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-rw-r--r--lib/CodeGen/VirtRegRewriter.cpp234
1 files changed, 128 insertions, 106 deletions
diff --git a/lib/CodeGen/VirtRegRewriter.cpp b/lib/CodeGen/VirtRegRewriter.cpp
index 14ee69d..ec149dd 100644
--- a/lib/CodeGen/VirtRegRewriter.cpp
+++ b/lib/CodeGen/VirtRegRewriter.cpp
@@ -216,7 +216,8 @@ public:
<< SlotOrReMat-VirtRegMap::MAX_STACK_SLOT-1);
else
DEBUG(dbgs() << "Remembering SS#" << SlotOrReMat);
- DEBUG(dbgs() << " in physreg " << TRI->getName(Reg) << "\n");
+ DEBUG(dbgs() << " in physreg " << TRI->getName(Reg)
+ << (CanClobber ? " canclobber" : "") << "\n");
}
/// canClobberPhysRegForSS - Return true if the spiller is allowed to change
@@ -462,25 +463,72 @@ static void findSinglePredSuccessor(MachineBasicBlock *MBB,
}
}
-/// InvalidateKill - Invalidate register kill information for a specific
-/// register. This also unsets the kills marker on the last kill operand.
-static void InvalidateKill(unsigned Reg,
- const TargetRegisterInfo* TRI,
- BitVector &RegKills,
- std::vector<MachineOperand*> &KillOps) {
- if (RegKills[Reg]) {
- KillOps[Reg]->setIsKill(false);
- // KillOps[Reg] might be a def of a super-register.
- unsigned KReg = KillOps[Reg]->getReg();
- KillOps[KReg] = NULL;
- RegKills.reset(KReg);
- for (const unsigned *SR = TRI->getSubRegisters(KReg); *SR; ++SR) {
- if (RegKills[*SR]) {
- KillOps[*SR]->setIsKill(false);
- KillOps[*SR] = NULL;
- RegKills.reset(*SR);
- }
- }
+/// ResurrectConfirmedKill - Helper for ResurrectKill. This register is killed
+/// but not re-defined and it's being reused. Remove the kill flag for the
+/// register and unset the kill's marker and last kill operand.
+static void ResurrectConfirmedKill(unsigned Reg, const TargetRegisterInfo* TRI,
+ BitVector &RegKills,
+ std::vector<MachineOperand*> &KillOps) {
+ DEBUG(dbgs() << "Resurrect " << TRI->getName(Reg) << "\n");
+
+ MachineOperand *KillOp = KillOps[Reg];
+ KillOp->setIsKill(false);
+ // KillOps[Reg] might be a def of a super-register.
+ unsigned KReg = KillOp->getReg();
+ if (!RegKills[KReg])
+ return;
+
+ assert(KillOps[KReg]->getParent() == KillOp->getParent() &&
+ "invalid superreg kill flags");
+ KillOps[KReg] = NULL;
+ RegKills.reset(KReg);
+
+ // If it's a def of a super-register. Its other sub-regsters are no
+ // longer killed as well.
+ for (const unsigned *SR = TRI->getSubRegisters(KReg); *SR; ++SR) {
+ DEBUG(dbgs() << " Resurrect subreg " << TRI->getName(*SR) << "\n");
+
+ assert(KillOps[*SR]->getParent() == KillOp->getParent() &&
+ "invalid subreg kill flags");
+ KillOps[*SR] = NULL;
+ RegKills.reset(*SR);
+ }
+}
+
+/// ResurrectKill - Invalidate kill info associated with a previous MI. An
+/// optimization may have decided that it's safe to reuse a previously killed
+/// register. If we fail to erase the invalid kill flags, then the register
+/// scavenger may later clobber the register used by this MI. Note that this
+/// must be done even if this MI is being deleted! Consider:
+///
+/// USE $r1 (vreg1) <kill>
+/// ...
+/// $r1(vreg3) = COPY $r1 (vreg2)
+///
+/// RegAlloc has smartly assigned all three vregs to the same physreg. Initially
+/// vreg1's only use is a kill. The rewriter doesn't know it should be live
+/// until it rewrites vreg2. At that points it sees that the copy is dead and
+/// deletes it. However, deleting the copy implicitly forwards liveness of $r1
+/// (it's copy coalescing). We must resurrect $r1 by removing the kill flag at
+/// vreg1 before deleting the copy.
