diff --git a/libcxxabi/CMakeLists.txt b/libcxxabi/CMakeLists.txt
--- a/libcxxabi/CMakeLists.txt
+++ b/libcxxabi/CMakeLists.txt
@@ -143,7 +143,24 @@
 option(LIBCXXABI_HERMETIC_STATIC_LIBRARY
   "Do not export any symbols from the static library." ${LIBCXXABI_HERMETIC_STATIC_LIBRARY_DEFAULT})
 
-set(LIBCXXABI_TEST_CONFIG "${CMAKE_CURRENT_SOURCE_DIR}/test/lit.site.cfg.in" CACHE STRING
+if (CMAKE_CXX_COMPILER_ID STREQUAL "GNU")
+  set(LIBCXXABI_DEFAULT_TEST_CONFIG "llvm-libc++abi-shared-gcc.cfg.in")
+elseif(MINGW)
+  set(LIBCXXABI_DEFAULT_TEST_CONFIG "llvm-libc++abi-mingw.cfg.in")
+elseif(WIN32) # clang-cl
+  if (LIBCXXABI_ENABLE_SHARED)
+    set(LIBCXXABI_DEFAULT_TEST_CONFIG "llvm-libc++abi-shared-clangcl.cfg.in")
+  else()
+    set(LIBCXXABI_DEFAULT_TEST_CONFIG "llvm-libc++abi-static-clangcl.cfg.in")
+  endif()
+else()
+  if (LIBCXXABI_ENABLE_SHARED)
+    set(LIBCXXABI_DEFAULT_TEST_CONFIG "llvm-libc++abi-shared.cfg.in")
+  else()
+    set(LIBCXXABI_DEFAULT_TEST_CONFIG "llvm-libc++abi-static.cfg.in")
+  endif()
+endif()
+set(LIBCXXABI_TEST_CONFIG "${LIBCXXABI_DEFAULT_TEST_CONFIG}" CACHE STRING
   "The path to the Lit testing configuration to use when running the tests.
    If a relative path is provided, it is assumed to be relative to '<monorepo>/libcxxabi/test/configs'.")
 if (NOT IS_ABSOLUTE "${LIBCXXABI_TEST_CONFIG}")
diff --git a/libcxxabi/test/configs/apple-libc++abi-backdeployment.cfg.in b/libcxxabi/test/configs/apple-libc++abi-backdeployment.cfg.in
--- a/libcxxabi/test/configs/apple-libc++abi-backdeployment.cfg.in
+++ b/libcxxabi/test/configs/apple-libc++abi-backdeployment.cfg.in
@@ -45,7 +45,7 @@
     '-isysroot {}'.format('@CMAKE_OSX_SYSROOT@') if '@CMAKE_OSX_SYSROOT@' else ''
 ))
 config.substitutions.append(('%{compile_flags}',
-    '-nostdinc++ -I %{include} -I %{cxx-include} -I %{cxx-target-include} -DLIBCXXABI_NO_TIMER -D_LIBCPP_ENABLE_CXX17_REMOVED_UNEXPECTED_FUNCTIONS ' +
+    '-nostdinc++ -I %{include} -I %{cxx-include} -I %{cxx-target-include} -D_LIBCPP_ENABLE_CXX17_REMOVED_UNEXPECTED_FUNCTIONS ' +
     '-I %{libcxx}/test/support -I %{libcxx}/src'
 ))
 config.substitutions.append(('%{link_flags}',
diff --git a/libcxxabi/test/configs/apple-libc++abi-shared.cfg.in b/libcxxabi/test/configs/apple-libc++abi-shared.cfg.in
--- a/libcxxabi/test/configs/apple-libc++abi-shared.cfg.in
+++ b/libcxxabi/test/configs/apple-libc++abi-shared.cfg.in
@@ -6,7 +6,7 @@
     '-isysroot {}'.format('@CMAKE_OSX_SYSROOT@') if '@CMAKE_OSX_SYSROOT@' else ''
 ))
 config.substitutions.append(('%{compile_flags}',
-    '-nostdinc++ -I %{include} -I %{cxx-include} -I %{cxx-target-include} -DLIBCXXABI_NO_TIMER -D_LIBCPP_ENABLE_CXX17_REMOVED_UNEXPECTED_FUNCTIONS ' +
+    '-nostdinc++ -I %{include} -I %{cxx-include} -I %{cxx-target-include} -D_LIBCPP_ENABLE_CXX17_REMOVED_UNEXPECTED_FUNCTIONS ' +
     '-I %{libcxx}/test/support -I %{libcxx}/src'
 ))
 config.substitutions.append(('%{link_flags}',
diff --git a/libcxxabi/test/configs/ibm-libc++abi-shared.cfg.in b/libcxxabi/test/configs/ibm-libc++abi-shared.cfg.in
--- a/libcxxabi/test/configs/ibm-libc++abi-shared.cfg.in
+++ b/libcxxabi/test/configs/ibm-libc++abi-shared.cfg.in
@@ -5,7 +5,7 @@
 config.substitutions.append(('%{flags}',''))
 config.substitutions.append(('%{compile_flags}',
     '-nostdinc++ -I %{include} -I %{cxx-include} -I %{cxx-target-include} ' +
-    '-D__LIBC_NO_CPP_MATH_OVERLOADS__ -DLIBCXXABI_NO_TIMER ' +
+    '-D__LIBC_NO_CPP_MATH_OVERLOADS__ ' +
     '-D_LIBCPP_ENABLE_CXX17_REMOVED_UNEXPECTED_FUNCTIONS ' +
     '-I %{libcxx}/test/support -I %{libcxx}/src'
 ))
diff --git a/libcxxabi/test/configs/llvm-libc++abi-merged.cfg.in b/libcxxabi/test/configs/llvm-libc++abi-merged.cfg.in
--- a/libcxxabi/test/configs/llvm-libc++abi-merged.cfg.in
+++ b/libcxxabi/test/configs/llvm-libc++abi-merged.cfg.in
@@ -6,7 +6,7 @@
     '-isysroot {}'.format('@CMAKE_OSX_SYSROOT@') if '@CMAKE_OSX_SYSROOT@' else ''
 ))
 config.substitutions.append(('%{compile_flags}',
-    '-nostdinc++ -I %{include} -I %{cxx-include} -I %{cxx-target-include} -DLIBCXXABI_NO_TIMER -D_LIBCPP_ENABLE_CXX17_REMOVED_UNEXPECTED_FUNCTIONS ' +
+    '-nostdinc++ -I %{include} -I %{cxx-include} -I %{cxx-target-include} -D_LIBCPP_ENABLE_CXX17_REMOVED_UNEXPECTED_FUNCTIONS ' +
     '-I %{libcxx}/test/support -I %{libcxx}/src'
 ))
 config.substitutions.append(('%{link_flags}',
diff --git a/libcxxabi/test/configs/apple-libc++abi-shared.cfg.in b/libcxxabi/test/configs/llvm-libc++abi-mingw.cfg.in
copy from libcxxabi/test/configs/apple-libc++abi-shared.cfg.in
copy to libcxxabi/test/configs/llvm-libc++abi-mingw.cfg.in
--- a/libcxxabi/test/configs/apple-libc++abi-shared.cfg.in
+++ b/libcxxabi/test/configs/llvm-libc++abi-mingw.cfg.in
@@ -1,24 +1,22 @@
-# Testing configuration for Apple's system libc++abi.
+# This testing configuration handles running the test suite against LLVM's libc++abi
+# using either a DLL or a static library, with MinGW/Clang on Windows.
 
