thread_id(_thread_id_address),
+        base_address(reinterpret_cast<int*>(/*_init_byte_address & ~0x3*/ _init_byte_address - 1)) {}
 
 public:
-  AcquireResult acquire_init_byte() {
+  /// The init byte portion of cxa_guard_acquire. Returns true if
+  /// initialization has already been completed.
+  bool acquire() {
     while (true) {
       uint8_t last_val = UNSET;
       if (init_byte.compare_exchange(&last_val, PENDING_BIT, std::_AO_Acq_Rel, std::_AO_Acquire)) {
         if (has_thread_id_support) {
           thread_id.store(current_thread_id.get(), std::_AO_Relaxed);
         }
-        return INIT_IS_PENDING;
+        return false;
       }
 
       if (last_val == COMPLETE_BIT)
-        return INIT_IS_DONE;
+        return true;
 
       if (last_val & PENDING_BIT) {
 
@@ -441,7 +467,7 @@ public:
           if (!init_byte.compare_exchange(&last_val, PENDING_BIT | WAITING_BIT, std::_AO_Acq_Rel, std::_AO_Release)) {
             // (1) success, via someone else's work!
             if (last_val == COMPLETE_BIT)
-              return INIT_IS_DONE;
+              return true;
 
             // (3) someone else, bailed on doing the work, retry from the start!
             if (last_val == UNSET)
@@ -455,13 +481,15 @@ public:
     }
   }
 
-  void release_init_byte() {
+  /// The init byte portion of cxa_guard_release.
+  void release() {
     uint8_t old = init_byte.exchange(COMPLETE_BIT, std::_AO_Acq_Rel);
     if (old & WAITING_BIT)
       wake_all();
   }
 
-  void abort_init_byte() {
+  /// The init byte portion of cxa_guard_abort.
+  void abort() {
     if (has_thread_id_support)
       thread_id.store(0, std::_AO_Relaxed);
 
@@ -472,12 +500,11 @@ public:
 
 private:
   /// Use the futex to wait on the current guard variable. Futex expects a
-  /// 32-bit 4-byte aligned address as the first argument, so we have to use use
-  /// the base address of the guard variable (not the init byte).
-  void wait_on_initialization() {
-    Wait(static_cast<int*>(this->base_address), expected_value_for_futex(PENDING_BIT | WAITING_BIT));
-  }
-  void wake_all() { Wake(static_cast<int*>(this->base_address)); }
+  /// 32-bit 4-byte aligned address as the first argument, so we use the 4-byte
+  /// aligned address that encompasses the init byte (i.e. the address of the
+  /// raw guard object that was passed to __cxa_guard_acquire/release/abort).
+  void wait_on_initialization() { Wait(base_address, expected_value_for_futex(PENDING_BIT | WAITING_BIT)); }
+  void wake_all() { Wake(base_address); }
 
 private:
   AtomicInt<uint8_t> init_byte;
@@ -487,6 +514,10 @@ private:
   AtomicInt<uint32_t> thread_id;
   LazyValue<uint32_t, GetThreadIDArg> current_thread_id;
 
+  /// the 4-byte-aligned address that encompasses the init byte (i.e. the
+  /// address of the raw guard object).
+  int* const base_address;
+
   /// Create the expected integer value for futex `wait(int* addr, int expected)`.
   /// We pass the base address as the first argument, So this function creates
   /// an zero-initialized integer  with `b` copied at the correct offset.
@@ -500,6 +531,86 @@ private:
 };
 
