lib/CodeGen/AllocationOrder.h

   1 //===-- llvm/CodeGen/AllocationOrder.h - Allocation Order -*- C++ -*-------===//
   2 //
   3 //                     The LLVM Compiler Infrastructure
   4 //
   5 // This file is distributed under the University of Illinois Open Source
   6 // License. See LICENSE.TXT for details.
   7 //
   8 //===----------------------------------------------------------------------===//
   9 //
  10 // This file implements an allocation order for virtual registers.
  11 //
  12 // The preferred allocation order for a virtual register depends on allocation
  13 // hints and target hooks. The AllocationOrder class encapsulates all of that.
  14 //
  15 //===----------------------------------------------------------------------===//
  16
  17 #ifndef LLVM_CODEGEN_ALLOCATIONORDER_H
  18 #define LLVM_CODEGEN_ALLOCATIONORDER_H
  19
  20 namespace llvm {
  21
  22 class RegisterClassInfo;
  23 class VirtRegMap;
  24
  25 class AllocationOrder {
  26   const unsigned *Begin;
  27   const unsigned *End;
  28   const unsigned *Pos;
  29   const RegisterClassInfo &RCI;
  30   unsigned Hint;
  31   bool OwnedBegin;
  32 public:
  33
  34   /// AllocationOrder - Create a new AllocationOrder for VirtReg.
  35   /// @param VirtReg      Virtual register to allocate for.
  36   /// @param VRM          Virtual register map for function.
  37   /// @param ReservedRegs Set of reserved registers as returned by
  38   ///        TargetRegisterInfo::getReservedRegs().
  39   AllocationOrder(unsigned VirtReg,
  40                   const VirtRegMap &VRM,
  41                   const RegisterClassInfo &RegClassInfo);
  42
  43   ~AllocationOrder();
  44
  45   /// next - Return the next physical register in the allocation order, or 0.
  46   /// It is safe to call next again after it returned 0.
  47   /// It will keep returning 0 until rewind() is called.
  48   unsigned next() {
  49     // First take the hint.
  50     if (!Pos) {
  51       Pos = Begin;
  52       if (Hint)
  53         return Hint;
  54     }
  55     // Then look at the order from TRI.
  56     while (Pos != End) {
  57       unsigned Reg = *Pos++;
  58       if (Reg != Hint)
  59         return Reg;
  60     }
  61     return 0;
  62   }
  63
  64   /// rewind - Start over from the beginning.
  65   void rewind() { Pos = 0; }
  66
  67   /// isHint - Return true if PhysReg is a preferred register.
  68   bool isHint(unsigned PhysReg) const { return PhysReg == Hint; }
  69 };
  70
  71 } // end namespace llvm
  72
  73 #endif