1 //===-- ConstantFolding.cpp - Fold instructions into constants ------------===//
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 defines routines for folding instructions into constants.
12 // Also, to supplement the basic VMCore ConstantExpr simplifications,
13 // this file defines some additional folding routines that can make use of
14 // TargetData information. These functions cannot go in VMCore due to library
17 //===----------------------------------------------------------------------===//
19 #include "llvm/Analysis/ConstantFolding.h"
20 #include "llvm/Constants.h"
21 #include "llvm/DerivedTypes.h"
22 #include "llvm/Function.h"
23 #include "llvm/GlobalVariable.h"
24 #include "llvm/Instructions.h"
25 #include "llvm/Intrinsics.h"
26 #include "llvm/Analysis/ValueTracking.h"
27 #include "llvm/Target/TargetData.h"
28 #include "llvm/ADT/SmallVector.h"
29 #include "llvm/ADT/StringMap.h"
30 #include "llvm/Support/ErrorHandling.h"
31 #include "llvm/Support/GetElementPtrTypeIterator.h"
32 #include "llvm/Support/MathExtras.h"
37 //===----------------------------------------------------------------------===//
38 // Constant Folding internal helper functions
39 //===----------------------------------------------------------------------===//
41 /// FoldBitCast - Constant fold bitcast, symbolically evaluating it with
42 /// TargetData. This always returns a non-null constant, but it may be a
43 /// ConstantExpr if unfoldable.
44 static Constant *FoldBitCast(Constant *C, const Type *DestTy,
45 const TargetData &TD) {
47 // This only handles casts to vectors currently.
48 const VectorType *DestVTy = dyn_cast<VectorType>(DestTy);
50 return ConstantExpr::getBitCast(C, DestTy);
52 // If this is a scalar -> vector cast, convert the input into a <1 x scalar>
53 // vector so the code below can handle it uniformly.
54 if (isa<ConstantFP>(C) || isa<ConstantInt>(C)) {
55 Constant *Ops = C; // don't take the address of C!
56 return FoldBitCast(ConstantVector::get(&Ops, 1), DestTy, TD);
59 // If this is a bitcast from constant vector -> vector, fold it.
60 ConstantVector *CV = dyn_cast<ConstantVector>(C);
62 return ConstantExpr::getBitCast(C, DestTy);
64 // If the element types match, VMCore can fold it.
65 unsigned NumDstElt = DestVTy->getNumElements();
66 unsigned NumSrcElt = CV->getNumOperands();
67 if (NumDstElt == NumSrcElt)
68 return ConstantExpr::getBitCast(C, DestTy);
70 const Type *SrcEltTy = CV->getType()->getElementType();
71 const Type *DstEltTy = DestVTy->getElementType();
73 // Otherwise, we're changing the number of elements in a vector, which
74 // requires endianness information to do the right thing. For example,
75 // bitcast (<2 x i64> <i64 0, i64 1> to <4 x i32>)
76 // folds to (little endian):
77 // <4 x i32> <i32 0, i32 0, i32 1, i32 0>
78 // and to (big endian):
79 // <4 x i32> <i32 0, i32 0, i32 0, i32 1>
81 // First thing is first. We only want to think about integer here, so if
82 // we have something in FP form, recast it as integer.
83 if (DstEltTy->isFloatingPointTy()) {
84 // Fold to an vector of integers with same size as our FP type.
85 unsigned FPWidth = DstEltTy->getPrimitiveSizeInBits();
86 const Type *DestIVTy =
87 VectorType::get(IntegerType::get(C->getContext(), FPWidth), NumDstElt);
88 // Recursively handle this integer conversion, if possible.
89 C = FoldBitCast(C, DestIVTy, TD);
90 if (!C) return ConstantExpr::getBitCast(C, DestTy);
92 // Finally, VMCore can handle this now that #elts line up.
93 return ConstantExpr::getBitCast(C, DestTy);
96 // Okay, we know the destination is integer, if the input is FP, convert
97 // it to integer first.
98 if (SrcEltTy->isFloatingPointTy()) {
99 unsigned FPWidth = SrcEltTy->getPrimitiveSizeInBits();
100 const Type *SrcIVTy =
101 VectorType::get(IntegerType::get(C->getContext(), FPWidth), NumSrcElt);
102 // Ask VMCore to do the conversion now that #elts line up.
103 C = ConstantExpr::getBitCast(C, SrcIVTy);
104 CV = dyn_cast<ConstantVector>(C);
105 if (!CV) // If VMCore wasn't able to fold it, bail out.
109 // Now we know that the input and output vectors are both integer vectors
110 // of the same size, and that their #elements is not the same. Do the
111 // conversion here, which depends on whether the input or output has
113 bool isLittleEndian = TD.isLittleEndian();
115 SmallVector<Constant*, 32> Result;
116 if (NumDstElt < NumSrcElt) {
117 // Handle: bitcast (<4 x i32> <i32 0, i32 1, i32 2, i32 3> to <2 x i64>)
118 Constant *Zero = Constant::getNullValue(DstEltTy);
119 unsigned Ratio = NumSrcElt/NumDstElt;
120 unsigned SrcBitSize = SrcEltTy->getPrimitiveSizeInBits();
122 for (unsigned i = 0; i != NumDstElt; ++i) {
123 // Build each element of the result.
124 Constant *Elt = Zero;
125 unsigned ShiftAmt = isLittleEndian ? 0 : SrcBitSize*(Ratio-1);
126 for (unsigned j = 0; j != Ratio; ++j) {
127 Constant *Src = dyn_cast<ConstantInt>(CV->getOperand(SrcElt++));
128 if (!Src) // Reject constantexpr elements.
129 return ConstantExpr::getBitCast(C, DestTy);
131 // Zero extend the element to the right size.
132 Src = ConstantExpr::getZExt(Src, Elt->getType());
134 // Shift it to the right place, depending on endianness.
135 Src = ConstantExpr::getShl(Src,
136 ConstantInt::get(Src->getType(), ShiftAmt));
137 ShiftAmt += isLittleEndian ? SrcBitSize : -SrcBitSize;
140 Elt = ConstantExpr::getOr(Elt, Src);
142 Result.push_back(Elt);
145 // Handle: bitcast (<2 x i64> <i64 0, i64 1> to <4 x i32>)
146 unsigned Ratio = NumDstElt/NumSrcElt;
147 unsigned DstBitSize = DstEltTy->getPrimitiveSizeInBits();
149 // Loop over each source value, expanding into multiple results.
