// SurveyFunction - This performs the initial survey of the specified function,
// checking out whether or not it uses any of its incoming arguments or whether
// any callers use the return value.  This fills in the LiveValues set and Uses
// map.
//
// We consider arguments of non-internal functions to be intrinsically alive as
// well as arguments to functions which have their "address taken".
//
void DAE::SurveyFunction(const Function &F) {
  unsigned RetCount = NumRetVals(&F);
  // Assume all return values are dead
  typedef SmallVector<Liveness, 5> RetVals;
  RetVals RetValLiveness(RetCount, MaybeLive);

  typedef SmallVector<UseVector, 5> RetUses;
  // These vectors map each return value to the uses that make it MaybeLive, so
  // we can add those to the Uses map if the return value really turns out to be
  // MaybeLive. Initialized to a list of RetCount empty lists.
  RetUses MaybeLiveRetUses(RetCount);

  for (Function::const_iterator BB = F.begin(), E = F.end(); BB != E; ++BB)
    if (const ReturnInst *RI = dyn_cast<ReturnInst>(BB->getTerminator()))
      if (RI->getNumOperands() != 0 && RI->getOperand(0)->getType()
          != F.getFunctionType()->getReturnType()) {
        // We don't support old style multiple return values.
        MarkLive(F);
        return;
      }

  if (!F.hasLocalLinkage() && (!ShouldHackArguments() || F.isIntrinsic())) {
    MarkLive(F);
    return;
  }

  DEBUG(dbgs() << "DAE - Inspecting callers for fn: " << F.getName() << "\n");
  // Keep track of the number of live retvals, so we can skip checks once all
  // of them turn out to be live.
  unsigned NumLiveRetVals = 0;
  Type *STy = dyn_cast<StructType>(F.getReturnType());
  // Loop all uses of the function.
  for (Value::const_use_iterator I = F.use_begin(), E = F.use_end();
       I != E; ++I) {
    // If the function is PASSED IN as an argument, its address has been
    // taken.
    ImmutableCallSite CS(*I);
    if (!CS || !CS.isCallee(I)) {
      MarkLive(F);
      return;
    }

    // If this use is anything other than a call site, the function is alive.
    const Instruction *TheCall = CS.getInstruction();
    if (!TheCall) {   // Not a direct call site?
      MarkLive(F);
      return;
    }

    // If we end up here, we are looking at a direct call to our function.

    // Now, check how our return value(s) is/are used in this caller. Don't
    // bother checking return values if all of them are live already.
    if (NumLiveRetVals != RetCount) {
      if (STy) {
        // Check all uses of the return value.
        for (Value::const_use_iterator I = TheCall->use_begin(),
             E = TheCall->use_end(); I != E; ++I) {
          const ExtractValueInst *Ext = dyn_cast<ExtractValueInst>(*I);
          if (Ext && Ext->hasIndices()) {
            // This use uses a part of our return value, survey the uses of
            // that part and store the results for this index only.
            unsigned Idx = *Ext->idx_begin();
            if (RetValLiveness[Idx] != Live) {
              RetValLiveness[Idx] = SurveyUses(Ext, MaybeLiveRetUses[Idx]);
              if (RetValLiveness[Idx] == Live)
                NumLiveRetVals++;
            }
          } else {
            // Used by something else than extractvalue. Mark all return
            // values as live.
            for (unsigned i = 0; i != RetCount; ++i )
              RetValLiveness[i] = Live;
            NumLiveRetVals = RetCount;
            break;
          }
        }
      } else {
        // Single return value
        RetValLiveness[0] = SurveyUses(TheCall, MaybeLiveRetUses[0]);
        if (RetValLiveness[0] == Live)
          NumLiveRetVals = RetCount;
      }
    }
  }

  // Now we've inspected all callers, record the liveness of our return values.
  for (unsigned i = 0; i != RetCount; ++i)
    MarkValue(CreateRet(&F, i), RetValLiveness[i], MaybeLiveRetUses[i]);

  DEBUG(dbgs() << "DAE - Inspecting args for fn: " << F.getName() << "\n");

  // Now, check all of our arguments.
  unsigned i = 0;
  UseVector MaybeLiveArgUses;
  for (Function::const_arg_iterator AI = F.arg_begin(),
       E = F.arg_end(); AI != E; ++AI, ++i) {
    // See what the effect of this use is (recording any uses that cause
    // MaybeLive in MaybeLiveArgUses).
    Liveness Result = SurveyUses(AI, MaybeLiveArgUses);
    // Mark the result.
    MarkValue(CreateArg(&F, i), Result, MaybeLiveArgUses);
    // Clear the vector again for the next iteration.
    MaybeLiveArgUses.clear();
  }
}
// SurveyFunction - This performs the initial survey of the specified function,
// checking out whether or not it uses any of its incoming arguments or whether
// any callers use the return value.  This fills in the LiveValues set and Uses
// map.
//
// We consider arguments of non-internal functions to be intrinsically alive as
// well as arguments to functions which have their "address taken".
//
void DAE::SurveyFunction(const Function &F) {
  // Functions with inalloca parameters are expecting args in a particular
  // register and memory layout.
  if (F.getAttributes().hasAttrSomewhere(Attribute::InAlloca)) {
    MarkLive(F);
    return;
  }

  // Don't touch naked functions. The assembly might be using an argument, or
  // otherwise rely on the frame layout in a way that this analysis will not
  // see.
  if (F.hasFnAttribute(Attribute::Naked)) {
    MarkLive(F);
    return;
  }

  unsigned RetCount = NumRetVals(&F);
  // Assume all return values are dead
  typedef SmallVector<Liveness, 5> RetVals;
  RetVals RetValLiveness(RetCount, MaybeLive);

  typedef SmallVector<UseVector, 5> RetUses;
  // These vectors map each return value to the uses that make it MaybeLive, so
  // we can add those to the Uses map if the return value really turns out to be
  // MaybeLive. Initialized to a list of RetCount empty lists.
  RetUses MaybeLiveRetUses(RetCount);

  for (Function::const_iterator BB = F.begin(), E = F.end(); BB != E; ++BB)
    if (const ReturnInst *RI = dyn_cast<ReturnInst>(BB->getTerminator()))
      if (RI->getNumOperands() != 0 && RI->getOperand(0)->getType()
          != F.getFunctionType()->getReturnType()) {
        // We don't support old style multiple return values.
        MarkLive(F);
        return;
      }

  if (!F.hasLocalLinkage() && (!ShouldHackArguments() || F.isIntrinsic())) {
    MarkLive(F);
    return;
  }

  DEBUG(dbgs() << "DAE - Inspecting callers for fn: " << F.getName() << "\n");
  // Keep track of the number of live retvals, so we can skip checks once all
  // of them turn out to be live.
  unsigned NumLiveRetVals = 0;
  // Loop all uses of the function.
  for (const Use &U : F.uses()) {
    // If the function is PASSED IN as an argument, its address has been
    // taken.
    ImmutableCallSite CS(U.getUser());
    if (!CS || !CS.isCallee(&U)) {
      MarkLive(F);
      return;
    }

    // If this use is anything other than a call site, the function is alive.
    const Instruction *TheCall = CS.getInstruction();
    if (!TheCall) {   // Not a direct call site?
      MarkLive(F);
      return;
    }

    // If we end up here, we are looking at a direct call to our function.

