class BranchInst;
class CmpInst;
class Constant;
+class DominatorTree;
class Function;
class Instruction;
class IntrinsicInst;
TargetLibraryInfo *TLI;
LazyValueInfo *LVI;
AliasAnalysis *AA;
+ DominatorTree *DT;
std::unique_ptr<BlockFrequencyInfo> BFI;
std::unique_ptr<BranchProbabilityInfo> BPI;
bool HasProfileData = false;
// Glue for old PM.
bool runImpl(Function &F, TargetLibraryInfo *TLI_, LazyValueInfo *LVI_,
- AliasAnalysis *AA_, bool HasProfileData_,
+ AliasAnalysis *AA_, DominatorTree *DT_, bool HasProfileData_,
std::unique_ptr<BlockFrequencyInfo> BFI_,
std::unique_ptr<BranchProbabilityInfo> BPI_);
/// conditions and indirectbr addresses this might make dead if
/// DeleteDeadConditions is true.
bool ConstantFoldTerminator(BasicBlock *BB, bool DeleteDeadConditions = false,
- const TargetLibraryInfo *TLI = nullptr);
+ const TargetLibraryInfo *TLI = nullptr,
+ DominatorTree *DT = nullptr);
//===----------------------------------------------------------------------===//
// Local dead code elimination.
///
/// .. and delete the predecessor corresponding to the '1', this will attempt to
/// recursively fold the 'and' to 0.
-void RemovePredecessorAndSimplify(BasicBlock *BB, BasicBlock *Pred);
+void RemovePredecessorAndSimplify(BasicBlock *BB, BasicBlock *Pred,
+ DominatorTree *DT = nullptr);
/// BB is a block with one predecessor and its predecessor is known to have one
/// successor (BB!). Eliminate the edge between them, moving the instructions in
/// other than PHI nodes, potential debug intrinsics and the branch. If
/// possible, eliminate BB by rewriting all the predecessors to branch to the
/// successor block and return true. If we can't transform, return false.
-bool TryToSimplifyUncondBranchFromEmptyBlock(BasicBlock *BB);
+bool TryToSimplifyUncondBranchFromEmptyBlock(BasicBlock *BB,
+ DominatorTree *DT = nullptr);
/// Check for and eliminate duplicate PHI nodes in this block. This doesn't try
/// to be clever about PHI nodes which differ only in the order of the incoming
/// Insert an unreachable instruction before the specified
/// instruction, making it and the rest of the code in the block dead.
unsigned changeToUnreachable(Instruction *I, bool UseLLVMTrap,
- bool PreserveLCSSA = false);
+ bool PreserveLCSSA = false,
+ DominatorTree *DT = nullptr);
/// Convert the CallInst to InvokeInst with the specified unwind edge basic
/// block. This also splits the basic block where CI is located, because
///
/// \param BB Block whose terminator will be replaced. Its terminator must
/// have an unwind successor.
-void removeUnwindEdge(BasicBlock *BB);
+void removeUnwindEdge(BasicBlock *BB, DominatorTree *DT = nullptr);
/// Remove all blocks that can not be reached from the function's entry.
///
/// Returns true if any basic block was removed.
-bool removeUnreachableBlocks(Function &F, LazyValueInfo *LVI = nullptr);
+bool removeUnreachableBlocks(Function &F, LazyValueInfo *LVI = nullptr,
+ DominatorTree *DT = nullptr);
/// Combine the metadata of two instructions so that K can replace J
///
bool runOnFunction(Function &F) override;
void getAnalysisUsage(AnalysisUsage &AU) const override {
+ AU.addRequired<DominatorTreeWrapperPass>();
AU.addRequired<LazyValueInfoWrapperPass>();
AU.addPreserved<GlobalsAAWrapperPass>();
}
char CorrelatedValuePropagation::ID = 0;
INITIALIZE_PASS_BEGIN(CorrelatedValuePropagation, "correlated-propagation",
"Value Propagation", false, false)
+INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)
INITIALIZE_PASS_DEPENDENCY(LazyValueInfoWrapperPass)
INITIALIZE_PASS_END(CorrelatedValuePropagation, "correlated-propagation",
"Value Propagation", false, false)
bool runOnFunction(Function &F) override;
void getAnalysisUsage(AnalysisUsage &AU) const override {
- if (PrintLVIAfterJumpThreading)
- AU.addRequired<DominatorTreeWrapperPass>();
+ AU.addRequired<DominatorTreeWrapperPass>();
+ AU.addPreserved<DominatorTreeWrapperPass>();
AU.addRequired<AAResultsWrapperPass>();
AU.addRequired<LazyValueInfoWrapperPass>();
+ AU.addPreserved<LazyValueInfoWrapperPass>();
AU.addPreserved<GlobalsAAWrapperPass>();
AU.addRequired<TargetLibraryInfoWrapperPass>();
}
INITIALIZE_PASS_BEGIN(JumpThreading, "jump-threading",
"Jump Threading", false, false)
+INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)
INITIALIZE_PASS_DEPENDENCY(LazyValueInfoWrapperPass)
INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfoWrapperPass)
INITIALIZE_PASS_DEPENDENCY(AAResultsWrapperPass)
if (skipFunction(F))
return false;
auto TLI = &getAnalysis<TargetLibraryInfoWrapperPass>().getTLI();
+ // Get DT analysis before LVI. When LVI is initialized it conditionally adds
+ // DT if it's available.
