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->isZero()) 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 |= 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 load with immediate integer if the result is an integer or fp
441
if ((NumBits >> 3) == StrLen + 1 && (NumBits & 7) == 0 &&
442
(isa<IntegerType>(Ty) || Ty->isFloatingPointTy())) {
443
APInt StrVal(NumBits, 0);
444
APInt SingleChar(NumBits, 0);
445
if (TD->isLittleEndian()) {
446
for (signed i = StrLen-1; i >= 0; i--) {
447
SingleChar = (uint64_t) Str[i] & UCHAR_MAX;
448
StrVal = (StrVal << 8) | SingleChar;
451
for (unsigned i = 0; i < StrLen; i++) {
452
SingleChar = (uint64_t) Str[i] & UCHAR_MAX;
453
StrVal = (StrVal << 8) | SingleChar;
455
// Append NULL at the end.
457
StrVal = (StrVal << 8) | SingleChar;
460
Constant *Res = ConstantInt::get(CE->getContext(), StrVal);
461
if (Ty->isFloatingPointTy())
462
Res = ConstantExpr::getBitCast(Res, Ty);
467
// If this load comes from anywhere in a constant global, and if the global
468
// is all undef or zero, we know what it loads.
469
if (GlobalVariable *GV = dyn_cast<GlobalVariable>(CE->getUnderlyingObject())){
470
if (GV->isConstant() && GV->hasDefinitiveInitializer()) {
471
const Type *ResTy = cast<PointerType>(C->getType())->getElementType();
472
if (GV->getInitializer()->isNullValue())
473
return Constant::getNullValue(ResTy);
474
if (isa<UndefValue>(GV->getInitializer()))
475
return UndefValue::get(ResTy);
479
// Try hard to fold loads from bitcasted strange and non-type-safe things. We
480
// currently don't do any of this for big endian systems. It can be
481
// generalized in the future if someone is interested.
482
if (TD && TD->isLittleEndian())
483
return FoldReinterpretLoadFromConstPtr(CE, *TD);
487
static Constant *ConstantFoldLoadInst(const LoadInst *LI, const TargetData *TD){
488
if (LI->isVolatile()) return 0;
490
if (Constant *C = dyn_cast<Constant>(LI->getOperand(0)))
491
return ConstantFoldLoadFromConstPtr(C, TD);
496
/// SymbolicallyEvaluateBinop - One of Op0/Op1 is a constant expression.
497
/// Attempt to symbolically evaluate the result of a binary operator merging
498
/// these together. If target data info is available, it is provided as TD,
499
/// otherwise TD is null.
500
static Constant *SymbolicallyEvaluateBinop(unsigned Opc, Constant *Op0,
501
Constant *Op1, const TargetData *TD){
504
// Fold (and 0xffffffff00000000, (shl x, 32)) -> shl.
505
// Fold (lshr (or X, Y), 32) -> (lshr [X/Y], 32) if one doesn't contribute
509
// If the constant expr is something like &A[123] - &A[4].f, fold this into a
510
// constant. This happens frequently when iterating over a global array.
511
if (Opc == Instruction::Sub && TD) {
512
GlobalValue *GV1, *GV2;
513
int64_t Offs1, Offs2;
515
if (IsConstantOffsetFromGlobal(Op0, GV1, Offs1, *TD))
516
if (IsConstantOffsetFromGlobal(Op1, GV2, Offs2, *TD) &&
518
// (&GV+C1) - (&GV+C2) -> C1-C2, pointer arithmetic cannot overflow.
519
return ConstantInt::get(Op0->getType(), Offs1-Offs2);
526
/// CastGEPIndices - If array indices are not pointer-sized integers,
527
/// explicitly cast them so that they aren't implicitly casted by the
529
static Constant *CastGEPIndices(Constant *const *Ops, unsigned NumOps,
530
const Type *ResultTy,
531
const TargetData *TD) {
533
const Type *IntPtrTy = TD->getIntPtrType(ResultTy->getContext());
536
SmallVector<Constant*, 32> NewIdxs;
537
for (unsigned i = 1; i != NumOps; ++i) {
539
!isa<StructType>(GetElementPtrInst::getIndexedType(Ops[0]->getType(),
540
reinterpret_cast<Value *const *>(Ops+1),
542
Ops[i]->getType() != IntPtrTy) {
544
NewIdxs.push_back(ConstantExpr::getCast(CastInst::getCastOpcode(Ops[i],
550
NewIdxs.push_back(Ops[i]);
555
ConstantExpr::getGetElementPtr(Ops[0], &NewIdxs[0], NewIdxs.size());
556
if (ConstantExpr *CE = dyn_cast<ConstantExpr>(C))
557
if (Constant *Folded = ConstantFoldConstantExpression(CE, TD))
562
/// SymbolicallyEvaluateGEP - If we can symbolically evaluate the specified GEP
563
/// constant expression, do so.
