C++ CallInst::setDoesNotThrow方法代码示例

void insert_function_limits(Function &F){
    
    //Functions to be inserted as pragmas
    FunctionType* funvoid = FunctionType::get(Type::getVoidTy( F.getParent()->getContext() ), false);
    
    InlineAsm* fun_begin;
    InlineAsm* fun_end;
    if (sizeof(void*)==sizeof(long long)){
        fun_begin = InlineAsm::get(funvoid, "callq\tpragma_function_begin", "", false);
        fun_end = InlineAsm::get(funvoid, "callq\tpragma_function_end", "", false);
    }
    else {
        fun_begin = InlineAsm::get(funvoid, "call\tpragma_function_begin", "", false);
        fun_end = InlineAsm::get(funvoid, "call\tpragma_function_end", "", false);
    }
    
    //In the beginning
    {
        BasicBlock& first = F.getEntryBlock();
        int preds = 0;
        for (pred_iterator pi = pred_begin(&first), pe = pred_end(&first); pi != pe; pi++){
            preds++;
        }
        if (preds > 0){
            report_fatal_error("Error: The first basic block has predecessor.\n");
            //TODO: insert a new basic block in the beginning
        }
        
        CallInst* before = CallInst::Create(fun_begin);
        before->setDoesNotThrow();
        before->insertBefore( first.getFirstNonPHI() );
    }
    
    //In the end
    for (Function::iterator bb = F.begin(), en = F.end(); bb != en; bb++){
        TerminatorInst* inst = bb->getTerminator();
        
        if ( isa<ReturnInst>(inst) ){
            CallInst* after = CallInst::Create(fun_end);
            after->setDoesNotThrow();
            //after->insertBefore( inst );
            after->insertBefore( bb->getFirstNonPHI() );
        }
    }
    
}

/// getTrapBB - create a basic block that traps. All overflowing conditions
/// branch to this block. There's only one trap block per function.
BasicBlock *BoundsChecking::getTrapBB() {
  if (TrapBB && SingleTrapBB)
    return TrapBB;

  Function *Fn = Inst->getParent()->getParent();
  BasicBlock::iterator PrevInsertPoint = Builder->GetInsertPoint();
  TrapBB = BasicBlock::Create(Fn->getContext(), "trap", Fn);
  Builder->SetInsertPoint(TrapBB);

  llvm::Value *F = Intrinsic::getDeclaration(Fn->getParent(), Intrinsic::trap);
  CallInst *TrapCall = Builder->CreateCall(F);
  TrapCall->setDoesNotReturn();
  TrapCall->setDoesNotThrow();
  TrapCall->setDebugLoc(Inst->getDebugLoc());
  Builder->CreateUnreachable();

  Builder->SetInsertPoint(PrevInsertPoint);
  return TrapBB;
}

/// setupEntryBlockAndCallSites - Setup the entry block by creating and filling
/// the function context and marking the call sites with the appropriate
/// values. These values are used by the DWARF EH emitter.
bool SjLjEHPrepare::setupEntryBlockAndCallSites(Function &F) {
  SmallVector<ReturnInst *, 16> Returns;
  SmallVector<InvokeInst *, 16> Invokes;
  SmallSetVector<LandingPadInst *, 16> LPads;

  // Look through the terminators of the basic blocks to find invokes.
  for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB)
    if (InvokeInst *II = dyn_cast<InvokeInst>(BB->getTerminator())) {
      if (Function *Callee = II->getCalledFunction())
        if (Callee->isIntrinsic() &&
            Callee->getIntrinsicID() == Intrinsic::donothing) {
          // Remove the NOP invoke.
          BranchInst::Create(II->getNormalDest(), II);
          II->eraseFromParent();
          continue;
        }

      Invokes.push_back(II);
      LPads.insert(II->getUnwindDest()->getLandingPadInst());
    } else if (ReturnInst *RI = dyn_cast<ReturnInst>(BB->getTerminator())) {
      Returns.push_back(RI);
    }

  if (Invokes.empty())
    return false;

  NumInvokes += Invokes.size();

  lowerIncomingArguments(F);
  lowerAcrossUnwindEdges(F, Invokes);

  Value *FuncCtx =
      setupFunctionContext(F, makeArrayRef(LPads.begin(), LPads.end()));
  BasicBlock *EntryBB = &F.front();
  IRBuilder<> Builder(EntryBB->getTerminator());

  // Get a reference to the jump buffer.
  Value *JBufPtr =
      Builder.CreateConstGEP2_32(FunctionContextTy, FuncCtx, 0, 5, "jbuf_gep");

