gn build: Add a stage2 host toolchain and make the hwasan runtime buildable on x86_64 Linux.

llvm/utils/gn/build/toolchain/BUILD.gn

unix_toolchain("unix") {
   }
 
   toolchain_args = {
     current_os = host_os
     current_cpu = host_cpu
   }
 }
 
-if (android_ndk_path != "") {
-  unix_toolchain("stage2_android_aarch64") {
+template("stage2_unix_toolchain") {
+  unix_toolchain(target_name) {
+    forward_variables_from(invoker, "*")
+
     cc = "bin/clang"
     cxx = "bin/clang++"
     ld = cxx
     ar = "bin/llvm-ar"
 
     deps = [
       "//:clang($host_toolchain)",
       "//:lld($host_toolchain)",
       "//:llvm-ar($host_toolchain)",
     ]
+  }
+}
+
+stage2_unix_toolchain("stage2_unix") {
+  toolchain_args = {
+    current_os = host_os
+    current_cpu = host_cpu
+    use_lld = host_os != "mac"
+  }
+}
 
+if (android_ndk_path != "") {
+  stage2_unix_toolchain("stage2_android_aarch64") {
     toolchain_args = {
       current_os = "android"
       current_cpu = "arm64"
       use_lld = true
     }
   }
 }
 

llvm/utils/gn/secondary/BUILD.gn

 import("//clang/lib/ARCMigrate/enable.gni")
 import("//clang/lib/StaticAnalyzer/Frontend/enable.gni")
 import("//llvm/utils/gn/build/toolchain/compiler.gni")
 
 group("default") {
   deps = [
     "//clang/test",
     "//lld/test",
     "//llvm/test",
   ]
 
-  if (android_ndk_path != "") {
-    # FIXME: This should be a dependency of a test target instead of being
-    # depended on from here.
+  if (android_ndk_path != "") {
     android_aarch64_toolchain =
         "//llvm/utils/gn/build/toolchain:stage2_android_aarch64"
     deps += [
       "//compiler-rt/lib/hwasan:hwasan_shared($android_aarch64_toolchain)",
       "//llvm/tools/llvm-symbolizer($android_aarch64_toolchain)",
     ]
   }
+  if (host_cpu == "x64" && host_os == "linux") {
+    deps += [ "//compiler-rt/lib/hwasan:hwasan_shared(//llvm/utils/gn/build/toolchain:stage2_unix)" ]
+  }
 
   testonly = true
 }
 
 # Symlink handling.
 # On POSIX, symlinks to the target can be created before the target exist,
 # and the target can depend on the symlink targets, so that building the
 # target ensures the symlinks exist.

llvm/utils/gn/secondary/compiler-rt/lib/hwasan/BUILD.gn

-import("//llvm/resource_dir.gni")
-
-# FIXME: Make this support more platforms.
-assert(current_os == "android")
-
-runtime_output_dir = "$llvm_resource_dir/lib/linux"
-runtime_target = "aarch64-android"
+import("//compiler-rt/target.gni")
 
 action("version_script") {
   script = "//compiler-rt/lib/sanitizer_common/scripts/gen_dynamic_list.py"
   sources = [
     "hwasan.syms.extra",
   ]
   deps = [
     ":hwasan",
     ":hwasan_cxx",
   ]
   outputs = [
     "$target_gen_dir/hwasan.vers",
   ]
   args = [
     "--version-list",
     "--extra",
     rebase_path(sources[0], root_build_dir),
-    rebase_path("$runtime_output_dir/libclang_rt.hwasan-$runtime_target.a",
+    rebase_path("$crt_current_out_dir/libclang_rt.hwasan-$crt_current_target.a",
                 root_build_dir),
-    rebase_path("$runtime_output_dir/libclang_rt.hwasan_cxx-$runtime_target.a",
-                root_build_dir),
+    rebase_path(
+        "$crt_current_out_dir/libclang_rt.hwasan_cxx-$crt_current_target.a",
     "-o",
     rebase_path(outputs[0], root_build_dir),
   ]
 }
 
