+++ /dev/null
-//===- Dominators.cpp - Dominator Calculation -----------------------------===//
-//
-// The LLVM Compiler Infrastructure
-//
-// This file is distributed under the University of Illinois Open Source
-// License. See LICENSE.TXT for details.
-//
-//===----------------------------------------------------------------------===//
-//
-// This file implements simple dominator construction algorithms for finding
-// forward dominators. Postdominators are available in libanalysis, but are not
-// included in libvmcore, because it's not needed. Forward dominators are
-// needed to support the Verifier pass.
-//
-//===----------------------------------------------------------------------===//
-
-#include "llvm/Analysis/Dominators.h"
-#include "llvm/ADT/DepthFirstIterator.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/CFG.h"
-#include "llvm/Support/CommandLine.h"
-#include "llvm/Support/Compiler.h"
-#include "llvm/Support/Debug.h"
-#include "llvm/Support/raw_ostream.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)"));
-
-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 DominatorInternals.h.
-//
-//===----------------------------------------------------------------------===//
-
-TEMPLATE_INSTANTIATION(class llvm::DomTreeNodeBase<BasicBlock>);
-TEMPLATE_INSTANTIATION(class llvm::DominatorTreeBase<BasicBlock>);
-
-char DominatorTree::ID = 0;
-INITIALIZE_PASS(DominatorTree, "domtree",
- "Dominator Tree Construction", true, true)
-
-bool DominatorTree::runOnFunction(Function &F) {
- DT->recalculate(F);
- return false;
-}
-
-void DominatorTree::verifyAnalysis() const {
- if (!VerifyDomInfo) return;
-
- Function &F = *getRoot()->getParent();
-
- 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();
- }
-}
-
-void DominatorTree::print(raw_ostream &OS, const Module *) const {
- DT->print(OS);
-}
-
-// 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;
-
- // 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 == 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;
-
- // Unreachable definitions don't dominate anything.
- if (!isReachableFromEntry(DefBB))
- return false;
-
- if (DefBB == UseBB)
- return false;
-
- 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);
-}
-
-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);
-}
-
-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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