1 //===-------- LegalizeTypesGeneric.cpp - Generic type legalization --------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
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.
20 //===----------------------------------------------------------------------===//
22 #include "LegalizeTypes.h"
23 #include "llvm/IR/DataLayout.h"
26 #define DEBUG_TYPE "legalize-types"
28 //===----------------------------------------------------------------------===//
29 // Generic Result Expansion.
30 //===----------------------------------------------------------------------===//
32 // These routines assume that the Lo/Hi part is stored first in memory on
33 // little/big-endian machines, followed by the Hi/Lo part. This means that
34 // they cannot be used as is on vectors, for which Lo is always stored first.
35 void DAGTypeLegalizer::ExpandRes_MERGE_VALUES(SDNode *N, unsigned ResNo,
36 SDValue &Lo, SDValue &Hi) {
37 SDValue Op = DisintegrateMERGE_VALUES(N, ResNo);
38 GetExpandedOp(Op, Lo, Hi);
41 void DAGTypeLegalizer::ExpandRes_BITCAST(SDNode *N, SDValue &Lo, SDValue &Hi) {
42 EVT OutVT = N->getValueType(0);
43 EVT NOutVT = TLI.getTypeToTransformTo(*DAG.getContext(), OutVT);
44 SDValue InOp = N->getOperand(0);
45 EVT InVT = InOp.getValueType();
48 // Handle some special cases efficiently.
49 switch (getTypeAction(InVT)) {
50 case TargetLowering::TypeLegal:
51 case TargetLowering::TypePromoteInteger:
53 case TargetLowering::TypePromoteFloat:
54 llvm_unreachable("Bitcast of a promotion-needing float should never need"
56 case TargetLowering::TypeSoftenFloat:
57 // Convert the integer operand instead.
58 SplitInteger(GetSoftenedFloat(InOp), Lo, Hi);
59 Lo = DAG.getNode(ISD::BITCAST, dl, NOutVT, Lo);
60 Hi = DAG.getNode(ISD::BITCAST, dl, NOutVT, Hi);
62 case TargetLowering::TypeExpandInteger:
63 case TargetLowering::TypeExpandFloat: {
64 auto &DL = DAG.getDataLayout();
65 // Convert the expanded pieces of the input.
66 GetExpandedOp(InOp, Lo, Hi);
67 if (TLI.hasBigEndianPartOrdering(InVT, DL) !=
68 TLI.hasBigEndianPartOrdering(OutVT, DL))
70 Lo = DAG.getNode(ISD::BITCAST, dl, NOutVT, Lo);
71 Hi = DAG.getNode(ISD::BITCAST, dl, NOutVT, Hi);
74 case TargetLowering::TypeSplitVector:
75 GetSplitVector(InOp, Lo, Hi);
76 if (TLI.hasBigEndianPartOrdering(OutVT, DAG.getDataLayout()))
78 Lo = DAG.getNode(ISD::BITCAST, dl, NOutVT, Lo);
79 Hi = DAG.getNode(ISD::BITCAST, dl, NOutVT, Hi);
81 case TargetLowering::TypeScalarizeVector:
82 // Convert the element instead.
83 SplitInteger(BitConvertToInteger(GetScalarizedVector(InOp)), Lo, Hi);
84 Lo = DAG.getNode(ISD::BITCAST, dl, NOutVT, Lo);
85 Hi = DAG.getNode(ISD::BITCAST, dl, NOutVT, Hi);
87 case TargetLowering::TypeWidenVector: {
88 assert(!(InVT.getVectorNumElements() & 1) && "Unsupported BITCAST");
89 InOp = GetWidenedVector(InOp);
91 std::tie(LoVT, HiVT) = DAG.GetSplitDestVTs(InVT);
92 std::tie(Lo, Hi) = DAG.SplitVector(InOp, dl, LoVT, HiVT);
93 if (TLI.hasBigEndianPartOrdering(OutVT, DAG.getDataLayout()))
95 Lo = DAG.getNode(ISD::BITCAST, dl, NOutVT, Lo);
96 Hi = DAG.getNode(ISD::BITCAST, dl, NOutVT, Hi);
101 if (InVT.isVector() && OutVT.isInteger()) {
102 // Handle cases like i64 = BITCAST v1i64 on x86, where the operand
103 // is legal but the result is not.
