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

src/IceCfg.cpp

 //===- subzero/src/IceCfg.cpp - Control flow graph implementation ---------===//
 //
 //                        The Subzero Code Generator
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 //
 // This file implements the Cfg class, including constant pool
@@ skipping 327 matching lines @@
   setCurrentNode(NULL);
   if (getContext()->isVerbose(IceV_Liveness)) {
     // Print summary info about variables
     for (VarList::const_iterator I = Variables.begin(), E = Variables.end();
          I != E; ++I) {
       Variable *Var = *I;
       Str << "//"
           << " 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";
     }
   }
   // Print each basic block
   for (NodeList::const_iterator I = Nodes.begin(), E = Nodes.end(); I != E;
        ++I) {
     (*I)->dump(this);
   }
   if (getContext()->isVerbose(IceV_Instructions)) {
     Str << "}\n";
   }
 }
 
 } // end of namespace Ice