In GrowMode, force the value to the right representation to avoid deopts between storing the length…

src/hydrogen-instructions.h

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_HYDROGEN_INSTRUCTIONS_H_
 #define V8_HYDROGEN_INSTRUCTIONS_H_
 
 #include "src/v8.h"
 
 #include "src/allocation.h"
@@ skipping 6954 matching lines @@
     // kind_external:           external[int32] = (double | int32)
     if (index == 0) {
       return is_external() ? Representation::External()
                            : Representation::Tagged();
     } else if (index == 1) {
       return ArrayInstructionInterface::KeyedAccessIndexRequirement(
           OperandAt(1)->representation());
     }
 
     ASSERT_EQ(index, 2);
-    if (IsDoubleOrFloatElementsKind(elements_kind())) {
+    return RequiredValueRepresentation(elements_kind_, store_mode_);
+  }
+
+  static Representation RequiredValueRepresentation(
+      ElementsKind kind, StoreFieldOrKeyedMode mode) {
+    if (IsDoubleOrFloatElementsKind(kind)) {
       return Representation::Double();
     }
-    if (SmiValuesAre32Bits() && store_mode_ == STORE_TO_INITIALIZED_ENTRY) {
-      return Representation::Integer32();
-    }
-    if (IsFastSmiElementsKind(elements_kind())) {
+
+    if (IsFastSmiElementsKind(kind)) {
+      if (SmiValuesAre32Bits() && mode == STORE_TO_INITIALIZED_ENTRY) {
+        return Representation::Integer32();
+      }
       return Representation::Smi();
     }
 
-    return is_external() || is_fixed_typed_array()
-        ? Representation::Integer32()
-        : Representation::Tagged();
+    return IsExternalArrayElementsKind(kind) ||
+                   IsFixedTypedArrayElementsKind(kind)
+               ? Representation::Integer32()
+               : Representation::Tagged();
   }
 
   bool is_external() const {
     return IsExternalArrayElementsKind(elements_kind());
   }
 
   bool is_fixed_typed_array() const {
     return IsFixedTypedArrayElementsKind(elements_kind());
   }
 
@@ skipping 861 matching lines @@
 };
 
 
 
 #undef DECLARE_INSTRUCTION
 #undef DECLARE_CONCRETE_INSTRUCTION
 
 } }  // namespace v8::internal
 
 #endif  // V8_HYDROGEN_INSTRUCTIONS_H_