 //===----------------------------------------------------------------------===//
+//                          GuardObject
+//===----------------------------------------------------------------------===//
+
+enum class AcquireResult {
+  INIT_IS_DONE,
+  INIT_IS_PENDING,
+};
+constexpr AcquireResult INIT_IS_DONE = AcquireResult::INIT_IS_DONE;
+constexpr AcquireResult INIT_IS_PENDING = AcquireResult::INIT_IS_PENDING;
+
+/// Co-ordinates between GuardByte and InitByte.
+template <class InitByteT>
+struct GuardObject {
+  GuardObject() = delete;
+  GuardObject(GuardObject const&) = delete;
+  GuardObject& operator=(GuardObject const&) = delete;
+
+private:
+  GuardByte guard_byte;
+  InitByteT init_byte;
+
+public:
+  /// ARM Constructor
+  explicit GuardObject(uint32_t* raw_guard_object)
+      : guard_byte(reinterpret_cast<uint8_t*>(raw_guard_object)),
+        init_byte(reinterpret_cast<uint8_t*>(raw_guard_object) + 1, nullptr) {}
+
+  /// Itanium Constructor
+  explicit GuardObject(uint64_t* raw_guard_object)
+      : guard_byte(reinterpret_cast<uint8_t*>(raw_guard_object)),
+        init_byte(reinterpret_cast<uint8_t*>(raw_guard_object) + 1, reinterpret_cast<uint32_t*>(raw_guard_object) + 1) {
+  }
+
+  /// Implements __cxa_guard_acquire.
+  AcquireResult cxa_guard_acquire() {
+    // Use short-circuit evaluation to avoid calling init_byte.acquire when
+    // guard_byte.acquire returns true. (i.e. don't call it when we know from
+    // the guard byte that initialization has already been completed)
+    if (guard_byte.acquire() || init_byte.acquire())
+      return INIT_IS_DONE;
+    return INIT_IS_PENDING;
+  }
+
+  /// Implements __cxa_guard_release.
+  void cxa_guard_release() {
+    // Update guard byte first, so if somebody is woken up by init_byte.release
+    // and comes all the way back around to __cxa_guard_acquire again, they see
+    // it as having completed initialization.
+    guard_byte.release();
+    init_byte.release();
+  }
+
+  /// Implements __cxa_guard_abort.
+  void cxa_guard_abort() {
+    guard_byte.abort();
+    init_byte.abort();
+  }
+};
+
+//===----------------------------------------------------------------------===//
+//                          Convenience Classes
+//===----------------------------------------------------------------------===//
+
+/// NoThreadsGuard - Manages initialization without performing any inter-thread
+/// synchronization.
+using NoThreadsGuard = GuardObject<InitByteNoThreads>;
+
+/// GlobalMutexGuard - Manages initialization using a global mutex and
+/// condition variable.
+template <class Mutex, class CondVar, Mutex& global_mutex, CondVar& global_cond,
+          uint32_t (*GetThreadID)() = PlatformThreadID>
+using GlobalMutexGuard = GuardObject<InitByteGlobalMutex<Mutex, CondVar, global_mutex, global_cond, GetThreadID>>;
+
+/// FutexGuard - Manages initialization using atomics and the futex syscall for
+/// waiting and waking.
+template <void (*Wait)(int*, int) = PlatformFutexWait, void (*Wake)(int*) = PlatformFutexWake,
+          uint32_t (*GetThreadIDArg)() = PlatformThreadID>
+using FutexGuard = GuardObject<InitByteFutex<Wait, Wake, GetThreadIDArg>>;
+
+//===----------------------------------------------------------------------===//
 //
 //===----------------------------------------------------------------------===//
 
@@ -510,25 +621,25 @@ struct GlobalStatic {
 template <class T>
 _LIBCPP_SAFE_STATIC T GlobalStatic<T>::instance = {};
 
-enum class Implementation { NoThreads, GlobalLock, Futex };
+enum class Implementation { NoThreads, GlobalMutex, Futex };
 
 template <Implementation Impl>
 struct SelectImplementation;
 
 template <>
 struct SelectImplementation<Implementation::NoThreads> {
-  using type = InitByteNoThreads;
+  using type = NoThreadsGuard;
 };
 
 template <>
-struct SelectImplementation<Implementation::GlobalLock> {
-  using type = InitByteGlobalMutex<LibcppMutex, LibcppCondVar, GlobalStatic<LibcppMutex>::instance,
-                                   GlobalStatic<LibcppCondVar>::instance, PlatformThreadID>;
+struct SelectImplementation<Implementation::GlobalMutex> {
+  using type = GlobalMutexGuard<LibcppMutex, LibcppCondVar, GlobalStatic<LibcppMutex>::instance,
+                                GlobalStatic<LibcppCondVar>::instance, PlatformThreadID>;
 };
 
 template <>
 struct SelectImplementation<Implementation::Futex> {
-  using type = InitByteFutex<PlatformFutexWait, PlatformFutexWake, PlatformThreadID>;
+  using type = FutexGuard<PlatformFutexWait, PlatformFutexWake, PlatformThreadID>;
 };
 
