1 //===- ConstantFold.cpp - LLVM constant folder ----------------------------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file implements folding of constants for LLVM. This implements the
11 // (internal) ConstantFold.h interface, which is used by the
12 // ConstantExpr::get* methods to automatically fold constants when possible.
14 // The current constant folding implementation is implemented in two pieces: the
15 // pieces that don't need DataLayout, and the pieces that do. This is to avoid
16 // a dependence in IR on Target.
18 //===----------------------------------------------------------------------===//
20 #include "ConstantFold.h"
21 #include "llvm/ADT/SmallVector.h"
22 #include "llvm/IR/Constants.h"
23 #include "llvm/IR/DerivedTypes.h"
24 #include "llvm/IR/Function.h"
25 #include "llvm/IR/GetElementPtrTypeIterator.h"
26 #include "llvm/IR/GlobalAlias.h"
27 #include "llvm/IR/GlobalVariable.h"
28 #include "llvm/IR/Instructions.h"
29 #include "llvm/IR/Operator.h"
30 #include "llvm/IR/PatternMatch.h"
31 #include "llvm/Support/Compiler.h"
32 #include "llvm/Support/ErrorHandling.h"
33 #include "llvm/Support/ManagedStatic.h"
34 #include "llvm/Support/MathExtras.h"
37 using namespace llvm::PatternMatch;
39 //===----------------------------------------------------------------------===//
40 // ConstantFold*Instruction Implementations
41 //===----------------------------------------------------------------------===//
43 /// BitCastConstantVector - Convert the specified vector Constant node to the
44 /// specified vector type. At this point, we know that the elements of the
45 /// input vector constant are all simple integer or FP values.
46 static Constant *BitCastConstantVector(Constant *CV, VectorType *DstTy) {
48 if (CV->isAllOnesValue()) return Constant::getAllOnesValue(DstTy);
49 if (CV->isNullValue()) return Constant::getNullValue(DstTy);
51 // If this cast changes element count then we can't handle it here:
52 // doing so requires endianness information. This should be handled by
53 // Analysis/ConstantFolding.cpp
54 unsigned NumElts = DstTy->getNumElements();
55 if (NumElts != CV->getType()->getVectorNumElements())
58 Type *DstEltTy = DstTy->getElementType();
60 SmallVector<Constant*, 16> Result;
61 Type *Ty = IntegerType::get(CV->getContext(), 32);
62 for (unsigned i = 0; i != NumElts; ++i) {
64 ConstantExpr::getExtractElement(CV, ConstantInt::get(Ty, i));
65 C = ConstantExpr::getBitCast(C, DstEltTy);
69 return ConstantVector::get(Result);
72 /// This function determines which opcode to use to fold two constant cast
73 /// expressions together. It uses CastInst::isEliminableCastPair to determine
74 /// the opcode. Consequently its just a wrapper around that function.
75 /// @brief Determine if it is valid to fold a cast of a cast
78 unsigned opc, ///< opcode of the second cast constant expression
79 ConstantExpr *Op, ///< the first cast constant expression
80 Type *DstTy ///< destination type of the first cast
82 assert(Op && Op->isCast() && "Can't fold cast of cast without a cast!");
83 assert(DstTy && DstTy->isFirstClassType() && "Invalid cast destination type");
84 assert(CastInst::isCast(opc) && "Invalid cast opcode");
86 // The the types and opcodes for the two Cast constant expressions
87 Type *SrcTy = Op->getOperand(0)->getType();
88 Type *MidTy = Op->getType();
89 Instruction::CastOps firstOp = Instruction::CastOps(Op->getOpcode());
90 Instruction::CastOps secondOp = Instruction::CastOps(opc);
92 // Assume that pointers are never more than 64 bits wide, and only use this
93 // for the middle type. Otherwise we could end up folding away illegal
94 // bitcasts between address spaces with different sizes.
95 IntegerType *FakeIntPtrTy = Type::getInt64Ty(DstTy->getContext());
97 // Let CastInst::isEliminableCastPair do the heavy lifting.
98 return CastInst::isEliminableCastPair(firstOp, secondOp, SrcTy, MidTy, DstTy,
99 nullptr, FakeIntPtrTy, nullptr);
102 static Constant *FoldBitCast(Constant *V, Type *DestTy) {
103 Type *SrcTy = V->getType();
105 return V; // no-op cast
107 // Check to see if we are casting a pointer to an aggregate to a pointer to
108 // the first element. If so, return the appropriate GEP instruction.
109 if (PointerType *PTy = dyn_cast<PointerType>(V->getType()))
110 if (PointerType *DPTy = dyn_cast<PointerType>(DestTy))
111 if (PTy->getAddressSpace() == DPTy->getAddressSpace()
112 && DPTy->getElementType()->isSized()) {
113 SmallVector<Value*, 8> IdxList;
115 Constant::getNullValue(Type::getInt32Ty(DPTy->getContext()));
116 IdxList.push_back(Zero);
117 Type *ElTy = PTy->getElementType();
118 while (ElTy != DPTy->getElementType()) {
119 if (StructType *STy = dyn_cast<StructType>(ElTy)) {
120 if (STy->getNumElements() == 0) break;
121 ElTy = STy->getElementType(0);
122 IdxList.push_back(Zero);
123 } else if (SequentialType *STy =
124 dyn_cast<SequentialType>(ElTy)) {
125 if (ElTy->isPointerTy()) break; // Can't index into pointers!
126 ElTy = STy->getElementType();
127 IdxList.push_back(Zero);
133 if (ElTy == DPTy->getElementType())
134 // This GEP is inbounds because all indices are zero.
135 return ConstantExpr::getInBoundsGetElementPtr(V, IdxList);
138 // Handle casts from one vector constant to another. We know that the src
139 // and dest type have the same size (otherwise its an illegal cast).
140 if (VectorType *DestPTy = dyn_cast<VectorType>(DestTy)) {
141 if (VectorType *SrcTy = dyn_cast<VectorType>(V->getType())) {
142 assert(DestPTy->getBitWidth() == SrcTy->getBitWidth() &&
143 "Not cast between same sized vectors!");
145 // First, check for null. Undef is already handled.
146 if (isa<ConstantAggregateZero>(V))
147 return Constant::getNullValue(DestTy);
149 // Handle ConstantVector and ConstantAggregateVector.
150 return BitCastConstantVector(V, DestPTy);
153 // Canonicalize scalar-to-vector bitcasts into vector-to-vector bitcasts
154 // This allows for other simplifications (although some of them
155 // can only be handled by Analysis/ConstantFolding.cpp).
156 if (isa<ConstantInt>(V) || isa<ConstantFP>(V))
157 return ConstantExpr::getBitCast(ConstantVector::get(V), DestPTy);
160 // Finally, implement bitcast folding now. The code below doesn't handle
162 if (isa<ConstantPointerNull>(V)) // ptr->ptr cast.
163 return ConstantPointerNull::get(cast<PointerType>(DestTy));
165 // Handle integral constant input.
166 if (ConstantInt *CI = dyn_cast<ConstantInt>(V)) {
167 if (DestTy->isIntegerTy())
168 // Integral -> Integral. This is a no-op because the bit widths must
169 // be the same. Consequently, we just fold to V.
172 if (DestTy->isFloatingPointTy())
173 return ConstantFP::get(DestTy->getContext(),
174 APFloat(DestTy->getFltSemantics(),
177 // Otherwise, can't fold this (vector?)
181 // Handle ConstantFP input: FP -> Integral.
182 if (ConstantFP *FP = dyn_cast<ConstantFP>(V))
183 return ConstantInt::get(FP->getContext(),
184 FP->getValueAPF().bitcastToAPInt());
190 /// ExtractConstantBytes - V is an integer constant which only has a subset of
191 /// its bytes used. The bytes used are indicated by ByteStart (which is the
192 /// first byte used, counting from the least significant byte) and ByteSize,
193 /// which is the number of bytes used.
195 /// This function analyzes the specified constant to see if the specified byte
196 /// range can be returned as a simplified constant. If so, the constant is
197 /// returned, otherwise null is returned.
199 static Constant *ExtractConstantBytes(Constant *C, unsigned ByteStart,
201 assert(C->getType()->isIntegerTy() &&
202 (cast<IntegerType>(C->getType())->getBitWidth() & 7) == 0 &&
203 "Non-byte sized integer input");
204 unsigned CSize = cast<IntegerType>(C->getType())->getBitWidth()/8;
205 assert(ByteSize && "Must be accessing some piece");
206 assert(ByteStart+ByteSize <= CSize && "Extracting invalid piece from input");
207 assert(ByteSize != CSize && "Should not extract everything");
209 // Constant Integers are simple.
210 if (ConstantInt *CI = dyn_cast<ConstantInt>(C)) {
211 APInt V = CI->getValue();
213 V = V.lshr(ByteStart*8);
214 V = V.trunc(ByteSize*8);
215 return ConstantInt::get(CI->getContext(), V);
218 // In the input is a constant expr, we might be able to recursively simplify.
219 // If not, we definitely can't do anything.
220 ConstantExpr *CE = dyn_cast<ConstantExpr>(C);
221 if (!CE) return nullptr;
223 switch (CE->getOpcode()) {
224 default: return nullptr;
225 case Instruction::Or: {
226 Constant *RHS = ExtractConstantBytes(CE->getOperand(1), ByteStart,ByteSize);
231 if (ConstantInt *RHSC = dyn_cast<ConstantInt>(RHS))
232 if (RHSC->isAllOnesValue())
235 Constant *LHS = ExtractConstantBytes(CE->getOperand(0), ByteStart,ByteSize);
238 return ConstantExpr::getOr(LHS, RHS);
240 case Instruction::And: {
241 Constant *RHS = ExtractConstantBytes(CE->getOperand(1), ByteStart,ByteSize);
246 if (RHS->isNullValue())
249 Constant *LHS = ExtractConstantBytes(CE->getOperand(0), ByteStart,ByteSize);
252 return ConstantExpr::getAnd(LHS, RHS);
254 case Instruction::LShr: {
255 ConstantInt *Amt = dyn_cast<ConstantInt>(CE->getOperand(1));
258 unsigned ShAmt = Amt->getZExtValue();
259 // Cannot analyze non-byte shifts.
