#include "llvm/Analysis/Dominators.h"
#include "llvm/Support/CFG.h"
#include "llvm/Support/Compiler.h"
+#include "llvm/Support/Debug.h"
#include "llvm/ADT/DepthFirstIterator.h"
-#include "llvm/ADT/SetOperations.h"
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/Analysis/DominatorInternals.h"
+#include "llvm/Assembly/Writer.h"
#include "llvm/Instructions.h"
#include "llvm/Support/raw_ostream.h"
+#include "llvm/Support/CommandLine.h"
#include <algorithm>
using namespace llvm;
+// Always verify dominfo if expensive checking is enabled.
+#ifdef XDEBUG
+static bool VerifyDomInfo = true;
+#else
+static bool VerifyDomInfo = false;
+#endif
+static cl::opt<bool,true>
+VerifyDomInfoX("verify-dom-info", cl::location(VerifyDomInfo),
+ cl::desc("Verify dominator info (time consuming)"));
+
//===----------------------------------------------------------------------===//
// DominatorTree Implementation
//===----------------------------------------------------------------------===//
//
// Provide public access to DominatorTree information. Implementation details
-// can be found in DominatorCalculation.h.
+// can be found in DominatorInternals.h.
//
//===----------------------------------------------------------------------===//
-TEMPLATE_INSTANTIATION(class DomTreeNodeBase<BasicBlock>);
-TEMPLATE_INSTANTIATION(class DominatorTreeBase<BasicBlock>);
+TEMPLATE_INSTANTIATION(class llvm::DomTreeNodeBase<BasicBlock>);
+TEMPLATE_INSTANTIATION(class llvm::DominatorTreeBase<BasicBlock>);
char DominatorTree::ID = 0;
-static RegisterPass<DominatorTree>
-E("domtree", "Dominator Tree Construction", true, true);
+INITIALIZE_PASS(DominatorTree, "domtree",
+ "Dominator Tree Construction", true, true)
bool DominatorTree::runOnFunction(Function &F) {
DT->recalculate(F);
return false;
}
-void DominatorTree::print(raw_ostream &OS, const Module *) const {
- DT->print(OS);
-}
-
-// dominates - Return true if A dominates a use in B. This performs the
-// special checks necessary if A and B are in the same basic block.
-bool DominatorTree::dominates(const Instruction *A, const Instruction *B) const{
- const BasicBlock *BBA = A->getParent(), *BBB = B->getParent();
-
- // If A is an invoke instruction, its value is only available in this normal
- // successor block.
- if (const InvokeInst *II = dyn_cast<InvokeInst>(A))
- BBA = II->getNormalDest();
-
- if (BBA != BBB) return dominates(BBA, BBB);
-
- // It is not possible to determine dominance between two PHI nodes
- // based on their ordering.
- if (isa<PHINode>(A) && isa<PHINode>(B))
- return false;
-
- // Loop through the basic block until we find A or B.
- BasicBlock::const_iterator I = BBA->begin();
- for (; &*I != A && &*I != B; ++I)
- /*empty*/;
-
- return &*I == A;
-}
+void DominatorTree::verifyAnalysis() const {
+ if (!VerifyDomInfo) return;
+ Function &F = *getRoot()->getParent();
-
-//===----------------------------------------------------------------------===//
-// DominanceFrontier Implementation
-//===----------------------------------------------------------------------===//
-
-char DominanceFrontier::ID = 0;
-static RegisterPass<DominanceFrontier>
-G("domfrontier", "Dominance Frontier Construction", true, true);
-
-// NewBB is split and now it has one successor. Update dominace frontier to
-// reflect this change.
-void DominanceFrontier::splitBlock(BasicBlock *NewBB) {
- assert(NewBB->getTerminator()->getNumSuccessors() == 1
- && "NewBB should have a single successor!");
- BasicBlock *NewBBSucc = NewBB->getTerminator()->getSuccessor(0);
-
- SmallVector<BasicBlock*, 8> PredBlocks;
- for (pred_iterator PI = pred_begin(NewBB), PE = pred_end(NewBB);
- PI != PE; ++PI)
- PredBlocks.push_back(*PI);
-
- if (PredBlocks.empty())
- // If NewBB does not have any predecessors then it is a entry block.
