llvm/lib/CodeGen/Spiller.h

325 lines
14 KiB
C++

//===-- llvm/CodeGen/Spiller.h - Spiller -*- C++ -*------------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
#ifndef LLVM_CODEGEN_SPILLER_H
#define LLVM_CODEGEN_SPILLER_H
#include "llvm/Target/TargetRegisterInfo.h"
#include "llvm/ADT/BitVector.h"
#include "llvm/ADT/IndexedMap.h"
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/Support/Streams.h"
#include "llvm/Function.h"
#include "llvm/CodeGen/MachineFrameInfo.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/Target/TargetMachine.h"
#include "llvm/Target/TargetInstrInfo.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
#include "llvm/ADT/BitVector.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/SmallSet.h"
#include "VirtRegMap.h"
#include <map>
namespace llvm {
/// Spiller interface: Implementations of this interface assign spilled
/// virtual registers to stack slots, rewriting the code.
struct Spiller {
virtual ~Spiller();
virtual bool runOnMachineFunction(MachineFunction &MF,
VirtRegMap &VRM) = 0;
};
/// createSpiller - Create an return a spiller object, as specified on the
/// command line.
Spiller* createSpiller();
// ************************************************************************ //
// Simple Spiller Implementation
struct VISIBILITY_HIDDEN SimpleSpiller : public Spiller {
bool runOnMachineFunction(MachineFunction& mf, VirtRegMap &VRM);
};
// ************************************************************************ //
/// AvailableSpills - As the local spiller is scanning and rewriting an MBB
/// from top down, keep track of which spills slots or remat are available in
/// each register.
///
/// Note that not all physregs are created equal here. In particular, some
/// physregs are reloads that we are allowed to clobber or ignore at any time.
/// Other physregs are values that the register allocated program is using
/// that we cannot CHANGE, but we can read if we like. We keep track of this
/// on a per-stack-slot / remat id basis as the low bit in the value of the
/// SpillSlotsAvailable entries. The predicate 'canClobberPhysReg()' checks
/// this bit and addAvailable sets it if.
class VISIBILITY_HIDDEN AvailableSpills {
const TargetRegisterInfo *TRI;
const TargetInstrInfo *TII;
// SpillSlotsOrReMatsAvailable - This map keeps track of all of the spilled
// or remat'ed virtual register values that are still available, due to
// being loaded or stored to, but not invalidated yet.
std::map<int, unsigned> SpillSlotsOrReMatsAvailable;
// PhysRegsAvailable - This is the inverse of SpillSlotsOrReMatsAvailable,
// indicating which stack slot values are currently held by a physreg. This
// is used to invalidate entries in SpillSlotsOrReMatsAvailable when a
// physreg is modified.
std::multimap<unsigned, int> PhysRegsAvailable;
void disallowClobberPhysRegOnly(unsigned PhysReg);
void ClobberPhysRegOnly(unsigned PhysReg);
public:
AvailableSpills(const TargetRegisterInfo *tri, const TargetInstrInfo *tii)
: TRI(tri), TII(tii) {
}
/// clear - Reset the state.
void clear() {
SpillSlotsOrReMatsAvailable.clear();
PhysRegsAvailable.clear();
}
const TargetRegisterInfo *getRegInfo() const { return TRI; }
/// getSpillSlotOrReMatPhysReg - If the specified stack slot or remat is
/// available in a physical register, return that PhysReg, otherwise
/// return 0.
unsigned getSpillSlotOrReMatPhysReg(int Slot) const {
std::map<int, unsigned>::const_iterator I =
SpillSlotsOrReMatsAvailable.find(Slot);
if (I != SpillSlotsOrReMatsAvailable.end()) {
return I->second >> 1; // Remove the CanClobber bit.
}
return 0;
}
/// addAvailable - Mark that the specified stack slot / remat is available
/// in the specified physreg. If CanClobber is true, the physreg can be
/// modified at any time without changing the semantics of the program.
void addAvailable(int SlotOrReMat, unsigned Reg, bool CanClobber = true) {
// If this stack slot is thought to be available in some other physreg,
// remove its record.
