+
+/// Find the max change in excess pressure across all sets.
+static void computeExcessPressureDelta(ArrayRef<unsigned> OldPressureVec,
+ ArrayRef<unsigned> NewPressureVec,
+ RegPressureDelta &Delta,
+ const RegisterClassInfo *RCI,
+ ArrayRef<unsigned> LiveThruPressureVec) {
+ Delta.Excess = PressureChange();
+ for (unsigned i = 0, e = OldPressureVec.size(); i < e; ++i) {
+ unsigned POld = OldPressureVec[i];
+ unsigned PNew = NewPressureVec[i];
+ int PDiff = (int)PNew - (int)POld;
+ if (!PDiff) // No change in this set in the common case.
+ continue;
+ // Only consider change beyond the limit.
+ unsigned Limit = RCI->getRegPressureSetLimit(i);
+ if (!LiveThruPressureVec.empty())
+ Limit += LiveThruPressureVec[i];
+
+ if (Limit > POld) {
+ if (Limit > PNew)
+ PDiff = 0; // Under the limit
+ else
+ PDiff = PNew - Limit; // Just exceeded limit.
+ }
+ else if (Limit > PNew)
+ PDiff = Limit - POld; // Just obeyed limit.
+
+ if (PDiff) {
+ Delta.Excess = PressureChange(i);
+ Delta.Excess.setUnitInc(PDiff);
+ break;
+ }
+ }
+}
+
+/// Find the max change in max pressure that either surpasses a critical PSet
+/// limit or exceeds the current MaxPressureLimit.
+///
+/// FIXME: comparing each element of the old and new MaxPressure vectors here is
+/// silly. It's done now to demonstrate the concept but will go away with a
+/// RegPressureTracker API change to work with pressure differences.
+static void computeMaxPressureDelta(ArrayRef<unsigned> OldMaxPressureVec,
+ ArrayRef<unsigned> NewMaxPressureVec,
+ ArrayRef<PressureChange> CriticalPSets,
+ ArrayRef<unsigned> MaxPressureLimit,
+ RegPressureDelta &Delta) {
+ Delta.CriticalMax = PressureChange();
+ Delta.CurrentMax = PressureChange();
+
+ unsigned CritIdx = 0, CritEnd = CriticalPSets.size();
+ for (unsigned i = 0, e = OldMaxPressureVec.size(); i < e; ++i) {
+ unsigned POld = OldMaxPressureVec[i];
+ unsigned PNew = NewMaxPressureVec[i];
+ if (PNew == POld) // No change in this set in the common case.
+ continue;
+
+ if (!Delta.CriticalMax.isValid()) {
+ while (CritIdx != CritEnd && CriticalPSets[CritIdx].getPSet() < i)
+ ++CritIdx;
+
+ if (CritIdx != CritEnd && CriticalPSets[CritIdx].getPSet() == i) {
+ int PDiff = (int)PNew - (int)CriticalPSets[CritIdx].getUnitInc();
+ if (PDiff > 0) {
+ Delta.CriticalMax = PressureChange(i);
+ Delta.CriticalMax.setUnitInc(PDiff);
+ }
+ }
+ }
+ // Find the first increase above MaxPressureLimit.
+ // (Ignores negative MDiff).
+ if (!Delta.CurrentMax.isValid() && PNew > MaxPressureLimit[i]) {
+ Delta.CurrentMax = PressureChange(i);
+ Delta.CurrentMax.setUnitInc(PNew - POld);
+ if (CritIdx == CritEnd || Delta.CriticalMax.isValid())
+ break;
+ }
+ }
+}
+
+/// Record the upward impact of a single instruction on current register
+/// pressure. Unlike the advance/recede pressure tracking interface, this does
+/// not discover live in/outs.
+///
+/// This is intended for speculative queries. It leaves pressure inconsistent
+/// with the current position, so must be restored by the caller.
+void RegPressureTracker::bumpUpwardPressure(const MachineInstr *MI) {
+ assert(!MI->isDebugValue() && "Expect a nondebug instruction.");
+
+ // Account for register pressure similar to RegPressureTracker::recede().
+ RegisterOperands RegOpers(TRI, MRI, /*IgnoreDead=*/true);
+ collectOperands(MI, RegOpers);
+
+ // Boost max pressure for all dead defs together.
+ // Since CurrSetPressure and MaxSetPressure
+ increaseRegPressure(RegOpers.DeadDefs);
+ decreaseRegPressure(RegOpers.DeadDefs);
+
+ // Kill liveness at live defs.
