[foozzie] Correctness-compare pointer compression build

This adds a fake toolchain for pointer compression, used for
correctness fuzzing. The toolchain enables us to have an extra build
with inverse pointer-compression defaults side-by-side.

The extra build is used similarly to existing x64/x86 comparisons,
except that we now compare builds with different compile-time flags.

Change-Id: I75491371262204b86eaa006ca8d04848f49121ac
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1829275Reviewed-by: Tamer Tas <tmrts@chromium.org>
Commit-Queue: Michael Achenbach <machenbach@chromium.org>
Cr-Commit-Position: refs/heads/master@{#64123}

BUILD.gn

@@ -202,6 +202,15 @@ declare_args() {
   v8_enable_regexp_interpreter_threaded_dispatch = true
 }
 
+# Toggle pointer compression for correctness fuzzing when building the
+# clang_x64_pointer_compression toolchain. We'll correctness-compare the
+# default build with the clang_x64_pointer_compression build.
+if (v8_multi_arch_build &&
+    rebase_path(get_label_info(":d8", "root_out_dir"), root_build_dir) ==
+    "clang_x64_pointer_compression") {
+  v8_enable_pointer_compression = !v8_enable_pointer_compression
+}
+
 # Derived defaults.
 if (v8_enable_verify_heap == "") {
   v8_enable_verify_heap = v8_enable_debugging_features
@@ -4085,6 +4094,7 @@ group("v8_clusterfuzz") {
       ":d8(//build/toolchain/linux:clang_x64_v8_arm64)",
       ":d8(//build/toolchain/linux:clang_x86)",
       ":d8(//build/toolchain/linux:clang_x86_v8_arm)",
+      ":d8(tools/clusterfuzz/toolchain:clang_x64_pointer_compression)",
     ]
   }
 }

tools/clusterfuzz/toolchain/BUILD.gn

+# Copyright 2019 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.
+
+import("//build/toolchain/gcc_toolchain.gni")
+
+# Fake toolchain to enable build output for a pointer-compression-comparison
+# build in a nested build sub-directory. We toggle pointer compression when
+# this toolchain is used in v8/BUILD.gn.
+clang_toolchain("clang_x64_pointer_compression") {
+  toolchain_args = {
+    current_cpu = "x64"
+    current_os = "linux"
+  }
+}

tools/clusterfuzz/v8_foozzie.py

@@ -213,14 +213,15 @@ def parse_args():
   assert os.path.exists(options.first_d8)
   assert os.path.exists(options.second_d8)
 
+  # Ensure we make a sane comparison.
+  if (options.first_d8 == options.second_d8 and
+      options.first_config == options.second_config):
+    parser.error('Need either executable or config difference.')
+
   # Infer architecture from build artifacts.
   options.first_arch = infer_arch(options.first_d8)
   options.second_arch = infer_arch(options.second_d8)
 
-  # Ensure we make a sane comparison.
-  if (options.first_arch == options.second_arch and
-      options.first_config == options.second_config):
-    parser.error('Need either arch or config difference.')
   assert options.first_arch in SUPPORTED_ARCHS
   assert options.second_arch in SUPPORTED_ARCHS
   assert options.first_config in CONFIGS

tools/clusterfuzz/v8_foozzie_test.py

@@ -38,7 +38,7 @@ class ConfigTest(unittest.TestCase):
         return 0.5
     self.assertEqual(
         [
-          '--first-config=ignition',
+          '--first-config=ignition_no_ic',
           '--second-config=ignition_turbo',
           '--second-d8=d8',
           '--second-config-extra-flags=--stress-scavenge=100',

tools/clusterfuzz/v8_fuzz_config.py

@@ -11,16 +11,18 @@ FOOZZIE_EXPERIMENTS = [
   [10, 'ignition', 'jitless', 'd8'],
   [10, 'ignition', 'slow_path', 'd8'],
   [5, 'ignition', 'slow_path_opt', 'd8'],
-  [26, 'ignition', 'ignition_turbo', 'd8'],
+  [25, 'ignition', 'ignition_turbo', 'd8'],
   [2, 'ignition_no_ic', 'ignition_turbo', 'd8'],
   [2, 'ignition', 'ignition_turbo_no_ic', 'd8'],
-  [18, 'ignition', 'ignition_turbo_opt', 'd8'],
+  [15, 'ignition', 'ignition_turbo_opt', 'd8'],
   [2, 'ignition_no_ic', 'ignition_turbo_opt', 'd8'],
-  [5, 'ignition_turbo_opt', 'ignition_turbo_opt', 'clang_x86/d8'],
-  [5, 'ignition_turbo', 'ignition_turbo', 'clang_x86/d8'],
-  [5, 'ignition', 'ignition', 'clang_x86/d8'],
-  [5, 'ignition', 'ignition', 'clang_x64_v8_arm64/d8'],
-  [5, 'ignition', 'ignition', 'clang_x86_v8_arm/d8'],
+  [4, 'ignition_turbo_opt', 'ignition_turbo_opt', 'clang_x64_pointer_compression/d8'],
+  [5, 'ignition_turbo', 'ignition_turbo', 'clang_x64_pointer_compression/d8'],
+  [4, 'ignition_turbo_opt', 'ignition_turbo_opt', 'clang_x86/d8'],
+  [4, 'ignition_turbo', 'ignition_turbo', 'clang_x86/d8'],
+  [4, 'ignition', 'ignition', 'clang_x86/d8'],
+  [4, 'ignition', 'ignition', 'clang_x64_v8_arm64/d8'],
+  [4, 'ignition', 'ignition', 'clang_x86_v8_arm/d8'],
 ]
 
 # Additional flag experiments. List of tuples like