 lit_config.load_config(config, '@CMAKE_CURRENT_BINARY_DIR@/cmake-bridge.cfg')
 
-config.substitutions.append(('%{flags}',
-    '-isysroot {}'.format('@CMAKE_OSX_SYSROOT@') if '@CMAKE_OSX_SYSROOT@' else ''
-))
+config.substitutions.append(('%{flags}', ''))
 config.substitutions.append(('%{compile_flags}',
-    '-nostdinc++ -I %{include} -I %{cxx-include} -I %{cxx-target-include} -DLIBCXXABI_NO_TIMER -D_LIBCPP_ENABLE_CXX17_REMOVED_UNEXPECTED_FUNCTIONS ' +
-    '-I %{libcxx}/test/support -I %{libcxx}/src'
+    '-nostdinc++ -I %{include} -I %{cxx-include} -I %{cxx-target-include} -I %{libcxx}/test/support -I %{libcxx}/src -D_LIBCPP_ENABLE_CXX17_REMOVED_UNEXPECTED_FUNCTIONS'
 ))
 config.substitutions.append(('%{link_flags}',
     '-nostdlib++ -L %{lib} -lc++ -lc++abi'
 ))
 config.substitutions.append(('%{exec}',
-    '%{executor} --execdir %T --env DYLD_LIBRARY_PATH=%{lib} -- '
+    '%{executor} --execdir %T --env PATH=%{lib} -- '
 ))
 
