C++ LandingPadInst::replaceAllUsesWith方法代码示例

/// SplitLandingPadPredecessors - This method transforms the landing pad,
/// OrigBB, by introducing two new basic blocks into the function. One of those
/// new basic blocks gets the predecessors listed in Preds. The other basic
/// block gets the remaining predecessors of OrigBB. The landingpad instruction
/// OrigBB is clone into both of the new basic blocks. The new blocks are given
/// the suffixes 'Suffix1' and 'Suffix2', and are returned in the NewBBs vector.
/// 
/// This currently updates the LLVM IR, AliasAnalysis, DominatorTree,
/// DominanceFrontier, LoopInfo, and LCCSA but no other analyses. In particular,
/// it does not preserve LoopSimplify (because it's complicated to handle the
/// case where one of the edges being split is an exit of a loop with other
/// exits).
/// 
void llvm::SplitLandingPadPredecessors(BasicBlock *OrigBB,
                                       ArrayRef<BasicBlock*> Preds,
                                       const char *Suffix1, const char *Suffix2,
                                       Pass *P,
                                       SmallVectorImpl<BasicBlock*> &NewBBs) {
  assert(OrigBB->isLandingPad() && "Trying to split a non-landing pad!");

  // Create a new basic block for OrigBB's predecessors listed in Preds. Insert
  // it right before the original block.
  BasicBlock *NewBB1 = BasicBlock::Create(OrigBB->getContext(),
                                          OrigBB->getName() + Suffix1,
                                          OrigBB->getParent(), OrigBB);
  NewBBs.push_back(NewBB1);

  // The new block unconditionally branches to the old block.
  BranchInst *BI1 = BranchInst::Create(OrigBB, NewBB1);

  // Move the edges from Preds to point to NewBB1 instead of OrigBB.
  for (unsigned i = 0, e = Preds.size(); i != e; ++i) {
    // This is slightly more strict than necessary; the minimum requirement
    // is that there be no more than one indirectbr branching to BB. And
    // all BlockAddress uses would need to be updated.
    assert(!isa<IndirectBrInst>(Preds[i]->getTerminator()) &&
           "Cannot split an edge from an IndirectBrInst");
    Preds[i]->getTerminator()->replaceUsesOfWith(OrigBB, NewBB1);
  }

  // Update DominatorTree, LoopInfo, and LCCSA analysis information.
  bool HasLoopExit = false;
  UpdateAnalysisInformation(OrigBB, NewBB1, Preds, P, HasLoopExit);

  // Update the PHI nodes in OrigBB with the values coming from NewBB1.
  UpdatePHINodes(OrigBB, NewBB1, Preds, BI1, P, HasLoopExit);

  // Move the remaining edges from OrigBB to point to NewBB2.
  SmallVector<BasicBlock*, 8> NewBB2Preds;
  for (pred_iterator i = pred_begin(OrigBB), e = pred_end(OrigBB);
       i != e; ) {
    BasicBlock *Pred = *i++;
    if (Pred == NewBB1) continue;
    assert(!isa<IndirectBrInst>(Pred->getTerminator()) &&
           "Cannot split an edge from an IndirectBrInst");
    NewBB2Preds.push_back(Pred);
    e = pred_end(OrigBB);
  }

  BasicBlock *NewBB2 = 0;
  if (!NewBB2Preds.empty()) {
    // Create another basic block for the rest of OrigBB's predecessors.
    NewBB2 = BasicBlock::Create(OrigBB->getContext(),
                                OrigBB->getName() + Suffix2,
                                OrigBB->getParent(), OrigBB);
    NewBBs.push_back(NewBB2);

    // The new block unconditionally branches to the old block.
    BranchInst *BI2 = BranchInst::Create(OrigBB, NewBB2);

    // Move the remaining edges from OrigBB to point to NewBB2.
    for (SmallVectorImpl<BasicBlock*>::iterator
           i = NewBB2Preds.begin(), e = NewBB2Preds.end(); i != e; ++i)
      (*i)->getTerminator()->replaceUsesOfWith(OrigBB, NewBB2);

    // Update DominatorTree, LoopInfo, and LCCSA analysis information.
    HasLoopExit = false;
    UpdateAnalysisInformation(OrigBB, NewBB2, NewBB2Preds, P, HasLoopExit);

    // Update the PHI nodes in OrigBB with the values coming from NewBB2.
    UpdatePHINodes(OrigBB, NewBB2, NewBB2Preds, BI2, P, HasLoopExit);
  }

  LandingPadInst *LPad = OrigBB->getLandingPadInst();
  Instruction *Clone1 = LPad->clone();
  Clone1->setName(Twine("lpad") + Suffix1);
  NewBB1->getInstList().insert(NewBB1->getFirstInsertionPt(), Clone1);

  if (NewBB2) {
    Instruction *Clone2 = LPad->clone();
    Clone2->setName(Twine("lpad") + Suffix2);
    NewBB2->getInstList().insert(NewBB2->getFirstInsertionPt(), Clone2);

    // Create a PHI node for the two cloned landingpad instructions.
    PHINode *PN = PHINode::Create(LPad->getType(), 2, "lpad.phi", LPad);
    PN->addIncoming(Clone1, NewBB1);
    PN->addIncoming(Clone2, NewBB2);
    LPad->replaceAllUsesWith(PN);
    LPad->eraseFromParent();
  } else {
//.........这里部分代码省略.........

