bool SIFixSGPRLiveRanges::runOnMachineFunction(MachineFunction &MF) {
MachineRegisterInfo &MRI = MF.getRegInfo();
const TargetInstrInfo *TII = MF.getSubtarget().getInstrInfo();
const SIRegisterInfo *TRI = static_cast<const SIRegisterInfo *>(
MF.getSubtarget().getRegisterInfo());
bool MadeChange = false;
MachinePostDominatorTree *PDT = &getAnalysis<MachinePostDominatorTree>();
std::vector<std::pair<unsigned, LiveRange *>> SGPRLiveRanges;
LiveIntervals *LIS = &getAnalysis<LiveIntervals>();
LiveVariables *LV = getAnalysisIfAvailable<LiveVariables>();
MachineBasicBlock *Entry = MF.begin();
// Use a depth first order so that in SSA, we encounter all defs before
// uses. Once the defs of the block have been found, attempt to insert
// SGPR_USE instructions in successor blocks if required.
for (MachineBasicBlock *MBB : depth_first(Entry)) {
for (const MachineInstr &MI : *MBB) {
for (const MachineOperand &MO : MI.defs()) {
if (MO.isImplicit())
continue;
unsigned Def = MO.getReg();
if (TargetRegisterInfo::isVirtualRegister(Def)) {
if (TRI->isSGPRClass(MRI.getRegClass(Def))) {
// Only consider defs that are live outs. We don't care about def /
// use within the same block.
LiveRange &LR = LIS->getInterval(Def);
if (LIS->isLiveOutOfMBB(LR, MBB))
SGPRLiveRanges.push_back(std::make_pair(Def, &LR));
}
} else if (TRI->isSGPRClass(TRI->getPhysRegClass(Def))) {
SGPRLiveRanges.push_back(std::make_pair(Def, &LIS->getRegUnit(Def)));
}
}
}
if (MBB->succ_size() < 2)
continue;
// We have structured control flow, so the number of successors should be
// two.
assert(MBB->succ_size() == 2);
MachineBasicBlock *SuccA = *MBB->succ_begin();
MachineBasicBlock *SuccB = *(++MBB->succ_begin());
MachineBasicBlock *NCD = PDT->findNearestCommonDominator(SuccA, SuccB);
if (!NCD)
continue;
MachineBasicBlock::iterator NCDTerm = NCD->getFirstTerminator();
if (NCDTerm != NCD->end() && NCDTerm->getOpcode() == AMDGPU::SI_ELSE) {
assert(NCD->succ_size() == 2);
// We want to make sure we insert the Use after the ENDIF, not after
// the ELSE.
NCD = PDT->findNearestCommonDominator(*NCD->succ_begin(),
*(++NCD->succ_begin()));
}
for (std::pair<unsigned, LiveRange*> RegLR : SGPRLiveRanges) {
unsigned Reg = RegLR.first;
LiveRange *LR = RegLR.second;
// FIXME: We could be smarter here. If the register is Live-In to one
// block, but the other doesn't have any SGPR defs, then there won't be a
// conflict. Also, if the branch condition is uniform then there will be
// no conflict.
bool LiveInToA = LIS->isLiveInToMBB(*LR, SuccA);
bool LiveInToB = LIS->isLiveInToMBB(*LR, SuccB);
if (!LiveInToA && !LiveInToB) {
DEBUG(dbgs() << PrintReg(Reg, TRI, 0)
<< " is live into neither successor\n");
continue;
}
if (LiveInToA && LiveInToB) {
DEBUG(dbgs() << PrintReg(Reg, TRI, 0)
<< " is live into both successors\n");
continue;
}
// This interval is live in to one successor, but not the other, so
// we need to update its range so it is live in to both.
DEBUG(dbgs() << "Possible SGPR conflict detected for "
<< PrintReg(Reg, TRI, 0) << " in " << *LR
<< " BB#" << SuccA->getNumber() << ", BB#"
<< SuccB->getNumber()
<< " with NCD = BB#" << NCD->getNumber() << '\n');
assert(TargetRegisterInfo::isVirtualRegister(Reg) &&
"Not expecting to extend live range of physreg");
// FIXME: Need to figure out how to update LiveRange here so this pass
// will be able to preserve LiveInterval analysis.