 // TODO(EricWF): We should prefer the futex implementation when available. But
@@ -539,7 +650,7 @@ constexpr Implementation CurrentImplementation =
 #elif defined(_LIBCXXABI_USE_FUTEX)
     Implementation::Futex;
 #else
-    Implementation::GlobalLock;
+    Implementation::GlobalMutex;
 #endif
 
 static_assert(CurrentImplementation != Implementation::Futex || PlatformSupportsFutex(),
diff --git a/contrib/libs/cxxsupp/libcxxabi/src/demangle/ItaniumDemangle.h b/contrib/libs/cxxsupp/libcxxabi/src/demangle/ItaniumDemangle.h
index 85e1511346..db65c60e7e 100644
--- a/contrib/libs/cxxsupp/libcxxabi/src/demangle/ItaniumDemangle.h
+++ b/contrib/libs/cxxsupp/libcxxabi/src/demangle/ItaniumDemangle.h
@@ -6,8 +6,10 @@
 //
 //===----------------------------------------------------------------------===//
 //
-// Generic itanium demangler library. This file has two byte-per-byte identical
-// copies in the source tree, one in libcxxabi, and the other in llvm.
+// Generic itanium demangler library.
+// There are two copies of this file in the source tree.  The one under
+// libcxxabi is the original and the one under llvm is the copy.  Use
+// cp-to-llvm.sh to update the copy.  See README.txt for more details.
 //
 //===----------------------------------------------------------------------===//
 
@@ -21,12 +23,13 @@
 #include "DemangleConfig.h"
 #include "StringView.h"
 #include "Utility.h"
+#include <algorithm>
 #include <cassert>
 #include <cctype>
 #include <cstdio>
 #include <cstdlib>
 #include <cstring>
-#include <numeric>
+#include <limits>
 #include <utility>
 
 #define FOR_EACH_NODE_KIND(X) \
@@ -310,7 +313,7 @@ public:
       printRight(OB);
   }
 
-  // Print the "left" side of this Node into OutputString.
+  // Print the "left" side of this Node into OutputBuffer.
   virtual void printLeft(OutputBuffer &) const = 0;
 
   // Print the "right". This distinction is necessary to represent C++ types
@@ -1210,7 +1213,8 @@ public:
 class ParameterPack final : public Node {
   NodeArray Data;
 
-  // Setup OutputString for a pack expansion unless we're already expanding one.
+  // Setup OutputBuffer for a pack expansion, unless we're already expanding
+  // one.
   void initializePackExpansion(OutputBuffer &OB) const {
     if (OB.CurrentPackMax == std::numeric_limits<unsigned>::max()) {
       OB.CurrentPackMax = static_cast<unsigned>(Data.size());
@@ -2473,7 +2477,7 @@ template <typename Derived, typename Alloc> struct AbstractManglingParser {
 
   char consume() { return First != Last ? *First++ : '\0'; }
 
-  char look(unsigned Lookahead = 0) {
+  char look(unsigned Lookahead = 0) const {
     if (static_cast<size_t>(Last - First) <= Lookahead)
       return '\0';
     return First[Lookahead];
@@ -2591,34 +2595,38 @@ Node *AbstractManglingParser<Derived, Alloc>::parseName(NameState *State) {
   if (look() == 'Z')
     return getDerived().parseLocalName(State);
 
-  //        ::= <unscoped-template-name> <template-args>
-  if (look() == 'S' && look(1) != 't') {
-    Node *S = getDerived().parseSubstitution();
-    if (S == nullptr)
-      return nullptr;
-    if (look() != 'I')
-      return nullptr;
-    Node *TA = getDerived().parseTemplateArgs(State != nullptr);
-    if (TA == nullptr)
-      return nullptr;
-    if (State) State->EndsWithTemplateArgs = true;
-    return make<NameWithTemplateArgs>(S, TA);
+  Node *Result = nullptr;
+  bool IsSubst = look() == 'S' && look(1) != 't';
+  if (IsSubst) {
+    // A substitution must lead to:
+    //        ::= <unscoped-template-name> <template-args>
+    Result = getDerived().parseSubstitution();
+  } else {
+    // An unscoped name can be one of:
+    //        ::= <unscoped-name>
+    //        ::= <unscoped-template-name> <template-args>
+    Result = getDerived().parseUnscopedName(State);
   }
-
-  Node *N = getDerived().parseUnscopedName(State);
-  if (N == nullptr)
+  if (Result == nullptr)
     return nullptr;
-  //        ::= <unscoped-template-name> <template-args>
+
   if (look() == 'I') {
-    Subs.push_back(N);
+    //        ::= <unscoped-template-name> <template-args>
+    if (!IsSubst)
+      // An unscoped-template-name is substitutable.
+      Subs.push_back(Result);
     Node *TA = getDerived().parseTemplateArgs(State != nullptr);
     if (TA == nullptr)
       return nullptr;
-    if (State) State->EndsWithTemplateArgs = true;
-    return make<NameWithTemplateArgs>(N, TA);
+    if (State)
+      State->EndsWithTemplateArgs = true;
+    Result = make<NameWithTemplateArgs>(Result, TA);
+  } else if (IsSubst) {
+    // The substitution case must be followed by <template-args>.
+    return nullptr;
   }
-  //        ::= <unscoped-name>
-  return N;
+
+  return Result;
 }
 
