//
//===----------------------------------------------------------------------===//
-#define DEBUG_TYPE "reg-scavenging"
#include "llvm/CodeGen/RegisterScavenging.h"
+#include "llvm/CodeGen/MachineBasicBlock.h"
#include "llvm/CodeGen/MachineFrameInfo.h"
#include "llvm/CodeGen/MachineFunction.h"
-#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/Target/TargetRegisterInfo.h"
+#include "llvm/Support/raw_ostream.h"
#include "llvm/Target/TargetInstrInfo.h"
-#include "llvm/Target/TargetMachine.h"
-#include "llvm/ADT/DenseMap.h"
-#include "llvm/ADT/SmallPtrSet.h"
-#include "llvm/ADT/SmallVector.h"
-#include "llvm/ADT/STLExtras.h"
+#include "llvm/Target/TargetRegisterInfo.h"
+#include "llvm/Target/TargetSubtargetInfo.h"
using namespace llvm;
-/// setUsed - Set the register and its sub-registers as being used.
-void RegScavenger::setUsed(unsigned Reg) {
- RegsAvailable.reset(Reg);
-
- for (const unsigned *SubRegs = TRI->getSubRegisters(Reg);
- unsigned SubReg = *SubRegs; ++SubRegs)
- RegsAvailable.reset(SubReg);
-}
+#define DEBUG_TYPE "reg-scavenging"
-bool RegScavenger::isAliasUsed(unsigned Reg) const {
- if (isUsed(Reg))
- return true;
- for (const unsigned *R = TRI->getAliasSet(Reg); *R; ++R)
- if (isUsed(*R))
- return true;
- return false;
+/// setUsed - Set the register units of this register as used.
+void RegScavenger::setRegUsed(unsigned Reg, LaneBitmask LaneMask) {
+ for (MCRegUnitMaskIterator RUI(Reg, TRI); RUI.isValid(); ++RUI) {
+ LaneBitmask UnitMask = (*RUI).second;
+ if (UnitMask == 0 || (LaneMask & UnitMask) != 0)
+ RegUnitsAvailable.reset((*RUI).first);
+ }
}
void RegScavenger::initRegState() {
- ScavengedReg = 0;
- ScavengedRC = NULL;
- ScavengeRestore = NULL;
-
- // All registers started out unused.
- RegsAvailable.set();
+ for (SmallVectorImpl<ScavengedInfo>::iterator I = Scavenged.begin(),
+ IE = Scavenged.end(); I != IE; ++I) {
+ I->Reg = 0;
+ I->Restore = nullptr;
+ }
- // Reserved registers are always used.
- RegsAvailable ^= ReservedRegs;
+ // All register units start out unused.
+ RegUnitsAvailable.set();
if (!MBB)
return;
// Live-in registers are in use.
- for (MachineBasicBlock::const_livein_iterator I = MBB->livein_begin(),
- E = MBB->livein_end(); I != E; ++I)
- setUsed(*I);
+ for (const auto &LI : MBB->liveins())
+ setRegUsed(LI.PhysReg, LI.LaneMask);
// Pristine CSRs are also unavailable.
- BitVector PR = MBB->getParent()->getFrameInfo()->getPristineRegs(MBB);
+ const MachineFunction &MF = *MBB->getParent();
+ BitVector PR = MF.getFrameInfo()->getPristineRegs(MF);
for (int I = PR.find_first(); I>0; I = PR.find_next(I))
- setUsed(I);
+ setRegUsed(I);
}
void RegScavenger::enterBasicBlock(MachineBasicBlock *mbb) {
MachineFunction &MF = *mbb->getParent();
- const TargetMachine &TM = MF.getTarget();
- TII = TM.getInstrInfo();
- TRI = TM.getRegisterInfo();
+ TII = MF.getSubtarget().getInstrInfo();
+ TRI = MF.getSubtarget().getRegisterInfo();
MRI = &MF.getRegInfo();
- assert((NumPhysRegs == 0 || NumPhysRegs == TRI->getNumRegs()) &&
+ assert((NumRegUnits == 0 || NumRegUnits == TRI->getNumRegUnits()) &&
"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);
-
- // Create reserved registers bitvector.