    // Now, check how our return value(s) is/are used in this caller. Don't
    // bother checking return values if all of them are live already.
    if (NumLiveRetVals == RetCount)
      continue;

    // Check all uses of the return value.
    for (const Use &U : TheCall->uses()) {
      if (ExtractValueInst *Ext = dyn_cast<ExtractValueInst>(U.getUser())) {
        // This use uses a part of our return value, survey the uses of
        // that part and store the results for this index only.
        unsigned Idx = *Ext->idx_begin();
        if (RetValLiveness[Idx] != Live) {
          RetValLiveness[Idx] = SurveyUses(Ext, MaybeLiveRetUses[Idx]);
          if (RetValLiveness[Idx] == Live)
            NumLiveRetVals++;
        }
      } else {
        // Used by something else than extractvalue. Survey, but assume that the
        // result applies to all sub-values.
        UseVector MaybeLiveAggregateUses;
        if (SurveyUse(&U, MaybeLiveAggregateUses) == Live) {
          NumLiveRetVals = RetCount;
          RetValLiveness.assign(RetCount, Live);
          break;
        } else {
          for (unsigned i = 0; i != RetCount; ++i) {
            if (RetValLiveness[i] != Live)
              MaybeLiveRetUses[i].append(MaybeLiveAggregateUses.begin(),
                                         MaybeLiveAggregateUses.end());
          }
        }
      }
    }
  }

  // Now we've inspected all callers, record the liveness of our return values.
  for (unsigned i = 0; i != RetCount; ++i)
    MarkValue(CreateRet(&F, i), RetValLiveness[i], MaybeLiveRetUses[i]);

  DEBUG(dbgs() << "DAE - Inspecting args for fn: " << F.getName() << "\n");

  // Now, check all of our arguments.
  unsigned i = 0;
  UseVector MaybeLiveArgUses;
  for (Function::const_arg_iterator AI = F.arg_begin(),
       E = F.arg_end(); AI != E; ++AI, ++i) {
    Liveness Result;
    if (F.getFunctionType()->isVarArg()) {
      // Variadic functions will already have a va_arg function expanded inside
      // them, making them potentially very sensitive to ABI changes resulting
      // from removing arguments entirely, so don't. For example AArch64 handles
      // register and stack HFAs very differently, and this is reflected in the
      // IR which has already been generated.
      Result = Live;
    } else {
      // See what the effect of this use is (recording any uses that cause
      // MaybeLive in MaybeLiveArgUses). 
      Result = SurveyUses(&*AI, MaybeLiveArgUses);
    }

    // Mark the result.
    MarkValue(CreateArg(&F, i), Result, MaybeLiveArgUses);
    // Clear the vector again for the next iteration.
    MaybeLiveArgUses.clear();
  }
}
void FunctionLoweringInfo::set(const Function &fn, MachineFunction &mf,
                               SelectionDAG *DAG) {
  Fn = &fn;
  MF = &mf;
  TLI = MF->getSubtarget().getTargetLowering();
  RegInfo = &MF->getRegInfo();
  MachineModuleInfo &MMI = MF->getMMI();

  // Check whether the function can return without sret-demotion.
  SmallVector<ISD::OutputArg, 4> Outs;
  GetReturnInfo(Fn->getReturnType(), Fn->getAttributes(), Outs, *TLI);
  CanLowerReturn = TLI->CanLowerReturn(Fn->getCallingConv(), *MF,
                                       Fn->isVarArg(), Outs, Fn->getContext());

  // Initialize the mapping of values to registers.  This is only set up for
  // instruction values that are used outside of the block that defines
  // them.
  Function::const_iterator BB = Fn->begin(), EB = Fn->end();
  for (; BB != EB; ++BB)
    for (BasicBlock::const_iterator I = BB->begin(), E = BB->end();
         I != E; ++I) {
      if (const AllocaInst *AI = dyn_cast<AllocaInst>(I)) {
        // Static allocas can be folded into the initial stack frame adjustment.
        if (AI->isStaticAlloca()) {
          const ConstantInt *CUI = cast<ConstantInt>(AI->getArraySize());
          Type *Ty = AI->getAllocatedType();
          uint64_t TySize = TLI->getDataLayout()->getTypeAllocSize(Ty);
          unsigned Align =
              std::max((unsigned)TLI->getDataLayout()->getPrefTypeAlignment(Ty),
                       AI->getAlignment());

          TySize *= CUI->getZExtValue();   // Get total allocated size.
          if (TySize == 0) TySize = 1; // Don't create zero-sized stack objects.

          StaticAllocaMap[AI] =
            MF->getFrameInfo()->CreateStackObject(TySize, Align, false, AI);

        } else {
          unsigned Align = std::max(
              (unsigned)TLI->getDataLayout()->getPrefTypeAlignment(
                AI->getAllocatedType()),
              AI->getAlignment());
          unsigned StackAlign =
              MF->getSubtarget().getFrameLowering()->getStackAlignment();
          if (Align <= StackAlign)
            Align = 0;
          // Inform the Frame Information that we have variable-sized objects.
          MF->getFrameInfo()->CreateVariableSizedObject(Align ? Align : 1, AI);
        }
      }

      // Look for inline asm that clobbers the SP register.
      if (isa<CallInst>(I) || isa<InvokeInst>(I)) {
        ImmutableCallSite CS(I);
        if (isa<InlineAsm>(CS.getCalledValue())) {
          unsigned SP = TLI->getStackPointerRegisterToSaveRestore();
          const TargetRegisterInfo *TRI = MF->getSubtarget().getRegisterInfo();
          std::vector<TargetLowering::AsmOperandInfo> Ops =
              TLI->ParseConstraints(TRI, CS);
          for (size_t I = 0, E = Ops.size(); I != E; ++I) {
            TargetLowering::AsmOperandInfo &Op = Ops[I];
            if (Op.Type == InlineAsm::isClobber) {
              // Clobbers don't have SDValue operands, hence SDValue().
              TLI->ComputeConstraintToUse(Op, SDValue(), DAG);
              std::pair<unsigned, const TargetRegisterClass *> PhysReg =
                  TLI->getRegForInlineAsmConstraint(TRI, Op.ConstraintCode,
                                                    Op.ConstraintVT);
              if (PhysReg.first == SP)
                MF->getFrameInfo()->setHasInlineAsmWithSPAdjust(true);
            }
          }
        }
      }

      // Look for calls to the @llvm.va_start intrinsic. We can omit some
      // prologue boilerplate for variadic functions that don't examine their
      // arguments.
      if (const auto *II = dyn_cast<IntrinsicInst>(I)) {
        if (II->getIntrinsicID() == Intrinsic::vastart)
          MF->getFrameInfo()->setHasVAStart(true);
      }

