Bug 1754443 - Do not schedule DelazifyTask if there is no inner funct…

…ion to delazify. r=arai

Differential Revision: https://phabricator.services.mozilla.com/D138292

js/src/jit-test/tests/parser/stencil-eager-delazify-empty.js

@@ -0,0 +1,22 @@
+// |jit-test| skip-if: helperThreadCount() === 0 || isLcovEnabled()
+
+// Extra GCs can empty the StencilCache to reclaim memory. This lines
+// re-configure the gc-zeal setting to prevent this from happening in this test
+// case which waits for the cache to contain some entry.
+if ('gczeal' in this)
+  gczeal(0);
+
+// Generate a source code with no inner functions.
+function justVariables(n) {
+    let text = "";
+    for (let i = 0; i < n; i++) {
+        text += `let v${i} = ${i};`;
+    }
+    return text;
+};
+
+// Create an extra task to test the case where there is nothing to delazify.
+let job = offThreadCompileToStencil(justVariables(10000), options);
+
+const stencil = finishOffThreadCompileToStencil(job);
+evalStencil(stencil, options);

js/src/vm/HelperThreads.cpp

@@ -686,8 +686,10 @@ void ParseTask::scheduleDelazifyTask(AutoLockHelperThreadState& lock) {
     task->errors_ = std::move(errors);
   }
 
-  // Schedule delazification task.
-  HelperThreadState().submitTask(task.release(), lock);
+  // Schedule delazification task if there is any function to delazify.
+  if (!task->strategy->done()) {
+    HelperThreadState().submitTask(task.release(), lock);
+  }
 }
 
 template <typename Unit>