+ for (unsigned i = 0, e = RegOpers.Defs.size(); i < e; ++i) {
+ unsigned Reg = RegOpers.Defs[i];
+ bool DeadDef = false;
+ if (RequireIntervals) {
+ const LiveRange *LR = getLiveRange(Reg);
+ if (LR) {
+ SlotIndex SlotIdx = LIS->getInstructionIndex(MI);
+ LiveQueryResult LRQ = LR->Query(SlotIdx);
+ DeadDef = LRQ.isDeadDef();
+ }
+ }
+ if (!DeadDef) {
+ if (!containsReg(RegOpers.Uses, Reg))
+ decreaseRegPressure(Reg);
+ }
+ }
+ // Generate liveness for uses.
+ for (unsigned i = 0, e = RegOpers.Uses.size(); i < e; ++i) {
+ unsigned Reg = RegOpers.Uses[i];
+ if (!LiveRegs.contains(Reg))
+ increaseRegPressure(Reg);
+ }
+}
+
+/// Consider the pressure increase caused by traversing this instruction
+/// bottom-up. Find the pressure set with the most change beyond its pressure
+/// limit based on the tracker's current pressure, and return the change in
+/// number of register units of that pressure set introduced by this
+/// instruction.
+///
+/// This assumes that the current LiveOut set is sufficient.
+///
+/// FIXME: This is expensive for an on-the-fly query. We need to cache the
+/// result per-SUnit with enough information to adjust for the current
+/// scheduling position. But this works as a proof of concept.
+void RegPressureTracker::
+getMaxUpwardPressureDelta(const MachineInstr *MI, PressureDiff *PDiff,
+ RegPressureDelta &Delta,
+ ArrayRef<PressureChange> CriticalPSets,
+ ArrayRef<unsigned> MaxPressureLimit) {
+ // Snapshot Pressure.
+ // FIXME: The snapshot heap space should persist. But I'm planning to
+ // summarize the pressure effect so we don't need to snapshot at all.
+ std::vector<unsigned> SavedPressure = CurrSetPressure;
+ std::vector<unsigned> SavedMaxPressure = P.MaxSetPressure;
+
+ bumpUpwardPressure(MI);
+
+ computeExcessPressureDelta(SavedPressure, CurrSetPressure, Delta, RCI,
+ LiveThruPressure);
+ computeMaxPressureDelta(SavedMaxPressure, P.MaxSetPressure, CriticalPSets,
+ MaxPressureLimit, Delta);
+ assert(Delta.CriticalMax.getUnitInc() >= 0 &&
+ Delta.CurrentMax.getUnitInc() >= 0 && "cannot decrease max pressure");
+
+ // Restore the tracker's state.
+ P.MaxSetPressure.swap(SavedMaxPressure);
+ CurrSetPressure.swap(SavedPressure);
+
+#ifndef NDEBUG
+ if (!PDiff)
+ return;
+
+ // Check if the alternate algorithm yields the same result.
+ RegPressureDelta Delta2;
+ getUpwardPressureDelta(MI, *PDiff, Delta2, CriticalPSets, MaxPressureLimit);
+ if (Delta != Delta2) {
+ dbgs() << "DELTA: " << *MI;
+ if (Delta.Excess.isValid())
+ dbgs() << "Excess1 " << TRI->getRegPressureSetName(Delta.Excess.getPSet())
+ << " " << Delta.Excess.getUnitInc() << "\n";
+ if (Delta.CriticalMax.isValid())
+ dbgs() << "Critic1 " << TRI->getRegPressureSetName(Delta.CriticalMax.getPSet())
+ << " " << Delta.CriticalMax.getUnitInc() << "\n";
+ if (Delta.CurrentMax.isValid())
+ dbgs() << "CurrMx1 " << TRI->getRegPressureSetName(Delta.CurrentMax.getPSet())
+ << " " << Delta.CurrentMax.getUnitInc() << "\n";
+ if (Delta2.Excess.isValid())
+ dbgs() << "Excess2 " << TRI->getRegPressureSetName(Delta2.Excess.getPSet())
+ << " " << Delta2.Excess.getUnitInc() << "\n";
+ if (Delta2.CriticalMax.isValid())
+ dbgs() << "Critic2 " << TRI->getRegPressureSetName(Delta2.CriticalMax.getPSet())
+ << " " << Delta2.CriticalMax.getUnitInc() << "\n";
+ if (Delta2.CurrentMax.isValid())
+ dbgs() << "CurrMx2 " << TRI->getRegPressureSetName(Delta2.CurrentMax.getPSet())
+ << " " << Delta2.CurrentMax.getUnitInc() << "\n";
+ llvm_unreachable("RegP Delta Mismatch");
+ }
+#endif
+}
+
+/// This is a prototype of the fast version of querying register pressure that
+/// does not directly depend on current liveness. It's still slow because we
+/// recompute pressure change on-the-fly. This implementation only exists to
+/// prove correctness.
