| //===-- 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/iTerminators.h" |
| #include "llvm/Type.h" |
| #include "llvm/Support/CFG.h" |
| #include "llvm/Constant.h" |
| #include "llvm/iPHINode.h" |
| #include "llvm/SymbolTable.h" |
| #include "Support/LeakDetector.h" |
| #include "SymbolTableListTraitsImpl.h" |
| #include <algorithm> |
| |
| namespace llvm { |
| |
| // 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) { |
| // 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>::createNode() { |
| 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 ctor - If the function parameter is specified, the basic block is |
| // automatically inserted at the end of the function. |
| // |
| BasicBlock::BasicBlock(const std::string &name, Function *Parent) |
| : 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 (Parent) |
| Parent->getBasicBlockList().push_back(this); |
| } |
| |
| /// BasicBlock ctor - If the InsertBefore parameter is specified, the basic |
| /// block is automatically inserted right before the specified block. |
| /// |
| BasicBlock::BasicBlock(const std::string &Name, 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(InsertBefore->getParent() && |
| "Cannot insert block before another block that is not embedded into" |
| " a function yet!"); |
| InsertBefore->getParent()->getBasicBlockList().insert(InsertBefore, this); |
| } |
| } |
| |
| |
| BasicBlock::~BasicBlock() { |
| dropAllReferences(); |
| InstList.clear(); |
| } |
| |
| void BasicBlock::setParent(Function *parent) { |
| if (getParent()) |
| LeakDetector::addGarbageObject(this); |
| |
| InstList.setParent(parent); |
| |
| if (getParent()) |
| LeakDetector::removeGarbageObject(this); |
| } |
| |
| // Specialize setName to take care of symbol table majik |
| void BasicBlock::setName(const std::string &name, SymbolTable *ST) { |
| Function *P; |
| assert((ST == 0 || (!getParent() || ST == &getParent()->getSymbolTable())) && |
| "Invalid symtab argument!"); |
| if ((P = getParent()) && hasName()) P->getSymbolTable().remove(this); |
| Value::setName(name); |
| if (P && hasName()) P->getSymbolTable().insert(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(); |
| } |
| |
| // hasConstantReferences() - This predicate is true if there is a |
| // reference to this basic block in the constant pool for this method. For |
| // example, if a block is reached through a switch table, that table resides |
| // in the constant pool, and the basic block is reference from it. |
| // |
| bool BasicBlock::hasConstantReferences() const { |
| for (use_const_iterator I = use_begin(), E = use_end(); I != E; ++I) |
| if (isa<Constant>((Value*)*I)) |
| return true; |
| |
| return false; |
| } |
| |
| // 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) { |
| assert(find(pred_begin(this), pred_end(this), Pred) != pred_end(this) && |
| "removePredecessor: BB is not a predecessor!"); |
| if (!isa<PHINode>(front())) return; // Quick exit. |
| |
| pred_iterator PI(pred_begin(this)), EI(pred_end(this)); |
| unsigned max_idx; |
| |
| // Loop over the rest of the predecessors until we run out, or until we find |
| // out that there are more than 2 predecessors. |
| for (max_idx = 0; PI != EI && max_idx < 3; ++PI, ++max_idx) /*empty*/; |
| |
| // If there are exactly two predecessors, then we want to nuke the PHI nodes |
| // altogether. We cannot do this, however if this in this case however: |
| // |
| // 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. |
| // |
| assert(max_idx != 0 && "PHI Node in block with 0 predecessors!?!?!"); |
| if (max_idx == 2) { |
| PI = pred_begin(this); |
| BasicBlock *Other = *PI == Pred ? *++PI : *PI; |
| |
| // Disable PHI elimination! |
| if (this == Other) max_idx = 3; |
| } |
| |
| if (max_idx <= 2) { // <= Two predecessors BEFORE I remove one? |
| // Yup, loop through and nuke the PHI nodes |
| while (PHINode *PN = dyn_cast<PHINode>(&front())) { |
| PN->removeIncomingValue(Pred); // Remove the predecessor first... |
| |
| // 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(Constant::getNullValue(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 |
| for (iterator II = begin(); PHINode *PN = dyn_cast<PHINode>(II); ++II) |
| PN->removeIncomingValue(Pred); |
| } |
| } |
| |
| |
| // 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()); |
| |
| // Go from the end of the basic block through to the iterator pointer, moving |
| // to the new basic block... |
| Instruction *Inst = 0; |
| do { |
| iterator EndIt = end(); |
| Inst = InstList.remove(--EndIt); // Remove from end |
| New->InstList.push_front(Inst); // Add to front |
| } while (Inst != &*I); // Loop until we move the specified instruction. |
| |
| // Add a branch instruction to the newly formed basic block. |
| InstList.push_back(new BranchInst(New)); |
| |
| // 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; |
| for (BasicBlock::iterator II = Successor->begin(); |
| PHINode *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; |
| } |
| |
| } // End llvm namespace |