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//===- llvm/CodeGen/LivePhysRegs.h - Live Physical Register Set -*- C++ -*-===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file implements the LivePhysRegs utility for tracking liveness of
// physical registers. This can be used for ad-hoc liveness tracking after
// register allocation. You can start with the live-ins/live-outs at the
// beginning/end of a block and update the information while walking the
// instructions inside the block. This implementation tracks the liveness on a
// sub-register granularity.
//
// We assume that the high bits of a physical super-register are not preserved
// unless the instruction has an implicit-use operand reading the super-
// register.
//
// X86 Example:
// %YMM0<def> = ...
// %XMM0<def> = ... (Kills %XMM0, all %XMM0s sub-registers, and %YMM0)
//
// %YMM0<def> = ...
// %XMM0<def> = ..., %YMM0<imp-use> (%YMM0 and all its sub-registers are alive)
//===----------------------------------------------------------------------===//
#ifndef LLVM_CODEGEN_LIVEPHYSREGS_H
#define LLVM_CODEGEN_LIVEPHYSREGS_H
#include "llvm/ADT/SparseSet.h"
#include "llvm/CodeGen/MachineBasicBlock.h"
#include "llvm/Target/TargetRegisterInfo.h"
#include <cassert>
namespace llvm {
class MachineInstr;
/// \brief A set of live physical registers with functions to track liveness
/// when walking backward/forward through a basic block.
class LivePhysRegs {
const TargetRegisterInfo *TRI;
SparseSet<unsigned> LiveRegs;
LivePhysRegs(const LivePhysRegs&) = delete;
LivePhysRegs &operator=(const LivePhysRegs&) = delete;
public:
/// \brief Constructs a new empty LivePhysRegs set.
LivePhysRegs() : TRI(nullptr), LiveRegs() {}
/// \brief Constructs and initialize an empty LivePhysRegs set.
LivePhysRegs(const TargetRegisterInfo *TRI) : TRI(TRI) {
assert(TRI && "Invalid TargetRegisterInfo pointer.");
LiveRegs.setUniverse(TRI->getNumRegs());
}
/// \brief Clear and initialize the LivePhysRegs set.
void init(const TargetRegisterInfo *_TRI) {
assert(_TRI && "Invalid TargetRegisterInfo pointer.");
TRI = _TRI;
LiveRegs.clear();
LiveRegs.setUniverse(TRI->getNumRegs());
}
/// \brief Clears the LivePhysRegs set.
void clear() { LiveRegs.clear(); }
/// \brief Returns true if the set is empty.
bool empty() const { return LiveRegs.empty(); }
/// \brief Adds a physical register and all its sub-registers to the set.
void addReg(unsigned Reg) {
assert(TRI && "LivePhysRegs is not initialized.");
assert(Reg <= TRI->getNumRegs() && "Expected a physical register.");
for (MCSubRegIterator SubRegs(Reg, TRI, /*IncludeSelf=*/true);
SubRegs.isValid(); ++SubRegs)
LiveRegs.insert(*SubRegs);
}
/// \brief Removes a physical register, all its sub-registers, and all its
/// super-registers from the set.
void removeReg(unsigned Reg) {
assert(TRI && "LivePhysRegs is not initialized.");
assert(Reg <= TRI->getNumRegs() && "Expected a physical register.");
for (MCSubRegIterator SubRegs(Reg, TRI, /*IncludeSelf=*/true);
SubRegs.isValid(); ++SubRegs)
LiveRegs.erase(*SubRegs);
for (MCSuperRegIterator SuperRegs(Reg, TRI, /*IncludeSelf=*/false);
SuperRegs.isValid(); ++SuperRegs)
LiveRegs.erase(*SuperRegs);
}
/// \brief Removes physical registers clobbered by the regmask operand @p MO.
void removeRegsInMask(const MachineOperand &MO);
/// \brief Returns true if register @p Reg is contained in the set. This also
/// works if only the super register of @p Reg has been defined, because we
/// always add also all sub-registers to the set.
bool contains(unsigned Reg) const { return LiveRegs.count(Reg); }
/// \brief Simulates liveness when stepping backwards over an
/// instruction(bundle): Remove Defs, add uses. This is the recommended way of
/// calculating liveness.
void stepBackward(const MachineInstr &MI);
/// \brief Simulates liveness when stepping forward over an
/// instruction(bundle): Remove killed-uses, add defs. This is the not
/// recommended way, because it depends on accurate kill flags. If possible
/// use stepBackwards() instead of this function.
void stepForward(const MachineInstr &MI);
/// \brief Adds all live-in registers of basic block @p MBB.
void addLiveIns(const MachineBasicBlock *MBB) {
for (MachineBasicBlock::livein_iterator LI = MBB->livein_begin(),
LE = MBB->livein_end(); LI != LE; ++LI)
addReg(*LI);
}
/// \brief Adds all live-out registers of basic block @p MBB.
void addLiveOuts(const MachineBasicBlock *MBB) {
for (MachineBasicBlock::const_succ_iterator SI = MBB->succ_begin(),
SE = MBB->succ_end(); SI != SE; ++SI)
addLiveIns(*SI);
}
typedef SparseSet<unsigned>::const_iterator const_iterator;
const_iterator begin() const { return LiveRegs.begin(); }
const_iterator end() const { return LiveRegs.end(); }
/// \brief Prints the currently live registers to @p OS.
void print(raw_ostream &OS) const;
/// \brief Dumps the currently live registers to the debug output.
void dump() const;
};
inline raw_ostream &operator<<(raw_ostream &OS, const LivePhysRegs& LR) {
LR.print(OS);
return OS;
}
} // namespace llvm
#endif
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