  // Save the frame pointer.
  Value *FramePtr = Builder.CreateConstGEP2_32(doubleUnderJBufTy, JBufPtr, 0, 0,
                                               "jbuf_fp_gep");

  Value *Val = Builder.CreateCall(FrameAddrFn, Builder.getInt32(0), "fp");
  Builder.CreateStore(Val, FramePtr, /*isVolatile=*/true);

  // Save the stack pointer.
  Value *StackPtr = Builder.CreateConstGEP2_32(doubleUnderJBufTy, JBufPtr, 0, 2,
                                               "jbuf_sp_gep");

  Val = Builder.CreateCall(StackAddrFn, {}, "sp");
  Builder.CreateStore(Val, StackPtr, /*isVolatile=*/true);

  // Call the setup_dispatch instrinsic. It fills in the rest of the jmpbuf.
  Builder.CreateCall(BuiltinSetupDispatchFn, {});

  // Store a pointer to the function context so that the back-end will know
  // where to look for it.
  Value *FuncCtxArg = Builder.CreateBitCast(FuncCtx, Builder.getInt8PtrTy());
  Builder.CreateCall(FuncCtxFn, FuncCtxArg);

  // At this point, we are all set up, update the invoke instructions to mark
  // their call_site values.
  for (unsigned I = 0, E = Invokes.size(); I != E; ++I) {
    insertCallSiteStore(Invokes[I], I + 1);

    ConstantInt *CallSiteNum =
        ConstantInt::get(Type::getInt32Ty(F.getContext()), I + 1);

    // Record the call site value for the back end so it stays associated with
    // the invoke.
    CallInst::Create(CallSiteFn, CallSiteNum, "", Invokes[I]);
  }

  // Mark call instructions that aren't nounwind as no-action (call_site ==
  // -1). Skip the entry block, as prior to then, no function context has been
  // created for this function and any unexpected exceptions thrown will go
  // directly to the caller's context, which is what we want anyway, so no need
  // to do anything here.
  for (Function::iterator BB = F.begin(), E = F.end(); ++BB != E;)
    for (BasicBlock::iterator I = BB->begin(), end = BB->end(); I != end; ++I)
      if (CallInst *CI = dyn_cast<CallInst>(I)) {
        if (!CI->doesNotThrow())
          insertCallSiteStore(CI, -1);
      } else if (ResumeInst *RI = dyn_cast<ResumeInst>(I)) {
        insertCallSiteStore(RI, -1);
      }

  // Register the function context and make sure it's known to not throw
  CallInst *Register =
      CallInst::Create(RegisterFn, FuncCtx, "", EntryBB->getTerminator());
  Register->setDoesNotThrow();

  // Following any allocas not in the entry block, update the saved SP in the
  // jmpbuf to the new value.
  for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB) {
//.........这里部分代码省略.........

/// Attempt to merge an objc_release with a store, load, and objc_retain to form
/// an objc_storeStrong. An objc_storeStrong:
///
///   objc_storeStrong(i8** %old_ptr, i8* new_value)
///
/// is equivalent to the following IR sequence:
///
///   ; Load old value.
///   %old_value = load i8** %old_ptr               (1)
///
///   ; Increment the new value and then release the old value. This must occur
///   ; in order in case old_value releases new_value in its destructor causing
///   ; us to potentially have a dangling ptr.
///   tail call i8* @objc_retain(i8* %new_value)    (2)
///   tail call void @objc_release(i8* %old_value)  (3)
///
///   ; Store the new_value into old_ptr
///   store i8* %new_value, i8** %old_ptr           (4)
///
/// The safety of this optimization is based around the following
/// considerations:
///
///  1. We are forming the store strong at the store. Thus to perform this
///     optimization it must be safe to move the retain, load, and release to
///     (4).
///  2. We need to make sure that any re-orderings of (1), (2), (3), (4) are
///     safe.
void ObjCARCContract::tryToContractReleaseIntoStoreStrong(Instruction *Release,
                                                          inst_iterator &Iter) {
  // See if we are releasing something that we just loaded.
  auto *Load = dyn_cast<LoadInst>(GetArgRCIdentityRoot(Release));
  if (!Load || !Load->isSimple())
    return;

  // For now, require everything to be in one basic block.
  BasicBlock *BB = Release->getParent();
  if (Load->getParent() != BB)
    return;

  // First scan down the BB from Load, looking for a store of the RCIdentityRoot
  // of Load's
  StoreInst *Store =
      findSafeStoreForStoreStrongContraction(Load, Release, PA, AA);
  // If we fail, bail.
  if (!Store)
    return;

