CriticalAntiDepBreaker.h revision 46388526963aba92344ee8ebd9e86d3556baa088 
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 "llvm/CodeGen/MachineBasicBlock.h"
21#include "llvm/CodeGen/MachineFrameInfo.h"
22#include "llvm/CodeGen/MachineFunction.h"
23#include "llvm/CodeGen/MachineRegisterInfo.h"
24#include "llvm/CodeGen/ScheduleDAG.h"
25#include "llvm/ADT/BitVector.h"
26#include "llvm/ADT/SmallSet.h"
27#include <map>
28
29namespace llvm {
30class TargetInstrInfo;
31class TargetRegisterInfo;
32
33  class CriticalAntiDepBreaker : public AntiDepBreaker {
34    MachineFunction& MF;
35    MachineRegisterInfo &MRI;
36    const TargetInstrInfo *TII;
37    const TargetRegisterInfo *TRI;
38
39    /// AllocatableSet - The set of allocatable registers.
40    /// We'll be ignoring anti-dependencies on non-allocatable registers,
41    /// because they may not be safe to break.
42    const BitVector AllocatableSet;
43
44    /// Classes - For live regs that are only used in one register class in a
45    /// live range, the register class. If the register is not live, the
46    /// corresponding value is null. If the register is live but used in
47    /// multiple register classes, the corresponding value is -1 casted to a
48    /// pointer.
49    std::vector<const TargetRegisterClass*> Classes;
50
51    /// RegRegs - Map registers to all their references within a live range.
52    std::multimap<unsigned, MachineOperand *> RegRefs;
53    typedef std::multimap<unsigned, MachineOperand *>::const_iterator
54      RegRefIter;
55
56    /// KillIndices - The index of the most recent kill (proceding bottom-up),
57    /// or ~0u if the register is not live.
58    std::vector<unsigned> KillIndices;
59
60    /// DefIndices - The index of the most recent complete def (proceding bottom
61    /// up), or ~0u if the register is live.
62    std::vector<unsigned> DefIndices;
63
64    /// KeepRegs - A set of registers which are live and cannot be changed to
65    /// break anti-dependencies.
66    SmallSet<unsigned, 4> KeepRegs;
67
68  public:
69    CriticalAntiDepBreaker(MachineFunction& MFi);
70    ~CriticalAntiDepBreaker();
71
72    /// Start - Initialize anti-dep breaking for a new basic block.
73    void StartBlock(MachineBasicBlock *BB);
74
75    /// BreakAntiDependencies - Identifiy anti-dependencies along the critical
76    /// path
77    /// of the ScheduleDAG and break them by renaming registers.
78    ///
79    unsigned BreakAntiDependencies(const std::vector<SUnit>& SUnits,
80                                   MachineBasicBlock::iterator Begin,
81                                   MachineBasicBlock::iterator End,
82                                   unsigned InsertPosIndex);
83
84    /// Observe - Update liveness information to account for the current
85    /// instruction, which will not be scheduled.
86    ///
87    void Observe(MachineInstr *MI, unsigned Count, unsigned InsertPosIndex);
88
89    /// Finish - Finish anti-dep breaking for a basic block.
90    void FinishBlock();
91
92  private:
93    void PrescanInstruction(MachineInstr *MI);
94    void ScanInstruction(MachineInstr *MI, unsigned Count);
95    bool isNewRegModifiedByRefs(RegRefIter RegRefBegin,
96                                RegRefIter RegRefEnd,
97                                unsigned NewReg);
98    unsigned findSuitableFreeRegister(RegRefIter RegRefBegin,
99                                      RegRefIter RegRefEnd,
100                                      unsigned AntiDepReg,
101                                      unsigned LastNewReg,
102                                      const TargetRegisterClass *RC);
103  };
104}
105
106#endif
107