Revert change 1656 which was unsafe until it can be properly fixed....

src/codegen-ia32.cc

Index: src/codegen-ia32.cc
===================================================================
--- src/codegen-ia32.cc	(revision 1661)
+++ src/codegen-ia32.cc	(working copy)
@@ -4799,25 +4799,17 @@
                                    target.size() * kPointerSize);
 
     Result value = frame_->Pop();
+    value.ToRegister();
+    ASSERT(value.is_valid());
 
     // Postfix: Store the old value as the result.
     if (is_postfix) {
-      if (value.is_register()) {
-        Result old_value = allocator_->Allocate();
-        ASSERT(old_value.is_valid());
-        __ mov(old_value.reg(), value.reg());
-        frame_->SetElementAt(target.size(), &old_value);
-      } else {
-        ASSERT(value.is_constant());
-        Result old_value = value;
-        frame_->SetElementAt(target.size(), &old_value);
-      }
+      Result old_value = value;
+      frame_->SetElementAt(target.size(), &old_value);
     }
 
     // Perform optimistic increment/decrement.  Ensure the value is
     // writable.
-    value.ToRegister();
-    ASSERT(value.is_valid());
     frame_->Spill(value.reg());
     ASSERT(allocator_->count(value.reg()) == 1);