260 if ((ShAmt & 7) != 0)
264 // If the extract is known to be all zeros, return zero.
265 if (ByteStart >= CSize-ShAmt)
266 return Constant::getNullValue(IntegerType::get(CE->getContext(),
268 // If the extract is known to be fully in the input, extract it.
269 if (ByteStart+ByteSize+ShAmt <= CSize)
270 return ExtractConstantBytes(CE->getOperand(0), ByteStart+ShAmt, ByteSize);
272 // TODO: Handle the 'partially zero' case.
276 case Instruction::Shl: {
277 ConstantInt *Amt = dyn_cast<ConstantInt>(CE->getOperand(1));
280 unsigned ShAmt = Amt->getZExtValue();
281 // Cannot analyze non-byte shifts.
282 if ((ShAmt & 7) != 0)
286 // If the extract is known to be all zeros, return zero.
287 if (ByteStart+ByteSize <= ShAmt)
288 return Constant::getNullValue(IntegerType::get(CE->getContext(),
290 // If the extract is known to be fully in the input, extract it.
291 if (ByteStart >= ShAmt)
292 return ExtractConstantBytes(CE->getOperand(0), ByteStart-ShAmt, ByteSize);
294 // TODO: Handle the 'partially zero' case.
298 case Instruction::ZExt: {
299 unsigned SrcBitSize =
300 cast<IntegerType>(CE->getOperand(0)->getType())->getBitWidth();
302 // If extracting something that is completely zero, return 0.
303 if (ByteStart*8 >= SrcBitSize)
304 return Constant::getNullValue(IntegerType::get(CE->getContext(),
307 // If exactly extracting the input, return it.
308 if (ByteStart == 0 && ByteSize*8 == SrcBitSize)
309 return CE->getOperand(0);
311 // If extracting something completely in the input, if if the input is a
312 // multiple of 8 bits, recurse.
313 if ((SrcBitSize&7) == 0 && (ByteStart+ByteSize)*8 <= SrcBitSize)
314 return ExtractConstantBytes(CE->getOperand(0), ByteStart, ByteSize);
316 // Otherwise, if extracting a subset of the input, which is not multiple of
317 // 8 bits, do a shift and trunc to get the bits.
318 if ((ByteStart+ByteSize)*8 < SrcBitSize) {
319 assert((SrcBitSize&7) && "Shouldn't get byte sized case here");
320 Constant *Res = CE->getOperand(0);
322 Res = ConstantExpr::getLShr(Res,
323 ConstantInt::get(Res->getType(), ByteStart*8));
324 return ConstantExpr::getTrunc(Res, IntegerType::get(C->getContext(),
328 // TODO: Handle the 'partially zero' case.
334 /// getFoldedSizeOf - Return a ConstantExpr with type DestTy for sizeof
335 /// on Ty, with any known factors factored out. If Folded is false,
336 /// return null if no factoring was possible, to avoid endlessly
337 /// bouncing an unfoldable expression back into the top-level folder.
339 static Constant *getFoldedSizeOf(Type *Ty, Type *DestTy,
341 if (ArrayType *ATy = dyn_cast<ArrayType>(Ty)) {
342 Constant *N = ConstantInt::get(DestTy, ATy->getNumElements());
343 Constant *E = getFoldedSizeOf(ATy->getElementType(), DestTy, true);
344 return ConstantExpr::getNUWMul(E, N);
347 if (StructType *STy = dyn_cast<StructType>(Ty))
348 if (!STy->isPacked()) {
349 unsigned NumElems = STy->getNumElements();
350 // An empty struct has size zero.
352 return ConstantExpr::getNullValue(DestTy);
353 // Check for a struct with all members having the same size.
354 Constant *MemberSize =
355 getFoldedSizeOf(STy->getElementType(0), DestTy, true);
357 for (unsigned i = 1; i != NumElems; ++i)
359 getFoldedSizeOf(STy->getElementType(i), DestTy, true)) {
364 Constant *N = ConstantInt::get(DestTy, NumElems);
365 return ConstantExpr::getNUWMul(MemberSize, N);
369 // Pointer size doesn't depend on the pointee type, so canonicalize them
370 // to an arbitrary pointee.
371 if (PointerType *PTy = dyn_cast<PointerType>(Ty))
372 if (!PTy->getElementType()->isIntegerTy(1))
374 getFoldedSizeOf(PointerType::get(IntegerType::get(PTy->getContext(), 1),
375 PTy->getAddressSpace()),
378 // If there's no interesting folding happening, bail so that we don't create
379 // a constant that looks like it needs folding but really doesn't.
383 // Base case: Get a regular sizeof expression.
384 Constant *C = ConstantExpr::getSizeOf(Ty);
385 C = ConstantExpr::getCast(CastInst::getCastOpcode(C, false,
391 /// getFoldedAlignOf - Return a ConstantExpr with type DestTy for alignof
392 /// on Ty, with any known factors factored out. If Folded is false,
393 /// return null if no factoring was possible, to avoid endlessly
394 /// bouncing an unfoldable expression back into the top-level folder.
396 static Constant *getFoldedAlignOf(Type *Ty, Type *DestTy,
398 // The alignment of an array is equal to the alignment of the
399 // array element. Note that this is not always true for vectors.
400 if (ArrayType *ATy = dyn_cast<ArrayType>(Ty)) {
401 Constant *C = ConstantExpr::getAlignOf(ATy->getElementType());
402 C = ConstantExpr::getCast(CastInst::getCastOpcode(C, false,
409 if (StructType *STy = dyn_cast<StructType>(Ty)) {
410 // Packed structs always have an alignment of 1.
412 return ConstantInt::get(DestTy, 1);
414 // Otherwise, struct alignment is the maximum alignment of any member.
415 // Without target data, we can't compare much, but we can check to see
416 // if all the members have the same alignment.
417 unsigned NumElems = STy->getNumElements();
418 // An empty struct has minimal alignment.
420 return ConstantInt::get(DestTy, 1);
421 // Check for a struct with all members having the same alignment.
422 Constant *MemberAlign =
423 getFoldedAlignOf(STy->getElementType(0), DestTy, true);
425 for (unsigned i = 1; i != NumElems; ++i)
426 if (MemberAlign != getFoldedAlignOf(STy->getElementType(i), DestTy, true)) {
434 // Pointer alignment doesn't depend on the pointee type, so canonicalize them
435 // to an arbitrary pointee.
436 if (PointerType *PTy = dyn_cast<PointerType>(Ty))
437 if (!PTy->getElementType()->isIntegerTy(1))
439 getFoldedAlignOf(PointerType::get(IntegerType::get(PTy->getContext(),
441 PTy->getAddressSpace()),
444 // If there's no interesting folding happening, bail so that we don't create
445 // a constant that looks like it needs folding but really doesn't.
449 // Base case: Get a regular alignof expression.
450 Constant *C = ConstantExpr::getAlignOf(Ty);
451 C = ConstantExpr::getCast(CastInst::getCastOpcode(C, false,
457 /// getFoldedOffsetOf - Return a ConstantExpr with type DestTy for offsetof
458 /// on Ty and FieldNo, with any known factors factored out. If Folded is false,
459 /// return null if no factoring was possible, to avoid endlessly
460 /// bouncing an unfoldable expression back into the top-level folder.
462 static Constant *getFoldedOffsetOf(Type *Ty, Constant *FieldNo,
465 if (ArrayType *ATy = dyn_cast<ArrayType>(Ty)) {
466 Constant *N = ConstantExpr::getCast(CastInst::getCastOpcode(FieldNo, false,
469 Constant *E = getFoldedSizeOf(ATy->getElementType(), DestTy, true);
470 return ConstantExpr::getNUWMul(E, N);
473 if (StructType *STy = dyn_cast<StructType>(Ty))
474 if (!STy->isPacked()) {
475 unsigned NumElems = STy->getNumElements();
476 // An empty struct has no members.
479 // Check for a struct with all members having the same size.
480 Constant *MemberSize =
481 getFoldedSizeOf(STy->getElementType(0), DestTy, true);
483 for (unsigned i = 1; i != NumElems; ++i)
485 getFoldedSizeOf(STy->getElementType(i), DestTy, true)) {
490 Constant *N = ConstantExpr::getCast(CastInst::getCastOpcode(FieldNo,
495 return ConstantExpr::getNUWMul(MemberSize, N);
499 // If there's no interesting folding happening, bail so that we don't create
500 // a constant that looks like it needs folding but really doesn't.
504 // Base case: Get a regular offsetof expression.
505 Constant *C = ConstantExpr::getOffsetOf(Ty, FieldNo);
506 C = ConstantExpr::getCast(CastInst::getCastOpcode(C, false,
512 Constant *llvm::ConstantFoldCastInstruction(unsigned opc, Constant *V,
514 if (isa<UndefValue>(V)) {
515 // zext(undef) = 0, because the top bits will be zero.
516 // sext(undef) = 0, because the top bits will all be the same.
517 // [us]itofp(undef) = 0, because the result value is bounded.
518 if (opc == Instruction::ZExt || opc == Instruction::SExt ||
519 opc == Instruction::UIToFP || opc == Instruction::SIToFP)
520 return Constant::getNullValue(DestTy);
521 return UndefValue::get(DestTy);
524 if (V->isNullValue() && !DestTy->isX86_MMXTy())
525 return Constant::getNullValue(DestTy);
527 // If the cast operand is a constant expression, there's a few things we can
528 // do to try to simplify it.
529 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V)) {
531 // Try hard to fold cast of cast because they are often eliminable.
532 if (unsigned newOpc = foldConstantCastPair(opc, CE, DestTy))
533 return ConstantExpr::getCast(newOpc, CE->getOperand(0), DestTy);
534 } else if (CE->getOpcode() == Instruction::GetElementPtr &&
535 // Do not fold addrspacecast (gep 0, .., 0). It might make the
536 // addrspacecast uncanonicalized.
537 opc != Instruction::AddrSpaceCast) {
538 // If all of the indexes in the GEP are null values, there is no pointer
539 // adjustment going on. We might as well cast the source pointer.