- // In this case, NewBB and its successor NewBBSucc dominates all
- // other blocks.
- return;
-
- // NewBBSucc inherits original NewBB frontier.
- DominanceFrontier::iterator NewBBI = find(NewBB);
- if (NewBBI != end()) {
- DominanceFrontier::DomSetType NewBBSet = NewBBI->second;
- DominanceFrontier::DomSetType NewBBSuccSet;
- NewBBSuccSet.insert(NewBBSet.begin(), NewBBSet.end());
- addBasicBlock(NewBBSucc, NewBBSuccSet);
+ DominatorTree OtherDT;
+ OtherDT.getBase().recalculate(F);
+ if (compare(OtherDT)) {
+ errs() << "DominatorTree is not up to date!\nComputed:\n";
+ print(errs());
+ errs() << "\nActual:\n";
+ OtherDT.print(errs());
+ abort();
}
+}
- // If NewBB dominates NewBBSucc, then DF(NewBB) is now going to be the
- // DF(PredBlocks[0]) without the stuff that the new block does not dominate
- // a predecessor of.
- DominatorTree &DT = getAnalysis<DominatorTree>();
- if (DT.dominates(NewBB, NewBBSucc)) {
- DominanceFrontier::iterator DFI = find(PredBlocks[0]);
- if (DFI != end()) {
- DominanceFrontier::DomSetType Set = DFI->second;
- // Filter out stuff in Set that we do not dominate a predecessor of.
- for (DominanceFrontier::DomSetType::iterator SetI = Set.begin(),
- E = Set.end(); SetI != E;) {
- bool DominatesPred = false;
- for (pred_iterator PI = pred_begin(*SetI), E = pred_end(*SetI);
- PI != E; ++PI)
- if (DT.dominates(NewBB, *PI))
- DominatesPred = true;
- if (!DominatesPred)
- Set.erase(SetI++);
- else
- ++SetI;
- }
-
- if (NewBBI != end()) {
- for (DominanceFrontier::DomSetType::iterator SetI = Set.begin(),
- E = Set.end(); SetI != E; ++SetI) {
- BasicBlock *SB = *SetI;
- addToFrontier(NewBBI, SB);
- }
- } else
- addBasicBlock(NewBB, Set);
- }
-
- } else {
- // DF(NewBB) is {NewBBSucc} because NewBB does not strictly dominate
- // NewBBSucc, but it does dominate itself (and there is an edge (NewBB ->
- // NewBBSucc)). NewBBSucc is the single successor of NewBB.
- DominanceFrontier::DomSetType NewDFSet;
- NewDFSet.insert(NewBBSucc);
- addBasicBlock(NewBB, NewDFSet);
- }
-
- // Now we must loop over all of the dominance frontiers in the function,
- // replacing occurrences of NewBBSucc with NewBB in some cases. All
- // blocks that dominate a block in PredBlocks and contained NewBBSucc in
- // their dominance frontier must be updated to contain NewBB instead.
- //
- for (Function::iterator FI = NewBB->getParent()->begin(),
- FE = NewBB->getParent()->end(); FI != FE; ++FI) {
- DominanceFrontier::iterator DFI = find(FI);
- if (DFI == end()) continue; // unreachable block.
-
- // Only consider nodes that have NewBBSucc in their dominator frontier.
- if (!DFI->second.count(NewBBSucc)) continue;
+void DominatorTree::print(raw_ostream &OS, const Module *) const {
+ DT->print(OS);
+}
- // Verify whether this block dominates a block in predblocks. If not, do
- // not update it.
- bool BlockDominatesAny = false;
- for (SmallVectorImpl<BasicBlock*>::const_iterator BI = PredBlocks.begin(),
- BE = PredBlocks.end(); BI != BE; ++BI) {
- if (DT.dominates(FI, *BI)) {
- BlockDominatesAny = true;
- break;
- }
- }
+// dominates - Return true if Def dominates a use in User. This performs
+// the special checks necessary if Def and User are in the same basic block.
