| //===-- BasicBlockUtils.cpp - BasicBlock Utilities -------------------------==// |
| // |
| // The LLVM Compiler Infrastructure |
| // |
| // This file was developed by the LLVM research group and is distributed under |
| // the University of Illinois Open Source License. See LICENSE.TXT for details. |
| // |
| //===----------------------------------------------------------------------===// |
| // |
| // This family of functions perform manipulations on basic blocks, and |
| // instructions contained within basic blocks. |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #include "llvm/Transforms/Utils/BasicBlockUtils.h" |
| #include "llvm/Function.h" |
| #include "llvm/Instructions.h" |
| #include "llvm/Constant.h" |
| #include "llvm/Type.h" |
| #include "llvm/Analysis/LoopInfo.h" |
| #include "llvm/Analysis/Dominators.h" |
| #include <algorithm> |
| using namespace llvm; |
| |
| /// ReplaceInstWithValue - Replace all uses of an instruction (specified by BI) |
| /// with a value, then remove and delete the original instruction. |
| /// |
| void llvm::ReplaceInstWithValue(BasicBlock::InstListType &BIL, |
| BasicBlock::iterator &BI, Value *V) { |
| Instruction &I = *BI; |
| // Replaces all of the uses of the instruction with uses of the value |
| I.replaceAllUsesWith(V); |
| |
| // Make sure to propagate a name if there is one already. |
| if (I.hasName() && !V->hasName()) |
| V->takeName(&I); |
| |
| // Delete the unnecessary instruction now... |
| BI = BIL.erase(BI); |
| } |
| |
| |
| /// ReplaceInstWithInst - Replace the instruction specified by BI with the |
| /// instruction specified by I. The original instruction is deleted and BI is |
| /// updated to point to the new instruction. |
| /// |
| void llvm::ReplaceInstWithInst(BasicBlock::InstListType &BIL, |
| BasicBlock::iterator &BI, Instruction *I) { |
| assert(I->getParent() == 0 && |
| "ReplaceInstWithInst: Instruction already inserted into basic block!"); |
| |
| // Insert the new instruction into the basic block... |
| BasicBlock::iterator New = BIL.insert(BI, I); |
| |
| // Replace all uses of the old instruction, and delete it. |
| ReplaceInstWithValue(BIL, BI, I); |
| |
| // Move BI back to point to the newly inserted instruction |
| BI = New; |
| } |
| |
| /// ReplaceInstWithInst - Replace the instruction specified by From with the |
| /// instruction specified by To. |
| /// |
| void llvm::ReplaceInstWithInst(Instruction *From, Instruction *To) { |
| BasicBlock::iterator BI(From); |
| ReplaceInstWithInst(From->getParent()->getInstList(), BI, To); |
| } |
| |
| /// RemoveSuccessor - Change the specified terminator instruction such that its |
| /// successor SuccNum no longer exists. Because this reduces the outgoing |
| /// degree of the current basic block, the actual terminator instruction itself |
| /// may have to be changed. In the case where the last successor of the block |
| /// is deleted, a return instruction is inserted in its place which can cause a |
| /// surprising change in program behavior if it is not expected. |
| /// |
| void llvm::RemoveSuccessor(TerminatorInst *TI, unsigned SuccNum) { |
| assert(SuccNum < TI->getNumSuccessors() && |
| "Trying to remove a nonexistant successor!"); |
| |
| // If our old successor block contains any PHI nodes, remove the entry in the |
| // PHI nodes that comes from this branch... |
| // |
| BasicBlock *BB = TI->getParent(); |
| TI->getSuccessor(SuccNum)->removePredecessor(BB); |
| |
| TerminatorInst *NewTI = 0; |
| switch (TI->getOpcode()) { |
| case Instruction::Br: |
| // If this is a conditional branch... convert to unconditional branch. |