      // If we have a musttail call in a variadic funciton, we need to ensure we
      // forward implicit register parameters.
      if (const auto *CI = dyn_cast<CallInst>(I)) {
        if (CI->isMustTailCall() && Fn->isVarArg())
          MF->getFrameInfo()->setHasMustTailInVarArgFunc(true);
      }

      // Mark values used outside their block as exported, by allocating
      // a virtual register for them.
      if (isUsedOutsideOfDefiningBlock(I))
        if (!isa<AllocaInst>(I) ||
            !StaticAllocaMap.count(cast<AllocaInst>(I)))
          InitializeRegForValue(I);

      // Collect llvm.dbg.declare information. This is done now instead of
      // during the initial isel pass through the IR so that it is done
      // in a predictable order.
      if (const DbgDeclareInst *DI = dyn_cast<DbgDeclareInst>(I)) {
        assert(DI->getVariable() && "Missing variable");
        assert(DI->getDebugLoc() && "Missing location");
        if (MMI.hasDebugInfo()) {
          // Don't handle byval struct arguments or VLAs, for example.
          // Non-byval arguments are handled here (they refer to the stack
          // temporary alloca at this point).
          const Value *Address = DI->getAddress();
          if (Address) {
            if (const BitCastInst *BCI = dyn_cast<BitCastInst>(Address))
              Address = BCI->getOperand(0);
            if (const AllocaInst *AI = dyn_cast<AllocaInst>(Address)) {
              DenseMap<const AllocaInst *, int>::iterator SI =
                StaticAllocaMap.find(AI);
              if (SI != StaticAllocaMap.end()) { // Check for VLAs.
                int FI = SI->second;
                MMI.setVariableDbgInfo(DI->getVariable(), DI->getExpression(),
                                       FI, DI->getDebugLoc());
              }
            }
          }
        }
      }

      // Decide the preferred extend type for a value.
      PreferredExtendType[I] = getPreferredExtendForValue(I);
    }

  // Create an initial MachineBasicBlock for each LLVM BasicBlock in F.  This
  // also creates the initial PHI MachineInstrs, though none of the input
  // operands are populated.
  for (BB = Fn->begin(); BB != EB; ++BB) {
    MachineBasicBlock *MBB = mf.CreateMachineBasicBlock(BB);
    MBBMap[BB] = MBB;
    MF->push_back(MBB);

    // Transfer the address-taken flag. This is necessary because there could
    // be multiple MachineBasicBlocks corresponding to one BasicBlock, and only
    // the first one should be marked.
    if (BB->hasAddressTaken())
      MBB->setHasAddressTaken();

    // Create Machine PHI nodes for LLVM PHI nodes, lowering them as
    // appropriate.
    for (BasicBlock::const_iterator I = BB->begin();
         const PHINode *PN = dyn_cast<PHINode>(I); ++I) {
      if (PN->use_empty()) continue;

      // Skip empty types
      if (PN->getType()->isEmptyTy())
        continue;

      DebugLoc DL = PN->getDebugLoc();
      unsigned PHIReg = ValueMap[PN];
      assert(PHIReg && "PHI node does not have an assigned virtual register!");

      SmallVector<EVT, 4> ValueVTs;
      ComputeValueVTs(*TLI, PN->getType(), ValueVTs);
      for (unsigned vti = 0, vte = ValueVTs.size(); vti != vte; ++vti) {
        EVT VT = ValueVTs[vti];
        unsigned NumRegisters = TLI->getNumRegisters(Fn->getContext(), VT);
        const TargetInstrInfo *TII = MF->getSubtarget().getInstrInfo();
        for (unsigned i = 0; i != NumRegisters; ++i)
          BuildMI(MBB, DL, TII->get(TargetOpcode::PHI), PHIReg + i);
        PHIReg += NumRegisters;
      }
    }
  }

  // Mark landing pad blocks.
  SmallVector<const LandingPadInst *, 4> LPads;
  for (BB = Fn->begin(); BB != EB; ++BB) {
    if (const auto *Invoke = dyn_cast<InvokeInst>(BB->getTerminator()))
      MBBMap[Invoke->getSuccessor(1)]->setIsLandingPad();
    if (BB->isLandingPad())
      LPads.push_back(BB->getLandingPadInst());
  }

  // If this is an MSVC EH personality, we need to do a bit more work.
  EHPersonality Personality = EHPersonality::Unknown;
  if (!LPads.empty())
    Personality = classifyEHPersonality(LPads.back()->getPersonalityFn());
  if (!isMSVCEHPersonality(Personality))
    return;

  if (Personality == EHPersonality::MSVC_Win64SEH ||
      Personality == EHPersonality::MSVC_X86SEH) {
    addSEHHandlersForLPads(LPads);
  }

  WinEHFuncInfo &EHInfo = MMI.getWinEHFuncInfo(&fn);
  if (Personality == EHPersonality::MSVC_CXX) {
    const Function *WinEHParentFn = MMI.getWinEHParent(&fn);
    calculateWinCXXEHStateNumbers(WinEHParentFn, EHInfo);
  }

  // Copy the state numbers to LandingPadInfo for the current function, which
  // could be a handler or the parent. This should happen for 32-bit SEH and
  // C++ EH.
  if (Personality == EHPersonality::MSVC_CXX ||
      Personality == EHPersonality::MSVC_X86SEH) {
    for (const LandingPadInst *LP : LPads) {
      MachineBasicBlock *LPadMBB = MBBMap[LP->getParent()];
      MMI.addWinEHState(LPadMBB, EHInfo.LandingPadStateMap[LP]);
    }
  }
}
void FunctionLoweringInfo::set(const Function &fn, MachineFunction &mf,
                               SelectionDAG *DAG) {
    const TargetLowering *TLI = TM.getTargetLowering();

    Fn = &fn;
    MF = &mf;
    RegInfo = &MF->getRegInfo();

    // Check whether the function can return without sret-demotion.
    SmallVector<ISD::OutputArg, 4> Outs;
    GetReturnInfo(Fn->getReturnType(), Fn->getAttributes(), Outs, *TLI);
    CanLowerReturn = TLI->CanLowerReturn(Fn->getCallingConv(), *MF,
                                         Fn->isVarArg(),
                                         Outs, Fn->getContext());

    // Initialize the mapping of values to registers.  This is only set up for
    // instruction values that are used outside of the block that defines
    // them.
    Function::const_iterator BB = Fn->begin(), EB = Fn->end();
    for (BasicBlock::const_iterator I = BB->begin(), E = BB->end(); I != E; ++I)
        if (const AllocaInst *AI = dyn_cast<AllocaInst>(I)) {
            // Don't fold inalloca allocas or other dynamic allocas into the initial
            // stack frame allocation, even if they are in the entry block.
            if (!AI->isStaticAlloca())
                continue;

            if (const ConstantInt *CUI = dyn_cast<ConstantInt>(AI->getArraySize())) {
                Type *Ty = AI->getAllocatedType();
                uint64_t TySize = TLI->getDataLayout()->getTypeAllocSize(Ty);
                unsigned Align =
                    std::max((unsigned)TLI->getDataLayout()->getPrefTypeAlignment(Ty),
                             AI->getAlignment());

                TySize *= CUI->getZExtValue();   // Get total allocated size.
                if (TySize == 0) TySize = 1; // Don't create zero-sized stack objects.

