}
virtual bool runOnMachineFunction(MachineFunction &MF);
-
+
virtual void getAnalysisUsage(AnalysisUsage &AU) const {
AU.setPreservesCFG();
MachineFunctionPass::getAnalysisUsage(AU);
virtual void releaseMemory() {
ScopeMap.clear();
Exps.clear();
+ AllocatableRegs.clear();
+ ReservedRegs.clear();
}
private:
ScopedHTType VNT;
SmallVector<MachineInstr*, 64> Exps;
unsigned CurrVN;
+ BitVector AllocatableRegs;
+ BitVector ReservedRegs;
bool PerformTrivialCoalescing(MachineInstr *MI, MachineBasicBlock *MBB);
bool isPhysDefTriviallyDead(unsigned Reg,
MachineBasicBlock::const_iterator I,
- MachineBasicBlock::const_iterator E) const ;
+ MachineBasicBlock::const_iterator E) const;
bool hasLivePhysRegDefUses(const MachineInstr *MI,
const MachineBasicBlock *MBB,
SmallSet<unsigned,8> &PhysRefs,
SmallVector<unsigned,2> &PhysDefs) const;
bool PhysRegDefsReach(MachineInstr *CSMI, MachineInstr *MI,
SmallSet<unsigned,8> &PhysRefs,
+ SmallVector<unsigned,2> &PhysDefs,
bool &NonLocal) const;
bool isCSECandidate(MachineInstr *MI);
bool isProfitableToCSE(unsigned CSReg, unsigned Reg,
void ExitScope(MachineBasicBlock *MBB);
bool ProcessBlock(MachineBasicBlock *MBB);
void ExitScopeIfDone(MachineDomTreeNode *Node,
- DenseMap<MachineDomTreeNode*, unsigned> &OpenChildren,
- DenseMap<MachineDomTreeNode*, MachineDomTreeNode*> &ParentMap);
+ DenseMap<MachineDomTreeNode*, unsigned> &OpenChildren);
bool PerformCSE(MachineDomTreeNode *Node);
};
} // end anonymous namespace
char MachineCSE::ID = 0;
+char &llvm::MachineCSEID = MachineCSE::ID;
INITIALIZE_PASS_BEGIN(MachineCSE, "machine-cse",
"Machine Common Subexpression Elimination", false, false)
INITIALIZE_PASS_DEPENDENCY(MachineDominatorTree)
INITIALIZE_PASS_END(MachineCSE, "machine-cse",
"Machine Common Subexpression Elimination", false, false)
-FunctionPass *llvm::createMachineCSEPass() { return new MachineCSE(); }
-
bool MachineCSE::PerformTrivialCoalescing(MachineInstr *MI,
MachineBasicBlock *MBB) {
bool Changed = false;
bool SeenDef = false;
for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i) {
const MachineOperand &MO = I->getOperand(i);
+ if (MO.isRegMask() && MO.clobbersPhysReg(Reg))
+ SeenDef = true;
if (!MO.isReg() || !MO.getReg())
continue;
if (!TRI->regsOverlap(MO.getReg(), Reg))
SeenDef = true;
}
if (SeenDef)
- // See a def of Reg (or an alias) before encountering any use, it's
+ // See a def of Reg (or an alias) before encountering any use, it's
// trivially dead.
return true;
if (MO.isDef() &&
(MO.isDead() || isPhysDefTriviallyDead(Reg, I, MBB->end())))
continue;
- PhysRefs.insert(Reg);
+ // Reading constant physregs is ok.
+ if (!MRI->isConstantPhysReg(Reg, *MBB->getParent()))
+ for (MCRegAliasIterator AI(Reg, TRI, true); AI.isValid(); ++AI)
+ PhysRefs.insert(*AI);
if (MO.isDef())
PhysDefs.push_back(Reg);
- for (const unsigned *Alias = TRI->getAliasSet(Reg); *Alias; ++Alias)
- PhysRefs.insert(*Alias);
}
return !PhysRefs.empty();
bool MachineCSE::PhysRegDefsReach(MachineInstr *CSMI, MachineInstr *MI,
SmallSet<unsigned,8> &PhysRefs,
+ SmallVector<unsigned,2> &PhysDefs,
bool &NonLocal) const {
// For now conservatively returns false if the common subexpression is
// not in the same basic block as the given instruction. The only exception
bool CrossMBB = false;
if (CSMBB != MBB) {
- if (MBB->pred_size() == 1 && *MBB->pred_begin() == CSMBB)
- CrossMBB = true;
- else
+ if (MBB->pred_size() != 1 || *MBB->pred_begin() != CSMBB)
return false;
+
+ for (unsigned i = 0, e = PhysDefs.size(); i != e; ++i) {
+ if (AllocatableRegs.test(PhysDefs[i]) || ReservedRegs.test(PhysDefs[i]))
+ // Avoid extending live range of physical registers if they are
+ //allocatable or reserved.
