[turbofan] Fix confusing broker warning

That warning about missing data was sometimes printed even
when nothing was missing.

(Also drop an outdated TODO.)

Bug: v8:7790
Change-Id: I9550b3237c87b7b0e59f740c34b13d3e38d8d36e
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1917153
Commit-Queue: Georg Neis <neis@chromium.org>
Auto-Submit: Georg Neis <neis@chromium.org>
Reviewed-by: Maya Lekova <mslekova@chromium.org>
Cr-Commit-Position: refs/heads/master@{#65010}

src/compiler/js-context-specialization.cc

@@ -160,7 +160,15 @@ Reduction JSContextSpecialization::ReduceJSLoadContext(Node* node) {
   // This will hold the final value, if we can figure it out.
   base::Optional<ObjectRef> maybe_value;
   maybe_value = concrete.get(static_cast<int>(access.index()));
-  if (maybe_value.has_value() && !maybe_value->IsSmi()) {
+
+  if (!maybe_value.has_value()) {
+    TRACE_BROKER_MISSING(broker(), "slot value " << access.index()
+                                                 << " for context "
+                                                 << concrete);
+    return SimplifyJSLoadContext(node, jsgraph()->Constant(concrete), depth);
+  }
+
+  if (!maybe_value->IsSmi()) {
     // Even though the context slot is immutable, the context might have escaped
     // before the function to which it belongs has initialized the slot.
     // We must be conservative and check if the value in the slot is currently
@@ -169,21 +177,11 @@ Reduction JSContextSpecialization::ReduceJSLoadContext(Node* node) {
     OddballType oddball_type = maybe_value->AsHeapObject().map().oddball_type();
     if (oddball_type == OddballType::kUndefined ||
         oddball_type == OddballType::kHole) {
-      maybe_value.reset();
-    }
-  }
-
-  if (!maybe_value.has_value()) {
-    TRACE_BROKER_MISSING(broker(), "slot value " << access.index()
-                                                 << " for context "
-                                                 << concrete);
       return SimplifyJSLoadContext(node, jsgraph()->Constant(concrete), depth);
     }
+  }
 
   // Success. The context load can be replaced with the constant.
-  // TODO(titzer): record the specialization for sharing code across
-  // multiple contexts that have the same value in the corresponding context
-  // slot.
   Node* constant = jsgraph_->Constant(*maybe_value);
   ReplaceWithValue(node, constant);
   return Replace(constant);