150 for (unsigned i = 0; i != NumSrcElt; ++i) {
151 Constant *Src = dyn_cast<ConstantInt>(CV->getOperand(i));
152 if (!Src) // Reject constantexpr elements.
153 return ConstantExpr::getBitCast(C, DestTy);
155 unsigned ShiftAmt = isLittleEndian ? 0 : DstBitSize*(Ratio-1);
156 for (unsigned j = 0; j != Ratio; ++j) {
157 // Shift the piece of the value into the right place, depending on
159 Constant *Elt = ConstantExpr::getLShr(Src,
160 ConstantInt::get(Src->getType(), ShiftAmt));
161 ShiftAmt += isLittleEndian ? DstBitSize : -DstBitSize;
163 // Truncate and remember this piece.
164 Result.push_back(ConstantExpr::getTrunc(Elt, DstEltTy));
169 return ConstantVector::get(Result.data(), Result.size());
173 /// IsConstantOffsetFromGlobal - If this constant is actually a constant offset
174 /// from a global, return the global and the constant. Because of
175 /// constantexprs, this function is recursive.
176 static bool IsConstantOffsetFromGlobal(Constant *C, GlobalValue *&GV,
177 int64_t &Offset, const TargetData &TD) {
178 // Trivial case, constant is the global.
179 if ((GV = dyn_cast<GlobalValue>(C))) {
184 // Otherwise, if this isn't a constant expr, bail out.
185 ConstantExpr *CE = dyn_cast<ConstantExpr>(C);
186 if (!CE) return false;
188 // Look through ptr->int and ptr->ptr casts.
189 if (CE->getOpcode() == Instruction::PtrToInt ||
190 CE->getOpcode() == Instruction::BitCast)
191 return IsConstantOffsetFromGlobal(CE->getOperand(0), GV, Offset, TD);
193 // i32* getelementptr ([5 x i32]* @a, i32 0, i32 5)
194 if (CE->getOpcode() == Instruction::GetElementPtr) {
195 // Cannot compute this if the element type of the pointer is missing size
197 if (!cast<PointerType>(CE->getOperand(0)->getType())
198 ->getElementType()->isSized())
201 // If the base isn't a global+constant, we aren't either.
202 if (!IsConstantOffsetFromGlobal(CE->getOperand(0), GV, Offset, TD))
205 // Otherwise, add any offset that our operands provide.
206 gep_type_iterator GTI = gep_type_begin(CE);
207 for (User::const_op_iterator i = CE->op_begin() + 1, e = CE->op_end();
208 i != e; ++i, ++GTI) {
209 ConstantInt *CI = dyn_cast<ConstantInt>(*i);
210 if (!CI) return false; // Index isn't a simple constant?
211 if (CI->getZExtValue() == 0) continue; // Not adding anything.
213 if (const StructType *ST = dyn_cast<StructType>(*GTI)) {
215 Offset += TD.getStructLayout(ST)->getElementOffset(CI->getZExtValue());
217 const SequentialType *SQT = cast<SequentialType>(*GTI);
218 Offset += TD.getTypeAllocSize(SQT->getElementType())*CI->getSExtValue();
227 /// ReadDataFromGlobal - Recursive helper to read bits out of global. C is the
228 /// constant being copied out of. ByteOffset is an offset into C. CurPtr is the
229 /// pointer to copy results into and BytesLeft is the number of bytes left in
230 /// the CurPtr buffer. TD is the target data.
231 static bool ReadDataFromGlobal(Constant *C, uint64_t ByteOffset,
232 unsigned char *CurPtr, unsigned BytesLeft,
233 const TargetData &TD) {
234 assert(ByteOffset <= TD.getTypeAllocSize(C->getType()) &&
235 "Out of range access");
237 // If this element is zero or undefined, we can just return since *CurPtr is
239 if (isa<ConstantAggregateZero>(C) || isa<UndefValue>(C))
242 if (ConstantInt *CI = dyn_cast<ConstantInt>(C)) {
243 if (CI->getBitWidth() > 64 ||
244 (CI->getBitWidth() & 7) != 0)
247 uint64_t Val = CI->getZExtValue();
248 unsigned IntBytes = unsigned(CI->getBitWidth()/8);
250 for (unsigned i = 0; i != BytesLeft && ByteOffset != IntBytes; ++i) {
251 CurPtr[i] = (unsigned char)(Val >> (ByteOffset * 8));
257 if (ConstantFP *CFP = dyn_cast<ConstantFP>(C)) {
258 if (CFP->getType()->isDoubleTy()) {
259 C = FoldBitCast(C, Type::getInt64Ty(C->getContext()), TD);
260 return ReadDataFromGlobal(C, ByteOffset, CurPtr, BytesLeft, TD);
262 if (CFP->getType()->isFloatTy()){
263 C = FoldBitCast(C, Type::getInt32Ty(C->getContext()), TD);
264 return ReadDataFromGlobal(C, ByteOffset, CurPtr, BytesLeft, TD);
269 if (ConstantStruct *CS = dyn_cast<ConstantStruct>(C)) {
270 const StructLayout *SL = TD.getStructLayout(CS->getType());
271 unsigned Index = SL->getElementContainingOffset(ByteOffset);
272 uint64_t CurEltOffset = SL->getElementOffset(Index);
273 ByteOffset -= CurEltOffset;
276 // If the element access is to the element itself and not to tail padding,
277 // read the bytes from the element.
278 uint64_t EltSize = TD.getTypeAllocSize(CS->getOperand(Index)->getType());
280 if (ByteOffset < EltSize &&
281 !ReadDataFromGlobal(CS->getOperand(Index), ByteOffset, CurPtr,
287 // Check to see if we read from the last struct element, if so we're done.
288 if (Index == CS->getType()->getNumElements())
291 // If we read all of the bytes we needed from this element we're done.
292 uint64_t NextEltOffset = SL->getElementOffset(Index);
294 if (BytesLeft <= NextEltOffset-CurEltOffset-ByteOffset)
297 // Move to the next element of the struct.