- ReservedRegs = TRI->getReservedRegs(MF);
-
- // Create callee-saved registers bitvector.
- CalleeSavedRegs.resize(NumPhysRegs);
- const unsigned *CSRegs = TRI->getCalleeSavedRegs();
- if (CSRegs != NULL)
- for (unsigned i = 0; CSRegs[i]; ++i)
- CalleeSavedRegs.set(CSRegs[i]);
+ NumRegUnits = TRI->getNumRegUnits();
+ RegUnitsAvailable.resize(NumRegUnits);
+ KillRegUnits.resize(NumRegUnits);
+ DefRegUnits.resize(NumRegUnits);
+ TmpRegUnits.resize(NumRegUnits);
}
- // RS used within emit{Pro,Epi}logue()
- if (mbb != MBB) {
- MBB = mbb;
- initRegState();
- }
+ MBB = mbb;
+ initRegState();
Tracking = false;
}
-#ifndef NDEBUG
-/// isLiveInButUnusedBefore - Return true if register is livein the MBB not
-/// not used before it reaches the MI that defines register.
-static bool isLiveInButUnusedBefore(unsigned Reg, MachineInstr *MI,
- MachineBasicBlock *MBB,
- const TargetRegisterInfo *TRI,
- MachineRegisterInfo* MRI) {
- // First check if register is livein.
- bool isLiveIn = false;
- for (MachineBasicBlock::const_livein_iterator I = MBB->livein_begin(),
- E = MBB->livein_end(); I != E; ++I)
- if (Reg == *I || TRI->isSuperRegister(Reg, *I)) {
- isLiveIn = true;
- break;
+void RegScavenger::addRegUnits(BitVector &BV, unsigned Reg) {
+ for (MCRegUnitIterator RUI(Reg, TRI); RUI.isValid(); ++RUI)
+ BV.set(*RUI);
+}
+
+void RegScavenger::determineKillsAndDefs() {
+ assert(Tracking && "Must be tracking to determine kills and defs");
+
+ MachineInstr *MI = MBBI;
+ assert(!MI->isDebugValue() && "Debug values have no kills or defs");
+
+ // Find out which registers are early clobbered, killed, defined, and marked
+ // def-dead in this instruction.
+ KillRegUnits.reset();
+ DefRegUnits.reset();
+ for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
+ const MachineOperand &MO = MI->getOperand(i);
+ if (MO.isRegMask()) {
+
+ TmpRegUnits.clear();
+ for (unsigned RU = 0, RUEnd = TRI->getNumRegUnits(); RU != RUEnd; ++RU) {
+ for (MCRegUnitRootIterator RURI(RU, TRI); RURI.isValid(); ++RURI) {
+ if (MO.clobbersPhysReg(*RURI)) {
+ TmpRegUnits.set(RU);
+ break;
+ }
+ }
+ }
+
+ // Apply the mask.
+ KillRegUnits |= TmpRegUnits;
}
- if (!isLiveIn)
- return false;
-
- // Is there any use of it before the specified MI?
- SmallPtrSet<MachineInstr*, 4> UsesInMBB;
- for (MachineRegisterInfo::use_iterator UI = MRI->use_begin(Reg),
- UE = MRI->use_end(); UI != UE; ++UI) {
- MachineOperand &UseMO = UI.getOperand();
- if (UseMO.isReg() && UseMO.isUndef())
+ if (!MO.isReg())
+ continue;
+ unsigned Reg = MO.getReg();
+ if (!Reg || TargetRegisterInfo::isVirtualRegister(Reg) || isReserved(Reg))
continue;
- MachineInstr *UseMI = &*UI;
- if (UseMI->getParent() == MBB)
- UsesInMBB.insert(UseMI);
- }
- if (UsesInMBB.empty())
- return true;
- for (MachineBasicBlock::iterator I = MBB->begin(), E = MI; I != E; ++I)
- if (UsesInMBB.count(&*I))
- return false;
- return true;
+ if (MO.isUse()) {
+ // Ignore undef uses.
