#define DEBUG_TYPE "simplifycfg"
#include "llvm/Transforms/Utils/Local.h"
#include "llvm/Constants.h"
#include "llvm/Instructions.h"
#include "llvm/IntrinsicInst.h"
#include "llvm/Type.h"
#include "llvm/DerivedTypes.h"
#include "llvm/GlobalVariable.h"
#include "llvm/Support/CFG.h"
#include "llvm/Support/Debug.h"
#include "llvm/Analysis/ConstantFolding.h"
#include "llvm/Transforms/Utils/BasicBlockUtils.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/Statistic.h"
#include <algorithm>
#include <functional>
#include <set>
#include <map>
using namespace llvm;
STATISTIC(NumSpeculations, "Number of speculative executed instructions");
static bool SafeToMergeTerminators(TerminatorInst *SI1, TerminatorInst *SI2) {
if (SI1 == SI2) return false;
BasicBlock *SI1BB = SI1->getParent();
BasicBlock *SI2BB = SI2->getParent();
SmallPtrSet<BasicBlock*, 16> SI1Succs(succ_begin(SI1BB), succ_end(SI1BB));
for (succ_iterator I = succ_begin(SI2BB), E = succ_end(SI2BB); I != E; ++I)
if (SI1Succs.count(*I))
for (BasicBlock::iterator BBI = (*I)->begin();
isa<PHINode>(BBI); ++BBI) {
PHINode *PN = cast<PHINode>(BBI);
if (PN->getIncomingValueForBlock(SI1BB) !=
PN->getIncomingValueForBlock(SI2BB))
return false;
}
return true;
}
static void AddPredecessorToBlock(BasicBlock *Succ, BasicBlock *NewPred,
BasicBlock *ExistPred) {
assert(std::find(succ_begin(ExistPred), succ_end(ExistPred), Succ) !=
succ_end(ExistPred) && "ExistPred is not a predecessor of Succ!");
if (!isa<PHINode>(Succ->begin())) return;
PHINode *PN;
for (BasicBlock::iterator I = Succ->begin();
(PN = dyn_cast<PHINode>(I)); ++I)
PN->addIncoming(PN->getIncomingValueForBlock(ExistPred), NewPred);
}
static bool CanPropagatePredecessorsForPHIs(BasicBlock *BB, BasicBlock *Succ) {
assert(*succ_begin(BB) == Succ && "Succ is not successor of BB!");
DOUT << "Looking to fold " << BB->getNameStart() << " into "
<< Succ->getNameStart() << "\n";
if (Succ->getSinglePredecessor()) return true;
typedef SmallPtrSet<Instruction*, 16> InstrSet;
InstrSet BBPHIs;
BasicBlock::iterator BBI = BB->begin();
while (isa<PHINode>(*BBI)) BBPHIs.insert(BBI++);
typedef SmallPtrSet<BasicBlock*, 16> BlockSet;
BlockSet BBPreds(pred_begin(BB), pred_end(BB));
BlockSet CommonPreds;
for (pred_iterator PI = pred_begin(Succ), PE = pred_end(Succ);
PI != PE; ++PI)
if (BBPreds.count(*PI))
CommonPreds.insert(*PI);
if (CommonPreds.empty())
return true;
for (BasicBlock::iterator I = Succ->begin(); isa<PHINode>(I); ++I) {
PHINode *PN = cast<PHINode>(I);
PHINode *BBPN = dyn_cast<PHINode>(PN->getIncomingValueForBlock(BB));
if (BBPN && BBPN->getParent() == BB) {
for (BlockSet::iterator PI = CommonPreds.begin(), PE = CommonPreds.end();
PI != PE; PI++) {
if (BBPN->getIncomingValueForBlock(*PI)
!= PN->getIncomingValueForBlock(*PI)) {
DOUT << "Can't fold, phi node " << *PN->getNameStart() << " in "
<< Succ->getNameStart() << " is conflicting with "
<< BBPN->getNameStart() << " with regard to common predecessor "
<< (*PI)->getNameStart() << "\n";
return false;
}
}
BBPHIs.erase(BBPN);
} else {
Value* Val = PN->getIncomingValueForBlock(BB);
for (BlockSet::iterator PI = CommonPreds.begin(), PE = CommonPreds.end();
PI != PE; PI++) {
if (Val != PN->getIncomingValueForBlock(*PI)) {
DOUT << "Can't fold, phi node " << *PN->getNameStart() << " in "
<< Succ->getNameStart() << " is conflicting with regard to common "
<< "predecessor " << (*PI)->getNameStart() << "\n";
return false;
}
}
}
}
for (InstrSet::iterator I = BBPHIs.begin(), E = BBPHIs.end();
I != E; I++) {
PHINode *PN = cast<PHINode>(*I);
for (BlockSet::iterator PI = CommonPreds.begin(), PE = CommonPreds.end();
PI != PE; PI++)
if (PN->getIncomingValueForBlock(*PI) != PN) {
DOUT << "Can't fold, phi node " << *PN->getNameStart() << " in "
<< BB->getNameStart() << " is conflicting with regard to common "
<< "predecessor " << (*PI)->getNameStart() << "\n";
return false;
}
}
return true;
}
static bool TryToSimplifyUncondBranchFromEmptyBlock(BasicBlock *BB,
BasicBlock *Succ) {
if (!CanPropagatePredecessorsForPHIs(BB, Succ)) return false;
DOUT << "Killing Trivial BB: \n" << *BB;
if (isa<PHINode>(Succ->begin())) {
const SmallVector<BasicBlock*, 16> BBPreds(pred_begin(BB), pred_end(BB));
for (BasicBlock::iterator I = Succ->begin(); isa<PHINode>(I); ++I) {
PHINode *PN = cast<PHINode>(I);
Value *OldVal = PN->removeIncomingValue(BB, false);
assert(OldVal && "No entry in PHI for Pred BB!");
if (isa<PHINode>(OldVal) && cast<PHINode>(OldVal)->getParent() == BB) {
PHINode *OldValPN = cast<PHINode>(OldVal);
for (unsigned i = 0, e = OldValPN->getNumIncomingValues(); i != e; ++i)
PN->addIncoming(OldValPN->getIncomingValue(i),
OldValPN->getIncomingBlock(i));
} else {
for (unsigned i = 0, e = BBPreds.size(); i != e; ++i)
PN->addIncoming(OldVal, BBPreds[i]);
}
}
}
if (isa<PHINode>(&BB->front())) {
SmallVector<BasicBlock*, 16>
OldSuccPreds(pred_begin(Succ), pred_end(Succ));
while (PHINode *PN = dyn_cast<PHINode>(&BB->front())) {
if (PN->use_empty()) {
PN->eraseFromParent();
continue;
}
Succ->getInstList().splice(Succ->begin(),
BB->getInstList(), BB->begin());
for (unsigned i = 0, e = OldSuccPreds.size(); i != e; ++i)
if (OldSuccPreds[i] != BB)
PN->addIncoming(PN, OldSuccPreds[i]);
}
}
BB->replaceAllUsesWith(Succ);
if (!Succ->hasName()) Succ->takeName(BB);
BB->eraseFromParent(); return true;
}
static Value *GetIfCondition(BasicBlock *BB,
BasicBlock *&IfTrue, BasicBlock *&IfFalse) {
assert(std::distance(pred_begin(BB), pred_end(BB)) == 2 &&
"Function can only handle blocks with 2 predecessors!");
BasicBlock *Pred1 = *pred_begin(BB);
BasicBlock *Pred2 = *++pred_begin(BB);
if (!isa<BranchInst>(Pred1->getTerminator()) ||
!isa<BranchInst>(Pred2->getTerminator()))
return 0;
BranchInst *Pred1Br = cast<BranchInst>(Pred1->getTerminator());
BranchInst *Pred2Br = cast<BranchInst>(Pred2->getTerminator());
if (Pred2Br->isConditional()) {
