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 //===- Transform/Utils/BasicBlockUtils.h - BasicBlock Utils -----*- C++ -*-===//
 //
 // 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 family of functions perform manipulations on basic blocks, and
 // instructions contained within basic blocks.
 //
 //===----------------------------------------------------------------------===//
 
 #ifndef LLVM_TRANSFORMS_UTILS_BASICBLOCKUTILS_H
 #define LLVM_TRANSFORMS_UTILS_BASICBLOCKUTILS_H
 
 // FIXME: Move to this file: BasicBlock::removePredecessor, BB::splitBasicBlock
 
 #include "llvm/ADT/ArrayRef.h"
 #include "llvm/ADT/SetVector.h"
 #include "llvm/IR/BasicBlock.h"
 #include "llvm/IR/Dominators.h"
 #include <cassert>
 
 namespace llvm {
 class BranchInst;
 class LandingPadInst;
 class Loop;
 class PHINode;
 template <typename PtrType> class SmallPtrSetImpl;
 class BlockFrequencyInfo;
 class BranchProbabilityInfo;
 class DomTreeUpdater;
 class Function;
 class IRBuilderBase;
 class LoopInfo;
 class MDNode;
 class MemoryDependenceResults;
 class MemorySSAUpdater;
 class PostDominatorTree;
 class ReturnInst;
 class TargetLibraryInfo;
 class Value;
 
 /// Replace contents of every block in \p BBs with single unreachable
 /// instruction. If \p Updates is specified, collect all necessary DT updates
 /// into this vector. If \p KeepOneInputPHIs is true, one-input Phis in
 /// successors of blocks being deleted will be preserved.
 void detachDeadBlocks(ArrayRef <BasicBlock *> BBs,
                       SmallVectorImpl<DominatorTree::UpdateType> *Updates,
                       bool KeepOneInputPHIs = false);
 
 /// Delete the specified block, which must have no predecessors.
 void DeleteDeadBlock(BasicBlock *BB, DomTreeUpdater *DTU = nullptr,
                      bool KeepOneInputPHIs = false);
 
 /// Delete the specified blocks from \p BB. The set of deleted blocks must have
 /// no predecessors that are not being deleted themselves. \p BBs must have no
 /// duplicating blocks. If there are loops among this set of blocks, all
 /// relevant loop info updates should be done before this function is called.
 /// If \p KeepOneInputPHIs is true, one-input Phis in successors of blocks
 /// being deleted will be preserved.
 void DeleteDeadBlocks(ArrayRef <BasicBlock *> BBs,
                       DomTreeUpdater *DTU = nullptr,
                       bool KeepOneInputPHIs = false);
 
 /// Delete all basic blocks from \p F that are not reachable from its entry
 /// node. If \p KeepOneInputPHIs is true, one-input Phis in successors of
 /// blocks being deleted will be preserved.
 bool EliminateUnreachableBlocks(Function &F, DomTreeUpdater *DTU = nullptr,
                                 bool KeepOneInputPHIs = false);
 
 /// We know that BB has one predecessor. If there are any single-entry PHI nodes
 /// in it, fold them away. This handles the case when all entries to the PHI
 /// nodes in a block are guaranteed equal, such as when the block has exactly
 /// one predecessor.
 bool FoldSingleEntryPHINodes(BasicBlock *BB,
                              MemoryDependenceResults *MemDep = nullptr);
 
 /// Examine each PHI in the given block and delete it if it is dead. Also
 /// recursively delete any operands that become dead as a result. This includes
 /// tracing the def-use list from the PHI to see if it is ultimately unused or
 /// if it reaches an unused cycle. Return true if any PHIs were deleted.
 bool DeleteDeadPHIs(BasicBlock *BB, const TargetLibraryInfo *TLI = nullptr,
                     MemorySSAUpdater *MSSAU = nullptr);
 
 /// Attempts to merge a block into its predecessor, if possible. The return
 /// value indicates success or failure.
 /// By default do not merge blocks if BB's predecessor has multiple successors.
 /// If PredecessorWithTwoSuccessors = true, the blocks can only be merged
 /// if BB's Pred has a branch to BB and to AnotherBB, and BB has a single
 /// successor Sing. In this case the branch will be updated with Sing instead of
 /// BB, and BB will still be merged into its predecessor and removed.
 /// If \p DT is not nullptr, update it directly; in that case, DTU must be
 /// nullptr.
 bool MergeBlockIntoPredecessor(BasicBlock *BB, DomTreeUpdater *DTU = nullptr,
                                LoopInfo *LI = nullptr,
                                MemorySSAUpdater *MSSAU = nullptr,
                                MemoryDependenceResults *MemDep = nullptr,
                                bool PredecessorWithTwoSuccessors = false,
                                DominatorTree *DT = nullptr);
 
