| //===-- BasicBlock.cpp - Implement BasicBlock related methods -------------===// |
| // |
| // 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 file implements the BasicBlock class for the VMCore library. |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #include "llvm/BasicBlock.h" |
| #include "llvm/Constants.h" |
| #include "llvm/Instructions.h" |
| #include "llvm/Type.h" |
| #include "llvm/Support/CFG.h" |
| #include "llvm/Support/LeakDetector.h" |
| #include "SymbolTableListTraitsImpl.h" |
| #include <algorithm> |
| using namespace llvm; |
| |
| namespace { |
| /// DummyInst - An instance of this class is used to mark the end of the |
| /// instruction list. This is not a real instruction. |
| struct DummyInst : public Instruction { |
| DummyInst() : Instruction(Type::VoidTy, OtherOpsEnd, 0, 0) { |
| // This should not be garbage monitored. |
| LeakDetector::removeGarbageObject(this); |
| } |
| |
| virtual Instruction *clone() const { |
| assert(0 && "Cannot clone EOL");abort(); |
| return 0; |
| } |
| virtual const char *getOpcodeName() const { return "*end-of-list-inst*"; } |
| |
| // Methods for support type inquiry through isa, cast, and dyn_cast... |
| static inline bool classof(const DummyInst *) { return true; } |
| static inline bool classof(const Instruction *I) { |
| return I->getOpcode() == OtherOpsEnd; |
| } |
| static inline bool classof(const Value *V) { |
| return isa<Instruction>(V) && classof(cast<Instruction>(V)); |
| } |
| }; |
| } |
| |
| Instruction *ilist_traits<Instruction>::createSentinel() { |
| return new DummyInst(); |
| } |
| iplist<Instruction> &ilist_traits<Instruction>::getList(BasicBlock *BB) { |
| return BB->getInstList(); |
| } |
| |
| // Explicit instantiation of SymbolTableListTraits since some of the methods |
| // are not in the public header file... |
| template class SymbolTableListTraits<Instruction, BasicBlock, Function>; |
| |
| |
| BasicBlock::BasicBlock(const std::string &Name, Function *Parent, |
| BasicBlock *InsertBefore) |
| : Value(Type::LabelTy, Value::BasicBlockVal, Name) { |
| // Initialize the instlist... |
| InstList.setItemParent(this); |
| |
| // Make sure that we get added to a function |
| LeakDetector::addGarbageObject(this); |
| |
| if (InsertBefore) { |
| assert(Parent && |
| "Cannot insert block before another block with no function!"); |
| Parent->getBasicBlockList().insert(InsertBefore, this); |
| } else if (Parent) { |
| Parent->getBasicBlockList().push_back(this); |
| } |
| } |
| |
| |
| BasicBlock::~BasicBlock() { |
| assert(getParent() == 0 && "BasicBlock still linked into the program!"); |
| dropAllReferences(); |
| InstList.clear(); |
| } |
| |
| void BasicBlock::setParent(Function *parent) { |
| if (getParent()) |
| LeakDetector::addGarbageObject(this); |
| |
| InstList.setParent(parent); |
| |
| if (getParent()) |
| LeakDetector::removeGarbageObject(this); |
| } |
| |
| void BasicBlock::removeFromParent() { |
| getParent()->getBasicBlockList().remove(this); |
| } |
| |
| void BasicBlock::eraseFromParent() { |
| getParent()->getBasicBlockList().erase(this); |
| } |
| |
| |
| TerminatorInst *BasicBlock::getTerminator() { |
| if (InstList.empty()) return 0; |
| return dyn_cast<TerminatorInst>(&InstList.back()); |
| } |
| |
| const TerminatorInst *const BasicBlock::getTerminator() const { |
| if (InstList.empty()) return 0; |
| return dyn_cast<TerminatorInst>(&InstList.back()); |
| } |
| |
| void BasicBlock::dropAllReferences() { |
| for(iterator I = begin(), E = end(); I != E; ++I) |
| I->dropAllReferences(); |
| } |
| |
| /// getSinglePredecessor - If this basic block has a single predecessor block, |
| /// return the block, otherwise return a null pointer. |
| BasicBlock *BasicBlock::getSinglePredecessor() { |
| pred_iterator PI = pred_begin(this), E = pred_end(this); |
| if (PI == E) return 0; // No preds. |
| BasicBlock *ThePred = *PI; |
| ++PI; |
| return (PI == E) ? ThePred : 0 /*multiple preds*/; |
| } |
| |
| /// removePredecessor - This method is used to notify a BasicBlock that the |
| /// specified Predecessor of the block is no longer able to reach it. This is |
| /// actually not used to update the Predecessor list, but is actually used to |
| /// update the PHI nodes that reside in the block. Note that this should be |
| /// called while the predecessor still refers to this block. |
| /// |
| void BasicBlock::removePredecessor(BasicBlock *Pred, |
