1 //=- llvm/CodeGen/CriticalAntiDepBreaker.h - Anti-Dep Support -*- C++ -*-=//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file implements the CriticalAntiDepBreaker class, which
11 // implements register anti-dependence breaking along a blocks
12 // critical path during post-RA scheduler.
14 //===----------------------------------------------------------------------===//
16 #ifndef LLVM_CODEGEN_CRITICALANTIDEPBREAKER_H
17 #define LLVM_CODEGEN_CRITICALANTIDEPBREAKER_H
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"
30 class CriticalAntiDepBreaker : public AntiDepBreaker {
32 MachineRegisterInfo &MRI;
33 const TargetRegisterInfo *TRI;
35 /// AllocatableSet - The set of allocatable registers.
36 /// We'll be ignoring anti-dependencies on non-allocatable registers,
37 /// because they may not be safe to break.
38 const BitVector AllocatableSet;
40 /// Classes - For live regs that are only used in one register class in a
41 /// live range, the register class. If the register is not live, the
42 /// corresponding value is null. If the register is live but used in
43 /// multiple register classes, the corresponding value is -1 casted to a
45 const TargetRegisterClass *
46 Classes[TargetRegisterInfo::FirstVirtualRegister];
48 /// RegRegs - Map registers to all their references within a live range.
49 std::multimap<unsigned, MachineOperand *> RegRefs;
51 /// KillIndices - The index of the most recent kill (proceding bottom-up),
52 /// or ~0u if the register is not live.
53 unsigned KillIndices[TargetRegisterInfo::FirstVirtualRegister];
55 /// DefIndices - The index of the most recent complete def (proceding bottom
56 /// up), or ~0u if the register is live.
57 unsigned DefIndices[TargetRegisterInfo::FirstVirtualRegister];
59 /// KeepRegs - A set of registers which are live and cannot be changed to
60 /// break anti-dependencies.
61 SmallSet<unsigned, 4> KeepRegs;
64 CriticalAntiDepBreaker(MachineFunction& MFi);
65 ~CriticalAntiDepBreaker();
67 /// GetMaxTrials - Critical path anti-dependence breaking requires
68 /// only a single pass
69 unsigned GetMaxTrials() { return 1; }
71 /// NeedCandidates - Candidates not needed.
72 bool NeedCandidates() { return false; }
74 /// Start - Initialize anti-dep breaking for a new basic block.
75 void StartBlock(MachineBasicBlock *BB);
77 /// BreakAntiDependencies - Identifiy anti-dependencies along the critical path
78 /// of the ScheduleDAG and break them by renaming registers.
80 unsigned BreakAntiDependencies(std::vector<SUnit>& SUnits,
81 CandidateMap& Candidates,
82 MachineBasicBlock::iterator& Begin,
83 MachineBasicBlock::iterator& End,
84 unsigned InsertPosIndex);
86 /// Observe - Update liveness information to account for the current
87 /// instruction, which will not be scheduled.
89 void Observe(MachineInstr *MI, unsigned Count, unsigned InsertPosIndex);
91 /// Finish - Finish anti-dep breaking for a basic block.
95 void PrescanInstruction(MachineInstr *MI);
96 void ScanInstruction(MachineInstr *MI, unsigned Count);
97 unsigned findSuitableFreeRegister(unsigned AntiDepReg,
99 const TargetRegisterClass *);