 // <local-name> := Z <function encoding> E <entity name> [<discriminator>]
@@ -2663,13 +2671,17 @@ Node *AbstractManglingParser<Derived, Alloc>::parseLocalName(NameState *State) {
 template <typename Derived, typename Alloc>
 Node *
 AbstractManglingParser<Derived, Alloc>::parseUnscopedName(NameState *State) {
-  if (consumeIf("StL") || consumeIf("St")) {
-    Node *R = getDerived().parseUnqualifiedName(State);
-    if (R == nullptr)
-      return nullptr;
-    return make<StdQualifiedName>(R);
-  }
-  return getDerived().parseUnqualifiedName(State);
+  bool IsStd = consumeIf("St");
+  if (IsStd)
+    consumeIf('L');
+
+  Node *Result = getDerived().parseUnqualifiedName(State);
+  if (Result == nullptr)
+    return nullptr;
+  if (IsStd)
+    Result = make<StdQualifiedName>(Result);
+
+  return Result;
 }
 
 // <unqualified-name> ::= <operator-name> [abi-tags]
@@ -4064,9 +4076,9 @@ Node *AbstractManglingParser<Derived, Alloc>::parseType() {
   }
   //             ::= <substitution>  # See Compression below
   case 'S': {
-    if (look(1) && look(1) != 't') {
-      Node *Sub = getDerived().parseSubstitution();
-      if (Sub == nullptr)
+    if (look(1) != 't') {
+      Result = getDerived().parseSubstitution();
+      if (Result == nullptr)
         return nullptr;
 
       // Sub could be either of:
@@ -4083,13 +4095,13 @@ Node *AbstractManglingParser<Derived, Alloc>::parseType() {
         Node *TA = getDerived().parseTemplateArgs();
         if (TA == nullptr)
           return nullptr;
-        Result = make<NameWithTemplateArgs>(Sub, TA);
-        break;
+        Result = make<NameWithTemplateArgs>(Result, TA);
+      } else {
+        // If all we parsed was a substitution, don't re-insert into the
+        // substitution table.
+        return Result;
       }
-
-      // If all we parsed was a substitution, don't re-insert into the
-      // substitution table.
-      return Sub;
+      break;
     }
     DEMANGLE_FALLTHROUGH;
   }
@@ -5437,38 +5449,35 @@ Node *AbstractManglingParser<Derived, Alloc>::parseSubstitution() {
   if (!consumeIf('S'))
     return nullptr;
 
-  if (std::islower(look())) {
-    Node *SpecialSub;
+  if (look() >= 'a' && look() <= 'z') {
+    SpecialSubKind Kind;
     switch (look()) {
     case 'a':
-      ++First;
-      SpecialSub = make<SpecialSubstitution>(SpecialSubKind::allocator);
+      Kind = SpecialSubKind::allocator;
       break;
     case 'b':
-      ++First;
-      SpecialSub = make<SpecialSubstitution>(SpecialSubKind::basic_string);
+      Kind = SpecialSubKind::basic_string;
       break;
-    case 's':
-      ++First;
-      SpecialSub = make<SpecialSubstitution>(SpecialSubKind::string);
+    case 'd':
+      Kind = SpecialSubKind::iostream;
       break;
     case 'i':
-      ++First;
-      SpecialSub = make<SpecialSubstitution>(SpecialSubKind::istream);
+      Kind = SpecialSubKind::istream;
       break;
     case 'o':
-      ++First;
-      SpecialSub = make<SpecialSubstitution>(SpecialSubKind::ostream);
+      Kind = SpecialSubKind::ostream;
       break;
-    case 'd':
-      ++First;
-      SpecialSub = make<SpecialSubstitution>(SpecialSubKind::iostream);
+    case 's':
+      Kind = SpecialSubKind::string;
       break;
     default:
       return nullptr;
     }
+    ++First;
+    auto *SpecialSub = make<SpecialSubstitution>(Kind);
     if (!SpecialSub)
       return nullptr;
+
     // Itanium C++ ABI 5.1.2: If a name that would use a built-in <substitution>
     // has ABI tags, the tags are appended to the substitution; the result is a
     // substitutable component.
diff --git a/contrib/libs/cxxsupp/libcxxabi/src/demangle/README.txt b/contrib/libs/cxxsupp/libcxxabi/src/demangle/README.txt
index 514ff6dd16..76470f61f9 100644
--- a/contrib/libs/cxxsupp/libcxxabi/src/demangle/README.txt
+++ b/contrib/libs/cxxsupp/libcxxabi/src/demangle/README.txt
@@ -4,41 +4,50 @@ Itanium Name Demangler Library
 Introduction
 ------------
 