                StaticAllocaMap[AI] =
                    MF->getFrameInfo()->CreateStackObject(TySize, Align, false, AI);
            }
        }

    for (; BB != EB; ++BB)
        for (BasicBlock::const_iterator I = BB->begin(), E = BB->end();
                I != E; ++I) {
            // Look for dynamic allocas.
            if (const AllocaInst *AI = dyn_cast<AllocaInst>(I)) {
                if (!AI->isStaticAlloca()) {
                    unsigned Align = std::max(
                                         (unsigned)TLI->getDataLayout()->getPrefTypeAlignment(
                                             AI->getAllocatedType()),
                                         AI->getAlignment());
                    unsigned StackAlign = TM.getFrameLowering()->getStackAlignment();
                    if (Align <= StackAlign)
                        Align = 0;
                    // Inform the Frame Information that we have variable-sized objects.
                    MF->getFrameInfo()->CreateVariableSizedObject(Align ? Align : 1, AI);
                }
            }

            // Look for inline asm that clobbers the SP register.
            if (isa<CallInst>(I) || isa<InvokeInst>(I)) {
                ImmutableCallSite CS(I);
                if (isa<InlineAsm>(CS.getCalledValue())) {
                    unsigned SP = TLI->getStackPointerRegisterToSaveRestore();
                    std::vector<TargetLowering::AsmOperandInfo> Ops =
                        TLI->ParseConstraints(CS);
                    for (size_t I = 0, E = Ops.size(); I != E; ++I) {
                        TargetLowering::AsmOperandInfo &Op = Ops[I];
                        if (Op.Type == InlineAsm::isClobber) {
                            // Clobbers don't have SDValue operands, hence SDValue().
                            TLI->ComputeConstraintToUse(Op, SDValue(), DAG);
                            std::pair<unsigned, const TargetRegisterClass*> PhysReg =
                                TLI->getRegForInlineAsmConstraint(Op.ConstraintCode,
                                                                  Op.ConstraintVT);
                            if (PhysReg.first == SP)
                                MF->getFrameInfo()->setHasInlineAsmWithSPAdjust(true);
                        }
                    }
                }
            }

            // Mark values used outside their block as exported, by allocating
            // a virtual register for them.
            if (isUsedOutsideOfDefiningBlock(I))
                if (!isa<AllocaInst>(I) ||
                        !StaticAllocaMap.count(cast<AllocaInst>(I)))
                    InitializeRegForValue(I);

            // Collect llvm.dbg.declare information. This is done now instead of
            // during the initial isel pass through the IR so that it is done
            // in a predictable order.
            if (const DbgDeclareInst *DI = dyn_cast<DbgDeclareInst>(I)) {
                MachineModuleInfo &MMI = MF->getMMI();
                DIVariable DIVar(DI->getVariable());
                assert((!DIVar || DIVar.isVariable()) &&
                       "Variable in DbgDeclareInst should be either null or a DIVariable.");
                if (MMI.hasDebugInfo() &&
                        DIVar &&
                        !DI->getDebugLoc().isUnknown()) {
                    // Don't handle byval struct arguments or VLAs, for example.
                    // Non-byval arguments are handled here (they refer to the stack
                    // temporary alloca at this point).
                    const Value *Address = DI->getAddress();
                    if (Address) {
                        if (const BitCastInst *BCI = dyn_cast<BitCastInst>(Address))
                            Address = BCI->getOperand(0);
                        if (const AllocaInst *AI = dyn_cast<AllocaInst>(Address)) {
                            DenseMap<const AllocaInst *, int>::iterator SI =
                                StaticAllocaMap.find(AI);
                            if (SI != StaticAllocaMap.end()) { // Check for VLAs.
                                int FI = SI->second;
                                MMI.setVariableDbgInfo(DI->getVariable(),
                                                       FI, DI->getDebugLoc());
                            }
                        }
                    }
                }
            }
        }

    // Create an initial MachineBasicBlock for each LLVM BasicBlock in F.  This
    // also creates the initial PHI MachineInstrs, though none of the input
    // operands are populated.
    for (BB = Fn->begin(); BB != EB; ++BB) {
        MachineBasicBlock *MBB = mf.CreateMachineBasicBlock(BB);
        MBBMap[BB] = MBB;
        MF->push_back(MBB);

        // Transfer the address-taken flag. This is necessary because there could
        // be multiple MachineBasicBlocks corresponding to one BasicBlock, and only
        // the first one should be marked.
        if (BB->hasAddressTaken())
            MBB->setHasAddressTaken();

        // Create Machine PHI nodes for LLVM PHI nodes, lowering them as
        // appropriate.
        for (BasicBlock::const_iterator I = BB->begin();
                const PHINode *PN = dyn_cast<PHINode>(I); ++I) {
            if (PN->use_empty()) continue;

            // Skip empty types
            if (PN->getType()->isEmptyTy())
                continue;

            DebugLoc DL = PN->getDebugLoc();
            unsigned PHIReg = ValueMap[PN];
            assert(PHIReg && "PHI node does not have an assigned virtual register!");

            SmallVector<EVT, 4> ValueVTs;
            ComputeValueVTs(*TLI, PN->getType(), ValueVTs);
            for (unsigned vti = 0, vte = ValueVTs.size(); vti != vte; ++vti) {
                EVT VT = ValueVTs[vti];
                unsigned NumRegisters = TLI->getNumRegisters(Fn->getContext(), VT);
                const TargetInstrInfo *TII = MF->getTarget().getInstrInfo();
                for (unsigned i = 0; i != NumRegisters; ++i)
                    BuildMI(MBB, DL, TII->get(TargetOpcode::PHI), PHIReg + i);
                PHIReg += NumRegisters;
            }
        }
    }

    // Mark landing pad blocks.
    for (BB = Fn->begin(); BB != EB; ++BB)
        if (const InvokeInst *Invoke = dyn_cast<InvokeInst>(BB->getTerminator()))
            MBBMap[Invoke->getSuccessor(1)]->setIsLandingPad();
}
Esempio n. 5
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/// InlineFunction - This function inlines the called function into the basic
/// block of the caller.  This returns false if it is not possible to inline
/// this call.  The program is still in a well defined state if this occurs
/// though.
///
/// Note that this only does one level of inlining.  For example, if the
/// instruction 'call B' is inlined, and 'B' calls 'C', then the call to 'C' now
/// exists in the instruction stream.  Similarly this will inline a recursive
/// function by one level.
bool llvm::InlineFunction(CallSite CS, InlineFunctionInfo &IFI,
                          bool InsertLifetime) {
  Instruction *TheCall = CS.getInstruction();
  assert(TheCall->getParent() && TheCall->getParent()->getParent() &&
         "Instruction not in function!");

