Remove support for using link order files on Windows

Since crrev.com/824529, we're using /call-graph-profile-sort instead,
which means the linker lays out the binary based on the PGO profile.

Bug: 1077279
Change-Id: I0f6a72902dd211fd0000deef4b9c76909db9782a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2550070
Commit-Queue: Hans Wennborg <hans@chromium.org>
Reviewed-by: Sébastien Marchand <sebmarchand@chromium.org>
Reviewed-by: Nico Weber <thakis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#829306}

.gitignore

@@ -83,10 +83,6 @@ vs-chromium-project.txt
 /chrome/android/profiles/local.txt
 /chrome/angle_unittests_run.xml
 /chrome/app/vector_icons/google_chrome/
-/chrome/build/chrome.x64.orderfile
-/chrome/build/chrome.x86.orderfile
-/chrome/build/chrome_child.x64.orderfile
-/chrome/build/chrome_child.x86.orderfile
 /chrome/build/pgo_profiles/
 /chrome/gl_tests_run.xml
 /chrome/gles2_conform_test_run.xml

DEPS

@@ -4459,20 +4459,6 @@ hooks = [
                '--bucket', 'chromium-webrtc-resources',
                '-d', 'src/third_party/opus/tests/resources'],
   },
-  # Pull order files for the win/clang build.
-  {
-    'name': 'orderfiles_win',
-    'pattern': '.',
-    'condition': 'checkout_win',
-    'action': [ 'python',
-                'src/third_party/depot_tools/download_from_google_storage.py',
-                '--no_resume',
-                '--no_auth',
-                '--num_threads=4',
-                '--bucket', 'chromium-browser-clang/orderfiles',
-                '-d', 'src/chrome/build',
-    ],
-  },
   {
     'name': 'apache_mac',
     'pattern': '\\.sha1',

build/config/BUILD.gn

@@ -266,10 +266,6 @@ group("common_deps") {
     public_deps += [ "//base/android/orderfile:orderfile_instrumentation" ]
   }
 
-  if (is_win && generate_order_files && !is_nacl) {
-    public_deps += [ "//tools/cygprofile_win" ]
-  }
-
   if (is_fuchsia) {
     public_deps +=
         [ "//third_party/fuchsia-sdk/sdk/build/config:runtime_library_group" ]

build/config/BUILDCONFIG.gn

@@ -361,11 +361,6 @@ if (is_android) {
       [ "//build/config/android:default_orderfile_instrumentation" ]
 }
 
-if (is_win) {
-  default_compiler_configs +=
-      [ "//build/config/win:default_cygprofile_instrumentation" ]
-}
-
 if (is_clang && !is_nacl) {
   default_compiler_configs += [
     "//build/config/clang:find_bad_constructs",

build/config/chrome_build.gni

@@ -7,10 +7,6 @@ declare_args() {
   # true means official Google Chrome branding (requires extra Google-internal
   # resources).
   is_chrome_branded = false
-
-  # Turn this on to generate order files. See
-  # https://chromium.googlesource.com/chromium/src/+/master/docs/win_order_files.md
-  generate_order_files = false
 }
 
 declare_args() {

build/config/compiler/BUILD.gn

@@ -176,7 +176,7 @@ declare_args() {
                                                        current_cpu == "x64"))))
 }
 
-if (is_win || is_android || (is_chromeos && is_chromeos_device)) {
+if (is_android || (is_chromeos && is_chromeos_device)) {
   # Set the path to use orderfile for linking Chrome
   # Note that this is for using only one orderfile for linking
   # the Chrome binary/library.
@@ -187,8 +187,6 @@ if (is_win || is_android || (is_chromeos && is_chromeos_device)) {
       # Allow downstream tools to set orderfile path with
       # another variable.
       chrome_orderfile_path = default_chrome_orderfile
-    } else if (is_win && is_clang && is_official_build) {
-      chrome_orderfile_path = "//chrome/build/chrome.$target_cpu.orderfile"
     } else if (is_chromeos && is_chromeos_device) {
       chrome_orderfile_path = "//chromeos/profiles/chromeos.orderfile.txt"
     }
@@ -2470,29 +2468,19 @@ if (is_chromeos && is_chromeos_device) {
   }
 }
 
-if (is_win || is_android || (is_chromeos && is_chromeos_device)) {
-  # Use orderfile for linking Chrome on win, android, and Chrome OS.
+if (is_android || (is_chromeos && is_chromeos_device)) {
+  # Use orderfile for linking Chrome on Android and Chrome OS.
   # This config enables using an orderfile for linking in LLD.
+  # TODO: Consider using call graph sort instead, at least on Android.
   config("chrome_orderfile_config") {
     if (chrome_orderfile_path != "" && !enable_call_graph_profile_sort) {
       assert(use_lld)
       _rebased_orderfile = rebase_path(chrome_orderfile_path, root_build_dir)
-      if (is_android || (is_chromeos && is_chromeos_device)) {
-        ldflags = [
-          "-Wl,--symbol-ordering-file",
-          "-Wl,$_rebased_orderfile",
-          "-Wl,--no-warn-symbol-ordering",
-        ]
-      } else {
-        ldflags = [
-          "/order:@$_rebased_orderfile",
-
-          # Ignore warnings about missing functions or functions not in their
-          # own section.
-          "/ignore:4037",
-          "/ignore:4065",
-        ]
-      }
+      ldflags = [
+        "-Wl,--symbol-ordering-file",
+        "-Wl,$_rebased_orderfile",
+        "-Wl,--no-warn-symbol-ordering",
+      ]
       inputs = [ chrome_orderfile_path ]
     }
   }