564
static Constant *SymbolicallyEvaluateGEP(Constant *const *Ops, unsigned NumOps,
565
const Type *ResultTy,
566
const TargetData *TD) {
567
Constant *Ptr = Ops[0];
568
if (!TD || !cast<PointerType>(Ptr->getType())->getElementType()->isSized())
572
TD->getTypeSizeInBits(TD->getIntPtrType(Ptr->getContext()));
574
// If this is a constant expr gep that is effectively computing an
575
// "offsetof", fold it into 'cast int Size to T*' instead of 'gep 0, 0, 12'
576
for (unsigned i = 1; i != NumOps; ++i)
577
if (!isa<ConstantInt>(Ops[i]))
580
APInt Offset = APInt(BitWidth,
581
TD->getIndexedOffset(Ptr->getType(),
582
(Value**)Ops+1, NumOps-1));
583
Ptr = cast<Constant>(Ptr->stripPointerCasts());
585
// If this is a GEP of a GEP, fold it all into a single GEP.
586
while (GEPOperator *GEP = dyn_cast<GEPOperator>(Ptr)) {
587
SmallVector<Value *, 4> NestedOps(GEP->op_begin()+1, GEP->op_end());
589
// Do not try the incorporate the sub-GEP if some index is not a number.
590
bool AllConstantInt = true;
591
for (unsigned i = 0, e = NestedOps.size(); i != e; ++i)
592
if (!isa<ConstantInt>(NestedOps[i])) {
593
AllConstantInt = false;
599
Ptr = cast<Constant>(GEP->getOperand(0));
600
Offset += APInt(BitWidth,
601
TD->getIndexedOffset(Ptr->getType(),
602
(Value**)NestedOps.data(),
604
Ptr = cast<Constant>(Ptr->stripPointerCasts());
607
// If the base value for this address is a literal integer value, fold the
608
// getelementptr to the resulting integer value casted to the pointer type.
609
APInt BasePtr(BitWidth, 0);
610
if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Ptr))
611
if (CE->getOpcode() == Instruction::IntToPtr)
612
if (ConstantInt *Base = dyn_cast<ConstantInt>(CE->getOperand(0))) {
613
BasePtr = Base->getValue();
614
BasePtr.zextOrTrunc(BitWidth);
616
if (Ptr->isNullValue() || BasePtr != 0) {
617
Constant *C = ConstantInt::get(Ptr->getContext(), Offset+BasePtr);
618
return ConstantExpr::getIntToPtr(C, ResultTy);
621
// Otherwise form a regular getelementptr. Recompute the indices so that
622
// we eliminate over-indexing of the notional static type array bounds.
623
// This makes it easy to determine if the getelementptr is "inbounds".
624
// Also, this helps GlobalOpt do SROA on GlobalVariables.
625
const Type *Ty = Ptr->getType();
626
SmallVector<Constant*, 32> NewIdxs;
628
if (const SequentialType *ATy = dyn_cast<SequentialType>(Ty)) {
629
if (ATy->isPointerTy()) {
630
// The only pointer indexing we'll do is on the first index of the GEP.
631
if (!NewIdxs.empty())
634
// Only handle pointers to sized types, not pointers to functions.
635
if (!ATy->getElementType()->isSized())
639
// Determine which element of the array the offset points into.
640
APInt ElemSize(BitWidth, TD->getTypeAllocSize(ATy->getElementType()));
643
APInt NewIdx = Offset.udiv(ElemSize);
644
Offset -= NewIdx * ElemSize;
645
NewIdxs.push_back(ConstantInt::get(TD->getIntPtrType(Ty->getContext()),
647
Ty = ATy->getElementType();
648
} else if (const StructType *STy = dyn_cast<StructType>(Ty)) {
649
// Determine which field of the struct the offset points into. The
650
// getZExtValue is at least as safe as the StructLayout API because we
651
// know the offset is within the struct at this point.