540 bool isAllNull = true;
541 for (unsigned i = 1, e = CE->getNumOperands(); i != e; ++i)
542 if (!CE->getOperand(i)->isNullValue()) {
547 // This is casting one pointer type to another, always BitCast
548 return ConstantExpr::getPointerCast(CE->getOperand(0), DestTy);
552 // If the cast operand is a constant vector, perform the cast by
553 // operating on each element. In the cast of bitcasts, the element
554 // count may be mismatched; don't attempt to handle that here.
555 if ((isa<ConstantVector>(V) || isa<ConstantDataVector>(V)) &&
556 DestTy->isVectorTy() &&
557 DestTy->getVectorNumElements() == V->getType()->getVectorNumElements()) {
558 SmallVector<Constant*, 16> res;
559 VectorType *DestVecTy = cast<VectorType>(DestTy);
560 Type *DstEltTy = DestVecTy->getElementType();
561 Type *Ty = IntegerType::get(V->getContext(), 32);
562 for (unsigned i = 0, e = V->getType()->getVectorNumElements(); i != e; ++i) {
564 ConstantExpr::getExtractElement(V, ConstantInt::get(Ty, i));
565 res.push_back(ConstantExpr::getCast(opc, C, DstEltTy));
567 return ConstantVector::get(res);
570 // We actually have to do a cast now. Perform the cast according to the
574 llvm_unreachable("Failed to cast constant expression");
575 case Instruction::FPTrunc:
576 case Instruction::FPExt:
577 if (ConstantFP *FPC = dyn_cast<ConstantFP>(V)) {
579 APFloat Val = FPC->getValueAPF();
580 Val.convert(DestTy->isHalfTy() ? APFloat::IEEEhalf :
581 DestTy->isFloatTy() ? APFloat::IEEEsingle :
582 DestTy->isDoubleTy() ? APFloat::IEEEdouble :
583 DestTy->isX86_FP80Ty() ? APFloat::x87DoubleExtended :
584 DestTy->isFP128Ty() ? APFloat::IEEEquad :
585 DestTy->isPPC_FP128Ty() ? APFloat::PPCDoubleDouble :
587 APFloat::rmNearestTiesToEven, &ignored);
588 return ConstantFP::get(V->getContext(), Val);
590 return nullptr; // Can't fold.
591 case Instruction::FPToUI:
592 case Instruction::FPToSI:
593 if (ConstantFP *FPC = dyn_cast<ConstantFP>(V)) {
594 const APFloat &V = FPC->getValueAPF();
597 uint32_t DestBitWidth = cast<IntegerType>(DestTy)->getBitWidth();
598 if (APFloat::opInvalidOp ==
599 V.convertToInteger(x, DestBitWidth, opc==Instruction::FPToSI,
600 APFloat::rmTowardZero, &ignored)) {
601 // Undefined behavior invoked - the destination type can't represent
602 // the input constant.
603 return UndefValue::get(DestTy);
605 APInt Val(DestBitWidth, x);
606 return ConstantInt::get(FPC->getContext(), Val);
608 return nullptr; // Can't fold.
609 case Instruction::IntToPtr: //always treated as unsigned
610 if (V->isNullValue()) // Is it an integral null value?
611 return ConstantPointerNull::get(cast<PointerType>(DestTy));
612 return nullptr; // Other pointer types cannot be casted
613 case Instruction::PtrToInt: // always treated as unsigned
614 // Is it a null pointer value?
615 if (V->isNullValue())
616 return ConstantInt::get(DestTy, 0);
617 // If this is a sizeof-like expression, pull out multiplications by
618 // known factors to expose them to subsequent folding. If it's an
619 // alignof-like expression, factor out known factors.
620 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V))
621 if (CE->getOpcode() == Instruction::GetElementPtr &&
622 CE->getOperand(0)->isNullValue()) {
624 cast<PointerType>(CE->getOperand(0)->getType())->getElementType();
625 if (CE->getNumOperands() == 2) {
626 // Handle a sizeof-like expression.
627 Constant *Idx = CE->getOperand(1);
628 bool isOne = isa<ConstantInt>(Idx) && cast<ConstantInt>(Idx)->isOne();
629 if (Constant *C = getFoldedSizeOf(Ty, DestTy, !isOne)) {
630 Idx = ConstantExpr::getCast(CastInst::getCastOpcode(Idx, true,
633 return ConstantExpr::getMul(C, Idx);
635 } else if (CE->getNumOperands() == 3 &&
636 CE->getOperand(1)->isNullValue()) {
637 // Handle an alignof-like expression.
638 if (StructType *STy = dyn_cast<StructType>(Ty))
639 if (!STy->isPacked()) {
640 ConstantInt *CI = cast<ConstantInt>(CE->getOperand(2));
642 STy->getNumElements() == 2 &&
643 STy->getElementType(0)->isIntegerTy(1)) {
644 return getFoldedAlignOf(STy->getElementType(1), DestTy, false);
647 // Handle an offsetof-like expression.
648 if (Ty->isStructTy() || Ty->isArrayTy()) {
649 if (Constant *C = getFoldedOffsetOf(Ty, CE->getOperand(2),
655 // Other pointer types cannot be casted
657 case Instruction::UIToFP:
658 case Instruction::SIToFP:
659 if (ConstantInt *CI = dyn_cast<ConstantInt>(V)) {
660 APInt api = CI->getValue();
661 APFloat apf(DestTy->getFltSemantics(),
662 APInt::getNullValue(DestTy->getPrimitiveSizeInBits()));
663 if (APFloat::opOverflow &
664 apf.convertFromAPInt(api, opc==Instruction::SIToFP,
665 APFloat::rmNearestTiesToEven)) {
666 // Undefined behavior invoked - the destination type can't represent
667 // the input constant.
668 return UndefValue::get(DestTy);
670 return ConstantFP::get(V->getContext(), apf);
673 case Instruction::ZExt:
674 if (ConstantInt *CI = dyn_cast<ConstantInt>(V)) {
675 uint32_t BitWidth = cast<IntegerType>(DestTy)->getBitWidth();
676 return ConstantInt::get(V->getContext(),
677 CI->getValue().zext(BitWidth));
680 case Instruction::SExt:
681 if (ConstantInt *CI = dyn_cast<ConstantInt>(V)) {
682 uint32_t BitWidth = cast<IntegerType>(DestTy)->getBitWidth();
683 return ConstantInt::get(V->getContext(),
684 CI->getValue().sext(BitWidth));
687 case Instruction::Trunc: {
688 if (V->getType()->isVectorTy())
691 uint32_t DestBitWidth = cast<IntegerType>(DestTy)->getBitWidth();
692 if (ConstantInt *CI = dyn_cast<ConstantInt>(V)) {
693 return ConstantInt::get(V->getContext(),
694 CI->getValue().trunc(DestBitWidth));
697 // The input must be a constantexpr. See if we can simplify this based on
698 // the bytes we are demanding. Only do this if the source and dest are an
699 // even multiple of a byte.
700 if ((DestBitWidth & 7) == 0 &&
701 (cast<IntegerType>(V->getType())->getBitWidth() & 7) == 0)
702 if (Constant *Res = ExtractConstantBytes(V, 0, DestBitWidth / 8))
707 case Instruction::BitCast:
708 return FoldBitCast(V, DestTy);
709 case Instruction::AddrSpaceCast:
714 Constant *llvm::ConstantFoldSelectInstruction(Constant *Cond,
715 Constant *V1, Constant *V2) {
716 // Check for i1 and vector true/false conditions.
717 if (Cond->isNullValue()) return V2;
718 if (Cond->isAllOnesValue()) return V1;
720 // If the condition is a vector constant, fold the result elementwise.
721 if (ConstantVector *CondV = dyn_cast<ConstantVector>(Cond)) {
722 SmallVector<Constant*, 16> Result;
723 Type *Ty = IntegerType::get(CondV->getContext(), 32);
724 for (unsigned i = 0, e = V1->getType()->getVectorNumElements(); i != e;++i){
726 Constant *V1Element = ConstantExpr::getExtractElement(V1,
727 ConstantInt::get(Ty, i));
728 Constant *V2Element = ConstantExpr::getExtractElement(V2,
729 ConstantInt::get(Ty, i));
730 Constant *Cond = dyn_cast<Constant>(CondV->getOperand(i));
731 if (V1Element == V2Element) {
733 } else if (isa<UndefValue>(Cond)) {
734 V = isa<UndefValue>(V1Element) ? V1Element : V2Element;
736 if (!isa<ConstantInt>(Cond)) break;
737 V = Cond->isNullValue() ? V2Element : V1Element;
742 // If we were able to build the vector, return it.
743 if (Result.size() == V1->getType()->getVectorNumElements())
744 return ConstantVector::get(Result);
747 if (isa<UndefValue>(Cond)) {
748 if (isa<UndefValue>(V1)) return V1;
751 if (isa<UndefValue>(V1)) return V2;
752 if (isa<UndefValue>(V2)) return V1;
753 if (V1 == V2) return V1;
755 if (ConstantExpr *TrueVal = dyn_cast<ConstantExpr>(V1)) {
756 if (TrueVal->getOpcode() == Instruction::Select)
757 if (TrueVal->getOperand(0) == Cond)
758 return ConstantExpr::getSelect(Cond, TrueVal->getOperand(1), V2);
760 if (ConstantExpr *FalseVal = dyn_cast<ConstantExpr>(V2)) {
761 if (FalseVal->getOpcode() == Instruction::Select)
762 if (FalseVal->getOperand(0) == Cond)
763 return ConstantExpr::getSelect(Cond, V1, FalseVal->getOperand(2));
769 Constant *llvm::ConstantFoldExtractElementInstruction(Constant *Val,
771 if (isa<UndefValue>(Val)) // ee(undef, x) -> undef
772 return UndefValue::get(Val->getType()->getVectorElementType());
773 if (Val->isNullValue()) // ee(zero, x) -> zero
774 return Constant::getNullValue(Val->getType()->getVectorElementType());
775 // ee({w,x,y,z}, undef) -> undef
776 if (isa<UndefValue>(Idx))
777 return UndefValue::get(Val->getType()->getVectorElementType());
779 if (ConstantInt *CIdx = dyn_cast<ConstantInt>(Idx)) {
780 uint64_t Index = CIdx->getZExtValue();
781 // ee({w,x,y,z}, wrong_value) -> undef
782 if (Index >= Val->getType()->getVectorNumElements())
783 return UndefValue::get(Val->getType()->getVectorElementType());
784 return Val->getAggregateElement(Index);
789 Constant *llvm::ConstantFoldInsertElementInstruction(Constant *Val,
792 ConstantInt *CIdx = dyn_cast<ConstantInt>(Idx);
793 if (!CIdx) return nullptr;
794 const APInt &IdxVal = CIdx->getValue();
796 SmallVector<Constant*, 16> Result;
797 Type *Ty = IntegerType::get(Val->getContext(), 32);
798 for (unsigned i = 0, e = Val->getType()->getVectorNumElements(); i != e; ++i){
800 Result.push_back(Elt);
805 ConstantExpr::getExtractElement(Val, ConstantInt::get(Ty, i));
809 return ConstantVector::get(Result);
812 Constant *llvm::ConstantFoldShuffleVectorInstruction(Constant *V1,
815 unsigned MaskNumElts = Mask->getType()->getVectorNumElements();
816 Type *EltTy = V1->getType()->getVectorElementType();
818 // Undefined shuffle mask -> undefined value.
