Revert r4782. Fix issues 728, 732.

src/x64/ic-x64.cc

Index: src/x64/ic-x64.cc
diff --git a/src/x64/ic-x64.cc b/src/x64/ic-x64.cc
index 21bb7e85f68e9f8c2c9fad5de49d110162f635f4..f98703b6d7d5dd06cf18b37670c96ac5452e0c0a 100644
--- a/src/x64/ic-x64.cc
+++ b/src/x64/ic-x64.cc
@@ -442,8 +442,8 @@ void KeyedLoadIC::GenerateGeneric(MacroAssembler* masm) {
   __ j(above_equal, &slow);
   // Is the string an array index, with cached numeric value?
   __ movl(rbx, FieldOperand(rax, String::kHashFieldOffset));
-  __ testl(rbx, Immediate(String::kIsArrayIndexMask));
-  __ j(not_zero, &index_string);  // The value in rbx is used at jump target.
+  __ testl(rbx, Immediate(String::kContainsCachedArrayIndexMask));
+  __ j(zero, &index_string);  // The value in rbx is used at jump target.
 
   // Is the string a symbol?
   ASSERT(kSymbolTag != 0);