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_BASICBLOCK_H 16#define LLVM_TRANSFORMS_UTILS_BASICBLOCK_H 17 18// FIXME: Move to this file: BasicBlock::removePredecessor, BB::splitBasicBlock 19 20#include "llvm/BasicBlock.h" 21#include "llvm/Support/CFG.h" 22#include "llvm/Support/DebugLoc.h" 23 24namespace llvm { 25 26class AliasAnalysis; 27class Instruction; 28class Pass; 29class ReturnInst; 30class TargetLibraryInfo; 31 32/// DeleteDeadBlock - Delete the specified block, which must have no 33/// predecessors. 34void DeleteDeadBlock(BasicBlock *BB); 35 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 = 0); 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 = 0); 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 = 0); 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/// FindFunctionBackedges - Analyze the specified function to find all of the 73/// loop backedges in the function and return them. This is a relatively cheap 74/// (compared to computing dominators and loop info) analysis. 75/// 76/// The output is added to Result, as pairs of <from,to> edge info. 77void FindFunctionBackedges(const Function &F, 78 SmallVectorImpl<std::pair<const BasicBlock*,const BasicBlock*> > &Result); 79 80 81/// GetSuccessorNumber - Search for the specified successor of basic block BB 82/// and return its position in the terminator instruction's list of 83/// successors. It is an error to call this with a block that is not a 84/// successor. 85unsigned GetSuccessorNumber(BasicBlock *BB, BasicBlock *Succ); 86 87/// isCriticalEdge - Return true if the specified edge is a critical edge. 88/// Critical edges are edges from a block with multiple successors to a block 89/// with multiple predecessors. 90/// 91bool isCriticalEdge(const TerminatorInst *TI, unsigned SuccNum, 92 bool AllowIdenticalEdges = false); 93 94/// SplitCriticalEdge - If this edge is a critical edge, insert a new node to 95/// split the critical edge. This will update DominatorTree and 96/// DominatorFrontier information if it is available, thus calling this pass 97/// will not invalidate either of them. This returns the new block if the edge 98/// was split, null otherwise. 99/// 100/// If MergeIdenticalEdges is true (not the default), *all* edges from TI to the 101/// specified successor will be merged into the same critical edge block. 102/// This is most commonly interesting with switch instructions, which may 103/// have many edges to any one destination. This ensures that all edges to that 104/// dest go to one block instead of each going to a different block, but isn't 105/// the standard definition of a "critical edge". 106/// 107/// It is invalid to call this function on a critical edge that starts at an 108/// IndirectBrInst. Splitting these edges will almost always create an invalid 109/// program because the address of the new block won't be the one that is jumped 110/// to. 111/// 112BasicBlock *SplitCriticalEdge(TerminatorInst *TI, unsigned SuccNum, 113 Pass *P = 0, bool MergeIdenticalEdges = false, 114 bool DontDeleteUselessPHIs = false, 115 bool SplitLandingPads = false); 116 117inline BasicBlock *SplitCriticalEdge(BasicBlock *BB, succ_iterator SI, 118 Pass *P = 0) { 119 return SplitCriticalEdge(BB->getTerminator(), SI.getSuccessorIndex(), P); 120} 121 122/// SplitCriticalEdge - If the edge from *PI to BB is not critical, return 123/// false. Otherwise, split all edges between the two blocks and return true. 124/// This updates all of the same analyses as the other SplitCriticalEdge 125/// function. If P is specified, it updates the analyses 126/// described above. 