652
const StructLayout &SL = *TD->getStructLayout(STy);
653
unsigned ElIdx = SL.getElementContainingOffset(Offset.getZExtValue());
654
NewIdxs.push_back(ConstantInt::get(Type::getInt32Ty(Ty->getContext()),
656
Offset -= APInt(BitWidth, SL.getElementOffset(ElIdx));
657
Ty = STy->getTypeAtIndex(ElIdx);
659
// We've reached some non-indexable type.
662
} while (Ty != cast<PointerType>(ResultTy)->getElementType());
664
// If we haven't used up the entire offset by descending the static
665
// type, then the offset is pointing into the middle of an indivisible
666
// member, so we can't simplify it.
672
ConstantExpr::getGetElementPtr(Ptr, &NewIdxs[0], NewIdxs.size());
673
assert(cast<PointerType>(C->getType())->getElementType() == Ty &&
674
"Computed GetElementPtr has unexpected type!");
676
// If we ended up indexing a member with a type that doesn't match
677
// the type of what the original indices indexed, add a cast.
678
if (Ty != cast<PointerType>(ResultTy)->getElementType())
679
C = FoldBitCast(C, ResultTy, *TD);
686
//===----------------------------------------------------------------------===//
687
// Constant Folding public APIs
688
//===----------------------------------------------------------------------===//
691
/// ConstantFoldInstruction - Attempt to constant fold the specified
692
/// instruction. If successful, the constant result is returned, if not, null
693
/// is returned. Note that this function can only fail when attempting to fold
694
/// instructions like loads and stores, which have no constant expression form.
696
Constant *llvm::ConstantFoldInstruction(Instruction *I, const TargetData *TD) {
697
if (PHINode *PN = dyn_cast<PHINode>(I)) {
698
if (PN->getNumIncomingValues() == 0)
699
return UndefValue::get(PN->getType());
701
Constant *Result = dyn_cast<Constant>(PN->getIncomingValue(0));
702
if (Result == 0) return 0;
704
// Handle PHI nodes specially here...
705
for (unsigned i = 1, e = PN->getNumIncomingValues(); i != e; ++i)
706
if (PN->getIncomingValue(i) != Result && PN->getIncomingValue(i) != PN)
707
return 0; // Not all the same incoming constants...
709
// If we reach here, all incoming values are the same constant.
713
// Scan the operand list, checking to see if they are all constants, if so,
714
// hand off to ConstantFoldInstOperands.
715
SmallVector<Constant*, 8> Ops;
716
for (User::op_iterator i = I->op_begin(), e = I->op_end(); i != e; ++i)
717
if (Constant *Op = dyn_cast<Constant>(*i))
720
return 0; // All operands not constant!
722
if (const CmpInst *CI = dyn_cast<CmpInst>(I))
723
return ConstantFoldCompareInstOperands(CI->getPredicate(), Ops[0], Ops[1],
726
if (const LoadInst *LI = dyn_cast<LoadInst>(I))
727
return ConstantFoldLoadInst(LI, TD);
729
return ConstantFoldInstOperands(I->getOpcode(), I->getType(),
730
Ops.data(), Ops.size(), TD);
733
/// ConstantFoldConstantExpression - Attempt to fold the constant expression
734
/// using the specified TargetData. If successful, the constant result is
735
/// result is returned, if not, null is returned.
736
Constant *llvm::ConstantFoldConstantExpression(const ConstantExpr *CE,
737
const TargetData *TD) {
738
SmallVector<Constant*, 8> Ops;
739
for (User::const_op_iterator i = CE->op_begin(), e = CE->op_end(); i != e; ++i) {
740
Constant *NewC = cast<Constant>(*i);
741
// Recursively fold the ConstantExpr's operands.
742
if (ConstantExpr *NewCE = dyn_cast<ConstantExpr>(NewC))
743
NewC = ConstantFoldConstantExpression(NewCE, TD);
748
return ConstantFoldCompareInstOperands(CE->getPredicate(), Ops[0], Ops[1],
750
return ConstantFoldInstOperands(CE->getOpcode(), CE->getType(),
751
Ops.data(), Ops.size(), TD);
754
/// ConstantFoldInstOperands - Attempt to constant fold an instruction with the
755
/// specified opcode and operands. If successful, the constant result is
756
/// returned, if not, null is returned. Note that this function can fail when
757
/// attempting to fold instructions like loads and stores, which have no
758
/// constant expression form.
