Exemplo n.º 1
0
/// RewriteUsesOfClonedInstructions - We just cloned the instructions from the
/// old header into the preheader.  If there were uses of the values produced by
/// these instruction that were outside of the loop, we have to insert PHI nodes
/// to merge the two values.  Do this now.
static void RewriteUsesOfClonedInstructions(BasicBlock *OrigHeader,
                                            BasicBlock *OrigPreheader,
                                            ValueToValueMapTy &ValueMap) {
  // Remove PHI node entries that are no longer live.
  BasicBlock::iterator I, E = OrigHeader->end();
  for (I = OrigHeader->begin(); PHINode *PN = dyn_cast<PHINode>(I); ++I)
    PN->removeIncomingValue(PN->getBasicBlockIndex(OrigPreheader));

  // Now fix up users of the instructions in OrigHeader, inserting PHI nodes
  // as necessary.
  SSAUpdater SSA;
  for (I = OrigHeader->begin(); I != E; ++I) {
    Value *OrigHeaderVal = I;

    // If there are no uses of the value (e.g. because it returns void), there
    // is nothing to rewrite.
    if (OrigHeaderVal->use_empty())
      continue;

    Value *OrigPreHeaderVal = ValueMap[OrigHeaderVal];

    // The value now exits in two versions: the initial value in the preheader
    // and the loop "next" value in the original header.
    SSA.Initialize(OrigHeaderVal->getType(), OrigHeaderVal->getName());
    SSA.AddAvailableValue(OrigHeader, OrigHeaderVal);
    SSA.AddAvailableValue(OrigPreheader, OrigPreHeaderVal);

    // Visit each use of the OrigHeader instruction.
    for (Value::use_iterator UI = OrigHeaderVal->use_begin(),
         UE = OrigHeaderVal->use_end(); UI != UE; ) {
      // Grab the use before incrementing the iterator.
      Use &U = UI.getUse();

      // Increment the iterator before removing the use from the list.
      ++UI;

      // SSAUpdater can't handle a non-PHI use in the same block as an
      // earlier def. We can easily handle those cases manually.
      Instruction *UserInst = cast<Instruction>(U.getUser());
      if (!isa<PHINode>(UserInst)) {
        BasicBlock *UserBB = UserInst->getParent();

        // The original users in the OrigHeader are already using the
        // original definitions.
        if (UserBB == OrigHeader)
          continue;

        // Users in the OrigPreHeader need to use the value to which the
        // original definitions are mapped.
        if (UserBB == OrigPreheader) {
          U = OrigPreHeaderVal;
          continue;
        }
      }

      // Anything else can be handled by SSAUpdater.
      SSA.RewriteUse(U);
    }
  }
}
/// If there's a single exit block, sink any loop-invariant values that
/// were defined in the preheader but not used inside the loop into the
/// exit block to reduce register pressure in the loop.
void IndVarSimplify::SinkUnusedInvariants(Loop *L) {
  BasicBlock *ExitBlock = L->getExitBlock();
  if (!ExitBlock) return;

  BasicBlock *Preheader = L->getLoopPreheader();
  if (!Preheader) return;

  Instruction *InsertPt = ExitBlock->getFirstNonPHI();
  BasicBlock::iterator I = Preheader->getTerminator();
  while (I != Preheader->begin()) {
    --I;
    // New instructions were inserted at the end of the preheader.
    if (isa<PHINode>(I))
      break;
    // Don't move instructions which might have side effects, since the side
    // effects need to complete before instructions inside the loop.  Also
    // don't move instructions which might read memory, since the loop may
    // modify memory. Note that it's okay if the instruction might have
    // undefined behavior: LoopSimplify guarantees that the preheader
    // dominates the exit block.
    if (I->mayHaveSideEffects() || I->mayReadFromMemory())
      continue;
    // Don't sink static AllocaInsts out of the entry block, which would
    // turn them into dynamic allocas!
    if (AllocaInst *AI = dyn_cast<AllocaInst>(I))
      if (AI->isStaticAlloca())
        continue;
    // Determine if there is a use in or before the loop (direct or
    // otherwise).
    bool UsedInLoop = false;
    for (Value::use_iterator UI = I->use_begin(), UE = I->use_end();
         UI != UE; ++UI) {
      BasicBlock *UseBB = cast<Instruction>(UI)->getParent();
      if (PHINode *P = dyn_cast<PHINode>(UI)) {
        unsigned i =
          PHINode::getIncomingValueNumForOperand(UI.getOperandNo());
        UseBB = P->getIncomingBlock(i);
      }
      if (UseBB == Preheader || L->contains(UseBB)) {
        UsedInLoop = true;
        break;
      }
    }
    // If there is, the def must remain in the preheader.
    if (UsedInLoop)
      continue;
    // Otherwise, sink it to the exit block.
    Instruction *ToMove = I;
    bool Done = false;
    if (I != Preheader->begin())
      --I;
    else
      Done = true;
    ToMove->moveBefore(InsertPt);
    if (Done)
      break;
    InsertPt = ToMove;
  }
}
Exemplo n.º 3
0
static Value::use_iterator skipToNextUser(Value::use_iterator I,
                                          Value::use_iterator End) {
  User *CurUser = I->getUser();
  ++I;

  while (I != End && I->getUser() == CurUser)
    ++I;

  return I;
}
Exemplo n.º 4
0
void detail::PtrUseVisitorBase::enqueueUsers(Instruction &I) {
  for (Value::use_iterator UI = I.use_begin(), UE = I.use_end();
       UI != UE; ++UI) {
    if (VisitedUses.insert(&UI.getUse())) {
      UseToVisit NewU = {
        UseToVisit::UseAndIsOffsetKnownPair(&UI.getUse(), IsOffsetKnown),
        Offset
      };
      Worklist.push_back(llvm_move(NewU));
    }
  }
}
Exemplo n.º 5
0
/// WriteThunk - Replace G with a simple tail call to bitcast(F). Also replace
/// direct uses of G with bitcast(F). Deletes G.
void MergeFunctions::WriteThunk(Function *F, Function *G) const {
  if (!G->mayBeOverridden()) {
    // Redirect direct callers of G to F.
    Constant *BitcastF = ConstantExpr::getBitCast(F, G->getType());
    for (Value::use_iterator UI = G->use_begin(), UE = G->use_end();
         UI != UE;) {
      Value::use_iterator TheIter = UI;
      ++UI;
      CallSite CS(*TheIter);
      if (CS && CS.isCallee(TheIter))
        TheIter.getUse().set(BitcastF);
    }
  }

  // If G was internal then we may have replaced all uses of G with F. If so,
  // stop here and delete G. There's no need for a thunk.
  if (G->hasLocalLinkage() && G->use_empty()) {
    G->eraseFromParent();
    return;
  }

  Function *NewG = Function::Create(G->getFunctionType(), G->getLinkage(), "",
                                    G->getParent());
  BasicBlock *BB = BasicBlock::Create(F->getContext(), "", NewG);
  IRBuilder<false> Builder(BB);

  SmallVector<Value *, 16> Args;
  unsigned i = 0;
  const FunctionType *FFTy = F->getFunctionType();
  for (Function::arg_iterator AI = NewG->arg_begin(), AE = NewG->arg_end();
       AI != AE; ++AI) {
    Args.push_back(Builder.CreateBitCast(AI, FFTy->getParamType(i)));
    ++i;
  }

  CallInst *CI = Builder.CreateCall(F, Args.begin(), Args.end());
  CI->setTailCall();
  CI->setCallingConv(F->getCallingConv());
  if (NewG->getReturnType()->isVoidTy()) {
    Builder.CreateRetVoid();
  } else {
    Builder.CreateRet(Builder.CreateBitCast(CI, NewG->getReturnType()));
  }

  NewG->copyAttributesFrom(G);
  NewG->takeName(G);
  G->replaceAllUsesWith(NewG);
  G->eraseFromParent();

