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"
33 #include "llvm/System/FEnv.h"
39 //===----------------------------------------------------------------------===//
40 // Constant Folding internal helper functions
41 //===----------------------------------------------------------------------===//
43 /// FoldBitCast - Constant fold bitcast, symbolically evaluating it with
44 /// TargetData. This always returns a non-null constant, but it may be a
45 /// ConstantExpr if unfoldable.
46 static Constant *FoldBitCast(Constant *C, const Type *DestTy,
47 const TargetData &TD) {
49 // This only handles casts to vectors currently.
50 const VectorType *DestVTy = dyn_cast<VectorType>(DestTy);
52 return ConstantExpr::getBitCast(C, DestTy);
54 // If this is a scalar -> vector cast, convert the input into a <1 x scalar>
55 // vector so the code below can handle it uniformly.
56 if (isa<ConstantFP>(C) || isa<ConstantInt>(C)) {
57 Constant *Ops = C; // don't take the address of C!
58 return FoldBitCast(ConstantVector::get(&Ops, 1), DestTy, TD);
61 // If this is a bitcast from constant vector -> vector, fold it.
62 ConstantVector *CV = dyn_cast<ConstantVector>(C);
64 return ConstantExpr::getBitCast(C, DestTy);
66 // If the element types match, VMCore can fold it.
67 unsigned NumDstElt = DestVTy->getNumElements();
68 unsigned NumSrcElt = CV->getNumOperands();
69 if (NumDstElt == NumSrcElt)
70 return ConstantExpr::getBitCast(C, DestTy);
72 const Type *SrcEltTy = CV->getType()->getElementType();
73 const Type *DstEltTy = DestVTy->getElementType();
75 // Otherwise, we're changing the number of elements in a vector, which
76 // requires endianness information to do the right thing. For example,
77 // bitcast (<2 x i64> <i64 0, i64 1> to <4 x i32>)
78 // folds to (little endian):
79 // <4 x i32> <i32 0, i32 0, i32 1, i32 0>
80 // and to (big endian):
81 // <4 x i32> <i32 0, i32 0, i32 0, i32 1>
83 // First thing is first. We only want to think about integer here, so if
84 // we have something in FP form, recast it as integer.
85 if (DstEltTy->isFloatingPointTy()) {
86 // Fold to an vector of integers with same size as our FP type.
87 unsigned FPWidth = DstEltTy->getPrimitiveSizeInBits();
88 const Type *DestIVTy =
89 VectorType::get(IntegerType::get(C->getContext(), FPWidth), NumDstElt);
90 // Recursively handle this integer conversion, if possible.
91 C = FoldBitCast(C, DestIVTy, TD);
92 if (!C) return ConstantExpr::getBitCast(C, DestTy);
94 // Finally, VMCore can handle this now that #elts line up.
95 return ConstantExpr::getBitCast(C, DestTy);
98 // Okay, we know the destination is integer, if the input is FP, convert
99 // it to integer first.
100 if (SrcEltTy->isFloatingPointTy()) {
101 unsigned FPWidth = SrcEltTy->getPrimitiveSizeInBits();
102 const Type *SrcIVTy =
103 VectorType::get(IntegerType::get(C->getContext(), FPWidth), NumSrcElt);
104 // Ask VMCore to do the conversion now that #elts line up.
105 C = ConstantExpr::getBitCast(C, SrcIVTy);
106 CV = dyn_cast<ConstantVector>(C);
107 if (!CV) // If VMCore wasn't able to fold it, bail out.
111 // Now we know that the input and output vectors are both integer vectors
112 // of the same size, and that their #elements is not the same. Do the
113 // conversion here, which depends on whether the input or output has
115 bool isLittleEndian = TD.isLittleEndian();
117 SmallVector<Constant*, 32> Result;
118 if (NumDstElt < NumSrcElt) {
119 // Handle: bitcast (<4 x i32> <i32 0, i32 1, i32 2, i32 3> to <2 x i64>)
120 Constant *Zero = Constant::getNullValue(DstEltTy);
121 unsigned Ratio = NumSrcElt/NumDstElt;
122 unsigned SrcBitSize = SrcEltTy->getPrimitiveSizeInBits();
124 for (unsigned i = 0; i != NumDstElt; ++i) {
125 // Build each element of the result.
126 Constant *Elt = Zero;
127 unsigned ShiftAmt = isLittleEndian ? 0 : SrcBitSize*(Ratio-1);
128 for (unsigned j = 0; j != Ratio; ++j) {
129 Constant *Src = dyn_cast<ConstantInt>(CV->getOperand(SrcElt++));
130 if (!Src) // Reject constantexpr elements.
131 return ConstantExpr::getBitCast(C, DestTy);
133 // Zero extend the element to the right size.
134 Src = ConstantExpr::getZExt(Src, Elt->getType());
136 // Shift it to the right place, depending on endianness.
137 Src = ConstantExpr::getShl(Src,
138 ConstantInt::get(Src->getType(), ShiftAmt));
139 ShiftAmt += isLittleEndian ? SrcBitSize : -SrcBitSize;
142 Elt = ConstantExpr::getOr(Elt, Src);
144 Result.push_back(Elt);
147 // Handle: bitcast (<2 x i64> <i64 0, i64 1> to <4 x i32>)
148 unsigned Ratio = NumDstElt/NumSrcElt;
149 unsigned DstBitSize = DstEltTy->getPrimitiveSizeInBits();
151 // Loop over each source value, expanding into multiple results.
152 for (unsigned i = 0; i != NumSrcElt; ++i) {
153 Constant *Src = dyn_cast<ConstantInt>(CV->getOperand(i));
154 if (!Src) // Reject constantexpr elements.
155 return ConstantExpr::getBitCast(C, DestTy);
157 unsigned ShiftAmt = isLittleEndian ? 0 : DstBitSize*(Ratio-1);
158 for (unsigned j = 0; j != Ratio; ++j) {
159 // Shift the piece of the value into the right place, depending on
161 Constant *Elt = ConstantExpr::getLShr(Src,
162 ConstantInt::get(Src->getType(), ShiftAmt));
163 ShiftAmt += isLittleEndian ? DstBitSize : -DstBitSize;
165 // Truncate and remember this piece.
166 Result.push_back(ConstantExpr::getTrunc(Elt, DstEltTy));
171 return ConstantVector::get(Result.data(), Result.size());
175 /// IsConstantOffsetFromGlobal - If this constant is actually a constant offset
176 /// from a global, return the global and the constant. Because of
177 /// constantexprs, this function is recursive.
