lib/CodeGen/SelectionDAG/LegalizeTypesGeneric.cpp

   1 //===-------- LegalizeTypesGeneric.cpp - Generic type legalization --------===//
   2 //
   3 //                     The LLVM Compiler Infrastructure
   4 //
   5 // This file is distributed under the University of Illinois Open Source
   6 // License. See LICENSE.TXT for details.
   7 //
   8 //===----------------------------------------------------------------------===//
   9 //
  10 // This file implements generic type expansion and splitting for LegalizeTypes.
  11 // The routines here perform legalization when the details of the type (such as
  12 // whether it is an integer or a float) do not matter.
  13 // Expansion is the act of changing a computation in an illegal type to be a
  14 // computation in two identical registers of a smaller type.  The Lo/Hi part
  15 // is required to be stored first in memory on little/big-endian machines.
  16 // Splitting is the act of changing a computation in an illegal type to be a
  17 // computation in two not necessarily identical registers of a smaller type.
  18 // There are no requirements on how the type is represented in memory.
  19 //
  20 //===----------------------------------------------------------------------===//
  21
  22 #include "LegalizeTypes.h"
  23 #include "llvm/Target/TargetData.h"
  24 #include "llvm/CodeGen/PseudoSourceValue.h"
  25 using namespace llvm;
  26
  27 //===----------------------------------------------------------------------===//
  28 // Generic Result Expansion.
  29 //===----------------------------------------------------------------------===//
  30
  31 // These routines assume that the Lo/Hi part is stored first in memory on
  32 // little/big-endian machines, followed by the Hi/Lo part.  This means that
  33 // they cannot be used as is on vectors, for which Lo is always stored first.
  34
  35 void DAGTypeLegalizer::ExpandRes_BIT_CONVERT(SDNode *N, SDValue &Lo,
  36                                              SDValue &Hi) {
  37   EVT OutVT = N->getValueType(0);
  38   EVT NOutVT = TLI.getTypeToTransformTo(*DAG.getContext(), OutVT);
  39   SDValue InOp = N->getOperand(0);
  40   EVT InVT = InOp.getValueType();
  41   DebugLoc dl = N->getDebugLoc();
  42
  43   // Handle some special cases efficiently.
  44   switch (getTypeAction(InVT)) {
  45     default:
  46       assert(false && "Unknown type action!");
  47     case Legal:
  48     case PromoteInteger:
  49       break;
  50     case SoftenFloat:
  51       // Convert the integer operand instead.
  52       SplitInteger(GetSoftenedFloat(InOp), Lo, Hi);
  53       Lo = DAG.getNode(ISD::BIT_CONVERT, dl, NOutVT, Lo);
  54       Hi = DAG.getNode(ISD::BIT_CONVERT, dl, NOutVT, Hi);
  55       return;
  56     case ExpandInteger:
  57     case ExpandFloat:
  58       // Convert the expanded pieces of the input.
  59       GetExpandedOp(InOp, Lo, Hi);
  60       Lo = DAG.getNode(ISD::BIT_CONVERT, dl, NOutVT, Lo);
  61       Hi = DAG.getNode(ISD::BIT_CONVERT, dl, NOutVT, Hi);
  62       return;
  63     case SplitVector:
  64       GetSplitVector(InOp, Lo, Hi);
  65       if (TLI.isBigEndian())
  66         std::swap(Lo, Hi);
  67       Lo = DAG.getNode(ISD::BIT_CONVERT, dl, NOutVT, Lo);
  68       Hi = DAG.getNode(ISD::BIT_CONVERT, dl, NOutVT, Hi);
  69       return;
  70     case ScalarizeVector:
  71       // Convert the element instead.