  DEBUG(dbgs() << "WriteThunk: " << NewG->getName() << '\n');
  ++NumThunksWritten;
}
Exemplo n.º 6
0
// Replace direct callers of Old with New.
void MergeFunctions::replaceDirectCallers(Function *Old, Function *New) {
  Constant *BitcastNew = ConstantExpr::getBitCast(New, Old->getType());
  for (Value::use_iterator UI = Old->use_begin(), UE = Old->use_end();
       UI != UE;) {
    Value::use_iterator TheIter = UI;
    ++UI;
    CallSite CS(*TheIter);
    if (CS && CS.isCallee(TheIter)) {
      remove(CS.getInstruction()->getParent()->getParent());
      TheIter.getUse().set(BitcastNew);
    }
  }
}
Exemplo n.º 7
0
/// OptimizeCmpExpression - sink the given CmpInst into user blocks to reduce
/// the number of virtual registers that must be created and coalesced.  This is
/// a clear win except on targets with multiple condition code registers
///  (PowerPC), where it might lose; some adjustment may be wanted there.
///
/// Return true if any changes are made.
static bool OptimizeCmpExpression(CmpInst *CI) {
  BasicBlock *DefBB = CI->getParent();

  /// InsertedCmp - Only insert a cmp in each block once.
  DenseMap<BasicBlock*, CmpInst*> InsertedCmps;

  bool MadeChange = false;
  for (Value::use_iterator UI = CI->use_begin(), E = CI->use_end();
       UI != E; ) {
    Use &TheUse = UI.getUse();
    Instruction *User = cast<Instruction>(*UI);

    // Preincrement use iterator so we don't invalidate it.
    ++UI;

    // Don't bother for PHI nodes.
    if (isa<PHINode>(User))
      continue;

    // Figure out which BB this cmp is used in.
    BasicBlock *UserBB = User->getParent();

    // If this user is in the same block as the cmp, don't change the cmp.
    if (UserBB == DefBB) continue;

    // If we have already inserted a cmp into this block, use it.
    CmpInst *&InsertedCmp = InsertedCmps[UserBB];

    if (!InsertedCmp) {
      BasicBlock::iterator InsertPt = UserBB->getFirstNonPHI();

      InsertedCmp =
        CmpInst::Create(CI->getOpcode(),
                        CI->getPredicate(),  CI->getOperand(0),
                        CI->getOperand(1), "", InsertPt);
      MadeChange = true;
    }

    // Replace a use of the cmp with a use of the new cmp.
    TheUse = InsertedCmp;
    ++NumCmpUses;
  }

  // If we removed all uses, nuke the cmp.
  if (CI->use_empty())
    CI->eraseFromParent();

  return MadeChange;
}
Exemplo n.º 8
0
// hasLifetimeMarkers - Check whether the given alloca already has
// lifetime.start or lifetime.end intrinsics.
static bool hasLifetimeMarkers(AllocaInst *AI) {
  Type *Int8PtrTy = Type::getInt8PtrTy(AI->getType()->getContext());
  if (AI->getType() == Int8PtrTy)
    return isUsedByLifetimeMarker(AI);

  // Do a scan to find all the casts to i8*.
  for (Value::use_iterator I = AI->use_begin(), E = AI->use_end(); I != E;
       ++I) {
    if (I->getType() != Int8PtrTy) continue;
    if (I->stripPointerCasts() != AI) continue;
    if (isUsedByLifetimeMarker(*I))
      return true;
  }
  return false;
}
Exemplo n.º 9
0
void BBCloner::UpdateSSA(Function &F) {
  DominatorTree &DT = getAnalysis<DominatorTree>();
  // The function has been greatly modified since the beginning.
  DT.runOnFunction(F);

  vector<pair<Instruction *, Use *> > ToResolve;
  for (ValueToValueMapTy::iterator I = CloneMap.begin();
       I != CloneMap.end();
       ++I) {
    Value *Key = const_cast<Value *>(I->first);
    if (Instruction *OldIns = dyn_cast<Instruction>(Key)) {
      for (Value::use_iterator UI = OldIns->use_begin();
           UI != OldIns->use_end();
           ++UI) {
        if (Instruction *User = dyn_cast<Instruction>(*UI)) {
          if (!DT.dominates(OldIns, User))
            ToResolve.push_back(make_pair(OldIns, &UI.getUse()));
        }
      }
      Instruction *NewIns = cast<Instruction>(I->second);
      for (Value::use_iterator UI = NewIns->use_begin();
           UI != NewIns->use_end();
           ++UI) {
        if (Instruction *User = dyn_cast<Instruction>(*UI)) {
          if (!DT.dominates(NewIns, User)) {
            // Use OldIns intentionally.
            ToResolve.push_back(make_pair(OldIns, &UI.getUse()));
          }
        }
      }
    }
  }

  for (size_t i = 0; i < ToResolve.size(); ) {
    Instruction *OldIns = ToResolve[i].first;
    Instruction *NewIns = cast<Instruction>(CloneMap.lookup(OldIns));
    SSAUpdater SU;
    SU.Initialize(OldIns->getType(), OldIns->getName());
    SU.AddAvailableValue(OldIns->getParent(), OldIns);
    SU.AddAvailableValue(NewIns->getParent(), NewIns);
    size_t j = i;
    while (j < ToResolve.size() && ToResolve[j].first == ToResolve[i].first) {
      SU.RewriteUse(*ToResolve[j].second);
      ++j;
    }
    i = j;
  }
}
Exemplo n.º 10
0
/// FindAllMemoryUses - Recursively walk all the uses of I until we find a
/// memory use.  If we find an obviously non-foldable instruction, return true.
/// Add the ultimately found memory instructions to MemoryUses.
static bool FindAllMemoryUses(Instruction *I,
                SmallVectorImpl<std::pair<Instruction*,unsigned> > &MemoryUses,
                              SmallPtrSet<Instruction*, 16> &ConsideredInsts,
                              const TargetLowering &TLI) {
  // If we already considered this instruction, we're done.
  if (!ConsideredInsts.insert(I))
    return false;
  
  // If this is an obviously unfoldable instruction, bail out.
  if (!MightBeFoldableInst(I))
    return true;

  // Loop over all the uses, recursively processing them.
  for (Value::use_iterator UI = I->use_begin(), E = I->use_end();
       UI != E; ++UI) {
    User *U = *UI;

    if (LoadInst *LI = dyn_cast<LoadInst>(U)) {
      MemoryUses.push_back(std::make_pair(LI, UI.getOperandNo()));
      continue;
    }
    
    if (StoreInst *SI = dyn_cast<StoreInst>(U)) {
      unsigned opNo = UI.getOperandNo();
      if (opNo == 0) return true; // Storing addr, not into addr.
      MemoryUses.push_back(std::make_pair(SI, opNo));
      continue;
    }
    
    if (CallInst *CI = dyn_cast<CallInst>(U)) {
      InlineAsm *IA = dyn_cast<InlineAsm>(CI->getCalledValue());
      if (!IA) return true;
      
      // If this is a memory operand, we're cool, otherwise bail out.
      if (!IsOperandAMemoryOperand(CI, IA, I, TLI))
        return true;
      continue;
    }
    
    if (FindAllMemoryUses(cast<Instruction>(U), MemoryUses, ConsideredInsts,
                          TLI))
      return true;
  }

  return false;
}
Exemplo n.º 11
0
void ARM64PromoteConstant::
  computeInsertionPoints(Constant *Val,
                         InsertionPointsPerFunc &InsPtsPerFunc) {
    DEBUG(dbgs() << "** Compute insertion points **\n");
  for (Value::use_iterator UseIt = Val->use_begin(), EndUseIt = Val->use_end();
       UseIt != EndUseIt; ++UseIt) {
    // If the user is not an Instruction, we cannot modify it
    if (!isa<Instruction>(*UseIt))
      continue;
    
    // Filter out uses that should not be converted
    if (!shouldConvertUse(Val, cast<Instruction>(*UseIt), UseIt.getOperandNo()))
      continue;
    
    DEBUG(dbgs() << "Considered use, opidx " << UseIt.getOperandNo() << ":\n");
    DEBUG(UseIt->print(dbgs()));
    DEBUG(dbgs() << '\n');
    
    Instruction *InsertionPoint = findInsertionPoint(UseIt);
    
    DEBUG(dbgs() << "Considered insertion point:\n");
    DEBUG(InsertionPoint->print(dbgs()));
    DEBUG(dbgs() << '\n');

