[turbofan] support for Int64 in CheckedLoad/CheckedStore on 64-bit platforms.

src/compiler/x64/instruction-selector-x64.cc

Index: src/compiler/x64/instruction-selector-x64.cc
diff --git a/src/compiler/x64/instruction-selector-x64.cc b/src/compiler/x64/instruction-selector-x64.cc
index 0bcd526322bcd7cef3f7710211b7ad96a4fb0914..fa63138f2799841c5af49c2ac93a7493541881cb 100644
--- a/src/compiler/x64/instruction-selector-x64.cc
+++ b/src/compiler/x64/instruction-selector-x64.cc
@@ -233,6 +233,9 @@ void InstructionSelector::VisitCheckedLoad(Node* node) {
     case kRepWord32:
       opcode = kCheckedLoadWord32;
       break;
+    case kRepWord64:
+      opcode = kCheckedLoadWord64;
+      break;
     case kRepFloat32:
       opcode = kCheckedLoadFloat32;
       break;
@@ -280,6 +283,9 @@ void InstructionSelector::VisitCheckedStore(Node* node) {
     case kRepWord32:
       opcode = kCheckedStoreWord32;
       break;
+    case kRepWord64:
+      opcode = kCheckedStoreWord64;
+      break;
     case kRepFloat32:
       opcode = kCheckedStoreFloat32;
       break;