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verifier does. This correctly handles invoke. Thanks to Duncan, Andrew and Chris for the comments. Thanks to Joerg for the early testing. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@151469 91177308-0d34-0410-b5e6-96231b3b80d8
177 lines
5.8 KiB
C++
177 lines
5.8 KiB
C++
//===- Dominators.cpp - Dominator Calculation -----------------------------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This file implements simple dominator construction algorithms for finding
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// forward dominators. Postdominators are available in libanalysis, but are not
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// included in libvmcore, because it's not needed. Forward dominators are
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// needed to support the Verifier pass.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/Analysis/Dominators.h"
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#include "llvm/Support/CFG.h"
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#include "llvm/Support/Compiler.h"
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#include "llvm/Support/Debug.h"
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#include "llvm/ADT/DepthFirstIterator.h"
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#include "llvm/ADT/SmallPtrSet.h"
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#include "llvm/ADT/SmallVector.h"
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#include "llvm/Analysis/DominatorInternals.h"
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#include "llvm/Assembly/Writer.h"
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#include "llvm/Instructions.h"
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#include "llvm/Support/raw_ostream.h"
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#include "llvm/Support/CommandLine.h"
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#include <algorithm>
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using namespace llvm;
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// Always verify dominfo if expensive checking is enabled.
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#ifdef XDEBUG
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static bool VerifyDomInfo = true;
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#else
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static bool VerifyDomInfo = false;
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#endif
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static cl::opt<bool,true>
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VerifyDomInfoX("verify-dom-info", cl::location(VerifyDomInfo),
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cl::desc("Verify dominator info (time consuming)"));
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//===----------------------------------------------------------------------===//
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// DominatorTree Implementation
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//===----------------------------------------------------------------------===//
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//
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// Provide public access to DominatorTree information. Implementation details
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// can be found in DominatorInternals.h.
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//
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//===----------------------------------------------------------------------===//
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TEMPLATE_INSTANTIATION(class llvm::DomTreeNodeBase<BasicBlock>);
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TEMPLATE_INSTANTIATION(class llvm::DominatorTreeBase<BasicBlock>);
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char DominatorTree::ID = 0;
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INITIALIZE_PASS(DominatorTree, "domtree",
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"Dominator Tree Construction", true, true)
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bool DominatorTree::runOnFunction(Function &F) {
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DT->recalculate(F);
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return false;
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}
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void DominatorTree::verifyAnalysis() const {
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if (!VerifyDomInfo) return;
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Function &F = *getRoot()->getParent();
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DominatorTree OtherDT;
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OtherDT.getBase().recalculate(F);
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if (compare(OtherDT)) {
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errs() << "DominatorTree is not up to date!\nComputed:\n";
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print(errs());
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errs() << "\nActual:\n";
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OtherDT.print(errs());
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abort();
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}
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}
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void DominatorTree::print(raw_ostream &OS, const Module *) const {
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DT->print(OS);
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}
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// dominates - Return true if Def dominates a use in User. This performs
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// the special checks necessary if Def and User are in the same basic block.
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// Note that Def doesn't dominate a use in Def itself!
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bool DominatorTree::dominates(const Instruction *Def,
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const Instruction *User) const {
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const BasicBlock *UseBB = User->getParent();
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const BasicBlock *DefBB = Def->getParent();
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assert(isReachableFromEntry(DefBB) && isReachableFromEntry(UseBB) &&
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"We only handle reachable blocks");
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// An instruction doesn't dominate a use in itself.
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if (Def == User)
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return false;
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// The value defined by an invoke dominates an instruction only if
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// it dominates every instruction in UseBB.
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// A PHI is dominated only if the instruction dominates every possible use
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// in the UseBB.
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if (isa<InvokeInst>(Def) || isa<PHINode>(User))
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return dominates(Def, UseBB);
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if (DefBB != UseBB)
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return dominates(DefBB, UseBB);
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// Loop through the basic block until we find Def or User.
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BasicBlock::const_iterator I = DefBB->begin();
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for (; &*I != Def && &*I != User; ++I)
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/*empty*/;
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return &*I == Def;
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}
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// true if Def would dominate a use in any instruction in UseBB.
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// note that dominates(Def, Def->getParent()) is false.
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bool DominatorTree::dominates(const Instruction *Def,
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const BasicBlock *UseBB) const {
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const BasicBlock *DefBB = Def->getParent();
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assert(isReachableFromEntry(DefBB) && isReachableFromEntry(UseBB) &&
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"We only handle reachable blocks");
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if (DefBB == UseBB)
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return false;
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const InvokeInst *II = dyn_cast<InvokeInst>(Def);
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if (!II)
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return dominates(DefBB, UseBB);
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// Invoke results are only usable in the normal destination, not in the
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// exceptional destination.
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BasicBlock *NormalDest = II->getNormalDest();
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if (!dominates(NormalDest, UseBB))
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return false;
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// Simple case: if the normal destination has a single predecessor, the
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// fact that it dominates the use block implies that we also do.
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if (NormalDest->getSinglePredecessor())
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return true;
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// The normal edge from the invoke is critical. Conceptually, what we would
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// like to do is split it and check if the new block dominates the use.
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// With X being the new block, the graph would look like:
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//
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// DefBB
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// /\ . .
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// / \ . .
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// / \ . .
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// / \ | |
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// A X B C
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// | \ | /
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// . \|/
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// . NormalDest
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// .
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//
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// Given the definition of dominance, NormalDest is dominated by X iff X
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// dominates all of NormalDest's predecessors (X, B, C in the example). X
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// trivially dominates itself, so we only have to find if it dominates the
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// other predecessors. Since the only way out of X is via NormalDest, X can
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// only properly dominate a node if NormalDest dominates that node too.
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for (pred_iterator PI = pred_begin(NormalDest),
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E = pred_end(NormalDest); PI != E; ++PI) {
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const BasicBlock *BB = *PI;
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if (BB == DefBB)
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continue;
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if (!DT->isReachableFromEntry(BB))
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continue;
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if (!dominates(NormalDest, BB))
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return false;
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}
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return true;
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}
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