    // Check if the current insertion point is useless, i.e., it is dominated
    // by another one.
    InsertionPoints &InsertPts =
      InsPtsPerFunc[InsertionPoint->getParent()->getParent()];
    if (isDominated(InsertionPoint, UseIt, InsertPts))
      continue;
    // This insertion point is useful, check if we can merge some insertion
    // point in a common dominator or if NewPt dominates an existing one.
    if (tryAndMerge(InsertionPoint, UseIt, InsertPts))
      continue;
    
    DEBUG(dbgs() << "Keep considered insertion point\n");
    
    // It is definitely useful by its own
    InsertPts[InsertionPoint].push_back(UseIt);
  }
}
Exemplo n.º 12
0
// For each instruction used by the value, remove() the function that contains
// the instruction. This should happen right before a call to RAUW.
void MergeFunctions::removeUsers(Value *V) {
  std::vector<Value *> Worklist;
  Worklist.push_back(V);
  while (!Worklist.empty()) {
    Value *V = Worklist.back();
    Worklist.pop_back();

    for (Value::use_iterator UI = V->use_begin(), UE = V->use_end();
         UI != UE; ++UI) {
      Use &U = UI.getUse();
      if (Instruction *I = dyn_cast<Instruction>(U.getUser())) {
        remove(I->getParent()->getParent());
      } else if (isa<GlobalValue>(U.getUser())) {
        // do nothing
      } else if (Constant *C = dyn_cast<Constant>(U.getUser())) {
        for (Value::use_iterator CUI = C->use_begin(), CUE = C->use_end();
             CUI != CUE; ++CUI)
          Worklist.push_back(*CUI);
      }
    }
  }
}
Exemplo n.º 13
0
bool HeterotbbTransform::runOnModule(Module &M) {

    bool localChange = true;
    TD = getAnalysisIfAvailable<DataLayout>();
    //hetero_f_const = NULL;
    rewrite_CPP(M);

#if 0
    Function *offload_func = M.getFunction("offload");
    for (Value::use_iterator i = offload_func->use_begin(), e = offload_func->use_end(); i != e; ++i) {
        Instruction *call;
        DEBUG(dbgs() << "Next _offload function:");
        i->dump();
        if ((call = dyn_cast<InvokeInst>(*i)) || (call = dyn_cast<CallInst>(*i))) {
            CallSite CI(cast<Instruction>(call));
            CI->dump();
        }
    }
#endif
    //M.dump();
    return localChange;
}
Exemplo n.º 14
0
/// AllUsesDominatedByBlock - Return true if all uses of the specified value
/// occur in blocks dominated by the specified block.
bool Sinking::AllUsesDominatedByBlock(Instruction *Inst,
                                      BasicBlock *BB) const {
  // Ignoring debug uses is necessary so debug info doesn't affect the code.
  // This may leave a referencing dbg_value in the original block, before
  // the definition of the vreg.  Dwarf generator handles this although the
  // user might not get the right info at runtime.
  for (Value::use_iterator I = Inst->use_begin(),
       E = Inst->use_end(); I != E; ++I) {
    // Determine the block of the use.
    Instruction *UseInst = cast<Instruction>(*I);
    BasicBlock *UseBlock = UseInst->getParent();
    if (PHINode *PN = dyn_cast<PHINode>(UseInst)) {
      // PHI nodes use the operand in the predecessor block, not the block with
      // the PHI.
      unsigned Num = PHINode::getIncomingValueNumForOperand(I.getOperandNo());
      UseBlock = PN->getIncomingBlock(Num);
    }
    // Check that it dominates.
    if (!DT->dominates(BB, UseBlock))
      return false;
  }
  return true;
}
Exemplo n.º 15
0
/// scanForInterest - This function decides which arguments would be worth
/// specializing on.
void PartSpec::scanForInterest(Function& F, InterestingArgVector& args) {
  for(Function::arg_iterator ii = F.arg_begin(), ee = F.arg_end();
      ii != ee; ++ii) {
    for(Value::use_iterator ui = ii->use_begin(), ue = ii->use_end();
        ui != ue; ++ui) {

      bool interesting = false;
      User *U = *ui;
      if (isa<CmpInst>(U)) interesting = true;
      else if (isa<CallInst>(U))
        interesting = ui->getOperand(0) == ii;
      else if (isa<InvokeInst>(U))
        interesting = ui->getOperand(0) == ii;
      else if (isa<SwitchInst>(U)) interesting = true;
      else if (isa<BranchInst>(U)) interesting = true;

      if (interesting) {
        args.push_back(std::distance(F.arg_begin(), ii));
        break;
      }
    }
  }
}
Exemplo n.º 16
0
/// OptimizeNoopCopyExpression - If the specified cast instruction is a noop
/// copy (e.g. it's casting from one pointer type to another, i32->i8 on PPC),
/// sink it into user blocks to reduce the number of virtual
/// registers that must be created and coalesced.
///
/// Return true if any changes are made.
///
static bool OptimizeNoopCopyExpression(CastInst *CI, const TargetLowering &TLI) {
    // If this is a noop copy,
    EVT SrcVT = TLI.getValueType(CI->getOperand(0)->getType());
    EVT DstVT = TLI.getValueType(CI->getType());

    // This is an fp<->int conversion?
    if (SrcVT.isInteger() != DstVT.isInteger())
        return false;

    // If this is an extension, it will be a zero or sign extension, which
    // isn't a noop.
    if (SrcVT.bitsLT(DstVT)) return false;

    // If these values will be promoted, find out what they will be promoted
    // to.  This helps us consider truncates on PPC as noop copies when they
    // are.
    if (TLI.getTypeAction(CI->getContext(), SrcVT) ==
            TargetLowering::TypePromoteInteger)
        SrcVT = TLI.getTypeToTransformTo(CI->getContext(), SrcVT);
    if (TLI.getTypeAction(CI->getContext(), DstVT) ==
            TargetLowering::TypePromoteInteger)
        DstVT = TLI.getTypeToTransformTo(CI->getContext(), DstVT);

    // If, after promotion, these are the same types, this is a noop copy.
    if (SrcVT != DstVT)
        return false;

    BasicBlock *DefBB = CI->getParent();

    /// InsertedCasts - Only insert a cast in each block once.
    DenseMap<BasicBlock*, CastInst*> InsertedCasts;

    bool MadeChange = false;
    for (Value::use_iterator UI = CI->use_begin(), E = CI->use_end();
            UI != E; ) {
        Use &TheUse = UI.getUse();
        Instruction *User = cast<Instruction>(*UI);

        // Figure out which BB this cast is used in.  For PHI's this is the
        // appropriate predecessor block.
        BasicBlock *UserBB = User->getParent();
        if (PHINode *PN = dyn_cast<PHINode>(User)) {
            UserBB = PN->getIncomingBlock(UI);
        }

        // Preincrement use iterator so we don't invalidate it.
        ++UI;

        // If this user is in the same block as the cast, don't change the cast.
        if (UserBB == DefBB) continue;

        // If we have already inserted a cast into this block, use it.
        CastInst *&InsertedCast = InsertedCasts[UserBB];

        if (!InsertedCast) {
            BasicBlock::iterator InsertPt = UserBB->getFirstInsertionPt();
            InsertedCast =
                CastInst::Create(CI->getOpcode(), CI->getOperand(0), CI->getType(), "",
                                 InsertPt);
            MadeChange = true;
        }

        // Replace a use of the cast with a use of the new cast.
        TheUse = InsertedCast;
        ++NumCastUses;
    }

    // If we removed all uses, nuke the cast.
    if (CI->use_empty()) {
        CI->eraseFromParent();
        MadeChange = true;
    }

    return MadeChange;
}
Exemplo n.º 17
0
bool CodeGenPrepare::OptimizeExtUses(Instruction *I) {
    BasicBlock *DefBB = I->getParent();

    // If the result of a {s|z}ext and its source are both live out, rewrite all
    // other uses of the source with result of extension.
    Value *Src = I->getOperand(0);
    if (Src->hasOneUse())
        return false;

    // Only do this xform if truncating is free.
    if (TLI && !TLI->isTruncateFree(I->getType(), Src->getType()))
        return false;