819 if (isa<UndefValue>(Mask))
820 return UndefValue::get(VectorType::get(EltTy, MaskNumElts));
822 // Don't break the bitcode reader hack.
823 if (isa<ConstantExpr>(Mask)) return nullptr;
825 unsigned SrcNumElts = V1->getType()->getVectorNumElements();
827 // Loop over the shuffle mask, evaluating each element.
828 SmallVector<Constant*, 32> Result;
829 for (unsigned i = 0; i != MaskNumElts; ++i) {
830 int Elt = ShuffleVectorInst::getMaskValue(Mask, i);
832 Result.push_back(UndefValue::get(EltTy));
836 if (unsigned(Elt) >= SrcNumElts*2)
837 InElt = UndefValue::get(EltTy);
838 else if (unsigned(Elt) >= SrcNumElts) {
839 Type *Ty = IntegerType::get(V2->getContext(), 32);
841 ConstantExpr::getExtractElement(V2,
842 ConstantInt::get(Ty, Elt - SrcNumElts));
844 Type *Ty = IntegerType::get(V1->getContext(), 32);
845 InElt = ConstantExpr::getExtractElement(V1, ConstantInt::get(Ty, Elt));
847 Result.push_back(InElt);
850 return ConstantVector::get(Result);
853 Constant *llvm::ConstantFoldExtractValueInstruction(Constant *Agg,
854 ArrayRef<unsigned> Idxs) {
855 // Base case: no indices, so return the entire value.
859 if (Constant *C = Agg->getAggregateElement(Idxs[0]))
860 return ConstantFoldExtractValueInstruction(C, Idxs.slice(1));
865 Constant *llvm::ConstantFoldInsertValueInstruction(Constant *Agg,
867 ArrayRef<unsigned> Idxs) {
868 // Base case: no indices, so replace the entire value.
873 if (StructType *ST = dyn_cast<StructType>(Agg->getType()))
874 NumElts = ST->getNumElements();
875 else if (ArrayType *AT = dyn_cast<ArrayType>(Agg->getType()))
876 NumElts = AT->getNumElements();
878 NumElts = Agg->getType()->getVectorNumElements();
880 SmallVector<Constant*, 32> Result;
881 for (unsigned i = 0; i != NumElts; ++i) {
882 Constant *C = Agg->getAggregateElement(i);
883 if (!C) return nullptr;
886 C = ConstantFoldInsertValueInstruction(C, Val, Idxs.slice(1));
891 if (StructType *ST = dyn_cast<StructType>(Agg->getType()))
892 return ConstantStruct::get(ST, Result);
893 if (ArrayType *AT = dyn_cast<ArrayType>(Agg->getType()))
894 return ConstantArray::get(AT, Result);
895 return ConstantVector::get(Result);
899 Constant *llvm::ConstantFoldBinaryInstruction(unsigned Opcode,
900 Constant *C1, Constant *C2) {
901 // Handle UndefValue up front.
902 if (isa<UndefValue>(C1) || isa<UndefValue>(C2)) {
904 case Instruction::Xor:
905 if (isa<UndefValue>(C1) && isa<UndefValue>(C2))
906 // Handle undef ^ undef -> 0 special case. This is a common
908 return Constant::getNullValue(C1->getType());
910 case Instruction::Add:
911 case Instruction::Sub:
912 return UndefValue::get(C1->getType());
913 case Instruction::And:
914 if (isa<UndefValue>(C1) && isa<UndefValue>(C2)) // undef & undef -> undef
916 return Constant::getNullValue(C1->getType()); // undef & X -> 0
917 case Instruction::Mul: {
918 // undef * undef -> undef
919 if (isa<UndefValue>(C1) && isa<UndefValue>(C2))
922 // X * undef -> undef if X is odd
923 if (match(C1, m_APInt(CV)) || match(C2, m_APInt(CV)))
925 return UndefValue::get(C1->getType());
927 // X * undef -> 0 otherwise
928 return Constant::getNullValue(C1->getType());
930 case Instruction::SDiv:
931 case Instruction::UDiv:
932 // X / undef -> undef
933 if (match(C1, m_Zero()))
935 // undef / 0 -> undef
936 // undef / 1 -> undef
937 if (match(C2, m_Zero()) || match(C2, m_One()))
939 // undef / X -> 0 otherwise
940 return Constant::getNullValue(C1->getType());
941 case Instruction::URem:
942 case Instruction::SRem:
943 // X % undef -> undef
944 if (match(C2, m_Undef()))
946 // undef % 0 -> undef
947 if (match(C2, m_Zero()))
949 // undef % X -> 0 otherwise
950 return Constant::getNullValue(C1->getType());
951 case Instruction::Or: // X | undef -> -1
952 if (isa<UndefValue>(C1) && isa<UndefValue>(C2)) // undef | undef -> undef
954 return Constant::getAllOnesValue(C1->getType()); // undef | X -> ~0
955 case Instruction::LShr:
956 // X >>l undef -> undef
957 if (isa<UndefValue>(C2))
959 // undef >>l 0 -> undef
960 if (match(C2, m_Zero()))
963 return Constant::getNullValue(C1->getType());
964 case Instruction::AShr:
965 // X >>a undef -> undef
966 if (isa<UndefValue>(C2))
968 // undef >>a 0 -> undef
969 if (match(C2, m_Zero()))
971 // TODO: undef >>a X -> undef if the shift is exact
973 return Constant::getNullValue(C1->getType());
974 case Instruction::Shl:
975 // X << undef -> undef
976 if (isa<UndefValue>(C2))
978 // undef << 0 -> undef
979 if (match(C2, m_Zero()))
982 return Constant::getNullValue(C1->getType());
986 // Handle simplifications when the RHS is a constant int.
987 if (ConstantInt *CI2 = dyn_cast<ConstantInt>(C2)) {
989 case Instruction::Add:
990 if (CI2->equalsInt(0)) return C1; // X + 0 == X
992 case Instruction::Sub:
993 if (CI2->equalsInt(0)) return C1; // X - 0 == X
995 case Instruction::Mul:
996 if (CI2->equalsInt(0)) return C2; // X * 0 == 0
997 if (CI2->equalsInt(1))
998 return C1; // X * 1 == X
1000 case Instruction::UDiv:
1001 case Instruction::SDiv:
1002 if (CI2->equalsInt(1))
1003 return C1; // X / 1 == X
1004 if (CI2->equalsInt(0))
1005 return UndefValue::get(CI2->getType()); // X / 0 == undef
1007 case Instruction::URem:
1008 case Instruction::SRem:
1009 if (CI2->equalsInt(1))
1010 return Constant::getNullValue(CI2->getType()); // X % 1 == 0
1011 if (CI2->equalsInt(0))
1012 return UndefValue::get(CI2->getType()); // X % 0 == undef
1014 case Instruction::And:
1015 if (CI2->isZero()) return C2; // X & 0 == 0
1016 if (CI2->isAllOnesValue())
1017 return C1; // X & -1 == X
1019 if (ConstantExpr *CE1 = dyn_cast<ConstantExpr>(C1)) {
1020 // (zext i32 to i64) & 4294967295 -> (zext i32 to i64)
1021 if (CE1->getOpcode() == Instruction::ZExt) {
1022 unsigned DstWidth = CI2->getType()->getBitWidth();
1024 CE1->getOperand(0)->getType()->getPrimitiveSizeInBits();
1025 APInt PossiblySetBits(APInt::getLowBitsSet(DstWidth, SrcWidth));
1026 if ((PossiblySetBits & CI2->getValue()) == PossiblySetBits)
1030 // If and'ing the address of a global with a constant, fold it.
1031 if (CE1->getOpcode() == Instruction::PtrToInt &&
1032 isa<GlobalValue>(CE1->getOperand(0))) {
1033 GlobalValue *GV = cast<GlobalValue>(CE1->getOperand(0));
1035 // Functions are at least 4-byte aligned.
1036 unsigned GVAlign = GV->getAlignment();
1037 if (isa<Function>(GV))
1038 GVAlign = std::max(GVAlign, 4U);
1041 unsigned DstWidth = CI2->getType()->getBitWidth();
1042 unsigned SrcWidth = std::min(DstWidth, Log2_32(GVAlign));
1043 APInt BitsNotSet(APInt::getLowBitsSet(DstWidth, SrcWidth));
1045 // If checking bits we know are clear, return zero.
1046 if ((CI2->getValue() & BitsNotSet) == CI2->getValue())
1047 return Constant::getNullValue(CI2->getType());
1052 case Instruction::Or:
1053 if (CI2->equalsInt(0)) return C1; // X | 0 == X
1054 if (CI2->isAllOnesValue())
1055 return C2; // X | -1 == -1
1057 case Instruction::Xor:
1058 if (CI2->equalsInt(0)) return C1; // X ^ 0 == X
1060 if (ConstantExpr *CE1 = dyn_cast<ConstantExpr>(C1)) {
1061 switch (CE1->getOpcode()) {
1063 case Instruction::ICmp:
1064 case Instruction::FCmp:
1065 // cmp pred ^ true -> cmp !pred
1066 assert(CI2->equalsInt(1));
1067 CmpInst::Predicate pred = (CmpInst::Predicate)CE1->getPredicate();
1068 pred = CmpInst::getInversePredicate(pred);
1069 return ConstantExpr::getCompare(pred, CE1->getOperand(0),
1070 CE1->getOperand(1));
1074 case Instruction::AShr:
1075 // ashr (zext C to Ty), C2 -> lshr (zext C, CSA), C2
1076 if (ConstantExpr *CE1 = dyn_cast<ConstantExpr>(C1))
1077 if (CE1->getOpcode() == Instruction::ZExt) // Top bits known zero.
