#include "llvm/CodeGen/MachineBasicBlock.h"
#include "llvm/CodeGen/MachineInstr.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
+#include "llvm/Support/Debug.h"
#include "llvm/Support/ErrorHandling.h"
+#include "llvm/Support/raw_ostream.h"
#include "llvm/Target/TargetRegisterInfo.h"
#include "llvm/Target/TargetInstrInfo.h"
#include "llvm/Target/TargetMachine.h"
void RegScavenger::setUsed(unsigned Reg) {
RegsAvailable.reset(Reg);
- for (const unsigned *SubRegs = TRI->getSubRegisters(Reg);
- unsigned SubReg = *SubRegs; ++SubRegs)
- RegsAvailable.reset(SubReg);
+ for (MCSubRegIterator SubRegs(Reg, TRI); SubRegs.isValid(); ++SubRegs)
+ RegsAvailable.reset(*SubRegs);
}
bool RegScavenger::isAliasUsed(unsigned Reg) const {
- if (isUsed(Reg))
- return true;
- for (const unsigned *R = TRI->getAliasSet(Reg); *R; ++R)
- if (isUsed(*R))
+ for (MCRegAliasIterator AI(Reg, TRI, true); AI.isValid(); ++AI)
+ if (isUsed(*AI))
return true;
return false;
}
// All registers started out unused.
RegsAvailable.set();
- // Reserved registers are always used.
- RegsAvailable ^= ReservedRegs;
-
if (!MBB)
return;
assert((NumPhysRegs == 0 || NumPhysRegs == TRI->getNumRegs()) &&
"Target changed?");
+ // It is not possible to use the register scavenger after late optimization
+ // passes that don't preserve accurate liveness information.
+ assert(MRI->tracksLiveness() &&
+ "Cannot use register scavenger with inaccurate liveness");
+
// Self-initialize.
if (!MBB) {
NumPhysRegs = TRI->getNumRegs();
RegsAvailable.resize(NumPhysRegs);
+ KillRegs.resize(NumPhysRegs);
+ DefRegs.resize(NumPhysRegs);
// Create reserved registers bitvector.
ReservedRegs = TRI->getReservedRegs(MF);
// Create callee-saved registers bitvector.
CalleeSavedRegs.resize(NumPhysRegs);
- const unsigned *CSRegs = TRI->getCalleeSavedRegs();
+ const uint16_t *CSRegs = TRI->getCalleeSavedRegs(&MF);
if (CSRegs != NULL)
for (unsigned i = 0; CSRegs[i]; ++i)
CalleeSavedRegs.set(CSRegs[i]);
void RegScavenger::addRegWithSubRegs(BitVector &BV, unsigned Reg) {
BV.set(Reg);
- for (const unsigned *R = TRI->getSubRegisters(Reg); *R; R++)
- BV.set(*R);
-}
-
-void RegScavenger::addRegWithAliases(BitVector &BV, unsigned Reg) {
- BV.set(Reg);
- for (const unsigned *R = TRI->getAliasSet(Reg); *R; R++)
- BV.set(*R);
+ for (MCSubRegIterator SubRegs(Reg, TRI); SubRegs.isValid(); ++SubRegs)
+ BV.set(*SubRegs);
}
void RegScavenger::forward() {
MBBI = MBB->begin();
Tracking = true;
} else {
- assert(MBBI != MBB->end() && "Already at the end of the basic block!");
+ assert(MBBI != MBB->end() && "Already past the end of the basic block!");
MBBI = llvm::next(MBBI);
}
+ assert(MBBI != MBB->end() && "Already at the end of the basic block!");
MachineInstr *MI = MBBI;
// Find out which registers are early clobbered, killed, defined, and marked
// def-dead in this instruction.
- BitVector EarlyClobberRegs(NumPhysRegs);
- BitVector KillRegs(NumPhysRegs);
- BitVector DefRegs(NumPhysRegs);
- BitVector DeadRegs(NumPhysRegs);
+ // FIXME: The scavenger is not predication aware. If the instruction is
+ // predicated, conservatively assume "kill" markers do not actually kill the
+ // register. Similarly ignores "dead" markers.
