diff options
Diffstat (limited to 'lib/CodeGen/RegisterPressure.cpp')
| -rw-r--r-- | lib/CodeGen/RegisterPressure.cpp | 89 |
1 files changed, 68 insertions, 21 deletions
diff --git a/lib/CodeGen/RegisterPressure.cpp b/lib/CodeGen/RegisterPressure.cpp index 912ed0dd7b..b30f76d05d 100644 --- a/lib/CodeGen/RegisterPressure.cpp +++ b/lib/CodeGen/RegisterPressure.cpp @@ -562,12 +562,13 @@ bool RegPressureTracker::advance() { return true; } -// Find the max change in excess pressure across all sets. -static int computeMaxPressureDelta(ArrayRef<unsigned> OldPressureVec, - ArrayRef<unsigned> NewPressureVec, - unsigned &PSetID, - const TargetRegisterInfo *TRI) { +/// Find the max change in excess pressure across all sets. +static void computeExcessPressureDelta(ArrayRef<unsigned> OldPressureVec, + ArrayRef<unsigned> NewPressureVec, + RegPressureDelta &Delta, + const TargetRegisterInfo *TRI) { int ExcessUnits = 0; + unsigned PSetID = ~0U; for (unsigned i = 0, e = OldPressureVec.size(); i < e; ++i) { unsigned POld = OldPressureVec[i]; unsigned PNew = NewPressureVec[i]; @@ -590,7 +591,50 @@ static int computeMaxPressureDelta(ArrayRef<unsigned> OldPressureVec, PSetID = i; } } - return ExcessUnits; + Delta.Excess.PSetID = PSetID; + Delta.Excess.UnitIncrease = ExcessUnits; +} + +/// 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<PressureElement> CriticalPSets, + ArrayRef<unsigned> MaxPressureLimit, + RegPressureDelta &Delta) { + Delta.CriticalMax = PressureElement(); + Delta.CurrentMax = PressureElement(); + + 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; + + while (CritIdx != CritEnd && CriticalPSets[CritIdx].PSetID < i) + ++CritIdx; + + if (CritIdx != CritEnd && CriticalPSets[CritIdx].PSetID == i) { + int PDiff = (int)PNew - (int)CriticalPSets[CritIdx].UnitIncrease; + if (PDiff > Delta.CriticalMax.UnitIncrease) { + Delta.CriticalMax.PSetID = i; + Delta.CriticalMax.UnitIncrease = PDiff; + } + } + + // Find the greatest increase above MaxPressureLimit. + // (Ignores negative MDiff). + int MDiff = (int)PNew - (int)MaxPressureLimit[i]; + if (MDiff > Delta.CurrentMax.UnitIncrease) { + Delta.CurrentMax.PSetID = i; + Delta.CurrentMax.UnitIncrease = PNew; + } + } } /// Consider the pressure increase caused by traversing this instruction @@ -605,13 +649,17 @@ static int computeMaxPressureDelta(ArrayRef<unsigned> OldPressureVec, /// 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, RegPressureDelta &Delta) { +getMaxUpwardPressureDelta(const MachineInstr *MI, RegPressureDelta &Delta, + ArrayRef<PressureElement> CriticalPSets, + ArrayRef<unsigned> MaxPressureLimit) { // Account for register pressure similar to RegPressureTracker::recede(). PhysRegOperands PhysRegOpers; VirtRegOperands VirtRegOpers; collectOperands(MI, PhysRegOpers, VirtRegOpers, TRI, RCI); // 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; @@ -643,13 +691,11 @@ getMaxUpwardPressureDelta(const MachineInstr *MI, RegPressureDelta &Delta) { increaseVirtRegPressure(Reg); } } - Delta.ExcessUnits = - computeMaxPressureDelta(SavedPressure, CurrSetPressure, - Delta.ExcessSetID, TRI); - Delta.MaxUnitIncrease = - computeMaxPressureDelta(SavedMaxPressure, P.MaxSetPressure, - Delta.MaxSetID, TRI); - assert(Delta.MaxUnitIncrease >= 0 && "cannot increase max pressure"); + computeExcessPressureDelta(SavedPressure, CurrSetPressure, Delta, TRI); + computeMaxPressureDelta(SavedMaxPressure, P.MaxSetPressure, CriticalPSets, + MaxPressureLimit, Delta); + assert(Delta.CriticalMax.UnitIncrease >= 0 && + Delta.CurrentMax.UnitIncrease >= 0 && "cannot decrease max pressure"); // Restore the tracker's state. P.MaxSetPressure.swap(SavedMaxPressure); @@ -679,7 +725,9 @@ static bool findUseBetween(unsigned Reg, /// /// This assumes that the current LiveIn set is sufficient. void RegPressureTracker:: -getMaxDownwardPressureDelta(const MachineInstr *MI, RegPressureDelta &Delta) { +getMaxDownwardPressureDelta(const MachineInstr *MI, RegPressureDelta &Delta, + ArrayRef<PressureElement> CriticalPSets, + ArrayRef<unsigned> MaxPressureLimit) { // Account for register pressure similar to RegPressureTracker::recede(). PhysRegOperands PhysRegOpers; VirtRegOperands VirtRegOpers; @@ -717,12 +765,11 @@ getMaxDownwardPressureDelta(const MachineInstr *MI, RegPressureDelta &Delta) { decreasePhysRegPressure(PhysRegOpers.DeadDefs); decreaseVirtRegPressure(VirtRegOpers.DeadDefs); - Delta.ExcessUnits = - computeMaxPressureDelta(SavedPressure, CurrSetPressure, - Delta.ExcessSetID, TRI); - Delta.MaxUnitIncrease = - computeMaxPressureDelta(SavedMaxPressure, P.MaxSetPressure, - Delta.MaxSetID, TRI); + computeExcessPressureDelta(SavedPressure, CurrSetPressure, Delta, TRI); + computeMaxPressureDelta(SavedMaxPressure, P.MaxSetPressure, CriticalPSets, + MaxPressureLimit, Delta); + assert(Delta.CriticalMax.UnitIncrease >= 0 && + Delta.CurrentMax.UnitIncrease >= 0 && "cannot decrease max pressure"); // Restore the tracker's state. P.MaxSetPressure.swap(SavedMaxPressure); |