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1 //=- llvm/CodeGen/CriticalAntiDepBreaker.h - Anti-Dep Support -*- 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 the CriticalAntiDepBreaker class, which
11 // implements register anti-dependence breaking along a blocks
12 // critical path during post-RA scheduler.
13 //
14 //===----------------------------------------------------------------------===//
15 
16 #ifndef LLVM_CODEGEN_CRITICALANTIDEPBREAKER_H
17 #define LLVM_CODEGEN_CRITICALANTIDEPBREAKER_H
18 
19 #include "AntiDepBreaker.h"
20 #include "RegisterClassInfo.h"
21 #include "llvm/CodeGen/MachineBasicBlock.h"
22 #include "llvm/CodeGen/MachineFrameInfo.h"
23 #include "llvm/CodeGen/MachineFunction.h"
24 #include "llvm/CodeGen/MachineRegisterInfo.h"
25 #include "llvm/CodeGen/ScheduleDAG.h"
26 #include "llvm/ADT/BitVector.h"
27 #include <map>
28 
29 namespace llvm {
30 class RegisterClassInfo;
31 class TargetInstrInfo;
32 class TargetRegisterInfo;
33 
34   class CriticalAntiDepBreaker : public AntiDepBreaker {
35     MachineFunction& MF;
36     MachineRegisterInfo &MRI;
37     const TargetInstrInfo *TII;
38     const TargetRegisterInfo *TRI;
39     const RegisterClassInfo &RegClassInfo;
40 
41     /// AllocatableSet - The set of allocatable registers.
42     /// We'll be ignoring anti-dependencies on non-allocatable registers,
43     /// because they may not be safe to break.
44     const BitVector AllocatableSet;
45 
46     /// Classes - For live regs that are only used in one register class in a
47     /// live range, the register class. If the register is not live, the
48     /// corresponding value is null. If the register is live but used in
49     /// multiple register classes, the corresponding value is -1 casted to a
50     /// pointer.
51     std::vector<const TargetRegisterClass*> Classes;
52 
53     /// RegRefs - Map registers to all their references within a live range.
54     std::multimap<unsigned, MachineOperand *> RegRefs;
55     typedef std::multimap<unsigned, MachineOperand *>::const_iterator
56       RegRefIter;
57 
58     /// KillIndices - The index of the most recent kill (proceding bottom-up),
59     /// or ~0u if the register is not live.
60     std::vector<unsigned> KillIndices;
61 
62     /// DefIndices - The index of the most recent complete def (proceding bottom
63     /// up), or ~0u if the register is live.
64     std::vector<unsigned> DefIndices;
65 
66     /// KeepRegs - A set of registers which are live and cannot be changed to
67     /// break anti-dependencies.
68     BitVector KeepRegs;
69 
70   public:
71     CriticalAntiDepBreaker(MachineFunction& MFi, const RegisterClassInfo&);
72     ~CriticalAntiDepBreaker();
73 
74     /// Start - Initialize anti-dep breaking for a new basic block.
75     void StartBlock(MachineBasicBlock *BB);
76 
77     /// BreakAntiDependencies - Identifiy anti-dependencies along the critical
78     /// path
79     /// of the ScheduleDAG and break them by renaming registers.
80     ///
81     unsigned BreakAntiDependencies(const std::vector<SUnit>& SUnits,
82                                    MachineBasicBlock::iterator Begin,
83                                    MachineBasicBlock::iterator End,
84                                    unsigned InsertPosIndex,
85                                    DbgValueVector &DbgValues);
86 
87     /// Observe - Update liveness information to account for the current
88     /// instruction, which will not be scheduled.
89     ///
90     void Observe(MachineInstr *MI, unsigned Count, unsigned InsertPosIndex);
91 
92     /// Finish - Finish anti-dep breaking for a basic block.
93     void FinishBlock();
94 
95   private:
96     void PrescanInstruction(MachineInstr *MI);
97     void ScanInstruction(MachineInstr *MI, unsigned Count);
98     bool isNewRegClobberedByRefs(RegRefIter RegRefBegin,
99                                  RegRefIter RegRefEnd,
100                                  unsigned NewReg);
101     unsigned findSuitableFreeRegister(RegRefIter RegRefBegin,
102                                       RegRefIter RegRefEnd,
103                                       unsigned AntiDepReg,
104                                       unsigned LastNewReg,
105                                       const TargetRegisterClass *RC);
106   };
107 }
108 
109 #endif
110