 /// Merge block(s) sucessors, if possible. Return true if at least two
 /// of the blocks were merged together.
 /// In order to merge, each block must be terminated by an unconditional
 /// branch. If L is provided, then the blocks merged into their predecessors
 /// must be in L. In addition, This utility calls on another utility:
 /// MergeBlockIntoPredecessor. Blocks are successfully merged when the call to
 /// MergeBlockIntoPredecessor returns true.
 bool MergeBlockSuccessorsIntoGivenBlocks(
     SmallPtrSetImpl<BasicBlock *> &MergeBlocks, Loop *L = nullptr,
     DomTreeUpdater *DTU = nullptr, LoopInfo *LI = nullptr);
 
 /// Try to remove redundant dbg.value instructions from given basic block.
 /// Returns true if at least one instruction was removed. Remove redundant
 /// pseudo ops when RemovePseudoOp is true.
 bool RemoveRedundantDbgInstrs(BasicBlock *BB);
 
 /// Replace all uses of an instruction (specified by BI) with a value, then
 /// remove and delete the original instruction.
 void ReplaceInstWithValue(BasicBlock::iterator &BI, Value *V);
 
 /// Replace the instruction specified by BI with the instruction specified by I.
 /// Copies DebugLoc from BI to I, if I doesn't already have a DebugLoc. The
 /// original instruction is deleted and BI is updated to point to the new
 /// instruction.
 void ReplaceInstWithInst(BasicBlock *BB, BasicBlock::iterator &BI,
                          Instruction *I);
 
 /// Replace the instruction specified by From with the instruction specified by
 /// To. Copies DebugLoc from BI to I, if I doesn't already have a DebugLoc.
 void ReplaceInstWithInst(Instruction *From, Instruction *To);
 
 /// Check if we can prove that all paths starting from this block converge
 /// to a block that either has a @llvm.experimental.deoptimize call
 /// prior to its terminating return instruction or is terminated by unreachable.
 /// All blocks in the traversed sequence must have an unique successor, maybe
 /// except for the last one.
 bool IsBlockFollowedByDeoptOrUnreachable(const BasicBlock *BB);
 
 /// Option class for critical edge splitting.
 ///
 /// This provides a builder interface for overriding the default options used
 /// during critical edge splitting.
 struct CriticalEdgeSplittingOptions {
   DominatorTree *DT;
   PostDominatorTree *PDT;
   LoopInfo *LI;
   MemorySSAUpdater *MSSAU;
   bool MergeIdenticalEdges = false;
   bool KeepOneInputPHIs = false;
   bool PreserveLCSSA = false;
   bool IgnoreUnreachableDests = false;
   /// SplitCriticalEdge is guaranteed to preserve loop-simplify form if LI is
   /// provided. If it cannot be preserved, no splitting will take place. If it
   /// is not set, preserve loop-simplify form if possible.
   bool PreserveLoopSimplify = true;
 
   CriticalEdgeSplittingOptions(DominatorTree *DT = nullptr,
                                LoopInfo *LI = nullptr,
                                MemorySSAUpdater *MSSAU = nullptr,
                                PostDominatorTree *PDT = nullptr)
       : DT(DT), PDT(PDT), LI(LI), MSSAU(MSSAU) {}
 
   CriticalEdgeSplittingOptions &setMergeIdenticalEdges() {
     MergeIdenticalEdges = true;
     return *this;
   }
 
   CriticalEdgeSplittingOptions &setKeepOneInputPHIs() {
     KeepOneInputPHIs = true;
     return *this;
   }
 
   CriticalEdgeSplittingOptions &setPreserveLCSSA() {
     PreserveLCSSA = true;
     return *this;
   }
 
   CriticalEdgeSplittingOptions &setIgnoreUnreachableDests() {
     IgnoreUnreachableDests = true;
     return *this;
   }
 
   CriticalEdgeSplittingOptions &unsetPreserveLoopSimplify() {
     PreserveLoopSimplify = false;
     return *this;
   }
 };
 
