Bug 1607930 - Enable deferred allocation mode by default r=tcampbell

Differential Revision: https://phabricator.services.mozilla.com/D59366

--HG--
extra : moz-landing-system : lando

js/public/RealmOptions.h

@@ -312,7 +312,7 @@ class JS_PUBLIC_API RealmBehaviors {
   // singleton, instead of returning the value which is baked in the JSScript.
   bool singletonsAsTemplates_ = true;
   bool isNonLive_ = false;
-  bool deferredParserAlloc_ = false;
+  bool deferredParserAlloc_ = true;
 };
 
 /**

js/src/shell/fuzz-flags.txt

@@ -50,7 +50,6 @@
 --nursery-strings=on
 --nursery-bigints=off
 --nursery-bigints=on
---parser-deferred-alloc
 --spectre-mitigations=off
 --spectre-mitigations=on
 --more-compartments

js/src/shell/js.cpp

@@ -472,7 +472,7 @@ struct MOZ_STACK_CLASS EnvironmentPreparer
   void invoke(JS::HandleObject global, Closure& closure) override;
 };
 
-bool shell::enableDeferredMode = false;
+bool shell::enableDeferredMode = true;
 bool shell::enableCodeCoverage = false;
 bool shell::enableDisassemblyDumps = false;
 bool shell::offthreadCompilation = false;
@@ -11107,8 +11107,9 @@ int main(int argc, char** argv, char** envp) {
                         "Print sub-ms runtime for each file that's run") ||
       !op.addBoolOption('\0', "code-coverage",
                         "Enable code coverage instrumentation.") ||
-      !op.addBoolOption('\0', "parser-deferred-alloc",
-                        "Defer allocation of GC objects until after parser") ||
+      !op.addBoolOption(
+          '\0', "disable-parser-deferred-alloc",
+          "Disable deferred allocation of GC objects until after parser") ||
 #ifdef DEBUG
       !op.addBoolOption('O', "print-alloc",
                         "Print the number of allocations at exit") ||
@@ -11431,8 +11432,8 @@ int main(int argc, char** argv, char** envp) {
     coverage::EnableLCov();
   }
 
-  enableDeferredMode = op.getBoolOption("parser-deferred-alloc") ||
-                       getenv("PARSER_DEFERRED_ALLOC") != nullptr;
+  enableDeferredMode = !op.getBoolOption("disable-parser-deferred-alloc") &&
+                       getenv("DISABLE_PARSER_DEFERRED_ALLOC") == nullptr;
 
 #ifdef JS_WITHOUT_NSPR
   if (!op.getMultiStringOption("dll").empty()) {

js/src/vm/SelfHosting.cpp

@@ -2591,8 +2591,8 @@ GlobalObject* JSRuntime::createSelfHostingGlobal(JSContext* cx) {
   options.creationOptions().setInvisibleToDebugger(true);
   options.behaviors().setDiscardSource(true);
 
-  bool enableDeferredMode = getenv("PARSER_DEFERRED_ALLOC") != nullptr;
-  options.behaviors().setDeferredParserAlloc(enableDeferredMode);
+  bool disableDeferredMode = getenv("DISABLE_PARSER_DEFERRED_ALLOC") != nullptr;
+  options.behaviors().setDeferredParserAlloc(!disableDeferredMode);
 
   Realm* realm = NewRealm(cx, nullptr, options);
   if (!realm) {

modules/libpref/init/StaticPrefList.yaml

@@ -4159,7 +4159,7 @@
 # Defer allocation of GC objects as late as possible in a parse
 - name: javascript.options.parser_defer_allocation
   type: RelaxedAtomicBool
-  value: false
+  value: true
   mirror: always
 
 - name: javascript.options.experimental.fields