//
//===----------------------------------------------------------------------===//
-#include "llvm/Analysis/DominanceFrontier.h"
+#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"
VerifyDomInfoX("verify-dom-info", cl::location(VerifyDomInfo),
cl::desc("Verify dominator info (time consuming)"));
+bool BasicBlockEdge::isSingleEdge() const {
+ const TerminatorInst *TI = Start->getTerminator();
+ unsigned NumEdgesToEnd = 0;
+ for (unsigned int i = 0, n = TI->getNumSuccessors(); i < n; ++i) {
+ if (TI->getSuccessor(i) == End)
+ ++NumEdgesToEnd;
+ if (NumEdgesToEnd >= 2)
+ return false;
+ }
+ assert(NumEdgesToEnd == 1);
+ return true;
+}
+
//===----------------------------------------------------------------------===//
// DominatorTree Implementation
//===----------------------------------------------------------------------===//
//
// Provide public access to DominatorTree information. Implementation details
-// can be found in DominatorCalculation.h.
+// can be found in DominatorInternals.h.
//
//===----------------------------------------------------------------------===//
DominatorTree OtherDT;
OtherDT.getBase().recalculate(F);
if (compare(OtherDT)) {
- errs() << "DominatorTree is not up to date! Computed:\n";
+ errs() << "DominatorTree is not up to date!\nComputed:\n";
print(errs());
-
errs() << "\nActual:\n";
OtherDT.print(errs());
abort();
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))
+// 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();
+
+ // Any unreachable use is dominated, even if Def == User.
+ if (!isReachableFromEntry(UseBB))
+ return true;
+
+ // Unreachable definitions don't dominate anything.
+ if (!isReachableFromEntry(DefBB))
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)
+
+ // An instruction doesn't dominate a use in itself.
+ if (Def == User)
+ return false;
+
+ // 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);
+
+ if (DefBB != UseBB)
+ return dominates(DefBB, UseBB);
+
+ // Loop through the basic block until we find Def or User.
+ BasicBlock::const_iterator I = DefBB->begin();
+ for (; &*I != Def && &*I != User; ++I)
/*empty*/;
-
- return &*I == A;
+
+ return &*I == Def;
}
+// 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();
+ // Any unreachable use is dominated, even if DefBB == UseBB.
+ if (!isReachableFromEntry(UseBB))
+ return true;
-//===----------------------------------------------------------------------===//
-// DominanceFrontier Implementation
-//===----------------------------------------------------------------------===//
+ // Unreachable definitions don't dominate anything.
+ if (!isReachableFromEntry(DefBB))
+ return false;
-char DominanceFrontier::ID = 0;
-INITIALIZE_PASS_BEGIN(DominanceFrontier, "domfrontier",
- "Dominance Frontier Construction", true, true)
-INITIALIZE_PASS_DEPENDENCY(DominatorTree)
-INITIALIZE_PASS_END(DominanceFrontier, "domfrontier",
- "Dominance Frontier Construction", true, 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;
- };
-}
+ if (DefBB == UseBB)
+ return false;
-const DominanceFrontier::DomSetType &
-DominanceFrontier::calculate(const DominatorTree &DT,
- const DomTreeNode *Node) {
- BasicBlock *BB = Node->getBlock();
- DomSetType *Result = NULL;
-
- std::vector<DFCalculateWorkObject> workList;
- SmallPtrSet<BasicBlock *, 32> visited;
-
- workList.push_back(DFCalculateWorkObject(BB, NULL, Node, NULL));
- do {
- DFCalculateWorkObject *currentW = &workList.back();
- assert (currentW && "Missing work object.");
-
- 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];
-
- // Visit each block only once.
- if (visited.count(currentBB) == 0) {
- visited.insert(currentBB);
-
- // 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);
- }
- }
-
- // 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;
- }
- }
-
- // If all children are visited or there is any child then pop this block
- // from the workList.
- if (!visitChild) {
-
- if (!parentBB) {
- Result = &S;
- break;
- }
-
- 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();
- }
-
- } while (!workList.empty());
-
- return *Result;
+ const InvokeInst *II = dyn_cast<InvokeInst>(Def);
+ if (!II)
+ return dominates(DefBB, UseBB);
+
+ // Invoke results are only usable in the normal destination, not in the
+ // exceptional destination.
+ BasicBlock *NormalDest = II->getNormalDest();
+ BasicBlockEdge E(DefBB, NormalDest);
+ return dominates(E, UseBB);
}
-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) {
- OS << ' ';
- if (*I)
- WriteAsOperand(OS, *I, false);
- else
- OS << "<<exit node>>";
- }
- OS << "\n";
+bool DominatorTree::dominates(const BasicBlockEdge &BBE,
+ const BasicBlock *UseBB) const {
+ // Assert that we have a single edge. We could handle them by simply
+ // returning false, but since isSingleEdge is linear on the number of
+ // edges, the callers can normally handle them more efficiently.