if (Pred1Br->isConditional())
return 0;
std::swap(Pred1, Pred2);
std::swap(Pred1Br, Pred2Br);
}
if (Pred1Br->isConditional()) {
if (Pred1Br->getSuccessor(0) == BB &&
Pred1Br->getSuccessor(1) == Pred2) {
IfTrue = Pred1;
IfFalse = Pred2;
} else if (Pred1Br->getSuccessor(0) == Pred2 &&
Pred1Br->getSuccessor(1) == BB) {
IfTrue = Pred2;
IfFalse = Pred1;
} else {
return 0;
}
if (++pred_begin(Pred2) != pred_end(Pred2))
return 0;
return Pred1Br->getCondition();
}
if (pred_begin(Pred1) == pred_end(Pred1) ||
++pred_begin(Pred1) != pred_end(Pred1) ||
pred_begin(Pred2) == pred_end(Pred2) ||
++pred_begin(Pred2) != pred_end(Pred2) ||
*pred_begin(Pred1) != *pred_begin(Pred2))
return 0;
BasicBlock *CommonPred = *pred_begin(Pred1);
if (BranchInst *BI = dyn_cast<BranchInst>(CommonPred->getTerminator())) {
assert(BI->isConditional() && "Two successors but not conditional?");
if (BI->getSuccessor(0) == Pred1) {
IfTrue = Pred1;
IfFalse = Pred2;
} else {
IfTrue = Pred2;
IfFalse = Pred1;
}
return BI->getCondition();
}
return 0;
}
static GlobalVariable* findGlobalVariableBase(ConstantExpr* CE) {
if (isa<GlobalVariable>(CE))
return dyn_cast<GlobalVariable>(CE);
if (CE->getOpcode()==Instruction::GetElementPtr ||
CE->getOpcode()==Instruction::BitCast) {
if (isa<GlobalVariable>(CE->getOperand(0)))
return dyn_cast<GlobalVariable>(CE->getOperand(0));
if (ConstantExpr *CE2 = dyn_cast<ConstantExpr>(CE->getOperand(0)))
return findGlobalVariableBase(CE2);
}
return NULL;
}
static bool DominatesMergePoint(Value *V, BasicBlock *BB,
std::set<Instruction*> *AggressiveInsts) {
Instruction *I = dyn_cast<Instruction>(V);
if (!I) {
if (ConstantExpr *C = dyn_cast<ConstantExpr>(V))
if (C->canTrap())
return false;
return true;
}
BasicBlock *PBB = I->getParent();
if (PBB == BB) return false;
if (BranchInst *BI = dyn_cast<BranchInst>(PBB->getTerminator()))
if (BI->isUnconditional() && BI->getSuccessor(0) == BB) {
if (!AggressiveInsts) return false;
switch (I->getOpcode()) {
default: return false; case Instruction::Load: {
if (cast<LoadInst>(I)->isVolatile())
return false;
if (!isa<AllocaInst>(I->getOperand(0)) &&
!isa<Constant>(I->getOperand(0)))
return false;
GlobalVariable* GV = dyn_cast<GlobalVariable>(I->getOperand(0));
if (GV && GV->hasExternalWeakLinkage())
return false;
if (ConstantExpr *CE = dyn_cast<ConstantExpr>(I->getOperand(0)))
GV = findGlobalVariableBase(CE);
if (GV && GV->hasExternalWeakLinkage())
return false;
BasicBlock::iterator IP = PBB->begin();
while (isa<DbgInfoIntrinsic>(IP))
IP++;
if (IP != BasicBlock::iterator(I))
return false;
break;
}
case Instruction::Add:
case Instruction::Sub:
case Instruction::And:
case Instruction::Or:
case Instruction::Xor:
case Instruction::Shl:
case Instruction::LShr:
case Instruction::AShr:
case Instruction::ICmp:
case Instruction::FCmp:
if (I->getOperand(0)->getType()->isFPOrFPVector())
return false; break; }
for (User::op_iterator i = I->op_begin(), e = I->op_end(); i != e; ++i)
if (!DominatesMergePoint(*i, BB, 0))
return false;
AggressiveInsts->insert(I);
}
return true;
}
static Value *GatherConstantSetEQs(Value *V, std::vector<ConstantInt*> &Values){
if (Instruction *Inst = dyn_cast<Instruction>(V)) {
if (Inst->getOpcode() == Instruction::ICmp &&
cast<ICmpInst>(Inst)->getPredicate() == ICmpInst::ICMP_EQ) {
if (ConstantInt *C = dyn_cast<ConstantInt>(Inst->getOperand(1))) {
Values.push_back(C);
return Inst->getOperand(0);
} else if (ConstantInt *C = dyn_cast<ConstantInt>(Inst->getOperand(0))) {
Values.push_back(C);
return Inst->getOperand(1);
}
} else if (Inst->getOpcode() == Instruction::Or) {
if (Value *LHS = GatherConstantSetEQs(Inst->getOperand(0), Values))
if (Value *RHS = GatherConstantSetEQs(Inst->getOperand(1), Values))
if (LHS == RHS)
return LHS;
}
}
return 0;
}
static Value *GatherConstantSetNEs(Value *V, std::vector<ConstantInt*> &Values){
if (Instruction *Inst = dyn_cast<Instruction>(V)) {
if (Inst->getOpcode() == Instruction::ICmp &&
cast<ICmpInst>(Inst)->getPredicate() == ICmpInst::ICMP_NE) {
if (ConstantInt *C = dyn_cast<ConstantInt>(Inst->getOperand(1))) {
Values.push_back(C);
return Inst->getOperand(0);
} else if (ConstantInt *C = dyn_cast<ConstantInt>(Inst->getOperand(0))) {
Values.push_back(C);
return Inst->getOperand(1);
}
} else if (Inst->getOpcode() == Instruction::And) {
if (Value *LHS = GatherConstantSetNEs(Inst->getOperand(0), Values))
if (Value *RHS = GatherConstantSetNEs(Inst->getOperand(1), Values))
if (LHS == RHS)
return LHS;
}
}
return 0;
}
static bool GatherValueComparisons(Instruction *Cond, Value *&CompVal,
std::vector<ConstantInt*> &Values) {
if (Cond->getOpcode() == Instruction::Or) {
CompVal = GatherConstantSetEQs(Cond, Values);
return true;
} else if (Cond->getOpcode() == Instruction::And) {
CompVal = GatherConstantSetNEs(Cond, Values);
return false;
}
return false;
}
static void EraseTerminatorInstAndDCECond(TerminatorInst *TI) {
Instruction* Cond = 0;
if (SwitchInst *SI = dyn_cast<SwitchInst>(TI)) {
Cond = dyn_cast<Instruction>(SI->getCondition());
} else if (BranchInst *BI = dyn_cast<BranchInst>(TI)) {
if (BI->isConditional())
Cond = dyn_cast<Instruction>(BI->getCondition());
}
TI->eraseFromParent();
if (Cond) RecursivelyDeleteTriviallyDeadInstructions(Cond);
}
static Value *isValueEqualityComparison(TerminatorInst *TI) {
if (SwitchInst *SI = dyn_cast<SwitchInst>(TI)) {
if (SI->getNumSuccessors() * std::distance(pred_begin(SI->getParent()),
pred_end(SI->getParent())) > 128)
return 0;
return SI->getCondition();
}
if (BranchInst *BI = dyn_cast<BranchInst>(TI))
if (BI->isConditional() && BI->getCondition()->hasOneUse())
if (ICmpInst *ICI = dyn_cast<ICmpInst>(BI->getCondition()))
if ((ICI->getPredicate() == ICmpInst::ICMP_EQ ||
ICI->getPredicate() == ICmpInst::ICMP_NE) &&
isa<ConstantInt>(ICI->getOperand(1)))
return ICI->getOperand(0);
return 0;
}
static BasicBlock *
GetValueEqualityComparisonCases(TerminatorInst *TI,
