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"
38 //===----------------------------------------------------------------------===//
39 // Constant Folding internal helper functions
40 //===----------------------------------------------------------------------===//
42 /// FoldBitCast - Constant fold bitcast, symbolically evaluating it with
43 /// TargetData. This always returns a non-null constant, but it may be a
44 /// ConstantExpr if unfoldable.
45 static Constant *FoldBitCast(Constant *C, const Type *DestTy,
46 const TargetData &TD) {
48 // This only handles casts to vectors currently.
49 const VectorType *DestVTy = dyn_cast<VectorType>(DestTy);
51 return ConstantExpr::getBitCast(C, DestTy);
53 // If this is a scalar -> vector cast, convert the input into a <1 x scalar>
54 // vector so the code below can handle it uniformly.
55 if (isa<ConstantFP>(C) || isa<ConstantInt>(C)) {
56 Constant *Ops = C; // don't take the address of C!
57 return FoldBitCast(ConstantVector::get(&Ops, 1), DestTy, TD);
60 // If this is a bitcast from constant vector -> vector, fold it.
61 ConstantVector *CV = dyn_cast<ConstantVector>(C);
63 return ConstantExpr::getBitCast(C, DestTy);
65 // If the element types match, VMCore can fold it.
66 unsigned NumDstElt = DestVTy->getNumElements();
67 unsigned NumSrcElt = CV->getNumOperands();
68 if (NumDstElt == NumSrcElt)
69 return ConstantExpr::getBitCast(C, DestTy);
71 const Type *SrcEltTy = CV->getType()->getElementType();
72 const Type *DstEltTy = DestVTy->getElementType();
74 // Otherwise, we're changing the number of elements in a vector, which
75 // requires endianness information to do the right thing. For example,
76 // bitcast (<2 x i64> <i64 0, i64 1> to <4 x i32>)
77 // folds to (little endian):
78 // <4 x i32> <i32 0, i32 0, i32 1, i32 0>
79 // and to (big endian):
80 // <4 x i32> <i32 0, i32 0, i32 0, i32 1>
82 // First thing is first. We only want to think about integer here, so if
83 // we have something in FP form, recast it as integer.
84 if (DstEltTy->isFloatingPointTy()) {
85 // Fold to an vector of integers with same size as our FP type.
86 unsigned FPWidth = DstEltTy->getPrimitiveSizeInBits();
87 const Type *DestIVTy =
88 VectorType::get(IntegerType::get(C->getContext(), FPWidth), NumDstElt);
89 // Recursively handle this integer conversion, if possible.
90 C = FoldBitCast(C, DestIVTy, TD);
91 if (!C) return ConstantExpr::getBitCast(C, DestTy);
93 // Finally, VMCore can handle this now that #elts line up.
94 return ConstantExpr::getBitCast(C, DestTy);
97 // Okay, we know the destination is integer, if the input is FP, convert
98 // it to integer first.
99 if (SrcEltTy->isFloatingPointTy()) {
100 unsigned FPWidth = SrcEltTy->getPrimitiveSizeInBits();
101 const Type *SrcIVTy =
102 VectorType::get(IntegerType::get(C->getContext(), FPWidth), NumSrcElt);
103 // Ask VMCore to do the conversion now that #elts line up.
104 C = ConstantExpr::getBitCast(C, SrcIVTy);
105 CV = dyn_cast<ConstantVector>(C);
106 if (!CV) // If VMCore wasn't able to fold it, bail out.
110 // Now we know that the input and output vectors are both integer vectors
111 // of the same size, and that their #elements is not the same. Do the
112 // conversion here, which depends on whether the input or output has
114 bool isLittleEndian = TD.isLittleEndian();
116 SmallVector<Constant*, 32> Result;
117 if (NumDstElt < NumSrcElt) {
118 // Handle: bitcast (<4 x i32> <i32 0, i32 1, i32 2, i32 3> to <2 x i64>)
119 Constant *Zero = Constant::getNullValue(DstEltTy);
120 unsigned Ratio = NumSrcElt/NumDstElt;
121 unsigned SrcBitSize = SrcEltTy->getPrimitiveSizeInBits();
123 for (unsigned i = 0; i != NumDstElt; ++i) {
124 // Build each element of the result.
125 Constant *Elt = Zero;
126 unsigned ShiftAmt = isLittleEndian ? 0 : SrcBitSize*(Ratio-1);
127 for (unsigned j = 0; j != Ratio; ++j) {
128 Constant *Src = dyn_cast<ConstantInt>(CV->getOperand(SrcElt++));
129 if (!Src) // Reject constantexpr elements.
130 return ConstantExpr::getBitCast(C, DestTy);
132 // Zero extend the element to the right size.
133 Src = ConstantExpr::getZExt(Src, Elt->getType());
135 // Shift it to the right place, depending on endianness.
136 Src = ConstantExpr::getShl(Src,
137 ConstantInt::get(Src->getType(), ShiftAmt));
138 ShiftAmt += isLittleEndian ? SrcBitSize : -SrcBitSize;
141 Elt = ConstantExpr::getOr(Elt, Src);
143 Result.push_back(Elt);
146 // Handle: bitcast (<2 x i64> <i64 0, i64 1> to <4 x i32>)
147 unsigned Ratio = NumDstElt/NumSrcElt;
148 unsigned DstBitSize = DstEltTy->getPrimitiveSizeInBits();
150 // Loop over each source value, expanding into multiple results.
151 for (unsigned i = 0; i != NumSrcElt; ++i) {
152 Constant *Src = dyn_cast<ConstantInt>(CV->getOperand(i));
153 if (!Src) // Reject constantexpr elements.
154 return ConstantExpr::getBitCast(C, DestTy);
156 unsigned ShiftAmt = isLittleEndian ? 0 : DstBitSize*(Ratio-1);
157 for (unsigned j = 0; j != Ratio; ++j) {
158 // Shift the piece of the value into the right place, depending on
160 Constant *Elt = ConstantExpr::getLShr(Src,
161 ConstantInt::get(Src->getType(), ShiftAmt));
162 ShiftAmt += isLittleEndian ? DstBitSize : -DstBitSize;
164 // Truncate and remember this piece.
165 Result.push_back(ConstantExpr::getTrunc(Elt, DstEltTy));
170 return ConstantVector::get(Result.data(), Result.size());
174 /// IsConstantOffsetFromGlobal - If this constant is actually a constant offset
175 /// from a global, return the global and the constant. Because of
176 /// constantexprs, this function is recursive.
