#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/Compiler.h"
+#include "llvm/ADT/BitVector.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/ADT/STLExtras.h"
+#include "llvm/ADT/SmallSet.h"
#include <algorithm>
using namespace llvm;
-namespace {
- static Statistic NumSpills("spiller", "Number of register spills");
- static Statistic NumStores("spiller", "Number of stores added");
- static Statistic NumLoads ("spiller", "Number of loads added");
- static Statistic NumReused("spiller", "Number of values reused");
- static Statistic NumDSE ("spiller", "Number of dead stores elided");
- static Statistic NumDCE ("spiller", "Number of copies elided");
+STATISTIC(NumSpills, "Number of register spills");
+STATISTIC(NumStores, "Number of stores added");
+STATISTIC(NumLoads , "Number of loads added");
+STATISTIC(NumReused, "Number of values reused");
+STATISTIC(NumDSE , "Number of dead stores elided");
+STATISTIC(NumDCE , "Number of copies elided");
+namespace {
enum SpillerName { simple, local };
static cl::opt<SpillerName>
ModRef MRInfo;
const TargetInstrDescriptor *TID = OldMI->getInstrDescriptor();
if (TID->getOperandConstraint(OpNo, TOI::TIED_TO) != -1 ||
- TII.findTiedToSrcOperand(TID, OpNo) != -1) {
+ TID->findTiedToSrcOperand(OpNo) != -1) {
// Folded a two-address operand.
MRInfo = isModRef;
} else if (OldMI->getOperand(OpNo).isDef()) {
}
void VirtRegMap::print(std::ostream &OS) const {
- OStream LOS(OS);
- print(LOS);
-}
-
-void VirtRegMap::print(OStream &OS) const {
const MRegisterInfo* MRI = MF.getTarget().getRegisterInfo();
OS << "********** REGISTER MAP **********\n";
}
void VirtRegMap::dump() const {
- OStream OS = DOUT;
- print(OS);
+ print(DOUT);
}
}
private:
void RewriteMBB(MachineBasicBlock &MBB, VirtRegMap &VRM);
- void ClobberPhysReg(unsigned PR, std::map<int, unsigned> &SpillSlots,
- std::multimap<unsigned, int> &PhysRegs);
- void ClobberPhysRegOnly(unsigned PR, std::map<int, unsigned> &SpillSlots,
- std::multimap<unsigned, int> &PhysRegs);
- void ModifyStackSlot(int Slot, std::map<int, unsigned> &SpillSlots,
- std::multimap<unsigned, int> &PhysRegs);
};
}
// SpillSlotsAvailable - This map keeps track of all of the spilled virtual
// register values that are still available, due to being loaded or stored to,
- // but not invalidated yet.
- std::map<int, unsigned> SpillSlotsAvailable;
+ // but not invalidated yet. It also tracks the instruction that last defined
+ // or used the register.
+ typedef std::pair<unsigned, MachineInstr*> SSInfo;
+ std::map<int, SSInfo> SpillSlotsAvailable;
// PhysRegsAvailable - This is the inverse of SpillSlotsAvailable, indicating
// which stack slot values are currently held by a physreg. This is used to
// invalidate entries in SpillSlotsAvailable when a physreg is modified.
std::multimap<unsigned, int> PhysRegsAvailable;
+ void disallowClobberPhysRegOnly(unsigned PhysReg);
+
void ClobberPhysRegOnly(unsigned PhysReg);
public:
AvailableSpills(const MRegisterInfo *mri, const TargetInstrInfo *tii)
: MRI(mri), TII(tii) {
}
+ const MRegisterInfo *getRegInfo() const { return MRI; }
+
/// getSpillSlotPhysReg - If the specified stack slot is available in a
- /// physical register, return that PhysReg, otherwise return 0.
- unsigned getSpillSlotPhysReg(int Slot) const {
- std::map<int, unsigned>::const_iterator I = SpillSlotsAvailable.find(Slot);
- if (I != SpillSlotsAvailable.end())
- return I->second >> 1; // Remove the CanClobber bit.
+ /// physical register, return that PhysReg, otherwise return 0. It also
+ /// returns by reference the instruction that either defines or last uses
+ /// the register.