+ if (MO.isUndef())
+ continue;
+ if (MO.isKill())
+ addRegUnits(KillRegUnits, Reg);
+ } else {
+ assert(MO.isDef());
+ if (MO.isDead())
+ addRegUnits(KillRegUnits, Reg);
+ else
+ addRegUnits(DefRegUnits, Reg);
+ }
+ }
}
-#endif
-void RegScavenger::addRegWithSubRegs(BitVector &BV, unsigned Reg) {
- BV.set(Reg);
- for (const unsigned *R = TRI->getSubRegisters(Reg); *R; R++)
- BV.set(*R);
-}
+void RegScavenger::unprocess() {
+ assert(Tracking && "Cannot unprocess because we're not tracking");
-void RegScavenger::addRegWithAliases(BitVector &BV, unsigned Reg) {
- BV.set(Reg);
- for (const unsigned *R = TRI->getAliasSet(Reg); *R; R++)
- BV.set(*R);
+ MachineInstr *MI = MBBI;
+ if (!MI->isDebugValue()) {
+ determineKillsAndDefs();
+
+ // Commit the changes.
+ setUsed(KillRegUnits);
+ setUnused(DefRegUnits);
+ }
+
+ if (MBBI == MBB->begin()) {
+ MBBI = MachineBasicBlock::iterator(nullptr);
+ Tracking = false;
+ } else
+ --MBBI;
}
void RegScavenger::forward() {
MBBI = MBB->begin();
Tracking = true;
} else {
- assert(MBBI != MBB->end() && "Already at the end of the basic block!");
- MBBI = next(MBBI);
+ assert(MBBI != MBB->end() && "Already past the end of the basic block!");
+ MBBI = std::next(MBBI);
}
+ assert(MBBI != MBB->end() && "Already at the end of the basic block!");
MachineInstr *MI = MBBI;
- if (MI == ScavengeRestore) {
- ScavengedReg = 0;
- ScavengedRC = NULL;
- ScavengeRestore = NULL;
- }
-
- // 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);
- for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
- const MachineOperand &MO = MI->getOperand(i);
- if (!MO.isReg() || MO.isUndef())
- continue;
- unsigned Reg = MO.getReg();
- if (!Reg || isReserved(Reg))
+ for (SmallVectorImpl<ScavengedInfo>::iterator I = Scavenged.begin(),
+ IE = Scavenged.end(); I != IE; ++I) {
+ if (I->Restore != MI)
continue;
- if (MO.isUse()) {
- // Two-address operands implicitly kill.
- if (MO.isKill() || MI->isRegTiedToDefOperand(i))
- addRegWithSubRegs(KillRegs, Reg);
- } else {
- assert(MO.isDef());
- if (MO.isDead())
- addRegWithSubRegs(DeadRegs, Reg);
- else
- addRegWithSubRegs(DefRegs, Reg);
- if (MO.isEarlyClobber())
- addRegWithAliases(EarlyClobberRegs, Reg);
- }
+ I->Reg = 0;
+ I->Restore = nullptr;
}
+ if (MI->isDebugValue())
+ return;
+
+ determineKillsAndDefs();
+
// 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))
+ if (!Reg || TargetRegisterInfo::isVirtualRegister(Reg) || isReserved(Reg))
continue;
if (MO.isUse()) {
- assert(isUsed(Reg) && "Using an undefined register!");
- assert((!EarlyClobberRegs.test(Reg) || MI->isRegTiedToDefOperand(i)) &&
- "Using an early clobbered register!");
+ if (MO.isUndef())
+ continue;
+ if (!isRegUsed(Reg)) {
+ // Check if it's partial live: e.g.
+ // D0 = insert_subreg D0<undef>, S0
+ // ... D0
+ // The problem is the insert_subreg could be eliminated. The use of
+ // D0 is using a partially undef value. This is not *incorrect* since
+ // S1 is can be freely clobbered.
