diff --git a/lib/libcxxabi/include/__cxxabi_config.h b/lib/libcxxabi/include/__cxxabi_config.h
index c97dd656e1..e8aa37e6d5 100644
--- a/lib/libcxxabi/include/__cxxabi_config.h
+++ b/lib/libcxxabi/include/__cxxabi_config.h
@@ -32,7 +32,7 @@
 #endif
 
 #if defined(_WIN32)
- #if defined(_LIBCXXABI_DISABLE_VISIBILITY_ANNOTATIONS)
+ #if defined(_LIBCXXABI_DISABLE_VISIBILITY_ANNOTATIONS) || (defined(__MINGW32__) && !defined(_LIBCXXABI_BUILDING_LIBRARY))
   #define _LIBCXXABI_HIDDEN
   #define _LIBCXXABI_DATA_VIS
   #define _LIBCXXABI_FUNC_VIS
diff --git a/lib/libcxxabi/src/aix_state_tab_eh.inc b/lib/libcxxabi/src/aix_state_tab_eh.inc
index 128a0ab34a..3bb09ed275 100644
--- a/lib/libcxxabi/src/aix_state_tab_eh.inc
+++ b/lib/libcxxabi/src/aix_state_tab_eh.inc
@@ -14,10 +14,6 @@
 #include <stdio.h>
 #include <sys/debug.h>
 
-#if !__has_cpp_attribute(clang::optnone)
-#error This file requires clang::optnone attribute support
-#endif
-
 /*
   The legacy IBM xlC and xlclang++ compilers use the state table for EH
   instead of the range table. Destructors, or addresses of the possible catch
@@ -563,7 +559,8 @@ __xlcxx_personality_v0(int version, _Unwind_Action actions, uint64_t exceptionCl
       uintptr_t *currentSP = reinterpret_cast<uintptr_t*>(_Unwind_GetGR(context, 1));
       uintptr_t *callersSP = reinterpret_cast<uintptr_t*>(currentSP[0]);
       callersSP[3] = reinterpret_cast<uintptr_t>(unwind_exception);
-      _LIBCXXABI_TRACE_STATETAB("Handshake: set unwind_exception=%p in stack=%p\n", reinterpret_cast<void*>(unwind_exception), reinterpret_cast<void*>(callersSP));
+      _LIBCXXABI_TRACE_STATETAB("Handshake: save unwind_exception=%p in stack=%p\n",
+                                reinterpret_cast<void*>(unwind_exception), reinterpret_cast<void*>(callersSP));
       // Jump to the handler.
       _Unwind_SetIP(context, results.landingPad);
       return _URC_INSTALL_CONTEXT;
@@ -641,38 +638,68 @@ _LIBCXXABI_FUNC_VIS void __xlc_throw_badexception() {
   __cxa_throw(newexception, const_cast<std::type_info*>(&typeid(std::bad_exception)), 0);
 }
 
-// force_a_stackframe
-// This function is called by __xlc_exception_handle() to ensure a stack frame
-// is created for __xlc_exception_handle().
-__attribute__((noinline, optnone))
-static void force_a_stackframe() {}
+// skip_non_cxx_eh_aware_frames
+// This function skips non-C++ EH aware stack frames by unwinding from the
+// stack frame pointed by 'Sp' and returns the first C++ EH aware stack frame
+// found. 'Pc' is an instruction address inside the function that owns the
+// stack frame pointed to by 'Sp'.
+static uintptr_t* skip_non_cxx_eh_aware_frames(uint32_t* Pc, uintptr_t* Sp) {
+  uint32_t* currentPc = Pc;
+  uintptr_t* currentStack = Sp;
+
+  // Loop until a C++ EH aware frame is found or the return address is 0,
+  // which is the return address of the startup function '__start'.
+  while (currentPc != 0) {
+    uint32_t* p = currentPc;
+
+    // Keep looking forward until a word of 0 is found. The traceback
+    // table starts at the following word.
+    while (*p)
+      ++p;
+    tbtable* TBTable = reinterpret_cast<tbtable*>(p + 1);
+
+    // A stack frame with a C++ state table is C++ EH aware.
+    if (TBTable->tb.lang == TB_CPLUSPLUS && TBTable->tb.has_ctl)
+      return currentStack;
+
+    // Move up one stack frame.
+    currentStack = reinterpret_cast<uintptr_t*>(currentStack[0]);
+    // Get the value of the LR (saved, prior to incrementing the SP, by the
+    // prolog of the function just inspected) from the frame.
+    currentPc = reinterpret_cast<uint32_t*>(currentStack[2]);
+  }
+  // This should not happen.
+  _LIBCXXABI_TRACE_STATETAB0("skip_non_cxx_eh_aware_frames() reached the end of stack frames, aborting\n");
+  abort();
+}
 
 // __xlc_exception_handle
 // This function is for xlclang++. It returns the address of the exception
 // object stored in the reserved field in the stack of the caller of the
 // function that calls __xlc_exception_handle() (within the link area for the
 // call to the latter). The address is stored by the personality routine for
-// xlclang++ compiled code. The implementation of __xlc_exception_handle()
-// assumes a stack frame is created for it. The following ensures this
-// assumption holds true: 1) a call to force_a_stackframe() is made inside
-// __xlc_exception_handle() to make it non-leaf; and 2) optimizations are
-// disabled for this function with attribute 'optnone'. Note: this function
-// may not work as expected if these are changed.
-__attribute__((optnone))
+// xlclang++ compiled code. If __xlc_exception_handle() is called by
+// non-C++ EH aware functions, their frames are skipped until a C++ EH aware
+// frame is found.
+// Note: make sure __xlc_excpetion_handle() is a non-leaf function. Currently
+// it calls skip_non_cxx_eh_aware_frames(), which in turn calls abort().
 _LIBCXXABI_FUNC_VIS uintptr_t __xlc_exception_handle() {
-  // Make a call to force_a_stackframe() so that the compiler creates a stack
-  // frame for this function.
-  force_a_stackframe();
-
   // Get the SP of this function, i.e., __xlc_exception_handle().
-  uintptr_t *lastStack;
-  asm("mr %0, 1" : "=r"(lastStack));
-  // Get the SP of the caller of __xlc_exception_handle().
-  uintptr_t *callerStack = reinterpret_cast<uintptr_t*>(lastStack[0]);
-  // Get the SP of the caller of the caller.
-  uintptr_t *callerStack2 = reinterpret_cast<uintptr_t*>(callerStack[0]);
-  uintptr_t exceptionObject = callerStack2[3];
-  _LIBCXXABI_TRACE_STATETAB("Handshake: exceptionObject=%p from stack=%p\n", reinterpret_cast<void*>(exceptionObject), reinterpret_cast<void*>(callerStack2));
+  uintptr_t* lastStack = reinterpret_cast<uintptr_t*>(__builtin_frame_address(0));
+  // Move one frame up to the frame of the caller of __xlc_exception_handle().
+  lastStack = reinterpret_cast<uintptr_t*>(lastStack[0]);
+  // Get the return address of this function, i.e., __xlc_exception_handle().
+  uint32_t* returnAddress = reinterpret_cast<uint32_t*>(__builtin_return_address(0));
+
+  // Skip non-C++ EH aware frames and get the first C++ EH aware frame.
+  uintptr_t* callerStack = skip_non_cxx_eh_aware_frames(returnAddress, lastStack);
+
+  // Get the SP of the caller of the C++ EH aware caller.
+  callerStack = reinterpret_cast<uintptr_t*>(callerStack[0]);
+  // Retrieve the exception object in the stack slot saved by the personality.
+  uintptr_t exceptionObject = callerStack[3];
+  _LIBCXXABI_TRACE_STATETAB("Handshake: retrieve exceptionObject=%p from stack=%p\n",
+                            reinterpret_cast<void*>(exceptionObject), reinterpret_cast<void*>(callerStack));
   return exceptionObject;
 }
 
diff --git a/lib/libcxxabi/src/cxa_aux_runtime.cpp b/lib/libcxxabi/src/cxa_aux_runtime.cpp
index a42990c7ef..5e6040d75a 100644
--- a/lib/libcxxabi/src/cxa_aux_runtime.cpp
+++ b/lib/libcxxabi/src/cxa_aux_runtime.cpp
@@ -10,6 +10,7 @@
 //===----------------------------------------------------------------------===//
 
 #include "cxxabi.h"
+#include <exception>
 #include <new>
 #include <typeinfo>
 
diff --git a/lib/libcxxabi/src/cxa_demangle.cpp b/lib/libcxxabi/src/cxa_demangle.cpp
index 7baac68007..03085cb590 100644
--- a/lib/libcxxabi/src/cxa_demangle.cpp
+++ b/lib/libcxxabi/src/cxa_demangle.cpp
@@ -10,6 +10,7 @@
 // file does not yet support:
 //   - C++ modules TS
 
