Exemple #1
0
bool llvm::UnrollRuntimeLoopRemainder(Loop *L, unsigned Count,
                                      bool AllowExpensiveTripCount,
                                      bool UseEpilogRemainder,
                                      bool UnrollRemainder,
                                      LoopInfo *LI, ScalarEvolution *SE,
                                      DominatorTree *DT, AssumptionCache *AC,
                                      OptimizationRemarkEmitter *ORE,
                                      bool PreserveLCSSA) {
  DEBUG(dbgs() << "Trying runtime unrolling on Loop: \n");
  DEBUG(L->dump());
  DEBUG(UseEpilogRemainder ? dbgs() << "Using epilog remainder.\n" :
        dbgs() << "Using prolog remainder.\n");

  // Make sure the loop is in canonical form.
  if (!L->isLoopSimplifyForm()) {
    DEBUG(dbgs() << "Not in simplify form!\n");
    return false;
  }

  // Guaranteed by LoopSimplifyForm.
  BasicBlock *Latch = L->getLoopLatch();
  BasicBlock *Header = L->getHeader();

  BranchInst *LatchBR = cast<BranchInst>(Latch->getTerminator());
  unsigned ExitIndex = LatchBR->getSuccessor(0) == Header ? 1 : 0;
  BasicBlock *LatchExit = LatchBR->getSuccessor(ExitIndex);
  // Cloning the loop basic blocks (`CloneLoopBlocks`) requires that one of the
  // targets of the Latch be an exit block out of the loop. This needs
  // to be guaranteed by the callers of UnrollRuntimeLoopRemainder.
  assert(!L->contains(LatchExit) &&
         "one of the loop latch successors should be the exit block!");
  // These are exit blocks other than the target of the latch exiting block.
  SmallVector<BasicBlock *, 4> OtherExits;
  bool isMultiExitUnrollingEnabled =
      canSafelyUnrollMultiExitLoop(L, OtherExits, LatchExit, PreserveLCSSA,
                                   UseEpilogRemainder) &&
      canProfitablyUnrollMultiExitLoop(L, OtherExits, LatchExit, PreserveLCSSA,
                                       UseEpilogRemainder);
  // Support only single exit and exiting block unless multi-exit loop unrolling is enabled.
  if (!isMultiExitUnrollingEnabled &&
      (!L->getExitingBlock() || OtherExits.size())) {
    DEBUG(
        dbgs()
        << "Multiple exit/exiting blocks in loop and multi-exit unrolling not "
           "enabled!\n");
    return false;
  }
  // Use Scalar Evolution to compute the trip count. This allows more loops to
  // be unrolled than relying on induction var simplification.
  if (!SE)
    return false;

  // Only unroll loops with a computable trip count, and the trip count needs
  // to be an int value (allowing a pointer type is a TODO item).
  // We calculate the backedge count by using getExitCount on the Latch block,
  // which is proven to be the only exiting block in this loop. This is same as
  // calculating getBackedgeTakenCount on the loop (which computes SCEV for all
  // exiting blocks).
  const SCEV *BECountSC = SE->getExitCount(L, Latch);
  if (isa<SCEVCouldNotCompute>(BECountSC) ||
      !BECountSC->getType()->isIntegerTy()) {
    DEBUG(dbgs() << "Could not compute exit block SCEV\n");
    return false;
  }

  unsigned BEWidth = cast<IntegerType>(BECountSC->getType())->getBitWidth();

  // Add 1 since the backedge count doesn't include the first loop iteration.
  const SCEV *TripCountSC =
      SE->getAddExpr(BECountSC, SE->getConstant(BECountSC->getType(), 1));
  if (isa<SCEVCouldNotCompute>(TripCountSC)) {
    DEBUG(dbgs() << "Could not compute trip count SCEV.\n");
    return false;
  }

  BasicBlock *PreHeader = L->getLoopPreheader();
  BranchInst *PreHeaderBR = cast<BranchInst>(PreHeader->getTerminator());
  const DataLayout &DL = Header->getModule()->getDataLayout();
  SCEVExpander Expander(*SE, DL, "loop-unroll");
  if (!AllowExpensiveTripCount &&
      Expander.isHighCostExpansion(TripCountSC, L, PreHeaderBR)) {
    DEBUG(dbgs() << "High cost for expanding trip count scev!\n");
    return false;
  }

  // This constraint lets us deal with an overflowing trip count easily; see the
  // comment on ModVal below.
  if (Log2_32(Count) > BEWidth) {
    DEBUG(dbgs()
          << "Count failed constraint on overflow trip count calculation.\n");
    return false;
  }

  // Loop structure is the following:
  //
  // PreHeader
  //   Header
  //   ...
  //   Latch
  // LatchExit

  BasicBlock *NewPreHeader;
  BasicBlock *NewExit = nullptr;
  BasicBlock *PrologExit = nullptr;
  BasicBlock *EpilogPreHeader = nullptr;
  BasicBlock *PrologPreHeader = nullptr;

  if (UseEpilogRemainder) {
    // If epilog remainder
    // Split PreHeader to insert a branch around loop for unrolling.
    NewPreHeader = SplitBlock(PreHeader, PreHeader->getTerminator(), DT, LI);
    NewPreHeader->setName(PreHeader->getName() + ".new");
    // Split LatchExit to create phi nodes from branch above.
    SmallVector<BasicBlock*, 4> Preds(predecessors(LatchExit));
    NewExit = SplitBlockPredecessors(LatchExit, Preds, ".unr-lcssa",
                                     DT, LI, PreserveLCSSA);
    // Split NewExit to insert epilog remainder loop.
    EpilogPreHeader = SplitBlock(NewExit, NewExit->getTerminator(), DT, LI);
    EpilogPreHeader->setName(Header->getName() + ".epil.preheader");
  } else {
    // If prolog remainder
    // Split the original preheader twice to insert prolog remainder loop
    PrologPreHeader = SplitEdge(PreHeader, Header, DT, LI);
    PrologPreHeader->setName(Header->getName() + ".prol.preheader");
    PrologExit = SplitBlock(PrologPreHeader, PrologPreHeader->getTerminator(),
                            DT, LI);
    PrologExit->setName(Header->getName() + ".prol.loopexit");
    // Split PrologExit to get NewPreHeader.
    NewPreHeader = SplitBlock(PrologExit, PrologExit->getTerminator(), DT, LI);
    NewPreHeader->setName(PreHeader->getName() + ".new");
  }
  // Loop structure should be the following:
  //  Epilog             Prolog
  //
  // PreHeader         PreHeader
  // *NewPreHeader     *PrologPreHeader
  //   Header          *PrologExit
  //   ...             *NewPreHeader
  //   Latch             Header
  // *NewExit            ...
  // *EpilogPreHeader    Latch
  // LatchExit              LatchExit

  // Calculate conditions for branch around loop for unrolling
  // in epilog case and around prolog remainder loop in prolog case.
  // Compute the number of extra iterations required, which is:
  //  extra iterations = run-time trip count % loop unroll factor
  PreHeaderBR = cast<BranchInst>(PreHeader->getTerminator());
  Value *TripCount = Expander.expandCodeFor(TripCountSC, TripCountSC->getType(),
                                            PreHeaderBR);
  Value *BECount = Expander.expandCodeFor(BECountSC, BECountSC->getType(),
                                          PreHeaderBR);
  IRBuilder<> B(PreHeaderBR);
  Value *ModVal;
  // Calculate ModVal = (BECount + 1) % Count.
  // Note that TripCount is BECount + 1.
  if (isPowerOf2_32(Count)) {
    // When Count is power of 2 we don't BECount for epilog case, however we'll
    // need it for a branch around unrolling loop for prolog case.
    ModVal = B.CreateAnd(TripCount, Count - 1, "xtraiter");
    //  1. There are no iterations to be run in the prolog/epilog loop.
    // OR
    //  2. The addition computing TripCount overflowed.
    //
    // If (2) is true, we know that TripCount really is (1 << BEWidth) and so
    // the number of iterations that remain to be run in the original loop is a
    // multiple Count == (1 << Log2(Count)) because Log2(Count) <= BEWidth (we
    // explicitly check this above).
  } else {
    // As (BECount + 1) can potentially unsigned overflow we count
    // (BECount % Count) + 1 which is overflow safe as BECount % Count < Count.
    Value *ModValTmp = B.CreateURem(BECount,
                                    ConstantInt::get(BECount->getType(),
                                                     Count));
    Value *ModValAdd = B.CreateAdd(ModValTmp,
                                   ConstantInt::get(ModValTmp->getType(), 1));
    // At that point (BECount % Count) + 1 could be equal to Count.
    // To handle this case we need to take mod by Count one more time.
    ModVal = B.CreateURem(ModValAdd,
                          ConstantInt::get(BECount->getType(), Count),
                          "xtraiter");
  }
  Value *BranchVal =
      UseEpilogRemainder ? B.CreateICmpULT(BECount,
                                           ConstantInt::get(BECount->getType(),
                                                            Count - 1)) :
                           B.CreateIsNotNull(ModVal, "lcmp.mod");
  BasicBlock *RemainderLoop = UseEpilogRemainder ? NewExit : PrologPreHeader;
  BasicBlock *UnrollingLoop = UseEpilogRemainder ? NewPreHeader : PrologExit;
  // Branch to either remainder (extra iterations) loop or unrolling loop.
  B.CreateCondBr(BranchVal, RemainderLoop, UnrollingLoop);
  PreHeaderBR->eraseFromParent();
  if (DT) {
    if (UseEpilogRemainder)
      DT->changeImmediateDominator(NewExit, PreHeader);
    else
      DT->changeImmediateDominator(PrologExit, PreHeader);
  }
  Function *F = Header->getParent();
  // Get an ordered list of blocks in the loop to help with the ordering of the
  // cloned blocks in the prolog/epilog code
  LoopBlocksDFS LoopBlocks(L);
  LoopBlocks.perform(LI);

  //
  // For each extra loop iteration, create a copy of the loop's basic blocks
  // and generate a condition that branches to the copy depending on the
  // number of 'left over' iterations.
  //
  std::vector<BasicBlock *> NewBlocks;
  ValueToValueMapTy VMap;

  // For unroll factor 2 remainder loop will have 1 iterations.
  // Do not create 1 iteration loop.
  bool CreateRemainderLoop = (Count != 2);

  // Clone all the basic blocks in the loop. If Count is 2, we don't clone
  // the loop, otherwise we create a cloned loop to execute the extra
  // iterations. This function adds the appropriate CFG connections.
  BasicBlock *InsertBot = UseEpilogRemainder ? LatchExit : PrologExit;
  BasicBlock *InsertTop = UseEpilogRemainder ? EpilogPreHeader : PrologPreHeader;
  Loop *remainderLoop = CloneLoopBlocks(
      L, ModVal, CreateRemainderLoop, UseEpilogRemainder, UnrollRemainder,
      InsertTop, InsertBot,
      NewPreHeader, NewBlocks, LoopBlocks, VMap, DT, LI);

  // Insert the cloned blocks into the function.
  F->getBasicBlockList().splice(InsertBot->getIterator(),
                                F->getBasicBlockList(),
                                NewBlocks[0]->getIterator(),
                                F->end());

  // Now the loop blocks are cloned and the other exiting blocks from the
  // remainder are connected to the original Loop's exit blocks. The remaining
  // work is to update the phi nodes in the original loop, and take in the
  // values from the cloned region. Also update the dominator info for
  // OtherExits and their immediate successors, since we have new edges into
  // OtherExits.
  SmallSet<BasicBlock*, 8> ImmediateSuccessorsOfExitBlocks;
  for (auto *BB : OtherExits) {
   for (auto &II : *BB) {

     // Given we preserve LCSSA form, we know that the values used outside the
     // loop will be used through these phi nodes at the exit blocks that are
     // transformed below.
     if (!isa<PHINode>(II))
       break;
     PHINode *Phi = cast<PHINode>(&II);
     unsigned oldNumOperands = Phi->getNumIncomingValues();
     // Add the incoming values from the remainder code to the end of the phi
     // node.
     for (unsigned i =0; i < oldNumOperands; i++){
       Value *newVal = VMap[Phi->getIncomingValue(i)];
       // newVal can be a constant or derived from values outside the loop, and
       // hence need not have a VMap value.
       if (!newVal)
         newVal = Phi->getIncomingValue(i);
       Phi->addIncoming(newVal,
                           cast<BasicBlock>(VMap[Phi->getIncomingBlock(i)]));
     }
   }
#if defined(EXPENSIVE_CHECKS) && !defined(NDEBUG)
    for (BasicBlock *SuccBB : successors(BB)) {
      assert(!(any_of(OtherExits,
                      [SuccBB](BasicBlock *EB) { return EB == SuccBB; }) ||
               SuccBB == LatchExit) &&
             "Breaks the definition of dedicated exits!");
    }
#endif
   // Update the dominator info because the immediate dominator is no longer the
   // header of the original Loop. BB has edges both from L and remainder code.
   // Since the preheader determines which loop is run (L or directly jump to
   // the remainder code), we set the immediate dominator as the preheader.
   if (DT) {
     DT->changeImmediateDominator(BB, PreHeader);
     // Also update the IDom for immediate successors of BB.  If the current
     // IDom is the header, update the IDom to be the preheader because that is
     // the nearest common dominator of all predecessors of SuccBB.  We need to
     // check for IDom being the header because successors of exit blocks can
     // have edges from outside the loop, and we should not incorrectly update
     // the IDom in that case.
     for (BasicBlock *SuccBB: successors(BB))
       if (ImmediateSuccessorsOfExitBlocks.insert(SuccBB).second) {
         if (DT->getNode(SuccBB)->getIDom()->getBlock() == Header) {
           assert(!SuccBB->getSinglePredecessor() &&
                  "BB should be the IDom then!");
           DT->changeImmediateDominator(SuccBB, PreHeader);
         }
       }
    }
  }

  // Loop structure should be the following:
  //  Epilog             Prolog
  //
  // PreHeader         PreHeader
  // NewPreHeader      PrologPreHeader
  //   Header            PrologHeader
  //   ...               ...
  //   Latch             PrologLatch
  // NewExit           PrologExit
  // EpilogPreHeader   NewPreHeader
  //   EpilogHeader      Header
  //   ...               ...
  //   EpilogLatch       Latch
  // LatchExit              LatchExit

  // Rewrite the cloned instruction operands to use the values created when the
  // clone is created.
  for (BasicBlock *BB : NewBlocks) {
    for (Instruction &I : *BB) {
      RemapInstruction(&I, VMap,
                       RF_NoModuleLevelChanges | RF_IgnoreMissingLocals);
    }
  }

  if (UseEpilogRemainder) {
    // Connect the epilog code to the original loop and update the
    // PHI functions.
    ConnectEpilog(L, ModVal, NewExit, LatchExit, PreHeader,
                  EpilogPreHeader, NewPreHeader, VMap, DT, LI,
                  PreserveLCSSA);

    // Update counter in loop for unrolling.
    // I should be multiply of Count.
    IRBuilder<> B2(NewPreHeader->getTerminator());
    Value *TestVal = B2.CreateSub(TripCount, ModVal, "unroll_iter");
    BranchInst *LatchBR = cast<BranchInst>(Latch->getTerminator());
    B2.SetInsertPoint(LatchBR);
    PHINode *NewIdx = PHINode::Create(TestVal->getType(), 2, "niter",
                                      Header->getFirstNonPHI());
    Value *IdxSub =
        B2.CreateSub(NewIdx, ConstantInt::get(NewIdx->getType(), 1),
                     NewIdx->getName() + ".nsub");
    Value *IdxCmp;
    if (LatchBR->getSuccessor(0) == Header)
      IdxCmp = B2.CreateIsNotNull(IdxSub, NewIdx->getName() + ".ncmp");
    else
      IdxCmp = B2.CreateIsNull(IdxSub, NewIdx->getName() + ".ncmp");
    NewIdx->addIncoming(TestVal, NewPreHeader);
    NewIdx->addIncoming(IdxSub, Latch);
    LatchBR->setCondition(IdxCmp);
  } else {
    // Connect the prolog code to the original loop and update the
    // PHI functions.
    ConnectProlog(L, BECount, Count, PrologExit, LatchExit, PreHeader,
                  NewPreHeader, VMap, DT, LI, PreserveLCSSA);
  }

  // If this loop is nested, then the loop unroller changes the code in the
  // parent loop, so the Scalar Evolution pass needs to be run again.
  if (Loop *ParentLoop = L->getParentLoop())
    SE->forgetLoop(ParentLoop);

  // Canonicalize to LoopSimplifyForm both original and remainder loops. We
  // cannot rely on the LoopUnrollPass to do this because it only does
  // canonicalization for parent/subloops and not the sibling loops.
  if (OtherExits.size() > 0) {
    // Generate dedicated exit blocks for the original loop, to preserve
    // LoopSimplifyForm.
    formDedicatedExitBlocks(L, DT, LI, PreserveLCSSA);
    // Generate dedicated exit blocks for the remainder loop if one exists, to
    // preserve LoopSimplifyForm.
    if (remainderLoop)
      formDedicatedExitBlocks(remainderLoop, DT, LI, PreserveLCSSA);
  }

  if (remainderLoop && UnrollRemainder) {
    DEBUG(dbgs() << "Unrolling remainder loop\n");
    UnrollLoop(remainderLoop, /*Count*/Count - 1, /*TripCount*/Count - 1,
               /*Force*/false, /*AllowRuntime*/false,
               /*AllowExpensiveTripCount*/false, /*PreserveCondBr*/true,
               /*PreserveOnlyFirst*/false, /*TripMultiple*/1,
               /*PeelCount*/0, /*UnrollRemainder*/false, LI, SE, DT, AC, ORE,
               PreserveLCSSA);
  }

