Subzero: Don't store std::string objects inside Variable.

src/IceInst.cpp

Index: src/IceInst.cpp
diff --git a/src/IceInst.cpp b/src/IceInst.cpp
index e1b5f436d9381816e9179899e775ea6a048a61fa..3e1ecf7d991bdddeb5a533597b655d5e51946b86 100644
--- a/src/IceInst.cpp
+++ b/src/IceInst.cpp
@@ -361,8 +361,9 @@ void InstPhi::livenessPhiOperand(LivenessBV &Live, CfgNode *Target,
 Inst *InstPhi::lower(Cfg *Func) {
   Variable *Dest = getDest();
   assert(Dest);
-  IceString PhiName = Dest->getName() + "_phi";
-  Variable *NewSrc = Func->makeVariable(Dest->getType(), PhiName);
+  Variable *NewSrc = Func->makeVariable(Dest->getType());
+  if (ALLOW_DUMP)
+    NewSrc->setName(Func, Dest->getName(Func) + "_phi");
   this->Dest = NewSrc;
   return InstAssign::create(Func, Dest, NewSrc);
 }