177 static bool IsConstantOffsetFromGlobal(Constant *C, GlobalValue *&GV,
178 int64_t &Offset, const TargetData &TD) {
179 // Trivial case, constant is the global.
180 if ((GV = dyn_cast<GlobalValue>(C))) {
185 // Otherwise, if this isn't a constant expr, bail out.
186 ConstantExpr *CE = dyn_cast<ConstantExpr>(C);
187 if (!CE) return false;
189 // Look through ptr->int and ptr->ptr casts.
190 if (CE->getOpcode() == Instruction::PtrToInt ||
191 CE->getOpcode() == Instruction::BitCast)
192 return IsConstantOffsetFromGlobal(CE->getOperand(0), GV, Offset, TD);
194 // i32* getelementptr ([5 x i32]* @a, i32 0, i32 5)
195 if (CE->getOpcode() == Instruction::GetElementPtr) {
196 // Cannot compute this if the element type of the pointer is missing size
198 if (!cast<PointerType>(CE->getOperand(0)->getType())
199 ->getElementType()->isSized())
202 // If the base isn't a global+constant, we aren't either.
203 if (!IsConstantOffsetFromGlobal(CE->getOperand(0), GV, Offset, TD))
206 // Otherwise, add any offset that our operands provide.
207 gep_type_iterator GTI = gep_type_begin(CE);
208 for (User::const_op_iterator i = CE->op_begin() + 1, e = CE->op_end();
209 i != e; ++i, ++GTI) {
210 ConstantInt *CI = dyn_cast<ConstantInt>(*i);
211 if (!CI) return false; // Index isn't a simple constant?
212 if (CI->isZero()) continue; // Not adding anything.
214 if (const StructType *ST = dyn_cast<StructType>(*GTI)) {
216 Offset += TD.getStructLayout(ST)->getElementOffset(CI->getZExtValue());
218 const SequentialType *SQT = cast<SequentialType>(*GTI);
219 Offset += TD.getTypeAllocSize(SQT->getElementType())*CI->getSExtValue();
228 /// ReadDataFromGlobal - Recursive helper to read bits out of global. C is the
229 /// constant being copied out of. ByteOffset is an offset into C. CurPtr is the
230 /// pointer to copy results into and BytesLeft is the number of bytes left in
231 /// the CurPtr buffer. TD is the target data.
232 static bool ReadDataFromGlobal(Constant *C, uint64_t ByteOffset,
233 unsigned char *CurPtr, unsigned BytesLeft,
234 const TargetData &TD) {
235 assert(ByteOffset <= TD.getTypeAllocSize(C->getType()) &&
236 "Out of range access");
238 // If this element is zero or undefined, we can just return since *CurPtr is
240 if (isa<ConstantAggregateZero>(C) || isa<UndefValue>(C))
243 if (ConstantInt *CI = dyn_cast<ConstantInt>(C)) {
244 if (CI->getBitWidth() > 64 ||
245 (CI->getBitWidth() & 7) != 0)
248 uint64_t Val = CI->getZExtValue();
249 unsigned IntBytes = unsigned(CI->getBitWidth()/8);
251 for (unsigned i = 0; i != BytesLeft && ByteOffset != IntBytes; ++i) {
252 CurPtr[i] = (unsigned char)(Val >> (ByteOffset * 8));
258 if (ConstantFP *CFP = dyn_cast<ConstantFP>(C)) {
259 if (CFP->getType()->isDoubleTy()) {
260 C = FoldBitCast(C, Type::getInt64Ty(C->getContext()), TD);
261 return ReadDataFromGlobal(C, ByteOffset, CurPtr, BytesLeft, TD);
263 if (CFP->getType()->isFloatTy()){
264 C = FoldBitCast(C, Type::getInt32Ty(C->getContext()), TD);
265 return ReadDataFromGlobal(C, ByteOffset, CurPtr, BytesLeft, TD);
270 if (ConstantStruct *CS = dyn_cast<ConstantStruct>(C)) {
271 const StructLayout *SL = TD.getStructLayout(CS->getType());
272 unsigned Index = SL->getElementContainingOffset(ByteOffset);
273 uint64_t CurEltOffset = SL->getElementOffset(Index);
274 ByteOffset -= CurEltOffset;
277 // If the element access is to the element itself and not to tail padding,
278 // read the bytes from the element.
279 uint64_t EltSize = TD.getTypeAllocSize(CS->getOperand(Index)->getType());
281 if (ByteOffset < EltSize &&
282 !ReadDataFromGlobal(CS->getOperand(Index), ByteOffset, CurPtr,
288 // Check to see if we read from the last struct element, if so we're done.
289 if (Index == CS->getType()->getNumElements())
292 // If we read all of the bytes we needed from this element we're done.
293 uint64_t NextEltOffset = SL->getElementOffset(Index);
295 if (BytesLeft <= NextEltOffset-CurEltOffset-ByteOffset)
298 // Move to the next element of the struct.
299 CurPtr += NextEltOffset-CurEltOffset-ByteOffset;
300 BytesLeft -= NextEltOffset-CurEltOffset-ByteOffset;
302 CurEltOffset = NextEltOffset;
307 if (ConstantArray *CA = dyn_cast<ConstantArray>(C)) {
308 uint64_t EltSize = TD.getTypeAllocSize(CA->getType()->getElementType());
309 uint64_t Index = ByteOffset / EltSize;
310 uint64_t Offset = ByteOffset - Index * EltSize;
311 for (; Index != CA->getType()->getNumElements(); ++Index) {
312 if (!ReadDataFromGlobal(CA->getOperand(Index), Offset, CurPtr,
315 if (EltSize >= BytesLeft)
319 BytesLeft -= EltSize;
325 if (ConstantVector *CV = dyn_cast<ConstantVector>(C)) {
326 uint64_t EltSize = TD.getTypeAllocSize(CV->getType()->getElementType());
327 uint64_t Index = ByteOffset / EltSize;
328 uint64_t Offset = ByteOffset - Index * EltSize;
329 for (; Index != CV->getType()->getNumElements(); ++Index) {
330 if (!ReadDataFromGlobal(CV->getOperand(Index), Offset, CurPtr,
333 if (EltSize >= BytesLeft)
337 BytesLeft -= EltSize;
343 // Otherwise, unknown initializer type.