  NumRuntimeUnrolled++;
  return true;
}
Exemple #2
0
/// optimizeCheck - replace the given check CallInst with the check's fast
/// version if all the source memory objects can be found and it is obvious
/// that none of them have been freed at the point where the check is made.
/// Returns the new call if possible and NULL otherwise.
///
/// This currently works only with memory objects that can't be freed:
/// * global variables
/// * allocas that trivially have function scope
/// * byval arguments
///
bool ExactCheckOpt::optimizeCheck(CallInst *CI, CheckInfoType *Info) {
  // Examined values
  SmallSet<Value*, 16> Visited;
  // Potential memory objects
  SmallSet<Value*, 4> Objects;

  std::queue<Value*> Q;
  // Start from the the pointer operand
  Value *StartPtr = CI->getArgOperand(Info->PtrArgNo)->stripPointerCasts();
  Q.push(StartPtr);

  // Use BFS to find all potential memory objects
  while(!Q.empty()) {
    Value *o = Q.front()->stripPointerCasts();
    Q.pop();
    if(Visited.count(o))
      continue;
    Visited.insert(o);

    if (ConstantExpr *CE = dyn_cast<ConstantExpr>(o)) {
      if (CE->getOpcode() == Instruction::GetElementPtr) {
        Q.push(CE->getOperand(0));
      } else {
        // Exit early if any of the objects are unsupported.
        if (!isSimpleMemoryObject(o))
          return false;
        Objects.insert(o);
      }
    } else if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(o)) {
      Q.push(GEP->getPointerOperand());
      // It is fine to ignore the case of indexing into null with a pointer
      // because that case is invalid for LLVM-aware objects such as allocas,
      // globals, and objects pointed to by noalias pointers.
    } else if(PHINode *PHI = dyn_cast<PHINode>(o)) {
      for (unsigned i = 0, num = PHI->getNumIncomingValues(); i != num; ++i)
        Q.push(PHI->getIncomingValue(i));
    } else if (SelectInst *SI = dyn_cast<SelectInst>(o)) {
      Q.push(SI->getTrueValue());
      Q.push(SI->getFalseValue());
    } else {
      // Exit early if any of the objects are unsupported.
      if (!isSimpleMemoryObject(o))
        return false;
      Objects.insert(o);
    }
  }

  // Mapping from the initial value to the corresponding size and void pointer:
  // * memory object -> its size and pointer
  // * phi/select -> corresponding phi/select for the sizes and pointers
  // * anything else -> the corresponding size and pointer on the path
  std::map <Value*, PtrSizePair> M;

  Module &Mod = *CI->getParent()->getParent()->getParent();
  Type *SizeTy = getSizeType(Info, Mod);

  // Add non-instruction non-constant allocation object pointers to the front
  // of the function's entry block.
  BasicBlock &EntryBlock = CI->getParent()->getParent()->getEntryBlock();
  Instruction *FirstInsertionPoint = ++BasicBlock::iterator(EntryBlock.begin());

  for (SmallSet<Value*, 16>::const_iterator It = Objects.begin(),
       E = Objects.end();
       It != E;
       ++It) {
    // Obj is a memory object pointer: alloca, argument, load, callinst, etc.
    Value *Obj = *It;

    // Insert instruction-based allocation pointers just after the allocation.
    Instruction *InsertBefore = FirstInsertionPoint;
    if (Instruction *I = dyn_cast<Instruction>(Obj))
      InsertBefore = ++BasicBlock::iterator(I);
    IRBuilder<> Builder(InsertBefore);

    SizeOffsetEvalType SizeOffset = ObjSizeEval->compute(Obj);
    assert(ObjSizeEval->bothKnown(SizeOffset));
    assert(dyn_cast<ConstantInt>(SizeOffset.second)->isZero());
    Value *Size = Builder.CreateIntCast(SizeOffset.first, SizeTy,
                                        /*isSigned=*/false);

    Value *Ptr = Builder.CreatePointerCast(Obj, VoidPtrTy);
    M[Obj] = std::make_pair(Ptr, Size);
  }

  // Create the rest of the size values and object pointers.
  // The phi nodes will be finished later.
  for (SmallSet<Value*, 16>::const_iterator I = Visited.begin(),
       E = Visited.end();
       I != E;
       ++I) {
    getPtrAndSize(*I, SizeTy, M);
  }

  // Finalize the phi nodes.
  for (SmallSet<Value*, 16>::const_iterator I = Visited.begin(),
       E = Visited.end();
       I != E;
       ++I) {
    if (PHINode *PHI = dyn_cast<PHINode>(*I)) {
      assert(M.count(PHI));
      PHINode *PtrPHI = cast<PHINode>(M[PHI].first);
      PHINode *SizePHI = cast<PHINode>(M[PHI].second);

      for(unsigned i = 0, num = PHI->getNumIncomingValues(); i != num; ++i) {
        Value *IncomingValue = PHI->getIncomingValue(i)->stripPointerCasts();
        assert(M.count(IncomingValue));

        PtrPHI->addIncoming(M[IncomingValue].first, PHI->getIncomingBlock(i));
        SizePHI->addIncoming(M[IncomingValue].second, PHI->getIncomingBlock(i));
      }
    }
  }

  // Insert the fast version of the check just before the regular version.
  assert(M.count(StartPtr) && "The memory object and its size should be known");
  createFastCheck(Info, CI, M[StartPtr].first, M[StartPtr].second);
  return true;
}
Exemple #3
0
void GNUstep::IMPCacher::CacheLookup(Instruction *lookup, Value *slot, Value
                                     *version, bool isSuperMessage) {

    // If this IMP is already cached, don't cache it again.
    if (lookup->getMetadata(IMPCacheFlagKind)) {
        return;
    }

    lookup->setMetadata(IMPCacheFlagKind, AlreadyCachedFlag);
    bool isInvoke = false;

    BasicBlock *beforeLookupBB = lookup->getParent();
    BasicBlock *lookupBB = SplitBlock(beforeLookupBB, lookup, Owner);
    BasicBlock *lookupFinishedBB = lookupBB;
    BasicBlock *afterLookupBB;

    if (InvokeInst *inv = dyn_cast<InvokeInst>(lookup)) {
        afterLookupBB = inv->getNormalDest();
        lookupFinishedBB =
            BasicBlock::Create(Context, "done_lookup", lookupBB->getParent());
        CGBuilder B(lookupFinishedBB);
        B.CreateBr(afterLookupBB);
        inv->setNormalDest(lookupFinishedBB);
        isInvoke = true;
    } else {
        BasicBlock::iterator iter = lookup;
        iter++;
        afterLookupBB = SplitBlock(iter->getParent(), iter, Owner);
    }

    removeTerminator(beforeLookupBB);

    CGBuilder B = CGBuilder(beforeLookupBB);
    // Load the slot and check that neither it nor the version is 0.
    Value *versionValue = B.CreateLoad(version);
    Value *receiverPtr = lookup->getOperand(0);
    Value *receiver = receiverPtr;
    if (!isSuperMessage) {
        receiver = B.CreateLoad(receiverPtr);
    }
    // For small objects, we skip the cache entirely.
    // FIXME: Class messages are never to small objects...
    bool is64Bit = llvm::Module::Pointer64 ==
                   B.GetInsertBlock()->getParent()->getParent()->getPointerSize();
    LLVMType *intPtrTy = is64Bit ? Type::getInt64Ty(Context) :
                         Type::getInt32Ty(Context);

    // Receiver as an integer
    Value *receiverSmallObject = B.CreatePtrToInt(receiver, intPtrTy);
    // Receiver is a small object...
    receiverSmallObject =
        B.CreateAnd(receiverSmallObject, is64Bit ? 7 : 1);
    // Receiver is not a small object.
    receiverSmallObject =
        B.CreateICmpNE(receiverSmallObject, Constant::getNullValue(intPtrTy));
    // Ideally, we'd call objc_msgSend() here, but for now just skip the cache
    // lookup

    Value *isCacheEmpty =
        B.CreateICmpEQ(versionValue, Constant::getNullValue(IntTy));
    Value *receiverNil =
        B.CreateICmpEQ(receiver, Constant::getNullValue(receiver->getType()));

    isCacheEmpty = B.CreateOr(isCacheEmpty, receiverNil);
    isCacheEmpty = B.CreateOr(isCacheEmpty, receiverSmallObject);

    BasicBlock *cacheLookupBB = BasicBlock::Create(Context, "cache_check",
                                lookupBB->getParent());

    B.CreateCondBr(isCacheEmpty, lookupBB, cacheLookupBB);

    // Check the cache node is current
    B.SetInsertPoint(cacheLookupBB);
    Value *slotValue = B.CreateLoad(slot, "slot_value");
    Value *slotVersion = B.CreateStructGEP(slotValue, 3);
    // Note: Volatile load because the slot version might have changed in
    // another thread.
    slotVersion = B.CreateLoad(slotVersion, true, "slot_version");
    Value *slotCachedFor = B.CreateStructGEP(slotValue, 1);
    slotCachedFor = B.CreateLoad(slotCachedFor, true, "slot_owner");
    Value *cls = B.CreateLoad(B.CreateBitCast(receiver, IdTy));
    Value *isVersionCorrect = B.CreateICmpEQ(slotVersion, versionValue);
    Value *isOwnerCorrect = B.CreateICmpEQ(slotCachedFor, cls);
    Value *isSlotValid = B.CreateAnd(isVersionCorrect, isOwnerCorrect);
    // If this slot is still valid, skip the lookup.
    B.CreateCondBr(isSlotValid, afterLookupBB, lookupBB);

    // Perform the real lookup and cache the result
    removeTerminator(lookupFinishedBB);
    // Replace the looked up slot with the loaded one
    B.SetInsertPoint(afterLookupBB, afterLookupBB->begin());
    PHINode *newLookup = IRBuilderCreatePHI(&B, lookup->getType(), 3, "new_lookup");
    // Not volatile, so a redundant load elimination pass can do some phi
    // magic with this later.
    lookup->replaceAllUsesWith(newLookup);

    B.SetInsertPoint(lookupFinishedBB);
    Value * newReceiver = receiver;
    if (!isSuperMessage) {
        newReceiver = B.CreateLoad(receiverPtr);
    }
    BasicBlock *storeCacheBB = BasicBlock::Create(Context, "cache_store",
                               lookupBB->getParent());

    // Don't store the cached lookup if we are doing forwarding tricks.
    // Also skip caching small object messages for now
    Value *skipCacheWrite =
        B.CreateOr(B.CreateICmpNE(receiver, newReceiver), receiverSmallObject);
    skipCacheWrite = B.CreateOr(skipCacheWrite, receiverNil);
    B.CreateCondBr(skipCacheWrite, afterLookupBB, storeCacheBB);
    B.SetInsertPoint(storeCacheBB);

    // Store it even if the version is 0, because we always check that the
    // version is not 0 at the start and an occasional redundant store is
    // probably better than a branch every time.
    B.CreateStore(lookup, slot);
    B.CreateStore(B.CreateLoad(B.CreateStructGEP(lookup, 3)), version);
    cls = B.CreateLoad(B.CreateBitCast(receiver, IdTy));
    B.CreateStore(cls, B.CreateStructGEP(lookup, 1));
    B.CreateBr(afterLookupBB);

    newLookup->addIncoming(lookup, lookupFinishedBB);
    newLookup->addIncoming(slotValue, cacheLookupBB);
    newLookup->addIncoming(lookup, storeCacheBB);
}
Exemple #4
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bool LoopInterchangeTransform::adjustLoopBranches() {

    DEBUG(dbgs() << "adjustLoopBranches called\n");
    // Adjust the loop preheader
    BasicBlock *InnerLoopHeader = InnerLoop->getHeader();
    BasicBlock *OuterLoopHeader = OuterLoop->getHeader();
    BasicBlock *InnerLoopLatch = InnerLoop->getLoopLatch();
    BasicBlock *OuterLoopLatch = OuterLoop->getLoopLatch();
    BasicBlock *OuterLoopPreHeader = OuterLoop->getLoopPreheader();
    BasicBlock *InnerLoopPreHeader = InnerLoop->getLoopPreheader();
    BasicBlock *OuterLoopPredecessor = OuterLoopPreHeader->getUniquePredecessor();
    BasicBlock *InnerLoopLatchPredecessor =
        InnerLoopLatch->getUniquePredecessor();
    BasicBlock *InnerLoopLatchSuccessor;
    BasicBlock *OuterLoopLatchSuccessor;

    BranchInst *OuterLoopLatchBI =
        dyn_cast<BranchInst>(OuterLoopLatch->getTerminator());
    BranchInst *InnerLoopLatchBI =
        dyn_cast<BranchInst>(InnerLoopLatch->getTerminator());
    BranchInst *OuterLoopHeaderBI =
        dyn_cast<BranchInst>(OuterLoopHeader->getTerminator());
    BranchInst *InnerLoopHeaderBI =
        dyn_cast<BranchInst>(InnerLoopHeader->getTerminator());

    if (!OuterLoopPredecessor || !InnerLoopLatchPredecessor ||
            !OuterLoopLatchBI || !InnerLoopLatchBI || !OuterLoopHeaderBI ||
            !InnerLoopHeaderBI)
        return false;

    BranchInst *InnerLoopLatchPredecessorBI =
        dyn_cast<BranchInst>(InnerLoopLatchPredecessor->getTerminator());
    BranchInst *OuterLoopPredecessorBI =
        dyn_cast<BranchInst>(OuterLoopPredecessor->getTerminator());

    if (!OuterLoopPredecessorBI || !InnerLoopLatchPredecessorBI)
        return false;
    BasicBlock *InnerLoopHeaderSuccessor = InnerLoopHeader->getUniqueSuccessor();
    if (!InnerLoopHeaderSuccessor)
        return false;

    // Adjust Loop Preheader and headers

    unsigned NumSucc = OuterLoopPredecessorBI->getNumSuccessors();
    for (unsigned i = 0; i < NumSucc; ++i) {
        if (OuterLoopPredecessorBI->getSuccessor(i) == OuterLoopPreHeader)
            OuterLoopPredecessorBI->setSuccessor(i, InnerLoopPreHeader);
    }

    NumSucc = OuterLoopHeaderBI->getNumSuccessors();
    for (unsigned i = 0; i < NumSucc; ++i) {
        if (OuterLoopHeaderBI->getSuccessor(i) == OuterLoopLatch)
            OuterLoopHeaderBI->setSuccessor(i, LoopExit);
        else if (OuterLoopHeaderBI->getSuccessor(i) == InnerLoopPreHeader)
            OuterLoopHeaderBI->setSuccessor(i, InnerLoopHeaderSuccessor);
    }

    // Adjust reduction PHI's now that the incoming block has changed.
    updateIncomingBlock(InnerLoopHeaderSuccessor, InnerLoopHeader,
                        OuterLoopHeader);

    BranchInst::Create(OuterLoopPreHeader, InnerLoopHeaderBI);
    InnerLoopHeaderBI->eraseFromParent();

    // -------------Adjust loop latches-----------
    if (InnerLoopLatchBI->getSuccessor(0) == InnerLoopHeader)
        InnerLoopLatchSuccessor = InnerLoopLatchBI->getSuccessor(1);
    else
        InnerLoopLatchSuccessor = InnerLoopLatchBI->getSuccessor(0);

    NumSucc = InnerLoopLatchPredecessorBI->getNumSuccessors();
    for (unsigned i = 0; i < NumSucc; ++i) {
        if (InnerLoopLatchPredecessorBI->getSuccessor(i) == InnerLoopLatch)
            InnerLoopLatchPredecessorBI->setSuccessor(i, InnerLoopLatchSuccessor);
    }

    // Adjust PHI nodes in InnerLoopLatchSuccessor. Update all uses of PHI with
    // the value and remove this PHI node from inner loop.
    SmallVector<PHINode *, 8> LcssaVec;
    for (auto I = InnerLoopLatchSuccessor->begin(); isa<PHINode>(I); ++I) {
        PHINode *LcssaPhi = cast<PHINode>(I);
        LcssaVec.push_back(LcssaPhi);
    }
    for (auto I = LcssaVec.begin(), E = LcssaVec.end(); I != E; ++I) {
        PHINode *P = *I;
        Value *Incoming = P->getIncomingValueForBlock(InnerLoopLatch);
        P->replaceAllUsesWith(Incoming);
        P->eraseFromParent();
    }

    if (OuterLoopLatchBI->getSuccessor(0) == OuterLoopHeader)
        OuterLoopLatchSuccessor = OuterLoopLatchBI->getSuccessor(1);
    else
        OuterLoopLatchSuccessor = OuterLoopLatchBI->getSuccessor(0);

    if (InnerLoopLatchBI->getSuccessor(1) == InnerLoopLatchSuccessor)
        InnerLoopLatchBI->setSuccessor(1, OuterLoopLatchSuccessor);
    else
        InnerLoopLatchBI->setSuccessor(0, OuterLoopLatchSuccessor);

    updateIncomingBlock(OuterLoopLatchSuccessor, OuterLoopLatch, InnerLoopLatch);

    if (OuterLoopLatchBI->getSuccessor(0) == OuterLoopLatchSuccessor) {
        OuterLoopLatchBI->setSuccessor(0, InnerLoopLatch);
    } else {
        OuterLoopLatchBI->setSuccessor(1, InnerLoopLatch);
    }

    return true;
}
/// CleanupAndPrepareModules - Get the specified modules ready for code
/// generator testing.
///
static void CleanupAndPrepareModules(BugDriver &BD, Module *&Test,
                                     Module *Safe) {
  // Clean up the modules, removing extra cruft that we don't need anymore...
  Test = BD.performFinalCleanups(Test);

  // If we are executing the JIT, we have several nasty issues to take care of.
  if (!BD.isExecutingJIT()) return;

  // First, if the main function is in the Safe module, we must add a stub to
  // the Test module to call into it.  Thus, we create a new function `main'
  // which just calls the old one.
  if (Function *oldMain = Safe->getFunction("main"))
    if (!oldMain->isDeclaration()) {
      // Rename it
      oldMain->setName("llvm_bugpoint_old_main");
      // Create a NEW `main' function with same type in the test module.
      Function *newMain = Function::Create(oldMain->getFunctionType(),
                                           GlobalValue::ExternalLinkage,
                                           "main", Test);
      // Create an `oldmain' prototype in the test module, which will
      // corresponds to the real main function in the same module.
      Function *oldMainProto = Function::Create(oldMain->getFunctionType(),
                                                GlobalValue::ExternalLinkage,
                                                oldMain->getName(), Test);
      // Set up and remember the argument list for the main function.
      std::vector<Value*> args;
      for (Function::arg_iterator
             I = newMain->arg_begin(), E = newMain->arg_end(),
             OI = oldMain->arg_begin(); I != E; ++I, ++OI) {
        I->setName(OI->getName());    // Copy argument names from oldMain
        args.push_back(I);
      }

      // Call the old main function and return its result
      BasicBlock *BB = BasicBlock::Create(Safe->getContext(), "entry", newMain);
      CallInst *call = CallInst::Create(oldMainProto, args.begin(), args.end(),
                                        "", BB);

      // If the type of old function wasn't void, return value of call
      ReturnInst::Create(Safe->getContext(), call, BB);
    }

  // The second nasty issue we must deal with in the JIT is that the Safe
  // module cannot directly reference any functions defined in the test
  // module.  Instead, we use a JIT API call to dynamically resolve the
  // symbol.

