Add --enable-pgo option to build clang with PGO

tools/clang/scripts/update.py

Index: tools/clang/scripts/update.py
diff --git a/tools/clang/scripts/update.py b/tools/clang/scripts/update.py
index 2ea0d6d3d21b8651672061f4e6df6abc2cd3ae42..a71b4a5706c03b49a9b90880ae47b229ad233e27 100755
--- a/tools/clang/scripts/update.py
+++ b/tools/clang/scripts/update.py
@@ -283,7 +283,6 @@ def CreateChromeToolsShim():
     f.write('# two arg version to specify where build artifacts go. CMake\n')
     f.write('# disallows reuse of the same binary dir for multiple source\n')
     f.write('# dirs, so the build artifacts need to go into a subdirectory.\n')
-    f.write('# dirs, so the build artifacts need to go into a subdirectory.\n')

[Nico, 2017/04/07 15:58:53]

Also a good change, but also unrelated.

     f.write('if (CHROMIUM_TOOLS_SRC)\n')
     f.write('  add_subdirectory(${CHROMIUM_TOOLS_SRC} ' +
               '${CMAKE_CURRENT_BINARY_DIR}/a)\n')
@@ -376,6 +375,62 @@ def CopyDiaDllTo(target_dir):
   CopyFile(dia_dll, target_dir)
 
 
+def GetNewCCAndCXX(install_dir):
+  if sys.platform == 'win32':
+    cc = os.path.join(install_dir, 'bin', 'clang-cl.exe')
+    cxx = os.path.join(install_dir, 'bin', 'clang-cl.exe')
+    # CMake has a hard time with backslashes in compiler paths:
+    # https://stackoverflow.com/questions/13050827
+    cc = cc.replace('\\', '/')
+    cxx = cxx.replace('\\', '/')
+  else:
+    cc = os.path.join(install_dir, 'bin', 'clang')
+    cxx = os.path.join(install_dir, 'bin', 'clang++')
+
+  return cc, cxx
+
+
+def BuildLLVMgold(args, install_dir, base_cmake_args, binutils_incdir, cc, cxx):
+  # Build LLVM gold plugin with LTO. That speeds up the linker by ~10%.
+  # We only use LTO for Linux now.
+  print 'Building LTO LLVM Gold plugin'
+  if os.path.exists(LLVM_LTO_GOLD_PLUGIN_DIR):
+    RmTree(LLVM_LTO_GOLD_PLUGIN_DIR)
+  EnsureDirExists(LLVM_LTO_GOLD_PLUGIN_DIR)
+  os.chdir(LLVM_LTO_GOLD_PLUGIN_DIR)
+
+  # Create a symlink to LLVMgold.so build in the previous step so that ar
+  # and ranlib could find it while linking LLVMgold.so with LTO.
+  EnsureDirExists(BFD_PLUGINS_DIR)
+  RunCommand(['ln', '-sf',
+              os.path.join(install_dir, 'lib', 'LLVMgold.so'),
+              os.path.join(BFD_PLUGINS_DIR, 'LLVMgold.so')])
+
+  lto_cflags = ['-flto=thin']
+  lto_ldflags = ['-fuse-ld=lld']
+  if args.gcc_toolchain:
+    # Tell the bootstrap compiler to use a specific gcc prefix to search
+    # for standard library headers and shared object files.
+    lto_cflags += ['--gcc-toolchain=' + args.gcc_toolchain]
+  lto_cmake_args = base_cmake_args + [
+      '-DLLVM_BINUTILS_INCDIR=' + binutils_incdir,
+      '-DCMAKE_C_COMPILER=' + cc,
+      '-DCMAKE_CXX_COMPILER=' + cxx,
+      '-DCMAKE_C_FLAGS=' + ' '.join(lto_cflags),
+      '-DCMAKE_CXX_FLAGS=' + ' '.join(lto_cflags),
+      '-DCMAKE_EXE_LINKER_FLAGS=' + ' '.join(lto_ldflags),
+      '-DCMAKE_SHARED_LINKER_FLAGS=' + ' '.join(lto_ldflags),
+      '-DCMAKE_MODULE_LINKER_FLAGS=' + ' '.join(lto_ldflags)]
+
+  # We need to use the proper binutils which support LLVM Gold plugin.
+  lto_env = os.environ.copy()
+  lto_env['PATH'] = BINUTILS_BIN_DIR + os.pathsep + lto_env.get('PATH', '')
+
+  RmCmakeCache('.')
+  RunCommand(['cmake'] + lto_cmake_args + [LLVM_DIR], env=lto_env)
+  RunCommand(['ninja', 'LLVMgold', 'lld'], env=lto_env)
+
+
 def VeryifyVersionOfBuiltClangMatchesVERSION():
   """Checks that `clang --version` outputs VERSION.  If this fails, VERSION
   in this file is out-of-date and needs to be updated (possibly in an
@@ -464,6 +519,10 @@ def UpdateClang(args):
     # make sure it's not around on future builds.
     RmTree(LLD_DIR)
   Checkout('compiler-rt', LLVM_REPO_URL + '/compiler-rt/trunk', COMPILER_RT_DIR)
+  if args.enable_pgo and sys.platform != 'win32':
+    # PGO requires compiler-rt.
+    Checkout('compiler-rt', LLVM_REPO_URL + '/compiler-rt/trunk',
+             os.path.join(LLVM_DIR, 'projects', 'compiler-rt'))

