diff --git a/clang/cmake/caches/Fuchsia-stage2.cmake b/clang/cmake/caches/Fuchsia-stage2.cmake
--- a/clang/cmake/caches/Fuchsia-stage2.cmake
+++ b/clang/cmake/caches/Fuchsia-stage2.cmake
@@ -110,6 +110,7 @@
     set(RUNTIMES_${target}_CMAKE_SHARED_LINKER_FLAGS "-fuse-ld=lld" CACHE STRING "")
     set(RUNTIMES_${target}_CMAKE_MODULE_LINKER_FLAGS "-fuse-ld=lld" CACHE STRING "")
     set(RUNTIMES_${target}_CMAKE_EXE_LINKER_FLAGS "-fuse-ld=lld" CACHE STRING "")
+    set(RUNTIMES_${target}_COMPILER_RT_CXX_LIBRARY "libcxx" CACHE STRING "")
     set(RUNTIMES_${target}_COMPILER_RT_USE_BUILTINS_LIBRARY ON CACHE BOOL "")
     set(RUNTIMES_${target}_COMPILER_RT_USE_LLVM_UNWINDER ON CACHE BOOL "")
     set(RUNTIMES_${target}_COMPILER_RT_CAN_EXECUTE_TESTS ON CACHE BOOL "")
@@ -178,6 +179,7 @@
     set(RUNTIMES_${target}_CMAKE_MODULE_LINKER_FLAGS ${FUCHSIA_${target}_LINKER_FLAGS} CACHE STRING "")
     set(RUNTIMES_${target}_CMAKE_EXE_LINKER_FLAGS ${FUCHSIA_${target}_LINKER_FLAGS} CACHE STRING "")
     set(RUNTIMES_${target}_CMAKE_SYSROOT ${FUCHSIA_${target}_SYSROOT} CACHE PATH "")
+    set(RUNTIMES_${target}_COMPILER_RT_CXX_LIBRARY "libcxx" CACHE STRING "")
     set(RUNTIMES_${target}_COMPILER_RT_USE_BUILTINS_LIBRARY ON CACHE BOOL "")
     set(RUNTIMES_${target}_COMPILER_RT_USE_LLVM_UNWINDER ON CACHE BOOL "")
     set(RUNTIMES_${target}_LIBUNWIND_USE_COMPILER_RT ON CACHE BOOL "")
diff --git a/compiler-rt/CMakeLists.txt b/compiler-rt/CMakeLists.txt
--- a/compiler-rt/CMakeLists.txt
+++ b/compiler-rt/CMakeLists.txt
@@ -199,6 +199,7 @@
 
 # This is either directly the C++ ABI library or the full C++ library
 # which pulls in the ABI transitively.
+# TODO: Mark this as internal flag, most users should use COMPILER_RT_CXX_LIBRARY.
 set(SANITIZER_CXX_ABI "default" CACHE STRING
     "Specify C++ ABI library to use.")
 set(CXXABIS none default libstdc++ libc++ libcxxabi)
@@ -206,6 +207,7 @@
 handle_default_cxx_lib(SANITIZER_CXX_ABI)
 
 # This needs to be a full C++ library for linking gtest and unit tests.
+# TODO: Mark this as internal flag, most users should use COMPILER_RT_CXX_LIBRARY.
 set(SANITIZER_TEST_CXX "default" CACHE STRING
     "Specify C++ library to use for tests.")
 set(CXXLIBS none default libstdc++ libc++)
@@ -246,6 +248,15 @@
   "Use static libc++ for tests." ${DEFAULT_SANITIZER_USE_STATIC_TEST_CXX})
 pythonize_bool(SANITIZER_USE_STATIC_TEST_CXX)
 