347 static Constant *FoldReinterpretLoadFromConstPtr(Constant *C,
348 const TargetData &TD) {
349 const Type *LoadTy = cast<PointerType>(C->getType())->getElementType();
350 const IntegerType *IntType = dyn_cast<IntegerType>(LoadTy);
352 // If this isn't an integer load we can't fold it directly.
354 // If this is a float/double load, we can try folding it as an int32/64 load
355 // and then bitcast the result. This can be useful for union cases. Note
356 // that address spaces don't matter here since we're not going to result in
357 // an actual new load.
359 if (LoadTy->isFloatTy())
360 MapTy = Type::getInt32PtrTy(C->getContext());
361 else if (LoadTy->isDoubleTy())
362 MapTy = Type::getInt64PtrTy(C->getContext());
363 else if (LoadTy->isVectorTy()) {
364 MapTy = IntegerType::get(C->getContext(),
365 TD.getTypeAllocSizeInBits(LoadTy));
366 MapTy = PointerType::getUnqual(MapTy);
370 C = FoldBitCast(C, MapTy, TD);
371 if (Constant *Res = FoldReinterpretLoadFromConstPtr(C, TD))
372 return FoldBitCast(Res, LoadTy, TD);
376 unsigned BytesLoaded = (IntType->getBitWidth() + 7) / 8;
377 if (BytesLoaded > 32 || BytesLoaded == 0) return 0;
381 if (!IsConstantOffsetFromGlobal(C, GVal, Offset, TD))
384 GlobalVariable *GV = dyn_cast<GlobalVariable>(GVal);
385 if (!GV || !GV->isConstant() || !GV->hasDefinitiveInitializer() ||
386 !GV->getInitializer()->getType()->isSized())
389 // If we're loading off the beginning of the global, some bytes may be valid,
390 // but we don't try to handle this.
391 if (Offset < 0) return 0;
393 // If we're not accessing anything in this constant, the result is undefined.
394 if (uint64_t(Offset) >= TD.getTypeAllocSize(GV->getInitializer()->getType()))
395 return UndefValue::get(IntType);
397 unsigned char RawBytes[32] = {0};
398 if (!ReadDataFromGlobal(GV->getInitializer(), Offset, RawBytes,
402 APInt ResultVal = APInt(IntType->getBitWidth(), RawBytes[BytesLoaded-1]);
403 for (unsigned i = 1; i != BytesLoaded; ++i) {
405 ResultVal |= RawBytes[BytesLoaded-1-i];
408 return ConstantInt::get(IntType->getContext(), ResultVal);
411 /// ConstantFoldLoadFromConstPtr - Return the value that a load from C would
412 /// produce if it is constant and determinable. If this is not determinable,
414 Constant *llvm::ConstantFoldLoadFromConstPtr(Constant *C,
415 const TargetData *TD) {
416 // First, try the easy cases:
417 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(C))
418 if (GV->isConstant() && GV->hasDefinitiveInitializer())
419 return GV->getInitializer();
421 // If the loaded value isn't a constant expr, we can't handle it.
422 ConstantExpr *CE = dyn_cast<ConstantExpr>(C);
425 if (CE->getOpcode() == Instruction::GetElementPtr) {
426 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(CE->getOperand(0)))
427 if (GV->isConstant() && GV->hasDefinitiveInitializer())
429 ConstantFoldLoadThroughGEPConstantExpr(GV->getInitializer(), CE))
433 // Instead of loading constant c string, use corresponding integer value
434 // directly if string length is small enough.
436 if (TD && GetConstantStringInfo(CE, Str) && !Str.empty()) {
437 unsigned StrLen = Str.length();
438 const Type *Ty = cast<PointerType>(CE->getType())->getElementType();
439 unsigned NumBits = Ty->getPrimitiveSizeInBits();
440 // Replace load with immediate integer if the result is an integer or fp
442 if ((NumBits >> 3) == StrLen + 1 && (NumBits & 7) == 0 &&
443 (isa<IntegerType>(Ty) || Ty->isFloatingPointTy())) {
444 APInt StrVal(NumBits, 0);
445 APInt SingleChar(NumBits, 0);
446 if (TD->isLittleEndian()) {
447 for (signed i = StrLen-1; i >= 0; i--) {
448 SingleChar = (uint64_t) Str[i] & UCHAR_MAX;
449 StrVal = (StrVal << 8) | SingleChar;
452 for (unsigned i = 0; i < StrLen; i++) {
453 SingleChar = (uint64_t) Str[i] & UCHAR_MAX;
454 StrVal = (StrVal << 8) | SingleChar;
456 // Append NULL at the end.
458 StrVal = (StrVal << 8) | SingleChar;
461 Constant *Res = ConstantInt::get(CE->getContext(), StrVal);
462 if (Ty->isFloatingPointTy())
463 Res = ConstantExpr::getBitCast(Res, Ty);
468 // If this load comes from anywhere in a constant global, and if the global
469 // is all undef or zero, we know what it loads.
470 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(CE->getUnderlyingObject())){
471 if (GV->isConstant() && GV->hasDefinitiveInitializer()) {
472 const Type *ResTy = cast<PointerType>(C->getType())->getElementType();
473 if (GV->getInitializer()->isNullValue())
474 return Constant::getNullValue(ResTy);
475 if (isa<UndefValue>(GV->getInitializer()))
476 return UndefValue::get(ResTy);
480 // Try hard to fold loads from bitcasted strange and non-type-safe things. We
481 // currently don't do any of this for big endian systems. It can be
482 // generalized in the future if someone is interested.
483 if (TD && TD->isLittleEndian())
484 return FoldReinterpretLoadFromConstPtr(CE, *TD);
488 static Constant *ConstantFoldLoadInst(const LoadInst *LI, const TargetData *TD){
489 if (LI->isVolatile()) return 0;
491 if (Constant *C = dyn_cast<Constant>(LI->getOperand(0)))
492 return ConstantFoldLoadFromConstPtr(C, TD);
497 /// SymbolicallyEvaluateBinop - One of Op0/Op1 is a constant expression.
498 /// Attempt to symbolically evaluate the result of a binary operator merging
499 /// these together. If target data info is available, it is provided as TD,
500 /// otherwise TD is null.
501 static Constant *SymbolicallyEvaluateBinop(unsigned Opc, Constant *Op0,
502 Constant *Op1, const TargetData *TD){
505 // Fold (and 0xffffffff00000000, (shl x, 32)) -> shl.