+ return false;
+ }
+ CrossMBB = true;
}
MachineBasicBlock::const_iterator I = CSMI; I = llvm::next(I);
MachineBasicBlock::const_iterator E = MI;
if (I == EE) {
assert(CrossMBB && "Reaching end-of-MBB without finding MI?");
+ (void)CrossMBB;
CrossMBB = false;
NonLocal = true;
I = MBB->begin();
for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i) {
const MachineOperand &MO = I->getOperand(i);
+ // RegMasks go on instructions like calls that clobber lots of physregs.
+ // Don't attempt to CSE across such an instruction.
+ if (MO.isRegMask())
+ return false;
if (!MO.isReg() || !MO.isDef())
continue;
unsigned MOReg = MO.getReg();
MachineInstr *CSMI, MachineInstr *MI) {
// FIXME: Heuristics that works around the lack the live range splitting.
+ // If CSReg is used at all uses of Reg, CSE should not increase register
+ // pressure of CSReg.
+ bool MayIncreasePressure = true;
+ if (TargetRegisterInfo::isVirtualRegister(CSReg) &&
+ TargetRegisterInfo::isVirtualRegister(Reg)) {
+ MayIncreasePressure = false;
+ SmallPtrSet<MachineInstr*, 8> CSUses;
+ for (MachineRegisterInfo::use_nodbg_iterator I =MRI->use_nodbg_begin(CSReg),
+ E = MRI->use_nodbg_end(); I != E; ++I) {
+ MachineInstr *Use = &*I;
+ CSUses.insert(Use);
+ }
+ for (MachineRegisterInfo::use_nodbg_iterator I = MRI->use_nodbg_begin(Reg),
+ E = MRI->use_nodbg_end(); I != E; ++I) {
+ MachineInstr *Use = &*I;
+ if (!CSUses.count(Use)) {
+ MayIncreasePressure = true;
+ break;
+ }
+ }
+ }
+ if (!MayIncreasePressure) return true;
+
// Heuristics #1: Don't CSE "cheap" computation if the def is not local or in
// an immediate predecessor. We don't want to increase register pressure and
// end up causing other computation to be spilled.
bool Changed = false;
SmallVector<std::pair<unsigned, unsigned>, 8> CSEPairs;
+ SmallVector<unsigned, 2> ImplicitDefsToUpdate;
for (MachineBasicBlock::iterator I = MBB->begin(), E = MBB->end(); I != E; ) {
MachineInstr *MI = &*I;
++I;
// used, then it's not safe to replace it with a common subexpression.
// It's also not safe if the instruction uses physical registers.
bool CrossMBBPhysDef = false;
- SmallSet<unsigned,8> PhysRefs;
+ SmallSet<unsigned, 8> PhysRefs;
SmallVector<unsigned, 2> PhysDefs;
if (FoundCSE && hasLivePhysRegDefUses(MI, MBB, PhysRefs, PhysDefs)) {
FoundCSE = false;
// in between and the physical register uses were not clobbered.
unsigned CSVN = VNT.lookup(MI);
MachineInstr *CSMI = Exps[CSVN];
- if (PhysRegDefsReach(CSMI, MI, PhysRefs, CrossMBBPhysDef))
+ if (PhysRegDefsReach(CSMI, MI, PhysRefs, PhysDefs, CrossMBBPhysDef))
FoundCSE = true;
}
// Check if it's profitable to perform this CSE.
bool DoCSE = true;
- unsigned NumDefs = MI->getDesc().getNumDefs();
+ unsigned NumDefs = MI->getDesc().getNumDefs() +
+ MI->getDesc().getNumImplicitDefs();
+
for (unsigned i = 0, e = MI->getNumOperands(); NumDefs && i != e; ++i) {
MachineOperand &MO = MI->getOperand(i);
if (!MO.isReg() || !MO.isDef())
continue;
unsigned OldReg = MO.getReg();
unsigned NewReg = CSMI->getOperand(i).getReg();
- if (OldReg == NewReg)
+
+ // Go through implicit defs of CSMI and MI, if a def is not dead at MI,
+ // we should make sure it is not dead at CSMI.
