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 
17 using namespace llvm;
18 
19 namespace llvm {
20 template class DominatorTreeBase<MachineBasicBlock, true>; // PostDomTreeBase
21 
22 extern bool VerifyMachineDomInfo;
23 } // namespace llvm
24 
25 char MachinePostDominatorTree::ID = 0;
26 
27 //declare initializeMachinePostDominatorTreePass
28 INITIALIZE_PASS(MachinePostDominatorTree, "machinepostdomtree",
29                 "MachinePostDominator Tree Construction", true, true)
30 
31 MachinePostDominatorTree::MachinePostDominatorTree()
32     : MachineFunctionPass(ID), PDT(nullptr) {
33   initializeMachinePostDominatorTreePass(*PassRegistry::getPassRegistry());
34 }
35 
36 FunctionPass *MachinePostDominatorTree::createMachinePostDominatorTreePass() {
37   return new MachinePostDominatorTree();
38 }
39 
40 bool MachinePostDominatorTree::runOnMachineFunction(MachineFunction &F) {
41   PDT = std::make_unique<PostDomTreeT>();
42   PDT->recalculate(F);
43   return false;
44 }
45 
46 void MachinePostDominatorTree::getAnalysisUsage(AnalysisUsage &AU) const {
47   AU.setPreservesAll();
48   MachineFunctionPass::getAnalysisUsage(AU);
49 }
50 
51 MachineBasicBlock *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 
67 void 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 
76 void MachinePostDominatorTree::print(llvm::raw_ostream &OS,
77                                      const Module *M) const {
78   PDT->print(OS);
79 }
80