298 CurPtr += NextEltOffset-CurEltOffset-ByteOffset;
299 BytesLeft -= NextEltOffset-CurEltOffset-ByteOffset;
301 CurEltOffset = NextEltOffset;
306 if (ConstantArray *CA = dyn_cast<ConstantArray>(C)) {
307 uint64_t EltSize = TD.getTypeAllocSize(CA->getType()->getElementType());
308 uint64_t Index = ByteOffset / EltSize;
309 uint64_t Offset = ByteOffset - Index * EltSize;
310 for (; Index != CA->getType()->getNumElements(); ++Index) {
311 if (!ReadDataFromGlobal(CA->getOperand(Index), Offset, CurPtr,
314 if (EltSize >= BytesLeft)
318 BytesLeft -= EltSize;
324 if (ConstantVector *CV = dyn_cast<ConstantVector>(C)) {
325 uint64_t EltSize = TD.getTypeAllocSize(CV->getType()->getElementType());
326 uint64_t Index = ByteOffset / EltSize;
327 uint64_t Offset = ByteOffset - Index * EltSize;
328 for (; Index != CV->getType()->getNumElements(); ++Index) {
329 if (!ReadDataFromGlobal(CV->getOperand(Index), Offset, CurPtr,
332 if (EltSize >= BytesLeft)
336 BytesLeft -= EltSize;
342 // Otherwise, unknown initializer type.
346 static Constant *FoldReinterpretLoadFromConstPtr(Constant *C,
347 const TargetData &TD) {
348 const Type *LoadTy = cast<PointerType>(C->getType())->getElementType();
349 const IntegerType *IntType = dyn_cast<IntegerType>(LoadTy);
351 // If this isn't an integer load we can't fold it directly.
353 // If this is a float/double load, we can try folding it as an int32/64 load
354 // and then bitcast the result. This can be useful for union cases. Note
355 // that address spaces don't matter here since we're not going to result in
356 // an actual new load.
358 if (LoadTy->isFloatTy())
359 MapTy = Type::getInt32PtrTy(C->getContext());
360 else if (LoadTy->isDoubleTy())
361 MapTy = Type::getInt64PtrTy(C->getContext());
362 else if (LoadTy->isVectorTy()) {
363 MapTy = IntegerType::get(C->getContext(),
364 TD.getTypeAllocSizeInBits(LoadTy));
365 MapTy = PointerType::getUnqual(MapTy);
369 C = FoldBitCast(C, MapTy, TD);
370 if (Constant *Res = FoldReinterpretLoadFromConstPtr(C, TD))
371 return FoldBitCast(Res, LoadTy, TD);
375 unsigned BytesLoaded = (IntType->getBitWidth() + 7) / 8;
376 if (BytesLoaded > 32 || BytesLoaded == 0) return 0;
380 if (!IsConstantOffsetFromGlobal(C, GVal, Offset, TD))
383 GlobalVariable *GV = dyn_cast<GlobalVariable>(GVal);
384 if (!GV || !GV->isConstant() || !GV->hasDefinitiveInitializer() ||
385 !GV->getInitializer()->getType()->isSized())
388 // If we're loading off the beginning of the global, some bytes may be valid,
389 // but we don't try to handle this.
390 if (Offset < 0) return 0;
392 // If we're not accessing anything in this constant, the result is undefined.
393 if (uint64_t(Offset) >= TD.getTypeAllocSize(GV->getInitializer()->getType()))
394 return UndefValue::get(IntType);
396 unsigned char RawBytes[32] = {0};
397 if (!ReadDataFromGlobal(GV->getInitializer(), Offset, RawBytes,
401 APInt ResultVal = APInt(IntType->getBitWidth(), RawBytes[BytesLoaded-1]);
402 for (unsigned i = 1; i != BytesLoaded; ++i) {
404 ResultVal |= APInt(IntType->getBitWidth(), RawBytes[BytesLoaded-1-i]);
407 return ConstantInt::get(IntType->getContext(), ResultVal);
410 /// ConstantFoldLoadFromConstPtr - Return the value that a load from C would
411 /// produce if it is constant and determinable. If this is not determinable,
413 Constant *llvm::ConstantFoldLoadFromConstPtr(Constant *C,
414 const TargetData *TD) {
415 // First, try the easy cases:
416 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(C))
417 if (GV->isConstant() && GV->hasDefinitiveInitializer())
418 return GV->getInitializer();
420 // If the loaded value isn't a constant expr, we can't handle it.
421 ConstantExpr *CE = dyn_cast<ConstantExpr>(C);
424 if (CE->getOpcode() == Instruction::GetElementPtr) {
425 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(CE->getOperand(0)))
426 if (GV->isConstant() && GV->hasDefinitiveInitializer())
428 ConstantFoldLoadThroughGEPConstantExpr(GV->getInitializer(), CE))
432 // Instead of loading constant c string, use corresponding integer value
433 // directly if string length is small enough.
435 if (TD && GetConstantStringInfo(CE, Str) && !Str.empty()) {
436 unsigned StrLen = Str.length();
437 const Type *Ty = cast<PointerType>(CE->getType())->getElementType();
438 unsigned NumBits = Ty->getPrimitiveSizeInBits();
439 // Replace LI with immediate integer store.
440 if ((NumBits >> 3) == StrLen + 1) {
441 APInt StrVal(NumBits, 0);
442 APInt SingleChar(NumBits, 0);
443 if (TD->isLittleEndian()) {
444 for (signed i = StrLen-1; i >= 0; i--) {
445 SingleChar = (uint64_t) Str[i] & UCHAR_MAX;
446 StrVal = (StrVal << 8) | SingleChar;
449 for (unsigned i = 0; i < StrLen; i++) {
450 SingleChar = (uint64_t) Str[i] & UCHAR_MAX;
451 StrVal = (StrVal << 8) | SingleChar;
453 // Append NULL at the end.
455 StrVal = (StrVal << 8) | SingleChar;
457 return ConstantInt::get(CE->getContext(), StrVal);
461 // If this load comes from anywhere in a constant global, and if the global
462 // is all undef or zero, we know what it loads.
463 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(CE->getUnderlyingObject())){
464 if (GV->isConstant() && GV->hasDefinitiveInitializer()) {
465 const Type *ResTy = cast<PointerType>(C->getType())->getElementType();
466 if (GV->getInitializer()->isNullValue())
467 return Constant::getNullValue(ResTy);
468 if (isa<UndefValue>(GV->getInitializer()))
469 return UndefValue::get(ResTy);
473 // Try hard to fold loads from bitcasted strange and non-type-safe things. We
474 // currently don't do any of this for big endian systems. It can be
475 // generalized in the future if someone is interested.