1078 return ConstantExpr::getLShr(C1, C2);
1081 } else if (isa<ConstantInt>(C1)) {
1082 // If C1 is a ConstantInt and C2 is not, swap the operands.
1083 if (Instruction::isCommutative(Opcode))
1084 return ConstantExpr::get(Opcode, C2, C1);
1087 // At this point we know neither constant is an UndefValue.
1088 if (ConstantInt *CI1 = dyn_cast<ConstantInt>(C1)) {
1089 if (ConstantInt *CI2 = dyn_cast<ConstantInt>(C2)) {
1090 const APInt &C1V = CI1->getValue();
1091 const APInt &C2V = CI2->getValue();
1095 case Instruction::Add:
1096 return ConstantInt::get(CI1->getContext(), C1V + C2V);
1097 case Instruction::Sub:
1098 return ConstantInt::get(CI1->getContext(), C1V - C2V);
1099 case Instruction::Mul:
1100 return ConstantInt::get(CI1->getContext(), C1V * C2V);
1101 case Instruction::UDiv:
1102 assert(!CI2->isNullValue() && "Div by zero handled above");
1103 return ConstantInt::get(CI1->getContext(), C1V.udiv(C2V));
1104 case Instruction::SDiv:
1105 assert(!CI2->isNullValue() && "Div by zero handled above");
1106 if (C2V.isAllOnesValue() && C1V.isMinSignedValue())
1107 return UndefValue::get(CI1->getType()); // MIN_INT / -1 -> undef
1108 return ConstantInt::get(CI1->getContext(), C1V.sdiv(C2V));
1109 case Instruction::URem:
1110 assert(!CI2->isNullValue() && "Div by zero handled above");
1111 return ConstantInt::get(CI1->getContext(), C1V.urem(C2V));
1112 case Instruction::SRem:
1113 assert(!CI2->isNullValue() && "Div by zero handled above");
1114 if (C2V.isAllOnesValue() && C1V.isMinSignedValue())
1115 return UndefValue::get(CI1->getType()); // MIN_INT % -1 -> undef
1116 return ConstantInt::get(CI1->getContext(), C1V.srem(C2V));
1117 case Instruction::And:
1118 return ConstantInt::get(CI1->getContext(), C1V & C2V);
1119 case Instruction::Or:
1120 return ConstantInt::get(CI1->getContext(), C1V | C2V);
1121 case Instruction::Xor:
1122 return ConstantInt::get(CI1->getContext(), C1V ^ C2V);
1123 case Instruction::Shl: {
1124 uint32_t shiftAmt = C2V.getZExtValue();
1125 if (shiftAmt < C1V.getBitWidth())
1126 return ConstantInt::get(CI1->getContext(), C1V.shl(shiftAmt));
1128 return UndefValue::get(C1->getType()); // too big shift is undef
1130 case Instruction::LShr: {
1131 uint32_t shiftAmt = C2V.getZExtValue();
1132 if (shiftAmt < C1V.getBitWidth())
1133 return ConstantInt::get(CI1->getContext(), C1V.lshr(shiftAmt));
1135 return UndefValue::get(C1->getType()); // too big shift is undef
1137 case Instruction::AShr: {
1138 uint32_t shiftAmt = C2V.getZExtValue();
1139 if (shiftAmt < C1V.getBitWidth())
1140 return ConstantInt::get(CI1->getContext(), C1V.ashr(shiftAmt));
1142 return UndefValue::get(C1->getType()); // too big shift is undef
1148 case Instruction::SDiv:
1149 case Instruction::UDiv:
1150 case Instruction::URem:
1151 case Instruction::SRem:
1152 case Instruction::LShr:
1153 case Instruction::AShr:
1154 case Instruction::Shl:
1155 if (CI1->equalsInt(0)) return C1;
1160 } else if (ConstantFP *CFP1 = dyn_cast<ConstantFP>(C1)) {
1161 if (ConstantFP *CFP2 = dyn_cast<ConstantFP>(C2)) {
1162 APFloat C1V = CFP1->getValueAPF();
1163 APFloat C2V = CFP2->getValueAPF();
1164 APFloat C3V = C1V; // copy for modification
1168 case Instruction::FAdd:
1169 (void)C3V.add(C2V, APFloat::rmNearestTiesToEven);
1170 return ConstantFP::get(C1->getContext(), C3V);
1171 case Instruction::FSub:
1172 (void)C3V.subtract(C2V, APFloat::rmNearestTiesToEven);
1173 return ConstantFP::get(C1->getContext(), C3V);
1174 case Instruction::FMul:
1175 (void)C3V.multiply(C2V, APFloat::rmNearestTiesToEven);
1176 return ConstantFP::get(C1->getContext(), C3V);
1177 case Instruction::FDiv:
1178 (void)C3V.divide(C2V, APFloat::rmNearestTiesToEven);
1179 return ConstantFP::get(C1->getContext(), C3V);
1180 case Instruction::FRem:
1181 (void)C3V.mod(C2V, APFloat::rmNearestTiesToEven);
1182 return ConstantFP::get(C1->getContext(), C3V);
1185 } else if (VectorType *VTy = dyn_cast<VectorType>(C1->getType())) {
1186 // Perform elementwise folding.
1187 SmallVector<Constant*, 16> Result;
1188 Type *Ty = IntegerType::get(VTy->getContext(), 32);
1189 for (unsigned i = 0, e = VTy->getNumElements(); i != e; ++i) {
1191 ConstantExpr::getExtractElement(C1, ConstantInt::get(Ty, i));
1193 ConstantExpr::getExtractElement(C2, ConstantInt::get(Ty, i));
1195 Result.push_back(ConstantExpr::get(Opcode, LHS, RHS));
1198 return ConstantVector::get(Result);
1201 if (ConstantExpr *CE1 = dyn_cast<ConstantExpr>(C1)) {
1202 // There are many possible foldings we could do here. We should probably
1203 // at least fold add of a pointer with an integer into the appropriate
1204 // getelementptr. This will improve alias analysis a bit.
1206 // Given ((a + b) + c), if (b + c) folds to something interesting, return
1208 if (Instruction::isAssociative(Opcode) && CE1->getOpcode() == Opcode) {
1209 Constant *T = ConstantExpr::get(Opcode, CE1->getOperand(1), C2);
1210 if (!isa<ConstantExpr>(T) || cast<ConstantExpr>(T)->getOpcode() != Opcode)
1211 return ConstantExpr::get(Opcode, CE1->getOperand(0), T);
1213 } else if (isa<ConstantExpr>(C2)) {
1214 // If C2 is a constant expr and C1 isn't, flop them around and fold the
1215 // other way if possible.
1216 if (Instruction::isCommutative(Opcode))
1217 return ConstantFoldBinaryInstruction(Opcode, C2, C1);
1220 // i1 can be simplified in many cases.
1221 if (C1->getType()->isIntegerTy(1)) {
1223 case Instruction::Add:
1224 case Instruction::Sub:
1225 return ConstantExpr::getXor(C1, C2);
1226 case Instruction::Mul:
1227 return ConstantExpr::getAnd(C1, C2);
1228 case Instruction::Shl:
1229 case Instruction::LShr:
1230 case Instruction::AShr:
1231 // We can assume that C2 == 0. If it were one the result would be
1232 // undefined because the shift value is as large as the bitwidth.
1234 case Instruction::SDiv:
1235 case Instruction::UDiv:
1236 // We can assume that C2 == 1. If it were zero the result would be
1237 // undefined through division by zero.
1239 case Instruction::URem:
1240 case Instruction::SRem:
1241 // We can assume that C2 == 1. If it were zero the result would be
1242 // undefined through division by zero.
1243 return ConstantInt::getFalse(C1->getContext());
1249 // We don't know how to fold this.
1253 /// isZeroSizedType - This type is zero sized if its an array or structure of
1254 /// zero sized types. The only leaf zero sized type is an empty structure.
1255 static bool isMaybeZeroSizedType(Type *Ty) {
1256 if (StructType *STy = dyn_cast<StructType>(Ty)) {
1257 if (STy->isOpaque()) return true; // Can't say.
1259 // If all of elements have zero size, this does too.
1260 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i)
1261 if (!isMaybeZeroSizedType(STy->getElementType(i))) return false;
1264 } else if (ArrayType *ATy = dyn_cast<ArrayType>(Ty)) {
1265 return isMaybeZeroSizedType(ATy->getElementType());
1270 /// IdxCompare - Compare the two constants as though they were getelementptr
1271 /// indices. This allows coersion of the types to be the same thing.
1273 /// If the two constants are the "same" (after coersion), return 0. If the
1274 /// first is less than the second, return -1, if the second is less than the
1275 /// first, return 1. If the constants are not integral, return -2.
1277 static int IdxCompare(Constant *C1, Constant *C2, Type *ElTy) {
1278 if (C1 == C2) return 0;
1280 // Ok, we found a different index. If they are not ConstantInt, we can't do
1281 // anything with them.
1282 if (!isa<ConstantInt>(C1) || !isa<ConstantInt>(C2))
1283 return -2; // don't know!
1285 // We cannot compare the indices if they don't fit in an int64_t.
1286 if (cast<ConstantInt>(C1)->getValue().getActiveBits() > 64 ||
1287 cast<ConstantInt>(C2)->getValue().getActiveBits() > 64)
1288 return -2; // don't know!
1290 // Ok, we have two differing integer indices. Sign extend them to be the same
1292 int64_t C1Val = cast<ConstantInt>(C1)->getSExtValue();
1293 int64_t C2Val = cast<ConstantInt>(C2)->getSExtValue();
1295 if (C1Val == C2Val) return 0; // They are equal
1297 // If the type being indexed over is really just a zero sized type, there is
1298 // no pointer difference being made here.