+#include "demangle/DemangleConfig.h"
 #include "demangle/ItaniumDemangle.h"
 #include "__cxxabi_config.h"
 #include <cassert>
@@ -19,6 +20,7 @@
 #include <cstring>
 #include <functional>
 #include <numeric>
+#include <string_view>
 #include <utility>
 
 using namespace itanium_demangle;
@@ -77,8 +79,8 @@ struct DumpVisitor {
   }
 
   void printStr(const char *S) { fprintf(stderr, "%s", S); }
-  void print(StringView SV) {
-    fprintf(stderr, "\"%.*s\"", (int)SV.size(), SV.begin());
+  void print(std::string_view SV) {
+    fprintf(stderr, "\"%.*s\"", (int)SV.size(), &*SV.begin());
   }
   void print(const Node *N) {
     if (N)
diff --git a/lib/libcxxabi/src/cxa_guard_impl.h b/lib/libcxxabi/src/cxa_guard_impl.h
index 47fe2b20bd..e00d54b3a7 100644
--- a/lib/libcxxabi/src/cxa_guard_impl.h
+++ b/lib/libcxxabi/src/cxa_guard_impl.h
@@ -255,7 +255,7 @@ struct InitByteNoThreads {
     if (*init_byte_address == COMPLETE_BIT)
       return true;
     if (*init_byte_address & PENDING_BIT)
-      ABORT_WITH_MESSAGE("__cxa_guard_acquire detected recursive initialization");
+      ABORT_WITH_MESSAGE("__cxa_guard_acquire detected recursive initialization: do you have a function-local static variable whose initialization depends on that function?");
     *init_byte_address = PENDING_BIT;
     return false;
   }
@@ -325,7 +325,7 @@ public:
     // Check for possible recursive initialization.
     if (has_thread_id_support && (*init_byte_address & PENDING_BIT)) {
       if (*thread_id_address == current_thread_id.get())
-        ABORT_WITH_MESSAGE("__cxa_guard_acquire detected recursive initialization");
+        ABORT_WITH_MESSAGE("__cxa_guard_acquire detected recursive initialization: do you have a function-local static variable whose initialization depends on that function?");
     }
 
     // Wait until the pending bit is not set.
@@ -460,7 +460,7 @@ public:
 
         // Check for recursive initialization
         if (has_thread_id_support && thread_id.load(std::_AO_Relaxed) == current_thread_id.get()) {
-          ABORT_WITH_MESSAGE("__cxa_guard_acquire detected recursive initialization");
+          ABORT_WITH_MESSAGE("__cxa_guard_acquire detected recursive initialization: do you have a function-local static variable whose initialization depends on that function?");
         }
 
         if ((last_val & WAITING_BIT) == 0) {
diff --git a/lib/libcxxabi/src/demangle/DemangleConfig.h b/lib/libcxxabi/src/demangle/DemangleConfig.h
index 9d818535b0..d5e11432d9 100644
--- a/lib/libcxxabi/src/demangle/DemangleConfig.h
+++ b/lib/libcxxabi/src/demangle/DemangleConfig.h
@@ -11,6 +11,14 @@
 #ifndef LIBCXXABI_DEMANGLE_DEMANGLE_CONFIG_H
 #define LIBCXXABI_DEMANGLE_DEMANGLE_CONFIG_H
 
+// Must be defined before pulling in headers from libc++. Allow downstream
+// build systems to override this value.
+// https://libcxx.llvm.org/UsingLibcxx.html#enabling-the-safe-libc-mode
+#ifndef _LIBCPP_VERBOSE_ABORT
+#define _LIBCPP_VERBOSE_ABORT(...) abort_message(__VA_ARGS__)
+#include "../abort_message.h"
+#endif
+
 #include <ciso646>
 
 #ifdef _MSC_VER
diff --git a/lib/libcxxabi/src/demangle/ItaniumDemangle.h b/lib/libcxxabi/src/demangle/ItaniumDemangle.h
index 66213c63f2..28562f0214 100644
--- a/lib/libcxxabi/src/demangle/ItaniumDemangle.h
+++ b/lib/libcxxabi/src/demangle/ItaniumDemangle.h
@@ -17,8 +17,9 @@
 #define DEMANGLE_ITANIUMDEMANGLE_H
 
 #include "DemangleConfig.h"
-#include "StringView.h"
+#include "StringViewExtras.h"
 #include "Utility.h"
+#include <__cxxabi_config.h>
 #include <algorithm>
 #include <cassert>
 #include <cctype>
@@ -27,8 +28,15 @@
 #include <cstring>
 #include <limits>
 #include <new>
+#include <string_view>
+#include <type_traits>
 #include <utility>
 
+#ifdef _LIBCXXABI_COMPILER_CLANG
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wunused-template"
+#endif
+
 DEMANGLE_NAMESPACE_BEGIN
 
 template <class T, size_t N> class PODSmallVector {
@@ -286,7 +294,7 @@ public:
   // implementation.
   virtual void printRight(OutputBuffer &) const {}
 
-  virtual StringView getBaseName() const { return StringView(); }
+  virtual std::string_view getBaseName() const { return {}; }
 
   // Silence compiler warnings, this dtor will never be called.
   virtual ~Node() = default;
@@ -345,10 +353,10 @@ struct NodeArrayNode : Node {
 
 class DotSuffix final : public Node {
   const Node *Prefix;
-  const StringView Suffix;
+  const std::string_view Suffix;
 
 public:
-  DotSuffix(const Node *Prefix_, StringView Suffix_)
+  DotSuffix(const Node *Prefix_, std::string_view Suffix_)
       : Node(KDotSuffix), Prefix(Prefix_), Suffix(Suffix_) {}
 
   template<typename Fn> void match(Fn F) const { F(Prefix, Suffix); }
@@ -363,15 +371,15 @@ public:
 
 class VendorExtQualType final : public Node {
   const Node *Ty;
-  StringView Ext;
+  std::string_view Ext;
   const Node *TA;
 
 public:
-  VendorExtQualType(const Node *Ty_, StringView Ext_, const Node *TA_)
+  VendorExtQualType(const Node *Ty_, std::string_view Ext_, const Node *TA_)
       : Node(KVendorExtQualType), Ty(Ty_), Ext(Ext_), TA(TA_) {}
 
   const Node *getTy() const { return Ty; }
-  StringView getExt() const { return Ext; }
+  std::string_view getExt() const { return Ext; }
   const Node *getTA() const { return TA; }
 
   template <typename Fn> void match(Fn F) const { F(Ty, Ext, TA); }
@@ -462,10 +470,10 @@ public:
 
 class PostfixQualifiedType final : public Node {
   const Node *Ty;
-  const StringView Postfix;
+  const std::string_view Postfix;
 
 public:
-  PostfixQualifiedType(const Node *Ty_, StringView Postfix_)
+  PostfixQualifiedType(const Node *Ty_, std::string_view Postfix_)
       : Node(KPostfixQualifiedType), Ty(Ty_), Postfix(Postfix_) {}
 
   template<typename Fn> void match(Fn F) const { F(Ty, Postfix); }
@@ -477,15 +485,15 @@ public:
 };
 
 class NameType final : public Node {
-  const StringView Name;
+  const std::string_view Name;
 
 public:
-  NameType(StringView Name_) : Node(KNameType), Name(Name_) {}
+  NameType(std::string_view Name_) : Node(KNameType), Name(Name_) {}
 
   template<typename Fn> void match(Fn F) const { F(Name); }
 
-  StringView getName() const { return Name; }
-  StringView getBaseName() const override { return Name; }
+  std::string_view getName() const { return Name; }
+  std::string_view getBaseName() const override { return Name; }
 
   void printLeft(OutputBuffer &OB) const override { OB += Name; }
 };
@@ -511,10 +519,10 @@ public:
 };
 
 class ElaboratedTypeSpefType : public Node {
-  StringView Kind;
+  std::string_view Kind;
   Node *Child;
 public:
-  ElaboratedTypeSpefType(StringView Kind_, Node *Child_)
+  ElaboratedTypeSpefType(std::string_view Kind_, Node *Child_)
       : Node(KElaboratedTypeSpefType), Kind(Kind_), Child(Child_) {}
 
   template<typename Fn> void match(Fn F) const { F(Kind, Child); }
@@ -528,15 +536,17 @@ public:
 
 struct AbiTagAttr : Node {
   Node *Base;
-  StringView Tag;
+  std::string_view Tag;
 
-  AbiTagAttr(Node* Base_, StringView Tag_)
-      : Node(KAbiTagAttr, Base_->RHSComponentCache,
-             Base_->ArrayCache, Base_->FunctionCache),
+  AbiTagAttr(Node *Base_, std::string_view Tag_)
+      : Node(KAbiTagAttr, Base_->RHSComponentCache, Base_->ArrayCache,
+             Base_->FunctionCache),
         Base(Base_), Tag(Tag_) {}
 
   template<typename Fn> void match(Fn F) const { F(Base, Tag); }
 
+  std::string_view getBaseName() const override { return Base->getBaseName(); }
+
   void printLeft(OutputBuffer &OB) const override {
     Base->printLeft(OB);
     OB += "[abi:";
@@ -562,12 +572,12 @@ public:
 
 class ObjCProtoName : public Node {
   const Node *Ty;
-  StringView Protocol;
+  std::string_view Protocol;
 
   friend class PointerType;
 
 public:
-  ObjCProtoName(const Node *Ty_, StringView Protocol_)
+  ObjCProtoName(const Node *Ty_, std::string_view Protocol_)
       : Node(KObjCProtoName), Ty(Ty_), Protocol(Protocol_) {}
 
   template<typename Fn> void match(Fn F) const { F(Ty, Protocol); }
@@ -944,11 +954,11 @@ public:
 };
 
 class SpecialName final : public Node {
-  const StringView Special;
+  const std::string_view Special;
   const Node *Child;
 
 public:
-  SpecialName(StringView Special_, const Node *Child_)
+  SpecialName(std::string_view Special_, const Node *Child_)
       : Node(KSpecialName), Special(Special_), Child(Child_) {}
 
   template<typename Fn> void match(Fn F) const { F(Special, Child); }
@@ -987,7 +997,7 @@ struct NestedName : Node {
 
   template<typename Fn> void match(Fn F) const { F(Qual, Name); }
 
-  StringView getBaseName() const override { return Name->getBaseName(); }
+  std::string_view getBaseName() const override { return Name->getBaseName(); }
 