  // If IFI has any state in it, zap it before we fill it in.
  IFI.reset();
  
  const Function *CalledFunc = CS.getCalledFunction();
  if (CalledFunc == 0 ||          // Can't inline external function or indirect
      CalledFunc->isDeclaration() || // call, or call to a vararg function!
      CalledFunc->getFunctionType()->isVarArg()) return false;

  // If the call to the callee is not a tail call, we must clear the 'tail'
  // flags on any calls that we inline.
  bool MustClearTailCallFlags =
    !(isa<CallInst>(TheCall) && cast<CallInst>(TheCall)->isTailCall());

  // If the call to the callee cannot throw, set the 'nounwind' flag on any
  // calls that we inline.
  bool MarkNoUnwind = CS.doesNotThrow();

  BasicBlock *OrigBB = TheCall->getParent();
  Function *Caller = OrigBB->getParent();

  // GC poses two hazards to inlining, which only occur when the callee has GC:
  //  1. If the caller has no GC, then the callee's GC must be propagated to the
  //     caller.
  //  2. If the caller has a differing GC, it is invalid to inline.
  if (CalledFunc->hasGC()) {
    if (!Caller->hasGC())
      Caller->setGC(CalledFunc->getGC());
    else if (CalledFunc->getGC() != Caller->getGC())
      return false;
  }

  // Get the personality function from the callee if it contains a landing pad.
  Value *CalleePersonality = 0;
  for (Function::const_iterator I = CalledFunc->begin(), E = CalledFunc->end();
       I != E; ++I)
    if (const InvokeInst *II = dyn_cast<InvokeInst>(I->getTerminator())) {
      const BasicBlock *BB = II->getUnwindDest();
      const LandingPadInst *LP = BB->getLandingPadInst();
      CalleePersonality = LP->getPersonalityFn();
      break;
    }

  // Find the personality function used by the landing pads of the caller. If it
  // exists, then check to see that it matches the personality function used in
  // the callee.
  if (CalleePersonality) {
    for (Function::const_iterator I = Caller->begin(), E = Caller->end();
         I != E; ++I)
      if (const InvokeInst *II = dyn_cast<InvokeInst>(I->getTerminator())) {
        const BasicBlock *BB = II->getUnwindDest();
        const LandingPadInst *LP = BB->getLandingPadInst();

        // If the personality functions match, then we can perform the
        // inlining. Otherwise, we can't inline.
        // TODO: This isn't 100% true. Some personality functions are proper
        //       supersets of others and can be used in place of the other.
        if (LP->getPersonalityFn() != CalleePersonality)
          return false;

        break;
      }
  }

  // Get an iterator to the last basic block in the function, which will have
  // the new function inlined after it.
  Function::iterator LastBlock = &Caller->back();

  // Make sure to capture all of the return instructions from the cloned
  // function.
  SmallVector<ReturnInst*, 8> Returns;
  ClonedCodeInfo InlinedFunctionInfo;
  Function::iterator FirstNewBlock;

  { // Scope to destroy VMap after cloning.
    ValueToValueMapTy VMap;

    assert(CalledFunc->arg_size() == CS.arg_size() &&
           "No varargs calls can be inlined!");

    // Calculate the vector of arguments to pass into the function cloner, which
    // matches up the formal to the actual argument values.
    CallSite::arg_iterator AI = CS.arg_begin();
    unsigned ArgNo = 0;
    for (Function::const_arg_iterator I = CalledFunc->arg_begin(),
         E = CalledFunc->arg_end(); I != E; ++I, ++AI, ++ArgNo) {
      Value *ActualArg = *AI;
      const Argument *Arg = I;

      // When byval arguments actually inlined, we need to make the copy implied
      // by them explicit.  However, we don't do this if the callee is readonly
      // or readnone, because the copy would be unneeded: the callee doesn't
      // modify the struct.
      if (CS.isByValArgument(ArgNo)) {
        ActualArg = HandleByValArgument(ActualArg, Arg, TheCall, CalledFunc, IFI,
                                        CalledFunc->getParamAlignment(ArgNo+1));
 
        // Calls that we inline may use the new alloca, so we need to clear
        // their 'tail' flags if HandleByValArgument introduced a new alloca and
        // the callee has calls.
        MustClearTailCallFlags |= ActualArg != *AI;
      }

      VMap[I] = ActualArg;
    }

    // We want the inliner to prune the code as it copies.  We would LOVE to
    // have no dead or constant instructions leftover after inlining occurs
    // (which can happen, e.g., because an argument was constant), but we'll be
    // happy with whatever the cloner can do.
    CloneAndPruneFunctionInto(Caller, CalledFunc, VMap, 
                              /*ModuleLevelChanges=*/false, Returns, ".i",
                              &InlinedFunctionInfo, IFI.TD, TheCall);

    // Remember the first block that is newly cloned over.
    FirstNewBlock = LastBlock; ++FirstNewBlock;

    // Update the callgraph if requested.
    if (IFI.CG)
      UpdateCallGraphAfterInlining(CS, FirstNewBlock, VMap, IFI);

    // Update inlined instructions' line number information.
    fixupLineNumbers(Caller, FirstNewBlock, TheCall);
  }

  // If there are any alloca instructions in the block that used to be the entry
  // block for the callee, move them to the entry block of the caller.  First
  // calculate which instruction they should be inserted before.  We insert the
  // instructions at the end of the current alloca list.
  {
    BasicBlock::iterator InsertPoint = Caller->begin()->begin();
    for (BasicBlock::iterator I = FirstNewBlock->begin(),
         E = FirstNewBlock->end(); I != E; ) {
      AllocaInst *AI = dyn_cast<AllocaInst>(I++);
      if (AI == 0) continue;
      
      // If the alloca is now dead, remove it.  This often occurs due to code
      // specialization.
      if (AI->use_empty()) {
        AI->eraseFromParent();
        continue;
      }

      if (!isa<Constant>(AI->getArraySize()))
        continue;
      
      // Keep track of the static allocas that we inline into the caller.
      IFI.StaticAllocas.push_back(AI);
      
      // Scan for the block of allocas that we can move over, and move them
      // all at once.
      while (isa<AllocaInst>(I) &&
             isa<Constant>(cast<AllocaInst>(I)->getArraySize())) {
        IFI.StaticAllocas.push_back(cast<AllocaInst>(I));
        ++I;
      }

      // Transfer all of the allocas over in a block.  Using splice means
      // that the instructions aren't removed from the symbol table, then
      // reinserted.
      Caller->getEntryBlock().getInstList().splice(InsertPoint,
                                                   FirstNewBlock->getInstList(),
                                                   AI, I);
    }
  }