MachineInstr *NCDSGPRUse =
BuildMI(*NCD, NCD->getFirstNonPHI(), DebugLoc(),
TII->get(AMDGPU::SGPR_USE))
.addReg(Reg, RegState::Implicit);
MadeChange = true;
SlotIndex SI = LIS->InsertMachineInstrInMaps(NCDSGPRUse);
LIS->extendToIndices(*LR, SI.getRegSlot());
if (LV) {
// TODO: This won't work post-SSA
LV->HandleVirtRegUse(Reg, NCD, NCDSGPRUse);
}
DEBUG(NCDSGPRUse->dump());
}
}
return MadeChange;
}
bool SIFixSGPRLiveRanges::runOnMachineFunction(MachineFunction &MF) {
MachineRegisterInfo &MRI = MF.getRegInfo();
const TargetInstrInfo *TII = MF.getSubtarget().getInstrInfo();
const SIRegisterInfo *TRI = static_cast<const SIRegisterInfo *>(
MF.getSubtarget().getRegisterInfo());
LiveIntervals *LIS = &getAnalysis<LiveIntervals>();
MachinePostDominatorTree *PDT = &getAnalysis<MachinePostDominatorTree>();
std::vector<std::pair<unsigned, LiveRange *>> SGPRLiveRanges;
// First pass, collect all live intervals for SGPRs
for (const MachineBasicBlock &MBB : MF) {
for (const MachineInstr &MI : MBB) {
for (const MachineOperand &MO : MI.defs()) {
if (MO.isImplicit())
continue;
unsigned Def = MO.getReg();
if (TargetRegisterInfo::isVirtualRegister(Def)) {
if (TRI->isSGPRClass(MRI.getRegClass(Def)))
SGPRLiveRanges.push_back(
std::make_pair(Def, &LIS->getInterval(Def)));
} else if (TRI->isSGPRClass(TRI->getPhysRegClass(Def))) {
SGPRLiveRanges.push_back(
std::make_pair(Def, &LIS->getRegUnit(Def)));
}
}
}
}
// Second pass fix the intervals
for (MachineFunction::iterator BI = MF.begin(), BE = MF.end();
BI != BE; ++BI) {
MachineBasicBlock &MBB = *BI;
if (MBB.succ_size() < 2)
continue;
// We have structured control flow, so number of succesors should be two.
assert(MBB.succ_size() == 2);
MachineBasicBlock *SuccA = *MBB.succ_begin();
MachineBasicBlock *SuccB = *(++MBB.succ_begin());
MachineBasicBlock *NCD = PDT->findNearestCommonDominator(SuccA, SuccB);
if (!NCD)
continue;
MachineBasicBlock::iterator NCDTerm = NCD->getFirstTerminator();
if (NCDTerm != NCD->end() && NCDTerm->getOpcode() == AMDGPU::SI_ELSE) {
assert(NCD->succ_size() == 2);
// We want to make sure we insert the Use after the ENDIF, not after
// the ELSE.
NCD = PDT->findNearestCommonDominator(*NCD->succ_begin(),
*(++NCD->succ_begin()));
}
assert(SuccA && SuccB);
for (std::pair<unsigned, LiveRange*> RegLR : SGPRLiveRanges) {
unsigned Reg = RegLR.first;
LiveRange *LR = RegLR.second;
// FIXME: We could be smarter here. If the register is Live-In to
// one block, but the other doesn't have any SGPR defs, then there
// won't be a conflict. Also, if the branch decision is based on
// a value in an SGPR, then there will be no conflict.
bool LiveInToA = LIS->isLiveInToMBB(*LR, SuccA);
bool LiveInToB = LIS->isLiveInToMBB(*LR, SuccB);
if ((!LiveInToA && !LiveInToB) ||
(LiveInToA && LiveInToB))
continue;
// This interval is live in to one successor, but not the other, so
// we need to update its range so it is live in to both.
DEBUG(dbgs() << "Possible SGPR conflict detected " << " in " << *LR <<
" BB#" << SuccA->getNumber() << ", BB#" <<
SuccB->getNumber() <<
" with NCD = " << NCD->getNumber() << '\n');
// FIXME: Need to figure out how to update LiveRange here so this pass
// will be able to preserve LiveInterval analysis.
BuildMI(*NCD, NCD->getFirstNonPHI(), DebugLoc(),
TII->get(AMDGPU::SGPR_USE))
.addReg(Reg, RegState::Implicit);
DEBUG(NCD->getFirstNonPHI()->dump());
}
}
return false;
}
