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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@169443 91177308-0d34-0410-b5e6-96231b3b80d8
321 lines
12 KiB
C++
321 lines
12 KiB
C++
//===-- RegisterPressure.h - Dynamic Register Pressure -*- C++ -*-------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This file defines the RegisterPressure class which can be used to track
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// MachineInstr level register pressure.
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_CODEGEN_REGISTERPRESSURE_H
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#define LLVM_CODEGEN_REGISTERPRESSURE_H
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#include "llvm/ADT/SparseSet.h"
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#include "llvm/CodeGen/SlotIndexes.h"
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#include "llvm/Target/TargetRegisterInfo.h"
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namespace llvm {
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class LiveIntervals;
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class LiveInterval;
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class RegisterClassInfo;
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class MachineInstr;
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/// Base class for register pressure results.
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struct RegisterPressure {
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/// Map of max reg pressure indexed by pressure set ID, not class ID.
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std::vector<unsigned> MaxSetPressure;
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/// List of live in virtual registers or physical register units.
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SmallVector<unsigned,8> LiveInRegs;
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SmallVector<unsigned,8> LiveOutRegs;
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/// Increase register pressure for each pressure set impacted by this register
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/// class. Normally called by RegPressureTracker, but may be called manually
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/// to account for live through (global liveness).
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///
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/// \param Reg is either a virtual register number or register unit number.
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void increase(unsigned Reg, const TargetRegisterInfo *TRI,
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const MachineRegisterInfo *MRI);
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/// Decrease register pressure for each pressure set impacted by this register
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/// class. This is only useful to account for spilling or rematerialization.
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///
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/// \param Reg is either a virtual register number or register unit number.
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void decrease(unsigned Reg, const TargetRegisterInfo *TRI,
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const MachineRegisterInfo *MRI);
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void dump(const TargetRegisterInfo *TRI) const;
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};
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/// RegisterPressure computed within a region of instructions delimited by
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/// TopIdx and BottomIdx. During pressure computation, the maximum pressure per
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/// register pressure set is increased. Once pressure within a region is fully
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/// computed, the live-in and live-out sets are recorded.
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///
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/// This is preferable to RegionPressure when LiveIntervals are available,
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/// because delimiting regions by SlotIndex is more robust and convenient than
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/// holding block iterators. The block contents can change without invalidating
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/// the pressure result.
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struct IntervalPressure : RegisterPressure {
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/// Record the boundary of the region being tracked.
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SlotIndex TopIdx;
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SlotIndex BottomIdx;
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void reset();
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void openTop(SlotIndex NextTop);
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void openBottom(SlotIndex PrevBottom);
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};
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/// RegisterPressure computed within a region of instructions delimited by
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/// TopPos and BottomPos. This is a less precise version of IntervalPressure for
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/// use when LiveIntervals are unavailable.
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struct RegionPressure : RegisterPressure {
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/// Record the boundary of the region being tracked.
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MachineBasicBlock::const_iterator TopPos;
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MachineBasicBlock::const_iterator BottomPos;
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void reset();
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void openTop(MachineBasicBlock::const_iterator PrevTop);
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void openBottom(MachineBasicBlock::const_iterator PrevBottom);
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};
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/// An element of pressure difference that identifies the pressure set and
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/// amount of increase or decrease in units of pressure.
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struct PressureElement {
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unsigned PSetID;
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int UnitIncrease;
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PressureElement(): PSetID(~0U), UnitIncrease(0) {}
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PressureElement(unsigned id, int inc): PSetID(id), UnitIncrease(inc) {}
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bool isValid() const { return PSetID != ~0U; }
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};
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/// Store the effects of a change in pressure on things that MI scheduler cares
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/// about.
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///
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/// Excess records the value of the largest difference in register units beyond
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/// the target's pressure limits across the affected pressure sets, where
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/// largest is defined as the absolute value of the difference. Negative
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/// ExcessUnits indicates a reduction in pressure that had already exceeded the
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/// target's limits.
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///
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/// CriticalMax records the largest increase in the tracker's max pressure that
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/// exceeds the critical limit for some pressure set determined by the client.