std::vector<std::pair<ConstantInt*,
BasicBlock*> > &Cases) {
if (SwitchInst *SI = dyn_cast<SwitchInst>(TI)) {
Cases.reserve(SI->getNumCases());
for (unsigned i = 1, e = SI->getNumCases(); i != e; ++i)
Cases.push_back(std::make_pair(SI->getCaseValue(i), SI->getSuccessor(i)));
return SI->getDefaultDest();
}
BranchInst *BI = cast<BranchInst>(TI);
ICmpInst *ICI = cast<ICmpInst>(BI->getCondition());
Cases.push_back(std::make_pair(cast<ConstantInt>(ICI->getOperand(1)),
BI->getSuccessor(ICI->getPredicate() ==
ICmpInst::ICMP_NE)));
return BI->getSuccessor(ICI->getPredicate() == ICmpInst::ICMP_EQ);
}
static void EliminateBlockCases(BasicBlock *BB,
std::vector<std::pair<ConstantInt*, BasicBlock*> > &Cases) {
for (unsigned i = 0, e = Cases.size(); i != e; ++i)
if (Cases[i].second == BB) {
Cases.erase(Cases.begin()+i);
--i; --e;
}
}
static bool
ValuesOverlap(std::vector<std::pair<ConstantInt*, BasicBlock*> > &C1,
std::vector<std::pair<ConstantInt*, BasicBlock*> > &C2) {
std::vector<std::pair<ConstantInt*, BasicBlock*> > *V1 = &C1, *V2 = &C2;
if (V1->size() > V2->size())
std::swap(V1, V2);
if (V1->size() == 0) return false;
if (V1->size() == 1) {
ConstantInt *TheVal = (*V1)[0].first;
for (unsigned i = 0, e = V2->size(); i != e; ++i)
if (TheVal == (*V2)[i].first)
return true;
}
std::sort(V1->begin(), V1->end());
std::sort(V2->begin(), V2->end());
unsigned i1 = 0, i2 = 0, e1 = V1->size(), e2 = V2->size();
while (i1 != e1 && i2 != e2) {
if ((*V1)[i1].first == (*V2)[i2].first)
return true;
if ((*V1)[i1].first < (*V2)[i2].first)
++i1;
else
++i2;
}
return false;
}
static bool SimplifyEqualityComparisonWithOnlyPredecessor(TerminatorInst *TI,
BasicBlock *Pred) {
Value *PredVal = isValueEqualityComparison(Pred->getTerminator());
if (!PredVal) return false;
Value *ThisVal = isValueEqualityComparison(TI);
assert(ThisVal && "This isn't a value comparison!!");
if (ThisVal != PredVal) return false;
std::vector<std::pair<ConstantInt*, BasicBlock*> > PredCases;
BasicBlock *PredDef = GetValueEqualityComparisonCases(Pred->getTerminator(),
PredCases);
EliminateBlockCases(PredDef, PredCases);
std::vector<std::pair<ConstantInt*, BasicBlock*> > ThisCases;
BasicBlock *ThisDef = GetValueEqualityComparisonCases(TI, ThisCases);
EliminateBlockCases(ThisDef, ThisCases);
if (PredDef == TI->getParent()) {
if (ValuesOverlap(PredCases, ThisCases)) {
if (isa<BranchInst>(TI)) {
assert(ThisCases.size() == 1 && "Branch can only have one case!");
Instruction *NI = BranchInst::Create(ThisDef, TI);
ThisCases[0].second->removePredecessor(TI->getParent());
DOUT << "Threading pred instr: " << *Pred->getTerminator()
<< "Through successor TI: " << *TI << "Leaving: " << *NI << "\n";
EraseTerminatorInstAndDCECond(TI);
return true;
} else {
SwitchInst *SI = cast<SwitchInst>(TI);
SmallPtrSet<Constant*, 16> DeadCases;
for (unsigned i = 0, e = PredCases.size(); i != e; ++i)
DeadCases.insert(PredCases[i].first);
DOUT << "Threading pred instr: " << *Pred->getTerminator()
<< "Through successor TI: " << *TI;
for (unsigned i = SI->getNumCases()-1; i != 0; --i)
if (DeadCases.count(SI->getCaseValue(i))) {
SI->getSuccessor(i)->removePredecessor(TI->getParent());
SI->removeCase(i);
}
DOUT << "Leaving: " << *TI << "\n";
return true;
}
}
} else {
ConstantInt *TIV = 0;
BasicBlock *TIBB = TI->getParent();
for (unsigned i = 0, e = PredCases.size(); i != e; ++i)
if (PredCases[i].second == TIBB) {
if (TIV == 0)
TIV = PredCases[i].first;
else
return false; }
assert(TIV && "No edge from pred to succ?");
BasicBlock *TheRealDest = 0;
for (unsigned i = 0, e = ThisCases.size(); i != e; ++i)
if (ThisCases[i].first == TIV) {
TheRealDest = ThisCases[i].second;
break;
}
if (TheRealDest == 0) TheRealDest = ThisDef;
BasicBlock *CheckEdge = TheRealDest;
for (succ_iterator SI = succ_begin(TIBB), e = succ_end(TIBB); SI != e; ++SI)
if (*SI != CheckEdge)
(*SI)->removePredecessor(TIBB);
else
CheckEdge = 0;
Instruction *NI = BranchInst::Create(TheRealDest, TI);
DOUT << "Threading pred instr: " << *Pred->getTerminator()
<< "Through successor TI: " << *TI << "Leaving: " << *NI << "\n";
EraseTerminatorInstAndDCECond(TI);
return true;
}
return false;
}
namespace {
struct ConstantIntOrdering {
bool operator()(const ConstantInt *LHS, const ConstantInt *RHS) const {
return LHS->getValue().ult(RHS->getValue());
}
};
}
static bool FoldValueComparisonIntoPredecessors(TerminatorInst *TI) {
BasicBlock *BB = TI->getParent();
Value *CV = isValueEqualityComparison(TI); assert(CV && "Not a comparison?");
bool Changed = false;
SmallVector<BasicBlock*, 16> Preds(pred_begin(BB), pred_end(BB));
while (!Preds.empty()) {
BasicBlock *Pred = Preds.back();
Preds.pop_back();
TerminatorInst *PTI = Pred->getTerminator();
Value *PCV = isValueEqualityComparison(PTI);
if (PCV == CV && SafeToMergeTerminators(TI, PTI)) {
std::vector<std::pair<ConstantInt*, BasicBlock*> > BBCases;
BasicBlock *BBDefault = GetValueEqualityComparisonCases(TI, BBCases);
std::vector<std::pair<ConstantInt*, BasicBlock*> > PredCases;
BasicBlock *PredDefault = GetValueEqualityComparisonCases(PTI, PredCases);
SmallVector<BasicBlock*, 8> NewSuccessors;
if (PredDefault == BB) {
std::set<ConstantInt*, ConstantIntOrdering> PTIHandled;
for (unsigned i = 0, e = PredCases.size(); i != e; ++i)
if (PredCases[i].second != BB)
PTIHandled.insert(PredCases[i].first);
else {
std::swap(PredCases[i], PredCases.back());
PredCases.pop_back();
--i; --e;
}
if (PredDefault != BBDefault) {
PredDefault->removePredecessor(Pred);
PredDefault = BBDefault;
NewSuccessors.push_back(BBDefault);
}
for (unsigned i = 0, e = BBCases.size(); i != e; ++i)
if (!PTIHandled.count(BBCases[i].first) &&
BBCases[i].second != BBDefault) {
PredCases.push_back(BBCases[i]);
NewSuccessors.push_back(BBCases[i].second);
}
} else {
std::set<ConstantInt*, ConstantIntOrdering> PTIHandled;
