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"
25 class TargetRegisterClass;
28 MachineBasicBlock *MBB;
29 MachineBasicBlock::iterator MBBI;
32 /// Tracking - True if RegScavenger is currently tracking the liveness of
36 /// RegStates - The current state of all the physical registers immediately
37 /// before MBBI. One bit per physical register. If bit is set that means it's
38 /// available, unset means the register is currently being used.
43 : MBB(NULL), NumPhysRegs(0), Tracking(false) {};
45 RegScavenger(MachineBasicBlock *mbb)
46 : MBB(mbb), NumPhysRegs(0), Tracking(false) {};
48 /// enterBasicBlock - Start tracking liveness from the begin of the specific
50 void enterBasicBlock(MachineBasicBlock *mbb);
52 /// forward / backward - Move the internal MBB iterator and update register
57 /// forward / backward - Move the internal MBB iterator and update register
58 /// states until it has reached but not processed the specific iterator.
59 void forward(MachineBasicBlock::iterator I) {
60 while (MBBI != I) forward();
62 void backward(MachineBasicBlock::iterator I) {
63 while (MBBI != I) backward();
66 /// isReserved - Returns true if a register is reserved. It is never "unused".
67 bool isReserved(unsigned Reg) const { return ReservedRegs[Reg]; }
69 /// isUsed / isUsed - Test if a register is currently being used.
71 bool isUsed(unsigned Reg) const { return !RegStates[Reg]; }
72 bool isUnused(unsigned Reg) const { return RegStates[Reg]; }
74 /// setUsed / setUnused - Mark the state of one or a number of registers.
76 void setUsed(unsigned Reg) { RegStates.reset(Reg); }
77 void setUsed(BitVector Regs) { RegStates &= ~Regs; }
78 void setUnused(unsigned Reg) { RegStates.set(Reg); }
79 void setUnused(BitVector Regs) { RegStates |= Regs; }
81 /// FindUnusedReg - Find a unused register of the specified register class
82 /// from the specified set of registers. It return 0 is none is found.
83 unsigned FindUnusedReg(const TargetRegisterClass *RegClass,
84 const BitVector &Candidates) const;
86 /// FindUnusedReg - Find a unused register of the specified register class.
87 /// Exclude callee saved registers if directed. It return 0 is none is found.
88 unsigned FindUnusedReg(const TargetRegisterClass *RegClass,
89 bool ExCalleeSaved = false) const;
92 /// CalleeSavedrRegs - A bitvector of callee saved registers for the target.
94 BitVector CalleeSavedRegs;
96 /// ReservedRegs - A bitvector of reserved registers.
98 BitVector ReservedRegs;
101 } // End llvm namespace