diff --git a/README_OE.md b/README_OE.md
index af956a923c04130b3e648c282c8f8719f20f36c7..ee97a9346a58af4de17ece0f0a540feb9d69a3fd 100644
--- a/README_OE.md
+++ b/README_OE.md
@@ -15,7 +15,14 @@
   libstdc++-static \
   libatomic
 
+ 交叉编译时需要额外安装autoconf、automake、libelf、libffi。
  具体的编译选项可以在build.sh中查看，也可以通过“./build.sh -h”命令查看。
  例如：
-   ./build.sh -r -b release -X X86
+   ./build.sh -r -b release -X X86 -i
+ 交叉编译:
+   export BISHENG_LIBELF_PATH=/xxx/libelf/install
+   export BISHENG_LIBFFI_PATH=/xxx/libffi/install
+   export BISHENG_CROSS_TOOLCHAIN=/xxx/gcc-arm-aarch64-none-linux-gnu/
+   export BISHENG_CROSS_SYSROOT=$BISHENG_CROSS_TOOLCHAIN/aarch64-none-linux-gnu/libc
+   ./build.sh -r -b release -X "AArch64;X86" -x aarch64 -i
 
diff --git a/build.sh b/build.sh
index 7b6b7908abbd185a34239ff96f5050a0c51b36d0..125109eb594bf66c9ab6e606ebacf3a874d282b1 100755
--- a/build.sh
+++ b/build.sh
@@ -4,10 +4,13 @@
 C_COMPILER_PATH=gcc
 CXX_COMPILER_PATH=g++
 
+gcc_toolchain="$BISHENG_CROSS_TOOLCHAIN"
+sysroot="$BISHENG_CROSS_SYSROOT"
+
 # Initialize our own variables:
 buildtype=RelWithDebInfo
 backends="ARM;AArch64;X86"
-enabled_projects="clang;lld;compiler-rt;openmp;clang-tools-extra"
+enabled_projects="clang;lld;openmp;clang-tools-extra"
 embedded_toolchain="0"
 split_dwarf=on
 use_ccache="0"
@@ -22,6 +25,8 @@ build_dir_name="build"
 install_dir_name="install"
 build_prefix="$dir/$build_dir_name"
 install_prefix="$dir/$install_dir_name"
+cross_compile_arch=""
+host_arch="$(uname -m)"
 
 # Use 8 threads for builds and tests by default. Use more threads if possible,
 # but avoid overloading the system by using up to 50% of available cores.
@@ -58,12 +63,13 @@ Options:
   -t       Enable unit tests for components that support them (make check-all).
   -v       Enable verbose build output (default: quiet).
   -X archs Build only the specified semi-colon-delimited list of backends (default: "$backends").
+  -x arch  Build cross-compiling toolchain for the specified target.
 EOF
 }
 
 # Process command-line options. Remember the options for passing to the
 # containerized build script.
-while getopts :b:cehiI:j:orstvX: optchr; do
+while getopts :b:cehiI:j:orstvX:x: optchr; do
   case "$optchr" in
     b)
       buildtype="$OPTARG"
@@ -117,7 +123,21 @@ while getopts :b:cehiI:j:orstvX: optchr; do
     X)
       backends="$OPTARG"
       ;;
-    :)
+    x)
+      cross_compile_arch=$OPTARG
+      case "${cross_compile_arch,,}" in
+        aarch64)
+          ;;
+        riscv64)
+          # RISCV backend is not built by default.
+          backends+=";RISCV"
+          ;;
+        *)
+          echo "$0: unsupported architecture for cross-compilation: $cross_compile_arch"
+          exit 1
+          ;;
+      esac
+      ;;    :)
       echo "$0: missing argument for option '-$OPTARG'"
       exit 1
       ;;
@@ -128,6 +148,23 @@ while getopts :b:cehiI:j:orstvX: optchr; do
   esac
 done
 