178 static bool IsConstantOffsetFromGlobal(Constant *C, GlobalValue *&GV,
179 int64_t &Offset, const TargetData &TD) {
180 // Trivial case, constant is the global.
181 if ((GV = dyn_cast<GlobalValue>(C))) {
186 // Otherwise, if this isn't a constant expr, bail out.
187 ConstantExpr *CE = dyn_cast<ConstantExpr>(C);
188 if (!CE) return false;
190 // Look through ptr->int and ptr->ptr casts.
191 if (CE->getOpcode() == Instruction::PtrToInt ||
192 CE->getOpcode() == Instruction::BitCast)
193 return IsConstantOffsetFromGlobal(CE->getOperand(0), GV, Offset, TD);
195 // i32* getelementptr ([5 x i32]* @a, i32 0, i32 5)
196 if (CE->getOpcode() == Instruction::GetElementPtr) {
197 // Cannot compute this if the element type of the pointer is missing size
199 if (!cast<PointerType>(CE->getOperand(0)->getType())
200 ->getElementType()->isSized())
203 // If the base isn't a global+constant, we aren't either.
204 if (!IsConstantOffsetFromGlobal(CE->getOperand(0), GV, Offset, TD))
207 // Otherwise, add any offset that our operands provide.
208 gep_type_iterator GTI = gep_type_begin(CE);
209 for (User::const_op_iterator i = CE->op_begin() + 1, e = CE->op_end();
210 i != e; ++i, ++GTI) {
211 ConstantInt *CI = dyn_cast<ConstantInt>(*i);
212 if (!CI) return false; // Index isn't a simple constant?
213 if (CI->isZero()) continue; // Not adding anything.
215 if (const StructType *ST = dyn_cast<StructType>(*GTI)) {
217 Offset += TD.getStructLayout(ST)->getElementOffset(CI->getZExtValue());
219 const SequentialType *SQT = cast<SequentialType>(*GTI);
220 Offset += TD.getTypeAllocSize(SQT->getElementType())*CI->getSExtValue();
229 /// ReadDataFromGlobal - Recursive helper to read bits out of global. C is the
230 /// constant being copied out of. ByteOffset is an offset into C. CurPtr is the
231 /// pointer to copy results into and BytesLeft is the number of bytes left in
232 /// the CurPtr buffer. TD is the target data.
233 static bool ReadDataFromGlobal(Constant *C, uint64_t ByteOffset,
234 unsigned char *CurPtr, unsigned BytesLeft,
235 const TargetData &TD) {
236 assert(ByteOffset <= TD.getTypeAllocSize(C->getType()) &&
237 "Out of range access");
239 // If this element is zero or undefined, we can just return since *CurPtr is
241 if (isa<ConstantAggregateZero>(C) || isa<UndefValue>(C))
244 if (ConstantInt *CI = dyn_cast<ConstantInt>(C)) {
245 if (CI->getBitWidth() > 64 ||
246 (CI->getBitWidth() & 7) != 0)
249 uint64_t Val = CI->getZExtValue();
250 unsigned IntBytes = unsigned(CI->getBitWidth()/8);
252 for (unsigned i = 0; i != BytesLeft && ByteOffset != IntBytes; ++i) {
253 CurPtr[i] = (unsigned char)(Val >> (ByteOffset * 8));
259 if (ConstantFP *CFP = dyn_cast<ConstantFP>(C)) {
260 if (CFP->getType()->isDoubleTy()) {
261 C = FoldBitCast(C, Type::getInt64Ty(C->getContext()), TD);
262 return ReadDataFromGlobal(C, ByteOffset, CurPtr, BytesLeft, TD);
264 if (CFP->getType()->isFloatTy()){
265 C = FoldBitCast(C, Type::getInt32Ty(C->getContext()), TD);
266 return ReadDataFromGlobal(C, ByteOffset, CurPtr, BytesLeft, TD);
271 if (ConstantStruct *CS = dyn_cast<ConstantStruct>(C)) {
272 const StructLayout *SL = TD.getStructLayout(CS->getType());
273 unsigned Index = SL->getElementContainingOffset(ByteOffset);
274 uint64_t CurEltOffset = SL->getElementOffset(Index);
275 ByteOffset -= CurEltOffset;
278 // If the element access is to the element itself and not to tail padding,
279 // read the bytes from the element.
280 uint64_t EltSize = TD.getTypeAllocSize(CS->getOperand(Index)->getType());
282 if (ByteOffset < EltSize &&
283 !ReadDataFromGlobal(CS->getOperand(Index), ByteOffset, CurPtr,
289 // Check to see if we read from the last struct element, if so we're done.
290 if (Index == CS->getType()->getNumElements())
293 // If we read all of the bytes we needed from this element we're done.
294 uint64_t NextEltOffset = SL->getElementOffset(Index);
296 if (BytesLeft <= NextEltOffset-CurEltOffset-ByteOffset)
299 // Move to the next element of the struct.
300 CurPtr += NextEltOffset-CurEltOffset-ByteOffset;
301 BytesLeft -= NextEltOffset-CurEltOffset-ByteOffset;
303 CurEltOffset = NextEltOffset;
308 if (ConstantArray *CA = dyn_cast<ConstantArray>(C)) {
309 uint64_t EltSize = TD.getTypeAllocSize(CA->getType()->getElementType());
310 uint64_t Index = ByteOffset / EltSize;
311 uint64_t Offset = ByteOffset - Index * EltSize;
312 for (; Index != CA->getType()->getNumElements(); ++Index) {
313 if (!ReadDataFromGlobal(CA->getOperand(Index), Offset, CurPtr,
316 if (EltSize >= BytesLeft)
320 BytesLeft -= EltSize;
326 if (ConstantVector *CV = dyn_cast<ConstantVector>(C)) {
327 uint64_t EltSize = TD.getTypeAllocSize(CV->getType()->getElementType());
328 uint64_t Index = ByteOffset / EltSize;
329 uint64_t Offset = ByteOffset - Index * EltSize;
330 for (; Index != CV->getType()->getNumElements(); ++Index) {
331 if (!ReadDataFromGlobal(CV->getOperand(Index), Offset, CurPtr,
334 if (EltSize >= BytesLeft)
338 BytesLeft -= EltSize;
344 // Otherwise, unknown initializer type.