  // Leave lifetime markers for the static alloca's, scoping them to the
  // function we just inlined.
  if (InsertLifetime && !IFI.StaticAllocas.empty()) {
    IRBuilder<> builder(FirstNewBlock->begin());
    for (unsigned ai = 0, ae = IFI.StaticAllocas.size(); ai != ae; ++ai) {
      AllocaInst *AI = IFI.StaticAllocas[ai];

      // If the alloca is already scoped to something smaller than the whole
      // function then there's no need to add redundant, less accurate markers.
      if (hasLifetimeMarkers(AI))
        continue;

      // Try to determine the size of the allocation.
      ConstantInt *AllocaSize = 0;
      if (ConstantInt *AIArraySize =
          dyn_cast<ConstantInt>(AI->getArraySize())) {
        if (IFI.TD) {
          Type *AllocaType = AI->getAllocatedType();
          uint64_t AllocaTypeSize = IFI.TD->getTypeAllocSize(AllocaType);
          uint64_t AllocaArraySize = AIArraySize->getLimitedValue();
          assert(AllocaArraySize > 0 && "array size of AllocaInst is zero");
          // Check that array size doesn't saturate uint64_t and doesn't
          // overflow when it's multiplied by type size.
          if (AllocaArraySize != ~0ULL &&
              UINT64_MAX / AllocaArraySize >= AllocaTypeSize) {
            AllocaSize = ConstantInt::get(Type::getInt64Ty(AI->getContext()),
                                          AllocaArraySize * AllocaTypeSize);
          }
        }
      }

      builder.CreateLifetimeStart(AI, AllocaSize);
      for (unsigned ri = 0, re = Returns.size(); ri != re; ++ri) {
        IRBuilder<> builder(Returns[ri]);
        builder.CreateLifetimeEnd(AI, AllocaSize);
      }
    }
  }

  // If the inlined code contained dynamic alloca instructions, wrap the inlined
  // code with llvm.stacksave/llvm.stackrestore intrinsics.
  if (InlinedFunctionInfo.ContainsDynamicAllocas) {
    Module *M = Caller->getParent();
    // Get the two intrinsics we care about.
    Function *StackSave = Intrinsic::getDeclaration(M, Intrinsic::stacksave);
    Function *StackRestore=Intrinsic::getDeclaration(M,Intrinsic::stackrestore);

    // Insert the llvm.stacksave.
    CallInst *SavedPtr = IRBuilder<>(FirstNewBlock, FirstNewBlock->begin())
      .CreateCall(StackSave, "savedstack");

    // Insert a call to llvm.stackrestore before any return instructions in the
    // inlined function.
    for (unsigned i = 0, e = Returns.size(); i != e; ++i) {
      IRBuilder<>(Returns[i]).CreateCall(StackRestore, SavedPtr);
    }
  }

  // If we are inlining tail call instruction through a call site that isn't
  // marked 'tail', we must remove the tail marker for any calls in the inlined
  // code.  Also, calls inlined through a 'nounwind' call site should be marked
  // 'nounwind'.
  if (InlinedFunctionInfo.ContainsCalls &&
      (MustClearTailCallFlags || MarkNoUnwind)) {
    for (Function::iterator BB = FirstNewBlock, E = Caller->end();
         BB != E; ++BB)
      for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I)
        if (CallInst *CI = dyn_cast<CallInst>(I)) {
          if (MustClearTailCallFlags)
            CI->setTailCall(false);
          if (MarkNoUnwind)
            CI->setDoesNotThrow();
        }
  }

  // If we are inlining for an invoke instruction, we must make sure to rewrite
  // any call instructions into invoke instructions.
  if (InvokeInst *II = dyn_cast<InvokeInst>(TheCall))
    HandleInlinedInvoke(II, FirstNewBlock, InlinedFunctionInfo);

  // If we cloned in _exactly one_ basic block, and if that block ends in a
  // return instruction, we splice the body of the inlined callee directly into
  // the calling basic block.
  if (Returns.size() == 1 && std::distance(FirstNewBlock, Caller->end()) == 1) {
    // Move all of the instructions right before the call.
    OrigBB->getInstList().splice(TheCall, FirstNewBlock->getInstList(),
                                 FirstNewBlock->begin(), FirstNewBlock->end());
    // Remove the cloned basic block.
    Caller->getBasicBlockList().pop_back();

    // If the call site was an invoke instruction, add a branch to the normal
    // destination.
    if (InvokeInst *II = dyn_cast<InvokeInst>(TheCall)) {
      BranchInst *NewBr = BranchInst::Create(II->getNormalDest(), TheCall);
      NewBr->setDebugLoc(Returns[0]->getDebugLoc());
    }

    // If the return instruction returned a value, replace uses of the call with
    // uses of the returned value.
    if (!TheCall->use_empty()) {
      ReturnInst *R = Returns[0];
      if (TheCall == R->getReturnValue())
        TheCall->replaceAllUsesWith(UndefValue::get(TheCall->getType()));
      else
        TheCall->replaceAllUsesWith(R->getReturnValue());
    }
    // Since we are now done with the Call/Invoke, we can delete it.
    TheCall->eraseFromParent();

    // Since we are now done with the return instruction, delete it also.
    Returns[0]->eraseFromParent();

    // We are now done with the inlining.
    return true;
  }

  // Otherwise, we have the normal case, of more than one block to inline or
  // multiple return sites.

  // We want to clone the entire callee function into the hole between the
  // "starter" and "ender" blocks.  How we accomplish this depends on whether
  // this is an invoke instruction or a call instruction.
  BasicBlock *AfterCallBB;
  BranchInst *CreatedBranchToNormalDest = NULL;
  if (InvokeInst *II = dyn_cast<InvokeInst>(TheCall)) {

    // Add an unconditional branch to make this look like the CallInst case...
    CreatedBranchToNormalDest = BranchInst::Create(II->getNormalDest(), TheCall);

    // Split the basic block.  This guarantees that no PHI nodes will have to be
    // updated due to new incoming edges, and make the invoke case more
    // symmetric to the call case.
    AfterCallBB = OrigBB->splitBasicBlock(CreatedBranchToNormalDest,
                                          CalledFunc->getName()+".exit");

  } else {  // It's a call
    // If this is a call instruction, we need to split the basic block that
    // the call lives in.
    //
    AfterCallBB = OrigBB->splitBasicBlock(TheCall,
                                          CalledFunc->getName()+".exit");
  }

  // Change the branch that used to go to AfterCallBB to branch to the first
  // basic block of the inlined function.
  //
  TerminatorInst *Br = OrigBB->getTerminator();
  assert(Br && Br->getOpcode() == Instruction::Br &&
         "splitBasicBlock broken!");
  Br->setOperand(0, FirstNewBlock);


  // Now that the function is correct, make it a little bit nicer.  In
  // particular, move the basic blocks inserted from the end of the function
  // into the space made by splitting the source basic block.
  Caller->getBasicBlockList().splice(AfterCallBB, Caller->getBasicBlockList(),
                                     FirstNewBlock, Caller->end());

  // Handle all of the return instructions that we just cloned in, and eliminate
  // any users of the original call/invoke instruction.
  Type *RTy = CalledFunc->getReturnType();