476 if (TD && TD->isLittleEndian())
477 return FoldReinterpretLoadFromConstPtr(CE, *TD);
481 static Constant *ConstantFoldLoadInst(const LoadInst *LI, const TargetData *TD){
482 if (LI->isVolatile()) return 0;
484 if (Constant *C = dyn_cast<Constant>(LI->getOperand(0)))
485 return ConstantFoldLoadFromConstPtr(C, TD);
490 /// SymbolicallyEvaluateBinop - One of Op0/Op1 is a constant expression.
491 /// Attempt to symbolically evaluate the result of a binary operator merging
492 /// these together. If target data info is available, it is provided as TD,
493 /// otherwise TD is null.
494 static Constant *SymbolicallyEvaluateBinop(unsigned Opc, Constant *Op0,
495 Constant *Op1, const TargetData *TD){
498 // Fold (and 0xffffffff00000000, (shl x, 32)) -> shl.
499 // Fold (lshr (or X, Y), 32) -> (lshr [X/Y], 32) if one doesn't contribute
503 // If the constant expr is something like &A[123] - &A[4].f, fold this into a
504 // constant. This happens frequently when iterating over a global array.
505 if (Opc == Instruction::Sub && TD) {
506 GlobalValue *GV1, *GV2;
507 int64_t Offs1, Offs2;
509 if (IsConstantOffsetFromGlobal(Op0, GV1, Offs1, *TD))
510 if (IsConstantOffsetFromGlobal(Op1, GV2, Offs2, *TD) &&
512 // (&GV+C1) - (&GV+C2) -> C1-C2, pointer arithmetic cannot overflow.
513 return ConstantInt::get(Op0->getType(), Offs1-Offs2);
520 /// CastGEPIndices - If array indices are not pointer-sized integers,
521 /// explicitly cast them so that they aren't implicitly casted by the
523 static Constant *CastGEPIndices(Constant *const *Ops, unsigned NumOps,
524 const Type *ResultTy,
525 const TargetData *TD) {
527 const Type *IntPtrTy = TD->getIntPtrType(ResultTy->getContext());
530 SmallVector<Constant*, 32> NewIdxs;
531 for (unsigned i = 1; i != NumOps; ++i) {
533 !isa<StructType>(GetElementPtrInst::getIndexedType(Ops[0]->getType(),
534 reinterpret_cast<Value *const *>(Ops+1),
536 Ops[i]->getType() != IntPtrTy) {
538 NewIdxs.push_back(ConstantExpr::getCast(CastInst::getCastOpcode(Ops[i],
544 NewIdxs.push_back(Ops[i]);
549 ConstantExpr::getGetElementPtr(Ops[0], &NewIdxs[0], NewIdxs.size());
550 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(C))
551 if (Constant *Folded = ConstantFoldConstantExpression(CE, TD))
556 /// SymbolicallyEvaluateGEP - If we can symbolically evaluate the specified GEP
557 /// constant expression, do so.
558 static Constant *SymbolicallyEvaluateGEP(Constant *const *Ops, unsigned NumOps,
559 const Type *ResultTy,
560 const TargetData *TD) {
561 Constant *Ptr = Ops[0];
562 if (!TD || !cast<PointerType>(Ptr->getType())->getElementType()->isSized())
566 TD->getTypeSizeInBits(TD->getIntPtrType(Ptr->getContext()));
567 APInt BasePtr(BitWidth, 0);
568 bool BaseIsInt = true;
569 if (!Ptr->isNullValue()) {
570 // If this is a inttoptr from a constant int, we can fold this as the base,
571 // otherwise we can't.
572 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Ptr))
573 if (CE->getOpcode() == Instruction::IntToPtr)
574 if (ConstantInt *Base = dyn_cast<ConstantInt>(CE->getOperand(0))) {
575 BasePtr = Base->getValue();
576 BasePtr.zextOrTrunc(BitWidth);
583 // If this is a constant expr gep that is effectively computing an
584 // "offsetof", fold it into 'cast int Size to T*' instead of 'gep 0, 0, 12'
585 for (unsigned i = 1; i != NumOps; ++i)
586 if (!isa<ConstantInt>(Ops[i]))
589 APInt Offset = APInt(BitWidth,
590 TD->getIndexedOffset(Ptr->getType(),
591 (Value**)Ops+1, NumOps-1));
593 // If this is a GEP of a GEP, fold it all into a single GEP.
594 while (GEPOperator *GEP = dyn_cast<GEPOperator>(Ptr)) {
595 SmallVector<Value *, 4> NestedOps(GEP->op_begin()+1, GEP->op_end());
596 Ptr = cast<Constant>(GEP->getOperand(0));
597 Offset += APInt(BitWidth,
598 TD->getIndexedOffset(Ptr->getType(),
599 (Value**)NestedOps.data(),
603 // If the base value for this address is a literal integer value, fold the
604 // getelementptr to the resulting integer value casted to the pointer type.
606 Constant *C = ConstantInt::get(Ptr->getContext(), Offset+BasePtr);
607 return ConstantExpr::getIntToPtr(C, ResultTy);
610 // Otherwise form a regular getelementptr. Recompute the indices so that
611 // we eliminate over-indexing of the notional static type array bounds.
612 // This makes it easy to determine if the getelementptr is "inbounds".
613 // Also, this helps GlobalOpt do SROA on GlobalVariables.
614 Ptr = cast<Constant>(Ptr->stripPointerCasts());
615 const Type *Ty = Ptr->getType();
616 SmallVector<Constant*, 32> NewIdxs;
618 if (const SequentialType *ATy = dyn_cast<SequentialType>(Ty)) {
619 if (ATy->isPointerTy()) {
620 // The only pointer indexing we'll do is on the first index of the GEP.
621 if (!NewIdxs.empty())
624 // Only handle pointers to sized types, not pointers to functions.
625 if (!ATy->getElementType()->isSized())
629 // Determine which element of the array the offset points into.
