[libc++abi] Implement __cxa_init_primary_exception and use it to optimize std::make_exception_ptr (#65534)

This patch implements __cxa_init_primary_exception, an extension to the 
Itanium C++ ABI. This extension is already present in both libsupc++ and 
libcxxrt. This patch also starts making use of this function in 
std::make_exception_ptr: instead of going through a full throw/catch 
cycle, we are now able to initialize an exception directly, thus making 
std::make_exception_ptr around 30x faster.

libcxx/benchmarks/CMakeLists.txt

@@ -202,6 +202,7 @@ set(BENCHMARK_TESTS
     allocation.bench.cpp
     deque.bench.cpp
     deque_iterator.bench.cpp
+    exception_ptr.bench.cpp
     filesystem.bench.cpp
     format_to_n.bench.cpp
     format_to.bench.cpp

libcxx/benchmarks/exception_ptr.bench.cpp

@@ -0,0 +1,19 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+#include <benchmark/benchmark.h>
+#include <exception>
+
+void bm_make_exception_ptr(benchmark::State& state) {
+  for (auto _ : state) {
+    benchmark::DoNotOptimize(std::make_exception_ptr(42));
+  }
+}
+BENCHMARK(bm_make_exception_ptr)->ThreadRange(1, 8);
+
+BENCHMARK_MAIN();

libcxx/docs/BuildingLibcxx.rst

@@ -563,6 +563,7 @@ We can now run CMake:
   $ cmake -G Ninja -S runtimes -B build       \
     -DLLVM_ENABLE_RUNTIMES="libcxx"           \
     -DLIBCXX_CXX_ABI=libstdc++                \
+    -DLIBCXXABI_USE_LLVM_UNWINDER=OFF         \
     -DLIBCXX_CXX_ABI_INCLUDE_PATHS="/usr/include/c++/4.7/;/usr/include/c++/4.7/x86_64-linux-gnu/"
   $ ninja -C build install-cxx
 
@@ -589,6 +590,8 @@ We can now run CMake like:
   $ cmake -G Ninja -S runtimes -B build                               \
           -DLLVM_ENABLE_RUNTIMES="libcxx"                             \
           -DLIBCXX_CXX_ABI=libcxxrt                                   \
+          -DLIBCXX_ENABLE_NEW_DELETE_DEFINITIONS=ON                   \
+          -DLIBCXXABI_USE_LLVM_UNWINDER=OFF                           \
           -DLIBCXX_CXX_ABI_INCLUDE_PATHS=path/to/libcxxrt-sources/src
   $ ninja -C build install-cxx
 

libcxx/include/__availability

@@ -101,6 +101,12 @@
 #  define _LIBCPP_AVAILABILITY_HAS_BAD_ANY_CAST 1
 #  define _LIBCPP_AVAILABILITY_BAD_ANY_CAST
 
+// These macros controls the availability of __cxa_init_primary_exception
+// in the built library, which std::make_exception_ptr might use
+// (see libcxx/include/__exception/exception_ptr.h).
+#  define _LIBCPP_AVAILABILITY_HAS_INIT_PRIMARY_EXCEPTION 1
+#  define _LIBCPP_AVAILABILITY_INIT_PRIMARY_EXCEPTION
+
 // These macros control the availability of all parts of <filesystem> that
 // depend on something in the dylib.
 #  define _LIBCPP_AVAILABILITY_HAS_FILESYSTEM_LIBRARY 1
@@ -136,9 +142,9 @@
 #  define _LIBCPP_AVAILABILITY_HAS_TZDB 1
 #  define _LIBCPP_AVAILABILITY_TZDB
 
-    // This controls the availability of C++23 <print>, which
-    // has a dependency on the built library (it needs access to
-    // the underlying buffer types of std::cout, std::cerr, and std::clog.
+// This controls the availability of C++23 <print>, which
+// has a dependency on the built library (it needs access to
+// the underlying buffer types of std::cout, std::cerr, and std::clog.
 #  define _LIBCPP_AVAILABILITY_HAS_PRINT 1
 #  define _LIBCPP_AVAILABILITY_PRINT
 
@@ -167,6 +173,10 @@
 #  define _LIBCPP_AVAILABILITY_BAD_VARIANT_ACCESS _LIBCPP_AVAILABILITY_BAD_OPTIONAL_ACCESS
 #  define _LIBCPP_AVAILABILITY_BAD_ANY_CAST _LIBCPP_AVAILABILITY_BAD_OPTIONAL_ACCESS
 
+// TODO: Update once this is released
+#  define _LIBCPP_AVAILABILITY_HAS_INIT_PRIMARY_EXCEPTION 0
+#  define _LIBCPP_AVAILABILITY_INIT_PRIMARY_EXCEPTION __attribute__((unavailable))
+
 // <filesystem>
 // clang-format off
 #  if (defined(__ENVIRONMENT_MAC_OS_X_VERSION_MIN_REQUIRED__) && __ENVIRONMENT_MAC_OS_X_VERSION_MIN_REQUIRED__ < 101500) ||   \
@@ -303,4 +313,13 @@
 #  define _LIBCPP_AVAILABILITY_THROW_BAD_VARIANT_ACCESS _LIBCPP_AVAILABILITY_BAD_VARIANT_ACCESS
 #endif
 