+# Run a command as a background process, wait for its termination, and die
+# if its exit code is non-zero. Running a command in the background and
+# waiting allows the trap handler in this script to catch a signal and
+# immediately stop all child processes. Note that sub-shells are not
+# interruptible unless they also enable job control and wait for background
+# commands. For this reason, sub-shells should be avoided.
+run_or_die() {
+  set -x
+  "$@" &
+  set +x
+  wait $! || exit 1
+}
+
+COMMON_CFLAGS="-pthread"
+
+generator="Unix Makefiles"
+
 CMAKE_OPTIONS="-DCMAKE_INSTALL_PREFIX=$install_prefix \
                -DCMAKE_BUILD_TYPE=$buildtype \
                -DCMAKE_C_COMPILER=$C_COMPILER_PATH \
@@ -136,11 +173,11 @@ CMAKE_OPTIONS="-DCMAKE_INSTALL_PREFIX=$install_prefix \
 
 # Warning: the -DLLVM_ENABLE_PROJECTS option is specified with cmake
 # to avoid issues with nested quotation marks
+llvm_use_ccache=""
 if [ $use_ccache == "1" ]; then
   echo "Build using ccache"
-  CMAKE_OPTIONS="$CMAKE_OPTIONS \
-                -DCMAKE_C_COMPILER_LAUNCHER=ccache \
-                -DCMAKE_CXX_COMPILER_LAUNCHER=ccache "
+  llvm_use_ccache="-DCMAKE_C_COMPILER_LAUNCHER=ccache \
+                   -DCMAKE_CXX_COMPILER_LAUNCHER=ccache "
 fi
 
 if [ $embedded_toolchain == "1" ]; then
@@ -167,15 +204,15 @@ fi
 
 mkdir -p "$build_prefix" && cd "$build_prefix"
 cmake $CMAKE_OPTIONS \
+      $llvm_use_ccache \
       -DCOMPILER_RT_BUILD_SANITIZERS=on \
       -DLLVM_ENABLE_PROJECTS=$enabled_projects \
-      -DLLVM_ENABLE_RUNTIMES="libcxx;libcxxabi;libunwind" \
+      -DLLVM_ENABLE_RUNTIMES="compiler-rt;libcxx;libcxxabi;libunwind" \
       -DLLVM_USE_LINKER=gold \
       -DLLVM_LIT_ARGS="-sv -j$threads" \
       -DLLVM_USE_SPLIT_DWARF=$split_dwarf \
       -DCMAKE_EXE_LINKER_FLAGS_RELWITHDEBINFO="-Wl,--gdb-index -Wl,--compress-debug-sections=zlib"\
       -DCMAKE_EXE_LINKER_FLAGS_DEBUG="-Wl,--gdb-index -Wl,--compress-debug-sections=zlib" \
-      $verbose \
       ../llvm
 
 make -j$threads
@@ -187,6 +224,178 @@ if [ -n "$unit_test" ]; then
   make -j$threads $verbose check-all
 fi
 