   void printLeft(OutputBuffer &OB) const override {
     Qual->print(OB);
@@ -1027,7 +1037,7 @@ struct ModuleEntity : Node {
 
   template <typename Fn> void match(Fn F) const { F(Module, Name); }
 
-  StringView getBaseName() const override { return Name->getBaseName(); }
+  std::string_view getBaseName() const override { return Name->getBaseName(); }
 
   void printLeft(OutputBuffer &OB) const override {
     Name->print(OB);
@@ -1063,7 +1073,7 @@ public:
 
   template<typename Fn> void match(Fn F) const { F(Qualifier, Name); }
 
-  StringView getBaseName() const override { return Name->getBaseName(); }
+  std::string_view getBaseName() const override { return Name->getBaseName(); }
 
   void printLeft(OutputBuffer &OB) const override {
     Qualifier->print(OB);
@@ -1485,7 +1495,7 @@ struct NameWithTemplateArgs : Node {
 
   template<typename Fn> void match(Fn F) const { F(Name, TemplateArgs); }
 
-  StringView getBaseName() const override { return Name->getBaseName(); }
+  std::string_view getBaseName() const override { return Name->getBaseName(); }
 
   void printLeft(OutputBuffer &OB) const override {
     Name->print(OB);
@@ -1502,7 +1512,7 @@ public:
 
   template<typename Fn> void match(Fn F) const { F(Child); }
 
-  StringView getBaseName() const override { return Child->getBaseName(); }
+  std::string_view getBaseName() const override { return Child->getBaseName(); }
 
   void printLeft(OutputBuffer &OB) const override {
     OB += "::";
@@ -1538,20 +1548,20 @@ protected:
     return unsigned(SSK) >= unsigned(SpecialSubKind::string);
   }
 
-  StringView getBaseName() const override {
+  std::string_view getBaseName() const override {
     switch (SSK) {
     case SpecialSubKind::allocator:
-      return StringView("allocator");
+      return {"allocator"};
     case SpecialSubKind::basic_string:
-      return StringView("basic_string");
+      return {"basic_string"};
     case SpecialSubKind::string:
-      return StringView("basic_string");
+      return {"basic_string"};
     case SpecialSubKind::istream:
-      return StringView("basic_istream");
+      return {"basic_istream"};
     case SpecialSubKind::ostream:
-      return StringView("basic_ostream");
+      return {"basic_ostream"};
     case SpecialSubKind::iostream:
-      return StringView("basic_iostream");
+      return {"basic_iostream"};
     }
     DEMANGLE_UNREACHABLE;
   }
@@ -1575,12 +1585,12 @@ public:
 
   template<typename Fn> void match(Fn F) const { F(SSK); }
 
-  StringView getBaseName() const override {
-    auto SV = ExpandedSpecialSubstitution::getBaseName ();
+  std::string_view getBaseName() const override {
+    std::string_view SV = ExpandedSpecialSubstitution::getBaseName();
     if (isInstantiation()) {
       // The instantiations are typedefs that drop the "basic_" prefix.
-      assert(SV.startsWith("basic_"));
-      SV = SV.dropFront(sizeof("basic_") - 1);
+      assert(starts_with(SV, "basic_"));
+      SV.remove_prefix(sizeof("basic_") - 1);
     }
     return SV;
   }
@@ -1628,10 +1638,11 @@ public:
 };
 
 class UnnamedTypeName : public Node {
-  const StringView Count;
+  const std::string_view Count;
 
 public:
-  UnnamedTypeName(StringView Count_) : Node(KUnnamedTypeName), Count(Count_) {}
+  UnnamedTypeName(std::string_view Count_)
+      : Node(KUnnamedTypeName), Count(Count_) {}
 
   template<typename Fn> void match(Fn F) const { F(Count); }
 
@@ -1645,11 +1656,11 @@ public:
 class ClosureTypeName : public Node {
   NodeArray TemplateParams;
   NodeArray Params;
-  StringView Count;
+  std::string_view Count;
 
 public:
   ClosureTypeName(NodeArray TemplateParams_, NodeArray Params_,
-                  StringView Count_)
+                  std::string_view Count_)
       : Node(KClosureTypeName), TemplateParams(TemplateParams_),
         Params(Params_), Count(Count_) {}
 
@@ -1696,12 +1707,12 @@ public:
 
 class BinaryExpr : public Node {
   const Node *LHS;
-  const StringView InfixOperator;
+  const std::string_view InfixOperator;
   const Node *RHS;
 
 public:
-  BinaryExpr(const Node *LHS_, StringView InfixOperator_, const Node *RHS_,
-             Prec Prec_)
+  BinaryExpr(const Node *LHS_, std::string_view InfixOperator_,
+             const Node *RHS_, Prec Prec_)
       : Node(KBinaryExpr, Prec_), LHS(LHS_), InfixOperator(InfixOperator_),
         RHS(RHS_) {}
 
@@ -1750,10 +1761,10 @@ public:
 
 class PostfixExpr : public Node {
   const Node *Child;
-  const StringView Operator;
+  const std::string_view Operator;
 
 public:
-  PostfixExpr(const Node *Child_, StringView Operator_, Prec Prec_)
+  PostfixExpr(const Node *Child_, std::string_view Operator_, Prec Prec_)
       : Node(KPostfixExpr, Prec_), Child(Child_), Operator(Operator_) {}
 
   template <typename Fn> void match(Fn F) const {
@@ -1791,11 +1802,12 @@ public:
 
 class MemberExpr : public Node {
   const Node *LHS;
-  const StringView Kind;
+  const std::string_view Kind;
   const Node *RHS;
 
 public:
-  MemberExpr(const Node *LHS_, StringView Kind_, const Node *RHS_, Prec Prec_)
+  MemberExpr(const Node *LHS_, std::string_view Kind_, const Node *RHS_,
+             Prec Prec_)
       : Node(KMemberExpr, Prec_), LHS(LHS_), Kind(Kind_), RHS(RHS_) {}
 
   template <typename Fn> void match(Fn F) const {
@@ -1812,13 +1824,14 @@ public:
 class SubobjectExpr : public Node {
   const Node *Type;
   const Node *SubExpr;
-  StringView Offset;
+  std::string_view Offset;
   NodeArray UnionSelectors;
   bool OnePastTheEnd;
 
 public:
-  SubobjectExpr(const Node *Type_, const Node *SubExpr_, StringView Offset_,
-                NodeArray UnionSelectors_, bool OnePastTheEnd_)
+  SubobjectExpr(const Node *Type_, const Node *SubExpr_,
+                std::string_view Offset_, NodeArray UnionSelectors_,
+                bool OnePastTheEnd_)
       : Node(KSubobjectExpr), Type(Type_), SubExpr(SubExpr_), Offset(Offset_),
         UnionSelectors(UnionSelectors_), OnePastTheEnd(OnePastTheEnd_) {}
 
@@ -1835,7 +1848,7 @@ public:
       OB += "0";
     } else if (Offset[0] == 'n') {
       OB += "-";
-      OB += Offset.dropFront();
+      OB += std::string_view(Offset.data() + 1, Offset.size() - 1);
     } else {
       OB += Offset;
     }
@@ -1844,12 +1857,12 @@ public:
 };
 
 class EnclosingExpr : public Node {
-  const StringView Prefix;
+  const std::string_view Prefix;
   const Node *Infix;
-  const StringView Postfix;
+  const std::string_view Postfix;
 
 public:
-  EnclosingExpr(StringView Prefix_, const Node *Infix_,
+  EnclosingExpr(std::string_view Prefix_, const Node *Infix_,
                 Prec Prec_ = Prec::Primary)
       : Node(KEnclosingExpr, Prec_), Prefix(Prefix_), Infix(Infix_) {}
 
@@ -1868,12 +1881,13 @@ public:
 
 class CastExpr : public Node {
   // cast_kind<to>(from)
-  const StringView CastKind;
+  const std::string_view CastKind;
   const Node *To;
   const Node *From;
 
 public:
-  CastExpr(StringView CastKind_, const Node *To_, const Node *From_, Prec Prec_)
+  CastExpr(std::string_view CastKind_, const Node *To_, const Node *From_,
+           Prec Prec_)
       : Node(KCastExpr, Prec_), CastKind(CastKind_), To(To_), From(From_) {}
 
   template <typename Fn> void match(Fn F) const {
@@ -1996,11 +2010,11 @@ public:
 };
 
 class PrefixExpr : public Node {
-  StringView Prefix;
+  std::string_view Prefix;
   Node *Child;
 
 public:
-  PrefixExpr(StringView Prefix_, Node *Child_, Prec Prec_)
+  PrefixExpr(std::string_view Prefix_, Node *Child_, Prec Prec_)
       : Node(KPrefixExpr, Prec_), Prefix(Prefix_), Child(Child_) {}
 
   template <typename Fn> void match(Fn F) const {
@@ -2014,10 +2028,11 @@ public:
 };
 
 class FunctionParam : public Node {
-  StringView Number;
+  std::string_view Number;
 
 public:
-  FunctionParam(StringView Number_) : Node(KFunctionParam), Number(Number_) {}
+  FunctionParam(std::string_view Number_)
+      : Node(KFunctionParam), Number(Number_) {}
 
   template<typename Fn> void match(Fn F) const { F(Number); }
 
@@ -2052,11 +2067,11 @@ public:
 class PointerToMemberConversionExpr : public Node {
   const Node *Type;
   const Node *SubExpr;
-  StringView Offset;
+  std::string_view Offset;
 
 public:
   PointerToMemberConversionExpr(const Node *Type_, const Node *SubExpr_,
-                                StringView Offset_, Prec Prec_)
+                                std::string_view Offset_, Prec Prec_)
       : Node(KPointerToMemberConversionExpr, Prec_), Type(Type_),
         SubExpr(SubExpr_), Offset(Offset_) {}
 