  // Add the resolver to the Safe module.
  // Prototype: void *getPointerToNamedFunction(const char* Name)
  Constant *resolverFunc =
    Safe->getOrInsertFunction("getPointerToNamedFunction",
                    PointerType::getUnqual(Type::getInt8Ty(Safe->getContext())),
                    PointerType::getUnqual(Type::getInt8Ty(Safe->getContext())),
                       (Type *)0);

  // Use the function we just added to get addresses of functions we need.
  for (Module::iterator F = Safe->begin(), E = Safe->end(); F != E; ++F) {
    if (F->isDeclaration() && !F->use_empty() && &*F != resolverFunc &&
        !F->isIntrinsic() /* ignore intrinsics */) {
      Function *TestFn = Test->getFunction(F->getName());

      // Don't forward functions which are external in the test module too.
      if (TestFn && !TestFn->isDeclaration()) {
        // 1. Add a string constant with its name to the global file
        Constant *InitArray = ConstantArray::get(F->getContext(), F->getName());
        GlobalVariable *funcName =
          new GlobalVariable(*Safe, InitArray->getType(), true /*isConstant*/,
                             GlobalValue::InternalLinkage, InitArray,
                             F->getName() + "_name");

        // 2. Use `GetElementPtr *funcName, 0, 0' to convert the string to an
        // sbyte* so it matches the signature of the resolver function.

        // GetElementPtr *funcName, ulong 0, ulong 0
        std::vector<Constant*> GEPargs(2,
                     Constant::getNullValue(Type::getInt32Ty(F->getContext())));
        Value *GEP =
                ConstantExpr::getGetElementPtr(funcName, &GEPargs[0], 2);
        std::vector<Value*> ResolverArgs;
        ResolverArgs.push_back(GEP);

        // Rewrite uses of F in global initializers, etc. to uses of a wrapper
        // function that dynamically resolves the calls to F via our JIT API
        if (!F->use_empty()) {
          // Create a new global to hold the cached function pointer.
          Constant *NullPtr = ConstantPointerNull::get(F->getType());
          GlobalVariable *Cache =
            new GlobalVariable(*F->getParent(), F->getType(), 
                               false, GlobalValue::InternalLinkage,
                               NullPtr,F->getName()+".fpcache");

          // Construct a new stub function that will re-route calls to F
          const FunctionType *FuncTy = F->getFunctionType();
          Function *FuncWrapper = Function::Create(FuncTy,
                                                   GlobalValue::InternalLinkage,
                                                   F->getName() + "_wrapper",
                                                   F->getParent());
          BasicBlock *EntryBB  = BasicBlock::Create(F->getContext(),
                                                    "entry", FuncWrapper);
          BasicBlock *DoCallBB = BasicBlock::Create(F->getContext(),
                                                    "usecache", FuncWrapper);
          BasicBlock *LookupBB = BasicBlock::Create(F->getContext(),
                                                    "lookupfp", FuncWrapper);

          // Check to see if we already looked up the value.
          Value *CachedVal = new LoadInst(Cache, "fpcache", EntryBB);
          Value *IsNull = new ICmpInst(*EntryBB, ICmpInst::ICMP_EQ, CachedVal,
                                       NullPtr, "isNull");
          BranchInst::Create(LookupBB, DoCallBB, IsNull, EntryBB);

          // Resolve the call to function F via the JIT API:
          //
          // call resolver(GetElementPtr...)
          CallInst *Resolver =
            CallInst::Create(resolverFunc, ResolverArgs.begin(),
                             ResolverArgs.end(), "resolver", LookupBB);

          // Cast the result from the resolver to correctly-typed function.
          CastInst *CastedResolver =
            new BitCastInst(Resolver,
                            PointerType::getUnqual(F->getFunctionType()),
                            "resolverCast", LookupBB);

          // Save the value in our cache.
          new StoreInst(CastedResolver, Cache, LookupBB);
          BranchInst::Create(DoCallBB, LookupBB);

          PHINode *FuncPtr = PHINode::Create(NullPtr->getType(),
                                             "fp", DoCallBB);
          FuncPtr->addIncoming(CastedResolver, LookupBB);
          FuncPtr->addIncoming(CachedVal, EntryBB);

          // Save the argument list.
          std::vector<Value*> Args;
          for (Function::arg_iterator i = FuncWrapper->arg_begin(),
                 e = FuncWrapper->arg_end(); i != e; ++i)
            Args.push_back(i);

          // Pass on the arguments to the real function, return its result
          if (F->getReturnType() == Type::getVoidTy(F->getContext())) {
            CallInst::Create(FuncPtr, Args.begin(), Args.end(), "", DoCallBB);
            ReturnInst::Create(F->getContext(), DoCallBB);
          } else {
            CallInst *Call = CallInst::Create(FuncPtr, Args.begin(), Args.end(),
                                              "retval", DoCallBB);
            ReturnInst::Create(F->getContext(),Call, DoCallBB);
          }

          // Use the wrapper function instead of the old function
          F->replaceAllUsesWith(FuncWrapper);
        }
      }
    }
  }

  if (verifyModule(*Test) || verifyModule(*Safe)) {
    errs() << "Bugpoint has a bug, which corrupted a module!!\n";
    abort();
  }
}
Exemple #6
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// First thing we need to do is scan the whole function for values that are
// live across unwind edges.  Each value that is live across an unwind edge
// we spill into a stack location, guaranteeing that there is nothing live
// across the unwind edge.  This process also splits all critical edges
// coming out of invoke's.
void LowerInvoke::
splitLiveRangesLiveAcrossInvokes(SmallVectorImpl<InvokeInst*> &Invokes) {
  // First step, split all critical edges from invoke instructions.
  for (unsigned i = 0, e = Invokes.size(); i != e; ++i) {
    InvokeInst *II = Invokes[i];
    SplitCriticalEdge(II, 0, this);
    SplitCriticalEdge(II, 1, this);
    assert(!isa<PHINode>(II->getNormalDest()) &&
           !isa<PHINode>(II->getUnwindDest()) &&
           "critical edge splitting left single entry phi nodes?");
  }

  Function *F = Invokes.back()->getParent()->getParent();

  // To avoid having to handle incoming arguments specially, we lower each arg
  // to a copy instruction in the entry block.  This ensures that the argument
  // value itself cannot be live across the entry block.
  BasicBlock::iterator AfterAllocaInsertPt = F->begin()->begin();
  while (isa<AllocaInst>(AfterAllocaInsertPt) &&
        isa<ConstantInt>(cast<AllocaInst>(AfterAllocaInsertPt)->getArraySize()))
    ++AfterAllocaInsertPt;
  for (Function::arg_iterator AI = F->arg_begin(), E = F->arg_end();
       AI != E; ++AI) {
    Type *Ty = AI->getType();
    // Aggregate types can't be cast, but are legal argument types, so we have
    // to handle them differently. We use an extract/insert pair as a
    // lightweight method to achieve the same goal.
    if (isa<StructType>(Ty) || isa<ArrayType>(Ty) || isa<VectorType>(Ty)) {
      Instruction *EI = ExtractValueInst::Create(AI, 0, "",AfterAllocaInsertPt);
      Instruction *NI = InsertValueInst::Create(AI, EI, 0);
      NI->insertAfter(EI);
      AI->replaceAllUsesWith(NI);
      // Set the operand of the instructions back to the AllocaInst.
      EI->setOperand(0, AI);
      NI->setOperand(0, AI);
    } else {
      // This is always a no-op cast because we're casting AI to AI->getType()
      // so src and destination types are identical. BitCast is the only
      // possibility.
      CastInst *NC = new BitCastInst(
        AI, AI->getType(), AI->getName()+".tmp", AfterAllocaInsertPt);
      AI->replaceAllUsesWith(NC);
      // Set the operand of the cast instruction back to the AllocaInst.
      // Normally it's forbidden to replace a CastInst's operand because it
      // could cause the opcode to reflect an illegal conversion. However,
      // we're replacing it here with the same value it was constructed with.
      // We do this because the above replaceAllUsesWith() clobbered the
      // operand, but we want this one to remain.
      NC->setOperand(0, AI);
    }
  }

  // Finally, scan the code looking for instructions with bad live ranges.
  for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB)
    for (BasicBlock::iterator II = BB->begin(), E = BB->end(); II != E; ++II) {
      // Ignore obvious cases we don't have to handle.  In particular, most
      // instructions either have no uses or only have a single use inside the
      // current block.  Ignore them quickly.
      Instruction *Inst = II;
      if (Inst->use_empty()) continue;
      if (Inst->hasOneUse() &&
          cast<Instruction>(Inst->use_back())->getParent() == BB &&
          !isa<PHINode>(Inst->use_back())) continue;

      // If this is an alloca in the entry block, it's not a real register
      // value.
      if (AllocaInst *AI = dyn_cast<AllocaInst>(Inst))
        if (isa<ConstantInt>(AI->getArraySize()) && BB == F->begin())
          continue;

      // Avoid iterator invalidation by copying users to a temporary vector.
      SmallVector<Instruction*,16> Users;
      for (Value::use_iterator UI = Inst->use_begin(), E = Inst->use_end();
           UI != E; ++UI) {
        Instruction *User = cast<Instruction>(*UI);
        if (User->getParent() != BB || isa<PHINode>(User))
          Users.push_back(User);
      }

      // Scan all of the uses and see if the live range is live across an unwind
      // edge.  If we find a use live across an invoke edge, create an alloca
      // and spill the value.
      std::set<InvokeInst*> InvokesWithStoreInserted;

      // Find all of the blocks that this value is live in.
      std::set<BasicBlock*> LiveBBs;
      LiveBBs.insert(Inst->getParent());
      while (!Users.empty()) {
        Instruction *U = Users.back();
        Users.pop_back();

        if (!isa<PHINode>(U)) {
          MarkBlocksLiveIn(U->getParent(), LiveBBs);
        } else {
          // Uses for a PHI node occur in their predecessor block.
          PHINode *PN = cast<PHINode>(U);
          for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
            if (PN->getIncomingValue(i) == Inst)
              MarkBlocksLiveIn(PN->getIncomingBlock(i), LiveBBs);
        }
      }

      // Now that we know all of the blocks that this thing is live in, see if
      // it includes any of the unwind locations.
      bool NeedsSpill = false;
      for (unsigned i = 0, e = Invokes.size(); i != e; ++i) {
        BasicBlock *UnwindBlock = Invokes[i]->getUnwindDest();
        if (UnwindBlock != BB && LiveBBs.count(UnwindBlock)) {
          NeedsSpill = true;
        }
      }

      // If we decided we need a spill, do it.
      if (NeedsSpill) {
        ++NumSpilled;
        DemoteRegToStack(*Inst, true);
      }
    }
}
// UnifyAllExitNodes - Unify all exit nodes of the CFG by creating a new
// BasicBlock, and converting all returns to unconditional branches to this
// new basic block.  The singular exit node is returned.
//
// If there are no return stmts in the Function, a null pointer is returned.
//
bool UnifyFunctionExitNodes::runOnFunction(Function &F) {
  // Loop over all of the blocks in a function, tracking all of the blocks that
  // return.
  //
  std::vector<BasicBlock*> ReturningBlocks;
  std::vector<BasicBlock*> UnreachableBlocks;
  for(Function::iterator I = F.begin(), E = F.end(); I != E; ++I)
    if (isa<ReturnInst>(I->getTerminator()))
      ReturningBlocks.push_back(I);
    else if (isa<UnreachableInst>(I->getTerminator()))
      UnreachableBlocks.push_back(I);

  // Then unreachable blocks.
  if (UnreachableBlocks.empty()) {
    UnreachableBlock = nullptr;
  } else if (UnreachableBlocks.size() == 1) {
    UnreachableBlock = UnreachableBlocks.front();
  } else {
    UnreachableBlock = BasicBlock::Create(F.getContext(),
                                          "UnifiedUnreachableBlock", &F);
    new UnreachableInst(F.getContext(), UnreachableBlock);

    for (std::vector<BasicBlock*>::iterator I = UnreachableBlocks.begin(),
           E = UnreachableBlocks.end(); I != E; ++I) {
      BasicBlock *BB = *I;
      BB->getInstList().pop_back();  // Remove the unreachable inst.
      BranchInst::Create(UnreachableBlock, BB);
    }
  }

  // Now handle return blocks.
  if (ReturningBlocks.empty()) {
    ReturnBlock = nullptr;
    return false;                          // No blocks return
  } else if (ReturningBlocks.size() == 1) {
    ReturnBlock = ReturningBlocks.front(); // Already has a single return block
    return false;
  }

  // Otherwise, we need to insert a new basic block into the function, add a PHI
  // nodes (if the function returns values), and convert all of the return
  // instructions into unconditional branches.
  //
  BasicBlock *NewRetBlock = BasicBlock::Create(F.getContext(),
                                               "UnifiedReturnBlock", &F);

  PHINode *PN = nullptr;
  if (F.getReturnType()->isVoidTy()) {
    ReturnInst::Create(F.getContext(), nullptr, NewRetBlock);
  } else {
    // If the function doesn't return void... add a PHI node to the block...
    PN = PHINode::Create(F.getReturnType(), ReturningBlocks.size(),
                         "UnifiedRetVal");
    NewRetBlock->getInstList().push_back(PN);
    ReturnInst::Create(F.getContext(), PN, NewRetBlock);
  }

  // Loop over all of the blocks, replacing the return instruction with an
  // unconditional branch.
  //
  for (std::vector<BasicBlock*>::iterator I = ReturningBlocks.begin(),
         E = ReturningBlocks.end(); I != E; ++I) {
    BasicBlock *BB = *I;

    // Add an incoming element to the PHI node for every return instruction that
    // is merging into this new block...
    if (PN)
      PN->addIncoming(BB->getTerminator()->getOperand(0), BB);

    BB->getInstList().pop_back();  // Remove the return insn
    BranchInst::Create(NewRetBlock, BB);
  }
  ReturnBlock = NewRetBlock;
  return true;
}
/// EliminateMostlyEmptyBlock - Eliminate a basic block that have only phi's and
/// an unconditional branch in it.
void CodeGenPrepare::EliminateMostlyEmptyBlock(BasicBlock *BB) {
  BranchInst *BI = cast<BranchInst>(BB->getTerminator());
  BasicBlock *DestBB = BI->getSuccessor(0);

  DEBUG(dbgs() << "MERGING MOSTLY EMPTY BLOCKS - BEFORE:\n" << *BB << *DestBB);

  // If the destination block has a single pred, then this is a trivial edge,
  // just collapse it.
  if (BasicBlock *SinglePred = DestBB->getSinglePredecessor()) {
    if (SinglePred != DestBB) {
      // Remember if SinglePred was the entry block of the function.  If so, we
      // will need to move BB back to the entry position.
      bool isEntry = SinglePred == &SinglePred->getParent()->getEntryBlock();
      MergeBasicBlockIntoOnlyPred(DestBB, this);

      if (isEntry && BB != &BB->getParent()->getEntryBlock())
        BB->moveBefore(&BB->getParent()->getEntryBlock());
      