-This directory contains the generic itanium name demangler library. The main
-purpose of the library is to demangle C++ symbols, i.e. convert the string
-"_Z1fv" into "f()". You can also use the CRTP base ManglingParser to perform
-some simple analysis on the mangled name, or (in LLVM) use the opaque
-ItaniumPartialDemangler to query the demangled AST.
+This directory contains the generic itanium name demangler
+library. The main purpose of the library is to demangle C++ symbols,
+i.e. convert the string "_Z1fv" into "f()". You can also use the CRTP
+base ManglingParser to perform some simple analysis on the mangled
+name, or (in LLVM) use the opaque ItaniumPartialDemangler to query the
+demangled AST.
 
 Why are there multiple copies of the this library in the source tree?
 ---------------------------------------------------------------------
 
-This directory is mirrored between libcxxabi/demangle and
-llvm/include/llvm/Demangle. The simple reason for this is that both projects
-need to demangle symbols, but neither can depend on each other. libcxxabi needs
-the demangler to implement __cxa_demangle, which is part of the itanium ABI
-spec. LLVM needs a copy for a bunch of places, but doesn't want to use the
-system's __cxa_demangle because it a) might not be available (i.e., on Windows),
-and b) probably isn't that up-to-date on the latest language features.
-
-The copy of the demangler in LLVM has some extra stuff that aren't needed in
-libcxxabi (ie, the MSVC demangler, ItaniumPartialDemangler), which depend on the
-shared generic components. Despite these differences, we want to keep the "core"
-generic demangling library identical between both copies to simplify development
-and testing.
-
-If you're working on the generic library, then do the work first in libcxxabi,
-then run the cp-to-llvm.sh script in src/demangle. This script takes as an
-argument the path to llvm, and re-copies the changes you made to libcxxabi over.
-Note that this script just blindly overwrites all changes to the generic library
-in llvm, so be careful.
-
-Because the core demangler needs to work in libcxxabi, everything needs to be
-declared in an anonymous namespace (see DEMANGLE_NAMESPACE_BEGIN), and you can't
-introduce any code that depends on the libcxx dylib.
-
-Hopefully, when LLVM becomes a monorepo, we can de-duplicate this code, and have
-both LLVM and libcxxabi depend on a shared demangler library.
+The canonical sources are in libcxxabi/src/demangle and some of the
+files are copied to llvm/include/llvm/Demangle.  The simple reason for
+this comes from before the monorepo, and both [sub]projects need to
+demangle symbols, but neither can depend on each other.
+
+* libcxxabi needs the demangler to implement __cxa_demangle, which is
+  part of the itanium ABI spec.
+
+* LLVM needs a copy for a bunch of places, and cannot rely on the
+  system's __cxa_demangle because it a) might not be available (i.e.,
+  on Windows), and b) may not be up-to-date on the latest language
+  features.
+
+The copy of the demangler in LLVM has some extra stuff that aren't
+needed in libcxxabi (ie, the MSVC demangler, ItaniumPartialDemangler),
+which depend on the shared generic components. Despite these
+differences, we want to keep the "core" generic demangling library
+identical between both copies to simplify development and testing.
+
+If you're working on the generic library, then do the work first in
+libcxxabi, then run the cp-to-llvm.sh script in src/demangle. This
+script takes as an optional argument the path to llvm, and copies the
+changes you made to libcxxabi over.  Note that this script just
+blindly overwrites all changes to the generic library in llvm, so be
+careful.
+
+Because the core demangler needs to work in libcxxabi, everything
+needs to be declared in an anonymous namespace (see
+DEMANGLE_NAMESPACE_BEGIN), and you can't introduce any code that
+depends on the libcxx dylib.
+
+FIXME: Now that LLVM is a monorepo, it should be possible to
+de-duplicate this code, and have both LLVM and libcxxabi depend on a
+shared demangler library.
 