 /// When a loop exit edge is split, LCSSA form may require new PHIs in the new
 /// exit block. This function inserts the new PHIs, as needed. Preds is a list
 /// of preds inside the loop, SplitBB is the new loop exit block, and DestBB is
 /// the old loop exit, now the successor of SplitBB.
 void createPHIsForSplitLoopExit(ArrayRef<BasicBlock *> Preds,
                                 BasicBlock *SplitBB, BasicBlock *DestBB);
 
 /// If this edge is a critical edge, insert a new node to split the critical
 /// edge. This will update the analyses passed in through the option struct.
 /// This returns the new block if the edge was split, null otherwise.
 ///
 /// If MergeIdenticalEdges in the options struct is true (not the default),
 /// *all* edges from TI to the specified successor will be merged into the same
 /// critical edge block. This is most commonly interesting with switch
 /// instructions, which may have many edges to any one destination.  This
 /// ensures that all edges to that dest go to one block instead of each going
 /// to a different block, but isn't the standard definition of a "critical
 /// edge".
 ///
 /// It is invalid to call this function on a critical edge that starts at an
 /// IndirectBrInst.  Splitting these edges will almost always create an invalid
 /// program because the address of the new block won't be the one that is jumped
 /// to.
 BasicBlock *SplitCriticalEdge(Instruction *TI, unsigned SuccNum,
                               const CriticalEdgeSplittingOptions &Options =
                                   CriticalEdgeSplittingOptions(),
                               const Twine &BBName = "");
 
 /// If it is known that an edge is critical, SplitKnownCriticalEdge can be
 /// called directly, rather than calling SplitCriticalEdge first.
 BasicBlock *SplitKnownCriticalEdge(Instruction *TI, unsigned SuccNum,
                                    const CriticalEdgeSplittingOptions &Options =
                                        CriticalEdgeSplittingOptions(),
                                    const Twine &BBName = "");
 
 /// If an edge from Src to Dst is critical, split the edge and return true,
 /// otherwise return false. This method requires that there be an edge between
 /// the two blocks. It updates the analyses passed in the options struct
 inline BasicBlock *
 SplitCriticalEdge(BasicBlock *Src, BasicBlock *Dst,
                   const CriticalEdgeSplittingOptions &Options =
                       CriticalEdgeSplittingOptions()) {
   Instruction *TI = Src->getTerminator();
   unsigned i = 0;
   while (true) {
     assert(i != TI->getNumSuccessors() && "Edge doesn't exist!");
     if (TI->getSuccessor(i) == Dst)
       return SplitCriticalEdge(TI, i, Options);
     ++i;
   }
 }
 
 /// Loop over all of the edges in the CFG, breaking critical edges as they are
 /// found. Returns the number of broken edges.
 unsigned SplitAllCriticalEdges(Function &F,
                                const CriticalEdgeSplittingOptions &Options =
                                    CriticalEdgeSplittingOptions());
 
 /// Split the edge connecting the specified blocks, and return the newly created
 /// basic block between \p From and \p To.
 BasicBlock *SplitEdge(BasicBlock *From, BasicBlock *To,
                       DominatorTree *DT = nullptr, LoopInfo *LI = nullptr,
                       MemorySSAUpdater *MSSAU = nullptr,
                       const Twine &BBName = "");
 
 /// Sets the unwind edge of an instruction to a particular successor.
 void setUnwindEdgeTo(Instruction *TI, BasicBlock *Succ);
 
 /// Replaces all uses of OldPred with the NewPred block in all PHINodes in a
 /// block.
 void updatePhiNodes(BasicBlock *DestBB, BasicBlock *OldPred,
                     BasicBlock *NewPred, PHINode *Until = nullptr);
 
 /// Split the edge connect the specficed blocks in the case that \p Succ is an
 /// Exception Handling Block
 BasicBlock *ehAwareSplitEdge(BasicBlock *BB, BasicBlock *Succ,
                              LandingPadInst *OriginalPad = nullptr,
                              PHINode *LandingPadReplacement = nullptr,
                              const CriticalEdgeSplittingOptions &Options =
                                  CriticalEdgeSplittingOptions(),
                              const Twine &BBName = "");
 
