[stubs] Enforce correct index representation on 64-bit.

src/code-stub-assembler.cc

 // Copyright 2016 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/code-stub-assembler.h"
 #include "src/code-factory.h"
 
 namespace v8 {
 namespace internal {
 
@@ skipping 1547 matching lines @@
     element_size_shift -= kSmiShiftBits;
     intptr_t temp = 0;
     constant_index = ToIntPtrConstant(index_node, temp);
     index = temp >> kSmiShiftBits;
   } else {
     constant_index = ToInt32Constant(index_node, index);
   }
   if (constant_index) {
     return IntPtrConstant(base_size + element_size * index);
   }
+  if (Is64() && mode == INTEGER_PARAMETERS) {
+    index_node = ChangeInt32ToInt64(index_node);
+  }
   if (base_size == 0) {
     return (element_size_shift >= 0)
                ? WordShl(index_node, IntPtrConstant(element_size_shift))
                : WordShr(index_node, IntPtrConstant(-element_size_shift));
   }
   return IntPtrAdd(
-      Int32Constant(base_size),
+      IntPtrConstant(base_size),
       (element_size_shift >= 0)
           ? WordShl(index_node, IntPtrConstant(element_size_shift))
           : WordShr(index_node, IntPtrConstant(-element_size_shift)));
 }
 
 }  // namespace internal
 }  // namespace v8