+ unsigned getSpillSlotPhysReg(int Slot, MachineInstr *&SSMI) const {
+ std::map<int, SSInfo>::const_iterator I = SpillSlotsAvailable.find(Slot);
+ if (I != SpillSlotsAvailable.end()) {
+ SSMI = I->second.second;
+ return I->second.first >> 1; // Remove the CanClobber bit.
+ }
return 0;
}
-
- const MRegisterInfo *getRegInfo() const { return MRI; }
+ /// UpdateLastUses - Update the last use information of all stack slots whose
+ /// values are available in the specific register.
+ void UpdateLastUse(unsigned PhysReg, MachineInstr *Use) {
+ std::multimap<unsigned, int>::iterator I =
+ PhysRegsAvailable.lower_bound(PhysReg);
+ while (I != PhysRegsAvailable.end() && I->first == PhysReg) {
+ int Slot = I->second;
+ I++;
+
+ std::map<int, SSInfo>::iterator II = SpillSlotsAvailable.find(Slot);
+ assert(II != SpillSlotsAvailable.end() && "Slot not available!");
+ unsigned Val = II->second.first;
+ assert((Val >> 1) == PhysReg && "Bidirectional map mismatch!");
+ SpillSlotsAvailable.erase(Slot);
+ SpillSlotsAvailable[Slot] = std::make_pair(Val, Use);
+ }
+ }
+
/// addAvailable - Mark that the specified stack slot 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 Slot, unsigned Reg, bool CanClobber = true) {
+ void addAvailable(int Slot, MachineInstr *MI, unsigned Reg,
+ bool CanClobber = true) {
// If this stack slot is thought to be available in some other physreg,
// remove its record.
ModifyStackSlot(Slot);
PhysRegsAvailable.insert(std::make_pair(Reg, Slot));
- SpillSlotsAvailable[Slot] = (Reg << 1) | (unsigned)CanClobber;
+ SpillSlotsAvailable[Slot] =
+ std::make_pair((Reg << 1) | (unsigned)CanClobber, MI);
DOUT << "Remembering SS#" << Slot << " in physreg "
<< MRI->getName(Reg) << "\n";
}
-
+
/// canClobberPhysReg - 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 canClobberPhysReg(int Slot) const {
assert(SpillSlotsAvailable.count(Slot) && "Slot not available!");
- return SpillSlotsAvailable.find(Slot)->second & 1;
+ return SpillSlotsAvailable.find(Slot)->second.first & 1;
}
+ /// 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 we thing lives in
/// it and any of its aliases.
};
}
+/// disallowClobberPhysRegOnly - Unset the CanClobber bit of the specified
+/// stackslot register. The register is still available but is no longer
+/// allowed to be modifed.
+void AvailableSpills::disallowClobberPhysRegOnly(unsigned PhysReg) {
+ std::multimap<unsigned, int>::iterator I =
+ PhysRegsAvailable.lower_bound(PhysReg);
+ while (I != PhysRegsAvailable.end() && I->first == PhysReg) {
+ int Slot = I->second;
+ I++;
+ assert((SpillSlotsAvailable[Slot].first >> 1) == PhysReg &&
+ "Bidirectional map mismatch!");
+ SpillSlotsAvailable[Slot].first &= ~1;
+ DOUT << "PhysReg " << MRI->getName(PhysReg)
+ << " copied, it is available for use but can no longer be modified\n";
+ }
+}
+
+/// disallowClobberPhysReg - Unset the CanClobber bit of the specified
+/// stackslot register and its aliases. The register and its aliases may
+/// still available but is no longer allowed to be modifed.
+void AvailableSpills::disallowClobberPhysReg(unsigned PhysReg) {
+ for (const unsigned *AS = MRI->getAliasSet(PhysReg); *AS; ++AS)
+ disallowClobberPhysRegOnly(*AS);
+ disallowClobberPhysRegOnly(PhysReg);
+}
+
/// ClobberPhysRegOnly - This is called when the specified physreg changes
/// value. We use this to invalidate any info about stuff we thing lives in it.
void AvailableSpills::ClobberPhysRegOnly(unsigned PhysReg) {
while (I != PhysRegsAvailable.end() && I->first == PhysReg) {
int Slot = I->second;
PhysRegsAvailable.erase(I++);
- assert((SpillSlotsAvailable[Slot] >> 1) == PhysReg &&
+ assert((SpillSlotsAvailable[Slot].first >> 1) == PhysReg &&
"Bidirectional map mismatch!");
SpillSlotsAvailable.erase(Slot);
DOUT << "PhysReg " << MRI->getName(PhysReg)
/// changes. This removes information about which register the previous value
/// for this slot lives in (as the previous value is dead now).