+// Define availability attributes that depend on both
+// _LIBCPP_HAS_NO_EXCEPTIONS and _LIBCPP_HAS_NO_RTTI.
+#if defined(_LIBCPP_HAS_NO_EXCEPTIONS) || defined(_LIBCPP_HAS_NO_RTTI)
+#  undef _LIBCPP_AVAILABILITY_HAS_INIT_PRIMARY_EXCEPTION
+#  undef _LIBCPP_AVAILABILITY_INIT_PRIMARY_EXCEPTION
+#  define _LIBCPP_AVAILABILITY_HAS_INIT_PRIMARY_EXCEPTION 0
+#  define _LIBCPP_AVAILABILITY_INIT_PRIMARY_EXCEPTION
+#endif
+
 #endif // _LIBCPP___AVAILABILITY

libcxx/include/__exception/exception_ptr.h

@@ -9,16 +9,44 @@
 #ifndef _LIBCPP___EXCEPTION_EXCEPTION_PTR_H
 #define _LIBCPP___EXCEPTION_EXCEPTION_PTR_H
 
+#include <__availability>
 #include <__config>
 #include <__exception/operations.h>
 #include <__memory/addressof.h>
+#include <__memory/construct_at.h>
+#include <__type_traits/decay.h>
 #include <cstddef>
 #include <cstdlib>
+#include <new>
+#include <typeinfo>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header
 #endif
 
+#ifndef _LIBCPP_ABI_MICROSOFT
+
+namespace __cxxabiv1 {
+
+extern "C" {
+_LIBCPP_OVERRIDABLE_FUNC_VIS void* __cxa_allocate_exception(size_t) throw();
+_LIBCPP_OVERRIDABLE_FUNC_VIS void __cxa_free_exception(void*) throw();
+
+struct __cxa_exception;
+_LIBCPP_OVERRIDABLE_FUNC_VIS __cxa_exception* __cxa_init_primary_exception(
+    void*,
+    std::type_info*,
+    void(
+#  if defined(_WIN32)
+        __thiscall
+#  endif
+            *)(void*)) throw();
+}
+
+} // namespace __cxxabiv1
+
+#endif
+
 namespace std { // purposefully not using versioning namespace
 
 #ifndef _LIBCPP_ABI_MICROSOFT
@@ -26,6 +54,11 @@ namespace std { // purposefully not using versioning namespace
 class _LIBCPP_EXPORTED_FROM_ABI exception_ptr {
   void* __ptr_;
 
+  static exception_ptr __from_native_exception_pointer(void*) _NOEXCEPT;
+
+  template <class _Ep>
+  friend _LIBCPP_HIDE_FROM_ABI exception_ptr make_exception_ptr(_Ep) _NOEXCEPT;
+
 public:
   _LIBCPP_HIDE_FROM_ABI exception_ptr() _NOEXCEPT : __ptr_() {}
   _LIBCPP_HIDE_FROM_ABI exception_ptr(nullptr_t) _NOEXCEPT : __ptr_() {}
@@ -51,11 +84,28 @@ public:
 template <class _Ep>
 _LIBCPP_HIDE_FROM_ABI exception_ptr make_exception_ptr(_Ep __e) _NOEXCEPT {
 #  ifndef _LIBCPP_HAS_NO_EXCEPTIONS
+#    if _LIBCPP_AVAILABILITY_HAS_INIT_PRIMARY_EXCEPTION && __cplusplus >= 201103L
+  using _Ep2 = __decay_t<_Ep>;
+
+  void* __ex = __cxxabiv1::__cxa_allocate_exception(sizeof(_Ep));
+  (void)__cxxabiv1::__cxa_init_primary_exception(__ex, const_cast<std::type_info*>(&typeid(_Ep)), [](void* __p) {
+    std::__destroy_at(static_cast<_Ep2*>(__p));
+  });
+
+  try {
+    ::new (__ex) _Ep2(__e);
+    return exception_ptr::__from_native_exception_pointer(__ex);
+  } catch (...) {
+    __cxxabiv1::__cxa_free_exception(__ex);
+    return current_exception();
+  }
+#    else
   try {
     throw __e;
   } catch (...) {
     return current_exception();
   }
+#    endif
 #  else
   ((void)__e);
   std::abort();

libcxx/include/new

@@ -362,7 +362,6 @@ _LIBCPP_END_NAMESPACE_STD
 
 #if !defined(_LIBCPP_REMOVE_TRANSITIVE_INCLUDES) && _LIBCPP_STD_VER <= 20
 #  include <cstdlib>
-#  include <exception>
 #  include <type_traits>
 #endif
 

libcxx/include/typeinfo

@@ -372,7 +372,6 @@ _LIBCPP_END_NAMESPACE_STD
 
 #if !defined(_LIBCPP_REMOVE_TRANSITIVE_INCLUDES) && _LIBCPP_STD_VER <= 20
 #  include <cstdlib>
-#  include <exception>
 #  include <type_traits>
 #endif
 