| if (TI->getNumSuccessors() == 2) { |
| cast<BranchInst>(TI)->setUnconditionalDest(TI->getSuccessor(1-SuccNum)); |
| } else { // Otherwise convert to a return instruction... |
| Value *RetVal = 0; |
| |
| // Create a value to return... if the function doesn't return null... |
| if (BB->getParent()->getReturnType() != Type::VoidTy) |
| RetVal = Constant::getNullValue(BB->getParent()->getReturnType()); |
| |
| // Create the return... |
| NewTI = new ReturnInst(RetVal); |
| } |
| break; |
| |
| case Instruction::Invoke: // Should convert to call |
| case Instruction::Switch: // Should remove entry |
| default: |
| case Instruction::Ret: // Cannot happen, has no successors! |
| assert(0 && "Unhandled terminator instruction type in RemoveSuccessor!"); |
| abort(); |
| } |
| |
| if (NewTI) // If it's a different instruction, replace. |
| ReplaceInstWithInst(TI, NewTI); |
| } |
| |
| /// SplitEdge - Split the edge connecting specified block. Pass P must |
| /// not be NULL. |
| BasicBlock *llvm::SplitEdge(BasicBlock *BB, BasicBlock *Succ, Pass *P) { |
| TerminatorInst *LatchTerm = BB->getTerminator(); |
| unsigned SuccNum = 0; |
| for (unsigned i = 0, e = LatchTerm->getNumSuccessors(); ; ++i) { |
| assert(i != e && "Didn't find edge?"); |
| if (LatchTerm->getSuccessor(i) == Succ) { |
| SuccNum = i; |
| break; |
| } |
| } |
| |
| // If this is a critical edge, let SplitCriticalEdge do it. |
| if (SplitCriticalEdge(BB->getTerminator(), SuccNum, P)) |
| return LatchTerm->getSuccessor(SuccNum); |
| |
| // If the edge isn't critical, then BB has a single successor or Succ has a |
| // single pred. Split the block. |
| BasicBlock::iterator SplitPoint; |
| if (BasicBlock *SP = Succ->getSinglePredecessor()) { |
| // If the successor only has a single pred, split the top of the successor |
| // block. |
| assert(SP == BB && "CFG broken"); |
| return SplitBlock(Succ, Succ->begin(), P); |
| } else { |
| // Otherwise, if BB has a single successor, split it at the bottom of the |
| // block. |
| assert(BB->getTerminator()->getNumSuccessors() == 1 && |
| "Should have a single succ!"); |
| return SplitBlock(BB, BB->getTerminator(), P); |
| } |
| } |
| |
| /// SplitBlock - Split the specified block at the specified instruction - every |
| /// thing before SplitPt stays in Old and everything starting with SplitPt moves |
| /// to a new block. The two blocks are joined by an unconditional branch and |
| /// the loop info is updated. |
| /// |
| BasicBlock *llvm::SplitBlock(BasicBlock *Old, Instruction *SplitPt, Pass *P) { |
| |
| LoopInfo &LI = P->getAnalysis<LoopInfo>(); |
| BasicBlock::iterator SplitIt = SplitPt; |
| while (isa<PHINode>(SplitIt)) |
| ++SplitIt; |
| BasicBlock *New = Old->splitBasicBlock(SplitIt, Old->getName()+".split"); |
| |
| // The new block lives in whichever loop the old one did. |
| if (Loop *L = LI.getLoopFor(Old)) |
| L->addBasicBlockToLoop(New, LI.getBase()); |
| |
| if (DominatorTree *DT = P->getAnalysisToUpdate<DominatorTree>()) |
| { |
| // Old dominates New. New node domiantes all other nodes dominated by Old. |
| DomTreeNode *OldNode = DT->getNode(Old); |
| std::vector<DomTreeNode *> Children; |
| for (DomTreeNode::iterator I = OldNode->begin(), E = OldNode->end(); |
| I != E; ++I) |
| Children.push_back(*I); |
| |
| DomTreeNode *NewNode = DT->addNewBlock(New,Old); |
| |
| for (std::vector<DomTreeNode *>::iterator I = Children.begin(), |
| E = Children.end(); I != E; ++I) |
| DT->changeImmediateDominator(*I, NewNode); |
| } |
| |
| if (DominanceFrontier *DF = P->getAnalysisToUpdate<DominanceFrontier>()) |
| DF->splitBlock(Old); |
| |
| return New; |
| } |