text: //===-- llvm/CodeGen/AllocationOrder.cpp - Allocation Order ---------------===//
  //
  //                     The LLVM Compiler Infrastructure
  //
  // This file is distributed under the University of Illinois Open Source
  // License. See LICENSE.TXT for details.
  //
  //===----------------------------------------------------------------------===//
  //
  // This file implements an allocation order for virtual registers.
  //
  // The preferred allocation order for a virtual register depends on allocation
  // hints and target hooks. The AllocationOrder class encapsulates all of that.
  //
  //===----------------------------------------------------------------------===//
  
  #include "AllocationOrder.h"
  #include "llvm/CodeGen/MachineFunction.h"
  #include "llvm/CodeGen/MachineRegisterInfo.h"
  #include "llvm/CodeGen/RegisterClassInfo.h"
  #include "llvm/CodeGen/VirtRegMap.h"
  #include "llvm/Support/Debug.h"
  #include "llvm/Support/raw_ostream.h"
  
  using namespace llvm;
  
  #define DEBUG_TYPE "regalloc"
  
  // Compare VirtRegMap::getRegAllocPref().
  AllocationOrder::AllocationOrder(unsigned VirtReg,
                                   const VirtRegMap &VRM,
                                   const RegisterClassInfo &RegClassInfo,
                                   const LiveRegMatrix *Matrix)
    : Pos(0), HardHints(false) {
    const MachineFunction &MF = VRM.getMachineFunction();
    const TargetRegisterInfo *TRI = &VRM.getTargetRegInfo();
    Order = RegClassInfo.getOrder(MF.getRegInfo().getRegClass(VirtReg));
    if (TRI->getRegAllocationHints(VirtReg, Order, Hints, MF, &VRM, Matrix))
      HardHints = true;
    rewind();
  
    DEBUG({
      if (!Hints.empty()) {
        dbgs() << "hints:";
        for (unsigned I = 0, E = Hints.size(); I != E; ++I)
          dbgs() << ' ' << printReg(Hints[I], TRI);
        dbgs() << '\n';
      }
    });
  #ifndef NDEBUG
    for (unsigned I = 0, E = Hints.size(); I != E; ++I)
      assert(is_contained(Order, Hints[I]) &&
             "Target hint is outside allocation order.");
  #endif
  }
  