HStoreKeyed for Smis optimized for x64 + related redundant moves of elements removed

src/hydrogen-instructions.h

Index: src/hydrogen-instructions.h
diff --git a/src/hydrogen-instructions.h b/src/hydrogen-instructions.h
index 4dd24fd871552456a10bb77ab8f6a0e4b4b25138..638630f834bec6e9a89ba942ef4c0cd4dfea8b9c 100644
--- a/src/hydrogen-instructions.h
+++ b/src/hydrogen-instructions.h
@@ -6693,7 +6693,9 @@ class HStoreKeyed V8_FINAL
     if (IsDoubleOrFloatElementsKind(elements_kind())) {
       return Representation::Double();
     }
-
+    if (SmiValuesAre32Bits() && IsFastPackedSmiElementsKind(elements_kind())) {
+      return Representation::Integer32();
+    }
     if (IsFastSmiElementsKind(elements_kind())) {
       return Representation::Smi();
     }
@@ -6711,12 +6713,15 @@ class HStoreKeyed V8_FINAL
     if (IsUninitialized()) {
       return Representation::None();
     }
-    if (IsFastSmiElementsKind(elements_kind())) {
-      return Representation::Smi();
-    }
     if (IsDoubleOrFloatElementsKind(elements_kind())) {
       return Representation::Double();
     }
+    if (SmiValuesAre32Bits() && IsFastPackedSmiElementsKind(elements_kind())) {
+      return Representation::Integer32();
+    }
+    if (IsFastSmiElementsKind(elements_kind())) {
+      return Representation::Smi();
+    }
     if (is_external()) {
       return Representation::Integer32();
     }
@@ -6730,6 +6735,14 @@ class HStoreKeyed V8_FINAL
   bool value_is_smi() const {
     return IsFastSmiElementsKind(elements_kind_);
   }
+  // Indicates whether this is a store to a item that was previously
+  // initialized.
+  bool store_to_initialized_element() const {
+    return store_to_initialized_element_;
+  }
+  void set_store_to_initialized_element(bool v) {
+    store_to_initialized_element_ = v;
+  }
   ElementsKind elements_kind() const { return elements_kind_; }
   uint32_t index_offset() { return index_offset_; }
   void SetIndexOffset(uint32_t index_offset) { index_offset_ = index_offset; }
@@ -6780,6 +6793,7 @@ class HStoreKeyed V8_FINAL
       index_offset_(0),
       is_dehoisted_(false),
       is_uninitialized_(false),
+      store_to_initialized_element_(false),
       new_space_dominator_(NULL) {
     SetOperandAt(0, obj);
     SetOperandAt(1, key);
@@ -6811,6 +6825,7 @@ class HStoreKeyed V8_FINAL
   uint32_t index_offset_;
   bool is_dehoisted_ : 1;
   bool is_uninitialized_ : 1;
+  bool store_to_initialized_element_: 1;
   HValue* new_space_dominator_;
 };