| bool DontDeleteUselessPHIs) { |
| assert((hasNUsesOrMore(16)||// Reduce cost of this assertion for complex CFGs. |
| find(pred_begin(this), pred_end(this), Pred) != pred_end(this)) && |
| "removePredecessor: BB is not a predecessor!"); |
| |
| if (InstList.empty()) return; |
| PHINode *APN = dyn_cast<PHINode>(&front()); |
| if (!APN) return; // Quick exit. |
| |
| // If there are exactly two predecessors, then we want to nuke the PHI nodes |
| // altogether. However, we cannot do this, if this in this case: |
| // |
| // Loop: |
| // %x = phi [X, Loop] |
| // %x2 = add %x, 1 ;; This would become %x2 = add %x2, 1 |
| // br Loop ;; %x2 does not dominate all uses |
| // |
| // This is because the PHI node input is actually taken from the predecessor |
| // basic block. The only case this can happen is with a self loop, so we |
| // check for this case explicitly now. |
| // |
| unsigned max_idx = APN->getNumIncomingValues(); |
| assert(max_idx != 0 && "PHI Node in block with 0 predecessors!?!?!"); |
| if (max_idx == 2) { |
| BasicBlock *Other = APN->getIncomingBlock(APN->getIncomingBlock(0) == Pred); |
| |
| // Disable PHI elimination! |
| if (this == Other) max_idx = 3; |
| } |
| |
| // <= Two predecessors BEFORE I remove one? |
| if (max_idx <= 2 && !DontDeleteUselessPHIs) { |
| // Yup, loop through and nuke the PHI nodes |
| while (PHINode *PN = dyn_cast<PHINode>(&front())) { |
| // Remove the predecessor first. |
| PN->removeIncomingValue(Pred, !DontDeleteUselessPHIs); |
| |
| // If the PHI _HAD_ two uses, replace PHI node with its now *single* value |
| if (max_idx == 2) { |
| if (PN->getOperand(0) != PN) |
| PN->replaceAllUsesWith(PN->getOperand(0)); |
| else |
| // We are left with an infinite loop with no entries: kill the PHI. |
| PN->replaceAllUsesWith(UndefValue::get(PN->getType())); |
| getInstList().pop_front(); // Remove the PHI node |
| } |
| |
| // If the PHI node already only had one entry, it got deleted by |
| // removeIncomingValue. |
| } |
| } else { |
| // Okay, now we know that we need to remove predecessor #pred_idx from all |
| // PHI nodes. Iterate over each PHI node fixing them up |
| PHINode *PN; |
| for (iterator II = begin(); (PN = dyn_cast<PHINode>(II)); ++II) |
| PN->removeIncomingValue(Pred, false); |
| } |
| } |
| |
| |
| /// splitBasicBlock - This splits a basic block into two at the specified |
| /// instruction. Note that all instructions BEFORE the specified iterator stay |
| /// as part of the original basic block, an unconditional branch is added to |
| /// the new BB, and the rest of the instructions in the BB are moved to the new |
| /// BB, including the old terminator. This invalidates the iterator. |
| /// |
| /// Note that this only works on well formed basic blocks (must have a |
| /// terminator), and 'I' must not be the end of instruction list (which would |
| /// cause a degenerate basic block to be formed, having a terminator inside of |
| /// the basic block). |
| /// |
| BasicBlock *BasicBlock::splitBasicBlock(iterator I, const std::string &BBName) { |
| assert(getTerminator() && "Can't use splitBasicBlock on degenerate BB!"); |
| assert(I != InstList.end() && |
| "Trying to get me to create degenerate basic block!"); |
| |
| BasicBlock *New = new BasicBlock(BBName, getParent(), getNext()); |
| |
| // Move all of the specified instructions from the original basic block into |
| // the new basic block. |
| New->getInstList().splice(New->end(), this->getInstList(), I, end()); |
| |
| // Add a branch instruction to the newly formed basic block. |
| new BranchInst(New, this); |
| |
| // Now we must loop through all of the successors of the New block (which |
| // _were_ the successors of the 'this' block), and update any PHI nodes in |
| // successors. If there were PHI nodes in the successors, then they need to |
| // know that incoming branches will be from New, not from Old. |
| // |
| for (succ_iterator I = succ_begin(New), E = succ_end(New); I != E; ++I) { |
| // Loop over any phi nodes in the basic block, updating the BB field of |
| // incoming values... |
| BasicBlock *Successor = *I; |
| PHINode *PN; |
| for (BasicBlock::iterator II = Successor->begin(); |
| (PN = dyn_cast<PHINode>(II)); ++II) { |
| int IDX = PN->getBasicBlockIndex(this); |
| while (IDX != -1) { |
| PN->setIncomingBlock((unsigned)IDX, New); |
| IDX = PN->getBasicBlockIndex(this); |
| } |
| } |
| } |
| return New; |
| } |