 import os, site
 site.addsitedir(os.path.join('@LIBCXXABI_LIBCXX_PATH@', 'utils'))
-import libcxx.test.params, libcxx.test.newconfig, libcxx.test.newconfig
+import libcxx.test.params, libcxx.test.newconfig
 libcxx.test.newconfig.configure(
     libcxx.test.params.DEFAULT_PARAMETERS,
     libcxx.test.features.DEFAULT_FEATURES,
diff --git a/libcxxabi/test/configs/llvm-libc++abi-shared-clangcl.cfg.in b/libcxxabi/test/configs/llvm-libc++abi-shared-clangcl.cfg.in
new file mode 100644
--- /dev/null
+++ b/libcxxabi/test/configs/llvm-libc++abi-shared-clangcl.cfg.in
@@ -0,0 +1,25 @@
+# This testing configuration handles running the test suite against LLVM's libc++abi
+# using a DLL, with Clang-cl on Windows.
+
+lit_config.load_config(config, '@CMAKE_CURRENT_BINARY_DIR@/cmake-bridge.cfg')
+
+config.substitutions.append(('%{flags}', '--driver-mode=g++'))
+config.substitutions.append(('%{compile_flags}',
+    '-nostdinc++ -I %{include} -I %{cxx-include} -I %{cxx-target-include} -I %{libcxx}/test/support -I %{libcxx}/src -D_LIBCPP_ENABLE_CXX17_REMOVED_UNEXPECTED_FUNCTIONS -D_CRT_SECURE_NO_WARNINGS -D_CRT_NONSTDC_NO_WARNINGS -D_CRT_STDIO_ISO_WIDE_SPECIFIERS -DNOMINMAX'
+))
+config.substitutions.append(('%{link_flags}',
+    '-nostdlib -L %{lib} -lc++ -lc++abi -lmsvcrt -lmsvcprt -loldnames'
+))
+config.substitutions.append(('%{exec}',
+    '%{executor} --execdir %T --env PATH=%{lib} -- '
+))
+
+import os, site
+site.addsitedir(os.path.join('@LIBCXXABI_LIBCXX_PATH@', 'utils'))
+import libcxx.test.params, libcxx.test.newconfig
+libcxx.test.newconfig.configure(
+    libcxx.test.params.DEFAULT_PARAMETERS,
+    libcxx.test.features.DEFAULT_FEATURES,
+    config,
+    lit_config
+)
diff --git a/libcxxabi/test/configs/llvm-libc++abi-merged.cfg.in b/libcxxabi/test/configs/llvm-libc++abi-shared-gcc.cfg.in
copy from libcxxabi/test/configs/llvm-libc++abi-merged.cfg.in
copy to libcxxabi/test/configs/llvm-libc++abi-shared-gcc.cfg.in
--- a/libcxxabi/test/configs/llvm-libc++abi-merged.cfg.in
+++ b/libcxxabi/test/configs/llvm-libc++abi-shared-gcc.cfg.in
@@ -1,16 +1,15 @@
-# Testing configuration for libc++abi when merged into a libc++ shared library.
+# This testing configuration handles running the test suite against LLVM's libc++abi
+# using a shared library, with GCC. This is done differently from Clang because
+# GCC does not support the -nostdlib++ command-line flag.
 
 lit_config.load_config(config, '@CMAKE_CURRENT_BINARY_DIR@/cmake-bridge.cfg')
 