+ auto DT = &getAnalysis<DominatorTreeWrapperPass>().getDomTree();
auto LVI = &getAnalysis<LazyValueInfoWrapperPass>().getLVI();
auto AA = &getAnalysis<AAResultsWrapperPass>().getAAResults();
std::unique_ptr<BlockFrequencyInfo> BFI;
BFI.reset(new BlockFrequencyInfo(F, *BPI, LI));
}
- bool Changed = Impl.runImpl(F, TLI, LVI, AA, HasProfileData, std::move(BFI),
- std::move(BPI));
+ bool Changed = Impl.runImpl(F, TLI, LVI, AA, DT, HasProfileData,
+ std::move(BFI), std::move(BPI));
if (PrintLVIAfterJumpThreading) {
dbgs() << "LVI for function '" << F.getName() << "':\n";
- LVI->printLVI(F, getAnalysis<DominatorTreeWrapperPass>().getDomTree(),
- dbgs());
+ LVI->printLVI(F, *DT, dbgs());
}
return Changed;
}
PreservedAnalyses JumpThreadingPass::run(Function &F,
FunctionAnalysisManager &AM) {
auto &TLI = AM.getResult<TargetLibraryAnalysis>(F);
+ // Get DT analysis before LVI. When LVI is initialized it conditionally adds
+ // DT if it's available.
+ auto &DT = AM.getResult<DominatorTreeAnalysis>(F);
auto &LVI = AM.getResult<LazyValueAnalysis>(F);
auto &AA = AM.getResult<AAManager>(F);
BFI.reset(new BlockFrequencyInfo(F, *BPI, LI));
}
- bool Changed = runImpl(F, &TLI, &LVI, &AA, HasProfileData, std::move(BFI),
- std::move(BPI));
+ bool Changed = runImpl(F, &TLI, &LVI, &AA, &DT, HasProfileData,
+ std::move(BFI), std::move(BPI));
if (!Changed)
return PreservedAnalyses::all();
PreservedAnalyses PA;
PA.preserve<GlobalsAA>();
+ PA.preserve<DominatorTreeAnalysis>();
+ PA.preserve<LazyValueAnalysis>();
return PA;
}
bool JumpThreadingPass::runImpl(Function &F, TargetLibraryInfo *TLI_,
LazyValueInfo *LVI_, AliasAnalysis *AA_,
- bool HasProfileData_,
+ DominatorTree *DT_, bool HasProfileData_,
std::unique_ptr<BlockFrequencyInfo> BFI_,
std::unique_ptr<BranchProbabilityInfo> BPI_) {
DEBUG(dbgs() << "Jump threading on function '" << F.getName() << "'\n");
TLI = TLI_;
LVI = LVI_;
AA = AA_;
+ DT = DT_;
BFI.reset();
BPI.reset();
// When profile data is available, we need to update edge weights after
// back edges. This works for normal cases but not for unreachable blocks as
// they may have cycle with no back edge.
bool EverChanged = false;
- EverChanged |= removeUnreachableBlocks(F, LVI);
-
+ EverChanged |= removeUnreachableBlocks(F, LVI, DT);
FindLoopHeaders(F);
bool Changed;
// awesome, but it allows us to use AssertingVH to prevent nasty
// dangling pointer issues within LazyValueInfo.
LVI->eraseBlock(BB);
- if (TryToSimplifyUncondBranchFromEmptyBlock(BB))
+ if (TryToSimplifyUncondBranchFromEmptyBlock(BB, DT))
Changed = true;
}
}
LoopHeaders.insert(BB);
LVI->eraseBlock(SinglePred);
- MergeBasicBlockIntoOnlyPred(BB);
+ MergeBasicBlockIntoOnlyPred(BB, DT);
// Now that BB is merged into SinglePred (i.e. SinglePred Code followed by
// BB code within one basic block `BB`), we need to invalidate the LVI
// successors to branch to. Let GetBestDestForJumpOnUndef decide.
if (isa<UndefValue>(Condition)) {
unsigned BestSucc = GetBestDestForJumpOnUndef(BB);
+ std::vector<DominatorTree::UpdateType> Updates;
// Fold the branch/switch.