+static void ResurrectKill(MachineInstr &MI, unsigned Reg,
+ const TargetRegisterInfo* TRI, BitVector &RegKills,
+ std::vector<MachineOperand*> &KillOps) {
+ if (RegKills[Reg] && KillOps[Reg]->getParent() != &MI) {
+ ResurrectConfirmedKill(Reg, TRI, RegKills, KillOps);
+ return;
+ }
+ // No previous kill for this reg. Check for subreg kills as well.
+ // d4 =
+ // store d4, fi#0
+ // ...
+ // = s8<kill>
+ // ...
+ // = d4 <avoiding reload>
+ for (const unsigned *SR = TRI->getSubRegisters(Reg); *SR; ++SR) {
+ unsigned SReg = *SR;
+ if (RegKills[SReg] && KillOps[SReg]->getParent() != &MI)
+ ResurrectConfirmedKill(SReg, TRI, RegKills, KillOps);
}
}
@@ -502,15 +550,22 @@ static void InvalidateKills(MachineInstr &MI,
KillRegs->push_back(Reg);
assert(Reg < KillOps.size());
if (KillOps[Reg] == &MO) {
+ // This operand was the kill, now no longer.
KillOps[Reg] = NULL;
RegKills.reset(Reg);
for (const unsigned *SR = TRI->getSubRegisters(Reg); *SR; ++SR) {
if (RegKills[*SR]) {
+ assert(KillOps[*SR] == &MO && "bad subreg kill flags");
KillOps[*SR] = NULL;
RegKills.reset(*SR);
}
}
}
+ else {
+ // This operand may have reused a previously killed reg. Keep it live in
+ // case it continues to be used after erasing this instruction.
+ ResurrectKill(MI, Reg, TRI, RegKills, KillOps);
+ }
}
}
@@ -578,44 +633,8 @@ static void UpdateKills(MachineInstr &MI, const TargetRegisterInfo* TRI,
if (Reg == 0)
continue;
- if (RegKills[Reg] && KillOps[Reg]->getParent() != &MI) {
- // That can't be right. Register is killed but not re-defined and it's
- // being reused. Let's fix that.
- KillOps[Reg]->setIsKill(false);
- // KillOps[Reg] might be a def of a super-register.
- unsigned KReg = KillOps[Reg]->getReg();
- KillOps[KReg] = NULL;
- RegKills.reset(KReg);
-
- // Must be a def of a super-register. Its other sub-regsters are no
- // longer killed as well.
- for (const unsigned *SR = TRI->getSubRegisters(KReg); *SR; ++SR) {
- KillOps[*SR] = NULL;
- RegKills.reset(*SR);
- }
- } else {
- // Check for subreg kills as well.
- // d4 =
- // store d4, fi#0
- // ...
- // = s8<kill>
- // ...
- // = d4 <avoiding reload>
- for (const unsigned *SR = TRI->getSubRegisters(Reg); *SR; ++SR) {
- unsigned SReg = *SR;
- if (RegKills[SReg] && KillOps[SReg]->getParent() != &MI) {
- KillOps[SReg]->setIsKill(false);
- unsigned KReg = KillOps[SReg]->getReg();
- KillOps[KReg] = NULL;
- RegKills.reset(KReg);
-
- for (const unsigned *SSR = TRI->getSubRegisters(KReg); *SSR; ++SSR) {
- KillOps[*SSR] = NULL;
- RegKills.reset(*SSR);
- }
- }
- }
- }
+ // This operand may have reused a previously killed reg. Keep it live.
+ ResurrectKill(MI, Reg, TRI, RegKills, KillOps);
if (MO.isKill()) {
RegKills.set(Reg);
@@ -770,7 +789,8 @@ void AvailableSpills::AddAvailableRegsToLiveIn(MachineBasicBlock &MBB,
NotAvailable.insert(Reg);
else {
MBB.addLiveIn(Reg);
- InvalidateKill(Reg, TRI, RegKills, KillOps);
+ if (RegKills[Reg])
+ ResurrectConfirmedKill(Reg, TRI, RegKills, KillOps);
}
// Skip over the same register.
