1 //===-- Transform/Utils/BasicBlockUtils.h - BasicBlock Utils ----*- C++ -*-===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This family of functions perform manipulations on basic blocks, and
11 // instructions contained within basic blocks.
13 //===----------------------------------------------------------------------===//
15 #ifndef LLVM_TRANSFORMS_UTILS_BASICBLOCKUTILS_H
16 #define LLVM_TRANSFORMS_UTILS_BASICBLOCKUTILS_H
18 // FIXME: Move to this file: BasicBlock::removePredecessor, BB::splitBasicBlock
20 #include "llvm/IR/BasicBlock.h"
21 #include "llvm/Support/CFG.h"
30 class TargetLibraryInfo;
33 /// DeleteDeadBlock - Delete the specified block, which must have no
35 void DeleteDeadBlock(BasicBlock *BB);
38 /// FoldSingleEntryPHINodes - We know that BB has one predecessor. If there are
39 /// any single-entry PHI nodes in it, fold them away. This handles the case
40 /// when all entries to the PHI nodes in a block are guaranteed equal, such as
41 /// when the block has exactly one predecessor.
42 void FoldSingleEntryPHINodes(BasicBlock *BB, Pass *P = 0);
44 /// DeleteDeadPHIs - Examine each PHI in the given block and delete it if it
45 /// is dead. Also recursively delete any operands that become dead as
46 /// a result. This includes tracing the def-use list from the PHI to see if
47 /// it is ultimately unused or if it reaches an unused cycle. Return true
48 /// if any PHIs were deleted.
49 bool DeleteDeadPHIs(BasicBlock *BB, const TargetLibraryInfo *TLI = 0);
51 /// MergeBlockIntoPredecessor - Attempts to merge a block into its predecessor,
52 /// if possible. The return value indicates success or failure.
53 bool MergeBlockIntoPredecessor(BasicBlock *BB, Pass *P = 0);
55 // ReplaceInstWithValue - Replace all uses of an instruction (specified by BI)
56 // with a value, then remove and delete the original instruction.
58 void ReplaceInstWithValue(BasicBlock::InstListType &BIL,
59 BasicBlock::iterator &BI, Value *V);
61 // ReplaceInstWithInst - Replace the instruction specified by BI with the
62 // instruction specified by I. The original instruction is deleted and BI is
63 // updated to point to the new instruction.
65 void ReplaceInstWithInst(BasicBlock::InstListType &BIL,
66 BasicBlock::iterator &BI, Instruction *I);
68 // ReplaceInstWithInst - Replace the instruction specified by From with the
69 // instruction specified by To.
71 void ReplaceInstWithInst(Instruction *From, Instruction *To);
73 /// FindFunctionBackedges - Analyze the specified function to find all of the
74 /// loop backedges in the function and return them. This is a relatively cheap
75 /// (compared to computing dominators and loop info) analysis.
77 /// The output is added to Result, as pairs of <from,to> edge info.
78 void FindFunctionBackedges(const Function &F,
79 SmallVectorImpl<std::pair<const BasicBlock*,const BasicBlock*> > &Result);
82 /// GetSuccessorNumber - Search for the specified successor of basic block BB
83 /// and return its position in the terminator instruction's list of
84 /// successors. It is an error to call this with a block that is not a
86 unsigned GetSuccessorNumber(BasicBlock *BB, BasicBlock *Succ);
88 /// isCriticalEdge - Return true if the specified edge is a critical edge.
89 /// Critical edges are edges from a block with multiple successors to a block
90 /// with multiple predecessors.
92 bool isCriticalEdge(const TerminatorInst *TI, unsigned SuccNum,
93 bool AllowIdenticalEdges = false);
95 /// SplitCriticalEdge - If this edge is a critical edge, insert a new node to
96 /// split the critical edge. This will update DominatorTree and
97 /// DominatorFrontier information if it is available, thus calling this pass
98 /// will not invalidate either of them. This returns the new block if the edge
99 /// was split, null otherwise.
101 /// If MergeIdenticalEdges is true (not the default), *all* edges from TI to the
102 /// specified successor will be merged into the same critical edge block.
103 /// This is most commonly interesting with switch instructions, which may
104 /// have many edges to any one destination. This ensures that all edges to that
105 /// dest go to one block instead of each going to a different block, but isn't
106 /// the standard definition of a "critical edge".
108 /// It is invalid to call this function on a critical edge that starts at an
109 /// IndirectBrInst. Splitting these edges will almost always create an invalid
110 /// program because the address of the new block won't be the one that is jumped
113 BasicBlock *SplitCriticalEdge(TerminatorInst *TI, unsigned SuccNum,
114 Pass *P = 0, bool MergeIdenticalEdges = false,
115 bool DontDeleteUselessPHIs = false,
116 bool SplitLandingPads = false);
118 inline BasicBlock *SplitCriticalEdge(BasicBlock *BB, succ_iterator SI,
120 return SplitCriticalEdge(BB->getTerminator(), SI.getSuccessorIndex(), P);
123 /// SplitCriticalEdge - If the edge from *PI to BB is not critical, return
124 /// false. Otherwise, split all edges between the two blocks and return true.
125 /// This updates all of the same analyses as the other SplitCriticalEdge
126 /// function. If P is specified, it updates the analyses
128 inline bool SplitCriticalEdge(BasicBlock *Succ, pred_iterator PI, Pass *P = 0) {
129 bool MadeChange = false;
130 TerminatorInst *TI = (*PI)->getTerminator();
131 for (unsigned i = 0, e = TI->getNumSuccessors(); i != e; ++i)
132 if (TI->getSuccessor(i) == Succ)
133 MadeChange |= !!SplitCriticalEdge(TI, i, P);
137 /// SplitCriticalEdge - If an edge from Src to Dst is critical, split the edge
138 /// and return true, otherwise return false. This method requires that there be
139 /// an edge between the two blocks. If P is specified, it updates the analyses
141 inline BasicBlock *SplitCriticalEdge(BasicBlock *Src, BasicBlock *Dst,
143 bool MergeIdenticalEdges = false,
144 bool DontDeleteUselessPHIs = false) {
145 TerminatorInst *TI = Src->getTerminator();
148 assert(i != TI->getNumSuccessors() && "Edge doesn't exist!");
149 if (TI->getSuccessor(i) == Dst)
150 return SplitCriticalEdge(TI, i, P, MergeIdenticalEdges,
151 DontDeleteUselessPHIs);
156 /// SplitEdge - Split the edge connecting specified block. Pass P must
158 BasicBlock *SplitEdge(BasicBlock *From, BasicBlock *To, Pass *P);
160 /// SplitBlock - Split the specified block at the specified instruction - every
161 /// thing before SplitPt stays in Old and everything starting with SplitPt moves
162 /// to a new block. The two blocks are joined by an unconditional branch and
163 /// the loop info is updated.
165 BasicBlock *SplitBlock(BasicBlock *Old, Instruction *SplitPt, Pass *P);
167 /// SplitBlockPredecessors - This method transforms BB by introducing a new
168 /// basic block into the function, and moving some of the predecessors of BB to
169 /// be predecessors of the new block. The new predecessors are indicated by the
170 /// Preds array, which has NumPreds elements in it. The new block is given a
171 /// suffix of 'Suffix'. This function returns the new block.
173 /// This currently updates the LLVM IR, AliasAnalysis, DominatorTree,
174 /// DominanceFrontier, LoopInfo, and LCCSA but no other analyses.
175 /// In particular, it does not preserve LoopSimplify (because it's
176 /// complicated to handle the case where one of the edges being split
177 /// is an exit of a loop with other exits).
179 BasicBlock *SplitBlockPredecessors(BasicBlock *BB, ArrayRef<BasicBlock*> Preds,
180 const char *Suffix, Pass *P = 0);
182 /// SplitLandingPadPredecessors - This method transforms the landing pad,
183 /// OrigBB, by introducing two new basic blocks into the function. One of those
184 /// new basic blocks gets the predecessors listed in Preds. The other basic
185 /// block gets the remaining predecessors of OrigBB. The landingpad instruction
186 /// OrigBB is clone into both of the new basic blocks. The new blocks are given
187 /// the suffixes 'Suffix1' and 'Suffix2', and are returned in the NewBBs vector.
189 /// This currently updates the LLVM IR, AliasAnalysis, DominatorTree,
190 /// DominanceFrontier, LoopInfo, and LCCSA but no other analyses. In particular,
191 /// it does not preserve LoopSimplify (because it's complicated to handle the
192 /// case where one of the edges being split is an exit of a loop with other
195 void SplitLandingPadPredecessors(BasicBlock *OrigBB,ArrayRef<BasicBlock*> Preds,
196 const char *Suffix, const char *Suffix2,
197 Pass *P, SmallVectorImpl<BasicBlock*> &NewBBs);
199 /// FoldReturnIntoUncondBranch - This method duplicates the specified return
200 /// instruction into a predecessor which ends in an unconditional branch. If
201 /// the return instruction returns a value defined by a PHI, propagate the
202 /// right value into the return. It returns the new return instruction in the
204 ReturnInst *FoldReturnIntoUncondBranch(ReturnInst *RI, BasicBlock *BB,
207 /// SplitBlockAndInsertIfThen - Split the containing block at the
208 /// specified instruction - everything before and including Cmp stays
209 /// in the old basic block, and everything after Cmp is moved to a
210 /// new block. The two blocks are connected by a conditional branch
211 /// (with value of Cmp being the condition).
223 /// If Unreachable is true, then ThenBlock ends with
224 /// UnreachableInst, otherwise it branches to Tail.
225 /// Returns the NewBasicBlock's terminator.
227 TerminatorInst *SplitBlockAndInsertIfThen(Instruction *Cmp,
228 bool Unreachable, MDNode *BranchWeights = 0);
230 } // End llvm namespace