506 // Fold (lshr (or X, Y), 32) -> (lshr [X/Y], 32) if one doesn't contribute
510 // If the constant expr is something like &A[123] - &A[4].f, fold this into a
511 // constant. This happens frequently when iterating over a global array.
512 if (Opc == Instruction::Sub && TD) {
513 GlobalValue *GV1, *GV2;
514 int64_t Offs1, Offs2;
516 if (IsConstantOffsetFromGlobal(Op0, GV1, Offs1, *TD))
517 if (IsConstantOffsetFromGlobal(Op1, GV2, Offs2, *TD) &&
519 // (&GV+C1) - (&GV+C2) -> C1-C2, pointer arithmetic cannot overflow.
520 return ConstantInt::get(Op0->getType(), Offs1-Offs2);
527 /// CastGEPIndices - If array indices are not pointer-sized integers,
528 /// explicitly cast them so that they aren't implicitly casted by the
530 static Constant *CastGEPIndices(Constant *const *Ops, unsigned NumOps,
531 const Type *ResultTy,
532 const TargetData *TD) {
534 const Type *IntPtrTy = TD->getIntPtrType(ResultTy->getContext());
537 SmallVector<Constant*, 32> NewIdxs;
538 for (unsigned i = 1; i != NumOps; ++i) {
540 !isa<StructType>(GetElementPtrInst::getIndexedType(Ops[0]->getType(),
541 reinterpret_cast<Value *const *>(Ops+1),
543 Ops[i]->getType() != IntPtrTy) {
545 NewIdxs.push_back(ConstantExpr::getCast(CastInst::getCastOpcode(Ops[i],
551 NewIdxs.push_back(Ops[i]);
556 ConstantExpr::getGetElementPtr(Ops[0], &NewIdxs[0], NewIdxs.size());
557 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(C))
558 if (Constant *Folded = ConstantFoldConstantExpression(CE, TD))
563 /// SymbolicallyEvaluateGEP - If we can symbolically evaluate the specified GEP
564 /// constant expression, do so.
565 static Constant *SymbolicallyEvaluateGEP(Constant *const *Ops, unsigned NumOps,
566 const Type *ResultTy,
567 const TargetData *TD) {
568 Constant *Ptr = Ops[0];
569 if (!TD || !cast<PointerType>(Ptr->getType())->getElementType()->isSized())
573 TD->getTypeSizeInBits(TD->getIntPtrType(Ptr->getContext()));
575 // If this is a constant expr gep that is effectively computing an
576 // "offsetof", fold it into 'cast int Size to T*' instead of 'gep 0, 0, 12'
577 for (unsigned i = 1; i != NumOps; ++i)
578 if (!isa<ConstantInt>(Ops[i]))
581 APInt Offset = APInt(BitWidth,
582 TD->getIndexedOffset(Ptr->getType(),
583 (Value**)Ops+1, NumOps-1));
584 Ptr = cast<Constant>(Ptr->stripPointerCasts());
586 // If this is a GEP of a GEP, fold it all into a single GEP.
587 while (GEPOperator *GEP = dyn_cast<GEPOperator>(Ptr)) {
588 SmallVector<Value *, 4> NestedOps(GEP->op_begin()+1, GEP->op_end());
590 // Do not try the incorporate the sub-GEP if some index is not a number.
591 bool AllConstantInt = true;
592 for (unsigned i = 0, e = NestedOps.size(); i != e; ++i)
593 if (!isa<ConstantInt>(NestedOps[i])) {
594 AllConstantInt = false;
600 Ptr = cast<Constant>(GEP->getOperand(0));
601 Offset += APInt(BitWidth,
602 TD->getIndexedOffset(Ptr->getType(),
603 (Value**)NestedOps.data(),
605 Ptr = cast<Constant>(Ptr->stripPointerCasts());
608 // If the base value for this address is a literal integer value, fold the
609 // getelementptr to the resulting integer value casted to the pointer type.
610 APInt BasePtr(BitWidth, 0);
611 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Ptr))
612 if (CE->getOpcode() == Instruction::IntToPtr)
613 if (ConstantInt *Base = dyn_cast<ConstantInt>(CE->getOperand(0))) {
614 BasePtr = Base->getValue();
615 BasePtr.zextOrTrunc(BitWidth);
617 if (Ptr->isNullValue() || BasePtr != 0) {
618 Constant *C = ConstantInt::get(Ptr->getContext(), Offset+BasePtr);
619 return ConstantExpr::getIntToPtr(C, ResultTy);
622 // Otherwise form a regular getelementptr. Recompute the indices so that
623 // we eliminate over-indexing of the notional static type array bounds.
624 // This makes it easy to determine if the getelementptr is "inbounds".
625 // Also, this helps GlobalOpt do SROA on GlobalVariables.
626 const Type *Ty = Ptr->getType();
627 SmallVector<Constant*, 32> NewIdxs;
629 if (const SequentialType *ATy = dyn_cast<SequentialType>(Ty)) {
630 if (ATy->isPointerTy()) {
631 // The only pointer indexing we'll do is on the first index of the GEP.
632 if (!NewIdxs.empty())
635 // Only handle pointers to sized types, not pointers to functions.
636 if (!ATy->getElementType()->isSized())
640 // Determine which element of the array the offset points into.
641 APInt ElemSize(BitWidth, TD->getTypeAllocSize(ATy->getElementType()));
644 APInt NewIdx = Offset.udiv(ElemSize);
645 Offset -= NewIdx * ElemSize;
646 NewIdxs.push_back(ConstantInt::get(TD->getIntPtrType(Ty->getContext()),
648 Ty = ATy->getElementType();
649 } else if (const StructType *STy = dyn_cast<StructType>(Ty)) {
650 // Determine which field of the struct the offset points into. The
651 // getZExtValue is at least as safe as the StructLayout API because we
652 // know the offset is within the struct at this point.
653 const StructLayout &SL = *TD->getStructLayout(STy);
654 unsigned ElIdx = SL.getElementContainingOffset(Offset.getZExtValue());
655 NewIdxs.push_back(ConstantInt::get(Type::getInt32Ty(Ty->getContext()),
657 Offset -= APInt(BitWidth, SL.getElementOffset(ElIdx));
658 Ty = STy->getTypeAtIndex(ElIdx);
660 // We've reached some non-indexable type.
663 } while (Ty != cast<PointerType>(ResultTy)->getElementType());
665 // If we haven't used up the entire offset by descending the static
666 // type, then the offset is pointing into the middle of an indivisible
667 // member, so we can't simplify it.