TerminatorInst *BBTerm = BB->getTerminator();
for (unsigned i = 0, e = BBTerm->getNumSuccessors(); i != e; ++i) {
if (i == BestSucc) continue;
- BBTerm->getSuccessor(i)->removePredecessor(BB, true);
+ BasicBlock *Succ = BBTerm->getSuccessor(i);
+ Succ->removePredecessor(BB, true);
+ if (Succ == BB)
+ continue;
+ DominatorTree::UpdateType UT = {DominatorTree::Delete, BB, Succ};
+ // Make sure to remove a DT edge exactly once and not an edge to itself.
+ if (std::find(Updates.begin(), Updates.end(), UT) == Updates.end())
+ Updates.push_back(UT);
}
DEBUG(dbgs() << " In block '" << BB->getName()
<< "' folding undef terminator: " << *BBTerm << '\n');
BranchInst::Create(BBTerm->getSuccessor(BestSucc), BBTerm);
BBTerm->eraseFromParent();
+ DT->applyUpdates(Updates);
return true;
}
DEBUG(dbgs() << " In block '" << BB->getName()
<< "' folding terminator: " << *BB->getTerminator() << '\n');
++NumFolds;
- ConstantFoldTerminator(BB, true);
+ ConstantFoldTerminator(BB, true, nullptr, DT);
return true;
}
if (Ret != LazyValueInfo::Unknown) {
unsigned ToRemove = Ret == LazyValueInfo::True ? 1 : 0;
unsigned ToKeep = Ret == LazyValueInfo::True ? 0 : 1;
- CondBr->getSuccessor(ToRemove)->removePredecessor(BB, true);
+ BasicBlock *ToRemoveSucc = CondBr->getSuccessor(ToRemove);
+ ToRemoveSucc->removePredecessor(BB, true);
BranchInst::Create(CondBr->getSuccessor(ToKeep), CondBr);
CondBr->eraseFromParent();
+ if (BB != ToRemoveSucc)
+ DT->deleteEdge(BB, ToRemoveSucc);
if (CondCmp->use_empty())
CondCmp->eraseFromParent();
// We can safely replace *some* uses of the CondInst if it has
Optional<bool> Implication =
isImpliedCondition(PBI->getCondition(), Cond, DL, CondIsTrue);
if (Implication) {
- BI->getSuccessor(*Implication ? 1 : 0)->removePredecessor(BB);
+ BasicBlock *RemoveSucc = BI->getSuccessor(*Implication ? 1 : 0);
+ RemoveSucc->removePredecessor(BB);
BranchInst::Create(BI->getSuccessor(*Implication ? 0 : 1), BI);
BI->eraseFromParent();
+ if (BB != RemoveSucc)
+ DT->deleteEdge(BB, RemoveSucc);
return true;
}
CurrentBB = CurrentPred;
if (OnlyDest && OnlyDest != MultipleDestSentinel) {
if (PredWithKnownDest ==
(size_t)std::distance(pred_begin(BB), pred_end(BB))) {
+ std::vector<DominatorTree::UpdateType> Updates;
bool SeenFirstBranchToOnlyDest = false;
for (BasicBlock *SuccBB : successors(BB)) {
- if (SuccBB == OnlyDest && !SeenFirstBranchToOnlyDest)
+ if (SuccBB == OnlyDest && !SeenFirstBranchToOnlyDest) {
SeenFirstBranchToOnlyDest = true; // Don't modify the first branch.
- else
+ } else {
SuccBB->removePredecessor(BB, true); // This is unreachable successor.
+ if (SuccBB != OnlyDest && SuccBB != BB) {
+ DominatorTree::UpdateType UT = {DominatorTree::Delete, BB, SuccBB};
+ // Make sure to remove a DT edge exactly once.
+ if (std::find(Updates.begin(), Updates.end(), UT) == Updates.end())
+ Updates.push_back(UT);
+ }
+ }
}
// Finally update the terminator.
TerminatorInst *Term = BB->getTerminator();
BranchInst::Create(OnlyDest, Term);
Term->eraseFromParent();
+ DT->applyUpdates(Updates);
// If the condition is now dead due to the removal of the old terminator,
// erase it.
UsesToRename.push_back(&U);
}
-
// If there are no uses outside the block, we're done with this instruction.
if (UsesToRename.empty())
continue;
PredTerm->setSuccessor(i, NewBB);
}
+ DT->applyUpdates({{DominatorTree::Insert, NewBB, SuccBB},
+ {DominatorTree::Insert, PredBB, NewBB},
+ {DominatorTree::Delete, PredBB, BB}});
+
// At this point, the IR is fully up to date and consistent. Do a quick scan
// over the new instructions and zap any that are constants or dead. This
// frequently happens because of phi translation.
for (auto Pred : Preds)
PredBBFreq += BFI->getBlockFreq(Pred) * BPI->getEdgeProbability(Pred, BB);
- BasicBlock *PredBB = SplitBlockPredecessors(BB, Preds, Suffix);
+ BasicBlock *PredBB = SplitBlockPredecessors(BB, Preds, Suffix, DT);
// Set the block frequency of the newly created PredBB, which is the sum of
// frequencies of Preds.
