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 /// Initialized - All states are initialized and ready to go!
35 /// RegStates - The current state of all the physical registers immediately
36 /// before MBBI. One bit per physical register. If bit is set that means it's
37 /// available, unset means the register is currently being used.
42 : MBB(NULL), Initialized(false) {};
44 RegScavenger(MachineBasicBlock *mbb)
45 : MBB(mbb), Initialized(false) {};
47 /// Init - Initialize the states.
49 void init(MachineBasicBlock *mbb = NULL);
51 /// Reset - Discard previous states and re-initialize the states given for
52 /// the specific basic block.
53 void reset(MachineBasicBlock *mbb) {
58 /// forward / backward - Move the internal MBB iterator and update register
63 /// forward / backward - Move the internal MBB iterator and update register
64 /// states until it has reached but not processed the specific iterator.
65 void forward(MachineBasicBlock::iterator I) {
66 while (MBBI != I) forward();
68 void backward(MachineBasicBlock::iterator I) {
69 while (MBBI != I) backward();
72 /// isReserved - Returns true if a register is reserved. It is never "unused".
73 bool isReserved(unsigned Reg) const { return ReservedRegs[Reg]; }
75 /// isUsed / isUsed - Test if a register is currently being used.
77 bool isUsed(unsigned Reg) const { return !RegStates[Reg]; }
78 bool isUnused(unsigned Reg) const { return RegStates[Reg]; }
80 /// setUsed / setUnused - Mark the state of one or a number of registers.
82 void setUsed(unsigned Reg) { RegStates.reset(Reg); }
83 void setUsed(BitVector Regs) { RegStates &= ~Regs; }
84 void setUnused(unsigned Reg) { RegStates.set(Reg); }
85 void setUnused(BitVector Regs) { RegStates |= Regs; }
87 /// FindUnusedReg - Find a unused register of the specified register class.
88 /// Exclude callee saved registers if directed. It return 0 is none is found.
89 unsigned FindUnusedReg(const TargetRegisterClass *RegClass,
90 bool ExCalleeSaved = false) const;
93 /// clear - Clear states.
97 /// CalleeSavedrRegs - A bitvector of callee saved registers for the target.
99 BitVector CalleeSavedRegs;
101 /// ReservedRegs - A bitvector of reserved registers.
103 BitVector ReservedRegs;
106 } // End llvm namespace