    // Only safe to perform the optimization if the source is also defined in
    // this block.
    if (!isa<Instruction>(Src) || DefBB != cast<Instruction>(Src)->getParent())
        return false;

    bool DefIsLiveOut = false;
    for (Value::use_iterator UI = I->use_begin(), E = I->use_end();
            UI != E; ++UI) {
        Instruction *User = cast<Instruction>(*UI);

        // Figure out which BB this ext is used in.
        BasicBlock *UserBB = User->getParent();
        if (UserBB == DefBB) continue;
        DefIsLiveOut = true;
        break;
    }
    if (!DefIsLiveOut)
        return false;

    // Make sure non of the uses are PHI nodes.
    for (Value::use_iterator UI = Src->use_begin(), E = Src->use_end();
            UI != E; ++UI) {
        Instruction *User = cast<Instruction>(*UI);
        BasicBlock *UserBB = User->getParent();
        if (UserBB == DefBB) continue;
        // Be conservative. We don't want this xform to end up introducing
        // reloads just before load / store instructions.
        if (isa<PHINode>(User) || isa<LoadInst>(User) || isa<StoreInst>(User))
            return false;
    }

    // InsertedTruncs - Only insert one trunc in each block once.
    DenseMap<BasicBlock*, Instruction*> InsertedTruncs;

    bool MadeChange = false;
    for (Value::use_iterator UI = Src->use_begin(), E = Src->use_end();
            UI != E; ++UI) {
        Use &TheUse = UI.getUse();
        Instruction *User = cast<Instruction>(*UI);

        // Figure out which BB this ext is used in.
        BasicBlock *UserBB = User->getParent();
        if (UserBB == DefBB) continue;

        // Both src and def are live in this block. Rewrite the use.
        Instruction *&InsertedTrunc = InsertedTruncs[UserBB];

        if (!InsertedTrunc) {
            BasicBlock::iterator InsertPt = UserBB->getFirstInsertionPt();
            InsertedTrunc = new TruncInst(I, Src->getType(), "", InsertPt);
        }

        // Replace a use of the {s|z}ext source with a use of the result.
        TheUse = InsertedTrunc;
        ++NumExtUses;
        MadeChange = true;
    }

    return MadeChange;
}
Exemplo n.º 18
0
//
// Method: runOnModule()
//
// Description:
//  Entry point for this LLVM pass.  Search for functions which could be called
//  indirectly and create clones for them which are only called by direct
//  calls.
//
// Inputs:
//  M - A reference to the LLVM module to transform.
//
// Outputs:
//  M - The transformed LLVM module.
//
// Return value:
//  true  - The module was modified.
//  false - The module was not modified.
//
bool
IndClone::runOnModule(Module& M) {
  // Set of functions to clone
  std::vector<Function*> toClone;

  //
  // Check all of the functions in the module.  If the function could be called
  // by an indirect function call, add it to our worklist of functions to
  // clone.
  //
  for (Module::iterator I = M.begin(); I != M.end(); ++I) {
    // Flag whether the function should be cloned
    bool pleaseCloneTheFunction = false;

    //
    // Only clone functions which are defined and cannot be replaced by another
    // function by the linker.
    //
    if (!I->isDeclaration() && !I->mayBeOverridden()) {
      for (Value::use_iterator ui = I->use_begin(), ue = I->use_end();
          ui != ue; ++ui) {
        if (!isa<CallInst>(*ui) && !isa<InvokeInst>(*ui)) {
          if(!ui->use_empty())
          //
          // If this function is used for anything other than a direct function
          // call, then we want to clone it.
          //
          pleaseCloneTheFunction = true;
        } else {
          //
          // This is a call instruction, but hold up ranger!  We need to make
          // sure that the function isn't passed as an argument to *another*
          // function.  That would make the function usable in an indirect
          // function call.
          //
          for (unsigned index = 1; index < ui->getNumOperands(); ++index) {
            if (ui->getOperand(index)->stripPointerCasts() == I) {
              pleaseCloneTheFunction = true;
              break;
            }
          }
        }

        //
        // If we've discovered that the function could be used by an indirect
        // call site, schedule it for cloning.
        //
        if (pleaseCloneTheFunction) {
          toClone.push_back(I);
          break;
        }
      }
    }
  }

  //
  // Update the statistics on the number of functions we'll be cloning.
  // We only update the statistic if we want to clone one or more functions;
  // due to the magic of how statistics work, avoiding assignment prevents it
  // from needlessly showing up.
  //
  if (toClone.size())
    numCloned += toClone.size();

  //
  // Go through the worklist and clone each function.  After cloning a
  // function, change all direct calls to use the clone instead of using the
  // original function.
  //
  for (unsigned index = 0; index < toClone.size(); ++index) {
    //
    // Clone the function and give it a name indicating that it is a clone to
    // be used for direct function calls.
    //
    Function * Original = toClone[index];
    Function* DirectF = CloneFunction(Original);
    DirectF->setName(Original->getName() + "_DIRECT");

    //
    // Make the clone internal; external code can use the original function.
    //
    DirectF->setLinkage(GlobalValue::InternalLinkage);

    //
    // Link the cloned function into the set of functions belonging to the
    // module.
    //
    Original->getParent()->getFunctionList().push_back(DirectF);

    //
    // Find all uses of the function that use it as a direct call.  Change
    // them to use the clone.
    //
    for (Value::use_iterator ui = Original->use_begin(),
                             ue = Original->use_end();
        ui != ue; ) {
      CallInst *CI = dyn_cast<CallInst>(*ui);
      ui++;
      if (CI) {
        if (CI->getCalledFunction() == Original) {
          ++numReplaced;
          CI->setCalledFunction(DirectF);
        }
      }
    }
  }
  
  //
  // Assume that we've cloned at least one function.
  //
  return true;
}
/// SplitCriticalEdge - If this edge is a critical edge, insert a new node to
/// split the critical edge.  This will update DominatorTree and
/// DominatorFrontier information if it is available, thus calling this pass
/// will not invalidate either of them. This returns the new block if the edge
/// was split, null otherwise.
///
/// If MergeIdenticalEdges is true (not the default), *all* edges from TI to the
/// specified successor will be merged into the same critical edge block.  
/// This is most commonly interesting with switch instructions, which may 
/// have many edges to any one destination.  This ensures that all edges to that
/// dest go to one block instead of each going to a different block, but isn't 
/// the standard definition of a "critical edge".
///
/// It is invalid to call this function on a critical edge that starts at an
/// IndirectBrInst.  Splitting these edges will almost always create an invalid
/// program because the address of the new block won't be the one that is jumped
/// to.
///
BasicBlock *llvm::SplitCriticalEdge(TerminatorInst *TI, unsigned SuccNum,
                                    Pass *P, bool MergeIdenticalEdges) {
  if (!isCriticalEdge(TI, SuccNum, MergeIdenticalEdges)) return 0;
  
  assert(!isa<IndirectBrInst>(TI) &&
         "Cannot split critical edge from IndirectBrInst");
  
  BasicBlock *TIBB = TI->getParent();
  BasicBlock *DestBB = TI->getSuccessor(SuccNum);

  // Create a new basic block, linking it into the CFG.
  BasicBlock *NewBB = BasicBlock::Create(TI->getContext(),
                      TIBB->getName() + "." + DestBB->getName() + "_crit_edge");
  // Create our unconditional branch.
  BranchInst::Create(DestBB, NewBB);

  // Branch to the new block, breaking the edge.
  TI->setSuccessor(SuccNum, NewBB);

  // Insert the block into the function... right after the block TI lives in.
  Function &F = *TIBB->getParent();
  Function::iterator FBBI = TIBB;
  F.getBasicBlockList().insert(++FBBI, NewBB);
  
  // If there are any PHI nodes in DestBB, we need to update them so that they
  // merge incoming values from NewBB instead of from TIBB.
  if (PHINode *APHI = dyn_cast<PHINode>(DestBB->begin())) {
    // This conceptually does:
    //  foreach (PHINode *PN in DestBB)
    //    PN->setIncomingBlock(PN->getIncomingBlock(TIBB), NewBB);
    // but is optimized for two cases.
    
    if (APHI->getNumIncomingValues() <= 8) {  // Small # preds case.
      unsigned BBIdx = 0;
      for (BasicBlock::iterator I = DestBB->begin(); isa<PHINode>(I); ++I) {
        // We no longer enter through TIBB, now we come in through NewBB.
        // Revector exactly one entry in the PHI node that used to come from
        // TIBB to come from NewBB.
        PHINode *PN = cast<PHINode>(I);
        