  72       SplitInteger(BitConvertToInteger(GetScalarizedVector(InOp)), Lo, Hi);
  73       Lo = DAG.getNode(ISD::BIT_CONVERT, dl, NOutVT, Lo);
  74       Hi = DAG.getNode(ISD::BIT_CONVERT, dl, NOutVT, Hi);
  75       return;
  76     case WidenVector: {
  77       assert(!(InVT.getVectorNumElements() & 1) && "Unsupported BIT_CONVERT");
  78       InOp = GetWidenedVector(InOp);
  79       EVT InNVT = EVT::getVectorVT(*DAG.getContext(), InVT.getVectorElementType(),
  80                                    InVT.getVectorNumElements()/2);
  81       Lo = DAG.getNode(ISD::EXTRACT_SUBVECTOR, dl, InNVT, InOp,
  82                        DAG.getIntPtrConstant(0));
  83       Hi = DAG.getNode(ISD::EXTRACT_SUBVECTOR, dl, InNVT, InOp,
  84                        DAG.getIntPtrConstant(InNVT.getVectorNumElements()));
  85       if (TLI.isBigEndian())
  86         std::swap(Lo, Hi);
  87       Lo = DAG.getNode(ISD::BIT_CONVERT, dl, NOutVT, Lo);
  88       Hi = DAG.getNode(ISD::BIT_CONVERT, dl, NOutVT, Hi);
  89       return;
  90     }
  91   }
  92
  93   if (InVT.isVector() && OutVT.isInteger()) {
  94     // Handle cases like i64 = BIT_CONVERT v1i64 on x86, where the operand
  95     // is legal but the result is not.
  96     EVT NVT = EVT::getVectorVT(*DAG.getContext(), NOutVT, 2);
  97
  98     if (isTypeLegal(NVT)) {
  99       SDValue CastInOp = DAG.getNode(ISD::BIT_CONVERT, dl, NVT, InOp);
 100       Lo = DAG.getNode(ISD::EXTRACT_VECTOR_ELT, dl, NOutVT, CastInOp,
 101                        DAG.getIntPtrConstant(0));
 102       Hi = DAG.getNode(ISD::EXTRACT_VECTOR_ELT, dl, NOutVT, CastInOp,
 103                        DAG.getIntPtrConstant(1));
 104
 105       if (TLI.isBigEndian())
 106         std::swap(Lo, Hi);
 107
 108       return;
 109     }
 110   }
 111
 112   // Lower the bit-convert to a store/load from the stack.
 113   assert(NOutVT.isByteSized() && "Expanded type not byte sized!");
 114
 115   // Create the stack frame object.  Make sure it is aligned for both
 116   // the source and expanded destination types.
 117   unsigned Alignment =
 118     TLI.getTargetData()->getPrefTypeAlignment(NOutVT.getTypeForEVT(*DAG.getContext()));
 119   SDValue StackPtr = DAG.CreateStackTemporary(InVT, Alignment);
 120   int SPFI = cast<FrameIndexSDNode>(StackPtr.getNode())->getIndex();
 121   const Value *SV = PseudoSourceValue::getFixedStack(SPFI);
 122
 123   // Emit a store to the stack slot.
 124   SDValue Store = DAG.getStore(DAG.getEntryNode(), dl, InOp, StackPtr, SV, 0);
 125
 126   // Load the first half from the stack slot.
 127   Lo = DAG.getLoad(NOutVT, dl, Store, StackPtr, SV, 0);
 128
 129   // Increment the pointer to the other half.
 130   unsigned IncrementSize = NOutVT.getSizeInBits() / 8;
 131   StackPtr = DAG.getNode(ISD::ADD, dl, StackPtr.getValueType(), StackPtr,
 132                          DAG.getIntPtrConstant(IncrementSize));
 133
 134   // Load the second half from the stack slot.
 135   Hi = DAG.getLoad(NOutVT, dl, Store, StackPtr, SV, IncrementSize, false,
 136                    MinAlign(Alignment, IncrementSize));
 137
 138   // Handle endianness of the load.
 139   if (TLI.isBigEndian())
 140     std::swap(Lo, Hi);
 141 }
 142
 143 void DAGTypeLegalizer::ExpandRes_BUILD_PAIR(SDNode *N, SDValue &Lo,
 144                                             SDValue &Hi) {
 145   // Return the operands.
 146   Lo = N->getOperand(0);
 147   Hi = N->getOperand(1);
 148 }
 149
 150 void DAGTypeLegalizer::ExpandRes_EXTRACT_ELEMENT(SDNode *N, SDValue &Lo,
 151                                                  SDValue &Hi) {
 152   GetExpandedOp(N->getOperand(0), Lo, Hi);
 153   SDValue Part = cast<ConstantSDNode>(N->getOperand(1))->getZExtValue() ?
 154                    Hi : Lo;
 155
 156   assert(Part.getValueType() == N->getValueType(0) &&
 157          "Type twice as big as expanded type not itself expanded!");
 158
 159   GetPairElements(Part, Lo, Hi);
 160 }
 161
 162 void DAGTypeLegalizer::ExpandRes_EXTRACT_VECTOR_ELT(SDNode *N, SDValue &Lo,
 163                                                     SDValue &Hi) {
 164   SDValue OldVec = N->getOperand(0);
 165   unsigned OldElts = OldVec.getValueType().getVectorNumElements();
 166   DebugLoc dl = N->getDebugLoc();
 167
 168   // Convert to a vector of the expanded element type, for example
 169   // <3 x i64> -> <6 x i32>.
