Add a change that should be part of "enhance gvn for commutative ops."

Change-Id: Id1a30afb095b2c7e27a4ef8a1ef7293022c1aaed
diff --git a/compiler/optimizing/code_generator_x86.cc b/compiler/optimizing/code_generator_x86.cc
index 116dd15..3c8f62c 100644
--- a/compiler/optimizing/code_generator_x86.cc
+++ b/compiler/optimizing/code_generator_x86.cc
@@ -922,7 +922,7 @@
     if (rhs.IsRegister()) {
       __ cmpl(lhs.AsRegister<Register>(), rhs.AsRegister<Register>());
     } else if (rhs.IsConstant()) {
-      int32_t constant = rhs.GetConstant()->AsIntConstant()->GetValue();
+      int32_t constant = CodeGenerator::GetInt32ValueOf(rhs.GetConstant());
       if (constant == 0) {
         __ testl(lhs.AsRegister<Register>(), lhs.AsRegister<Register>());
       } else {