  PHINode *PHI = 0;
  if (Returns.size() > 1) {
    // The PHI node should go at the front of the new basic block to merge all
    // possible incoming values.
    if (!TheCall->use_empty()) {
      PHI = PHINode::Create(RTy, Returns.size(), TheCall->getName(),
                            AfterCallBB->begin());
      // Anything that used the result of the function call should now use the
      // PHI node as their operand.
      TheCall->replaceAllUsesWith(PHI);
    }

    // Loop over all of the return instructions adding entries to the PHI node
    // as appropriate.
    if (PHI) {
      for (unsigned i = 0, e = Returns.size(); i != e; ++i) {
        ReturnInst *RI = Returns[i];
        assert(RI->getReturnValue()->getType() == PHI->getType() &&
               "Ret value not consistent in function!");
        PHI->addIncoming(RI->getReturnValue(), RI->getParent());
      }
    }


    // Add a branch to the merge points and remove return instructions.
    DebugLoc Loc;
    for (unsigned i = 0, e = Returns.size(); i != e; ++i) {
      ReturnInst *RI = Returns[i];
      BranchInst* BI = BranchInst::Create(AfterCallBB, RI);
      Loc = RI->getDebugLoc();
      BI->setDebugLoc(Loc);
      RI->eraseFromParent();
    }
    // We need to set the debug location to *somewhere* inside the
    // inlined function. The line number may be nonsensical, but the
    // instruction will at least be associated with the right
    // function.
    if (CreatedBranchToNormalDest)
      CreatedBranchToNormalDest->setDebugLoc(Loc);
  } else if (!Returns.empty()) {
    // Otherwise, if there is exactly one return value, just replace anything
    // using the return value of the call with the computed value.
    if (!TheCall->use_empty()) {
      if (TheCall == Returns[0]->getReturnValue())
        TheCall->replaceAllUsesWith(UndefValue::get(TheCall->getType()));
      else
        TheCall->replaceAllUsesWith(Returns[0]->getReturnValue());
    }

    // Update PHI nodes that use the ReturnBB to use the AfterCallBB.
    BasicBlock *ReturnBB = Returns[0]->getParent();
    ReturnBB->replaceAllUsesWith(AfterCallBB);

    // Splice the code from the return block into the block that it will return
    // to, which contains the code that was after the call.
    AfterCallBB->getInstList().splice(AfterCallBB->begin(),
                                      ReturnBB->getInstList());

    if (CreatedBranchToNormalDest)
      CreatedBranchToNormalDest->setDebugLoc(Returns[0]->getDebugLoc());

    // Delete the return instruction now and empty ReturnBB now.
    Returns[0]->eraseFromParent();
    ReturnBB->eraseFromParent();
  } else if (!TheCall->use_empty()) {
    // No returns, but something is using the return value of the call.  Just
    // nuke the result.
    TheCall->replaceAllUsesWith(UndefValue::get(TheCall->getType()));
  }

  // Since we are now done with the Call/Invoke, we can delete it.
  TheCall->eraseFromParent();

  // We should always be able to fold the entry block of the function into the
  // single predecessor of the block...
  assert(cast<BranchInst>(Br)->isUnconditional() && "splitBasicBlock broken!");
  BasicBlock *CalleeEntry = cast<BranchInst>(Br)->getSuccessor(0);

  // Splice the code entry block into calling block, right before the
  // unconditional branch.
  CalleeEntry->replaceAllUsesWith(OrigBB);  // Update PHI nodes
  OrigBB->getInstList().splice(Br, CalleeEntry->getInstList());

  // Remove the unconditional branch.
  OrigBB->getInstList().erase(Br);

  // Now we can remove the CalleeEntry block, which is now empty.
  Caller->getBasicBlockList().erase(CalleeEntry);

  // If we inserted a phi node, check to see if it has a single value (e.g. all
  // the entries are the same or undef).  If so, remove the PHI so it doesn't
  // block other optimizations.
  if (PHI) {
    if (Value *V = SimplifyInstruction(PHI, IFI.TD)) {
      PHI->replaceAllUsesWith(V);
      PHI->eraseFromParent();
    }
  }

  return true;
}
Esempio n. 6
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void FunctionLoweringInfo::set(const Function &fn, MachineFunction &mf) {
  Fn = &fn;
  MF = &mf;
  RegInfo = &MF->getRegInfo();

  // Check whether the function can return without sret-demotion.
  SmallVector<ISD::OutputArg, 4> Outs;
  GetReturnInfo(Fn->getReturnType(),
                Fn->getAttributes().getRetAttributes(), Outs, TLI);
  CanLowerReturn = TLI.CanLowerReturn(Fn->getCallingConv(), *MF,
				      Fn->isVarArg(),
                                      Outs, Fn->getContext());

  // Initialize the mapping of values to registers.  This is only set up for
  // instruction values that are used outside of the block that defines
  // them.
  Function::const_iterator BB = Fn->begin(), EB = Fn->end();
  for (BasicBlock::const_iterator I = BB->begin(), E = BB->end(); I != E; ++I)
    if (const AllocaInst *AI = dyn_cast<AllocaInst>(I))
      if (const ConstantInt *CUI = dyn_cast<ConstantInt>(AI->getArraySize())) {
        const Type *Ty = AI->getAllocatedType();
        uint64_t TySize = TLI.getTargetData()->getTypeAllocSize(Ty);
        unsigned Align =
          std::max((unsigned)TLI.getTargetData()->getPrefTypeAlignment(Ty),
                   AI->getAlignment());

        TySize *= CUI->getZExtValue();   // Get total allocated size.
        if (TySize == 0) TySize = 1; // Don't create zero-sized stack objects.

        // The object may need to be placed onto the stack near the stack
        // protector if one exists. Determine here if this object is a suitable
        // candidate. I.e., it would trigger the creation of a stack protector.
        bool MayNeedSP =
          (AI->isArrayAllocation() ||
           (TySize > 8 && isa<ArrayType>(Ty) &&
            cast<ArrayType>(Ty)->getElementType()->isIntegerTy(8)));
        StaticAllocaMap[AI] =
          MF->getFrameInfo()->CreateStackObject(TySize, Align, false, MayNeedSP);
      }

  for (; BB != EB; ++BB)
    for (BasicBlock::const_iterator I = BB->begin(), E = BB->end(); I != E; ++I) {
      // Mark values used outside their block as exported, by allocating
      // a virtual register for them.
      if (isUsedOutsideOfDefiningBlock(I))
        if (!isa<AllocaInst>(I) ||
            !StaticAllocaMap.count(cast<AllocaInst>(I)))
          InitializeRegForValue(I);

