| //===-- RegisterPressure.h - Dynamic Register Pressure -*- C++ -*-------===// |
| // |
| // The LLVM Compiler Infrastructure |
| // |
| // This file is distributed under the University of Illinois Open Source |
| // License. See LICENSE.TXT for details. |
| // |
| //===----------------------------------------------------------------------===// |
| // |
| // This file defines the RegisterPressure class which can be used to track |
| // MachineInstr level register pressure. |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #ifndef LLVM_CODEGEN_REGISTERPRESSURE_H |
| #define LLVM_CODEGEN_REGISTERPRESSURE_H |
| |
| #include "llvm/CodeGen/SlotIndexes.h" |
| #include "llvm/Target/TargetRegisterInfo.h" |
| #include "llvm/ADT/SparseSet.h" |
| |
| namespace llvm { |
| |
| class LiveIntervals; |
| class RegisterClassInfo; |
| class MachineInstr; |
| |
| /// Base class for register pressure results. |
| struct RegisterPressure { |
| /// Map of max reg pressure indexed by pressure set ID, not class ID. |
| std::vector<unsigned> MaxSetPressure; |
| |
| /// List of live in registers. |
| SmallVector<unsigned,8> LiveInRegs; |
| SmallVector<unsigned,8> LiveOutRegs; |
| |
| /// Increase register pressure for each pressure set impacted by this register |
| /// class. Normally called by RegPressureTracker, but may be called manually |
| /// to account for live through (global liveness). |
| void increase(const TargetRegisterClass *RC, const TargetRegisterInfo *TRI); |
| |
| /// Decrease register pressure for each pressure set impacted by this register |
| /// class. This is only useful to account for spilling or rematerialization. |
| void decrease(const TargetRegisterClass *RC, const TargetRegisterInfo *TRI); |
| |
| void dump(const TargetRegisterInfo *TRI) const; |
| }; |
| |
| /// RegisterPressure computed within a region of instructions delimited by |
| /// TopIdx and BottomIdx. During pressure computation, the maximum pressure per |
| /// register pressure set is increased. Once pressure within a region is fully |
| /// computed, the live-in and live-out sets are recorded. |
| /// |
| /// This is preferable to RegionPressure when LiveIntervals are available, |
| /// because delimiting regions by SlotIndex is more robust and convenient than |
| /// holding block iterators. The block contents can change without invalidating |
| /// the pressure result. |
| struct IntervalPressure : RegisterPressure { |
| /// Record the boundary of the region being tracked. |
| SlotIndex TopIdx; |
| SlotIndex BottomIdx; |
| |
| void reset(); |
| |
| void openTop(SlotIndex NextTop); |
| |
| void openBottom(SlotIndex PrevBottom); |
| }; |
| |
| /// RegisterPressure computed within a region of instructions delimited by |
| /// TopPos and BottomPos. This is a less precise version of IntervalPressure for |
| /// use when LiveIntervals are unavailable. |
| struct RegionPressure : RegisterPressure { |
| /// Record the boundary of the region being tracked. |
| MachineBasicBlock::const_iterator TopPos; |
| MachineBasicBlock::const_iterator BottomPos; |
| |
| void reset(); |
| |
| void openTop(MachineBasicBlock::const_iterator PrevTop); |
| |
| void openBottom(MachineBasicBlock::const_iterator PrevBottom); |
| }; |
| |
| /// An element of pressure difference that identifies the pressure set and |
| /// amount of increase or decrease in units of pressure. |
| struct PressureElement { |
| unsigned PSetID; |
| int UnitIncrease; |
| |
| PressureElement(): PSetID(~0U), UnitIncrease(0) {} |
| PressureElement(unsigned id, int inc): PSetID(id), UnitIncrease(inc) {} |
| |
| bool isValid() const { return PSetID != ~0U; } |
| }; |
| |
| /// Store the effects of a change in pressure on things that MI scheduler cares |
| /// about. |
| /// |
| /// Excess records the value of the largest difference in register units beyond |
| /// the target's pressure limits across the affected pressure sets, where |