673 ConstantExpr::getGetElementPtr(Ptr, &NewIdxs[0], NewIdxs.size());
674 assert(cast<PointerType>(C->getType())->getElementType() == Ty &&
675 "Computed GetElementPtr has unexpected type!");
677 // If we ended up indexing a member with a type that doesn't match
678 // the type of what the original indices indexed, add a cast.
679 if (Ty != cast<PointerType>(ResultTy)->getElementType())
680 C = FoldBitCast(C, ResultTy, *TD);
687 //===----------------------------------------------------------------------===//
688 // Constant Folding public APIs
689 //===----------------------------------------------------------------------===//
692 /// ConstantFoldInstruction - Attempt to constant fold the specified
693 /// instruction. If successful, the constant result is returned, if not, null
694 /// is returned. Note that this function can only fail when attempting to fold
695 /// instructions like loads and stores, which have no constant expression form.
697 Constant *llvm::ConstantFoldInstruction(Instruction *I, const TargetData *TD) {
698 if (PHINode *PN = dyn_cast<PHINode>(I)) {
699 if (PN->getNumIncomingValues() == 0)
700 return UndefValue::get(PN->getType());
702 Constant *Result = dyn_cast<Constant>(PN->getIncomingValue(0));
703 if (Result == 0) return 0;
705 // Handle PHI nodes specially here...
706 for (unsigned i = 1, e = PN->getNumIncomingValues(); i != e; ++i)
707 if (PN->getIncomingValue(i) != Result && PN->getIncomingValue(i) != PN)
708 return 0; // Not all the same incoming constants...
710 // If we reach here, all incoming values are the same constant.
714 // Scan the operand list, checking to see if they are all constants, if so,
715 // hand off to ConstantFoldInstOperands.
716 SmallVector<Constant*, 8> Ops;
717 for (User::op_iterator i = I->op_begin(), e = I->op_end(); i != e; ++i)
718 if (Constant *Op = dyn_cast<Constant>(*i))
721 return 0; // All operands not constant!
723 if (const CmpInst *CI = dyn_cast<CmpInst>(I))
724 return ConstantFoldCompareInstOperands(CI->getPredicate(), Ops[0], Ops[1],
727 if (const LoadInst *LI = dyn_cast<LoadInst>(I))
728 return ConstantFoldLoadInst(LI, TD);
730 return ConstantFoldInstOperands(I->getOpcode(), I->getType(),
731 Ops.data(), Ops.size(), TD);
734 /// ConstantFoldConstantExpression - Attempt to fold the constant expression
735 /// using the specified TargetData. If successful, the constant result is
736 /// result is returned, if not, null is returned.
737 Constant *llvm::ConstantFoldConstantExpression(const ConstantExpr *CE,
738 const TargetData *TD) {
739 SmallVector<Constant*, 8> Ops;
740 for (User::const_op_iterator i = CE->op_begin(), e = CE->op_end(); i != e; ++i) {
741 Constant *NewC = cast<Constant>(*i);
742 // Recursively fold the ConstantExpr's operands.
743 if (ConstantExpr *NewCE = dyn_cast<ConstantExpr>(NewC))
744 NewC = ConstantFoldConstantExpression(NewCE, TD);
749 return ConstantFoldCompareInstOperands(CE->getPredicate(), Ops[0], Ops[1],
751 return ConstantFoldInstOperands(CE->getOpcode(), CE->getType(),
752 Ops.data(), Ops.size(), TD);
755 /// ConstantFoldInstOperands - Attempt to constant fold an instruction with the
756 /// specified opcode and operands. If successful, the constant result is
757 /// returned, if not, null is returned. Note that this function can fail when
758 /// attempting to fold instructions like loads and stores, which have no
759 /// constant expression form.
761 /// TODO: This function neither utilizes nor preserves nsw/nuw/inbounds/etc
762 /// information, due to only being passed an opcode and operands. Constant
763 /// folding using this function strips this information.
765 Constant *llvm::ConstantFoldInstOperands(unsigned Opcode, const Type *DestTy,
766 Constant* const* Ops, unsigned NumOps,
767 const TargetData *TD) {
768 // Handle easy binops first.
769 if (Instruction::isBinaryOp(Opcode)) {
770 if (isa<ConstantExpr>(Ops[0]) || isa<ConstantExpr>(Ops[1]))
771 if (Constant *C = SymbolicallyEvaluateBinop(Opcode, Ops[0], Ops[1], TD))
774 return ConstantExpr::get(Opcode, Ops[0], Ops[1]);
779 case Instruction::ICmp:
780 case Instruction::FCmp: assert(0 && "Invalid for compares");
781 case Instruction::Call:
782 if (Function *F = dyn_cast<Function>(Ops[NumOps - 1]))
783 if (canConstantFoldCallTo(F))
784 return ConstantFoldCall(F, Ops, NumOps - 1);
786 case Instruction::PtrToInt:
787 // If the input is a inttoptr, eliminate the pair. This requires knowing
788 // the width of a pointer, so it can't be done in ConstantExpr::getCast.
789 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Ops[0])) {
790 if (TD && CE->getOpcode() == Instruction::IntToPtr) {
791 Constant *Input = CE->getOperand(0);
792 unsigned InWidth = Input->getType()->getScalarSizeInBits();
793 if (TD->getPointerSizeInBits() < InWidth) {
795 ConstantInt::get(CE->getContext(), APInt::getLowBitsSet(InWidth,
796 TD->getPointerSizeInBits()));
797 Input = ConstantExpr::getAnd(Input, Mask);
799 // Do a zext or trunc to get to the dest size.
800 return ConstantExpr::getIntegerCast(Input, DestTy, false);
803 return ConstantExpr::getCast(Opcode, Ops[0], DestTy);
804 case Instruction::IntToPtr:
805 // If the input is a ptrtoint, turn the pair into a ptr to ptr bitcast if
806 // the int size is >= the ptr size. This requires knowing the width of a
807 // pointer, so it can't be done in ConstantExpr::getCast.
