C++ StoreInst::eraseFromParent方法代码示例

StoreInst *
StackAllocationPromoter::promoteAllocationInBlock(SILBasicBlock *BB) {
  LLVM_DEBUG(llvm::dbgs() << "*** Promoting ASI in block: " << *ASI);

  // We don't know the value of the alloca until we find the first store.
  SILValue RunningVal = SILValue();
  // Keep track of the last StoreInst that we found.
  StoreInst *LastStore = nullptr;

  // For all instructions in the block.
  for (auto BBI = BB->begin(), E = BB->end(); BBI != E;) {
    SILInstruction *Inst = &*BBI;
    ++BBI;

    if (isLoadFromStack(Inst, ASI)) {
      auto Load = cast<LoadInst>(Inst);
      if (RunningVal) {
        // If we are loading from the AllocStackInst and we already know the
        // content of the Alloca then use it.
        LLVM_DEBUG(llvm::dbgs() << "*** Promoting load: " << *Load);
        
        replaceLoad(Load, RunningVal, ASI);
        NumInstRemoved++;
      } else if (Load->getOperand() == ASI) {
        // If we don't know the content of the AllocStack then the loaded
        // value *is* the new value;
        LLVM_DEBUG(llvm::dbgs() << "*** First load: " << *Load);
        RunningVal = Load;
      }
      continue;
    }

    // Remove stores and record the value that we are saving as the running
    // value.
    if (auto *SI = dyn_cast<StoreInst>(Inst)) {
      if (SI->getDest() != ASI)
        continue;

      // The stored value is the new running value.
      RunningVal = SI->getSrc();

      // If we met a store before this one, delete it.
      if (LastStore) {
        NumInstRemoved++;
        LLVM_DEBUG(llvm::dbgs() << "*** Removing redundant store: "
                                << *LastStore);
        LastStore->eraseFromParent();
      }
      LastStore = SI;
      continue;
    }

    // Replace debug_value_addr with debug_value of the promoted value
    // if we have a valid value to use at this point. Otherwise we'll
    // promote this when we deal with hooking up phis.
    if (auto *DVAI = dyn_cast<DebugValueAddrInst>(Inst)) {
      if (DVAI->getOperand() == ASI &&
          RunningVal)
        promoteDebugValueAddr(DVAI, RunningVal, B);
      continue;
    }

    // Replace destroys with a release of the value.
    if (auto *DAI = dyn_cast<DestroyAddrInst>(Inst)) {
      if (DAI->getOperand() == ASI &&
          RunningVal) {
        replaceDestroy(DAI, RunningVal);
      }
      continue;
    }

    // Stop on deallocation.
    if (auto *DSI = dyn_cast<DeallocStackInst>(Inst)) {
      if (DSI->getOperand() == ASI)
        break;
    }
  }
  if (LastStore) {
    LLVM_DEBUG(llvm::dbgs() << "*** Finished promotion. Last store: "
                            << *LastStore);
  } else {
    LLVM_DEBUG(llvm::dbgs() << "*** Finished promotion with no stores.\n");
  }
  return LastStore;
}

/// Attempt to merge an objc_release with a store, load, and objc_retain to form
/// an objc_storeStrong. This can be a little tricky because the instructions
/// don't always appear in order, and there may be unrelated intervening
/// instructions.
void ObjCARCContract::ContractRelease(Instruction *Release,
                                      inst_iterator &Iter) {
  LoadInst *Load = dyn_cast<LoadInst>(GetObjCArg(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;

  // Walk down to find the store and the release, which may be in either order.
  BasicBlock::iterator I = Load, End = BB->end();
  ++I;
  AliasAnalysis::Location Loc = AA->getLocation(Load);
  StoreInst *Store = 0;
  bool SawRelease = false;
  for (; !Store || !SawRelease; ++I) {
    if (I == End)
      return;

    Instruction *Inst = I;
    if (Inst == Release) {
      SawRelease = true;
      continue;
    }

    InstructionClass Class = GetBasicInstructionClass(Inst);