104 unsigned NumElems = 2;
106 EVT NVT = EVT::getVectorVT(*DAG.getContext(), ElemVT, NumElems);
108 // If <ElemVT * N> is not a legal type, try <ElemVT/2 * (N*2)>.
109 while (!isTypeLegal(NVT)) {
110 unsigned NewSizeInBits = ElemVT.getSizeInBits() / 2;
111 // If the element size is smaller than byte, bail.
112 if (NewSizeInBits < 8)
115 ElemVT = EVT::getIntegerVT(*DAG.getContext(), NewSizeInBits);
116 NVT = EVT::getVectorVT(*DAG.getContext(), ElemVT, NumElems);
119 if (isTypeLegal(NVT)) {
120 SDValue CastInOp = DAG.getNode(ISD::BITCAST, dl, NVT, InOp);
122 SmallVector<SDValue, 8> Vals;
123 for (unsigned i = 0; i < NumElems; ++i)
124 Vals.push_back(DAG.getNode(
125 ISD::EXTRACT_VECTOR_ELT, dl, ElemVT, CastInOp,
126 DAG.getConstant(i, dl, TLI.getVectorIdxTy(DAG.getDataLayout()))));
128 // Build Lo, Hi pair by pairing extracted elements if needed.
130 for (unsigned e = Vals.size(); e - Slot > 2; Slot += 2, e += 1) {
131 // Each iteration will BUILD_PAIR two nodes and append the result until
132 // there are only two nodes left, i.e. Lo and Hi.
133 SDValue LHS = Vals[Slot];
134 SDValue RHS = Vals[Slot + 1];
136 if (DAG.getDataLayout().isBigEndian())
139 Vals.push_back(DAG.getNode(ISD::BUILD_PAIR, dl,
142 LHS.getValueType().getSizeInBits() << 1),
148 if (DAG.getDataLayout().isBigEndian())
155 // Lower the bit-convert to a store/load from the stack.
156 assert(NOutVT.isByteSized() && "Expanded type not byte sized!");
158 // Create the stack frame object. Make sure it is aligned for both
159 // the source and expanded destination types.
160 unsigned Alignment = DAG.getDataLayout().getPrefTypeAlignment(
161 NOutVT.getTypeForEVT(*DAG.getContext()));
162 SDValue StackPtr = DAG.CreateStackTemporary(InVT, Alignment);
163 int SPFI = cast<FrameIndexSDNode>(StackPtr.getNode())->getIndex();
164 MachinePointerInfo PtrInfo =
165 MachinePointerInfo::getFixedStack(DAG.getMachineFunction(), SPFI);
167 // Emit a store to the stack slot.
168 SDValue Store = DAG.getStore(DAG.getEntryNode(), dl, InOp, StackPtr, PtrInfo,
171 // Load the first half from the stack slot.
172 Lo = DAG.getLoad(NOutVT, dl, Store, StackPtr, PtrInfo,
173 false, false, false, 0);
175 // Increment the pointer to the other half.
176 unsigned IncrementSize = NOutVT.getSizeInBits() / 8;
177 StackPtr = DAG.getNode(ISD::ADD, dl, StackPtr.getValueType(), StackPtr,
178 DAG.getConstant(IncrementSize, dl,
179 StackPtr.getValueType()));
181 // Load the second half from the stack slot.
182 Hi = DAG.getLoad(NOutVT, dl, Store, StackPtr,
183 PtrInfo.getWithOffset(IncrementSize), false,
184 false, false, MinAlign(Alignment, IncrementSize));
186 // Handle endianness of the load.
187 if (TLI.hasBigEndianPartOrdering(OutVT, DAG.getDataLayout()))
191 void DAGTypeLegalizer::ExpandRes_BUILD_PAIR(SDNode *N, SDValue &Lo,
193 // Return the operands.