void AvailableSpills::ModifyStackSlot(int Slot) {
- std::map<int, unsigned>::iterator It = SpillSlotsAvailable.find(Slot);
+ std::map<int, SSInfo>::iterator It = SpillSlotsAvailable.find(Slot);
if (It == SpillSlotsAvailable.end()) return;
- unsigned Reg = It->second >> 1;
+ unsigned Reg = It->second.first >> 1;
SpillSlotsAvailable.erase(It);
// This register may hold the value of multiple stack slots, only remove this
class VISIBILITY_HIDDEN ReuseInfo {
MachineInstr &MI;
std::vector<ReusedOp> Reuses;
- bool *PhysRegsClobbered;
+ BitVector PhysRegsClobbered;
public:
ReuseInfo(MachineInstr &mi, const MRegisterInfo *mri) : MI(mi) {
- PhysRegsClobbered = new bool[mri->getNumRegs()];
- std::fill(PhysRegsClobbered, PhysRegsClobbered+mri->getNumRegs(), false);
- }
- ~ReuseInfo() {
- delete[] PhysRegsClobbered;
+ PhysRegsClobbered.resize(mri->getNumRegs());
}
bool hasReuses() const {
}
void markClobbered(unsigned PhysReg) {
- PhysRegsClobbered[PhysReg] = true;
+ PhysRegsClobbered.set(PhysReg);
}
bool isClobbered(unsigned PhysReg) const {
- return PhysRegsClobbered[PhysReg];
+ return PhysRegsClobbered.test(PhysReg);
}
/// GetRegForReload - We are about to emit a reload into PhysReg. If there
/// a new register to use, or evict the previous reload and use this reg.
unsigned GetRegForReload(unsigned PhysReg, MachineInstr *MI,
AvailableSpills &Spills,
- std::map<int, MachineInstr*> &MaybeDeadStores) {
+ std::map<int, MachineInstr*> &MaybeDeadStores,
+ SmallSet<unsigned, 8> &Rejected) {
if (Reuses.empty()) return PhysReg; // This is most often empty.
for (unsigned ro = 0, e = Reuses.size(); ro != e; ++ro) {
ReusedOp &Op = Reuses[ro];
// If we find some other reuse that was supposed to use this register
// exactly for its reload, we can change this reload to use ITS reload
- // register.
- if (Op.PhysRegReused == PhysReg) {
+ // register. That is, unless its reload register has already been
+ // considered and subsequently rejected because it has also been reused
+ // by another operand.
+ if (Op.PhysRegReused == PhysReg &&
+ Rejected.count(Op.AssignedPhysReg) == 0) {
// Yup, use the reload register that we didn't use before.
- unsigned NewReg = Op.AssignedPhysReg;
- return GetRegForReload(NewReg, MI, Spills, MaybeDeadStores);
+ unsigned NewReg = Op.AssignedPhysReg;
+ Rejected.insert(PhysReg);
+ return GetRegForReload(NewReg, MI, Spills, MaybeDeadStores, Rejected);
} else {
// Otherwise, we might also have a problem if a previously reused
// value aliases the new register. If so, codegen the previous reload
// register could hold a reuse. Check to see if it conflicts or
// would prefer us to use a different register.
unsigned NewPhysReg = GetRegForReload(NewOp.AssignedPhysReg,
- MI, Spills, MaybeDeadStores);
+ MI, Spills, MaybeDeadStores, Rejected);
MRI->loadRegFromStackSlot(*MBB, MI, NewPhysReg,
NewOp.StackSlot, AliasRC);
MI->getOperand(NewOp.Operand).setReg(NewPhysReg);
- Spills.addAvailable(NewOp.StackSlot, NewPhysReg);
+ Spills.addAvailable(NewOp.StackSlot, MI, NewPhysReg);
++NumLoads;
DEBUG(MachineBasicBlock::iterator MII = MI;
DOUT << '\t' << *prior(MII));
}
return PhysReg;
}
+
+ /// 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::map<int, MachineInstr*> &MaybeDeadStores) {
+ SmallSet<unsigned, 8> Rejected;
+ return GetRegForReload(PhysReg, MI, Spills, MaybeDeadStores, Rejected);
+ }
};
}
// Loop over all of the implicit defs, clearing them from our available
// sets.