//.........这里部分代码省略.........
  NewBlocks.reserve(LoopBlocks.size());
  ValueToValueMapTy VMap;
  for (unsigned i = 0, e = LoopBlocks.size(); i != e; ++i) {
    BasicBlock *NewBB = CloneBasicBlock(LoopBlocks[i], VMap, ".us", F);

    NewBlocks.push_back(NewBB);
    VMap[LoopBlocks[i]] = NewBB;  // Keep the BB mapping.
    LPM->cloneBasicBlockSimpleAnalysis(LoopBlocks[i], NewBB, L);
  }

  // Splice the newly inserted blocks into the function right before the
  // original preheader.
  F->getBasicBlockList().splice(NewPreheader, F->getBasicBlockList(),
                                NewBlocks[0], F->end());

  // Now we create the new Loop object for the versioned loop.
  Loop *NewLoop = CloneLoop(L, L->getParentLoop(), VMap, LI, LPM);

  // Recalculate unswitching quota, inherit simplified switches info for NewBB,
  // Probably clone more loop-unswitch related loop properties.
  BranchesInfo.cloneData(NewLoop, L, VMap);

  Loop *ParentLoop = L->getParentLoop();
  if (ParentLoop) {
    // Make sure to add the cloned preheader and exit blocks to the parent loop
    // as well.
    ParentLoop->addBasicBlockToLoop(NewBlocks[0], LI->getBase());
  }

  for (unsigned i = 0, e = ExitBlocks.size(); i != e; ++i) {
    BasicBlock *NewExit = cast<BasicBlock>(VMap[ExitBlocks[i]]);
    // The new exit block should be in the same loop as the old one.
    if (Loop *ExitBBLoop = LI->getLoopFor(ExitBlocks[i]))
      ExitBBLoop->addBasicBlockToLoop(NewExit, LI->getBase());

    assert(NewExit->getTerminator()->getNumSuccessors() == 1 &&
           "Exit block should have been split to have one successor!");
    BasicBlock *ExitSucc = NewExit->getTerminator()->getSuccessor(0);

    // If the successor of the exit block had PHI nodes, add an entry for
    // NewExit.
    PHINode *PN;
    for (BasicBlock::iterator I = ExitSucc->begin(); isa<PHINode>(I); ++I) {
      PN = cast<PHINode>(I);
      Value *V = PN->getIncomingValueForBlock(ExitBlocks[i]);
      ValueToValueMapTy::iterator It = VMap.find(V);
      if (It != VMap.end()) V = It->second;
      PN->addIncoming(V, NewExit);
    }

    if (LandingPadInst *LPad = NewExit->getLandingPadInst()) {
      PN = PHINode::Create(LPad->getType(), 0, "",
                           ExitSucc->getFirstInsertionPt());

      for (pred_iterator I = pred_begin(ExitSucc), E = pred_end(ExitSucc);
           I != E; ++I) {
        BasicBlock *BB = *I;
        LandingPadInst *LPI = BB->getLandingPadInst();
        LPI->replaceAllUsesWith(PN);
        PN->addIncoming(LPI, BB);
      }
    }
  }

  // Rewrite the code to refer to itself.
  for (unsigned i = 0, e = NewBlocks.size(); i != e; ++i)
    for (BasicBlock::iterator I = NewBlocks[i]->begin(),
           E = NewBlocks[i]->end(); I != E; ++I)
      RemapInstruction(I, VMap,RF_NoModuleLevelChanges|RF_IgnoreMissingEntries);

  // Rewrite the original preheader to select between versions of the loop.
  BranchInst *OldBR = cast<BranchInst>(loopPreheader->getTerminator());
  assert(OldBR->isUnconditional() && OldBR->getSuccessor(0) == LoopBlocks[0] &&
         "Preheader splitting did not work correctly!");

  // Emit the new branch that selects between the two versions of this loop.
  EmitPreheaderBranchOnCondition(LIC, Val, NewBlocks[0], LoopBlocks[0], OldBR);
  LPM->deleteSimpleAnalysisValue(OldBR, L);
  OldBR->eraseFromParent();

