1249259Sdim//===-- BasicBlock.cpp - Implement BasicBlock related methods -------------===// 2249259Sdim// 3249259Sdim// The LLVM Compiler Infrastructure 4249259Sdim// 5249259Sdim// This file is distributed under the University of Illinois Open Source 6249259Sdim// License. See LICENSE.TXT for details. 7249259Sdim// 8249259Sdim//===----------------------------------------------------------------------===// 9249259Sdim// 10249259Sdim// This file implements the BasicBlock class for the IR library. 11249259Sdim// 12249259Sdim//===----------------------------------------------------------------------===// 13249259Sdim 14249259Sdim#include "llvm/IR/BasicBlock.h" 15249259Sdim#include "SymbolTableListTraitsImpl.h" 16249259Sdim#include "llvm/ADT/STLExtras.h" 17249259Sdim#include "llvm/IR/Constants.h" 18249259Sdim#include "llvm/IR/Instructions.h" 19249259Sdim#include "llvm/IR/IntrinsicInst.h" 20249259Sdim#include "llvm/IR/LLVMContext.h" 21249259Sdim#include "llvm/IR/Type.h" 22249259Sdim#include "llvm/Support/CFG.h" 23249259Sdim#include "llvm/Support/LeakDetector.h" 24249259Sdim#include <algorithm> 25249259Sdimusing namespace llvm; 26249259Sdim 27249259SdimValueSymbolTable *BasicBlock::getValueSymbolTable() { 28249259Sdim if (Function *F = getParent()) 29249259Sdim return &F->getValueSymbolTable(); 30249259Sdim return 0; 31249259Sdim} 32249259Sdim 33249259SdimLLVMContext &BasicBlock::getContext() const { 34249259Sdim return getType()->getContext(); 35249259Sdim} 36249259Sdim 37249259Sdim// Explicit instantiation of SymbolTableListTraits since some of the methods 38249259Sdim// are not in the public header file... 39249259Sdimtemplate class llvm::SymbolTableListTraits<Instruction, BasicBlock>; 40249259Sdim 41249259Sdim 42249259SdimBasicBlock::BasicBlock(LLVMContext &C, const Twine &Name, Function *NewParent, 43249259Sdim BasicBlock *InsertBefore) 44249259Sdim : Value(Type::getLabelTy(C), Value::BasicBlockVal), Parent(0) { 45249259Sdim 46249259Sdim // Make sure that we get added to a function 47249259Sdim LeakDetector::addGarbageObject(this); 48249259Sdim 49249259Sdim if (InsertBefore) { 50249259Sdim assert(NewParent && 51249259Sdim "Cannot insert block before another block with no function!"); 52249259Sdim NewParent->getBasicBlockList().insert(InsertBefore, this); 53249259Sdim } else if (NewParent) { 54249259Sdim NewParent->getBasicBlockList().push_back(this); 55249259Sdim } 56249259Sdim 57249259Sdim setName(Name); 58249259Sdim} 59249259Sdim 60249259Sdim 61249259SdimBasicBlock::~BasicBlock() { 62249259Sdim // If the address of the block is taken and it is being deleted (e.g. because 63249259Sdim // it is dead), this means that there is either a dangling constant expr 64249259Sdim // hanging off the block, or an undefined use of the block (source code 65249259Sdim // expecting the address of a label to keep the block alive even though there 66249259Sdim // is no indirect branch). Handle these cases by zapping the BlockAddress 67249259Sdim // nodes. There are no other possible uses at this point. 68249259Sdim if (hasAddressTaken()) { 69249259Sdim assert(!use_empty() && "There should be at least one blockaddress!"); 70249259Sdim Constant *Replacement = 71249259Sdim ConstantInt::get(llvm::Type::getInt32Ty(getContext()), 1); 72249259Sdim while (!use_empty()) { 73249259Sdim BlockAddress *BA = cast<BlockAddress>(use_back()); 74249259Sdim BA->replaceAllUsesWith(ConstantExpr::getIntToPtr(Replacement, 75249259Sdim BA->getType())); 76249259Sdim BA->destroyConstant(); 77249259Sdim } 78249259Sdim } 79249259Sdim 80249259Sdim assert(getParent() == 0 && "BasicBlock still linked into the program!"); 81249259Sdim dropAllReferences(); 82249259Sdim InstList.clear(); 83249259Sdim} 84249259Sdim 85249259Sdimvoid BasicBlock::setParent(Function *parent) { 86249259Sdim if (getParent()) 87249259Sdim LeakDetector::addGarbageObject(this); 88249259Sdim 89249259Sdim // Set Parent=parent, updating instruction symtab entries as appropriate. 