static cl::opt<bool>
SplitEdges("machine-sink-split",
cl::desc("Split critical edges during machine sinking"),
- cl::init(false), cl::Hidden);
-static cl::opt<unsigned>
-SplitLimit("split-limit",
- cl::init(~0u), cl::Hidden);
+ cl::init(true), cl::Hidden);
STATISTIC(NumSunk, "Number of machine instructions sunk");
STATISTIC(NumSplit, "Number of critical edges split");
public:
static char ID; // Pass identification
- MachineSinking() : MachineFunctionPass(ID) {}
+ MachineSinking() : MachineFunctionPass(ID) {
+ initializeMachineSinkingPass(*PassRegistry::getPassRegistry());
+ }
virtual bool runOnMachineFunction(MachineFunction &MF);
MachineBasicBlock *SplitCriticalEdge(MachineInstr *MI,
MachineBasicBlock *From,
MachineBasicBlock *To,
- bool HasNonePHIUse);
+ bool BreakPHIEdge);
bool SinkInstruction(MachineInstr *MI, bool &SawStore);
bool AllUsesDominatedByBlock(unsigned Reg, MachineBasicBlock *MBB,
MachineBasicBlock *DefMBB,
- SmallPtrSet<MachineInstr*, 4> &PHIUses,
- bool &NonPHIUse, bool &LocalUse) const;
+ bool &BreakPHIEdge, bool &LocalUse) const;
bool PerformTrivialForwardCoalescing(MachineInstr *MI,
MachineBasicBlock *MBB);
};
} // end anonymous namespace
char MachineSinking::ID = 0;
-INITIALIZE_PASS(MachineSinking, "machine-sink",
- "Machine code sinking", false, false);
+INITIALIZE_PASS_BEGIN(MachineSinking, "machine-sink",
+ "Machine code sinking", false, false)
+INITIALIZE_PASS_DEPENDENCY(MachineDominatorTree)
+INITIALIZE_PASS_DEPENDENCY(MachineLoopInfo)
+INITIALIZE_AG_DEPENDENCY(AliasAnalysis)
+INITIALIZE_PASS_END(MachineSinking, "machine-sink",
+ "Machine code sinking", false, false)
FunctionPass *llvm::createMachineSinkingPass() { return new MachineSinking(); }
MachineSinking::AllUsesDominatedByBlock(unsigned Reg,
MachineBasicBlock *MBB,
MachineBasicBlock *DefMBB,
- SmallPtrSet<MachineInstr*, 4> &PHIUses,
- bool &NonPHIUse, bool &LocalUse) const {
+ bool &BreakPHIEdge,
+ bool &LocalUse) const {
assert(TargetRegisterInfo::isVirtualRegister(Reg) &&
"Only makes sense for vregs");
+
+ if (MRI->use_nodbg_empty(Reg))
+ return true;
+
// Ignoring debug uses is necessary so debug info doesn't affect the code.
// This may leave a referencing dbg_value in the original block, before
// the definition of the vreg. Dwarf generator handles this although the
// user might not get the right info at runtime.
+
+ // BreakPHIEdge is true if all the uses are in the successor MBB being sunken
+ // into and they are all PHI nodes. In this case, machine-sink must break
+ // the critical edge first. e.g.
+ //
+ // BB#1: derived from LLVM BB %bb4.preheader
+ // Predecessors according to CFG: BB#0
+ // ...
+ // %reg16385<def> = DEC64_32r %reg16437, %EFLAGS<imp-def,dead>
+ // ...
+ // JE_4 <BB#37>, %EFLAGS<imp-use>
+ // Successors according to CFG: BB#37 BB#2
+ //
+ // BB#2: derived from LLVM BB %bb.nph
+ // Predecessors according to CFG: BB#0 BB#1
+ // %reg16386<def> = PHI %reg16434, <BB#0>, %reg16385, <BB#1>
+ BreakPHIEdge = true;
for (MachineRegisterInfo::use_nodbg_iterator
I = MRI->use_nodbg_begin(Reg), E = MRI->use_nodbg_end();
I != E; ++I) {
- // Determine the block of the use.
MachineInstr *UseInst = &*I;
MachineBasicBlock *UseBlock = UseInst->getParent();
+ if (!(UseBlock == MBB && UseInst->isPHI() &&
+ UseInst->getOperand(I.getOperandNo()+1).getMBB() == DefMBB)) {
+ BreakPHIEdge = false;
+ break;
+ }
+ }
+ if (BreakPHIEdge)
+ return true;
- bool isPHI = UseInst->isPHI();
- if (isPHI)
- PHIUses.insert(UseInst);
-
- if (isPHI) {
- if (SplitEdges && UseBlock == MBB)
- // PHI is in the successor BB. e.g.
- // BB#1: derived from LLVM BB %bb4.preheader
- // Predecessors according to CFG: BB#0
- // ...
- // %reg16385<def> = DEC64_32r %reg16437, %EFLAGS<imp-def,dead>
- // ...