    // Unrelated retains are harmless.
    if (IsRetain(Class))
      continue;

    if (Store) {
      // The store is the point where we're going to put the objc_storeStrong,
      // so make sure there are no uses after it.
      if (CanUse(Inst, Load, PA, Class))
        return;
    } else if (AA->getModRefInfo(Inst, Loc) & AliasAnalysis::Mod) {
      // We are moving the load down to the store, so check for anything
      // else which writes to the memory between the load and the store.
      Store = dyn_cast<StoreInst>(Inst);
      if (!Store || !Store->isSimple()) return;
      if (Store->getPointerOperand() != Loc.Ptr) return;
    }
  }

  Value *New = StripPointerCastsAndObjCCalls(Store->getValueOperand());

  // Walk up to find the retain.
  I = Store;
  BasicBlock::iterator Begin = BB->begin();
  while (I != Begin && GetBasicInstructionClass(I) != IC_Retain)
    --I;
  Instruction *Retain = I;
  if (GetBasicInstructionClass(Retain) != IC_Retain) return;
  if (GetObjCArg(Retain) != New) return;

  Changed = true;
  ++NumStoreStrongs;

  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);
  CallInst *StoreStrong =
    CallInst::Create(getStoreStrongCallee(BB->getParent()->getParent()),
                     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);

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

/// \brief Removes instructions that create the callee value if they are no
/// longer necessary after inlining.
static void
cleanupCalleeValue(SILValue CalleeValue, ArrayRef<SILValue> CaptureArgs,
                   ArrayRef<SILValue> FullArgs) {
  SmallVector<SILInstruction*, 16> InstsToDelete;
  for (SILValue V : FullArgs) {
    if (SILInstruction *I = dyn_cast<SILInstruction>(V))
      if (I != CalleeValue &&
          isInstructionTriviallyDead(I))
        InstsToDelete.push_back(I);
  }
  recursivelyDeleteTriviallyDeadInstructions(InstsToDelete, true);

  // Handle the case where the callee of the apply is a load instruction.
  if (LoadInst *LI = dyn_cast<LoadInst>(CalleeValue)) {
    auto *PBI = cast<ProjectBoxInst>(LI->getOperand());
    auto *ABI = cast<AllocBoxInst>(PBI->getOperand());

    // The load instruction must have no more uses left to erase it.
    if (!LI->use_empty())
      return;
    LI->eraseFromParent();

    // Look through uses of the alloc box the load is loading from to find up to
    // one store and up to one strong release.
    StrongReleaseInst *SRI = nullptr;
    for (Operand *ABIUse : ABI->getUses()) {
      if (SRI == nullptr && isa<StrongReleaseInst>(ABIUse->getUser())) {
        SRI = cast<StrongReleaseInst>(ABIUse->getUser());
      } else if (ABIUse->getUser() != PBI)
        return;
    }
    StoreInst *SI = nullptr;
    for (Operand *PBIUse : PBI->getUses()) {
      if (SI == nullptr && isa<StoreInst>(PBIUse->getUser())) {
        SI = cast<StoreInst>(PBIUse->getUser());
      } else
        return;
    }

    // If we found a store, record its source and erase it.
    if (SI) {
      CalleeValue = SI->getSrc();
      SI->eraseFromParent();
    } else {
      CalleeValue = SILValue();
    }

    // If we found a strong release, replace it with a strong release of the
    // source of the store and erase it.
    if (SRI) {
      if (CalleeValue)
        SILBuilderWithScope(SRI)
            .emitStrongReleaseAndFold(SRI->getLoc(), CalleeValue);
      SRI->eraseFromParent();
    }

    assert(PBI->use_empty());
    PBI->eraseFromParent();
    assert(ABI->use_empty());
    ABI->eraseFromParent();
    if (!CalleeValue)
      return;
  }

  if (auto *PAI = dyn_cast<PartialApplyInst>(CalleeValue)) {
    SILValue Callee = PAI->getCallee();
    if (!tryDeleteDeadClosure(PAI))
      return;
    CalleeValue = Callee;
  }

  if (auto *TTTFI = dyn_cast<ThinToThickFunctionInst>(CalleeValue)) {
    SILValue Callee = TTTFI->getCallee();
    if (!tryDeleteDeadClosure(TTTFI))
      return;
    CalleeValue = Callee;
  }

  if (FunctionRefInst *FRI = dyn_cast<FunctionRefInst>(CalleeValue)) {
    if (!FRI->use_empty())
      return;
    FRI->eraseFromParent();
  }
}

bool NVPTXLowerAggrCopies::runOnFunction(Function &F) {
  SmallVector<LoadInst *, 4> aggrLoads;
  SmallVector<MemTransferInst *, 4> aggrMemcpys;
  SmallVector<MemSetInst *, 4> aggrMemsets;

  const DataLayout &DL = F.getParent()->getDataLayout();
  LLVMContext &Context = F.getParent()->getContext();

