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
@@ -102,6 +102,18 @@
     set(BUILTINS_${target}_CMAKE_MODULE_LINKER_FLAGS "-fuse-ld=lld" CACHE STRING "")
     set(BUILTINS_${target}_CMAKE_EXE_LINKER_FLAG "-fuse-ld=lld" CACHE STRING "")
 
+    list(APPEND CRT_TARGETS "${target}")
+    set(CRT_${target}_CMAKE_SYSTEM_NAME Linux CACHE STRING "")
+    set(CRT_${target}_CMAKE_BUILD_TYPE RelWithDebInfo CACHE STRING "")
+    set(CRT_${target}_CMAKE_POSITION_INDEPENDENT_CODE ON CACHE BOOL "")
+    set(CRT_${target}_CMAKE_C_FLAGS "--target=${target}" CACHE STRING "")
+    set(CRT_${target}_CMAKE_CXX_FLAGS "--target=${target}" CACHE STRING "")
+    set(CRT_${target}_CMAKE_ASM_FLAGS "--target=${target}" CACHE STRING "")
+    set(CRT_${target}_CMAKE_SYSROOT ${LINUX_${target}_SYSROOT} CACHE STRING "")
+    set(CRT_${target}_CMAKE_SHARED_LINKER_FLAGS "-fuse-ld=lld" CACHE STRING "")
+    set(CRT_${target}_CMAKE_MODULE_LINKER_FLAGS "-fuse-ld=lld" CACHE STRING "")
+    set(CRT_${target}_CMAKE_EXE_LINKER_FLAG "-fuse-ld=lld" CACHE STRING "")
+
     # Set the per-target runtimes options.
     list(APPEND RUNTIME_TARGETS "${target}")
     set(RUNTIMES_${target}_CMAKE_SYSTEM_NAME Linux CACHE STRING "")
@@ -251,6 +263,7 @@
 endif()
 
 set(LLVM_BUILTIN_TARGETS "${BUILTIN_TARGETS}" CACHE STRING "")
+set(LLVM_CRT_TARGETS "${CRT_TARGETS}" CACHE STRING "")
 set(LLVM_RUNTIME_TARGETS "${RUNTIME_TARGETS}" CACHE STRING "")
 
 # Setup toolchain.
@@ -303,6 +316,7 @@
   clang-tidy
   clangd
   find-all-symbols
+  crt
   builtins
   runtimes
   ${LLVM_TOOLCHAIN_TOOLS}
diff --git a/llvm/runtimes/CMakeLists.txt b/llvm/runtimes/CMakeLists.txt
--- a/llvm/runtimes/CMakeLists.txt
+++ b/llvm/runtimes/CMakeLists.txt
@@ -120,6 +120,62 @@
                            ${EXTRA_ARGS})
 endfunction()
 