build/config/win/BUILD.gn

@@ -579,21 +579,3 @@ config("lean_and_mean") {
 config("nominmax") {
   defines = [ "NOMINMAX" ]
 }
-
-# Generating order files -------------------------------------------------------
-
-config("default_cygprofile_instrumentation") {
-  if (generate_order_files) {
-    assert(is_clang, "cygprofile instrumentation only works with clang")
-    assert(is_official_build, "order files should be made w/ official builds")
-    assert(!is_chrome_branded, "order files could leak internal symbol names")
-    configs = [ ":cygprofile_instrumentation" ]
-  }
-}
-
-config("cygprofile_instrumentation") {
-  cflags = [
-    "-Xclang",
-    "-finstrument-functions-after-inlining",
-  ]
-}

chrome/BUILD.gn

@@ -360,8 +360,6 @@ if (is_win) {
       "//content/public/app",
       "//headless:headless_renderer",
     ]
-
-    configs += [ "//build/config/compiler:chrome_orderfile_config" ]
   }
 
   copy("copy_first_run") {

chrome/build/OWNERS

-hans@chromium.org
-thakis@chromium.org
-
-per-file *.pgo.txt=liaoyuke@chromium.org
-per-file *.pgo.txt=sebmarchand@chromium.org
+liaoyuke@chromium.org
+sebmarchand@chromium.org

chrome/build/README

-See
-https://chromium.googlesource.com/chromium/src/+/master/docs/win_order_files.md
-for how to update the order files.

chrome/build/chrome.x64.orderfile.sha1

-d5482a02f41670416a7302b49e5e3f9dede25e61
\ No newline at end of file

chrome/build/chrome.x86.orderfile.sha1

-d00f8f154ccdf38ef8a3018ea5bb165e8b279c22
\ No newline at end of file

docs/win_order_files.md

 # Updating the Windows .order files
 
-The `chrome/build/*.orderfile` files are used to specify the order in which
-the linker should lay out symbols in the binary it's producing. By ordering
-functions in the order they're typically executed during start-up, the start-up
-time can be reduced slightly.
-
-The order files are used automatically when building with Clang for Windows with
-the gn flag `is_official_build` set to `true`.
-
-To update the order files:
-
-1.  Build with instrumentation enabled:
-
-    The instrumentation will capture the couple of million function calls
-    in a binary as it runs and write them to a file in the `\src\tmp` directory.
-    Make sure this directory exists.
-
-    ```shell
-    gn gen out\instrument --args="is_debug=false is_official_build=true generate_order_files=true symbol_level=1"
-    ninja -C out\instrument chrome
-    ```
-
-    (If you have access to Goma, add `use_goma=true` to the gn args and `-j500`
-    to the Ninja invocation.)
-
-
-1.  Run the instrumented binaries:
-
-    (Some binaries such as `mksnapshot`, `yasm`, and `protoc` already ran with
-    instrumentation during the build process. The instrumentation output should
-    be available under `\src\tmp`.)
-
-    Open the Task Manager's Details tab or
-    [Process Explorer](https://docs.microsoft.com/en-us/sysinternals/downloads/process-explorer)
-    to be able to see the Process IDs of running programs.
-
-    Run Chrome:
-
-    ```shell
-    out\instrument\chrome
-    ```
-
-    Note the Process ID of the browser process.
-
-    Check in `\src\tmp\` for instrumentation output from the process, for
-    example `cygprofile_14652.txt`. The files are only written once a certain
-    number of function calls have been made, so sometimes you need to browse a
-    bit for the file to be produced.
-
-1.  If the file appears to have sensible contents (a long list of function names
-    that eventually seem related to what the browser should
-    do), copy it into `chrome\build\`:
-
-    ```shell
-    copy \src\tmp\cygprofile_25392.txt chrome\build\chrome.x64.orderfile
-    ```
-
-1.  Re-build the `chrome` target. This will re-link `chrome.dll`
-    using the new order file and surface any link errors if
-    the order file is broken.
-
-    ```shell
-    ninja -C out\instrument chrome
-    ```
-
-
-1.  Repeat the previous steps with a 32-bit build, i.e. passing
-    `target_cpu="x86"` to gn and storing the file as `.x86.orderfile`.
-
-
-1.  Upload the order files to Google Cloud Storage. They will get downloaded
-    by a `gclient` hook based on the contents of the `.orderfile.sha1` files.
-
-    You need to have write access to the `chromium-browser-clang` GCS bucket
-    for this step.
-
-    ```shell
-    cd chrome\build\
-    upload_to_google_storage.py -b chromium-browser-clang/orderfiles -z orderfile chrome.x64.orderfile chrome.x86.orderfile
-    gsutil.py setacl public-read gs://chromium-browser-clang/orderfiles/*
-    ```
-
-
-1.  Check in the `.sha1` files corresponding to the orderfiles created by the
-    previous step.
+Since [#824529](https://crrev.com/824529), order files are no longer used for
+linking Chromium on Windows. Instead, the linker orders the binary contents
+based on profile-guided optimization (PGO) data, using LLD's call graph profile
+sort feature. That provides similar benefits and uses use the existing PGO
+infrastructure instead of requiring maintenance of the order files. See
+[crbug.com/1077279](https://crbug.com/1077279).