      DEBUG(dbgs() << "AFTER:\n" << *DestBB << "\n\n\n");
      return;
    }
  }

  // Otherwise, we have multiple predecessors of BB.  Update the PHIs in DestBB
  // to handle the new incoming edges it is about to have.
  PHINode *PN;
  for (BasicBlock::iterator BBI = DestBB->begin();
       (PN = dyn_cast<PHINode>(BBI)); ++BBI) {
    // Remove the incoming value for BB, and remember it.
    Value *InVal = PN->removeIncomingValue(BB, false);

    // Two options: either the InVal is a phi node defined in BB or it is some
    // value that dominates BB.
    PHINode *InValPhi = dyn_cast<PHINode>(InVal);
    if (InValPhi && InValPhi->getParent() == BB) {
      // Add all of the input values of the input PHI as inputs of this phi.
      for (unsigned i = 0, e = InValPhi->getNumIncomingValues(); i != e; ++i)
        PN->addIncoming(InValPhi->getIncomingValue(i),
                        InValPhi->getIncomingBlock(i));
    } else {
      // Otherwise, add one instance of the dominating value for each edge that
      // we will be adding.
      if (PHINode *BBPN = dyn_cast<PHINode>(BB->begin())) {
        for (unsigned i = 0, e = BBPN->getNumIncomingValues(); i != e; ++i)
          PN->addIncoming(InVal, BBPN->getIncomingBlock(i));
      } else {
        for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI)
          PN->addIncoming(InVal, *PI);
      }
    }
  }

  // The PHIs are now updated, change everything that refers to BB to use
  // DestBB and remove BB.
  BB->replaceAllUsesWith(DestBB);
  if (PFI) {
    PFI->replaceAllUses(BB, DestBB);
    PFI->removeEdge(ProfileInfo::getEdge(BB, DestBB));
  }
  BB->eraseFromParent();
  ++NumElim;

  DEBUG(dbgs() << "AFTER:\n" << *DestBB << "\n\n\n");
}
Exemple #9
0
void IrGen::visit(AstOperator& op) {
  const auto& astOperands = op.args().childs();
  Value* llvmResult = nullptr;

  // unary non-arithmetic operators
  if (op.op() == AstOperator::eNot) {
    llvmResult = m_builder.CreateNot(callAcceptOn(*astOperands.front()), "not");
  }
  else if (op.op() == AstOperator::eAddrOf) {
    astOperands.front()->accept(*this);
    llvmResult = astOperands.front()->ir().irAddrOfIrObject();
  }
  else if (op.op() == AstOperator::eDeref) {
    op.ir().setAddrOfIrObject(
      callAcceptOn(*astOperands.front()), EInitStatus::eInitialized);
  }

  // binary logical short circuit operators
  else if (op.isBinaryLogicalShortCircuit()) {
    const auto opname =
      op.op() == AstOperator::eAnd ? string{"and"} : string{"or"};
    Function* functionIr = m_builder.GetInsertBlock()->getParent();
    BasicBlock* rhsBB = BasicBlock::Create(llvmContext, opname + "_rhs");
    BasicBlock* mergeBB = BasicBlock::Create(llvmContext, opname + "_merge");

    // current/lhs BB:
    auto llvmLhs = callAcceptOn(*astOperands.front());
    assert(llvmLhs);
    if (op.op() == AstOperator::eAnd) {
      m_builder.CreateCondBr(llvmLhs, rhsBB, mergeBB);
    }
    else if (op.op() == AstOperator::eOr) {
      m_builder.CreateCondBr(llvmLhs, mergeBB, rhsBB);
    }
    else {
      assert(false);
    }
    BasicBlock* lhsLastBB = m_builder.GetInsertBlock();

    // rhsBB:
    functionIr->getBasicBlockList().push_back(rhsBB);
    m_builder.SetInsertPoint(rhsBB);
    auto llvmRhs = callAcceptOn(*astOperands.back());
    m_builder.CreateBr(mergeBB);
    BasicBlock* rhsLastBB = m_builder.GetInsertBlock();

    // mergeBB:
    functionIr->getBasicBlockList().push_back(mergeBB);
    m_builder.SetInsertPoint(mergeBB);
    PHINode* phi = m_builder.CreatePHI(Type::getInt1Ty(llvmContext), 2, opname);
    assert(phi);
    phi->addIncoming(llvmLhs, lhsLastBB);
    phi->addIncoming(llvmRhs, rhsLastBB);
    llvmResult = phi;
  }

  // assignment operators
  else if (op.op() == AstOperator::eAssign ||
    op.op() == AstOperator::eVoidAssign) {
    astOperands.front()->accept(*this);
    auto llvmRhs = callAcceptOn(*astOperands.back());
    m_builder.CreateStore(
      llvmRhs, astOperands.front()->ir().irAddrOfIrObject());
    if (op.op() == AstOperator::eVoidAssign) {
      llvmResult = m_abstractObject; // void
    }
    else {
      // op.object() is the same as astOperands.front().object(), so
      // 'returning the result' is now a nop.
    }
  }

  // binary arithmetic operators
  else if (astOperands.size() == 2) {
    auto llvmLhs = callAcceptOn(*astOperands.front());
    auto llvmRhs = callAcceptOn(*astOperands.back());
    if (astOperands.front()->objType().is(ObjType::eStoredAsIntegral)) {
      switch (op.op()) {
        // clang-format off
      case AstOperator::eSub      : llvmResult = m_builder.CreateSub   (llvmLhs, llvmRhs, "sub"); break;
      case AstOperator::eAdd      : llvmResult = m_builder.CreateAdd   (llvmLhs, llvmRhs, "add"); break;
      case AstOperator::eMul      : llvmResult = m_builder.CreateMul   (llvmLhs, llvmRhs, "mul"); break;
      case AstOperator::eDiv      : llvmResult = m_builder.CreateSDiv  (llvmLhs, llvmRhs, "div"); break;
      case AstOperator::eEqualTo  : llvmResult = m_builder.CreateICmpEQ(llvmLhs, llvmRhs, "cmp"); break;
      default: assert(false);
        // clang-format on
      }
    }
    else {
      switch (op.op()) {
        // clang-format off
      case AstOperator::eSub      : llvmResult = m_builder.CreateFSub   (llvmLhs, llvmRhs, "fsub"); break;
      case AstOperator::eAdd      : llvmResult = m_builder.CreateFAdd   (llvmLhs, llvmRhs, "add"); break;
      case AstOperator::eMul      : llvmResult = m_builder.CreateFMul   (llvmLhs, llvmRhs, "mul"); break;
      case AstOperator::eDiv      : llvmResult = m_builder.CreateFDiv   (llvmLhs, llvmRhs, "div"); break;
      case AstOperator::eEqualTo  : llvmResult = m_builder.CreateFCmpOEQ(llvmLhs, llvmRhs, "cmp"); break;
      default: assert(false);
        // clang-format on
      }
    }
    assert(llvmResult);
  }

  // unary arithmetic operators
  else {
    assert(astOperands.size() == 1);
    const auto& operand = astOperands.front();
    const auto& objType = operand->objType();
    auto llvmOperand = callAcceptOn(*operand);

    if (objType.is(ObjType::eStoredAsIntegral)) {
      auto llvmZero = ConstantInt::get(llvmContext, APInt(objType.size(), 0));
      switch (op.op()) {
      case '-':
        llvmResult = m_builder.CreateSub(llvmZero, llvmOperand, "neg");
        break;
      case '+': llvmResult = llvmOperand; break;
      default: assert(false);
      }
    }
    else {
      auto llvmZero = ConstantFP::get(llvmContext, APFloat(0.0));
      switch (op.op()) {
      case '-':
        llvmResult = m_builder.CreateFSub(llvmZero, llvmOperand, "fneg");
        break;
      case '+': llvmResult = llvmOperand; break;
      default: assert(false);
      }
    }
    assert(llvmResult);
  }

  if (llvmResult) { allocateAndInitLocalIrObjectFor(op, llvmResult); }
}
/// Create a clone of the blocks in a loop and connect them together.
/// If UnrollProlog is true, loop structure will not be cloned, otherwise a new
/// loop will be created including all cloned blocks, and the iterator of it
/// switches to count NewIter down to 0.
///
static void CloneLoopBlocks(Loop *L, Value *NewIter, const bool UnrollProlog,
                            BasicBlock *InsertTop, BasicBlock *InsertBot,
                            std::vector<BasicBlock *> &NewBlocks,
                            LoopBlocksDFS &LoopBlocks, ValueToValueMapTy &VMap,
                            LoopInfo *LI) {
    BasicBlock *Preheader = L->getLoopPreheader();
    BasicBlock *Header = L->getHeader();
    BasicBlock *Latch = L->getLoopLatch();
    Function *F = Header->getParent();
    LoopBlocksDFS::RPOIterator BlockBegin = LoopBlocks.beginRPO();
    LoopBlocksDFS::RPOIterator BlockEnd = LoopBlocks.endRPO();
    Loop *NewLoop = 0;
    Loop *ParentLoop = L->getParentLoop();
    if (!UnrollProlog) {
        NewLoop = new Loop();
        if (ParentLoop)
            ParentLoop->addChildLoop(NewLoop);
        else
            LI->addTopLevelLoop(NewLoop);
    }

    // For each block in the original loop, create a new copy,
    // and update the value map with the newly created values.
    for (LoopBlocksDFS::RPOIterator BB = BlockBegin; BB != BlockEnd; ++BB) {
        BasicBlock *NewBB = CloneBasicBlock(*BB, VMap, ".prol", F);
        NewBlocks.push_back(NewBB);

        if (NewLoop)
            NewLoop->addBasicBlockToLoop(NewBB, *LI);
        else if (ParentLoop)
            ParentLoop->addBasicBlockToLoop(NewBB, *LI);

        VMap[*BB] = NewBB;
        if (Header == *BB) {
            // For the first block, add a CFG connection to this newly
            // created block.
            InsertTop->getTerminator()->setSuccessor(0, NewBB);

        }
        if (Latch == *BB) {
            // For the last block, if UnrollProlog is true, create a direct jump to
            // InsertBot. If not, create a loop back to cloned head.
            VMap.erase((*BB)->getTerminator());
            BasicBlock *FirstLoopBB = cast<BasicBlock>(VMap[Header]);
            BranchInst *LatchBR = cast<BranchInst>(NewBB->getTerminator());
            IRBuilder<> Builder(LatchBR);
            if (UnrollProlog) {
                Builder.CreateBr(InsertBot);
            } else {
                PHINode *NewIdx = PHINode::Create(NewIter->getType(), 2, "prol.iter",
                                                  FirstLoopBB->getFirstNonPHI());
                Value *IdxSub =
                    Builder.CreateSub(NewIdx, ConstantInt::get(NewIdx->getType(), 1),
                                      NewIdx->getName() + ".sub");
                Value *IdxCmp =
                    Builder.CreateIsNotNull(IdxSub, NewIdx->getName() + ".cmp");
                Builder.CreateCondBr(IdxCmp, FirstLoopBB, InsertBot);
                NewIdx->addIncoming(NewIter, InsertTop);
                NewIdx->addIncoming(IdxSub, NewBB);
            }
            LatchBR->eraseFromParent();
        }
    }

    // Change the incoming values to the ones defined in the preheader or
    // cloned loop.
    for (BasicBlock::iterator I = Header->begin(); isa<PHINode>(I); ++I) {
        PHINode *NewPHI = cast<PHINode>(VMap[I]);
        if (UnrollProlog) {
            VMap[I] = NewPHI->getIncomingValueForBlock(Preheader);
            cast<BasicBlock>(VMap[Header])->getInstList().erase(NewPHI);
        } else {
            unsigned idx = NewPHI->getBasicBlockIndex(Preheader);
            NewPHI->setIncomingBlock(idx, InsertTop);
            BasicBlock *NewLatch = cast<BasicBlock>(VMap[Latch]);
            idx = NewPHI->getBasicBlockIndex(Latch);
            Value *InVal = NewPHI->getIncomingValue(idx);
            NewPHI->setIncomingBlock(idx, NewLatch);
            if (VMap[InVal])
                NewPHI->setIncomingValue(idx, VMap[InVal]);
        }
    }
    if (NewLoop) {
        // Add unroll disable metadata to disable future unrolling for this loop.
        SmallVector<Metadata *, 4> MDs;
        // Reserve first location for self reference to the LoopID metadata node.
        MDs.push_back(nullptr);
        MDNode *LoopID = NewLoop->getLoopID();
        if (LoopID) {
            // First remove any existing loop unrolling metadata.
            for (unsigned i = 1, ie = LoopID->getNumOperands(); i < ie; ++i) {
                bool IsUnrollMetadata = false;
                MDNode *MD = dyn_cast<MDNode>(LoopID->getOperand(i));
                if (MD) {
                    const MDString *S = dyn_cast<MDString>(MD->getOperand(0));
                    IsUnrollMetadata = S && S->getString().startswith("llvm.loop.unroll.");
                }
                if (!IsUnrollMetadata)
                    MDs.push_back(LoopID->getOperand(i));
            }
        }

        LLVMContext &Context = NewLoop->getHeader()->getContext();
        SmallVector<Metadata *, 1> DisableOperands;
        DisableOperands.push_back(MDString::get(Context, "llvm.loop.unroll.disable"));
        MDNode *DisableNode = MDNode::get(Context, DisableOperands);
        MDs.push_back(DisableNode);

        MDNode *NewLoopID = MDNode::get(Context, MDs);
        // Set operand 0 to refer to the loop id itself.
        NewLoopID->replaceOperandWith(0, NewLoopID);
        NewLoop->setLoopID(NewLoopID);
    }
}
/// Connect the unrolling prolog code to the original loop.
/// The unrolling prolog code contains code to execute the
/// 'extra' iterations if the run-time trip count modulo the
/// unroll count is non-zero.
///
/// This function performs the following:
/// - Create PHI nodes at prolog end block to combine values
///   that exit the prolog code and jump around the prolog.
/// - Add a PHI operand to a PHI node at the loop exit block
///   for values that exit the prolog and go around the loop.
/// - Branch around the original loop if the trip count is less
///   than the unroll factor.
///
static void ConnectProlog(Loop *L, Value *BECount, unsigned Count,
                          BasicBlock *LastPrologBB, BasicBlock *PrologEnd,
                          BasicBlock *OrigPH, BasicBlock *NewPH,
                          ValueToValueMapTy &VMap, AliasAnalysis *AA,
                          DominatorTree *DT, LoopInfo *LI, Pass *P) {
    BasicBlock *Latch = L->getLoopLatch();
    assert(Latch && "Loop must have a latch");

    // Create a PHI node for each outgoing value from the original loop
    // (which means it is an outgoing value from the prolog code too).
    // The new PHI node is inserted in the prolog end basic block.
    // The new PHI name is added as an operand of a PHI node in either
    // the loop header or the loop exit block.
    for (succ_iterator SBI = succ_begin(Latch), SBE = succ_end(Latch);
            SBI != SBE; ++SBI) {
        for (BasicBlock::iterator BBI = (*SBI)->begin();
                PHINode *PN = dyn_cast<PHINode>(BBI); ++BBI) {

            // Add a new PHI node to the prolog end block and add the
            // appropriate incoming values.
            PHINode *NewPN = PHINode::Create(PN->getType(), 2, PN->getName()+".unr",
                                             PrologEnd->getTerminator());
            // Adding a value to the new PHI node from the original loop preheader.
            // This is the value that skips all the prolog code.
            if (L->contains(PN)) {
                NewPN->addIncoming(PN->getIncomingValueForBlock(NewPH), OrigPH);
            } else {
                NewPN->addIncoming(UndefValue::get(PN->getType()), OrigPH);
            }

            Value *V = PN->getIncomingValueForBlock(Latch);
            if (Instruction *I = dyn_cast<Instruction>(V)) {
                if (L->contains(I)) {
                    V = VMap[I];
                }
            }
            // Adding a value to the new PHI node from the last prolog block
            // that was created.
            NewPN->addIncoming(V, LastPrologBB);

            // Update the existing PHI node operand with the value from the
            // new PHI node.  How this is done depends on if the existing
            // PHI node is in the original loop block, or the exit block.
            if (L->contains(PN)) {
                PN->setIncomingValue(PN->getBasicBlockIndex(NewPH), NewPN);
            } else {
                PN->addIncoming(NewPN, PrologEnd);
            }
        }
    }

    // Create a branch around the orignal loop, which is taken if there are no
    // iterations remaining to be executed after running the prologue.
    Instruction *InsertPt = PrologEnd->getTerminator();
    IRBuilder<> B(InsertPt);

    assert(Count != 0 && "nonsensical Count!");