760
/// TODO: This function neither utilizes nor preserves nsw/nuw/inbounds/etc
761
/// information, due to only being passed an opcode and operands. Constant
762
/// folding using this function strips this information.
764
Constant *llvm::ConstantFoldInstOperands(unsigned Opcode, const Type *DestTy,
765
Constant* const* Ops, unsigned NumOps,
766
const TargetData *TD) {
767
// Handle easy binops first.
768
if (Instruction::isBinaryOp(Opcode)) {
769
if (isa<ConstantExpr>(Ops[0]) || isa<ConstantExpr>(Ops[1]))
770
if (Constant *C = SymbolicallyEvaluateBinop(Opcode, Ops[0], Ops[1], TD))
773
return ConstantExpr::get(Opcode, Ops[0], Ops[1]);
778
case Instruction::ICmp:
779
case Instruction::FCmp: assert(0 && "Invalid for compares");
780
case Instruction::Call:
781
if (Function *F = dyn_cast<Function>(Ops[NumOps - 1]))
782
if (canConstantFoldCallTo(F))
783
return ConstantFoldCall(F, Ops, NumOps - 1);
785
case Instruction::PtrToInt:
786
// If the input is a inttoptr, eliminate the pair. This requires knowing
787
// the width of a pointer, so it can't be done in ConstantExpr::getCast.
788
if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Ops[0])) {
789
if (TD && CE->getOpcode() == Instruction::IntToPtr) {
790
Constant *Input = CE->getOperand(0);
791
unsigned InWidth = Input->getType()->getScalarSizeInBits();
792
if (TD->getPointerSizeInBits() < InWidth) {
794
ConstantInt::get(CE->getContext(), APInt::getLowBitsSet(InWidth,
795
TD->getPointerSizeInBits()));
796
Input = ConstantExpr::getAnd(Input, Mask);
798
// Do a zext or trunc to get to the dest size.
799
return ConstantExpr::getIntegerCast(Input, DestTy, false);
802
return ConstantExpr::getCast(Opcode, Ops[0], DestTy);
803
case Instruction::IntToPtr:
804
// If the input is a ptrtoint, turn the pair into a ptr to ptr bitcast if
805
// the int size is >= the ptr size. This requires knowing the width of a
806
// pointer, so it can't be done in ConstantExpr::getCast.
807
if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Ops[0]))
809
TD->getPointerSizeInBits() <= CE->getType()->getScalarSizeInBits() &&
810
CE->getOpcode() == Instruction::PtrToInt)
811
return FoldBitCast(CE->getOperand(0), DestTy, *TD);
813
return ConstantExpr::getCast(Opcode, Ops[0], DestTy);
814
case Instruction::Trunc:
815
case Instruction::ZExt:
816
case Instruction::SExt:
817
case Instruction::FPTrunc:
818
case Instruction::FPExt:
819
case Instruction::UIToFP:
820
case Instruction::SIToFP:
821
case Instruction::FPToUI:
822
case Instruction::FPToSI:
823
return ConstantExpr::getCast(Opcode, Ops[0], DestTy);
824
case Instruction::BitCast:
826
return FoldBitCast(Ops[0], DestTy, *TD);
827
return ConstantExpr::getBitCast(Ops[0], DestTy);
828
case Instruction::Select:
829
return ConstantExpr::getSelect(Ops[0], Ops[1], Ops[2]);
830
case Instruction::ExtractElement:
831
return ConstantExpr::getExtractElement(Ops[0], Ops[1]);
832
case Instruction::InsertElement:
833
return ConstantExpr::getInsertElement(Ops[0], Ops[1], Ops[2]);
834
case Instruction::ShuffleVector:
835
return ConstantExpr::getShuffleVector(Ops[0], Ops[1], Ops[2]);
836
case Instruction::GetElementPtr:
837
if (Constant *C = CastGEPIndices(Ops, NumOps, DestTy, TD))
839
if (Constant *C = SymbolicallyEvaluateGEP(Ops, NumOps, DestTy, TD))
842
return ConstantExpr::getGetElementPtr(Ops[0], Ops+1, NumOps-1);
846
/// ConstantFoldCompareInstOperands - Attempt to constant fold a compare
847
/// instruction (icmp/fcmp) with the specified operands. If it fails, it
848
/// returns a constant expression of the specified operands.