ModifyStackSlotOrReMat(SlotOrReMat);
PhysRegsAvailable.insert(std::make_pair(Reg, SlotOrReMat));
SpillSlotsOrReMatsAvailable[SlotOrReMat]= (Reg << 1) |
(unsigned)CanClobber;
if (SlotOrReMat > VirtRegMap::MAX_STACK_SLOT)
DOUT << "Remembering RM#" << SlotOrReMat-VirtRegMap::MAX_STACK_SLOT-1;
else
DOUT << "Remembering SS#" << SlotOrReMat;
DOUT << " in physreg " << TRI->getName(Reg) << "\n";
}
/// canClobberPhysRegForSS - Return true if the spiller is allowed to change
/// the value of the specified stackslot register if it desires. The
/// specified stack slot must be available in a physreg for this query to
/// make sense.
bool canClobberPhysRegForSS(int SlotOrReMat) const {
assert(SpillSlotsOrReMatsAvailable.count(SlotOrReMat) &&
"Value not available!");
return SpillSlotsOrReMatsAvailable.find(SlotOrReMat)->second & 1;
}
/// canClobberPhysReg - Return true if the spiller is allowed to clobber the
/// physical register where values for some stack slot(s) might be
/// available.
bool canClobberPhysReg(unsigned PhysReg) const {
std::multimap<unsigned, int>::const_iterator I =
PhysRegsAvailable.lower_bound(PhysReg);
while (I != PhysRegsAvailable.end() && I->first == PhysReg) {
int SlotOrReMat = I->second;
I++;
if (!canClobberPhysRegForSS(SlotOrReMat))
return false;
}
return true;
}
/// disallowClobberPhysReg - Unset the CanClobber bit of the specified
/// stackslot register. The register is still available but is no longer
/// allowed to be modifed.
void disallowClobberPhysReg(unsigned PhysReg);
/// ClobberPhysReg - This is called when the specified physreg changes
/// value. We use this to invalidate any info about stuff that lives in
/// it and any of its aliases.
void ClobberPhysReg(unsigned PhysReg);
/// ModifyStackSlotOrReMat - This method is called when the value in a stack
/// slot changes. This removes information about which register the
/// previous value for this slot lives in (as the previous value is dead
/// now).
void ModifyStackSlotOrReMat(int SlotOrReMat);
/// AddAvailableRegsToLiveIn - Availability information is being kept coming
/// into the specified MBB. Add available physical registers as potential
/// live-in's. If they are reused in the MBB, they will be added to the
/// live-in set to make register scavenger and post-allocation scheduler.
void AddAvailableRegsToLiveIn(MachineBasicBlock &MBB, BitVector &RegKills,
std::vector<MachineOperand*> &KillOps);
};
// ************************************************************************ //
// ReusedOp - For each reused operand, we keep track of a bit of information,
// in case we need to rollback upon processing a new operand. See comments
// below.
struct ReusedOp {
// The MachineInstr operand that reused an available value.
unsigned Operand;
// StackSlotOrReMat - The spill slot or remat id of the value being reused.
unsigned StackSlotOrReMat;
// PhysRegReused - The physical register the value was available in.
unsigned PhysRegReused;
// AssignedPhysReg - The physreg that was assigned for use by the reload.
unsigned AssignedPhysReg;
// VirtReg - The virtual register itself.
unsigned VirtReg;
ReusedOp(unsigned o, unsigned ss, unsigned prr, unsigned apr,
unsigned vreg)
: Operand(o), StackSlotOrReMat(ss), PhysRegReused(prr),
AssignedPhysReg(apr), VirtReg(vreg) {}
};
/// ReuseInfo - This maintains a collection of ReuseOp's for each operand that
/// is reused instead of reloaded.
class VISIBILITY_HIDDEN ReuseInfo {
MachineInstr &MI;
std::vector<ReusedOp> Reuses;
BitVector PhysRegsClobbered;
public:
ReuseInfo(MachineInstr &mi, const TargetRegisterInfo *tri) : MI(mi) {
PhysRegsClobbered.resize(tri->getNumRegs());
}
bool hasReuses() const {
return !Reuses.empty();
}
/// addReuse - If we choose to reuse a virtual register that is already
/// available instead of reloading it, remember that we did so.
void addReuse(unsigned OpNo, unsigned StackSlotOrReMat,
unsigned PhysRegReused, unsigned AssignedPhysReg,
unsigned VirtReg) {
// If the reload is to the assigned register anyway, no undo will be
// required.
if (PhysRegReused == AssignedPhysReg) return;
// Otherwise, remember this.
