BasicBlockUtils.cpp [plain text]
#include "llvm/Transforms/Utils/BasicBlockUtils.h"
#include "llvm/Analysis/AliasAnalysis.h"
#include "llvm/Analysis/Dominators.h"
#include "llvm/Analysis/LoopInfo.h"
#include "llvm/Analysis/MemoryDependenceAnalysis.h"
#include "llvm/IR/Constant.h"
#include "llvm/IR/DataLayout.h"
#include "llvm/IR/Function.h"
#include "llvm/IR/Instructions.h"
#include "llvm/IR/IntrinsicInst.h"
#include "llvm/IR/Type.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/ValueHandle.h"
#include "llvm/Transforms/Scalar.h"
#include "llvm/Transforms/Utils/Local.h"
#include <algorithm>
using namespace llvm;
void llvm::DeleteDeadBlock(BasicBlock *BB) {
assert((pred_begin(BB) == pred_end(BB) ||
BB->getSinglePredecessor() == BB) && "Block is not dead!");
TerminatorInst *BBTerm = BB->getTerminator();
for (unsigned i = 0, e = BBTerm->getNumSuccessors(); i != e; ++i)
BBTerm->getSuccessor(i)->removePredecessor(BB);
while (!BB->empty()) {
Instruction &I = BB->back();
if (!I.use_empty())
I.replaceAllUsesWith(UndefValue::get(I.getType()));
BB->getInstList().pop_back();
}
BB->eraseFromParent();
}
void llvm::FoldSingleEntryPHINodes(BasicBlock *BB, Pass *P) {
if (!isa<PHINode>(BB->begin())) return;
AliasAnalysis *AA = 0;
MemoryDependenceAnalysis *MemDep = 0;
if (P) {
AA = P->getAnalysisIfAvailable<AliasAnalysis>();
MemDep = P->getAnalysisIfAvailable<MemoryDependenceAnalysis>();
}
while (PHINode *PN = dyn_cast<PHINode>(BB->begin())) {
if (PN->getIncomingValue(0) != PN)
PN->replaceAllUsesWith(PN->getIncomingValue(0));
else
PN->replaceAllUsesWith(UndefValue::get(PN->getType()));
if (MemDep)
MemDep->removeInstruction(PN); else if (AA && isa<PointerType>(PN->getType()))
AA->deleteValue(PN);
PN->eraseFromParent();
}
}
bool llvm::DeleteDeadPHIs(BasicBlock *BB, const TargetLibraryInfo *TLI) {
SmallVector<WeakVH, 8> PHIs;
for (BasicBlock::iterator I = BB->begin();
PHINode *PN = dyn_cast<PHINode>(I); ++I)
PHIs.push_back(PN);
bool Changed = false;
for (unsigned i = 0, e = PHIs.size(); i != e; ++i)
if (PHINode *PN = dyn_cast_or_null<PHINode>(PHIs[i].operator Value*()))
Changed |= RecursivelyDeleteDeadPHINode(PN, TLI);
return Changed;
}
bool llvm::MergeBlockIntoPredecessor(BasicBlock *BB, Pass *P) {
if (BB->hasAddressTaken()) return false;
BasicBlock *PredBB = BB->getUniquePredecessor();
if (!PredBB) return false;
if (PredBB == BB) return false;
if (isa<InvokeInst>(PredBB->getTerminator())) return false;
succ_iterator SI(succ_begin(PredBB)), SE(succ_end(PredBB));
BasicBlock *OnlySucc = BB;
for (; SI != SE; ++SI)
if (*SI != OnlySucc) {
OnlySucc = 0; break;
}
if (!OnlySucc) return false;
for (BasicBlock::iterator BI = BB->begin(), BE = BB->end(); BI != BE; ++BI) {
if (PHINode *PN = dyn_cast<PHINode>(BI)) {
for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
if (PN->getIncomingValue(i) == PN)
return false;
} else
break;
}