 170   EVT OldVT = N->getValueType(0);
 171   EVT NewVT = TLI.getTypeToTransformTo(*DAG.getContext(), OldVT);
 172
 173   SDValue NewVec = DAG.getNode(ISD::BIT_CONVERT, dl,
 174                                  EVT::getVectorVT(*DAG.getContext(), NewVT, 2*OldElts),
 175                                  OldVec);
 176
 177   // Extract the elements at 2 * Idx and 2 * Idx + 1 from the new vector.
 178   SDValue Idx = N->getOperand(1);
 179
 180   // Make sure the type of Idx is big enough to hold the new values.
 181   if (Idx.getValueType().bitsLT(TLI.getPointerTy()))
 182     Idx = DAG.getNode(ISD::ZERO_EXTEND, dl, TLI.getPointerTy(), Idx);
 183
 184   Idx = DAG.getNode(ISD::ADD, dl, Idx.getValueType(), Idx, Idx);
 185   Lo = DAG.getNode(ISD::EXTRACT_VECTOR_ELT, dl, NewVT, NewVec, Idx);
 186
 187   Idx = DAG.getNode(ISD::ADD, dl, Idx.getValueType(), Idx,
 188                     DAG.getConstant(1, Idx.getValueType()));
 189   Hi = DAG.getNode(ISD::EXTRACT_VECTOR_ELT, dl, NewVT, NewVec, Idx);
 190
 191   if (TLI.isBigEndian())
 192     std::swap(Lo, Hi);
 193 }
 194
 195 void DAGTypeLegalizer::ExpandRes_NormalLoad(SDNode *N, SDValue &Lo,
 196                                             SDValue &Hi) {
 197   assert(ISD::isNormalLoad(N) && "This routine only for normal loads!");
 198   DebugLoc dl = N->getDebugLoc();
 199
 200   LoadSDNode *LD = cast<LoadSDNode>(N);
 201   EVT NVT = TLI.getTypeToTransformTo(*DAG.getContext(), LD->getValueType(0));
 202   SDValue Chain = LD->getChain();
 203   SDValue Ptr = LD->getBasePtr();
 204   int SVOffset = LD->getSrcValueOffset();
 205   unsigned Alignment = LD->getAlignment();
 206   bool isVolatile = LD->isVolatile();
 207
 208   assert(NVT.isByteSized() && "Expanded type not byte sized!");
 209
 210   Lo = DAG.getLoad(NVT, dl, Chain, Ptr, LD->getSrcValue(), SVOffset,
 211                    isVolatile, Alignment);
 212
 213   // Increment the pointer to the other half.
 214   unsigned IncrementSize = NVT.getSizeInBits() / 8;
 215   Ptr = DAG.getNode(ISD::ADD, dl, Ptr.getValueType(), Ptr,
 216                     DAG.getIntPtrConstant(IncrementSize));
 217   Hi = DAG.getLoad(NVT, dl, Chain, Ptr, LD->getSrcValue(),
 218                    SVOffset+IncrementSize,
 219                    isVolatile, MinAlign(Alignment, IncrementSize));
 220
 221   // Build a factor node to remember that this load is independent of the
 222   // other one.
 223   Chain = DAG.getNode(ISD::TokenFactor, dl, MVT::Other, Lo.getValue(1),
 224                       Hi.getValue(1));
 225
 226   // Handle endianness of the load.
 227   if (TLI.isBigEndian())
 228     std::swap(Lo, Hi);
 229
 230   // Modified the chain - switch anything that used the old chain to use
 231   // the new one.
