BasicBlockUtils.cpp [plain text]
#include "llvm/Transforms/Utils/BasicBlockUtils.h"
#include "llvm/Function.h"
#include "llvm/Instructions.h"
#include "llvm/IntrinsicInst.h"
#include "llvm/Constant.h"
#include "llvm/Type.h"
#include "llvm/Analysis/AliasAnalysis.h"
#include "llvm/Analysis/Dominators.h"
#include "llvm/Analysis/LoopInfo.h"
#include "llvm/Analysis/MemoryDependenceAnalysis.h"
#include "llvm/Target/TargetData.h"
#include "llvm/Transforms/Utils/Local.h"
#include "llvm/Transforms/Scalar.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/ValueHandle.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) {
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);
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();
PredBB->getInstList().splice(PredBB->end(), BB->getInstList());
BB->replaceAllUsesWith(PredBB);
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;
}
return 0;
}
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))
++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>()) {
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;
}
BasicBlock *llvm::SplitBlockPredecessors(BasicBlock *BB,
BasicBlock *const *Preds,
unsigned NumPreds, const char *Suffix,
Pass *P) {
BasicBlock *NewBB = BasicBlock::Create(BB->getContext(), BB->getName()+Suffix,
BB->getParent(), BB);
BranchInst *BI = BranchInst::Create(BB, NewBB);
LoopInfo *LI = P ? P->getAnalysisIfAvailable<LoopInfo>() : 0;
Loop *L = LI ? LI->getLoopFor(BB) : 0;
bool PreserveLCSSA = P->mustPreserveAnalysisID(LCSSAID);
bool HasLoopExit = false;
bool IsLoopEntry = !!L;
bool SplitMakesNewLoopHeader = false;
for (unsigned i = 0; i != NumPreds; ++i) {
assert(!isa<IndirectBrInst>(Preds[i]->getTerminator()) &&
"Cannot split an edge from an IndirectBrInst");
Preds[i]->getTerminator()->replaceUsesOfWith(BB, NewBB);
if (LI) {
if (PreserveLCSSA)
if (Loop *PL = LI->getLoopFor(Preds[i]))
if (!PL->contains(BB))
HasLoopExit = true;
if (L) {
if (L->contains(Preds[i]))
IsLoopEntry = false;
else
SplitMakesNewLoopHeader = true;
}
}
}
DominatorTree *DT = P ? P->getAnalysisIfAvailable<DominatorTree>() : 0;
if (DT)
DT->splitBlock(NewBB);
if (NumPreds == 0) {
for (BasicBlock::iterator I = BB->begin(); isa<PHINode>(I); ++I)
cast<PHINode>(I)->addIncoming(UndefValue::get(I->getType()), NewBB);
return NewBB;
}
AliasAnalysis *AA = P ? P->getAnalysisIfAvailable<AliasAnalysis>() : 0;
if (L) {
if (IsLoopEntry) {
Loop *InnermostPredLoop = 0;
for (unsigned i = 0; i != NumPreds; ++i)
if (Loop *PredLoop = LI->getLoopFor(Preds[i])) {
while (PredLoop && !PredLoop->contains(BB))
PredLoop = PredLoop->getParentLoop();
if (PredLoop &&
PredLoop->contains(BB) &&
(!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);
}
}
for (BasicBlock::iterator I = BB->begin(); isa<PHINode>(I); ) {
PHINode *PN = cast<PHINode>(I++);
Value *InVal = 0;
if (!HasLoopExit) {
InVal = PN->getIncomingValueForBlock(Preds[0]);
for (unsigned i = 1; i != NumPreds; ++i)
if (InVal != PN->getIncomingValueForBlock(Preds[i])) {
InVal = 0;
break;
}
}
if (InVal) {
for (unsigned i = 0; i != NumPreds; ++i)
PN->removeIncomingValue(Preds[i], false);
} else {
PHINode *NewPHI =
PHINode::Create(PN->getType(), NumPreds, PN->getName()+".ph", BI);
if (AA) AA->copyValue(PN, NewPHI);
for (unsigned i = 0; i != NumPreds; ++i) {
Value *V = PN->removeIncomingValue(Preds[i], false);
NewPHI->addIncoming(V, Preds[i]);
}
InVal = NewPHI;
}
PN->addIncoming(InVal, NewBB);
}
return NewBB;
}
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)
if (PHINode *PN = dyn_cast<PHINode>(*i))
if (PN->getParent() == BB)
*i = PN->getIncomingValueForBlock(Pred);
BB->removePredecessor(Pred);
UncondBranch->eraseFromParent();
return cast<ReturnInst>(NewRet);
}
DebugLoc llvm::GetFirstDebugLocInBasicBlock(const BasicBlock *BB) {
if (const Instruction *I = BB->getFirstNonPHI())
return I->getDebugLoc();
return DebugLoc();
}