@@ -1056,6 +1076,7 @@ class LocalRewriter : public VirtRegRewriter {
const TargetRegisterInfo *TRI;
const TargetInstrInfo *TII;
VirtRegMap *VRM;
+ LiveIntervals *LIs;
BitVector AllocatableRegs;
DenseMap<MachineInstr*, unsigned> DistanceMap;
DenseMap<int, SmallVector<MachineInstr*,4> > Slot2DbgValues;
@@ -1068,6 +1089,11 @@ public:
LiveIntervals* LIs);
private:
+ void EraseInstr(MachineInstr *MI) {
+ VRM->RemoveMachineInstrFromMaps(MI);
+ LIs->RemoveMachineInstrFromMaps(MI);
+ MI->eraseFromParent();
+ }
bool OptimizeByUnfold2(unsigned VirtReg, int SS,
MachineBasicBlock::iterator &MII,
@@ -1123,17 +1149,18 @@ private:
}
bool LocalRewriter::runOnMachineFunction(MachineFunction &MF, VirtRegMap &vrm,
- LiveIntervals* LIs) {
+ LiveIntervals* lis) {
MRI = &MF.getRegInfo();
TRI = MF.getTarget().getRegisterInfo();
TII = MF.getTarget().getInstrInfo();
VRM = &vrm;
+ LIs = lis;
AllocatableRegs = TRI->getAllocatableSet(MF);
DEBUG(dbgs() << "\n**** Local spiller rewriting function '"
<< MF.getFunction()->getName() << "':\n");
DEBUG(dbgs() << "**** Machine Instrs (NOTE! Does not include spills and"
" reloads!) ****\n");
- DEBUG(MF.dump());
+ DEBUG(MF.print(dbgs(), LIs->getSlotIndexes()));
// Spills - Keep track of which spilled values are available in physregs
// so that we can choose to reuse the physregs instead of emitting
@@ -1184,7 +1211,7 @@ bool LocalRewriter::runOnMachineFunction(MachineFunction &MF, VirtRegMap &vrm,
}
DEBUG(dbgs() << "**** Post Machine Instrs ****\n");
- DEBUG(MF.dump());
+ DEBUG(MF.print(dbgs(), LIs->getSlotIndexes()));
// Mark unused spill slots.
MachineFrameInfo *MFI = MF.getFrameInfo();
@@ -1196,10 +1223,8 @@ bool LocalRewriter::runOnMachineFunction(MachineFunction &MF, VirtRegMap &vrm,
MFI->RemoveStackObject(SS);
for (unsigned j = 0, ee = DbgValues.size(); j != ee; ++j) {
MachineInstr *DVMI = DbgValues[j];
- MachineBasicBlock *DVMBB = DVMI->getParent();
DEBUG(dbgs() << "Removing debug info referencing FI#" << SS << '\n');
- VRM->RemoveMachineInstrFromMaps(DVMI);
- DVMBB->erase(DVMI);
+ EraseInstr(DVMI);
}
++NumDSS;
}
@@ -1279,8 +1304,7 @@ OptimizeByUnfold2(unsigned VirtReg, int SS,
VRM->transferRestorePts(&MI, NewMIs[0]);
MII = MBB->insert(MII, NewMIs[0]);
InvalidateKills(MI, TRI, RegKills, KillOps);
- VRM->RemoveMachineInstrFromMaps(&MI);
- MBB->erase(&MI);
+ EraseInstr(&MI);
++NumModRefUnfold;
// Unfold next instructions that fold the same SS.
@@ -1295,8 +1319,7 @@ OptimizeByUnfold2(unsigned VirtReg, int SS,
VRM->transferRestorePts(&NextMI, NewMIs[0]);
MBB->insert(NextMII, NewMIs[0]);
InvalidateKills(NextMI, TRI, RegKills, KillOps);
- VRM->RemoveMachineInstrFromMaps(&NextMI);
- MBB->erase(&NextMI);
+ EraseInstr(&NextMI);
++NumModRefUnfold;
// Skip over dbg_value instructions.
while (NextMII != MBB->end() && NextMII->isDebugValue())
@@ -1423,8 +1446,7 @@ OptimizeByUnfold(MachineBasicBlock::iterator &MII,
VRM->virtFolded(VirtReg, FoldedMI, VirtRegMap::isRef);
MII = FoldedMI;
InvalidateKills(MI, TRI, RegKills, KillOps);
- VRM->RemoveMachineInstrFromMaps(&MI);
- MBB->erase(&MI);
+ EraseInstr(&MI);
return true;
}
}
@@ -1530,14 +1552,11 @@ CommuteToFoldReload(MachineBasicBlock::iterator &MII,
// Delete all 3 old instructions.
InvalidateKills(*ReloadMI, TRI, RegKills, KillOps);
- VRM->RemoveMachineInstrFromMaps(ReloadMI);
- MBB->erase(ReloadMI);
+ EraseInstr(ReloadMI);
InvalidateKills(*DefMI, TRI, RegKills, KillOps);
- VRM->RemoveMachineInstrFromMaps(DefMI);
- MBB->erase(DefMI);
+ EraseInstr(DefMI);
InvalidateKills(MI, TRI, RegKills, KillOps);
- VRM->RemoveMachineInstrFromMaps(&MI);
- MBB->erase(&MI);
+ EraseInstr(&MI);
// If NewReg was previously holding value of some SS, it's now clobbered.