194 Lo = N->getOperand(0);
195 Hi = N->getOperand(1);
198 void DAGTypeLegalizer::ExpandRes_EXTRACT_ELEMENT(SDNode *N, SDValue &Lo,
200 GetExpandedOp(N->getOperand(0), Lo, Hi);
201 SDValue Part = cast<ConstantSDNode>(N->getOperand(1))->getZExtValue() ?
204 assert(Part.getValueType() == N->getValueType(0) &&
205 "Type twice as big as expanded type not itself expanded!");
207 GetPairElements(Part, Lo, Hi);
210 void DAGTypeLegalizer::ExpandRes_EXTRACT_VECTOR_ELT(SDNode *N, SDValue &Lo,
212 SDValue OldVec = N->getOperand(0);
213 unsigned OldElts = OldVec.getValueType().getVectorNumElements();
214 EVT OldEltVT = OldVec.getValueType().getVectorElementType();
217 // Convert to a vector of the expanded element type, for example
218 // <3 x i64> -> <6 x i32>.
219 EVT OldVT = N->getValueType(0);
220 EVT NewVT = TLI.getTypeToTransformTo(*DAG.getContext(), OldVT);
222 if (OldVT != OldEltVT) {
223 // The result of EXTRACT_VECTOR_ELT may be larger than the element type of
224 // the input vector. If so, extend the elements of the input vector to the
225 // same bitwidth as the result before expanding.
226 assert(OldEltVT.bitsLT(OldVT) && "Result type smaller then element type!");
227 EVT NVecVT = EVT::getVectorVT(*DAG.getContext(), OldVT, OldElts);
228 OldVec = DAG.getNode(ISD::ANY_EXTEND, dl, NVecVT, N->getOperand(0));
231 SDValue NewVec = DAG.getNode(ISD::BITCAST, dl,
232 EVT::getVectorVT(*DAG.getContext(),
236 // Extract the elements at 2 * Idx and 2 * Idx + 1 from the new vector.
237 SDValue Idx = N->getOperand(1);
239 Idx = DAG.getNode(ISD::ADD, dl, Idx.getValueType(), Idx, Idx);
240 Lo = DAG.getNode(ISD::EXTRACT_VECTOR_ELT, dl, NewVT, NewVec, Idx);
242 Idx = DAG.getNode(ISD::ADD, dl, Idx.getValueType(), Idx,
243 DAG.getConstant(1, dl, Idx.getValueType()));
244 Hi = DAG.getNode(ISD::EXTRACT_VECTOR_ELT, dl, NewVT, NewVec, Idx);
246 if (DAG.getDataLayout().isBigEndian())
250 void DAGTypeLegalizer::ExpandRes_NormalLoad(SDNode *N, SDValue &Lo,
252 assert(ISD::isNormalLoad(N) && "This routine only for normal loads!");
255 LoadSDNode *LD = cast<LoadSDNode>(N);
256 EVT ValueVT = LD->getValueType(0);
257 EVT NVT = TLI.getTypeToTransformTo(*DAG.getContext(), ValueVT);
258 SDValue Chain = LD->getChain();
259 SDValue Ptr = LD->getBasePtr();
260 unsigned Alignment = LD->getAlignment();
261 bool isVolatile = LD->isVolatile();
262 bool isNonTemporal = LD->isNonTemporal();
263 bool isInvariant = LD->isInvariant();
264 AAMDNodes AAInfo = LD->getAAInfo();
266 assert(NVT.isByteSized() && "Expanded type not byte sized!");
268 Lo = DAG.getLoad(NVT, dl, Chain, Ptr, LD->getPointerInfo(),
269 isVolatile, isNonTemporal, isInvariant, Alignment,
272 // Increment the pointer to the other half.
273 unsigned IncrementSize = NVT.getSizeInBits() / 8;
274 Ptr = DAG.getNode(ISD::ADD, dl, Ptr.getValueType(), Ptr,
275 DAG.getConstant(IncrementSize, dl, Ptr.getValueType()));
276 Hi = DAG.getLoad(NVT, dl, Chain, Ptr,
277 LD->getPointerInfo().getWithOffset(IncrementSize),
278 isVolatile, isNonTemporal, isInvariant,
279 MinAlign(Alignment, IncrementSize), AAInfo);
281 // Build a factor node to remember that this load is independent of the
283 Chain = DAG.getNode(ISD::TokenFactor, dl, MVT::Other, Lo.getValue(1),
286 // Handle endianness of the load.