        // Reuse the previous value of BBIdx if it lines up.  In cases where we
        // have multiple phi nodes with *lots* of predecessors, this is a speed
        // win because we don't have to scan the PHI looking for TIBB.  This
        // happens because the BB list of PHI nodes are usually in the same
        // order.
        if (PN->getIncomingBlock(BBIdx) != TIBB)
          BBIdx = PN->getBasicBlockIndex(TIBB);
        PN->setIncomingBlock(BBIdx, NewBB);
      }
    } else {
      // However, the foreach loop is slow for blocks with lots of predecessors
      // because PHINode::getIncomingBlock is O(n) in # preds.  Instead, walk
      // the user list of TIBB to find the PHI nodes.
      SmallPtrSet<PHINode*, 16> UpdatedPHIs;
    
      for (Value::use_iterator UI = TIBB->use_begin(), E = TIBB->use_end();
           UI != E; ) {
        Value::use_iterator Use = UI++;
        if (PHINode *PN = dyn_cast<PHINode>(Use)) {
          // Remove one entry from each PHI.
          if (PN->getParent() == DestBB && UpdatedPHIs.insert(PN))
            PN->setOperand(Use.getOperandNo(), NewBB);
        }
      }
    }
  }
   
  // If there are any other edges from TIBB to DestBB, update those to go
  // through the split block, making those edges non-critical as well (and
  // reducing the number of phi entries in the DestBB if relevant).
  if (MergeIdenticalEdges) {
    for (unsigned i = SuccNum+1, e = TI->getNumSuccessors(); i != e; ++i) {
      if (TI->getSuccessor(i) != DestBB) continue;
      
      // Remove an entry for TIBB from DestBB phi nodes.
      DestBB->removePredecessor(TIBB);
      
      // We found another edge to DestBB, go to NewBB instead.
      TI->setSuccessor(i, NewBB);
    }
  }
  
  

  // If we don't have a pass object, we can't update anything...
  if (P == 0) return NewBB;
  
  DominatorTree *DT = P->getAnalysisIfAvailable<DominatorTree>();
  DominanceFrontier *DF = P->getAnalysisIfAvailable<DominanceFrontier>();
  LoopInfo *LI = P->getAnalysisIfAvailable<LoopInfo>();
  ProfileInfo *PI = P->getAnalysisIfAvailable<ProfileInfo>();
  
  // If we have nothing to update, just return.
  if (DT == 0 && DF == 0 && LI == 0 && PI == 0)
    return NewBB;

  // Now update analysis information.  Since the only predecessor of NewBB is
  // the TIBB, TIBB clearly dominates NewBB.  TIBB usually doesn't dominate
  // anything, as there are other successors of DestBB.  However, if all other
  // predecessors of DestBB are already dominated by DestBB (e.g. DestBB is a
  // loop header) then NewBB dominates DestBB.
  SmallVector<BasicBlock*, 8> OtherPreds;

  // If there is a PHI in the block, loop over predecessors with it, which is
  // faster than iterating pred_begin/end.
  if (PHINode *PN = dyn_cast<PHINode>(DestBB->begin())) {
    for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
      if (PN->getIncomingBlock(i) != NewBB)
        OtherPreds.push_back(PN->getIncomingBlock(i));
  } else {
    for (pred_iterator I = pred_begin(DestBB), E = pred_end(DestBB);
         I != E; ++I)
      if (*I != NewBB)
        OtherPreds.push_back(*I);
  }
  
  bool NewBBDominatesDestBB = true;
  
  // Should we update DominatorTree information?
  if (DT) {
    DomTreeNode *TINode = DT->getNode(TIBB);

    // The new block is not the immediate dominator for any other nodes, but
    // TINode is the immediate dominator for the new node.
    //
    if (TINode) {       // Don't break unreachable code!
      DomTreeNode *NewBBNode = DT->addNewBlock(NewBB, TIBB);
      DomTreeNode *DestBBNode = 0;
     
      // If NewBBDominatesDestBB hasn't been computed yet, do so with DT.
      if (!OtherPreds.empty()) {
        DestBBNode = DT->getNode(DestBB);
        while (!OtherPreds.empty() && NewBBDominatesDestBB) {
          if (DomTreeNode *OPNode = DT->getNode(OtherPreds.back()))
            NewBBDominatesDestBB = DT->dominates(DestBBNode, OPNode);
          OtherPreds.pop_back();
        }
        OtherPreds.clear();
      }
      
      // If NewBBDominatesDestBB, then NewBB dominates DestBB, otherwise it
      // doesn't dominate anything.
      if (NewBBDominatesDestBB) {
        if (!DestBBNode) DestBBNode = DT->getNode(DestBB);
        DT->changeImmediateDominator(DestBBNode, NewBBNode);
      }
    }
  }

  // Should we update DominanceFrontier information?
  if (DF) {
    // If NewBBDominatesDestBB hasn't been computed yet, do so with DF.
    if (!OtherPreds.empty()) {
      // FIXME: IMPLEMENT THIS!
      llvm_unreachable("Requiring domfrontiers but not idom/domtree/domset."
                       " not implemented yet!");
    }
    
    // Since the new block is dominated by its only predecessor TIBB,
    // it cannot be in any block's dominance frontier.  If NewBB dominates
    // DestBB, its dominance frontier is the same as DestBB's, otherwise it is
    // just {DestBB}.
    DominanceFrontier::DomSetType NewDFSet;
    if (NewBBDominatesDestBB) {
      DominanceFrontier::iterator I = DF->find(DestBB);
      if (I != DF->end()) {
        DF->addBasicBlock(NewBB, I->second);
        
        if (I->second.count(DestBB)) {
          // However NewBB's frontier does not include DestBB.
          DominanceFrontier::iterator NF = DF->find(NewBB);
          DF->removeFromFrontier(NF, DestBB);
        }
      }
      else
        DF->addBasicBlock(NewBB, DominanceFrontier::DomSetType());
    } else {
      DominanceFrontier::DomSetType NewDFSet;
      NewDFSet.insert(DestBB);
      DF->addBasicBlock(NewBB, NewDFSet);
    }
  }
  
  // Update LoopInfo if it is around.
  if (LI) {
    if (Loop *TIL = LI->getLoopFor(TIBB)) {
      // If one or the other blocks were not in a loop, the new block is not
      // either, and thus LI doesn't need to be updated.
      if (Loop *DestLoop = LI->getLoopFor(DestBB)) {
        if (TIL == DestLoop) {
          // Both in the same loop, the NewBB joins loop.
          DestLoop->addBasicBlockToLoop(NewBB, LI->getBase());
        } else if (TIL->contains(DestLoop)) {
          // Edge from an outer loop to an inner loop.  Add to the outer loop.
          TIL->addBasicBlockToLoop(NewBB, LI->getBase());
        } else if (DestLoop->contains(TIL)) {
          // Edge from an inner loop to an outer loop.  Add to the outer loop.
          DestLoop->addBasicBlockToLoop(NewBB, LI->getBase());
        } else {
          // Edge from two loops with no containment relation.  Because these
          // are natural loops, we know that the destination block must be the
          // header of its loop (adding a branch into a loop elsewhere would
          // create an irreducible loop).
          assert(DestLoop->getHeader() == DestBB &&
                 "Should not create irreducible loops!");
          if (Loop *P = DestLoop->getParentLoop())
            P->addBasicBlockToLoop(NewBB, LI->getBase());
        }
      }
      // If TIBB is in a loop and DestBB is outside of that loop, split the
      // other exit blocks of the loop that also have predecessors outside
      // the loop, to maintain a LoopSimplify guarantee.
      if (!TIL->contains(DestBB) &&
          P->mustPreserveAnalysisID(LoopSimplifyID)) {
        assert(!TIL->contains(NewBB) &&
               "Split point for loop exit is contained in loop!");

        // Update LCSSA form in the newly created exit block.
        if (P->mustPreserveAnalysisID(LCSSAID)) {
          SmallVector<BasicBlock *, 1> OrigPred;
          OrigPred.push_back(TIBB);
          CreatePHIsForSplitLoopExit(OrigPred, NewBB, DestBB);
        }

