1 //===-- RegisterScavenging.h - Machine register scavenging ------*- C++ -*-===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // 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_REGISTERSCAVENGING_H
18 #define LLVM_CODEGEN_REGISTERSCAVENGING_H
20 #include "llvm/ADT/BitVector.h"
21 #include "llvm/CodeGen/MachineBasicBlock.h"
22 #include "llvm/CodeGen/MachineRegisterInfo.h"
26 class MachineRegisterInfo;
27 class TargetRegisterInfo;
28 class TargetInstrInfo;
29 class TargetRegisterClass;
32 const TargetRegisterInfo *TRI;
33 const TargetInstrInfo *TII;
34 MachineRegisterInfo* MRI;
35 MachineBasicBlock *MBB;
36 MachineBasicBlock::iterator MBBI;
39 /// Tracking - True if RegScavenger is currently tracking the liveness of
43 /// ScavengingFrameIndex - Special spill slot used for scavenging a register
44 /// post register allocation.
45 int ScavengingFrameIndex;
47 /// ScavengedReg - If none zero, the specific register is currently being
48 /// scavenged. That is, it is spilled to the special scavenging stack slot.
49 unsigned ScavengedReg;
51 /// ScavengeRestore - Instruction that restores the scavenged register from
53 const MachineInstr *ScavengeRestore;
55 /// CalleeSavedrRegs - A bitvector of callee saved registers for the target.
57 BitVector CalleeSavedRegs;
59 /// RegsAvailable - The current state of all the physical registers immediately
60 /// before MBBI. One bit per physical register. If bit is set that means it's
61 /// available, unset means the register is currently being used.
62 BitVector RegsAvailable;
64 // These BitVectors are only used internally to forward(). They are members
65 // to avoid frequent reallocations.
66 BitVector KillRegs, DefRegs;
70 : MBB(NULL), NumPhysRegs(0), Tracking(false),
71 ScavengingFrameIndex(-1), ScavengedReg(0) {}
73 /// enterBasicBlock - Start tracking liveness from the begin of the specific
75 void enterBasicBlock(MachineBasicBlock *mbb);
77 /// initRegState - allow resetting register state info for multiple
78 /// passes over/within the same function.
81 /// forward - Move the internal MBB iterator and update register states.
84 /// forward - Move the internal MBB iterator and update register states until
85 /// it has processed the specific iterator.
86 void forward(MachineBasicBlock::iterator I) {
87 if (!Tracking && MBB->begin() != I) forward();
88 while (MBBI != I) forward();
91 /// skipTo - Move the internal MBB iterator but do not update register states.
93 void skipTo(MachineBasicBlock::iterator I) { MBBI = I; }
95 /// getRegsUsed - return all registers currently in use in used.
96 void getRegsUsed(BitVector &used, bool includeReserved);
98 /// getRegsAvailable - Return all available registers in the register class
100 BitVector getRegsAvailable(const TargetRegisterClass *RC);
102 /// FindUnusedReg - Find a unused register of the specified register class.
103 /// Return 0 if none is found.
104 unsigned FindUnusedReg(const TargetRegisterClass *RegClass) const;
106 /// setScavengingFrameIndex / getScavengingFrameIndex - accessor and setter of
107 /// ScavengingFrameIndex.
108 void setScavengingFrameIndex(int FI) { ScavengingFrameIndex = FI; }
109 int getScavengingFrameIndex() const { return ScavengingFrameIndex; }
111 /// scavengeRegister - Make a register of the specific register class
112 /// available and do the appropriate bookkeeping. SPAdj is the stack
113 /// adjustment due to call frame, it's passed along to eliminateFrameIndex().
114 /// Returns the scavenged register.
115 unsigned scavengeRegister(const TargetRegisterClass *RegClass,
116 MachineBasicBlock::iterator I, int SPAdj);
117 unsigned scavengeRegister(const TargetRegisterClass *RegClass, int SPAdj) {
118 return scavengeRegister(RegClass, MBBI, SPAdj);
121 /// setUsed - Tell the scavenger a register is used.
123 void setUsed(unsigned Reg);
125 /// isReserved - Returns true if a register is reserved. It is never "unused".
126 bool isReserved(unsigned Reg) const { return MRI->isReserved(Reg); }
128 /// isUsed - Test if a register is currently being used. When called by the
129 /// isAliasUsed function, we only check isReserved if this is the original
130 /// register, not an alias register.
132 bool isUsed(unsigned Reg, bool CheckReserved = true) const {
133 return !RegsAvailable.test(Reg) || (CheckReserved && isReserved(Reg));
136 /// isAliasUsed - Is Reg or an alias currently in use?
137 bool isAliasUsed(unsigned Reg) const;
139 /// setUsed / setUnused - Mark the state of one or a number of registers.
141 void setUsed(BitVector &Regs) {
142 RegsAvailable.reset(Regs);
144 void setUnused(BitVector &Regs) {
145 RegsAvailable |= Regs;
148 /// Add Reg and all its sub-registers to BV.
149 void addRegWithSubRegs(BitVector &BV, unsigned Reg);
151 /// findSurvivorReg - Return the candidate register that is unused for the
152 /// longest after StartMI. UseMI is set to the instruction where the search
155 /// No more than InstrLimit instructions are inspected.
156 unsigned findSurvivorReg(MachineBasicBlock::iterator StartMI,
157 BitVector &Candidates,
159 MachineBasicBlock::iterator &UseMI);
163 } // End llvm namespace