Include libclang_rt.builtins.a for Fuchsia

Based on https://codereview.chromium.org/2897463003/.

Test: Run update.py --force-local-build, remove https://cs.chromium.org/chromium/src/build/config/fuchsia/BUILD.gn?l=41 and referenced files, and rebuild some Fuchsia binaries
Test: Run package.py and verify the .a's are included.
Bug: 724204
Change-Id: If1492138829846a0f970d034f28a84d517554401
Reviewed-on: https://chromium-review.googlesource.com/1211879Reviewed-by: Nico Weber <thakis@chromium.org>
Commit-Queue: Scott Graham <scottmg@chromium.org>
Cr-Commit-Position: refs/heads/master@{#590521}

build/config/fuchsia/BUILD.gn

@@ -30,16 +30,6 @@ config("compiler") {
   asmflags = cflags
 
   ldflags += [
-    # TODO(thakis): Once Fuchsia's libclang_rt.builtin no longer has upstream
-    # patches, we might want to make tools/clang/scripts/update.py build it
-    # and bundle it with the clang package instead of using the library from
-    # the SDK, https://crbug.com/724204
-    # Note: Intentionally 8.0.0 instead of $clang_version because the clang
-    # version of the toolchain_libs directory in the Fuchsia SDK can be
-    # different from the version of Chromium's clang.
-    "-resource-dir",
-    rebase_path(fuchsia_sdk, root_build_dir) + "/toolchain_libs/clang/8.0.0",
-
     # The stack defaults to 256k on Fuchsia (see
     # https://fuchsia.googlesource.com/zircon/+/master/system/private/zircon/stack.h#9),
     # but on other platforms it's much higher, so a variety of code assumes more

tools/clang/scripts/package.py

@@ -282,6 +282,12 @@ def main():
                  'lib/clang/*/lib/windows/clang_rt.ubsan*.lib',
                  ])
 
+  if sys.platform in ('linux2', 'darwin'):
+    # Include libclang_rt.builtins.a for Fuchsia targets.
+    want.extend(['lib/clang/*/aarch64-fuchsia/lib/libclang_rt.builtins.a',
+                 'lib/clang/*/x86_64-fuchsia/lib/libclang_rt.builtins.a',
+                 ])
+
   for root, dirs, files in os.walk(LLVM_RELEASE_DIR):
     # root: third_party/llvm-build/Release+Asserts/lib/..., rel_root: lib/...
     rel_root = root[len(LLVM_RELEASE_DIR)+1:]

tools/clang/scripts/update.py

@@ -35,7 +35,7 @@ if use_head_revision:
   CLANG_REVISION = 'HEAD'
 
 # This is incremented when pushing a new build of Clang at the same revision.
-CLANG_SUB_REVISION=1
+CLANG_SUB_REVISION=2
 
 PACKAGE_VERSION = "%s-%s" % (CLANG_REVISION, CLANG_SUB_REVISION)
 
@@ -71,6 +71,8 @@ STAMP_FILE = os.path.normpath(
 VERSION = '8.0.0'
 ANDROID_NDK_DIR = os.path.join(
     CHROMIUM_DIR, 'third_party', 'android_ndk')
+FUCHSIA_SDK_DIR = os.path.join(CHROMIUM_DIR, 'third_party', 'fuchsia-sdk',
+                               'sdk')
 
 # URL for pre-built binaries.
 CDS_URL = os.environ.get('CDS_CLANG_BUCKET_OVERRIDE',
@@ -483,6 +485,16 @@ def UpdateClang(args):
     print 'for how to install the NDK, or pass --without-android.'
     return 1
 
+  if args.with_fuchsia and not os.path.exists(FUCHSIA_SDK_DIR):
+    print 'Fuchsia SDK not found at ' + FUCHSIA_SDK_DIR
+    print 'The Fuchsia SDK is needed to build libclang_rt for Fuchsia.'
+    print 'Install the Fuchsia SDK by adding fuchsia to the '
+    print 'target_os section in your .gclient and running hooks, '
+    print 'or pass --without-fuchsia.'
+    print 'https://chromium.googlesource.com/chromium/src/+/master/docs/fuchsia_build_instructions.md'
+    print 'for general Fuchsia build instructions.'
+    return 1
+
   print 'Locally building Clang %s...' % PACKAGE_VERSION
 
   AddCMakeToPath(args)
@@ -816,6 +828,57 @@ def UpdateClang(args):
       if os.path.exists(lib_path):
         shutil.copy(lib_path, rt_lib_dst_dir)
 
