Subzero: Automatically infer regalloc preferences and overlap.

src/IceInst.cpp

 //===- subzero/src/IceInst.cpp - High-level instruction 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 Inst class, primarily the various
@@ skipping 328 matching lines @@
 }
 
 // Change "a=phi(...)" to "a_phi=phi(...)" and return a new
 // instruction "a=a_phi".
 Inst *InstPhi::lower(Cfg *Func) {
   Variable *Dest = getDest();
   assert(Dest);
   IceString PhiName = Dest->getName() + "_phi";
   Variable *NewSrc = Func->makeVariable(Dest->getType(), PhiName);
   this->Dest = NewSrc;
-  InstAssign *NewInst = InstAssign::create(Func, Dest, NewSrc);
-  // Set Dest and NewSrc to have affinity with each other, as a hint
-  // for register allocation.
-  Dest->setPreferredRegister(NewSrc, false);
-  NewSrc->setPreferredRegister(Dest, false);
-  return NewInst;
+  return InstAssign::create(Func, Dest, NewSrc);
 }
 
 InstRet::InstRet(Cfg *Func, Operand *RetValue)
     : Inst(Func, Ret, RetValue ? 1 : 0, NULL) {
   if (RetValue)
     addSource(RetValue);
 }
 
 InstSelect::InstSelect(Cfg *Func, Variable *Dest, Operand *Condition,
                        Operand *SourceTrue, Operand *SourceFalse)
@@ skipping 390 matching lines @@
 
 void InstTarget::dump(const Cfg *Func) const {
   Ostream &Str = Func->getContext()->getStrDump();
   Str << "[TARGET] ";
   Inst::dump(Func);
 }
 
 void InstTarget::dumpExtras(const Cfg *Func) const { Inst::dumpExtras(Func); }
 
 } // end of namespace Ice