 232   ReplaceValueWith(SDValue(N, 1), Chain);
 233 }
 234
 235 void DAGTypeLegalizer::ExpandRes_VAARG(SDNode *N, SDValue &Lo, SDValue &Hi) {
 236   EVT NVT = TLI.getTypeToTransformTo(*DAG.getContext(), N->getValueType(0));
 237   SDValue Chain = N->getOperand(0);
 238   SDValue Ptr = N->getOperand(1);
 239   DebugLoc dl = N->getDebugLoc();
 240
 241   Lo = DAG.getVAArg(NVT, dl, Chain, Ptr, N->getOperand(2));
 242   Hi = DAG.getVAArg(NVT, dl, Lo.getValue(1), Ptr, N->getOperand(2));
 243
 244   // Handle endianness of the load.
 245   if (TLI.isBigEndian())
 246     std::swap(Lo, Hi);
 247
 248   // Modified the chain - switch anything that used the old chain to use
 249   // the new one.
 250   ReplaceValueWith(SDValue(N, 1), Hi.getValue(1));
 251 }
 252
 253
 254 //===--------------------------------------------------------------------===//
 255 // Generic Operand Expansion.
 256 //===--------------------------------------------------------------------===//
 257
 258 SDValue DAGTypeLegalizer::ExpandOp_BIT_CONVERT(SDNode *N) {
 259   DebugLoc dl = N->getDebugLoc();
 260   if (N->getValueType(0).isVector()) {
 261     // An illegal expanding type is being converted to a legal vector type.
 262     // Make a two element vector out of the expanded parts and convert that
 263     // instead, but only if the new vector type is legal (otherwise there
 264     // is no point, and it might create expansion loops).  For example, on
 265     // x86 this turns v1i64 = BIT_CONVERT i64 into v1i64 = BIT_CONVERT v2i32.
 266     EVT OVT = N->getOperand(0).getValueType();
 267     EVT NVT = EVT::getVectorVT(*DAG.getContext(), TLI.getTypeToTransformTo(*DAG.getContext(), OVT), 2);
 268
 269     if (isTypeLegal(NVT)) {
 270       SDValue Parts[2];
 271       GetExpandedOp(N->getOperand(0), Parts[0], Parts[1]);
 272
 273       if (TLI.isBigEndian())
 274         std::swap(Parts[0], Parts[1]);
 275
 276       SDValue Vec = DAG.getNode(ISD::BUILD_VECTOR, dl, NVT, Parts, 2);
 277       return DAG.getNode(ISD::BIT_CONVERT, dl, N->getValueType(0), Vec);
 278     }
 279   }
 280
 281   // Otherwise, store to a temporary and load out again as the new type.
 282   return CreateStackStoreLoad(N->getOperand(0), N->getValueType(0));
 283 }
 284
 285 SDValue DAGTypeLegalizer::ExpandOp_BUILD_VECTOR(SDNode *N) {
 286   // The vector type is legal but the element type needs expansion.
 287   EVT VecVT = N->getValueType(0);
 288   unsigned NumElts = VecVT.getVectorNumElements();
 289   EVT OldVT = N->getOperand(0).getValueType();
 290   EVT NewVT = TLI.getTypeToTransformTo(*DAG.getContext(), OldVT);
 291   DebugLoc dl = N->getDebugLoc();
 292
 293   assert(OldVT == VecVT.getVectorElementType() &&
 294          "BUILD_VECTOR operand type doesn't match vector element type!");
 295
 296   // Build a vector of twice the length out of the expanded elements.
 297   // For example <3 x i64> -> <6 x i32>.
 298   std::vector<SDValue> NewElts;
 299   NewElts.reserve(NumElts*2);
 300
 301   for (unsigned i = 0; i < NumElts; ++i) {
 302     SDValue Lo, Hi;
 303     GetExpandedOp(N->getOperand(i), Lo, Hi);
 304     if (TLI.isBigEndian())
 305       std::swap(Lo, Hi);
 306     NewElts.push_back(Lo);
 307     NewElts.push_back(Hi);
 308   }
 309
 310   SDValue NewVec = DAG.getNode(ISD::BUILD_VECTOR, dl,
 311                                  EVT::getVectorVT(*DAG.getContext(), NewVT, NewElts.size()),
 312                                  &NewElts[0], NewElts.size());
 313
 314   // Convert the new vector to the old vector type.