630 APInt ElemSize(BitWidth, TD->getTypeAllocSize(ATy->getElementType()));
633 APInt NewIdx = Offset.udiv(ElemSize);
634 Offset -= NewIdx * ElemSize;
635 NewIdxs.push_back(ConstantInt::get(TD->getIntPtrType(Ty->getContext()),
637 Ty = ATy->getElementType();
638 } else if (const StructType *STy = dyn_cast<StructType>(Ty)) {
639 // Determine which field of the struct the offset points into. The
640 // getZExtValue is at least as safe as the StructLayout API because we
641 // know the offset is within the struct at this point.
642 const StructLayout &SL = *TD->getStructLayout(STy);
643 unsigned ElIdx = SL.getElementContainingOffset(Offset.getZExtValue());
644 NewIdxs.push_back(ConstantInt::get(Type::getInt32Ty(Ty->getContext()),
646 Offset -= APInt(BitWidth, SL.getElementOffset(ElIdx));
647 Ty = STy->getTypeAtIndex(ElIdx);
649 // We've reached some non-indexable type.
652 } while (Ty != cast<PointerType>(ResultTy)->getElementType());
654 // If we haven't used up the entire offset by descending the static
655 // type, then the offset is pointing into the middle of an indivisible
656 // member, so we can't simplify it.
662 ConstantExpr::getGetElementPtr(Ptr, &NewIdxs[0], NewIdxs.size());
663 assert(cast<PointerType>(C->getType())->getElementType() == Ty &&
664 "Computed GetElementPtr has unexpected type!");
666 // If we ended up indexing a member with a type that doesn't match
667 // the type of what the original indices indexed, add a cast.
668 if (Ty != cast<PointerType>(ResultTy)->getElementType())
669 C = FoldBitCast(C, ResultTy, *TD);
676 //===----------------------------------------------------------------------===//
677 // Constant Folding public APIs
678 //===----------------------------------------------------------------------===//
681 /// ConstantFoldInstruction - Attempt to constant fold the specified
682 /// instruction. If successful, the constant result is returned, if not, null
683 /// is returned. Note that this function can only fail when attempting to fold
684 /// instructions like loads and stores, which have no constant expression form.
686 Constant *llvm::ConstantFoldInstruction(Instruction *I, const TargetData *TD) {
687 if (PHINode *PN = dyn_cast<PHINode>(I)) {
688 if (PN->getNumIncomingValues() == 0)
689 return UndefValue::get(PN->getType());
691 Constant *Result = dyn_cast<Constant>(PN->getIncomingValue(0));
692 if (Result == 0) return 0;
694 // Handle PHI nodes specially here...
695 for (unsigned i = 1, e = PN->getNumIncomingValues(); i != e; ++i)
696 if (PN->getIncomingValue(i) != Result && PN->getIncomingValue(i) != PN)
697 return 0; // Not all the same incoming constants...
699 // If we reach here, all incoming values are the same constant.
703 // Scan the operand list, checking to see if they are all constants, if so,
704 // hand off to ConstantFoldInstOperands.
705 SmallVector<Constant*, 8> Ops;
706 for (User::op_iterator i = I->op_begin(), e = I->op_end(); i != e; ++i)
707 if (Constant *Op = dyn_cast<Constant>(*i))
710 return 0; // All operands not constant!
712 if (const CmpInst *CI = dyn_cast<CmpInst>(I))
713 return ConstantFoldCompareInstOperands(CI->getPredicate(), Ops[0], Ops[1],
716 if (const LoadInst *LI = dyn_cast<LoadInst>(I))
717 return ConstantFoldLoadInst(LI, TD);
719 return ConstantFoldInstOperands(I->getOpcode(), I->getType(),
720 Ops.data(), Ops.size(), TD);
723 /// ConstantFoldConstantExpression - Attempt to fold the constant expression
724 /// using the specified TargetData. If successful, the constant result is
725 /// result is returned, if not, null is returned.
726 Constant *llvm::ConstantFoldConstantExpression(const ConstantExpr *CE,
727 const TargetData *TD) {
728 SmallVector<Constant*, 8> Ops;
729 for (User::const_op_iterator i = CE->op_begin(), e = CE->op_end(); i != e; ++i) {
730 Constant *NewC = cast<Constant>(*i);
731 // Recursively fold the ConstantExpr's operands.
732 if (ConstantExpr *NewCE = dyn_cast<ConstantExpr>(NewC))
733 NewC = ConstantFoldConstantExpression(NewCE, TD);
738 return ConstantFoldCompareInstOperands(CE->getPredicate(), Ops[0], Ops[1],
740 return ConstantFoldInstOperands(CE->getOpcode(), CE->getType(),
741 Ops.data(), Ops.size(), TD);
744 /// ConstantFoldInstOperands - Attempt to constant fold an instruction with the
745 /// specified opcode and operands. If successful, the constant result is
746 /// returned, if not, null is returned. Note that this function can fail when
747 /// attempting to fold instructions like loads and stores, which have no
748 /// constant expression form.
750 /// TODO: This function neither utilizes nor preserves nsw/nuw/inbounds/etc
751 /// information, due to only being passed an opcode and operands. Constant
752 /// folding using this function strips this information.
754 Constant *llvm::ConstantFoldInstOperands(unsigned Opcode, const Type *DestTy,
755 Constant* const* Ops, unsigned NumOps,
756 const TargetData *TD) {
757 // Handle easy binops first.
758 if (Instruction::isBinaryOp(Opcode)) {
759 if (isa<ConstantExpr>(Ops[0]) || isa<ConstantExpr>(Ops[1]))
760 if (Constant *C = SymbolicallyEvaluateBinop(Opcode, Ops[0], Ops[1], TD))
763 return ConstantExpr::get(Opcode, Ops[0], Ops[1]);
768 case Instruction::ICmp:
769 case Instruction::FCmp: assert(0 && "Invalid for compares");
770 case Instruction::Call:
771 if (Function *F = dyn_cast<Function>(Ops[0]))
772 if (canConstantFoldCallTo(F))
773 return ConstantFoldCall(F, Ops+1, NumOps-1);
775 case Instruction::PtrToInt:
776 // If the input is a inttoptr, eliminate the pair. This requires knowing
777 // the width of a pointer, so it can't be done in ConstantExpr::getCast.
778 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Ops[0])) {
779 if (TD && CE->getOpcode() == Instruction::IntToPtr) {
780 Constant *Input = CE->getOperand(0);
781 unsigned InWidth = Input->getType()->getScalarSizeInBits();
782 if (TD->getPointerSizeInBits() < InWidth) {
784 ConstantInt::get(CE->getContext(), APInt::getLowBitsSet(InWidth,
785 TD->getPointerSizeInBits()));
786 Input = ConstantExpr::getAnd(Input, Mask);
788 // Do a zext or trunc to get to the dest size.
