[linux] Improve link time with Chromium-bundled binutils.

Also enabled concurrent linking with gold on Linux.

Mostly copy and paste from Chromium with customization for
V8 where necessary.

BUG=v8:3880
LOG=n

Review URL: https://codereview.chromium.org/896703003

Cr-Commit-Position: refs/heads/master@{#26536}

DEPS

@@ -80,6 +80,17 @@ hooks = [
                 "-s", "v8/buildtools/linux64/clang-format.sha1",
     ],
   },
+  # Pull binutils for linux, enabled debug fission for faster linking /
+  # debugging when used with clang on Ubuntu Precise.
+  # https://code.google.com/p/chromium/issues/detail?id=352046
+  {
+    'name': 'binutils',
+    'pattern': 'v8/third_party/binutils',
+    'action': [
+        'python',
+        'v8/third_party/binutils/download.py',
+    ],
+  },
   {
     # Pull clang if needed or requested via GYP_DEFINES.
     # Note: On Win, this should run after win_toolchain, as it may use it.

build/toolchain.gypi

@@ -86,6 +86,46 @@
     # Allow to suppress the array bounds warning (default is no suppression).
     'wno_array_bounds%': '',
 
+    # Override where to find binutils
+    'binutils_dir%': '',
+
+    'conditions': [
+      ['OS=="linux" and host_arch=="x64"', {
+        'binutils_dir%': 'third_party/binutils/Linux_x64/Release/bin',
+      }],
+      ['OS=="linux" and host_arch=="ia32"', {
+        'binutils_dir%': 'third_party/binutils/Linux_ia32/Release/bin',
+      }],
+
+      # linux_use_bundled_gold: whether to use the gold linker binary checked
+      # into third_party/binutils.  Force this off via GYP_DEFINES when you
+      # are using a custom toolchain and need to control -B in ldflags.
+      # Do not use 32-bit gold on 32-bit hosts as it runs out address space
+      # for component=static_library builds.
+      ['OS=="linux" and (target_arch=="x64" or target_arch=="arm")', {
+        'linux_use_bundled_gold%': 1,
+      }, {
+        'linux_use_bundled_gold%': 0,
+      }],
+      # linux_use_bundled_binutils: whether to use the binary binutils
+      # checked into third_party/binutils.  These are not multi-arch so cannot
+      # be used except on x86 and x86-64 (the only two architectures which
+      # are currently checke in).  Force this off via GYP_DEFINES when you
+      # are using a custom toolchain and need to control -B in cflags.
+      ['OS=="linux" and (target_arch=="ia32" or target_arch=="x64")', {
+        'linux_use_bundled_binutils%': 1,
+      }, {
+        'linux_use_bundled_binutils%': 0,
+      }],
+      # linux_use_gold_flags: whether to use build flags that rely on gold.
+      # On by default for x64 Linux.
+      ['OS=="linux" and target_arch=="x64"', {
+        'linux_use_gold_flags%': 1,
+      }, {
+        'linux_use_gold_flags%': 0,
+      }],
+    ],
+
     # Link-Time Optimizations
     'use_lto%': 0,
 
@@ -797,6 +837,26 @@
           '-mx32',
         ],
       }],  # v8_target_arch=="x32"
+      ['linux_use_gold_flags==1', {
+        # Newer gccs and clangs support -fuse-ld, use the flag to force gold
+        # selection.
+        # gcc -- http://gcc.gnu.org/onlinedocs/gcc-4.8.0/gcc/Optimize-Options.html
+        'ldflags': [ '-fuse-ld=gold', ],
+      }],
+      ['linux_use_bundled_binutils==1', {
+        'cflags': [
+          '-B<!(cd <(DEPTH) && pwd -P)/<(binutils_dir)',
+        ],
+      }],
+      ['linux_use_bundled_gold==1', {
+        # Put our binutils, which contains gold in the search path. We pass
+        # the path to gold to the compiler. gyp leaves unspecified what the
+        # cwd is when running the compiler, so the normal gyp path-munging
+        # fails us. This hack gets the right path.
+        'ldflags': [
+          '-B<!(cd <(DEPTH) && pwd -P)/<(binutils_dir)',
+        ],
+      }],
       ['OS=="win"', {
         'defines': [
           'WIN32',
@@ -1083,6 +1143,21 @@
               }],
             ],
           }],
+          ['linux_use_gold_flags==1', {
+            'target_conditions': [
+              ['_toolset=="target"', {
+                'ldflags': [
+                  # Experimentation found that using four linking threads
+                  # saved ~20% of link time.
+                  # https://groups.google.com/a/chromium.org/group/chromium-dev/browse_thread/thread/281527606915bb36
+                  # Only apply this to the target linker, since the host
+                  # linker might not be gold, but isn't used much anyway.
+                  '-Wl,--threads',
+                  '-Wl,--thread-count=4',
+                ],
+              }],
+            ],
+          }],
         ],
       },  # DebugBaseCommon
       'Debug': {

