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Diffstat (limited to 'contrib/llvm-project/llvm/lib/Transforms/Scalar/CallSiteSplitting.cpp')
| -rw-r--r-- | contrib/llvm-project/llvm/lib/Transforms/Scalar/CallSiteSplitting.cpp | 590 | 
1 files changed, 590 insertions, 0 deletions
diff --git a/contrib/llvm-project/llvm/lib/Transforms/Scalar/CallSiteSplitting.cpp b/contrib/llvm-project/llvm/lib/Transforms/Scalar/CallSiteSplitting.cpp new file mode 100644 index 000000000000..b26bd1114bd4 --- /dev/null +++ b/contrib/llvm-project/llvm/lib/Transforms/Scalar/CallSiteSplitting.cpp @@ -0,0 +1,590 @@ +//===- CallSiteSplitting.cpp ----------------------------------------------===// +// +// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. +// See https://llvm.org/LICENSE.txt for license information. +// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception +// +//===----------------------------------------------------------------------===// +// +// This file implements a transformation that tries to split a call-site to pass +// more constrained arguments if its argument is predicated in the control flow +// so that we can expose better context to the later passes (e.g, inliner, jump +// threading, or IPA-CP based function cloning, etc.). +// As of now we support two cases : +// +// 1) Try to a split call-site with constrained arguments, if any constraints +// on any argument can be found by following the single predecessors of the +// all site's predecessors. Currently this pass only handles call-sites with 2 +// predecessors. For example, in the code below, we try to split the call-site +// since we can predicate the argument(ptr) based on the OR condition. +// +// Split from : +//   if (!ptr || c) +//     callee(ptr); +// to : +//   if (!ptr) +//     callee(null)         // set the known constant value +//   else if (c) +//     callee(nonnull ptr)  // set non-null attribute in the argument +// +// 2) We can also split a call-site based on constant incoming values of a PHI +// For example, +// from : +//   Header: +//    %c = icmp eq i32 %i1, %i2 +//    br i1 %c, label %Tail, label %TBB +//   TBB: +//    br label Tail% +//   Tail: +//    %p = phi i32 [ 0, %Header], [ 1, %TBB] +//    call void @bar(i32 %p) +// to +//   Header: +//    %c = icmp eq i32 %i1, %i2 +//    br i1 %c, label %Tail-split0, label %TBB +//   TBB: +//    br label %Tail-split1 +//   Tail-split0: +//    call void @bar(i32 0) +//    br label %Tail +//   Tail-split1: +//    call void @bar(i32 1) +//    br label %Tail +//   Tail: +//    %p = phi i32 [ 0, %Tail-split0 ], [ 1, %Tail-split1 ] +// +//===----------------------------------------------------------------------===// + +#include "llvm/Transforms/Scalar/CallSiteSplitting.h" +#include "llvm/ADT/Statistic.h" +#include "llvm/Analysis/TargetLibraryInfo.h" +#include "llvm/Analysis/TargetTransformInfo.h" +#include "llvm/IR/IntrinsicInst.h" +#include "llvm/IR/PatternMatch.h" +#include "llvm/InitializePasses.h" +#include "llvm/Support/CommandLine.h" +#include "llvm/Support/Debug.h" +#include "llvm/Transforms/Scalar.h" +#include "llvm/Transforms/Utils/BasicBlockUtils.h" +#include "llvm/Transforms/Utils/Cloning.h" +#include "llvm/Transforms/Utils/Local.h" + +using namespace llvm; +using namespace PatternMatch; + +#define DEBUG_TYPE "callsite-splitting" + +STATISTIC(NumCallSiteSplit, "Number of call-site split"); + +/// Only allow instructions before a call, if their CodeSize cost is below +/// DuplicationThreshold. Those instructions need to be duplicated in all +/// split blocks. +static cl::opt<unsigned> +    DuplicationThreshold("callsite-splitting-duplication-threshold", cl::Hidden, +                         cl::desc("Only allow instructions before a call, if " +                                  "their cost is below DuplicationThreshold"), +                         