789 return ConstantExpr::getIntegerCast(Input, DestTy, false);
792 return ConstantExpr::getCast(Opcode, Ops[0], DestTy);
793 case Instruction::IntToPtr:
794 // If the input is a ptrtoint, turn the pair into a ptr to ptr bitcast if
795 // the int size is >= the ptr size. This requires knowing the width of a
796 // pointer, so it can't be done in ConstantExpr::getCast.
797 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Ops[0]))
799 TD->getPointerSizeInBits() <= CE->getType()->getScalarSizeInBits() &&
800 CE->getOpcode() == Instruction::PtrToInt)
801 return FoldBitCast(CE->getOperand(0), DestTy, *TD);
803 return ConstantExpr::getCast(Opcode, Ops[0], DestTy);
804 case Instruction::Trunc:
805 case Instruction::ZExt:
806 case Instruction::SExt:
807 case Instruction::FPTrunc:
808 case Instruction::FPExt:
809 case Instruction::UIToFP:
810 case Instruction::SIToFP:
811 case Instruction::FPToUI:
812 case Instruction::FPToSI:
813 return ConstantExpr::getCast(Opcode, Ops[0], DestTy);
814 case Instruction::BitCast:
816 return FoldBitCast(Ops[0], DestTy, *TD);
817 return ConstantExpr::getBitCast(Ops[0], DestTy);
818 case Instruction::Select:
819 return ConstantExpr::getSelect(Ops[0], Ops[1], Ops[2]);
820 case Instruction::ExtractElement:
821 return ConstantExpr::getExtractElement(Ops[0], Ops[1]);
822 case Instruction::InsertElement:
823 return ConstantExpr::getInsertElement(Ops[0], Ops[1], Ops[2]);
824 case Instruction::ShuffleVector:
825 return ConstantExpr::getShuffleVector(Ops[0], Ops[1], Ops[2]);
826 case Instruction::GetElementPtr:
827 if (Constant *C = CastGEPIndices(Ops, NumOps, DestTy, TD))
829 if (Constant *C = SymbolicallyEvaluateGEP(Ops, NumOps, DestTy, TD))
832 return ConstantExpr::getGetElementPtr(Ops[0], Ops+1, NumOps-1);
836 /// ConstantFoldCompareInstOperands - Attempt to constant fold a compare
837 /// instruction (icmp/fcmp) with the specified operands. If it fails, it
838 /// returns a constant expression of the specified operands.
840 Constant *llvm::ConstantFoldCompareInstOperands(unsigned Predicate,
841 Constant *Ops0, Constant *Ops1,
842 const TargetData *TD) {
843 // fold: icmp (inttoptr x), null -> icmp x, 0
844 // fold: icmp (ptrtoint x), 0 -> icmp x, null
845 // fold: icmp (inttoptr x), (inttoptr y) -> icmp trunc/zext x, trunc/zext y
846 // fold: icmp (ptrtoint x), (ptrtoint y) -> icmp x, y
848 // ConstantExpr::getCompare cannot do this, because it doesn't have TD
849 // around to know if bit truncation is happening.
850 if (ConstantExpr *CE0 = dyn_cast<ConstantExpr>(Ops0)) {
851 if (TD && Ops1->isNullValue()) {
852 const Type *IntPtrTy = TD->getIntPtrType(CE0->getContext());
853 if (CE0->getOpcode() == Instruction::IntToPtr) {
854 // Convert the integer value to the right size to ensure we get the
855 // proper extension or truncation.
856 Constant *C = ConstantExpr::getIntegerCast(CE0->getOperand(0),
858 Constant *Null = Constant::getNullValue(C->getType());
859 return ConstantFoldCompareInstOperands(Predicate, C, Null, TD);
862 // Only do this transformation if the int is intptrty in size, otherwise
863 // there is a truncation or extension that we aren't modeling.
864 if (CE0->getOpcode() == Instruction::PtrToInt &&
865 CE0->getType() == IntPtrTy) {
866 Constant *C = CE0->getOperand(0);
867 Constant *Null = Constant::getNullValue(C->getType());
868 return ConstantFoldCompareInstOperands(Predicate, C, Null, TD);
872 if (ConstantExpr *CE1 = dyn_cast<ConstantExpr>(Ops1)) {
873 if (TD && CE0->getOpcode() == CE1->getOpcode()) {
874 const Type *IntPtrTy = TD->getIntPtrType(CE0->getContext());
876 if (CE0->getOpcode() == Instruction::IntToPtr) {
877 // Convert the integer value to the right size to ensure we get the
878 // proper extension or truncation.
879 Constant *C0 = ConstantExpr::getIntegerCast(CE0->getOperand(0),
881 Constant *C1 = ConstantExpr::getIntegerCast(CE1->getOperand(0),
883 return ConstantFoldCompareInstOperands(Predicate, C0, C1, TD);
886 // Only do this transformation if the int is intptrty in size, otherwise
887 // there is a truncation or extension that we aren't modeling.
888 if ((CE0->getOpcode() == Instruction::PtrToInt &&
889 CE0->getType() == IntPtrTy &&
890 CE0->getOperand(0)->getType() == CE1->getOperand(0)->getType()))
891 return ConstantFoldCompareInstOperands(Predicate, CE0->getOperand(0),
892 CE1->getOperand(0), TD);
896 // icmp eq (or x, y), 0 -> (icmp eq x, 0) & (icmp eq y, 0)
897 // icmp ne (or x, y), 0 -> (icmp ne x, 0) | (icmp ne y, 0)
898 if ((Predicate == ICmpInst::ICMP_EQ || Predicate == ICmpInst::ICMP_NE) &&
899 CE0->getOpcode() == Instruction::Or && Ops1->isNullValue()) {
901 ConstantFoldCompareInstOperands(Predicate, CE0->getOperand(0), Ops1,TD);
903 ConstantFoldCompareInstOperands(Predicate, CE0->getOperand(1), Ops1,TD);
905 Predicate == ICmpInst::ICMP_EQ ? Instruction::And : Instruction::Or;
906 Constant *Ops[] = { LHS, RHS };
907 return ConstantFoldInstOperands(OpC, LHS->getType(), Ops, 2, TD);
911 return ConstantExpr::getCompare(Predicate, Ops0, Ops1);
915 /// ConstantFoldLoadThroughGEPConstantExpr - Given a constant and a
916 /// getelementptr constantexpr, return the constant value being addressed by the
917 /// constant expression, or null if something is funny and we can't decide.
