build: add flag to enable pointer compression

The --experimental-enable-pointer-compression is experimental
as it breaks ABI compatibility.

PR-URL: #30463
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: Rod Vagg <rod@vagg.org>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: David Carlier <devnexen@gmail.com>
Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: Denys Otrishko <shishugi@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Tobias Nießen <tniessen@tnie.de>
Reviewed-By: Rich Trott <rtrott@gmail.com>

Author: mcollina

common.gypi

@@ -73,9 +73,6 @@
     # TODO(refack): make v8-perfetto happen
     'v8_use_perfetto': 0,
 
-    'v8_enable_pointer_compression': 0,
-    'v8_enable_31bit_smis_on_64bit_arch': 0,
-
     ##### end V8 defaults #####
 
     'conditions': [

configure.py

@@ -346,6 +346,11 @@
     dest='trace_maps',
     help='Enable the --trace-maps flag in V8 (use at your own risk)')
 
+parser.add_option('--experimental-enable-pointer-compression',
+    action='store_true',
+    dest='enable_pointer_compression',
+    help='[Experimental] Enable V8 pointer compression (limits max heap to 4GB and breaks ABI compatibility)')
+
 parser.add_option('--v8-options',
     action='store',
     dest='v8_options',
@@ -1192,6 +1197,8 @@ def configure_v8(o):
   o['variables']['v8_random_seed'] = 0  # Use a random seed for hash tables.
   o['variables']['v8_promise_internal_field_count'] = 1 # Add internal field to promises for async hooks.
   o['variables']['v8_use_siphash'] = 0 if options.without_siphash else 1
+  o['variables']['v8_enable_pointer_compression'] = 1 if options.enable_pointer_compression else 0
+  o['variables']['v8_enable_31bit_smis_on_64bit_arch'] = 1 if options.enable_pointer_compression else 0
   o['variables']['v8_trace_maps'] = 1 if options.trace_maps else 0
   o['variables']['node_use_v8_platform'] = b(not options.without_v8_platform)
   o['variables']['node_use_bundled_v8'] = b(not options.without_bundled_v8)

node.gyp

@@ -2,6 +2,8 @@
   'variables': {
     'v8_use_siphash%': 0,
     'v8_trace_maps%': 0,
+    'v8_enable_pointer_compression%': 0,
+    'v8_enable_31bit_smis_on_64bit_arch%': 0,
     'node_use_dtrace%': 'false',
     'node_use_etw%': 'false',
     'node_no_browser_globals%': 'false',