348 static Constant *FoldReinterpretLoadFromConstPtr(Constant *C,
349 const TargetData &TD) {
350 const Type *LoadTy = cast<PointerType>(C->getType())->getElementType();
351 const IntegerType *IntType = dyn_cast<IntegerType>(LoadTy);
353 // If this isn't an integer load we can't fold it directly.
355 // If this is a float/double load, we can try folding it as an int32/64 load
356 // and then bitcast the result. This can be useful for union cases. Note
357 // that address spaces don't matter here since we're not going to result in
358 // an actual new load.
360 if (LoadTy->isFloatTy())
361 MapTy = Type::getInt32PtrTy(C->getContext());
362 else if (LoadTy->isDoubleTy())
363 MapTy = Type::getInt64PtrTy(C->getContext());
364 else if (LoadTy->isVectorTy()) {
365 MapTy = IntegerType::get(C->getContext(),
366 TD.getTypeAllocSizeInBits(LoadTy));
367 MapTy = PointerType::getUnqual(MapTy);
371 C = FoldBitCast(C, MapTy, TD);
372 if (Constant *Res = FoldReinterpretLoadFromConstPtr(C, TD))
373 return FoldBitCast(Res, LoadTy, TD);
377 unsigned BytesLoaded = (IntType->getBitWidth() + 7) / 8;
378 if (BytesLoaded > 32 || BytesLoaded == 0) return 0;
382 if (!IsConstantOffsetFromGlobal(C, GVal, Offset, TD))
385 GlobalVariable *GV = dyn_cast<GlobalVariable>(GVal);
386 if (!GV || !GV->isConstant() || !GV->hasDefinitiveInitializer() ||
387 !GV->getInitializer()->getType()->isSized())
390 // If we're loading off the beginning of the global, some bytes may be valid,
391 // but we don't try to handle this.
392 if (Offset < 0) return 0;
394 // If we're not accessing anything in this constant, the result is undefined.
395 if (uint64_t(Offset) >= TD.getTypeAllocSize(GV->getInitializer()->getType()))
396 return UndefValue::get(IntType);
398 unsigned char RawBytes[32] = {0};
399 if (!ReadDataFromGlobal(GV->getInitializer(), Offset, RawBytes,
403 APInt ResultVal = APInt(IntType->getBitWidth(), RawBytes[BytesLoaded-1]);
404 for (unsigned i = 1; i != BytesLoaded; ++i) {
406 ResultVal |= RawBytes[BytesLoaded-1-i];
409 return ConstantInt::get(IntType->getContext(), ResultVal);
412 /// ConstantFoldLoadFromConstPtr - Return the value that a load from C would
413 /// produce if it is constant and determinable. If this is not determinable,
415 Constant *llvm::ConstantFoldLoadFromConstPtr(Constant *C,
416 const TargetData *TD) {
417 // First, try the easy cases:
418 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(C))
419 if (GV->isConstant() && GV->hasDefinitiveInitializer())
420 return GV->getInitializer();
422 // If the loaded value isn't a constant expr, we can't handle it.
423 ConstantExpr *CE = dyn_cast<ConstantExpr>(C);
426 if (CE->getOpcode() == Instruction::GetElementPtr) {
427 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(CE->getOperand(0)))
428 if (GV->isConstant() && GV->hasDefinitiveInitializer())
430 ConstantFoldLoadThroughGEPConstantExpr(GV->getInitializer(), CE))
434 // Instead of loading constant c string, use corresponding integer value
435 // directly if string length is small enough.
437 if (TD && GetConstantStringInfo(CE, Str) && !Str.empty()) {
438 unsigned StrLen = Str.length();
439 const Type *Ty = cast<PointerType>(CE->getType())->getElementType();
440 unsigned NumBits = Ty->getPrimitiveSizeInBits();
441 // Replace load with immediate integer if the result is an integer or fp
443 if ((NumBits >> 3) == StrLen + 1 && (NumBits & 7) == 0 &&
444 (isa<IntegerType>(Ty) || Ty->isFloatingPointTy())) {
445 APInt StrVal(NumBits, 0);
446 APInt SingleChar(NumBits, 0);
447 if (TD->isLittleEndian()) {
448 for (signed i = StrLen-1; i >= 0; i--) {
449 SingleChar = (uint64_t) Str[i] & UCHAR_MAX;
450 StrVal = (StrVal << 8) | SingleChar;
453 for (unsigned i = 0; i < StrLen; i++) {
454 SingleChar = (uint64_t) Str[i] & UCHAR_MAX;
455 StrVal = (StrVal << 8) | SingleChar;
457 // Append NULL at the end.
459 StrVal = (StrVal << 8) | SingleChar;
462 Constant *Res = ConstantInt::get(CE->getContext(), StrVal);
463 if (Ty->isFloatingPointTy())
464 Res = ConstantExpr::getBitCast(Res, Ty);
469 // If this load comes from anywhere in a constant global, and if the global
470 // is all undef or zero, we know what it loads.
471 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(CE->getUnderlyingObject())){
472 if (GV->isConstant() && GV->hasDefinitiveInitializer()) {
473 const Type *ResTy = cast<PointerType>(C->getType())->getElementType();
474 if (GV->getInitializer()->isNullValue())
475 return Constant::getNullValue(ResTy);
476 if (isa<UndefValue>(GV->getInitializer()))
477 return UndefValue::get(ResTy);
481 // Try hard to fold loads from bitcasted strange and non-type-safe things. We
482 // currently don't do any of this for big endian systems. It can be
483 // generalized in the future if someone is interested.
484 if (TD && TD->isLittleEndian())
485 return FoldReinterpretLoadFromConstPtr(CE, *TD);
489 static Constant *ConstantFoldLoadInst(const LoadInst *LI, const TargetData *TD){
490 if (LI->isVolatile()) return 0;
492 if (Constant *C = dyn_cast<Constant>(LI->getOperand(0)))
493 return ConstantFoldLoadFromConstPtr(C, TD);
498 /// SymbolicallyEvaluateBinop - One of Op0/Op1 is a constant expression.
499 /// Attempt to symbolically evaluate the result of a binary operator merging
500 /// these together. If target data info is available, it is provided as TD,
501 /// otherwise TD is null.
502 static Constant *SymbolicallyEvaluateBinop(unsigned Opc, Constant *Op0,
503 Constant *Op1, const TargetData *TD){
506 // Fold (and 0xffffffff00000000, (shl x, 32)) -> shl.