918 Constant *llvm::ConstantFoldLoadThroughGEPConstantExpr(Constant *C,
920 if (CE->getOperand(1) != Constant::getNullValue(CE->getOperand(1)->getType()))
921 return 0; // Do not allow stepping over the value!
923 // Loop over all of the operands, tracking down which value we are
925 gep_type_iterator I = gep_type_begin(CE), E = gep_type_end(CE);
926 for (++I; I != E; ++I)
927 if (const StructType *STy = dyn_cast<StructType>(*I)) {
928 ConstantInt *CU = cast<ConstantInt>(I.getOperand());
929 assert(CU->getZExtValue() < STy->getNumElements() &&
930 "Struct index out of range!");
931 unsigned El = (unsigned)CU->getZExtValue();
932 if (ConstantStruct *CS = dyn_cast<ConstantStruct>(C)) {
933 C = CS->getOperand(El);
934 } else if (isa<ConstantAggregateZero>(C)) {
935 C = Constant::getNullValue(STy->getElementType(El));
936 } else if (isa<UndefValue>(C)) {
937 C = UndefValue::get(STy->getElementType(El));
941 } else if (ConstantInt *CI = dyn_cast<ConstantInt>(I.getOperand())) {
942 if (const ArrayType *ATy = dyn_cast<ArrayType>(*I)) {
943 if (CI->getZExtValue() >= ATy->getNumElements())
945 if (ConstantArray *CA = dyn_cast<ConstantArray>(C))
946 C = CA->getOperand(CI->getZExtValue());
947 else if (isa<ConstantAggregateZero>(C))
948 C = Constant::getNullValue(ATy->getElementType());
949 else if (isa<UndefValue>(C))
950 C = UndefValue::get(ATy->getElementType());
953 } else if (const VectorType *VTy = dyn_cast<VectorType>(*I)) {
954 if (CI->getZExtValue() >= VTy->getNumElements())
956 if (ConstantVector *CP = dyn_cast<ConstantVector>(C))
957 C = CP->getOperand(CI->getZExtValue());
958 else if (isa<ConstantAggregateZero>(C))
959 C = Constant::getNullValue(VTy->getElementType());
960 else if (isa<UndefValue>(C))
961 C = UndefValue::get(VTy->getElementType());
974 //===----------------------------------------------------------------------===//
975 // Constant Folding for Calls
978 /// canConstantFoldCallTo - Return true if its even possible to fold a call to
979 /// the specified function.
981 llvm::canConstantFoldCallTo(const Function *F) {
982 switch (F->getIntrinsicID()) {
983 case Intrinsic::sqrt:
984 case Intrinsic::powi:
985 case Intrinsic::bswap:
986 case Intrinsic::ctpop:
987 case Intrinsic::ctlz:
988 case Intrinsic::cttz:
989 case Intrinsic::uadd_with_overflow:
990 case Intrinsic::usub_with_overflow:
991 case Intrinsic::sadd_with_overflow:
992 case Intrinsic::ssub_with_overflow:
999 if (!F->hasName()) return false;
1000 StringRef Name = F->getName();
1002 // In these cases, the check of the length is required. We don't want to
1003 // return true for a name like "cos\0blah" which strcmp would return equal to
1004 // "cos", but has length 8.
1006 default: return false;
1008 return Name == "acos" || Name == "asin" ||
1009 Name == "atan" || Name == "atan2";
1011 return Name == "cos" || Name == "ceil" || Name == "cosf" || Name == "cosh";
1013 return Name == "exp";
1015 return Name == "fabs" || Name == "fmod" || Name == "floor";
1017 return Name == "log" || Name == "log10";
1019 return Name == "pow";
1021 return Name == "sin" || Name == "sinh" || Name == "sqrt" ||
1022 Name == "sinf" || Name == "sqrtf";
1024 return Name == "tan" || Name == "tanh";
1028 static Constant *ConstantFoldFP(double (*NativeFP)(double), double V,
1037 if (Ty->isFloatTy())
1038 return ConstantFP::get(Ty->getContext(), APFloat((float)V));
1039 if (Ty->isDoubleTy())
1040 return ConstantFP::get(Ty->getContext(), APFloat(V));
1041 llvm_unreachable("Can only constant fold float/double");
1042 return 0; // dummy return to suppress warning
1045 static Constant *ConstantFoldBinaryFP(double (*NativeFP)(double, double),
1046 double V, double W, const Type *Ty) {
1054 if (Ty->isFloatTy())
1055 return ConstantFP::get(Ty->getContext(), APFloat((float)V));
1056 if (Ty->isDoubleTy())
1057 return ConstantFP::get(Ty->getContext(), APFloat(V));
1058 llvm_unreachable("Can only constant fold float/double");
1059 return 0; // dummy return to suppress warning
1062 /// ConstantFoldCall - Attempt to constant fold a call to the specified function
1063 /// with the specified arguments, returning null if unsuccessful.
1065 llvm::ConstantFoldCall(Function *F,
1066 Constant *const *Operands, unsigned NumOperands) {
1067 if (!F->hasName()) return 0;
1068 StringRef Name = F->getName();
1070 const Type *Ty = F->getReturnType();
1071 if (NumOperands == 1) {
1072 if (ConstantFP *Op = dyn_cast<ConstantFP>(Operands[0])) {
1073 if (!Ty->isFloatTy() && !Ty->isDoubleTy())
1075 /// Currently APFloat versions of these functions do not exist, so we use
1076 /// the host native double versions. Float versions are not called
1077 /// directly but for all these it is true (float)(f((double)arg)) ==
1078 /// f(arg). Long double not supported yet.