+ bool isPred = TII->isPredicated(MI);
+ KillRegs.reset();
+ DefRegs.reset();
for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
const MachineOperand &MO = MI->getOperand(i);
- if (!MO.isReg() || MO.isUndef())
+ if (MO.isRegMask())
+ (isPred ? DefRegs : KillRegs).setBitsNotInMask(MO.getRegMask());
+ if (!MO.isReg())
continue;
unsigned Reg = MO.getReg();
if (!Reg || isReserved(Reg))
continue;
if (MO.isUse()) {
- // Two-address operands implicitly kill.
- if (MO.isKill() || MI->isRegTiedToDefOperand(i))
+ // Ignore undef uses.
+ if (MO.isUndef())
+ continue;
+ if (!isPred && MO.isKill())
addRegWithSubRegs(KillRegs, Reg);
} else {
assert(MO.isDef());
- if (MO.isDead())
- addRegWithSubRegs(DeadRegs, Reg);
+ if (!isPred && MO.isDead())
+ addRegWithSubRegs(KillRegs, Reg);
else
addRegWithSubRegs(DefRegs, Reg);
- if (MO.isEarlyClobber())
- addRegWithAliases(EarlyClobberRegs, Reg);
}
}
// Verify uses and defs.
+#ifndef NDEBUG
for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
const MachineOperand &MO = MI->getOperand(i);
- if (!MO.isReg() || MO.isUndef())
+ if (!MO.isReg())
continue;
unsigned Reg = MO.getReg();
if (!Reg || isReserved(Reg))
continue;
if (MO.isUse()) {
+ if (MO.isUndef())
+ continue;
if (!isUsed(Reg)) {
// Check if it's partial live: e.g.
// D0 = insert_subreg D0<undef>, S0
// Ideally we would like a way to model this, but leaving the
// insert_subreg around causes both correctness and performance issues.
bool SubUsed = false;
- for (const unsigned *SubRegs = TRI->getSubRegisters(Reg);
- unsigned SubReg = *SubRegs; ++SubRegs)
- if (isUsed(SubReg)) {
+ for (MCSubRegIterator SubRegs(Reg, TRI); SubRegs.isValid(); ++SubRegs)
+ if (isUsed(*SubRegs)) {
SubUsed = true;
break;
}
- assert(SubUsed && "Using an undefined register!");
+ if (!SubUsed) {
+ MBB->getParent()->verify(NULL, "In Register Scavenger");
+ llvm_unreachable("Using an undefined register!");
+ }
+ (void)SubUsed;
}
- assert((!EarlyClobberRegs.test(Reg) || MI->isRegTiedToDefOperand(i)) &&
- "Using an early clobbered register!");
} else {
assert(MO.isDef());
#if 0
#endif
}
}
+#endif // NDEBUG
// Commit the changes.
setUnused(KillRegs);
- setUnused(DeadRegs);
setUsed(DefRegs);
}
void RegScavenger::getRegsUsed(BitVector &used, bool includeReserved) {
+ used = RegsAvailable;
+ used.flip();
if (includeReserved)
- used = ~RegsAvailable;
+ used |= ReservedRegs;
else
- used = ~RegsAvailable & ~ReservedRegs;
-}
-
-/// CreateRegClassMask - Set the bits that represent the registers in the
-/// TargetRegisterClass.
-static void CreateRegClassMask(const TargetRegisterClass *RC, BitVector &Mask) {
- for (TargetRegisterClass::iterator I = RC->begin(), E = RC->end(); I != E;
- ++I)
- Mask.set(*I);
+ used.reset(ReservedRegs);
}
unsigned RegScavenger::FindUnusedReg(const TargetRegisterClass *RC) const {
for (TargetRegisterClass::iterator I = RC->begin(), E = RC->end();
I != E; ++I)
- if (!isAliasUsed(*I))
+ if (!isAliasUsed(*I)) {
+ DEBUG(dbgs() << "Scavenger found unused reg: " << TRI->getName(*I) <<
+ "\n");
return *I;
+ }
return 0;
}
+/// getRegsAvailable - Return all available registers in the register class
+/// in Mask.
+BitVector RegScavenger::getRegsAvailable(const TargetRegisterClass *RC) {
+ BitVector Mask(TRI->getNumRegs());
+ for (TargetRegisterClass::iterator I = RC->begin(), E = RC->end();
+ I != E; ++I)
+ if (!isAliasUsed(*I))
+ Mask.set(*I);
+ return Mask;
+}
+
/// findSurvivorReg - Return the candidate register that is unused for the
-/// longest after MBBI. UseMI is set to the instruction where the search
+/// longest after StargMII. UseMI is set to the instruction where the search
/// stopped.