for (unsigned i = 0, e = PredCases.size(); i != e; ++i)
if (PredCases[i].second == BB) {
PTIHandled.insert(PredCases[i].first);
std::swap(PredCases[i], PredCases.back());
PredCases.pop_back();
--i; --e;
}
for (unsigned i = 0, e = BBCases.size(); i != e; ++i)
if (PTIHandled.count(BBCases[i].first)) {
PredCases.push_back(BBCases[i]);
NewSuccessors.push_back(BBCases[i].second);
PTIHandled.erase(BBCases[i].first); }
for (std::set<ConstantInt*, ConstantIntOrdering>::iterator I =
PTIHandled.begin(),
E = PTIHandled.end(); I != E; ++I) {
PredCases.push_back(std::make_pair(*I, BBDefault));
NewSuccessors.push_back(BBDefault);
}
}
for (unsigned i = 0, e = NewSuccessors.size(); i != e; ++i)
AddPredecessorToBlock(NewSuccessors[i], Pred, BB);
SwitchInst *NewSI = SwitchInst::Create(CV, PredDefault,
PredCases.size(), PTI);
for (unsigned i = 0, e = PredCases.size(); i != e; ++i)
NewSI->addCase(PredCases[i].first, PredCases[i].second);
EraseTerminatorInstAndDCECond(PTI);
BasicBlock *InfLoopBlock = 0;
for (unsigned i = 0, e = NewSI->getNumSuccessors(); i != e; ++i)
if (NewSI->getSuccessor(i) == BB) {
if (InfLoopBlock == 0) {
InfLoopBlock = BasicBlock::Create("infloop", BB->getParent());
BranchInst::Create(InfLoopBlock, InfLoopBlock);
}
NewSI->setSuccessor(i, InfLoopBlock);
}
Changed = true;
}
}
return Changed;
}
static bool isSafeToHoistInvoke(BasicBlock *BB1, BasicBlock *BB2,
Instruction *I1, Instruction *I2) {
for (succ_iterator SI = succ_begin(BB1), E = succ_end(BB1); SI != E; ++SI) {
PHINode *PN;
for (BasicBlock::iterator BBI = SI->begin();
(PN = dyn_cast<PHINode>(BBI)); ++BBI) {
Value *BB1V = PN->getIncomingValueForBlock(BB1);
Value *BB2V = PN->getIncomingValueForBlock(BB2);
if (BB1V != BB2V && (BB1V==I1 || BB2V==I2)) {
return false;
}
}
}
return true;
}
static bool HoistThenElseCodeToIf(BranchInst *BI) {
BasicBlock *BB1 = BI->getSuccessor(0); BasicBlock *BB2 = BI->getSuccessor(1);
BasicBlock::iterator BB1_Itr = BB1->begin();
BasicBlock::iterator BB2_Itr = BB2->begin();
Instruction *I1 = BB1_Itr++, *I2 = BB2_Itr++;
while (isa<DbgInfoIntrinsic>(I1))
I1 = BB1_Itr++;
while (isa<DbgInfoIntrinsic>(I2))
I2 = BB2_Itr++;
if (I1->getOpcode() != I2->getOpcode() || isa<PHINode>(I1) ||
!I1->isIdenticalTo(I2) ||
(isa<InvokeInst>(I1) && !isSafeToHoistInvoke(BB1, BB2, I1, I2)))
return false;
BasicBlock *BIParent = BI->getParent();
do {
if (isa<TerminatorInst>(I1))
goto HoistTerminator;
BIParent->getInstList().splice(BI, BB1->getInstList(), I1);
if (!I2->use_empty())
I2->replaceAllUsesWith(I1);
BB2->getInstList().erase(I2);
I1 = BB1_Itr++;
while (isa<DbgInfoIntrinsic>(I1))
I1 = BB1_Itr++;
I2 = BB2_Itr++;
while (isa<DbgInfoIntrinsic>(I2))
I2 = BB2_Itr++;
} while (I1->getOpcode() == I2->getOpcode() && I1->isIdenticalTo(I2));
return true;
HoistTerminator:
if (isa<InvokeInst>(I1) && !isSafeToHoistInvoke(BB1, BB2, I1, I2))
return true;
Instruction *NT = I1->clone();
BIParent->getInstList().insert(BI, NT);
if (NT->getType() != Type::VoidTy) {
I1->replaceAllUsesWith(NT);
I2->replaceAllUsesWith(NT);
NT->takeName(I1);
}
std::map<std::pair<Value*,Value*>, SelectInst*> InsertedSelects;
for (succ_iterator SI = succ_begin(BB1), E = succ_end(BB1); SI != E; ++SI) {
PHINode *PN;
for (BasicBlock::iterator BBI = SI->begin();
(PN = dyn_cast<PHINode>(BBI)); ++BBI) {
Value *BB1V = PN->getIncomingValueForBlock(BB1);
Value *BB2V = PN->getIncomingValueForBlock(BB2);
if (BB1V != BB2V) {
SelectInst *&SI = InsertedSelects[std::make_pair(BB1V, BB2V)];
if (SI == 0)
SI = SelectInst::Create(BI->getCondition(), BB1V, BB2V,
BB1V->getName()+"."+BB2V->getName(), NT);
for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
if (PN->getIncomingBlock(i) == BB1 || PN->getIncomingBlock(i) == BB2)
PN->setIncomingValue(i, SI);
}
}
}
for (succ_iterator SI = succ_begin(BB1), E = succ_end(BB1); SI != E; ++SI)
AddPredecessorToBlock(*SI, BIParent, BB1);
EraseTerminatorInstAndDCECond(BI);
return true;
}
static bool SpeculativelyExecuteBB(BranchInst *BI, BasicBlock *BB1) {
Instruction *HInst = NULL;
Instruction *Term = BB1->getTerminator();
for (BasicBlock::iterator BBI = BB1->begin(), BBE = BB1->end();
BBI != BBE; ++BBI) {
Instruction *I = BBI;
if (isa<DbgInfoIntrinsic>(I)) continue;
if (I == Term) break;
if (!HInst)
HInst = I;
else
return false;
}
if (!HInst)
return false;
Value *BrCond = BI->getCondition();
if (isa<Instruction>(BrCond) &&
cast<Instruction>(BrCond)->getOpcode() == Instruction::FCmp)
return false;
bool Invert = false;
if (BB1 != BI->getSuccessor(0)) {
assert(BB1 == BI->getSuccessor(1) && "No edge from 'if' block?");
Invert = true;
}
switch (HInst->getOpcode()) {
default: return false; case Instruction::Add:
case Instruction::Sub:
if (HInst->getType()->isFloatingPoint()
|| isa<VectorType>(HInst->getType()))
return false;
break;
case Instruction::And:
case Instruction::Or:
case Instruction::Xor:
case Instruction::Shl:
case Instruction::LShr:
case Instruction::AShr:
if (isa<VectorType>(HInst->getType()))
return false;
break; }
if (HInst->use_empty()) {
HInst->eraseFromParent();
return true;
}
BasicBlock *BIParent = BI->getParent();
SmallVector<PHINode*, 4> PHIUses;
Value *FalseV = NULL;
BasicBlock *BB2 = BB1->getTerminator()->getSuccessor(0);
for (Value::use_iterator UI = HInst->use_begin(), E = HInst->use_end();
UI != E; ++UI) {
PHINode *PN = dyn_cast<PHINode>(UI);
if (!PN || PN->getParent() != BB2)
return false;
PHIUses.push_back(PN);
Value *PHIV = PN->getIncomingValueForBlock(BIParent);
if (!FalseV)
FalseV = PHIV;
else if (FalseV != PHIV)
return false; }
assert(FalseV && "Must have at least one user, and it must be a PHI");
for (User::op_iterator i = HInst->op_begin(), e = HInst->op_end();
i != e; ++i) {
Instruction *OpI = dyn_cast<Instruction>(*i);
if (OpI && OpI->getParent() == BIParent &&
!OpI->isUsedInBasicBlock(BIParent))
return false;
}
BasicBlock::iterator InsertPos = BI;
if (InsertPos != BIParent->begin())
