ARM, ARM64: Optimize array copy

src/hydrogen.cc

Index: src/hydrogen.cc
diff --git a/src/hydrogen.cc b/src/hydrogen.cc
index 3162eb606ad687924ae6bcd9ff04d0a1e9570869..cf48732b157b5e8bcc8ef1c86e3ded0fed578ae1 100644
--- a/src/hydrogen.cc
+++ b/src/hydrogen.cc
@@ -2696,6 +2696,11 @@ void HGraphBuilder::BuildFillElementsWithValue(HValue* elements,
     to = AddLoadFixedArrayLength(elements);
   }
 
+#if V8_TARGET_ARCH_ARM || V8_TARGET_ARCH_ARM64
+  from = AddUncasted<HForceRepresentation>(from, Representation::Integer32());
+  to = AddUncasted<HForceRepresentation>(to, Representation::Integer32());
+  Add<HFillElements>(elements, from, to, value);
+#else
   // Special loop unfolding case
   STATIC_ASSERT(JSArray::kPreallocatedArrayElements <=
                 kElementLoopUnrollThreshold);
@@ -2736,6 +2741,7 @@ void HGraphBuilder::BuildFillElementsWithValue(HValue* elements,
 
     builder.EndBody();
   }
+#endif
 }
 
 
@@ -2803,42 +2809,52 @@ void HGraphBuilder::BuildCopyElements(HValue* from_elements,
       capacity = AddLoadFixedArrayLength(to_elements);
     }
 
-    LoopBuilder builder(this, context(), LoopBuilder::kPostDecrement);
-
-    HValue* key = builder.BeginBody(length, graph()->GetConstant0(),
-                                    Token::GT);
-
-    key = AddUncasted<HSub>(key, graph()->GetConstant1());
-    key->ClearFlag(HValue::kCanOverflow);
-
-    HValue* element = Add<HLoadKeyed>(from_elements, key,
-                                      static_cast<HValue*>(NULL),
-                                      from_elements_kind,
-                                      ALLOW_RETURN_HOLE);
-
-    ElementsKind kind = (IsHoleyElementsKind(from_elements_kind) &&
-                         IsFastSmiElementsKind(to_elements_kind))
-      ? FAST_HOLEY_ELEMENTS : to_elements_kind;
-
-    if (IsHoleyElementsKind(from_elements_kind) &&
-        from_elements_kind != to_elements_kind) {
-      IfBuilder if_hole(this);
-      if_hole.If<HCompareHoleAndBranch>(element);
-      if_hole.Then();
-      HConstant* hole_constant = IsFastDoubleElementsKind(to_elements_kind)
-        ? Add<HConstant>(FixedDoubleArray::hole_nan_as_double())
-        : graph()->GetConstantHole();
-      Add<HStoreKeyed>(to_elements, key, hole_constant, kind);
-      if_hole.Else();
-      HStoreKeyed* store = Add<HStoreKeyed>(to_elements, key, element, kind);
-      store->SetFlag(HValue::kAllowUndefinedAsNaN);
-      if_hole.End();
+#if V8_TARGET_ARCH_ARM || V8_TARGET_ARCH_ARM64
+    if (from_elements_kind == to_elements_kind) {
+      length =
+         AddUncasted<HForceRepresentation>(length, Representation::Integer32());
+      Add<HCopyElements>(from_elements, to_elements, length, to_elements_kind);
     } else {
-      HStoreKeyed* store = Add<HStoreKeyed>(to_elements, key, element, kind);
-      store->SetFlag(HValue::kAllowUndefinedAsNaN);
-    }
+#endif
+      LoopBuilder builder(this, context(), LoopBuilder::kPostDecrement);
+
+      HValue* key = builder.BeginBody(length, graph()->GetConstant0(),
+                                      Token::GT);
+
+      key = AddUncasted<HSub>(key, graph()->GetConstant1());
+      key->ClearFlag(HValue::kCanOverflow);
+
+      HValue* element = Add<HLoadKeyed>(from_elements, key,
+                                        static_cast<HValue*>(NULL),
+                                        from_elements_kind,
+                                        ALLOW_RETURN_HOLE);
+
+      ElementsKind kind = (IsHoleyElementsKind(from_elements_kind) &&
+                          IsFastSmiElementsKind(to_elements_kind))
+        ? FAST_HOLEY_ELEMENTS : to_elements_kind;
+
+      if (IsHoleyElementsKind(from_elements_kind) &&
+          from_elements_kind != to_elements_kind) {
+        IfBuilder if_hole(this);
+        if_hole.If<HCompareHoleAndBranch>(element);
+        if_hole.Then();
+        HConstant* hole_constant = IsFastDoubleElementsKind(to_elements_kind)
+          ? Add<HConstant>(FixedDoubleArray::hole_nan_as_double())
+          : graph()->GetConstantHole();
+        Add<HStoreKeyed>(to_elements, key, hole_constant, kind);
+        if_hole.Else();
+        HStoreKeyed* store = Add<HStoreKeyed>(to_elements, key, element, kind);
+        store->SetFlag(HValue::kAllowUndefinedAsNaN);
+        if_hole.End();
+      } else {
+        HStoreKeyed* store = Add<HStoreKeyed>(to_elements, key, element, kind);
+        store->SetFlag(HValue::kAllowUndefinedAsNaN);
+      }
 
-    builder.EndBody();
+      builder.EndBody();
+#if V8_TARGET_ARCH_ARM || V8_TARGET_ARCH_ARM64
+    }
+#endif
   }
 
   Counters* counters = isolate()->counters();