    // If BECount <u (Count - 1) then (BECount + 1) & (Count - 1) == (BECount + 1)
    // (since Count is a power of 2).  This means %xtraiter is (BECount + 1) and
    // and all of the iterations of this loop were executed by the prologue.  Note
    // that if BECount <u (Count - 1) then (BECount + 1) cannot unsigned-overflow.
    Value *BrLoopExit =
        B.CreateICmpULT(BECount, ConstantInt::get(BECount->getType(), Count - 1));
    BasicBlock *Exit = L->getUniqueExitBlock();
    assert(Exit && "Loop must have a single exit block only");
    // Split the exit to maintain loop canonicalization guarantees
    SmallVector<BasicBlock*, 4> Preds(pred_begin(Exit), pred_end(Exit));
    SplitBlockPredecessors(Exit, Preds, ".unr-lcssa", AA, DT, LI,
                           P->mustPreserveAnalysisID(LCSSAID));
    // Add the branch to the exit block (around the unrolled loop)
    B.CreateCondBr(BrLoopExit, Exit, NewPH);
    InsertPt->eraseFromParent();
}
Exemple #12
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/// lowerAcrossUnwindEdges - Find all variables which are alive across an unwind
/// edge and spill them.
void SjLjEHPass::lowerAcrossUnwindEdges(Function &F,
                                        ArrayRef<InvokeInst*> Invokes) {
  // Finally, scan the code looking for instructions with bad live ranges.
  for (Function::iterator
         BB = F.begin(), BBE = F.end(); BB != BBE; ++BB) {
    for (BasicBlock::iterator
           II = BB->begin(), IIE = BB->end(); II != IIE; ++II) {
      // Ignore obvious cases we don't have to handle. In particular, most
      // instructions either have no uses or only have a single use inside the
      // current block. Ignore them quickly.
      Instruction *Inst = II;
      if (Inst->use_empty()) continue;
      if (Inst->hasOneUse() &&
          cast<Instruction>(Inst->use_back())->getParent() == BB &&
          !isa<PHINode>(Inst->use_back())) continue;

      // If this is an alloca in the entry block, it's not a real register
      // value.
      if (AllocaInst *AI = dyn_cast<AllocaInst>(Inst))
        if (isa<ConstantInt>(AI->getArraySize()) && BB == F.begin())
          continue;

      // Avoid iterator invalidation by copying users to a temporary vector.
      SmallVector<Instruction*, 16> Users;
      for (Value::use_iterator
             UI = Inst->use_begin(), E = Inst->use_end(); UI != E; ++UI) {
        Instruction *User = cast<Instruction>(*UI);
        if (User->getParent() != BB || isa<PHINode>(User))
          Users.push_back(User);
      }

      // Find all of the blocks that this value is live in.
      SmallPtrSet<BasicBlock*, 64> LiveBBs;
      LiveBBs.insert(Inst->getParent());
      while (!Users.empty()) {
        Instruction *U = Users.back();
        Users.pop_back();

        if (!isa<PHINode>(U)) {
          MarkBlocksLiveIn(U->getParent(), LiveBBs);
        } else {
          // Uses for a PHI node occur in their predecessor block.
          PHINode *PN = cast<PHINode>(U);
          for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
            if (PN->getIncomingValue(i) == Inst)
              MarkBlocksLiveIn(PN->getIncomingBlock(i), LiveBBs);
        }
      }

      // Now that we know all of the blocks that this thing is live in, see if
      // it includes any of the unwind locations.
      bool NeedsSpill = false;
      for (unsigned i = 0, e = Invokes.size(); i != e; ++i) {
        BasicBlock *UnwindBlock = Invokes[i]->getUnwindDest();
        if (UnwindBlock != BB && LiveBBs.count(UnwindBlock)) {
          DEBUG(dbgs() << "SJLJ Spill: " << *Inst << " around "
                << UnwindBlock->getName() << "\n");
          NeedsSpill = true;
          break;
        }
      }

      // If we decided we need a spill, do it.
      // FIXME: Spilling this way is overkill, as it forces all uses of
      // the value to be reloaded from the stack slot, even those that aren't
      // in the unwind blocks. We should be more selective.
      if (NeedsSpill) {
        DemoteRegToStack(*Inst, true);
        ++NumSpilled;
      }
    }
  }

  // Go through the landing pads and remove any PHIs there.
  for (unsigned i = 0, e = Invokes.size(); i != e; ++i) {
    BasicBlock *UnwindBlock = Invokes[i]->getUnwindDest();
    LandingPadInst *LPI = UnwindBlock->getLandingPadInst();

    // Place PHIs into a set to avoid invalidating the iterator.
    SmallPtrSet<PHINode*, 8> PHIsToDemote;
    for (BasicBlock::iterator
           PN = UnwindBlock->begin(); isa<PHINode>(PN); ++PN)
      PHIsToDemote.insert(cast<PHINode>(PN));
    if (PHIsToDemote.empty()) continue;

    // Demote the PHIs to the stack.
    for (SmallPtrSet<PHINode*, 8>::iterator
           I = PHIsToDemote.begin(), E = PHIsToDemote.end(); I != E; ++I)
      DemotePHIToStack(*I);

    // Move the landingpad instruction back to the top of the landing pad block.
    LPI->moveBefore(UnwindBlock->begin());
  }
}
Exemple #13
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// This function indicates the current limitations in the transform as a result
// of which we do not proceed.
bool LoopInterchangeLegality::currentLimitations() {

  BasicBlock *InnerLoopPreHeader = InnerLoop->getLoopPreheader();
  BasicBlock *InnerLoopHeader = InnerLoop->getHeader();
  BasicBlock *OuterLoopHeader = OuterLoop->getHeader();
  BasicBlock *InnerLoopLatch = InnerLoop->getLoopLatch();
  BasicBlock *OuterLoopLatch = OuterLoop->getLoopLatch();

  PHINode *InnerInductionVar;
  PHINode *OuterInductionVar;

  // We currently handle only 1 induction variable inside the loop. We also do
  // not handle reductions as of now.
  if (getPHICount(InnerLoopHeader) > 1)
    return true;

  if (getPHICount(OuterLoopHeader) > 1)
    return true;

  InnerInductionVar = getInductionVariable(InnerLoop, SE);
  OuterInductionVar = getInductionVariable(OuterLoop, SE);

  if (!OuterInductionVar || !InnerInductionVar) {
    DEBUG(dbgs() << "Induction variable not found\n");
    return true;
  }

  // TODO: Triangular loops are not handled for now.
  if (!isLoopStructureUnderstood(InnerInductionVar)) {
    DEBUG(dbgs() << "Loop structure not understood by pass\n");
    return true;
  }

  // TODO: Loops with LCSSA PHI's are currently not handled.
  if (isa<PHINode>(OuterLoopLatch->begin())) {
    DEBUG(dbgs() << "Found and LCSSA PHI in outer loop latch\n");
    return true;
  }
  if (InnerLoopLatch != InnerLoopHeader &&
      isa<PHINode>(InnerLoopLatch->begin())) {
    DEBUG(dbgs() << "Found and LCSSA PHI in inner loop latch\n");
    return true;
  }

  // TODO: Current limitation: Since we split the inner loop latch at the point
  // were induction variable is incremented (induction.next); We cannot have
  // more than 1 user of induction.next since it would result in broken code
  // after split.
  // e.g.
  // for(i=0;i<N;i++) {
  //    for(j = 0;j<M;j++) {
  //      A[j+1][i+2] = A[j][i]+k;
  //  }
  // }
  bool FoundInduction = false;
  Instruction *InnerIndexVarInc = nullptr;
  if (InnerInductionVar->getIncomingBlock(0) == InnerLoopPreHeader)
    InnerIndexVarInc =
        dyn_cast<Instruction>(InnerInductionVar->getIncomingValue(1));
  else
    InnerIndexVarInc =
        dyn_cast<Instruction>(InnerInductionVar->getIncomingValue(0));

  if (!InnerIndexVarInc)
    return true;

  // Since we split the inner loop latch on this induction variable. Make sure
  // we do not have any instruction between the induction variable and branch
  // instruction.

  for (auto I = InnerLoopLatch->rbegin(), E = InnerLoopLatch->rend();
       I != E && !FoundInduction; ++I) {
    if (isa<BranchInst>(*I) || isa<CmpInst>(*I) || isa<TruncInst>(*I))
      continue;
    const Instruction &Ins = *I;
    // We found an instruction. If this is not induction variable then it is not
    // safe to split this loop latch.
    if (!Ins.isIdenticalTo(InnerIndexVarInc))
      return true;
    else
      FoundInduction = true;
  }
  // The loop latch ended and we didnt find the induction variable return as
  // current limitation.
  if (!FoundInduction)
    return true;

  return false;
}
Exemple #14
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/// Connect the unrolling prolog code to the original loop.
/// The unrolling prolog code contains code to execute the
/// 'extra' iterations if the run-time trip count modulo the
/// unroll count is non-zero.
///
/// This function performs the following:
/// - Create PHI nodes at prolog end block to combine values
///   that exit the prolog code and jump around the prolog.
/// - Add a PHI operand to a PHI node at the loop exit block
///   for values that exit the prolog and go around the loop.
/// - Branch around the original loop if the trip count is less
///   than the unroll factor.
///
static void ConnectProlog(Loop *L, Value *BECount, unsigned Count,
                          BasicBlock *PrologExit,
                          BasicBlock *OriginalLoopLatchExit,
                          BasicBlock *PreHeader, BasicBlock *NewPreHeader,
                          ValueToValueMapTy &VMap, DominatorTree *DT,
                          LoopInfo *LI, bool PreserveLCSSA) {
  BasicBlock *Latch = L->getLoopLatch();
  assert(Latch && "Loop must have a latch");
  BasicBlock *PrologLatch = cast<BasicBlock>(VMap[Latch]);

  // Create a PHI node for each outgoing value from the original loop
  // (which means it is an outgoing value from the prolog code too).
  // The new PHI node is inserted in the prolog end basic block.
  // The new PHI node value is added as an operand of a PHI node in either
  // the loop header or the loop exit block.
  for (BasicBlock *Succ : successors(Latch)) {
    for (Instruction &BBI : *Succ) {
      PHINode *PN = dyn_cast<PHINode>(&BBI);
      // Exit when we passed all PHI nodes.
      if (!PN)
        break;
      // Add a new PHI node to the prolog end block and add the
      // appropriate incoming values.
      PHINode *NewPN = PHINode::Create(PN->getType(), 2, PN->getName() + ".unr",
                                       PrologExit->getFirstNonPHI());
      // Adding a value to the new PHI node from the original loop preheader.
      // This is the value that skips all the prolog code.
      if (L->contains(PN)) {
        NewPN->addIncoming(PN->getIncomingValueForBlock(NewPreHeader),
                           PreHeader);
      } else {
        NewPN->addIncoming(UndefValue::get(PN->getType()), PreHeader);
      }

      Value *V = PN->getIncomingValueForBlock(Latch);
      if (Instruction *I = dyn_cast<Instruction>(V)) {
        if (L->contains(I)) {
          V = VMap.lookup(I);
        }
      }
      // Adding a value to the new PHI node from the last prolog block
      // that was created.
      NewPN->addIncoming(V, PrologLatch);

      // Update the existing PHI node operand with the value from the
      // new PHI node.  How this is done depends on if the existing
      // PHI node is in the original loop block, or the exit block.
      if (L->contains(PN)) {
        PN->setIncomingValue(PN->getBasicBlockIndex(NewPreHeader), NewPN);
      } else {
        PN->addIncoming(NewPN, PrologExit);
      }
    }
  }

  // Make sure that created prolog loop is in simplified form
  SmallVector<BasicBlock *, 4> PrologExitPreds;
  Loop *PrologLoop = LI->getLoopFor(PrologLatch);
  if (PrologLoop) {
    for (BasicBlock *PredBB : predecessors(PrologExit))
      if (PrologLoop->contains(PredBB))
        PrologExitPreds.push_back(PredBB);

    SplitBlockPredecessors(PrologExit, PrologExitPreds, ".unr-lcssa", DT, LI,
                           PreserveLCSSA);
  }

  // Create a branch around the original loop, which is taken if there are no
  // iterations remaining to be executed after running the prologue.
  Instruction *InsertPt = PrologExit->getTerminator();
  IRBuilder<> B(InsertPt);

  assert(Count != 0 && "nonsensical Count!");

  // If BECount <u (Count - 1) then (BECount + 1) % Count == (BECount + 1)
  // This means %xtraiter is (BECount + 1) and all of the iterations of this
  // loop were executed by the prologue.  Note that if BECount <u (Count - 1)
  // then (BECount + 1) cannot unsigned-overflow.
  Value *BrLoopExit =
      B.CreateICmpULT(BECount, ConstantInt::get(BECount->getType(), Count - 1));
  // Split the exit to maintain loop canonicalization guarantees
  SmallVector<BasicBlock *, 4> Preds(predecessors(OriginalLoopLatchExit));
  SplitBlockPredecessors(OriginalLoopLatchExit, Preds, ".unr-lcssa", DT, LI,
                         PreserveLCSSA);
  // Add the branch to the exit block (around the unrolled loop)
  B.CreateCondBr(BrLoopExit, OriginalLoopLatchExit, NewPreHeader);
  InsertPt->eraseFromParent();
  if (DT)
    DT->changeImmediateDominator(OriginalLoopLatchExit, PrologExit);
}
Value *SSAUpdater::GetValueInMiddleOfBlock(BasicBlock *BB) {
  // If there is no definition of the renamed variable in this block, just use
  // GetValueAtEndOfBlock to do our work.
  if (!HasValueForBlock(BB))
    return GetValueAtEndOfBlock(BB);

  // Otherwise, we have the hard case.  Get the live-in values for each
  // predecessor.
  SmallVector<std::pair<BasicBlock*, Value*>, 8> PredValues;
  Value *SingularValue = nullptr;

  // We can get our predecessor info by walking the pred_iterator list, but it
  // is relatively slow.  If we already have PHI nodes in this block, walk one
  // of them to get the predecessor list instead.
  if (PHINode *SomePhi = dyn_cast<PHINode>(BB->begin())) {
    for (unsigned i = 0, e = SomePhi->getNumIncomingValues(); i != e; ++i) {
      BasicBlock *PredBB = SomePhi->getIncomingBlock(i);
      Value *PredVal = GetValueAtEndOfBlock(PredBB);
      PredValues.push_back(std::make_pair(PredBB, PredVal));

      // Compute SingularValue.
      if (i == 0)
        SingularValue = PredVal;
      else if (PredVal != SingularValue)
        SingularValue = nullptr;
    }
  } else {
    bool isFirstPred = true;
    for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI) {
      BasicBlock *PredBB = *PI;
      Value *PredVal = GetValueAtEndOfBlock(PredBB);
      PredValues.push_back(std::make_pair(PredBB, PredVal));

      // Compute SingularValue.
      if (isFirstPred) {
        SingularValue = PredVal;
        isFirstPred = false;
      } else if (PredVal != SingularValue)
        SingularValue = nullptr;
    }
  }

  // If there are no predecessors, just return undef.
  if (PredValues.empty())
    return UndefValue::get(ProtoType);

  // Otherwise, if all the merged values are the same, just use it.
  if (SingularValue)
    return SingularValue;

  // Otherwise, we do need a PHI: check to see if we already have one available
  // in this block that produces the right value.
  if (isa<PHINode>(BB->begin())) {
    SmallDenseMap<BasicBlock*, Value*, 8> ValueMapping(PredValues.begin(),
                                                       PredValues.end());
    PHINode *SomePHI;
    for (BasicBlock::iterator It = BB->begin();
         (SomePHI = dyn_cast<PHINode>(It)); ++It) {
      if (IsEquivalentPHI(SomePHI, ValueMapping))
        return SomePHI;
    }
  }

  // Ok, we have no way out, insert a new one now.
  PHINode *InsertedPHI = PHINode::Create(ProtoType, PredValues.size(),
                                         ProtoName, &BB->front());

  // Fill in all the predecessors of the PHI.
  for (unsigned i = 0, e = PredValues.size(); i != e; ++i)
    InsertedPHI->addIncoming(PredValues[i].second, PredValues[i].first);

  // See if the PHI node can be merged to a single value.  This can happen in
  // loop cases when we get a PHI of itself and one other value.
  if (Value *V =
          SimplifyInstruction(InsertedPHI, BB->getModule()->getDataLayout())) {
    InsertedPHI->eraseFromParent();
    return V;
  }

  // Set the DebugLoc of the inserted PHI, if available.
  DebugLoc DL;
  if (const Instruction *I = BB->getFirstNonPHI())
      DL = I->getDebugLoc();
  InsertedPHI->setDebugLoc(DL);

  // If the client wants to know about all new instructions, tell it.
  if (InsertedPHIs) InsertedPHIs->push_back(InsertedPHI);

  DEBUG(dbgs() << "  Inserted PHI: " << *InsertedPHI << "\n");
  return InsertedPHI;
}
Exemple #16
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/// SplitLandingPadPredecessors - This method transforms the landing pad,
/// OrigBB, by introducing two new basic blocks into the function. One of those
/// new basic blocks gets the predecessors listed in Preds. The other basic
/// block gets the remaining predecessors of OrigBB. The landingpad instruction
/// OrigBB is clone into both of the new basic blocks. The new blocks are given
/// the suffixes 'Suffix1' and 'Suffix2', and are returned in the NewBBs vector.
///
/// This currently updates the LLVM IR, AliasAnalysis, DominatorTree,
/// DominanceFrontier, LoopInfo, and LCCSA but no other analyses. In particular,
/// it does not preserve LoopSimplify (because it's complicated to handle the
/// case where one of the edges being split is an exit of a loop with other
/// exits).
///
void llvm::SplitLandingPadPredecessors(BasicBlock *OrigBB,
                                       ArrayRef<BasicBlock*> Preds,
                                       const char *Suffix1, const char *Suffix2,
                                       Pass *P,
                                       SmallVectorImpl<BasicBlock*> &NewBBs) {
  assert(OrigBB->isLandingPad() && "Trying to split a non-landing pad!");

  // Create a new basic block for OrigBB's predecessors listed in Preds. Insert
  // it right before the original block.
  BasicBlock *NewBB1 = BasicBlock::Create(OrigBB->getContext(),
                                          OrigBB->getName() + Suffix1,
                                          OrigBB->getParent(), OrigBB);
  NewBBs.push_back(NewBB1);