808 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Ops[0]))
810 TD->getPointerSizeInBits() <= CE->getType()->getScalarSizeInBits() &&
811 CE->getOpcode() == Instruction::PtrToInt)
812 return FoldBitCast(CE->getOperand(0), DestTy, *TD);
814 return ConstantExpr::getCast(Opcode, Ops[0], DestTy);
815 case Instruction::Trunc:
816 case Instruction::ZExt:
817 case Instruction::SExt:
818 case Instruction::FPTrunc:
819 case Instruction::FPExt:
820 case Instruction::UIToFP:
821 case Instruction::SIToFP:
822 case Instruction::FPToUI:
823 case Instruction::FPToSI:
824 return ConstantExpr::getCast(Opcode, Ops[0], DestTy);
825 case Instruction::BitCast:
827 return FoldBitCast(Ops[0], DestTy, *TD);
828 return ConstantExpr::getBitCast(Ops[0], DestTy);
829 case Instruction::Select:
830 return ConstantExpr::getSelect(Ops[0], Ops[1], Ops[2]);
831 case Instruction::ExtractElement:
832 return ConstantExpr::getExtractElement(Ops[0], Ops[1]);
833 case Instruction::InsertElement:
834 return ConstantExpr::getInsertElement(Ops[0], Ops[1], Ops[2]);
835 case Instruction::ShuffleVector:
836 return ConstantExpr::getShuffleVector(Ops[0], Ops[1], Ops[2]);
837 case Instruction::GetElementPtr:
838 if (Constant *C = CastGEPIndices(Ops, NumOps, DestTy, TD))
840 if (Constant *C = SymbolicallyEvaluateGEP(Ops, NumOps, DestTy, TD))
843 return ConstantExpr::getGetElementPtr(Ops[0], Ops+1, NumOps-1);
847 /// ConstantFoldCompareInstOperands - Attempt to constant fold a compare
848 /// instruction (icmp/fcmp) with the specified operands. If it fails, it
849 /// returns a constant expression of the specified operands.
851 Constant *llvm::ConstantFoldCompareInstOperands(unsigned Predicate,
852 Constant *Ops0, Constant *Ops1,
853 const TargetData *TD) {
854 // fold: icmp (inttoptr x), null -> icmp x, 0
855 // fold: icmp (ptrtoint x), 0 -> icmp x, null
856 // fold: icmp (inttoptr x), (inttoptr y) -> icmp trunc/zext x, trunc/zext y
857 // fold: icmp (ptrtoint x), (ptrtoint y) -> icmp x, y
859 // ConstantExpr::getCompare cannot do this, because it doesn't have TD
860 // around to know if bit truncation is happening.
861 if (ConstantExpr *CE0 = dyn_cast<ConstantExpr>(Ops0)) {
862 if (TD && Ops1->isNullValue()) {
863 const Type *IntPtrTy = TD->getIntPtrType(CE0->getContext());
864 if (CE0->getOpcode() == Instruction::IntToPtr) {
865 // Convert the integer value to the right size to ensure we get the
866 // proper extension or truncation.
867 Constant *C = ConstantExpr::getIntegerCast(CE0->getOperand(0),
869 Constant *Null = Constant::getNullValue(C->getType());
870 return ConstantFoldCompareInstOperands(Predicate, C, Null, TD);
873 // Only do this transformation if the int is intptrty in size, otherwise
874 // there is a truncation or extension that we aren't modeling.
875 if (CE0->getOpcode() == Instruction::PtrToInt &&
876 CE0->getType() == IntPtrTy) {
877 Constant *C = CE0->getOperand(0);
878 Constant *Null = Constant::getNullValue(C->getType());
879 return ConstantFoldCompareInstOperands(Predicate, C, Null, TD);
883 if (ConstantExpr *CE1 = dyn_cast<ConstantExpr>(Ops1)) {
884 if (TD && CE0->getOpcode() == CE1->getOpcode()) {
885 const Type *IntPtrTy = TD->getIntPtrType(CE0->getContext());
887 if (CE0->getOpcode() == Instruction::IntToPtr) {
888 // Convert the integer value to the right size to ensure we get the
889 // proper extension or truncation.
890 Constant *C0 = ConstantExpr::getIntegerCast(CE0->getOperand(0),
892 Constant *C1 = ConstantExpr::getIntegerCast(CE1->getOperand(0),
894 return ConstantFoldCompareInstOperands(Predicate, C0, C1, TD);
897 // Only do this transformation if the int is intptrty in size, otherwise
898 // there is a truncation or extension that we aren't modeling.
899 if ((CE0->getOpcode() == Instruction::PtrToInt &&
900 CE0->getType() == IntPtrTy &&
901 CE0->getOperand(0)->getType() == CE1->getOperand(0)->getType()))
902 return ConstantFoldCompareInstOperands(Predicate, CE0->getOperand(0),
903 CE1->getOperand(0), TD);
907 // icmp eq (or x, y), 0 -> (icmp eq x, 0) & (icmp eq y, 0)
908 // icmp ne (or x, y), 0 -> (icmp ne x, 0) | (icmp ne y, 0)
909 if ((Predicate == ICmpInst::ICMP_EQ || Predicate == ICmpInst::ICMP_NE) &&
910 CE0->getOpcode() == Instruction::Or && Ops1->isNullValue()) {
912 ConstantFoldCompareInstOperands(Predicate, CE0->getOperand(0), Ops1,TD);
914 ConstantFoldCompareInstOperands(Predicate, CE0->getOperand(1), Ops1,TD);
916 Predicate == ICmpInst::ICMP_EQ ? Instruction::And : Instruction::Or;
917 Constant *Ops[] = { LHS, RHS };
918 return ConstantFoldInstOperands(OpC, LHS->getType(), Ops, 2, TD);
922 return ConstantExpr::getCompare(Predicate, Ops0, Ops1);
926 /// ConstantFoldLoadThroughGEPConstantExpr - Given a constant and a
927 /// getelementptr constantexpr, return the constant value being addressed by the
928 /// constant expression, or null if something is funny and we can't decide.
929 Constant *llvm::ConstantFoldLoadThroughGEPConstantExpr(Constant *C,
931 if (CE->getOperand(1) != Constant::getNullValue(CE->getOperand(1)->getType()))
932 return 0; // Do not allow stepping over the value!