850
Constant *llvm::ConstantFoldCompareInstOperands(unsigned Predicate,
851
Constant *Ops0, Constant *Ops1,
852
const TargetData *TD) {
853
// fold: icmp (inttoptr x), null -> icmp x, 0
854
// fold: icmp (ptrtoint x), 0 -> icmp x, null
855
// fold: icmp (inttoptr x), (inttoptr y) -> icmp trunc/zext x, trunc/zext y
856
// fold: icmp (ptrtoint x), (ptrtoint y) -> icmp x, y
858
// ConstantExpr::getCompare cannot do this, because it doesn't have TD
859
// around to know if bit truncation is happening.
860
if (ConstantExpr *CE0 = dyn_cast<ConstantExpr>(Ops0)) {
861
if (TD && Ops1->isNullValue()) {
862
const Type *IntPtrTy = TD->getIntPtrType(CE0->getContext());
863
if (CE0->getOpcode() == Instruction::IntToPtr) {
864
// Convert the integer value to the right size to ensure we get the
865
// proper extension or truncation.
866
Constant *C = ConstantExpr::getIntegerCast(CE0->getOperand(0),
868
Constant *Null = Constant::getNullValue(C->getType());
869
return ConstantFoldCompareInstOperands(Predicate, C, Null, TD);
872
// Only do this transformation if the int is intptrty in size, otherwise
873
// there is a truncation or extension that we aren't modeling.
874
if (CE0->getOpcode() == Instruction::PtrToInt &&
875
CE0->getType() == IntPtrTy) {
876
Constant *C = CE0->getOperand(0);
877
Constant *Null = Constant::getNullValue(C->getType());
878
return ConstantFoldCompareInstOperands(Predicate, C, Null, TD);
882
if (ConstantExpr *CE1 = dyn_cast<ConstantExpr>(Ops1)) {
883
if (TD && CE0->getOpcode() == CE1->getOpcode()) {
884
const Type *IntPtrTy = TD->getIntPtrType(CE0->getContext());
886
if (CE0->getOpcode() == Instruction::IntToPtr) {
887
// Convert the integer value to the right size to ensure we get the
888
// proper extension or truncation.
889
Constant *C0 = ConstantExpr::getIntegerCast(CE0->getOperand(0),
891
Constant *C1 = ConstantExpr::getIntegerCast(CE1->getOperand(0),
893
return ConstantFoldCompareInstOperands(Predicate, C0, C1, TD);
896
// Only do this transformation if the int is intptrty in size, otherwise
897
// there is a truncation or extension that we aren't modeling.
898
if ((CE0->getOpcode() == Instruction::PtrToInt &&
899
CE0->getType() == IntPtrTy &&
900
CE0->getOperand(0)->getType() == CE1->getOperand(0)->getType()))
901
return ConstantFoldCompareInstOperands(Predicate, CE0->getOperand(0),
902
CE1->getOperand(0), TD);
906
// icmp eq (or x, y), 0 -> (icmp eq x, 0) & (icmp eq y, 0)
907
// icmp ne (or x, y), 0 -> (icmp ne x, 0) | (icmp ne y, 0)
908
if ((Predicate == ICmpInst::ICMP_EQ || Predicate == ICmpInst::ICMP_NE) &&
909
CE0->getOpcode() == Instruction::Or && Ops1->isNullValue()) {
911
ConstantFoldCompareInstOperands(Predicate, CE0->getOperand(0), Ops1,TD);
913
ConstantFoldCompareInstOperands(Predicate, CE0->getOperand(1), Ops1,TD);
915
Predicate == ICmpInst::ICMP_EQ ? Instruction::And : Instruction::Or;
916
Constant *Ops[] = { LHS, RHS };
917
return ConstantFoldInstOperands(OpC, LHS->getType(), Ops, 2, TD);
921
return ConstantExpr::getCompare(Predicate, Ops0, Ops1);
925
/// ConstantFoldLoadThroughGEPConstantExpr - Given a constant and a
926
/// getelementptr constantexpr, return the constant value being addressed by the
927
/// constant expression, or null if something is funny and we can't decide.
928
Constant *llvm::ConstantFoldLoadThroughGEPConstantExpr(Constant *C,
930
if (CE->getOperand(1) != Constant::getNullValue(CE->getOperand(1)->getType()))
931
return 0; // Do not allow stepping over the value!