  // Then find what new_value's RCIdentity Root is.
  Value *New = GetRCIdentityRoot(Store->getValueOperand());

  // Then walk up the BB and look for a retain on New without any intervening
  // instructions which conservatively might decrement ref counts.
  Instruction *Retain =
      findRetainForStoreStrongContraction(New, Store, Release, PA);

  // If we fail, bail.
  if (!Retain)
    return;

  Changed = true;
  ++NumStoreStrongs;

  DEBUG(
      llvm::dbgs() << "    Contracting retain, release into objc_storeStrong.\n"
                   << "        Old:\n"
                   << "            Store:   " << *Store << "\n"
                   << "            Release: " << *Release << "\n"
                   << "            Retain:  " << *Retain << "\n"
                   << "            Load:    " << *Load << "\n");

  LLVMContext &C = Release->getContext();
  Type *I8X = PointerType::getUnqual(Type::getInt8Ty(C));
  Type *I8XX = PointerType::getUnqual(I8X);

  Value *Args[] = { Load->getPointerOperand(), New };
  if (Args[0]->getType() != I8XX)
    Args[0] = new BitCastInst(Args[0], I8XX, "", Store);
  if (Args[1]->getType() != I8X)
    Args[1] = new BitCastInst(Args[1], I8X, "", Store);
  Constant *Decl = EP.get(ARCRuntimeEntryPointKind::StoreStrong);
  CallInst *StoreStrong = CallInst::Create(Decl, Args, "", Store);
  StoreStrong->setDoesNotThrow();
  StoreStrong->setDebugLoc(Store->getDebugLoc());

  // We can't set the tail flag yet, because we haven't yet determined
  // whether there are any escaping allocas. Remember this call, so that
  // we can set the tail flag once we know it's safe.
  StoreStrongCalls.insert(StoreStrong);

  DEBUG(llvm::dbgs() << "        New Store Strong: " << *StoreStrong << "\n");

  if (&*Iter == Store) ++Iter;
  Store->eraseFromParent();
  Release->eraseFromParent();
  EraseInstruction(Retain);
  if (Load->use_empty())
    Load->eraseFromParent();
}

static bool addBoundsChecking(Function &F, TargetLibraryInfo &TLI,
                              ScalarEvolution &SE) {
  const DataLayout &DL = F.getParent()->getDataLayout();
  ObjectSizeOffsetEvaluator ObjSizeEval(DL, &TLI, F.getContext(),
                                           /*RoundToAlign=*/true);

  // check HANDLE_MEMORY_INST in include/llvm/Instruction.def for memory
  // touching instructions
  SmallVector<std::pair<Instruction *, Value *>, 4> TrapInfo;
  for (Instruction &I : instructions(F)) {
    Value *Or = nullptr;
    BuilderTy IRB(I.getParent(), BasicBlock::iterator(&I), TargetFolder(DL));
    if (LoadInst *LI = dyn_cast<LoadInst>(&I)) {
      Or = getBoundsCheckCond(LI->getPointerOperand(), LI, DL, TLI,
                              ObjSizeEval, IRB, SE);
    } else if (StoreInst *SI = dyn_cast<StoreInst>(&I)) {
      Or = getBoundsCheckCond(SI->getPointerOperand(), SI->getValueOperand(),
                              DL, TLI, ObjSizeEval, IRB, SE);
    } else if (AtomicCmpXchgInst *AI = dyn_cast<AtomicCmpXchgInst>(&I)) {
      Or = getBoundsCheckCond(AI->getPointerOperand(), AI->getCompareOperand(),
                              DL, TLI, ObjSizeEval, IRB, SE);
    } else if (AtomicRMWInst *AI = dyn_cast<AtomicRMWInst>(&I)) {
      Or = getBoundsCheckCond(AI->getPointerOperand(), AI->getValOperand(), DL,
                              TLI, ObjSizeEval, IRB, SE);
    }
    if (Or)
      TrapInfo.push_back(std::make_pair(&I, Or));
  }

  // Create a trapping basic block on demand using a callback. Depending on
  // flags, this will either create a single block for the entire function or
  // will create a fresh block every time it is called.
  BasicBlock *TrapBB = nullptr;
  auto GetTrapBB = [&TrapBB](BuilderTy &IRB) {
    if (TrapBB && SingleTrapBB)
      return TrapBB;

