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/IR/CFG.h"
30 class TargetLibraryInfo;
33 /// DeleteDeadBlock - Delete the specified block, which must have no
35 void DeleteDeadBlock(BasicBlock *BB);
37 /// FoldSingleEntryPHINodes - We know that BB has one predecessor. If there are
38 /// any single-entry PHI nodes in it, fold them away. This handles the case
39 /// when all entries to the PHI nodes in a block are guaranteed equal, such as
40 /// when the block has exactly one predecessor.
41 void FoldSingleEntryPHINodes(BasicBlock *BB, Pass *P = nullptr);
43 /// DeleteDeadPHIs - Examine each PHI in the given block and delete it if it
44 /// is dead. Also recursively delete any operands that become dead as
45 /// a result. This includes tracing the def-use list from the PHI to see if
46 /// it is ultimately unused or if it reaches an unused cycle. Return true
47 /// if any PHIs were deleted.
48 bool DeleteDeadPHIs(BasicBlock *BB, const TargetLibraryInfo *TLI = nullptr);
50 /// MergeBlockIntoPredecessor - Attempts to merge a block into its predecessor,
51 /// if possible. The return value indicates success or failure.
52 bool MergeBlockIntoPredecessor(BasicBlock *BB, Pass *P = nullptr);
54 // ReplaceInstWithValue - Replace all uses of an instruction (specified by BI)
55 // with a value, then remove and delete the original instruction.
57 void ReplaceInstWithValue(BasicBlock::InstListType &BIL,
58 BasicBlock::iterator &BI, Value *V);
60 // ReplaceInstWithInst - Replace the instruction specified by BI with the
61 // instruction specified by I. The original instruction is deleted and BI is
62 // updated to point to the new instruction.
64 void ReplaceInstWithInst(BasicBlock::InstListType &BIL,
65 BasicBlock::iterator &BI, Instruction *I);
67 // ReplaceInstWithInst - Replace the instruction specified by From with the
68 // instruction specified by To.
70 void ReplaceInstWithInst(Instruction *From, Instruction *To);
72 /// SplitCriticalEdge - If this edge is a critical edge, insert a new node to
73 /// split the critical edge. This will update DominatorTree and
74 /// DominatorFrontier information if it is available, thus calling this pass
75 /// will not invalidate either of them. This returns the new block if the edge
76 /// was split, null otherwise.
78 /// If MergeIdenticalEdges is true (not the default), *all* edges from TI to the
79 /// specified successor will be merged into the same critical edge block.
80 /// This is most commonly interesting with switch instructions, which may
81 /// have many edges to any one destination. This ensures that all edges to that
82 /// dest go to one block instead of each going to a different block, but isn't
83 /// the standard definition of a "critical edge".
85 /// It is invalid to call this function on a critical edge that starts at an
86 /// IndirectBrInst. Splitting these edges will almost always create an invalid
87 /// program because the address of the new block won't be the one that is jumped
90 BasicBlock *SplitCriticalEdge(TerminatorInst *TI, unsigned SuccNum,
92 bool MergeIdenticalEdges = false,
93 bool DontDeleteUselessPHIs = false,
94 bool SplitLandingPads = false);
96 inline BasicBlock *SplitCriticalEdge(BasicBlock *BB, succ_iterator SI,
98 return SplitCriticalEdge(BB->getTerminator(), SI.getSuccessorIndex(), P);
101 /// SplitCriticalEdge - If the edge from *PI to BB is not critical, return
102 /// false. Otherwise, split all edges between the two blocks and return true.
103 /// This updates all of the same analyses as the other SplitCriticalEdge
104 /// function. If P is specified, it updates the analyses
106 inline bool SplitCriticalEdge(BasicBlock *Succ, pred_iterator PI,
108 bool MadeChange = false;
109 TerminatorInst *TI = (*PI)->getTerminator();
110 for (unsigned i = 0, e = TI->getNumSuccessors(); i != e; ++i)
111 if (TI->getSuccessor(i) == Succ)
112 MadeChange |= !!SplitCriticalEdge(TI, i, P);
116 /// SplitCriticalEdge - If an edge from Src to Dst is critical, split the edge
117 /// and return true, otherwise return false. This method requires that there be
118 /// an edge between the two blocks. If P is specified, it updates the analyses
120 inline BasicBlock *SplitCriticalEdge(BasicBlock *Src, BasicBlock *Dst,
122 bool MergeIdenticalEdges = false,
123 bool DontDeleteUselessPHIs = false) {
124 TerminatorInst *TI = Src->getTerminator();
127 assert(i != TI->getNumSuccessors() && "Edge doesn't exist!");
128 if (TI->getSuccessor(i) == Dst)
129 return SplitCriticalEdge(TI, i, P, MergeIdenticalEdges,
130 DontDeleteUselessPHIs);
135 /// SplitEdge - Split the edge connecting specified block. Pass P must
137 BasicBlock *SplitEdge(BasicBlock *From, BasicBlock *To, Pass *P);
139 /// SplitBlock - Split the specified block at the specified instruction - every
140 /// thing before SplitPt stays in Old and everything starting with SplitPt moves
141 /// to a new block. The two blocks are joined by an unconditional branch and
142 /// the loop info is updated.