+ // 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 (MCSubRegIterator SubRegs(Reg, TRI); SubRegs.isValid(); ++SubRegs)
+ if (isRegUsed(*SubRegs)) {
+ SubUsed = true;
+ break;
+ }
+ bool SuperUsed = false;
+ for (MCSuperRegIterator SR(Reg, TRI); SR.isValid(); ++SR) {
+ if (isRegUsed(*SR)) {
+ SuperUsed = true;
+ break;
+ }
+ }
+ if (!SubUsed && !SuperUsed) {
+ MBB->getParent()->verify(nullptr, "In Register Scavenger");
+ llvm_unreachable("Using an undefined register!");
+ }
+ (void)SubUsed;
+ (void)SuperUsed;
+ }
} else {
assert(MO.isDef());
+#if 0
+ // FIXME: Enable this once we've figured out how to correctly transfer
+ // implicit kills during codegen passes like the coalescer.
assert((KillRegs.test(Reg) || isUnused(Reg) ||
isLiveInButUnusedBefore(Reg, MI, MBB, TRI, MRI)) &&
"Re-defining a live register!");
+#endif
}
}
+#endif // NDEBUG
// Commit the changes.
- setUnused(KillRegs);
- setUnused(DeadRegs);
- setUsed(DefRegs);
-}
-
-void RegScavenger::getRegsUsed(BitVector &used, bool includeReserved) {
- if (includeReserved)
- used = ~RegsAvailable;
- else
- used = ~RegsAvailable & ~ReservedRegs;
+ setUnused(KillRegUnits);
+ setUsed(DefRegUnits);
}
-/// 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);
+bool RegScavenger::isRegUsed(unsigned Reg, bool includeReserved) const {
+ if (includeReserved && isReserved(Reg))
+ return true;
+ for (MCRegUnitIterator RUI(Reg, TRI); RUI.isValid(); ++RUI)
+ if (!RegUnitsAvailable.test(*RUI))
+ return true;
+ return false;
}
unsigned RegScavenger::FindUnusedReg(const TargetRegisterClass *RC) const {
for (TargetRegisterClass::iterator I = RC->begin(), E = RC->end();
I != E; ++I)
- if (!isAliasUsed(*I))
+ if (!isRegUsed(*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 (!isRegUsed(*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 StartMII. UseMI is set to the instruction where the search
/// stopped.
///
/// No more than InstrLimit instructions are inspected.
///
-unsigned RegScavenger::findSurvivorReg(MachineBasicBlock::iterator MI,
+unsigned RegScavenger::findSurvivorReg(MachineBasicBlock::iterator StartMI,
BitVector &Candidates,
unsigned InstrLimit,
MachineBasicBlock::iterator &UseMI) {
assert(Survivor > 0 && "No candidates for scavenging");
MachineBasicBlock::iterator ME = MBB->getFirstTerminator();
- assert(MI != ME && "MI already at terminator");
+ assert(StartMI != ME && "MI already at terminator");
+ MachineBasicBlock::iterator RestorePointMI = StartMI;
+ MachineBasicBlock::iterator MI = StartMI;
+ 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;
- Candidates.reset(MO.getReg());
- for (const unsigned *R = TRI->getAliasSet(MO.getReg()); *R; R++)
- Candidates.reset(*R);
+ if (TargetRegisterInfo::isVirtualRegister(MO.getReg())) {
+ if (MO.isDef())
+ isVirtDefInsn = true;
+ else if (MO.isKill())
+ isVirtKillInsn = true;
+ continue;
+ }
+ 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.
+ if (!inVirtLiveRange) RestorePointMI = MI;
+
+ // Update whether we're in the live range of a virtual register
+ if (isVirtKillInsn) inVirtLiveRange = false;
+ if (isVirtDefInsn) inVirtLiveRange = true;
// Was our survivor untouched by this instruction?
if (Candidates.test(Survivor))
Survivor = Candidates.find_first();
}
+ // If we ran off the end, that's where we want to restore.
+ if (MI == ME) RestorePointMI = ME;
+ assert (RestorePointMI != StartMI &&
+ "No available scavenger restore location!");
// We ran out of candidates, so stop the search.
