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R=jarin@chromium.org

Change-Id: I82a8173bb3ecd86d980ccb5169c4bedac49989f8
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1561071Reviewed-by: Jaroslav Sevcik <jarin@chromium.org>
Commit-Queue: Georg Neis <neis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#60742}

src/compiler/js-native-context-specialization.cc

@@ -1844,6 +1844,8 @@ Reduction JSNativeContextSpecialization::ReduceKeyedAccess(
   }
 
   // Try to lower element access based on the {receiver_maps}.
+  // Only do so if the feedback is not megamorphic so that we can learn
+  // something when the ReduceElementAccess code deopts.
   if (nexus.GetKeyType() == ELEMENT && nexus.ic_state() != MEGAMORPHIC) {
     return ReduceElementAccess(node, key, value, nexus, receiver_maps,
                                access_mode, load_mode, store_mode);