feat: enable pointer compression and 31bit smis (#21468)

build/args/all.gn

@@ -8,12 +8,6 @@ v8_promise_internal_field_count = 1
 v8_typed_array_max_size_in_heap = 0
 v8_embedder_string = "-electron.0"
 
-# TODO: this breaks native modules. See e.g. https://www.github.com/nodejs/node/pull/30463
-# We can probably enable this as long as we make sure node native modules
-# also build with the relevant #defines (V8_COMPRESS_POINTERS etc.)
-v8_enable_pointer_compression = false
-v8_enable_31bit_smis_on_64bit_arch = false
-
 # TODO: this breaks mksnapshot
 v8_enable_snapshot_native_code_counters = false
 

patches/node/.patches

@@ -37,3 +37,4 @@ fix_don_t_use_node-controlled_preparestacktrace.patch
 fix_remove_uses_of_node_use_v8_platform.patch
 fix_call_initializecontextruntime_in_initializecontext.patch
 refactor_transferrablemodule_is_deprecated_use_compiledwasmmodule.patch
+enable_31_bit_smis_on_64bit_arch_and_ptr_compression.patch

patches/node/enable_31_bit_smis_on_64bit_arch_and_ptr_compression.patch

@@ -0,0 +1,46 @@
+From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
+From: Jeremy Apthorp <nornagon@nornagon.net>
+Date: Tue, 10 Dec 2019 15:02:21 -0800
+Subject: enable 31 bit smis on 64bit arch and ptr compression
+
+This aligns with the defaults set on the Chromium build. Without this, native
+node modules will have different (wrong) ideas about how v8 structs are laid
+out in memory on 64-bit machines, and will summarily fail to work.
+
+diff --git a/common.gypi b/common.gypi
+index 412f613e7cfcf563fa6a000b932723166ab567da..6e2ad757781f794333b3656ec05f6e48ade86d2e 100644
+--- a/common.gypi
++++ b/common.gypi
+@@ -75,6 +75,9 @@
+     # TODO(refack): make v8-perfetto happen
+     'v8_use_perfetto': 0,
+ 
++    'v8_enable_pointer_compression%': 0,
++    'v8_enable_31bit_smis_on_64bit_arch': 1,
++
+     ##### end V8 defaults #####
+ 
+     # When building native modules using 'npm install' with the system npm,
+@@ -152,6 +155,9 @@
+       ['OS=="mac"', {
+         'clang%': 1,
+       }],
++      ['target_arch == "arm64" or target_arch == "x64"', {
++        'v8_enable_pointer_compression': 1,
++      }],
+     ],
+   },
+ 
+@@ -375,6 +381,12 @@
+           }],
+         ],
+       }],
++      ['v8_enable_pointer_compression == 1', {
++        'defines': ['V8_COMPRESS_POINTERS'],
++      }],
++      ['v8_enable_pointer_compression == 1 or v8_enable_31bit_smis_on_64bit_arch == 1', {
++        'defines': ['V8_31BIT_SMIS_ON_64BIT_ARCH'],
++      }],
+       ['OS == "win"', {
+         'defines': [
+           'WIN32',