Subzero: Automatically infer regalloc preferences and overlap.

src/IceCfgNode.cpp

Index: src/IceCfgNode.cpp
diff --git a/src/IceCfgNode.cpp b/src/IceCfgNode.cpp
index eff4e973288c6a04b98356a5cb5639584f50b697..4efec9304adbc773d17ef86f0f517caf87186667 100644
--- a/src/IceCfgNode.cpp
+++ b/src/IceCfgNode.cpp
@@ -200,13 +200,6 @@ void CfgNode::placePhiStores() {
       Variable *Dest = (*I2)->getDest();
       assert(Dest);
       InstAssign *NewInst = InstAssign::create(Func, Dest, Operand);
-      // If Src is a variable, set the Src and Dest variables to
-      // prefer each other for register allocation.
-      if (Variable *Src = llvm::dyn_cast<Variable>(Operand)) {
-        bool AllowOverlap = false;
-        Dest->setPreferredRegister(Src, AllowOverlap);
-        Src->setPreferredRegister(Dest, AllowOverlap);
-      }
       if (CmpInstDest == Operand)
         Insts.insert(SafeInsertionPoint, NewInst);
       else