      // Collect llvm.dbg.declare information. This is done now instead of
      // during the initial isel pass through the IR so that it is done
      // in a predictable order.
      if (const DbgDeclareInst *DI = dyn_cast<DbgDeclareInst>(I)) {
        MachineModuleInfo &MMI = MF->getMMI();
        if (MMI.hasDebugInfo() &&
            DIVariable(DI->getVariable()).Verify() &&
            !DI->getDebugLoc().isUnknown()) {
          // Don't handle byval struct arguments or VLAs, for example.
          // Non-byval arguments are handled here (they refer to the stack
          // temporary alloca at this point).
          const Value *Address = DI->getAddress();
          if (Address) {
            if (const BitCastInst *BCI = dyn_cast<BitCastInst>(Address))
              Address = BCI->getOperand(0);
            if (const AllocaInst *AI = dyn_cast<AllocaInst>(Address)) {
              DenseMap<const AllocaInst *, int>::iterator SI =
                StaticAllocaMap.find(AI);
              if (SI != StaticAllocaMap.end()) { // Check for VLAs.
                int FI = SI->second;
                MMI.setVariableDbgInfo(DI->getVariable(),
                                       FI, DI->getDebugLoc());
              }
            }
          }
        }
      }
    }

  // Create an initial MachineBasicBlock for each LLVM BasicBlock in F.  This
  // also creates the initial PHI MachineInstrs, though none of the input
  // operands are populated.
  for (BB = Fn->begin(); BB != EB; ++BB) {
    MachineBasicBlock *MBB = mf.CreateMachineBasicBlock(BB);
    MBBMap[BB] = MBB;
    MF->push_back(MBB);

    // Transfer the address-taken flag. This is necessary because there could
    // be multiple MachineBasicBlocks corresponding to one BasicBlock, and only
    // the first one should be marked.
    if (BB->hasAddressTaken())
      MBB->setHasAddressTaken();

    // Create Machine PHI nodes for LLVM PHI nodes, lowering them as
    // appropriate.
    for (BasicBlock::const_iterator I = BB->begin();
         const PHINode *PN = dyn_cast<PHINode>(I); ++I) {
      if (PN->use_empty()) continue;

      // Skip empty types
      if (PN->getType()->isEmptyTy())
        continue;

      DebugLoc DL = PN->getDebugLoc();
      unsigned PHIReg = ValueMap[PN];
      assert(PHIReg && "PHI node does not have an assigned virtual register!");

      SmallVector<EVT, 4> ValueVTs;
      ComputeValueVTs(TLI, PN->getType(), ValueVTs);
      for (unsigned vti = 0, vte = ValueVTs.size(); vti != vte; ++vti) {
        EVT VT = ValueVTs[vti];
        unsigned NumRegisters = TLI.getNumRegisters(Fn->getContext(), VT);
        const TargetInstrInfo *TII = MF->getTarget().getInstrInfo();
        for (unsigned i = 0; i != NumRegisters; ++i)
          BuildMI(MBB, DL, TII->get(TargetOpcode::PHI), PHIReg + i);
        PHIReg += NumRegisters;
      }
    }
  }

  // Mark landing pad blocks.
  for (BB = Fn->begin(); BB != EB; ++BB)
    if (const InvokeInst *Invoke = dyn_cast<InvokeInst>(BB->getTerminator()))
      MBBMap[Invoke->getSuccessor(1)]->setIsLandingPad();
}
void FunctionLoweringInfo::set(const Function &fn, MachineFunction &mf) {
  Fn = &fn;
  MF = &mf;
  RegInfo = &MF->getRegInfo();

  // Create a vreg for each argument register that is not dead and is used
  // outside of the entry block for the function.
  for (Function::const_arg_iterator AI = Fn->arg_begin(), E = Fn->arg_end();
       AI != E; ++AI)
    if (!isOnlyUsedInEntryBlock(AI, EnableFastISel))
      InitializeRegForValue(AI);

  // Initialize the mapping of values to registers.  This is only set up for
  // instruction values that are used outside of the block that defines
  // them.
  Function::const_iterator BB = Fn->begin(), EB = Fn->end();
  for (BasicBlock::const_iterator I = BB->begin(), E = BB->end(); I != E; ++I)
    if (const AllocaInst *AI = dyn_cast<AllocaInst>(I))
      if (const ConstantInt *CUI = dyn_cast<ConstantInt>(AI->getArraySize())) {
        const Type *Ty = AI->getAllocatedType();
        uint64_t TySize = TLI.getTargetData()->getTypeAllocSize(Ty);
        unsigned Align =
          std::max((unsigned)TLI.getTargetData()->getPrefTypeAlignment(Ty),
                   AI->getAlignment());

        TySize *= CUI->getZExtValue();   // Get total allocated size.
        if (TySize == 0) TySize = 1; // Don't create zero-sized stack objects.
        StaticAllocaMap[AI] =
          MF->getFrameInfo()->CreateStackObject(TySize, Align, false);
      }

  for (; BB != EB; ++BB)
    for (BasicBlock::const_iterator I = BB->begin(), E = BB->end(); I != E; ++I)
      if (isUsedOutsideOfDefiningBlock(I))
        if (!isa<AllocaInst>(I) ||
            !StaticAllocaMap.count(cast<AllocaInst>(I)))
          InitializeRegForValue(I);

  // Create an initial MachineBasicBlock for each LLVM BasicBlock in F.  This
  // also creates the initial PHI MachineInstrs, though none of the input
  // operands are populated.
  for (BB = Fn->begin(); BB != EB; ++BB) {
    MachineBasicBlock *MBB = mf.CreateMachineBasicBlock(BB);
    MBBMap[BB] = MBB;
    MF->push_back(MBB);

    // Transfer the address-taken flag. This is necessary because there could
    // be multiple MachineBasicBlocks corresponding to one BasicBlock, and only
    // the first one should be marked.
    if (BB->hasAddressTaken())
      MBB->setHasAddressTaken();

    // Create Machine PHI nodes for LLVM PHI nodes, lowering them as
    // appropriate.
    for (BasicBlock::const_iterator I = BB->begin();
         const PHINode *PN = dyn_cast<PHINode>(I); ++I) {
      if (PN->use_empty()) continue;

      DebugLoc DL = PN->getDebugLoc();
      unsigned PHIReg = ValueMap[PN];
      assert(PHIReg && "PHI node does not have an assigned virtual register!");

      SmallVector<EVT, 4> ValueVTs;
      ComputeValueVTs(TLI, PN->getType(), ValueVTs);
      for (unsigned vti = 0, vte = ValueVTs.size(); vti != vte; ++vti) {
        EVT VT = ValueVTs[vti];
        unsigned NumRegisters = TLI.getNumRegisters(Fn->getContext(), VT);
        const TargetInstrInfo *TII = MF->getTarget().getInstrInfo();
        for (unsigned i = 0; i != NumRegisters; ++i)
          BuildMI(MBB, DL, TII->get(TargetOpcode::PHI), PHIReg + i);
        PHIReg += NumRegisters;
      }
    }
  }

  // Mark landing pad blocks.
  for (BB = Fn->begin(); BB != EB; ++BB)
    if (const InvokeInst *Invoke = dyn_cast<InvokeInst>(BB->getTerminator()))
      MBBMap[Invoke->getSuccessor(1)]->setIsLandingPad();
}