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///
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/// CurrentMax records the largest increase in the tracker's max pressure that
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/// exceeds the current limit for some pressure set determined by the client.
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struct RegPressureDelta {
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PressureElement Excess;
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PressureElement CriticalMax;
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PressureElement CurrentMax;
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RegPressureDelta() {}
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};
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/// \brief A set of live virtual registers and physical register units.
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///
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/// Virtual and physical register numbers require separate sparse sets, but most
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/// of the RegisterPressureTracker handles them uniformly.
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struct LiveRegSet {
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SparseSet<unsigned> PhysRegs;
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SparseSet<unsigned, VirtReg2IndexFunctor> VirtRegs;
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bool contains(unsigned Reg) {
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if (TargetRegisterInfo::isVirtualRegister(Reg))
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return VirtRegs.count(Reg);
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return PhysRegs.count(Reg);
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}
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bool insert(unsigned Reg) {
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if (TargetRegisterInfo::isVirtualRegister(Reg))
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return VirtRegs.insert(Reg).second;
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return PhysRegs.insert(Reg).second;
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}
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bool erase(unsigned Reg) {
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if (TargetRegisterInfo::isVirtualRegister(Reg))
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return VirtRegs.erase(Reg);
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return PhysRegs.erase(Reg);
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}
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};
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/// Track the current register pressure at some position in the instruction
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/// stream, and remember the high water mark within the region traversed. This
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/// does not automatically consider live-through ranges. The client may
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/// independently adjust for global liveness.
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///
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/// Each RegPressureTracker only works within a MachineBasicBlock. Pressure can
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/// be tracked across a larger region by storing a RegisterPressure result at
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/// each block boundary and explicitly adjusting pressure to account for block
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/// live-in and live-out register sets.
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///
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/// RegPressureTracker holds a reference to a RegisterPressure result that it
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/// computes incrementally. During downward tracking, P.BottomIdx or P.BottomPos
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/// is invalid until it reaches the end of the block or closeRegion() is
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/// explicitly called. Similarly, P.TopIdx is invalid during upward
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/// tracking. Changing direction has the side effect of closing region, and
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/// traversing past TopIdx or BottomIdx reopens it.
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class RegPressureTracker {
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const MachineFunction *MF;
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const TargetRegisterInfo *TRI;
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const RegisterClassInfo *RCI;
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const MachineRegisterInfo *MRI;
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const LiveIntervals *LIS;
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/// We currently only allow pressure tracking within a block.
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const MachineBasicBlock *MBB;
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/// Track the max pressure within the region traversed so far.
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RegisterPressure &P;
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/// Run in two modes dependending on whether constructed with IntervalPressure
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/// or RegisterPressure. If requireIntervals is false, LIS are ignored.
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bool RequireIntervals;
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/// Register pressure corresponds to liveness before this instruction
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/// iterator. It may point to the end of the block or a DebugValue rather than
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/// an instruction.
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MachineBasicBlock::const_iterator CurrPos;
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/// Pressure map indexed by pressure set ID, not class ID.
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std::vector<unsigned> CurrSetPressure;
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/// Set of live registers.
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LiveRegSet LiveRegs;
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public:
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RegPressureTracker(IntervalPressure &rp) :
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MF(0), TRI(0), RCI(0), LIS(0), MBB(0), P(rp), RequireIntervals(true) {}
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RegPressureTracker(RegionPressure &rp) :
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MF(0), TRI(0), RCI(0), LIS(0), MBB(0), P(rp), RequireIntervals(false) {}
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void init(const MachineFunction *mf, const RegisterClassInfo *rci,
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const LiveIntervals *lis, const MachineBasicBlock *mbb,
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MachineBasicBlock::const_iterator pos);
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/// Force liveness of virtual registers or physical register
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/// units. Particularly useful to initialize the livein/out state of the
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/// tracker before the first call to advance/recede.
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void addLiveRegs(ArrayRef<unsigned> Regs);
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/// Get the MI position corresponding to this register pressure.
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MachineBasicBlock::const_iterator getPos() const { return CurrPos; }
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// Reset the MI position corresponding to the register pressure. This allows
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// schedulers to move instructions above the RegPressureTracker's
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// CurrPos. Since the pressure is computed before CurrPos, the iterator
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// position changes while pressure does not.