[Nico, 2017/04/07 15:58:53]

IIRC package.py packages based on blacklists instead of whitelists – have you
checked we don't bundle more stuff due to this being present?

[matthewtff.asm, 2017/04/11 12:14:43]

The only diff I've got is one header file:
lib/clang/5.0.0/include/xray/xray_interface.h

I beleive it's ok to bundle this one since it's size is 3KB

   if sys.platform == 'darwin':
     # clang needs a libc++ checkout, else -stdlib=libc++ won't find includes
     # (i.e. this is needed for bootstrap builds).
@@ -530,17 +589,7 @@ def UpdateClang(args):
       # Copy that gcc's stdlibc++.so.6 to the build dir, so the bootstrap
       # compiler can start.
       CopyFile(libstdcpp, os.path.join(LLVM_BOOTSTRAP_INSTALL_DIR, 'lib'))
-
-    if sys.platform == 'win32':
-      cc = os.path.join(LLVM_BOOTSTRAP_INSTALL_DIR, 'bin', 'clang-cl.exe')
-      cxx = os.path.join(LLVM_BOOTSTRAP_INSTALL_DIR, 'bin', 'clang-cl.exe')
-      # CMake has a hard time with backslashes in compiler paths:
-      # https://stackoverflow.com/questions/13050827
-      cc = cc.replace('\\', '/')
-      cxx = cxx.replace('\\', '/')
-    else:
-      cc = os.path.join(LLVM_BOOTSTRAP_INSTALL_DIR, 'bin', 'clang')
-      cxx = os.path.join(LLVM_BOOTSTRAP_INSTALL_DIR, 'bin', 'clang++')
+    cc, cxx = GetNewCCAndCXX(LLVM_BOOTSTRAP_INSTALL_DIR)
 
     if args.gcc_toolchain:
       # Tell the bootstrap compiler to use a specific gcc prefix to search
@@ -549,46 +598,9 @@ def UpdateClang(args):
       cxxflags = ['--gcc-toolchain=' + args.gcc_toolchain]
     print 'Building final compiler'
 
-  # Build LLVM gold plugin with LTO. That speeds up the linker by ~10%.
-  # We only use LTO for Linux now.
   if args.bootstrap and args.lto_gold_plugin:

[Nico, 2017/04/07 15:58:53]

This is now never true (assuming we default to PGO) since we only pass
--bootstrap on Windows and lto_gold_plugin is only true on Linux.