| /// largest is defined as the absolute value of the difference. Negative |
| /// ExcessUnits indicates a reduction in pressure that had already exceeded the |
| /// target's limits. |
| /// |
| /// CriticalMax records the largest increase in the tracker's max pressure that |
| /// exceeds the critical limit for some pressure set determined by the client. |
| /// |
| /// CurrentMax records the largest increase in the tracker's max pressure that |
| /// exceeds the current limit for some pressure set determined by the client. |
| struct RegPressureDelta { |
| PressureElement Excess; |
| PressureElement CriticalMax; |
| PressureElement CurrentMax; |
| |
| RegPressureDelta() {} |
| }; |
| |
| /// Track the current register pressure at some position in the instruction |
| /// stream, and remember the high water mark within the region traversed. This |
| /// does not automatically consider live-through ranges. The client may |
| /// independently adjust for global liveness. |
| /// |
| /// Each RegPressureTracker only works within a MachineBasicBlock. Pressure can |
| /// be tracked across a larger region by storing a RegisterPressure result at |
| /// each block boundary and explicitly adjusting pressure to account for block |
| /// live-in and live-out register sets. |
| /// |
| /// RegPressureTracker holds a reference to a RegisterPressure result that it |
| /// computes incrementally. During downward tracking, P.BottomIdx or P.BottomPos |
| /// is invalid until it reaches the end of the block or closeRegion() is |
| /// explicitly called. Similarly, P.TopIdx is invalid during upward |
| /// tracking. Changing direction has the side effect of closing region, and |
| /// traversing past TopIdx or BottomIdx reopens it. |
| class RegPressureTracker { |
| const MachineFunction *MF; |
| const TargetRegisterInfo *TRI; |
| const RegisterClassInfo *RCI; |
| const MachineRegisterInfo *MRI; |
| const LiveIntervals *LIS; |
| |
| /// We currently only allow pressure tracking within a block. |
| const MachineBasicBlock *MBB; |
| |
| /// Track the max pressure within the region traversed so far. |
| RegisterPressure &P; |
| |
| /// Run in two modes dependending on whether constructed with IntervalPressure |
| /// or RegisterPressure. If requireIntervals is false, LIS are ignored. |
| bool RequireIntervals; |
| |
| /// Register pressure corresponds to liveness before this instruction |
| /// iterator. It may point to the end of the block rather than an instruction. |
| MachineBasicBlock::const_iterator CurrPos; |
| |
| /// Pressure map indexed by pressure set ID, not class ID. |
| std::vector<unsigned> CurrSetPressure; |
| |
| /// List of live registers. |
| SparseSet<unsigned> LivePhysRegs; |
| SparseSet<unsigned, VirtReg2IndexFunctor> LiveVirtRegs; |
| |
| public: |
| RegPressureTracker(IntervalPressure &rp) : |
| MF(0), TRI(0), RCI(0), LIS(0), MBB(0), P(rp), RequireIntervals(true) {} |
| |
| RegPressureTracker(RegionPressure &rp) : |
| MF(0), TRI(0), RCI(0), LIS(0), MBB(0), P(rp), RequireIntervals(false) {} |
| |
| void init(const MachineFunction *mf, const RegisterClassInfo *rci, |
| const LiveIntervals *lis, const MachineBasicBlock *mbb, |
| MachineBasicBlock::const_iterator pos); |
| |
| /// Force liveness of registers. Particularly useful to initialize the |
| /// livein/out state of the tracker before the first call to advance/recede. |
| void addLiveRegs(ArrayRef<unsigned> Regs); |
| |
| /// Get the MI position corresponding to this register pressure. |
| MachineBasicBlock::const_iterator getPos() const { return CurrPos; } |
| |
| // Reset the MI position corresponding to the register pressure. This allows |
| // schedulers to move instructions above the RegPressureTracker's |
| // CurrPos. Since the pressure is computed before CurrPos, the iterator |
| // position changes while pressure does not. |
