Bug 1877258 - Add use counter for optimize get iterator fuse being popped r=iain

Differential Revision: https://phabricator.services.mozilla.com/D229217

dom/base/UseCounters.conf

@@ -71,6 +71,8 @@ custom JS_asmjs uses asm.js
 custom JS_wasm uses WebAssembly
 custom JS_wasm_legacy_exceptions uses WebAssembly legacy exception-handling
 custom JS_isHTMLDDA_fuse has used the document.all getter (popping the EmulatesUndefined Fuse)
+custom JS_OptimizeGetIterator_fuse has modified any builtins such that the GetIterator fuse is popped
+
 
 // Console API
 method console.assert

dom/base/use_counter_metrics.yaml

@@ -107,8 +107,8 @@ use.counter:
     send_in_pings:
       - use-counters
 
-# Total of 2329 use counter metrics (excludes denominators).
-# Total of 355 'page' use counters.
+# Total of 2331 use counter metrics (excludes denominators).
+# Total of 356 'page' use counters.
 use.counter.page:
   svgsvgelement_getelementbyid:
     type: counter
@@ -552,6 +552,23 @@ use.counter.page:
     send_in_pings:
       - use-counters
 
+  js__optimize_get_iterator_fuse:
+    type: counter
+    description: >
+      Whether a page has modified any builtins such that the GetIterator fuse is popped.
+      Compare against `use.counter.top_level_content_documents_destroyed`
+      to calculate the rate.
+    bugs:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1852098
+    data_reviews:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1852098
+    notification_emails:
+      - dom-core@mozilla.com
+      - emilio@mozilla.com
+    expires: never
+    send_in_pings:
+      - use-counters
+
   console_assert:
     type: counter
     description: >
@@ -6145,7 +6162,7 @@ use.counter.page:
     send_in_pings:
       - use-counters
 
-# Total of 355 'document' use counters.
+# Total of 356 'document' use counters.
 use.counter.doc:
   svgsvgelement_getelementbyid:
     type: counter
@@ -6589,6 +6606,23 @@ use.counter.doc:
     send_in_pings:
       - use-counters
 
+  js__optimize_get_iterator_fuse:
+    type: counter
+    description: >
+      Whether a document has modified any builtins such that the GetIterator fuse is popped.
+      Compare against `use.counter.content_documents_destroyed`
+      to calculate the rate.
+    bugs:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1852098
+    data_reviews:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1852098
+    notification_emails:
+      - dom-core@mozilla.com
+      - emilio@mozilla.com
+    expires: never
+    send_in_pings:
+      - use-counters
+
   console_assert:
     type: counter
     description: >

js/public/friend/UsageStatistics.h

@@ -99,7 +99,8 @@ extern JS_PUBLIC_API void JS_SetAccumulateTelemetryCallback(
   _(ASMJS, AsmJS)                                 \
   _(WASM, Wasm)                                   \
   _(WASM_LEGACY_EXCEPTIONS, WasmLegacyExceptions) \
-  _(ISHTMLDDA_FUSE, IsHTMLDDAFuse)
+  _(ISHTMLDDA_FUSE, IsHTMLDDAFuse)                \
+  _(OPTIMIZE_GET_ITERATOR_FUSE, OptimizeGetIteratorFuse)
 
 /*
  * Use counter names passed to the accumulate use counter callback.

js/src/vm/RealmFuses.cpp

@@ -76,6 +76,14 @@ const char* js::RealmFuses::getFuseName(RealmFuses::FuseIndex index) {
   return fuseNames[rawIndex];
 }
 
+void js::OptimizeGetIteratorFuse::popFuse(JSContext* cx,
+                                          RealmFuses& realmFuses) {
+  InvalidatingRealmFuse::popFuse(cx, realmFuses);
+  MOZ_ASSERT(cx->global());
+  cx->runtime()->setUseCounter(cx->global(),
+                               JSUseCounter::OPTIMIZE_GET_ITERATOR_FUSE);
+}
+
 bool js::OptimizeGetIteratorFuse::checkInvariant(JSContext* cx) {
   // Simple invariant: this fuse merely reflects the conjunction of a group of
   // fuses, so if this fuse is intact, then the invariant it asserts is that

js/src/vm/RealmFuses.h

@@ -44,6 +44,7 @@ class InvalidatingRealmFuse : public InvalidatingFuse {
 struct OptimizeGetIteratorFuse final : public InvalidatingRealmFuse {
   virtual const char* name() override { return "OptimizeGetIteratorFuse"; }
   virtual bool checkInvariant(JSContext* cx) override;
+  virtual void popFuse(JSContext* cx, RealmFuses& realmFuses) override;
 };
 
 struct PopsOptimizedGetIteratorFuse : public RealmFuse {

js/xpconnect/src/XPCJSRuntime.cpp

@@ -2647,6 +2647,9 @@ static void SetUseCounterCallback(JSObject* obj, JSUseCounter counter) {
     case JSUseCounter::ISHTMLDDA_FUSE:
       SetUseCounter(obj, eUseCounter_custom_JS_isHTMLDDA_fuse);
       return;
+    case JSUseCounter::OPTIMIZE_GET_ITERATOR_FUSE:
+      SetUseCounter(obj, eUseCounter_custom_JS_OptimizeGetIterator_fuse);
+      return;
     case JSUseCounter::COUNT:
       break;
   }