- const unsigned *ImpDef = TII->getImplicitDefs(MI.getOpcode());
+ const TargetInstrDescriptor *TID = MI.getInstrDescriptor();
+ const unsigned *ImpDef = TID->ImplicitDefs;
if (ImpDef) {
for ( ; *ImpDef; ++ImpDef) {
PhysRegsUsed[*ImpDef] = true;
unsigned PhysReg;
// Check to see if this stack slot is available.
- if ((PhysReg = Spills.getSpillSlotPhysReg(StackSlot))) {
-
+ MachineInstr *SSMI = NULL;
+ if ((PhysReg = Spills.getSpillSlotPhysReg(StackSlot, SSMI))) {
// This spilled operand might be part of a two-address operand. If this
// is the case, then changing it will necessarily require changing the
// def part of the instruction as well. However, in some cases, we
// aren't allowed to modify the reused register. If none of these cases
// apply, reuse it.
bool CanReuse = true;
- int ti = MI.getInstrDescriptor()->getOperandConstraint(i, TOI::TIED_TO);
+ int ti = TID->getOperandConstraint(i, TOI::TIED_TO);
if (ti != -1 &&
MI.getOperand(ti).isReg() &&
MI.getOperand(ti).getReg() == VirtReg) {
// Okay, we have a two address operand. We can reuse this physreg as
- // long as we are allowed to clobber the value and there is an earlier
- // def that has already clobbered the physreg.
+ // long as we are allowed to clobber the value and there isn't an
+ // earlier def that has already clobbered the physreg.
CanReuse = Spills.canClobberPhysReg(StackSlot) &&
!ReusedOperands.isClobbered(PhysReg);
}
<< MRI->getName(VRM.getPhys(VirtReg)) << "\n";
MI.getOperand(i).setReg(PhysReg);
+ // Extend the live range of the MI that last kill the register if
+ // necessary.
+ MachineOperand *MOK = SSMI->findRegisterUseOperand(PhysReg, true);
+ if (MOK) {
+ MOK->unsetIsKill();
+ if (ti == -1) {
+ // Unless it's the use of a two-address code, transfer the kill
+ // of the reused register to this use.
+ MI.getOperand(i).setIsKill();
+ Spills.UpdateLastUse(PhysReg, &MI);
+ }
+ }
+
// The only technical detail we have is that we don't know that
// PhysReg won't be clobbered by a reloaded stack slot that occurs
// later in the instruction. In particular, consider 'op V1, V2'.
PhysRegsUsed[DesignatedReg] = true;
ReusedOperands.markClobbered(DesignatedReg);
MRI->copyRegToReg(MBB, &MI, DesignatedReg, PhysReg, RC);
-
+
+ // Extend the live range of the MI that last kill the register if
+ // necessary.
+ if (SSMI) {
+ MachineOperand *MOK = SSMI->findRegisterUseOperand(PhysReg, true);
+ if (MOK) {
+ MachineInstr *CopyMI = prior(MII);
+ MachineOperand *MOU = CopyMI->findRegisterUseOperand(PhysReg);
+ MOU->setIsKill();
+ MOK->unsetIsKill();
+ Spills.UpdateLastUse(PhysReg, &MI);
+ }
+ }
+
// This invalidates DesignatedReg.
Spills.ClobberPhysReg(DesignatedReg);
- Spills.addAvailable(StackSlot, DesignatedReg);
+ Spills.addAvailable(StackSlot, &MI, DesignatedReg);
MI.getOperand(i).setReg(DesignatedReg);
DOUT << '\t' << *prior(MII);
++NumReused;
// Any stores to this stack slot are not dead anymore.
MaybeDeadStores.erase(StackSlot);
- Spills.addAvailable(StackSlot, PhysReg);
+ Spills.addAvailable(StackSlot, &MI, PhysReg);
+ // Assumes this is the last use. IsKill will be unset if reg is reused
+ // unless it's a two-address operand.
