VectorICs: megamorphic keyed loads in crankshaft don't need a vector.

src/hydrogen.cc

Index: src/hydrogen.cc
diff --git a/src/hydrogen.cc b/src/hydrogen.cc
index c79a8170b64ddfa0b8b3125fb6f4977db993ae6d..6e6eb9c7d686ee0183844508c5936afa7af4bfc9 100644
--- a/src/hydrogen.cc
+++ b/src/hydrogen.cc
@@ -5406,11 +5406,8 @@ void HOptimizedGraphBuilder::VisitVariableProxy(VariableProxy* expr) {
                                     variable->name(),
                                     ast_context()->is_for_typeof());
         if (FLAG_vector_ics) {
-          Handle<SharedFunctionInfo> current_shared =
-              function_state()->compilation_info()->shared_info();
-          instr->SetVectorAndSlot(
-              handle(current_shared->feedback_vector(), isolate()),
-              expr->VariableFeedbackSlot());
+          instr->SetVectorAndSlot(handle(current_feedback_vector(), isolate()),
+                                  expr->VariableFeedbackSlot());
         }
         return ast_context()->ReturnInstruction(instr, expr->id());
       }
@@ -6901,10 +6898,8 @@ HInstruction* HOptimizedGraphBuilder::BuildNamedGeneric(
     HLoadNamedGeneric* result =
         New<HLoadNamedGeneric>(object, name, PREMONOMORPHIC);
     if (FLAG_vector_ics) {
-      Handle<SharedFunctionInfo> current_shared =
-          function_state()->compilation_info()->shared_info();
       Handle<TypeFeedbackVector> vector =
-          handle(current_shared->feedback_vector(), isolate());
+          handle(current_feedback_vector(), isolate());
       FeedbackVectorICSlot slot = expr->AsProperty()->PropertyFeedbackSlot();
       result->SetVectorAndSlot(vector, slot);
     }
@@ -6924,16 +6919,10 @@ HInstruction* HOptimizedGraphBuilder::BuildKeyedGeneric(
     HValue* key,
     HValue* value) {
   if (access_type == LOAD) {
-    HLoadKeyedGeneric* result =
-        New<HLoadKeyedGeneric>(object, key, PREMONOMORPHIC);
-    if (FLAG_vector_ics) {
-      Handle<SharedFunctionInfo> current_shared =
-          function_state()->compilation_info()->shared_info();
-      Handle<TypeFeedbackVector> vector =
-          handle(current_shared->feedback_vector(), isolate());
-      FeedbackVectorICSlot slot = expr->AsProperty()->PropertyFeedbackSlot();
-      result->SetVectorAndSlot(vector, slot);
-    }
+    // HLoadKeyedGeneric with vector ics benefits from being encoded as
+    // MEGAMORPHIC because the vector/slot combo becomes unnecessary.
+    HLoadKeyedGeneric* result = New<HLoadKeyedGeneric>(
+        object, key, FLAG_vector_ics ? MEGAMORPHIC : PREMONOMORPHIC);
     return result;
   } else {
     return New<HStoreKeyedGeneric>(object, key, value, function_language_mode(),
@@ -9325,10 +9314,8 @@ void HOptimizedGraphBuilder::VisitCall(Call* expr) {
           expr->IsUsingCallFeedbackICSlot(isolate())) {
         // We've never seen this call before, so let's have Crankshaft learn
         // through the type vector.
-        Handle<SharedFunctionInfo> current_shared =
-            function_state()->compilation_info()->shared_info();
         Handle<TypeFeedbackVector> vector =
-            handle(current_shared->feedback_vector(), isolate());
+            handle(current_feedback_vector(), isolate());
         FeedbackVectorICSlot slot = expr->CallFeedbackICSlot();
         call_function->SetVectorAndSlot(vector, slot);
       }