+///
+/// @param Delta captures information needed for heuristics.
+///
+/// @param CriticalPSets Are the pressure sets that are known to exceed some
+/// limit within the region, not necessarily at the current position.
+///
+/// @param MaxPressureLimit Is the max pressure within the region, not
+/// necessarily at the current position.
+void RegPressureTracker::
+getUpwardPressureDelta(const MachineInstr *MI, /*const*/ PressureDiff &PDiff,
+ RegPressureDelta &Delta,
+ ArrayRef<PressureChange> CriticalPSets,
+ ArrayRef<unsigned> MaxPressureLimit) const {
+ unsigned CritIdx = 0, CritEnd = CriticalPSets.size();
+ for (PressureDiff::const_iterator
+ PDiffI = PDiff.begin(), PDiffE = PDiff.end();
+ PDiffI != PDiffE && PDiffI->isValid(); ++PDiffI) {
+
+ unsigned PSetID = PDiffI->getPSet();
+ unsigned Limit = RCI->getRegPressureSetLimit(PSetID);
+ if (!LiveThruPressure.empty())
+ Limit += LiveThruPressure[PSetID];
+
+ unsigned POld = CurrSetPressure[PSetID];
+ unsigned MOld = P.MaxSetPressure[PSetID];
+ unsigned MNew = MOld;
+ // Ignore DeadDefs here because they aren't captured by PressureChange.
+ unsigned PNew = POld + PDiffI->getUnitInc();
+ assert((PDiffI->getUnitInc() >= 0) == (PNew >= POld) && "PSet overflow");
+ if (PNew > MOld)
+ MNew = PNew;
+ // Check if current pressure has exceeded the limit.
+ if (!Delta.Excess.isValid()) {
+ unsigned ExcessInc = 0;
+ if (PNew > Limit)
+ ExcessInc = POld > Limit ? PNew - POld : PNew - Limit;
+ else if (POld > Limit)
+ ExcessInc = Limit - POld;
+ if (ExcessInc) {
+ Delta.Excess = PressureChange(PSetID);
+ Delta.Excess.setUnitInc(ExcessInc);
+ }
+ }
+ // Check if max pressure has exceeded a critical pressure set max.
+ if (MNew == MOld)
+ continue;
+ if (!Delta.CriticalMax.isValid()) {
+ while (CritIdx != CritEnd && CriticalPSets[CritIdx].getPSet() < PSetID)
+ ++CritIdx;
+
+ if (CritIdx != CritEnd && CriticalPSets[CritIdx].getPSet() == PSetID) {
+ int CritInc = (int)MNew - (int)CriticalPSets[CritIdx].getUnitInc();
+ if (CritInc > 0 && CritInc <= INT16_MAX) {
+ Delta.CriticalMax = PressureChange(PSetID);
+ Delta.CriticalMax.setUnitInc(CritInc);
+ }
+ }
+ }
+ // Check if max pressure has exceeded the current max.
+ if (!Delta.CurrentMax.isValid() && MNew > MaxPressureLimit[PSetID]) {
+ Delta.CurrentMax = PressureChange(PSetID);
+ Delta.CurrentMax.setUnitInc(MNew - MOld);
+ }
+ }
+}
+
+/// Helper to find a vreg use between two indices [PriorUseIdx, NextUseIdx).
+static bool findUseBetween(unsigned Reg,
+ SlotIndex PriorUseIdx, SlotIndex NextUseIdx,
+ const MachineRegisterInfo *MRI,
+ const LiveIntervals *LIS) {
+ for (MachineRegisterInfo::use_nodbg_iterator
+ UI = MRI->use_nodbg_begin(Reg), UE = MRI->use_nodbg_end();
+ UI != UE; UI.skipInstruction()) {
+ const MachineInstr* MI = &*UI;
+ if (MI->isDebugValue())
+ continue;
+ SlotIndex InstSlot = LIS->getInstructionIndex(MI).getRegSlot();
+ if (InstSlot >= PriorUseIdx && InstSlot < NextUseIdx)
+ return true;
+ }
+ return false;
+}
+
+/// Record the downward impact of a single instruction on current register
+/// pressure. Unlike the advance/recede pressure tracking interface, this does
+/// not discover live in/outs.
+///
+/// This is intended for speculative queries. It leaves pressure inconsistent
+/// with the current position, so must be restored by the caller.