@@ -2141,11 +2156,11 @@ public:
 
 class FoldExpr : public Node {
   const Node *Pack, *Init;
-  StringView OperatorName;
+  std::string_view OperatorName;
   bool IsLeftFold;
 
 public:
-  FoldExpr(bool IsLeftFold_, StringView OperatorName_, const Node *Pack_,
+  FoldExpr(bool IsLeftFold_, std::string_view OperatorName_, const Node *Pack_,
            const Node *Init_)
       : Node(KFoldExpr), Pack(Pack_), Init(Init_), OperatorName(OperatorName_),
         IsLeftFold(IsLeftFold_) {}
@@ -2209,7 +2224,7 @@ public:
   template<typename Fn> void match(Fn F) const { F(Value); }
 
   void printLeft(OutputBuffer &OB) const override {
-    OB += Value ? StringView("true") : StringView("false");
+    OB += Value ? std::string_view("true") : std::string_view("false");
   }
 };
 
@@ -2247,10 +2262,10 @@ public:
 class EnumLiteral : public Node {
   // ty(integer)
   const Node *Ty;
-  StringView Integer;
+  std::string_view Integer;
 
 public:
-  EnumLiteral(const Node *Ty_, StringView Integer_)
+  EnumLiteral(const Node *Ty_, std::string_view Integer_)
       : Node(KEnumLiteral), Ty(Ty_), Integer(Integer_) {}
 
   template<typename Fn> void match(Fn F) const { F(Ty, Integer); }
@@ -2261,18 +2276,18 @@ public:
     OB.printClose();
 
     if (Integer[0] == 'n')
-      OB << "-" << Integer.dropFront(1);
+      OB << '-' << std::string_view(Integer.data() + 1, Integer.size() - 1);
     else
       OB << Integer;
   }
 };
 
 class IntegerLiteral : public Node {
-  StringView Type;
-  StringView Value;
+  std::string_view Type;
+  std::string_view Value;
 
 public:
-  IntegerLiteral(StringView Type_, StringView Value_)
+  IntegerLiteral(std::string_view Type_, std::string_view Value_)
       : Node(KIntegerLiteral), Type(Type_), Value(Value_) {}
 
   template<typename Fn> void match(Fn F) const { F(Type, Value); }
@@ -2284,10 +2299,9 @@ public:
       OB.printClose();
     }
 
-    if (Value[0] == 'n') {
-      OB += '-';
-      OB += Value.dropFront(1);
-    } else
+    if (Value[0] == 'n')
+      OB << '-' << std::string_view(Value.data() + 1, Value.size() - 1);
+    else
       OB += Value;
 
     if (Type.size() <= 3)
@@ -2310,29 +2324,26 @@ constexpr Node::Kind getFloatLiteralKind(long double *) {
 }
 
 template <class Float> class FloatLiteralImpl : public Node {
-  const StringView Contents;
+  const std::string_view Contents;
 
   static constexpr Kind KindForClass =
       float_literal_impl::getFloatLiteralKind((Float *)nullptr);
 
 public:
-  FloatLiteralImpl(StringView Contents_)
+  FloatLiteralImpl(std::string_view Contents_)
       : Node(KindForClass), Contents(Contents_) {}
 
   template<typename Fn> void match(Fn F) const { F(Contents); }
 
   void printLeft(OutputBuffer &OB) const override {
-    const char *first = Contents.begin();
-    const char *last = Contents.end() + 1;
-
     const size_t N = FloatData<Float>::mangled_size;
-    if (static_cast<std::size_t>(last - first) > N) {
-      last = first + N;
+    if (Contents.size() >= N) {
       union {
         Float value;
         char buf[sizeof(Float)];
       };
-      const char *t = first;
+      const char *t = Contents.data();
+      const char *last = t + N;
       char *e = buf;
       for (; t != last; ++t, ++e) {
         unsigned d1 = isdigit(*t) ? static_cast<unsigned>(*t - '0')
@@ -2347,7 +2358,7 @@ public:
 #endif
       char num[FloatData<Float>::max_demangled_size] = {0};
       int n = snprintf(num, sizeof(num), FloatData<Float>::spec, value);
-      OB += StringView(num, num + n);
+      OB += std::string_view(num, n);
     }
   }
 };
@@ -2474,8 +2485,8 @@ template <typename Derived, typename Alloc> struct AbstractManglingParser {
     return res;
   }
 
-  bool consumeIf(StringView S) {
-    if (StringView(First, Last).startsWith(S)) {
+  bool consumeIf(std::string_view S) {
+    if (starts_with(std::string_view(First, Last - First), S)) {
       First += S.size();
       return true;
     }
@@ -2500,10 +2511,10 @@ template <typename Derived, typename Alloc> struct AbstractManglingParser {
 
   size_t numLeft() const { return static_cast<size_t>(Last - First); }
 
-  StringView parseNumber(bool AllowNegative = false);
+  std::string_view parseNumber(bool AllowNegative = false);
   Qualifiers parseCVQualifiers();
   bool parsePositiveInteger(size_t *Out);
-  StringView parseBareSourceName();
+  std::string_view parseBareSourceName();
 
   bool parseSeqId(size_t *Out);
   Node *parseSubstitution();
@@ -2514,9 +2525,9 @@ template <typename Derived, typename Alloc> struct AbstractManglingParser {
 
   /// Parse the <expr> production.
   Node *parseExpr();
-  Node *parsePrefixExpr(StringView Kind, Node::Prec Prec);
-  Node *parseBinaryExpr(StringView Kind, Node::Prec Prec);
-  Node *parseIntegerLiteral(StringView Lit);
+  Node *parsePrefixExpr(std::string_view Kind, Node::Prec Prec);
+  Node *parseBinaryExpr(std::string_view Kind, Node::Prec Prec);
+  Node *parseIntegerLiteral(std::string_view Lit);
   Node *parseExprPrimary();
   template <class Float> Node *parseFloatingLiteral();
   Node *parseFunctionParam();
@@ -2624,17 +2635,18 @@ template <typename Derived, typename Alloc> struct AbstractManglingParser {
     bool operator!=(const char *Peek) const { return !this->operator==(Peek); }
 
   public:
-    StringView getSymbol() const {
-      StringView Res = Name;
+    std::string_view getSymbol() const {
+      std::string_view Res = Name;
       if (Kind < Unnameable) {
-        assert(Res.startsWith("operator") &&
+        assert(starts_with(Res, "operator") &&
                "operator name does not start with 'operator'");
-        Res = Res.dropFront(sizeof("operator") - 1);
-        Res.consumeFront(' ');
+        Res.remove_prefix(sizeof("operator") - 1);
+        if (starts_with(Res, ' '))
+          Res.remove_prefix(1);
       }
       return Res;
     }
-    StringView getName() const { return Name; }
+    std::string_view getName() const { return Name; }
     OIKind getKind() const { return Kind; }
     bool getFlag() const { return Flag; }
     Node::Prec getPrecedence() const { return Prec; }
@@ -2854,7 +2866,7 @@ AbstractManglingParser<Derived, Alloc>::parseUnnamedTypeName(NameState *State) {
     TemplateParams.clear();
 
   if (consumeIf("Ut")) {
-    StringView Count = parseNumber();
+    std::string_view Count = parseNumber();
     if (!consumeIf('_'))
       return nullptr;
     return make<UnnamedTypeName>(Count);
@@ -2866,7 +2878,7 @@ AbstractManglingParser<Derived, Alloc>::parseUnnamedTypeName(NameState *State) {
 
     size_t ParamsBegin = Names.size();
     while (look() == 'T' &&
-           StringView("yptn").find(look(1)) != StringView::npos) {
+           std::string_view("yptn").find(look(1)) != std::string_view::npos) {
       Node *T = parseTemplateParamDecl();
       if (!T)
         return nullptr;
@@ -2909,7 +2921,7 @@ AbstractManglingParser<Derived, Alloc>::parseUnnamedTypeName(NameState *State) {
     }
     NodeArray Params = popTrailingNodeArray(ParamsBegin);
 
-    StringView Count = parseNumber();
+    std::string_view Count = parseNumber();
     if (!consumeIf('_'))
       return nullptr;
     return make<ClosureTypeName>(TempParams, Params, Count);
@@ -2931,9 +2943,9 @@ Node *AbstractManglingParser<Derived, Alloc>::parseSourceName(NameState *) {
     return nullptr;
   if (numLeft() < Length || Length == 0)
     return nullptr;
-  StringView Name(First, First + Length);
+  std::string_view Name(First, Length);
   First += Length;
-  if (Name.startsWith("_GLOBAL__N"))
+  if (starts_with(Name, "_GLOBAL__N"))
     return make<NameType>("(anonymous namespace)");
   return make<NameType>(Name);
 }
@@ -3447,7 +3459,7 @@ Node *AbstractManglingParser<Derived, Alloc>::parseUnresolvedName(bool Global) {
 template <typename Derived, typename Alloc>
 Node *AbstractManglingParser<Derived, Alloc>::parseAbiTags(Node *N) {
   while (consumeIf('B')) {
-    StringView SN = parseBareSourceName();
+    std::string_view SN = parseBareSourceName();
     if (SN.empty())
       return nullptr;
     N = make<AbiTagAttr>(N, SN);
@@ -3459,16 +3471,16 @@ Node *AbstractManglingParser<Derived, Alloc>::parseAbiTags(Node *N) {
 
