1 //=- llvm/CodeGen/AggressiveAntiDepBreaker.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 AggressiveAntiDepBreaker class, which
11 // implements register anti-dependence breaking during post-RA
12 // scheduling. It attempts to break all anti-dependencies within a
15 //===----------------------------------------------------------------------===//
17 #ifndef LLVM_CODEGEN_AGGRESSIVEANTIDEPBREAKER_H
18 #define LLVM_CODEGEN_AGGRESSIVEANTIDEPBREAKER_H
20 #include "AntiDepBreaker.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/Target/TargetRegisterInfo.h"
27 #include "llvm/ADT/BitVector.h"
28 #include "llvm/ADT/SmallSet.h"
31 /// Class AggressiveAntiDepState
32 /// Contains all the state necessary for anti-dep breaking. We place
33 /// into a separate class so be can conveniently save/restore it to
34 /// enable multi-pass anti-dep breaking.
35 class AggressiveAntiDepState {
37 /// RegisterReference - Information about a register reference
38 /// within a liverange
40 /// Operand - The registers operand
41 MachineOperand *Operand;
42 /// RC - The register class
43 const TargetRegisterClass *RC;
47 /// GroupNodes - Implements a disjoint-union data structure to
48 /// form register groups. A node is represented by an index into
49 /// the vector. A node can "point to" itself to indicate that it
50 /// is the parent of a group, or point to another node to indicate
51 /// that it is a member of the same group as that node.
52 std::vector<unsigned> GroupNodes;
54 /// GroupNodeIndices - For each register, the index of the GroupNode
55 /// currently representing the group that the register belongs to.
56 /// Register 0 is always represented by the 0 group, a group
57 /// composed of registers that are not eligible for anti-aliasing.
58 unsigned GroupNodeIndices[TargetRegisterInfo::FirstVirtualRegister];
60 /// RegRefs - Map registers to all their references within a live range.
61 std::multimap<unsigned, RegisterReference> RegRefs;
63 /// KillIndices - The index of the most recent kill (proceding bottom-up),
64 /// or ~0u if the register is not live.
65 unsigned KillIndices[TargetRegisterInfo::FirstVirtualRegister];
67 /// DefIndices - The index of the most recent complete def (proceding bottom
68 /// up), or ~0u if the register is live.
69 unsigned DefIndices[TargetRegisterInfo::FirstVirtualRegister];
72 AggressiveAntiDepState(MachineBasicBlock *BB);
74 /// GetKillIndices - Return the kill indices.
75 unsigned *GetKillIndices() { return KillIndices; }
77 /// GetDefIndices - Return the define indices.
78 unsigned *GetDefIndices() { return DefIndices; }
80 /// GetRegRefs - Return the RegRefs map.
81 std::multimap<unsigned, RegisterReference>& GetRegRefs() { return RegRefs; }
83 // GetGroup - Get the group for a register. The returned value is
84 // the index of the GroupNode representing the group.
85 unsigned GetGroup(unsigned Reg);
87 // GetGroupRegs - Return a vector of the registers belonging to a
89 void GetGroupRegs(unsigned Group, std::vector<unsigned> &Regs);
91 // UnionGroups - Union Reg1's and Reg2's groups to form a new
92 // group. Return the index of the GroupNode representing the
94 unsigned UnionGroups(unsigned Reg1, unsigned Reg2);
96 // LeaveGroup - Remove a register from its current group and place
97 // it alone in its own group. Return the index of the GroupNode
98 // representing the registers new group.
99 unsigned LeaveGroup(unsigned Reg);
101 /// IsLive - Return true if Reg is live
102 bool IsLive(unsigned Reg);
106 /// Class AggressiveAntiDepBreaker
107 class AggressiveAntiDepBreaker : public AntiDepBreaker {
109 MachineRegisterInfo &MRI;
110 const TargetRegisterInfo *TRI;
112 /// AllocatableSet - The set of allocatable registers.
113 /// We'll be ignoring anti-dependencies on non-allocatable registers,
114 /// because they may not be safe to break.
115 const BitVector AllocatableSet;
117 /// State - The state used to identify and rename anti-dependence
119 AggressiveAntiDepState *State;
121 /// SavedState - The state for the start of an anti-dep
122 /// region. Used to restore the state at the beginning of each
124 AggressiveAntiDepState *SavedState;
127 AggressiveAntiDepBreaker(MachineFunction& MFi);
128 ~AggressiveAntiDepBreaker();
130 /// GetMaxTrials - As anti-dependencies are broken, additional
131 /// dependencies may be exposed, so multiple passes are required.
132 unsigned GetMaxTrials();
134 /// Start - Initialize anti-dep breaking for a new basic block.
135 void StartBlock(MachineBasicBlock *BB);
137 /// BreakAntiDependencies - Identifiy anti-dependencies along the critical path
138 /// of the ScheduleDAG and break them by renaming registers.
140 unsigned BreakAntiDependencies(std::vector<SUnit>& SUnits,
141 MachineBasicBlock::iterator& Begin,
142 MachineBasicBlock::iterator& End,
143 unsigned InsertPosIndex);
145 /// Observe - Update liveness information to account for the current
146 /// instruction, which will not be scheduled.
148 void Observe(MachineInstr *MI, unsigned Count, unsigned InsertPosIndex);
150 /// Finish - Finish anti-dep breaking for a basic block.
154 /// IsImplicitDefUse - Return true if MO represents a register
155 /// that is both implicitly used and defined in MI
156 bool IsImplicitDefUse(MachineInstr *MI, MachineOperand& MO);
158 /// GetPassthruRegs - If MI implicitly def/uses a register, then
159 /// return that register and all subregisters.
160 void GetPassthruRegs(MachineInstr *MI, std::set<unsigned>& PassthruRegs);
162 void PrescanInstruction(MachineInstr *MI, unsigned Count,
163 std::set<unsigned>& PassthruRegs);
164 void ScanInstruction(MachineInstr *MI, unsigned Count);
165 BitVector GetRenameRegisters(unsigned Reg);
166 bool FindSuitableFreeRegisters(unsigned AntiDepGroupIndex,
167 std::map<unsigned, unsigned> &RenameMap);