+ if (MO.isImplicit() && !MO.isDead() && CSMI->getOperand(i).isDead())
+ ImplicitDefsToUpdate.push_back(i);
+ if (OldReg == NewReg) {
+ --NumDefs;
continue;
+ }
assert(TargetRegisterInfo::isVirtualRegister(OldReg) &&
TargetRegisterInfo::isVirtualRegister(NewReg) &&
"Do not CSE physical register defs!");
if (!isProfitableToCSE(NewReg, OldReg, CSMI, MI)) {
+ DEBUG(dbgs() << "*** Not profitable, avoid CSE!\n");
DoCSE = false;
break;
}
// within the register class of the new instruction.
const TargetRegisterClass *OldRC = MRI->getRegClass(OldReg);
if (!MRI->constrainRegClass(NewReg, OldRC)) {
+ DEBUG(dbgs() << "*** Not the same register class, avoid CSE!\n");
DoCSE = false;
break;
}
MRI->clearKillFlags(CSEPairs[i].second);
}
+ // Go through implicit defs of CSMI and MI, if a def is not dead at MI,
+ // we should make sure it is not dead at CSMI.
+ for (unsigned i = 0, e = ImplicitDefsToUpdate.size(); i != e; ++i)
+ CSMI->getOperand(ImplicitDefsToUpdate[i]).setIsDead(false);
+
if (CrossMBBPhysDef) {
// Add physical register defs now coming in from a predecessor to MBB
// livein list.
++NumCommutes;
Changed = true;
} else {
- DEBUG(dbgs() << "*** Not profitable, avoid CSE!\n");
VNT.insert(MI, CurrVN++);
Exps.push_back(MI);
}
CSEPairs.clear();
+ ImplicitDefsToUpdate.clear();
}
return Changed;
/// up the dominator tree to destroy ancestors which are now done.
void
MachineCSE::ExitScopeIfDone(MachineDomTreeNode *Node,
- DenseMap<MachineDomTreeNode*, unsigned> &OpenChildren,
- DenseMap<MachineDomTreeNode*, MachineDomTreeNode*> &ParentMap) {
+ DenseMap<MachineDomTreeNode*, unsigned> &OpenChildren) {
if (OpenChildren[Node])
return;
ExitScope(Node->getBlock());
// Now traverse upwards to pop ancestors whose offsprings are all done.
- while (MachineDomTreeNode *Parent = ParentMap[Node]) {
+ while (MachineDomTreeNode *Parent = Node->getIDom()) {
unsigned Left = --OpenChildren[Parent];
if (Left != 0)
break;
bool MachineCSE::PerformCSE(MachineDomTreeNode *Node) {
SmallVector<MachineDomTreeNode*, 32> Scopes;
SmallVector<MachineDomTreeNode*, 8> WorkList;
- DenseMap<MachineDomTreeNode*, MachineDomTreeNode*> ParentMap;
DenseMap<MachineDomTreeNode*, unsigned> OpenChildren;
CurrVN = 0;
OpenChildren[Node] = NumChildren;
for (unsigned i = 0; i != NumChildren; ++i) {
MachineDomTreeNode *Child = Children[i];
- ParentMap[Child] = Node;
WorkList.push_back(Child);
}
} while (!WorkList.empty());
EnterScope(MBB);
Changed |= ProcessBlock(MBB);
// If it's a leaf node, it's done. Traverse upwards to pop ancestors.
- ExitScopeIfDone(Node, OpenChildren, ParentMap);
+ ExitScopeIfDone(Node, OpenChildren);
}
return Changed;
MRI = &MF.getRegInfo();
AA = &getAnalysis<AliasAnalysis>();
DT = &getAnalysis<MachineDominatorTree>();
+ AllocatableRegs = TRI->getAllocatableSet(MF);
+ ReservedRegs = TRI->getReservedRegs(MF);
return PerformCSE(DT->getRootNode());
}
projects / oota-llvm.git / blobdiff