diff --git a/clang/cmake/caches/Fuchsia-stage2.cmake b/clang/cmake/caches/Fuchsia-stage2.cmake
index 9ecf8f300e75..4d9b8526d0c4 100644
--- a/clang/cmake/caches/Fuchsia-stage2.cmake
+++ b/clang/cmake/caches/Fuchsia-stage2.cmake
@@ -5,7 +5,6 @@ set(LLVM_TARGETS_TO_BUILD X86;ARM;AArch64;RISCV CACHE STRING "")
 set(PACKAGE_VENDOR Fuchsia CACHE STRING "")
 
 set(LLVM_ENABLE_PROJECTS "clang;clang-tools-extra;lld;llvm" CACHE STRING "")
-set(LLVM_ENABLE_RUNTIMES "compiler-rt;libcxx;libcxxabi;libunwind" CACHE STRING "")
 
 set(LLVM_ENABLE_BACKTRACES OFF CACHE BOOL "")
 if(NOT APPLE)
@@ -22,6 +21,10 @@ set(LLVM_INCLUDE_GO_TESTS OFF CACHE BOOL "")
 set(LLVM_USE_RELATIVE_PATHS_IN_FILES ON CACHE BOOL "")
 set(LLVM_ENABLE_Z3_SOLVER OFF CACHE BOOL "")
 
+if(MSVC)
+  set(LLVM_USE_CRT_RELEASE "MT" CACHE STRING "")
+endif()
+
 set(CLANG_DEFAULT_CXX_STDLIB libc++ CACHE STRING "")
 if(NOT APPLE)
   set(CLANG_DEFAULT_LINKER lld CACHE STRING "")
@@ -39,6 +42,8 @@ set(ENABLE_X86_RELAX_RELOCATIONS ON CACHE BOOL "")
 set(CMAKE_BUILD_TYPE Release CACHE STRING "")
 if (APPLE)
   set(MACOSX_DEPLOYMENT_TARGET 10.7 CACHE STRING "")
+elseif(MSVC)
+  set(CMAKE_MSVC_RUNTIME_LIBRARY "MultiThreaded" CACHE STRING "")
 endif()
 
 if(APPLE)
@@ -65,6 +70,26 @@ if(APPLE)
   set(DARWIN_iossim_ARCHS i386;x86_64 CACHE STRING "")
   set(DARWIN_osx_ARCHS x86_64 CACHE STRING "")
   set(SANITIZER_MIN_OSX_VERSION 10.7 CACHE STRING "")
+  set(LLVM_ENABLE_RUNTIMES "compiler-rt;libcxx;libcxxabi;libunwind" CACHE STRING "")
+endif()
+
+if(WIN32)
+  set(target "x86_64-pc-windows-msvc")
+
+  list(APPEND BUILTIN_TARGETS "${target}")
+  set(BUILTINS_${target}_CMAKE_SYSTEM_NAME Windows CACHE STRING "")
+  set(BUILTINS_${target}_CMAKE_BUILD_TYPE RelWithDebInfo CACHE STRING "")
+
+  list(APPEND RUNTIME_TARGETS "${target}")
+  set(RUNTIMES_${target}_CMAKE_SYSTEM_NAME Windows CACHE STRING "")
+  set(RUNTIMES_${target}_CMAKE_BUILD_TYPE RelWithDebInfo CACHE STRING "")
+  set(RUNTIMES_${target}_LIBCXX_ABI_VERSION 2 CACHE STRING "")
+  set(RUNTIMES_${target}_LIBCXX_HAS_WIN32_THREAD_API ON CACHE BOOL "")
+  set(RUNTIMES_${target}_LIBCXX_ENABLE_EXPERIMENTAL_LIBRARY OFF CACHE BOOL "")
+  set(RUNTIMES_${target}_LIBCXX_ENABLE_FILESYSTEM OFF CACHE BOOL "")
+  set(RUNTIMES_${target}_LIBCXX_ENABLE_ABI_LINKER_SCRIPT OFF CACHE BOOL "")
+  set(RUNTIMES_${target}_LIBCXX_ENABLE_SHARED OFF CACHE BOOL "")
+  set(RUNTIMES_${target}_LLVM_ENABLE_RUNTIMES "compiler-rt;libcxx" CACHE STRING "")
 endif()
 
