| //===-- Transform/Utils/BasicBlockUtils.h - BasicBlock Utils ----*- C++ -*-===// |
| // |
| // The LLVM Compiler Infrastructure |
| // |
| // This file is distributed under the University of Illinois Open Source |
| // License. See LICENSE.TXT for details. |
| // |
| //===----------------------------------------------------------------------===// |
| // |
| // 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/IR/BasicBlock.h" |
| #include "llvm/IR/CFG.h" |
| #include "llvm/IR/InstrTypes.h" |
| #include <cassert> |
| |
| namespace llvm { |
| |
| class MemoryDependenceResults; |
| class DominatorTree; |
| class LoopInfo; |
| class Instruction; |
| class MDNode; |
| class ReturnInst; |
| class TargetLibraryInfo; |
| |
| /// Delete the specified block, which must have no predecessors. |
| void DeleteDeadBlock(BasicBlock *BB); |
| |
| /// 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. |
| void 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); |
| |
| /// Attempts to merge a block into its predecessor, if possible. The return |
| /// value indicates success or failure. |
| bool MergeBlockIntoPredecessor(BasicBlock *BB, DominatorTree *DT = nullptr, |
| LoopInfo *LI = nullptr, |
| MemoryDependenceResults *MemDep = nullptr); |
| |
| /// Replace all uses of an instruction (specified by BI) with a value, then |
| /// remove and delete the original instruction. |
| void ReplaceInstWithValue(BasicBlock::InstListType &BIL, |
| 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::InstListType &BIL, |
| 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); |
| |
| /// 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; |
| LoopInfo *LI; |
| bool MergeIdenticalEdges = false; |
| bool DontDeleteUselessPHIs = false; |
| bool PreserveLCSSA = false; |
| |
| CriticalEdgeSplittingOptions(DominatorTree *DT = nullptr, |
| LoopInfo *LI = nullptr) |
| : DT(DT), LI(LI) {} |
| |
| CriticalEdgeSplittingOptions &setMergeIdenticalEdges() { |
| MergeIdenticalEdges = true; |
| return *this; |
| } |
| |
| CriticalEdgeSplittingOptions &setDontDeleteUselessPHIs() { |
| DontDeleteUselessPHIs = true; |
| return *this; |
| } |
| |
| CriticalEdgeSplittingOptions &setPreserveLCSSA() { |
| PreserveLCSSA = true; |
| return *this; |
| } |
| }; |
| |
| /// 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(TerminatorInst *TI, unsigned SuccNum, |
| const CriticalEdgeSplittingOptions &Options = |
| CriticalEdgeSplittingOptions()); |
| |
| inline BasicBlock * |
| SplitCriticalEdge(BasicBlock *BB, succ_iterator SI, |
| const CriticalEdgeSplittingOptions &Options = |
| CriticalEdgeSplittingOptions()) { |
| return SplitCriticalEdge(BB->getTerminator(), SI.getSuccessorIndex(), |
| Options); |
| } |
| |
| /// If the edge from *PI to BB is not critical, return false. Otherwise, split |
| /// all edges between the two blocks and return true. This updates all of the |
| /// same analyses as the other SplitCriticalEdge function. If P is specified, it |
| /// updates the analyses described above. |
| inline bool SplitCriticalEdge(BasicBlock *Succ, pred_iterator PI, |
| const CriticalEdgeSplittingOptions &Options = |
| CriticalEdgeSplittingOptions()) { |
| bool MadeChange = false; |
| TerminatorInst *TI = (*PI)->getTerminator(); |
| for (unsigned i = 0, e = TI->getNumSuccessors(); i != e; ++i) |
| if (TI->getSuccessor(i) == Succ) |
| MadeChange |= !!SplitCriticalEdge(TI, i, Options); |
| return MadeChange; |
| } |
| |
| /// 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()) { |
| TerminatorInst *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 specified block. |
| BasicBlock *SplitEdge(BasicBlock *From, BasicBlock *To, |
| DominatorTree *DT = nullptr, LoopInfo *LI = nullptr); |
| |
| /// Split the specified block at the specified instruction - everything before |
| /// SplitPt stays in Old and everything starting with SplitPt moves to a new |
| /// block. The two blocks are joined by an unconditional branch and the loop |
| /// info is updated. |
| BasicBlock *SplitBlock(BasicBlock *Old, Instruction *SplitPt, |
| DominatorTree *DT = nullptr, LoopInfo *LI = nullptr); |
| |
| /// 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, |
| DominatorTree *DT = nullptr, |
| LoopInfo *LI = 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, |
| DominatorTree *DT = nullptr, |
| LoopInfo *LI = 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); |
| |
| /// 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 Unreachable is true, then ThenBlock ends with |
| /// UnreachableInst, otherwise it branches to Tail. |
| /// Returns the NewBasicBlock's terminator. |
| /// |
| /// Updates DT and LI if given. |
| TerminatorInst *SplitBlockAndInsertIfThen(Value *Cond, Instruction *SplitBefore, |
| bool Unreachable, |
| MDNode *BranchWeights = nullptr, |
| DominatorTree *DT = nullptr, |
| LoopInfo *LI = nullptr); |
| |
| /// SplitBlockAndInsertIfThenElse is similar to SplitBlockAndInsertIfThen, |
| /// but also creates the ElseBlock. |
| /// Before: |
| /// Head |
| /// SplitBefore |
| /// Tail |
| /// After: |
| /// Head |
| /// if (Cond) |
| /// ThenBlock |
| /// else |
| /// ElseBlock |
| /// SplitBefore |
| /// Tail |
| void SplitBlockAndInsertIfThenElse(Value *Cond, Instruction *SplitBefore, |
| TerminatorInst **ThenTerm, |
| TerminatorInst **ElseTerm, |
| MDNode *BranchWeights = nullptr); |
| |
| /// Check whether BB is the merge point of a if-region. |
| /// If so, return the boolean condition 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. |
| Value *GetIfCondition(BasicBlock *BB, BasicBlock *&IfTrue, |
| BasicBlock *&IfFalse); |
| |
| } // end namespace llvm |
| |
| #endif // LLVM_TRANSFORMS_UTILS_BASICBLOCKUTILS_H |