C++ CallInst::doesNotReturn方法代码示例

bool ScopDetection::isValidCallInst(CallInst &CI) {
  if (CI.mayHaveSideEffects() || CI.doesNotReturn())
    return false;

  if (CI.doesNotAccessMemory())
    return true;

  Function *CalledFunction = CI.getCalledFunction();

  // Indirect calls are not supported.
  if (CalledFunction == 0)
    return false;

  // TODO: Intrinsics.
  return false;
}

bool ScopDetection::isValidCallInst(CallInst &CI) {
  if (CI.doesNotReturn())
    return false;

  if (CI.doesNotAccessMemory())
    return true;

  Function *CalledFunction = CI.getCalledFunction();

  // Indirect calls are not supported.
  if (CalledFunction == 0)
    return false;

  // Check if we can handle the intrinsic call.
  if (auto *IT = dyn_cast<IntrinsicInst>(&CI)) {
    switch (IT->getIntrinsicID()) {
    // Lifetime markers are supported/ignored.
    case llvm::Intrinsic::lifetime_start:
    case llvm::Intrinsic::lifetime_end:
    // Invariant markers are supported/ignored.
    case llvm::Intrinsic::invariant_start:
    case llvm::Intrinsic::invariant_end:
    // Some misc annotations are supported/ignored.
    case llvm::Intrinsic::var_annotation:
    case llvm::Intrinsic::ptr_annotation:
    case llvm::Intrinsic::annotation:
    case llvm::Intrinsic::donothing:
    case llvm::Intrinsic::assume:
    case llvm::Intrinsic::expect:
      return true;
    default:
      // Other intrinsics which may access the memory are not yet supported.
      break;
    }
  }

  return false;
}

//.........这里部分代码省略.........
    Function *F = I->first;
    Phis& P = I->second;

    CallInst::Create(PrepSetjmp, "", F->begin()->begin());

    // Update each call that can longjmp so it can return to a setjmp where relevant

    for (Function::iterator BBI = F->begin(), E = F->end(); BBI != E; ) {
      BasicBlock *BB = BBI++;
      for (BasicBlock::iterator Iter = BB->begin(), E = BB->end(); Iter != E; ) {
        Instruction *I = Iter++;
        CallInst *CI;
        if ((CI = dyn_cast<CallInst>(I))) {
          Value *V = CI->getCalledValue();
          if (V == PrepSetjmp || V == EmSetjmp || V == CheckLongjmp || V == GetLongjmpResult || V == PreInvoke || V == PostInvoke) continue;
          if (Function *CF = dyn_cast<Function>(V)) if (CF->isIntrinsic()) continue;
          // TODO: proper analysis of what can actually longjmp. Currently we assume anything but setjmp can.
          // This may longjmp, so we need to check if it did. Split at that point, and
          // envelop the call in pre/post invoke, if we need to
          CallInst *After;
          Instruction *Check = NULL;
          if (Iter != E && (After = dyn_cast<CallInst>(Iter)) && After->getCalledValue() == PostInvoke) {
            // use the pre|postinvoke that exceptions lowering already made
            Check = Iter++;
          }
          BasicBlock *Tail = SplitBlock(BB, Iter); // Iter already points to the next instruction, as we need
          TerminatorInst *TI = BB->getTerminator();
          if (!Check) {
            // no existing pre|postinvoke, create our own
            CallInst::Create(PreInvoke, "", CI);
            Check = CallInst::Create(PostInvoke, "", TI); // CI is at the end of the block

            // If we are calling a function that is noreturn, we must remove that attribute. The code we
            // insert here does expect it to return, after we catch the exception.
            if (CI->doesNotReturn()) {
              if (Function *F = dyn_cast<Function>(CI->getCalledValue())) {
                F->removeFnAttr(Attribute::NoReturn);
              }
              CI->setAttributes(CI->getAttributes().removeAttribute(TheModule->getContext(), AttributeSet::FunctionIndex, Attribute::NoReturn));
              assert(!CI->doesNotReturn());
            }
          }

          // We need to replace the terminator in Tail - SplitBlock makes BB go straight to Tail, we need to check if a longjmp occurred, and
          // go to the right setjmp-tail if so
          SmallVector<Value *, 1> Args;
          Args.push_back(Check);
          Instruction *LongjmpCheck = CallInst::Create(CheckLongjmp, Args, "", BB);
          Instruction *LongjmpResult = CallInst::Create(GetLongjmpResult, Args, "", BB);
          SwitchInst *SI = SwitchInst::Create(LongjmpCheck, Tail, 2, BB);
          // -1 means no longjmp happened, continue normally (will hit the default switch case). 0 means a longjmp that is not ours to handle, needs a rethrow. Otherwise
          // the index mean is the same as the index in P+1 (to avoid 0).
          for (unsigned i = 0; i < P.size(); i++) {
            SI->addCase(cast<ConstantInt>(ConstantInt::get(i32, i+1)), P[i]->getParent());
            P[i]->addIncoming(LongjmpResult, BB);
          }
          ToErase.push_back(TI); // new terminator is now the switch

          // we are splitting the block here, and must continue to find other calls in the block - which is now split. so continue
          // to traverse in the Tail
          BB = Tail;
          Iter = BB->begin();
          E = BB->end();
        } else if (InvokeInst *CI = dyn_cast<InvokeInst>(I)) { // XXX check if target is setjmp
          (void)CI;
          report_fatal_error("TODO: invoke inside setjmping functions");
        }
      }
    }

    // add a cleanup before each return
    for (Function::iterator BBI = F->begin(), E = F->end(); BBI != E; ) {
      BasicBlock *BB = BBI++;
      TerminatorInst *TI = BB->getTerminator();
      if (isa<ReturnInst>(TI)) {
        CallInst::Create(CleanupSetjmp, "", TI);
      }
    }
  }

  for (unsigned i = 0; i < ToErase.size(); i++) {
    ToErase[i]->eraseFromParent();
  }

  // Finally, our modifications to the cfg can break dominance of SSA variables. For example,
  //   if (x()) { .. setjmp() .. }
  //   if (y()) { .. longjmp() .. }
  // We must split the longjmp block, and it can jump into the setjmp one. But that means that when
  // we split the setjmp block, it's first part no longer dominates its second part - there is
  // a theoretically possible control flow path where x() is false, then y() is true and we
  // reach the second part of the setjmp block, without ever reaching the first part. So,
  // we recalculate regs vs. mem
  for (FunctionPhisMap::iterator I = SetjmpOutputPhis.begin(); I != SetjmpOutputPhis.end(); I++) {
    Function *F = I->first;
    doRegToMem(*F);
    doMemToReg(*F);
  }

  return true;
}