127inline bool SplitCriticalEdge(BasicBlock *Succ, pred_iterator PI, Pass *P = 0) { 128 bool MadeChange = false; 129 TerminatorInst *TI = (*PI)->getTerminator(); 130 for (unsigned i = 0, e = TI->getNumSuccessors(); i != e; ++i) 131 if (TI->getSuccessor(i) == Succ) 132 MadeChange |= !!SplitCriticalEdge(TI, i, P); 133 return MadeChange; 134} 135 136/// SplitCriticalEdge - If an edge from Src to Dst is critical, split the edge 137/// and return true, otherwise return false. This method requires that there be 138/// an edge between the two blocks. If P is specified, it updates the analyses 139/// described above. 140inline BasicBlock *SplitCriticalEdge(BasicBlock *Src, BasicBlock *Dst, 141 Pass *P = 0, 142 bool MergeIdenticalEdges = false, 143 bool DontDeleteUselessPHIs = false) { 144 TerminatorInst *TI = Src->getTerminator(); 145 unsigned i = 0; 146 while (1) { 147 assert(i != TI->getNumSuccessors() && "Edge doesn't exist!"); 148 if (TI->getSuccessor(i) == Dst) 149 return SplitCriticalEdge(TI, i, P, MergeIdenticalEdges, 150 DontDeleteUselessPHIs); 151 ++i; 152 } 153} 154 155/// SplitEdge - Split the edge connecting specified block. Pass P must 156/// not be NULL. 157BasicBlock *SplitEdge(BasicBlock *From, BasicBlock *To, Pass *P); 158 159/// SplitBlock - Split the specified block at the specified instruction - every 160/// thing before SplitPt stays in Old and everything starting with SplitPt moves 161/// to a new block. The two blocks are joined by an unconditional branch and 162/// the loop info is updated. 163/// 164BasicBlock *SplitBlock(BasicBlock *Old, Instruction *SplitPt, Pass *P); 165 166/// SplitBlockPredecessors - This method transforms BB by introducing a new 167/// basic block into the function, and moving some of the predecessors of BB to 168/// be predecessors of the new block. The new predecessors are indicated by the 169/// Preds array, which has NumPreds elements in it. The new block is given a 170/// suffix of 'Suffix'. This function returns the new block. 171/// 172/// This currently updates the LLVM IR, AliasAnalysis, DominatorTree, 173/// DominanceFrontier, LoopInfo, and LCCSA but no other analyses. 174/// In particular, it does not preserve LoopSimplify (because it's 175/// complicated to handle the case where one of the edges being split 176/// is an exit of a loop with other exits). 177/// 178BasicBlock *SplitBlockPredecessors(BasicBlock *BB, ArrayRef<BasicBlock*> Preds, 179 const char *Suffix, Pass *P = 0); 180 181/// SplitLandingPadPredecessors - This method transforms the landing pad, 182/// OrigBB, by introducing two new basic blocks into the function. One of those 183/// new basic blocks gets the predecessors listed in Preds. The other basic 184/// block gets the remaining predecessors of OrigBB. The landingpad instruction 185/// OrigBB is clone into both of the new basic blocks. The new blocks are given 186/// the suffixes 'Suffix1' and 'Suffix2', and are returned in the NewBBs vector. 187/// 188/// This currently updates the LLVM IR, AliasAnalysis, DominatorTree, 189/// DominanceFrontier, LoopInfo, and LCCSA but no other analyses. In particular, 190/// it does not preserve LoopSimplify (because it's complicated to handle the 191/// case where one of the edges being split is an exit of a loop with other 192/// exits). 193/// 194void SplitLandingPadPredecessors(BasicBlock *OrigBB,ArrayRef<BasicBlock*> Preds, 195 const char *Suffix, const char *Suffix2, 196 Pass *P, SmallVectorImpl<BasicBlock*> &NewBBs); 197 198/// FoldReturnIntoUncondBranch - This method duplicates the specified return 199/// instruction into a predecessor which ends in an unconditional branch. If 200/// the return instruction returns a value defined by a PHI, propagate the 201/// right value into the return. It returns the new return instruction in the 202/// predecessor. 203ReturnInst *FoldReturnIntoUncondBranch(ReturnInst *RI, BasicBlock *BB, 204 BasicBlock *Pred); 205 206} // End llvm namespace 207 208#endif 209