1299 if (isMaybeZeroSizedType(ElTy))
1300 return -2; // dunno.
1302 // If they are really different, now that they are the same type, then we
1303 // found a difference!
1310 /// evaluateFCmpRelation - This function determines if there is anything we can
1311 /// decide about the two constants provided. This doesn't need to handle simple
1312 /// things like ConstantFP comparisons, but should instead handle ConstantExprs.
1313 /// If we can determine that the two constants have a particular relation to
1314 /// each other, we should return the corresponding FCmpInst predicate,
1315 /// otherwise return FCmpInst::BAD_FCMP_PREDICATE. This is used below in
1316 /// ConstantFoldCompareInstruction.
1318 /// To simplify this code we canonicalize the relation so that the first
1319 /// operand is always the most "complex" of the two. We consider ConstantFP
1320 /// to be the simplest, and ConstantExprs to be the most complex.
1321 static FCmpInst::Predicate evaluateFCmpRelation(Constant *V1, Constant *V2) {
1322 assert(V1->getType() == V2->getType() &&
1323 "Cannot compare values of different types!");
1325 // Handle degenerate case quickly
1326 if (V1 == V2) return FCmpInst::FCMP_OEQ;
1328 if (!isa<ConstantExpr>(V1)) {
1329 if (!isa<ConstantExpr>(V2)) {
1330 // We distilled thisUse the standard constant folder for a few cases
1331 ConstantInt *R = nullptr;
1332 R = dyn_cast<ConstantInt>(
1333 ConstantExpr::getFCmp(FCmpInst::FCMP_OEQ, V1, V2));
1334 if (R && !R->isZero())
1335 return FCmpInst::FCMP_OEQ;
1336 R = dyn_cast<ConstantInt>(
1337 ConstantExpr::getFCmp(FCmpInst::FCMP_OLT, V1, V2));
1338 if (R && !R->isZero())
1339 return FCmpInst::FCMP_OLT;
1340 R = dyn_cast<ConstantInt>(
1341 ConstantExpr::getFCmp(FCmpInst::FCMP_OGT, V1, V2));
1342 if (R && !R->isZero())
1343 return FCmpInst::FCMP_OGT;
1345 // Nothing more we can do
1346 return FCmpInst::BAD_FCMP_PREDICATE;
1349 // If the first operand is simple and second is ConstantExpr, swap operands.
1350 FCmpInst::Predicate SwappedRelation = evaluateFCmpRelation(V2, V1);
1351 if (SwappedRelation != FCmpInst::BAD_FCMP_PREDICATE)
1352 return FCmpInst::getSwappedPredicate(SwappedRelation);
1354 // Ok, the LHS is known to be a constantexpr. The RHS can be any of a
1355 // constantexpr or a simple constant.
1356 ConstantExpr *CE1 = cast<ConstantExpr>(V1);
1357 switch (CE1->getOpcode()) {
1358 case Instruction::FPTrunc:
1359 case Instruction::FPExt:
1360 case Instruction::UIToFP:
1361 case Instruction::SIToFP:
1362 // We might be able to do something with these but we don't right now.
1368 // There are MANY other foldings that we could perform here. They will
1369 // probably be added on demand, as they seem needed.
1370 return FCmpInst::BAD_FCMP_PREDICATE;
1373 static ICmpInst::Predicate areGlobalsPotentiallyEqual(const GlobalValue *GV1,
1374 const GlobalValue *GV2) {
1375 auto isGlobalUnsafeForEquality = [](const GlobalValue *GV) {
1376 if (GV->hasExternalWeakLinkage() || GV->hasWeakAnyLinkage())
1378 if (const auto *GVar = dyn_cast<GlobalVariable>(GV)) {
1379 Type *Ty = GVar->getType()->getPointerElementType();
1380 // A global with opaque type might end up being zero sized.
1383 // A global with an empty type might lie at the address of any other
1385 if (Ty->isEmptyTy())
1390 // Don't try to decide equality of aliases.
1391 if (!isa<GlobalAlias>(GV1) && !isa<GlobalAlias>(GV2))
1392 if (!isGlobalUnsafeForEquality(GV1) && !isGlobalUnsafeForEquality(GV2))
1393 return ICmpInst::ICMP_NE;
1394 return ICmpInst::BAD_ICMP_PREDICATE;
1397 /// evaluateICmpRelation - This function determines if there is anything we can
1398 /// decide about the two constants provided. This doesn't need to handle simple
1399 /// things like integer comparisons, but should instead handle ConstantExprs
1400 /// and GlobalValues. If we can determine that the two constants have a
1401 /// particular relation to each other, we should return the corresponding ICmp
1402 /// predicate, otherwise return ICmpInst::BAD_ICMP_PREDICATE.
1404 /// To simplify this code we canonicalize the relation so that the first
1405 /// operand is always the most "complex" of the two. We consider simple
1406 /// constants (like ConstantInt) to be the simplest, followed by
1407 /// GlobalValues, followed by ConstantExpr's (the most complex).
1409 static ICmpInst::Predicate evaluateICmpRelation(Constant *V1, Constant *V2,
1411 assert(V1->getType() == V2->getType() &&
1412 "Cannot compare different types of values!");
1413 if (V1 == V2) return ICmpInst::ICMP_EQ;
1415 if (!isa<ConstantExpr>(V1) && !isa<GlobalValue>(V1) &&
1416 !isa<BlockAddress>(V1)) {
1417 if (!isa<GlobalValue>(V2) && !isa<ConstantExpr>(V2) &&
1418 !isa<BlockAddress>(V2)) {
1419 // We distilled this down to a simple case, use the standard constant
1421 ConstantInt *R = nullptr;
1422 ICmpInst::Predicate pred = ICmpInst::ICMP_EQ;
1423 R = dyn_cast<ConstantInt>(ConstantExpr::getICmp(pred, V1, V2));
1424 if (R && !R->isZero())
1426 pred = isSigned ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT;
1427 R = dyn_cast<ConstantInt>(ConstantExpr::getICmp(pred, V1, V2));
1428 if (R && !R->isZero())
1430 pred = isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT;
1431 R = dyn_cast<ConstantInt>(ConstantExpr::getICmp(pred, V1, V2));
1432 if (R && !R->isZero())
1435 // If we couldn't figure it out, bail.
1436 return ICmpInst::BAD_ICMP_PREDICATE;
1439 // If the first operand is simple, swap operands.
1440 ICmpInst::Predicate SwappedRelation =
1441 evaluateICmpRelation(V2, V1, isSigned);
1442 if (SwappedRelation != ICmpInst::BAD_ICMP_PREDICATE)
1443 return ICmpInst::getSwappedPredicate(SwappedRelation);
1445 } else if (const GlobalValue *GV = dyn_cast<GlobalValue>(V1)) {
1446 if (isa<ConstantExpr>(V2)) { // Swap as necessary.
1447 ICmpInst::Predicate SwappedRelation =
1448 evaluateICmpRelation(V2, V1, isSigned);
1449 if (SwappedRelation != ICmpInst::BAD_ICMP_PREDICATE)
1450 return ICmpInst::getSwappedPredicate(SwappedRelation);
1451 return ICmpInst::BAD_ICMP_PREDICATE;
1454 // Now we know that the RHS is a GlobalValue, BlockAddress or simple
1455 // constant (which, since the types must match, means that it's a
1456 // ConstantPointerNull).
1457 if (const GlobalValue *GV2 = dyn_cast<GlobalValue>(V2)) {
1458 return areGlobalsPotentiallyEqual(GV, GV2);
1459 } else if (isa<BlockAddress>(V2)) {
1460 return ICmpInst::ICMP_NE; // Globals never equal labels.
1462 assert(isa<ConstantPointerNull>(V2) && "Canonicalization guarantee!");
1463 // GlobalVals can never be null unless they have external weak linkage.
1464 // We don't try to evaluate aliases here.
1465 if (!GV->hasExternalWeakLinkage() && !isa<GlobalAlias>(GV))
1466 return ICmpInst::ICMP_NE;
1468 } else if (const BlockAddress *BA = dyn_cast<BlockAddress>(V1)) {
1469 if (isa<ConstantExpr>(V2)) { // Swap as necessary.
1470 ICmpInst::Predicate SwappedRelation =
1471 evaluateICmpRelation(V2, V1, isSigned);
1472 if (SwappedRelation != ICmpInst::BAD_ICMP_PREDICATE)
1473 return ICmpInst::getSwappedPredicate(SwappedRelation);
1474 return ICmpInst::BAD_ICMP_PREDICATE;
1477 // Now we know that the RHS is a GlobalValue, BlockAddress or simple
1478 // constant (which, since the types must match, means that it is a
1479 // ConstantPointerNull).
1480 if (const BlockAddress *BA2 = dyn_cast<BlockAddress>(V2)) {
1481 // Block address in another function can't equal this one, but block
1482 // addresses in the current function might be the same if blocks are
1484 if (BA2->getFunction() != BA->getFunction())
1485 return ICmpInst::ICMP_NE;
1487 // Block addresses aren't null, don't equal the address of globals.
1488 assert((isa<ConstantPointerNull>(V2) || isa<GlobalValue>(V2)) &&
1489 "Canonicalization guarantee!");
1490 return ICmpInst::ICMP_NE;
1493 // Ok, the LHS is known to be a constantexpr. The RHS can be any of a
1494 // constantexpr, a global, block address, or a simple constant.
1495 ConstantExpr *CE1 = cast<ConstantExpr>(V1);
1496 Constant *CE1Op0 = CE1->getOperand(0);
1498 switch (CE1->getOpcode()) {
1499 case Instruction::Trunc:
1500 case Instruction::FPTrunc:
1501 case Instruction::FPExt:
1502 case Instruction::FPToUI:
1503 case Instruction::FPToSI:
1504 break; // We can't evaluate floating point casts or truncations.
1506 case Instruction::UIToFP:
1507 case Instruction::SIToFP:
1508 case Instruction::BitCast:
1509 case Instruction::ZExt:
1510 case Instruction::SExt:
1511 // If the cast is not actually changing bits, and the second operand is a
1512 // null pointer, do the comparison with the pre-casted value.