  // The new block unconditionally branches to the old block.
  BranchInst *BI1 = BranchInst::Create(OrigBB, NewBB1);

  // Move the edges from Preds to point to NewBB1 instead of OrigBB.
  for (unsigned i = 0, e = Preds.size(); i != e; ++i) {
    // This is slightly more strict than necessary; the minimum requirement
    // is that there be no more than one indirectbr branching to BB. And
    // all BlockAddress uses would need to be updated.
    assert(!isa<IndirectBrInst>(Preds[i]->getTerminator()) &&
           "Cannot split an edge from an IndirectBrInst");
    Preds[i]->getTerminator()->replaceUsesOfWith(OrigBB, NewBB1);
  }

  // Update DominatorTree, LoopInfo, and LCCSA analysis information.
  bool HasLoopExit = false;
  UpdateAnalysisInformation(OrigBB, NewBB1, Preds, P, HasLoopExit);

  // Update the PHI nodes in OrigBB with the values coming from NewBB1.
  UpdatePHINodes(OrigBB, NewBB1, Preds, BI1, P, HasLoopExit);

  // Move the remaining edges from OrigBB to point to NewBB2.
  SmallVector<BasicBlock*, 8> NewBB2Preds;
  for (pred_iterator i = pred_begin(OrigBB), e = pred_end(OrigBB);
       i != e; ) {
    BasicBlock *Pred = *i++;
    if (Pred == NewBB1) continue;
    assert(!isa<IndirectBrInst>(Pred->getTerminator()) &&
           "Cannot split an edge from an IndirectBrInst");
    NewBB2Preds.push_back(Pred);
    e = pred_end(OrigBB);
  }

  BasicBlock *NewBB2 = 0;
  if (!NewBB2Preds.empty()) {
    // Create another basic block for the rest of OrigBB's predecessors.
    NewBB2 = BasicBlock::Create(OrigBB->getContext(),
                                OrigBB->getName() + Suffix2,
                                OrigBB->getParent(), OrigBB);
    NewBBs.push_back(NewBB2);

    // The new block unconditionally branches to the old block.
    BranchInst *BI2 = BranchInst::Create(OrigBB, NewBB2);

    // Move the remaining edges from OrigBB to point to NewBB2.
    for (SmallVectorImpl<BasicBlock*>::iterator
           i = NewBB2Preds.begin(), e = NewBB2Preds.end(); i != e; ++i)
      (*i)->getTerminator()->replaceUsesOfWith(OrigBB, NewBB2);

    // Update DominatorTree, LoopInfo, and LCCSA analysis information.
    HasLoopExit = false;
    UpdateAnalysisInformation(OrigBB, NewBB2, NewBB2Preds, P, HasLoopExit);

    // Update the PHI nodes in OrigBB with the values coming from NewBB2.
    UpdatePHINodes(OrigBB, NewBB2, NewBB2Preds, BI2, P, HasLoopExit);
  }

  LandingPadInst *LPad = OrigBB->getLandingPadInst();
  Instruction *Clone1 = LPad->clone();
  Clone1->setName(Twine("lpad") + Suffix1);
  NewBB1->getInstList().insert(NewBB1->getFirstInsertionPt(), Clone1);

  if (NewBB2) {
    Instruction *Clone2 = LPad->clone();
    Clone2->setName(Twine("lpad") + Suffix2);
    NewBB2->getInstList().insert(NewBB2->getFirstInsertionPt(), Clone2);

    // Create a PHI node for the two cloned landingpad instructions.
    PHINode *PN = PHINode::Create(LPad->getType(), 2, "lpad.phi", LPad);
    PN->addIncoming(Clone1, NewBB1);
    PN->addIncoming(Clone2, NewBB2);
    LPad->replaceAllUsesWith(PN);
    LPad->eraseFromParent();
  } else {
    // There is no second clone. Just replace the landing pad with the first
    // clone.
    LPad->replaceAllUsesWith(Clone1);
    LPad->eraseFromParent();
  }
}
Exemple #17
0
/// CloneAndPruneFunctionInto - This works exactly like CloneFunctionInto,
/// except that it does some simple constant prop and DCE on the fly.  The
/// effect of this is to copy significantly less code in cases where (for
/// example) a function call with constant arguments is inlined, and those
/// constant arguments cause a significant amount of code in the callee to be
/// dead.  Since this doesn't produce an exact copy of the input, it can't be
/// used for things like CloneFunction or CloneModule.
void llvm::CloneAndPruneFunctionInto(Function *NewFunc, const Function *OldFunc,
                                     DenseMap<const Value*, Value*> &ValueMap,
                                     SmallVectorImpl<ReturnInst*> &Returns,
                                     const char *NameSuffix, 
                                     ClonedCodeInfo *CodeInfo,
                                     const TargetData *TD,
                                     Instruction *TheCall) {
  assert(NameSuffix && "NameSuffix cannot be null!");
  
#ifndef NDEBUG
  for (Function::const_arg_iterator II = OldFunc->arg_begin(), 
       E = OldFunc->arg_end(); II != E; ++II)
    assert(ValueMap.count(II) && "No mapping from source argument specified!");
#endif

  PruningFunctionCloner PFC(NewFunc, OldFunc, ValueMap, Returns,
                            NameSuffix, CodeInfo, TD);

  // Clone the entry block, and anything recursively reachable from it.
  std::vector<const BasicBlock*> CloneWorklist;
  CloneWorklist.push_back(&OldFunc->getEntryBlock());
  while (!CloneWorklist.empty()) {
    const BasicBlock *BB = CloneWorklist.back();
    CloneWorklist.pop_back();
    PFC.CloneBlock(BB, CloneWorklist);
  }
  
  // Loop over all of the basic blocks in the old function.  If the block was
  // reachable, we have cloned it and the old block is now in the value map:
  // insert it into the new function in the right order.  If not, ignore it.
  //
  // Defer PHI resolution until rest of function is resolved.
  SmallVector<const PHINode*, 16> PHIToResolve;
  for (Function::const_iterator BI = OldFunc->begin(), BE = OldFunc->end();
       BI != BE; ++BI) {
    BasicBlock *NewBB = cast_or_null<BasicBlock>(ValueMap[BI]);
    if (NewBB == 0) continue;  // Dead block.

    // Add the new block to the new function.
    NewFunc->getBasicBlockList().push_back(NewBB);
    
    // Loop over all of the instructions in the block, fixing up operand
    // references as we go.  This uses ValueMap to do all the hard work.
    //
    BasicBlock::iterator I = NewBB->begin();

    LLVMContext &Context = OldFunc->getContext();
    unsigned DbgKind = Context.getMetadata().getMDKind("dbg");
    MDNode *TheCallMD = NULL;
    SmallVector<Value *, 4> MDVs;
    if (TheCall && TheCall->hasMetadata()) 
      TheCallMD = Context.getMetadata().getMD(DbgKind, TheCall);
    
    // Handle PHI nodes specially, as we have to remove references to dead
    // blocks.
    if (PHINode *PN = dyn_cast<PHINode>(I)) {
      // Skip over all PHI nodes, remembering them for later.
      BasicBlock::const_iterator OldI = BI->begin();
      for (; (PN = dyn_cast<PHINode>(I)); ++I, ++OldI) {
        if (I->hasMetadata()) {
          if (TheCallMD) {
            if (MDNode *IMD = Context.getMetadata().getMD(DbgKind, I)) {
              MDNode *NewMD = UpdateInlinedAtInfo(IMD, TheCallMD, Context);
              Context.getMetadata().addMD(DbgKind, NewMD, I);
            }
          } else {
            // The cloned instruction has dbg info but the call instruction
            // does not have dbg info. Remove dbg info from cloned instruction.
            Context.getMetadata().removeMD(DbgKind, I);
          }
        }
        PHIToResolve.push_back(cast<PHINode>(OldI));
      }
    }
    
    // Otherwise, remap the rest of the instructions normally.
    for (; I != NewBB->end(); ++I) {
      if (I->hasMetadata()) {
        if (TheCallMD) {
          if (MDNode *IMD = Context.getMetadata().getMD(DbgKind, I)) {
            MDNode *NewMD = UpdateInlinedAtInfo(IMD, TheCallMD, Context);
            Context.getMetadata().addMD(DbgKind, NewMD, I);
          }
        } else {
          // The cloned instruction has dbg info but the call instruction
          // does not have dbg info. Remove dbg info from cloned instruction.
          Context.getMetadata().removeMD(DbgKind, I);
        }
      }
      RemapInstruction(I, ValueMap);
    }
  }
  
  // Defer PHI resolution until rest of function is resolved, PHI resolution
  // requires the CFG to be up-to-date.
  for (unsigned phino = 0, e = PHIToResolve.size(); phino != e; ) {
    const PHINode *OPN = PHIToResolve[phino];
    unsigned NumPreds = OPN->getNumIncomingValues();
    const BasicBlock *OldBB = OPN->getParent();
    BasicBlock *NewBB = cast<BasicBlock>(ValueMap[OldBB]);

    // Map operands for blocks that are live and remove operands for blocks
    // that are dead.
    for (; phino != PHIToResolve.size() &&
         PHIToResolve[phino]->getParent() == OldBB; ++phino) {
      OPN = PHIToResolve[phino];
      PHINode *PN = cast<PHINode>(ValueMap[OPN]);
      for (unsigned pred = 0, e = NumPreds; pred != e; ++pred) {
        if (BasicBlock *MappedBlock = 
            cast_or_null<BasicBlock>(ValueMap[PN->getIncomingBlock(pred)])) {
          Value *InVal = MapValue(PN->getIncomingValue(pred),
                                  ValueMap);
          assert(InVal && "Unknown input value?");
          PN->setIncomingValue(pred, InVal);
          PN->setIncomingBlock(pred, MappedBlock);
        } else {
          PN->removeIncomingValue(pred, false);
          --pred, --e;  // Revisit the next entry.
        }
      } 
    }
    
    // The loop above has removed PHI entries for those blocks that are dead
    // and has updated others.  However, if a block is live (i.e. copied over)
    // but its terminator has been changed to not go to this block, then our
    // phi nodes will have invalid entries.  Update the PHI nodes in this
    // case.
    PHINode *PN = cast<PHINode>(NewBB->begin());
    NumPreds = std::distance(pred_begin(NewBB), pred_end(NewBB));
    if (NumPreds != PN->getNumIncomingValues()) {
      assert(NumPreds < PN->getNumIncomingValues());
      // Count how many times each predecessor comes to this block.
      std::map<BasicBlock*, unsigned> PredCount;
      for (pred_iterator PI = pred_begin(NewBB), E = pred_end(NewBB);
           PI != E; ++PI)
        --PredCount[*PI];
      
      // Figure out how many entries to remove from each PHI.
      for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
        ++PredCount[PN->getIncomingBlock(i)];
      
      // At this point, the excess predecessor entries are positive in the
      // map.  Loop over all of the PHIs and remove excess predecessor
      // entries.
      BasicBlock::iterator I = NewBB->begin();
      for (; (PN = dyn_cast<PHINode>(I)); ++I) {
        for (std::map<BasicBlock*, unsigned>::iterator PCI =PredCount.begin(),
             E = PredCount.end(); PCI != E; ++PCI) {
          BasicBlock *Pred     = PCI->first;
          for (unsigned NumToRemove = PCI->second; NumToRemove; --NumToRemove)
            PN->removeIncomingValue(Pred, false);
        }
      }
    }
    
    // If the loops above have made these phi nodes have 0 or 1 operand,
    // replace them with undef or the input value.  We must do this for
    // correctness, because 0-operand phis are not valid.
    PN = cast<PHINode>(NewBB->begin());
    if (PN->getNumIncomingValues() == 0) {
      BasicBlock::iterator I = NewBB->begin();
      BasicBlock::const_iterator OldI = OldBB->begin();
      while ((PN = dyn_cast<PHINode>(I++))) {
        Value *NV = UndefValue::get(PN->getType());
        PN->replaceAllUsesWith(NV);
        assert(ValueMap[OldI] == PN && "ValueMap mismatch");
        ValueMap[OldI] = NV;
        PN->eraseFromParent();
        ++OldI;
      }
    }
    // NOTE: We cannot eliminate single entry phi nodes here, because of
    // ValueMap.  Single entry phi nodes can have multiple ValueMap entries
    // pointing at them.  Thus, deleting one would require scanning the ValueMap
    // to update any entries in it that would require that.  This would be
    // really slow.
  }
  
  // Now that the inlined function body has been fully constructed, go through
  // and zap unconditional fall-through branches.  This happen all the time when
  // specializing code: code specialization turns conditional branches into
  // uncond branches, and this code folds them.
  Function::iterator I = cast<BasicBlock>(ValueMap[&OldFunc->getEntryBlock()]);
  while (I != NewFunc->end()) {
    BranchInst *BI = dyn_cast<BranchInst>(I->getTerminator());
    if (!BI || BI->isConditional()) { ++I; continue; }
    
    // Note that we can't eliminate uncond branches if the destination has
    // single-entry PHI nodes.  Eliminating the single-entry phi nodes would
    // require scanning the ValueMap to update any entries that point to the phi
    // node.
    BasicBlock *Dest = BI->getSuccessor(0);
    if (!Dest->getSinglePredecessor() || isa<PHINode>(Dest->begin())) {
      ++I; continue;
    }
    
    // We know all single-entry PHI nodes in the inlined function have been
    // removed, so we just need to splice the blocks.
    BI->eraseFromParent();
    
    // Move all the instructions in the succ to the pred.
    I->getInstList().splice(I->end(), Dest->getInstList());
    
    // Make all PHI nodes that referred to Dest now refer to I as their source.
    Dest->replaceAllUsesWith(I);

    // Remove the dest block.
    Dest->eraseFromParent();
    
    // Do not increment I, iteratively merge all things this block branches to.
  }
}
Exemple #18
0
/// Renames all variables in the specified BasicBlock.
/// Only variables that need to be rename will be.
///
void SSI::rename(BasicBlock *BB) {
  SmallPtrSet<Instruction*, 8> defined;

  // Iterate through instructions and make appropriate renaming.
  // For SSI_PHI (b = PHI()), store b at value_stack as a new
  // definition of the variable it represents.
  // For SSI_SIG (b = PHI(a)), substitute a with the current
  // value of a, present in the value_stack.
  // Then store bin the value_stack as the new definition of a.
  // For all other instructions (b = OP(a, c, d, ...)), we need to substitute
  // all operands with its current value, present in value_stack.
  for (BasicBlock::iterator begin = BB->begin(), end = BB->end();
       begin != end; ++begin) {
    Instruction *I = begin;
    if (PHINode *PN = dyn_cast<PHINode>(I)) { // Treat PHI functions
      Instruction* position;

      // Treat SSI_PHI
      if ((position = getPositionPhi(PN))) {
        value_stack[position].push_back(PN);
        defined.insert(position);
      // Treat SSI_SIG
      } else if ((position = getPositionSigma(PN))) {
        substituteUse(I);
        value_stack[position].push_back(PN);
        defined.insert(position);
      }

      // Treat all other PHI functions
      else {
        substituteUse(I);
      }
    }

    // Treat all other functions
    else {
      substituteUse(I);
    }
  }

  // This loop iterates in all BasicBlocks that are successors of the current
  // BasicBlock. For each SSI_PHI instruction found, insert an operand.
  // This operand is the current operand in value_stack for the variable
  // in "position". And the BasicBlock this operand represents is the current
  // BasicBlock.
  for (succ_iterator SI = succ_begin(BB), SE = succ_end(BB); SI != SE; ++SI) {
    BasicBlock *BB_succ = *SI;

    for (BasicBlock::iterator begin = BB_succ->begin(),
         notPhi = BB_succ->getFirstNonPHI(); begin != *notPhi; ++begin) {
      Instruction *I = begin;
      PHINode *PN = dyn_cast<PHINode>(I);
      Instruction* position;
      if (PN && ((position = getPositionPhi(PN)))) {
        PN->addIncoming(value_stack[position].back(), BB);
      }
    }
  }

  // This loop calls rename on all children from this block. This time children
  // refers to a successor block in the dominance tree.
  DomTreeNode *DTN = DT_->getNode(BB);
  for (DomTreeNode::iterator begin = DTN->begin(), end = DTN->end();
       begin != end; ++begin) {
    DomTreeNodeBase<BasicBlock> *DTN_children = *begin;
    BasicBlock *BB_children = DTN_children->getBlock();
    rename(BB_children);
  }

  // Now we remove all inserted definitions of a variable from the top of
  // the stack leaving the previous one as the top.
  for (SmallPtrSet<Instruction*, 8>::iterator DI = defined.begin(),
       DE = defined.end(); DI != DE; ++DI)
    value_stack[*DI].pop_back();
}
/// InsertUnwindResumeCalls - Convert the ResumeInsts that are still present
/// into calls to the appropriate _Unwind_Resume function.
bool DwarfEHPrepare::InsertUnwindResumeCalls(Function &Fn) {
    bool UsesNewEH = false;
    SmallVector<ResumeInst*, 16> Resumes;
    for (Function::iterator I = Fn.begin(), E = Fn.end(); I != E; ++I) {
        TerminatorInst *TI = I->getTerminator();
        if (ResumeInst *RI = dyn_cast<ResumeInst>(TI))
            Resumes.push_back(RI);
        else if (InvokeInst *II = dyn_cast<InvokeInst>(TI))
            UsesNewEH = II->getUnwindDest()->isLandingPad();
    }

    if (Resumes.empty())
        return UsesNewEH;