-config.substitutions.append(('%{flags}',
-    '-isysroot {}'.format('@CMAKE_OSX_SYSROOT@') if '@CMAKE_OSX_SYSROOT@' else ''
-))
+config.substitutions.append(('%{flags}', ''))
 config.substitutions.append(('%{compile_flags}',
-    '-nostdinc++ -I %{include} -I %{cxx-include} -I %{cxx-target-include} -DLIBCXXABI_NO_TIMER -D_LIBCPP_ENABLE_CXX17_REMOVED_UNEXPECTED_FUNCTIONS ' +
-    '-I %{libcxx}/test/support -I %{libcxx}/src'
+    '-nostdinc++ -I %{include} -I %{cxx-include} -I %{cxx-target-include} -I %{libcxx}/test/support -I %{libcxx}/src -D_LIBCPP_ENABLE_CXX17_REMOVED_UNEXPECTED_FUNCTIONS'
 ))
 config.substitutions.append(('%{link_flags}',
-    '-nostdlib++ -L %{lib} -Wl,-rpath,%{lib} -lc++ -pthread'
+    '-L %{lib} -Wl,-rpath,%{lib} -nodefaultlibs -lc++ -lc++abi -lm -lgcc_s -lgcc -lpthread -lc -lgcc_s -lgcc -latomic'
 ))
 config.substitutions.append(('%{exec}',
     '%{executor} --execdir %T -- '
@@ -18,7 +17,7 @@
 
 import os, site
 site.addsitedir(os.path.join('@LIBCXXABI_LIBCXX_PATH@', 'utils'))
-import libcxx.test.params, libcxx.test.newconfig, libcxx.test.newconfig
+import libcxx.test.params, libcxx.test.newconfig
 libcxx.test.newconfig.configure(
     libcxx.test.params.DEFAULT_PARAMETERS,
     libcxx.test.features.DEFAULT_FEATURES,
diff --git a/libcxxabi/test/configs/llvm-libc++abi-merged.cfg.in b/libcxxabi/test/configs/llvm-libc++abi-shared.cfg.in
copy from libcxxabi/test/configs/llvm-libc++abi-merged.cfg.in
copy to libcxxabi/test/configs/llvm-libc++abi-shared.cfg.in
--- a/libcxxabi/test/configs/llvm-libc++abi-merged.cfg.in
+++ b/libcxxabi/test/configs/llvm-libc++abi-shared.cfg.in
@@ -1,4 +1,5 @@
-# Testing configuration for libc++abi when merged into a libc++ shared library.
+# This testing configuration handles running the test suite against LLVM's libc++abi
+# using a shared library.
 
 lit_config.load_config(config, '@CMAKE_CURRENT_BINARY_DIR@/cmake-bridge.cfg')
 
@@ -6,11 +7,10 @@
     '-isysroot {}'.format('@CMAKE_OSX_SYSROOT@') if '@CMAKE_OSX_SYSROOT@' else ''
 ))
 config.substitutions.append(('%{compile_flags}',
-    '-nostdinc++ -I %{include} -I %{cxx-include} -I %{cxx-target-include} -DLIBCXXABI_NO_TIMER -D_LIBCPP_ENABLE_CXX17_REMOVED_UNEXPECTED_FUNCTIONS ' +
-    '-I %{libcxx}/test/support -I %{libcxx}/src'
+    '-nostdinc++ -I %{include} -I %{cxx-include} -I %{cxx-target-include} -I %{libcxx}/test/support -I %{libcxx}/src -D_LIBCPP_ENABLE_CXX17_REMOVED_UNEXPECTED_FUNCTIONS'
 ))
 config.substitutions.append(('%{link_flags}',
-    '-nostdlib++ -L %{lib} -Wl,-rpath,%{lib} -lc++ -pthread'
+    '-nostdlib++ -L %{lib} -Wl,-rpath,%{lib} -lc++ -lc++abi -pthread'
 ))
 config.substitutions.append(('%{exec}',
     '%{executor} --execdir %T -- '
@@ -18,7 +18,7 @@
 
