Revert r4715.

src/x64/full-codegen-x64.cc

 // Copyright 2010 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 992 matching lines @@
 
   // We got a map in register rax. Get the enumeration cache from it.
   __ movq(rcx, FieldOperand(rax, Map::kInstanceDescriptorsOffset));
   __ movq(rcx, FieldOperand(rcx, DescriptorArray::kEnumerationIndexOffset));
   __ movq(rdx, FieldOperand(rcx, DescriptorArray::kEnumCacheBridgeCacheOffset));
 
   // Setup the four remaining stack slots.
   __ push(rax);  // Map.
   __ push(rdx);  // Enumeration cache.
   __ movq(rax, FieldOperand(rdx, FixedArray::kLengthOffset));
+  __ Integer32ToSmi(rax, rax);
   __ push(rax);  // Enumeration cache length (as smi).
   __ Push(Smi::FromInt(0));  // Initial index.
   __ jmp(&loop);
 
   // We got a fixed array in register rax. Iterate through that.
   __ bind(&fixed_array);
   __ Push(Smi::FromInt(0));  // Map (0) - force slow check.
   __ push(rax);
   __ movq(rax, FieldOperand(rax, FixedArray::kLengthOffset));
+  __ Integer32ToSmi(rax, rax);
   __ push(rax);  // Fixed array length (as smi).
   __ Push(Smi::FromInt(0));  // Initial index.
 
   // Generate code for doing the condition check.
   __ bind(&loop);
   __ movq(rax, Operand(rsp, 0 * kPointerSize));  // Get the current index.
   __ cmpq(rax, Operand(rsp, 1 * kPointerSize));  // Compare to the array length.
   __ j(above_equal, loop_statement.break_target());
 
   // Get the current entry of the array into register rbx.
@@ skipping 2178 matching lines @@
   __ ret(0);
 }
 
 
 #undef __
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_X64