BasicBlockUtils.h revision 276479
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 DominatorTree; 27class Instruction; 28class MDNode; 29class Pass; 30class ReturnInst; 31class TargetLibraryInfo; 32class TerminatorInst; 33 34/// DeleteDeadBlock - Delete the specified block, which must have no 35/// predecessors. 36void DeleteDeadBlock(BasicBlock *BB); 37 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. 42void FoldSingleEntryPHINodes(BasicBlock *BB, Pass *P = nullptr); 43 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. 49bool DeleteDeadPHIs(BasicBlock *BB, const TargetLibraryInfo *TLI = nullptr); 50 51/// MergeBlockIntoPredecessor - Attempts to merge a block into its predecessor, 52/// if possible. The return value indicates success or failure. 53bool MergeBlockIntoPredecessor(BasicBlock *BB, Pass *P = nullptr); 54 55// ReplaceInstWithValue - Replace all uses of an instruction (specified by BI) 56// with a value, then remove and delete the original instruction. 57// 58void ReplaceInstWithValue(BasicBlock::InstListType &BIL, 59 BasicBlock::iterator &BI, Value *V); 60 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. 64// 65void ReplaceInstWithInst(BasicBlock::InstListType &BIL, 66 BasicBlock::iterator &BI, Instruction *I); 67 68// ReplaceInstWithInst - Replace the instruction specified by From with the 69// instruction specified by To. 70// 71void ReplaceInstWithInst(Instruction *From, Instruction *To); 72 73/// SplitCriticalEdge - If this edge is a critical edge, insert a new node to 74/// split the critical edge. This will update DominatorTree and 75/// DominatorFrontier information if it is available, thus calling this pass 76/// will not invalidate either of them. This returns the new block if the edge 77/// was split, null otherwise. 78/// 79/// If MergeIdenticalEdges is true (not the default), *all* edges from TI to the 80/// specified successor will be merged into the same critical edge block. 81/// This is most commonly interesting with switch instructions, which may 82/// have many edges to any one destination. This ensures that all edges to that 83/// dest go to one block instead of each going to a different block, but isn't 84/// the standard definition of a "critical edge". 85/// 86/// It is invalid to call this function on a critical edge that starts at an 87/// IndirectBrInst. Splitting these edges will almost always create an invalid 88/// program because the address of the new block won't be the one that is jumped 89/// to. 90/// 91BasicBlock *SplitCriticalEdge(TerminatorInst *TI, unsigned SuccNum, 92 Pass *P = nullptr, 93 bool MergeIdenticalEdges = false, 94 bool DontDeleteUselessPHIs = false, 95 bool SplitLandingPads = false); 96 97inline BasicBlock *SplitCriticalEdge(BasicBlock *BB, succ_iterator SI, 98 Pass *P = nullptr) { 99 return SplitCriticalEdge(BB->getTerminator(), SI.getSuccessorIndex(), P); 100} 101 102/// SplitCriticalEdge - If the edge from *PI to BB is not critical, return 103/// false. Otherwise, split all edges between the two blocks and return true. 104/// This updates all of the same analyses as the other SplitCriticalEdge 105/// function. If P is specified, it updates the analyses 106/// described above. 107inline bool SplitCriticalEdge(BasicBlock *Succ, pred_iterator PI, 108 Pass *P = nullptr) { 109 bool MadeChange = false; 110 TerminatorInst *TI = (*PI)->getTerminator(); 111 for (unsigned i = 0, e = TI->getNumSuccessors(); i != e; ++i) 112 if (TI->getSuccessor(i) == Succ) 113 MadeChange |= !!SplitCriticalEdge(TI, i, P); 114 return MadeChange; 115} 116 117/// SplitCriticalEdge - If an edge from Src to Dst is critical, split the edge 118/// and return true, otherwise return false. This method requires that there be 119/// an edge between the two blocks. If P is specified, it updates the analyses 120/// described above. 121inline BasicBlock *SplitCriticalEdge(BasicBlock *Src, BasicBlock *Dst, 122 Pass *P = nullptr, 123 bool MergeIdenticalEdges = false, 124 bool DontDeleteUselessPHIs = false) { 125 TerminatorInst *TI = Src->getTerminator(); 126 unsigned i = 0; 127 while (1) { 128 assert(i != TI->getNumSuccessors() && "Edge doesn't exist!"); 129 if (TI->getSuccessor(i) == Dst) 130 return SplitCriticalEdge(TI, i, P, MergeIdenticalEdges, 131 DontDeleteUselessPHIs); 132 ++i; 133 } 134} 135 136/// SplitEdge - Split the edge connecting specified block. Pass P must 137/// not be NULL. 138BasicBlock *SplitEdge(BasicBlock *From, BasicBlock *To, Pass *P); 139 140/// SplitBlock - Split the specified block at the specified instruction - every 141/// thing before SplitPt stays in Old and everything starting with SplitPt moves 142/// to a new block. The two blocks are joined by an unconditional branch and 143/// the loop info is updated. 