+set(COMPILER_RT_SUPPORTED_CXX_LIBRARIES none default libcxx)
+set(COMPILER_RT_CXX_LIBRARY "default" CACHE STRING "Specify C++ library to use. Supported values are ${COMPILER_RT_SUPPORTED_CXX_LIBRARIES}.")
+if (NOT "${COMPILER_RT_CXX_LIBRARY}" IN_LIST COMPILER_RT_SUPPORTED_CXX_LIBRARIES)
+  message(FATAL_ERROR "Unsupported C++ library: '${COMPILER_RT_CXX_LIBRARY}'. Supported values are ${COMPILER_RT_SUPPORTED_CXX_LIBRARIES}.")
+endif()
+cmake_dependent_option(COMPILER_RT_STATIC_CXX_LIBRARY
+  "Statically link the C++ library." OFF
+  "COMPILER_RT_CXX_LIBRARY" OFF)
+
 set(DEFAULT_COMPILER_RT_USE_BUILTINS_LIBRARY OFF)
 if (FUCHSIA)
   set(DEFAULT_COMPILER_RT_USE_BUILTINS_LIBRARY ON)
@@ -519,6 +530,26 @@
   list(APPEND SANITIZER_CXX_ABI_LIBRARIES "$<$<TARGET_EXISTS:${unwinder_target}>:$<TARGET_LINKER_FILE:${unwinder_target}>>")
 endif()
 
+if (COMPILER_RT_CXX_LIBRARY STREQUAL "libcxx")
+  # We are using the in-tree libc++ so avoid including the default one.
+  append_list_if(COMPILER_RT_HAS_NOSTDINCXX_FLAG -nostdinc++ COMPILER_RT_COMMON_CFLAGS)
+  append_list_if(COMPILER_RT_HAS_NOSTDLIBXX_FLAG -nostdlib++ COMPILER_RT_COMMON_LINK_FLAGS)
+  # Use the in-tree libc++ through explicit include and library paths.
+  if (COMPILER_RT_STATIC_CXX_LIBRARY)
+    set(cxx_target cxx_static)
+  else()
+    set(cxx_target cxx_shared)
+  endif()
+  list(APPEND COMPILER_RT_CXX_CFLAGS "$<$<TARGET_EXISTS:cxx-headers>:-isystem$<JOIN:$<TARGET_PROPERTY:cxx-headers,INTERFACE_INCLUDE_DIRECTORIES>,$<SEMICOLON>-isystem>>")
+  list(APPEND COMPILER_RT_CXX_LINK_LIBS "$<$<TARGET_EXISTS:${cxx_target}>:$<TARGET_LINKER_FILE:${cxx_target}>>")
+elseif (COMPILER_RT_CXX_LIBRARY STREQUAL "none")
+  # We aren't using any C++ standard library so avoid including the default one.
+  append_list_if(COMPILER_RT_HAS_NOSTDINCXX_FLAG -nostdinc++ COMPILER_RT_COMMON_CFLAGS)
+  append_list_if(COMPILER_RT_HAS_NOSTDLIBXX_FLAG -nostdlib++ COMPILER_RT_COMMON_LINK_FLAGS)
+else()
+  # Nothing to be done for `default`.
+endif()
+
 macro(append_libcxx_libs var)
   if (${var}_INTREE)
     if (SANITIZER_USE_STATIC_LLVM_UNWINDER AND (TARGET unwind_static OR HAVE_LIBUNWIND))
diff --git a/compiler-rt/lib/fuzzer/CMakeLists.txt b/compiler-rt/lib/fuzzer/CMakeLists.txt
--- a/compiler-rt/lib/fuzzer/CMakeLists.txt
+++ b/compiler-rt/lib/fuzzer/CMakeLists.txt
@@ -66,6 +66,7 @@
   append_list_if(COMPILER_RT_HAS_NOSTDINCXX_FLAG -nostdinc++ LIBFUZZER_CFLAGS)
 elseif(TARGET cxx-headers OR HAVE_LIBCXX)
   # libFuzzer uses C++ standard library headers.
+  list(APPEND LIBFUZZER_CFLAGS ${COMPILER_RT_CXX_CFLAGS})
   set(LIBFUZZER_DEPS cxx-headers)
 endif()
 
diff --git a/compiler-rt/lib/orc/CMakeLists.txt b/compiler-rt/lib/orc/CMakeLists.txt
--- a/compiler-rt/lib/orc/CMakeLists.txt
+++ b/compiler-rt/lib/orc/CMakeLists.txt
@@ -49,7 +49,11 @@
 include_directories(..)
 include_directories(../../include)
 