+ assert(BBE.isSingleEdge());
+
+ // If the BB the edge ends in doesn't dominate the use BB, then the
+ // edge also doesn't.
+ const BasicBlock *Start = BBE.getStart();
+ const BasicBlock *End = BBE.getEnd();
+ if (!dominates(End, UseBB))
+ return false;
+
+ // Simple case: if the end BB has a single predecessor, the fact that it
+ // dominates the use block implies that the edge also does.
+ if (End->getSinglePredecessor())
+ return true;
+
+ // 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 (const_pred_iterator PI = pred_begin(End), E = pred_end(End);
+ PI != E; ++PI) {
+ const BasicBlock *BB = *PI;
+ if (BB == Start)
+ continue;
+
+ if (!dominates(End, BB))
+ return false;
}
+ return true;
+}
+
+bool DominatorTree::dominates(const BasicBlockEdge &BBE,
+ const Use &U) const {
+ // Assert that we have a single edge. We could handle them by simply
+ // returning false, but since isSingleEdge is linear on the number of
+ // edges, the callers can normally handle them more efficiently.
+ assert(BBE.isSingleEdge());
+
+ Instruction *UserInst = cast<Instruction>(U.getUser());
+ // A PHI in the end of the edge is dominated by it.
+ PHINode *PN = dyn_cast<PHINode>(UserInst);
+ if (PN && PN->getParent() == BBE.getEnd() &&
+ PN->getIncomingBlock(U) == BBE.getStart())
+ return true;
+
+ // Otherwise use the edge-dominates-block query, which
+ // handles the crazy critical edge cases properly.
+ const BasicBlock *UseBB;
+ if (PN)
+ UseBB = PN->getIncomingBlock(U);
+ else
+ UseBB = UserInst->getParent();
+ return dominates(BBE, UseBB);
}
-void DominanceFrontierBase::dump() const {
- print(dbgs());
+bool DominatorTree::dominates(const Instruction *Def,
+ const Use &U) const {
+ Instruction *UserInst = cast<Instruction>(U.getUser());
+ const BasicBlock *DefBB = Def->getParent();
+
+ // Determine the block in which the use happens. PHI nodes use
+ // their operands on edges; simulate this by thinking of the use
+ // happening at the end of the predecessor block.
+ const BasicBlock *UseBB;
+ if (PHINode *PN = dyn_cast<PHINode>(UserInst))
+ UseBB = PN->getIncomingBlock(U);
+ else
+ UseBB = UserInst->getParent();
+
+ // Any unreachable use is dominated, even if Def == User.
+ if (!isReachableFromEntry(UseBB))
+ return true;
+
+ // Unreachable definitions don't dominate anything.
+ if (!isReachableFromEntry(DefBB))
+ return false;
+
+ // Invoke instructions define their return values on the edges
+ // to their normal successors, so we have to handle them specially.
+ // Among other things, this means they don't dominate anything in
+ // their own block, except possibly a phi, so we don't need to
+ // walk the block in any case.
+ if (const InvokeInst *II = dyn_cast<InvokeInst>(Def)) {
+ BasicBlock *NormalDest = II->getNormalDest();
+ BasicBlockEdge E(DefBB, NormalDest);
+ return dominates(E, U);
+ }
+
+ // If the def and use are in different blocks, do a simple CFG dominator
+ // tree query.
+ if (DefBB != UseBB)
+ return dominates(DefBB, UseBB);
+
+ // Ok, def and use are in the same block. If the def is an invoke, it
+ // doesn't dominate anything in the block. If it's a PHI, it dominates
+ // everything in the block.
+ if (isa<PHINode>(UserInst))
+ return true;
+
+ // Otherwise, just loop through the basic block until we find Def or User.
+ BasicBlock::const_iterator I = DefBB->begin();
+ for (; &*I != Def && &*I != UserInst; ++I)
+ /*empty*/;
+
+ return &*I != UserInst;
}
+bool DominatorTree::isReachableFromEntry(const Use &U) const {
+ Instruction *I = dyn_cast<Instruction>(U.getUser());
+
+ // ConstantExprs aren't really reachable from the entry block, but they
+ // don't need to be treated like unreachable code either.
+ if (!I) return true;
+
+ // PHI nodes use their operands on their incoming edges.
+ if (PHINode *PN = dyn_cast<PHINode>(I))
+ return isReachableFromEntry(PN->getIncomingBlock(U));
+
+ // Everything else uses their operands in their own block.
+ return isReachableFromEntry(I->getParent());
+}
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