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 #include "llvm/ADT/ArrayRef.h" 21 #include "llvm/MC/MCRegisterInfo.h" 22 23 namespace llvm { 24 25 class RegisterClassInfo; 26 class VirtRegMap; 27 28 class AllocationOrder { 29 SmallVector<MCPhysReg, 16> Hints; 30 ArrayRef<MCPhysReg> Order; 31 int Pos; 32 33 public: 34 /// Create a new AllocationOrder for VirtReg. 35 /// @param VirtReg Virtual register to allocate for. 36 /// @param VRM Virtual register map for function. 37 /// @param RegClassInfo Information about reserved and allocatable registers. 38 AllocationOrder(unsigned VirtReg, 39 const VirtRegMap &VRM, 40 const RegisterClassInfo &RegClassInfo); 41 42 /// Get the allocation order without reordered hints. 43 ArrayRef<MCPhysReg> getOrder() const { return Order; } 44 45 /// Return the next physical register in the allocation order, or 0. 46 /// It is safe to call next() again after it returned 0, it will keep 47 /// returning 0 until rewind() is called. 48 unsigned next(unsigned Limit = 0) { 49 if (Pos < 0) 50 return Hints.end()[Pos++]; 51 if (!Limit) 52 Limit = Order.size(); 53 while (Pos < int(Limit)) { 54 unsigned Reg = Order[Pos++]; 55 if (!isHint(Reg)) 56 return Reg; 57 } 58 return 0; 59 } 60 61 /// As next(), but allow duplicates to be returned, and stop before the 62 /// Limit'th register in the RegisterClassInfo allocation order. 63 /// 64 /// This can produce more than Limit registers if there are hints. 65 unsigned nextWithDups(unsigned Limit) { 66 if (Pos < 0) 67 return Hints.end()[Pos++]; 68 if (Pos < int(Limit)) 69 return Order[Pos++]; 70 return 0; 71 } 72 73 /// Start over from the beginning. 74 void rewind() { Pos = -int(Hints.size()); } 75 76 /// Return true if the last register returned from next() was a preferred register. 77 bool isHint() const { return Pos <= 0; } 78 79 /// Return true if PhysReg is a preferred register. 80 bool isHint(unsigned PhysReg) const { 81 return std::find(Hints.begin(), Hints.end(), PhysReg) != Hints.end(); 82 } 83 }; 84 85 } // end namespace llvm 86 87 #endif 88