90249259Sdim InstList.setSymTabObject(&Parent, parent); 91249259Sdim 92249259Sdim if (getParent()) 93249259Sdim LeakDetector::removeGarbageObject(this); 94249259Sdim} 95249259Sdim 96249259Sdimvoid BasicBlock::removeFromParent() { 97249259Sdim getParent()->getBasicBlockList().remove(this); 98249259Sdim} 99249259Sdim 100249259Sdimvoid BasicBlock::eraseFromParent() { 101249259Sdim getParent()->getBasicBlockList().erase(this); 102249259Sdim} 103249259Sdim 104249259Sdim/// moveBefore - Unlink this basic block from its current function and 105249259Sdim/// insert it into the function that MovePos lives in, right before MovePos. 106249259Sdimvoid BasicBlock::moveBefore(BasicBlock *MovePos) { 107249259Sdim MovePos->getParent()->getBasicBlockList().splice(MovePos, 108249259Sdim getParent()->getBasicBlockList(), this); 109249259Sdim} 110249259Sdim 111249259Sdim/// moveAfter - Unlink this basic block from its current function and 112249259Sdim/// insert it into the function that MovePos lives in, right after MovePos. 113249259Sdimvoid BasicBlock::moveAfter(BasicBlock *MovePos) { 114249259Sdim Function::iterator I = MovePos; 115249259Sdim MovePos->getParent()->getBasicBlockList().splice(++I, 116249259Sdim getParent()->getBasicBlockList(), this); 117249259Sdim} 118249259Sdim 119249259Sdim 120249259SdimTerminatorInst *BasicBlock::getTerminator() { 121249259Sdim if (InstList.empty()) return 0; 122249259Sdim return dyn_cast<TerminatorInst>(&InstList.back()); 123249259Sdim} 124249259Sdim 125249259Sdimconst TerminatorInst *BasicBlock::getTerminator() const { 126249259Sdim if (InstList.empty()) return 0; 127249259Sdim return dyn_cast<TerminatorInst>(&InstList.back()); 128249259Sdim} 129249259Sdim 130249259SdimInstruction* BasicBlock::getFirstNonPHI() { 131249259Sdim BasicBlock::iterator i = begin(); 132249259Sdim // All valid basic blocks should have a terminator, 133249259Sdim // which is not a PHINode. If we have an invalid basic 134249259Sdim // block we'll get an assertion failure when dereferencing 135249259Sdim // a past-the-end iterator. 136249259Sdim while (isa<PHINode>(i)) ++i; 137249259Sdim return &*i; 138249259Sdim} 139249259Sdim 140249259SdimInstruction* BasicBlock::getFirstNonPHIOrDbg() { 141249259Sdim BasicBlock::iterator i = begin(); 142249259Sdim // All valid basic blocks should have a terminator, 143249259Sdim // which is not a PHINode. If we have an invalid basic 144249259Sdim // block we'll get an assertion failure when dereferencing 145249259Sdim // a past-the-end iterator. 146249259Sdim while (isa<PHINode>(i) || isa<DbgInfoIntrinsic>(i)) ++i; 147249259Sdim return &*i; 148249259Sdim} 149249259Sdim 150249259SdimInstruction* BasicBlock::getFirstNonPHIOrDbgOrLifetime() { 151249259Sdim // All valid basic blocks should have a terminator, 152249259Sdim // which is not a PHINode. If we have an invalid basic 153249259Sdim // block we'll get an assertion failure when dereferencing 154249259Sdim // a past-the-end iterator. 