--InsertPos;
while (InsertPos != BIParent->begin() && isa<DbgInfoIntrinsic>(InsertPos))
--InsertPos;
if (InsertPos == BrCond && !isa<PHINode>(BrCond)) {
SmallPtrSet<Instruction *, 4> BB1Insns;
for(BasicBlock::iterator BB1I = BB1->begin(), BB1E = BB1->end();
BB1I != BB1E; ++BB1I)
BB1Insns.insert(BB1I);
for(Value::use_iterator UI = BrCond->use_begin(), UE = BrCond->use_end();
UI != UE; ++UI) {
Instruction *Use = cast<Instruction>(*UI);
if (BB1Insns.count(Use)) {
InsertPos = BI;
break;
}
}
} else
InsertPos = BI;
BIParent->getInstList().splice(InsertPos, BB1->getInstList(), HInst);
SelectInst *SI;
if (Invert)
SI = SelectInst::Create(BrCond, FalseV, HInst,
FalseV->getName() + "." + HInst->getName(), BI);
else
SI = SelectInst::Create(BrCond, HInst, FalseV,
HInst->getName() + "." + FalseV->getName(), BI);
for (unsigned i = 0, e = PHIUses.size(); i != e; ++i) {
PHINode *PN = PHIUses[i];
for (unsigned j = 0, ee = PN->getNumIncomingValues(); j != ee; ++j)
if (PN->getIncomingBlock(j) == BB1 ||
PN->getIncomingBlock(j) == BIParent)
PN->setIncomingValue(j, SI);
}
++NumSpeculations;
return true;
}
static bool BlockIsSimpleEnoughToThreadThrough(BasicBlock *BB) {
BranchInst *BI = cast<BranchInst>(BB->getTerminator());
unsigned Size = 0;
for (BasicBlock::iterator BBI = BB->begin(); &*BBI != BI; ++BBI) {
if (isa<DbgInfoIntrinsic>(BBI))
continue;
if (Size > 10) return false; ++Size;
for (Value::use_iterator UI = BBI->use_begin(), E = BBI->use_end();
UI != E; ++UI) {
Instruction *U = cast<Instruction>(*UI);
if (U->getParent() != BB || isa<PHINode>(U)) return false;
}
}
return true;
}
static bool FoldCondBranchOnPHI(BranchInst *BI) {
BasicBlock *BB = BI->getParent();
PHINode *PN = dyn_cast<PHINode>(BI->getCondition());
if (!PN || PN->getParent() != BB || !PN->hasOneUse())
return false;
if (PN->getNumIncomingValues() == 1) {
FoldSingleEntryPHINodes(PN->getParent());
return true;
}
if (!BlockIsSimpleEnoughToThreadThrough(BB)) return false;
for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
ConstantInt *CB;
if ((CB = dyn_cast<ConstantInt>(PN->getIncomingValue(i))) &&
CB->getType() == Type::Int1Ty) {
BasicBlock *PredBB = PN->getIncomingBlock(i);
BasicBlock *RealDest = BI->getSuccessor(!CB->getZExtValue());
if (RealDest == BB) continue;
BasicBlock *EdgeBB = BasicBlock::Create(RealDest->getName()+".critedge",
RealDest->getParent(), RealDest);
BranchInst::Create(RealDest, EdgeBB);
PHINode *PN;
for (BasicBlock::iterator BBI = RealDest->begin();
(PN = dyn_cast<PHINode>(BBI)); ++BBI) {
Value *V = PN->getIncomingValueForBlock(BB);
PN->addIncoming(V, EdgeBB);
}
BasicBlock::iterator InsertPt = EdgeBB->begin();
std::map<Value*, Value*> TranslateMap; for (BasicBlock::iterator BBI = BB->begin(); &*BBI != BI; ++BBI) {
if (PHINode *PN = dyn_cast<PHINode>(BBI)) {
TranslateMap[PN] = PN->getIncomingValueForBlock(PredBB);
} else {
Instruction *N = BBI->clone();
if (BBI->hasName()) N->setName(BBI->getName()+".c");
for (User::op_iterator i = N->op_begin(), e = N->op_end();
i != e; ++i) {
std::map<Value*, Value*>::iterator PI =
TranslateMap.find(*i);
if (PI != TranslateMap.end())
*i = PI->second;
}
if (Constant *C = ConstantFoldInstruction(N)) {
TranslateMap[BBI] = C;
delete N; } else {
EdgeBB->getInstList().insert(InsertPt, N);
if (!BBI->use_empty())
TranslateMap[BBI] = N;
}
}
}
TerminatorInst *PredBBTI = PredBB->getTerminator();
for (unsigned i = 0, e = PredBBTI->getNumSuccessors(); i != e; ++i)
if (PredBBTI->getSuccessor(i) == BB) {
BB->removePredecessor(PredBB);
PredBBTI->setSuccessor(i, EdgeBB);
}
return FoldCondBranchOnPHI(BI) | true;
}
}
return false;
}
static bool FoldTwoEntryPHINode(PHINode *PN) {
BasicBlock *BB = PN->getParent();
BasicBlock *IfTrue, *IfFalse;
Value *IfCond = GetIfCondition(BB, IfTrue, IfFalse);
if (!IfCond) return false;
unsigned NumPhis = 0;
for (BasicBlock::iterator I = BB->begin(); isa<PHINode>(I); ++NumPhis, ++I)
if (NumPhis > 2)
return false;
DOUT << "FOUND IF CONDITION! " << *IfCond << " T: "
<< IfTrue->getName() << " F: " << IfFalse->getName() << "\n";
std::set<Instruction*> AggressiveInsts;
BasicBlock::iterator AfterPHIIt = BB->begin();
while (isa<PHINode>(AfterPHIIt)) {
PHINode *PN = cast<PHINode>(AfterPHIIt++);
if (PN->getIncomingValue(0) == PN->getIncomingValue(1)) {
if (PN->getIncomingValue(0) != PN)
PN->replaceAllUsesWith(PN->getIncomingValue(0));
else
PN->replaceAllUsesWith(UndefValue::get(PN->getType()));
} else if (!DominatesMergePoint(PN->getIncomingValue(0), BB,
&AggressiveInsts) ||
!DominatesMergePoint(PN->getIncomingValue(1), BB,
&AggressiveInsts)) {
return false;
}
}
BasicBlock *DomBlock = 0, *IfBlock1 = 0, *IfBlock2 = 0;
PN = cast<PHINode>(BB->begin());
BasicBlock *Pred = PN->getIncomingBlock(0);
if (cast<BranchInst>(Pred->getTerminator())->isUnconditional()) {
IfBlock1 = Pred;
DomBlock = *pred_begin(Pred);
for (BasicBlock::iterator I = Pred->begin();
!isa<TerminatorInst>(I); ++I)
if (!AggressiveInsts.count(I) && !isa<DbgInfoIntrinsic>(I)) {
return false;
}
}
Pred = PN->getIncomingBlock(1);
if (cast<BranchInst>(Pred->getTerminator())->isUnconditional()) {
IfBlock2 = Pred;
DomBlock = *pred_begin(Pred);
for (BasicBlock::iterator I = Pred->begin();
!isa<TerminatorInst>(I); ++I)
if (!AggressiveInsts.count(I) && !isa<DbgInfoIntrinsic>(I)) {
return false;
}
}
if (IfBlock1) {
DomBlock->getInstList().splice(DomBlock->getTerminator(),
IfBlock1->getInstList(),
IfBlock1->begin(),
IfBlock1->getTerminator());
}
if (IfBlock2) {
DomBlock->getInstList().splice(DomBlock->getTerminator(),
IfBlock2->getInstList(),
IfBlock2->begin(),
IfBlock2->getTerminator());
}
while (PHINode *PN = dyn_cast<PHINode>(BB->begin())) {
Value *TrueVal =
PN->getIncomingValue(PN->getIncomingBlock(0) == IfFalse);
Value *FalseVal =
PN->getIncomingValue(PN->getIncomingBlock(0) == IfTrue);
Value *NV = SelectInst::Create(IfCond, TrueVal, FalseVal, "", AfterPHIIt);