BranchInst *OldPredBranch = dyn_cast<BranchInst>(PredBB->getTerminator());
if (!OldPredBranch || !OldPredBranch->isUnconditional()) {
- PredBB = SplitEdge(PredBB, BB);
+ PredBB = SplitEdge(PredBB, BB, DT);
OldPredBranch = cast<BranchInst>(PredBB->getTerminator());
}
// Remove the unconditional branch at the end of the PredBB block.
OldPredBranch->eraseFromParent();
+ if (BB != PredBB)
+ DT->deleteEdge(PredBB, BB);
++NumDupes;
return true;
// Move the unconditional branch to NewBB.
PredTerm->removeFromParent();
NewBB->getInstList().insert(NewBB->end(), PredTerm);
+ DT->insertEdge(NewBB, BB);
// Create a conditional branch and update PHI nodes.
BranchInst::Create(NewBB, BB, SI->getCondition(), Pred);
CondLHS->setIncomingValue(I, SI->getFalseValue());
// The select is now dead.
SI->eraseFromParent();
+ DT->insertEdge(Pred, NewBB);
// Update any other PHI nodes in BB.
for (BasicBlock::iterator BI = BB->begin();
PHINode *Phi = dyn_cast<PHINode>(BI); ++BI)
continue;
// Expand the select.
TerminatorInst *Term =
- SplitBlockAndInsertIfThen(SI->getCondition(), SI, false);
+ SplitBlockAndInsertIfThen(SI->getCondition(), SI, false, nullptr, DT);
PHINode *NewPN = PHINode::Create(SI->getType(), 2, "", SI);
NewPN->addIncoming(SI->getTrueValue(), Term->getParent());
NewPN->addIncoming(SI->getFalseValue(), BB);
if (!TrueDestIsSafe && !FalseDestIsSafe)
return false;
- BasicBlock *UnguardedBlock = TrueDestIsSafe ? TrueDest : FalseDest;
- BasicBlock *GuardedBlock = FalseDestIsSafe ? TrueDest : FalseDest;
+ BasicBlock *PredUnguardedBlock = TrueDestIsSafe ? TrueDest : FalseDest;
+ BasicBlock *PredGuardedBlock = FalseDestIsSafe ? TrueDest : FalseDest;
ValueToValueMapTy UnguardedMapping, GuardedMapping;
Instruction *AfterGuard = Guard->getNextNode();
return false;
// Duplicate all instructions before the guard and the guard itself to the
// branch where implication is not proved.
- GuardedBlock = DuplicateInstructionsInSplitBetween(
- BB, GuardedBlock, AfterGuard, GuardedMapping);
+ BasicBlock *GuardedBlock = DuplicateInstructionsInSplitBetween(
+ BB, PredGuardedBlock, AfterGuard, GuardedMapping);
assert(GuardedBlock && "Could not create the guarded block?");
// Duplicate all instructions before the guard in the unguarded branch.
// Since we have successfully duplicated the guarded block and this block
// has fewer instructions, we expect it to succeed.
- UnguardedBlock = DuplicateInstructionsInSplitBetween(BB, UnguardedBlock,
- Guard, UnguardedMapping);
+ BasicBlock *UnguardedBlock = DuplicateInstructionsInSplitBetween(
+ BB, PredUnguardedBlock, Guard, UnguardedMapping);
assert(UnguardedBlock && "Could not create the unguarded block?");
DEBUG(dbgs() << "Moved guard " << *Guard << " to block "
<< GuardedBlock->getName() << "\n");
+ // DuplicateInstructionsInSplitBetween inserts a new block, BB.split, between
+ // PredBB and BB. We need to perform two inserts and one delete in DT for each
+ // of the above calls.
+ DT->applyUpdates({// Guarded block split.
+ {DominatorTree::Delete, PredGuardedBlock, BB},
+ {DominatorTree::Insert, PredGuardedBlock, GuardedBlock},
+ {DominatorTree::Insert, GuardedBlock, BB},
+ // Unguarded block split.
+ {DominatorTree::Delete, PredUnguardedBlock, BB},
+ {DominatorTree::Insert, PredUnguardedBlock, UnguardedBlock},
+ {DominatorTree::Insert, UnguardedBlock, BB}});
// Some instructions before the guard may still have uses. For them, we need
// to create Phi nodes merging their copies in both guarded and unguarded
/// conditions and indirectbr addresses this might make dead if
/// DeleteDeadConditions is true.
bool llvm::ConstantFoldTerminator(BasicBlock *BB, bool DeleteDeadConditions,
- const TargetLibraryInfo *TLI) {
+ const TargetLibraryInfo *TLI,
+ DominatorTree *DT) {
TerminatorInst *T = BB->getTerminator();
IRBuilder<> Builder(T);
// Replace the conditional branch with an unconditional one.
