BasicBlockUtils.h revision 234353
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; 30 31/// DeleteDeadBlock - Delete the specified block, which must have no 32/// predecessors. 33void DeleteDeadBlock(BasicBlock *BB); 34 35 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. 40void FoldSingleEntryPHINodes(BasicBlock *BB, Pass *P = 0); 41 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. 47bool DeleteDeadPHIs(BasicBlock *BB); 48 49/// MergeBlockIntoPredecessor - Attempts to merge a block into its predecessor, 50/// if possible. The return value indicates success or failure. 51bool MergeBlockIntoPredecessor(BasicBlock *BB, Pass *P = 0); 52 53// ReplaceInstWithValue - Replace all uses of an instruction (specified by BI) 54// with a value, then remove and delete the original instruction. 55// 56void ReplaceInstWithValue(BasicBlock::InstListType &BIL, 57 BasicBlock::iterator &BI, Value *V); 58 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. 62// 63void ReplaceInstWithInst(BasicBlock::InstListType &BIL, 64 BasicBlock::iterator &BI, Instruction *I); 65 66// ReplaceInstWithInst - Replace the instruction specified by From with the 67// instruction specified by To. 68// 69void ReplaceInstWithInst(Instruction *From, Instruction *To); 70 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. 74/// 75/// The output is added to Result, as pairs of <from,to> edge info. 76void FindFunctionBackedges(const Function &F, 77 SmallVectorImpl<std::pair<const BasicBlock*,const BasicBlock*> > &Result); 78 79 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 83/// successor. 84unsigned GetSuccessorNumber(BasicBlock *BB, BasicBlock *Succ); 85 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. 89/// 90bool isCriticalEdge(const TerminatorInst *TI, unsigned SuccNum, 91 bool AllowIdenticalEdges = false); 92 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. 98/// 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". 105/// 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 109/// to. 110/// 111BasicBlock *SplitCriticalEdge(TerminatorInst *TI, unsigned SuccNum, 112 Pass *P = 0, bool MergeIdenticalEdges = false, 113 bool DontDeleteUselessPHIs = false); 114 115inline BasicBlock *SplitCriticalEdge(BasicBlock *BB, succ_iterator SI, 116 Pass *P = 0) { 117 return SplitCriticalEdge(BB->getTerminator(), SI.getSuccessorIndex(), P); 118} 119 120/// SplitCriticalEdge - If the edge from *PI to BB is not critical, return 121/// false. Otherwise, split all edges between the two blocks and return true. 122/// This updates all of the same analyses as the other SplitCriticalEdge 123/// function. If P is specified, it updates the analyses 124/// described above. 125inline bool SplitCriticalEdge(BasicBlock *Succ, pred_iterator PI, Pass *P = 0) { 126 bool MadeChange = false; 127 TerminatorInst *TI = (*PI)->getTerminator(); 128 for (unsigned i = 0, e = TI->getNumSuccessors(); i != e; ++i) 129 if (TI->getSuccessor(i) == Succ) 130 MadeChange |= !!SplitCriticalEdge(TI, i, P); 131 return MadeChange; 132} 133 134/// SplitCriticalEdge - If an edge from Src to Dst is critical, split the edge 135/// and return true, otherwise return false. This method requires that there be 136/// an edge between the two blocks. If P is specified, it updates the analyses 137/// described above. 138inline BasicBlock *SplitCriticalEdge(BasicBlock *Src, BasicBlock *Dst, 139 Pass *P = 0, 140 bool MergeIdenticalEdges = false, 141 bool DontDeleteUselessPHIs = false) { 142 TerminatorInst *TI = Src->getTerminator(); 143 unsigned i = 0; 144 while (1) { 145 assert(i != TI->getNumSuccessors() && "Edge doesn't exist!"); 146 if (TI->getSuccessor(i) == Dst) 147 return SplitCriticalEdge(TI, i, P, MergeIdenticalEdges, 148 DontDeleteUselessPHIs); 149 ++i; 150 } 151} 152 153/// SplitEdge - Split the edge connecting specified block. Pass P must 154/// not be NULL. 155BasicBlock *SplitEdge(BasicBlock *From, BasicBlock *To, Pass *P); 156 157/// SplitBlock - Split the specified block at the specified instruction - every 158/// thing before SplitPt stays in Old and everything starting with SplitPt moves 159/// to a new block. The two blocks are joined by an unconditional branch and 160/// the loop info is updated. 161/// 162BasicBlock *SplitBlock(BasicBlock *Old, Instruction *SplitPt, Pass *P); 163 164/// SplitBlockPredecessors - This method transforms BB by introducing a new 165/// basic block into the function, and moving some of the predecessors of BB to 166/// be predecessors of the new block. The new predecessors are indicated by the 167/// Preds array, which has NumPreds elements in it. The new block is given a 168/// suffix of 'Suffix'. This function returns the new block. 169/// 170/// This currently updates the LLVM IR, AliasAnalysis, DominatorTree, 171/// DominanceFrontier, LoopInfo, and LCCSA but no other analyses. 172/// In particular, it does not preserve LoopSimplify (because it's 173/// complicated to handle the case where one of the edges being split 174/// is an exit of a loop with other exits). 175/// 176BasicBlock *SplitBlockPredecessors(BasicBlock *BB, ArrayRef<BasicBlock*> Preds, 177 const char *Suffix, Pass *P = 0); 178 179/// SplitLandingPadPredecessors - This method transforms the landing pad, 180/// OrigBB, by introducing two new basic blocks into the function. One of those 181/// new basic blocks gets the predecessors listed in Preds. The other basic 182/// block gets the remaining predecessors of OrigBB. The landingpad instruction 183/// OrigBB is clone into both of the new basic blocks. The new blocks are given 184/// the suffixes 'Suffix1' and 'Suffix2', and are returned in the NewBBs vector. 185/// 186/// This currently updates the LLVM IR, AliasAnalysis, DominatorTree, 187/// DominanceFrontier, LoopInfo, and LCCSA but no other analyses. In particular, 188/// it does not preserve LoopSimplify (because it's complicated to handle the 189/// case where one of the edges being split is an exit of a loop with other 190/// exits). 191/// 192void SplitLandingPadPredecessors(BasicBlock *OrigBB,ArrayRef<BasicBlock*> Preds, 193 const char *Suffix, const char *Suffix2, 194 Pass *P, SmallVectorImpl<BasicBlock*> &NewBBs); 195 196/// FoldReturnIntoUncondBranch - This method duplicates the specified return 197/// instruction into a predecessor which ends in an unconditional branch. If 198/// the return instruction returns a value defined by a PHI, propagate the 199/// right value into the return. It returns the new return instruction in the 200/// predecessor. 201ReturnInst *FoldReturnIntoUncondBranch(ReturnInst *RI, BasicBlock *BB, 202 BasicBlock *Pred); 203 204/// GetFirstDebugLocInBasicBlock - Return first valid DebugLoc entry in a 205/// given basic block. 206DebugLoc GetFirstDebugLocInBasicBlock(const BasicBlock *BB); 207 208} // End llvm namespace 209 210#endif 211