 source_set("sources") {
   configs -= [ "//llvm/utils/gn/build:llvm_code" ]
   configs += [ "//llvm/utils/gn/build:crt_code" ]
deps = [
     "//compiler-rt/lib/ubsan:cxx_sources",
   ]
   sources = [
     "hwasan_new_delete.cc",
   ]
 }
 
 static_library("hwasan") {
-  output_dir = runtime_output_dir
-  output_name = "clang_rt.hwasan-$runtime_target"
+  output_dir = crt_current_out_dir
+  output_name = "clang_rt.hwasan-$crt_current_target"
   complete_static_lib = true
   configs -= [ "//llvm/utils/gn/build:llvm_code" ]
   configs += [ "//llvm/utils/gn/build:crt_code" ]
   deps = [
     ":sources",
   ]
 }
 
 static_library("hwasan_cxx") {
-  output_dir = runtime_output_dir
-  output_name = "clang_rt.hwasan_cxx-$runtime_target"
+  output_dir = crt_current_out_dir
+  output_name = "clang_rt.hwasan_cxx-$crt_current_target"
   complete_static_lib = true
   configs -= [ "//llvm/utils/gn/build:llvm_code" ]
   configs += [ "//llvm/utils/gn/build:crt_code" ]
   deps = [
     ":cxx_sources",
   ]
 }
 
 shared_library("hwasan_shared") {
-  output_dir = runtime_output_dir
-  output_name = "clang_rt.hwasan-$runtime_target"
+  output_dir = crt_current_out_dir
+  output_name = "clang_rt.hwasan-$crt_current_target"
   configs -= [ "//llvm/utils/gn/build:llvm_code" ]
   configs += [ "//llvm/utils/gn/build:crt_code" ]
   deps = [
     ":cxx_sources",
     ":sources",
     ":version_script",
   ]
   inputs = [
     "$target_gen_dir/hwasan.vers",
   ]
   ldflags = [
     "-Wl,--version-script," + rebase_path(inputs[0], root_build_dir),
     "-Wl,-z,global",
   ]
 }

llvm/utils/gn/secondary/compiler-rt/lib/sanitizer_common/BUILD.gn

 source_set("sources") {
   configs -= [ "//llvm/utils/gn/build:llvm_code" ]
   configs += [ "//llvm/utils/gn/build:crt_code" ]
+  deps = [
+    "//llvm/utils/gn/build/libs/pthread",
+  ]
+  libs = []
+  if (current_os == "linux" || current_os == "android") {
+    libs += [ "dl" ]
+  }
+  if (current_os == "linux") {
+    libs += [ "rt" ]
+  }
   sources = [
     "sancov_flags.cc",
     "sanitizer_allocator.cc",
     "sanitizer_allocator_checks.cc",
     "sanitizer_allocator_report.cc",
     "sanitizer_common.cc",
     "sanitizer_common_libcdep.cc",
     "sanitizer_coverage_fuchsia.cc",
sources = [
     "sanitizer_symbolizer_win.cc",
     "sanitizer_termination.cc",
     "sanitizer_thread_registry.cc",
     "sanitizer_tls_get_addr.cc",
     "sanitizer_unwind_linux_libcdep.cc",
     "sanitizer_unwind_win.cc",
     "sanitizer_win.cc",
   ]
+  if (current_cpu == "x64") {
+    sources += [ "sanitizer_linux_x86_64.S" ]
+  }
 }

llvm/utils/gn/secondary/compiler-rt/target.gni

+import("//llvm/resource_dir.gni")
+
+if (current_os == "linux" || current_os == "android") {
+  crt_current_out_dir = "$llvm_resource_dir/lib/linux"
+} else {
+  assert(false, "unimplemented current_os " + current_os)
+}
+
+if (current_cpu == "x64") {
+  crt_current_target_arch = "x86_64"
+} else if (current_cpu == "arm64") {
+  crt_current_target_arch = "aarch64"
+} else {
+  assert(false, "unimplemented current_cpu " + current_cpu)
+}
+
+crt_current_target = crt_current_target_arch
+if (current_os == "android") {
+  crt_current_target += "-android"
+}