+// Note that Def doesn't dominate a use in Def itself!
+bool DominatorTree::dominates(const Instruction *Def,
+ const Instruction *User) const {
+ const BasicBlock *UseBB = User->getParent();
+ const BasicBlock *DefBB = Def->getParent();
- // If NewBBSucc should not stay in our dominator frontier, remove it.
- // We remove it unless there is a predecessor of NewBBSucc that we
- // dominate, but we don't strictly dominate NewBBSucc.
- bool ShouldRemove = true;
- if ((BasicBlock*)FI == NewBBSucc || !DT.dominates(FI, NewBBSucc)) {
- // Okay, we know that PredDom does not strictly dominate NewBBSucc.
- // Check to see if it dominates any predecessors of NewBBSucc.
- for (pred_iterator PI = pred_begin(NewBBSucc),
- E = pred_end(NewBBSucc); PI != E; ++PI)
- if (DT.dominates(FI, *PI)) {
- ShouldRemove = false;
- break;
- }
- }
-
- if (ShouldRemove)
- removeFromFrontier(DFI, NewBBSucc);
- if (BlockDominatesAny && (&*FI == NewBB || !DT.dominates(FI, NewBB)))
- addToFrontier(DFI, NewBB);
- }
-}
+ // Any unreachable use is dominated, even if Def == User.
+ if (!isReachableFromEntry(UseBB))
+ return true;
-namespace {
- class DFCalculateWorkObject {
- public:
- DFCalculateWorkObject(BasicBlock *B, BasicBlock *P,
- const DomTreeNode *N,
- const DomTreeNode *PN)
- : currentBB(B), parentBB(P), Node(N), parentNode(PN) {}
- BasicBlock *currentBB;
- BasicBlock *parentBB;
- const DomTreeNode *Node;
- const DomTreeNode *parentNode;
- };
-}
+ // Unreachable definitions don't dominate anything.
+ if (!isReachableFromEntry(DefBB))
+ return false;
-const DominanceFrontier::DomSetType &
-DominanceFrontier::calculate(const DominatorTree &DT,
- const DomTreeNode *Node) {
- BasicBlock *BB = Node->getBlock();
- DomSetType *Result = NULL;
+ // An instruction doesn't dominate a use in itself.
+ if (Def == User)
+ return false;
- std::vector<DFCalculateWorkObject> workList;
- SmallPtrSet<BasicBlock *, 32> visited;
+ // The value defined by an invoke dominates an instruction only if
+ // it dominates every instruction in UseBB.
+ // A PHI is dominated only if the instruction dominates every possible use
+ // in the UseBB.
+ if (isa<InvokeInst>(Def) || isa<PHINode>(User))
+ return dominates(Def, UseBB);
- workList.push_back(DFCalculateWorkObject(BB, NULL, Node, NULL));
- do {
- DFCalculateWorkObject *currentW = &workList.back();
- assert (currentW && "Missing work object.");
+ if (DefBB != UseBB)
+ return dominates(DefBB, UseBB);
- BasicBlock *currentBB = currentW->currentBB;
- BasicBlock *parentBB = currentW->parentBB;
- const DomTreeNode *currentNode = currentW->Node;
- const DomTreeNode *parentNode = currentW->parentNode;
- assert (currentBB && "Invalid work object. Missing current Basic Block");
- assert (currentNode && "Invalid work object. Missing current Node");
- DomSetType &S = Frontiers[currentBB];
+ // Loop through the basic block until we find Def or User.
+ BasicBlock::const_iterator I = DefBB->begin();
+ for (; &*I != Def && &*I != User; ++I)
+ /*empty*/;
- // Visit each block only once.
- if (visited.count(currentBB) == 0) {
- visited.insert(currentBB);
+ return &*I == Def;
+}
- // Loop over CFG successors to calculate DFlocal[currentNode]
- for (succ_iterator SI = succ_begin(currentBB), SE = succ_end(currentBB);
- SI != SE; ++SI) {
- // Does Node immediately dominate this successor?
- if (DT[*SI]->getIDom() != currentNode)
- S.insert(*SI);
- }
- }
+// true if Def would dominate a use in any instruction in UseBB.