Builder.CreateBr(Destination);
BI->eraseFromParent();
+ if (DT && OldDest != Destination && OldDest != BB)
+ DT->deleteEdge(BB, OldDest);
return true;
}
createBranchWeights(Weights));
}
// Remove this entry.
- DefaultDest->removePredecessor(SI->getParent());
+ BasicBlock *ParentBB = SI->getParent();
+ DefaultDest->removePredecessor(ParentBB);
i = SI->removeCase(i);
e = SI->case_end();
+ if (DT && DefaultDest != ParentBB) {
+ // DefaultDest may still be a successor of a non-default case.
+ if (none_of(successors(ParentBB), [DefaultDest](BasicBlock *S) {
+ return S == DefaultDest;
+ }))
+ DT->deleteEdge(ParentBB, DefaultDest);
+ }
continue;
}
// Insert the new branch.
Builder.CreateBr(TheOnlyDest);
BasicBlock *BB = SI->getParent();
+ BasicBlock *TheOnlyDestCheck = TheOnlyDest;
+ std::vector<DominatorTree::UpdateType> Updates;
// Remove entries from PHI nodes which we no longer branch to...
for (BasicBlock *Succ : SI->successors()) {
// Found case matching a constant operand?
- if (Succ == TheOnlyDest)
+ if (Succ == TheOnlyDest) {
TheOnlyDest = nullptr; // Don't modify the first branch to TheOnlyDest
- else
+ } else {
Succ->removePredecessor(BB);
+ if (DT && Succ != TheOnlyDestCheck && Succ != BB) {
+ DominatorTree::UpdateType UT = {DominatorTree::Delete, BB, Succ};
+ if (std::find(Updates.begin(), Updates.end(), UT) == Updates.end())
+ Updates.push_back(UT);
+ }
+ }
}
// Delete the old switch.
Value *Cond = SI->getCondition();
SI->eraseFromParent();
+ if (DT && !Updates.empty())
+ DT->applyUpdates(Updates);
if (DeleteDeadConditions)
RecursivelyDeleteTriviallyDeadInstructions(Cond, TLI);
return true;
if (BlockAddress *BA =
dyn_cast<BlockAddress>(IBI->getAddress()->stripPointerCasts())) {
BasicBlock *TheOnlyDest = BA->getBasicBlock();
+ BasicBlock *TheOnlyDestCheck = TheOnlyDest;
+ std::vector<DominatorTree::UpdateType> Updates;
// Insert the new branch.
Builder.CreateBr(TheOnlyDest);
for (unsigned i = 0, e = IBI->getNumDestinations(); i != e; ++i) {
- if (IBI->getDestination(i) == TheOnlyDest)
+ if (IBI->getDestination(i) == TheOnlyDest) {
TheOnlyDest = nullptr;
- else
- IBI->getDestination(i)->removePredecessor(IBI->getParent());
+ } else {
+ BasicBlock *ParentBB = IBI->getParent();
+ BasicBlock *DestBB = IBI->getDestination(i);
+ DestBB->removePredecessor(ParentBB);
+ if (DT && DestBB != TheOnlyDestCheck && DestBB != ParentBB) {
+ DominatorTree::UpdateType UT = {DominatorTree::Delete, ParentBB,
+ DestBB};
+ if (std::find(Updates.begin(), Updates.end(), UT) == Updates.end())
+ Updates.push_back(UT);
+ }
+ }
}
Value *Address = IBI->getAddress();
IBI->eraseFromParent();
+ if (DT && !Updates.empty())
+ DT->applyUpdates(Updates);
if (DeleteDeadConditions)
RecursivelyDeleteTriviallyDeadInstructions(Address, TLI);
///
/// .. and delete the predecessor corresponding to the '1', this will attempt to
/// recursively fold the and to 0.
-void llvm::RemovePredecessorAndSimplify(BasicBlock *BB, BasicBlock *Pred) {
+void llvm::RemovePredecessorAndSimplify(BasicBlock *BB, BasicBlock *Pred,
+ DominatorTree *DT) {
// This only adjusts blocks with PHI nodes.
if (!isa<PHINode>(BB->begin()))
return;
// of the block.
if (PhiIt != OldPhiIt) PhiIt = &BB->front();
}
+ if (DT && BB != Pred)
+ DT->deleteEdge(Pred, BB);
}
BasicBlock *PredBB = DestBB->getSinglePredecessor();
assert(PredBB && "Block doesn't have a single predecessor!");
+ // Collect all the edges that enter PredBB, discarding edges to itself and
+ // duplicates. These dominator edges will be redirected to DestBB.
+ std::vector<DominatorTree::UpdateType> Updates;
+ if (DT)
+ for (pred_iterator PI = pred_begin(PredBB), E = pred_end(PredBB); PI != E;
+ ++PI) {
+ if (*PI == PredBB)
+ continue;
+ DominatorTree::UpdateType UT = {DominatorTree::Delete, *PI, PredBB};
+ if (std::find(Updates.begin(), Updates.end(), UT) == Updates.end()) {
+ Updates.push_back(UT);
+ // DestBB cannot dominate itself.