144/// 145BasicBlock *SplitBlock(BasicBlock *Old, Instruction *SplitPt, Pass *P); 146 147/// SplitBlockPredecessors - This method transforms BB by introducing a new 148/// basic block into the function, and moving some of the predecessors of BB to 149/// be predecessors of the new block. The new predecessors are indicated by the 150/// Preds array, which has NumPreds elements in it. The new block is given a 151/// suffix of 'Suffix'. This function returns the new block. 152/// 153/// This currently updates the LLVM IR, AliasAnalysis, DominatorTree, 154/// DominanceFrontier, LoopInfo, and LCCSA but no other analyses. 155/// In particular, it does not preserve LoopSimplify (because it's 156/// complicated to handle the case where one of the edges being split 157/// is an exit of a loop with other exits). 158/// 159BasicBlock *SplitBlockPredecessors(BasicBlock *BB, ArrayRef<BasicBlock*> Preds, 160 const char *Suffix, Pass *P = nullptr); 161 162/// SplitLandingPadPredecessors - This method transforms the landing pad, 163/// OrigBB, by introducing two new basic blocks into the function. One of those 164/// new basic blocks gets the predecessors listed in Preds. The other basic 165/// block gets the remaining predecessors of OrigBB. The landingpad instruction 166/// OrigBB is clone into both of the new basic blocks. The new blocks are given 167/// the suffixes 'Suffix1' and 'Suffix2', and are returned in the NewBBs vector. 168/// 169/// This currently updates the LLVM IR, AliasAnalysis, DominatorTree, 170/// DominanceFrontier, LoopInfo, and LCCSA but no other analyses. In particular, 171/// it does not preserve LoopSimplify (because it's complicated to handle the 172/// case where one of the edges being split is an exit of a loop with other 173/// exits). 174/// 175void SplitLandingPadPredecessors(BasicBlock *OrigBB,ArrayRef<BasicBlock*> Preds, 176 const char *Suffix, const char *Suffix2, 177 Pass *P, SmallVectorImpl<BasicBlock*> &NewBBs); 178 179/// FoldReturnIntoUncondBranch - This method duplicates the specified return 180/// instruction into a predecessor which ends in an unconditional branch. If 181/// the return instruction returns a value defined by a PHI, propagate the 182/// right value into the return. It returns the new return instruction in the 183/// predecessor. 184ReturnInst *FoldReturnIntoUncondBranch(ReturnInst *RI, BasicBlock *BB, 185 BasicBlock *Pred); 186 187/// SplitBlockAndInsertIfThen - Split the containing block at the 188/// specified instruction - everything before and including SplitBefore stays 189/// in the old basic block, and everything after SplitBefore is moved to a 190/// new block. The two blocks are connected by a conditional branch 191/// (with value of Cmp being the condition). 192/// Before: 193/// Head 194/// SplitBefore 195/// Tail 196/// After: 197/// Head 198/// if (Cond) 199/// ThenBlock 200/// SplitBefore 201/// Tail 202/// 203/// If Unreachable is true, then ThenBlock ends with 204/// UnreachableInst, otherwise it branches to Tail. 205/// Returns the NewBasicBlock's terminator. 206/// 207/// Updates DT if given. 208TerminatorInst *SplitBlockAndInsertIfThen(Value *Cond, Instruction *SplitBefore, 209 bool Unreachable, 210 MDNode *BranchWeights = nullptr, 211 DominatorTree *DT = nullptr); 212 213/// SplitBlockAndInsertIfThenElse is similar to SplitBlockAndInsertIfThen, 214/// but also creates the ElseBlock. 215/// Before: 216/// Head 217/// SplitBefore 218/// Tail 219/// After: 220/// Head 221/// if (Cond) 222/// ThenBlock 223/// else 224/// ElseBlock 225/// SplitBefore 226/// Tail 227void SplitBlockAndInsertIfThenElse(Value *Cond, Instruction *SplitBefore, 228 TerminatorInst **ThenTerm, 229 TerminatorInst **ElseTerm, 230 MDNode *BranchWeights = nullptr); 231 232/// 233/// GetIfCondition - Check whether BB is the merge point of a if-region. 234/// If so, return the boolean condition that determines which entry into 235/// BB will be taken. Also, return by references the block that will be 236/// entered from if the condition is true, and the block that will be 237/// entered if the condition is false. 238Value *GetIfCondition(BasicBlock *BB, BasicBlock *&IfTrue, 239 BasicBlock *&IfFalse); 240} // End llvm namespace 241 242#endif 243