-    print 'Building LTO LLVM Gold plugin'
-    if os.path.exists(LLVM_LTO_GOLD_PLUGIN_DIR):
-      RmTree(LLVM_LTO_GOLD_PLUGIN_DIR)
-    EnsureDirExists(LLVM_LTO_GOLD_PLUGIN_DIR)
-    os.chdir(LLVM_LTO_GOLD_PLUGIN_DIR)
-
-    # Create a symlink to LLVMgold.so build in the previous step so that ar
-    # and ranlib could find it while linking LLVMgold.so with LTO.
-    EnsureDirExists(BFD_PLUGINS_DIR)
-    RunCommand(['ln', '-sf',
-                os.path.join(LLVM_BOOTSTRAP_INSTALL_DIR, 'lib', 'LLVMgold.so'),
-                os.path.join(BFD_PLUGINS_DIR, 'LLVMgold.so')])
-
-    lto_cflags = ['-flto=thin']
-    lto_ldflags = ['-fuse-ld=lld']
-    if args.gcc_toolchain:
-      # Tell the bootstrap compiler to use a specific gcc prefix to search
-      # for standard library headers and shared object files.
-      lto_cflags += ['--gcc-toolchain=' + args.gcc_toolchain]
-    lto_cmake_args = base_cmake_args + [
-        '-DLLVM_BINUTILS_INCDIR=' + binutils_incdir,
-        '-DCMAKE_C_COMPILER=' + cc,
-        '-DCMAKE_CXX_COMPILER=' + cxx,
-        '-DCMAKE_C_FLAGS=' + ' '.join(lto_cflags),
-        '-DCMAKE_CXX_FLAGS=' + ' '.join(lto_cflags),
-        '-DCMAKE_EXE_LINKER_FLAGS=' + ' '.join(lto_ldflags),
-        '-DCMAKE_SHARED_LINKER_FLAGS=' + ' '.join(lto_ldflags),
-        '-DCMAKE_MODULE_LINKER_FLAGS=' + ' '.join(lto_ldflags)]
-
-    # We need to use the proper binutils which support LLVM Gold plugin.
-    lto_env = os.environ.copy()
-    lto_env['PATH'] = BINUTILS_BIN_DIR + os.pathsep + lto_env.get('PATH', '')
-
-    RmCmakeCache('.')
-    RunCommand(['cmake'] + lto_cmake_args + [LLVM_DIR], env=lto_env)
-    RunCommand(['ninja', 'LLVMgold', 'lld'], env=lto_env)
-
+    BuildLLVMgold(args, LLVM_BOOTSTRAP_INSTALL_DIR, binutils_incdir,
+                  base_cmake_args, cc, cxx)
 
   # LLVM uses C++11 starting in llvm 3.5. On Linux, this means libstdc++4.7+ is
   # needed, on OS X it requires libc++. clang only automatically links to libc++
@@ -596,7 +608,7 @@ def UpdateClang(args):
   # on OS X versions as old as 10.7.
   deployment_target = ''
 
-  if sys.platform == 'darwin' and args.bootstrap:
+  if sys.platform == 'darwin' and (args.bootstrap or args.enable_pgo):
     # When building on 10.9, /usr/include usually doesn't exist, and while
     # Xcode's clang automatically sets a sysroot, self-built clangs don't.
     cflags = ['-isysroot', subprocess.check_output(
@@ -604,10 +616,11 @@ def UpdateClang(args):
     cxxflags = ['-stdlib=libc++'] + cflags
     ldflags += ['-stdlib=libc++']
     deployment_target = '10.7'
-    # Running libc++ tests takes a long time. Since it was only needed for
-    # the install step above, don't build it as part of the main build.
-    # This makes running package.py over 10% faster (30 min instead of 34 min)
-    RmTree(LIBCXX_DIR)
+    if not args.enable_pgo:

[Nico, 2017/04/07 15:58:53]

Why this change?