+ if (*PI != DestBB)
+ Updates.push_back({DominatorTree::Insert, *PI, DestBB});
+ }
+ }
+
// Zap anything that took the address of DestBB. Not doing this will give the
// address an invalid value.
if (DestBB->hasAddressTaken()) {
// If the PredBB is the entry block of the function, move DestBB up to
// become the entry block after we erase PredBB.
- if (PredBB == &DestBB->getParent()->getEntryBlock())
+ bool ReplacedEntryBB = false;
+ if (PredBB == &DestBB->getParent()->getEntryBlock()) {
DestBB->moveAfter(PredBB);
+ ReplacedEntryBB = true;
+ }
- if (DT) {
- BasicBlock *PredBBIDom = DT->getNode(PredBB)->getIDom()->getBlock();
- DT->changeImmediateDominator(DestBB, PredBBIDom);
- DT->eraseNode(PredBB);
+ if (DT && !ReplacedEntryBB) {
+ Updates.push_back({DominatorTree::Delete, PredBB, DestBB});
+ DT->applyUpdates(Updates);
}
+
// Nuke BB.
PredBB->eraseFromParent();
+
+ // The entry block was removed and there is no external interface for the
+ // dominator tree to be notified of this change. In this corner-case we
+ // recalculate the entire tree.
+ if (DT && ReplacedEntryBB)
+ DT->recalculate(*(DestBB->getParent()));
}
/// CanMergeValues - Return true if we can choose one of these values to use
/// potential side-effect free intrinsics and the branch. If possible,
/// eliminate BB by rewriting all the predecessors to branch to the successor
/// block and return true. If we can't transform, return false.
-bool llvm::TryToSimplifyUncondBranchFromEmptyBlock(BasicBlock *BB) {
+bool llvm::TryToSimplifyUncondBranchFromEmptyBlock(BasicBlock *BB,
+ DominatorTree *DT) {
assert(BB != &BB->getParent()->getEntryBlock() &&
"TryToSimplifyUncondBranchFromEmptyBlock called on entry block!");
DEBUG(dbgs() << "Killing Trivial BB: \n" << *BB);
+ // Collect all the edges that enter BB, discarding edges to itself and
+ // duplicates. These dominator edges will be redirected to Succ.
+ std::vector<DominatorTree::UpdateType> Updates;
+ if (DT)
+ for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI) {
+ if (*PI == BB)
+ continue;
+ DominatorTree::UpdateType UT = {DominatorTree::Delete, *PI, BB};
+ if (std::find(Updates.begin(), Updates.end(), UT) == Updates.end()) {
+ Updates.push_back(UT);
+ Updates.push_back({DominatorTree::Insert, *PI, Succ});
+ }
+ }
+
if (isa<PHINode>(Succ->begin())) {
// If there is more than one pred of succ, and there are PHI nodes in
// the successor, then we need to add incoming edges for the PHI nodes
// add the metadata to the branch instructions in the predecessors.
unsigned LoopMDKind = BB->getContext().getMDKindID("llvm.loop");
Instruction *TI = BB->getTerminator();
- if (TI)
+ if (TI) {
if (MDNode *LoopMD = TI->getMetadata(LoopMDKind))
for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI) {
BasicBlock *Pred = *PI;
Pred->getTerminator()->setMetadata(LoopMDKind, LoopMD);
}
+ // Replace the terminator instruction with unreachable to ensure the CFG is
+ // consistent. This is necessary for dominance to be correctly calculated.
+ new UnreachableInst(BB->getContext(), TI);
+ TI->eraseFromParent();
+ }
// Everything that jumped to BB now goes to Succ.
BB->replaceAllUsesWith(Succ);
if (!Succ->hasName()) Succ->takeName(BB);
+
+ if (DT) {
+ Updates.push_back({DominatorTree::Delete, BB, Succ});
+ DT->applyUpdates(Updates);
+ }
+
BB->eraseFromParent(); // Delete the old basic block.
return true;
}
}
unsigned llvm::changeToUnreachable(Instruction *I, bool UseLLVMTrap,
- bool PreserveLCSSA) {
+ bool PreserveLCSSA, DominatorTree *DT) {
BasicBlock *BB = I->getParent();
+ std::vector<DominatorTree::UpdateType> Updates;
// Loop over all of the successors, removing BB's entry from any PHI
// nodes.