 foreach(target aarch64-unknown-linux-gnu;armv7-unknown-linux-gnueabihf;i386-unknown-linux-gnu;x86_64-unknown-linux-gnu)
@@ -73,6 +98,9 @@ foreach(target aarch64-unknown-linux-gnu;armv7-unknown-linux-gnueabihf;i386-unkn
     list(APPEND BUILTIN_TARGETS "${target}")
     set(BUILTINS_${target}_CMAKE_SYSTEM_NAME Linux CACHE STRING "")
     set(BUILTINS_${target}_CMAKE_BUILD_TYPE RelWithDebInfo CACHE STRING "")
+    set(BUILTINS_${target}_CMAKE_C_FLAGS "--target=${target}" CACHE STRING "")
+    set(BUILTINS_${target}_CMAKE_CXX_FLAGS "--target=${target}" CACHE STRING "")
+    set(BUILTINS_${target}_CMAKE_ASM_FLAGS "--target=${target}" CACHE STRING "")
     set(BUILTINS_${target}_CMAKE_SYSROOT ${LINUX_${target}_SYSROOT} CACHE STRING "")
     set(BUILTINS_${target}_CMAKE_SHARED_LINKER_FLAGS "-fuse-ld=lld" CACHE STRING "")
     set(BUILTINS_${target}_CMAKE_MODULE_LINKER_FLAGS "-fuse-ld=lld" CACHE STRING "")
@@ -82,6 +110,9 @@ foreach(target aarch64-unknown-linux-gnu;armv7-unknown-linux-gnueabihf;i386-unkn
     list(APPEND RUNTIME_TARGETS "${target}")
     set(RUNTIMES_${target}_CMAKE_SYSTEM_NAME Linux CACHE STRING "")
     set(RUNTIMES_${target}_CMAKE_BUILD_TYPE RelWithDebInfo CACHE STRING "")
+    set(RUNTIMES_${target}_CMAKE_C_FLAGS "--target=${target}" CACHE STRING "")
+    set(RUNTIMES_${target}_CMAKE_CXX_FLAGS "--target=${target}" CACHE STRING "")
+    set(RUNTIMES_${target}_CMAKE_ASM_FLAGS "--target=${target}" CACHE STRING "")
     set(RUNTIMES_${target}_CMAKE_SYSROOT ${LINUX_${target}_SYSROOT} CACHE STRING "")
     set(RUNTIMES_${target}_CMAKE_SHARED_LINKER_FLAGS "-fuse-ld=lld" CACHE STRING "")
     set(RUNTIMES_${target}_CMAKE_MODULE_LINKER_FLAGS "-fuse-ld=lld" CACHE STRING "")
@@ -100,9 +131,9 @@ foreach(target aarch64-unknown-linux-gnu;armv7-unknown-linux-gnueabihf;i386-unkn
     set(RUNTIMES_${target}_LIBCXX_ENABLE_STATIC_ABI_LIBRARY ON CACHE BOOL "")
     set(RUNTIMES_${target}_LIBCXX_ABI_VERSION 2 CACHE STRING "")
     set(RUNTIMES_${target}_LLVM_ENABLE_ASSERTIONS ON CACHE BOOL "")
-    set(RUNTIMES_${target}_LLVM_ENABLE_RUNTIMES "compiler-rt;libcxx;libcxxabi;libunwind" CACHE STRING "")
     set(RUNTIMES_${target}_SANITIZER_CXX_ABI "libc++" CACHE STRING "")
     set(RUNTIMES_${target}_SANITIZER_CXX_ABI_INTREE ON CACHE BOOL "")
+    set(RUNTIMES_${target}_LLVM_ENABLE_RUNTIMES "compiler-rt;libcxx;libcxxabi;libunwind" CACHE STRING "")
 
     # Use .build-id link.
     list(APPEND RUNTIME_BUILD_ID_LINK "${target}")
@@ -115,7 +146,7 @@ if(FUCHSIA_SDK)
   set(FUCHSIA_x86_64_NAME x64)
   set(FUCHSIA_riscv64_NAME riscv64)
   foreach(target i386;x86_64;aarch64;riscv64)
-    set(FUCHSIA_${target}_COMPILER_FLAGS "-I${FUCHSIA_SDK}/pkg/fdio/include")
+    set(FUCHSIA_${target}_COMPILER_FLAGS "--target=${target}-unknown-fuchsia -I${FUCHSIA_SDK}/pkg/fdio/include")
     set(FUCHSIA_${target}_LINKER_FLAGS "-L${FUCHSIA_SDK}/arch/${FUCHSIA_${target}_NAME}/lib")
     set(FUCHSIA_${target}_SYSROOT "${FUCHSIA_SDK}/arch/${FUCHSIA_${target}_NAME}/sysroot")
   endforeach()
diff --git a/clang/cmake/caches/Fuchsia.cmake b/clang/cmake/caches/Fuchsia.cmake
index bb22a00fa5c7..8688b71ecc75 100644
--- a/clang/cmake/caches/Fuchsia.cmake
+++ b/clang/cmake/caches/Fuchsia.cmake
@@ -5,7 +5,6 @@ set(LLVM_TARGETS_TO_BUILD X86;ARM;AArch64;RISCV CACHE STRING "")
 set(PACKAGE_VENDOR Fuchsia CACHE STRING "")
 
