CriticalAntiDepBreaker.h revision 207618 
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/Target/TargetRegisterInfo.h"
26#include "llvm/ADT/BitVector.h"
27#include "llvm/ADT/SmallSet.h"
28#include <map>
29
30namespace llvm {
31  class CriticalAntiDepBreaker : public AntiDepBreaker {
32    MachineFunction& MF;
33    MachineRegisterInfo &MRI;
34    const TargetRegisterInfo *TRI;
35
36    /// AllocatableSet - The set of allocatable registers.
37    /// We'll be ignoring anti-dependencies on non-allocatable registers,
38    /// because they may not be safe to break.
39    const BitVector AllocatableSet;
40
41    /// Classes - For live regs that are only used in one register class in a
42    /// live range, the register class. If the register is not live, the
43    /// corresponding value is null. If the register is live but used in
44    /// multiple register classes, the corresponding value is -1 casted to a
45    /// pointer.
46    const TargetRegisterClass *
47      Classes[TargetRegisterInfo::FirstVirtualRegister];
48
49    /// RegRegs - Map registers to all their references within a live range.
50    std::multimap<unsigned, MachineOperand *> RegRefs;
51
52    /// KillIndices - The index of the most recent kill (proceding bottom-up),
53    /// or ~0u if the register is not live.
54    unsigned KillIndices[TargetRegisterInfo::FirstVirtualRegister];
55
56    /// DefIndices - The index of the most recent complete def (proceding bottom
57    /// up), or ~0u if the register is live.
58    unsigned DefIndices[TargetRegisterInfo::FirstVirtualRegister];
59
60    /// KeepRegs - A set of registers which are live and cannot be changed to
61    /// break anti-dependencies.
62    SmallSet<unsigned, 4> KeepRegs;
63
64  public:
65    CriticalAntiDepBreaker(MachineFunction& MFi);
66    ~CriticalAntiDepBreaker();
67
68    /// Start - Initialize anti-dep breaking for a new basic block.
69    void StartBlock(MachineBasicBlock *BB);
70
71    /// BreakAntiDependencies - Identifiy anti-dependencies along the critical
72    /// path
73    /// of the ScheduleDAG and break them by renaming registers.
74    ///
75    unsigned BreakAntiDependencies(const std::vector<SUnit>& SUnits,
76                                   MachineBasicBlock::iterator Begin,
77                                   MachineBasicBlock::iterator End,
78                                   unsigned InsertPosIndex);
79
80    /// Observe - Update liveness information to account for the current
81    /// instruction, which will not be scheduled.
82    ///
83    void Observe(MachineInstr *MI, unsigned Count, unsigned InsertPosIndex);
84
85    /// Finish - Finish anti-dep breaking for a basic block.
86    void FinishBlock();
87
88  private:
89    void PrescanInstruction(MachineInstr *MI);
90    void ScanInstruction(MachineInstr *MI, unsigned Count);
91    unsigned findSuitableFreeRegister(MachineInstr *MI,
92                                      unsigned AntiDepReg,
93                                      unsigned LastNewReg,
94                                      const TargetRegisterClass *);
95  };
96}
97
98#endif
99