- for (BasicBlock *Successor : successors(BB))
+ for (BasicBlock *Successor : successors(BB)) {
Successor->removePredecessor(BB, PreserveLCSSA);
-
+ if (DT && BB != Successor) {
+ DominatorTree::UpdateType UT = {DominatorTree::Delete, BB, Successor};
+ if (std::find(Updates.begin(), Updates.end(), UT) == Updates.end())
+ Updates.push_back(UT);
+ }
+ }
// Insert a call to llvm.trap right before this. This turns the undefined
// behavior into a hard fail instead of falling through into random code.
if (UseLLVMTrap) {
BB->getInstList().erase(BBI++);
++NumInstrsRemoved;
}
+ if (DT && !Updates.empty())
+ DT->applyUpdates(Updates);
return NumInstrsRemoved;
}
/// changeToCall - Convert the specified invoke into a normal call.
-static void changeToCall(InvokeInst *II) {
+static void changeToCall(InvokeInst *II, DominatorTree *DT = nullptr) {
SmallVector<Value*, 8> Args(II->arg_begin(), II->arg_end());
SmallVector<OperandBundleDef, 1> OpBundles;
II->getOperandBundlesAsDefs(OpBundles);
II->replaceAllUsesWith(NewCall);
// Follow the call by a branch to the normal destination.
- BranchInst::Create(II->getNormalDest(), II);
+ BasicBlock *NormalDestBB = II->getNormalDest();
+ BranchInst::Create(NormalDestBB, II);
// Update PHI nodes in the unwind destination
- II->getUnwindDest()->removePredecessor(II->getParent());
+ BasicBlock *BB = II->getParent();
+ BasicBlock *UnwindDestBB = II->getUnwindDest();
+ UnwindDestBB->removePredecessor(BB);
II->eraseFromParent();
+ if (DT && BB != UnwindDestBB && NormalDestBB != UnwindDestBB)
+ DT->deleteEdge(BB, UnwindDestBB);
}
BasicBlock *llvm::changeToInvokeAndSplitBasicBlock(CallInst *CI,
}
static bool markAliveBlocks(Function &F,
- SmallPtrSetImpl<BasicBlock*> &Reachable) {
+ SmallPtrSetImpl<BasicBlock *> &Reachable,
+ DominatorTree *DT = nullptr) {
SmallVector<BasicBlock*, 128> Worklist;
BasicBlock *BB = &F.front();
if (II->getIntrinsicID() == Intrinsic::assume) {
if (match(II->getArgOperand(0), m_CombineOr(m_Zero(), m_Undef()))) {
// Don't insert a call to llvm.trap right before the unreachable.
- changeToUnreachable(II, false);
+ changeToUnreachable(II, false, false, DT);
Changed = true;
break;
}
// still be useful for widening.
if (match(II->getArgOperand(0), m_Zero()))
if (!isa<UnreachableInst>(II->getNextNode())) {
- changeToUnreachable(II->getNextNode(), /*UseLLVMTrap=*/ false);
+ changeToUnreachable(II->getNextNode(), /*UseLLVMTrap=*/false,
+ false, DT);
Changed = true;
break;
}
if (auto *CI = dyn_cast<CallInst>(&I)) {
Value *Callee = CI->getCalledValue();
if (isa<ConstantPointerNull>(Callee) || isa<UndefValue>(Callee)) {
- changeToUnreachable(CI, /*UseLLVMTrap=*/false);
+ changeToUnreachable(CI, /*UseLLVMTrap=*/false, false, DT);
Changed = true;
break;
}
// though.
if (!isa<UnreachableInst>(CI->getNextNode())) {
// Don't insert a call to llvm.trap right before the unreachable.
- changeToUnreachable(CI->getNextNode(), false);
+ changeToUnreachable(CI->getNextNode(), false, false, DT);
Changed = true;
}
break;
if (isa<UndefValue>(Ptr) ||
(isa<ConstantPointerNull>(Ptr) &&
SI->getPointerAddressSpace() == 0)) {
- changeToUnreachable(SI, true);
+ changeToUnreachable(SI, true, false, DT);
Changed = true;
break;
}
// Turn invokes that call 'nounwind' functions into ordinary calls.
Value *Callee = II->getCalledValue();
if (isa<ConstantPointerNull>(Callee) || isa<UndefValue>(Callee)) {
- changeToUnreachable(II, true);
+ changeToUnreachable(II, true, false, DT);
Changed = true;
} else if (II->doesNotThrow() && canSimplifyInvokeNoUnwind(&F)) {
if (II->use_empty() && II->onlyReadsMemory()) {
// jump to the normal destination branch.