cl::init(5)); + +static void addNonNullAttribute(CallBase &CB, Value *Op) { +  unsigned ArgNo = 0; +  for (auto &I : CB.args()) { +    if (&*I == Op) +      CB.addParamAttr(ArgNo, Attribute::NonNull); +    ++ArgNo; +  } +} + +static void setConstantInArgument(CallBase &CB, Value *Op, +                                  Constant *ConstValue) { +  unsigned ArgNo = 0; +  for (auto &I : CB.args()) { +    if (&*I == Op) { +      // It is possible we have already added the non-null attribute to the +      // parameter by using an earlier constraining condition. +      CB.removeParamAttr(ArgNo, Attribute::NonNull); +      CB.setArgOperand(ArgNo, ConstValue); +    } +    ++ArgNo; +  } +} + +static bool isCondRelevantToAnyCallArgument(ICmpInst *Cmp, CallBase &CB) { +  assert(isa<Constant>(Cmp->getOperand(1)) && "Expected a constant operand."); +  Value *Op0 = Cmp->getOperand(0); +  unsigned ArgNo = 0; +  for (auto I = CB.arg_begin(), E = CB.arg_end(); I != E; ++I, ++ArgNo) { +    // Don't consider constant or arguments that are already known non-null. +    if (isa<Constant>(*I) || CB.paramHasAttr(ArgNo, Attribute::NonNull)) +      continue; + +    if (*I == Op0) +      return true; +  } +  return false; +} + +typedef std::pair<ICmpInst *, unsigned> ConditionTy; +typedef SmallVector<ConditionTy, 2> ConditionsTy; + +/// If From has a conditional jump to To, add the condition to Conditions, +/// if it is relevant to any argument at CB. +static void recordCondition(CallBase &CB, BasicBlock *From, BasicBlock *To, +                            ConditionsTy &Conditions) { +  auto *BI = dyn_cast<BranchInst>(From->getTerminator()); +  if (!BI || !BI->isConditional()) +    return; + +  CmpInst::Predicate Pred; +  Value *Cond = BI->getCondition(); +  if (!match(Cond, m_ICmp(Pred, m_Value(), m_Constant()))) +    return; + +  ICmpInst *Cmp = cast<ICmpInst>(Cond); +  if (Pred == ICmpInst::ICMP_EQ || Pred == ICmpInst::ICMP_NE) +    if (isCondRelevantToAnyCallArgument(Cmp, CB)) +      Conditions.push_back({Cmp, From->getTerminator()->getSuccessor(0) == To +                                     ? Pred +                                     : Cmp->getInversePredicate()}); +} + +/// Record ICmp conditions relevant to any argument in CB following Pred's +/// single predecessors. If there are conflicting conditions along a path, like +/// x == 1 and x == 0, the first condition will be used. We stop once we reach +/// an edge to StopAt. +static void recordConditions(CallBase &CB, BasicBlock *Pred, +                             ConditionsTy &Conditions, BasicBlock *StopAt) { +  BasicBlock *From = Pred; +  BasicBlock *To = Pred; +  SmallPtrSet<BasicBlock *, 4> Visited; +  while (To != StopAt && !Visited.count(From->getSinglePredecessor()) && +         (From = From->getSinglePredecessor())) { +    recordCondition(CB, From, To, Conditions); +    Visited.insert(From); +    To = From; +  } +} + +static void addConditions(CallBase &CB, const ConditionsTy &Conditions) { +  for (auto &Cond : Conditions) { +    Value *Arg = Cond.first->getOperand(0); +    Constant *ConstVal = cast<Constant>(Cond.first->getOperand(1)); +    if (Cond.second == ICmpInst::ICMP_EQ) +      setConstantInArgument(CB, Arg, ConstVal); +    else if (ConstVal->getType()->isPointerTy() && ConstVal->isNullValue()) { +      assert(Cond.second == ICmpInst::ICMP_NE); +      addNonNullAttribute(CB, Arg); +    } +  } +} + +static SmallVector<BasicBlock *, 2> getTwoPredecessors(BasicBlock *BB) { +  SmallVector<BasicBlock *, 2> Preds(predecessors((BB))); +  assert(Preds.size() == 2 && "Expected exactly 2 predecessors!"); +  return Preds; +} + +static bool canSplitCallSite(CallBase &CB, TargetTransformInfo &TTI) { +  if (CB.isConvergent() || CB.cannotDuplicate()) +    return false; + +  // FIXME: As of now we handle only CallInst. InvokeInst could be handled +  // without