1 //===- Dominators.cpp - Dominator Calculation -----------------------------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file implements simple dominator construction algorithms for finding
11 // forward dominators. Postdominators are available in libanalysis, but are not
12 // included in libvmcore, because it's not needed. Forward dominators are
13 // needed to support the Verifier pass.
15 //===----------------------------------------------------------------------===//
17 #include "llvm/Analysis/Dominators.h"
18 #include "llvm/Support/CFG.h"
19 #include "llvm/Support/Compiler.h"
20 #include "llvm/Support/Debug.h"
21 #include "llvm/ADT/DepthFirstIterator.h"
22 #include "llvm/ADT/SetOperations.h"
23 #include "llvm/ADT/SmallPtrSet.h"
24 #include "llvm/ADT/SmallVector.h"
25 #include "llvm/Analysis/DominatorInternals.h"
26 #include "llvm/Assembly/Writer.h"
27 #include "llvm/Instructions.h"
28 #include "llvm/Support/raw_ostream.h"
29 #include "llvm/Support/CommandLine.h"
33 // Always verify dominfo if expensive checking is enabled.
35 static bool VerifyDomInfo = true;
37 static bool VerifyDomInfo = false;
39 static cl::opt<bool,true>
40 VerifyDomInfoX("verify-dom-info", cl::location(VerifyDomInfo),
41 cl::desc("Verify dominator info (time consuming)"));
43 //===----------------------------------------------------------------------===//
44 // DominatorTree Implementation
45 //===----------------------------------------------------------------------===//
47 // Provide public access to DominatorTree information. Implementation details
48 // can be found in DominatorCalculation.h.
50 //===----------------------------------------------------------------------===//
52 TEMPLATE_INSTANTIATION(class llvm::DomTreeNodeBase<BasicBlock>);
53 TEMPLATE_INSTANTIATION(class llvm::DominatorTreeBase<BasicBlock>);
55 char DominatorTree::ID = 0;
56 INITIALIZE_PASS(DominatorTree, "domtree",
57 "Dominator Tree Construction", true, true)
59 bool DominatorTree::runOnFunction(Function &F) {
64 void DominatorTree::verifyAnalysis() const {
65 if (!VerifyDomInfo) return;
67 Function &F = *getRoot()->getParent();
69 DominatorTree OtherDT;
70 OtherDT.getBase().recalculate(F);
71 if (compare(OtherDT)) {
72 errs() << "DominatorTree is not up to date! Computed:\n";
75 errs() << "\nActual:\n";
76 OtherDT.print(errs());
81 void DominatorTree::print(raw_ostream &OS, const Module *) const {
85 // dominates - Return true if A dominates a use in B. This performs the
86 // special checks necessary if A and B are in the same basic block.
87 bool DominatorTree::dominates(const Instruction *A, const Instruction *B) const{
88 const BasicBlock *BBA = A->getParent(), *BBB = B->getParent();
90 // If A is an invoke instruction, its value is only available in this normal
92 if (const InvokeInst *II = dyn_cast<InvokeInst>(A))
93 BBA = II->getNormalDest();
95 if (BBA != BBB) return dominates(BBA, BBB);
97 // It is not possible to determine dominance between two PHI nodes
98 // based on their ordering.
99 if (isa<PHINode>(A) && isa<PHINode>(B))
102 // Loop through the basic block until we find A or B.
103 BasicBlock::const_iterator I = BBA->begin();
104 for (; &*I != A && &*I != B; ++I)