2 files changed, 52 insertions, 10 deletions

diff --git a/llvm/utils/gn/build/toolchain/BUILD.gn b/llvm/utils/gn/build/toolchain/BUILD.gn
index c53f753bf57..87276ea98fd 100644
--- a/llvm/utils/gn/build/toolchain/BUILD.gn
+++ b/llvm/utils/gn/build/toolchain/BUILD.gn
@@ -12,10 +12,16 @@ declare_args() {
 template("unix_toolchain") {
   toolchain(target_name) {
     forward_variables_from(invoker, "*")
+    if (!defined(target_cflags)) {
+      target_cflags = ""
+    }
+    if (!defined(target_ldflags)) {
+      target_ldflags = ""
+    }
 
     tool("cc") {
       depfile = "{{output}}.d"
-      command = "$cc -MMD -MF $depfile -o {{output}} -c {{source}} {{defines}} {{include_dirs}} {{cflags}} {{cflags_c}}"
+      command = "$cc -MMD -MF $depfile -o {{output}} -c {{source}} {{defines}} {{include_dirs}} {{cflags}} {{cflags_c}} $target_cflags"
       depsformat = "gcc"
       description = "CC {{output}}"
       outputs = [
@@ -25,7 +31,7 @@ template("unix_toolchain") {
 
     tool("cxx") {
       depfile = "{{output}}.d"
-      command = "$cxx -MMD -MF $depfile -o {{output}} -c {{source}} {{defines}} {{include_dirs}} {{cflags}} {{cflags_cc}}"
+      command = "$cxx -MMD -MF $depfile -o {{output}} -c {{source}} {{defines}} {{include_dirs}} {{cflags}} {{cflags_cc}} $target_cflags"
       depsformat = "gcc"
       description = "CXX {{output}}"
       outputs = [
@@ -39,7 +45,8 @@ template("unix_toolchain") {
       } else {
         # Remove the output file first so that ar doesn't try to modify the
         # existing file.
-        command = "rm -f {{output}} && $ar rcsDT {{arflags}} {{output}} {{inputs}}"
+        command =
+            "rm -f {{output}} && $ar rcsDT {{arflags}} {{output}} {{inputs}}"
       }
       description = "AR {{output}}"
       outputs = [
@@ -52,11 +59,10 @@ template("unix_toolchain") {
     tool("solink") {
       outfile = "{{output_dir}}/{{target_output_name}}{{output_extension}}"
       if (current_os == "mac") {
-        command = "$ld -shared {{ldflags}} -o $outfile {{libs}} {{inputs}}"
+        command = "$ld -shared {{ldflags}} -o $outfile {{libs}} {{inputs}} $target_ldflags"
         default_output_extension = ".dylib"
       } else {
-        command =
-            "$ld -shared {{ldflags}} -Wl,-z,defs -o $outfile {{libs}} {{inputs}}"
+        command = "$ld -shared {{ldflags}} -Wl,-z,defs -o $outfile {{libs}} {{inputs}} $target_ldflags"
         default_output_extension = ".so"
       }
       description = "SOLINK $outfile"
@@ -71,10 +77,10 @@ template("unix_toolchain") {
     tool("solink_module") {
       outfile = "{{output_dir}}/{{target_output_name}}{{output_extension}}"
       if (current_os == "mac") {
-        command = "$ld -shared {{ldflags}} -Wl,-flat_namespace -Wl,-undefined,suppress -o $outfile {{libs}} {{inputs}}"
+        command = "$ld -shared {{ldflags}} -Wl,-flat_namespace -Wl,-undefined,suppress -o $outfile {{libs}} {{inputs}} $target_ldflags"
         default_output_extension = ".dylib"
       } else {
-        command = "$ld -shared {{ldflags}} -o $outfile {{libs}} {{inputs}}"
+        command = "$ld -shared {{ldflags}} -o $outfile {{libs}} {{inputs}} $target_ldflags"
         default_output_extension = ".so"
       }
       description = "SOLINK $outfile"
@@ -88,9 +94,10 @@ template("unix_toolchain") {
     tool("link") {
       outfile = "{{output_dir}}/{{target_output_name}}{{output_extension}}"
       if (current_os == "mac") {
-        command = "$ld {{ldflags}} -o $outfile {{libs}} {{inputs}}"
+        command =
+            "$ld {{ldflags}} -o $outfile {{libs}} {{inputs}} $target_ldflags"
       } else {
-        command = "$ld {{ldflags}} -o $outfile {{libs}} -Wl,--start-group {{inputs}} -Wl,--end-group"
+        command = "$ld {{ldflags}} -o $outfile {{libs}} -Wl,--start-group {{inputs}} -Wl,--end-group $target_ldflags"
       }
       description = "LINK $outfile"
       outputs = [
@@ -137,6 +144,37 @@ unix_toolchain("unix") {
   }
 }
 
+if (android_ndk_path != "") {
+  unix_toolchain("stage2_android_aarch64") {
+    cc = "bin/clang"
+    cxx = "bin/clang++"
+    ld = cxx
+    ar = "bin/llvm-ar"
+
+    deps = [
+      "//:clang($host_toolchain)",
+      "//:lld($host_toolchain)",
+      "//:llvm-ar($host_toolchain)",
+    ]
+
+    toolchain_args = {
+      current_os = "android"
+    }
+
+    libcxx_path = "$android_ndk_path/sources/cxx-stl/llvm-libc++"
+    platform_lib_path =
+        "$android_ndk_path/platforms/android-21/arch-arm64/usr/lib"
+    libgcc_path = "$android_ndk_path/toolchains/aarch64-linux-android-4.9/prebuilt/linux-x86_64/lib/gcc/aarch64-linux-android/4.9.x"
+
+    target_flags =
+        "--target=aarch64-linux-android21 --sysroot=$android_ndk_path/sysroot"
+    target_cflags = "$target_flags -isystem $libcxx_path/include"
+    target_ldflags = "$target_flags -fuse-ld=lld -B$platform_lib_path -L$platform_lib_path -L$libgcc_path"
+    target_ldflags +=
+        " -nostdlib++ -L$libcxx_path/libs/arm64-v8a -l:libc++.a.21"
+  }
+}
+
 toolchain("win") {
   cl = "cl"
   link = "link"
diff --git a/llvm/utils/gn/build/toolchain/compiler.gni b/llvm/utils/gn/build/toolchain/compiler.gni
index 92d965ef967..c7e89b32a74 100644
--- a/llvm/utils/gn/build/toolchain/compiler.gni
+++ b/llvm/utils/gn/build/toolchain/compiler.gni
@@ -9,6 +9,10 @@ declare_args() {
   # On Windows, setting this also causes lld-link to be used as linker.
   # Example value: getenv("HOME") + "/src/llvm-build/Release+Asserts"
   clang_base_path = ""
+
+  # Set this to the path to Android NDK r18b. If set, cross compilation targeting
+  # Android will be enabled.
+  android_ndk_path = ""
 }
 
 declare_args() {