libcxx/lib/abi/arm64-apple-darwin.libcxxabi.v1.stable.exceptions.nonew.abilist

@@ -300,6 +300,7 @@
 {'is_defined': False, 'name': '___cxa_guard_acquire', 'type': 'U'}
 {'is_defined': False, 'name': '___cxa_guard_release', 'type': 'U'}
 {'is_defined': False, 'name': '___cxa_increment_exception_refcount', 'type': 'U'}
+{'is_defined': False, 'name': '___cxa_init_primary_exception', 'type': 'U'}
 {'is_defined': False, 'name': '___cxa_pure_virtual', 'type': 'U'}
 {'is_defined': False, 'name': '___cxa_rethrow', 'type': 'U'}
 {'is_defined': False, 'name': '___cxa_rethrow_primary_exception', 'type': 'U'}
@@ -811,6 +812,7 @@
 {'is_defined': True, 'name': '__ZNSt13bad_exceptionD0Ev', 'type': 'I'}
 {'is_defined': True, 'name': '__ZNSt13bad_exceptionD1Ev', 'type': 'I'}
 {'is_defined': True, 'name': '__ZNSt13bad_exceptionD2Ev', 'type': 'I'}
+{'is_defined': True, 'name': '__ZNSt13exception_ptr31__from_native_exception_pointerEPv', 'type': 'FUNC'}
 {'is_defined': True, 'name': '__ZNSt13exception_ptrC1ERKS_', 'type': 'FUNC'}
 {'is_defined': True, 'name': '__ZNSt13exception_ptrC2ERKS_', 'type': 'FUNC'}
 {'is_defined': True, 'name': '__ZNSt13exception_ptrD1Ev', 'type': 'FUNC'}
@@ -2509,6 +2511,7 @@
 {'is_defined': True, 'name': '___cxa_guard_abort', 'type': 'I'}
 {'is_defined': True, 'name': '___cxa_guard_acquire', 'type': 'I'}
 {'is_defined': True, 'name': '___cxa_guard_release', 'type': 'I'}
+{'is_defined': True, 'name': '___cxa_init_primary_exception', 'type': 'I'}
 {'is_defined': True, 'name': '___cxa_pure_virtual', 'type': 'I'}
 {'is_defined': True, 'name': '___cxa_rethrow', 'type': 'I'}
 {'is_defined': True, 'name': '___cxa_throw', 'type': 'I'}

libcxx/lib/abi/i686-linux-android21.libcxxabi.v1.stable.exceptions.nonew.abilist

@@ -493,6 +493,7 @@
 {'is_defined': True, 'name': '_ZNSt13bad_exceptionD0Ev', 'type': 'FUNC'}
 {'is_defined': True, 'name': '_ZNSt13bad_exceptionD1Ev', 'type': 'FUNC'}
 {'is_defined': True, 'name': '_ZNSt13bad_exceptionD2Ev', 'type': 'FUNC'}
+{'is_defined': True, 'name': '_ZNSt13exception_ptr31__from_native_exception_pointerEPv', 'type': 'FUNC'}
 {'is_defined': True, 'name': '_ZNSt13exception_ptrC1ERKS_', 'type': 'FUNC'}
 {'is_defined': True, 'name': '_ZNSt13exception_ptrC2ERKS_', 'type': 'FUNC'}
 {'is_defined': True, 'name': '_ZNSt13exception_ptrD1Ev', 'type': 'FUNC'}
@@ -2311,6 +2312,7 @@
 {'is_defined': True, 'name': '__cxa_guard_acquire', 'type': 'FUNC'}
 {'is_defined': True, 'name': '__cxa_guard_release', 'type': 'FUNC'}
 {'is_defined': True, 'name': '__cxa_increment_exception_refcount', 'type': 'FUNC'}
+{'is_defined': True, 'name': '__cxa_init_primary_exception', 'type': 'FUNC'}
 {'is_defined': True, 'name': '__cxa_new_handler', 'size': 4, 'type': 'OBJECT'}
 {'is_defined': True, 'name': '__cxa_pure_virtual', 'type': 'FUNC'}
 {'is_defined': True, 'name': '__cxa_rethrow', 'type': 'FUNC'}