[matthewtff.asm, 2017/04/11 12:14:43]

We need to build clang with libcxx checked out in tree to get standart include
files. Previously those used to be copied from bootstrap build, but now it's no
longer possible.
Actually 4 minutes are no longer an issue as with PGO build takes much more than
30min :(

+      # Running libc++ tests takes a long time. Since it was only needed for
+      # the install step above, don't build it as part of the main build.
+      # This makes running package.py over 10% faster (30 min instead of 34 min)
+      RmTree(LIBCXX_DIR)
 
   # Build clang.
 
@@ -638,6 +651,30 @@ def UpdateClang(args):
   if cc is not None:  cc_args.append('-DCMAKE_C_COMPILER=' + cc)
   if cxx is not None: cc_args.append('-DCMAKE_CXX_COMPILER=' + cxx)
   chrome_tools = list(set(['plugins', 'blink_gc_plugin'] + args.extra_tools))
+
+
+  if args.enable_pgo:
+    pgo_cache_path = os.path.join(
+        LLVM_DIR, 'tools', 'clang', 'cmake', 'caches', 'PGO.cmake')
+    pgo_stage2_cache = os.path.join(
+        CHROMIUM_DIR, 'tools', 'clang', 'PGO-stage2.cmake')
+    cmake_args += [
+        '-DBOOTSTRAP_BOOTSTRAP_CHROMIUM_TOOLS=%s' % ','.join(chrome_tools),
+        '-DCMAKE_VERBOSE_MAKEFILE=ON',
+        '-DBOOTSTRAP_CMAKE_VERBOSE_MAKEFILE=ON',
+        '-DBOOTSTRAP_BOOTSTRAP_CMAKE_VERBOSE_MAKEFILE=ON',
+        '-DPGO_BUILD_CONFIGURATION=%s' % pgo_stage2_cache,
+        '-C', pgo_cache_path,
+        '-DBOOTSTRAP_LLVM_BINUTILS_INCDIR=' + binutils_incdir,
+        '-DBOOTSTRAP_CMAKE_C_FLAGS=' + ' '.join(cflags),
+        '-DBOOTSTRAP_CMAKE_CXX_FLAGS=' + ' '.join(cxxflags),
+        '-DBOOTSTRAP_BOOTSTRAP_LLVM_BINUTILS_INCDIR=' + binutils_incdir,
+        '-DBOOTSTRAP_BOOTSTRAP_CMAKE_C_FLAGS=' + ' '.join(cflags),
+        '-DBOOTSTRAP_BOOTSTRAP_CMAKE_CXX_FLAGS=' + ' '.join(cxxflags),
+        '-DBOOTSTRAP_BOOTSTRAP_CMAKE_EXE_LINKER_FLAGS=' + ' '.join(ldflags),
+        '-DBOOTSTRAP_BOOTSTRAP_CMAKE_SHARED_LINKER_FLAGS=' + ' '.join(ldflags),
+        '-DBOOTSTRAP_BOOTSTRAP_CMAKE_MODULE_LINKER_FLAGS=' + ' '.join(ldflags),
+    ]
   cmake_args += base_cmake_args + [
       '-DLLVM_ENABLE_THREADS=OFF',
       '-DLLVM_BINUTILS_INCDIR=' + binutils_incdir,
@@ -651,7 +688,7 @@ def UpdateClang(args):
       # explicitly, https://crbug.com/622775
       '-DENABLE_LINKER_BUILD_ID=ON',
       '-DCHROMIUM_TOOLS_SRC=%s' % os.path.join(CHROMIUM_DIR, 'tools', 'clang'),
-      '-DCHROMIUM_TOOLS=%s' % ';'.join(chrome_tools)]
+      '-DCHROMIUM_TOOLS=%s' % ','.join(chrome_tools)]
 