+ BasicBlock *UnwindDestBB = II->getUnwindDest();
BranchInst::Create(II->getNormalDest(), II);
- II->getUnwindDest()->removePredecessor(II->getParent());
+ UnwindDestBB->removePredecessor(II->getParent());
II->eraseFromParent();
+ if (DT && BB != UnwindDestBB)
+ DT->deleteEdge(BB, UnwindDestBB);
} else
- changeToCall(II);
+ changeToCall(II, DT);
Changed = true;
}
} else if (auto *CatchSwitch = dyn_cast<CatchSwitchInst>(Terminator)) {
}
}
- Changed |= ConstantFoldTerminator(BB, true);
+ Changed |= ConstantFoldTerminator(BB, true, nullptr, DT);
for (BasicBlock *Successor : successors(BB))
if (Reachable.insert(Successor).second)
Worklist.push_back(Successor);
return Changed;
}
-void llvm::removeUnwindEdge(BasicBlock *BB) {
+void llvm::removeUnwindEdge(BasicBlock *BB, DominatorTree *DT) {
TerminatorInst *TI = BB->getTerminator();
if (auto *II = dyn_cast<InvokeInst>(TI)) {
- changeToCall(II);
+ changeToCall(II, DT);
return;
}
UnwindDest->removePredecessor(BB);
TI->replaceAllUsesWith(NewTI);
TI->eraseFromParent();
+ if (DT && BB != UnwindDest)
+ DT->deleteEdge(BB, UnwindDest);
}
/// removeUnreachableBlocks - Remove blocks that are not reachable, even
/// if they are in a dead cycle. Return true if a change was made, false
/// otherwise. If `LVI` is passed, this function preserves LazyValueInfo
/// after modifying the CFG.
-bool llvm::removeUnreachableBlocks(Function &F, LazyValueInfo *LVI) {
+bool llvm::removeUnreachableBlocks(Function &F, LazyValueInfo *LVI,
+ DominatorTree *DT) {
SmallPtrSet<BasicBlock*, 16> Reachable;
- bool Changed = markAliveBlocks(F, Reachable);
+ bool Changed = markAliveBlocks(F, Reachable, DT);
+ std::vector<DominatorTree::UpdateType> Updates;
// If there are unreachable blocks in the CFG...
if (Reachable.size() == F.size())
assert(Reachable.size() < F.size());
NumRemoved += F.size()-Reachable.size();
+ SmallPtrSet<TerminatorInst *, 4> TIRemoved;
+
// Loop over all of the basic blocks that are not reachable, dropping all of
// their internal references...
for (Function::iterator BB = ++F.begin(), E = F.end(); BB != E; ++BB) {
continue;
for (BasicBlock *Successor : successors(&*BB))
- if (Reachable.count(Successor))
+ if (Reachable.count(Successor)) {
Successor->removePredecessor(&*BB);
+ if (DT && &*BB != Successor) {
+ DominatorTree::UpdateType UT = {DominatorTree::Delete, &*BB,
+ Successor};
+ if (std::find(Updates.begin(), Updates.end(), UT) == Updates.end())
+ Updates.push_back(UT);
+ }
+ }
+
if (LVI)
LVI->eraseBlock(&*BB);
+
+ TerminatorInst *TI = BB->getTerminator();
+ TIRemoved.insert(TI);
+ new UnreachableInst(BB->getContext(), TI);
+
BB->dropAllReferences();
}
+ // Remove all the terminator instructions after dropping all references. This
+ // keeps the state of the CFG consistent and prevents asserts from circular
+ // use counts in groups of unreachable basic blocks.
+ for (TerminatorInst *TI : TIRemoved)
+ TI->eraseFromParent();
+
+ if (DT && !Updates.empty())
+ DT->applyUpdates(Updates);
+
for (Function::iterator I = ++F.begin(); I != F.end();)
if (!Reachable.count(&*I))
I = F.getBasicBlockList().erase(I);
; CHECK-NEXT: ; LatticeVal for: 'i32 %a' is: overdefined
; CHECK-NEXT: ; LatticeVal for: 'i32 %length' is: overdefined
; CHECK-NEXT: ; LatticeVal for: ' %iv = phi i32 [ 0, %entry ], [ %iv.next, %backedge ]' in BB: '%backedge' is: constantrange<0, 400>
+; CHECK-NEXT: ; LatticeVal for: ' %iv = phi i32 [ 0, %entry ], [ %iv.next, %backedge ]' in BB: '%exit' is: constantrange<399, 400>
; CHECK-NEXT: %iv = phi i32 [ 0, %entry ], [ %iv.next, %backedge ]
; CHECK-NEXT: ; LatticeVal for: ' %iv.next = add nsw i32 %iv, 1' in BB: '%backedge' is: constantrange<1, 401>
+; CHECK-NEXT: ; LatticeVal for: ' %iv.next = add nsw i32 %iv, 1' in BB: '%exit' is: constantrange<400, 401>
; CHECK-NEXT: %iv.next = add nsw i32 %iv, 1
; CHECK-NEXT: ; LatticeVal for: ' %cont = icmp slt i32 %iv.next, 400' in BB: '%backedge' is: overdefined
+; CHECK-NEXT: ; LatticeVal for: ' %cont = icmp slt i32 %iv.next, 400' in BB: '%exit' is: constantrange<0, -1>
; CHECK-NEXT: %cont = icmp slt i32 %iv.next, 400
; CHECK-NOT: loop
loop:
projects / llvm / commitdiff