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//===--- LivePhysRegs.cpp - Live Physical Register Set --------------------===//
//
// 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 across machine instructions in forward or backward order.
// A more detailed description can be found in the corresponding header file.
//
//===----------------------------------------------------------------------===//
#include "llvm/CodeGen/LivePhysRegs.h"
#include "llvm/CodeGen/MachineInstrBundle.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/raw_ostream.h"
using namespace llvm;
/// \brief Remove all registers from the set that get clobbered by the register
/// mask.
/// The clobbers set will be the list of live registers clobbered
/// by the regmask.
void LivePhysRegs::removeRegsInMask(const MachineOperand &MO,
SmallVectorImpl<std::pair<unsigned, const MachineOperand*>> *Clobbers) {
SparseSet<unsigned>::iterator LRI = LiveRegs.begin();
while (LRI != LiveRegs.end()) {
if (MO.clobbersPhysReg(*LRI)) {
if (Clobbers)
Clobbers->push_back(std::make_pair(*LRI, &MO));
LRI = LiveRegs.erase(LRI);
} else
++LRI;
}
}
/// Simulates liveness when stepping backwards over an instruction(bundle):
/// Remove Defs, add uses. This is the recommended way of calculating liveness.
void LivePhysRegs::stepBackward(const MachineInstr &MI) {
// Remove defined registers and regmask kills from the set.
for (ConstMIBundleOperands O(&MI); O.isValid(); ++O) {
if (O->isReg()) {
if (!O->isDef())
continue;
unsigned Reg = O->getReg();
if (Reg == 0)
continue;
removeReg(Reg);
} else if (O->isRegMask())
removeRegsInMask(*O, nullptr);
}
// Add uses to the set.
for (ConstMIBundleOperands O(&MI); O.isValid(); ++O) {
if (!O->isReg() || !O->readsReg() || O->isUndef())
continue;
unsigned Reg = O->getReg();
if (Reg == 0)
continue;
addReg(Reg);
}
}
/// 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 LivePhysRegs::stepForward(const MachineInstr &MI,
SmallVectorImpl<std::pair<unsigned, const MachineOperand*>> &Clobbers) {
// Remove killed registers from the set.
for (ConstMIBundleOperands O(&MI); O.isValid(); ++O) {
if (O->isReg()) {
unsigned Reg = O->getReg();
if (Reg == 0)
continue;
if (O->isDef()) {
// Note, dead defs are still recorded. The caller should decide how to
// handle them.
Clobbers.push_back(std::make_pair(Reg, &*O));
} else {
if (!O->isKill())
continue;
assert(O->isUse());
removeReg(Reg);
}
} else if (O->isRegMask())
removeRegsInMask(*O, &Clobbers);
}
// Add defs to the set.
for (auto Reg : Clobbers) {
// Skip dead defs. They shouldn't be added to the set.
if (Reg.second->isReg() && Reg.second->isDead())
continue;
addReg(Reg.first);
}
}
/// Prin the currently live registers to OS.
void LivePhysRegs::print(raw_ostream &OS) const {
OS << "Live Registers:";
if (!TRI) {
OS << " (uninitialized)\n";
return;
}
if (empty()) {
OS << " (empty)\n";
return;
}
for (const_iterator I = begin(), E = end(); I != E; ++I)
OS << " " << PrintReg(*I, TRI);
OS << "\n";
}
/// Dumps the currently live registers to the debug output.
void LivePhysRegs::dump() const {
#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
dbgs() << " " << *this;
#endif
}
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