934 // Loop over all of the operands, tracking down which value we are
936 gep_type_iterator I = gep_type_begin(CE), E = gep_type_end(CE);
937 for (++I; I != E; ++I)
938 if (const StructType *STy = dyn_cast<StructType>(*I)) {
939 ConstantInt *CU = cast<ConstantInt>(I.getOperand());
940 assert(CU->getZExtValue() < STy->getNumElements() &&
941 "Struct index out of range!");
942 unsigned El = (unsigned)CU->getZExtValue();
943 if (ConstantStruct *CS = dyn_cast<ConstantStruct>(C)) {
944 C = CS->getOperand(El);
945 } else if (isa<ConstantAggregateZero>(C)) {
946 C = Constant::getNullValue(STy->getElementType(El));
947 } else if (isa<UndefValue>(C)) {
948 C = UndefValue::get(STy->getElementType(El));
952 } else if (ConstantInt *CI = dyn_cast<ConstantInt>(I.getOperand())) {
953 if (const ArrayType *ATy = dyn_cast<ArrayType>(*I)) {
954 if (CI->getZExtValue() >= ATy->getNumElements())
956 if (ConstantArray *CA = dyn_cast<ConstantArray>(C))
957 C = CA->getOperand(CI->getZExtValue());
958 else if (isa<ConstantAggregateZero>(C))
959 C = Constant::getNullValue(ATy->getElementType());
960 else if (isa<UndefValue>(C))
961 C = UndefValue::get(ATy->getElementType());
964 } else if (const VectorType *VTy = dyn_cast<VectorType>(*I)) {
965 if (CI->getZExtValue() >= VTy->getNumElements())
967 if (ConstantVector *CP = dyn_cast<ConstantVector>(C))
968 C = CP->getOperand(CI->getZExtValue());
969 else if (isa<ConstantAggregateZero>(C))
970 C = Constant::getNullValue(VTy->getElementType());
971 else if (isa<UndefValue>(C))
972 C = UndefValue::get(VTy->getElementType());
985 //===----------------------------------------------------------------------===//
986 // Constant Folding for Calls
989 /// canConstantFoldCallTo - Return true if its even possible to fold a call to
990 /// the specified function.
992 llvm::canConstantFoldCallTo(const Function *F) {
993 switch (F->getIntrinsicID()) {
994 case Intrinsic::sqrt:
995 case Intrinsic::powi:
996 case Intrinsic::bswap:
997 case Intrinsic::ctpop:
998 case Intrinsic::ctlz:
999 case Intrinsic::cttz:
1000 case Intrinsic::uadd_with_overflow:
1001 case Intrinsic::usub_with_overflow:
1002 case Intrinsic::sadd_with_overflow:
1003 case Intrinsic::ssub_with_overflow:
1004 case Intrinsic::convert_from_fp16:
1005 case Intrinsic::convert_to_fp16:
1012 if (!F->hasName()) return false;
1013 StringRef Name = F->getName();
1015 // In these cases, the check of the length is required. We don't want to
1016 // return true for a name like "cos\0blah" which strcmp would return equal to
1017 // "cos", but has length 8.
1019 default: return false;
1021 return Name == "acos" || Name == "asin" ||
1022 Name == "atan" || Name == "atan2";
1024 return Name == "cos" || Name == "ceil" || Name == "cosf" || Name == "cosh";
1026 return Name == "exp";
1028 return Name == "fabs" || Name == "fmod" || Name == "floor";
1030 return Name == "log" || Name == "log10";
1032 return Name == "pow";
1034 return Name == "sin" || Name == "sinh" || Name == "sqrt" ||
1035 Name == "sinf" || Name == "sqrtf";
1037 return Name == "tan" || Name == "tanh";
1041 static Constant *ConstantFoldFP(double (*NativeFP)(double), double V,
1043 feclearexcept(FE_ALL_EXCEPT);
1047 fetestexcept(FE_DIVBYZERO | FE_UNDERFLOW | FE_OVERFLOW | FE_INVALID)) {
1048 feclearexcept(FE_ALL_EXCEPT);
1053 if (Ty->isFloatTy())
1054 return ConstantFP::get(Ty->getContext(), APFloat((float)V));
1055 if (Ty->isDoubleTy())
1056 return ConstantFP::get(Ty->getContext(), APFloat(V));
1057 llvm_unreachable("Can only constant fold float/double");
1058 return 0; // dummy return to suppress warning
1061 static Constant *ConstantFoldBinaryFP(double (*NativeFP)(double, double),
1062 double V, double W, const Type *Ty) {
1063 feclearexcept(FE_ALL_EXCEPT);
1067 fetestexcept(FE_DIVBYZERO | FE_UNDERFLOW | FE_OVERFLOW | FE_INVALID)) {
1068 feclearexcept(FE_ALL_EXCEPT);
1073 if (Ty->isFloatTy())
1074 return ConstantFP::get(Ty->getContext(), APFloat((float)V));
1075 if (Ty->isDoubleTy())
1076 return ConstantFP::get(Ty->getContext(), APFloat(V));
1077 llvm_unreachable("Can only constant fold float/double");
1078 return 0; // dummy return to suppress warning
1081 /// ConstantFoldCall - Attempt to constant fold a call to the specified function
1082 /// with the specified arguments, returning null if unsuccessful.
1084 llvm::ConstantFoldCall(Function *F,
1085 Constant *const *Operands, unsigned NumOperands) {
1086 if (!F->hasName()) return 0;
1087 StringRef Name = F->getName();
1089 const Type *Ty = F->getReturnType();
1090 if (NumOperands == 1) {
1091 if (ConstantFP *Op = dyn_cast<ConstantFP>(Operands[0])) {
1092 if (Name == "llvm.convert.to.fp16") {
1093 APFloat Val(Op->getValueAPF());
1096 Val.convert(APFloat::IEEEhalf, APFloat::rmNearestTiesToEven, &lost);
1098 return ConstantInt::get(F->getContext(), Val.bitcastToAPInt());
1101 if (!Ty->isFloatTy() && !Ty->isDoubleTy())
1103 /// Currently APFloat versions of these functions do not exist, so we use
1104 /// the host native double versions. Float versions are not called
1105 /// directly but for all these it is true (float)(f((double)arg)) ==
1106 /// f(arg). Long double not supported yet.