third_party/binutils/Linux_ia32/binutils.tar.bz2.sha1

+fd80d8d02666517d0781d3039499b4131e5d3e4e
\ No newline at end of file

third_party/binutils/Linux_x64/binutils.tar.bz2.sha1

+905e9e6eb9b0e11f0587177cfbaf9f7822736f34
\ No newline at end of file

third_party/binutils/download.py

+#!/usr/bin/env python
+# Copyright 2014 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+# vim: set ts=2 sw=2 et sts=2 ai:
+
+"""Minimal tool to download binutils from Google storage.
+
+TODO(mithro): Replace with generic download_and_extract tool.
+"""
+
+import os
+import platform
+import re
+import shutil
+import subprocess
+import sys
+
+
+BINUTILS_DIR = os.path.abspath(os.path.dirname(__file__))
+BINUTILS_FILE = 'binutils.tar.bz2'
+BINUTILS_TOOLS = ['bin/ld.gold', 'bin/objcopy', 'bin/objdump']
+BINUTILS_OUT = 'Release'
+
+DETECT_HOST_ARCH = os.path.abspath(os.path.join(
+    BINUTILS_DIR, '../../build/detect_v8_host_arch.py'))
+
+
+def ReadFile(filename):
+  with file(filename, 'r') as f:
+    return f.read().strip()
+
+
+def WriteFile(filename, content):
+  assert not os.path.exists(filename)
+  with file(filename, 'w') as f:
+    f.write(content)
+    f.write('\n')
+
+
+def GetArch():
+  gyp_host_arch = re.search(
+      'host_arch=(\S*)', os.environ.get('GYP_DEFINES', ''))
+  if gyp_host_arch:
+    arch = gyp_host_arch.group(1)
+    # This matches detect_host_arch.py.
+    if arch == 'x86_64':
+      return 'x64'
+    return arch
+
+  return subprocess.check_output(['python', DETECT_HOST_ARCH]).strip()
+
+
+def FetchAndExtract(arch):
+  archdir = os.path.join(BINUTILS_DIR, 'Linux_' + arch)
+  tarball = os.path.join(archdir, BINUTILS_FILE)
+  outdir = os.path.join(archdir, BINUTILS_OUT)
+
+  sha1file = tarball + '.sha1'
+  if not os.path.exists(sha1file):
+    print "WARNING: No binutils found for your architecture (%s)!" % arch
+    return 0
+
+  checksum = ReadFile(sha1file)
+
+  stampfile = tarball + '.stamp'
+  if os.path.exists(stampfile):
+    if (os.path.exists(tarball) and
+        os.path.exists(outdir) and
+        checksum == ReadFile(stampfile)):
+      return 0
+    else:
+      os.unlink(stampfile)
+
+  print "Downloading", tarball
+  subprocess.check_call([
+      'download_from_google_storage',
+      '--no_resume',
+      '--no_auth',
+      '--bucket', 'chromium-binutils',
+      '-s', sha1file])
+  assert os.path.exists(tarball)
+
+  if os.path.exists(outdir):
+    shutil.rmtree(outdir)
+  assert not os.path.exists(outdir)
+  os.makedirs(outdir)
+  assert os.path.exists(outdir)
+
+  print "Extracting", tarball
+  subprocess.check_call(['tar', 'axf', tarball], cwd=outdir)
+
+  for tool in BINUTILS_TOOLS:
+    assert os.path.exists(os.path.join(outdir, tool))
+
+  WriteFile(stampfile, checksum)
+  return 0
+
+
+def main(args):
+  if not sys.platform.startswith('linux'):
+    return 0
+
+  arch = GetArch()
+  if arch == 'x64':
+    return FetchAndExtract(arch)
+  if arch == 'ia32':
+    ret = FetchAndExtract(arch)
+    if ret != 0:
+      return ret
+    # Fetch the x64 toolchain as well for official bots with 64-bit kernels.
+    return FetchAndExtract('x64')
+  print "Host architecture %s is not supported." % arch
+  return 1
+
+
+if __name__ == '__main__':
+  sys.exit(main(sys.argv))