PN->replaceAllUsesWith(NV);
NV->takeName(PN);
BB->getInstList().erase(PN);
}
return true;
}
static bool isTerminatorFirstRelevantInsn(BasicBlock *BB, Instruction *Term) {
BasicBlock::iterator BBI = Term;
while (BBI != BB->begin()) {
--BBI;
if (!isa<DbgInfoIntrinsic>(BBI))
break;
}
if (isa<PHINode>(BBI) || &*BBI == Term || isa<DbgInfoIntrinsic>(BBI))
return true;
return false;
}
static bool SimplifyCondBranchToTwoReturns(BranchInst *BI) {
assert(BI->isConditional() && "Must be a conditional branch");
BasicBlock *TrueSucc = BI->getSuccessor(0);
BasicBlock *FalseSucc = BI->getSuccessor(1);
ReturnInst *TrueRet = cast<ReturnInst>(TrueSucc->getTerminator());
ReturnInst *FalseRet = cast<ReturnInst>(FalseSucc->getTerminator());
if (!isTerminatorFirstRelevantInsn(TrueSucc, TrueRet))
return false;
if (!isTerminatorFirstRelevantInsn(FalseSucc, FalseRet))
return false;
if (FalseRet->getNumOperands() == 0) {
TrueSucc->removePredecessor(BI->getParent());
FalseSucc->removePredecessor(BI->getParent());
ReturnInst::Create(0, BI);
EraseTerminatorInstAndDCECond(BI);
return true;
}
Value *TrueValue = TrueRet->getReturnValue();
Value *FalseValue = FalseRet->getReturnValue();
if (PHINode *TVPN = dyn_cast_or_null<PHINode>(TrueValue))
if (TVPN->getParent() == TrueSucc)
TrueValue = TVPN->getIncomingValueForBlock(BI->getParent());
if (PHINode *FVPN = dyn_cast_or_null<PHINode>(FalseValue))
if (FVPN->getParent() == FalseSucc)
FalseValue = FVPN->getIncomingValueForBlock(BI->getParent());
if (ConstantExpr *TCV = dyn_cast_or_null<ConstantExpr>(TrueValue))
if (TCV->canTrap())
return false;
if (ConstantExpr *FCV = dyn_cast_or_null<ConstantExpr>(FalseValue))
if (FCV->canTrap())
return false;
TrueSucc->removePredecessor(BI->getParent());
FalseSucc->removePredecessor(BI->getParent());
Value *BrCond = BI->getCondition();
if (TrueValue) {
if (TrueValue == FalseValue || isa<UndefValue>(FalseValue)) {
} else if (isa<UndefValue>(TrueValue)) {
TrueValue = FalseValue;
} else {
TrueValue = SelectInst::Create(BrCond, TrueValue,
FalseValue, "retval", BI);
}
}
Value *RI = !TrueValue ?
ReturnInst::Create(BI) :
ReturnInst::Create(TrueValue, BI);
DOUT << "\nCHANGING BRANCH TO TWO RETURNS INTO SELECT:"
<< "\n " << *BI << "NewRet = " << *RI
<< "TRUEBLOCK: " << *TrueSucc << "FALSEBLOCK: "<< *FalseSucc;
EraseTerminatorInstAndDCECond(BI);
return true;
}
static bool FoldBranchToCommonDest(BranchInst *BI) {
BasicBlock *BB = BI->getParent();
Instruction *Cond = dyn_cast<Instruction>(BI->getCondition());
if (Cond == 0) return false;
BasicBlock::iterator FrontIt = BB->front();
while(isa<DbgInfoIntrinsic>(FrontIt))
++FrontIt;
if ((!isa<CmpInst>(Cond) && !isa<BinaryOperator>(Cond)) ||
Cond->getParent() != BB || &*FrontIt != Cond || !Cond->hasOneUse()) {
return false;
}
BasicBlock::iterator CondIt = Cond; ++CondIt;
while(isa<DbgInfoIntrinsic>(CondIt))
++CondIt;
if (&*CondIt != BI) {
assert (!isa<DbgInfoIntrinsic>(CondIt) && "Hey do not forget debug info!");
return false;
}
if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Cond->getOperand(0)))
if (CE->canTrap())
return false;
if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Cond->getOperand(1)))
if (CE->canTrap())
return false;
BasicBlock *TrueDest = BI->getSuccessor(0);
BasicBlock *FalseDest = BI->getSuccessor(1);
if (TrueDest == BB || FalseDest == BB)
return false;
for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI) {
BasicBlock *PredBlock = *PI;
BranchInst *PBI = dyn_cast<BranchInst>(PredBlock->getTerminator());
if (PBI == 0 || PBI->isUnconditional() ||
!SafeToMergeTerminators(BI, PBI))
continue;
Instruction::BinaryOps Opc;
bool InvertPredCond = false;
if (PBI->getSuccessor(0) == TrueDest)
Opc = Instruction::Or;
else if (PBI->getSuccessor(1) == FalseDest)
Opc = Instruction::And;
else if (PBI->getSuccessor(0) == FalseDest)
Opc = Instruction::And, InvertPredCond = true;
else if (PBI->getSuccessor(1) == TrueDest)
Opc = Instruction::Or, InvertPredCond = true;
else
continue;
DOUT << "FOLDING BRANCH TO COMMON DEST:\n" << *PBI << *BB;
if (InvertPredCond) {
Value *NewCond =
BinaryOperator::CreateNot(PBI->getCondition(),
PBI->getCondition()->getName()+".not", PBI);
PBI->setCondition(NewCond);
BasicBlock *OldTrue = PBI->getSuccessor(0);
BasicBlock *OldFalse = PBI->getSuccessor(1);
PBI->setSuccessor(0, OldFalse);
PBI->setSuccessor(1, OldTrue);
}
Instruction *New = Cond->clone();
PredBlock->getInstList().insert(PBI, New);
New->takeName(Cond);
Cond->setName(New->getName()+".old");
Value *NewCond = BinaryOperator::Create(Opc, PBI->getCondition(),
New, "or.cond", PBI);
PBI->setCondition(NewCond);
if (PBI->getSuccessor(0) == BB) {
AddPredecessorToBlock(TrueDest, PredBlock, BB);
PBI->setSuccessor(0, TrueDest);
}
if (PBI->getSuccessor(1) == BB) {
AddPredecessorToBlock(FalseDest, PredBlock, BB);
PBI->setSuccessor(1, FalseDest);
}
return true;
}
return false;
}
static bool SimplifyCondBranchToCondBranch(BranchInst *PBI, BranchInst *BI) {
assert(PBI->isConditional() && BI->isConditional());
BasicBlock *BB = BI->getParent();
if (PBI->getCondition() == BI->getCondition() &&
PBI->getSuccessor(0) != PBI->getSuccessor(1)) {
if (BB->getSinglePredecessor()) {
bool CondIsTrue = PBI->getSuccessor(0) == BB;
BI->setCondition(ConstantInt::get(Type::Int1Ty, CondIsTrue));
return true; }
if (BlockIsSimpleEnoughToThreadThrough(BB)) {
PHINode *NewPN = PHINode::Create(Type::Int1Ty,
BI->getCondition()->getName() + ".pr",
BB->begin());
for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI)
if ((PBI = dyn_cast<BranchInst>((*PI)->getTerminator())) &&
PBI != BI && PBI->isConditional() &&
PBI->getCondition() == BI->getCondition() &&
PBI->getSuccessor(0) != PBI->getSuccessor(1)) {
bool CondIsTrue = PBI->getSuccessor(0) == BB;
NewPN->addIncoming(ConstantInt::get(Type::Int1Ty,
CondIsTrue), *PI);
} else {
NewPN->addIncoming(BI->getCondition(), *PI);
}
BI->setCondition(NewPN);