155249259Sdim BasicBlock::iterator i = begin(); 156249259Sdim for (;; ++i) { 157249259Sdim if (isa<PHINode>(i) || isa<DbgInfoIntrinsic>(i)) 158249259Sdim continue; 159249259Sdim 160249259Sdim const IntrinsicInst *II = dyn_cast<IntrinsicInst>(i); 161249259Sdim if (!II) 162249259Sdim break; 163249259Sdim if (II->getIntrinsicID() != Intrinsic::lifetime_start && 164249259Sdim II->getIntrinsicID() != Intrinsic::lifetime_end) 165249259Sdim break; 166249259Sdim } 167249259Sdim return &*i; 168249259Sdim} 169249259Sdim 170249259SdimBasicBlock::iterator BasicBlock::getFirstInsertionPt() { 171249259Sdim iterator InsertPt = getFirstNonPHI(); 172249259Sdim if (isa<LandingPadInst>(InsertPt)) ++InsertPt; 173249259Sdim return InsertPt; 174249259Sdim} 175249259Sdim 176249259Sdimvoid BasicBlock::dropAllReferences() { 177249259Sdim for(iterator I = begin(), E = end(); I != E; ++I) 178249259Sdim I->dropAllReferences(); 179249259Sdim} 180249259Sdim 181249259Sdim/// getSinglePredecessor - If this basic block has a single predecessor block, 182249259Sdim/// return the block, otherwise return a null pointer. 183249259SdimBasicBlock *BasicBlock::getSinglePredecessor() { 184249259Sdim pred_iterator PI = pred_begin(this), E = pred_end(this); 185249259Sdim if (PI == E) return 0; // No preds. 186249259Sdim BasicBlock *ThePred = *PI; 187249259Sdim ++PI; 188249259Sdim return (PI == E) ? ThePred : 0 /*multiple preds*/; 189249259Sdim} 190249259Sdim 191249259Sdim/// getUniquePredecessor - If this basic block has a unique predecessor block, 192249259Sdim/// return the block, otherwise return a null pointer. 193249259Sdim/// Note that unique predecessor doesn't mean single edge, there can be 194249259Sdim/// multiple edges from the unique predecessor to this block (for example 195249259Sdim/// a switch statement with multiple cases having the same destination). 196249259SdimBasicBlock *BasicBlock::getUniquePredecessor() { 197249259Sdim pred_iterator PI = pred_begin(this), E = pred_end(this); 198249259Sdim if (PI == E) return 0; // No preds. 199249259Sdim BasicBlock *PredBB = *PI; 200249259Sdim ++PI; 201249259Sdim for (;PI != E; ++PI) { 202249259Sdim if (*PI != PredBB) 203249259Sdim return 0; 204249259Sdim // The same predecessor appears multiple times in the predecessor list. 205249259Sdim // This is OK. 206249259Sdim } 207249259Sdim return PredBB; 208249259Sdim} 209249259Sdim 210249259Sdim/// removePredecessor - This method is used to notify a BasicBlock that the 211249259Sdim/// specified Predecessor of the block is no longer able to reach it. This is 212249259Sdim/// actually not used to update the Predecessor list, but is actually used to 213249259Sdim/// update the PHI nodes that reside in the block. Note that this should be 214249259Sdim/// called while the predecessor still refers to this block. 215249259Sdim/// 216249259Sdimvoid BasicBlock::removePredecessor(BasicBlock *Pred, 217249259Sdim bool DontDeleteUselessPHIs) { 218249259Sdim assert((hasNUsesOrMore(16)||// Reduce cost of this assertion for complex CFGs. 219249259Sdim find(pred_begin(this), pred_end(this), Pred) != pred_end(this)) && 220249259Sdim "removePredecessor: BB is not a predecessor!"); 221249259Sdim 222249259Sdim if (InstList.empty()) return; 223249259Sdim PHINode *APN = dyn_cast<PHINode>(&front()); 224249259Sdim if (!APN) return; // Quick exit. 225249259Sdim 226249259Sdim // If there are exactly two predecessors, then we want to nuke the PHI nodes 227249259Sdim // altogether. However, we cannot do this, if this in this case: 228249259Sdim // 229249259Sdim // Loop: 230249259Sdim // %x = phi [X, Loop] 231249259Sdim // %x2 = add %x, 1 ;; This would become %x2 = add %x2, 1 232249259Sdim // br Loop ;; %x2 does not dominate all uses 233249259Sdim // 234249259Sdim // This is because the PHI node input is actually taken from the predecessor 235249259Sdim // basic block. The only case this can happen is with a self loop, so we 236249259Sdim // check for this case explicitly now. 237249259Sdim // 238249259Sdim unsigned max_idx = APN->getNumIncomingValues(); 239249259Sdim assert(max_idx != 0 && "PHI Node in block with 0 predecessors!?!?!"); 240249259Sdim if (max_idx == 2) { 241249259Sdim BasicBlock *Other = APN->getIncomingBlock(APN->getIncomingBlock(0) == Pred); 242249259Sdim 243249259Sdim // Disable PHI elimination! 244249259Sdim if (this == Other) max_idx = 3; 245249259Sdim } 246249259Sdim 247249259Sdim // <= Two predecessors BEFORE I remove one? 248249259Sdim if (max_idx <= 2 && !DontDeleteUselessPHIs) { 249249259Sdim // Yup, loop through and nuke the PHI nodes 250249259Sdim while (PHINode *PN = dyn_cast<PHINode>(&front())) { 251249259Sdim // Remove the predecessor first. 252249259Sdim PN->removeIncomingValue(Pred, !DontDeleteUselessPHIs); 253249259Sdim 254249259Sdim // If the PHI _HAD_ two uses, replace PHI node with its now *single* value 255249259Sdim if (max_idx == 2) { 256249259Sdim if (PN->getIncomingValue(0) != PN) 257249259Sdim PN->replaceAllUsesWith(PN->getIncomingValue(0)); 258249259Sdim else 259249259Sdim // We are left with an infinite loop with no entries: kill the PHI. 260249259Sdim PN->replaceAllUsesWith(UndefValue::get(PN->getType())); 261249259Sdim getInstList().pop_front(); // Remove the PHI node 262249259Sdim } 263249259Sdim 264249259Sdim // If the PHI node already only had one entry, it got deleted by 265249259Sdim // removeIncomingValue. 266249259Sdim } 267249259Sdim } else { 268249259Sdim // Okay, now we know that we need to remove predecessor #pred_idx from all 269249259Sdim // PHI nodes. Iterate over each PHI node fixing them up 270249259Sdim PHINode *PN; 271249259Sdim for (iterator II = begin(); (PN = dyn_cast<PHINode>(II)); ) { 272249259Sdim ++II; 273249259Sdim PN->removeIncomingValue(Pred, false); 274249259Sdim // If all incoming values to the Phi are the same, we can replace the Phi 275249259Sdim // with that value. 276249259Sdim Value* PNV = 0; 277249259Sdim if (!DontDeleteUselessPHIs && (PNV = PN->hasConstantValue())) 278249259Sdim if (PNV != PN) { 279249259Sdim PN->replaceAllUsesWith(PNV); 280249259Sdim PN->eraseFromParent(); 281249259Sdim } 282249259Sdim } 283249259Sdim } 284249259Sdim} 285249259Sdim 286249259Sdim 287249259Sdim/// splitBasicBlock - This splits a basic block into two at the specified 288249259Sdim/// instruction. Note that all instructions BEFORE the specified iterator stay 289249259Sdim/// as part of the original basic block, an unconditional branch is added to 290249259Sdim/// the new BB, and the rest of the instructions in the BB are moved to the new 291249259Sdim/// BB, including the old terminator. This invalidates the iterator. 292249259Sdim/// 293249259Sdim/// Note that this only works on well formed basic blocks (must have a 294249259Sdim/// terminator), and 'I' must not be the end of instruction list (which would 295249259Sdim/// cause a degenerate basic block to be formed, having a terminator inside of 296249259Sdim/// the basic block). 