        // For each unique exit block...
        SmallVector<BasicBlock *, 4> ExitBlocks;
        TIL->getExitBlocks(ExitBlocks);
        for (unsigned i = 0, e = ExitBlocks.size(); i != e; ++i) {
          // Collect all the preds that are inside the loop, and note
          // whether there are any preds outside the loop.
          SmallVector<BasicBlock *, 4> Preds;
          bool HasPredOutsideOfLoop = false;
          BasicBlock *Exit = ExitBlocks[i];
          for (pred_iterator I = pred_begin(Exit), E = pred_end(Exit);
               I != E; ++I)
            if (TIL->contains(*I))
              Preds.push_back(*I);
            else
              HasPredOutsideOfLoop = true;
          // If there are any preds not in the loop, we'll need to split
          // the edges. The Preds.empty() check is needed because a block
          // may appear multiple times in the list. We can't use
          // getUniqueExitBlocks above because that depends on LoopSimplify
          // form, which we're in the process of restoring!
          if (!Preds.empty() && HasPredOutsideOfLoop) {
            BasicBlock *NewExitBB =
              SplitBlockPredecessors(Exit, Preds.data(), Preds.size(),
                                     "split", P);
            if (P->mustPreserveAnalysisID(LCSSAID))
              CreatePHIsForSplitLoopExit(Preds, NewExitBB, Exit);
          }
        }
      }
      // LCSSA form was updated above for the case where LoopSimplify is
      // available, which means that all predecessors of loop exit blocks
      // are within the loop. Without LoopSimplify form, it would be
      // necessary to insert a new phi.
      assert((!P->mustPreserveAnalysisID(LCSSAID) ||
              P->mustPreserveAnalysisID(LoopSimplifyID)) &&
             "SplitCriticalEdge doesn't know how to update LCCSA form "
             "without LoopSimplify!");
    }
  }

  // Update ProfileInfo if it is around.
  if (PI)
    PI->splitEdge(TIBB, DestBB, NewBB, MergeIdenticalEdges);

  return NewBB;
}
Exemplo n.º 20
0
Arquivo: LICM.cpp Projeto: nobled/llvm
/// sink - When an instruction is found to only be used outside of the loop,
/// this function moves it to the exit blocks and patches up SSA form as needed.
/// This method is guaranteed to remove the original instruction from its
/// position, and may either delete it or move it to outside of the loop.
///
void LICM::sink(Instruction &I) {
  DEBUG(dbgs() << "LICM sinking instruction: " << I << "\n");

  SmallVector<BasicBlock*, 8> ExitBlocks;
  CurLoop->getUniqueExitBlocks(ExitBlocks);

  if (isa<LoadInst>(I)) ++NumMovedLoads;
  else if (isa<CallInst>(I)) ++NumMovedCalls;
  ++NumSunk;
  Changed = true;

  // The case where there is only a single exit node of this loop is common
  // enough that we handle it as a special (more efficient) case.  It is more
  // efficient to handle because there are no PHI nodes that need to be placed.
  if (ExitBlocks.size() == 1) {
    if (!DT->dominates(I.getParent(), ExitBlocks[0])) {
      // Instruction is not used, just delete it.
      CurAST->deleteValue(&I);
      // If I has users in unreachable blocks, eliminate.
      // If I is not void type then replaceAllUsesWith undef.
      // This allows ValueHandlers and custom metadata to adjust itself.
      if (!I.use_empty())
        I.replaceAllUsesWith(UndefValue::get(I.getType()));
      I.eraseFromParent();
    } else {
      // Move the instruction to the start of the exit block, after any PHI
      // nodes in it.
      I.moveBefore(ExitBlocks[0]->getFirstInsertionPt());

      // This instruction is no longer in the AST for the current loop, because
      // we just sunk it out of the loop.  If we just sunk it into an outer
      // loop, we will rediscover the operation when we process it.
      CurAST->deleteValue(&I);
    }
    return;
  }

  if (ExitBlocks.empty()) {
    // The instruction is actually dead if there ARE NO exit blocks.
    CurAST->deleteValue(&I);
    // If I has users in unreachable blocks, eliminate.
    // If I is not void type then replaceAllUsesWith undef.
    // This allows ValueHandlers and custom metadata to adjust itself.
    if (!I.use_empty())
      I.replaceAllUsesWith(UndefValue::get(I.getType()));
    I.eraseFromParent();
    return;
  }

  // Otherwise, if we have multiple exits, use the SSAUpdater to do all of the
  // hard work of inserting PHI nodes as necessary.
  SmallVector<PHINode*, 8> NewPHIs;
  SSAUpdater SSA(&NewPHIs);

  if (!I.use_empty())
    SSA.Initialize(I.getType(), I.getName());

  // Insert a copy of the instruction in each exit block of the loop that is
  // dominated by the instruction.  Each exit block is known to only be in the
  // ExitBlocks list once.
  BasicBlock *InstOrigBB = I.getParent();
  unsigned NumInserted = 0;

  for (unsigned i = 0, e = ExitBlocks.size(); i != e; ++i) {
    BasicBlock *ExitBlock = ExitBlocks[i];

    if (!DT->dominates(InstOrigBB, ExitBlock))
      continue;

    // Insert the code after the last PHI node.
    BasicBlock::iterator InsertPt = ExitBlock->getFirstInsertionPt();

    // If this is the first exit block processed, just move the original
    // instruction, otherwise clone the original instruction and insert
    // the copy.
    Instruction *New;
    if (NumInserted++ == 0) {
      I.moveBefore(InsertPt);
      New = &I;
    } else {
      New = I.clone();
      if (!I.getName().empty())
        New->setName(I.getName()+".le");
      ExitBlock->getInstList().insert(InsertPt, New);
    }

    // Now that we have inserted the instruction, inform SSAUpdater.
    if (!I.use_empty())
      SSA.AddAvailableValue(ExitBlock, New);
  }

  // If the instruction doesn't dominate any exit blocks, it must be dead.
  if (NumInserted == 0) {
    CurAST->deleteValue(&I);
    if (!I.use_empty())
      I.replaceAllUsesWith(UndefValue::get(I.getType()));
    I.eraseFromParent();
    return;
  }

  // Next, rewrite uses of the instruction, inserting PHI nodes as needed.
  for (Value::use_iterator UI = I.use_begin(), UE = I.use_end(); UI != UE; ) {
    // Grab the use before incrementing the iterator.
    Use &U = UI.getUse();
    // Increment the iterator before removing the use from the list.
    ++UI;
    SSA.RewriteUseAfterInsertions(U);
  }

  // Update CurAST for NewPHIs if I had pointer type.
  if (I.getType()->isPointerTy())
    for (unsigned i = 0, e = NewPHIs.size(); i != e; ++i)
      CurAST->copyValue(&I, NewPHIs[i]);

  // Finally, remove the instruction from CurAST.  It is no longer in the loop.
  CurAST->deleteValue(&I);
}
Exemplo n.º 21
0
void DuettoNativeRewriter::rewriteConstructorImplementation(Module& M, Function& F)
{
	//Copy the code in a function with the right signature
	Function* newFunc=getReturningConstructor(M, &F);
	if(!newFunc->empty())
		return;

	//Visit each instruction and take note of the ones that needs to be replaced
	Function::const_iterator B=F.begin();
	Function::const_iterator BE=F.end();
	ValueToValueMapTy valueMap;
	CallInst* lowerConstructor = NULL;
	const CallInst* oldLowerConstructor = NULL;
	for(;B!=BE;++B)
	{
		BasicBlock::const_iterator I=B->begin();
		BasicBlock::const_iterator IE=B->end();
		for(;I!=IE;++I)
		{
			if(I->getOpcode()!=Instruction::Call)
				continue;
			const CallInst* callInst=cast<CallInst>(&(*I));
			Function* f=callInst->getCalledFunction();
			if(!f)
				continue;
			const char* startOfType;
			const char* endOfType;
			if(!DuettoNativeRewriter::isBuiltinConstructor(f->getName().data(), startOfType, endOfType))
				continue;
			//Check that the constructor is for 'this'
			if(callInst->getOperand(0)!=F.arg_begin())
				continue;
			//If this is another constructor for the same type, change it to a
			//returning constructor and use it as the 'this' argument
			Function* newFunc = getReturningConstructor(M, f);
			llvm::SmallVector<Value*, 4> newArgs;
			for(unsigned i=1;i<callInst->getNumArgOperands();i++)
				newArgs.push_back(callInst->getArgOperand(i));
			lowerConstructor = CallInst::Create(newFunc, newArgs);
			oldLowerConstructor = callInst;
			break;
		}
		if(lowerConstructor)
			break;
	}