return true;
}
}
BasicBlock::iterator BBI = BB->begin();
while (isa<DbgInfoIntrinsic>(BBI))
++BBI;
if (&*BBI != BI)
return false;
if (ConstantExpr *CE = dyn_cast<ConstantExpr>(BI->getCondition()))
if (CE->canTrap())
return false;
int PBIOp, BIOp;
if (PBI->getSuccessor(0) == BI->getSuccessor(0))
PBIOp = BIOp = 0;
else if (PBI->getSuccessor(0) == BI->getSuccessor(1))
PBIOp = 0, BIOp = 1;
else if (PBI->getSuccessor(1) == BI->getSuccessor(0))
PBIOp = 1, BIOp = 0;
else if (PBI->getSuccessor(1) == BI->getSuccessor(1))
PBIOp = BIOp = 1;
else
return false;
if (PBI->getSuccessor(PBIOp) == BB)
return false;
BasicBlock *CommonDest = PBI->getSuccessor(PBIOp);
unsigned NumPhis = 0;
for (BasicBlock::iterator II = CommonDest->begin();
isa<PHINode>(II); ++II, ++NumPhis)
if (NumPhis > 2) return false;
BasicBlock *OtherDest = BI->getSuccessor(BIOp ^ 1);
DOUT << "FOLDING BRs:" << *PBI->getParent()
<< "AND: " << *BI->getParent();
if (OtherDest == BB) {
BasicBlock *InfLoopBlock = BasicBlock::Create("infloop", BB->getParent());
BranchInst::Create(InfLoopBlock, InfLoopBlock);
OtherDest = InfLoopBlock;
}
DOUT << *PBI->getParent()->getParent();
Value *PBICond = PBI->getCondition();
if (PBIOp)
PBICond = BinaryOperator::CreateNot(PBICond,
PBICond->getName()+".not",
PBI);
Value *BICond = BI->getCondition();
if (BIOp)
BICond = BinaryOperator::CreateNot(BICond,
BICond->getName()+".not",
PBI);
Value *Cond = BinaryOperator::CreateOr(PBICond, BICond, "brmerge", PBI);
PBI->setCondition(Cond);
PBI->setSuccessor(0, CommonDest);
PBI->setSuccessor(1, OtherDest);
PHINode *PN;
for (BasicBlock::iterator II = OtherDest->begin();
(PN = dyn_cast<PHINode>(II)); ++II) {
Value *V = PN->getIncomingValueForBlock(BB);
PN->addIncoming(V, PBI->getParent());
}
for (BasicBlock::iterator II = CommonDest->begin();
(PN = dyn_cast<PHINode>(II)); ++II) {
Value *BIV = PN->getIncomingValueForBlock(BB);
unsigned PBBIdx = PN->getBasicBlockIndex(PBI->getParent());
Value *PBIV = PN->getIncomingValue(PBBIdx);
if (BIV != PBIV) {
Value *NV = SelectInst::Create(PBICond, PBIV, BIV,
PBIV->getName()+".mux", PBI);
PN->setIncomingValue(PBBIdx, NV);
}
}
DOUT << "INTO: " << *PBI->getParent();
DOUT << *PBI->getParent()->getParent();
return true;
}
bool llvm::SimplifyCFG(BasicBlock *BB) {
bool Changed = false;
Function *M = BB->getParent();
assert(BB && BB->getParent() && "Block not embedded in function!");
assert(BB->getTerminator() && "Degenerate basic block encountered!");
assert(&BB->getParent()->getEntryBlock() != BB &&
"Can't Simplify entry block!");
if (pred_begin(BB) == pred_end(BB) || BB->getSinglePredecessor() == BB) {
DOUT << "Removing BB: \n" << *BB;
DeleteDeadBlock(BB);
return true;
}
Changed |= ConstantFoldTerminator(BB);
if (PHINode *PN = dyn_cast<PHINode>(BB->begin()))
if (PN->getNumIncomingValues() == 2)
Changed |= FoldTwoEntryPHINode(PN);
if (ReturnInst *RI = dyn_cast<ReturnInst>(BB->getTerminator())) {
if (isTerminatorFirstRelevantInsn(BB, BB->getTerminator())) {
SmallVector<BasicBlock*, 8> UncondBranchPreds;
SmallVector<BranchInst*, 8> CondBranchPreds;
for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI) {
TerminatorInst *PTI = (*PI)->getTerminator();
if (BranchInst *BI = dyn_cast<BranchInst>(PTI)) {
if (BI->isUnconditional())
UncondBranchPreds.push_back(*PI);
else
CondBranchPreds.push_back(BI);
}
}
if (!UncondBranchPreds.empty()) {
while (!UncondBranchPreds.empty()) {
BasicBlock *Pred = UncondBranchPreds.back();
DOUT << "FOLDING: " << *BB
<< "INTO UNCOND BRANCH PRED: " << *Pred;
UncondBranchPreds.pop_back();
Instruction *UncondBranch = Pred->getTerminator();
Instruction *NewRet = RI->clone();
Pred->getInstList().push_back(NewRet);
BasicBlock::iterator BBI = RI;
if (BBI != BB->begin()) {
if (DbgRegionEndInst *DREI = dyn_cast<DbgRegionEndInst>(--BBI))
DREI->moveBefore(NewRet);
}
for (User::op_iterator i = NewRet->op_begin(), e = NewRet->op_end();
i != e; ++i)
if (PHINode *PN = dyn_cast<PHINode>(*i))
if (PN->getParent() == BB)
*i = PN->getIncomingValueForBlock(Pred);
BB->removePredecessor(Pred);
Pred->getInstList().erase(UncondBranch);
}
if (pred_begin(BB) == pred_end(BB))
M->getBasicBlockList().erase(BB);
return true;
}
while (!CondBranchPreds.empty()) {
BranchInst *BI = CondBranchPreds.back();
CondBranchPreds.pop_back();
if (isa<ReturnInst>(BI->getSuccessor(0)->getTerminator()) &&
isa<ReturnInst>(BI->getSuccessor(1)->getTerminator()) &&
SimplifyCondBranchToTwoReturns(BI))
return true;
}
}
} else if (isa<UnwindInst>(BB->begin())) {
SmallVector<BasicBlock*, 8> Preds(pred_begin(BB), pred_end(BB));
while (!Preds.empty()) {
BasicBlock *Pred = Preds.back();
if (BranchInst *BI = dyn_cast<BranchInst>(Pred->getTerminator())) {
if (BI->isUnconditional()) {
Pred->getInstList().pop_back(); new UnwindInst(Pred); Changed = true;
}
} else if (InvokeInst *II = dyn_cast<InvokeInst>(Pred->getTerminator()))
if (II->getUnwindDest() == BB) {
BranchInst *BI = BranchInst::Create(II->getNormalDest(), II);
Pred->getInstList().remove(II);
SmallVector<Value*,8> Args(II->op_begin()+3, II->op_end());
CallInst *CI = CallInst::Create(II->getCalledValue(),
Args.begin(), Args.end(),
II->getName(), BI);
CI->setCallingConv(II->getCallingConv());
CI->setAttributes(II->getAttributes());
II->replaceAllUsesWith(CI);
delete II;
Changed = true;
}
Preds.pop_back();
}
if (pred_begin(BB) == pred_end(BB)) {
M->getBasicBlockList().erase(BB);
return true;
}
} else if (SwitchInst *SI = dyn_cast<SwitchInst>(BB->getTerminator())) {
if (isValueEqualityComparison(SI)) {
if (BasicBlock *OnlyPred = BB->getSinglePredecessor())
if (SimplifyEqualityComparisonWithOnlyPredecessor(SI, OnlyPred))
return SimplifyCFG(BB) || 1;
BasicBlock::iterator BBI = BB->begin();
while (isa<DbgInfoIntrinsic>(BBI))
++BBI;
if (SI == &*BBI)
if (FoldValueComparisonIntoPredecessors(SI))
return SimplifyCFG(BB) || 1;
}
} else if (BranchInst *BI = dyn_cast<BranchInst>(BB->getTerminator())) {