    Function *Fn = IRB.GetInsertBlock()->getParent();
    // FIXME: This debug location doesn't make a lot of sense in the
    // `SingleTrapBB` case.
    auto DebugLoc = IRB.getCurrentDebugLocation();
    IRBuilder<>::InsertPointGuard Guard(IRB);
    TrapBB = BasicBlock::Create(Fn->getContext(), "trap", Fn);
    IRB.SetInsertPoint(TrapBB);

    auto *F = Intrinsic::getDeclaration(Fn->getParent(), Intrinsic::trap);
    CallInst *TrapCall = IRB.CreateCall(F, {});
    TrapCall->setDoesNotReturn();
    TrapCall->setDoesNotThrow();
    TrapCall->setDebugLoc(DebugLoc);
    IRB.CreateUnreachable();

    return TrapBB;
  };

  // Add the checks.
  for (const auto &Entry : TrapInfo) {
    Instruction *Inst = Entry.first;
    BuilderTy IRB(Inst->getParent(), BasicBlock::iterator(Inst), TargetFolder(DL));
    insertBoundsCheck(Entry.second, IRB, GetTrapBB);
  }

  return !TrapInfo.empty();
}

void WasmEHPrepare::prepareEHPad(BasicBlock *BB, unsigned Index) {
  assert(BB->isEHPad() && "BB is not an EHPad!");
  IRBuilder<> IRB(BB->getContext());

  IRB.SetInsertPoint(&*BB->getFirstInsertionPt());
  // The argument to wasm.catch() is the tag for C++ exceptions, which we set to
  // 0 for this module.
  // Pseudocode: void *exn = wasm.catch(0);
  Instruction *Exn = IRB.CreateCall(CatchF, IRB.getInt32(0), "exn");
  // Replace the return value of wasm.get.exception() with the return value from
  // wasm.catch().
  auto *FPI = cast<FuncletPadInst>(BB->getFirstNonPHI());
  Instruction *GetExnCI = nullptr, *GetSelectorCI = nullptr;
  for (auto &U : FPI->uses()) {
    if (auto *CI = dyn_cast<CallInst>(U.getUser())) {
      if (CI->getCalledValue() == GetExnF)
        GetExnCI = CI;
      else if (CI->getCalledValue() == GetSelectorF)
        GetSelectorCI = CI;
    }
  }

  assert(GetExnCI && "wasm.get.exception() call does not exist");
  GetExnCI->replaceAllUsesWith(Exn);
  GetExnCI->eraseFromParent();

  // In case it is a catchpad with single catch (...) or a cleanuppad, we don't
  // need to call personality function because we don't need a selector.
  if (FPI->getNumArgOperands() == 0 ||
      (FPI->getNumArgOperands() == 1 &&
       cast<Constant>(FPI->getArgOperand(0))->isNullValue())) {
    if (GetSelectorCI) {
      assert(GetSelectorCI->use_empty() &&
             "wasm.get.ehselector() still has uses!");
      GetSelectorCI->eraseFromParent();
    }
    return;
  }
  IRB.SetInsertPoint(Exn->getNextNode());

  // This is to create a map of <landingpad EH label, landingpad index> in
  // SelectionDAGISel, which is to be used in EHStreamer to emit LSDA tables.
  // Pseudocode: wasm.landingpad.index(Index);
  IRB.CreateCall(LPadIndexF, IRB.getInt32(Index));

  // Pseudocode: __wasm_lpad_context.lpad_index = index;
  IRB.CreateStore(IRB.getInt32(Index), LPadIndexField);

  // Store LSDA address only if this catchpad belongs to a top-level
  // catchswitch. If there is another catchpad that dominates this pad, we don't
  // need to store LSDA address again, because they are the same throughout the
  // function and have been already stored before.
  // TODO Can we not store LSDA address in user function but make libcxxabi
  // compute it?
  auto *CPI = cast<CatchPadInst>(FPI);
  if (isa<ConstantTokenNone>(CPI->getCatchSwitch()->getParentPad()))
    // Pseudocode: __wasm_lpad_context.lsda = wasm.lsda();
    IRB.CreateStore(IRB.CreateCall(LSDAF), LSDAField);

  // Pseudocode: _Unwind_CallPersonality(exn);
  CallInst *PersCI =
      IRB.CreateCall(CallPersonalityF, Exn, OperandBundleDef("funclet", CPI));
  PersCI->setDoesNotThrow();

  // Pseudocode: int selector = __wasm.landingpad_context.selector;
  Instruction *Selector = IRB.CreateLoad(SelectorField, "selector");

  // Replace the return value from wasm.get.ehselector() with the selector value
  // loaded from __wasm_lpad_context.selector.
  assert(GetSelectorCI && "wasm.get.ehselector() call does not exist");
  GetSelectorCI->replaceAllUsesWith(Selector);
  GetSelectorCI->eraseFromParent();
}