507 // Fold (lshr (or X, Y), 32) -> (lshr [X/Y], 32) if one doesn't contribute
511 // If the constant expr is something like &A[123] - &A[4].f, fold this into a
512 // constant. This happens frequently when iterating over a global array.
513 if (Opc == Instruction::Sub && TD) {
514 GlobalValue *GV1, *GV2;
515 int64_t Offs1, Offs2;
517 if (IsConstantOffsetFromGlobal(Op0, GV1, Offs1, *TD))
518 if (IsConstantOffsetFromGlobal(Op1, GV2, Offs2, *TD) &&
520 // (&GV+C1) - (&GV+C2) -> C1-C2, pointer arithmetic cannot overflow.
521 return ConstantInt::get(Op0->getType(), Offs1-Offs2);
528 /// CastGEPIndices - If array indices are not pointer-sized integers,
529 /// explicitly cast them so that they aren't implicitly casted by the
531 static Constant *CastGEPIndices(Constant *const *Ops, unsigned NumOps,
532 const Type *ResultTy,
533 const TargetData *TD) {
535 const Type *IntPtrTy = TD->getIntPtrType(ResultTy->getContext());
538 SmallVector<Constant*, 32> NewIdxs;
539 for (unsigned i = 1; i != NumOps; ++i) {
541 !isa<StructType>(GetElementPtrInst::getIndexedType(Ops[0]->getType(),
542 reinterpret_cast<Value *const *>(Ops+1),
544 Ops[i]->getType() != IntPtrTy) {
546 NewIdxs.push_back(ConstantExpr::getCast(CastInst::getCastOpcode(Ops[i],
552 NewIdxs.push_back(Ops[i]);
557 ConstantExpr::getGetElementPtr(Ops[0], &NewIdxs[0], NewIdxs.size());
558 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(C))
559 if (Constant *Folded = ConstantFoldConstantExpression(CE, TD))
564 /// SymbolicallyEvaluateGEP - If we can symbolically evaluate the specified GEP
565 /// constant expression, do so.
566 static Constant *SymbolicallyEvaluateGEP(Constant *const *Ops, unsigned NumOps,
567 const Type *ResultTy,
568 const TargetData *TD) {
569 Constant *Ptr = Ops[0];
570 if (!TD || !cast<PointerType>(Ptr->getType())->getElementType()->isSized())
574 TD->getTypeSizeInBits(TD->getIntPtrType(Ptr->getContext()));
576 // If this is a constant expr gep that is effectively computing an
577 // "offsetof", fold it into 'cast int Size to T*' instead of 'gep 0, 0, 12'
578 for (unsigned i = 1; i != NumOps; ++i)
579 if (!isa<ConstantInt>(Ops[i]))
582 APInt Offset = APInt(BitWidth,
583 TD->getIndexedOffset(Ptr->getType(),
584 (Value**)Ops+1, NumOps-1));
585 Ptr = cast<Constant>(Ptr->stripPointerCasts());
587 // If this is a GEP of a GEP, fold it all into a single GEP.
588 while (GEPOperator *GEP = dyn_cast<GEPOperator>(Ptr)) {
589 SmallVector<Value *, 4> NestedOps(GEP->op_begin()+1, GEP->op_end());
591 // Do not try the incorporate the sub-GEP if some index is not a number.
592 bool AllConstantInt = true;
593 for (unsigned i = 0, e = NestedOps.size(); i != e; ++i)
594 if (!isa<ConstantInt>(NestedOps[i])) {
595 AllConstantInt = false;
601 Ptr = cast<Constant>(GEP->getOperand(0));
602 Offset += APInt(BitWidth,
603 TD->getIndexedOffset(Ptr->getType(),
604 (Value**)NestedOps.data(),
606 Ptr = cast<Constant>(Ptr->stripPointerCasts());
609 // If the base value for this address is a literal integer value, fold the
610 // getelementptr to the resulting integer value casted to the pointer type.
611 APInt BasePtr(BitWidth, 0);
612 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Ptr))
613 if (CE->getOpcode() == Instruction::IntToPtr)
614 if (ConstantInt *Base = dyn_cast<ConstantInt>(CE->getOperand(0))) {
615 BasePtr = Base->getValue();
616 BasePtr.zextOrTrunc(BitWidth);
618 if (Ptr->isNullValue() || BasePtr != 0) {
619 Constant *C = ConstantInt::get(Ptr->getContext(), Offset+BasePtr);
620 return ConstantExpr::getIntToPtr(C, ResultTy);
623 // Otherwise form a regular getelementptr. Recompute the indices so that
624 // we eliminate over-indexing of the notional static type array bounds.
625 // This makes it easy to determine if the getelementptr is "inbounds".
626 // Also, this helps GlobalOpt do SROA on GlobalVariables.
627 const Type *Ty = Ptr->getType();
628 SmallVector<Constant*, 32> NewIdxs;
630 if (const SequentialType *ATy = dyn_cast<SequentialType>(Ty)) {
631 if (ATy->isPointerTy()) {
632 // The only pointer indexing we'll do is on the first index of the GEP.
633 if (!NewIdxs.empty())
636 // Only handle pointers to sized types, not pointers to functions.
637 if (!ATy->getElementType()->isSized())
641 // Determine which element of the array the offset points into.
642 APInt ElemSize(BitWidth, TD->getTypeAllocSize(ATy->getElementType()));
645 APInt NewIdx = Offset.udiv(ElemSize);
646 Offset -= NewIdx * ElemSize;
647 NewIdxs.push_back(ConstantInt::get(TD->getIntPtrType(Ty->getContext()),
649 Ty = ATy->getElementType();
650 } else if (const StructType *STy = dyn_cast<StructType>(Ty)) {
651 // Determine which field of the struct the offset points into. The
652 // getZExtValue is at least as safe as the StructLayout API because we
653 // know the offset is within the struct at this point.
654 const StructLayout &SL = *TD->getStructLayout(STy);
655 unsigned ElIdx = SL.getElementContainingOffset(Offset.getZExtValue());
656 NewIdxs.push_back(ConstantInt::get(Type::getInt32Ty(Ty->getContext()),
658 Offset -= APInt(BitWidth, SL.getElementOffset(ElIdx));
659 Ty = STy->getTypeAtIndex(ElIdx);
661 // We've reached some non-indexable type.
664 } while (Ty != cast<PointerType>(ResultTy)->getElementType());
666 // If we haven't used up the entire offset by descending the static
667 // type, then the offset is pointing into the middle of an indivisible
668 // member, so we can't simplify it.
