1//===-- Transform/Utils/BasicBlockUtils.h - BasicBlock Utils ----*- C++ -*-===// 2// 3// The LLVM Compiler Infrastructure 4// 5// This file is distributed under the University of Illinois Open Source 6// License. See LICENSE.TXT for details. 7// 8//===----------------------------------------------------------------------===// 9// 10// This family of functions perform manipulations on basic blocks, and 11// instructions contained within basic blocks. 12// 13//===----------------------------------------------------------------------===// 14 15#ifndef LLVM_TRANSFORMS_UTILS_BASICBLOCKUTILS_H 16#define LLVM_TRANSFORMS_UTILS_BASICBLOCKUTILS_H 17 18// FIXME: Move to this file: BasicBlock::removePredecessor, BB::splitBasicBlock 19 20#include "llvm/IR/BasicBlock.h" 21#include "llvm/IR/CFG.h" 22 23namespace llvm { 24 25class AliasAnalysis; 26class Instruction; 27class MDNode; 28class Pass; 29class ReturnInst; 30class TargetLibraryInfo; 31class TerminatorInst; 32 33/// DeleteDeadBlock - Delete the specified block, which must have no 34/// predecessors. 35void DeleteDeadBlock(BasicBlock *BB); 36 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. 41void FoldSingleEntryPHINodes(BasicBlock *BB, Pass *P = nullptr); 42 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. 48bool DeleteDeadPHIs(BasicBlock *BB, const TargetLibraryInfo *TLI = nullptr); 49 50/// MergeBlockIntoPredecessor - Attempts to merge a block into its predecessor, 51/// if possible. The return value indicates success or failure. 52bool MergeBlockIntoPredecessor(BasicBlock *BB, Pass *P = nullptr); 53 54// ReplaceInstWithValue - Replace all uses of an instruction (specified by BI) 55// with a value, then remove and delete the original instruction. 56// 57void ReplaceInstWithValue(BasicBlock::InstListType &BIL, 58 BasicBlock::iterator &BI, Value *V); 59 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. 63// 64void ReplaceInstWithInst(BasicBlock::InstListType &BIL, 65 BasicBlock::iterator &BI, Instruction *I); 66 67// ReplaceInstWithInst - Replace the instruction specified by From with the 68// instruction specified by To. 69// 70void ReplaceInstWithInst(Instruction *From, Instruction *To); 71 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. 77/// 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". 84/// 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 88/// to. 89/// 90BasicBlock *SplitCriticalEdge(TerminatorInst *TI, unsigned SuccNum, 91 Pass *P = nullptr, 92 bool MergeIdenticalEdges = false, 93 bool DontDeleteUselessPHIs = false, 94 bool SplitLandingPads = false); 95 96inline BasicBlock *SplitCriticalEdge(BasicBlock *BB, succ_iterator SI, 97 Pass *P = nullptr) { 98 return SplitCriticalEdge(BB->getTerminator(), SI.getSuccessorIndex(), P); 99} 100 101/// 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 105/// described above. 106inline bool SplitCriticalEdge(BasicBlock *Succ, pred_iterator PI, 107 Pass *P = nullptr) { 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); 113 return MadeChange; 114} 115 116/// 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 119/// described above. 120inline BasicBlock *SplitCriticalEdge(BasicBlock *Src, BasicBlock *Dst, 121 Pass *P = nullptr, 122 bool MergeIdenticalEdges = false, 123 bool DontDeleteUselessPHIs = false) { 124 TerminatorInst *TI = Src->getTerminator(); 125 unsigned i = 0; 126 while (1) { 127 assert(i != TI->getNumSuccessors() && "Edge doesn't exist!"); 128 if (TI->getSuccessor(i) == Dst) 129 return SplitCriticalEdge(TI, i, P, MergeIdenticalEdges, 130 DontDeleteUselessPHIs); 131 ++i; 132 } 133} 134 135/// SplitEdge - Split the edge connecting specified block. Pass P must 136/// not be NULL. 137BasicBlock *SplitEdge(BasicBlock *From, BasicBlock *To, Pass *P); 138 139/// 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. 143/// 144BasicBlock *SplitBlock(BasicBlock *Old, Instruction *SplitPt, Pass *P); 145 146/// 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. 151/// 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). 157/// 158BasicBlock *SplitBlockPredecessors(BasicBlock *BB, ArrayRef<BasicBlock*> Preds, 159 const char *Suffix, Pass *P = nullptr); 160 161/// 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. 167/// 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 172/// exits). 173/// 174void SplitLandingPadPredecessors(BasicBlock *OrigBB,ArrayRef<BasicBlock*> Preds, 175 const char *Suffix, const char *Suffix2, 176 Pass *P, SmallVectorImpl<BasicBlock*> &NewBBs); 177 178/// 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 182/// predecessor. 183ReturnInst *FoldReturnIntoUncondBranch(ReturnInst *RI, BasicBlock *BB, 184 BasicBlock *Pred); 185 186/// 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). 191/// Before: 192/// Head 193/// SplitBefore 194/// Tail 195/// After: 196/// Head 197/// if (Cond) 198/// ThenBlock 199/// SplitBefore 200/// Tail 201/// 202/// If Unreachable is true, then ThenBlock ends with 203/// UnreachableInst, otherwise it branches to Tail. 204/// Returns the NewBasicBlock's terminator. 205TerminatorInst *SplitBlockAndInsertIfThen(Value *Cond, Instruction *SplitBefore, 206 bool Unreachable, 207 MDNode *BranchWeights = nullptr); 208 209/// SplitBlockAndInsertIfThenElse is similar to SplitBlockAndInsertIfThen, 210/// but also creates the ElseBlock. 211/// Before: 212/// Head 213/// SplitBefore 214/// Tail 215/// After: 216/// Head 217/// if (Cond) 218/// ThenBlock 219/// else 220/// ElseBlock 221/// SplitBefore 222/// Tail 223void SplitBlockAndInsertIfThenElse(Value *Cond, Instruction *SplitBefore, 224 TerminatorInst **ThenTerm, 225 TerminatorInst **ElseTerm, 226 MDNode *BranchWeights = nullptr); 227 228/// 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. 234Value *GetIfCondition(BasicBlock *BB, BasicBlock *&IfTrue, 235 BasicBlock *&IfFalse); 236} // End llvm namespace 237 238#endif 239