1513 if (V2->isNullValue() &&
1514 (CE1->getType()->isPointerTy() || CE1->getType()->isIntegerTy())) {
1515 if (CE1->getOpcode() == Instruction::ZExt) isSigned = false;
1516 if (CE1->getOpcode() == Instruction::SExt) isSigned = true;
1517 return evaluateICmpRelation(CE1Op0,
1518 Constant::getNullValue(CE1Op0->getType()),
1523 case Instruction::GetElementPtr: {
1524 GEPOperator *CE1GEP = cast<GEPOperator>(CE1);
1525 // Ok, since this is a getelementptr, we know that the constant has a
1526 // pointer type. Check the various cases.
1527 if (isa<ConstantPointerNull>(V2)) {
1528 // If we are comparing a GEP to a null pointer, check to see if the base
1529 // of the GEP equals the null pointer.
1530 if (const GlobalValue *GV = dyn_cast<GlobalValue>(CE1Op0)) {
1531 if (GV->hasExternalWeakLinkage())
1532 // Weak linkage GVals could be zero or not. We're comparing that
1533 // to null pointer so its greater-or-equal
1534 return isSigned ? ICmpInst::ICMP_SGE : ICmpInst::ICMP_UGE;
1536 // If its not weak linkage, the GVal must have a non-zero address
1537 // so the result is greater-than
1538 return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT;
1539 } else if (isa<ConstantPointerNull>(CE1Op0)) {
1540 // If we are indexing from a null pointer, check to see if we have any
1541 // non-zero indices.
1542 for (unsigned i = 1, e = CE1->getNumOperands(); i != e; ++i)
1543 if (!CE1->getOperand(i)->isNullValue())
1544 // Offsetting from null, must not be equal.
1545 return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT;
1546 // Only zero indexes from null, must still be zero.
1547 return ICmpInst::ICMP_EQ;
1549 // Otherwise, we can't really say if the first operand is null or not.
1550 } else if (const GlobalValue *GV2 = dyn_cast<GlobalValue>(V2)) {
1551 if (isa<ConstantPointerNull>(CE1Op0)) {
1552 if (GV2->hasExternalWeakLinkage())
1553 // Weak linkage GVals could be zero or not. We're comparing it to
1554 // a null pointer, so its less-or-equal
1555 return isSigned ? ICmpInst::ICMP_SLE : ICmpInst::ICMP_ULE;
1557 // If its not weak linkage, the GVal must have a non-zero address
1558 // so the result is less-than
1559 return isSigned ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT;
1560 } else if (const GlobalValue *GV = dyn_cast<GlobalValue>(CE1Op0)) {
1562 // If this is a getelementptr of the same global, then it must be
1563 // different. Because the types must match, the getelementptr could
1564 // only have at most one index, and because we fold getelementptr's
1565 // with a single zero index, it must be nonzero.
1566 assert(CE1->getNumOperands() == 2 &&
1567 !CE1->getOperand(1)->isNullValue() &&
1568 "Surprising getelementptr!");
1569 return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT;
1571 if (CE1GEP->hasAllZeroIndices())
1572 return areGlobalsPotentiallyEqual(GV, GV2);
1573 return ICmpInst::BAD_ICMP_PREDICATE;
1577 ConstantExpr *CE2 = cast<ConstantExpr>(V2);
1578 Constant *CE2Op0 = CE2->getOperand(0);
1580 // There are MANY other foldings that we could perform here. They will
1581 // probably be added on demand, as they seem needed.
1582 switch (CE2->getOpcode()) {
1584 case Instruction::GetElementPtr:
1585 // By far the most common case to handle is when the base pointers are
1586 // obviously to the same global.
1587 if (isa<GlobalValue>(CE1Op0) && isa<GlobalValue>(CE2Op0)) {
1588 // Don't know relative ordering, but check for inequality.
1589 if (CE1Op0 != CE2Op0) {
1590 GEPOperator *CE2GEP = cast<GEPOperator>(CE2);
1591 if (CE1GEP->hasAllZeroIndices() && CE2GEP->hasAllZeroIndices())
1592 return areGlobalsPotentiallyEqual(cast<GlobalValue>(CE1Op0),
1593 cast<GlobalValue>(CE2Op0));
1594 return ICmpInst::BAD_ICMP_PREDICATE;
1596 // Ok, we know that both getelementptr instructions are based on the
1597 // same global. From this, we can precisely determine the relative
1598 // ordering of the resultant pointers.
1601 // The logic below assumes that the result of the comparison
1602 // can be determined by finding the first index that differs.
1603 // This doesn't work if there is over-indexing in any
1604 // subsequent indices, so check for that case first.
1605 if (!CE1->isGEPWithNoNotionalOverIndexing() ||
1606 !CE2->isGEPWithNoNotionalOverIndexing())
1607 return ICmpInst::BAD_ICMP_PREDICATE; // Might be equal.
1609 // Compare all of the operands the GEP's have in common.
1610 gep_type_iterator GTI = gep_type_begin(CE1);
1611 for (;i != CE1->getNumOperands() && i != CE2->getNumOperands();
1613 switch (IdxCompare(CE1->getOperand(i),
1614 CE2->getOperand(i), GTI.getIndexedType())) {
1615 case -1: return isSigned ? ICmpInst::ICMP_SLT:ICmpInst::ICMP_ULT;
1616 case 1: return isSigned ? ICmpInst::ICMP_SGT:ICmpInst::ICMP_UGT;
1617 case -2: return ICmpInst::BAD_ICMP_PREDICATE;
1620 // Ok, we ran out of things they have in common. If any leftovers
1621 // are non-zero then we have a difference, otherwise we are equal.
1622 for (; i < CE1->getNumOperands(); ++i)
1623 if (!CE1->getOperand(i)->isNullValue()) {
1624 if (isa<ConstantInt>(CE1->getOperand(i)))
1625 return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT;
1627 return ICmpInst::BAD_ICMP_PREDICATE; // Might be equal.
1630 for (; i < CE2->getNumOperands(); ++i)
1631 if (!CE2->getOperand(i)->isNullValue()) {
1632 if (isa<ConstantInt>(CE2->getOperand(i)))
1633 return isSigned ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT;
1635 return ICmpInst::BAD_ICMP_PREDICATE; // Might be equal.
1637 return ICmpInst::ICMP_EQ;
1647 return ICmpInst::BAD_ICMP_PREDICATE;
1650 Constant *llvm::ConstantFoldCompareInstruction(unsigned short pred,
1651 Constant *C1, Constant *C2) {
1653 if (VectorType *VT = dyn_cast<VectorType>(C1->getType()))
1654 ResultTy = VectorType::get(Type::getInt1Ty(C1->getContext()),
1655 VT->getNumElements());
1657 ResultTy = Type::getInt1Ty(C1->getContext());
1659 // Fold FCMP_FALSE/FCMP_TRUE unconditionally.
1660 if (pred == FCmpInst::FCMP_FALSE)
1661 return Constant::getNullValue(ResultTy);
1663 if (pred == FCmpInst::FCMP_TRUE)
1664 return Constant::getAllOnesValue(ResultTy);
1666 // Handle some degenerate cases first
1667 if (isa<UndefValue>(C1) || isa<UndefValue>(C2)) {
1668 // For EQ and NE, we can always pick a value for the undef to make the
1669 // predicate pass or fail, so we can return undef.
1670 // Also, if both operands are undef, we can return undef.
1671 if (ICmpInst::isEquality(ICmpInst::Predicate(pred)) ||
1672 (isa<UndefValue>(C1) && isa<UndefValue>(C2)))
1673 return UndefValue::get(ResultTy);
1674 // Otherwise, pick the same value as the non-undef operand, and fold
1675 // it to true or false.
1676 return ConstantInt::get(ResultTy, CmpInst::isTrueWhenEqual(pred));
1679 // icmp eq/ne(null,GV) -> false/true
1680 if (C1->isNullValue()) {
1681 if (const GlobalValue *GV = dyn_cast<GlobalValue>(C2))
1682 // Don't try to evaluate aliases. External weak GV can be null.
1683 if (!isa<GlobalAlias>(GV) && !GV->hasExternalWeakLinkage()) {
1684 if (pred == ICmpInst::ICMP_EQ)
1685 return ConstantInt::getFalse(C1->getContext());
1686 else if (pred == ICmpInst::ICMP_NE)
1687 return ConstantInt::getTrue(C1->getContext());
1689 // icmp eq/ne(GV,null) -> false/true
1690 } else if (C2->isNullValue()) {
1691 if (const GlobalValue *GV = dyn_cast<GlobalValue>(C1))
1692 // Don't try to evaluate aliases. External weak GV can be null.
1693 if (!isa<GlobalAlias>(GV) && !GV->hasExternalWeakLinkage()) {
1694 if (pred == ICmpInst::ICMP_EQ)
1695 return ConstantInt::getFalse(C1->getContext());
1696 else if (pred == ICmpInst::ICMP_NE)
1697 return ConstantInt::getTrue(C1->getContext());
1701 // If the comparison is a comparison between two i1's, simplify it.
