try v8

build/config/BUILDCONFIG.gn

 # Copyright (c) 2013 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.
 
 # =============================================================================
 # PLATFORM SELECTION
 # =============================================================================
 #
 # There are two main things to set: "os" and "cpu". The "toolchain" is the name
 # of the GN thing that encodes combinations of these things.
@@ skipping 124 matching lines @@
              current_os == "linux" || current_os == "chromeos"
 
   # Allows the path to a custom target toolchain to be injected as a single
   # argument, and set as the default toolchain.
   custom_toolchain = ""
 
   # This should not normally be set as a build argument.  It's here so that
   # every toolchain can pass through the "global" value via toolchain_args().
   host_toolchain = ""
 
+  # This arg is used when we want to tell the JIT-code-generating v8 code
+  # that we want to have it generate code for an architecture that is different
+  # than the architecture that v8 will actually run on, and that we will
+  # then run the code under an emulator. For example, we might run v8
+  # on x86, but generate arm code and run that under emulation.
+  #
+  # This arg is defined here rather than in the v8 project because we want
+  # some of the common architecture-specific args (like arm_float_abi or
+  # mips_arch_variant) to be set to their defaults either if the current_cpu
+  # applies *or* if the v8_target_cpu applies.
+  v8_target_cpu = ""
+
+  # Compile for Memory Sanitizer to find uninitialized reads.
+  #
+  # TODO: This is here so that we can set a good default for v8_target_cpu
+  # when running under the sanitizer, but this is something of a layering
+  # violation and it would be nice if there was some other way to do this.
+  is_msan = false
+
   # DON'T ADD MORE FLAGS HERE. Read the comment above.
 }
 
+if (v8_target_cpu == "") {
+  if (is_msan) {
+    # Running the V8-generated code on an ARM simulator is a powerful hack that
+    # allows the tool to see the memory accesses from JITted code. Without this
+    # flag, JS code causes false positive reports from MSan.
+    v8_target_cpu = "arm64"
+  } else {
+    v8_target_cpu = target_cpu
+  }
+}
+
+declare_args() {
+  # This argument is declared here so that it can be overridden in
+  # toolchains. It should never be explicitly set by the user.
+  v8_current_cpu = v8_target_cpu
+}
+
 assert(!(is_debug && is_official_build), "Can't do official debug builds")
 
 # ==============================================================================
 # TOOLCHAIN SETUP
 # ==============================================================================
 #
 # Here we set the default toolchain, as well as the variable host_toolchain
 # which will identify the toolchain corresponding to the local system when
 # doing cross-compiles. When not cross-compiling, this will be the same as the
 # default toolchain.
@@ skipping 50 matching lines @@
   assert(host_os == "linux",
          "ChromeOS builds are only supported on Linux hosts.")
   if (is_clang) {
     _default_toolchain = "//build/toolchain/cros:clang_target"
   } else {
     _default_toolchain = "//build/toolchain/cros:target"
   }
 } else if (target_os == "ios") {
   _default_toolchain = "//build/toolchain/mac:ios_clang_$target_cpu"
 } else if (target_os == "linux") {
+  if (v8_current_cpu != current_cpu) {
+    _target_cpus = "${target_cpu}_v8_${v8_current_cpu}"
+  } else {
+    _target_cpus = target_cpu
+  }
   if (is_clang) {
-    _default_toolchain = "//build/toolchain/linux:clang_$target_cpu"
+    _default_toolchain = "//build/toolchain/linux:clang_${_target_cpus}"
   } else {
-    _default_toolchain = "//build/toolchain/linux:$target_cpu"
+    _default_toolchain = "//build/toolchain/linux:${_target_cpus}"
   }
 } else if (target_os == "mac") {
   assert(host_os == "mac", "Mac cross-compiles are unsupported.")
   _default_toolchain = host_toolchain
 } else if (target_os == "win") {
   # On Windows we use the same toolchain for host and target by default.
   assert(target_os == host_os, "Win cross-compiles only work on win hosts.")
   if (is_clang) {
     _default_toolchain = "//build/toolchain/win:clang_$target_cpu"
   } else {
@@ skipping 426 matching lines @@
     forward_variables_from(invoker, "*", [ "visibility" ])
 
     # All shared libraries must have the sanitizer deps to properly link in
     # asan mode (this target will be empty in other cases).
     if (!defined(deps)) {
       deps = []
     }
     deps += [ "//build/config/sanitizers:deps" ]
   }
 }