	//Clone the linkage first
	newFunc->setLinkage(F.getLinkage());
	Function::arg_iterator origArg=++F.arg_begin();
	Function::arg_iterator newArg=newFunc->arg_begin();
	valueMap.insert(make_pair(F.arg_begin(), lowerConstructor));

	for(unsigned i=1;i<F.arg_size();i++)
	{
		valueMap.insert(make_pair(&(*origArg), &(*newArg)));
		++origArg;
		++newArg;
	}
	SmallVector<ReturnInst*, 4> returns;
	CloneFunctionInto(newFunc, &F, valueMap, false, returns);

	//Find the right place to add the base construtor call
	assert(lowerConstructor->getNumArgOperands()<=1 && "Native constructors with multiple args are not supported");
	Instruction* callPred = NULL;
	if (lowerConstructor->getNumArgOperands()==1 && Instruction::classof(lowerConstructor->getArgOperand(0)))
	{
		//Switch the argument to the one in the new func
		lowerConstructor->setArgOperand(0, valueMap[lowerConstructor->getArgOperand(0)]);
		callPred = cast<Instruction>(lowerConstructor->getArgOperand(0));
	}
	else
		callPred = &newFunc->getEntryBlock().front();

	//Add add it
	lowerConstructor->insertAfter(callPred);

	//Override the returs values
	for(unsigned i=0;i<returns.size();i++)
	{
		Instruction* newInst = ReturnInst::Create(M.getContext(),lowerConstructor);
		newInst->insertBefore(returns[i]);
		returns[i]->removeFromParent();
	}
	//Recursively move all the users of the lower constructor after the call itself
	Instruction* insertPoint = lowerConstructor->getNextNode();
	SmallVector<Value*, 4> usersQueue(lowerConstructor->getNumUses());
	unsigned int i;
	Value::use_iterator it;
	for(i=usersQueue.size()-1,it=lowerConstructor->use_begin();it!=lowerConstructor->use_end();++it,i--)
		usersQueue[i]=it->getUser();

	SmallSet<Instruction*, 4> movedInstructions;
	while(!usersQueue.empty())
	{
		Instruction* cur=dyn_cast<Instruction>(usersQueue.pop_back_val());
		if(!cur)
			continue;
		if(movedInstructions.count(cur))
			continue;
		movedInstructions.insert(cur);
		cur->moveBefore(insertPoint);
		//Add users of this instrucution as well
		usersQueue.resize(usersQueue.size()+cur->getNumUses());
		for(i=usersQueue.size()-1,it=cur->use_begin();it!=cur->use_end();++it,i--)
			usersQueue[i]=it->getUser();
	}
	cast<Instruction>(valueMap[oldLowerConstructor])->eraseFromParent();
}
Exemplo n.º 22
0
/// SurveyUse - This looks at a single use of an argument or return value
/// and determines if it should be alive or not. Adds this use to MaybeLiveUses
/// if it causes the used value to become MaybeAlive.
///
/// RetValNum is the return value number to use when this use is used in a
/// return instruction. This is used in the recursion, you should always leave
/// it at 0.
DAE::Liveness DAE::SurveyUse(Value::use_iterator U, UseVector &MaybeLiveUses,
                             unsigned RetValNum) {
    Value *V = *U;
    if (ReturnInst *RI = dyn_cast<ReturnInst>(V)) {
      // The value is returned from a function. It's only live when the
      // function's return value is live. We use RetValNum here, for the case
      // that U is really a use of an insertvalue instruction that uses the
      // orginal Use.
      RetOrArg Use = CreateRet(RI->getParent()->getParent(), RetValNum);
      // We might be live, depending on the liveness of Use.
      return MarkIfNotLive(Use, MaybeLiveUses);
    }
    if (InsertValueInst *IV = dyn_cast<InsertValueInst>(V)) {
      if (U.getOperandNo() != InsertValueInst::getAggregateOperandIndex()
          && IV->hasIndices())
        // The use we are examining is inserted into an aggregate. Our liveness
        // depends on all uses of that aggregate, but if it is used as a return
        // value, only index at which we were inserted counts.
        RetValNum = *IV->idx_begin();

      // Note that if we are used as the aggregate operand to the insertvalue,
      // we don't change RetValNum, but do survey all our uses.

      Liveness Result = MaybeLive;
      for (Value::use_iterator I = IV->use_begin(),
           E = V->use_end(); I != E; ++I) {
        Result = SurveyUse(I, MaybeLiveUses, RetValNum);
        if (Result == Live)
          break;
      }
      return Result;
    }
    CallSite CS = CallSite::get(V);
    if (CS.getInstruction()) {
      Function *F = CS.getCalledFunction();
      if (F) {
        // Used in a direct call.
  
        // Find the argument number. We know for sure that this use is an
        // argument, since if it was the function argument this would be an
        // indirect call and the we know can't be looking at a value of the
        // label type (for the invoke instruction).
        unsigned ArgNo = CS.getArgumentNo(U.getOperandNo());

        if (ArgNo >= F->getFunctionType()->getNumParams())
          // The value is passed in through a vararg! Must be live.
          return Live;

        assert(CS.getArgument(ArgNo) 
               == CS.getInstruction()->getOperand(U.getOperandNo()) 
               && "Argument is not where we expected it");

        // Value passed to a normal call. It's only live when the corresponding
        // argument to the called function turns out live.
        RetOrArg Use = CreateArg(F, ArgNo);
        return MarkIfNotLive(Use, MaybeLiveUses);
      }
    }
    // Used in any other way? Value must be live.
    return Live;
}
Exemplo n.º 23
0
AllocaInst* Variables::changeLocal(Value* value, PointerType* newType) {
  AllocaInst *oldTarget = dyn_cast<AllocaInst>(value);
  PointerType* oldPointerType = dyn_cast<PointerType>(oldTarget->getType());
  PointerType *oldType = dyn_cast<PointerType>(oldPointerType->getElementType());
  AllocaInst *newTarget = NULL;

  errs() << "Changing the precision of pointer variable \"" << oldTarget->getName() << "\" from " << *oldType 
	 << " to " << *newType << ".\n";

  if (diffTypes(newType, oldType)) {
    newTarget = new AllocaInst(newType, getInt32(1), "", oldTarget);

    // we are not calling getAlignment because in this case double requires 16. Investigate further.
    unsigned alignment;
    switch(newType->getElementType()->getTypeID()) {
      case Type::FloatTyID: 
        alignment = 4;
        break;
      case Type::DoubleTyID:
        alignment = 8;
        break;
      case Type::X86_FP80TyID:
        alignment = 16;
      break;
    default:
      alignment = 0;
    } 
    
    newTarget->setAlignment(alignment); // depends on type? 8 for float? 16 for double?
    newTarget->takeName(oldTarget);

    // iterating through instructions using old AllocaInst
    vector<Instruction*> erase;
    Value::use_iterator it = oldTarget->use_begin();

#ifdef DEBUG
    errs() << "\nOld target: ";
    oldTarget->dump();
#endif

    for(; it != oldTarget->use_end(); it++) {
#ifdef DEBUG
      errs() << "\nA use: ";
      it->dump();

      errs() << "\n===============================\n";
      errs() << "\nTransforming use\n";
#endif

      bool is_erased = Transformer::transform(it, newTarget, oldTarget, newType, oldType, alignment);

      if (!is_erased) {
        erase.push_back(dyn_cast<Instruction>(*it));
      }

#ifdef DEBUG
      errs() << "\nDone transforming use\n";
#endif
    }
    
    // erasing uses of old instructions
    for(unsigned int i = 0; i < erase.size(); i++) {
      erase[i]->eraseFromParent();
    }
    // erase old instruction
    //oldTarget->eraseFromParent();