 // <number> ::= [n] <non-negative decimal integer>
 template <typename Alloc, typename Derived>
-StringView
+std::string_view
 AbstractManglingParser<Alloc, Derived>::parseNumber(bool AllowNegative) {
   const char *Tmp = First;
   if (AllowNegative)
     consumeIf('n');
   if (numLeft() == 0 || !std::isdigit(*First))
-    return StringView();
+    return std::string_view();
   while (numLeft() != 0 && std::isdigit(*First))
     ++First;
-  return StringView(Tmp, First);
+  return std::string_view(Tmp, First - Tmp);
 }
 
 // <positive length number> ::= [0-9]*
@@ -3485,11 +3497,11 @@ bool AbstractManglingParser<Alloc, Derived>::parsePositiveInteger(size_t *Out) {
 }
 
 template <typename Alloc, typename Derived>
-StringView AbstractManglingParser<Alloc, Derived>::parseBareSourceName() {
+std::string_view AbstractManglingParser<Alloc, Derived>::parseBareSourceName() {
   size_t Int = 0;
   if (parsePositiveInteger(&Int) || numLeft() < Int)
-    return StringView();
-  StringView R(First, First + Int);
+    return {};
+  std::string_view R(First, Int);
   First += Int;
   return R;
 }
@@ -3673,7 +3685,7 @@ Node *AbstractManglingParser<Derived, Alloc>::parsePointerToMemberType() {
 //                   ::= Te <name>  # dependent elaborated type specifier using 'enum'
 template <typename Derived, typename Alloc>
 Node *AbstractManglingParser<Derived, Alloc>::parseClassEnumType() {
-  StringView ElabSpef;
+  std::string_view ElabSpef;
   if (consumeIf("Ts"))
     ElabSpef = "struct";
   else if (consumeIf("Tu"))
@@ -3697,17 +3709,18 @@ Node *AbstractManglingParser<Derived, Alloc>::parseClassEnumType() {
 template <typename Derived, typename Alloc>
 Node *AbstractManglingParser<Derived, Alloc>::parseQualifiedType() {
   if (consumeIf('U')) {
-    StringView Qual = parseBareSourceName();
+    std::string_view Qual = parseBareSourceName();
     if (Qual.empty())
       return nullptr;
 
     // extension            ::= U <objc-name> <objc-type>  # objc-type<identifier>
-    if (Qual.startsWith("objcproto")) {
-      StringView ProtoSourceName = Qual.dropFront(std::strlen("objcproto"));
-      StringView Proto;
+    if (starts_with(Qual, "objcproto")) {
+      constexpr size_t Len = sizeof("objcproto") - 1;
+      std::string_view ProtoSourceName(Qual.data() + Len, Qual.size() - Len);
+      std::string_view Proto;
       {
-        ScopedOverride<const char *> SaveFirst(First, ProtoSourceName.begin()),
-            SaveLast(Last, ProtoSourceName.end());
+        ScopedOverride<const char *> SaveFirst(First, ProtoSourceName.data()),
+            SaveLast(Last, &*ProtoSourceName.rbegin() + 1);
         Proto = parseBareSourceName();
       }
       if (Proto.empty())
@@ -3875,7 +3888,7 @@ Node *AbstractManglingParser<Derived, Alloc>::parseType() {
   // <builtin-type> ::= u <source-name>    # vendor extended type
   case 'u': {
     ++First;
-    StringView Res = parseBareSourceName();
+    std::string_view Res = parseBareSourceName();
     if (Res.empty())
       return nullptr;
     // Typically, <builtin-type>s are not considered substitution candidates,
@@ -4123,8 +4136,9 @@ Node *AbstractManglingParser<Derived, Alloc>::parseType() {
 }
 
 template <typename Derived, typename Alloc>
-Node *AbstractManglingParser<Derived, Alloc>::parsePrefixExpr(StringView Kind,
-                                                              Node::Prec Prec) {
+Node *
+AbstractManglingParser<Derived, Alloc>::parsePrefixExpr(std::string_view Kind,
+                                                        Node::Prec Prec) {
   Node *E = getDerived().parseExpr();
   if (E == nullptr)
     return nullptr;
@@ -4132,8 +4146,9 @@ Node *AbstractManglingParser<Derived, Alloc>::parsePrefixExpr(StringView Kind,
 }
 
 template <typename Derived, typename Alloc>
-Node *AbstractManglingParser<Derived, Alloc>::parseBinaryExpr(StringView Kind,
-                                                              Node::Prec Prec) {
+Node *
+AbstractManglingParser<Derived, Alloc>::parseBinaryExpr(std::string_view Kind,
+                                                        Node::Prec Prec) {
   Node *LHS = getDerived().parseExpr();
   if (LHS == nullptr)
     return nullptr;
@@ -4144,9 +4159,9 @@ Node *AbstractManglingParser<Derived, Alloc>::parseBinaryExpr(StringView Kind,
 }
 
 template <typename Derived, typename Alloc>
-Node *
-AbstractManglingParser<Derived, Alloc>::parseIntegerLiteral(StringView Lit) {
-  StringView Tmp = parseNumber(true);
+Node *AbstractManglingParser<Derived, Alloc>::parseIntegerLiteral(
+    std::string_view Lit) {
+  std::string_view Tmp = parseNumber(true);
   if (!Tmp.empty() && consumeIf('E'))
     return make<IntegerLiteral>(Lit, Tmp);
   return nullptr;
@@ -4176,7 +4191,7 @@ Node *AbstractManglingParser<Derived, Alloc>::parseFunctionParam() {
     return make<NameType>("this");
   if (consumeIf("fp")) {
     parseCVQualifiers();
-    StringView Num = parseNumber();
+    std::string_view Num = parseNumber();
     if (!consumeIf('_'))
       return nullptr;
     return make<FunctionParam>(Num);
@@ -4187,7 +4202,7 @@ Node *AbstractManglingParser<Derived, Alloc>::parseFunctionParam() {
     if (!consumeIf('p'))
       return nullptr;
     parseCVQualifiers();
-    StringView Num = parseNumber();
+    std::string_view Num = parseNumber();
     if (!consumeIf('_'))
       return nullptr;
     return make<FunctionParam>(Num);
@@ -4341,7 +4356,7 @@ Node *AbstractManglingParser<Derived, Alloc>::parseExprPrimary() {
     Node *T = getDerived().parseType();
     if (T == nullptr)
       return nullptr;
-    StringView N = parseNumber(/*AllowNegative=*/true);
+    std::string_view N = parseNumber(/*AllowNegative=*/true);
     if (N.empty())
       return nullptr;
     if (!consumeIf('E'))
@@ -4464,7 +4479,7 @@ AbstractManglingParser<Derived, Alloc>::parsePointerToMemberConversionExpr(
   Node *Expr = getDerived().parseExpr();
   if (!Expr)
     return nullptr;
-  StringView Offset = getDerived().parseNumber(true);
+  std::string_view Offset = getDerived().parseNumber(true);
   if (!consumeIf('E'))
     return nullptr;
   return make<PointerToMemberConversionExpr>(Ty, Expr, Offset, Prec);
@@ -4482,7 +4497,7 @@ Node *AbstractManglingParser<Derived, Alloc>::parseSubobjectExpr() {
   Node *Expr = getDerived().parseExpr();
   if (!Expr)
     return nullptr;
-  StringView Offset = getDerived().parseNumber(true);
+  std::string_view Offset = getDerived().parseNumber(true);
   size_t SelectorsBegin = Names.size();
   while (consumeIf('_')) {
     Node *Selector = make<NameType>(parseNumber());
@@ -5141,7 +5156,7 @@ Node *AbstractManglingParser<Alloc, Derived>::parseFloatingLiteral() {
   const size_t N = FloatData<Float>::mangled_size;
   if (numLeft() <= N)
     return nullptr;
-  StringView Data(First, First + N);
+  std::string_view Data(First, N);
   for (char C : Data)
     if (!std::isxdigit(C))
       return nullptr;
@@ -5461,7 +5476,8 @@ Node *AbstractManglingParser<Derived, Alloc>::parse() {
     if (Encoding == nullptr)
       return nullptr;
     if (look() == '.') {
-      Encoding = make<DotSuffix>(Encoding, StringView(First, Last));
+      Encoding =
+          make<DotSuffix>(Encoding, std::string_view(First, Last - First));
       First = Last;
     }
     if (numLeft() != 0)
@@ -5497,4 +5513,8 @@ struct ManglingParser : AbstractManglingParser<ManglingParser<Alloc>, Alloc> {
 