libcxx/lib/abi/powerpc-ibm-aix.libcxxabi.v1.stable.exceptions.nonew.abilist

@@ -249,6 +249,7 @@
 {'import_export': 'EXP', 'is_defined': True, 'name': '_ZNSt12experimental19bad_optional_accessD0Ev', 'storage_mapping_class': 'DS', 'type': 'FUNC'}
 {'import_export': 'EXP', 'is_defined': True, 'name': '_ZNSt12experimental19bad_optional_accessD1Ev', 'storage_mapping_class': 'DS', 'type': 'FUNC'}
 {'import_export': 'EXP', 'is_defined': True, 'name': '_ZNSt12experimental19bad_optional_accessD2Ev', 'storage_mapping_class': 'DS', 'type': 'FUNC'}
+{'import_export': 'EXP', 'is_defined': True, 'name': '_ZNSt13exception_ptr31__from_native_exception_pointerEPv', 'storage_mapping_class': 'DS', 'type': 'FUNC'}
 {'import_export': 'EXP', 'is_defined': True, 'name': '_ZNSt13exception_ptrC1ERKS_', 'storage_mapping_class': 'DS', 'type': 'FUNC'}
 {'import_export': 'EXP', 'is_defined': True, 'name': '_ZNSt13exception_ptrC2ERKS_', 'storage_mapping_class': 'DS', 'type': 'FUNC'}
 {'import_export': 'EXP', 'is_defined': True, 'name': '_ZNSt13exception_ptrD1Ev', 'storage_mapping_class': 'DS', 'type': 'FUNC'}
@@ -1111,6 +1112,7 @@
 {'import_export': 'IMP', 'is_defined': False, 'name': '__cxa_guard_acquire', 'storage_mapping_class': 'DS', 'type': 'FUNC'}
 {'import_export': 'IMP', 'is_defined': False, 'name': '__cxa_guard_release', 'storage_mapping_class': 'DS', 'type': 'FUNC'}
 {'import_export': 'IMP', 'is_defined': False, 'name': '__cxa_increment_exception_refcount', 'storage_mapping_class': 'DS', 'type': 'FUNC'}
+{'import_export': 'IMP', 'is_defined': False, 'name': '__cxa_init_primary_exception', 'storage_mapping_class': 'DS', 'type': 'FUNC'}
 {'import_export': 'IMP', 'is_defined': False, 'name': '__cxa_pure_virtual', 'storage_mapping_class': 'DS', 'type': 'FUNC'}
 {'import_export': 'IMP', 'is_defined': False, 'name': '__cxa_rethrow', 'storage_mapping_class': 'DS', 'type': 'FUNC'}
 {'import_export': 'IMP', 'is_defined': False, 'name': '__cxa_rethrow_primary_exception', 'storage_mapping_class': 'DS', 'type': 'FUNC'}

libcxx/lib/abi/powerpc64-ibm-aix.libcxxabi.v1.stable.exceptions.nonew.abilist

@@ -249,6 +249,7 @@
 {'import_export': 'EXP', 'is_defined': True, 'name': '_ZNSt12experimental19bad_optional_accessD0Ev', 'storage_mapping_class': 'DS', 'type': 'FUNC'}
 {'import_export': 'EXP', 'is_defined': True, 'name': '_ZNSt12experimental19bad_optional_accessD1Ev', 'storage_mapping_class': 'DS', 'type': 'FUNC'}
 {'import_export': 'EXP', 'is_defined': True, 'name': '_ZNSt12experimental19bad_optional_accessD2Ev', 'storage_mapping_class': 'DS', 'type': 'FUNC'}
+{'import_export': 'EXP', 'is_defined': True, 'name': '_ZNSt13exception_ptr31__from_native_exception_pointerEPv', 'storage_mapping_class': 'DS', 'type': 'FUNC'}
 {'import_export': 'EXP', 'is_defined': True, 'name': '_ZNSt13exception_ptrC1ERKS_', 'storage_mapping_class': 'DS', 'type': 'FUNC'}
 {'import_export': 'EXP', 'is_defined': True, 'name': '_ZNSt13exception_ptrC2ERKS_', 'storage_mapping_class': 'DS', 'type': 'FUNC'}
 {'import_export': 'EXP', 'is_defined': True, 'name': '_ZNSt13exception_ptrD1Ev', 'storage_mapping_class': 'DS', 'type': 'FUNC'}
@@ -1111,6 +1112,7 @@
 {'import_export': 'IMP', 'is_defined': False, 'name': '__cxa_guard_acquire', 'storage_mapping_class': 'DS', 'type': 'FUNC'}
 {'import_export': 'IMP', 'is_defined': False, 'name': '__cxa_guard_release', 'storage_mapping_class': 'DS', 'type': 'FUNC'}
 {'import_export': 'IMP', 'is_defined': False, 'name': '__cxa_increment_exception_refcount', 'storage_mapping_class': 'DS', 'type': 'FUNC'}
+{'import_export': 'IMP', 'is_defined': False, 'name': '__cxa_init_primary_exception', 'storage_mapping_class': 'DS', 'type': 'FUNC'}
 {'import_export': 'IMP', 'is_defined': False, 'name': '__cxa_pure_virtual', 'storage_mapping_class': 'DS', 'type': 'FUNC'}
 {'import_export': 'IMP', 'is_defined': False, 'name': '__cxa_rethrow', 'storage_mapping_class': 'DS', 'type': 'FUNC'}
 {'import_export': 'IMP', 'is_defined': False, 'name': '__cxa_rethrow_primary_exception', 'storage_mapping_class': 'DS', 'type': 'FUNC'}

