llvm/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 #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 }