    // Find the rewind function if we didn't already.
    if (!RewindFunction) {
        LLVMContext &Ctx = Resumes[0]->getContext();
        FunctionType *FTy = FunctionType::get(Type::getVoidTy(Ctx),
                                              Type::getInt8PtrTy(Ctx), false);
        const char *RewindName = TLI->getLibcallName(RTLIB::UNWIND_RESUME);
        RewindFunction = Fn.getParent()->getOrInsertFunction(RewindName, FTy);
    }

    // Create the basic block where the _Unwind_Resume call will live.
    LLVMContext &Ctx = Fn.getContext();
    unsigned ResumesSize = Resumes.size();

    if (ResumesSize == 1) {
        // Instead of creating a new BB and PHI node, just append the call to
        // _Unwind_Resume to the end of the single resume block.
        ResumeInst *RI = Resumes.front();
        BasicBlock *UnwindBB = RI->getParent();
        Value *ExnObj = GetExceptionObject(RI);

        // Call the _Unwind_Resume function.
        CallInst *CI = CallInst::Create(RewindFunction, ExnObj, "", UnwindBB);
        CI->setCallingConv(TLI->getLibcallCallingConv(RTLIB::UNWIND_RESUME));

        // We never expect _Unwind_Resume to return.
        new UnreachableInst(Ctx, UnwindBB);
        return true;
    }

    BasicBlock *UnwindBB = BasicBlock::Create(Ctx, "unwind_resume", &Fn);
    PHINode *PN = PHINode::Create(Type::getInt8PtrTy(Ctx), ResumesSize,
                                  "exn.obj", UnwindBB);

    // Extract the exception object from the ResumeInst and add it to the PHI node
    // that feeds the _Unwind_Resume call.
    for (SmallVectorImpl<ResumeInst*>::iterator
            I = Resumes.begin(), E = Resumes.end(); I != E; ++I) {
        ResumeInst *RI = *I;
        BasicBlock *Parent = RI->getParent();
        BranchInst::Create(UnwindBB, Parent);

        Value *ExnObj = GetExceptionObject(RI);
        PN->addIncoming(ExnObj, Parent);

        ++NumResumesLowered;
    }

    // Call the function.
    CallInst *CI = CallInst::Create(RewindFunction, PN, "", UnwindBB);
    CI->setCallingConv(TLI->getLibcallCallingConv(RTLIB::UNWIND_RESUME));

    // We never expect _Unwind_Resume to return.
    new UnreachableInst(Ctx, UnwindBB);
    return true;
}
Exemple #20
0
/// When there is a phi node that is created in a BasicBlock and it is used
/// as an operand of another phi function used in the same BasicBlock,
/// LLVM looks this as an error. So on the second phi, the first phi is called
/// P and the BasicBlock it incomes is B. This P will be replaced by the value
/// it has for BasicBlock B. It also includes undef values for predecessors
/// that were not included in the phi.
///
void SSI::fixPhis() {
  for (SmallPtrSet<PHINode *, 1>::iterator begin = phisToFix.begin(),
       end = phisToFix.end(); begin != end; ++begin) {
    PHINode *PN = *begin;
    for (unsigned i = 0, e = PN->getNumIncomingValues(); i < e; ++i) {
      PHINode *PN_father = dyn_cast<PHINode>(PN->getIncomingValue(i));
      if (PN_father && PN->getParent() == PN_father->getParent() &&
          !DT_->dominates(PN->getParent(), PN->getIncomingBlock(i))) {
        BasicBlock *BB = PN->getIncomingBlock(i);
        int pos = PN_father->getBasicBlockIndex(BB);
        PN->setIncomingValue(i, PN_father->getIncomingValue(pos));
      }
    }
  }

  for (DenseMapIterator<PHINode *, Instruction*> begin = phis.begin(),
       end = phis.end(); begin != end; ++begin) {
    PHINode *PN = begin->first;
    BasicBlock *BB = PN->getParent();
    pred_iterator PI = pred_begin(BB), PE = pred_end(BB);
    SmallVector<BasicBlock*, 8> Preds(PI, PE);
    for (unsigned size = Preds.size();
         PI != PE && PN->getNumIncomingValues() != size; ++PI) {
      bool found = false;
      for (unsigned i = 0, pn_end = PN->getNumIncomingValues();
           i < pn_end; ++i) {
        if (PN->getIncomingBlock(i) == *PI) {
          found = true;
          break;
        }
      }
      if (!found) {
        PN->addIncoming(UndefValue::get(PN->getType()), *PI);
      }
    }
  }
}
Exemple #21
0
/// mergeEmptyReturnBlocks - If we have more than one empty (other than phi
/// node) return blocks, merge them together to promote recursive block merging.
static bool mergeEmptyReturnBlocks(Function &F) {
  bool Changed = false;

  BasicBlock *RetBlock = 0;

  // Scan all the blocks in the function, looking for empty return blocks.
  for (Function::iterator BBI = F.begin(), E = F.end(); BBI != E; ) {
    BasicBlock &BB = *BBI++;

    // Only look at return blocks.
    ReturnInst *Ret = dyn_cast<ReturnInst>(BB.getTerminator());
    if (Ret == 0) continue;

    // Only look at the block if it is empty or the only other thing in it is a
    // single PHI node that is the operand to the return.
    if (Ret != &BB.front()) {
      // Check for something else in the block.
      BasicBlock::iterator I = Ret;
      --I;
      // Skip over debug info.
      while (isa<DbgInfoIntrinsic>(I) && I != BB.begin())
        --I;
      if (!isa<DbgInfoIntrinsic>(I) &&
          (!isa<PHINode>(I) || I != BB.begin() ||
           Ret->getNumOperands() == 0 ||
           Ret->getOperand(0) != I))
        continue;
    }

    // If this is the first returning block, remember it and keep going.
    if (RetBlock == 0) {
      RetBlock = &BB;
      continue;
    }

    // Otherwise, we found a duplicate return block.  Merge the two.
    Changed = true;

    // Case when there is no input to the return or when the returned values
    // agree is trivial.  Note that they can't agree if there are phis in the
    // blocks.
    if (Ret->getNumOperands() == 0 ||
        Ret->getOperand(0) ==
          cast<ReturnInst>(RetBlock->getTerminator())->getOperand(0)) {
      BB.replaceAllUsesWith(RetBlock);
      BB.eraseFromParent();
      continue;
    }

    // If the canonical return block has no PHI node, create one now.
    PHINode *RetBlockPHI = dyn_cast<PHINode>(RetBlock->begin());
    if (RetBlockPHI == 0) {
      Value *InVal = cast<ReturnInst>(RetBlock->getTerminator())->getOperand(0);
      pred_iterator PB = pred_begin(RetBlock), PE = pred_end(RetBlock);
      RetBlockPHI = PHINode::Create(Ret->getOperand(0)->getType(),
                                    std::distance(PB, PE), "merge",
                                    &RetBlock->front());

      for (pred_iterator PI = PB; PI != PE; ++PI)
        RetBlockPHI->addIncoming(InVal, *PI);
      RetBlock->getTerminator()->setOperand(0, RetBlockPHI);
    }

    // Turn BB into a block that just unconditionally branches to the return
    // block.  This handles the case when the two return blocks have a common
    // predecessor but that return different things.
    RetBlockPHI->addIncoming(Ret->getOperand(0), &BB);
    BB.getTerminator()->eraseFromParent();
    BranchInst::Create(RetBlock, &BB);
  }

  return Changed;
}
 PHI_iterator(PHINode *P, bool) // end iterator
   : PHI(P), idx(PHI->getNumIncomingValues()) {}
Exemple #23
0
// This function indicates the current limitations in the transform as a result
// of which we do not proceed.
bool LoopInterchangeLegality::currentLimitations() {

    BasicBlock *InnerLoopPreHeader = InnerLoop->getLoopPreheader();
    BasicBlock *InnerLoopHeader = InnerLoop->getHeader();
    BasicBlock *InnerLoopLatch = InnerLoop->getLoopLatch();
    BasicBlock *OuterLoopLatch = OuterLoop->getLoopLatch();
    BasicBlock *OuterLoopHeader = OuterLoop->getHeader();

    PHINode *InnerInductionVar;
    SmallVector<PHINode *, 8> Inductions;
    SmallVector<PHINode *, 8> Reductions;
    if (!findInductionAndReductions(InnerLoop, Inductions, Reductions))
        return true;

    // TODO: Currently we handle only loops with 1 induction variable.
    if (Inductions.size() != 1) {
        DEBUG(dbgs() << "We currently only support loops with 1 induction variable."
              << "Failed to interchange due to current limitation\n");
        return true;
    }
    if (Reductions.size() > 0)
        InnerLoopHasReduction = true;

    InnerInductionVar = Inductions.pop_back_val();
    Reductions.clear();
    if (!findInductionAndReductions(OuterLoop, Inductions, Reductions))
        return true;

    // Outer loop cannot have reduction because then loops will not be tightly
    // nested.
    if (!Reductions.empty())
        return true;
    // TODO: Currently we handle only loops with 1 induction variable.
    if (Inductions.size() != 1)
        return true;

    // TODO: Triangular loops are not handled for now.
    if (!isLoopStructureUnderstood(InnerInductionVar)) {
        DEBUG(dbgs() << "Loop structure not understood by pass\n");
        return true;
    }

    // TODO: We only handle LCSSA PHI's corresponding to reduction for now.
    BasicBlock *LoopExitBlock =
        getLoopLatchExitBlock(OuterLoopLatch, OuterLoopHeader);
    if (!LoopExitBlock || !containsSafePHI(LoopExitBlock, true))
        return true;

    LoopExitBlock = getLoopLatchExitBlock(InnerLoopLatch, InnerLoopHeader);
    if (!LoopExitBlock || !containsSafePHI(LoopExitBlock, false))
        return true;

    // TODO: Current limitation: Since we split the inner loop latch at the point
    // were induction variable is incremented (induction.next); We cannot have
    // more than 1 user of induction.next since it would result in broken code
    // after split.
    // e.g.
    // for(i=0;i<N;i++) {
    //    for(j = 0;j<M;j++) {
    //      A[j+1][i+2] = A[j][i]+k;
    //  }
    // }
    Instruction *InnerIndexVarInc = nullptr;
    if (InnerInductionVar->getIncomingBlock(0) == InnerLoopPreHeader)
        InnerIndexVarInc =
            dyn_cast<Instruction>(InnerInductionVar->getIncomingValue(1));
    else
        InnerIndexVarInc =
            dyn_cast<Instruction>(InnerInductionVar->getIncomingValue(0));

    if (!InnerIndexVarInc)
        return true;

    // Since we split the inner loop latch on this induction variable. Make sure
    // we do not have any instruction between the induction variable and branch
    // instruction.

    bool FoundInduction = false;
    for (const Instruction &I : reverse(*InnerLoopLatch)) {
        if (isa<BranchInst>(I) || isa<CmpInst>(I) || isa<TruncInst>(I))
            continue;
        // We found an instruction. If this is not induction variable then it is not
        // safe to split this loop latch.
        if (!I.isIdenticalTo(InnerIndexVarInc))
            return true;

        FoundInduction = true;
        break;
    }
    // The loop latch ended and we didn't find the induction variable return as
    // current limitation.
    if (!FoundInduction)
        return true;

    return false;
}
 Value *getIncomingValue() { return PHI->getIncomingValue(idx); }
void PromoteMem2Reg::run() {
  Function &F = *DT.getRoot()->getParent();

  if (AST)
    PointerAllocaValues.resize(Allocas.size());
  AllocaDbgDeclares.resize(Allocas.size());

  AllocaInfo Info;
  LargeBlockInfo LBI;

  for (unsigned AllocaNum = 0; AllocaNum != Allocas.size(); ++AllocaNum) {
    AllocaInst *AI = Allocas[AllocaNum];

    assert(isAllocaPromotable(AI) && "Cannot promote non-promotable alloca!");
    assert(AI->getParent()->getParent() == &F &&
           "All allocas should be in the same function, which is same as DF!");

    removeLifetimeIntrinsicUsers(AI);

    if (AI->use_empty()) {
      // If there are no uses of the alloca, just delete it now.
      if (AST)
        AST->deleteValue(AI);
      AI->eraseFromParent();

      // Remove the alloca from the Allocas list, since it has been processed
      RemoveFromAllocasList(AllocaNum);
      ++NumDeadAlloca;
      continue;
    }

    // Calculate the set of read and write-locations for each alloca.  This is
    // analogous to finding the 'uses' and 'definitions' of each variable.
    Info.AnalyzeAlloca(AI);

    // If there is only a single store to this value, replace any loads of
    // it that are directly dominated by the definition with the value stored.
    if (Info.DefiningBlocks.size() == 1) {
      if (rewriteSingleStoreAlloca(AI, Info, LBI, DT, AST)) {
        // The alloca has been processed, move on.
        RemoveFromAllocasList(AllocaNum);
        ++NumSingleStore;
        continue;
      }
    }

    // If the alloca is only read and written in one basic block, just perform a
    // linear sweep over the block to eliminate it.
    if (Info.OnlyUsedInOneBlock) {
      promoteSingleBlockAlloca(AI, Info, LBI, AST);

      // The alloca has been processed, move on.
      RemoveFromAllocasList(AllocaNum);
      continue;
    }

    // If we haven't computed dominator tree levels, do so now.
    if (DomLevels.empty()) {
      SmallVector<DomTreeNode *, 32> Worklist;

      DomTreeNode *Root = DT.getRootNode();
      DomLevels[Root] = 0;
      Worklist.push_back(Root);

      while (!Worklist.empty()) {
        DomTreeNode *Node = Worklist.pop_back_val();
        unsigned ChildLevel = DomLevels[Node] + 1;
        for (DomTreeNode::iterator CI = Node->begin(), CE = Node->end();
             CI != CE; ++CI) {
          DomLevels[*CI] = ChildLevel;
          Worklist.push_back(*CI);
        }
      }
    }

    // If we haven't computed a numbering for the BB's in the function, do so
    // now.
    if (BBNumbers.empty()) {
      unsigned ID = 0;
      for (Function::iterator I = F.begin(), E = F.end(); I != E; ++I)
        BBNumbers[I] = ID++;
    }

    // If we have an AST to keep updated, remember some pointer value that is
    // stored into the alloca.
    if (AST)
      PointerAllocaValues[AllocaNum] = Info.AllocaPointerVal;

    // Remember the dbg.declare intrinsic describing this alloca, if any.
    if (Info.DbgDeclare)
      AllocaDbgDeclares[AllocaNum] = Info.DbgDeclare;

    // Keep the reverse mapping of the 'Allocas' array for the rename pass.
    AllocaLookup[Allocas[AllocaNum]] = AllocaNum;

    // At this point, we're committed to promoting the alloca using IDF's, and
    // the standard SSA construction algorithm.  Determine which blocks need PHI
    // nodes and see if we can optimize out some work by avoiding insertion of
    // dead phi nodes.
    DetermineInsertionPoint(AI, AllocaNum, Info);
  }

  if (Allocas.empty())
    return; // All of the allocas must have been trivial!