 /// Split the specified block at the specified instruction.
 ///
 /// If \p Before is true, splitBlockBefore handles the block
 /// splitting. Otherwise, execution proceeds as described below.
 ///
 /// Everything before \p SplitPt stays in \p Old and everything starting with \p
 /// SplitPt moves to a new block. The two blocks are joined by an unconditional
 /// branch. The new block with name \p BBName is returned.
 ///
 /// FIXME: deprecated, switch to the DomTreeUpdater-based one.
 BasicBlock *SplitBlock(BasicBlock *Old, BasicBlock::iterator SplitPt, DominatorTree *DT,
                        LoopInfo *LI = nullptr,
                        MemorySSAUpdater *MSSAU = nullptr,
                        const Twine &BBName = "", bool Before = false);
 inline BasicBlock *SplitBlock(BasicBlock *Old, Instruction *SplitPt, DominatorTree *DT,
                        LoopInfo *LI = nullptr,
                        MemorySSAUpdater *MSSAU = nullptr,
                        const Twine &BBName = "", bool Before = false) {
   return SplitBlock(Old, SplitPt->getIterator(), DT, LI, MSSAU, BBName, Before);
 }
 
 /// Split the specified block at the specified instruction.
 ///
 /// If \p Before is true, splitBlockBefore handles the block
 /// splitting. Otherwise, execution proceeds as described below.
 ///
 /// Everything before \p SplitPt stays in \p Old and everything starting with \p
 /// SplitPt moves to a new block. The two blocks are joined by an unconditional
 /// branch. The new block with name \p BBName is returned.
 BasicBlock *SplitBlock(BasicBlock *Old, BasicBlock::iterator SplitPt,
                        DomTreeUpdater *DTU = nullptr, LoopInfo *LI = nullptr,
                        MemorySSAUpdater *MSSAU = nullptr,
                        const Twine &BBName = "", bool Before = false);
 inline BasicBlock *SplitBlock(BasicBlock *Old, Instruction *SplitPt,
                        DomTreeUpdater *DTU = nullptr, LoopInfo *LI = nullptr,
                        MemorySSAUpdater *MSSAU = nullptr,
                        const Twine &BBName = "", bool Before = false) {
   return SplitBlock(Old, SplitPt->getIterator(), DTU, LI, MSSAU, BBName, Before);
 }
 
 /// Split the specified block at the specified instruction \p SplitPt.
 /// All instructions before \p SplitPt are moved to a new block and all
 /// instructions after \p SplitPt stay in the old block. The new block and the
 /// old block are joined by inserting an unconditional branch to the end of the
 /// new block. The new block with name \p BBName is returned.
 BasicBlock *splitBlockBefore(BasicBlock *Old, BasicBlock::iterator SplitPt,
                              DomTreeUpdater *DTU, LoopInfo *LI,
                              MemorySSAUpdater *MSSAU, const Twine &BBName = "");
 inline BasicBlock *splitBlockBefore(BasicBlock *Old, Instruction *SplitPt,
                              DomTreeUpdater *DTU, LoopInfo *LI,
                              MemorySSAUpdater *MSSAU, const Twine &BBName = "") {
   return splitBlockBefore(Old, SplitPt->getIterator(), DTU, LI, MSSAU, BBName);
 }
 
 /// This method introduces at least one new basic block into the function and
 /// moves some of the predecessors of BB to be predecessors of the new block.
 /// The new predecessors are indicated by the Preds array. The new block is
 /// given a suffix of 'Suffix'. Returns new basic block to which predecessors
 /// from Preds are now pointing.
 ///
 /// If BB is a landingpad block then additional basicblock might be introduced.
 /// It will have Suffix+".split_lp". See SplitLandingPadPredecessors for more
 /// details on this case.
 ///
 /// This currently updates the LLVM IR, DominatorTree, 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).
 ///
 /// FIXME: deprecated, switch to the DomTreeUpdater-based one.
 BasicBlock *SplitBlockPredecessors(BasicBlock *BB, ArrayRef<BasicBlock *> Preds,
                                    const char *Suffix, DominatorTree *DT,
                                    LoopInfo *LI = nullptr,
                                    MemorySSAUpdater *MSSAU = nullptr,
                                    bool PreserveLCSSA = false);
 