if (isa<PHINode>(BB->front()))
FoldSingleEntryPHINodes(BB, P);
PredBB->getInstList().pop_back();
BB->replaceAllUsesWith(PredBB);
PredBB->getInstList().splice(PredBB->end(), BB->getInstList());
if (!PredBB->hasName())
PredBB->takeName(BB);
if (P) {
if (DominatorTree *DT = P->getAnalysisIfAvailable<DominatorTree>()) {
if (DomTreeNode *DTN = DT->getNode(BB)) {
DomTreeNode *PredDTN = DT->getNode(PredBB);
SmallVector<DomTreeNode*, 8> Children(DTN->begin(), DTN->end());
for (SmallVector<DomTreeNode*, 8>::iterator DI = Children.begin(),
DE = Children.end(); DI != DE; ++DI)
DT->changeImmediateDominator(*DI, PredDTN);
DT->eraseNode(BB);
}
if (LoopInfo *LI = P->getAnalysisIfAvailable<LoopInfo>())
LI->removeBlock(BB);
if (MemoryDependenceAnalysis *MD =
P->getAnalysisIfAvailable<MemoryDependenceAnalysis>())
MD->invalidateCachedPredecessors();
}
}
BB->eraseFromParent();
return true;
}
void llvm::ReplaceInstWithValue(BasicBlock::InstListType &BIL,
BasicBlock::iterator &BI, Value *V) {
Instruction &I = *BI;
I.replaceAllUsesWith(V);
if (I.hasName() && !V->hasName())
V->takeName(&I);
BI = BIL.erase(BI);
}
void llvm::ReplaceInstWithInst(BasicBlock::InstListType &BIL,
BasicBlock::iterator &BI, Instruction *I) {
assert(I->getParent() == 0 &&
"ReplaceInstWithInst: Instruction already inserted into basic block!");
BasicBlock::iterator New = BIL.insert(BI, I);
ReplaceInstWithValue(BIL, BI, I);
BI = New;
}
void llvm::ReplaceInstWithInst(Instruction *From, Instruction *To) {
BasicBlock::iterator BI(From);
ReplaceInstWithInst(From->getParent()->getInstList(), BI, To);
}
unsigned llvm::GetSuccessorNumber(BasicBlock *BB, BasicBlock *Succ) {
TerminatorInst *Term = BB->getTerminator();
#ifndef NDEBUG
unsigned e = Term->getNumSuccessors();
#endif
for (unsigned i = 0; ; ++i) {
assert(i != e && "Didn't find edge?");
if (Term->getSuccessor(i) == Succ)
return i;
}
}
BasicBlock *llvm::SplitEdge(BasicBlock *BB, BasicBlock *Succ, Pass *P) {
unsigned SuccNum = GetSuccessorNumber(BB, Succ);
TerminatorInst *LatchTerm = BB->getTerminator();
if (SplitCriticalEdge(LatchTerm, SuccNum, P))
return LatchTerm->getSuccessor(SuccNum);
BasicBlock::iterator SplitPoint;
if (BasicBlock *SP = Succ->getSinglePredecessor()) {
assert(SP == BB && "CFG broken");
SP = NULL;
return SplitBlock(Succ, Succ->begin(), P);
}
assert(BB->getTerminator()->getNumSuccessors() == 1 &&
"Should have a single succ!");
return SplitBlock(BB, BB->getTerminator(), P);
}
BasicBlock *llvm::SplitBlock(BasicBlock *Old, Instruction *SplitPt, Pass *P) {
BasicBlock::iterator SplitIt = SplitPt;
while (isa<PHINode>(SplitIt) || isa<LandingPadInst>(SplitIt))
++SplitIt;
BasicBlock *New = Old->splitBasicBlock(SplitIt, Old->getName()+".split");
if (LoopInfo *LI = P->getAnalysisIfAvailable<LoopInfo>())
if (Loop *L = LI->getLoopFor(Old))
L->addBasicBlockToLoop(New, LI->getBase());
