MachinePostDominators.cpp revision 360784 
1//===- MachinePostDominators.cpp -Machine Post Dominator Calculation ------===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8//
9// This file implements simple dominator construction algorithms for finding
10// post dominators on machine functions.
11//
12//===----------------------------------------------------------------------===//
13
14#include "llvm/CodeGen/MachinePostDominators.h"
15#include "llvm/InitializePasses.h"
16
17using namespace llvm;
18
19namespace llvm {
20template class DominatorTreeBase<MachineBasicBlock, true>; // PostDomTreeBase
21
22extern bool VerifyMachineDomInfo;
23} // namespace llvm
24
25char MachinePostDominatorTree::ID = 0;
26
27//declare initializeMachinePostDominatorTreePass
28INITIALIZE_PASS(MachinePostDominatorTree, "machinepostdomtree",
29                "MachinePostDominator Tree Construction", true, true)
30
31MachinePostDominatorTree::MachinePostDominatorTree()
32    : MachineFunctionPass(ID), PDT(nullptr) {
33  initializeMachinePostDominatorTreePass(*PassRegistry::getPassRegistry());
34}
35
36FunctionPass *MachinePostDominatorTree::createMachinePostDominatorTreePass() {
37  return new MachinePostDominatorTree();
38}
39
40bool MachinePostDominatorTree::runOnMachineFunction(MachineFunction &F) {
41  PDT = std::make_unique<PostDomTreeT>();
42  PDT->recalculate(F);
43  return false;
44}
45
46void MachinePostDominatorTree::getAnalysisUsage(AnalysisUsage &AU) const {
47  AU.setPreservesAll();
48  MachineFunctionPass::getAnalysisUsage(AU);
49}
50
51MachineBasicBlock *MachinePostDominatorTree::findNearestCommonDominator(
52    ArrayRef<MachineBasicBlock *> Blocks) const {
53  assert(!Blocks.empty());
54
55  MachineBasicBlock *NCD = Blocks.front();
56  for (MachineBasicBlock *BB : Blocks.drop_front()) {
57    NCD = PDT->findNearestCommonDominator(NCD, BB);
58
59    // Stop when the root is reached.
60    if (PDT->isVirtualRoot(PDT->getNode(NCD)))
61      return nullptr;
62  }
63
64  return NCD;
65}
66
67void MachinePostDominatorTree::verifyAnalysis() const {
68  if (PDT && VerifyMachineDomInfo)
69    if (!PDT->verify(PostDomTreeT::VerificationLevel::Basic)) {
70      errs() << "MachinePostDominatorTree verification failed\n";
71
72      abort();
73    }
74}
75
76void MachinePostDominatorTree::print(llvm::raw_ostream &OS,
77                                     const Module *M) const {
78  PDT->print(OS);
79}
80