144 BasicBlock *SplitBlock(BasicBlock *Old, Instruction *SplitPt, Pass *P);
146 /// SplitBlockPredecessors - This method transforms BB by introducing a new
147 /// basic block into the function, and moving some of the predecessors of BB to
148 /// be predecessors of the new block. The new predecessors are indicated by the
149 /// Preds array, which has NumPreds elements in it. The new block is given a
150 /// suffix of 'Suffix'. This function returns the new block.
152 /// This currently updates the LLVM IR, AliasAnalysis, DominatorTree,
153 /// DominanceFrontier, LoopInfo, and LCCSA but no other analyses.
154 /// In particular, it does not preserve LoopSimplify (because it's
155 /// complicated to handle the case where one of the edges being split
156 /// is an exit of a loop with other exits).
158 BasicBlock *SplitBlockPredecessors(BasicBlock *BB, ArrayRef<BasicBlock*> Preds,
159 const char *Suffix, Pass *P = nullptr);
161 /// SplitLandingPadPredecessors - This method transforms the landing pad,
162 /// OrigBB, by introducing two new basic blocks into the function. One of those
163 /// new basic blocks gets the predecessors listed in Preds. The other basic
164 /// block gets the remaining predecessors of OrigBB. The landingpad instruction
165 /// OrigBB is clone into both of the new basic blocks. The new blocks are given
166 /// the suffixes 'Suffix1' and 'Suffix2', and are returned in the NewBBs vector.
168 /// This currently updates the LLVM IR, AliasAnalysis, DominatorTree,
169 /// DominanceFrontier, LoopInfo, and LCCSA but no other analyses. In particular,
170 /// it does not preserve LoopSimplify (because it's complicated to handle the
171 /// case where one of the edges being split is an exit of a loop with other
174 void SplitLandingPadPredecessors(BasicBlock *OrigBB,ArrayRef<BasicBlock*> Preds,
175 const char *Suffix, const char *Suffix2,
176 Pass *P, SmallVectorImpl<BasicBlock*> &NewBBs);
178 /// FoldReturnIntoUncondBranch - This method duplicates the specified return
179 /// instruction into a predecessor which ends in an unconditional branch. If
180 /// the return instruction returns a value defined by a PHI, propagate the
181 /// right value into the return. It returns the new return instruction in the
183 ReturnInst *FoldReturnIntoUncondBranch(ReturnInst *RI, BasicBlock *BB,
186 /// SplitBlockAndInsertIfThen - Split the containing block at the
187 /// specified instruction - everything before and including SplitBefore stays
188 /// in the old basic block, and everything after SplitBefore is moved to a
189 /// new block. The two blocks are connected by a conditional branch
190 /// (with value of Cmp being the condition).
202 /// If Unreachable is true, then ThenBlock ends with
203 /// UnreachableInst, otherwise it branches to Tail.
204 /// Returns the NewBasicBlock's terminator.
205 TerminatorInst *SplitBlockAndInsertIfThen(Value *Cond, Instruction *SplitBefore,
207 MDNode *BranchWeights = nullptr);
209 /// SplitBlockAndInsertIfThenElse is similar to SplitBlockAndInsertIfThen,
210 /// but also creates the ElseBlock.
223 void SplitBlockAndInsertIfThenElse(Value *Cond, Instruction *SplitBefore,
224 TerminatorInst **ThenTerm,
225 TerminatorInst **ElseTerm,
226 MDNode *BranchWeights = nullptr);
229 /// GetIfCondition - Check whether BB is the merge point of a if-region.
230 /// If so, return the boolean condition that determines which entry into
231 /// BB will be taken. Also, return by references the block that will be
232 /// entered from if the condition is true, and the block that will be
233 /// entered if the condition is false.
234 Value *GetIfCondition(BasicBlock *BB, BasicBlock *&IfTrue,
235 BasicBlock *&IfFalse);
236 } // End llvm namespace