+  if args.with_fuchsia:
+    # Fuchsia links against libclang_rt.builtins-<arch>.a instead of libgcc.a.
+    for target_arch in ['aarch64', 'x86_64']:
+      fuchsia_arch_name = {'aarch64': 'arm64', 'x86_64': 'x64'}[target_arch]
+      toolchain_dir = os.path.join(
+          FUCHSIA_SDK_DIR, 'arch', fuchsia_arch_name, 'sysroot')
+      # Build clang_rt runtime for Fuchsia in a separate build tree.
+      build_dir = os.path.join(LLVM_BUILD_DIR, 'fuchsia-' + target_arch)
+      if not os.path.exists(build_dir):
+        os.mkdir(os.path.join(build_dir))
+      os.chdir(build_dir)
+      target_spec = target_arch + '-fuchsia'
+      # TODO(thakis): Might have to pass -B here once sysroot contains
+      # binaries (e.g. gas for arm64?)
+      fuchsia_args = base_cmake_args + [
+        '-DLLVM_ENABLE_THREADS=OFF',
+        '-DCMAKE_C_COMPILER=' + os.path.join(LLVM_BUILD_DIR, 'bin/clang'),
+        '-DCMAKE_CXX_COMPILER=' + os.path.join(LLVM_BUILD_DIR, 'bin/clang++'),
+        '-DCMAKE_LINKER=' + os.path.join(LLVM_BUILD_DIR, 'bin/clang'),
+        '-DCMAKE_AR=' + os.path.join(LLVM_BUILD_DIR, 'bin/llvm-ar'),
+        '-DLLVM_CONFIG_PATH=' + os.path.join(LLVM_BUILD_DIR, 'bin/llvm-config'),
+        '-DCMAKE_SYSTEM_NAME=Fuchsia',
+        '-DCMAKE_C_COMPILER_TARGET=%s-fuchsia' % target_arch,
+        '-DCMAKE_ASM_COMPILER_TARGET=%s-fuchsia' % target_arch,
+        '-DCOMPILER_RT_DEFAULT_TARGET_ONLY=ON',
+        '-DCMAKE_SYSROOT=%s' % toolchain_dir,
+        # TODO(thakis|scottmg): Use PER_TARGET_RUNTIME_DIR for all platforms.
+        # https://crbug.com/882485.
+        '-DLLVM_ENABLE_PER_TARGET_RUNTIME_DIR=ON',
+
+        # These are necessary because otherwise CMake tries to build an
+        # executable to test to see if the compiler is working, but in doing so,
+        # it links against the builtins.a that we're about to build.
+        '-DCMAKE_C_COMPILER_WORKS=ON',
+        '-DCMAKE_ASM_COMPILER_WORKS=ON',
+        ]
+      RmCmakeCache('.')
+      RunCommand(['cmake'] +
+                 fuchsia_args +
+                 [os.path.join(COMPILER_RT_DIR, 'lib', 'builtins')])
+      builtins_a = 'libclang_rt.builtins.a'
+      RunCommand(['ninja', builtins_a])
+
+      # And copy it into the main build tree.
+      fuchsia_lib_dst_dir = os.path.join(LLVM_BUILD_DIR, 'lib', 'clang',
+                                         VERSION, target_spec, 'lib')
+      if not os.path.exists(fuchsia_lib_dst_dir):
+        os.makedirs(fuchsia_lib_dst_dir)
+      CopyFile(os.path.join(build_dir, target_spec, 'lib', builtins_a),
+               fuchsia_lib_dst_dir)
+
   # Run tests.
   if args.run_tests or use_head_revision:
     os.chdir(LLVM_BUILD_DIR)
@@ -869,6 +932,10 @@ def main():
                       help='don\'t build Android ASan runtime (linux only)',
                       dest='with_android',
                       default=sys.platform.startswith('linux'))
+  parser.add_argument('--without-fuchsia', action='store_false',
+                      help='don\'t build Fuchsia clang_rt runtime (linux/mac)',
+                      dest='with_fuchsia',
+                      default=sys.platform in ('linux2', 'darwin'))
   args = parser.parse_args()
 
   if args.lto_lld and not args.bootstrap:
@@ -921,6 +988,8 @@ def main():
     if 'OS=android' not in os.environ.get('GYP_DEFINES', ''):
       # Only build the Android ASan rt on ToT bots when targetting Android.
       args.with_android = False
+    # Don't build fuchsia runtime on ToT bots at all.
+    args.with_fuchsia = False
 
   return UpdateClang(args)