diff --git a/lib/libcxx/src/support/solaris/README b/lib/libcxx/src/support/solaris/README
deleted file mode 100644
index 89c887a3b..000000000
--- a/lib/libcxx/src/support/solaris/README
+++ /dev/null
@@ -1,4 +0,0 @@
-This directory contains a partial implementation of the xlocale APIs for
-Solaris.  Some portions are lifted from FreeBSD libc, and so are covered by a
-2-clause BSD license instead of the MIT/UUIC license that the rest of libc++ is
-distributed under.
diff --git a/lib/libcxxabi/src/demangle/.clang-format b/lib/libcxxabi/src/demangle/.clang-format
deleted file mode 100644
index 5bead5f39..000000000
--- a/lib/libcxxabi/src/demangle/.clang-format
+++ /dev/null
@@ -1,2 +0,0 @@
-BasedOnStyle: LLVM
-
diff --git a/lib/libcxxabi/src/demangle/README.txt b/lib/libcxxabi/src/demangle/README.txt
deleted file mode 100644
index 514ff6dd1..000000000
--- a/lib/libcxxabi/src/demangle/README.txt
+++ /dev/null
@@ -1,52 +0,0 @@
-Itanium Name Demangler Library
-==============================
-
-Introduction
-------------
-
-This directory contains the generic itanium name demangler library. The main
-purpose of the library is to demangle C++ symbols, i.e. convert the string
-"_Z1fv" into "f()". You can also use the CRTP base ManglingParser to perform
-some simple analysis on the mangled name, or (in LLVM) use the opaque
-ItaniumPartialDemangler to query the demangled AST.
-
-Why are there multiple copies of the this library in the source tree?
----------------------------------------------------------------------
-
-This directory is mirrored between libcxxabi/demangle and
-llvm/include/llvm/Demangle. The simple reason for this is that both projects
-need to demangle symbols, but neither can depend on each other. libcxxabi needs
-the demangler to implement __cxa_demangle, which is part of the itanium ABI
-spec. LLVM needs a copy for a bunch of places, but doesn't want to use the
-system's __cxa_demangle because it a) might not be available (i.e., on Windows),
-and b) probably isn't that up-to-date on the latest language features.
-
-The copy of the demangler in LLVM has some extra stuff that aren't needed in
-libcxxabi (ie, the MSVC demangler, ItaniumPartialDemangler), which depend on the
-shared generic components. Despite these differences, we want to keep the "core"
-generic demangling library identical between both copies to simplify development
-and testing.
-
-If you're working on the generic library, then do the work first in libcxxabi,
-then run the cp-to-llvm.sh script in src/demangle. This script takes as an
-argument the path to llvm, and re-copies the changes you made to libcxxabi over.
-Note that this script just blindly overwrites all changes to the generic library
-in llvm, so be careful.
-
-Because the core demangler needs to work in libcxxabi, everything needs to be
-declared in an anonymous namespace (see DEMANGLE_NAMESPACE_BEGIN), and you can't
-introduce any code that depends on the libcxx dylib.
-
-Hopefully, when LLVM becomes a monorepo, we can de-duplicate this code, and have
-both LLVM and libcxxabi depend on a shared demangler library.
-
-Testing
--------
-
-The tests are split up between libcxxabi/test/{unit,}test_demangle.cpp, and
-llvm/unittest/Demangle. The llvm directory should only get tests for stuff not
-included in the core library. In the future though, we should probably move all
-the tests to LLVM.
-
-It is also a really good idea to run libFuzzer after non-trivial changes, see
-libcxxabi/fuzz/cxa_demangle_fuzzer.cpp and https://llvm.org/docs/LibFuzzer.html.
diff --git a/lib/libcxxabi/src/demangle/cp-to-llvm.sh b/lib/libcxxabi/src/demangle/cp-to-llvm.sh
deleted file mode 100755
index 808abbcd9..000000000
--- a/lib/libcxxabi/src/demangle/cp-to-llvm.sh
+++ /dev/null
@@ -1,27 +0,0 @@
-#!/bin/bash
-
-# Copies the 'demangle' library, excluding 'DemangleConfig.h', to llvm. If no
-# llvm directory is specified, then assume a monorepo layout.
-
-set -e
-
-FILES="ItaniumDemangle.h StringView.h Utility.h README.txt"
-LLVM_DEMANGLE_DIR=$1
-
-if [[ -z "$LLVM_DEMANGLE_DIR" ]]; then
-    LLVM_DEMANGLE_DIR="../../../llvm/include/llvm/Demangle"
-fi
-
-if [[ ! -d "$LLVM_DEMANGLE_DIR" ]]; then
-    echo "No such directory: $LLVM_DEMANGLE_DIR" >&2
-    exit 1
-fi
-
-read -p "This will overwrite the copies of $FILES in $LLVM_DEMANGLE_DIR; are you sure? [y/N]" -n 1 -r ANSWER
-echo
-
-if [[ $ANSWER =~ ^[Yy]$ ]]; then
-    for I in $FILES ; do
-        cp $I $LLVM_DEMANGLE_DIR/$I
-    done
-fi
diff --git a/src/install_files.h b/src/install_files.h
index 8e7431145..90dd085aa 100644
--- a/src/install_files.h
+++ b/src/install_files.h
@@ -1853,18 +1853,20 @@ static const char *ZIG_LIBCXXABI_FILES[] = {
 "src/cxa_noexception.cpp",
 "src/cxa_personality.cpp",
 "src/cxa_thread_atexit.cpp",
-"src/cxa_unexpected.cpp",
 "src/cxa_vector.cpp",
 "src/cxa_virtual.cpp",
 "src/fallback_malloc.cpp",
 "src/private_typeinfo.cpp",
 "src/stdlib_exception.cpp",
+"src/stdlib_new_delete.cpp",
 "src/stdlib_stdexcept.cpp",
 "src/stdlib_typeinfo.cpp",
 };
 static const char *ZIG_LIBCXX_FILES[] = {
 "src/algorithm.cpp",
 "src/any.cpp",
+"src/atomic.cpp",
+"src/barrier.cpp",
 "src/bind.cpp",
 "src/charconv.cpp",
 "src/chrono.cpp",
@@ -1874,6 +1876,7 @@ static const char *ZIG_LIBCXX_FILES[] = {
 "src/exception.cpp",
 "src/experimental/memory_resource.cpp",
 "src/filesystem/directory_iterator.cpp",
+"src/filesystem/int128_builtins.cpp",
 "src/filesystem/operations.cpp",
 "src/functional.cpp",
 "src/future.cpp",
@@ -1887,6 +1890,7 @@ static const char *ZIG_LIBCXX_FILES[] = {
 "src/new.cpp",
 "src/optional.cpp",
 "src/random.cpp",
+"src/random_shuffle.cpp",
 "src/regex.cpp",
 "src/shared_mutex.cpp",
 "src/stdexcept.cpp",