  LoopProcessWorklist.push_back(NewLoop);
  redoLoop = true;

  // Keep a WeakVH holding onto LIC.  If the first call to RewriteLoopBody
  // deletes the instruction (for example by simplifying a PHI that feeds into
  // the condition that we're unswitching on), we don't rewrite the second
  // iteration.
  WeakVH LICHandle(LIC);

  // Now we rewrite the original code to know that the condition is true and the
  // new code to know that the condition is false.
  RewriteLoopBodyWithConditionConstant(L, LIC, Val, false);

  // It's possible that simplifying one loop could cause the other to be
  // changed to another value or a constant.  If its a constant, don't simplify
  // it.
  if (!LoopProcessWorklist.empty() && LoopProcessWorklist.back() == NewLoop &&
      LICHandle && !isa<Constant>(LICHandle))
    RewriteLoopBodyWithConditionConstant(NewLoop, LICHandle, Val, true);
}

bool LowerEmExceptions::runOnModule(Module &M) {
  TheModule = &M;

  // Add functions

  Type *i32 = Type::getInt32Ty(M.getContext());
  Type *i8 = Type::getInt8Ty(M.getContext());
  Type *i1 = Type::getInt1Ty(M.getContext());
  Type *i8P = i8->getPointerTo();
  Type *Void = Type::getVoidTy(M.getContext());

  if (!(GetHigh = TheModule->getFunction("getHigh32"))) {
    FunctionType *GetHighFunc = FunctionType::get(i32, false);
    GetHigh = Function::Create(GetHighFunc, GlobalValue::ExternalLinkage,
                               "getHigh32", TheModule);
  }

  if (!(PreInvoke = TheModule->getFunction("emscripten_preinvoke"))) {
    FunctionType *VoidFunc = FunctionType::get(Void, false);
    PreInvoke = Function::Create(VoidFunc, GlobalValue::ExternalLinkage, "emscripten_preinvoke", TheModule);
  }

  if (!(PostInvoke = TheModule->getFunction("emscripten_postinvoke"))) {
    FunctionType *IntFunc = FunctionType::get(i32, false);
    PostInvoke = Function::Create(IntFunc, GlobalValue::ExternalLinkage, "emscripten_postinvoke", TheModule);
  }

  FunctionType *LandingPadFunc = FunctionType::get(i8P, true);
  LandingPad = Function::Create(LandingPadFunc, GlobalValue::ExternalLinkage, "emscripten_landingpad", TheModule);

  FunctionType *ResumeFunc = FunctionType::get(Void, true);
  Resume = Function::Create(ResumeFunc, GlobalValue::ExternalLinkage, "emscripten_resume", TheModule);
  
  // Process

  bool HasWhitelist = Whitelist.size() > 0;
  std::string WhitelistChecker;
  if (HasWhitelist) WhitelistChecker = "," + Whitelist + ",";

  bool Changed = false;

  for (Module::iterator Iter = M.begin(), E = M.end(); Iter != E; ) {
    Function *F = Iter++;

    std::vector<Instruction*> ToErase;
    std::set<LandingPadInst*> LandingPads;

    bool AllowExceptionsInFunc = !HasWhitelist || int(WhitelistChecker.find(F->getName())) > 0;

    for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB) {
      // check terminator for invokes
      if (InvokeInst *II = dyn_cast<InvokeInst>(BB->getTerminator())) {
        LandingPads.insert(II->getLandingPadInst());

        bool NeedInvoke = AllowExceptionsInFunc && canThrow(II->getCalledValue());

        if (NeedInvoke) {
          // Insert a normal call instruction folded in between pre- and post-invoke
          CallInst::Create(PreInvoke, "", II);

          SmallVector<Value*,16> CallArgs(II->op_begin(), II->op_end() - 3);
          CallInst *NewCall = CallInst::Create(II->getCalledValue(),
                                               CallArgs, "", II);
          NewCall->takeName(II);
          NewCall->setCallingConv(II->getCallingConv());
          NewCall->setAttributes(II->getAttributes());
          NewCall->setDebugLoc(II->getDebugLoc());
          II->replaceAllUsesWith(NewCall);
          ToErase.push_back(II);

          CallInst *Post = CallInst::Create(PostInvoke, "", II);
          Instruction *Post1 = new TruncInst(Post, i1, "", II);