287 if (TLI.hasBigEndianPartOrdering(ValueVT, DAG.getDataLayout()))
290 // Modified the chain - switch anything that used the old chain to use
292 ReplaceValueWith(SDValue(N, 1), Chain);
295 void DAGTypeLegalizer::ExpandRes_VAARG(SDNode *N, SDValue &Lo, SDValue &Hi) {
296 EVT OVT = N->getValueType(0);
297 EVT NVT = TLI.getTypeToTransformTo(*DAG.getContext(), OVT);
298 SDValue Chain = N->getOperand(0);
299 SDValue Ptr = N->getOperand(1);
301 const unsigned Align = N->getConstantOperandVal(3);
303 Lo = DAG.getVAArg(NVT, dl, Chain, Ptr, N->getOperand(2), Align);
304 Hi = DAG.getVAArg(NVT, dl, Lo.getValue(1), Ptr, N->getOperand(2), 0);
306 // Handle endianness of the load.
307 if (TLI.hasBigEndianPartOrdering(OVT, DAG.getDataLayout()))
310 // Modified the chain - switch anything that used the old chain to use
312 ReplaceValueWith(SDValue(N, 1), Hi.getValue(1));
316 //===--------------------------------------------------------------------===//
317 // Generic Operand Expansion.
318 //===--------------------------------------------------------------------===//
320 void DAGTypeLegalizer::IntegerToVector(SDValue Op, unsigned NumElements,
321 SmallVectorImpl<SDValue> &Ops,
323 assert(Op.getValueType().isInteger());
327 if (NumElements > 1) {
329 SplitInteger(Op, Parts[0], Parts[1]);
330 if (DAG.getDataLayout().isBigEndian())
331 std::swap(Parts[0], Parts[1]);
332 IntegerToVector(Parts[0], NumElements, Ops, EltVT);
333 IntegerToVector(Parts[1], NumElements, Ops, EltVT);
335 Ops.push_back(DAG.getNode(ISD::BITCAST, DL, EltVT, Op));
339 SDValue DAGTypeLegalizer::ExpandOp_BITCAST(SDNode *N) {
341 if (N->getValueType(0).isVector()) {
342 // An illegal expanding type is being converted to a legal vector type.
343 // Make a two element vector out of the expanded parts and convert that
344 // instead, but only if the new vector type is legal (otherwise there
345 // is no point, and it might create expansion loops). For example, on
346 // x86 this turns v1i64 = BITCAST i64 into v1i64 = BITCAST v2i32.
348 // FIXME: I'm not sure why we are first trying to split the input into
349 // a 2 element vector, so I'm leaving it here to maintain the current
351 unsigned NumElts = 2;
352 EVT OVT = N->getOperand(0).getValueType();
353 EVT NVT = EVT::getVectorVT(*DAG.getContext(),
354 TLI.getTypeToTransformTo(*DAG.getContext(), OVT),
356 if (!isTypeLegal(NVT)) {
357 // If we can't find a legal type by splitting the integer in half,
358 // then we can use the node's value type.
359 NumElts = N->getValueType(0).getVectorNumElements();
360 NVT = N->getValueType(0);
363 SmallVector<SDValue, 8> Ops;
364 IntegerToVector(N->getOperand(0), NumElts, Ops, NVT.getVectorElementType());
366 SDValue Vec = DAG.getNode(ISD::BUILD_VECTOR, dl, NVT,
367 makeArrayRef(Ops.data(), NumElts));
368 return DAG.getNode(ISD::BITCAST, dl, N->getValueType(0), Vec);
371 // Otherwise, store to a temporary and load out again as the new type.
372 return CreateStackStoreLoad(N->getOperand(0), N->getValueType(0));
375 SDValue DAGTypeLegalizer::ExpandOp_BUILD_VECTOR(SDNode *N) {
376 // The vector type is legal but the element type needs expansion.
377 EVT VecVT = N->getValueType(0);
378 unsigned NumElts = VecVT.getVectorNumElements();
379 EVT OldVT = N->getOperand(0).getValueType();
380 EVT NewVT = TLI.getTypeToTransformTo(*DAG.getContext(), OldVT);
383 assert(OldVT == VecVT.getVectorElementType() &&
384 "BUILD_VECTOR operand type doesn't match vector element type!");
386 // Build a vector of twice the length out of the expanded elements.