too much effort. +  if (!isa<CallInst>(CB)) +    return false; + +  BasicBlock *CallSiteBB = CB.getParent(); +  // Need 2 predecessors and cannot split an edge from an IndirectBrInst. +  SmallVector<BasicBlock *, 2> Preds(predecessors(CallSiteBB)); +  if (Preds.size() != 2 || isa<IndirectBrInst>(Preds[0]->getTerminator()) || +      isa<IndirectBrInst>(Preds[1]->getTerminator())) +    return false; + +  // BasicBlock::canSplitPredecessors is more aggressive, so checking for +  // BasicBlock::isEHPad as well. +  if (!CallSiteBB->canSplitPredecessors() || CallSiteBB->isEHPad()) +    return false; + +  // Allow splitting a call-site only when the CodeSize cost of the +  // instructions before the call is less then DuplicationThreshold. The +  // instructions before the call will be duplicated in the split blocks and +  // corresponding uses will be updated. +  unsigned Cost = 0; +  for (auto &InstBeforeCall : +       llvm::make_range(CallSiteBB->begin(), CB.getIterator())) { +    Cost += TTI.getInstructionCost(&InstBeforeCall, +                                   TargetTransformInfo::TCK_CodeSize); +    if (Cost >= DuplicationThreshold) +      return false; +  } + +  return true; +} + +static Instruction *cloneInstForMustTail(Instruction *I, Instruction *Before, +                                         Value *V) { +  Instruction *Copy = I->clone(); +  Copy->setName(I->getName()); +  Copy->insertBefore(Before); +  if (V) +    Copy->setOperand(0, V); +  return Copy; +} + +/// Copy mandatory `musttail` return sequence that follows original `CI`, and +/// link it up to `NewCI` value instead: +/// +///   * (optional) `bitcast NewCI to ...` +///   * `ret bitcast or NewCI` +/// +/// Insert this sequence right before `SplitBB`'s terminator, which will be +/// cleaned up later in `splitCallSite` below. +static void copyMustTailReturn(BasicBlock *SplitBB, Instruction *CI, +                               Instruction *NewCI) { +  bool IsVoid = SplitBB->getParent()->getReturnType()->isVoidTy(); +  auto II = std::next(CI->getIterator()); + +  BitCastInst* BCI = dyn_cast<BitCastInst>(&*II); +  if (BCI) +    ++II; + +  ReturnInst* RI = dyn_cast<ReturnInst>(&*II); +  assert(RI && "`musttail` call must be followed by `ret` instruction"); + +  Instruction *TI = SplitBB->getTerminator(); +  Value *V = NewCI; +  if (BCI) +    V = cloneInstForMustTail(BCI, TI, V); +  cloneInstForMustTail(RI, TI, IsVoid ? nullptr : V); + +  // FIXME: remove TI here, `DuplicateInstructionsInSplitBetween` has a bug +  // that prevents doing this now. +} + +/// For each (predecessor, conditions from predecessors) pair, it will split the +/// basic block containing the call site, hook it up to the predecessor and +/// replace the call instruction with new call instructions, which contain +/// constraints based on the conditions from their predecessors. +/// For example, in the IR below with an OR condition, the call-site can +/// be split. In this case, Preds for Tail is [(Header, a == null), +/// (TBB, a != null, b == null)]. Tail is replaced by 2 split blocks, containing +/// CallInst1, which has constraints based on the conditions from Head and +/// CallInst2, which has constraints based on the conditions coming from TBB. +/// +/// From : +/// +///   Header: +///     %c = icmp eq i32* %a, null +///     br i1 %c %Tail, %TBB +///   TBB: +///     %c2 = icmp eq i32* %b, null +///     br i1 %c %Tail, %End +///   Tail: +///     %ca = call i1  @callee (i32* %a, i32* %b) +/// +///  to : +/// +///   Header:                          // PredBB1 is Header +///     %c = icmp eq i32* %a, null +///     br i1 %c %Tail-split1, %TBB +///   TBB:                             // PredBB2 is TBB +///     %c2 = icmp eq i32* %b, null +///     br i1 %c %Tail-split2, %End +///   Tail-split1: +///     %ca1 = call @callee (i32* null, i32* %b)         // CallInst1 +///    br %Tail +///   Tail-split2: +///     %ca2 = call @callee (i32* nonnull %a, i32* null) // CallInst2 +///    br %Tail +///   Tail: +///    %p = phi i1 [%ca1, %Tail-split1],[%ca2, %Tail-split2] +/// +/// Note that in case any arguments at the call-site are constrained by its +/// predecessors, new call-sites with more constrained arguments will be +/// created in createCallSitesOnPredicatedArgument(). +static void splitCallSite( +    CallBase &CB, +    const SmallVectorImpl<std::pair<BasicBlock *, ConditionsTy>> &Preds, +    DomTreeUpdater &DTU) { +  BasicBlock *TailBB = CB.getParent(); +  bool IsMustTailCall = CB.isMustTailCall(); + +  PHINode *CallPN = nullptr; + +  // `musttail` calls must be followed by optional `bitcast`, and `ret`. The +  // split blocks will be terminated right after that so there're no users for +  // this phi in a `TailBB`. +  if (!IsMustTailCall && !CB.use_empty()) { +    CallPN = PHINode::Create(CB.getType(), Preds.size(), "phi.call"); +    CallPN->setDebugLoc(CB.getDebugLoc()); +  } + +  LLVM_DEBUG(dbgs() << "split call-site : " << CB << " into \n"); + +  assert(Preds.size() == 2 && "The ValueToValueMaps array has size 2."); +  // ValueToValueMapTy is neither copy nor moveable, so we use a simple array +  // here. +  ValueToValueMapTy ValueToValueMaps[2]; +  for (unsigned i = 0; i < Preds.size(); i++) { +    BasicBlock *PredBB = Preds[i].first; +    BasicBlock *SplitBlock = DuplicateInstructionsInSplitBetween( +        TailBB, PredBB, &*std::next(CB.getIterator()), ValueToValueMaps[i], +        DTU); +    assert(SplitBlock && "Unexpected new basic block split."); + +    auto *NewCI = +        cast<CallBase>(&*std::prev(SplitBlock->getTerminator()->getIterator())); +    addConditions(*NewCI, Preds[i].second); + +    // Handle PHIs used as arguments in the call-site. +    for (PHINode &PN : TailBB->phis()) { +      unsigned ArgNo = 0; +      for (auto &CI : CB.args()) { +        if (&*CI == &PN) { +          NewCI->setArgOperand(ArgNo, PN.getIncomingValueForBlock(SplitBlock)); +        } +        ++ArgNo; +      } +    } +    LLVM_DEBUG(dbgs() << "    " << *NewCI << " in " << SplitBlock->getName() +                      << "\n"); +    if (CallPN) +      CallPN->addIncoming(NewCI, SplitBlock); + +    // Clone and place bitcast and return instructions before `TI` +    if (IsMustTailCall) +      copyMustTailReturn(SplitBlock, &CB, NewCI); +  } + +  NumCallSiteSplit++; + +  // FIXME: remove TI in `copyMustTailReturn` +  if (IsMustTailCall) { +    // Remove superfluous `br` terminators from the end of the Split blocks +    // NOTE: Removing terminator removes the SplitBlock from the TailBB's +    // predecessors. Therefore we must get complete list of Splits before +    // attempting removal. +    SmallVector<BasicBlock *, 2> Splits(predecessors((TailBB))); +    assert(Splits.size() == 2 && "Expected exactly 2 splits!"); +    for (unsigned i = 0; i < Splits.size(); i++) { +      Splits[i]->getTerminator()->eraseFromParent(); +      DTU.applyUpdatesPermissive({{DominatorTree::Delete, Splits[i], TailBB}}); +    } + +    // Erase the tail block once done with musttail patching +    DTU.deleteBB(TailBB); +    return; +  } + +  auto *OriginalBegin = &*TailBB->begin(); +  // Replace users of the original call with a PHI mering call-sites split. +  if (CallPN) { +    CallPN->insertBefore(OriginalBegin); +    CB.replaceAllUsesWith(CallPN); +  } + +  // Remove instructions moved to split blocks from TailBB, from the duplicated +  // call instruction to the beginning of the basic block. If an instruction +  // has any uses, add a new PHI node to combine the values coming from the +  // split blocks. The new PHI nodes are placed before the first original +  // instruction, so we do not end up deleting them. By using reverse-order, we +  // do not introduce unnecessary