- // JE_4 <BB#37>, %EFLAGS<imp-use>
- // Successors according to CFG: BB#37 BB#2
- //
- // BB#2: derived from LLVM BB %bb.nph
- // Predecessors according to CFG: BB#0 BB#1
- // %reg16386<def> = PHI %reg16434, <BB#0>, %reg16385, <BB#1>
- //
- // Machine sink should break the critical edge first.
- continue;
+ for (MachineRegisterInfo::use_nodbg_iterator
+ I = MRI->use_nodbg_begin(Reg), E = MRI->use_nodbg_end();
+ I != E; ++I) {
+ // Determine the block of the use.
+ MachineInstr *UseInst = &*I;
+ MachineBasicBlock *UseBlock = UseInst->getParent();
+ if (UseInst->isPHI()) {
// PHI nodes use the operand in the predecessor block, not the block with
// the PHI.
UseBlock = UseInst->getOperand(I.getOperandNo()+1).getMBB();
if (MI->isDebugValue())
continue;
- if (PerformTrivialForwardCoalescing(MI, &MBB))
+ bool Joined = PerformTrivialForwardCoalescing(MI, &MBB);
+ if (Joined) {
+ MadeChange = true;
continue;
+ }
if (SinkInstruction(MI, SawStore))
++NumSunk, MadeChange = true;
if (!CEBCandidates.insert(std::make_pair(From, To)))
return true;
- if (!(MI->isCopyLike() || MI->getDesc().isAsCheapAsAMove()))
+ if (!MI->isCopy() && !MI->getDesc().isAsCheapAsAMove())
return true;
// MI is cheap, we probably don't want to break the critical edge for it.
MachineBasicBlock *MachineSinking::SplitCriticalEdge(MachineInstr *MI,
MachineBasicBlock *FromBB,
MachineBasicBlock *ToBB,
- bool HasNonePHIUse) {
+ bool BreakPHIEdge) {
if (!isWorthBreakingCriticalEdge(MI, FromBB, ToBB))
return 0;
// Avoid breaking back edge. From == To means backedge for single BB loop.
- if (!SplitEdges || NumSplit == SplitLimit || FromBB == ToBB)
+ if (!SplitEdges || FromBB == ToBB)
return 0;
// Check for backedges of more "complex" loops.
//
// There is no need to do this check if all the uses are PHI nodes. PHI
// sources are only defined on the specific predecessor edges.
- if (HasNonePHIUse) {
+ if (!BreakPHIEdge) {
for (MachineBasicBlock::pred_iterator PI = ToBB->pred_begin(),
E = ToBB->pred_end(); PI != E; ++PI) {
if (*PI == FromBB)
return FromBB->SplitCriticalEdge(ToBB, this);
}
+static bool AvoidsSinking(MachineInstr *MI, MachineRegisterInfo *MRI) {
+ return MI->isInsertSubreg() || MI->isSubregToReg() || MI->isRegSequence();
+}
+
+/// collectDebgValues - Scan instructions following MI and collect any
+/// matching DBG_VALUEs.
+static void collectDebugValues(MachineInstr *MI,
+ SmallVector<MachineInstr *, 2> & DbgValues) {
+ DbgValues.clear();
+ if (!MI->getOperand(0).isReg())
+ return;
+
+ MachineBasicBlock::iterator DI = MI; ++DI;
+ for (MachineBasicBlock::iterator DE = MI->getParent()->end();
+ DI != DE; ++DI) {
+ if (!DI->isDebugValue())
+ return;
+ if (DI->getOperand(0).isReg() &&
+ DI->getOperand(0).getReg() == MI->getOperand(0).getReg())
+ DbgValues.push_back(DI);
+ }
+}
+
/// SinkInstruction - Determine whether it is safe to sink the specified machine
/// instruction out of its current block into a successor.
bool MachineSinking::SinkInstruction(MachineInstr *MI, bool &SawStore) {
+ // Don't sink insert_subreg, subreg_to_reg, reg_sequence. These are meant to
+ // be close to the source to make it easier to coalesce.
+ if (AvoidsSinking(MI, MRI))
+ return false;
+
// Check if it's safe to move the instruction.
if (!MI->isSafeToMove(TII, AA, SawStore))
return false;
// decide.
MachineBasicBlock *SuccToSinkTo = 0;
- SmallSet<unsigned, 4> Defs;
- SmallPtrSet<MachineInstr*, 4> PHIUses;
- bool HasNonPHIUse = false;
+ bool BreakPHIEdge = false;
for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
const MachineOperand &MO = MI->getOperand(i);
if (!MO.isReg()) continue; // Ignore non-register operands.