387 // For example <3 x i64> -> <6 x i32>.
388 std::vector<SDValue> NewElts;
389 NewElts.reserve(NumElts*2);
391 for (unsigned i = 0; i < NumElts; ++i) {
393 GetExpandedOp(N->getOperand(i), Lo, Hi);
394 if (DAG.getDataLayout().isBigEndian())
396 NewElts.push_back(Lo);
397 NewElts.push_back(Hi);
400 SDValue NewVec = DAG.getNode(ISD::BUILD_VECTOR, dl,
401 EVT::getVectorVT(*DAG.getContext(),
402 NewVT, NewElts.size()),
405 // Convert the new vector to the old vector type.
406 return DAG.getNode(ISD::BITCAST, dl, VecVT, NewVec);
409 SDValue DAGTypeLegalizer::ExpandOp_EXTRACT_ELEMENT(SDNode *N) {
411 GetExpandedOp(N->getOperand(0), Lo, Hi);
412 return cast<ConstantSDNode>(N->getOperand(1))->getZExtValue() ? Hi : Lo;
415 SDValue DAGTypeLegalizer::ExpandOp_INSERT_VECTOR_ELT(SDNode *N) {
416 // The vector type is legal but the element type needs expansion.
417 EVT VecVT = N->getValueType(0);
418 unsigned NumElts = VecVT.getVectorNumElements();
421 SDValue Val = N->getOperand(1);
422 EVT OldEVT = Val.getValueType();
423 EVT NewEVT = TLI.getTypeToTransformTo(*DAG.getContext(), OldEVT);
425 assert(OldEVT == VecVT.getVectorElementType() &&
426 "Inserted element type doesn't match vector element type!");
428 // Bitconvert to a vector of twice the length with elements of the expanded
429 // type, insert the expanded vector elements, and then convert back.
430 EVT NewVecVT = EVT::getVectorVT(*DAG.getContext(), NewEVT, NumElts*2);
431 SDValue NewVec = DAG.getNode(ISD::BITCAST, dl,
432 NewVecVT, N->getOperand(0));
435 GetExpandedOp(Val, Lo, Hi);
436 if (DAG.getDataLayout().isBigEndian())
439 SDValue Idx = N->getOperand(2);
440 Idx = DAG.getNode(ISD::ADD, dl, Idx.getValueType(), Idx, Idx);
441 NewVec = DAG.getNode(ISD::INSERT_VECTOR_ELT, dl, NewVecVT, NewVec, Lo, Idx);
442 Idx = DAG.getNode(ISD::ADD, dl,
443 Idx.getValueType(), Idx,
444 DAG.getConstant(1, dl, Idx.getValueType()));
445 NewVec = DAG.getNode(ISD::INSERT_VECTOR_ELT, dl, NewVecVT, NewVec, Hi, Idx);
447 // Convert the new vector to the old vector type.