297249259Sdim/// 298249259SdimBasicBlock *BasicBlock::splitBasicBlock(iterator I, const Twine &BBName) { 299249259Sdim assert(getTerminator() && "Can't use splitBasicBlock on degenerate BB!"); 300249259Sdim assert(I != InstList.end() && 301249259Sdim "Trying to get me to create degenerate basic block!"); 302249259Sdim 303249259Sdim BasicBlock *InsertBefore = llvm::next(Function::iterator(this)) 304249259Sdim .getNodePtrUnchecked(); 305249259Sdim BasicBlock *New = BasicBlock::Create(getContext(), BBName, 306249259Sdim getParent(), InsertBefore); 307249259Sdim 308249259Sdim // Move all of the specified instructions from the original basic block into 309249259Sdim // the new basic block. 310249259Sdim New->getInstList().splice(New->end(), this->getInstList(), I, end()); 311249259Sdim 312249259Sdim // Add a branch instruction to the newly formed basic block. 313249259Sdim BranchInst::Create(New, this); 314249259Sdim 315249259Sdim // Now we must loop through all of the successors of the New block (which 316249259Sdim // _were_ the successors of the 'this' block), and update any PHI nodes in 317249259Sdim // successors. If there were PHI nodes in the successors, then they need to 318249259Sdim // know that incoming branches will be from New, not from Old. 319249259Sdim // 320249259Sdim for (succ_iterator I = succ_begin(New), E = succ_end(New); I != E; ++I) { 321249259Sdim // Loop over any phi nodes in the basic block, updating the BB field of 322249259Sdim // incoming values... 323249259Sdim BasicBlock *Successor = *I; 324249259Sdim PHINode *PN; 325249259Sdim for (BasicBlock::iterator II = Successor->begin(); 326249259Sdim (PN = dyn_cast<PHINode>(II)); ++II) { 327249259Sdim int IDX = PN->getBasicBlockIndex(this); 328249259Sdim while (IDX != -1) { 329249259Sdim PN->setIncomingBlock((unsigned)IDX, New); 330249259Sdim IDX = PN->getBasicBlockIndex(this); 331249259Sdim } 332249259Sdim } 333249259Sdim } 334249259Sdim return New; 335249259Sdim} 336249259Sdim 337249259Sdimvoid BasicBlock::replaceSuccessorsPhiUsesWith(BasicBlock *New) { 338249259Sdim TerminatorInst *TI = getTerminator(); 339249259Sdim if (!TI) 340249259Sdim // Cope with being called on a BasicBlock that doesn't have a terminator 341249259Sdim // yet. Clang's CodeGenFunction::EmitReturnBlock() likes to do this. 342249259Sdim return; 343249259Sdim for (unsigned i = 0, e = TI->getNumSuccessors(); i != e; ++i) { 344249259Sdim BasicBlock *Succ = TI->getSuccessor(i); 345249259Sdim // N.B. Succ might not be a complete BasicBlock, so don't assume 346249259Sdim // that it ends with a non-phi instruction. 347249259Sdim for (iterator II = Succ->begin(), IE = Succ->end(); II != IE; ++II) { 348249259Sdim PHINode *PN = dyn_cast<PHINode>(II); 349249259Sdim if (!PN) 350249259Sdim break; 351249259Sdim int i; 352249259Sdim while ((i = PN->getBasicBlockIndex(this)) >= 0) 353249259Sdim PN->setIncomingBlock(i, New); 354249259Sdim } 355249259Sdim } 356249259Sdim} 357249259Sdim 358249259Sdim/// isLandingPad - Return true if this basic block is a landing pad. I.e., it's 359249259Sdim/// the destination of the 'unwind' edge of an invoke instruction. 360249259Sdimbool BasicBlock::isLandingPad() const { 361249259Sdim return isa<LandingPadInst>(getFirstNonPHI()); 362249259Sdim} 363249259Sdim 364249259Sdim/// getLandingPadInst() - Return the landingpad instruction associated with 365249259Sdim/// the landing pad. 366249259SdimLandingPadInst *BasicBlock::getLandingPadInst() { 367249259Sdim return dyn_cast<LandingPadInst>(getFirstNonPHI()); 368249259Sdim} 369249259Sdimconst LandingPadInst *BasicBlock::getLandingPadInst() const { 370249259Sdim return dyn_cast<LandingPadInst>(getFirstNonPHI()); 371249259Sdim} 372