   EnsureDirExists(LLVM_BUILD_DIR)
   os.chdir(LLVM_BUILD_DIR)
@@ -659,6 +696,14 @@ def UpdateClang(args):
   RunCommand(['cmake'] + cmake_args + [LLVM_DIR],
              msvc_arch='x64', env=deployment_env)
 
+  ninja_target = 'stage2' if args.enable_pgo else 'all'
+  RunCommand(['ninja', ninja_target], env=deployment_env, msvc_arch='x64')
+
+  if args.enable_pgo:
+    global LLVM_BUILD_DIR
+    LLVM_BUILD_DIR = os.path.join(LLVM_BUILD_DIR, 'tools', 'clang',
+        'stage2-instrumented-bins', 'tools', 'clang', 'stage2-bins')
+
   if args.gcc_toolchain:
     # Copy in the right stdlibc++.so.6 so clang can start.
     if not os.path.exists(os.path.join(LLVM_BUILD_DIR, 'lib')):
@@ -667,17 +712,20 @@ def UpdateClang(args):
         [cxx] + cxxflags + ['-print-file-name=libstdc++.so.6']).rstrip()
     CopyFile(libstdcpp, os.path.join(LLVM_BUILD_DIR, 'lib'))
 
-  RunCommand(['ninja'], msvc_arch='x64')
-
-  # Copy LTO-optimized lld, if any.
-  if args.bootstrap and args.lto_gold_plugin:
-    CopyFile(os.path.join(LLVM_LTO_GOLD_PLUGIN_DIR, 'bin', 'lld'),
-             os.path.join(LLVM_BUILD_DIR, 'bin'))
-
   if chrome_tools:
     # If any Chromium tools were built, install those now.
     RunCommand(['ninja', 'cr-install'], msvc_arch='x64')
 
+  # Copy LTO-optimized lld, if any.
+  if args.lto_gold_plugin:
+    if args.enable_pgo:
+      cc, cxx = GetNewCCAndCXX(LLVM_BUILD_DIR)
+      BuildLLVMgold(args, LLVM_BUILD_DIR, base_cmake_args,
+                    binutils_incdir, cc, cxx)
+    if args.bootstrap or args.enable_pgo:
+      CopyFile(os.path.join(LLVM_LTO_GOLD_PLUGIN_DIR, 'bin', 'lld'),
+               os.path.join(LLVM_BUILD_DIR, 'bin'))
+
   if sys.platform == 'darwin':
     # See http://crbug.com/256342
     RunCommand(['strip', '-x', os.path.join(LLVM_BUILD_DIR, 'bin', 'clang')])
@@ -865,14 +913,25 @@ def main():
                       help='don\'t build Android ASan runtime (linux only)',
                       dest='with_android',
                       default=sys.platform.startswith('linux'))
+  parser.add_argument('--enable-pgo', action='store_true',
+                      help='build clang in 2 stages using PGO')
   args = parser.parse_args()
 
-  if args.lto_gold_plugin and not args.bootstrap:
-    print '--lto-gold-plugin requires --bootstrap'
+  if args.lto_gold_plugin and (not args.bootstrap and not args.enable_pgo):
+    print '--lto-gold-plugin requires --bootstrap or --enable-pgo'
     return 1
   if args.lto_gold_plugin and not sys.platform.startswith('linux'):
     print '--lto-gold-plugin is only effective on Linux. Ignoring the option.'
     args.lto_gold_plugin = False
+  if args.enable_pgo:
+    if args.bootstrap:
+      print '--bootstrap makes no sense with --enable-pgo specified'
+      return 1
+    if not args.force_local_build:
+      print '--enable-pgo makes no sense without --force-local-build'
+      return 1
+    if sys.platform == 'win32':
+      print '--enable-pgo not supported on Windows'
 
   if args.if_needed:
     # TODO(thakis): Can probably remove this and --if-needed altogether.