if (DominatorTree *DT = P->getAnalysisIfAvailable<DominatorTree>()) {
if (DomTreeNode *OldNode = DT->getNode(Old)) {
std::vector<DomTreeNode *> Children;
for (DomTreeNode::iterator I = OldNode->begin(), E = OldNode->end();
I != E; ++I)
Children.push_back(*I);
DomTreeNode *NewNode = DT->addNewBlock(New,Old);
for (std::vector<DomTreeNode *>::iterator I = Children.begin(),
E = Children.end(); I != E; ++I)
DT->changeImmediateDominator(*I, NewNode);
}
}
return New;
}
static void UpdateAnalysisInformation(BasicBlock *OldBB, BasicBlock *NewBB,
ArrayRef<BasicBlock *> Preds,
Pass *P, bool &HasLoopExit) {
if (!P) return;
LoopInfo *LI = P->getAnalysisIfAvailable<LoopInfo>();
Loop *L = LI ? LI->getLoopFor(OldBB) : 0;
bool IsLoopEntry = !!L;
bool SplitMakesNewLoopHeader = false;
if (LI) {
bool PreserveLCSSA = P->mustPreserveAnalysisID(LCSSAID);
for (ArrayRef<BasicBlock*>::iterator
i = Preds.begin(), e = Preds.end(); i != e; ++i) {
BasicBlock *Pred = *i;
if (PreserveLCSSA)
if (Loop *PL = LI->getLoopFor(Pred))
if (!PL->contains(OldBB))
HasLoopExit = true;
if (!L) continue;
if (L->contains(Pred))
IsLoopEntry = false;
else
SplitMakesNewLoopHeader = true;
}
}
DominatorTree *DT = P->getAnalysisIfAvailable<DominatorTree>();
if (DT)
DT->splitBlock(NewBB);
if (!L) return;
if (IsLoopEntry) {
Loop *InnermostPredLoop = 0;
for (ArrayRef<BasicBlock*>::iterator
i = Preds.begin(), e = Preds.end(); i != e; ++i) {
BasicBlock *Pred = *i;
if (Loop *PredLoop = LI->getLoopFor(Pred)) {
while (PredLoop && !PredLoop->contains(OldBB))
PredLoop = PredLoop->getParentLoop();
if (PredLoop && PredLoop->contains(OldBB) &&
(!InnermostPredLoop ||
InnermostPredLoop->getLoopDepth() < PredLoop->getLoopDepth()))
InnermostPredLoop = PredLoop;
}
}
if (InnermostPredLoop)
InnermostPredLoop->addBasicBlockToLoop(NewBB, LI->getBase());
} else {
L->addBasicBlockToLoop(NewBB, LI->getBase());
if (SplitMakesNewLoopHeader)
L->moveToHeader(NewBB);
}
}
static void UpdatePHINodes(BasicBlock *OrigBB, BasicBlock *NewBB,
ArrayRef<BasicBlock*> Preds, BranchInst *BI,
Pass *P, bool HasLoopExit) {
AliasAnalysis *AA = P ? P->getAnalysisIfAvailable<AliasAnalysis>() : 0;
for (BasicBlock::iterator I = OrigBB->begin(); isa<PHINode>(I); ) {
PHINode *PN = cast<PHINode>(I++);
Value *InVal = 0;
if (!HasLoopExit) {
InVal = PN->getIncomingValueForBlock(Preds[0]);
for (unsigned i = 1, e = Preds.size(); i != e; ++i)
if (InVal != PN->getIncomingValueForBlock(Preds[i])) {
InVal = 0;
break;
}
}
if (InVal) {
for (unsigned i = 0, e = Preds.size(); i != e; ++i)
PN->removeIncomingValue(Preds[i], false);
} else {
PHINode *NewPHI =
PHINode::Create(PN->getType(), Preds.size(), PN->getName() + ".ph", BI);
if (AA) AA->copyValue(PN, NewPHI);
for (unsigned i = 0, e = Preds.size(); i != e; ++i) {
Value *V = PN->removeIncomingValue(Preds[i], false);
NewPHI->addIncoming(V, Preds[i]);
}
InVal = NewPHI;
}
PN->addIncoming(InVal, NewBB);
}
}
