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/MC/MCRegisterInfo.h"
35 #include "llvm/Target/TargetRegisterInfo.h"
43 /// \brief A set of live physical registers with functions to track liveness
44 /// when walking backward/forward through a basic block.
46 const TargetRegisterInfo *TRI = nullptr;
47 SparseSet<unsigned> LiveRegs;
49 LivePhysRegs(const LivePhysRegs&) = delete;
50 LivePhysRegs &operator=(const LivePhysRegs&) = delete;
53 /// \brief Constructs a new empty LivePhysRegs set.
54 LivePhysRegs() = default;
56 /// \brief Constructs and initialize an empty LivePhysRegs set.
57 LivePhysRegs(const TargetRegisterInfo *TRI) : TRI(TRI) {
58 assert(TRI && "Invalid TargetRegisterInfo pointer.");
59 LiveRegs.setUniverse(TRI->getNumRegs());
62 /// \brief Clear and initialize the LivePhysRegs set.
63 void init(const TargetRegisterInfo &TRI) {
66 LiveRegs.setUniverse(TRI.getNumRegs());
69 /// \brief Clears the LivePhysRegs set.
70 void clear() { LiveRegs.clear(); }
72 /// \brief Returns true if the set is empty.
73 bool empty() const { return LiveRegs.empty(); }
75 /// \brief Adds a physical register and all its sub-registers to the set.
76 void addReg(unsigned Reg) {
77 assert(TRI && "LivePhysRegs is not initialized.");
78 assert(Reg <= TRI->getNumRegs() && "Expected a physical register.");
79 for (MCSubRegIterator SubRegs(Reg, TRI, /*IncludeSelf=*/true);
80 SubRegs.isValid(); ++SubRegs)
81 LiveRegs.insert(*SubRegs);
84 /// \brief Removes a physical register, all its sub-registers, and all its
85 /// super-registers from the set.
86 void removeReg(unsigned Reg) {
87 assert(TRI && "LivePhysRegs is not initialized.");
88 assert(Reg <= TRI->getNumRegs() && "Expected a physical register.");
89 for (MCRegAliasIterator R(Reg, TRI, true); R.isValid(); ++R)
93 /// \brief Removes physical registers clobbered by the regmask operand @p MO.
94 void removeRegsInMask(const MachineOperand &MO,
95 SmallVectorImpl<std::pair<unsigned, const MachineOperand*>> *Clobbers);
97 /// \brief Returns true if register @p Reg is contained in the set. This also
98 /// works if only the super register of @p Reg has been defined, because
99 /// addReg() always adds all sub-registers to the set as well.
100 /// Note: Returns false if just some sub registers are live, use available()
101 /// when searching a free register.
102 bool contains(unsigned Reg) const { return LiveRegs.count(Reg); }
104 /// Returns true if register \p Reg and no aliasing register is in the set.
105 bool available(const MachineRegisterInfo &MRI, unsigned Reg) const;
107 /// \brief Simulates liveness when stepping backwards over an
108 /// instruction(bundle): Remove Defs, add uses. This is the recommended way of
109 /// calculating liveness.
110 void stepBackward(const MachineInstr &MI);
112 /// \brief Simulates liveness when stepping forward over an
113 /// instruction(bundle): Remove killed-uses, add defs. This is the not
114 /// recommended way, because it depends on accurate kill flags. If possible
115 /// use stepBackward() instead of this function.
116 /// The clobbers set will be the list of registers either defined or clobbered
117 /// by a regmask. The operand will identify whether this is a regmask or
118 /// register operand.
119 void stepForward(const MachineInstr &MI,
120 SmallVectorImpl<std::pair<unsigned, const MachineOperand*>> &Clobbers);
122 /// Adds all live-in registers of basic block @p MBB.
123 /// Live in registers are the registers in the blocks live-in list and the
124 /// pristine registers.
125 void addLiveIns(const MachineBasicBlock &MBB);
127 /// Adds all live-out registers of basic block @p MBB.
128 /// Live out registers are the union of the live-in registers of the successor
129 /// blocks and pristine registers. Live out registers of the end block are the
130 /// callee saved registers.
131 void addLiveOuts(const MachineBasicBlock &MBB);
133 /// Like addLiveOuts() but does not add pristine registers/callee saved
135 void addLiveOutsNoPristines(const MachineBasicBlock &MBB);
137 typedef SparseSet<unsigned>::const_iterator const_iterator;
138 const_iterator begin() const { return LiveRegs.begin(); }
139 const_iterator end() const { return LiveRegs.end(); }
141 /// \brief Prints the currently live registers to @p OS.
142 void print(raw_ostream &OS) const;
144 /// \brief Dumps the currently live registers to the debug output.
148 /// Adds live-in registers from basic block @p MBB, taking associated
149 /// lane masks into consideration.
150 void addBlockLiveIns(const MachineBasicBlock &MBB);
153 inline raw_ostream &operator<<(raw_ostream &OS, const LivePhysRegs& LR) {
158 /// Compute the live-in list for \p MBB assuming all of its successors live-in
159 /// lists are up-to-date. Uses the given LivePhysReg instance \p LiveRegs; This
160 /// is just here to avoid repeated heap allocations when calling this multiple
162 void computeLiveIns(LivePhysRegs &LiveRegs, const TargetRegisterInfo &TRI,
163 MachineBasicBlock &MBB);
165 } // end namespace llvm
167 #endif // LLVM_CODEGEN_LIVEPHYSREGS_H