 315   return DAG.getNode(ISD::BIT_CONVERT, dl, VecVT, NewVec);
 316 }
 317
 318 SDValue DAGTypeLegalizer::ExpandOp_EXTRACT_ELEMENT(SDNode *N) {
 319   SDValue Lo, Hi;
 320   GetExpandedOp(N->getOperand(0), Lo, Hi);
 321   return cast<ConstantSDNode>(N->getOperand(1))->getZExtValue() ? Hi : Lo;
 322 }
 323
 324 SDValue DAGTypeLegalizer::ExpandOp_INSERT_VECTOR_ELT(SDNode *N) {
 325   // The vector type is legal but the element type needs expansion.
 326   EVT VecVT = N->getValueType(0);
 327   unsigned NumElts = VecVT.getVectorNumElements();
 328   DebugLoc dl = N->getDebugLoc();
 329
 330   SDValue Val = N->getOperand(1);
 331   EVT OldEVT = Val.getValueType();
 332   EVT NewEVT = TLI.getTypeToTransformTo(*DAG.getContext(), OldEVT);
 333
 334   assert(OldEVT == VecVT.getVectorElementType() &&
 335          "Inserted element type doesn't match vector element type!");
 336
 337   // Bitconvert to a vector of twice the length with elements of the expanded
 338   // type, insert the expanded vector elements, and then convert back.
 339   EVT NewVecVT = EVT::getVectorVT(*DAG.getContext(), NewEVT, NumElts*2);
 340   SDValue NewVec = DAG.getNode(ISD::BIT_CONVERT, dl,
 341                                NewVecVT, N->getOperand(0));
 342
 343   SDValue Lo, Hi;
 344   GetExpandedOp(Val, Lo, Hi);
 345   if (TLI.isBigEndian())
 346     std::swap(Lo, Hi);
 347
 348   SDValue Idx = N->getOperand(2);
 349   Idx = DAG.getNode(ISD::ADD, dl, Idx.getValueType(), Idx, Idx);
 350   NewVec = DAG.getNode(ISD::INSERT_VECTOR_ELT, dl, NewVecVT, NewVec, Lo, Idx);
 351   Idx = DAG.getNode(ISD::ADD, dl,
 352                     Idx.getValueType(), Idx, DAG.getIntPtrConstant(1));
 353   NewVec =  DAG.getNode(ISD::INSERT_VECTOR_ELT, dl, NewVecVT, NewVec, Hi, Idx);
 354
 355   // Convert the new vector to the old vector type.
 356   return DAG.getNode(ISD::BIT_CONVERT, dl, VecVT, NewVec);
 357 }
 358
 359 SDValue DAGTypeLegalizer::ExpandOp_SCALAR_TO_VECTOR(SDNode *N) {
 360   DebugLoc dl = N->getDebugLoc();
 361   EVT VT = N->getValueType(0);
 362   assert(VT.getVectorElementType() == N->getOperand(0).getValueType() &&
 363          "SCALAR_TO_VECTOR operand type doesn't match vector element type!");
 364   unsigned NumElts = VT.getVectorNumElements();
 365   SmallVector<SDValue, 16> Ops(NumElts);
 366   Ops[0] = N->getOperand(0);
 367   SDValue UndefVal = DAG.getUNDEF(Ops[0].getValueType());
 368   for (unsigned i = 1; i < NumElts; ++i)
 369     Ops[i] = UndefVal;
 370   return DAG.getNode(ISD::BUILD_VECTOR, dl, VT, &Ops[0], NumElts);
 371 }
 372
 373 SDValue DAGTypeLegalizer::ExpandOp_NormalStore(SDNode *N, unsigned OpNo) {
 374   assert(ISD::isNormalStore(N) && "This routine only for normal stores!");
 375   assert(OpNo == 1 && "Can only expand the stored value so far");
 376   DebugLoc dl = N->getDebugLoc();
 377
 378   StoreSDNode *St = cast<StoreSDNode>(N);
 379   EVT NVT = TLI.getTypeToTransformTo(*DAG.getContext(), St->getValue().getValueType());
 380   SDValue Chain = St->getChain();
 381   SDValue Ptr = St->getBasePtr();
 382   int SVOffset = St->getSrcValueOffset();
 383   unsigned Alignment = St->getAlignment();
 384   bool isVolatile = St->isVolatile();
 385
 386   assert(NVT.isByteSized() && "Expanded type not byte sized!");
 387   unsigned IncrementSize = NVT.getSizeInBits() / 8;
 388
 389   SDValue Lo, Hi;
 390   GetExpandedOp(St->getValue(), Lo, Hi);
 391
 392   if (TLI.isBigEndian())
 393     std::swap(Lo, Hi);
 394
 395   Lo = DAG.getStore(Chain, dl, Lo, Ptr, St->getSrcValue(), SVOffset,
 396                     isVolatile, Alignment);
 397
 398   Ptr = DAG.getNode(ISD::ADD, dl, Ptr.getValueType(), Ptr,
 399                     DAG.getIntPtrConstant(IncrementSize));
 400   assert(isTypeLegal(Ptr.getValueType()) && "Pointers must be legal!");
 401   Hi = DAG.getStore(Chain, dl, Hi, Ptr, St->getSrcValue(),
 402                     SVOffset + IncrementSize,
 403                     isVolatile, MinAlign(Alignment, IncrementSize));
 404
 405   return DAG.getNode(ISD::TokenFactor, dl, MVT::Other, Lo, Hi);
 406 }
 407
 408
 409 //===--------------------------------------------------------------------===//
 410 // Generic Result Splitting.