 Testing
 -------
diff --git a/contrib/libs/cxxsupp/libcxxabi/src/demangle/StringView.h b/contrib/libs/cxxsupp/libcxxabi/src/demangle/StringView.h
index 1e4d3803f0..90890e3771 100644
--- a/contrib/libs/cxxsupp/libcxxabi/src/demangle/StringView.h
+++ b/contrib/libs/cxxsupp/libcxxabi/src/demangle/StringView.h
@@ -7,6 +7,9 @@
 //===----------------------------------------------------------------------===//
 //
 // FIXME: Use std::string_view instead when we support C++17.
+// There are two copies of this file in the source tree.  The one under
+// libcxxabi is the original and the one under llvm is the copy.  Use
+// cp-to-llvm.sh to update the copy.  See README.txt for more details.
 //
 //===----------------------------------------------------------------------===//
 
@@ -14,7 +17,6 @@
 #define DEMANGLE_STRINGVIEW_H
 
 #include "DemangleConfig.h"
-#include <algorithm>
 #include <cassert>
 #include <cstring>
 
@@ -38,15 +40,16 @@ public:
 
   StringView substr(size_t Pos, size_t Len = npos) const {
     assert(Pos <= size());
-    return StringView(begin() + Pos, std::min(Len, size() - Pos));
+    if (Len > size() - Pos)
+      Len = size() - Pos;
+    return StringView(begin() + Pos, Len);
   }
 
   size_t find(char C, size_t From = 0) const {
-    size_t FindBegin = std::min(From, size());
     // Avoid calling memchr with nullptr.
-    if (FindBegin < size()) {
+    if (From < size()) {
       // Just forward to memchr, which is faster than a hand-rolled loop.
-      if (const void *P = ::memchr(First + FindBegin, C, size() - FindBegin))
+      if (const void *P = ::memchr(First + From, C, size() - From))
         return size_t(static_cast<const char *>(P) - First);
     }
     return npos;
@@ -98,7 +101,7 @@ public:
   bool startsWith(StringView Str) const {
     if (Str.size() > size())
       return false;
-    return std::equal(Str.begin(), Str.end(), begin());
+    return std::strncmp(Str.begin(), begin(), Str.size()) == 0;
   }
 
   const char &operator[](size_t Idx) const { return *(begin() + Idx); }
@@ -111,7 +114,7 @@ public:
 
 inline bool operator==(const StringView &LHS, const StringView &RHS) {
   return LHS.size() == RHS.size() &&
-         std::equal(LHS.begin(), LHS.end(), RHS.begin());
+         std::strncmp(LHS.begin(), RHS.begin(), LHS.size()) == 0;
 }
 
 DEMANGLE_NAMESPACE_END
diff --git a/contrib/libs/cxxsupp/libcxxabi/src/demangle/Utility.h b/contrib/libs/cxxsupp/libcxxabi/src/demangle/Utility.h
index 733d83ad1b..3b27328522 100644
--- a/contrib/libs/cxxsupp/libcxxabi/src/demangle/Utility.h
+++ b/contrib/libs/cxxsupp/libcxxabi/src/demangle/Utility.h
@@ -6,7 +6,10 @@
 //
 //===----------------------------------------------------------------------===//
 //
-// Provide some utility classes for use in the demangler(s).
+// Provide some utility classes for use in the demangler.
+// There are two copies of this file in the source tree.  The one in libcxxabi
+// is the original and the one in llvm is the copy.  Use cp-to-llvm.sh to update
+// the copy.  See README.txt for more details.
 //
 //===----------------------------------------------------------------------===//
 
@@ -14,10 +17,11 @@
 #define DEMANGLE_UTILITY_H
 
 #include "StringView.h"
+#include <array>
 #include <cstdint>
 #include <cstdlib>
 #include <cstring>
-#include <iterator>
+#include <exception>
 #include <limits>
 
 DEMANGLE_NAMESPACE_BEGIN
@@ -48,8 +52,8 @@ class OutputBuffer {
       return;
     }
 
-    char Temp[21];
-    char *TempPtr = std::end(Temp);
+    std::array<char, 21> Temp;
+    char *TempPtr = Temp.data() + Temp.size();
 
     while (N) {
       *--TempPtr = char('0' + N % 10);
@@ -59,7 +63,7 @@ class OutputBuffer {
     // Add negative sign...
     if (isNeg)
       *--TempPtr = '-';
-    this->operator<<(StringView(TempPtr, std::end(Temp)));
+    this->operator<<(StringView(TempPtr, Temp.data() + Temp.size()));
   }
 
 public: