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_BASICBLOCK_H
16 #define LLVM_TRANSFORMS_UTILS_BASICBLOCK_H
18 // FIXME: Move to this file: BasicBlock::removePredecessor, BB::splitBasicBlock
20 #include "llvm/BasicBlock.h"
21 #include "llvm/Support/CFG.h"
22 #include "llvm/Support/DebugLoc.h"
31 /// DeleteDeadBlock - Delete the specified block, which must have no
33 void DeleteDeadBlock(BasicBlock *BB);
36 /// FoldSingleEntryPHINodes - We know that BB has one predecessor. If there are
37 /// any single-entry PHI nodes in it, fold them away. This handles the case
38 /// when all entries to the PHI nodes in a block are guaranteed equal, such as
39 /// when the block has exactly one predecessor.
40 void FoldSingleEntryPHINodes(BasicBlock *BB, Pass *P = 0);
42 /// DeleteDeadPHIs - Examine each PHI in the given block and delete it if it
43 /// is dead. Also recursively delete any operands that become dead as
44 /// a result. This includes tracing the def-use list from the PHI to see if
45 /// it is ultimately unused or if it reaches an unused cycle. Return true
46 /// if any PHIs were deleted.
47 bool DeleteDeadPHIs(BasicBlock *BB);
49 /// MergeBlockIntoPredecessor - Attempts to merge a block into its predecessor,
50 /// if possible. The return value indicates success or failure.
51 bool MergeBlockIntoPredecessor(BasicBlock *BB, Pass *P = 0);
53 // ReplaceInstWithValue - Replace all uses of an instruction (specified by BI)
54 // with a value, then remove and delete the original instruction.
56 void ReplaceInstWithValue(BasicBlock::InstListType &BIL,
57 BasicBlock::iterator &BI, Value *V);
59 // ReplaceInstWithInst - Replace the instruction specified by BI with the
60 // instruction specified by I. The original instruction is deleted and BI is
61 // updated to point to the new instruction.
63 void ReplaceInstWithInst(BasicBlock::InstListType &BIL,
64 BasicBlock::iterator &BI, Instruction *I);
66 // ReplaceInstWithInst - Replace the instruction specified by From with the
67 // instruction specified by To.
69 void ReplaceInstWithInst(Instruction *From, Instruction *To);
71 /// FindFunctionBackedges - Analyze the specified function to find all of the
72 /// loop backedges in the function and return them. This is a relatively cheap
73 /// (compared to computing dominators and loop info) analysis.
75 /// The output is added to Result, as pairs of <from,to> edge info.
76 void FindFunctionBackedges(const Function &F,
77 SmallVectorImpl<std::pair<const BasicBlock*,const BasicBlock*> > &Result);
80 /// GetSuccessorNumber - Search for the specified successor of basic block BB
81 /// and return its position in the terminator instruction's list of
82 /// successors. It is an error to call this with a block that is not a
84 unsigned GetSuccessorNumber(BasicBlock *BB, BasicBlock *Succ);
86 /// isCriticalEdge - Return true if the specified edge is a critical edge.
87 /// Critical edges are edges from a block with multiple successors to a block
88 /// with multiple predecessors.
90 bool isCriticalEdge(const TerminatorInst *TI, unsigned SuccNum,
91 bool AllowIdenticalEdges = false);
93 /// SplitCriticalEdge - If this edge is a critical edge, insert a new node to
94 /// split the critical edge. This will update DominatorTree and
95 /// DominatorFrontier information if it is available, thus calling this pass
96 /// will not invalidate either of them. This returns the new block if the edge
97 /// was split, null otherwise.
99 /// If MergeIdenticalEdges is true (not the default), *all* edges from TI to the
100 /// specified successor will be merged into the same critical edge block.
101 /// This is most commonly interesting with switch instructions, which may
102 /// have many edges to any one destination. This ensures that all edges to that
103 /// dest go to one block instead of each going to a different block, but isn't
104 /// the standard definition of a "critical edge".
106 /// It is invalid to call this function on a critical edge that starts at an
107 /// IndirectBrInst. Splitting these edges will almost always create an invalid
108 /// program because the address of the new block won't be the one that is jumped
111 BasicBlock *SplitCriticalEdge(TerminatorInst *TI, unsigned SuccNum,
112 Pass *P = 0, bool MergeIdenticalEdges = false);
114 inline BasicBlock *SplitCriticalEdge(BasicBlock *BB, succ_iterator SI,
116 return SplitCriticalEdge(BB->getTerminator(), SI.getSuccessorIndex(), P);
119 /// SplitCriticalEdge - If the edge from *PI to BB is not critical, return
120 /// false. Otherwise, split all edges between the two blocks and return true.
121 /// This updates all of the same analyses as the other SplitCriticalEdge
122 /// function. If P is specified, it updates the analyses
124 inline bool SplitCriticalEdge(BasicBlock *Succ, pred_iterator PI, Pass *P = 0) {
125 bool MadeChange = false;
126 TerminatorInst *TI = (*PI)->getTerminator();
127 for (unsigned i = 0, e = TI->getNumSuccessors(); i != e; ++i)
128 if (TI->getSuccessor(i) == Succ)
129 MadeChange |= !!SplitCriticalEdge(TI, i, P);
133 /// SplitCriticalEdge - If an edge from Src to Dst is critical, split the edge
134 /// and return true, otherwise return false. This method requires that there be
135 /// an edge between the two blocks. If P is specified, it updates the analyses
137 inline BasicBlock *SplitCriticalEdge(BasicBlock *Src, BasicBlock *Dst,
139 bool MergeIdenticalEdges = false) {
140 TerminatorInst *TI = Src->getTerminator();
143 assert(i != TI->getNumSuccessors() && "Edge doesn't exist!");
144 if (TI->getSuccessor(i) == Dst)
145 return SplitCriticalEdge(TI, i, P, MergeIdenticalEdges);
150 /// SplitEdge - Split the edge connecting specified block. Pass P must
152 BasicBlock *SplitEdge(BasicBlock *From, BasicBlock *To, Pass *P);
154 /// SplitBlock - Split the specified block at the specified instruction - every
155 /// thing before SplitPt stays in Old and everything starting with SplitPt moves
156 /// to a new block. The two blocks are joined by an unconditional branch and
157 /// the loop info is updated.
159 BasicBlock *SplitBlock(BasicBlock *Old, Instruction *SplitPt, Pass *P);
161 /// SplitBlockPredecessors - This method transforms BB by introducing a new
162 /// basic block into the function, and moving some of the predecessors of BB to
163 /// be predecessors of the new block. The new predecessors are indicated by the
164 /// Preds array, which has NumPreds elements in it. The new block is given a
165 /// suffix of 'Suffix'. This function returns the new block.
167 /// This currently updates the LLVM IR, AliasAnalysis, DominatorTree,
168 /// DominanceFrontier, LoopInfo, and LCCSA but no other analyses.
169 /// In particular, it does not preserve LoopSimplify (because it's
170 /// complicated to handle the case where one of the edges being split
171 /// is an exit of a loop with other exits).
173 BasicBlock *SplitBlockPredecessors(BasicBlock *BB, BasicBlock *const *Preds,
174 unsigned NumPreds, const char *Suffix,
177 /// SplitLandingPadPredecessors - This method transforms the landing pad,
178 /// OrigBB, by introducing two new basic blocks into the function. One of those
179 /// new basic blocks gets the predecessors listed in Preds. The other basic
180 /// block gets the remaining predecessors of OrigBB. The landingpad instruction
181 /// OrigBB is clone into both of the new basic blocks. The new blocks are given
182 /// the suffixes 'Suffix1' and 'Suffix2', and are returned in the NewBBs vector.
184 /// This currently updates the LLVM IR, AliasAnalysis, DominatorTree,
185 /// DominanceFrontier, LoopInfo, and LCCSA but no other analyses. In particular,
186 /// it does not preserve LoopSimplify (because it's complicated to handle the
187 /// case where one of the edges being split is an exit of a loop with other
190 void SplitLandingPadPredecessors(BasicBlock *OrigBB,ArrayRef<BasicBlock*> Preds,
191 const char *Suffix, const char *Suffix2,
192 Pass *P, SmallVectorImpl<BasicBlock*> &NewBBs);
194 /// FoldReturnIntoUncondBranch - This method duplicates the specified return
195 /// instruction into a predecessor which ends in an unconditional branch. If
196 /// the return instruction returns a value defined by a PHI, propagate the
197 /// right value into the return. It returns the new return instruction in the
199 ReturnInst *FoldReturnIntoUncondBranch(ReturnInst *RI, BasicBlock *BB,
202 /// GetFirstDebugLocInBasicBlock - Return first valid DebugLoc entry in a
203 /// given basic block.
204 DebugLoc GetFirstDebugLocInBasicBlock(const BasicBlock *BB);
206 } // End llvm namespace