 DEMANGLE_NAMESPACE_END
 
+#ifdef _LIBCXXABI_COMPILER_CLANG
+#pragma clang diagnostic pop
+#endif
+
 #endif // DEMANGLE_ITANIUMDEMANGLE_H
diff --git a/lib/libcxxabi/src/demangle/StringView.h b/lib/libcxxabi/src/demangle/StringView.h
deleted file mode 100644
index 90890e3771..0000000000
--- a/lib/libcxxabi/src/demangle/StringView.h
+++ /dev/null
@@ -1,122 +0,0 @@
-//===--- StringView.h -------------------------------------------*- 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
-//
-//===----------------------------------------------------------------------===//
-//
-// 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.
-//
-//===----------------------------------------------------------------------===//
-
-#ifndef DEMANGLE_STRINGVIEW_H
-#define DEMANGLE_STRINGVIEW_H
-
-#include "DemangleConfig.h"
-#include <cassert>
-#include <cstring>
-
-DEMANGLE_NAMESPACE_BEGIN
-
-class StringView {
-  const char *First;
-  const char *Last;
-
-public:
-  static const size_t npos = ~size_t(0);
-
-  template <size_t N>
-  StringView(const char (&Str)[N]) : First(Str), Last(Str + N - 1) {}
-  StringView(const char *First_, const char *Last_)
-      : First(First_), Last(Last_) {}
-  StringView(const char *First_, size_t Len)
-      : First(First_), Last(First_ + Len) {}
-  StringView(const char *Str) : First(Str), Last(Str + std::strlen(Str)) {}
-  StringView() : First(nullptr), Last(nullptr) {}
-
-  StringView substr(size_t Pos, size_t Len = npos) const {
-    assert(Pos <= size());
-    if (Len > size() - Pos)
-      Len = size() - Pos;
-    return StringView(begin() + Pos, Len);
-  }
-
-  size_t find(char C, size_t From = 0) const {
-    // Avoid calling memchr with nullptr.
-    if (From < size()) {
-      // Just forward to memchr, which is faster than a hand-rolled loop.
-      if (const void *P = ::memchr(First + From, C, size() - From))
-        return size_t(static_cast<const char *>(P) - First);
-    }
-    return npos;
-  }
-
-  StringView dropFront(size_t N = 1) const {
-    if (N >= size())
-      N = size();
-    return StringView(First + N, Last);
-  }
-
-  StringView dropBack(size_t N = 1) const {
-    if (N >= size())
-      N = size();
-    return StringView(First, Last - N);
-  }
-
-  char front() const {
-    assert(!empty());
-    return *begin();
-  }
-
-  char back() const {
-    assert(!empty());
-    return *(end() - 1);
-  }
-
-  char popFront() {
-    assert(!empty());
-    return *First++;
-  }
-
-  bool consumeFront(char C) {
-    if (!startsWith(C))
-      return false;
-    *this = dropFront(1);
-    return true;
-  }
-
-  bool consumeFront(StringView S) {
-    if (!startsWith(S))
-      return false;
-    *this = dropFront(S.size());
-    return true;
-  }
-
-  bool startsWith(char C) const { return !empty() && *begin() == C; }
-
-  bool startsWith(StringView Str) const {
-    if (Str.size() > size())
-      return false;
-    return std::strncmp(Str.begin(), begin(), Str.size()) == 0;
-  }
-
-  const char &operator[](size_t Idx) const { return *(begin() + Idx); }
-
-  const char *begin() const { return First; }
-  const char *end() const { return Last; }
-  size_t size() const { return static_cast<size_t>(Last - First); }
-  bool empty() const { return First == Last; }
-};
-
-inline bool operator==(const StringView &LHS, const StringView &RHS) {
-  return LHS.size() == RHS.size() &&
-         std::strncmp(LHS.begin(), RHS.begin(), LHS.size()) == 0;
-}
-
-DEMANGLE_NAMESPACE_END
-
-#endif
diff --git a/lib/libcxxabi/src/demangle/StringViewExtras.h b/lib/libcxxabi/src/demangle/StringViewExtras.h
new file mode 100644
index 0000000000..0ad1f8c8a2
--- /dev/null
+++ b/lib/libcxxabi/src/demangle/StringViewExtras.h
@@ -0,0 +1,38 @@
+//===--- StringViewExtras.h -------------------------------------*- 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
+//
+//===----------------------------------------------------------------------===//
+//
+// 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.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef DEMANGLE_STRINGVIEW_H
+#define DEMANGLE_STRINGVIEW_H
+
+#include "DemangleConfig.h"
+
+#include <string_view>
+
+DEMANGLE_NAMESPACE_BEGIN
+
+inline bool starts_with(std::string_view self, char C) noexcept {
+  return !self.empty() && *self.begin() == C;
+}
+
+inline bool starts_with(std::string_view haystack,
+                        std::string_view needle) noexcept {
+  if (needle.size() > haystack.size())
+    return false;
+  haystack.remove_suffix(haystack.size() - needle.size());
+  return haystack == needle;
+}
+
+DEMANGLE_NAMESPACE_END
+
+#endif
diff --git a/lib/libcxxabi/src/demangle/Utility.h b/lib/libcxxabi/src/demangle/Utility.h
index c9b211b544..8370633ace 100644
--- a/lib/libcxxabi/src/demangle/Utility.h
+++ b/lib/libcxxabi/src/demangle/Utility.h
@@ -16,13 +16,16 @@
 #ifndef DEMANGLE_UTILITY_H
 #define DEMANGLE_UTILITY_H
 
-#include "StringView.h"
+#include "DemangleConfig.h"
+
 #include <array>
+#include <cassert>
 #include <cstdint>
 #include <cstdlib>
 #include <cstring>
 #include <exception>
 #include <limits>
+#include <string_view>
 
 DEMANGLE_NAMESPACE_BEGIN
 
@@ -64,7 +67,8 @@ class OutputBuffer {
     if (isNeg)
       *--TempPtr = '-';
 
-    return operator+=(StringView(TempPtr, Temp.data() + Temp.size()));
+    return operator+=(
+        std::string_view(TempPtr, Temp.data() + Temp.size() - TempPtr));
   }
 
 public:
@@ -77,7 +81,9 @@ public:
   OutputBuffer(const OutputBuffer &) = delete;
   OutputBuffer &operator=(const OutputBuffer &) = delete;
 
-  operator StringView() const { return StringView(Buffer, CurrentPosition); }
+  operator std::string_view() const {
+    return std::string_view(Buffer, CurrentPosition);
+  }
 
   /// If a ParameterPackExpansion (or similar type) is encountered, the offset
   /// into the pack that we're currently printing.
@@ -99,10 +105,10 @@ public:
     *this += Close;
   }
 
-  OutputBuffer &operator+=(StringView R) {
+  OutputBuffer &operator+=(std::string_view R) {
     if (size_t Size = R.size()) {
       grow(Size);
-      std::memcpy(Buffer + CurrentPosition, R.begin(), Size);
+      std::memcpy(Buffer + CurrentPosition, &*R.begin(), Size);
       CurrentPosition += Size;
     }
     return *this;
@@ -114,18 +120,18 @@ public:
     return *this;
   }
 
-  OutputBuffer &prepend(StringView R) {
+  OutputBuffer &prepend(std::string_view R) {
     size_t Size = R.size();
 
     grow(Size);
     std::memmove(Buffer + Size, Buffer, CurrentPosition);
-    std::memcpy(Buffer, R.begin(), Size);
+    std::memcpy(Buffer, &*R.begin(), Size);
     CurrentPosition += Size;
 
     return *this;
   }
 
-  OutputBuffer &operator<<(StringView R) { return (*this += R); }
+  OutputBuffer &operator<<(std::string_view R) { return (*this += R); }
 
   OutputBuffer &operator<<(char C) { return (*this += C); }
 
diff --git a/lib/libcxxabi/src/fallback_malloc.cpp b/lib/libcxxabi/src/fallback_malloc.cpp
index 591efbefc8..f9fb1bc463 100644
--- a/lib/libcxxabi/src/fallback_malloc.cpp
+++ b/lib/libcxxabi/src/fallback_malloc.cpp
@@ -15,10 +15,10 @@
 #endif
 #endif
 
+#include <__memory/aligned_alloc.h>
 #include <assert.h>
 #include <stdlib.h> // for malloc, calloc, free
 #include <string.h> // for memset
-#include <new> // for std::__libcpp_aligned_{alloc,free}
 
 //  A small, simple heap manager based (loosely) on
 //  the startup heap manager from FreeBSD, optimized for space.
diff --git a/lib/libcxxabi/src/private_typeinfo.cpp b/lib/libcxxabi/src/private_typeinfo.cpp
index e1086661c0..83d1f9f130 100644
--- a/lib/libcxxabi/src/private_typeinfo.cpp
+++ b/lib/libcxxabi/src/private_typeinfo.cpp
@@ -41,6 +41,7 @@
 // Defining _LIBCXXABI_FORGIVING_DYNAMIC_CAST does not help since can_catch() calls
 // is_equal() with use_strcmp=false so the string names are not compared.
 