-set(ORC_CFLAGS ${COMPILER_RT_COMMON_CFLAGS})
+set(ORC_CFLAGS
+  ${COMPILER_RT_COMMON_CFLAGS}
+  ${COMPILER_RT_CXX_CFLAGS})
+set(ORC_LINK_FLAGS ${COMPILER_RT_COMMON_LINK_FLAGS})
+set(ORC_LINK_LIBS ${COMPILER_RT_CXX_LINK_LIBS})
 
 # Allow the ORC runtime to reference LLVM headers.
 foreach (DIR ${LLVM_INCLUDE_DIR} ${LLVM_MAIN_INCLUDE_DIR})
@@ -83,7 +87,7 @@
     ARCHS ${ORC_SUPPORTED_ARCH}
     OBJECT_LIBS RTOrc
     CFLAGS ${ORC_CFLAGS}
-    LINK_FLAGS ${SANITIZER_COMMON_LINK_FLAGS} ${WEAK_SYMBOL_LINK_FLAGS}
+    LINK_FLAGS ${ORC_LINK_FLAGS} ${WEAK_SYMBOL_LINK_FLAGS}
     LINK_LIBS ${ORC_LINK_LIBS}
     PARENT_TARGET orc)
 else() # not Apple
@@ -109,6 +113,8 @@
      STATIC
      ARCHS ${arch}
      CFLAGS ${ORC_CFLAGS}
+     LINK_FLAGS ${ORC_LINK_FLAGS}
+     LINK_LIBS ${ORC_LINK_LIBS}
      OBJECT_LIBS ${ORC_COMMON_RUNTIME_OBJECT_LIBS} RTOrc
      PARENT_TARGET orc)
   endforeach()
diff --git a/compiler-rt/lib/xray/CMakeLists.txt b/compiler-rt/lib/xray/CMakeLists.txt
--- a/compiler-rt/lib/xray/CMakeLists.txt
+++ b/compiler-rt/lib/xray/CMakeLists.txt
@@ -138,7 +138,9 @@
 include_directories(..)
 include_directories(../../include)
 
-set(XRAY_CFLAGS ${COMPILER_RT_COMMON_CFLAGS})
+set(XRAY_CFLAGS
+  ${COMPILER_RT_COMMON_CFLAGS}
+  ${COMPILER_RT_CXX_CFLAGS})
 set(XRAY_COMMON_DEFINITIONS XRAY_HAS_EXCEPTIONS=1)
 
 # Too many existing bugs, needs cleanup.
@@ -147,6 +149,9 @@
 # We don't need RTTI in XRay, so turn that off.
 append_rtti_flag(OFF XRAY_CFLAGS)
 
+set(XRAY_LINK_FLAGS ${COMPILER_RT_COMMON_LINK_FLAGS})
+set(XRAY_LINK_LIBS ${COMPILER_RT_CXX_LINK_LIBS})
+
 append_list_if(
   COMPILER_RT_HAS_XRAY_COMPILER_FLAG XRAY_SUPPORTED=1 XRAY_COMMON_DEFINITIONS)
 append_list_if(
@@ -164,7 +169,6 @@
 endif()
 
 if (APPLE)
-  set(XRAY_LINK_LIBS ${SANITIZER_COMMON_LINK_LIBS})
   add_asm_sources(XRAY_ASM_SOURCES xray_trampoline_x86_64.S)
 
