C++ TerminatorInst::getContext方法代码示例

/// LowerUnwinds - Turn unwind instructions into calls to _Unwind_Resume,
/// rethrowing any previously caught exception.  This will crash horribly
/// at runtime if there is no such exception: using unwind to throw a new
/// exception is currently not supported.
bool DwarfEHPrepare::LowerUnwinds() {
  SmallVector<TerminatorInst*, 16> UnwindInsts;

  for (Function::iterator I = F->begin(), E = F->end(); I != E; ++I) {
    TerminatorInst *TI = I->getTerminator();
    if (isa<UnwindInst>(TI))
      UnwindInsts.push_back(TI);
  }

  if (UnwindInsts.empty()) return false;

  // Find the rewind function if we didn't already.
  if (!RewindFunction) {
    LLVMContext &Ctx = UnwindInsts[0]->getContext();
    std::vector<const Type*>
      Params(1, Type::getInt8PtrTy(Ctx));
    FunctionType *FTy = FunctionType::get(Type::getVoidTy(Ctx),
                                          Params, false);
    const char *RewindName = TLI->getLibcallName(RTLIB::UNWIND_RESUME);
    RewindFunction = F->getParent()->getOrInsertFunction(RewindName, FTy);
  }

  bool Changed = false;

  for (SmallVectorImpl<TerminatorInst*>::iterator
         I = UnwindInsts.begin(), E = UnwindInsts.end(); I != E; ++I) {
    TerminatorInst *TI = *I;

    // Replace the unwind instruction with a call to _Unwind_Resume (or the
    // appropriate target equivalent) followed by an UnreachableInst.

    // Create the call...
    CallInst *CI = CallInst::Create(RewindFunction,
                                    CreateReadOfExceptionValue(TI->getParent()),
                                    "", TI);
    CI->setCallingConv(TLI->getLibcallCallingConv(RTLIB::UNWIND_RESUME));
    // ...followed by an UnreachableInst.
    new UnreachableInst(TI->getContext(), TI);

    // Nuke the unwind instruction.
    TI->eraseFromParent();
    ++NumUnwindsLowered;
    Changed = true;
  }

  return Changed;
}

/// setBranchWeightMetadata - Translate the counter values associated with each
/// edge into branch weights for each conditional branch (a branch with 2 or
/// more desinations).
void ProfileMetadataLoaderPass::setBranchWeightMetadata(Module &M,
                                                        ProfileData &PB) {
  for (Module::iterator F = M.begin(), E = M.end(); F != E; ++F) {
    if (F->isDeclaration()) continue;
    DEBUG(dbgs() << "Setting branch metadata in '" << F->getName() << "'\n");

    for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB) {
      TerminatorInst *TI = BB->getTerminator();
      unsigned NumSuccessors = TI->getNumSuccessors();

      // If there is only one successor then we can not set a branch
      // probability as the target is certain.
      if (NumSuccessors < 2) continue;

      // Load the weights of all edges leading from this terminator.
      DEBUG(dbgs() << "-- Terminator with " << NumSuccessors
                   << " successors:\n");
      SmallVector<uint32_t, 4> Weights(NumSuccessors);
      for (unsigned s = 0 ; s < NumSuccessors ; ++s) {
          ProfileData::Edge edge = PB.getEdge(BB, TI->getSuccessor(s));
          Weights[s] = (uint32_t)PB.getEdgeWeight(edge);
          DEBUG(dbgs() << "---- Edge '" << edge << "' has weight "
                       << Weights[s] << "\n");
      }

      // Set branch weight metadata.  This will set branch probabilities of
      // 100%/0% if that is true of the dynamic execution.
      // BranchProbabilityInfo can account for this when it loads this metadata
      // (it gives the unexectuted branch a weight of 1 for the purposes of
      // probability calculations).
      MDBuilder MDB(TI->getContext());
      MDNode *Node = MDB.createBranchWeights(Weights);
      TI->setMetadata(LLVMContext::MD_prof, Node);
      NumTermsAnnotated++;
    }
  }
}