1107 double V = Ty->isFloatTy() ? (double)Op->getValueAPF().convertToFloat() :
1108 Op->getValueAPF().convertToDouble();
1112 return ConstantFoldFP(acos, V, Ty);
1113 else if (Name == "asin")
1114 return ConstantFoldFP(asin, V, Ty);
1115 else if (Name == "atan")
1116 return ConstantFoldFP(atan, V, Ty);
1120 return ConstantFoldFP(ceil, V, Ty);
1121 else if (Name == "cos")
1122 return ConstantFoldFP(cos, V, Ty);
1123 else if (Name == "cosh")
1124 return ConstantFoldFP(cosh, V, Ty);
1125 else if (Name == "cosf")
1126 return ConstantFoldFP(cos, V, Ty);
1130 return ConstantFoldFP(exp, V, Ty);
1134 return ConstantFoldFP(fabs, V, Ty);
1135 else if (Name == "floor")
1136 return ConstantFoldFP(floor, V, Ty);
1139 if (Name == "log" && V > 0)
1140 return ConstantFoldFP(log, V, Ty);
1141 else if (Name == "log10" && V > 0)
1142 return ConstantFoldFP(log10, V, Ty);
1143 else if (Name == "llvm.sqrt.f32" ||
1144 Name == "llvm.sqrt.f64") {
1146 return ConstantFoldFP(sqrt, V, Ty);
1148 return Constant::getNullValue(Ty);
1153 return ConstantFoldFP(sin, V, Ty);
1154 else if (Name == "sinh")
1155 return ConstantFoldFP(sinh, V, Ty);
1156 else if (Name == "sqrt" && V >= 0)
1157 return ConstantFoldFP(sqrt, V, Ty);
1158 else if (Name == "sqrtf" && V >= 0)
1159 return ConstantFoldFP(sqrt, V, Ty);
1160 else if (Name == "sinf")
1161 return ConstantFoldFP(sin, V, Ty);
1165 return ConstantFoldFP(tan, V, Ty);
1166 else if (Name == "tanh")
1167 return ConstantFoldFP(tanh, V, Ty);
1176 if (ConstantInt *Op = dyn_cast<ConstantInt>(Operands[0])) {
1177 if (Name.startswith("llvm.bswap"))
1178 return ConstantInt::get(F->getContext(), Op->getValue().byteSwap());
1179 else if (Name.startswith("llvm.ctpop"))
1180 return ConstantInt::get(Ty, Op->getValue().countPopulation());
1181 else if (Name.startswith("llvm.cttz"))
1182 return ConstantInt::get(Ty, Op->getValue().countTrailingZeros());
1183 else if (Name.startswith("llvm.ctlz"))
1184 return ConstantInt::get(Ty, Op->getValue().countLeadingZeros());
1185 else if (Name == "llvm.convert.from.fp16") {
1186 APFloat Val(Op->getValue());
1189 APFloat::opStatus status =
1190 Val.convert(APFloat::IEEEsingle, APFloat::rmNearestTiesToEven, &lost);
1192 // Conversion is always precise.
1194 assert(status == APFloat::opOK && !lost &&
1195 "Precision lost during fp16 constfolding");
1197 return ConstantFP::get(F->getContext(), Val);
1202 if (isa<UndefValue>(Operands[0])) {
1203 if (Name.startswith("llvm.bswap"))
1211 if (NumOperands == 2) {
1212 if (ConstantFP *Op1 = dyn_cast<ConstantFP>(Operands[0])) {
1213 if (!Ty->isFloatTy() && !Ty->isDoubleTy())
1215 double Op1V = Ty->isFloatTy() ?
1216 (double)Op1->getValueAPF().convertToFloat() :
1217 Op1->getValueAPF().convertToDouble();
1218 if (ConstantFP *Op2 = dyn_cast<ConstantFP>(Operands[1])) {
1219 if (Op2->getType() != Op1->getType())
1222 double Op2V = Ty->isFloatTy() ?
1223 (double)Op2->getValueAPF().convertToFloat():
1224 Op2->getValueAPF().convertToDouble();
1227 return ConstantFoldBinaryFP(pow, Op1V, Op2V, Ty);
1229 return ConstantFoldBinaryFP(fmod, Op1V, Op2V, Ty);
1230 if (Name == "atan2")
1231 return ConstantFoldBinaryFP(atan2, Op1V, Op2V, Ty);
1232 } else if (ConstantInt *Op2C = dyn_cast<ConstantInt>(Operands[1])) {
1233 if (Name == "llvm.powi.f32")
1234 return ConstantFP::get(F->getContext(),
1235 APFloat((float)std::pow((float)Op1V,
1236 (int)Op2C->getZExtValue())));
1237 if (Name == "llvm.powi.f64")
1238 return ConstantFP::get(F->getContext(),
1239 APFloat((double)std::pow((double)Op1V,
1240 (int)Op2C->getZExtValue())));
1246 if (ConstantInt *Op1 = dyn_cast<ConstantInt>(Operands[0])) {
1247 if (ConstantInt *Op2 = dyn_cast<ConstantInt>(Operands[1])) {
1248 switch (F->getIntrinsicID()) {
1250 case Intrinsic::uadd_with_overflow: {
1251 Constant *Res = ConstantExpr::getAdd(Op1, Op2); // result.
1253 Res, ConstantExpr::getICmp(CmpInst::ICMP_ULT, Res, Op1) // overflow.
1255 return ConstantStruct::get(F->getContext(), Ops, 2, false);
1257 case Intrinsic::usub_with_overflow: {
1258 Constant *Res = ConstantExpr::getSub(Op1, Op2); // result.
1260 Res, ConstantExpr::getICmp(CmpInst::ICMP_UGT, Res, Op1) // overflow.
1262 return ConstantStruct::get(F->getContext(), Ops, 2, false);
1264 case Intrinsic::sadd_with_overflow: {
1265 Constant *Res = ConstantExpr::getAdd(Op1, Op2); // result.
1266 Constant *Overflow = ConstantExpr::getSelect(
1267 ConstantExpr::getICmp(CmpInst::ICMP_SGT,
1268 ConstantInt::get(Op1->getType(), 0), Op1),
1269 ConstantExpr::getICmp(CmpInst::ICMP_SGT, Res, Op2),
1270 ConstantExpr::getICmp(CmpInst::ICMP_SLT, Res, Op2)); // overflow.
1272 Constant *Ops[] = { Res, Overflow };
1273 return ConstantStruct::get(F->getContext(), Ops, 2, false);
1275 case Intrinsic::ssub_with_overflow: {
1276 Constant *Res = ConstantExpr::getSub(Op1, Op2); // result.
1277 Constant *Overflow = ConstantExpr::getSelect(
1278 ConstantExpr::getICmp(CmpInst::ICMP_SGT,
1279 ConstantInt::get(Op2->getType(), 0), Op2),
1280 ConstantExpr::getICmp(CmpInst::ICMP_SLT, Res, Op1),
1281 ConstantExpr::getICmp(CmpInst::ICMP_SGT, Res, Op1)); // overflow.
1283 Constant *Ops[] = { Res, Overflow };
1284 return ConstantStruct::get(F->getContext(), Ops, 2, false);