X-Git-Url: http://demsky.eecs.uci.edu/git/?a=blobdiff_plain;f=lib%2FVMCore%2FBasicBlock.cpp;h=955a0285b2602056a68ea8dbee0eaa0b5d0e08a5;hb=691c05bb29d3e2ec9c2ed6b1c082ce5d484b75da;hp=bf7191c659328fa5435731abd9cf756c277f0e4a;hpb=d1e693f2a3883dacf213aa2b477540c57b53b714;p=oota-llvm.git diff --git a/lib/VMCore/BasicBlock.cpp b/lib/VMCore/BasicBlock.cpp index bf7191c6593..955a0285b26 100644 --- a/lib/VMCore/BasicBlock.cpp +++ b/lib/VMCore/BasicBlock.cpp @@ -1,73 +1,83 @@ //===-- BasicBlock.cpp - Implement BasicBlock related methods -------------===// // +// The LLVM Compiler Infrastructure +// +// This file 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/Constants.h" +#include "llvm/Instructions.h" +#include "llvm/IntrinsicInst.h" +#include "llvm/LLVMContext.h" #include "llvm/Type.h" +#include "llvm/ADT/STLExtras.h" #include "llvm/Support/CFG.h" -#include "llvm/Constant.h" -#include "llvm/iPHINode.h" -#include "llvm/SymbolTable.h" -#include "Support/LeakDetector.h" +#include "llvm/Support/LeakDetector.h" #include "SymbolTableListTraitsImpl.h" #include +using 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, NumOtherOps) { - // 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() == NumOtherOps; - } - static inline bool classof(const Value *V) { - return isa(V) && classof(cast(V)); - } -}; - -Instruction *ilist_traits::createNode() { - return new DummyInst(); +ValueSymbolTable *BasicBlock::getValueSymbolTable() { + if (Function *F = getParent()) + return &F->getValueSymbolTable(); + return 0; } -iplist &ilist_traits::getList(BasicBlock *BB) { - return BB->getInstList(); + +LLVMContext &BasicBlock::getContext() const { + return getType()->getContext(); } // Explicit instantiation of SymbolTableListTraits since some of the methods // are not in the public header file... -template SymbolTableListTraits; +template class llvm::SymbolTableListTraits; -// 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); +BasicBlock::BasicBlock(LLVMContext &C, const Twine &Name, Function *NewParent, + BasicBlock *InsertBefore) + : Value(Type::getLabelTy(C), Value::BasicBlockVal), Parent(0) { // Make sure that we get added to a function LeakDetector::addGarbageObject(this); - if (Parent) - Parent->getBasicBlockList().push_back(this); + if (InsertBefore) { + assert(NewParent && + "Cannot insert block before another block with no function!"); + NewParent->getBasicBlockList().insert(InsertBefore, this); + } else if (NewParent) { + NewParent->getBasicBlockList().push_back(this); + } + + setName(Name); } + BasicBlock::~BasicBlock() { + // If the address of the block is taken and it is being deleted (e.g. because + // it is dead), this means that there is either a dangling constant expr + // hanging off the block, or an undefined use of the block (source code + // expecting the address of a label to keep the block alive even though there + // is no indirect branch). Handle these cases by zapping the BlockAddress + // nodes. There are no other possible uses at this point. + if (hasAddressTaken()) { + assert(!use_empty() && "There should be at least one blockaddress!"); + Constant *Replacement = + ConstantInt::get(llvm::Type::getInt32Ty(getContext()), 1); + while (!use_empty()) { + BlockAddress *BA = cast(use_back()); + BA->replaceAllUsesWith(ConstantExpr::getIntToPtr(Replacement, + BA->getType())); + BA->destroyConstant(); + } + } + + assert(getParent() == 0 && "BasicBlock still linked into the program!"); dropAllReferences(); InstList.clear(); } @@ -76,70 +86,119 @@ void BasicBlock::setParent(Function *parent) { if (getParent()) LeakDetector::addGarbageObject(this); - InstList.setParent(parent); + // Set Parent=parent, updating instruction symtab entries as appropriate. + InstList.setSymTabObject(&Parent, 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); +void BasicBlock::removeFromParent() { + getParent()->getBasicBlockList().remove(this); } +void BasicBlock::eraseFromParent() { + getParent()->getBasicBlockList().erase(this); +} + +/// moveBefore - Unlink this basic block from its current function and +/// insert it into the function that MovePos lives in, right before MovePos. +void BasicBlock::moveBefore(BasicBlock *MovePos) { + MovePos->getParent()->getBasicBlockList().splice(MovePos, + getParent()->getBasicBlockList(), this); +} + +/// moveAfter - Unlink this basic block from its current function and +/// insert it into the function that MovePos lives in, right after MovePos. +void BasicBlock::moveAfter(BasicBlock *MovePos) { + Function::iterator I = MovePos; + MovePos->getParent()->getBasicBlockList().splice(++I, + getParent()->getBasicBlockList(), this); +} + + TerminatorInst *BasicBlock::getTerminator() { if (InstList.empty()) return 0; return dyn_cast(&InstList.back()); } -const TerminatorInst *const BasicBlock::getTerminator() const { +const TerminatorInst *BasicBlock::getTerminator() const { if (InstList.empty()) return 0; return dyn_cast(&InstList.back()); } +Instruction* BasicBlock::getFirstNonPHI() { + BasicBlock::iterator