933
// Loop over all of the operands, tracking down which value we are
935
gep_type_iterator I = gep_type_begin(CE), E = gep_type_end(CE);
936
for (++I; I != E; ++I)
937
if (const StructType *STy = dyn_cast<StructType>(*I)) {
938
ConstantInt *CU = cast<ConstantInt>(I.getOperand());
939
assert(CU->getZExtValue() < STy->getNumElements() &&
940
"Struct index out of range!");
941
unsigned El = (unsigned)CU->getZExtValue();
942
if (ConstantStruct *CS = dyn_cast<ConstantStruct>(C)) {
943
C = CS->getOperand(El);
944
} else if (isa<ConstantAggregateZero>(C)) {
945
C = Constant::getNullValue(STy->getElementType(El));
946
} else if (isa<UndefValue>(C)) {
947
C = UndefValue::get(STy->getElementType(El));
951
} else if (ConstantInt *CI = dyn_cast<ConstantInt>(I.getOperand())) {
952
if (const ArrayType *ATy = dyn_cast<ArrayType>(*I)) {
953
if (CI->getZExtValue() >= ATy->getNumElements())
955
if (ConstantArray *CA = dyn_cast<ConstantArray>(C))
956
C = CA->getOperand(CI->getZExtValue());
957
else if (isa<ConstantAggregateZero>(C))
958
C = Constant::getNullValue(ATy->getElementType());
959
else if (isa<UndefValue>(C))
960
C = UndefValue::get(ATy->getElementType());
963
} else if (const VectorType *VTy = dyn_cast<VectorType>(*I)) {
964
if (CI->getZExtValue() >= VTy->getNumElements())
966
if (ConstantVector *CP = dyn_cast<ConstantVector>(C))
967
C = CP->getOperand(CI->getZExtValue());
968
else if (isa<ConstantAggregateZero>(C))
969
C = Constant::getNullValue(VTy->getElementType());
970
else if (isa<UndefValue>(C))
971
C = UndefValue::get(VTy->getElementType());
984
//===----------------------------------------------------------------------===//
985
// Constant Folding for Calls
988
/// canConstantFoldCallTo - Return true if its even possible to fold a call to
989
/// the specified function.
991
llvm::canConstantFoldCallTo(const Function *F) {
992
switch (F->getIntrinsicID()) {
993
case Intrinsic::sqrt:
994
case Intrinsic::powi:
995
case Intrinsic::bswap:
996
case Intrinsic::ctpop:
997
case Intrinsic::ctlz:
998
case Intrinsic::cttz:
999
case Intrinsic::uadd_with_overflow:
1000
case Intrinsic::usub_with_overflow:
1001
case Intrinsic::sadd_with_overflow:
1002
case Intrinsic::ssub_with_overflow:
1003
case Intrinsic::convert_from_fp16:
1004
case Intrinsic::convert_to_fp16:
1011
if (!F->hasName()) return false;
1012
StringRef Name = F->getName();
1014
// In these cases, the check of the length is required. We don't want to
1015
// return true for a name like "cos\0blah" which strcmp would return equal to
1016
// "cos", but has length 8.
1018
default: return false;
1020
return Name == "acos" || Name == "asin" ||
1021
Name == "atan" || Name == "atan2";
1023
return Name == "cos" || Name == "ceil" || Name == "cosf" || Name == "cosh";
1025
return Name == "exp";
1027
return Name == "fabs" || Name == "fmod" || Name == "floor";
1029
return Name == "log" || Name == "log10";
1031
return Name == "pow";
1033
return Name == "sin" || Name == "sinh" || Name == "sqrt" ||
1034
Name == "sinf" || Name == "sqrtf";
1036
return Name == "tan" || Name == "tanh";
1040
static Constant *ConstantFoldFP(double (*NativeFP)(double), double V,
1049
if (Ty->isFloatTy())
1050
return ConstantFP::get(Ty->getContext(), APFloat((float)V));
1051
if (Ty->isDoubleTy())
1052
return ConstantFP::get(Ty->getContext(), APFloat(V));
1053
llvm_unreachable("Can only constant fold float/double");
1054
return 0; // dummy return to suppress warning
1057
static Constant *ConstantFoldBinaryFP(double (*NativeFP)(double, double),
1058
double V, double W, const Type *Ty) {
1066
if (Ty->isFloatTy())
1067
return ConstantFP::get(Ty->getContext(), APFloat((float)V));
1068
if (Ty->isDoubleTy())
1069
return ConstantFP::get(Ty->getContext(), APFloat(V));
1070
llvm_unreachable("Can only constant fold float/double");
1071
return 0; // dummy return to suppress warning
1074
/// ConstantFoldCall - Attempt to constant fold a call to the specified function
1075
/// with the specified arguments, returning null if unsuccessful.