if (BI->isUnconditional()) {
BasicBlock::iterator BBI = BB->getFirstNonPHI();
BasicBlock *Succ = BI->getSuccessor(0);
while (isa<DbgInfoIntrinsic>(BBI))
++BBI;
if (BBI->isTerminator() && Succ != BB) if (TryToSimplifyUncondBranchFromEmptyBlock(BB, Succ))
return true;
} else { if (isValueEqualityComparison(BI)) {
if (BasicBlock *OnlyPred = BB->getSinglePredecessor())
if (SimplifyEqualityComparisonWithOnlyPredecessor(BI, OnlyPred))
return SimplifyCFG(BB) || 1;
BasicBlock::iterator I = BB->begin();
while (isa<DbgInfoIntrinsic>(I))
++I;
if (&*I == BI) {
if (FoldValueComparisonIntoPredecessors(BI))
return SimplifyCFG(BB) | true;
} else if (&*I == cast<Instruction>(BI->getCondition())){
++I;
while (isa<DbgInfoIntrinsic>(I))
++I;
if(&*I == BI) {
if (FoldValueComparisonIntoPredecessors(BI))
return SimplifyCFG(BB) | true;
}
}
}
if (PHINode *PN = dyn_cast<PHINode>(BI->getCondition()))
if (PN->getParent() == BI->getParent())
if (FoldCondBranchOnPHI(BI))
return SimplifyCFG(BB) | true;
if (FoldBranchToCommonDest(BI))
return SimplifyCFG(BB) | 1;
for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI)
if (BranchInst *PBI = dyn_cast<BranchInst>((*PI)->getTerminator()))
if (PBI != BI && PBI->isConditional())
if (SimplifyCondBranchToCondBranch(PBI, BI))
return SimplifyCFG(BB) | true;
}
} else if (isa<UnreachableInst>(BB->getTerminator())) {
Instruction *Unreachable = BB->getTerminator();
while (Unreachable != BB->begin()) {
BasicBlock::iterator BBI = Unreachable;
--BBI;
if (isa<CallInst>(BBI) && !isa<DbgInfoIntrinsic>(BBI)) break;
if (StoreInst *SI = dyn_cast<StoreInst>(BBI))
if (SI->isVolatile())
break;
if (LoadInst *LI = dyn_cast<LoadInst>(BBI))
if (LI->isVolatile())
break;
BB->getInstList().erase(BBI);
Changed = true;
}
if (&BB->front() == Unreachable) {
SmallVector<BasicBlock*, 8> Preds(pred_begin(BB), pred_end(BB));
for (unsigned i = 0, e = Preds.size(); i != e; ++i) {
TerminatorInst *TI = Preds[i]->getTerminator();
if (BranchInst *BI = dyn_cast<BranchInst>(TI)) {
if (BI->isUnconditional()) {
if (BI->getSuccessor(0) == BB) {
new UnreachableInst(TI);
TI->eraseFromParent();
Changed = true;
}
} else {
if (BI->getSuccessor(0) == BB) {
BranchInst::Create(BI->getSuccessor(1), BI);
EraseTerminatorInstAndDCECond(BI);
} else if (BI->getSuccessor(1) == BB) {
BranchInst::Create(BI->getSuccessor(0), BI);
EraseTerminatorInstAndDCECond(BI);
Changed = true;
}
}
} else if (SwitchInst *SI = dyn_cast<SwitchInst>(TI)) {
for (unsigned i = 1, e = SI->getNumCases(); i != e; ++i)
if (SI->getSuccessor(i) == BB) {
BB->removePredecessor(SI->getParent());
SI->removeCase(i);
--i; --e;
Changed = true;
}
if (SI->getSuccessor(0) == BB) {
std::map<BasicBlock*, unsigned> Popularity;
for (unsigned i = 1, e = SI->getNumCases(); i != e; ++i)
Popularity[SI->getSuccessor(i)]++;
unsigned MaxPop = 0;
BasicBlock *MaxBlock = 0;
for (std::map<BasicBlock*, unsigned>::iterator
I = Popularity.begin(), E = Popularity.end(); I != E; ++I) {
if (I->second > MaxPop) {
MaxPop = I->second;
MaxBlock = I->first;
}
}
if (MaxBlock) {
SI->setSuccessor(0, MaxBlock);
Changed = true;
if (isa<PHINode>(MaxBlock->begin()))
for (unsigned i = 0; i != MaxPop-1; ++i)
MaxBlock->removePredecessor(SI->getParent());
for (unsigned i = 1, e = SI->getNumCases(); i != e; ++i)
if (SI->getSuccessor(i) == MaxBlock) {
SI->removeCase(i);
--i; --e;
}
}
}
} else if (InvokeInst *II = dyn_cast<InvokeInst>(TI)) {
if (II->getUnwindDest() == BB) {
BranchInst *BI = BranchInst::Create(II->getNormalDest(), II);
II->removeFromParent();
SmallVector<Value*, 8> Args(II->op_begin()+3, II->op_end());
CallInst *CI = CallInst::Create(II->getCalledValue(),
Args.begin(), Args.end(),
II->getName(), BI);
CI->setCallingConv(II->getCallingConv());
CI->setAttributes(II->getAttributes());
II->replaceAllUsesWith(CI);
delete II;
Changed = true;
}
}
}
if (pred_begin(BB) == pred_end(BB)) {
M->getBasicBlockList().erase(BB);
return true;
}
}
}
if (MergeBlockIntoPredecessor(BB))
return true;
pred_iterator PI(pred_begin(BB)), PE(pred_end(BB));
BasicBlock *OnlyPred = *PI++;
for (; PI != PE; ++PI) if (*PI != OnlyPred) {
OnlyPred = 0; break;
}
if (OnlyPred)
if (BranchInst *BI = dyn_cast<BranchInst>(OnlyPred->getTerminator()))
if (BI->isConditional()) {
BasicBlock *OtherBB = BI->getSuccessor(BI->getSuccessor(0) == BB);
PI = pred_begin(OtherBB);
++PI;
if (PI == pred_end(OtherBB)) {
Changed |= HoistThenElseCodeToIf(BI);
} else {
BasicBlock* OnlySucc = NULL;
for (succ_iterator SI = succ_begin(BB), SE = succ_end(BB);
SI != SE; ++SI) {
if (!OnlySucc)
OnlySucc = *SI;
else if (*SI != OnlySucc) {
OnlySucc = 0; break;
}
}
if (OnlySucc == OtherBB) {
Changed |= SpeculativelyExecuteBB(BI, BB);
}
}
}
for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI)
if (BranchInst *BI = dyn_cast<BranchInst>((*PI)->getTerminator()))
if (BI->isConditional() && isa<Instruction>(BI->getCondition())) {
Instruction *Cond = cast<Instruction>(BI->getCondition());
Value *CompVal = 0;
std::vector<ConstantInt*> Values;
bool TrueWhenEqual = GatherValueComparisons(Cond, CompVal, Values);
if (CompVal && CompVal->getType()->isInteger()) {
std::sort(Values.begin(), Values.end(), ConstantIntOrdering());
Values.erase(std::unique(Values.begin(), Values.end()), Values.end());
BasicBlock *DefaultBB = BI->getSuccessor(1);
BasicBlock *EdgeBB = BI->getSuccessor(0);
if (!TrueWhenEqual) std::swap(DefaultBB, EdgeBB);
SwitchInst *New = SwitchInst::Create(CompVal, DefaultBB,
Values.size(), BI);
for (unsigned i = 0, e = Values.size(); i != e; ++i)
New->addCase(Values[i], EdgeBB);
for (BasicBlock::iterator BBI = EdgeBB->begin();
isa<PHINode>(BBI); ++BBI) {
PHINode *PN = cast<PHINode>(BBI);
Value *InVal = PN->getIncomingValueForBlock(*PI);
for (unsigned i = 0, e = Values.size()-1; i != e; ++i)
PN->addIncoming(InVal, *PI);
}
EraseTerminatorInstAndDCECond(BI);
return true;
}
}
return Changed;
}