 import os, site
 site.addsitedir(os.path.join('@LIBCXXABI_LIBCXX_PATH@', 'utils'))
-import libcxx.test.params, libcxx.test.newconfig, libcxx.test.newconfig
+import libcxx.test.params, libcxx.test.newconfig
 libcxx.test.newconfig.configure(
     libcxx.test.params.DEFAULT_PARAMETERS,
     libcxx.test.features.DEFAULT_FEATURES,
diff --git a/libcxxabi/test/configs/llvm-libc++abi-static-clangcl.cfg.in b/libcxxabi/test/configs/llvm-libc++abi-static-clangcl.cfg.in
new file mode 100644
--- /dev/null
+++ b/libcxxabi/test/configs/llvm-libc++abi-static-clangcl.cfg.in
@@ -0,0 +1,25 @@
+# This testing configuration handles running the test suite against LLVM's libc++abi
+# using a static library, with Clang-cl on Windows.
+
+lit_config.load_config(config, '@CMAKE_CURRENT_BINARY_DIR@/cmake-bridge.cfg')
+
+config.substitutions.append(('%{flags}', '--driver-mode=g++'))
+config.substitutions.append(('%{compile_flags}',
+    '-nostdinc++ -I %{include} -I %{cxx-include} -I %{cxx-target-include} -I %{libcxx}/test/support  -I %{libcxx}/src -D_LIBCPP_ENABLE_CXX17_REMOVED_UNEXPECTED_FUNCTIONS -D_CRT_SECURE_NO_WARNINGS -D_CRT_NONSTDC_NO_WARNINGS -D_CRT_STDIO_ISO_WIDE_SPECIFIERS -DNOMINMAX'
+))
+config.substitutions.append(('%{link_flags}',
+    '-nostdlib -L %{lib} -llibc++ -llibc++abi -lmsvcrt -lmsvcprt -loldnames'
+))
+config.substitutions.append(('%{exec}',
+    '%{executor} --execdir %T --env PATH=%{lib} -- '
+))
+
+import os, site
+site.addsitedir(os.path.join('@LIBCXXABI_LIBCXX_PATH@', 'utils'))
+import libcxx.test.params, libcxx.test.newconfig
+libcxx.test.newconfig.configure(
+    libcxx.test.params.DEFAULT_PARAMETERS,
+    libcxx.test.features.DEFAULT_FEATURES,
+    config,
+    lit_config
+)
diff --git a/libcxxabi/test/configs/llvm-libc++abi-merged.cfg.in b/libcxxabi/test/configs/llvm-libc++abi-static.cfg.in
copy from libcxxabi/test/configs/llvm-libc++abi-merged.cfg.in
copy to libcxxabi/test/configs/llvm-libc++abi-static.cfg.in
--- a/libcxxabi/test/configs/llvm-libc++abi-merged.cfg.in
+++ b/libcxxabi/test/configs/llvm-libc++abi-static.cfg.in
@@ -1,4 +1,5 @@
-# Testing configuration for libc++abi when merged into a libc++ shared library.
+# This testing configuration handles running the test suite against LLVM's libc++abi
+# using a static library.
 
 lit_config.load_config(config, '@CMAKE_CURRENT_BINARY_DIR@/cmake-bridge.cfg')
 
@@ -6,11 +7,10 @@
     '-isysroot {}'.format('@CMAKE_OSX_SYSROOT@') if '@CMAKE_OSX_SYSROOT@' else ''
 ))
 config.substitutions.append(('%{compile_flags}',
-    '-nostdinc++ -I %{include} -I %{cxx-include} -I %{cxx-target-include} -DLIBCXXABI_NO_TIMER -D_LIBCPP_ENABLE_CXX17_REMOVED_UNEXPECTED_FUNCTIONS ' +
-    '-I %{libcxx}/test/support -I %{libcxx}/src'
+    '-nostdinc++ -I %{include} -I %{cxx-include} -I %{cxx-target-include} -I %{libcxx}/test/support -I %{libcxx}/src -D_LIBCPP_ENABLE_CXX17_REMOVED_UNEXPECTED_FUNCTIONS'
 ))
 config.substitutions.append(('%{link_flags}',
-    '-nostdlib++ -L %{lib} -Wl,-rpath,%{lib} -lc++ -pthread'
+    '-nostdlib++ -L %{lib} -lc++ -lc++abi -pthread'
 ))
 config.substitutions.append(('%{exec}',
     '%{executor} --execdir %T -- '
@@ -18,7 +18,7 @@
 
 import os, site
 site.addsitedir(os.path.join('@LIBCXXABI_LIBCXX_PATH@', 'utils'))
-import libcxx.test.params, libcxx.test.newconfig, libcxx.test.newconfig
+import libcxx.test.params, libcxx.test.newconfig
 libcxx.test.newconfig.configure(
     libcxx.test.params.DEFAULT_PARAMETERS,
     libcxx.test.features.DEFAULT_FEATURES,