C++ TerminatorInst::getParent方法代码示例

// visitCallInst - This converts all LLVM call instructions into invoke
// instructions. The except part of the invoke goes to the "LongJmpBlkPre"
// that grabs the exception and proceeds to determine if it's a longjmp
// exception or not.
void LowerSetJmp::visitCallInst(CallInst& CI)
{
  if (CI.getCalledFunction())
    if (!IsTransformableFunction(CI.getCalledFunction()->getName()) ||
        CI.getCalledFunction()->isIntrinsic()) return;

  BasicBlock* OldBB = CI.getParent();

  // If not reachable from a setjmp call, don't transform.
  if (!DFSBlocks.count(OldBB)) return;

  BasicBlock* NewBB = OldBB->splitBasicBlock(CI);
  assert(NewBB && "Couldn't split BB of \"call\" instruction!!");
  DFSBlocks.insert(NewBB);
  NewBB->setName("Call2Invoke");

  Function* Func = OldBB->getParent();

  // Construct the new "invoke" instruction.
  TerminatorInst* Term = OldBB->getTerminator();
  std::vector<Value*> Params(CI.op_begin() + 1, CI.op_end());
  InvokeInst* II =
    InvokeInst::Create(CI.getCalledValue(), NewBB, PrelimBBMap[Func],
                       Params.begin(), Params.end(), CI.getName(), Term);
  II->setCallingConv(CI.getCallingConv());
  II->setParamAttrs(CI.getParamAttrs());

  // Replace the old call inst with the invoke inst and remove the call.
  CI.replaceAllUsesWith(II);
  CI.getParent()->getInstList().erase(&CI);

  // The old terminator is useless now that we have the invoke inst.
  Term->getParent()->getInstList().erase(Term);
  ++CallsTransformed;
}

/// 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;
}

bool PlaceSafepoints::runOnFunction(Function &F) {
  if (F.isDeclaration() || F.empty()) {
    // This is a declaration, nothing to do.  Must exit early to avoid crash in
    // dom tree calculation
    return false;
  }

  bool modified = false;

  // In various bits below, we rely on the fact that uses are reachable from
  // defs.  When there are basic blocks unreachable from the entry, dominance
  // and reachablity queries return non-sensical results.  Thus, we preprocess
  // the function to ensure these properties hold.
  modified |= removeUnreachableBlocks(F);

  // STEP 1 - Insert the safepoint polling locations.  We do not need to
  // actually insert parse points yet.  That will be done for all polls and
  // calls in a single pass.

  // Note: With the migration, we need to recompute this for each 'pass'.  Once
  // we merge these, we'll do it once before the analysis
  DominatorTree DT;

  std::vector<CallSite> ParsePointNeeded;

  if (EnableBackedgeSafepoints) {
    // Construct a pass manager to run the LoopPass backedge logic.  We
    // need the pass manager to handle scheduling all the loop passes
    // appropriately.  Doing this by hand is painful and just not worth messing
    // with for the moment.
    FunctionPassManager FPM(F.getParent());
    PlaceBackedgeSafepointsImpl *PBS =
        new PlaceBackedgeSafepointsImpl(EnableCallSafepoints);
    FPM.add(PBS);
    // Note: While the analysis pass itself won't modify the IR, LoopSimplify
    // (which it depends on) may.  i.e. analysis must be recalculated after run
    FPM.run(F);

    // We preserve dominance information when inserting the poll, otherwise
    // we'd have to recalculate this on every insert
    DT.recalculate(F);

    // Insert a poll at each point the analysis pass identified
    for (size_t i = 0; i < PBS->PollLocations.size(); i++) {
      // We are inserting a poll, the function is modified
      modified = true;

      // The poll location must be the terminator of a loop latch block.
      TerminatorInst *Term = PBS->PollLocations[i];

      std::vector<CallSite> ParsePoints;
      if (SplitBackedge) {
        // Split the backedge of the loop and insert the poll within that new
        // basic block.  This creates a loop with two latches per original
        // latch (which is non-ideal), but this appears to be easier to
        // optimize in practice than inserting the poll immediately before the
        // latch test.

        // Since this is a latch, at least one of the successors must dominate
        // it. Its possible that we have a) duplicate edges to the same header
        // and b) edges to distinct loop headers.  We need to insert pools on
        // each. (Note: This still relies on LoopSimplify.)
        DenseSet<BasicBlock *> Headers;
        for (unsigned i = 0; i < Term->getNumSuccessors(); i++) {
          BasicBlock *Succ = Term->getSuccessor(i);
          if (DT.dominates(Succ, Term->getParent())) {
            Headers.insert(Succ);
          }
        }
        assert(!Headers.empty() && "poll location is not a loop latch?");

        // The split loop structure here is so that we only need to recalculate
        // the dominator tree once.  Alternatively, we could just keep it up to
        // date and use a more natural merged loop.
        DenseSet<BasicBlock *> SplitBackedges;
        for (BasicBlock *Header : Headers) {
          BasicBlock *NewBB = SplitEdge(Term->getParent(), Header, nullptr);
          SplitBackedges.insert(NewBB);
        }
        DT.recalculate(F);
        for (BasicBlock *NewBB : SplitBackedges) {
          InsertSafepointPoll(DT, NewBB->getTerminator(), ParsePoints);
          NumBackedgeSafepoints++;
        }

      } else {
        // Split the latch block itself, right before the terminator.
        InsertSafepointPoll(DT, Term, ParsePoints);
        NumBackedgeSafepoints++;
      }

      // Record the parse points for later use
      ParsePointNeeded.insert(ParsePointNeeded.end(), ParsePoints.begin(),
                              ParsePoints.end());
    }
  }

  if (EnableEntrySafepoints) {
    DT.recalculate(F);
    Instruction *term = findLocationForEntrySafepoint(F, DT);
//.........这里部分代码省略.........