1 //===-- RegisterScavenging.h - Machine register scavenging ------*- C++ -*-===//
3 // The LLVM Compiler Infrastructure
5 // This file was developed by the Evan Cheng and is distributed under the
6 // University of Illinois Open Source License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file declares the machine register scavenger class. It can provide
11 // information such as unused register at any point in a machine basic block.
12 // It also provides a mechanism to make registers availbale by evicting them
15 //===----------------------------------------------------------------------===//
17 #ifndef LLVM_CODEGEN_REGISTER_SCAVENGING_H
18 #define LLVM_CODEGEN_REGISTER_SCAVENGING_H
20 #include "llvm/CodeGen/MachineBasicBlock.h"
21 #include "llvm/ADT/BitVector.h"
26 class TargetInstrInfo;
27 class TargetRegisterClass;
30 MachineBasicBlock *MBB;
31 MachineBasicBlock::iterator MBBI;
34 /// Tracking - True if RegScavenger is currently tracking the liveness of
38 /// ScavengingFrameIndex - Special spill slot used for scavenging a register
39 /// post register allocation.
40 int ScavengingFrameIndex;
42 /// ScavengedReg - If none zero, the specific register is currently being
43 /// scavenged. That is, it is spilled to the special scavenging stack slot.
44 unsigned ScavengedReg;
46 /// ScavengedRC - Register class of the scavenged register.
48 const TargetRegisterClass *ScavengedRC;
50 /// RegStates - The current state of all the physical registers immediately
51 /// before MBBI. One bit per physical register. If bit is set that means it's
52 /// available, unset means the register is currently being used.
57 : MBB(NULL), NumPhysRegs(0), Tracking(false),
58 ScavengingFrameIndex(-1), ScavengedReg(0), ScavengedRC(NULL) {};
60 RegScavenger(MachineBasicBlock *mbb)
61 : MBB(mbb), NumPhysRegs(0), Tracking(false),
62 ScavengingFrameIndex(-1), ScavengedReg(0), ScavengedRC(NULL) {};
64 /// enterBasicBlock - Start tracking liveness from the begin of the specific
66 void enterBasicBlock(MachineBasicBlock *mbb);
68 /// forward / backward - Move the internal MBB iterator and update register
73 /// forward / backward - Move the internal MBB iterator and update register
74 /// states until it has reached but not processed the specific iterator.
75 void forward(MachineBasicBlock::iterator I) {
76 while (MBBI != I) forward();
78 void backward(MachineBasicBlock::iterator I) {
79 while (MBBI != I) backward();
82 /// skipTo - Move the internal MBB iterator but do not update register states.
84 void skipTo(MachineBasicBlock::iterator I) { MBBI = I; }
86 /// isReserved - Returns true if a register is reserved. It is never "unused".
87 bool isReserved(unsigned Reg) const { return ReservedRegs[Reg]; }
89 /// isUsed / isUsed - Test if a register is currently being used.
91 bool isUsed(unsigned Reg) const { return !RegStates[Reg]; }
92 bool isUnused(unsigned Reg) const { return RegStates[Reg]; }
94 /// setUsed / setUnused - Mark the state of one or a number of registers.
96 void setUsed(unsigned Reg) { RegStates.reset(Reg); }
97 void setUsed(BitVector Regs) { RegStates &= ~Regs; }
98 void setUnused(unsigned Reg) { RegStates.set(Reg); }
99 void setUnused(BitVector Regs) { RegStates |= Regs; }
101 /// FindUnusedReg - Find a unused register of the specified register class
102 /// from the specified set of registers. It return 0 is none is found.
103 unsigned FindUnusedReg(const TargetRegisterClass *RegClass,
104 const BitVector &Candidates) const;
106 /// FindUnusedReg - Find a unused register of the specified register class.
107 /// Exclude callee saved registers if directed. It return 0 is none is found.
108 unsigned FindUnusedReg(const TargetRegisterClass *RegClass,
109 bool ExCalleeSaved = false) const;
111 /// setScavengingFrameIndex / getScavengingFrameIndex - accessor and setter of
112 /// ScavengingFrameIndex.
113 void setScavengingFrameIndex(int FI) { ScavengingFrameIndex = FI; }
114 int getScavengingFrameIndex() const { return ScavengingFrameIndex; }
116 /// scavengeRegister - Make a register of the specific register class
117 /// available and do the appropriate bookkeeping. Returns the scavenged
119 unsigned scavengeRegister(const TargetRegisterClass *RegClass,
120 MachineBasicBlock::iterator I);
121 unsigned scavengeRegister(const TargetRegisterClass *RegClass) {
122 return scavengeRegister(RegClass, MBBI);
126 const MRegisterInfo *RegInfo;
127 const TargetInstrInfo *TII;
129 /// CalleeSavedrRegs - A bitvector of callee saved registers for the target.
131 BitVector CalleeSavedRegs;
133 /// ReservedRegs - A bitvector of reserved registers.
135 BitVector ReservedRegs;
137 /// restoreScavengedReg - Restore scavenged by loading it back from the
138 /// emergency spill slot. Mark it used.
139 void restoreScavengedReg();
142 } // End llvm namespace