+ if (TID->getOperandConstraint(i, TOI::TIED_TO) == -1)
+ MI.getOperand(i).setIsKill();
++NumLoads;
MI.getOperand(i).setReg(PhysReg);
DOUT << '\t' << *prior(MII);
if (FrameIdx == SS) {
// If this spill slot is available, turn it into a copy (or nothing)
// instead of leaving it as a load!
- if (unsigned InReg = Spills.getSpillSlotPhysReg(SS)) {
+ MachineInstr *SSMI = NULL;
+ if (unsigned InReg = Spills.getSpillSlotPhysReg(SS, SSMI)) {
DOUT << "Promoted Load To Copy: " << MI;
MachineFunction &MF = *MBB.getParent();
if (DestReg != InReg) {
// virtual or needing to clobber any values if it's physical).
NextMII = &MI;
--NextMII; // backtrack to the copy.
+ } else
+ DOUT << "Removing now-noop copy: " << MI;
+
+ // Extend the live range of the MI that last kill the register if
+ // the next MI reuse it.
+ MachineOperand *MOK = SSMI->findRegisterUseOperand(InReg, true);
+ if (MOK && NextMII != MBB.end()) {
+ MachineOperand *MOU = NextMII->findRegisterUseOperand(InReg);
+ if (MOU) {
+ MOU->setIsKill();
+ MOK->unsetIsKill();
+ Spills.UpdateLastUse(InReg, &(*NextMII));
+ }
}
+
VRM.RemoveFromFoldedVirtMap(&MI);
MBB.erase(&MI);
goto ProcessNextInst;
// If the stack slot value was previously available in some other
// register, change it now. Otherwise, make the register available,
// in PhysReg.
- Spills.addAvailable(StackSlot, SrcReg, false /*don't clobber*/);
+ Spills.addAvailable(StackSlot, &MI, SrcReg, false/*don't clobber*/);
}
}
}
DOUT << "Removing now-noop copy: " << MI;
MBB.erase(&MI);
VRM.RemoveFromFoldedVirtMap(&MI);
+ Spills.disallowClobberPhysReg(VirtReg);
goto ProcessNextInst;
}
assert(DestReg == VirtReg && "Unknown load situation!");
// Otherwise, if it wasn't available, remember that it is now!
- Spills.addAvailable(FrameIdx, DestReg);
+ Spills.addAvailable(FrameIdx, &MI, DestReg);
goto ProcessNextInst;
}
// If this def is part of a two-address operand, make sure to execute
// the store from the correct physical register.
unsigned PhysReg;
- int TiedOp = TII->findTiedToSrcOperand(MI.getInstrDescriptor(), i);
+ int TiedOp = MI.getInstrDescriptor()->findTiedToSrcOperand(i);
if (TiedOp != -1)
PhysReg = MI.getOperand(TiedOp).getReg();
else {
DOUT << "Store:\t" << *next(MII);
MI.getOperand(i).setReg(PhysReg);
- // Check to see if this is a noop copy. If so, eliminate the
- // instruction before considering the dest reg to be changed.
- {
- unsigned Src, Dst;
- if (TII->isMoveInstr(MI, Src, Dst) && Src == Dst) {
- ++NumDCE;
- DOUT << "Removing now-noop copy: " << MI;
- MBB.erase(&MI);
- VRM.RemoveFromFoldedVirtMap(&MI);
- goto ProcessNextInst;
- }
- }
-
// If there is a dead store to this stack slot, nuke it now.
MachineInstr *&LastStore = MaybeDeadStores[StackSlot];
if (LastStore) {
// in PhysReg.
Spills.ModifyStackSlot(StackSlot);
Spills.ClobberPhysReg(PhysReg);
- Spills.addAvailable(StackSlot, PhysReg);
+ Spills.addAvailable(StackSlot, LastStore, PhysReg);
++NumStores;
+
+ // Check to see if this is a noop copy. If so, eliminate the
+ // instruction before considering the dest reg to be changed.
+ {
+ unsigned Src, Dst;
+ if (TII->isMoveInstr(MI, Src, Dst) && Src == Dst) {
+ ++NumDCE;
+ DOUT << "Removing now-noop copy: " << MI;
+ MBB.erase(&MI);
+ VRM.RemoveFromFoldedVirtMap(&MI);
+ goto ProcessNextInst;
+ }
+ }
}
}
ProcessNextInst:
projects / oota-llvm.git / blobdiff