- UseMI = MI;
+ UseMI = RestorePointMI;
return Survivor;
}
+static unsigned getFrameIndexOperandNum(MachineInstr *MI) {
+ unsigned i = 0;
+ while (!MI->getOperand(i).isFI()) {
+ ++i;
+ assert(i < MI->getNumOperands() &&
+ "Instr doesn't have FrameIndex operand!");
+ }
+ return i;
+}
+
unsigned RegScavenger::scavengeRegister(const TargetRegisterClass *RC,
MachineBasicBlock::iterator I,
int SPAdj) {
- assert(ScavengingFrameIndex >= 0 &&
- "Cannot scavenge a register without an emergency spill slot!");
-
- // 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) {
MachineOperand &MO = I->getOperand(i);
- if (MO.isReg())
+ if (MO.isReg() && MO.getReg() != 0 && !(MO.isUse() && MO.isUndef()) &&
+ !TargetRegisterInfo::isVirtualRegister(MO.getReg()))
Candidates.reset(MO.getReg());
}
+ // Try to find a register that's unused if there is one, as then we won't
+ // have to spill.
+ 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 (!isRegUsed(SReg)) {
+ DEBUG(dbgs() << "Scavenged register: " << TRI->getName(SReg) << "\n");
return SReg;
+ }
- assert(ScavengedReg == 0 &&
- "Scavenger slot is live, unable to scavenge another register!");
+ // Find an available scavenging slot.
+ unsigned SI;
+ for (SI = 0; SI < Scavenged.size(); ++SI)
+ if (Scavenged[SI].Reg == 0)
+ break;
+
+ if (SI == Scavenged.size()) {
+ // We need to scavenge a register but have no spill slot, the target
+ // must know how to do it (if not, we'll assert below).
+ Scavenged.push_back(ScavengedInfo());
+ }
// Avoid infinite regress
- ScavengedReg = SReg;
+ Scavenged[SI].Reg = SReg;
+
+ // If the target knows how to save/restore the register, let it do so;
+ // otherwise, use the emergency stack spill slot.
+ if (!TRI->saveScavengerRegister(*MBB, I, UseMI, RC, SReg)) {
+ // Spill the scavenged register before I.
+ assert(Scavenged[SI].FrameIndex >= 0 &&
+ "Cannot scavenge register without an emergency spill slot!");
+ TII->storeRegToStackSlot(*MBB, I, SReg, true, Scavenged[SI].FrameIndex,
+ RC, TRI);
+ MachineBasicBlock::iterator II = std::prev(I);
+
+ unsigned FIOperandNum = getFrameIndexOperandNum(II);
+ TRI->eliminateFrameIndex(II, SPAdj, FIOperandNum, this);
+
+ // Restore the scavenged register before its use (or first terminator).
+ TII->loadRegFromStackSlot(*MBB, UseMI, SReg, Scavenged[SI].FrameIndex,
+ RC, TRI);
+ II = std::prev(UseMI);
+
+ FIOperandNum = getFrameIndexOperandNum(II);
+ TRI->eliminateFrameIndex(II, SPAdj, FIOperandNum, this);
+ }
- // Spill the scavenged register before I.
- TII->storeRegToStackSlot(*MBB, I, SReg, true, ScavengingFrameIndex, RC);
- MachineBasicBlock::iterator II = prior(I);
- TRI->eliminateFrameIndex(II, SPAdj, this);
+ Scavenged[SI].Restore = std::prev(UseMI);
- // Restore the scavenged register before its use (or first terminator).
- TII->loadRegFromStackSlot(*MBB, UseMI, SReg, ScavengingFrameIndex, RC);
- ScavengeRestore = prior(UseMI);
// Doing this here leads to infinite regress.
- // ScavengedReg = SReg;
- ScavengedRC = RC;
+ // Scavenged[SI].Reg = SReg;
+
+ DEBUG(dbgs() << "Scavenged register (with spill): " << TRI->getName(SReg) <<
+ "\n");
return SReg;
}
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