  //
  // Collect all the aggrLoads, aggrMemcpys and addrMemsets.
  //
  //const BasicBlock *firstBB = &F.front();  // first BB in F
  for (Function::iterator BI = F.begin(), BE = F.end(); BI != BE; ++BI) {
    //BasicBlock *bb = BI;
    for (BasicBlock::iterator II = BI->begin(), IE = BI->end(); II != IE;
         ++II) {
      if (LoadInst *load = dyn_cast<LoadInst>(II)) {

        if (!load->hasOneUse())
          continue;

        if (DL.getTypeStoreSize(load->getType()) < MaxAggrCopySize)
          continue;

        User *use = load->user_back();
        if (StoreInst *store = dyn_cast<StoreInst>(use)) {
          if (store->getOperand(0) != load) //getValueOperand
            continue;
          aggrLoads.push_back(load);
        }
      } else if (MemTransferInst *intr = dyn_cast<MemTransferInst>(II)) {
        Value *len = intr->getLength();
        // If the number of elements being copied is greater
        // than MaxAggrCopySize, lower it to a loop
        if (ConstantInt *len_int = dyn_cast<ConstantInt>(len)) {
          if (len_int->getZExtValue() >= MaxAggrCopySize) {
            aggrMemcpys.push_back(intr);
          }
        } else {
          // turn variable length memcpy/memmov into loop
          aggrMemcpys.push_back(intr);
        }
      } else if (MemSetInst *memsetintr = dyn_cast<MemSetInst>(II)) {
        Value *len = memsetintr->getLength();
        if (ConstantInt *len_int = dyn_cast<ConstantInt>(len)) {
          if (len_int->getZExtValue() >= MaxAggrCopySize) {
            aggrMemsets.push_back(memsetintr);
          }
        } else {
          // turn variable length memset into loop
          aggrMemsets.push_back(memsetintr);
        }
      }
    }
  }
  if ((aggrLoads.size() == 0) && (aggrMemcpys.size() == 0) &&
      (aggrMemsets.size() == 0))
    return false;

  //
  // Do the transformation of an aggr load/copy/set to a loop
  //
  for (unsigned i = 0, e = aggrLoads.size(); i != e; ++i) {
    LoadInst *load = aggrLoads[i];
    StoreInst *store = dyn_cast<StoreInst>(*load->user_begin());
    Value *srcAddr = load->getOperand(0);
    Value *dstAddr = store->getOperand(1);
    unsigned numLoads = DL.getTypeStoreSize(load->getType());
    Value *len = ConstantInt::get(Type::getInt32Ty(Context), numLoads);

    convertTransferToLoop(store, srcAddr, dstAddr, len, load->isVolatile(),
                          store->isVolatile(), Context, F);

    store->eraseFromParent();
    load->eraseFromParent();
  }

  for (unsigned i = 0, e = aggrMemcpys.size(); i != e; ++i) {
    MemTransferInst *cpy = aggrMemcpys[i];
    Value *len = cpy->getLength();
    // llvm 2.7 version of memcpy does not have volatile
    // operand yet. So always making it non-volatile
    // optimistically, so that we don't see unnecessary
    // st.volatile in ptx
    convertTransferToLoop(cpy, cpy->getSource(), cpy->getDest(), len, false,
                          false, Context, F);
    cpy->eraseFromParent();
  }

  for (unsigned i = 0, e = aggrMemsets.size(); i != e; ++i) {
    MemSetInst *memsetinst = aggrMemsets[i];
    Value *len = memsetinst->getLength();
    Value *val = memsetinst->getValue();
    convertMemSetToLoop(memsetinst, memsetinst->getDest(), len, val, Context,
                        F);
    memsetinst->eraseFromParent();
  }

  return true;
}