448 return DAG.getNode(ISD::BITCAST, dl, VecVT, NewVec);
451 SDValue DAGTypeLegalizer::ExpandOp_SCALAR_TO_VECTOR(SDNode *N) {
453 EVT VT = N->getValueType(0);
454 assert(VT.getVectorElementType() == N->getOperand(0).getValueType() &&
455 "SCALAR_TO_VECTOR operand type doesn't match vector element type!");
456 unsigned NumElts = VT.getVectorNumElements();
457 SmallVector<SDValue, 16> Ops(NumElts);
458 Ops[0] = N->getOperand(0);
459 SDValue UndefVal = DAG.getUNDEF(Ops[0].getValueType());
460 for (unsigned i = 1; i < NumElts; ++i)
462 return DAG.getNode(ISD::BUILD_VECTOR, dl, VT, Ops);
465 SDValue DAGTypeLegalizer::ExpandOp_NormalStore(SDNode *N, unsigned OpNo) {
466 assert(ISD::isNormalStore(N) && "This routine only for normal stores!");
467 assert(OpNo == 1 && "Can only expand the stored value so far");
470 StoreSDNode *St = cast<StoreSDNode>(N);
471 EVT ValueVT = St->getValue().getValueType();
472 EVT NVT = TLI.getTypeToTransformTo(*DAG.getContext(), ValueVT);
473 SDValue Chain = St->getChain();
474 SDValue Ptr = St->getBasePtr();
475 unsigned Alignment = St->getAlignment();
476 bool isVolatile = St->isVolatile();
477 bool isNonTemporal = St->isNonTemporal();
478 AAMDNodes AAInfo = St->getAAInfo();
480 assert(NVT.isByteSized() && "Expanded type not byte sized!");
481 unsigned IncrementSize = NVT.getSizeInBits() / 8;
484 GetExpandedOp(St->getValue(), Lo, Hi);
486 if (TLI.hasBigEndianPartOrdering(ValueVT, DAG.getDataLayout()))
489 Lo = DAG.getStore(Chain, dl, Lo, Ptr, St->getPointerInfo(),
490 isVolatile, isNonTemporal, Alignment, AAInfo);
492 Ptr = DAG.getNode(ISD::ADD, dl, Ptr.getValueType(), Ptr,
493 DAG.getConstant(IncrementSize, dl, Ptr.getValueType()));
494 Hi = DAG.getStore(Chain, dl, Hi, Ptr,
495 St->getPointerInfo().getWithOffset(IncrementSize),
496 isVolatile, isNonTemporal,
497 MinAlign(Alignment, IncrementSize), AAInfo);
499 return DAG.getNode(ISD::TokenFactor, dl, MVT::Other, Lo, Hi);
503 //===--------------------------------------------------------------------===//
504 // Generic Result Splitting.
505 //===--------------------------------------------------------------------===//
507 // Be careful to make no assumptions about which of Lo/Hi is stored first in
508 // memory (for vectors it is always Lo first followed by Hi in the following
509 // bytes; for integers and floats it is Lo first if and only if the machine is
512 void DAGTypeLegalizer::SplitRes_MERGE_VALUES(SDNode *N, unsigned ResNo,
513 SDValue &Lo, SDValue &Hi) {
514 SDValue Op = DisintegrateMERGE_VALUES(N, ResNo);
515 GetSplitOp(Op, Lo, Hi);
518 void DAGTypeLegalizer::SplitRes_SELECT(SDNode *N, SDValue &Lo,
520 SDValue LL, LH, RL, RH, CL, CH;
522 GetSplitOp(N->getOperand(1), LL, LH);
523 GetSplitOp(N->getOperand(2), RL, RH);
525 SDValue Cond = N->getOperand(0);
527 if (Cond.getValueType().isVector()) {
528 // Check if there are already splitted versions of the vector available and
529 // use those instead of splitting the mask operand again.
530 if (getTypeAction(Cond.getValueType()) == TargetLowering::TypeSplitVector)
531 GetSplitVector(Cond, CL, CH);
533 std::tie(CL, CH) = DAG.SplitVector(Cond, dl);
536 Lo = DAG.getNode(N->getOpcode(), dl, LL.getValueType(), CL, LL, RL);
537 Hi = DAG.getNode(N->getOpcode(), dl, LH.getValueType(), CH, LH, RH);
540 void DAGTypeLegalizer::SplitRes_SELECT_CC(SDNode *N, SDValue &Lo,
542 SDValue LL, LH, RL, RH;
544 GetSplitOp(N->getOperand(2), LL, LH);
545 GetSplitOp(N->getOperand(3), RL, RH);
547 Lo = DAG.getNode(ISD::SELECT_CC, dl, LL.getValueType(), N->getOperand(0),
548 N->getOperand(1), LL, RL, N->getOperand(4));
549 Hi = DAG.getNode(ISD::SELECT_CC, dl, LH.getValueType(), N->getOperand(0),
550 N->getOperand(1), LH, RH, N->getOperand(4));
553 void DAGTypeLegalizer::SplitRes_UNDEF(SDNode *N, SDValue &Lo, SDValue &Hi) {
555 std::tie(LoVT, HiVT) = DAG.GetSplitDestVTs(N->getValueType(0));
556 Lo = DAG.getUNDEF(LoVT);
557 Hi = DAG.getUNDEF(HiVT);