// This has to be done now because it's a physical register. When this
@@ -1580,8 +1599,7 @@ SpillRegToStackSlot(MachineBasicBlock::iterator &MII,
bool CheckDef = PrevMII != MBB->begin();
if (CheckDef)
--PrevMII;
- VRM->RemoveMachineInstrFromMaps(LastStore);
- MBB->erase(LastStore);
+ EraseInstr(LastStore);
if (CheckDef) {
// Look at defs of killed registers on the store. Mark the defs
// as dead since the store has been deleted and they aren't
@@ -1592,8 +1610,7 @@ SpillRegToStackSlot(MachineBasicBlock::iterator &MII,
MachineInstr *DeadDef = PrevMII;
if (ReMatDefs.count(DeadDef) && !HasOtherDef) {
// FIXME: This assumes a remat def does not have side effects.
- VRM->RemoveMachineInstrFromMaps(DeadDef);
- MBB->erase(DeadDef);
+ EraseInstr(DeadDef);
++NumDRM;
}
}
@@ -1618,10 +1635,18 @@ SpillRegToStackSlot(MachineBasicBlock::iterator &MII,
/// effect and all of its defs are dead.
static bool isSafeToDelete(MachineInstr &MI) {
const TargetInstrDesc &TID = MI.getDesc();
- if (TID.mayLoad() || TID.mayStore() || TID.isCall() || TID.isTerminator() ||
+ if (TID.mayLoad() || TID.mayStore() || TID.isTerminator() ||
TID.isCall() || TID.isBarrier() || TID.isReturn() ||
- TID.hasUnmodeledSideEffects())
+ MI.isLabel() || MI.isDebugValue() ||
+ MI.hasUnmodeledSideEffects())
return false;
+
+ // Technically speaking inline asm without side effects and no defs can still
+ // be deleted. But there is so much bad inline asm code out there, we should
+ // let them be.
+ if (MI.isInlineAsm())
+ return false;
+
for (unsigned i = 0, e = MI.getNumOperands(); i != e; ++i) {
MachineOperand &MO = MI.getOperand(i);
if (!MO.isReg() || !MO.getReg())
@@ -1681,8 +1706,7 @@ TransferDeadness(unsigned Reg, BitVector &RegKills,
LastUD->setIsDead();
break;
}
- VRM->RemoveMachineInstrFromMaps(LastUDMI);
- MBB->erase(LastUDMI);
+ EraseInstr(LastUDMI);
} else {
LastUD->setIsKill();
RegKills.set(Reg);
@@ -1770,6 +1794,10 @@ bool LocalRewriter::InsertRestores(MachineInstr *MI,
<< TRI->getName(InReg) << " for vreg"
<< VirtReg <<" instead of reloading into physreg "
<< TRI->getName(Phys) << '\n');
+
+ // Reusing a physreg may resurrect it. But we expect ProcessUses to update
+ // the kill flags for the current instruction after processing it.
+
++NumOmitted;
continue;
} else if (InReg && InReg != Phys) {
@@ -1878,6 +1906,7 @@ void LocalRewriter::ProcessUses(MachineInstr &MI, AvailableSpills &Spills,
continue; // Ignore non-register operands.
unsigned VirtReg = MO.getReg();
+
if (TargetRegisterInfo::isPhysicalRegister(VirtReg)) {
// Ignore physregs for spilling, but remember that it is used by this
// function.
@@ -2017,6 +2046,9 @@ void LocalRewriter::ProcessUses(MachineInstr &MI, AvailableSpills &Spills,
MI.getOperand(i).setReg(RReg);
MI.getOperand(i).setSubReg(0);
+ // Reusing a physreg may resurrect it. But we expect ProcessUses to
+ // update the kill flags for the current instr after processing it.
+
// 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'.
@@ -2057,7 +2089,6 @@ void LocalRewriter::ProcessUses(MachineInstr &MI, AvailableSpills &Spills,
MI.getOperand(i).setIsKill();
KilledMIRegs.insert(VirtReg);
}
-
continue;
} // CanReuse
@@ -2131,7 +2162,7 @@ void LocalRewriter::ProcessUses(MachineInstr &MI, AvailableSpills &Spills,
continue;
} // if (PhysReg)
- // Otherwise, reload it and remember that we have it.
+ // Otherwise, reload it and remember that we have it.