674 ConstantExpr::getGetElementPtr(Ptr, &NewIdxs[0], NewIdxs.size());
675 assert(cast<PointerType>(C->getType())->getElementType() == Ty &&
676 "Computed GetElementPtr has unexpected type!");
678 // If we ended up indexing a member with a type that doesn't match
679 // the type of what the original indices indexed, add a cast.
680 if (Ty != cast<PointerType>(ResultTy)->getElementType())
681 C = FoldBitCast(C, ResultTy, *TD);
688 //===----------------------------------------------------------------------===//
689 // Constant Folding public APIs
690 //===----------------------------------------------------------------------===//
693 /// ConstantFoldInstruction - Attempt to constant fold the specified
694 /// instruction. If successful, the constant result is returned, if not, null
695 /// is returned. Note that this function can only fail when attempting to fold
696 /// instructions like loads and stores, which have no constant expression form.
698 Constant *llvm::ConstantFoldInstruction(Instruction *I, const TargetData *TD) {
699 if (PHINode *PN = dyn_cast<PHINode>(I)) {
700 if (PN->getNumIncomingValues() == 0)
701 return UndefValue::get(PN->getType());
703 Constant *Result = dyn_cast<Constant>(PN->getIncomingValue(0));
704 if (Result == 0) return 0;
706 // Handle PHI nodes specially here...
707 for (unsigned i = 1, e = PN->getNumIncomingValues(); i != e; ++i)
708 if (PN->getIncomingValue(i) != Result && PN->getIncomingValue(i) != PN)
709 return 0; // Not all the same incoming constants...
711 // If we reach here, all incoming values are the same constant.
715 // Scan the operand list, checking to see if they are all constants, if so,
716 // hand off to ConstantFoldInstOperands.
717 SmallVector<Constant*, 8> Ops;
718 for (User::op_iterator i = I->op_begin(), e = I->op_end(); i != e; ++i)
719 if (Constant *Op = dyn_cast<Constant>(*i))
722 return 0; // All operands not constant!
724 if (const CmpInst *CI = dyn_cast<CmpInst>(I))
725 return ConstantFoldCompareInstOperands(CI->getPredicate(), Ops[0], Ops[1],
728 if (const LoadInst *LI = dyn_cast<LoadInst>(I))
729 return ConstantFoldLoadInst(LI, TD);
731 return ConstantFoldInstOperands(I->getOpcode(), I->getType(),
732 Ops.data(), Ops.size(), TD);
735 /// ConstantFoldConstantExpression - Attempt to fold the constant expression
736 /// using the specified TargetData. If successful, the constant result is
737 /// result is returned, if not, null is returned.
738 Constant *llvm::ConstantFoldConstantExpression(const ConstantExpr *CE,
739 const TargetData *TD) {
740 SmallVector<Constant*, 8> Ops;
741 for (User::const_op_iterator i = CE->op_begin(), e = CE->op_end(); i != e; ++i) {
742 Constant *NewC = cast<Constant>(*i);
743 // Recursively fold the ConstantExpr's operands.
744 if (ConstantExpr *NewCE = dyn_cast<ConstantExpr>(NewC))
745 NewC = ConstantFoldConstantExpression(NewCE, TD);
750 return ConstantFoldCompareInstOperands(CE->getPredicate(), Ops[0], Ops[1],
752 return ConstantFoldInstOperands(CE->getOpcode(), CE->getType(),
753 Ops.data(), Ops.size(), TD);
756 /// ConstantFoldInstOperands - Attempt to constant fold an instruction with the
757 /// specified opcode and operands. If successful, the constant result is
758 /// returned, if not, null is returned. Note that this function can fail when
759 /// attempting to fold instructions like loads and stores, which have no
760 /// constant expression form.
762 /// TODO: This function neither utilizes nor preserves nsw/nuw/inbounds/etc
763 /// information, due to only being passed an opcode and operands. Constant
764 /// folding using this function strips this information.
766 Constant *llvm::ConstantFoldInstOperands(unsigned Opcode, const Type *DestTy,
767 Constant* const* Ops, unsigned NumOps,
768 const TargetData *TD) {
769 // Handle easy binops first.
770 if (Instruction::isBinaryOp(Opcode)) {
771 if (isa<ConstantExpr>(Ops[0]) || isa<ConstantExpr>(Ops[1]))
772 if (Constant *C = SymbolicallyEvaluateBinop(Opcode, Ops[0], Ops[1], TD))
775 return ConstantExpr::get(Opcode, Ops[0], Ops[1]);
780 case Instruction::ICmp:
781 case Instruction::FCmp: assert(0 && "Invalid for compares");
782 case Instruction::Call:
783 if (Function *F = dyn_cast<Function>(Ops[NumOps - 1]))
784 if (canConstantFoldCallTo(F))
785 return ConstantFoldCall(F, Ops, NumOps - 1);
787 case Instruction::PtrToInt:
788 // If the input is a inttoptr, eliminate the pair. This requires knowing
789 // the width of a pointer, so it can't be done in ConstantExpr::getCast.
790 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Ops[0])) {
791 if (TD && CE->getOpcode() == Instruction::IntToPtr) {
792 Constant *Input = CE->getOperand(0);
793 unsigned InWidth = Input->getType()->getScalarSizeInBits();
794 if (TD->getPointerSizeInBits() < InWidth) {
796 ConstantInt::get(CE->getContext(), APInt::getLowBitsSet(InWidth,
797 TD->getPointerSizeInBits()));
798 Input = ConstantExpr::getAnd(Input, Mask);
800 // Do a zext or trunc to get to the dest size.
801 return ConstantExpr::getIntegerCast(Input, DestTy, false);
804 return ConstantExpr::getCast(Opcode, Ops[0], DestTy);
805 case Instruction::IntToPtr:
806 // If the input is a ptrtoint, turn the pair into a ptr to ptr bitcast if
807 // the int size is >= the ptr size. This requires knowing the width of a
808 // pointer, so it can't be done in ConstantExpr::getCast.
