Fix int64 lowering on big-endian architectures.

src/compiler/int64-lowering.h

Index: src/compiler/int64-lowering.h
diff --git a/src/compiler/int64-lowering.h b/src/compiler/int64-lowering.h
index 054c4219948bb640fc4bc43adb89f655046c4987..4ec4e821eb978f9a0dc2e8908c19745b49639962 100644
--- a/src/compiler/int64-lowering.h
+++ b/src/compiler/int64-lowering.h
@@ -26,6 +26,9 @@ class Int64Lowering {
   static int GetParameterCountAfterLowering(
       Signature<MachineRepresentation>* signature);
 
+  static const int kLowerWordOffset;
+  static const int kHigherWordOffset;
+
  private:
   enum class State : uint8_t { kUnvisited, kOnStack, kVisited };
 
@@ -54,6 +57,7 @@ class Int64Lowering {
   bool HasReplacementHigh(Node* node);
   Node* GetReplacementHigh(Node* node);
   void PreparePhiReplacement(Node* phi);
+  void GetIndexNodes(Node* index, Node*& index_low, Node*& index_high);
 
   struct NodeState {
     Node* node;