PHI nodes for def-use chains from the call +  // instruction to the beginning of the block. +  auto I = CB.getReverseIterator(); +  while (I != TailBB->rend()) { +    Instruction *CurrentI = &*I++; +    if (!CurrentI->use_empty()) { +      // If an existing PHI has users after the call, there is no need to create +      // a new one. +      if (isa<PHINode>(CurrentI)) +        continue; +      PHINode *NewPN = PHINode::Create(CurrentI->getType(), Preds.size()); +      NewPN->setDebugLoc(CurrentI->getDebugLoc()); +      for (auto &Mapping : ValueToValueMaps) +        NewPN->addIncoming(Mapping[CurrentI], +                           cast<Instruction>(Mapping[CurrentI])->getParent()); +      NewPN->insertBefore(&*TailBB->begin()); +      CurrentI->replaceAllUsesWith(NewPN); +    } +    CurrentI->eraseFromParent(); +    // We are done once we handled the first original instruction in TailBB. +    if (CurrentI == OriginalBegin) +      break; +  } +} + +// Return true if the call-site has an argument which is a PHI with only +// constant incoming values. +static bool isPredicatedOnPHI(CallBase &CB) { +  BasicBlock *Parent = CB.getParent(); +  if (&CB != Parent->getFirstNonPHIOrDbg()) +    return false; + +  for (auto &PN : Parent->phis()) { +    for (auto &Arg : CB.args()) { +      if (&*Arg != &PN) +        continue; +      assert(PN.getNumIncomingValues() == 2 && +             "Unexpected number of incoming values"); +      if (PN.getIncomingBlock(0) == PN.getIncomingBlock(1)) +        return false; +      if (PN.getIncomingValue(0) == PN.getIncomingValue(1)) +        continue; +      if (isa<Constant>(PN.getIncomingValue(0)) && +          isa<Constant>(PN.getIncomingValue(1))) +        return true; +    } +  } +  return false; +} + +using PredsWithCondsTy = SmallVector<std::pair<BasicBlock *, ConditionsTy>, 2>; + +// Check if any of the arguments in CS are predicated on a PHI node and return +// the set of predecessors we should use for splitting. +static PredsWithCondsTy shouldSplitOnPHIPredicatedArgument(CallBase &CB) { +  if (!isPredicatedOnPHI(CB)) +    return {}; + +  auto Preds = getTwoPredecessors(CB.getParent()); +  return {{Preds[0], {}}, {Preds[1], {}}}; +} + +// Checks if any of the arguments in CS are predicated in a predecessor and +// returns a list of predecessors with the conditions that hold on their edges +// to CS. +static PredsWithCondsTy shouldSplitOnPredicatedArgument(CallBase &CB, +                                                        DomTreeUpdater &DTU) { +  auto Preds = getTwoPredecessors(CB.getParent()); +  if (Preds[0] == Preds[1]) +    return {}; + +  // We can stop recording conditions once we reached the immediate dominator +  // for the block containing the call site. Conditions in predecessors of the +  // that node will be the same for all paths to the call site and splitting +  // is not beneficial. +  assert(DTU.hasDomTree() && "We need a DTU with a valid DT!"); +  auto *CSDTNode = DTU.getDomTree().getNode(CB.getParent()); +  BasicBlock *StopAt = CSDTNode ? CSDTNode->getIDom()->getBlock() : nullptr; + +  SmallVector<std::pair<BasicBlock *, ConditionsTy>, 2> PredsCS; +  for (auto *Pred : make_range(Preds.rbegin(), Preds.rend())) { +    ConditionsTy Conditions; +    // Record condition on edge BB(CS) <- Pred +    recordCondition(CB, Pred, CB.getParent(), Conditions); +    // Record conditions following Pred's single predecessors. +    recordConditions(CB, Pred, Conditions, StopAt); +    PredsCS.push_back({Pred, Conditions}); +  } + +  if (all_of(PredsCS, [](const std::pair<BasicBlock *, ConditionsTy> &P) { +        return P.second.empty(); +      })) +    return {}; + +  return PredsCS; +} + +static bool tryToSplitCallSite(CallBase &CB, TargetTransformInfo &TTI, +                               DomTreeUpdater &DTU) { +  // Check if we can split the