libcxx/lib/abi/x86_64-apple-darwin.libcxxabi.v1.stable.exceptions.nonew.abilist

@@ -300,6 +300,7 @@
 {'is_defined': False, 'name': '___cxa_guard_acquire', 'type': 'U'}
 {'is_defined': False, 'name': '___cxa_guard_release', 'type': 'U'}
 {'is_defined': False, 'name': '___cxa_increment_exception_refcount', 'type': 'U'}
+{'is_defined': False, 'name': '___cxa_init_primary_exception', 'type': 'U'}
 {'is_defined': False, 'name': '___cxa_pure_virtual', 'type': 'U'}
 {'is_defined': False, 'name': '___cxa_rethrow', 'type': 'U'}
 {'is_defined': False, 'name': '___cxa_rethrow_primary_exception', 'type': 'U'}
@@ -811,6 +812,7 @@
 {'is_defined': True, 'name': '__ZNSt13bad_exceptionD0Ev', 'type': 'I'}
 {'is_defined': True, 'name': '__ZNSt13bad_exceptionD1Ev', 'type': 'I'}
 {'is_defined': True, 'name': '__ZNSt13bad_exceptionD2Ev', 'type': 'I'}
+{'is_defined': True, 'name': '__ZNSt13exception_ptr31__from_native_exception_pointerEPv', 'type': 'FUNC'}
 {'is_defined': True, 'name': '__ZNSt13exception_ptrC1ERKS_', 'type': 'FUNC'}
 {'is_defined': True, 'name': '__ZNSt13exception_ptrC2ERKS_', 'type': 'FUNC'}
 {'is_defined': True, 'name': '__ZNSt13exception_ptrD1Ev', 'type': 'FUNC'}
@@ -2543,6 +2545,7 @@
 {'is_defined': True, 'name': '___cxa_guard_abort', 'type': 'I'}
 {'is_defined': True, 'name': '___cxa_guard_acquire', 'type': 'I'}
 {'is_defined': True, 'name': '___cxa_guard_release', 'type': 'I'}
+{'is_defined': True, 'name': '___cxa_init_primary_exception', 'type': 'I'}
 {'is_defined': True, 'name': '___cxa_pure_virtual', 'type': 'I'}
 {'is_defined': True, 'name': '___cxa_rethrow', 'type': 'I'}
 {'is_defined': True, 'name': '___cxa_throw', 'type': 'I'}

libcxx/lib/abi/x86_64-linux-android21.libcxxabi.v1.stable.exceptions.nonew.abilist

@@ -493,6 +493,7 @@
 {'is_defined': True, 'name': '_ZNSt13bad_exceptionD0Ev', 'type': 'FUNC'}
 {'is_defined': True, 'name': '_ZNSt13bad_exceptionD1Ev', 'type': 'FUNC'}
 {'is_defined': True, 'name': '_ZNSt13bad_exceptionD2Ev', 'type': 'FUNC'}
+{'is_defined': True, 'name': '_ZNSt13exception_ptr31__from_native_exception_pointerEPv', 'type': 'FUNC'}
 {'is_defined': True, 'name': '_ZNSt13exception_ptrC1ERKS_', 'type': 'FUNC'}
 {'is_defined': True, 'name': '_ZNSt13exception_ptrC2ERKS_', 'type': 'FUNC'}
 {'is_defined': True, 'name': '_ZNSt13exception_ptrD1Ev', 'type': 'FUNC'}
@@ -2305,6 +2306,7 @@
 {'is_defined': True, 'name': '__cxa_guard_acquire', 'type': 'FUNC'}
 {'is_defined': True, 'name': '__cxa_guard_release', 'type': 'FUNC'}
 {'is_defined': True, 'name': '__cxa_increment_exception_refcount', 'type': 'FUNC'}
+{'is_defined': True, 'name': '__cxa_init_primary_exception', 'type': 'FUNC'}
 {'is_defined': True, 'name': '__cxa_new_handler', 'size': 8, 'type': 'OBJECT'}
 {'is_defined': True, 'name': '__cxa_pure_virtual', 'type': 'FUNC'}
 {'is_defined': True, 'name': '__cxa_rethrow', 'type': 'FUNC'}

libcxx/lib/abi/x86_64-unknown-freebsd.libcxxabi.v1.stable.exceptions.nonew.abilist

@@ -56,6 +56,7 @@
 {'is_defined': False, 'name': '__cxa_guard_acquire', 'type': 'FUNC'}
 {'is_defined': False, 'name': '__cxa_guard_release', 'type': 'FUNC'}
 {'is_defined': False, 'name': '__cxa_increment_exception_refcount', 'type': 'FUNC'}
+{'is_defined': False, 'name': '__cxa_init_primary_exception', 'type': 'FUNC'}
 {'is_defined': False, 'name': '__cxa_pure_virtual', 'type': 'FUNC'}
 {'is_defined': False, 'name': '__cxa_rethrow', 'type': 'FUNC'}
 {'is_defined': False, 'name': '__cxa_rethrow_primary_exception', 'type': 'FUNC'}
@@ -523,6 +524,7 @@
 {'is_defined': True, 'name': '_ZNSt12experimental19bad_optional_accessD0Ev', 'type': 'FUNC'}
 {'is_defined': True, 'name': '_ZNSt12experimental19bad_optional_accessD1Ev', 'type': 'FUNC'}
 {'is_defined': True, 'name': '_ZNSt12experimental19bad_optional_accessD2Ev', 'type': 'FUNC'}
+{'is_defined': True, 'name': '_ZNSt13exception_ptr31__from_native_exception_pointerEPv', 'type': 'FUNC'}
 {'is_defined': True, 'name': '_ZNSt13exception_ptrC1ERKS_', 'type': 'FUNC'}
 {'is_defined': True, 'name': '_ZNSt13exception_ptrC2ERKS_', 'type': 'FUNC'}
 {'is_defined': True, 'name': '_ZNSt13exception_ptrD1Ev', 'type': 'FUNC'}

libcxx/lib/abi/x86_64-unknown-linux-gnu.libcxxabi.v1.stable.exceptions.nonew.abilist