} else {
// Virtual register uses are always safe to sink.
if (MO.isUse()) continue;
- Defs.insert(Reg);
// If it's not safe to move defs of the register class, then abort.
if (!TII->isSafeToMoveRegClassDefs(MRI->getRegClass(Reg)))
// If a previous operand picked a block to sink to, then this operand
// must be sinkable to the same block.
bool LocalUse = false;
- if (!AllUsesDominatedByBlock(Reg, SuccToSinkTo, ParentBlock, PHIUses,
- HasNonPHIUse, LocalUse))
+ if (!AllUsesDominatedByBlock(Reg, SuccToSinkTo, ParentBlock,
+ BreakPHIEdge, LocalUse))
return false;
continue;
for (MachineBasicBlock::succ_iterator SI = ParentBlock->succ_begin(),
E = ParentBlock->succ_end(); SI != E; ++SI) {
bool LocalUse = false;
- if (AllUsesDominatedByBlock(Reg, *SI, ParentBlock, PHIUses,
- HasNonPHIUse, LocalUse)) {
+ if (AllUsesDominatedByBlock(Reg, *SI, ParentBlock,
+ BreakPHIEdge, LocalUse)) {
SuccToSinkTo = *SI;
break;
}
DEBUG(dbgs() << "Sinking along critical edge.\n");
else {
MachineBasicBlock *NewSucc =
- SplitCriticalEdge(MI, ParentBlock, SuccToSinkTo, HasNonPHIUse);
+ SplitCriticalEdge(MI, ParentBlock, SuccToSinkTo, BreakPHIEdge);
if (!NewSucc) {
DEBUG(dbgs() << " *** PUNTING: Not legal or profitable to "
"break critical edge\n");
<< " -- BB#" << SuccToSinkTo->getNumber() << '\n');
SuccToSinkTo = NewSucc;
++NumSplit;
+ BreakPHIEdge = false;
}
}
}
+ if (BreakPHIEdge) {
+ // BreakPHIEdge is true if all the uses are in the successor MBB being
+ // sunken into and they are all PHI nodes. In this case, machine-sink must
+ // break the critical edge first.
+ MachineBasicBlock *NewSucc = SplitCriticalEdge(MI, ParentBlock,
+ SuccToSinkTo, BreakPHIEdge);
+ if (!NewSucc) {
+ DEBUG(dbgs() << " *** PUNTING: Not legal or profitable to "
+ "break critical edge\n");
+ return false;
+ }
+
+ DEBUG(dbgs() << " *** Splitting critical edge:"
+ " BB#" << ParentBlock->getNumber()
+ << " -- BB#" << NewSucc->getNumber()
+ << " -- BB#" << SuccToSinkTo->getNumber() << '\n');
+ SuccToSinkTo = NewSucc;
+ ++NumSplit;
+ }
+
// Determine where to insert into. Skip phi nodes.
MachineBasicBlock::iterator InsertPos = SuccToSinkTo->begin();
- while (InsertPos != SuccToSinkTo->end() && InsertPos->isPHI()) {
- MachineInstr *PHI = &*InsertPos;
+ while (InsertPos != SuccToSinkTo->end() && InsertPos->isPHI())
++InsertPos;
- if (SplitEdges && PHIUses.count(PHI)) {
- if (NumSplit == SplitLimit)
- return false;
-
- // A PHI use is in the destination successor so we can't sink the
- // instruction here. Break the critical edge first!
- for (unsigned i = 1, e = PHI->getNumOperands(); i != e; i += 2) {
- unsigned SrcReg = PHI->getOperand(i).getReg();
- if (Defs.count(SrcReg)) {
- MachineBasicBlock *SrcMBB = PHI->getOperand(i+1).getMBB();
- MachineBasicBlock *NewSucc =
- SplitCriticalEdge(MI, SrcMBB, SuccToSinkTo, HasNonPHIUse);
- if (!NewSucc) {
- DEBUG(dbgs() << " *** PUNTING: Not legal or profitable to "
- "break critical edge\n");
- return false;
- }
-
- DEBUG(dbgs() << " *** Splitting critical edge:"
- " BB#" << SrcMBB->getNumber()
- << " -- BB#" << NewSucc->getNumber()
- << " -- BB#" << SuccToSinkTo->getNumber() << '\n');
- SuccToSinkTo = NewSucc;
- InsertPos = NewSucc->begin();
- ++NumSplit;
- break;
- }
- }
- }
- }
+ // collect matching debug values.
+ SmallVector<MachineInstr *, 2> DbgValuesToSink;
+ collectDebugValues(MI, DbgValuesToSink);
// Move the instruction.
SuccToSinkTo->splice(InsertPos, ParentBlock, MI,
++MachineBasicBlock::iterator(MI));
+ // Move debug values.
+ for (SmallVector<MachineInstr *, 2>::iterator DBI = DbgValuesToSink.begin(),
+ DBE = DbgValuesToSink.end(); DBI != DBE; ++DBI) {
+ MachineInstr *DbgMI = *DBI;
+ SuccToSinkTo->splice(InsertPos, ParentBlock, DbgMI,
+ ++MachineBasicBlock::iterator(DbgMI));
+ }
+
// Conservatively, clear any kill flags, since it's possible that they are no
// longer correct.
MI->clearKillInfo();
projects / oota-llvm.git / blobdiff