Bug 1865929: Apply delazify strategy to small scripts in ScriptLoader…

…. r=nbp

Differential Revision: https://phabricator.services.mozilla.com/D194647

dom/script/ScriptLoader.cpp

@@ -1713,6 +1713,14 @@ class OffThreadCompilationCompleteTask : public Task {
 
 } /* anonymous namespace */
 
+// TODO: This uses the same heuristics and the same threshold as the
+//       JS::CanCompileOffThread / JS::CanDecodeOffThread APIs, but the
+//       heuristics needs to be updated to reflect the change regarding the
+//       Stencil API, and also the thread management on the consumer side
+//       (bug 1846160).
+static constexpr size_t OffThreadMinimumTextLength = 5 * 1000;
+static constexpr size_t OffThreadMinimumBytecodeLength = 5 * 1000;
+
 nsresult ScriptLoader::AttemptOffThreadScriptCompile(
     ScriptLoadRequest* aRequest, bool* aCouldCompileOut) {
   // If speculative parsing is enabled, the request may not be ready to run if
@@ -1749,14 +1757,6 @@ nsresult ScriptLoader::AttemptOffThreadScriptCompile(
     return rv;
   }
 
-  // TODO: This uses the same heuristics and the same threshold as the
-  //       JS::CanCompileOffThread / JS::CanDecodeOffThread APIs, but the
-  //       heuristics needs to be updated to reflect the change regarding the
-  //       Stencil API, and also the thread management on the consumer side
-  //       (bug 1846160).
-  static constexpr size_t OffThreadMinimumTextLength = 5 * 1000;
-  static constexpr size_t OffThreadMinimumBytecodeLength = 5 * 1000;
-
   if (aRequest->IsTextSource()) {
     if (!StaticPrefs::javascript_options_parallel_parsing() ||
         aRequest->ScriptTextLength() < OffThreadMinimumTextLength) {
@@ -2048,8 +2048,8 @@ nsresult ScriptLoader::CreateOffThreadTask(
             : 0;
 
     LOG(
-        ("ScriptLoadRequest (%p): non-on-demand-only Parsing Enabled for "
-         "url=%s mTotalFullParseSize=%u",
+        ("ScriptLoadRequest (%p): non-on-demand-only (omt) Parsing Enabled "
+         "for url=%s mTotalFullParseSize=%u",
          aRequest, aRequest->mURI->GetSpecOrDefault().get(),
          mTotalFullParseSize));
   }
@@ -2763,6 +2763,23 @@ nsresult ScriptLoader::EvaluateScript(nsIGlobalObject* aGlobalObject,
     return rv;
   }
 
+  // Apply the delazify strategy if the script is small.
+  if (aRequest->IsTextSource() &&
+      aRequest->ScriptTextLength() < OffThreadMinimumTextLength &&
+      ShouldApplyDelazifyStrategy(aRequest)) {
+    ApplyDelazifyStrategy(&options);
+    mTotalFullParseSize +=
+        aRequest->ScriptTextLength() > 0
+            ? static_cast<uint32_t>(aRequest->ScriptTextLength())
+            : 0;
+
+    LOG(
+        ("ScriptLoadRequest (%p): non-on-demand-only (non-omt) Parsing Enabled "
+         "for url=%s mTotalFullParseSize=%u",
+         aRequest, aRequest->mURI->GetSpecOrDefault().get(),
+         mTotalFullParseSize));
+  }
+
   TRACE_FOR_TEST(aRequest->GetScriptLoadContext()->GetScriptElement(),
                  "scriptloader_execute");
   JS::Rooted<JSObject*> global(cx, aGlobalObject->GetGlobalJSObject());