build: add configuration flag to enable Maglev

This adds a configuration flag to enable V8's Maglev compiler.

Unfortunately compilation fails unless you have clang-14+ or gcc-13+,
but I sent a patch for that upstream. Other than that, it builds and all
tests pass locally on my x86-64 Linux machine.

The gn scraper regexes were broken preventing the compilation from
linking. Fix them. As a drive-by, also add additional conditionals for
compilation on 32-bit arm.

Refs: #50690
PR-URL: #50692
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: Michael Dawson <midawson@redhat.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

configure.py

@@ -812,6 +812,12 @@
     help='Enable V8 transparent hugepage support. This feature is only '+
          'available on Linux platform.')
 
+parser.add_argument('--v8-enable-maglev',
+    action='store_true',
+    dest='v8_enable_maglev',
+    default=None,
+    help='Enable V8 Maglev compiler. Not available on all platforms.')
+
 parser.add_argument('--v8-enable-short-builtin-calls',
     action='store_true',
     dest='v8_enable_short_builtin_calls',
@@ -1494,6 +1500,7 @@ 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_maglev'] = 1 if options.v8_enable_maglev else 0
   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_enable_shared_ro_heap'] = 0 if options.enable_pointer_compression or options.disable_shared_ro_heap else 1

tools/v8_gypfiles/v8.gyp

@@ -546,6 +546,11 @@
               '<!@pymod_do_main(GN-scraper "<(V8_ROOT)/BUILD.gn"  "v8_header_set.\\"v8_internal_headers\\".*?v8_enable_maglev.*?sources \\+= ")',
             ],
             'conditions': [
+              ['v8_target_arch=="arm"', {
+                'sources': [
+                  '<!@pymod_do_main(GN-scraper "<(V8_ROOT)/BUILD.gn"  "v8_header_set.\\"v8_internal_headers\\".*?v8_enable_maglev.*?v8_current_cpu == \\"arm\\".*?sources \\+= ")',
+                ],
+              }],
               ['v8_target_arch=="arm64"', {
                 'sources': [
                   '<!@pymod_do_main(GN-scraper "<(V8_ROOT)/BUILD.gn"  "v8_header_set.\\"v8_internal_headers\\".*?v8_enable_maglev.*?v8_current_cpu == \\"arm64\\".*?sources \\+= ")',
@@ -891,14 +896,19 @@
             '<!@pymod_do_main(GN-scraper "<(V8_ROOT)/BUILD.gn"  "\\"v8_base_without_compiler.*?v8_enable_maglev.*?sources \\+= ")',
           ],
           'conditions': [
+            ['v8_target_arch=="arm"', {
+              'sources': [
+                '<!@pymod_do_main(GN-scraper "<(V8_ROOT)/BUILD.gn"  "\\"v8_base_without_compiler.*?v8_enable_maglev.*?v8_current_cpu == \\"arm\\".*?sources \\+= ")',
+              ],
+            }],
             ['v8_target_arch=="arm64"', {
               'sources': [
-                '<!@pymod_do_main(GN-scraper "<(V8_ROOT)/BUILD.gn"  "v8_base_without_compiler.*?v8_enable_maglev.*?v8_current_cpu == \\"arm64\\".*?sources \\+= ")',
+                '<!@pymod_do_main(GN-scraper "<(V8_ROOT)/BUILD.gn"  "\\"v8_base_without_compiler.*?v8_enable_maglev.*?v8_current_cpu == \\"arm64\\".*?sources \\+= ")',
               ],
             }],
             ['v8_target_arch=="x64"', {
               'sources': [
-                '<!@pymod_do_main(GN-scraper "<(V8_ROOT)/BUILD.gn"  "v8_base_without_compiler.*?v8_enable_maglev.*?v8_current_cpu == \\"x64\\".*?sources \\+= ")',
+                '<!@pymod_do_main(GN-scraper "<(V8_ROOT)/BUILD.gn"  "\\"v8_base_without_compiler.*?v8_enable_maglev.*?v8_current_cpu == \\"x64\\".*?sources \\+= ")',
               ],
             }],
           ],