deps: upgrade to V8 4.8.271.17

Pick up V8 4.8 branch-head. This branch brings in @@isConcatSpreadable,
@@toPrimitive and ToLength ES6 changes. For full details see:
http://v8project.blogspot.de/2015/11/v8-release-48.html

https://github.com/v8/v8/commit/fa163e2

Ref: https://github.com/nodejs/node/pull/4399
PR-URL: https://github.com/nodejs/node/pull/4785
Reviewed-By: bnoordhuis - Ben Noordhuis <info@bnoordhuis.nl>

1 files changed, 72 insertions, 0 deletions

diff --git a/deps/v8/src/crankshaft/hydrogen-dehoist.cc b/deps/v8/src/crankshaft/hydrogen-dehoist.cc
new file mode 100644
index 0000000000..34de94afc5
--- /dev/null
+++ b/deps/v8/src/crankshaft/hydrogen-dehoist.cc
@@ -0,0 +1,72 @@
+// Copyright 2013 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.
+
+#include "src/crankshaft/hydrogen-dehoist.h"
+
+#include "src/base/safe_math.h"
+
+namespace v8 {
+namespace internal {
+
+static void DehoistArrayIndex(ArrayInstructionInterface* array_operation) {
+  HValue* index = array_operation->GetKey()->ActualValue();
+  if (!index->representation().IsSmiOrInteger32()) return;
+  if (!index->IsAdd() && !index->IsSub()) return;
+
+  HConstant* constant;
+  HValue* subexpression;
+  HBinaryOperation* binary_operation = HBinaryOperation::cast(index);
+  if (binary_operation->left()->IsConstant() && index->IsAdd()) {
+    subexpression = binary_operation->right();
+    constant = HConstant::cast(binary_operation->left());
+  } else if (binary_operation->right()->IsConstant()) {
+    subexpression = binary_operation->left();
+    constant = HConstant::cast(binary_operation->right());
+  } else {
+    return;
+  }
+
+  if (!constant->HasInteger32Value()) return;
+  v8::base::internal::CheckedNumeric<int32_t> checked_value =
+      constant->Integer32Value();
+  int32_t sign = binary_operation->IsSub() ? -1 : 1;
+  checked_value = checked_value * sign;
+
+  // Multiply value by elements size, bailing out on overflow.
+  int32_t elements_kind_size =
+      1 << ElementsKindToShiftSize(array_operation->elements_kind());
+  checked_value = checked_value * elements_kind_size;
+  if (!checked_value.IsValid()) return;
+  int32_t value = checked_value.ValueOrDie();
+  if (value < 0) return;
+
+  // Ensure that the array operation can add value to existing base offset
+  // without overflowing.
+  if (!array_operation->TryIncreaseBaseOffset(value)) return;
+
+  array_operation->SetKey(subexpression);
+  if (binary_operation->HasNoUses()) {
+    binary_operation->DeleteAndReplaceWith(NULL);
+  }
+
+  array_operation->SetDehoisted(true);
+}
+
+
+void HDehoistIndexComputationsPhase::Run() {
+  const ZoneList<HBasicBlock*>* blocks(graph()->blocks());
+  for (int i = 0; i < blocks->length(); ++i) {
+    for (HInstructionIterator it(blocks->at(i)); !it.Done(); it.Advance()) {
+      HInstruction* instr = it.Current();
+      if (instr->IsLoadKeyed()) {
+        DehoistArrayIndex(HLoadKeyed::cast(instr));
+      } else if (instr->IsStoreKeyed()) {
+        DehoistArrayIndex(HStoreKeyed::cast(instr));
+      }
+    }
+  }
+}
+
+}  // namespace internal
+}  // namespace v8