 /// This method introduces at least one new basic block into the function and
 /// moves some of the predecessors of BB to be predecessors of the new block.
 /// The new predecessors are indicated by the Preds array. The new block is
 /// given a suffix of 'Suffix'. Returns new basic block to which predecessors
 /// from Preds are now pointing.
 ///
 /// If BB is a landingpad block then additional basicblock might be introduced.
 /// It will have Suffix+".split_lp". See SplitLandingPadPredecessors for more
 /// details on this case.
 ///
 /// This currently updates the LLVM IR, DominatorTree, 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).
 BasicBlock *SplitBlockPredecessors(BasicBlock *BB, ArrayRef<BasicBlock *> Preds,
                                    const char *Suffix,
                                    DomTreeUpdater *DTU = nullptr,
                                    LoopInfo *LI = nullptr,
                                    MemorySSAUpdater *MSSAU = nullptr,
                                    bool PreserveLCSSA = false);
 
 /// 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, DominatorTree, 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 SplitLandingPadPredecessors(
     BasicBlock *OrigBB, ArrayRef<BasicBlock *> Preds, const char *Suffix,
     const char *Suffix2, SmallVectorImpl<BasicBlock *> &NewBBs,
     DomTreeUpdater *DTU = nullptr, LoopInfo *LI = nullptr,
     MemorySSAUpdater *MSSAU = nullptr, bool PreserveLCSSA = false);
 
 /// This method duplicates the specified return instruction into a predecessor
 /// which ends in an unconditional branch. If the return instruction returns a
 /// value defined by a PHI, propagate the right value into the return. It
 /// returns the new return instruction in the predecessor.
 ReturnInst *FoldReturnIntoUncondBranch(ReturnInst *RI, BasicBlock *BB,
                                        BasicBlock *Pred,
                                        DomTreeUpdater *DTU = nullptr);
 
 /// Split the containing block at the specified instruction - everything before
 /// SplitBefore stays in the old basic block, and the rest of the instructions
 /// in the BB are moved to a new block. The two blocks are connected by a
 /// conditional branch (with value of Cmp being the condition).
 /// Before:
 ///   Head
 ///   SplitBefore
 ///   Tail
 /// After:
 ///   Head
 ///   if (Cond)
 ///     ThenBlock
 ///   SplitBefore
 ///   Tail
 ///
 /// If \p ThenBlock is not specified, a new block will be created for it.
 /// If \p Unreachable is true, the newly created block will end with
 /// UnreachableInst, otherwise it branches to Tail.
 /// Returns the NewBasicBlock's terminator.
 ///
 /// Updates DTU and LI if given.
 Instruction *SplitBlockAndInsertIfThen(Value *Cond, BasicBlock::iterator SplitBefore,
                                        bool Unreachable,
                                        MDNode *BranchWeights = nullptr,
                                        DomTreeUpdater *DTU = nullptr,
                                        LoopInfo *LI = nullptr,
                                        BasicBlock *ThenBlock = nullptr);
 
 inline Instruction *SplitBlockAndInsertIfThen(Value *Cond, Instruction *SplitBefore,
                                        bool Unreachable,
                                        MDNode *BranchWeights = nullptr,
                                        DomTreeUpdater *DTU = nullptr,
                                        LoopInfo *LI = nullptr,
                                        BasicBlock *ThenBlock = nullptr) {
   return SplitBlockAndInsertIfThen(Cond, SplitBefore->getIterator(),
                                    Unreachable, BranchWeights, DTU, LI,
                                    ThenBlock);
 }
 
 /// Similar to SplitBlockAndInsertIfThen, but the inserted block is on the false
 /// path of the branch.
 Instruction *SplitBlockAndInsertIfElse(Value *Cond, BasicBlock::iterator SplitBefore,
                                        bool Unreachable,
                                        MDNode *BranchWeights = nullptr,
                                        DomTreeUpdater *DTU = nullptr,
                                        LoopInfo *LI = nullptr,
                                        BasicBlock *ElseBlock = nullptr);
 
 inline Instruction *SplitBlockAndInsertIfElse(Value *Cond, Instruction *SplitBefore,
                                        bool Unreachable,
                                        MDNode *BranchWeights = nullptr,
                                        DomTreeUpdater *DTU = nullptr,
                                        LoopInfo *LI = nullptr,
                                        BasicBlock *ElseBlock = nullptr) {
   return SplitBlockAndInsertIfElse(Cond, SplitBefore->getIterator(),
                                    Unreachable, BranchWeights, DTU, LI,
                                    ElseBlock);
 }
 
