[gn] Automatically derive build configs in test runner.

This executes an action as part of the build, writing a json
configuration that includes all build flags relevant to v8
testing.

The test runner will derive all build-dependent flags from
the file if it detects it.

BUG=chromium:474921

Review-Url: https://codereview.chromium.org/2106423002
Cr-Commit-Position: refs/heads/master@{#37446}

BUILD.gn

@@ -626,6 +626,26 @@ action("run_mksnapshot") {
   }
 }
 
+action("v8_dump_build_config") {
+  script = "tools/testrunner/utils/dump_build_config.py"
+  outputs = [ "$root_out_dir/v8_build_config.json" ]
+  args = [
+    rebase_path("$root_out_dir/v8_build_config.json", root_build_dir),
+    "dcheck_always_on=$dcheck_always_on",
+    "is_asan=$is_asan",
+    "is_cfi=$is_cfi",
+    "is_component_build=$is_component_build",
+    "is_debug=$is_debug",
+    "is_msan=$is_msan",
+    "is_tsan=$is_tsan",
+    "target_cpu=\"$target_cpu\"",
+    "v8_enable_i18n_support=$v8_enable_i18n_support",
+    "v8_target_cpu=\"$v8_target_cpu\"",
+    "v8_use_snapshot=$v8_use_snapshot",
+  ]  
+}
+
+
 ###############################################################################
 # Source Sets (aka static libraries)
 #
@@ -2109,6 +2129,8 @@ if (is_component_build) {
       "src/v8dll-main.cc",
     ]
 
+    deps = [ ":v8_dump_build_config" ]
+
     public_deps = [
       ":v8_base",
       ":v8_maybe_snapshot",
@@ -2120,6 +2142,8 @@ if (is_component_build) {
   }
 } else {
   group("v8") {
+    deps = [ ":v8_dump_build_config" ]
+
     public_deps = [
       ":v8_base",
       ":v8_maybe_snapshot",

tools/run-tests.py

@@ -30,6 +30,7 @@
 
 from collections import OrderedDict
 import itertools
+import json
 import multiprocessing
 import optparse
 import os
@@ -434,6 +435,34 @@ def ProcessOptions(options):
   global EXHAUSTIVE_VARIANTS
   global VARIANTS
 
+  # First try to auto-detect configurations based on the build if GN was
+  # used. This can't be overridden by cmd-line arguments.
+  options.auto_detect = False
+  build_config_path = os.path.join(
+      BASE_DIR, options.outdir, "v8_build_config.json")
+  if os.path.exists(build_config_path):
+    try:
+      with open(build_config_path) as f:
+        build_config = json.load(f)
+    except Exception:
+      print ("%s exists but contains invalid json. Is your build up-to-date?" %
+             build_config_path)
+      return False
+    options.auto_detect = True
+
+    options.arch_and_mode = None
+    options.arch = build_config["v8_target_cpu"]
+    if options.arch == 'x86':
+      # TODO(machenbach): Transform all to x86 eventually.
+      options.arch = 'ia32'
+    options.asan = build_config["is_asan"]
+    options.dcheck_always_on = build_config["dcheck_always_on"]
+    options.mode = 'debug' if build_config["is_debug"] else 'release'
+    options.msan = build_config["is_msan"]
+    options.no_i18n = not build_config["v8_enable_i18n_support"]
+    options.no_snap = not build_config["v8_use_snapshot"]
+    options.tsan = build_config["is_tsan"]
+
   # Architecture and mode related stuff.
   if options.arch_and_mode:
     options.arch_and_mode = [arch_and_mode.split(".")
@@ -667,6 +696,10 @@ def Execute(arch, mode, args, options, suites):
       # buildbot. Currently this is capitalized Release and Debug.
       shell_dir = os.path.join(BASE_DIR, options.outdir, mode)
       mode = BuildbotToV8Mode(mode)
+    elif options.auto_detect:
+      # If an output dir with a build was passed, test directly in that
+      # directory.
+      shell_dir = os.path.join(BASE_DIR, options.outdir)
     else:
       shell_dir = os.path.join(
           BASE_DIR,
@@ -712,6 +745,8 @@ def Execute(arch, mode, args, options, suites):
                         sancov_dir=options.sancov_dir)
 
   # TODO(all): Combine "simulator" and "simulator_run".
+  # TODO(machenbach): In GN we can derive simulator run from
+  # target_arch != v8_target_arch in the dumped build config.
   simulator_run = not options.dont_skip_simulator_slow_tests and \
       arch in ['arm64', 'arm', 'mipsel', 'mips', 'mips64', 'mips64el', \
                'ppc', 'ppc64'] and \

tools/testrunner/utils/dump_build_config.py

+# Copyright 2016 the V8 project authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+"""Writes a dictionary to a json file with the passed key-value pairs.
+
+Expected to be called like:
+dump_build_config.py path/to/file.json [key1=value1 ...]
+
+The values are expected to be valid json. E.g. true is a boolean and "true" is
+the string "true".
+"""
+
+import json
+import os
+import sys
+
+assert len(sys.argv) > 1
+
+def as_json(kv):
+  assert '=' in kv
+  k, v = kv.split('=', 1)
+  return k, json.loads(v)
+
+with open(sys.argv[1], 'w') as f:
+  json.dump(dict(as_json(kv) for kv in sys.argv[2:]), f)