tools/cygprofile_win/BUILD.gn

-# Copyright 2017 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.
-
-static_library("cygprofile_win") {
-  sources = [ "cygprofile.cc" ]
-
-  # Don't instrument this library.
-  configs -= [ "//build/config/win:default_cygprofile_instrumentation" ]
-}

tools/cygprofile_win/OWNERS

-hans@chromium.org

tools/cygprofile_win/cygprofile.cc

-// Copyright (c) 2017 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.
-
-#include <stdio.h>
-#include <atomic>
-#include <string>
-#include <unordered_set>
-
-#include <windows.h>  // Needs to be included before the others.
-
-#include <dbghelp.h>
-#include <process.h>
-
-namespace {
-
-// The main purpose of the order file is to optimize startup time,
-// so capturing the first N function calls is enough.
-static constexpr int kSamplesCapacity = 25 * 1024 * 1024;
-
-void* samples[kSamplesCapacity];
-std::atomic_int num_samples;
-std::atomic_int done;
-
-// Path to the dump file. %lu will be substituted by the process id.
-static const char kDumpFile[] = "/src/tmp/cygprofile_%lu.txt";
-
-// Symbolize the samples and write them to disk.
-void dump(void*) {
-  HMODULE dbghelp = LoadLibraryA("dbghelp.dll");
-  auto sym_from_addr = reinterpret_cast<decltype(::SymFromAddr)*>(
-      ::GetProcAddress(dbghelp, "SymFromAddr"));
-  auto sym_initialize = reinterpret_cast<decltype(::SymInitialize)*>(
-      ::GetProcAddress(dbghelp, "SymInitialize"));
-  auto sym_set_options = reinterpret_cast<decltype(::SymSetOptions)*>(
-      ::GetProcAddress(dbghelp, "SymSetOptions"));
-
-  char filename[MAX_PATH];
-  snprintf(filename, sizeof(filename), kDumpFile, ::GetCurrentProcessId());
-  FILE* f = fopen(filename, "w");
-  if (!f)
-    return;
-
-  sym_initialize(::GetCurrentProcess(), NULL, TRUE);
-  sym_set_options(SYMOPT_DEFERRED_LOADS | SYMOPT_PUBLICS_ONLY);
-  char sym_buf[sizeof(SYMBOL_INFO) + MAX_SYM_NAME * sizeof(TCHAR)];
-
-  std::unordered_set<void*> seen;
-  std::unordered_set<std::string> seen_names;
-
-  for (void* sample : samples) {
-    // Only print the first call of a function.
-    if (seen.count(sample))
-      continue;
-    seen.insert(sample);
-
-    SYMBOL_INFO* symbol = reinterpret_cast<SYMBOL_INFO*>(sym_buf);
-    symbol->SizeOfStruct = sizeof(SYMBOL_INFO);
-    symbol->MaxNameLen = MAX_SYM_NAME;
-    DWORD64 offset = 0;
-
-    if (sym_from_addr(::GetCurrentProcess(), reinterpret_cast<DWORD64>(sample),
-                      &offset, symbol)) {
-      const char* name = symbol->Name;
-      if (name[0] == '_')
-        name++;
-      if (seen_names.count(name))
-        continue;
-      seen_names.insert(name);
-
-      fprintf(f, "%s\n", name);
-    }
-  }
-
-  fclose(f);
-}
-
-}  // namespace
-
-extern "C" {
-
-void __cyg_profile_func_enter(void* this_fn, void* call_site_unused) {
-  if (done)
-    return;
-
-  // Get our index for the samples array atomically.
-  int n = num_samples++;
-
-  if (n < kSamplesCapacity) {
-    samples[n] = this_fn;
-
-    if (n + 1 == kSamplesCapacity) {
-      // This is the final sample; start dumping the samples to a file (on a
-      // separate thread so as not to disturb the main program).
-      done = 1;
-      _beginthread(dump, 0, nullptr);
-    }
-  }
-}
-
-void __cyg_profile_func_exit(void* this_fn, void* call_site) {}
-
-}  // extern "C"