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void setPos(MachineBasicBlock::const_iterator Pos) { CurrPos = Pos; }
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/// \brief Get the SlotIndex for the first nondebug instruction including or
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/// after the current position.
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SlotIndex getCurrSlot() const;
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/// Recede across the previous instruction.
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bool recede();
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/// Advance across the current instruction.
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bool advance();
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/// Finalize the region boundaries and recored live ins and live outs.
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void closeRegion();
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/// Get the resulting register pressure over the traversed region.
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/// This result is complete if either advance() or recede() has returned true,
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/// or if closeRegion() was explicitly invoked.
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RegisterPressure &getPressure() { return P; }
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const RegisterPressure &getPressure() const { return P; }
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/// Get the register set pressure at the current position, which may be less
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/// than the pressure across the traversed region.
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std::vector<unsigned> &getRegSetPressureAtPos() { return CurrSetPressure; }
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void discoverLiveOut(unsigned Reg);
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void discoverLiveIn(unsigned Reg);
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bool isTopClosed() const;
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bool isBottomClosed() const;
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void closeTop();
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void closeBottom();
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/// Consider the pressure increase caused by traversing this instruction
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/// bottom-up. Find the pressure set with the most change beyond its pressure
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/// limit based on the tracker's current pressure, and record the number of
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/// excess register units of that pressure set introduced by this instruction.
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void getMaxUpwardPressureDelta(const MachineInstr *MI,
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RegPressureDelta &Delta,
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ArrayRef<PressureElement> CriticalPSets,
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ArrayRef<unsigned> MaxPressureLimit);
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/// Consider the pressure increase caused by traversing this instruction
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/// top-down. Find the pressure set with the most change beyond its pressure
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/// limit based on the tracker's current pressure, and record the number of
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/// excess register units of that pressure set introduced by this instruction.
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void getMaxDownwardPressureDelta(const MachineInstr *MI,
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RegPressureDelta &Delta,
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ArrayRef<PressureElement> CriticalPSets,
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ArrayRef<unsigned> MaxPressureLimit);
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/// Find the pressure set with the most change beyond its pressure limit after
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/// traversing this instruction either upward or downward depending on the
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/// closed end of the current region.
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void getMaxPressureDelta(const MachineInstr *MI, RegPressureDelta &Delta,
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ArrayRef<PressureElement> CriticalPSets,
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ArrayRef<unsigned> MaxPressureLimit) {
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if (isTopClosed())
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return getMaxDownwardPressureDelta(MI, Delta, CriticalPSets,
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MaxPressureLimit);
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assert(isBottomClosed() && "Uninitialized pressure tracker");
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return getMaxUpwardPressureDelta(MI, Delta, CriticalPSets,
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MaxPressureLimit);
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}
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/// Get the pressure of each PSet after traversing this instruction bottom-up.
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void getUpwardPressure(const MachineInstr *MI,
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std::vector<unsigned> &PressureResult,
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std::vector<unsigned> &MaxPressureResult);
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/// Get the pressure of each PSet after traversing this instruction top-down.
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void getDownwardPressure(const MachineInstr *MI,
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std::vector<unsigned> &PressureResult,
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std::vector<unsigned> &MaxPressureResult);
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void getPressureAfterInst(const MachineInstr *MI,
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std::vector<unsigned> &PressureResult,
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std::vector<unsigned> &MaxPressureResult) {
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if (isTopClosed())
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return getUpwardPressure(MI, PressureResult, MaxPressureResult);
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assert(isBottomClosed() && "Uninitialized pressure tracker");
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return getDownwardPressure(MI, PressureResult, MaxPressureResult);
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}
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void dump() const;
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protected:
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const LiveInterval *getInterval(unsigned Reg) const;
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void increaseRegPressure(ArrayRef<unsigned> Regs);
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void decreaseRegPressure(ArrayRef<unsigned> Regs);
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void bumpUpwardPressure(const MachineInstr *MI);
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void bumpDownwardPressure(const MachineInstr *MI);
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};
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} // end namespace llvm
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#endif
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