///
/// No more than InstrLimit instructions are inspected.
bool inVirtLiveRange = false;
for (++MI; InstrLimit > 0 && MI != ME; ++MI, --InstrLimit) {
+ if (MI->isDebugValue()) {
+ ++InstrLimit; // Don't count debug instructions
+ continue;
+ }
bool isVirtKillInsn = false;
bool isVirtDefInsn = false;
// Remove any candidates touched by instruction.
for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
const MachineOperand &MO = MI->getOperand(i);
+ if (MO.isRegMask())
+ Candidates.clearBitsNotInMask(MO.getRegMask());
if (!MO.isReg() || MO.isUndef() || !MO.getReg())
continue;
if (TargetRegisterInfo::isVirtualRegister(MO.getReg())) {
isVirtKillInsn = true;
continue;
}
- Candidates.reset(MO.getReg());
- for (const unsigned *R = TRI->getAliasSet(MO.getReg()); *R; R++)
- Candidates.reset(*R);
+ for (MCRegAliasIterator AI(MO.getReg(), TRI, true); AI.isValid(); ++AI)
+ Candidates.reset(*AI);
}
// If we're not in a virtual reg's live range, this is a valid
// restore point.
unsigned RegScavenger::scavengeRegister(const TargetRegisterClass *RC,
MachineBasicBlock::iterator I,
int SPAdj) {
- // Mask off the registers which are not in the TargetRegisterClass.
- BitVector Candidates(NumPhysRegs, false);
- CreateRegClassMask(RC, Candidates);
- // Do not include reserved registers.
- Candidates ^= ReservedRegs & Candidates;
+ // Consider all allocatable registers in the register class initially
+ BitVector Candidates =
+ TRI->getAllocatableSet(*I->getParent()->getParent(), RC);
// Exclude all the registers being used by the instruction.
for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i) {
Candidates.reset(MO.getReg());
}
+ // Try to find a register that's unused if there is one, as then we won't
+ // have to spill. Search explicitly rather than masking out based on
+ // RegsAvailable, as RegsAvailable does not take aliases into account.
+ // That's what getRegsAvailable() is for.
+ BitVector Available = getRegsAvailable(RC);
+ Available &= Candidates;
+ if (Available.any())
+ Candidates = Available;
+
// Find the register whose use is furthest away.
MachineBasicBlock::iterator UseMI;
unsigned SReg = findSurvivorReg(I, Candidates, 25, UseMI);
- // If we found an unused register there is no reason to spill it. We have
- // probably found a callee-saved register that has been saved in the
- // prologue, but happens to be unused at this point.
- if (!isAliasUsed(SReg))
+ // If we found an unused register there is no reason to spill it.
+ if (!isAliasUsed(SReg)) {
+ DEBUG(dbgs() << "Scavenged register: " << TRI->getName(SReg) << "\n");
return SReg;
+ }
assert(ScavengedReg == 0 &&
"Scavenger slot is live, unable to scavenge another register!");
// Spill the scavenged register before I.
assert(ScavengingFrameIndex >= 0 &&
"Cannot scavenge register without an emergency spill slot!");
- TII->storeRegToStackSlot(*MBB, I, SReg, true, ScavengingFrameIndex, RC);
+ TII->storeRegToStackSlot(*MBB, I, SReg, true, ScavengingFrameIndex, RC,TRI);
MachineBasicBlock::iterator II = prior(I);
- TRI->eliminateFrameIndex(II, SPAdj, NULL, this);
+ TRI->eliminateFrameIndex(II, SPAdj, this);
// Restore the scavenged register before its use (or first terminator).
- TII->loadRegFromStackSlot(*MBB, UseMI, SReg, ScavengingFrameIndex, RC);
+ TII->loadRegFromStackSlot(*MBB, UseMI, SReg, ScavengingFrameIndex, RC, TRI);
II = prior(UseMI);
- TRI->eliminateFrameIndex(II, SPAdj, NULL, this);
+ TRI->eliminateFrameIndex(II, SPAdj, this);
}
ScavengeRestore = prior(UseMI);
// ScavengedReg = SReg;
ScavengedRC = RC;
+ DEBUG(dbgs() << "Scavenged register (with spill): " << TRI->getName(SReg) <<
+ "\n");
+
return SReg;
}
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