   add_weak_symbols("sanitizer_common" WEAK_SYMBOL_LINK_FLAGS)
@@ -213,7 +217,7 @@
                 RTSanitizerCommonLibc
     CFLAGS ${XRAY_CFLAGS}
     DEFS ${XRAY_COMMON_DEFINITIONS}
-    LINK_FLAGS ${SANITIZER_COMMON_LINK_FLAGS} ${WEAK_SYMBOL_LINK_FLAGS}
+    LINK_FLAGS ${XRAY_LINK_FLAGS} ${WEAK_SYMBOL_LINK_FLAGS}
     LINK_LIBS ${XRAY_LINK_LIBS}
     PARENT_TARGET xray)
   add_compiler_rt_runtime(clang_rt.xray-fdr
@@ -223,7 +227,7 @@
     OBJECT_LIBS RTXrayFDR
     CFLAGS ${XRAY_CFLAGS}
     DEFS ${XRAY_COMMON_DEFINITIONS}
-    LINK_FLAGS ${SANITIZER_COMMON_LINK_FLAGS} ${WEAK_SYMBOL_LINK_FLAGS}
+    LINK_FLAGS ${XRAY_LINK_FLAGS} ${WEAK_SYMBOL_LINK_FLAGS}
     LINK_LIBS ${XRAY_LINK_LIBS}
     PARENT_TARGET xray)
   add_compiler_rt_runtime(clang_rt.xray-basic
@@ -233,7 +237,7 @@
     OBJECT_LIBS RTXrayBASIC
     CFLAGS ${XRAY_CFLAGS}
     DEFS ${XRAY_COMMON_DEFINITIONS}
-    LINK_FLAGS ${SANITIZER_COMMON_LINK_FLAGS} ${WEAK_SYMBOL_LINK_FLAGS}
+    LINK_FLAGS ${XRAY_LINK_FLAGS} ${WEAK_SYMBOL_LINK_FLAGS}
     LINK_LIBS ${XRAY_LINK_LIBS}
     PARENT_TARGET xray)
   add_compiler_rt_runtime(clang_rt.xray-profiling
@@ -243,7 +247,7 @@
     OBJECT_LIBS RTXrayPROFILING
     CFLAGS ${XRAY_CFLAGS}
     DEFS ${XRAY_COMMON_DEFINITIONS}
-    LINK_FLAGS ${SANITIZER_COMMON_LINK_FLAGS} ${WEAK_SYMBOL_LINK_FLAGS}
+    LINK_FLAGS ${XRAY_LINK_FLAGS} ${WEAK_SYMBOL_LINK_FLAGS}
     LINK_LIBS ${XRAY_LINK_LIBS}
     PARENT_TARGET xray)
 else() # not Apple
@@ -285,6 +289,8 @@
      STATIC
      ARCHS ${arch}
      CFLAGS ${XRAY_CFLAGS}
+     LINK_FLAGS ${XRAY_LINK_FLAGS}
+     LINK_LIBS ${XRAY_LINK_LIBS}
      DEFS ${XRAY_COMMON_DEFINITIONS}
      OBJECT_LIBS ${XRAY_COMMON_RUNTIME_OBJECT_LIBS} RTXray
      PARENT_TARGET xray)
@@ -293,6 +299,8 @@
       STATIC
       ARCHS ${arch}
       CFLAGS ${XRAY_CFLAGS}
+      LINK_FLAGS ${XRAY_LINK_FLAGS}
+      LINK_LIBS ${XRAY_LINK_LIBS}
       DEFS ${XRAY_COMMON_DEFINITIONS}
       OBJECT_LIBS RTXrayFDR
       PARENT_TARGET xray)
@@ -301,6 +309,8 @@
       STATIC
       ARCHS ${arch}
       CFLAGS ${XRAY_CFLAGS}
+      LINK_FLAGS ${XRAY_LINK_FLAGS}
+      LINK_LIBS ${XRAY_LINK_LIBS}
       DEFS ${XRAY_COMMON_DEFINITIONS}
       OBJECT_LIBS RTXrayBASIC
       PARENT_TARGET xray)
@@ -309,6 +319,8 @@
      STATIC
      ARCHS ${arch}
      CFLAGS ${XRAY_CFLAGS}
+     LINK_FLAGS ${XRAY_LINK_FLAGS}
+     LINK_LIBS ${XRAY_LINK_LIBS}
      DEFS ${XRAY_COMMON_DEFINITIONS}
      OBJECT_LIBS RTXrayPROFILING
      PARENT_TARGET xray)