+build_openmp() {
+  local cross_suffix="-cross"
+  local stage_install_prefix="$cross_compile_install_prefix"
+  local cross_cmake_flags="$cross_cmake_flags \
+                           -DOPENMP_ENABLE_LIBOMPTARGET=off"
+  if [ -d "$libelf_path" ]; then
+    cross_cmake_flags="$cross_cmake_flags \
+                       -DLIBOMPTARGET_DEP_LIBELF_INCLUDE_DIR=$libelf_path/include \
+                       -DLIBOMPTARGET_DEP_LIBELF_LIBRARIES=$libelf_path/lib"
+  fi
+  if [ -d "$libffi_path" ]; then
+    cross_cmake_flags="$cross_cmake_flags \
+                       -DLIBOMPTARGET_DEP_LIBFFI_INCLUDE_DIR=$libffi_path/include \
+                       -DLIBOMPTARGET_DEP_LIBFFI_LIBRARIES=$libffi_path/lib64"
+  fi
+
+  echo $1
+  if [ "$1" = "static" ]; then
+    local static_suffix="-static"
+    local static_cmake_flags="-DLIBOMP_ENABLE_SHARED=off \
+                              -DLIBOMP_OMPT_SUPPORT=off \
+                              -DOPENMP_ENABLE_LIBOMPTARGET=off \
+                              -DOPENMP_ENABLE_OMPT_TOOLS=off"
+  else
+    local static_suffix=""
+    local static_cmake_flags=""
+  fi
+
+  echo "$0: building openmp$static_suffix$cross_suffix"
+
+  if [ $clean -eq 1 ]; then
+    rm -rf "$build_prefix"/projects/openmp"$static_suffix$cross_suffix"
+  fi
+	
+  mkdir -p "$build_prefix"/projects/openmp"$static_suffix$cross_suffix" && cd "$build_prefix"/projects/openmp"$static_suffix$cross_suffix"
+  # Disable OMPT and libomptarget, to prevent overwriting shared libraries
+  # that have already been built when building static archives.
+  run_or_die \
+    cmake -Wno-dev -G "$generator" \
+          -DCMAKE_BUILD_TYPE=$buildtype \
+          -DCMAKE_INSTALL_PREFIX="$stage_install_prefix" \
+          -DCMAKE_INSTALL_MESSAGE=LAZY \
+          $llvm_use_ccache \
+          -DCMAKE_C_COMPILER=clang \
+          -DCMAKE_CXX_COMPILER=clang++ \
+          -DLIBOMP_ENABLE_ASSERTIONS=off \
+          $static_cmake_flags \
+          -DOPENMP_LLVM_TOOLS_DIR="$(dirname $llvm_lit)" \
+          -DOPENMP_LIT_ARGS="-sv -j$threads" \
+          -DOPENMP_TEST_CXX_COMPILER="$stage_install_prefix/bin/clang++" \
+          -DOPENMP_TEST_C_COMPILER="$stage_install_prefix/bin/clang" \
+          $cross_cmake_flags \
+          ../../../openmp
+
+  run_or_die make -j$threads
+  run_or_die make -j$threads $verbose install
+}
+
+build_libunwind() {
+  local stage_install_prefix="$cross_compile_install_prefix"
+  local cross_cmake_flags="$cross_cmake_flags"
+
+  echo "$0: building libunwind-cross"
+  if [ $clean -eq 1 ]; then
+    rm -rf "$build_prefix"/projects/libunwind-cross
+  fi
+  mkdir -p "$build_prefix"/projects/libunwind-cross && cd "$build_prefix"/projects/libunwind-cross
+  run_or_die \
+    cmake -Wno-dev -G "$generator" \
+          -DCMAKE_BUILD_TYPE=$buildtype \
+          -DCMAKE_INSTALL_PREFIX="$stage_install_prefix" \
+          -DCMAKE_INSTALL_MESSAGE=LAZY \
+          $llvm_use_ccache \
+          -DCMAKE_C_COMPILER=clang \
+          -DCMAKE_CXX_COMPILER=clang++ \
+          $cross_cmake_flags \
+          ../../../libunwind
+
+  run_or_die make -j$threads
+  run_or_die make -j$threads $verbose install
+}
+
+build_compiler_rt() {
+  local cross_cmake_flags="$cross_cmake_flags"
+  local stage_install_prefix="$($install_prefix/bin/clang --print-resource-dir)"