+function(crt_default_target compiler_rt_path)
+  cmake_parse_arguments(ARG "" "" "DEPENDS" ${ARGN})
+
+  set(LLVM_ENABLE_PER_TARGET_RUNTIME_DIR_default ON)
+  # AIX should fold 32-bit & 64-bit arch libraries into a single archive.
+  if (LLVM_TARGET_TRIPLE MATCHES "aix")
+    set(LLVM_ENABLE_PER_TARGET_RUNTIME_DIR_default OFF)
+  endif()
+
+  llvm_ExternalProject_Add(crt
+                           ${compiler_rt_path}/lib/crt
+                           DEPENDS ${ARG_DEPENDS}
+                           CMAKE_ARGS -DLLVM_LIBRARY_OUTPUT_INTDIR=${LLVM_LIBRARY_DIR}
+                                      -DLLVM_RUNTIME_OUTPUT_INTDIR=${LLVM_TOOLS_BINARY_DIR}
+                                      -DLLVM_DEFAULT_TARGET_TRIPLE=${LLVM_TARGET_TRIPLE}
+                                      -DLLVM_ENABLE_PER_TARGET_RUNTIME_DIR=${LLVM_ENABLE_PER_TARGET_RUNTIME_DIR_default}
+                                      -DCMAKE_C_COMPILER_WORKS=ON
+                                      ${COMMON_CMAKE_ARGS}
+                                      ${CRT_CMAKE_ARGS}
+                           PASSTHROUGH_PREFIXES COMPILER_RT
+                           USE_TOOLCHAIN
+                           TARGET_TRIPLE ${LLVM_TARGET_TRIPLE}
+                           ${EXTRA_ARGS})
+endfunction()
+
+function(crt_register_target compiler_rt_path target)
+  cmake_parse_arguments(ARG "" "" "DEPENDS" ${ARGN})
+
+  check_apple_target(${target} crt)
+
+  get_cmake_property(variableNames VARIABLES)
+  foreach(variableName ${variableNames})
+    string(FIND "${variableName}" "CRT_${target}" out)
+    if("${out}" EQUAL 0)
+      string(REPLACE "CRT_${target}_" "" new_name ${variableName})
+      string(REPLACE ";" "|" new_value "${${variableName}}")
+      list(APPEND ${target}_extra_args "-D${new_name}=${new_value}")
+    endif()
+  endforeach()
+
+  llvm_ExternalProject_Add(crt-${target}
+                           ${compiler_rt_path}/lib/crt
+                           DEPENDS ${ARG_DEPENDS}
+                           CMAKE_ARGS -DLLVM_LIBRARY_OUTPUT_INTDIR=${LLVM_LIBRARY_DIR}
+                                      -DLLVM_RUNTIME_OUTPUT_INTDIR=${LLVM_TOOLS_BINARY_DIR}
+                                      -DLLVM_DEFAULT_TARGET_TRIPLE=${target}
+                                      -DLLVM_ENABLE_PER_TARGET_RUNTIME_DIR=ON
+                                      -DCMAKE_C_COMPILER_WORKS=ON
+                                      -DCOMPILER_RT_DEFAULT_TARGET_ONLY=ON
+                                      ${COMMON_CMAKE_ARGS}
+                                      ${${target}_extra_args}
+                           USE_TOOLCHAIN
+                           TARGET_TRIPLE ${target}
+                           ${EXTRA_ARGS})
+endfunction()
+
 # If compiler-rt is present we need to build the builtin libraries first. This
 # is required because the other runtimes need the builtin libraries present
 # before the just-built compiler can pass the configuration tests.
@@ -148,12 +204,42 @@
       add_dependencies(install-builtins-stripped install-builtins-${target}-stripped)
     endforeach()
   endif()
-  set(deps builtins)
+  list(APPEND deps builtins)
   # We don't need to depend on the builtins if we're building instrumented
   # because the next stage will use the same compiler used to build this stage.
   if(NOT LLVM_BUILD_INSTRUMENTED AND CLANG_ENABLE_BOOTSTRAP)
     add_dependencies(clang-bootstrap-deps builtins)
   endif()
+
+  if(NOT LLVM_CRT_TARGETS)
+    crt_default_target(${compiler_rt_path}
+      DEPENDS clang-resource-headers)
+  else()
+    if("default" IN_LIST LLVM_CRT_TARGETS)
+      crt_default_target(${compiler_rt_path}
+        DEPENDS clang-resource-headers)
+      list(REMOVE_ITEM LLVM_CRT_TARGETS "default")
+    else()
+      add_custom_target(crt)
+      add_custom_target(install-crt)
+      add_custom_target(install-crt-stripped)
+    endif()
+
+    foreach(target ${LLVM_CRT_TARGETS})
+      crt_register_target(${compiler_rt_path} ${target}
+        DEPENDS clang-resource-headers)
+
+      add_dependencies(crt crt-${target})
+      add_dependencies(install-crt install-crt-${target})
+      add_dependencies(install-crt-stripped install-crt-${target}-stripped)
+    endforeach()
+  endif()
+  list(APPEND deps crt)
+  # We don't need to depend on the crt if we're building instrumented
+  # because the next stage will use the same compiler used to build this stage.
+  if(NOT LLVM_BUILD_INSTRUMENTED AND CLANG_ENABLE_BOOTSTRAP)
+    add_dependencies(clang-bootstrap-deps crt)
+  endif()
 endif()
 
 # Create a list with the names of all the runtime projects in all uppercase and
@@ -223,7 +309,8 @@
                            ${CMAKE_CURRENT_SOURCE_DIR}/../../runtimes
                            DEPENDS ${ARG_DEPENDS}
                            # Builtins were built separately above
-                           CMAKE_ARGS -DCOMPILER_RT_BUILD_BUILTINS=Off
+                           CMAKE_ARGS -DCOMPILER_RT_BUILD_BUILTINS=OFF
+                                      -DCOMPILER_RT_BUILD_CRT=OFF
                                       -DLLVM_INCLUDE_TESTS=${LLVM_INCLUDE_TESTS}
                                       -DLLVM_DEFAULT_TARGET_TRIPLE=${LLVM_TARGET_TRIPLE}
                                       -DLLVM_ENABLE_PROJECTS_USED=${LLVM_ENABLE_PROJECTS_USED}
@@ -332,7 +419,8 @@
                            ${CMAKE_CURRENT_SOURCE_DIR}/../../runtimes
                            DEPENDS ${${name}_deps}
                            # Builtins were built separately above
-                           CMAKE_ARGS -DCOMPILER_RT_BUILD_BUILTINS=Off
+                           CMAKE_ARGS -DCOMPILER_RT_BUILD_BUILTINS=OFF
+                                      -DCOMPILER_RT_BUILD_CRT=OFF
                                       -DLLVM_INCLUDE_TESTS=${LLVM_INCLUDE_TESTS}
                                       -DLLVM_DEFAULT_TARGET_TRIPLE=${target}
                                       -DLLVM_ENABLE_PROJECTS_USED=${LLVM_ENABLE_PROJECTS_USED}