 411 //===--------------------------------------------------------------------===//
 412
 413 // Be careful to make no assumptions about which of Lo/Hi is stored first in
 414 // memory (for vectors it is always Lo first followed by Hi in the following
 415 // bytes; for integers and floats it is Lo first if and only if the machine is
 416 // little-endian).
 417
 418 void DAGTypeLegalizer::SplitRes_MERGE_VALUES(SDNode *N,
 419                                              SDValue &Lo, SDValue &Hi) {
 420   // A MERGE_VALUES node can produce any number of values.  We know that the
 421   // first illegal one needs to be expanded into Lo/Hi.
 422   unsigned i;
 423
 424   // The string of legal results gets turned into input operands, which have
 425   // the same type.
 426   for (i = 0; isTypeLegal(N->getValueType(i)); ++i)
 427     ReplaceValueWith(SDValue(N, i), SDValue(N->getOperand(i)));
 428
 429   // The first illegal result must be the one that needs to be expanded.
 430   GetSplitOp(N->getOperand(i), Lo, Hi);
 431
 432   // Legalize the rest of the results into the input operands whether they are
 433   // legal or not.
 434   unsigned e = N->getNumValues();
 435   for (++i; i != e; ++i)
 436     ReplaceValueWith(SDValue(N, i), SDValue(N->getOperand(i)));
 437 }
 438
 439 void DAGTypeLegalizer::SplitRes_SELECT(SDNode *N, SDValue &Lo,
 440                                        SDValue &Hi) {
 441   SDValue LL, LH, RL, RH;
 442   DebugLoc dl = N->getDebugLoc();
 443   GetSplitOp(N->getOperand(1), LL, LH);
 444   GetSplitOp(N->getOperand(2), RL, RH);
 445
 446   SDValue Cond = N->getOperand(0);
 447   Lo = DAG.getNode(ISD::SELECT, dl, LL.getValueType(), Cond, LL, RL);
 448   Hi = DAG.getNode(ISD::SELECT, dl, LH.getValueType(), Cond, LH, RH);
 449 }
 450
 451 void DAGTypeLegalizer::SplitRes_SELECT_CC(SDNode *N, SDValue &Lo,
 452                                           SDValue &Hi) {
 453   SDValue LL, LH, RL, RH;
 454   DebugLoc dl = N->getDebugLoc();
 455   GetSplitOp(N->getOperand(2), LL, LH);
 456   GetSplitOp(N->getOperand(3), RL, RH);
 457
 458   Lo = DAG.getNode(ISD::SELECT_CC, dl, LL.getValueType(), N->getOperand(0),
 459                    N->getOperand(1), LL, RL, N->getOperand(4));
 460   Hi = DAG.getNode(ISD::SELECT_CC, dl, LH.getValueType(), N->getOperand(0),
 461                    N->getOperand(1), LH, RH, N->getOperand(4));
 462 }
 463
 464 void DAGTypeLegalizer::SplitRes_UNDEF(SDNode *N, SDValue &Lo, SDValue &Hi) {
 465   EVT LoVT, HiVT;
 466   DebugLoc dl = N->getDebugLoc();
 467   GetSplitDestVTs(N->getValueType(0), LoVT, HiVT);
 468   Lo = DAG.getUNDEF(LoVT);
 469   Hi = DAG.getUNDEF(HiVT);
 470 }