BasicBlock *llvm::SplitBlockPredecessors(BasicBlock *BB,
ArrayRef<BasicBlock*> Preds,
const char *Suffix, Pass *P) {
BasicBlock *NewBB = BasicBlock::Create(BB->getContext(), BB->getName()+Suffix,
BB->getParent(), BB);
BranchInst *BI = BranchInst::Create(BB, NewBB);
for (unsigned i = 0, e = Preds.size(); i != e; ++i) {
assert(!isa<IndirectBrInst>(Preds[i]->getTerminator()) &&
"Cannot split an edge from an IndirectBrInst");
Preds[i]->getTerminator()->replaceUsesOfWith(BB, NewBB);
}
if (Preds.size() == 0) {
for (BasicBlock::iterator I = BB->begin(); isa<PHINode>(I); ++I)
cast<PHINode>(I)->addIncoming(UndefValue::get(I->getType()), NewBB);
return NewBB;
}
bool HasLoopExit = false;
UpdateAnalysisInformation(BB, NewBB, Preds, P, HasLoopExit);
UpdatePHINodes(BB, NewBB, Preds, BI, P, HasLoopExit);
return NewBB;
}
void llvm::SplitLandingPadPredecessors(BasicBlock *OrigBB,
ArrayRef<BasicBlock*> Preds,
const char *Suffix1, const char *Suffix2,
Pass *P,
SmallVectorImpl<BasicBlock*> &NewBBs) {
assert(OrigBB->isLandingPad() && "Trying to split a non-landing pad!");
BasicBlock *NewBB1 = BasicBlock::Create(OrigBB->getContext(),
OrigBB->getName() + Suffix1,
OrigBB->getParent(), OrigBB);
NewBBs.push_back(NewBB1);
BranchInst *BI1 = BranchInst::Create(OrigBB, NewBB1);
for (unsigned i = 0, e = Preds.size(); i != e; ++i) {
assert(!isa<IndirectBrInst>(Preds[i]->getTerminator()) &&
"Cannot split an edge from an IndirectBrInst");
Preds[i]->getTerminator()->replaceUsesOfWith(OrigBB, NewBB1);
}
bool HasLoopExit = false;
UpdateAnalysisInformation(OrigBB, NewBB1, Preds, P, HasLoopExit);
UpdatePHINodes(OrigBB, NewBB1, Preds, BI1, P, HasLoopExit);
SmallVector<BasicBlock*, 8> NewBB2Preds;
for (pred_iterator i = pred_begin(OrigBB), e = pred_end(OrigBB);
i != e; ) {
BasicBlock *Pred = *i++;
if (Pred == NewBB1) continue;
assert(!isa<IndirectBrInst>(Pred->getTerminator()) &&
"Cannot split an edge from an IndirectBrInst");
NewBB2Preds.push_back(Pred);
e = pred_end(OrigBB);
}
BasicBlock *NewBB2 = 0;
if (!NewBB2Preds.empty()) {
NewBB2 = BasicBlock::Create(OrigBB->getContext(),
OrigBB->getName() + Suffix2,
OrigBB->getParent(), OrigBB);
NewBBs.push_back(NewBB2);
BranchInst *BI2 = BranchInst::Create(OrigBB, NewBB2);
for (SmallVectorImpl<BasicBlock*>::iterator
i = NewBB2Preds.begin(), e = NewBB2Preds.end(); i != e; ++i)
(*i)->getTerminator()->replaceUsesOfWith(OrigBB, NewBB2);
HasLoopExit = false;
UpdateAnalysisInformation(OrigBB, NewBB2, NewBB2Preds, P, HasLoopExit);
UpdatePHINodes(OrigBB, NewBB2, NewBB2Preds, BI2, P, HasLoopExit);
}
LandingPadInst *LPad = OrigBB->getLandingPadInst();
Instruction *Clone1 = LPad->clone();
Clone1->setName(Twine("lpad") + Suffix1);
NewBB1->getInstList().insert(NewBB1->getFirstInsertionPt(), Clone1);
if (NewBB2) {
Instruction *Clone2 = LPad->clone();
Clone2->setName(Twine("lpad") + Suffix2);
NewBB2->getInstList().insert(NewBB2->getFirstInsertionPt(), Clone2);