Reuses.push_back(ReusedOp(OpNo, StackSlotOrReMat, PhysRegReused,
AssignedPhysReg, VirtReg));
}
void markClobbered(unsigned PhysReg) {
PhysRegsClobbered.set(PhysReg);
}
bool isClobbered(unsigned PhysReg) const {
return PhysRegsClobbered.test(PhysReg);
}
/// GetRegForReload - We are about to emit a reload into PhysReg. If there
/// is some other operand that is using the specified register, either pick
/// a new register to use, or evict the previous reload and use this reg.
unsigned GetRegForReload(unsigned PhysReg, MachineInstr *MI,
AvailableSpills &Spills,
std::vector<MachineInstr*> &MaybeDeadStores,
SmallSet<unsigned, 8> &Rejected,
BitVector &RegKills,
std::vector<MachineOperand*> &KillOps,
VirtRegMap &VRM);
/// GetRegForReload - Helper for the above GetRegForReload(). Add a
/// 'Rejected' set to remember which registers have been considered and
/// rejected for the reload. This avoids infinite looping in case like
/// this:
/// t1 := op t2, t3
/// t2 <- assigned r0 for use by the reload but ended up reuse r1
/// t3 <- assigned r1 for use by the reload but ended up reuse r0
/// t1 <- desires r1
/// sees r1 is taken by t2, tries t2's reload register r0
/// sees r0 is taken by t3, tries t3's reload register r1
/// sees r1 is taken by t2, tries t2's reload register r0 ...
unsigned GetRegForReload(unsigned PhysReg, MachineInstr *MI,
AvailableSpills &Spills,
std::vector<MachineInstr*> &MaybeDeadStores,
BitVector &RegKills,
std::vector<MachineOperand*> &KillOps,
VirtRegMap &VRM) {
SmallSet<unsigned, 8> Rejected;
return GetRegForReload(PhysReg, MI, Spills, MaybeDeadStores, Rejected,
RegKills, KillOps, VRM);
}
};
// ************************************************************************ //
/// LocalSpiller - This spiller does a simple pass over the machine basic
/// block to attempt to keep spills in registers as much as possible for
/// blocks that have low register pressure (the vreg may be spilled due to
/// register pressure in other blocks).
class VISIBILITY_HIDDEN LocalSpiller : public Spiller {
MachineRegisterInfo *RegInfo;
const TargetRegisterInfo *TRI;
const TargetInstrInfo *TII;
DenseMap<MachineInstr*, unsigned> DistanceMap;
public:
bool runOnMachineFunction(MachineFunction &MF, VirtRegMap &VRM);
private:
void TransferDeadness(MachineBasicBlock *MBB, unsigned CurDist,
unsigned Reg, BitVector &RegKills,
std::vector<MachineOperand*> &KillOps);
bool PrepForUnfoldOpti(MachineBasicBlock &MBB,
MachineBasicBlock::iterator &MII,
std::vector<MachineInstr*> &MaybeDeadStores,
AvailableSpills &Spills, BitVector &RegKills,
std::vector<MachineOperand*> &KillOps,
VirtRegMap &VRM);
bool CommuteToFoldReload(MachineBasicBlock &MBB,
MachineBasicBlock::iterator &MII,
unsigned VirtReg, unsigned SrcReg, int SS,
AvailableSpills &Spills,
BitVector &RegKills,
std::vector<MachineOperand*> &KillOps,
const TargetRegisterInfo *TRI,
VirtRegMap &VRM);
void SpillRegToStackSlot(MachineBasicBlock &MBB,
MachineBasicBlock::iterator &MII,
int Idx, unsigned PhysReg, int StackSlot,
const TargetRegisterClass *RC,
bool isAvailable, MachineInstr *&LastStore,
AvailableSpills &Spills,
SmallSet<MachineInstr*, 4> &ReMatDefs,
BitVector &RegKills,
std::vector<MachineOperand*> &KillOps,
VirtRegMap &VRM);
void RewriteMBB(MachineBasicBlock &MBB, VirtRegMap &VRM,
AvailableSpills &Spills,
BitVector &RegKills, std::vector<MachineOperand*> &KillOps);
};
}
#endif