#ifdef DEBUG
    errs() << "DONE ALL TRANSFORMATION FOR POINTER\n";
#endif

  } else {
    errs() << "\tNo changes required.\n";
  }

  return newTarget;
}
Exemplo n.º 24
0
/// ProcessInstruction - Given an instruction in the loop, check to see if it
/// has any uses that are outside the current loop.  If so, insert LCSSA PHI
/// nodes and rewrite the uses.
bool LCSSA::ProcessInstruction(Instruction *Inst,
                               const SmallVectorImpl<BasicBlock*> &ExitBlocks) {
  SmallVector<Use*, 16> UsesToRewrite;
  
  BasicBlock *InstBB = Inst->getParent();
  
  for (Value::use_iterator UI = Inst->use_begin(), E = Inst->use_end();
       UI != E; ++UI) {
    User *U = *UI;
    BasicBlock *UserBB = cast<Instruction>(U)->getParent();
    if (PHINode *PN = dyn_cast<PHINode>(U))
      UserBB = PN->getIncomingBlock(UI);
    
    if (InstBB != UserBB && !inLoop(UserBB))
      UsesToRewrite.push_back(&UI.getUse());
  }

  // If there are no uses outside the loop, exit with no change.
  if (UsesToRewrite.empty()) return false;
  
  ++NumLCSSA; // We are applying the transformation

  // Invoke instructions are special in that their result value is not available
  // along their unwind edge. The code below tests to see whether DomBB dominates
  // the value, so adjust DomBB to the normal destination block, which is
  // effectively where the value is first usable.
  BasicBlock *DomBB = Inst->getParent();
  if (InvokeInst *Inv = dyn_cast<InvokeInst>(Inst))
    DomBB = Inv->getNormalDest();

  DomTreeNode *DomNode = DT->getNode(DomBB);

  SSAUpdater SSAUpdate;
  SSAUpdate.Initialize(Inst->getType(), Inst->getName());
  
  // Insert the LCSSA phi's into all of the exit blocks dominated by the
  // value, and add them to the Phi's map.
  for (SmallVectorImpl<BasicBlock*>::const_iterator BBI = ExitBlocks.begin(),
      BBE = ExitBlocks.end(); BBI != BBE; ++BBI) {
    BasicBlock *ExitBB = *BBI;
    if (!DT->dominates(DomNode, DT->getNode(ExitBB))) continue;
    
    // If we already inserted something for this BB, don't reprocess it.
    if (SSAUpdate.HasValueForBlock(ExitBB)) continue;
    
    PHINode *PN = PHINode::Create(Inst->getType(), Inst->getName()+".lcssa",
                                  ExitBB->begin());
    PN->reserveOperandSpace(PredCache.GetNumPreds(ExitBB));

    // Add inputs from inside the loop for this PHI.
    for (BasicBlock **PI = PredCache.GetPreds(ExitBB); *PI; ++PI) {
      PN->addIncoming(Inst, *PI);

      // If the exit block has a predecessor not within the loop, arrange for
      // the incoming value use corresponding to that predecessor to be
      // rewritten in terms of a different LCSSA PHI.
      if (!inLoop(*PI))
        UsesToRewrite.push_back(
          &PN->getOperandUse(
            PN->getOperandNumForIncomingValue(PN->getNumIncomingValues()-1)));
    }
    
    // Remember that this phi makes the value alive in this block.
    SSAUpdate.AddAvailableValue(ExitBB, PN);
  }
  
  // Rewrite all uses outside the loop in terms of the new PHIs we just
  // inserted.
  for (unsigned i = 0, e = UsesToRewrite.size(); i != e; ++i) {
    // If this use is in an exit block, rewrite to use the newly inserted PHI.
    // This is required for correctness because SSAUpdate doesn't handle uses in
    // the same block.  It assumes the PHI we inserted is at the end of the
    // block.
    Instruction *User = cast<Instruction>(UsesToRewrite[i]->getUser());
    BasicBlock *UserBB = User->getParent();
    if (PHINode *PN = dyn_cast<PHINode>(User))
      UserBB = PN->getIncomingBlock(*UsesToRewrite[i]);

    if (isa<PHINode>(UserBB->begin()) &&
        isExitBlock(UserBB, ExitBlocks)) {
      UsesToRewrite[i]->set(UserBB->begin());
      continue;
    }
    
    // Otherwise, do full PHI insertion.
    SSAUpdate.RewriteUse(*UsesToRewrite[i]);
  }
  
  return true;
}
/// isOnlyCopiedFromConstantGlobal - Recursively walk the uses of a (derived)
/// pointer to an alloca.  Ignore any reads of the pointer, return false if we
/// see any stores or other unknown uses.  If we see pointer arithmetic, keep
/// track of whether it moves the pointer (with IsOffset) but otherwise traverse
/// the uses.  If we see a memcpy/memmove that targets an unoffseted pointer to
/// the alloca, and if the source pointer is a pointer to a constant global, we
/// can optimize this.
static bool
isOnlyCopiedFromConstantGlobal(Value *V, MemTransferInst *&TheCopy,
                               SmallVectorImpl<Instruction *> &ToDelete,
                               bool IsOffset = false) {
  // We track lifetime intrinsics as we encounter them.  If we decide to go
  // ahead and replace the value with the global, this lets the caller quickly
  // eliminate the markers.

  for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI!=E; ++UI) {
    User *U = cast<Instruction>(*UI);

    if (LoadInst *LI = dyn_cast<LoadInst>(U)) {
      // Ignore non-volatile loads, they are always ok.
      if (!LI->isSimple()) return false;
      continue;
    }

    if (BitCastInst *BCI = dyn_cast<BitCastInst>(U)) {
      // If uses of the bitcast are ok, we are ok.
      if (!isOnlyCopiedFromConstantGlobal(BCI, TheCopy, ToDelete, IsOffset))
        return false;
      continue;
    }
    if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(U)) {
      // If the GEP has all zero indices, it doesn't offset the pointer.  If it
      // doesn't, it does.
      if (!isOnlyCopiedFromConstantGlobal(GEP, TheCopy, ToDelete,
                                          IsOffset || !GEP->hasAllZeroIndices()))
        return false;
      continue;
    }

    if (CallSite CS = U) {
      // If this is the function being called then we treat it like a load and
      // ignore it.
      if (CS.isCallee(UI))
        continue;

      // If this is a readonly/readnone call site, then we know it is just a
      // load (but one that potentially returns the value itself), so we can
      // ignore it if we know that the value isn't captured.
      unsigned ArgNo = CS.getArgumentNo(UI);
      if (CS.onlyReadsMemory() &&
          (CS.getInstruction()->use_empty() || CS.doesNotCapture(ArgNo)))
        continue;

      // If this is being passed as a byval argument, the caller is making a
      // copy, so it is only a read of the alloca.
      if (CS.isByValArgument(ArgNo))
        continue;
    }

    // Lifetime intrinsics can be handled by the caller.
    if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(U)) {
      if (II->getIntrinsicID() == Intrinsic::lifetime_start ||
          II->getIntrinsicID() == Intrinsic::lifetime_end) {
        assert(II->use_empty() && "Lifetime markers have no result to use!");
        ToDelete.push_back(II);
        continue;
      }
    }

    // If this is isn't our memcpy/memmove, reject it as something we can't
    // handle.
    MemTransferInst *MI = dyn_cast<MemTransferInst>(U);
    if (MI == 0)
      return false;

    // If the transfer is using the alloca as a source of the transfer, then
    // ignore it since it is a load (unless the transfer is volatile).
    if (UI.getOperandNo() == 1) {
      if (MI->isVolatile()) return false;
      continue;
    }

    // If we already have seen a copy, reject the second one.
    if (TheCopy) return false;

    // If the pointer has been offset from the start of the alloca, we can't
    // safely handle this.
    if (IsOffset) return false;

    // If the memintrinsic isn't using the alloca as the dest, reject it.
    if (UI.getOperandNo() != 0) return false;

    // If the source of the memcpy/move is not a constant global, reject it.
    if (!pointsToConstantGlobal(MI->getSource()))
      return false;

    // Otherwise, the transform is safe.  Remember the copy instruction.
    TheCopy = MI;
  }
  return true;
}