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Diffstat (limited to 'clang-r353983e/include/llvm/Transforms/Utils/BasicBlockUtils.h')
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diff --git a/clang-r353983e/include/llvm/Transforms/Utils/BasicBlockUtils.h b/clang-r353983e/include/llvm/Transforms/Utils/BasicBlockUtils.h new file mode 100644 index 00000000..4e763289 --- /dev/null +++ b/clang-r353983e/include/llvm/Transforms/Utils/BasicBlockUtils.h @@ -0,0 +1,339 @@ +//===- 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/Analysis/DomTreeUpdater.h" +#include "llvm/IR/BasicBlock.h" +#include "llvm/IR/CFG.h" +#include "llvm/IR/InstrTypes.h" +#include <cassert> + +namespace llvm { + +class BlockFrequencyInfo; +class BranchProbabilityInfo; +class DominatorTree; +class DomTreeUpdater; +class Function; +class Instruction; +class LoopInfo; +class MDNode; +class MemoryDependenceResults; +class MemorySSAUpdater; +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 DetatchDeadBlocks(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); + +/// 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, DomTreeUpdater *DTU = nullptr, + LoopInfo *LI = nullptr, + MemorySSAUpdater *MSSAU = 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; + MemorySSAUpdater *MSSAU; + bool MergeIdenticalEdges = false; + bool KeepOneInputPHIs = false; + bool PreserveLCSSA = false; + + CriticalEdgeSplittingOptions(DominatorTree *DT = nullptr, + LoopInfo *LI = nullptr, + MemorySSAUpdater *MSSAU = nullptr) + : DT(DT), LI(LI), MSSAU(MSSAU) {} + + CriticalEdgeSplittingOptions &setMergeIdenticalEdges() { + MergeIdenticalEdges = true; + return *this; + } + + CriticalEdgeSplittingOptions &setKeepOneInputPHIs() { + KeepOneInputPHIs = 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(Instruction *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; + Instruction *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()) { + 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 specified block. +BasicBlock *SplitEdge(BasicBlock *From, BasicBlock *To, + DominatorTree *DT = nullptr, LoopInfo *LI = nullptr, + MemorySSAUpdater *MSSAU = 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, + MemorySSAUpdater *MSSAU = 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, + 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, + DominatorTree *DT = 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 Unreachable is true, then ThenBlock ends with +/// UnreachableInst, otherwise it branches to Tail. +/// Returns the NewBasicBlock's terminator. +/// +/// Updates DT and LI if given. +Instruction *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, + Instruction **ThenTerm, + Instruction **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); + +// 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. +bool SplitIndirectBrCriticalEdges(Function &F, + BranchProbabilityInfo *BPI = nullptr, + BlockFrequencyInfo *BFI = nullptr); + +} // end namespace llvm + +#endif // LLVM_TRANSFORMS_UTILS_BASICBLOCKUTILS_H |