llvm-6502/include/llvm/CodeGen/RegisterPressure.h
2012-12-05 23:05:22 +00:00

321 lines
12 KiB
C++

//===-- 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/ADT/SparseSet.h"
#include "llvm/CodeGen/SlotIndexes.h"
#include "llvm/Target/TargetRegisterInfo.h"
namespace llvm {
class LiveIntervals;
class LiveInterval;
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 virtual registers or physical register units.
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).
///
/// \param Reg is either a virtual register number or register unit number.
void increase(unsigned Reg, const TargetRegisterInfo *TRI,
const MachineRegisterInfo *MRI);
/// Decrease register pressure for each pressure set impacted by this register
/// class. This is only useful to account for spilling or rematerialization.
///
/// \param Reg is either a virtual register number or register unit number.
void decrease(unsigned Reg, const TargetRegisterInfo *TRI,
const MachineRegisterInfo *MRI);
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() {}
};
/// \brief A set of live virtual registers and physical register units.
///
/// Virtual and physical register numbers require separate sparse sets, but most
/// of the RegisterPressureTracker handles them uniformly.
struct LiveRegSet {
SparseSet<unsigned> PhysRegs;
SparseSet<unsigned, VirtReg2IndexFunctor> VirtRegs;
bool contains(unsigned Reg) {
if (TargetRegisterInfo::isVirtualRegister(Reg))
return VirtRegs.count(Reg);
return PhysRegs.count(Reg);
}
bool insert(unsigned Reg) {
if (TargetRegisterInfo::isVirtualRegister(Reg))
return VirtRegs.insert(Reg).second;
return PhysRegs.insert(Reg).second;
}
bool erase(unsigned Reg) {
if (TargetRegisterInfo::isVirtualRegister(Reg))
return VirtRegs.erase(Reg);
return PhysRegs.erase(Reg);
}
};
/// 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 or a DebugValue rather than
/// an instruction.
MachineBasicBlock::const_iterator CurrPos;
/// Pressure map indexed by pressure set ID, not class ID.
std::vector<unsigned> CurrSetPressure;
/// Set of live registers.
LiveRegSet LiveRegs;
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 virtual registers or physical register
/// units. 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; }
/// \brief Get the SlotIndex for the first nondebug instruction including or
/// after the current position.
SlotIndex getCurrSlot() const;
/// 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 discoverLiveOut(unsigned Reg);
void discoverLiveIn(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);
}
void dump() const;
protected:
const LiveInterval *getInterval(unsigned Reg) const;
void increaseRegPressure(ArrayRef<unsigned> Regs);
void decreaseRegPressure(ArrayRef<unsigned> Regs);
void bumpUpwardPressure(const MachineInstr *MI);
void bumpDownwardPressure(const MachineInstr *MI);
};
} // end namespace llvm
#endif