+// note that dominates(Def, Def->getParent()) is false.
+bool DominatorTree::dominates(const Instruction *Def,
+ const BasicBlock *UseBB) const {
+ const BasicBlock *DefBB = Def->getParent();
- // At this point, S is DFlocal. Now we union in DFup's of our children...
- // Loop through and visit the nodes that Node immediately dominates (Node's
- // children in the IDomTree)
- bool visitChild = false;
- for (DomTreeNode::const_iterator NI = currentNode->begin(),
- NE = currentNode->end(); NI != NE; ++NI) {
- DomTreeNode *IDominee = *NI;
- BasicBlock *childBB = IDominee->getBlock();
- if (visited.count(childBB) == 0) {
- workList.push_back(DFCalculateWorkObject(childBB, currentBB,
- IDominee, currentNode));
- visitChild = true;
- }
- }
+ // Any unreachable use is dominated, even if DefBB == UseBB.
+ if (!isReachableFromEntry(UseBB))
+ return true;
- // If all children are visited or there is any child then pop this block
- // from the workList.
- if (!visitChild) {
+ // Unreachable definitions don't dominate anything.
+ if (!isReachableFromEntry(DefBB))
+ return false;
- if (!parentBB) {
- Result = &S;
- break;
- }
+ if (DefBB == UseBB)
+ return false;
- DomSetType::const_iterator CDFI = S.begin(), CDFE = S.end();
- DomSetType &parentSet = Frontiers[parentBB];
- for (; CDFI != CDFE; ++CDFI) {
- if (!DT.properlyDominates(parentNode, DT[*CDFI]))
- parentSet.insert(*CDFI);
- }
- workList.pop_back();
- }
+ const InvokeInst *II = dyn_cast<InvokeInst>(Def);
+ if (!II)
+ return dominates(DefBB, UseBB);
- } while (!workList.empty());
+ // Invoke results are only usable in the normal destination, not in the
+ // exceptional destination.
+ BasicBlock *NormalDest = II->getNormalDest();
+ if (!dominates(NormalDest, UseBB))
+ return false;
- return *Result;
-}
+ // Simple case: if the normal destination has a single predecessor, the
+ // fact that it dominates the use block implies that we also do.
+ if (NormalDest->getSinglePredecessor())
+ return true;
-void DominanceFrontierBase::print(raw_ostream &OS, const Module* ) const {
- for (const_iterator I = begin(), E = end(); I != E; ++I) {
- OS << " DomFrontier for BB";
- if (I->first)
- WriteAsOperand(OS, I->first, false);
- else
- OS << " <<exit node>>";
- OS << " is:\t";
-
- const std::set<BasicBlock*> &BBs = I->second;
-
- for (std::set<BasicBlock*>::const_iterator I = BBs.begin(), E = BBs.end();
- I != E; ++I)
- if (*I)
- WriteAsOperand(OS, *I, false);
- else
- OS << " <<exit node>>";
- OS << "\n";
+ // The normal edge from the invoke is critical. Conceptually, what we would
+ // like to do is split it and check if the new block dominates the use.
+ // With X being the new block, the graph would look like:
+ //
+ // DefBB
+ // /\ . .
+ // / \ . .
+ // / \ . .
+ // / \ | |
+ // A X B C
+ // | \ | /
+ // . \|/
+ // . NormalDest
+ // .
+ //
+ // Given the definition of dominance, NormalDest is dominated by X iff X
+ // dominates all of NormalDest's predecessors (X, B, C in the example). X
+ // trivially dominates itself, so we only have to find if it dominates the
+ // other predecessors. Since the only way out of X is via NormalDest, X can
+ // only properly dominate a node if NormalDest dominates that node too.
+ for (pred_iterator PI = pred_begin(NormalDest),
+ E = pred_end(NormalDest); PI != E; ++PI) {
+ const BasicBlock *BB = *PI;
+ if (BB == DefBB)
+ continue;
+
+ if (!DT->isReachableFromEntry(BB))
+ continue;
+
+ if (!dominates(NormalDest, BB))
+ return false;
}
+ return true;
}
-