+void RegPressureTracker::bumpDownwardPressure(const MachineInstr *MI) {
+ assert(!MI->isDebugValue() && "Expect a nondebug instruction.");
+
+ // Account for register pressure similar to RegPressureTracker::recede().
+ RegisterOperands RegOpers(TRI, MRI);
+ collectOperands(MI, RegOpers);
+
+ // Kill liveness at last uses. Assume allocatable physregs are single-use
+ // rather than checking LiveIntervals.
+ SlotIndex SlotIdx;
+ if (RequireIntervals)
+ SlotIdx = LIS->getInstructionIndex(MI).getRegSlot();
+
+ for (unsigned i = 0, e = RegOpers.Uses.size(); i < e; ++i) {
+ unsigned Reg = RegOpers.Uses[i];
+ if (RequireIntervals) {
+ // FIXME: allow the caller to pass in the list of vreg uses that remain
+ // to be bottom-scheduled to avoid searching uses at each query.
+ SlotIndex CurrIdx = getCurrSlot();
+ const LiveRange *LR = getLiveRange(Reg);
+ if (LR) {
+ LiveQueryResult LRQ = LR->Query(SlotIdx);
+ if (LRQ.isKill() && !findUseBetween(Reg, CurrIdx, SlotIdx, MRI, LIS)) {
+ decreaseRegPressure(Reg);
+ }
+ }
+ }
+ else if (!TargetRegisterInfo::isVirtualRegister(Reg)) {
+ // Allocatable physregs are always single-use before register rewriting.
+ decreaseRegPressure(Reg);
+ }
+ }
+
+ // Generate liveness for defs.
+ increaseRegPressure(RegOpers.Defs);
+
+ // Boost pressure for all dead defs together.
+ increaseRegPressure(RegOpers.DeadDefs);
+ decreaseRegPressure(RegOpers.DeadDefs);
+}
+
+/// Consider the pressure increase caused by traversing this instruction
+/// top-down. Find the register class with the most change in its pressure limit
+/// based on the tracker's current pressure, and return the number of excess
+/// register units of that pressure set introduced by this instruction.
+///
+/// This assumes that the current LiveIn set is sufficient.
+void RegPressureTracker::
+getMaxDownwardPressureDelta(const MachineInstr *MI, RegPressureDelta &Delta,
+ ArrayRef<PressureChange> CriticalPSets,
+ ArrayRef<unsigned> MaxPressureLimit) {
+ // Snapshot Pressure.
+ std::vector<unsigned> SavedPressure = CurrSetPressure;
+ std::vector<unsigned> SavedMaxPressure = P.MaxSetPressure;
+
+ bumpDownwardPressure(MI);
+
+ computeExcessPressureDelta(SavedPressure, CurrSetPressure, Delta, RCI,
+ LiveThruPressure);
+ computeMaxPressureDelta(SavedMaxPressure, P.MaxSetPressure, CriticalPSets,
+ MaxPressureLimit, Delta);
+ assert(Delta.CriticalMax.getUnitInc() >= 0 &&
+ Delta.CurrentMax.getUnitInc() >= 0 && "cannot decrease max pressure");
+
+ // Restore the tracker's state.
+ P.MaxSetPressure.swap(SavedMaxPressure);
+ CurrSetPressure.swap(SavedPressure);
+}
+
+/// Get the pressure of each PSet after traversing this instruction bottom-up.
+void RegPressureTracker::
+getUpwardPressure(const MachineInstr *MI,
+ std::vector<unsigned> &PressureResult,
+ std::vector<unsigned> &MaxPressureResult) {
+ // Snapshot pressure.
+ PressureResult = CurrSetPressure;
+ MaxPressureResult = P.MaxSetPressure;
+
+ bumpUpwardPressure(MI);
+
+ // Current pressure becomes the result. Restore current pressure.
+ P.MaxSetPressure.swap(MaxPressureResult);
+ CurrSetPressure.swap(PressureResult);
+}
+
+/// Get the pressure of each PSet after traversing this instruction top-down.
+void RegPressureTracker::
+getDownwardPressure(const MachineInstr *MI,
+ std::vector<unsigned> &PressureResult,
+ std::vector<unsigned> &MaxPressureResult) {
+ // Snapshot pressure.
+ PressureResult = CurrSetPressure;
+ MaxPressureResult = P.MaxSetPressure;
+
+ bumpDownwardPressure(MI);
+
+ // Current pressure becomes the result. Restore current pressure.
+ P.MaxSetPressure.swap(MaxPressureResult);
+ CurrSetPressure.swap(PressureResult);
+}