1077
llvm::ConstantFoldCall(Function *F,
1078
Constant *const *Operands, unsigned NumOperands) {
1079
if (!F->hasName()) return 0;
1080
StringRef Name = F->getName();
1082
const Type *Ty = F->getReturnType();
1083
if (NumOperands == 1) {
1084
if (ConstantFP *Op = dyn_cast<ConstantFP>(Operands[0])) {
1085
if (Name == "llvm.convert.to.fp16") {
1086
APFloat Val(Op->getValueAPF());
1089
Val.convert(APFloat::IEEEhalf, APFloat::rmNearestTiesToEven, &lost);
1091
return ConstantInt::get(F->getContext(), Val.bitcastToAPInt());
1094
if (!Ty->isFloatTy() && !Ty->isDoubleTy())
1096
/// Currently APFloat versions of these functions do not exist, so we use
1097
/// the host native double versions. Float versions are not called
1098
/// directly but for all these it is true (float)(f((double)arg)) ==
1099
/// f(arg). Long double not supported yet.
1100
double V = Ty->isFloatTy() ? (double)Op->getValueAPF().convertToFloat() :
1101
Op->getValueAPF().convertToDouble();
1105
return ConstantFoldFP(acos, V, Ty);
1106
else if (Name == "asin")
1107
return ConstantFoldFP(asin, V, Ty);
1108
else if (Name == "atan")
1109
return ConstantFoldFP(atan, V, Ty);
1113
return ConstantFoldFP(ceil, V, Ty);
1114
else if (Name == "cos")
1115
return ConstantFoldFP(cos, V, Ty);
1116
else if (Name == "cosh")
1117
return ConstantFoldFP(cosh, V, Ty);
1118
else if (Name == "cosf")
1119
return ConstantFoldFP(cos, V, Ty);
1123
return ConstantFoldFP(exp, V, Ty);
1127
return ConstantFoldFP(fabs, V, Ty);
1128
else if (Name == "floor")
1129
return ConstantFoldFP(floor, V, Ty);
1132
if (Name == "log" && V > 0)
1133
return ConstantFoldFP(log, V, Ty);
1134
else if (Name == "log10" && V > 0)
1135
return ConstantFoldFP(log10, V, Ty);
1136
else if (Name == "llvm.sqrt.f32" ||
1137
Name == "llvm.sqrt.f64") {
1139
return ConstantFoldFP(sqrt, V, Ty);
1141
return Constant::getNullValue(Ty);
1146
return ConstantFoldFP(sin, V, Ty);
1147
else if (Name == "sinh")
1148
return ConstantFoldFP(sinh, V, Ty);
1149
else if (Name == "sqrt" && V >= 0)
1150
return ConstantFoldFP(sqrt, V, Ty);
1151
else if (Name == "sqrtf" && V >= 0)
1152
return ConstantFoldFP(sqrt, V, Ty);
1153
else if (Name == "sinf")
1154
return ConstantFoldFP(sin, V, Ty);
1158
return ConstantFoldFP(tan, V, Ty);
1159
else if (Name == "tanh")
1160
return ConstantFoldFP(tanh, V, Ty);
1169
if (ConstantInt *Op = dyn_cast<ConstantInt>(Operands[0])) {
1170
if (Name.startswith("llvm.bswap"))
1171
return ConstantInt::get(F->getContext(), Op->getValue().byteSwap());
1172
else if (Name.startswith("llvm.ctpop"))
1173
return ConstantInt::get(Ty, Op->getValue().countPopulation());
1174
else if (Name.startswith("llvm.cttz"))
1175
return ConstantInt::get(Ty, Op->getValue().countTrailingZeros());
1176
else if (Name.startswith("llvm.ctlz"))
1177
return ConstantInt::get(Ty, Op->getValue().countLeadingZeros());
1178
else if (Name == "llvm.convert.from.fp16") {
1179
APFloat Val(Op->getValue());
1182
APFloat::opStatus status =
1183
Val.convert(APFloat::IEEEsingle, APFloat::rmNearestTiesToEven, &lost);
1185
// Conversion is always precise.
