1 //===- llvm/CodeGen/LivePhysRegs.h - Live Physical Register Set -*- 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 LivePhysRegs utility for tracking liveness of
11 // physical registers. This can be used for ad-hoc liveness tracking after
12 // register allocation. You can start with the live-ins/live-outs at the
13 // beginning/end of a block and update the information while walking the
14 // instructions inside the block. This implementation tracks the liveness on a
15 // sub-register granularity.
17 // We assume that the high bits of a physical super-register are not preserved
18 // unless the instruction has an implicit-use operand reading the super-
23 // %XMM0<def> = ... (Kills %XMM0, all %XMM0s sub-registers, and %YMM0)
26 // %XMM0<def> = ..., %YMM0<imp-use> (%YMM0 and all its sub-registers are alive)
27 //===----------------------------------------------------------------------===//
29 #ifndef LLVM_CODEGEN_LIVEPHYSREGS_H
30 #define LLVM_CODEGEN_LIVEPHYSREGS_H
32 #include "llvm/ADT/SparseSet.h"
33 #include "llvm/CodeGen/MachineBasicBlock.h"
34 #include "llvm/Target/TargetRegisterInfo.h"
41 /// \brief A set of live physical registers with functions to track liveness
42 /// when walking backward/forward through a basic block.
44 const TargetRegisterInfo *TRI;
45 SparseSet<unsigned> LiveRegs;
47 LivePhysRegs(const LivePhysRegs&) = delete;
48 LivePhysRegs &operator=(const LivePhysRegs&) = delete;
50 /// \brief Constructs a new empty LivePhysRegs set.
51 LivePhysRegs() : TRI(nullptr), LiveRegs() {}
53 /// \brief Constructs and initialize an empty LivePhysRegs set.
54 LivePhysRegs(const TargetRegisterInfo *TRI) : TRI(TRI) {
55 assert(TRI && "Invalid TargetRegisterInfo pointer.");
56 LiveRegs.setUniverse(TRI->getNumRegs());
59 /// \brief Clear and initialize the LivePhysRegs set.
60 void init(const TargetRegisterInfo *TRI) {
61 assert(TRI && "Invalid TargetRegisterInfo pointer.");
64 LiveRegs.setUniverse(TRI->getNumRegs());
67 /// \brief Clears the LivePhysRegs set.
68 void clear() { LiveRegs.clear(); }
70 /// \brief Returns true if the set is empty.
71 bool empty() const { return LiveRegs.empty(); }
73 /// \brief Adds a physical register and all its sub-registers to the set.
74 void addReg(unsigned Reg) {
75 assert(TRI && "LivePhysRegs is not initialized.");
76 assert(Reg <= TRI->getNumRegs() && "Expected a physical register.");
77 for (MCSubRegIterator SubRegs(Reg, TRI, /*IncludeSelf=*/true);
78 SubRegs.isValid(); ++SubRegs)
79 LiveRegs.insert(*SubRegs);
82 /// \brief Removes a physical register, all its sub-registers, and all its
83 /// super-registers from the set.
84 void removeReg(unsigned Reg) {
85 assert(TRI && "LivePhysRegs is not initialized.");
86 assert(Reg <= TRI->getNumRegs() && "Expected a physical register.");
87 for (MCSubRegIterator SubRegs(Reg, TRI, /*IncludeSelf=*/true);
88 SubRegs.isValid(); ++SubRegs)
89 LiveRegs.erase(*SubRegs);
90 for (MCSuperRegIterator SuperRegs(Reg, TRI, /*IncludeSelf=*/false);
91 SuperRegs.isValid(); ++SuperRegs)
92 LiveRegs.erase(*SuperRegs);
95 /// \brief Removes physical registers clobbered by the regmask operand @p MO.
96 void removeRegsInMask(const MachineOperand &MO,
97 SmallVectorImpl<std::pair<unsigned, const MachineOperand*>> *Clobbers);
99 /// \brief Returns true if register @p Reg is contained in the set. This also
100 /// works if only the super register of @p Reg has been defined, because we
101 /// always add also all sub-registers to the set.
102 bool contains(unsigned Reg) const { return LiveRegs.count(Reg); }
104 /// \brief Simulates liveness when stepping backwards over an
105 /// instruction(bundle): Remove Defs, add uses. This is the recommended way of
106 /// calculating liveness.
107 void stepBackward(const MachineInstr &MI);
109 /// \brief Simulates liveness when stepping forward over an
110 /// instruction(bundle): Remove killed-uses, add defs. This is the not
111 /// recommended way, because it depends on accurate kill flags. If possible
112 /// use stepBackwards() instead of this function.
113 /// The clobbers set will be the list of registers either defined or clobbered
114 /// by a regmask. The operand will identify whether this is a regmask or
115 /// register operand.
116 void stepForward(const MachineInstr &MI,
117 SmallVectorImpl<std::pair<unsigned, const MachineOperand*>> &Clobbers);
119 /// \brief Adds all live-in registers of basic block @p MBB; After prologue/
120 /// epilogue insertion \p AddPristines should be set to true to insert the
121 /// pristine registers.
122 void addLiveIns(const MachineBasicBlock *MBB, bool AddPristines = false);
124 /// \brief Adds all live-out registers of basic block @p MBB; After prologue/
125 /// epilogue insertion \p AddPristines should be set to true to insert the
126 /// pristine registers.
127 void addLiveOuts(const MachineBasicBlock *MBB, bool AddPristines = false);
129 typedef SparseSet<unsigned>::const_iterator const_iterator;
130 const_iterator begin() const { return LiveRegs.begin(); }
131 const_iterator end() const { return LiveRegs.end(); }
133 /// \brief Prints the currently live registers to @p OS.
134 void print(raw_ostream &OS) const;
136 /// \brief Dumps the currently live registers to the debug output.
140 inline raw_ostream &operator<<(raw_ostream &OS, const LivePhysRegs& LR) {