call site. +  if (!CB.arg_size() || !canSplitCallSite(CB, TTI)) +    return false; + +  auto PredsWithConds = shouldSplitOnPredicatedArgument(CB, DTU); +  if (PredsWithConds.empty()) +    PredsWithConds = shouldSplitOnPHIPredicatedArgument(CB); +  if (PredsWithConds.empty()) +    return false; + +  splitCallSite(CB, PredsWithConds, DTU); +  return true; +} + +static bool doCallSiteSplitting(Function &F, TargetLibraryInfo &TLI, +                                TargetTransformInfo &TTI, DominatorTree &DT) { + +  DomTreeUpdater DTU(&DT, DomTreeUpdater::UpdateStrategy::Lazy); +  bool Changed = false; +  for (Function::iterator BI = F.begin(), BE = F.end(); BI != BE;) { +    BasicBlock &BB = *BI++; +    auto II = BB.getFirstNonPHIOrDbg()->getIterator(); +    auto IE = BB.getTerminator()->getIterator(); +    // Iterate until we reach the terminator instruction. tryToSplitCallSite +    // can replace BB's terminator in case BB is a successor of itself. In that +    // case, IE will be invalidated and we also have to check the current +    // terminator. +    while (II != IE && &*II != BB.getTerminator()) { +      CallBase *CB = dyn_cast<CallBase>(&*II++); +      if (!CB || isa<IntrinsicInst>(CB) || isInstructionTriviallyDead(CB, &TLI)) +        continue; + +      Function *Callee = CB->getCalledFunction(); +      if (!Callee || Callee->isDeclaration()) +        continue; + +      // Successful musttail call-site splits result in erased CI and erased BB. +      // Check if such path is possible before attempting the splitting. +      bool IsMustTail = CB->isMustTailCall(); + +      Changed |= tryToSplitCallSite(*CB, TTI, DTU); + +      // There're no interesting instructions after this. The call site +      // itself might have been erased on splitting. +      if (IsMustTail) +        break; +    } +  } +  return Changed; +} + +namespace { +struct CallSiteSplittingLegacyPass : public FunctionPass { +  static char ID; +  CallSiteSplittingLegacyPass() : FunctionPass(ID) { +    initializeCallSiteSplittingLegacyPassPass(*PassRegistry::getPassRegistry()); +  } + +  void getAnalysisUsage(AnalysisUsage &AU) const override { +    AU.addRequired<TargetLibraryInfoWrapperPass>(); +    AU.addRequired<TargetTransformInfoWrapperPass>(); +    AU.addRequired<DominatorTreeWrapperPass>(); +    AU.addPreserved<DominatorTreeWrapperPass>(); +    FunctionPass::getAnalysisUsage(AU); +  } + +  bool runOnFunction(Function &F) override { +    if (skipFunction(F)) +      return false; + +    auto &TLI = getAnalysis<TargetLibraryInfoWrapperPass>().getTLI(F); +    auto &TTI = getAnalysis<TargetTransformInfoWrapperPass>().getTTI(F); +    auto &DT = getAnalysis<DominatorTreeWrapperPass>().getDomTree(); +    return doCallSiteSplitting(F, TLI, TTI, DT); +  } +}; +} // namespace + +char CallSiteSplittingLegacyPass::ID = 0; +INITIALIZE_PASS_BEGIN(CallSiteSplittingLegacyPass, "callsite-splitting", +                      "Call-site splitting", false, false) +INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfoWrapperPass) +INITIALIZE_PASS_DEPENDENCY(TargetTransformInfoWrapperPass) +INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass) +INITIALIZE_PASS_END(CallSiteSplittingLegacyPass, "callsite-splitting", +                    "Call-site splitting", false, false) +FunctionPass *llvm::createCallSiteSplittingPass() { +  return new CallSiteSplittingLegacyPass(); +} + +PreservedAnalyses CallSiteSplittingPass::run(Function &F, +                                             FunctionAnalysisManager &AM) { +  auto &TLI = AM.getResult<TargetLibraryAnalysis>(F); +  auto &TTI = AM.getResult<TargetIRAnalysis>(F); +  auto &DT = AM.getResult<DominatorTreeAnalysis>(F); + +  if (!doCallSiteSplitting(F, TLI, TTI, DT)) +    return PreservedAnalyses::all(); +  PreservedAnalyses PA; +  PA.preserve<DominatorTreeAnalysis>(); +  return PA; +}  | 