+#include <cstdint>
 #include <string.h>
 
 #ifdef _LIBCXXABI_FORGIVING_DYNAMIC_CAST
@@ -656,77 +657,138 @@ __dynamic_cast(const void *static_ptr, const __class_type_info *static_type,
     // Find out if we can use a giant short cut in the search
     if (is_equal(dynamic_type, dst_type, false))
     {
-        // Using giant short cut.  Add that information to info.
-        info.number_of_dst_type = 1;
-        // Do the  search
-        dynamic_type->search_above_dst(&info, dynamic_ptr, dynamic_ptr, public_path, false);
-#ifdef _LIBCXXABI_FORGIVING_DYNAMIC_CAST
-        // The following if should always be false because we should definitely
-        //   find (static_ptr, static_type), either on a public or private path
-        if (info.path_dst_ptr_to_static_ptr == unknown)
+        // We're downcasting from src_type to the complete object's dynamic
+        //   type. This is a really hot path that can be further optimized
+        //   with the `src2dst_offset` hint.
+        // In such a case, dynamic_ptr already gives the casting result if the
+        //   casting ever succeeds. All we have to do now is to check
+        //   static_ptr points to a public base sub-object of dynamic_ptr.
+
+        if (src2dst_offset >= 0)
         {
-            // We get here only if there is some kind of visibility problem
-            //   in client code.
-            static_assert(std::atomic<size_t>::is_always_lock_free, "");
-            static std::atomic<size_t> error_count(0);
-            size_t error_count_snapshot = error_count.fetch_add(1, std::memory_order_relaxed);
-            if ((error_count_snapshot & (error_count_snapshot-1)) == 0)
-                syslog(LOG_ERR, "dynamic_cast error 1: Both of the following type_info's "
-                        "should have public visibility. At least one of them is hidden. %s"
-                        ", %s.\n", static_type->name(), dynamic_type->name());
-            // Redo the search comparing type_info's using strcmp
-            info = {dst_type, static_ptr, static_type, src2dst_offset, 0};
-            info.number_of_dst_type = 1;
-            dynamic_type->search_above_dst(&info, dynamic_ptr, dynamic_ptr, public_path, true);
+            // The static type is a unique public non-virtual base type of
+            //   dst_type at offset `src2dst_offset` from the origin of dst.
+            // Note that there might be other non-public static_type bases. The
+            //   hint only guarantees that the public base is non-virtual and
+            //   unique. So we have to check whether static_ptr points to that
+            //   unique public base sub-object.
+            if (offset_to_derived == -src2dst_offset)
+                dst_ptr = dynamic_ptr;
         }
+        else if (src2dst_offset == -2)
+        {
+            // static_type is not a public base of dst_type.
+            dst_ptr = nullptr;
+        }
+        else
+        {
+            // If src2dst_offset == -3, then:
+            //   src_type is a multiple public base type but never a virtual
+            //   base type. We can't conclude that static_ptr points to those
+            //   public base sub-objects because there might be other non-
+            //   public static_type bases. The search is inevitable.
+
+            // Fallback to the slow path to check that static_type is a public
+            //   base type of dynamic_type.
+            // Using giant short cut.  Add that information to info.
+            info.number_of_dst_type = 1;
+            // Do the  search
+            dynamic_type->search_above_dst(&info, dynamic_ptr, dynamic_ptr, public_path, false);
+#ifdef _LIBCXXABI_FORGIVING_DYNAMIC_CAST
+            // The following if should always be false because we should
+            //   definitely find (static_ptr, static_type), either on a public
+            //   or private path
+            if (info.path_dst_ptr_to_static_ptr == unknown)
+            {
+                // We get here only if there is some kind of visibility problem
+                //   in client code.
+                static_assert(std::atomic<size_t>::is_always_lock_free, "");
+                static std::atomic<size_t> error_count(0);
+                size_t error_count_snapshot = error_count.fetch_add(1, std::memory_order_relaxed);
+                if ((error_count_snapshot & (error_count_snapshot-1)) == 0)
+                    syslog(LOG_ERR, "dynamic_cast error 1: Both of the following type_info's "
+                            "should have public visibility. At least one of them is hidden. %s"
+                            ", %s.\n", static_type->name(), dynamic_type->name());
+                // Redo the search comparing type_info's using strcmp
+                info = {dst_type, static_ptr, static_type, src2dst_offset, 0};
+                info.number_of_dst_type = 1;
+                dynamic_type->search_above_dst(&info, dynamic_ptr, dynamic_ptr, public_path, true);
+            }
 #endif // _LIBCXXABI_FORGIVING_DYNAMIC_CAST
-        // Query the search.
-        if (info.path_dst_ptr_to_static_ptr == public_path)
-            dst_ptr = dynamic_ptr;
+            // Query the search.
+            if (info.path_dst_ptr_to_static_ptr == public_path)
+                dst_ptr = dynamic_ptr;
+        }
     }
     else
     {
-        // Not using giant short cut.  Do the search
-        dynamic_type->search_below_dst(&info, dynamic_ptr, public_path, false);
- #ifdef _LIBCXXABI_FORGIVING_DYNAMIC_CAST
-        // The following if should always be false because we should definitely
-        //   find (static_ptr, static_type), either on a public or private path
-        if (info.path_dst_ptr_to_static_ptr == unknown &&
-            info.path_dynamic_ptr_to_static_ptr == unknown)
+        if (src2dst_offset >= 0)
         {
-            static_assert(std::atomic<size_t>::is_always_lock_free, "");
-            static std::atomic<size_t> error_count(0);
-            size_t error_count_snapshot = error_count.fetch_add(1, std::memory_order_relaxed);
-            if ((error_count_snapshot & (error_count_snapshot-1)) == 0)
-                syslog(LOG_ERR, "dynamic_cast error 2: One or more of the following type_info's "
-                                "has hidden visibility or is defined in more than one translation "
-                                "unit. They should all have public visibility. "
-                                "%s, %s, %s.\n", static_type->name(), dynamic_type->name(),
-                        dst_type->name());
-            // Redo the search comparing type_info's using strcmp
-            info = {dst_type, static_ptr, static_type, src2dst_offset, 0};
-            dynamic_type->search_below_dst(&info, dynamic_ptr, public_path, true);
+            // Optimize toward downcasting: dst_type has one unique public
+            //   static_type bases. Let's first try to do a downcast before
+            //   falling back to the slow path. The downcast succeeds if there
+            //   is at least one path regardless of visibility from
+            //   dynamic_type to dst_type.
+            const void* dst_ptr_to_static = reinterpret_cast<const char*>(static_ptr) - src2dst_offset;
+            if (reinterpret_cast<std::intptr_t>(dst_ptr_to_static) >= reinterpret_cast<std::intptr_t>(dynamic_ptr))
+            {
+                // Try to search a path from dynamic_type to dst_type.
+                __dynamic_cast_info dynamic_to_dst_info = {dynamic_type, dst_ptr_to_static, dst_type, src2dst_offset};
+                dynamic_to_dst_info.number_of_dst_type = 1;
+                dynamic_type->search_above_dst(&dynamic_to_dst_info, dynamic_ptr, dynamic_ptr, public_path, false);
+                if (dynamic_to_dst_info.path_dst_ptr_to_static_ptr != unknown) {
+                    // We have found at least one path from dynamic_ptr to
+                    //   dst_ptr. The downcast can succeed.
+                    dst_ptr = dst_ptr_to_static;
+                }
+            }
         }
-#endif // _LIBCXXABI_FORGIVING_DYNAMIC_CAST
-        // Query the search.
-        switch (info.number_to_static_ptr)
+
+        if (!dst_ptr)
         {
-        case 0:
-            if (info.number_to_dst_ptr == 1 &&
-                    info.path_dynamic_ptr_to_static_ptr == public_path &&
-                    info.path_dynamic_ptr_to_dst_ptr == public_path)
-                dst_ptr = info.dst_ptr_not_leading_to_static_ptr;
-            break;
-        case 1:
-            if (info.path_dst_ptr_to_static_ptr == public_path ||
-                   (
-                       info.number_to_dst_ptr == 0 &&
-                       info.path_dynamic_ptr_to_static_ptr == public_path &&
-                       info.path_dynamic_ptr_to_dst_ptr == public_path
-                   )
-               )
-                dst_ptr = info.dst_ptr_leading_to_static_ptr;
-            break;
+            // Not using giant short cut.  Do the search
+            dynamic_type->search_below_dst(&info, dynamic_ptr, public_path, false);
+#ifdef _LIBCXXABI_FORGIVING_DYNAMIC_CAST
+            // The following if should always be false because we should
+            //   definitely find (static_ptr, static_type), either on a public
+            //   or private path
+            if (info.path_dst_ptr_to_static_ptr == unknown &&
+                info.path_dynamic_ptr_to_static_ptr == unknown)
+            {
+                static_assert(std::atomic<size_t>::is_always_lock_free, "");
+                static std::atomic<size_t> error_count(0);
+                size_t error_count_snapshot = error_count.fetch_add(1, std::memory_order_relaxed);
+                if ((error_count_snapshot & (error_count_snapshot-1)) == 0)
+                    syslog(LOG_ERR, "dynamic_cast error 2: One or more of the following type_info's "
+                                    "has hidden visibility or is defined in more than one translation "
+                                    "unit. They should all have public visibility. "
+                                    "%s, %s, %s.\n", static_type->name(), dynamic_type->name(),
+                            dst_type->name());
+                // Redo the search comparing type_info's using strcmp
+                info = {dst_type, static_ptr, static_type, src2dst_offset, 0};
+                dynamic_type->search_below_dst(&info, dynamic_ptr, public_path, true);
+            }
+#endif // _LIBCXXABI_FORGIVING_DYNAMIC_CAST
+            // Query the search.
+            switch (info.number_to_static_ptr)
+            {
+            case 0:
+                if (info.number_to_dst_ptr == 1 &&
+                        info.path_dynamic_ptr_to_static_ptr == public_path &&
+                        info.path_dynamic_ptr_to_dst_ptr == public_path)
+                    dst_ptr = info.dst_ptr_not_leading_to_static_ptr;
+                break;
+            case 1:
+                if (info.path_dst_ptr_to_static_ptr == public_path ||
+                    (
+                        info.number_to_dst_ptr == 0 &&
+                        info.path_dynamic_ptr_to_static_ptr == public_path &&
+                        info.path_dynamic_ptr_to_dst_ptr == public_path
+                    )
+                )
+                    dst_ptr = info.dst_ptr_leading_to_static_ptr;
+                break;
+            }
         }
     }
     return const_cast<void*>(dst_ptr);
diff --git a/lib/libcxxabi/src/stdlib_new_delete.cpp b/lib/libcxxabi/src/stdlib_new_delete.cpp
index 4a664e15a5..080f932ccc 100644
--- a/lib/libcxxabi/src/stdlib_new_delete.cpp
+++ b/lib/libcxxabi/src/stdlib_new_delete.cpp
@@ -4,30 +4,40 @@
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-//
-// This file implements the new and delete operators.
 //===----------------------------------------------------------------------===//
 
 #include "__cxxabi_config.h"
-#include <new>
+#include <__memory/aligned_alloc.h>
 #include <cstdlib>
+#include <new>
 
-#if !defined(_THROW_BAD_ALLOC) || !defined(_LIBCXXABI_WEAK)
-#error The _THROW_BAD_ALLOC and _LIBCXXABI_WEAK libc++ macros must \
-       already be defined by libc++.
+// Perform a few sanity checks on libc++ and libc++abi macros to ensure that
+// the code below can be an exact copy of the code in libcxx/src/new.cpp.
+#if !defined(_THROW_BAD_ALLOC)
+#  error The _THROW_BAD_ALLOC macro should be already defined by libc++
 #endif
+
+#ifndef _LIBCPP_WEAK
+#  error The _LIBCPP_WEAK macro should be already defined by libc++
+#endif
+
+#if defined(_LIBCXXABI_NO_EXCEPTIONS) != defined(_LIBCPP_HAS_NO_EXCEPTIONS)
+#  error libc++ and libc++abi seem to disagree on whether exceptions are enabled
+#endif
+
+// ------------------ BEGIN COPY ------------------
 // Implement all new and delete operators as weak definitions
 // in this shared library, so that they can be overridden by programs
 // that define non-weak copies of the functions.
 