          // Insert a branch based on the postInvoke
          BranchInst::Create(II->getUnwindDest(), II->getNormalDest(), Post1, II);
        } else {
          // This can't throw, and we don't need this invoke, just replace it with a call+branch
          SmallVector<Value*,16> CallArgs(II->op_begin(), II->op_end() - 3);
          CallInst *NewCall = CallInst::Create(II->getCalledValue(),
                                               CallArgs, "", II);
          NewCall->takeName(II);
          NewCall->setCallingConv(II->getCallingConv());
          NewCall->setAttributes(II->getAttributes());
          NewCall->setDebugLoc(II->getDebugLoc());
          II->replaceAllUsesWith(NewCall);
          ToErase.push_back(II);

          BranchInst::Create(II->getNormalDest(), II);

          // Remove any PHI node entries from the exception destination.
          II->getUnwindDest()->removePredecessor(BB);
        }

        Changed = true;
      }
      // scan the body of the basic block for resumes
      for (BasicBlock::iterator Iter = BB->begin(), E = BB->end();
           Iter != E; ) {
        Instruction *I = Iter++;
        if (ResumeInst *R = dyn_cast<ResumeInst>(I)) {
//.........这里部分代码省略.........

/// setupFunctionContext - Allocate the function context on the stack and fill
/// it with all of the data that we know at this point.
Value *SjLjEHPass::
setupFunctionContext(Function &F, ArrayRef<LandingPadInst*> LPads) {
  BasicBlock *EntryBB = F.begin();

  // Create an alloca for the incoming jump buffer ptr and the new jump buffer
  // that needs to be restored on all exits from the function. This is an alloca
  // because the value needs to be added to the global context list.
  unsigned Align =
    TLI->getTargetData()->getPrefTypeAlignment(FunctionContextTy);
  AllocaInst *FuncCtx =
    new AllocaInst(FunctionContextTy, 0, Align, "fn_context", EntryBB->begin());

  // Fill in the function context structure.
  Value *Idxs[2];
  Type *Int32Ty = Type::getInt32Ty(F.getContext());
  Value *Zero = ConstantInt::get(Int32Ty, 0);
  Value *One = ConstantInt::get(Int32Ty, 1);

  // Keep around a reference to the call_site field.
  Idxs[0] = Zero;
  Idxs[1] = One;
  CallSite = GetElementPtrInst::Create(FuncCtx, Idxs, "call_site",
                                       EntryBB->getTerminator());

  // Reference the __data field.
  Idxs[1] = ConstantInt::get(Int32Ty, 2);
  Value *FCData = GetElementPtrInst::Create(FuncCtx, Idxs, "__data",
                                            EntryBB->getTerminator());

  // The exception value comes back in context->__data[0].
  Idxs[1] = Zero;
  Value *ExceptionAddr = GetElementPtrInst::Create(FCData, Idxs,
                                                   "exception_gep",
                                                   EntryBB->getTerminator());

  // The exception selector comes back in context->__data[1].
  Idxs[1] = One;
  Value *SelectorAddr = GetElementPtrInst::Create(FCData, Idxs,
                                                  "exn_selector_gep",
                                                  EntryBB->getTerminator());

  for (unsigned I = 0, E = LPads.size(); I != E; ++I) {
    LandingPadInst *LPI = LPads[I];
    IRBuilder<> Builder(LPI->getParent()->getFirstInsertionPt());

    Value *ExnVal = Builder.CreateLoad(ExceptionAddr, true, "exn_val");
    ExnVal = Builder.CreateIntToPtr(ExnVal, Type::getInt8PtrTy(F.getContext()));
    Value *SelVal = Builder.CreateLoad(SelectorAddr, true, "exn_selector_val");

    Type *LPadType = LPI->getType();
    Value *LPadVal = UndefValue::get(LPadType);
    LPadVal = Builder.CreateInsertValue(LPadVal, ExnVal, 0, "lpad.val");
    LPadVal = Builder.CreateInsertValue(LPadVal, SelVal, 1, "lpad.val");

    LPI->replaceAllUsesWith(LPadVal);
  }

  // Personality function
  Idxs[1] = ConstantInt::get(Int32Ty, 3);
  if (!PersonalityFn)
    PersonalityFn = LPads[0]->getPersonalityFn();
  Value *PersonalityFieldPtr =
    GetElementPtrInst::Create(FuncCtx, Idxs, "pers_fn_gep",
                              EntryBB->getTerminator());
  new StoreInst(PersonalityFn, PersonalityFieldPtr, true,
                EntryBB->getTerminator());

  // LSDA address
  Idxs[1] = ConstantInt::get(Int32Ty, 4);
  Value *LSDAFieldPtr = GetElementPtrInst::Create(FuncCtx, Idxs, "lsda_gep",
                                                  EntryBB->getTerminator());
  Value *LSDA = CallInst::Create(LSDAAddrFn, "lsda_addr",
                                 EntryBB->getTerminator());
  new StoreInst(LSDA, LSDAFieldPtr, true, EntryBB->getTerminator());

  return FuncCtx;
}