i = begin(); + // All valid basic blocks should have a terminator, + // which is not a PHINode. If we have an invalid basic + // block we'll get an assertion failure when dereferencing + // a past-the-end iterator. + while (isa(i)) ++i; + return &*i; +} + +Instruction* BasicBlock::getFirstNonPHIOrDbg() { + BasicBlock::iterator i = begin(); + // All valid basic blocks should have a terminator, + // which is not a PHINode. If we have an invalid basic + // block we'll get an assertion failure when dereferencing + // a past-the-end iterator. + while (isa(i) || isa(i)) ++i; + return &*i; +} + 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((Value*)*I)) - return true; - - return false; +/// 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) { - assert(find(pred_begin(this), pred_end(this), Pred) != pred_end(this) && - "removePredecessor: BB is not a predecessor!"); - if (!isa(front())) return; // Quick exit. - - pred_iterator PI(pred_begin(this)), EI(pred_end(this)); - unsigned max_idx; +/// getUniquePredecessor - If this basic block has a unique predecessor block, +/// return the block, otherwise return a null pointer. +/// Note that unique predecessor doesn't mean single edge, there can be +/// multiple edges from the unique predecessor to this block (for example +/// a switch statement with multiple cases having the same destination). +BasicBlock *BasicBlock::getUniquePredecessor() { + pred_iterator PI = pred_begin(this), E = pred_end(this); + if (PI == E) return 0; // No preds. + BasicBlock *PredBB = *PI; + ++PI; + for (;PI != E; ++PI) { + if (*PI != PredBB) + return 0; + // The same predecessor appears multiple times in the predecessor list. + // This is OK. + } + return PredBB; +} - // 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*/; +/// 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(&front()); + if (!APN) return; // Quick exit. // 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: + // altogether. However, we cannot do this, if this in this case: // // Loop: // %x = phi [X, Loop] @@ -147,84 +206,98 @@ void BasicBlock::removePredecessor(BasicBlock *Pred) { // 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 + // 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) { - PI = pred_begin(this); - BasicBlock *Other = *PI == Pred ? *++PI : *PI; + BasicBlock *Other = APN->getIncomingBlock(APN->getIncomingBlock(0) == Pred); // Disable PHI elimination! if (this == Other) max_idx = 3; } - if (max_idx <= 2) { // <= Two predecessors BEFORE I remove one? + // <= Two predecessors BEFORE I remove one? + if (max_idx <= 2 && !DontDeleteUselessPHIs) { // Yup, loop through and nuke the PHI nodes while (PHINode *PN = dyn_cast(&front())) { - PN->removeIncomingValue(Pred); // Remove the predecessor first... - - assert(PN->getNumIncomingValues() == max_idx-1 && - "PHI node shouldn't have this many values!!!"); + // 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) - PN->replaceAllUsesWith(PN->getOperand(0)); - else // Otherwise there are no incoming values/edges, replace with dummy - PN->replaceAllUsesWith(Constant::getNullValue(PN->getType())); - getInstList().pop_front(); // Remove the PHI node + 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 - for (iterator II = begin(); PHINode *PN = dyn_cast(&*II); ++II) - PN->removeIncomingValue(Pred); + PHINode *PN; + for (iterator II = begin(); (PN = dyn_cast(II)); ) { + ++II; + PN->removeIncomingValue(Pred, false); + // If all incoming values to the Phi are the same, we can replace the Phi + // with that value. + Value* PNV = 0; + if (!DontDeleteUselessPHIs && (PNV = PN->hasConstantValue())) + if (PNV != PN) { + PN->replaceAllUsesWith(PNV); + PN->eraseFromParent(); + } + } } } -// 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) { +/// 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 Twine &BBName) { assert(getTerminator() && "Can't use splitBasicBlock on degenerate BB!"); - assert(I != InstList.end() && - "Trying to get me to create degenerate basic block!"); + assert(I != InstList.end() && + "Trying to get me to create degenerate basic block!"); - BasicBlock *New = new BasicBlock("", getParent()); + BasicBlock *InsertBefore = llvm::next(Function::iterator(this)) + .getNodePtrUnchecked(); + BasicBlock *New = BasicBlock::Create(getContext(), BBName, + getParent(), InsertBefore); - // 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. + // 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. - InstList.push_back(new BranchInst(New)); + BranchInst::Create(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 (BasicBlock::succ_iterator I = succ_begin(New), E = succ_end(New); - I != E; ++I) { + 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(); - PHINode *PN = dyn_cast(&*II); ++II) { + (PN = dyn_cast(II)); ++II) { int IDX = PN->getBasicBlockIndex(this); while (IDX != -1) { PN->setIncomingBlock((unsigned)IDX, New); @@ -234,3 +307,4 @@ BasicBlock *BasicBlock::splitBasicBlock(iterator I) { } return New; } +