lib/CodeGen/MachinePostDominators.cpp

   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
  16 using namespace llvm;
  17
  18 namespace llvm {
  19 template class DominatorTreeBase<MachineBasicBlock, true>; // PostDomTreeBase
  20
  21 extern bool VerifyMachineDomInfo;
  22 } // namespace llvm
  23
  24 char MachinePostDominatorTree::ID = 0;
  25
  26 //declare initializeMachinePostDominatorTreePass
  27 INITIALIZE_PASS(MachinePostDominatorTree, "machinepostdomtree",
  28                 "MachinePostDominator Tree Construction", true, true)
  29
  30 MachinePostDominatorTree::MachinePostDominatorTree()
  31     : MachineFunctionPass(ID), PDT(nullptr) {
  32   initializeMachinePostDominatorTreePass(*PassRegistry::getPassRegistry());
  33 }
  34
  35 FunctionPass *MachinePostDominatorTree::createMachinePostDominatorTreePass() {
  36   return new MachinePostDominatorTree();
  37 }
  38
  39 bool MachinePostDominatorTree::runOnMachineFunction(MachineFunction &F) {
  40   PDT = std::make_unique<PostDomTreeT>();
  41   PDT->recalculate(F);
  42   return false;
  43 }
  44
  45 void MachinePostDominatorTree::getAnalysisUsage(AnalysisUsage &AU) const {
  46   AU.setPreservesAll();
  47   MachineFunctionPass::getAnalysisUsage(AU);
  48 }
  49
  50 MachineBasicBlock *MachinePostDominatorTree::findNearestCommonDominator(
  51     ArrayRef<MachineBasicBlock *> Blocks) const {
  52   assert(!Blocks.empty());
  53
  54   MachineBasicBlock *NCD = Blocks.front();
  55   for (MachineBasicBlock *BB : Blocks.drop_front()) {
  56     NCD = PDT->findNearestCommonDominator(NCD, BB);
  57
  58     // Stop when the root is reached.
  59     if (PDT->isVirtualRoot(PDT->getNode(NCD)))
  60       return nullptr;
  61   }
  62
  63   return NCD;
  64 }
  65
  66 void MachinePostDominatorTree::verifyAnalysis() const {
  67   if (PDT && VerifyMachineDomInfo)
  68     if (!PDT->verify(PostDomTreeT::VerificationLevel::Basic)) {
  69       errs() << "MachinePostDominatorTree verification failed\n";
  70
  71       abort();
  72     }
  73 }
  74
  75 void MachinePostDominatorTree::print(llvm::raw_ostream &OS,
  76                                      const Module *M) const {
  77   PDT->print(OS);
  78 }