 /// SplitBlockAndInsertIfThenElse is similar to SplitBlockAndInsertIfThen,
 /// but also creates the ElseBlock.
 /// Before:
 ///   Head
 ///   SplitBefore
 ///   Tail
 /// After:
 ///   Head
 ///   if (Cond)
 ///     ThenBlock
 ///   else
 ///     ElseBlock
 ///   SplitBefore
 ///   Tail
 ///
 /// Updates DT if given.
 void SplitBlockAndInsertIfThenElse(Value *Cond,
                                    BasicBlock::iterator SplitBefore,
                                    Instruction **ThenTerm,
                                    Instruction **ElseTerm,
                                    MDNode *BranchWeights = nullptr,
                                    DomTreeUpdater *DTU = nullptr,
                                    LoopInfo *LI = nullptr);
 
 inline void SplitBlockAndInsertIfThenElse(Value *Cond, Instruction *SplitBefore,
                                    Instruction **ThenTerm,
                                    Instruction **ElseTerm,
                                    MDNode *BranchWeights = nullptr,
                                    DomTreeUpdater *DTU = nullptr,
                                    LoopInfo *LI = nullptr)
 {
   SplitBlockAndInsertIfThenElse(Cond, SplitBefore->getIterator(), ThenTerm,
                                ElseTerm, BranchWeights, DTU, LI);
 }
 
 /// Split the containing block at the specified instruction - everything before
 /// SplitBefore stays in the old basic block, and the rest of the instructions
 /// in the BB are moved to a new block. The two blocks are connected by a
 /// conditional branch (with value of Cmp being the condition).
 /// Before:
 ///   Head
 ///   SplitBefore
 ///   Tail
 /// After:
 ///   Head
 ///   if (Cond)
 ///     TrueBlock
 ///   else
 ////    FalseBlock
 ///   SplitBefore
 ///   Tail
 ///
 /// If \p ThenBlock is null, the resulting CFG won't contain the TrueBlock. If
 /// \p ThenBlock is non-null and points to non-null BasicBlock pointer, that
 /// block will be inserted as the TrueBlock. Otherwise a new block will be
 /// created. Likewise for the \p ElseBlock parameter.
 /// If \p UnreachableThen or \p UnreachableElse is true, the corresponding newly
 /// created blocks will end with UnreachableInst, otherwise with branches to
 /// Tail. The function will not modify existing basic blocks passed to it. The
 /// caller must ensure that Tail is reachable from Head.
 /// Returns the newly created blocks in \p ThenBlock and \p ElseBlock.
 /// Updates DTU and LI if given.
 void SplitBlockAndInsertIfThenElse(Value *Cond,
                                    BasicBlock::iterator SplitBefore,
                                    BasicBlock **ThenBlock,
                                    BasicBlock **ElseBlock,
                                    bool UnreachableThen = false,
                                    bool UnreachableElse = false,
                                    MDNode *BranchWeights = nullptr,
                                    DomTreeUpdater *DTU = nullptr,
                                    LoopInfo *LI = nullptr);
 
 inline void SplitBlockAndInsertIfThenElse(Value *Cond, Instruction *SplitBefore,
                                    BasicBlock **ThenBlock,
                                    BasicBlock **ElseBlock,
                                    bool UnreachableThen = false,
                                    bool UnreachableElse = false,
                                    MDNode *BranchWeights = nullptr,
                                    DomTreeUpdater *DTU = nullptr,
                                    LoopInfo *LI = nullptr) {
   SplitBlockAndInsertIfThenElse(Cond, SplitBefore->getIterator(), ThenBlock,
     ElseBlock, UnreachableThen, UnreachableElse, BranchWeights, DTU, LI);
 }
 
 /// Insert a for (int i = 0; i < End; i++) loop structure (with the exception
 /// that \p End is assumed > 0, and thus not checked on entry) at \p
 /// SplitBefore.  Returns the first insert point in the loop body, and the
 /// PHINode for the induction variable (i.e. "i" above).
 std::pair<Instruction*, Value*>
 SplitBlockAndInsertSimpleForLoop(Value *End, BasicBlock::iterator SplitBefore);
 
 /// Utility function for performing a given action on each lane of a vector
 /// with \p EC elements.  To simplify porting legacy code, this defaults to
 /// unrolling the implied loop for non-scalable element counts, but this is
 /// not considered to be part of the contract of this routine, and is
 /// expected to change in the future. The callback takes as arguments an
 /// IRBuilder whose insert point is correctly set for instantiating the
 /// given index, and a value which is (at runtime) the index to access.
 /// This index *may* be a constant.
 void SplitBlockAndInsertForEachLane(
     ElementCount EC, Type *IndexTy, BasicBlock::iterator InsertBefore,
     std::function<void(IRBuilderBase &, Value *)> Func);
 