@@ -54,6 +54,7 @@
 {'is_defined': False, 'name': '__cxa_guard_acquire', 'type': 'FUNC'}
 {'is_defined': False, 'name': '__cxa_guard_release', 'type': 'FUNC'}
 {'is_defined': False, 'name': '__cxa_increment_exception_refcount', 'type': 'FUNC'}
+{'is_defined': False, 'name': '__cxa_init_primary_exception', 'type': 'FUNC'}
 {'is_defined': False, 'name': '__cxa_pure_virtual', 'type': 'FUNC'}
 {'is_defined': False, 'name': '__cxa_rethrow', 'type': 'FUNC'}
 {'is_defined': False, 'name': '__cxa_rethrow_primary_exception', 'type': 'FUNC'}
@@ -521,6 +522,7 @@
 {'is_defined': True, 'name': '_ZNSt12experimental19bad_optional_accessD0Ev', 'type': 'FUNC'}
 {'is_defined': True, 'name': '_ZNSt12experimental19bad_optional_accessD1Ev', 'type': 'FUNC'}
 {'is_defined': True, 'name': '_ZNSt12experimental19bad_optional_accessD2Ev', 'type': 'FUNC'}
+{'is_defined': True, 'name': '_ZNSt13exception_ptr31__from_native_exception_pointerEPv', 'type': 'FUNC'}
 {'is_defined': True, 'name': '_ZNSt13exception_ptrC1ERKS_', 'type': 'FUNC'}
 {'is_defined': True, 'name': '_ZNSt13exception_ptrC2ERKS_', 'type': 'FUNC'}
 {'is_defined': True, 'name': '_ZNSt13exception_ptrD1Ev', 'type': 'FUNC'}

libcxx/lib/abi/x86_64-unknown-linux-gnu.libcxxabi.v1.stable.noexceptions.nonew.abilist

@@ -493,6 +493,7 @@
 {'is_defined': True, 'name': '_ZNSt12experimental19bad_optional_accessD0Ev', 'type': 'FUNC'}
 {'is_defined': True, 'name': '_ZNSt12experimental19bad_optional_accessD1Ev', 'type': 'FUNC'}
 {'is_defined': True, 'name': '_ZNSt12experimental19bad_optional_accessD2Ev', 'type': 'FUNC'}
+{'is_defined': True, 'name': '_ZNSt13exception_ptr31__from_native_exception_pointerEPv', 'type': 'FUNC'}
 {'is_defined': True, 'name': '_ZNSt13exception_ptrC1ERKS_', 'type': 'FUNC'}
 {'is_defined': True, 'name': '_ZNSt13exception_ptrC2ERKS_', 'type': 'FUNC'}
 {'is_defined': True, 'name': '_ZNSt13exception_ptrD1Ev', 'type': 'FUNC'}
@@ -1999,4 +2000,4 @@
 {'is_defined': True, 'name': '_ZTv0_n24_NSt3__114basic_iostreamIcNS_11char_traitsIcEEED0Ev', 'type': 'FUNC'}
 {'is_defined': True, 'name': '_ZTv0_n24_NSt3__114basic_iostreamIcNS_11char_traitsIcEEED1Ev', 'type': 'FUNC'}
 {'is_defined': True, 'name': '_ZTv0_n24_NSt3__19strstreamD0Ev', 'type': 'FUNC'}
-{'is_defined': True, 'name': '_ZTv0_n24_NSt3__19strstreamD1Ev', 'type': 'FUNC'}
+{'is_defined': True, 'name': '_ZTv0_n24_NSt3__19strstreamD1Ev', 'type': 'FUNC'}

libcxx/src/support/runtime/exception_pointer_cxxabi.ipp

@@ -28,6 +28,14 @@ exception_ptr& exception_ptr::operator=(const exception_ptr& other) noexcept {
   return *this;
 }
 
+exception_ptr exception_ptr::__from_native_exception_pointer(void* __e) noexcept {
+  exception_ptr ptr;
+  ptr.__ptr_ = __e;
+  __cxa_increment_exception_refcount(ptr.__ptr_);
+
+  return ptr;
+}
+
 nested_exception::nested_exception() noexcept : __ptr_(current_exception()) {}
 
 nested_exception::~nested_exception() noexcept {}

libcxx/src/support/runtime/exception_pointer_glibcxx.ipp

@@ -23,6 +23,7 @@ namespace __exception_ptr {
 struct exception_ptr {
   void* __ptr_;
 