+
+  echo "$0: building compiler-rt-cross"
+  if [ $clean -eq 1 ]; then
+    rm -rf "$build_prefix"/projects/compiler-rt-cross
+  fi
+
+  mkdir -p "$build_prefix"/projects/compiler-rt-cross && cd "$build_prefix"/projects/compiler-rt-cross
+  run_or_die \
+     cmake -Wno-dev -G "$generator" \
+           -DCMAKE_BUILD_TYPE=$buildtype \
+           -DCMAKE_INSTALL_PREFIX="$stage_install_prefix" \
+           -DCMAKE_INSTALL_MESSAGE=LAZY \
+           -DCMAKE_C_COMPILER=clang \
+           -DCMAKE_CXX_COMPILER=clang++ \
+           -DCOMPILER_RT_BUILD_BUILTINS=on \
+           -DCOMPILER_RT_BUILD_LIBFUZZER=off \
+           -DCOMPILER_RT_BUILD_PROFILE=on \
+           -DCOMPILER_RT_BUILD_SANITIZERS=off \
+           -DCOMPILER_RT_BUILD_XRAY=off \
+           -DCOMPILER_RT_DEFAULT_TARGET_ONLY=ON \
+           $cross_cmake_flags \
+           ../../../compiler-rt
+
+  run_or_die make -j$threads
+  run_or_die make -j$threads $verbose install
+}
+
+build_libcxx() {
+  echo $install_libcxx
+  local stage_install_prefix="$cross_compile_install_prefix"
+  local cross_cmake_flags="$cross_cmake_flags"
+
+  echo "$0: building libcxx-cross"
+  if [ $clean -eq 1 -a -e "$build_prefix/projects/libcxx-cross" ]; then
+    rm -rf "$build_prefix/projects/libcxx-cross"
+  fi
+  mkdir -p "$build_prefix/projects/libcxx-cross" && cd "$build_prefix/projects/libcxx-cross"
+  run_or_die \
+    cmake -Wno-dev -G "$generator" \
+          -DLLVM_ENABLE_PROJECTS="libcxx;libcxxabi" \
+	  -DCMAKE_BUILD_TYPE=$buildtype \
+          -DCMAKE_C_COMPILER=clang \
+          -DCMAKE_CXX_COMPILER=clang++ \
+          -DLLVM_TABLEGEN=$install_prefix/bin/llvm-tblgen \
+          -DCMAKE_INSTALL_PREFIX="$stage_install_prefix" \
+          -DCMAKE_INSTALL_MESSAGE=LAZY \
+          -DLLVM_ENABLE_ASSERTIONS=off \
+          -DLLVM_ENABLE_ZSTD=off \
+          -DLLVM_USE_SPLIT_DWARF=$split_dwarf \
+          -DLLVM_LIT_ARGS="-sv -j$threads" \
+          $cross_cmake_flags \
+          ../../../llvm
+
+  run_or_die make -j$threads $verbose
+  run_or_die make -j$threads $verbose install
+}
+
+path_orig="$PATH"
+ld_library_path_orig="$LD_LIBRARY_PATH"
+export PATH="$install_prefix/bin:$path_orig"
+export LD_LIBRARY_PATH="$install_prefix/lib:$ld_library_path_orig"
+
+if [ "$cross_compile_arch" != "" ]; then
+  if [ "$host_arch" = "$cross_compile_arch" ]; then
+    echo "$0: cannot cross-compile from $host_arch to $cross_compile_arch"
+    exit 1
+  fi
+
+  host_triple="$(llvm-config --host-target)"
+  cross_compile_triple="${host_triple/$host_arch/$cross_compile_arch}"
+  cross_compile_install_prefix="$install_prefix/$cross_compile_triple"
+  mkdir -p "$cross_compile_install_prefix"
+
+  cross_cmake_flags="-DCMAKE_C_COMPILER_TARGET=$cross_compile_triple \
+                     -DCMAKE_CXX_COMPILER_TARGET=$cross_compile_triple \
+                     -DCMAKE_ASM_COMPILER_TARGET=$cross_compile_triple \
+                     -DCMAKE_SYSROOT=$sysroot \
+                     -DCMAKE_C_COMPILER_EXTERNAL_TOOLCHAIN=$gcc_toolchain \
+                     -DCMAKE_CXX_COMPILER_EXTERNAL_TOOLCHAIN=$gcc_toolchain"
+
+  build_openmp shared
+  build_openmp static
+  build_libunwind
+  build_compiler_rt
+  build_libcxx
+fi
+
 cd ..
 
 # When building official deliverables, minimize file permissions under the