809 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Ops[0]))
811 TD->getPointerSizeInBits() <= CE->getType()->getScalarSizeInBits() &&
812 CE->getOpcode() == Instruction::PtrToInt)
813 return FoldBitCast(CE->getOperand(0), DestTy, *TD);
815 return ConstantExpr::getCast(Opcode, Ops[0], DestTy);
816 case Instruction::Trunc:
817 case Instruction::ZExt:
818 case Instruction::SExt:
819 case Instruction::FPTrunc:
820 case Instruction::FPExt:
821 case Instruction::UIToFP:
822 case Instruction::SIToFP:
823 case Instruction::FPToUI:
824 case Instruction::FPToSI:
825 return ConstantExpr::getCast(Opcode, Ops[0], DestTy);
826 case Instruction::BitCast:
828 return FoldBitCast(Ops[0], DestTy, *TD);
829 return ConstantExpr::getBitCast(Ops[0], DestTy);
830 case Instruction::Select:
831 return ConstantExpr::getSelect(Ops[0], Ops[1], Ops[2]);
832 case Instruction::ExtractElement:
833 return ConstantExpr::getExtractElement(Ops[0], Ops[1]);
834 case Instruction::InsertElement:
835 return ConstantExpr::getInsertElement(Ops[0], Ops[1], Ops[2]);
836 case Instruction::ShuffleVector:
837 return ConstantExpr::getShuffleVector(Ops[0], Ops[1], Ops[2]);
838 case Instruction::GetElementPtr:
839 if (Constant *C = CastGEPIndices(Ops, NumOps, DestTy, TD))
841 if (Constant *C = SymbolicallyEvaluateGEP(Ops, NumOps, DestTy, TD))
844 return ConstantExpr::getGetElementPtr(Ops[0], Ops+1, NumOps-1);
848 /// ConstantFoldCompareInstOperands - Attempt to constant fold a compare
849 /// instruction (icmp/fcmp) with the specified operands. If it fails, it
850 /// returns a constant expression of the specified operands.
852 Constant *llvm::ConstantFoldCompareInstOperands(unsigned Predicate,
853 Constant *Ops0, Constant *Ops1,
854 const TargetData *TD) {
855 // fold: icmp (inttoptr x), null -> icmp x, 0
856 // fold: icmp (ptrtoint x), 0 -> icmp x, null
857 // fold: icmp (inttoptr x), (inttoptr y) -> icmp trunc/zext x, trunc/zext y
858 // fold: icmp (ptrtoint x), (ptrtoint y) -> icmp x, y
860 // ConstantExpr::getCompare cannot do this, because it doesn't have TD
861 // around to know if bit truncation is happening.
862 if (ConstantExpr *CE0 = dyn_cast<ConstantExpr>(Ops0)) {
863 if (TD && Ops1->isNullValue()) {
864 const Type *IntPtrTy = TD->getIntPtrType(CE0->getContext());
865 if (CE0->getOpcode() == Instruction::IntToPtr) {
866 // Convert the integer value to the right size to ensure we get the
867 // proper extension or truncation.
868 Constant *C = ConstantExpr::getIntegerCast(CE0->getOperand(0),
870 Constant *Null = Constant::getNullValue(C->getType());
871 return ConstantFoldCompareInstOperands(Predicate, C, Null, TD);
874 // Only do this transformation if the int is intptrty in size, otherwise
875 // there is a truncation or extension that we aren't modeling.
876 if (CE0->getOpcode() == Instruction::PtrToInt &&
877 CE0->getType() == IntPtrTy) {
878 Constant *C = CE0->getOperand(0);
879 Constant *Null = Constant::getNullValue(C->getType());
880 return ConstantFoldCompareInstOperands(Predicate, C, Null, TD);
884 if (ConstantExpr *CE1 = dyn_cast<ConstantExpr>(Ops1)) {
885 if (TD && CE0->getOpcode() == CE1->getOpcode()) {
886 const Type *IntPtrTy = TD->getIntPtrType(CE0->getContext());
888 if (CE0->getOpcode() == Instruction::IntToPtr) {
889 // Convert the integer value to the right size to ensure we get the
890 // proper extension or truncation.
891 Constant *C0 = ConstantExpr::getIntegerCast(CE0->getOperand(0),
893 Constant *C1 = ConstantExpr::getIntegerCast(CE1->getOperand(0),
895 return ConstantFoldCompareInstOperands(Predicate, C0, C1, TD);
898 // Only do this transformation if the int is intptrty in size, otherwise
899 // there is a truncation or extension that we aren't modeling.
900 if ((CE0->getOpcode() == Instruction::PtrToInt &&
901 CE0->getType() == IntPtrTy &&
902 CE0->getOperand(0)->getType() == CE1->getOperand(0)->getType()))
903 return ConstantFoldCompareInstOperands(Predicate, CE0->getOperand(0),
904 CE1->getOperand(0), TD);
908 // icmp eq (or x, y), 0 -> (icmp eq x, 0) & (icmp eq y, 0)
909 // icmp ne (or x, y), 0 -> (icmp ne x, 0) | (icmp ne y, 0)
910 if ((Predicate == ICmpInst::ICMP_EQ || Predicate == ICmpInst::ICMP_NE) &&
911 CE0->getOpcode() == Instruction::Or && Ops1->isNullValue()) {
913 ConstantFoldCompareInstOperands(Predicate, CE0->getOperand(0), Ops1,TD);
915 ConstantFoldCompareInstOperands(Predicate, CE0->getOperand(1), Ops1,TD);
917 Predicate == ICmpInst::ICMP_EQ ? Instruction::And : Instruction::Or;
918 Constant *Ops[] = { LHS, RHS };
919 return ConstantFoldInstOperands(OpC, LHS->getType(), Ops, 2, TD);
923 return ConstantExpr::getCompare(Predicate, Ops0, Ops1);
927 /// ConstantFoldLoadThroughGEPConstantExpr - Given a constant and a
928 /// getelementptr constantexpr, return the constant value being addressed by the
929 /// constant expression, or null if something is funny and we can't decide.
930 Constant *llvm::ConstantFoldLoadThroughGEPConstantExpr(Constant *C,
932 if (CE->getOperand(1) != Constant::getNullValue(CE->getOperand(1)->getType()))
933 return 0; // Do not allow stepping over the value!