+  explicit exception_ptr(void*) noexcept;
   exception_ptr(const exception_ptr&) noexcept;
   exception_ptr& operator=(const exception_ptr&) noexcept;
   ~exception_ptr() noexcept;
@@ -45,6 +46,13 @@ exception_ptr& exception_ptr::operator=(const exception_ptr& other) noexcept {
   return *this;
 }
 
+exception_ptr exception_ptr::__from_native_exception_pointer(void* __e) noexcept {
+  exception_ptr ptr{};
+  new (reinterpret_cast<void*>(&ptr)) __exception_ptr::exception_ptr(__e);
+
+  return ptr;
+}
+
 nested_exception::nested_exception() noexcept : __ptr_(current_exception()) {}
 
 _LIBCPP_NORETURN void nested_exception::rethrow_nested() const {

libcxx/test/libcxx/transitive_includes/cxx03.csv

@@ -221,7 +221,9 @@ deque typeinfo
 deque version
 exception cstddef
 exception cstdlib
+exception new
 exception type_traits
+exception typeinfo
 exception version
 execution cstddef
 execution version
@@ -536,7 +538,6 @@ mutex typeinfo
 mutex version
 new cstddef
 new cstdlib
-new exception
 new type_traits
 new version
 numbers concepts
@@ -643,7 +644,6 @@ ranges initializer_list
 ranges iosfwd
 ranges iterator
 ranges limits
-ranges new
 ranges optional
 ranges span
 ranges tuple
@@ -875,7 +875,6 @@ typeindex version
 typeinfo cstddef
 typeinfo cstdint
 typeinfo cstdlib
-typeinfo exception
 typeinfo type_traits
 unordered_map algorithm
 unordered_map bit

libcxx/test/libcxx/transitive_includes/cxx11.csv

@@ -222,7 +222,9 @@ deque typeinfo
 deque version
 exception cstddef
 exception cstdlib
+exception new
 exception type_traits
+exception typeinfo
 exception version
 execution cstddef
 execution version
@@ -541,7 +543,6 @@ mutex typeinfo
 mutex version
 new cstddef
 new cstdlib
-new exception
 new type_traits
 new version
 numbers concepts
@@ -648,7 +649,6 @@ ranges initializer_list
 ranges iosfwd
 ranges iterator
 ranges limits
-ranges new
 ranges optional
 ranges span
 ranges tuple
@@ -881,7 +881,6 @@ typeindex version
 typeinfo cstddef
 typeinfo cstdint
 typeinfo cstdlib
-typeinfo exception
 typeinfo type_traits
 unordered_map algorithm
 unordered_map bit

libcxx/test/libcxx/transitive_includes/cxx14.csv

@@ -222,7 +222,9 @@ deque typeinfo
 deque version
 exception cstddef
 exception cstdlib
+exception new
 exception type_traits
+exception typeinfo
 exception version
 execution cstddef
 execution version
@@ -543,7 +545,6 @@ mutex typeinfo
 mutex version
 new cstddef
 new cstdlib
-new exception
 new type_traits
 new version
 numbers concepts
@@ -650,7 +651,6 @@ ranges initializer_list
 ranges iosfwd
 ranges iterator
 ranges limits
-ranges new
 ranges optional
 ranges span
 ranges tuple
@@ -883,7 +883,6 @@ typeindex version
 typeinfo cstddef
 typeinfo cstdint
 typeinfo cstdlib
-typeinfo exception
 typeinfo type_traits
 unordered_map algorithm
 unordered_map bit

libcxx/test/libcxx/transitive_includes/cxx17.csv

@@ -222,7 +222,9 @@ deque typeinfo
 deque version
 exception cstddef
 exception cstdlib
+exception new
 exception type_traits
+exception typeinfo
 exception version
 execution cstddef
 execution version
@@ -543,7 +545,6 @@ mutex typeinfo
 mutex version
 new cstddef
 new cstdlib
-new exception
 new type_traits
 new version
 numbers concepts
@@ -650,7 +651,6 @@ ranges initializer_list
 ranges iosfwd
 ranges iterator
 ranges limits
-ranges new
 ranges optional
 ranges span
 ranges tuple
@@ -883,7 +883,6 @@ typeindex version
 typeinfo cstddef
 typeinfo cstdint
 typeinfo cstdlib
-typeinfo exception
 typeinfo type_traits
 unordered_map algorithm
 unordered_map bit

libcxx/test/libcxx/transitive_includes/cxx20.csv

@@ -228,7 +228,9 @@ deque typeinfo
 deque version
 exception cstddef
 exception cstdlib
+exception new
 exception type_traits
+exception typeinfo
 exception version
 execution cstddef
 execution version
@@ -548,7 +550,6 @@ mutex typeinfo
 mutex version
 new cstddef
 new cstdlib
-new exception
 new type_traits
 new version
 numbers concepts
@@ -655,7 +656,6 @@ ranges initializer_list
 ranges iosfwd
 ranges iterator
 ranges limits
-ranges new
 ranges optional
 ranges span
 ranges tuple
@@ -887,7 +887,6 @@ typeindex version
 typeinfo cstddef
 typeinfo cstdint
 typeinfo cstdlib
-typeinfo exception
 typeinfo type_traits
 unordered_map algorithm
 unordered_map bit

