Bug 1438121: Add jit-test async-livecache.js. r=fitzgen

MozReview-Commit-ID: Jbe1GMPGwKj

--HG--
extra : rebase_source : 60ff2bd3f06bf6cb7b0056efe187a6e2c9bb4c1a
extra : amend_source : 7af0b2cf8165ef689e2ed8248763b64ee5183141

js/src/jit-test/tests/saved-stacks/async-livecache.js

@@ -0,0 +1,43 @@
+// Async stacks should not supplant LiveSavedFrameCache hits.
+
+top();
+
+// An ordinary function, to give the frame a convenient name.
+function top() {
+  // Perform an async call. F will run in an activation that has an async stack
+  // supplied.
+  f().catch(catchError);
+}
+
+async function f() {
+  // Perform an ordinary call. Its parent frame will be a LiveSavedFrameCache
+  // hit.
+  g();
+}
+
+function g() {
+  // Populate the LiveSavedFrameCache.
+  saveStack();
+
+  // Capturing the stack again should find f (if not g) in the cache. The async
+  // stack supplied below the call to f should not supplant f's own frame.
+  let frame = saveStack();
+
+  assertEq(frame.functionDisplayName, 'g');
+  assertEq(parent(frame).functionDisplayName, 'f');
+  assertEq(parent(parent(frame)).functionDisplayName, 'top');
+}
+
+// Return the parent of |frame|, skipping self-hosted code and following async
+// parent links.
+function parent(frame) {
+  do {
+    frame = frame.parent || frame.asyncParent;
+  } while (frame.source.match(/self-hosted/));
+  return frame;
+}
+
+function catchError(e) {
+  print(`${e}\n${e.stack}`);
+  quit(1)
+}