Subzero: Fix a regalloc bug involving too-aggressive AllowRegisterOverlap.

src/IceCfg.cpp

Index: src/IceCfg.cpp
diff --git a/src/IceCfg.cpp b/src/IceCfg.cpp
index bc1bf63386bfd5fad4537e9c8f46c54ce25c30e7..3e32d755219d4600b5803a0cba1df05518d24a90 100644
--- a/src/IceCfg.cpp
+++ b/src/IceCfg.cpp
@@ -345,6 +345,13 @@ void Cfg::dump(const IceString &Message) {
           << " multiblock=" << Var->isMultiblockLife() << " "
           << " weight=" << Var->getWeight() << " ";
       Var->dump(this);
+      if (Variable *Pref = Var->getPreferredRegister()) {
+        Str << " pref=";
+        Pref->dump(this);
+        if (Var->getRegisterOverlap())
+          Str << ",overlap";
+        Str << " ";
+      }
       Str << " LIVE=" << Var->getLiveRange() << "\n";
     }
   }