libcxx/test/libcxx/transitive_includes/cxx23.csv

@@ -153,6 +153,8 @@ deque tuple
 deque version
 exception cstddef
 exception cstdlib
+exception new
+exception typeinfo
 exception version
 execution cstddef
 execution version

libcxx/test/libcxx/transitive_includes/cxx26.csv

@@ -153,6 +153,8 @@ deque tuple
 deque version
 exception cstddef
 exception cstdlib
+exception new
+exception typeinfo
 exception version
 execution cstddef
 execution version

libcxxabi/include/cxxabi.h

@@ -36,6 +36,9 @@ class type_info; // forward declaration
 
 // runtime routines use C calling conventions, but are in __cxxabiv1 namespace
 namespace __cxxabiv1 {
+
+struct __cxa_exception;
+
 extern "C"  {
 
 // 2.4.2 Allocating the Exception Object
@@ -43,6 +46,9 @@ extern _LIBCXXABI_FUNC_VIS void *
 __cxa_allocate_exception(size_t thrown_size) throw();
 extern _LIBCXXABI_FUNC_VIS void
 __cxa_free_exception(void *thrown_exception) throw();
+// This function is an LLVM extension, which mirrors the same extension in libsupc++ and libcxxrt
+extern _LIBCXXABI_FUNC_VIS __cxa_exception*
+__cxa_init_primary_exception(void* object, std::type_info* tinfo, void(_LIBCXXABI_DTOR_FUNC* dest)(void*)) throw();
 
 // 2.4.3 Throwing the Exception Object
 extern _LIBCXXABI_FUNC_VIS _LIBCXXABI_NORETURN void

libcxxabi/lib/exceptions.exp

@@ -7,5 +7,6 @@ ___cxa_end_catch
 ___cxa_free_dependent_exception
 ___cxa_free_exception
 ___cxa_get_exception_ptr
+___cxa_init_primary_exception
 ___cxa_rethrow
 ___cxa_throw

libcxxabi/src/cxa_exception.cpp

@@ -206,6 +206,19 @@ void __cxa_free_exception(void *thrown_object) throw() {
     __aligned_free_with_fallback((void *)raw_buffer);
 }
 
+__cxa_exception* __cxa_init_primary_exception(void* object, std::type_info* tinfo,
+                                              void(_LIBCXXABI_DTOR_FUNC* dest)(void*)) throw() {
+  __cxa_exception* exception_header = cxa_exception_from_thrown_object(object);
+  exception_header->referenceCount = 0;
+  exception_header->unexpectedHandler = std::get_unexpected();
+  exception_header->terminateHandler = std::get_terminate();
+  exception_header->exceptionType = tinfo;
+  exception_header->exceptionDestructor = dest;
+  setOurExceptionClass(&exception_header->unwindHeader);
+  exception_header->unwindHeader.exception_cleanup = exception_cleanup_func;
+
+  return exception_header;
+}
 
 //  This function shall allocate a __cxa_dependent_exception and
 //  return a pointer to it. (Really to the object, not past its' end).
@@ -260,22 +273,15 @@ __cxa_throw(void *thrown_object, std::type_info *tinfo, void *(_LIBCXXABI_DTOR_F
 #else
 __cxa_throw(void *thrown_object, std::type_info *tinfo, void (_LIBCXXABI_DTOR_FUNC *dest)(void *)) {
 #endif
-    __cxa_eh_globals *globals = __cxa_get_globals();
-    __cxa_exception* exception_header = cxa_exception_from_thrown_object(thrown_object);
+  __cxa_eh_globals* globals = __cxa_get_globals();
+  globals->uncaughtExceptions += 1; // Not atomically, since globals are thread-local
 
-    exception_header->unexpectedHandler = std::get_unexpected();
-    exception_header->terminateHandler  = std::get_terminate();
-    exception_header->exceptionType = tinfo;
-    exception_header->exceptionDestructor = dest;
-    setOurExceptionClass(&exception_header->unwindHeader);
-    exception_header->referenceCount = 1;  // This is a newly allocated exception, no need for thread safety.
-    globals->uncaughtExceptions += 1;   // Not atomically, since globals are thread-local
-
-    exception_header->unwindHeader.exception_cleanup = exception_cleanup_func;
+  __cxa_exception* exception_header = __cxa_init_primary_exception(thrown_object, tinfo, dest);
+  exception_header->referenceCount = 1; // This is a newly allocated exception, no need for thread safety.
 
 #if __has_feature(address_sanitizer)
-    // Inform the ASan runtime that now might be a good time to clean stuff up.
-    __asan_handle_no_return();
+  // Inform the ASan runtime that now might be a good time to clean stuff up.
+  __asan_handle_no_return();
 #endif
 
 #ifdef __USING_SJLJ_EXCEPTIONS__