  LBI.clear();

  // Set the incoming values for the basic block to be null values for all of
  // the alloca's.  We do this in case there is a load of a value that has not
  // been stored yet.  In this case, it will get this null value.
  //
  RenamePassData::ValVector Values(Allocas.size());
  for (unsigned i = 0, e = Allocas.size(); i != e; ++i)
    Values[i] = UndefValue::get(Allocas[i]->getAllocatedType());

  // Walks all basic blocks in the function performing the SSA rename algorithm
  // and inserting the phi nodes we marked as necessary
  //
  std::vector<RenamePassData> RenamePassWorkList;
  RenamePassWorkList.push_back(RenamePassData(F.begin(), 0, Values));
  do {
    RenamePassData RPD;
    RPD.swap(RenamePassWorkList.back());
    RenamePassWorkList.pop_back();
    // RenamePass may add new worklist entries.
    RenamePass(RPD.BB, RPD.Pred, RPD.Values, RenamePassWorkList);
  } while (!RenamePassWorkList.empty());

  // The renamer uses the Visited set to avoid infinite loops.  Clear it now.
  Visited.clear();

  // Remove the allocas themselves from the function.
  for (unsigned i = 0, e = Allocas.size(); i != e; ++i) {
    Instruction *A = Allocas[i];

    // If there are any uses of the alloca instructions left, they must be in
    // unreachable basic blocks that were not processed by walking the dominator
    // tree. Just delete the users now.
    if (!A->use_empty())
      A->replaceAllUsesWith(UndefValue::get(A->getType()));
    if (AST)
      AST->deleteValue(A);
    A->eraseFromParent();
  }

  // Remove alloca's dbg.declare instrinsics from the function.
  for (unsigned i = 0, e = AllocaDbgDeclares.size(); i != e; ++i)
    if (DbgDeclareInst *DDI = AllocaDbgDeclares[i])
      DDI->eraseFromParent();

  // Loop over all of the PHI nodes and see if there are any that we can get
  // rid of because they merge all of the same incoming values.  This can
  // happen due to undef values coming into the PHI nodes.  This process is
  // iterative, because eliminating one PHI node can cause others to be removed.
  bool EliminatedAPHI = true;
  while (EliminatedAPHI) {
    EliminatedAPHI = false;

    // Iterating over NewPhiNodes is deterministic, so it is safe to try to
    // simplify and RAUW them as we go.  If it was not, we could add uses to
    // the values we replace with in a non-deterministic order, thus creating
    // non-deterministic def->use chains.
    for (DenseMap<std::pair<unsigned, unsigned>, PHINode *>::iterator
             I = NewPhiNodes.begin(),
             E = NewPhiNodes.end();
         I != E;) {
      PHINode *PN = I->second;

      // If this PHI node merges one value and/or undefs, get the value.
      if (Value *V = SimplifyInstruction(PN, 0, 0, &DT)) {
        if (AST && PN->getType()->isPointerTy())
          AST->deleteValue(PN);
        PN->replaceAllUsesWith(V);
        PN->eraseFromParent();
        NewPhiNodes.erase(I++);
        EliminatedAPHI = true;
        continue;
      }
      ++I;
    }
  }

  // At this point, the renamer has added entries to PHI nodes for all reachable
  // code.  Unfortunately, there may be unreachable blocks which the renamer
  // hasn't traversed.  If this is the case, the PHI nodes may not
  // have incoming values for all predecessors.  Loop over all PHI nodes we have
  // created, inserting undef values if they are missing any incoming values.
  //
  for (DenseMap<std::pair<unsigned, unsigned>, PHINode *>::iterator
           I = NewPhiNodes.begin(),
           E = NewPhiNodes.end();
       I != E; ++I) {
    // We want to do this once per basic block.  As such, only process a block
    // when we find the PHI that is the first entry in the block.
    PHINode *SomePHI = I->second;
    BasicBlock *BB = SomePHI->getParent();
    if (&BB->front() != SomePHI)
      continue;

    // Only do work here if there the PHI nodes are missing incoming values.  We
    // know that all PHI nodes that were inserted in a block will have the same
    // number of incoming values, so we can just check any of them.
    if (SomePHI->getNumIncomingValues() == getNumPreds(BB))
      continue;

    // Get the preds for BB.
    SmallVector<BasicBlock *, 16> Preds(pred_begin(BB), pred_end(BB));

    // Ok, now we know that all of the PHI nodes are missing entries for some
    // basic blocks.  Start by sorting the incoming predecessors for efficient
    // access.
    std::sort(Preds.begin(), Preds.end());

    // Now we loop through all BB's which have entries in SomePHI and remove
    // them from the Preds list.
    for (unsigned i = 0, e = SomePHI->getNumIncomingValues(); i != e; ++i) {
      // Do a log(n) search of the Preds list for the entry we want.
      SmallVectorImpl<BasicBlock *>::iterator EntIt = std::lower_bound(
          Preds.begin(), Preds.end(), SomePHI->getIncomingBlock(i));
      assert(EntIt != Preds.end() && *EntIt == SomePHI->getIncomingBlock(i) &&
             "PHI node has entry for a block which is not a predecessor!");

      // Remove the entry
      Preds.erase(EntIt);
    }

    // At this point, the blocks left in the preds list must have dummy
    // entries inserted into every PHI nodes for the block.  Update all the phi
    // nodes in this block that we are inserting (there could be phis before
    // mem2reg runs).
    unsigned NumBadPreds = SomePHI->getNumIncomingValues();
    BasicBlock::iterator BBI = BB->begin();
    while ((SomePHI = dyn_cast<PHINode>(BBI++)) &&
           SomePHI->getNumIncomingValues() == NumBadPreds) {
      Value *UndefVal = UndefValue::get(SomePHI->getType());
      for (unsigned pred = 0, e = Preds.size(); pred != e; ++pred)
        SomePHI->addIncoming(UndefVal, Preds[pred]);
    }
  }

  NewPhiNodes.clear();
}
 BasicBlock *getIncomingBlock() { return PHI->getIncomingBlock(idx); }
Exemple #27
0
void GNUstep::IMPCacher::SpeculativelyInline(Instruction *call, Function
        *function) {
    BasicBlock *beforeCallBB = call->getParent();
    BasicBlock *callBB = SplitBlock(beforeCallBB, call, Owner);
    BasicBlock *inlineBB = BasicBlock::Create(Context, "inline",
                           callBB->getParent());


    BasicBlock::iterator iter = call;
    iter++;

    BasicBlock *afterCallBB = SplitBlock(iter->getParent(), iter, Owner);

    removeTerminator(beforeCallBB);

    // Put a branch before the call, testing whether the callee really is the
    // function
    IRBuilder<> B = IRBuilder<>(beforeCallBB);
    Value *callee = isa<CallInst>(call) ? cast<CallInst>(call)->getCalledValue()
                    : cast<InvokeInst>(call)->getCalledValue();

    const FunctionType *FTy = function->getFunctionType();
    const FunctionType *calleeTy = cast<FunctionType>(
                                       cast<PointerType>(callee->getType())->getElementType());
    if (calleeTy != FTy) {
        callee = B.CreateBitCast(callee, function->getType());
    }

    Value *isInlineValid = B.CreateICmpEQ(callee, function);
    B.CreateCondBr(isInlineValid, inlineBB, callBB);

    // In the inline BB, add a copy of the call, but this time calling the real
    // version.
    Instruction *inlineCall = call->clone();
    Value *inlineResult= inlineCall;
    inlineBB->getInstList().push_back(inlineCall);

    B.SetInsertPoint(inlineBB);

    if (calleeTy != FTy) {
        for (unsigned i=0 ; i<FTy->getNumParams() ; i++) {
            LLVMType *callType = calleeTy->getParamType(i);
            LLVMType *argType = FTy->getParamType(i);
            if (callType != argType) {
                inlineCall->setOperand(i, new
                                       BitCastInst(inlineCall->getOperand(i), argType, "", inlineCall));
            }
        }
        if (FTy->getReturnType() != calleeTy->getReturnType()) {
            if (FTy->getReturnType() == Type::getVoidTy(Context)) {
                inlineResult = Constant::getNullValue(calleeTy->getReturnType());
            } else {
                inlineResult =
                    new BitCastInst(inlineCall, calleeTy->getReturnType(), "", inlineBB);
            }
        }
    }

    B.CreateBr(afterCallBB);

    // Unify the return values
    if (call->getType() != Type::getVoidTy(Context)) {
        PHINode *phi = CreatePHI(call->getType(), 2, "", afterCallBB->begin());
        call->replaceAllUsesWith(phi);
        phi->addIncoming(call, callBB);
        phi->addIncoming(inlineResult, inlineBB);
    }

    // Really do the real inlining
    InlineFunctionInfo IFI(0, 0);
    if (CallInst *c = dyn_cast<CallInst>(inlineCall)) {
        c->setCalledFunction(function);
        InlineFunction(c, IFI);
    } else if (InvokeInst *c = dyn_cast<InvokeInst>(inlineCall)) {
        c->setCalledFunction(function);
        InlineFunction(c, IFI);
    }
}
 /// ValueIsNewPHI - Like ValueIsPHI but also check if the PHI has no source
 /// operands, i.e., it was just added.
 static PHINode *ValueIsNewPHI(Value *Val, SSAUpdater *Updater) {
   PHINode *PHI = ValueIsPHI(Val, Updater);
   if (PHI && PHI->getNumIncomingValues() == 0)
     return PHI;
   return nullptr;
 }
Exemple #29
0
// Output for-loop as:
//   ...
//   start = startexpr
//   goto loop
// loop:
//   variable = phi [start, loopheader], [nextvariable, loopend]
//   ...
//   bodyexpr
//   ...
// loopend:
//   step = stepexpr
//   nextvariable = variable + step
//   endcond = endexpr
//   br endcond, loop, endloop
// outloop:
Value *ForExprAST::codegen() {
  // Emit the start code first, without 'variable' in scope.
  Value *StartVal = Start->codegen();
  if (!StartVal)
    return nullptr;

  // Make the new basic block for the loop header, inserting after current
  // block.
  Function *TheFunction = Builder.GetInsertBlock()->getParent();
  BasicBlock *PreheaderBB = Builder.GetInsertBlock();
  BasicBlock *LoopBB =
      BasicBlock::Create(getGlobalContext(), "loop", TheFunction);

  // Insert an explicit fall through from the current block to the LoopBB.
  Builder.CreateBr(LoopBB);

  // Start insertion in LoopBB.
  Builder.SetInsertPoint(LoopBB);

  // Start the PHI node with an entry for Start.
  PHINode *Variable = Builder.CreatePHI(Type::getDoubleTy(getGlobalContext()),
                                        2, VarName.c_str());
  Variable->addIncoming(StartVal, PreheaderBB);

  // Within the loop, the variable is defined equal to the PHI node.  If it
  // shadows an existing variable, we have to restore it, so save it now.
  Value *OldVal = NamedValues[VarName];
  NamedValues[VarName] = Variable;

  // Emit the body of the loop.  This, like any other expr, can change the
  // current BB.  Note that we ignore the value computed by the body, but don't
  // allow an error.
  if (!Body->codegen())
    return nullptr;

  // Emit the step value.
  Value *StepVal = nullptr;
  if (Step) {
    StepVal = Step->codegen();
    if (!StepVal)
      return nullptr;
  } else {
    // If not specified, use 1.0.
    StepVal = ConstantFP::get(getGlobalContext(), APFloat(1.0));
  }

  Value *NextVar = Builder.CreateFAdd(Variable, StepVal, "nextvar");

  // Compute the end condition.
  Value *EndCond = End->codegen();
  if (!EndCond)
    return nullptr;

  // Convert condition to a bool by comparing equal to 0.0.
  EndCond = Builder.CreateFCmpONE(
      EndCond, ConstantFP::get(getGlobalContext(), APFloat(0.0)), "loopcond");

  // Create the "after loop" block and insert it.
  BasicBlock *LoopEndBB = Builder.GetInsertBlock();
  BasicBlock *AfterBB =
      BasicBlock::Create(getGlobalContext(), "afterloop", TheFunction);

  // Insert the conditional branch into the end of LoopEndBB.
  Builder.CreateCondBr(EndCond, LoopBB, AfterBB);

  // Any new code will be inserted in AfterBB.
  Builder.SetInsertPoint(AfterBB);

  // Add a new entry to the PHI node for the backedge.
  Variable->addIncoming(NextVar, LoopEndBB);

  // Restore the unshadowed variable.
  if (OldVal)
    NamedValues[VarName] = OldVal;
  else
    NamedValues.erase(VarName);

  // for expr always returns 0.0.
  return Constant::getNullValue(Type::getDoubleTy(getGlobalContext()));
}
Exemple #30
0
/// Create a clone of the blocks in a loop and connect them together.
/// If CreateRemainderLoop is false, loop structure will not be cloned,
/// otherwise a new loop will be created including all cloned blocks, and the
/// iterator of it switches to count NewIter down to 0.
/// The cloned blocks should be inserted between InsertTop and InsertBot.
/// If loop structure is cloned InsertTop should be new preheader, InsertBot
/// new loop exit.
/// Return the new cloned loop that is created when CreateRemainderLoop is true.
static Loop *
CloneLoopBlocks(Loop *L, Value *NewIter, const bool CreateRemainderLoop,
                const bool UseEpilogRemainder, const bool UnrollRemainder,
                BasicBlock *InsertTop,
                BasicBlock *InsertBot, BasicBlock *Preheader,
                std::vector<BasicBlock *> &NewBlocks, LoopBlocksDFS &LoopBlocks,
                ValueToValueMapTy &VMap, DominatorTree *DT, LoopInfo *LI) {
  StringRef suffix = UseEpilogRemainder ? "epil" : "prol";
  BasicBlock *Header = L->getHeader();
  BasicBlock *Latch = L->getLoopLatch();
  Function *F = Header->getParent();
  LoopBlocksDFS::RPOIterator BlockBegin = LoopBlocks.beginRPO();
  LoopBlocksDFS::RPOIterator BlockEnd = LoopBlocks.endRPO();
  Loop *ParentLoop = L->getParentLoop();
  NewLoopsMap NewLoops;
  NewLoops[ParentLoop] = ParentLoop;
  if (!CreateRemainderLoop)
    NewLoops[L] = ParentLoop;

  // For each block in the original loop, create a new copy,
  // and update the value map with the newly created values.
  for (LoopBlocksDFS::RPOIterator BB = BlockBegin; BB != BlockEnd; ++BB) {
    BasicBlock *NewBB = CloneBasicBlock(*BB, VMap, "." + suffix, F);
    NewBlocks.push_back(NewBB);

    // If we're unrolling the outermost loop, there's no remainder loop,
    // and this block isn't in a nested loop, then the new block is not
    // in any loop. Otherwise, add it to loopinfo.
    if (CreateRemainderLoop || LI->getLoopFor(*BB) != L || ParentLoop)
      addClonedBlockToLoopInfo(*BB, NewBB, LI, NewLoops);

    VMap[*BB] = NewBB;
    if (Header == *BB) {
      // For the first block, add a CFG connection to this newly
      // created block.
      InsertTop->getTerminator()->setSuccessor(0, NewBB);
    }

    if (DT) {
      if (Header == *BB) {
        // The header is dominated by the preheader.
        DT->addNewBlock(NewBB, InsertTop);
      } else {
        // Copy information from original loop to unrolled loop.
        BasicBlock *IDomBB = DT->getNode(*BB)->getIDom()->getBlock();
        DT->addNewBlock(NewBB, cast<BasicBlock>(VMap[IDomBB]));
      }
    }

    if (Latch == *BB) {
      // For the last block, if CreateRemainderLoop is false, create a direct
      // jump to InsertBot. If not, create a loop back to cloned head.
      VMap.erase((*BB)->getTerminator());
      BasicBlock *FirstLoopBB = cast<BasicBlock>(VMap[Header]);
      BranchInst *LatchBR = cast<BranchInst>(NewBB->getTerminator());
      IRBuilder<> Builder(LatchBR);
      if (!CreateRemainderLoop) {
        Builder.CreateBr(InsertBot);
      } else {
        PHINode *NewIdx = PHINode::Create(NewIter->getType(), 2,
                                          suffix + ".iter",
                                          FirstLoopBB->getFirstNonPHI());
        Value *IdxSub =
            Builder.CreateSub(NewIdx, ConstantInt::get(NewIdx->getType(), 1),
                              NewIdx->getName() + ".sub");
        Value *IdxCmp =
            Builder.CreateIsNotNull(IdxSub, NewIdx->getName() + ".cmp");
        Builder.CreateCondBr(IdxCmp, FirstLoopBB, InsertBot);
        NewIdx->addIncoming(NewIter, InsertTop);
        NewIdx->addIncoming(IdxSub, NewBB);
      }
      LatchBR->eraseFromParent();
    }
  }

  // Change the incoming values to the ones defined in the preheader or
  // cloned loop.
  for (BasicBlock::iterator I = Header->begin(); isa<PHINode>(I); ++I) {
    PHINode *NewPHI = cast<PHINode>(VMap[&*I]);
    if (!CreateRemainderLoop) {
      if (UseEpilogRemainder) {
        unsigned idx = NewPHI->getBasicBlockIndex(Preheader);
        NewPHI->setIncomingBlock(idx, InsertTop);
        NewPHI->removeIncomingValue(Latch, false);
      } else {
        VMap[&*I] = NewPHI->getIncomingValueForBlock(Preheader);
        cast<BasicBlock>(VMap[Header])->getInstList().erase(NewPHI);
      }
    } else {
      unsigned idx = NewPHI->getBasicBlockIndex(Preheader);
      NewPHI->setIncomingBlock(idx, InsertTop);
      BasicBlock *NewLatch = cast<BasicBlock>(VMap[Latch]);
      idx = NewPHI->getBasicBlockIndex(Latch);
      Value *InVal = NewPHI->getIncomingValue(idx);
      NewPHI->setIncomingBlock(idx, NewLatch);
      if (Value *V = VMap.lookup(InVal))
        NewPHI->setIncomingValue(idx, V);
    }
  }
  if (CreateRemainderLoop) {
    Loop *NewLoop = NewLoops[L];
    assert(NewLoop && "L should have been cloned");

    // Only add loop metadata if the loop is not going to be completely
    // unrolled.
    if (UnrollRemainder)
      return NewLoop;

    // Add unroll disable metadata to disable future unrolling for this loop.
    SmallVector<Metadata *, 4> MDs;
    // Reserve first location for self reference to the LoopID metadata node.
    MDs.push_back(nullptr);
    MDNode *LoopID = NewLoop->getLoopID();
    if (LoopID) {
      // First remove any existing loop unrolling metadata.
      for (unsigned i = 1, ie = LoopID->getNumOperands(); i < ie; ++i) {
        bool IsUnrollMetadata = false;
        MDNode *MD = dyn_cast<MDNode>(LoopID->getOperand(i));
        if (MD) {
          const MDString *S = dyn_cast<MDString>(MD->getOperand(0));
          IsUnrollMetadata = S && S->getString().startswith("llvm.loop.unroll.");
        }
        if (!IsUnrollMetadata)
          MDs.push_back(LoopID->getOperand(i));
      }
    }

    LLVMContext &Context = NewLoop->getHeader()->getContext();
    SmallVector<Metadata *, 1> DisableOperands;
    DisableOperands.push_back(MDString::get(Context,
                                            "llvm.loop.unroll.disable"));
    MDNode *DisableNode = MDNode::get(Context, DisableOperands);
    MDs.push_back(DisableNode);

    MDNode *NewLoopID = MDNode::get(Context, MDs);
    // Set operand 0 to refer to the loop id itself.
    NewLoopID->replaceOperandWith(0, NewLoopID);
    NewLoop->setLoopID(NewLoopID);
    return NewLoop;
  }
  else
    return nullptr;
}