935 // Loop over all of the operands, tracking down which value we are
937 gep_type_iterator I = gep_type_begin(CE), E = gep_type_end(CE);
938 for (++I; I != E; ++I)
939 if (const StructType *STy = dyn_cast<StructType>(*I)) {
940 ConstantInt *CU = cast<ConstantInt>(I.getOperand());
941 assert(CU->getZExtValue() < STy->getNumElements() &&
942 "Struct index out of range!");
943 unsigned El = (unsigned)CU->getZExtValue();
944 if (ConstantStruct *CS = dyn_cast<ConstantStruct>(C)) {
945 C = CS->getOperand(El);
946 } else if (isa<ConstantAggregateZero>(C)) {
947 C = Constant::getNullValue(STy->getElementType(El));
948 } else if (isa<UndefValue>(C)) {
949 C = UndefValue::get(STy->getElementType(El));
953 } else if (ConstantInt *CI = dyn_cast<ConstantInt>(I.getOperand())) {
954 if (const ArrayType *ATy = dyn_cast<ArrayType>(*I)) {
955 if (CI->getZExtValue() >= ATy->getNumElements())
957 if (ConstantArray *CA = dyn_cast<ConstantArray>(C))
958 C = CA->getOperand(CI->getZExtValue());
959 else if (isa<ConstantAggregateZero>(C))
960 C = Constant::getNullValue(ATy->getElementType());
961 else if (isa<UndefValue>(C))
962 C = UndefValue::get(ATy->getElementType());
965 } else if (const VectorType *VTy = dyn_cast<VectorType>(*I)) {
966 if (CI->getZExtValue() >= VTy->getNumElements())
968 if (ConstantVector *CP = dyn_cast<ConstantVector>(C))
969 C = CP->getOperand(CI->getZExtValue());
970 else if (isa<ConstantAggregateZero>(C))
971 C = Constant::getNullValue(VTy->getElementType());
972 else if (isa<UndefValue>(C))
973 C = UndefValue::get(VTy->getElementType());
986 //===----------------------------------------------------------------------===//
987 // Constant Folding for Calls
990 /// canConstantFoldCallTo - Return true if its even possible to fold a call to
991 /// the specified function.
993 llvm::canConstantFoldCallTo(const Function *F) {
994 switch (F->getIntrinsicID()) {
995 case Intrinsic::sqrt:
996 case Intrinsic::powi:
997 case Intrinsic::bswap:
998 case Intrinsic::ctpop:
999 case Intrinsic::ctlz:
1000 case Intrinsic::cttz:
1001 case Intrinsic::uadd_with_overflow:
1002 case Intrinsic::usub_with_overflow:
1003 case Intrinsic::sadd_with_overflow:
1004 case Intrinsic::ssub_with_overflow:
1005 case Intrinsic::convert_from_fp16:
1006 case Intrinsic::convert_to_fp16:
1013 if (!F->hasName()) return false;
1014 StringRef Name = F->getName();
1016 // In these cases, the check of the length is required. We don't want to
1017 // return true for a name like "cos\0blah" which strcmp would return equal to
1018 // "cos", but has length 8.
1020 default: return false;
1022 return Name == "acos" || Name == "asin" ||
1023 Name == "atan" || Name == "atan2";
1025 return Name == "cos" || Name == "ceil" || Name == "cosf" || Name == "cosh";
1027 return Name == "exp";
1029 return Name == "fabs" || Name == "fmod" || Name == "floor";
1031 return Name == "log" || Name == "log10";
1033 return Name == "pow";
1035 return Name == "sin" || Name == "sinh" || Name == "sqrt" ||
1036 Name == "sinf" || Name == "sqrtf";
1038 return Name == "tan" || Name == "tanh";
1042 static Constant *ConstantFoldFP(double (*NativeFP)(double), double V,
1044 sys::llvm_fenv_clearexcept();
1046 if (sys::llvm_fenv_testexcept()) {
1047 sys::llvm_fenv_clearexcept();
1051 if (Ty->isFloatTy())
1052 return ConstantFP::get(Ty->getContext(), APFloat((float)V));
1053 if (Ty->isDoubleTy())
1054 return ConstantFP::get(Ty->getContext(), APFloat(V));
1055 llvm_unreachable("Can only constant fold float/double");
1056 return 0; // dummy return to suppress warning
1059 static Constant *ConstantFoldBinaryFP(double (*NativeFP)(double, double),
1060 double V, double W, const Type *Ty) {
1061 sys::llvm_fenv_clearexcept();
1063 if (sys::llvm_fenv_testexcept()) {
1064 sys::llvm_fenv_clearexcept();
1068 if (Ty->isFloatTy())
1069 return ConstantFP::get(Ty->getContext(), APFloat((float)V));
1070 if (Ty->isDoubleTy())
1071 return ConstantFP::get(Ty->getContext(), APFloat(V));
1072 llvm_unreachable("Can only constant fold float/double");
1073 return 0; // dummy return to suppress warning
1076 /// ConstantFoldCall - Attempt to constant fold a call to the specified function
1077 /// with the specified arguments, returning null if unsuccessful.
1079 llvm::ConstantFoldCall(Function *F,
1080 Constant *const *Operands, unsigned NumOperands) {
1081 if (!F->hasName()) return 0;
1082 StringRef Name = F->getName();
1084 const Type *Ty = F->getReturnType();
1085 if (NumOperands == 1) {
1086 if (ConstantFP *Op = dyn_cast<ConstantFP>(Operands[0])) {
1087 if (Name == "llvm.convert.to.fp16") {
1088 APFloat Val(Op->getValueAPF());
1091 Val.convert(APFloat::IEEEhalf, APFloat::rmNearestTiesToEven, &lost);
1093 return ConstantInt::get(F->getContext(), Val.bitcastToAPInt());
1096 if (!Ty->isFloatTy() && !Ty->isDoubleTy())
1098 /// Currently APFloat versions of these functions do not exist, so we use
1099 /// the host native double versions. Float versions are not called
1100 /// directly but for all these it is true (float)(f((double)arg)) ==
1101 /// f(arg). Long double not supported yet.