-_LIBCXXABI_WEAK
+_LIBCPP_WEAK
 void *
 operator new(std::size_t size) _THROW_BAD_ALLOC
 {
     if (size == 0)
         size = 1;
     void* p;
-    while ((p = ::malloc(size)) == nullptr)
+    while ((p = std::malloc(size)) == nullptr)
     {
         // If malloc fails and there is a new_handler,
         // call it to try free up memory.
@@ -35,7 +45,7 @@ operator new(std::size_t size) _THROW_BAD_ALLOC
         if (nh)
             nh();
         else
-#ifndef _LIBCXXABI_NO_EXCEPTIONS
+#ifndef _LIBCPP_HAS_NO_EXCEPTIONS
             throw std::bad_alloc();
 #else
             break;
@@ -44,87 +54,87 @@ operator new(std::size_t size) _THROW_BAD_ALLOC
     return p;
 }
 
-_LIBCXXABI_WEAK
+_LIBCPP_WEAK
 void*
 operator new(size_t size, const std::nothrow_t&) noexcept
 {
     void* p = nullptr;
-#ifndef _LIBCXXABI_NO_EXCEPTIONS
+#ifndef _LIBCPP_HAS_NO_EXCEPTIONS
     try
     {
-#endif // _LIBCXXABI_NO_EXCEPTIONS
+#endif // _LIBCPP_HAS_NO_EXCEPTIONS
         p = ::operator new(size);
-#ifndef _LIBCXXABI_NO_EXCEPTIONS
+#ifndef _LIBCPP_HAS_NO_EXCEPTIONS
     }
     catch (...)
     {
     }
-#endif // _LIBCXXABI_NO_EXCEPTIONS
+#endif // _LIBCPP_HAS_NO_EXCEPTIONS
     return p;
 }
 
-_LIBCXXABI_WEAK
+_LIBCPP_WEAK
 void*
 operator new[](size_t size) _THROW_BAD_ALLOC
 {
     return ::operator new(size);
 }
 
-_LIBCXXABI_WEAK
+_LIBCPP_WEAK
 void*
 operator new[](size_t size, const std::nothrow_t&) noexcept
 {
     void* p = nullptr;
-#ifndef _LIBCXXABI_NO_EXCEPTIONS
+#ifndef _LIBCPP_HAS_NO_EXCEPTIONS
     try
     {
-#endif // _LIBCXXABI_NO_EXCEPTIONS
+#endif // _LIBCPP_HAS_NO_EXCEPTIONS
         p = ::operator new[](size);
-#ifndef _LIBCXXABI_NO_EXCEPTIONS
+#ifndef _LIBCPP_HAS_NO_EXCEPTIONS
     }
     catch (...)
     {
     }
-#endif // _LIBCXXABI_NO_EXCEPTIONS
+#endif // _LIBCPP_HAS_NO_EXCEPTIONS
     return p;
 }
 
-_LIBCXXABI_WEAK
+_LIBCPP_WEAK
 void
 operator delete(void* ptr) noexcept
 {
-    ::free(ptr);
+    std::free(ptr);
 }
 
-_LIBCXXABI_WEAK
+_LIBCPP_WEAK
 void
 operator delete(void* ptr, const std::nothrow_t&) noexcept
 {
     ::operator delete(ptr);
 }
 
-_LIBCXXABI_WEAK
+_LIBCPP_WEAK
 void
 operator delete(void* ptr, size_t) noexcept
 {
     ::operator delete(ptr);
 }
 
-_LIBCXXABI_WEAK
+_LIBCPP_WEAK
 void
 operator delete[] (void* ptr) noexcept
 {
     ::operator delete(ptr);
 }
 
-_LIBCXXABI_WEAK
+_LIBCPP_WEAK
 void
 operator delete[] (void* ptr, const std::nothrow_t&) noexcept
 {
     ::operator delete[](ptr);
 }
 
-_LIBCXXABI_WEAK
+_LIBCPP_WEAK
 void
 operator delete[] (void* ptr, size_t) noexcept
 {
@@ -133,7 +143,7 @@ operator delete[] (void* ptr, size_t) noexcept
 
 #if !defined(_LIBCPP_HAS_NO_LIBRARY_ALIGNED_ALLOCATION)
 
-_LIBCXXABI_WEAK
+_LIBCPP_WEAK
 void *
 operator new(std::size_t size, std::align_val_t alignment) _THROW_BAD_ALLOC
 {
@@ -155,7 +165,7 @@ operator new(std::size_t size, std::align_val_t alignment) _THROW_BAD_ALLOC
         if (nh)
             nh();
         else {
-#ifndef _LIBCXXABI_NO_EXCEPTIONS
+#ifndef _LIBCPP_HAS_NO_EXCEPTIONS
             throw std::bad_alloc();
 #else
             break;
@@ -165,87 +175,87 @@ operator new(std::size_t size, std::align_val_t alignment) _THROW_BAD_ALLOC
     return p;
 }
 
-_LIBCXXABI_WEAK
+_LIBCPP_WEAK
 void*
 operator new(size_t size, std::align_val_t alignment, const std::nothrow_t&) noexcept
 {
     void* p = nullptr;
-#ifndef _LIBCXXABI_NO_EXCEPTIONS
+#ifndef _LIBCPP_HAS_NO_EXCEPTIONS
     try
     {
-#endif // _LIBCXXABI_NO_EXCEPTIONS
+#endif // _LIBCPP_HAS_NO_EXCEPTIONS
         p = ::operator new(size, alignment);
-#ifndef _LIBCXXABI_NO_EXCEPTIONS
+#ifndef _LIBCPP_HAS_NO_EXCEPTIONS
     }
     catch (...)
     {
     }
-#endif // _LIBCXXABI_NO_EXCEPTIONS
+#endif // _LIBCPP_HAS_NO_EXCEPTIONS
     return p;
 }
 
-_LIBCXXABI_WEAK
+_LIBCPP_WEAK
 void*
 operator new[](size_t size, std::align_val_t alignment) _THROW_BAD_ALLOC
 {
     return ::operator new(size, alignment);
 }
 
-_LIBCXXABI_WEAK
+_LIBCPP_WEAK
 void*
 operator new[](size_t size, std::align_val_t alignment, const std::nothrow_t&) noexcept
 {
     void* p = nullptr;
-#ifndef _LIBCXXABI_NO_EXCEPTIONS
+#ifndef _LIBCPP_HAS_NO_EXCEPTIONS
     try
     {
-#endif // _LIBCXXABI_NO_EXCEPTIONS
+#endif // _LIBCPP_HAS_NO_EXCEPTIONS
         p = ::operator new[](size, alignment);
-#ifndef _LIBCXXABI_NO_EXCEPTIONS
+#ifndef _LIBCPP_HAS_NO_EXCEPTIONS
     }
     catch (...)
     {
     }
-#endif // _LIBCXXABI_NO_EXCEPTIONS
+#endif // _LIBCPP_HAS_NO_EXCEPTIONS
     return p;
 }
 
-_LIBCXXABI_WEAK
+_LIBCPP_WEAK
 void
 operator delete(void* ptr, std::align_val_t) noexcept
 {
     std::__libcpp_aligned_free(ptr);
 }
 
-_LIBCXXABI_WEAK
+_LIBCPP_WEAK
 void
 operator delete(void* ptr, std::align_val_t alignment, const std::nothrow_t&) noexcept
 {
     ::operator delete(ptr, alignment);
 }
 
-_LIBCXXABI_WEAK
+_LIBCPP_WEAK
 void
 operator delete(void* ptr, size_t, std::align_val_t alignment) noexcept
 {
     ::operator delete(ptr, alignment);
 }
 
-_LIBCXXABI_WEAK
+_LIBCPP_WEAK
 void
 operator delete[] (void* ptr, std::align_val_t alignment) noexcept
 {
     ::operator delete(ptr, alignment);
 }
 
-_LIBCXXABI_WEAK
+_LIBCPP_WEAK
 void
 operator delete[] (void* ptr, std::align_val_t alignment, const std::nothrow_t&) noexcept
 {
     ::operator delete[](ptr, alignment);
 }
 
-_LIBCXXABI_WEAK
+_LIBCPP_WEAK
 void
 operator delete[] (void* ptr, size_t, std::align_val_t alignment) noexcept
 {
@@ -253,3 +263,4 @@ operator delete[] (void* ptr, size_t, std::align_val_t alignment) noexcept
 }
 
 #endif // !_LIBCPP_HAS_NO_LIBRARY_ALIGNED_ALLOCATION
+// ------------------ END COPY ------------------