| void setPos(MachineBasicBlock::const_iterator Pos) { CurrPos = Pos; } |
| |
| /// Recede across the previous instruction. |
| bool recede(); |
| |
| /// Advance across the current instruction. |
| bool advance(); |
| |
| /// Finalize the region boundaries and recored live ins and live outs. |
| void closeRegion(); |
| |
| /// Get the resulting register pressure over the traversed region. |
| /// This result is complete if either advance() or recede() has returned true, |
| /// or if closeRegion() was explicitly invoked. |
| RegisterPressure &getPressure() { return P; } |
| const RegisterPressure &getPressure() const { return P; } |
| |
| /// Get the register set pressure at the current position, which may be less |
| /// than the pressure across the traversed region. |
| std::vector<unsigned> &getRegSetPressureAtPos() { return CurrSetPressure; } |
| |
| void discoverPhysLiveIn(unsigned Reg); |
| void discoverPhysLiveOut(unsigned Reg); |
| |
| void discoverVirtLiveIn(unsigned Reg); |
| void discoverVirtLiveOut(unsigned Reg); |
| |
| bool isTopClosed() const; |
| bool isBottomClosed() const; |
| |
| void closeTop(); |
| void closeBottom(); |
| |
| /// 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 record the number of |
| /// excess register units of that pressure set introduced by this instruction. |
| void getMaxUpwardPressureDelta(const MachineInstr *MI, |
| RegPressureDelta &Delta, |
| ArrayRef<PressureElement> CriticalPSets, |
| ArrayRef<unsigned> MaxPressureLimit); |
| |
| /// Consider the pressure increase caused by traversing this instruction |
| /// top-down. Find the pressure set with the most change beyond its pressure |
| /// limit based on the tracker's current pressure, and record the number of |
| /// excess register units of that pressure set introduced by this instruction. |
| void getMaxDownwardPressureDelta(const MachineInstr *MI, |
| RegPressureDelta &Delta, |
| ArrayRef<PressureElement> CriticalPSets, |
| ArrayRef<unsigned> MaxPressureLimit); |
| |
| /// Find the pressure set with the most change beyond its pressure limit after |
| /// traversing this instruction either upward or downward depending on the |
| /// closed end of the current region. |
| void getMaxPressureDelta(const MachineInstr *MI, RegPressureDelta &Delta, |
| ArrayRef<PressureElement> CriticalPSets, |
| ArrayRef<unsigned> MaxPressureLimit) { |
| if (isTopClosed()) |
| return getMaxDownwardPressureDelta(MI, Delta, CriticalPSets, |
| MaxPressureLimit); |
| |
| assert(isBottomClosed() && "Uninitialized pressure tracker"); |
| return getMaxUpwardPressureDelta(MI, Delta, CriticalPSets, |
| MaxPressureLimit); |
| } |
| |
| /// Get the pressure of each PSet after traversing this instruction bottom-up. |
| void getUpwardPressure(const MachineInstr *MI, |
| std::vector<unsigned> &PressureResult, |
| std::vector<unsigned> &MaxPressureResult); |
| |
| /// Get the pressure of each PSet after traversing this instruction top-down. |
| void getDownwardPressure(const MachineInstr *MI, |
| std::vector<unsigned> &PressureResult, |
| std::vector<unsigned> &MaxPressureResult); |
| |
| void getPressureAfterInst(const MachineInstr *MI, |
| std::vector<unsigned> &PressureResult, |
| std::vector<unsigned> &MaxPressureResult) { |
| if (isTopClosed()) |
| return getUpwardPressure(MI, PressureResult, MaxPressureResult); |
| |
| assert(isBottomClosed() && "Uninitialized pressure tracker"); |
| return getDownwardPressure(MI, PressureResult, MaxPressureResult); |
| } |
| |
| protected: |
| void increasePhysRegPressure(ArrayRef<unsigned> Regs); |
| void decreasePhysRegPressure(ArrayRef<unsigned> Regs); |
| |
| void increaseVirtRegPressure(ArrayRef<unsigned> Regs); |
| void decreaseVirtRegPressure(ArrayRef<unsigned> Regs); |
| |
| void bumpUpwardPressure(const MachineInstr *MI); |
| void bumpDownwardPressure(const MachineInstr *MI); |
| }; |
| } // end namespace llvm |
| |
| #endif |