1187
assert(status == APFloat::opOK && !lost &&
1188
"Precision lost during fp16 constfolding");
1190
return ConstantFP::get(F->getContext(), Val);
1195
if (isa<UndefValue>(Operands[0])) {
1196
if (Name.startswith("llvm.bswap"))
1204
if (NumOperands == 2) {
1205
if (ConstantFP *Op1 = dyn_cast<ConstantFP>(Operands[0])) {
1206
if (!Ty->isFloatTy() && !Ty->isDoubleTy())
1208
double Op1V = Ty->isFloatTy() ?
1209
(double)Op1->getValueAPF().convertToFloat() :
1210
Op1->getValueAPF().convertToDouble();
1211
if (ConstantFP *Op2 = dyn_cast<ConstantFP>(Operands[1])) {
1212
if (Op2->getType() != Op1->getType())
1215
double Op2V = Ty->isFloatTy() ?
1216
(double)Op2->getValueAPF().convertToFloat():
1217
Op2->getValueAPF().convertToDouble();
1220
return ConstantFoldBinaryFP(pow, Op1V, Op2V, Ty);
1222
return ConstantFoldBinaryFP(fmod, Op1V, Op2V, Ty);
1223
if (Name == "atan2")
1224
return ConstantFoldBinaryFP(atan2, Op1V, Op2V, Ty);
1225
} else if (ConstantInt *Op2C = dyn_cast<ConstantInt>(Operands[1])) {
1226
if (Name == "llvm.powi.f32")
1227
return ConstantFP::get(F->getContext(),
1228
APFloat((float)std::pow((float)Op1V,
1229
(int)Op2C->getZExtValue())));
1230
if (Name == "llvm.powi.f64")
1231
return ConstantFP::get(F->getContext(),
1232
APFloat((double)std::pow((double)Op1V,
1233
(int)Op2C->getZExtValue())));
1239
if (ConstantInt *Op1 = dyn_cast<ConstantInt>(Operands[0])) {
1240
if (ConstantInt *Op2 = dyn_cast<ConstantInt>(Operands[1])) {
1241
switch (F->getIntrinsicID()) {
1243
case Intrinsic::uadd_with_overflow: {
1244
Constant *Res = ConstantExpr::getAdd(Op1, Op2); // result.
1246
Res, ConstantExpr::getICmp(CmpInst::ICMP_ULT, Res, Op1) // overflow.
1248
return ConstantStruct::get(F->getContext(), Ops, 2, false);
1250
case Intrinsic::usub_with_overflow: {
1251
Constant *Res = ConstantExpr::getSub(Op1, Op2); // result.
1253
Res, ConstantExpr::getICmp(CmpInst::ICMP_UGT, Res, Op1) // overflow.
1255
return ConstantStruct::get(F->getContext(), Ops, 2, false);
1257
case Intrinsic::sadd_with_overflow: {
1258
Constant *Res = ConstantExpr::getAdd(Op1, Op2); // result.
1259
Constant *Overflow = ConstantExpr::getSelect(
1260
ConstantExpr::getICmp(CmpInst::ICMP_SGT,
1261
ConstantInt::get(Op1->getType(), 0), Op1),
1262
ConstantExpr::getICmp(CmpInst::ICMP_SGT, Res, Op2),
1263
ConstantExpr::getICmp(CmpInst::ICMP_SLT, Res, Op2)); // overflow.
1265
Constant *Ops[] = { Res, Overflow };
1266
return ConstantStruct::get(F->getContext(), Ops, 2, false);
1268
case Intrinsic::ssub_with_overflow: {
1269
Constant *Res = ConstantExpr::getSub(Op1, Op2); // result.
1270
Constant *Overflow = ConstantExpr::getSelect(
1271
ConstantExpr::getICmp(CmpInst::ICMP_SGT,
1272
ConstantInt::get(Op2->getType(), 0), Op2),
1273
ConstantExpr::getICmp(CmpInst::ICMP_SLT, Res, Op1),
1274
ConstantExpr::getICmp(CmpInst::ICMP_SGT, Res, Op1)); // overflow.
1276
Constant *Ops[] = { Res, Overflow };
1277
return ConstantStruct::get(F->getContext(), Ops, 2, false);
added
removed
libclamav/c++/llvm/lib/Analysis/ConstantFolding.cpp