PhysReg = VRM->getPhys(VirtReg);
assert(PhysReg && "Must map virtreg to physreg!");
@@ -2195,13 +2226,11 @@ void LocalRewriter::ProcessUses(MachineInstr &MI, AvailableSpills &Spills,
if (DeadStore) {
DEBUG(dbgs() << "Removed dead store:\t" << *DeadStore);
InvalidateKills(*DeadStore, TRI, RegKills, KillOps);
- VRM->RemoveMachineInstrFromMaps(DeadStore);
- MBB->erase(DeadStore);
+ EraseInstr(DeadStore);
MaybeDeadStores[PDSSlot] = NULL;
++NumDSE;
}
}
-
}
/// rewriteMBB - Keep track of which spills are available even after the
@@ -2318,14 +2347,13 @@ LocalRewriter::RewriteMBB(LiveIntervals *LIs,
BackTracked = true;
} else {
DEBUG(dbgs() << "Removing now-noop copy: " << MI);
- // Unset last kill since it's being reused.
- InvalidateKill(InReg, TRI, RegKills, KillOps);
+ // InvalidateKills resurrects any prior kill of the copy's source
+ // allowing the source reg to be reused in place of the copy.
Spills.disallowClobberPhysReg(InReg);
}
InvalidateKills(MI, TRI, RegKills, KillOps);
- VRM->RemoveMachineInstrFromMaps(&MI);
- MBB->erase(&MI);
+ EraseInstr(&MI);
Erased = true;
goto ProcessNextInst;
}
@@ -2336,8 +2364,7 @@ LocalRewriter::RewriteMBB(LiveIntervals *LIs,
TII->unfoldMemoryOperand(MF, &MI, PhysReg, false, false, NewMIs)){
MBB->insert(MII, NewMIs[0]);
InvalidateKills(MI, TRI, RegKills, KillOps);
- VRM->RemoveMachineInstrFromMaps(&MI);
- MBB->erase(&MI);
+ EraseInstr(&MI);
Erased = true;
--NextMII; // backtrack to the unfolded instruction.
BackTracked = true;
@@ -2373,8 +2400,7 @@ LocalRewriter::RewriteMBB(LiveIntervals *LIs,
MBB->insert(MII, NewStore);
VRM->addSpillSlotUse(SS, NewStore);
InvalidateKills(MI, TRI, RegKills, KillOps);
- VRM->RemoveMachineInstrFromMaps(&MI);
- MBB->erase(&MI);
+ EraseInstr(&MI);
Erased = true;
--NextMII;
--NextMII; // backtrack to the unfolded instruction.
@@ -2389,8 +2415,7 @@ LocalRewriter::RewriteMBB(LiveIntervals *LIs,
// If we get here, the store is dead, nuke it now.
DEBUG(dbgs() << "Removed dead store:\t" << *DeadStore);
InvalidateKills(*DeadStore, TRI, RegKills, KillOps);
- VRM->RemoveMachineInstrFromMaps(DeadStore);
- MBB->erase(DeadStore);
+ EraseInstr(DeadStore);
if (!NewStore)
++NumDSE;
}
@@ -2467,8 +2492,7 @@ LocalRewriter::RewriteMBB(LiveIntervals *LIs,
// Last def is now dead.
TransferDeadness(MI.getOperand(1).getReg(), RegKills, KillOps);
}
- VRM->RemoveMachineInstrFromMaps(&MI);
- MBB->erase(&MI);
+ EraseInstr(&MI);
Erased = true;
Spills.disallowClobberPhysReg(VirtReg);
goto ProcessNextInst;
@@ -2544,8 +2568,7 @@ LocalRewriter::RewriteMBB(LiveIntervals *LIs,
++NumDCE;
DEBUG(dbgs() << "Removing now-noop copy: " << MI);
InvalidateKills(MI, TRI, RegKills, KillOps);
- VRM->RemoveMachineInstrFromMaps(&MI);
- MBB->erase(&MI);
+ EraseInstr(&MI);
Erased = true;
UpdateKills(*LastStore, TRI, RegKills, KillOps);
goto ProcessNextInst;
@@ -2556,8 +2579,7 @@ LocalRewriter::RewriteMBB(LiveIntervals *LIs,
// Delete dead instructions without side effects.
if (!Erased && !BackTracked && isSafeToDelete(MI)) {
InvalidateKills(MI, TRI, RegKills, KillOps);
- VRM->RemoveMachineInstrFromMaps(&MI);
- MBB->erase(&MI);
+ EraseInstr(&MI);
Erased = true;
}
if (!Erased)
generated by cgit v1.1 at 2025-07-03 18:54:15 +0000