 /// Utility function for performing a given action on each lane of a vector
 /// with \p EVL effective length. EVL is assumed > 0. To simplify porting legacy
 /// code, this defaults to unrolling the implied loop for non-scalable element
 /// counts, but this is not considered to be part of the contract of this
 /// routine, and is expected to change in the future. The callback takes as
 /// arguments an IRBuilder whose insert point is correctly set for instantiating
 /// the given index, and a value which is (at runtime) the index to access. This
 /// index *may* be a constant.
 void SplitBlockAndInsertForEachLane(
     Value *End, BasicBlock::iterator InsertBefore,
     std::function<void(IRBuilderBase &, Value *)> Func);
 
 /// Check whether BB is the merge point of a if-region.
 /// If so, return the branch instruction that determines which entry into
 /// BB will be taken.  Also, return by references the block that will be
 /// entered from if the condition is true, and the block that will be
 /// entered if the condition is false.
 ///
 /// This does no checking to see if the true/false blocks have large or unsavory
 /// instructions in them.
 BranchInst *GetIfCondition(BasicBlock *BB, BasicBlock *&IfTrue,
                            BasicBlock *&IfFalse);
 
 // Split critical edges where the source of the edge is an indirectbr
 // instruction. This isn't always possible, but we can handle some easy cases.
 // This is useful because MI is unable to split such critical edges,
 // which means it will not be able to sink instructions along those edges.
 // This is especially painful for indirect branches with many successors, where
 // we end up having to prepare all outgoing values in the origin block.
 //
 // Our normal algorithm for splitting critical edges requires us to update
 // the outgoing edges of the edge origin block, but for an indirectbr this
 // is hard, since it would require finding and updating the block addresses
 // the indirect branch uses. But if a block only has a single indirectbr
 // predecessor, with the others being regular branches, we can do it in a
 // different way.
 // Say we have A -> D, B -> D, I -> D where only I -> D is an indirectbr.
 // We can split D into D0 and D1, where D0 contains only the PHIs from D,
 // and D1 is the D block body. We can then duplicate D0 as D0A and D0B, and
 // create the following structure:
 // A -> D0A, B -> D0A, I -> D0B, D0A -> D1, D0B -> D1
 // If BPI and BFI aren't non-null, BPI/BFI will be updated accordingly.
 // When `IgnoreBlocksWithoutPHI` is set to `true` critical edges leading to a
 // block without phi-instructions will not be split.
 bool SplitIndirectBrCriticalEdges(Function &F, bool IgnoreBlocksWithoutPHI,
                                   BranchProbabilityInfo *BPI = nullptr,
                                   BlockFrequencyInfo *BFI = nullptr);
 
 // Utility function for inverting branch condition and for swapping its
 // successors
 void InvertBranch(BranchInst *PBI, IRBuilderBase &Builder);
 
 // Check whether the function only has simple terminator:
 // br/brcond/unreachable/ret
 bool hasOnlySimpleTerminator(const Function &F);
 
 // Returns true if these basic blocks belong to a presplit coroutine and the
 // edge corresponds to the 'default' case in the switch statement in the
 // pattern:
 //
 // %0 = call i8 @llvm.coro.suspend(token none, i1 false)
 // switch i8 %0, label %suspend [i8 0, label %resume
 //                               i8 1, label %cleanup]
 //
 // i.e. the edge to the `%suspend` BB. This edge is special in that it will
 // be elided by coroutine lowering (coro-split), and the `%suspend` BB needs
 // to be kept as-is. It's not a real CFG edge - post-lowering, it will end
 // up being a `ret`, and it must be thus lowerable to support symmetric
 // transfer. For example:
 //  - this edge is not a loop exit edge if encountered in a loop (and should
 //    be ignored)
 //  - must not be split for PGO instrumentation, for example.
 bool isPresplitCoroSuspendExitEdge(const BasicBlock &Src,
                                    const BasicBlock &Dest);
 } // end namespace llvm
 
 #endif // LLVM_TRANSFORMS_UTILS_BASICBLOCKUTILS_H

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