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
//===----------------------------------------------------------------------===//
// Invoke results are only usable in the normal destination, not in the
// exceptional destination.
BasicBlock *NormalDest = II->getNormalDest();
- if (!dominates(NormalDest, UseBB))
+ BasicBlockEdge E(DefBB, NormalDest);
+ return dominates(E, UseBB);
+}
+
+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 normal destination has a single predecessor, the
- // fact that it dominates the use block implies that we also do.
- if (NormalDest->getSinglePredecessor())
+ // 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
// 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) {
+ for (const_pred_iterator PI = pred_begin(End), E = pred_end(End);
+ PI != E; ++PI) {
const BasicBlock *BB = *PI;
- if (BB == DefBB)
+ if (BB == Start)
continue;
- if (!DT->isReachableFromEntry(BB))
- continue;
-
- if (!dominates(NormalDest, BB))
+ 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);
+}
+
+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());
+}
projects / oota-llvm.git / blobdiff