1079 double V = Ty->isFloatTy() ? (double)Op->getValueAPF().convertToFloat() :
1080 Op->getValueAPF().convertToDouble();
1084 return ConstantFoldFP(acos, V, Ty);
1085 else if (Name == "asin")
1086 return ConstantFoldFP(asin, V, Ty);
1087 else if (Name == "atan")
1088 return ConstantFoldFP(atan, V, Ty);
1092 return ConstantFoldFP(ceil, V, Ty);
1093 else if (Name == "cos")
1094 return ConstantFoldFP(cos, V, Ty);
1095 else if (Name == "cosh")
1096 return ConstantFoldFP(cosh, V, Ty);
1097 else if (Name == "cosf")
1098 return ConstantFoldFP(cos, V, Ty);
1102 return ConstantFoldFP(exp, V, Ty);
1106 return ConstantFoldFP(fabs, V, Ty);
1107 else if (Name == "floor")
1108 return ConstantFoldFP(floor, V, Ty);
1111 if (Name == "log" && V > 0)
1112 return ConstantFoldFP(log, V, Ty);
1113 else if (Name == "log10" && V > 0)
1114 return ConstantFoldFP(log10, V, Ty);
1115 else if (Name == "llvm.sqrt.f32" ||
1116 Name == "llvm.sqrt.f64") {
1118 return ConstantFoldFP(sqrt, V, Ty);
1120 return Constant::getNullValue(Ty);
1125 return ConstantFoldFP(sin, V, Ty);
1126 else if (Name == "sinh")
1127 return ConstantFoldFP(sinh, V, Ty);
1128 else if (Name == "sqrt" && V >= 0)
1129 return ConstantFoldFP(sqrt, V, Ty);
1130 else if (Name == "sqrtf" && V >= 0)
1131 return ConstantFoldFP(sqrt, V, Ty);
1132 else if (Name == "sinf")
1133 return ConstantFoldFP(sin, V, Ty);
1137 return ConstantFoldFP(tan, V, Ty);
1138 else if (Name == "tanh")
1139 return ConstantFoldFP(tanh, V, Ty);
1148 if (ConstantInt *Op = dyn_cast<ConstantInt>(Operands[0])) {
1149 if (Name.startswith("llvm.bswap"))
1150 return ConstantInt::get(F->getContext(), Op->getValue().byteSwap());
1151 else if (Name.startswith("llvm.ctpop"))
1152 return ConstantInt::get(Ty, Op->getValue().countPopulation());
1153 else if (Name.startswith("llvm.cttz"))
1154 return ConstantInt::get(Ty, Op->getValue().countTrailingZeros());
1155 else if (Name.startswith("llvm.ctlz"))
1156 return ConstantInt::get(Ty, Op->getValue().countLeadingZeros());
1160 if (isa<UndefValue>(Operands[0])) {
1161 if (Name.startswith("llvm.bswap"))
1169 if (NumOperands == 2) {
1170 if (ConstantFP *Op1 = dyn_cast<ConstantFP>(Operands[0])) {
1171 if (!Ty->isFloatTy() && !Ty->isDoubleTy())
1173 double Op1V = Ty->isFloatTy() ?
1174 (double)Op1->getValueAPF().convertToFloat() :
1175 Op1->getValueAPF().convertToDouble();
1176 if (ConstantFP *Op2 = dyn_cast<ConstantFP>(Operands[1])) {
1177 if (Op2->getType() != Op1->getType())
1180 double Op2V = Ty->isFloatTy() ?
1181 (double)Op2->getValueAPF().convertToFloat():
1182 Op2->getValueAPF().convertToDouble();
1185 return ConstantFoldBinaryFP(pow, Op1V, Op2V, Ty);
1187 return ConstantFoldBinaryFP(fmod, Op1V, Op2V, Ty);
1188 if (Name == "atan2")
1189 return ConstantFoldBinaryFP(atan2, Op1V, Op2V, Ty);
1190 } else if (ConstantInt *Op2C = dyn_cast<ConstantInt>(Operands[1])) {
1191 if (Name == "llvm.powi.f32")
1192 return ConstantFP::get(F->getContext(),
1193 APFloat((float)std::pow((float)Op1V,
1194 (int)Op2C->getZExtValue())));
1195 if (Name == "llvm.powi.f64")
1196 return ConstantFP::get(F->getContext(),
1197 APFloat((double)std::pow((double)Op1V,
1198 (int)Op2C->getZExtValue())));
1204 if (ConstantInt *Op1 = dyn_cast<ConstantInt>(Operands[0])) {
1205 if (ConstantInt *Op2 = dyn_cast<ConstantInt>(Operands[1])) {
1206 switch (F->getIntrinsicID()) {
1208 case Intrinsic::uadd_with_overflow: {
1209 Constant *Res = ConstantExpr::getAdd(Op1, Op2); // result.
1211 Res, ConstantExpr::getICmp(CmpInst::ICMP_ULT, Res, Op1) // overflow.
1213 return ConstantStruct::get(F->getContext(), Ops, 2, false);
1215 case Intrinsic::usub_with_overflow: {
1216 Constant *Res = ConstantExpr::getSub(Op1, Op2); // result.
1218 Res, ConstantExpr::getICmp(CmpInst::ICMP_UGT, Res, Op1) // overflow.
1220 return ConstantStruct::get(F->getContext(), Ops, 2, false);
1222 case Intrinsic::sadd_with_overflow: {
1223 Constant *Res = ConstantExpr::getAdd(Op1, Op2); // result.
1224 Constant *Overflow = ConstantExpr::getSelect(
1225 ConstantExpr::getICmp(CmpInst::ICMP_SGT,
1226 ConstantInt::get(Op1->getType(), 0), Op1),
1227 ConstantExpr::getICmp(CmpInst::ICMP_SGT, Res, Op2),
1228 ConstantExpr::getICmp(CmpInst::ICMP_SLT, Res, Op2)); // overflow.
1230 Constant *Ops[] = { Res, Overflow };
1231 return ConstantStruct::get(F->getContext(), Ops, 2, false);
1233 case Intrinsic::ssub_with_overflow: {
1234 Constant *Res = ConstantExpr::getSub(Op1, Op2); // result.
1235 Constant *Overflow = ConstantExpr::getSelect(
1236 ConstantExpr::getICmp(CmpInst::ICMP_SGT,
1237 ConstantInt::get(Op2->getType(), 0), Op2),
1238 ConstantExpr::getICmp(CmpInst::ICMP_SLT, Res, Op1),
1239 ConstantExpr::getICmp(CmpInst::ICMP_SGT, Res, Op1)); // overflow.
1241 Constant *Ops[] = { Res, Overflow };
1242 return ConstantStruct::get(F->getContext(), Ops, 2, false);