 set(LLVM_ENABLE_PROJECTS "clang;clang-tools-extra;lld;llvm" CACHE STRING "")
-set(LLVM_ENABLE_RUNTIMES "compiler-rt;libcxx;libcxxabi;libunwind" CACHE STRING "")
 
 set(LLVM_ENABLE_BACKTRACES OFF CACHE BOOL "")
 set(LLVM_ENABLE_PER_TARGET_RUNTIME_DIR ON CACHE BOOL "")
@@ -16,6 +15,10 @@ set(LLVM_INCLUDE_DOCS OFF CACHE BOOL "")
 set(LLVM_INCLUDE_EXAMPLES OFF CACHE BOOL "")
 set(LLVM_INCLUDE_GO_TESTS OFF CACHE BOOL "")
 
+if(MSVC)
+  set(LLVM_USE_CRT_RELEASE "MT" CACHE STRING "")
+endif()
+
 set(CLANG_DEFAULT_CXX_STDLIB libc++ CACHE STRING "")
 if(NOT APPLE)
   set(CLANG_DEFAULT_LINKER lld CACHE STRING "")
@@ -32,8 +35,10 @@ set(ENABLE_X86_RELAX_RELOCATIONS ON CACHE BOOL "")
 
 set(LLVM_ENABLE_ASSERTIONS ON CACHE BOOL "")
 set(CMAKE_BUILD_TYPE Release CACHE STRING "")
-if (APPLE)
+if(APPLE)
   set(MACOSX_DEPLOYMENT_TARGET 10.7 CACHE STRING "")
+elseif(MSVC)
+  set(CMAKE_MSVC_RUNTIME_LIBRARY "MultiThreaded" CACHE STRING "")
 endif()
 
 if(APPLE)
@@ -52,8 +57,19 @@ set(LIBCXXABI_USE_COMPILER_RT ON CACHE BOOL "")
 set(LIBCXXABI_USE_LLVM_UNWINDER ON CACHE BOOL "")
 set(LIBCXX_ABI_VERSION 2 CACHE STRING "")
 set(LIBCXX_ENABLE_SHARED OFF CACHE BOOL "")
-set(LIBCXX_ENABLE_STATIC_ABI_LIBRARY ON CACHE BOOL "")
-set(LIBCXX_USE_COMPILER_RT ON CACHE BOOL "")
+if(WIN32)
+  set(LIBCXX_HAS_WIN32_THREAD_API ON CACHE BOOL "")
+  set(LIBCXX_ENABLE_EXPERIMENTAL_LIBRARY OFF CACHE BOOL "")
+  set(LIBCXX_ENABLE_FILESYSTEM OFF CACHE BOOL "")
+  set(LIBCXX_ENABLE_ABI_LINKER_SCRIPT OFF CACHE BOOL "")
+  set(LIBCXX_ENABLE_STATIC_ABI_LIBRARY OFF CACHE BOOL "")
+  set(BUILTINS_CMAKE_ARGS -DCMAKE_SYSTEM_NAME=Windows CACHE STRING "")
+  set(RUNTIMES_CMAKE_ARGS -DCMAKE_SYSTEM_NAME=Windows CACHE STRING "")
+  set(LLVM_ENABLE_RUNTIMES "compiler-rt;libcxx" CACHE STRING "")
+else()
+  set(LIBCXX_ENABLE_STATIC_ABI_LIBRARY ON CACHE BOOL "")
+  set(LLVM_ENABLE_RUNTIMES "compiler-rt;libcxx;libcxxabi;libunwind" CACHE STRING "")
+endif()
 
 if(BOOTSTRAP_CMAKE_SYSTEM_NAME)
   set(target "${BOOTSTRAP_CMAKE_CXX_COMPILER_TARGET}")