1102 double V = Ty->isFloatTy() ? (double)Op->getValueAPF().convertToFloat() :
1103 Op->getValueAPF().convertToDouble();
1107 return ConstantFoldFP(acos, V, Ty);
1108 else if (Name == "asin")
1109 return ConstantFoldFP(asin, V, Ty);
1110 else if (Name == "atan")
1111 return ConstantFoldFP(atan, V, Ty);
1115 return ConstantFoldFP(ceil, V, Ty);
1116 else if (Name == "cos")
1117 return ConstantFoldFP(cos, V, Ty);
1118 else if (Name == "cosh")
1119 return ConstantFoldFP(cosh, V, Ty);
1120 else if (Name == "cosf")
1121 return ConstantFoldFP(cos, V, Ty);
1125 return ConstantFoldFP(exp, V, Ty);
1129 return ConstantFoldFP(fabs, V, Ty);
1130 else if (Name == "floor")
1131 return ConstantFoldFP(floor, V, Ty);
1134 if (Name == "log" && V > 0)
1135 return ConstantFoldFP(log, V, Ty);
1136 else if (Name == "log10" && V > 0)
1137 return ConstantFoldFP(log10, V, Ty);
1138 else if (Name == "llvm.sqrt.f32" ||
1139 Name == "llvm.sqrt.f64") {
1141 return ConstantFoldFP(sqrt, V, Ty);
1143 return Constant::getNullValue(Ty);
1148 return ConstantFoldFP(sin, V, Ty);
1149 else if (Name == "sinh")
1150 return ConstantFoldFP(sinh, V, Ty);
1151 else if (Name == "sqrt" && V >= 0)
1152 return ConstantFoldFP(sqrt, V, Ty);
1153 else if (Name == "sqrtf" && V >= 0)
1154 return ConstantFoldFP(sqrt, V, Ty);
1155 else if (Name == "sinf")
1156 return ConstantFoldFP(sin, V, Ty);
1160 return ConstantFoldFP(tan, V, Ty);
1161 else if (Name == "tanh")
1162 return ConstantFoldFP(tanh, V, Ty);
1171 if (ConstantInt *Op = dyn_cast<ConstantInt>(Operands[0])) {
1172 if (Name.startswith("llvm.bswap"))
1173 return ConstantInt::get(F->getContext(), Op->getValue().byteSwap());
1174 else if (Name.startswith("llvm.ctpop"))
1175 return ConstantInt::get(Ty, Op->getValue().countPopulation());
1176 else if (Name.startswith("llvm.cttz"))
1177 return ConstantInt::get(Ty, Op->getValue().countTrailingZeros());
1178 else if (Name.startswith("llvm.ctlz"))
1179 return ConstantInt::get(Ty, Op->getValue().countLeadingZeros());
1180 else if (Name == "llvm.convert.from.fp16") {
1181 APFloat Val(Op->getValue());
1184 APFloat::opStatus status =
1185 Val.convert(APFloat::IEEEsingle, APFloat::rmNearestTiesToEven, &lost);
1187 // Conversion is always precise.
1189 assert(status == APFloat::opOK && !lost &&
1190 "Precision lost during fp16 constfolding");
1192 return ConstantFP::get(F->getContext(), Val);
1197 if (isa<UndefValue>(Operands[0])) {
1198 if (Name.startswith("llvm.bswap"))
1206 if (NumOperands == 2) {
1207 if (ConstantFP *Op1 = dyn_cast<ConstantFP>(Operands[0])) {
1208 if (!Ty->isFloatTy() && !Ty->isDoubleTy())
1210 double Op1V = Ty->isFloatTy() ?
1211 (double)Op1->getValueAPF().convertToFloat() :
1212 Op1->getValueAPF().convertToDouble();
1213 if (ConstantFP *Op2 = dyn_cast<ConstantFP>(Operands[1])) {
1214 if (Op2->getType() != Op1->getType())
1217 double Op2V = Ty->isFloatTy() ?
1218 (double)Op2->getValueAPF().convertToFloat():
1219 Op2->getValueAPF().convertToDouble();
1222 return ConstantFoldBinaryFP(pow, Op1V, Op2V, Ty);
1224 return ConstantFoldBinaryFP(fmod, Op1V, Op2V, Ty);
1225 if (Name == "atan2")
1226 return ConstantFoldBinaryFP(atan2, Op1V, Op2V, Ty);
1227 } else if (ConstantInt *Op2C = dyn_cast<ConstantInt>(Operands[1])) {
1228 if (Name == "llvm.powi.f32")
1229 return ConstantFP::get(F->getContext(),
1230 APFloat((float)std::pow((float)Op1V,
1231 (int)Op2C->getZExtValue())));
1232 if (Name == "llvm.powi.f64")
1233 return ConstantFP::get(F->getContext(),
1234 APFloat((double)std::pow((double)Op1V,
1235 (int)Op2C->getZExtValue())));
1241 if (ConstantInt *Op1 = dyn_cast<ConstantInt>(Operands[0])) {
1242 if (ConstantInt *Op2 = dyn_cast<ConstantInt>(Operands[1])) {
1243 switch (F->getIntrinsicID()) {
1245 case Intrinsic::uadd_with_overflow: {
1246 Constant *Res = ConstantExpr::getAdd(Op1, Op2); // result.
1248 Res, ConstantExpr::getICmp(CmpInst::ICMP_ULT, Res, Op1) // overflow.
1250 return ConstantStruct::get(F->getContext(), Ops, 2, false);
1252 case Intrinsic::usub_with_overflow: {
1253 Constant *Res = ConstantExpr::getSub(Op1, Op2); // result.
1255 Res, ConstantExpr::getICmp(CmpInst::ICMP_UGT, Res, Op1) // overflow.
1257 return ConstantStruct::get(F->getContext(), Ops, 2, false);
1259 case Intrinsic::sadd_with_overflow: {
1260 Constant *Res = ConstantExpr::getAdd(Op1, Op2); // result.
1261 Constant *Overflow = ConstantExpr::getSelect(
1262 ConstantExpr::getICmp(CmpInst::ICMP_SGT,
1263 ConstantInt::get(Op1->getType(), 0), Op1),
1264 ConstantExpr::getICmp(CmpInst::ICMP_SGT, Res, Op2),
1265 ConstantExpr::getICmp(CmpInst::ICMP_SLT, Res, Op2)); // overflow.
1267 Constant *Ops[] = { Res, Overflow };
1268 return ConstantStruct::get(F->getContext(), Ops, 2, false);
1270 case Intrinsic::ssub_with_overflow: {
1271 Constant *Res = ConstantExpr::getSub(Op1, Op2); // result.
1272 Constant *Overflow = ConstantExpr::getSelect(
1273 ConstantExpr::getICmp(CmpInst::ICMP_SGT,
1274 ConstantInt::get(Op2->getType(), 0), Op2),
1275 ConstantExpr::getICmp(CmpInst::ICMP_SLT, Res, Op1),
1276 ConstantExpr::getICmp(CmpInst::ICMP_SGT, Res, Op1)); // overflow.
1278 Constant *Ops[] = { Res, Overflow };
1279 return ConstantStruct::get(F->getContext(), Ops, 2, false);