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A spill kills the register being stored. But it is later being reused by spiller, its live range has to be extended. 

llvm-svn: 34517
This commit is contained in:
Evan Cheng 2007-02-23 01:13:26 +00:00
parent 1e56453585
commit f7e320c9e0
1 changed files with 39 additions and 25 deletions
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64
llvm/lib/CodeGen/VirtRegMap.cpp
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@ -255,7 +255,8 @@ class VISIBILITY_HIDDEN AvailableSpills {
// 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;
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
@ -270,27 +271,33 @@ public:
: 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; }
/// 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";
@ -301,7 +308,7 @@ public:
/// 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
@ -330,9 +337,9 @@ void AvailableSpills::disallowClobberPhysRegOnly(unsigned PhysReg) {
while (I != PhysRegsAvailable.end() && I->first == PhysReg) {
int Slot = I->second;
I++;
assert((SpillSlotsAvailable[Slot] >> 1) == PhysReg &&
assert((SpillSlotsAvailable[Slot].first >> 1) == PhysReg &&
"Bidirectional map mismatch!");
SpillSlotsAvailable[Slot] &= ~1;
SpillSlotsAvailable[Slot].first &= ~1;
DOUT << "PhysReg " << MRI->getName(PhysReg)
<< " copied, it is available for use but can no longer be modified\n";
}
@ -355,7 +362,7 @@ 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)
@ -376,9 +383,9 @@ void AvailableSpills::ClobberPhysReg(unsigned 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
@ -514,7 +521,7 @@ namespace {
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));
@ -628,8 +635,8 @@ void LocalSpiller::RewriteMBB(MachineBasicBlock &MBB, VirtRegMap &VRM) {
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
@ -655,6 +662,12 @@ void LocalSpiller::RewriteMBB(MachineBasicBlock &MBB, VirtRegMap &VRM) {
<< 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();
// 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'.
@ -723,7 +736,7 @@ void LocalSpiller::RewriteMBB(MachineBasicBlock &MBB, VirtRegMap &VRM) {
// 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;
@ -752,7 +765,7 @@ void LocalSpiller::RewriteMBB(MachineBasicBlock &MBB, VirtRegMap &VRM) {
// Any stores to this stack slot are not dead anymore.
MaybeDeadStores.erase(StackSlot);
Spills.addAvailable(StackSlot, PhysReg);
Spills.addAvailable(StackSlot, &MI, PhysReg);
++NumLoads;
MI.getOperand(i).setReg(PhysReg);
DOUT << '\t' << *prior(MII);
@ -784,7 +797,8 @@ void LocalSpiller::RewriteMBB(MachineBasicBlock &MBB, VirtRegMap &VRM) {
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 *Dummy = NULL;
if (unsigned InReg = Spills.getSpillSlotPhysReg(SS, Dummy)) {
DOUT << "Promoted Load To Copy: " << MI;
MachineFunction &MF = *MBB.getParent();
if (DestReg != InReg) {
@ -844,7 +858,7 @@ void LocalSpiller::RewriteMBB(MachineBasicBlock &MBB, VirtRegMap &VRM) {
// 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*/);
}
}
}
@ -880,7 +894,7 @@ void LocalSpiller::RewriteMBB(MachineBasicBlock &MBB, VirtRegMap &VRM) {
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;
}
@ -929,7 +943,7 @@ void LocalSpiller::RewriteMBB(MachineBasicBlock &MBB, VirtRegMap &VRM) {
// 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