PHINode *PN = PHINode::Create(LPad->getType(), 2, "lpad.phi", LPad);
PN->addIncoming(Clone1, NewBB1);
PN->addIncoming(Clone2, NewBB2);
LPad->replaceAllUsesWith(PN);
LPad->eraseFromParent();
} else {
LPad->replaceAllUsesWith(Clone1);
LPad->eraseFromParent();
}
}
void llvm::FindFunctionBackedges(const Function &F,
SmallVectorImpl<std::pair<const BasicBlock*,const BasicBlock*> > &Result) {
const BasicBlock *BB = &F.getEntryBlock();
if (succ_begin(BB) == succ_end(BB))
return;
SmallPtrSet<const BasicBlock*, 8> Visited;
SmallVector<std::pair<const BasicBlock*, succ_const_iterator>, 8> VisitStack;
SmallPtrSet<const BasicBlock*, 8> InStack;
Visited.insert(BB);
VisitStack.push_back(std::make_pair(BB, succ_begin(BB)));
InStack.insert(BB);
do {
std::pair<const BasicBlock*, succ_const_iterator> &Top = VisitStack.back();
const BasicBlock *ParentBB = Top.first;
succ_const_iterator &I = Top.second;
bool FoundNew = false;
while (I != succ_end(ParentBB)) {
BB = *I++;
if (Visited.insert(BB)) {
FoundNew = true;
break;
}
if (InStack.count(BB))
Result.push_back(std::make_pair(ParentBB, BB));
}
if (FoundNew) {
InStack.insert(BB);
VisitStack.push_back(std::make_pair(BB, succ_begin(BB)));
} else {
InStack.erase(VisitStack.pop_back_val().first);
}
} while (!VisitStack.empty());
}
ReturnInst *llvm::FoldReturnIntoUncondBranch(ReturnInst *RI, BasicBlock *BB,
BasicBlock *Pred) {
Instruction *UncondBranch = Pred->getTerminator();
Instruction *NewRet = RI->clone();
Pred->getInstList().push_back(NewRet);
for (User::op_iterator i = NewRet->op_begin(), e = NewRet->op_end();
i != e; ++i) {
Value *V = *i;
Instruction *NewBC = 0;
if (BitCastInst *BCI = dyn_cast<BitCastInst>(V)) {
V = BCI->getOperand(0);
NewBC = BCI->clone();
Pred->getInstList().insert(NewRet, NewBC);
*i = NewBC;
}
if (PHINode *PN = dyn_cast<PHINode>(V)) {
if (PN->getParent() == BB) {
if (NewBC)
NewBC->setOperand(0, PN->getIncomingValueForBlock(Pred));
else
*i = PN->getIncomingValueForBlock(Pred);
}
}
}
BB->removePredecessor(Pred);
UncondBranch->eraseFromParent();
return cast<ReturnInst>(NewRet);
}
TerminatorInst *llvm::SplitBlockAndInsertIfThen(Instruction *Cmp,
bool Unreachable, MDNode *BranchWeights) {
Instruction *SplitBefore = Cmp->getNextNode();
BasicBlock *Head = SplitBefore->getParent();
BasicBlock *Tail = Head->splitBasicBlock(SplitBefore);
TerminatorInst *HeadOldTerm = Head->getTerminator();
LLVMContext &C = Head->getContext();
BasicBlock *ThenBlock = BasicBlock::Create(C, "", Head->getParent(), Tail);
TerminatorInst *CheckTerm;
if (Unreachable)
CheckTerm = new UnreachableInst(C, ThenBlock);
else
CheckTerm = BranchInst::Create(Tail, ThenBlock);
BranchInst *HeadNewTerm =
BranchInst::Create(ThenBlock, Tail, Cmp);
HeadNewTerm->setMetadata(LLVMContext::MD_prof, BranchWeights);
ReplaceInstWithInst(HeadOldTerm, HeadNewTerm);
return CheckTerm;
}