1702 if (C1->getType()->isIntegerTy(1)) {
1704 case ICmpInst::ICMP_EQ:
1705 if (isa<ConstantInt>(C2))
1706 return ConstantExpr::getXor(C1, ConstantExpr::getNot(C2));
1707 return ConstantExpr::getXor(ConstantExpr::getNot(C1), C2);
1708 case ICmpInst::ICMP_NE:
1709 return ConstantExpr::getXor(C1, C2);
1715 if (isa<ConstantInt>(C1) && isa<ConstantInt>(C2)) {
1716 APInt V1 = cast<ConstantInt>(C1)->getValue();
1717 APInt V2 = cast<ConstantInt>(C2)->getValue();
1719 default: llvm_unreachable("Invalid ICmp Predicate");
1720 case ICmpInst::ICMP_EQ: return ConstantInt::get(ResultTy, V1 == V2);
1721 case ICmpInst::ICMP_NE: return ConstantInt::get(ResultTy, V1 != V2);
1722 case ICmpInst::ICMP_SLT: return ConstantInt::get(ResultTy, V1.slt(V2));
1723 case ICmpInst::ICMP_SGT: return ConstantInt::get(ResultTy, V1.sgt(V2));
1724 case ICmpInst::ICMP_SLE: return ConstantInt::get(ResultTy, V1.sle(V2));
1725 case ICmpInst::ICMP_SGE: return ConstantInt::get(ResultTy, V1.sge(V2));
1726 case ICmpInst::ICMP_ULT: return ConstantInt::get(ResultTy, V1.ult(V2));
1727 case ICmpInst::ICMP_UGT: return ConstantInt::get(ResultTy, V1.ugt(V2));
1728 case ICmpInst::ICMP_ULE: return ConstantInt::get(ResultTy, V1.ule(V2));
1729 case ICmpInst::ICMP_UGE: return ConstantInt::get(ResultTy, V1.uge(V2));
1731 } else if (isa<ConstantFP>(C1) && isa<ConstantFP>(C2)) {
1732 APFloat C1V = cast<ConstantFP>(C1)->getValueAPF();
1733 APFloat C2V = cast<ConstantFP>(C2)->getValueAPF();
1734 APFloat::cmpResult R = C1V.compare(C2V);
1736 default: llvm_unreachable("Invalid FCmp Predicate");
1737 case FCmpInst::FCMP_FALSE: return Constant::getNullValue(ResultTy);
1738 case FCmpInst::FCMP_TRUE: return Constant::getAllOnesValue(ResultTy);
1739 case FCmpInst::FCMP_UNO:
1740 return ConstantInt::get(ResultTy, R==APFloat::cmpUnordered);
1741 case FCmpInst::FCMP_ORD:
1742 return ConstantInt::get(ResultTy, R!=APFloat::cmpUnordered);
1743 case FCmpInst::FCMP_UEQ:
1744 return ConstantInt::get(ResultTy, R==APFloat::cmpUnordered ||
1745 R==APFloat::cmpEqual);
1746 case FCmpInst::FCMP_OEQ:
1747 return ConstantInt::get(ResultTy, R==APFloat::cmpEqual);
1748 case FCmpInst::FCMP_UNE:
1749 return ConstantInt::get(ResultTy, R!=APFloat::cmpEqual);
1750 case FCmpInst::FCMP_ONE:
1751 return ConstantInt::get(ResultTy, R==APFloat::cmpLessThan ||
1752 R==APFloat::cmpGreaterThan);
1753 case FCmpInst::FCMP_ULT:
1754 return ConstantInt::get(ResultTy, R==APFloat::cmpUnordered ||
1755 R==APFloat::cmpLessThan);
1756 case FCmpInst::FCMP_OLT:
1757 return ConstantInt::get(ResultTy, R==APFloat::cmpLessThan);
1758 case FCmpInst::FCMP_UGT:
1759 return ConstantInt::get(ResultTy, R==APFloat::cmpUnordered ||
1760 R==APFloat::cmpGreaterThan);
1761 case FCmpInst::FCMP_OGT:
1762 return ConstantInt::get(ResultTy, R==APFloat::cmpGreaterThan);
1763 case FCmpInst::FCMP_ULE:
1764 return ConstantInt::get(ResultTy, R!=APFloat::cmpGreaterThan);
1765 case FCmpInst::FCMP_OLE:
1766 return ConstantInt::get(ResultTy, R==APFloat::cmpLessThan ||
1767 R==APFloat::cmpEqual);
1768 case FCmpInst::FCMP_UGE:
1769 return ConstantInt::get(ResultTy, R!=APFloat::cmpLessThan);
1770 case FCmpInst::FCMP_OGE:
1771 return ConstantInt::get(ResultTy, R==APFloat::cmpGreaterThan ||
1772 R==APFloat::cmpEqual);
1774 } else if (C1->getType()->isVectorTy()) {
1775 // If we can constant fold the comparison of each element, constant fold
1776 // the whole vector comparison.
1777 SmallVector<Constant*, 4> ResElts;
1778 Type *Ty = IntegerType::get(C1->getContext(), 32);
1779 // Compare the elements, producing an i1 result or constant expr.
1780 for (unsigned i = 0, e = C1->getType()->getVectorNumElements(); i != e;++i){
1782 ConstantExpr::getExtractElement(C1, ConstantInt::get(Ty, i));
1784 ConstantExpr::getExtractElement(C2, ConstantInt::get(Ty, i));
1786 ResElts.push_back(ConstantExpr::getCompare(pred, C1E, C2E));
1789 return ConstantVector::get(ResElts);
1792 if (C1->getType()->isFloatingPointTy()) {
1793 int Result = -1; // -1 = unknown, 0 = known false, 1 = known true.
1794 switch (evaluateFCmpRelation(C1, C2)) {
1795 default: llvm_unreachable("Unknown relation!");
1796 case FCmpInst::FCMP_UNO:
1797 case FCmpInst::FCMP_ORD:
1798 case FCmpInst::FCMP_UEQ:
1799 case FCmpInst::FCMP_UNE:
1800 case FCmpInst::FCMP_ULT:
1801 case FCmpInst::FCMP_UGT:
1802 case FCmpInst::FCMP_ULE:
1803 case FCmpInst::FCMP_UGE:
1804 case FCmpInst::FCMP_TRUE:
1805 case FCmpInst::FCMP_FALSE:
1806 case FCmpInst::BAD_FCMP_PREDICATE:
1807 break; // Couldn't determine anything about these constants.
1808 case FCmpInst::FCMP_OEQ: // We know that C1 == C2
1809 Result = (pred == FCmpInst::FCMP_UEQ || pred == FCmpInst::FCMP_OEQ ||
1810 pred == FCmpInst::FCMP_ULE || pred == FCmpInst::FCMP_OLE ||
1811 pred == FCmpInst::FCMP_UGE || pred == FCmpInst::FCMP_OGE);
1813 case FCmpInst::FCMP_OLT: // We know that C1 < C2
1814 Result = (pred == FCmpInst::FCMP_UNE || pred == FCmpInst::FCMP_ONE ||
1815 pred == FCmpInst::FCMP_ULT || pred == FCmpInst::FCMP_OLT ||
1816 pred == FCmpInst::FCMP_ULE || pred == FCmpInst::FCMP_OLE);
1818 case FCmpInst::FCMP_OGT: // We know that C1 > C2
1819 Result = (pred == FCmpInst::FCMP_UNE || pred == FCmpInst::FCMP_ONE ||
1820 pred == FCmpInst::FCMP_UGT || pred == FCmpInst::FCMP_OGT ||
1821 pred == FCmpInst::FCMP_UGE || pred == FCmpInst::FCMP_OGE);
1823 case FCmpInst::FCMP_OLE: // We know that C1 <= C2
1824 // We can only partially decide this relation.
1825 if (pred == FCmpInst::FCMP_UGT || pred == FCmpInst::FCMP_OGT)
1827 else if (pred == FCmpInst::FCMP_ULT || pred == FCmpInst::FCMP_OLT)
1830 case FCmpInst::FCMP_OGE: // We known that C1 >= C2
1831 // We can only partially decide this relation.
1832 if (pred == FCmpInst::FCMP_ULT || pred == FCmpInst::FCMP_OLT)
1834 else if (pred == FCmpInst::FCMP_UGT || pred == FCmpInst::FCMP_OGT)
1837 case FCmpInst::FCMP_ONE: // We know that C1 != C2
1838 // We can only partially decide this relation.
1839 if (pred == FCmpInst::FCMP_OEQ || pred == FCmpInst::FCMP_UEQ)
1841 else if (pred == FCmpInst::FCMP_ONE || pred == FCmpInst::FCMP_UNE)
1846 // If we evaluated the result, return it now.
1848 return ConstantInt::get(ResultTy, Result);
1851 // Evaluate the relation between the two constants, per the predicate.
1852 int Result = -1; // -1 = unknown, 0 = known false, 1 = known true.
1853 switch (evaluateICmpRelation(C1, C2, CmpInst::isSigned(pred))) {
1854 default: llvm_unreachable("Unknown relational!");
1855 case ICmpInst::BAD_ICMP_PREDICATE:
1856 break; // Couldn't determine anything about these constants.
1857 case ICmpInst::ICMP_EQ: // We know the constants are equal!
1858 // If we know the constants are equal, we can decide the result of this
1859 // computation precisely.
1860 Result = ICmpInst::isTrueWhenEqual((ICmpInst::Predicate)pred);
1862 case ICmpInst::ICMP_ULT:
1864 case ICmpInst::ICMP_ULT: case ICmpInst::ICMP_NE: case ICmpInst::ICMP_ULE:
1866 case ICmpInst::ICMP_UGT: case ICmpInst::ICMP_EQ: case ICmpInst::ICMP_UGE:
1870 case ICmpInst::ICMP_SLT:
1872 case ICmpInst::ICMP_SLT: case ICmpInst::ICMP_NE: case ICmpInst::ICMP_SLE:
1874 case ICmpInst::ICMP_SGT: case ICmpInst::ICMP_EQ: case ICmpInst::ICMP_SGE:
1878 case ICmpInst::ICMP_UGT:
1880 case ICmpInst::ICMP_UGT: case ICmpInst::ICMP_NE: case ICmpInst::ICMP_UGE:
1882 case ICmpInst::ICMP_ULT: case ICmpInst::ICMP_EQ: case ICmpInst::ICMP_ULE:
1886 case ICmpInst::ICMP_SGT:
1888 case ICmpInst::ICMP_SGT: case ICmpInst::ICMP_NE: case ICmpInst::ICMP_SGE:
1890 case ICmpInst::ICMP_SLT: case ICmpInst::ICMP_EQ: case ICmpInst::ICMP_SLE:
1894 case ICmpInst::ICMP_ULE:
1895 if (pred == ICmpInst::ICMP_UGT) Result = 0;
1896 if (pred == ICmpInst::ICMP_ULT || pred == ICmpInst::ICMP_ULE) Result = 1;
1898 case ICmpInst::ICMP_SLE:
1899 if (pred == ICmpInst::ICMP_SGT) Result = 0;
1900 if (pred == ICmpInst::ICMP_SLT || pred == ICmpInst::ICMP_SLE) Result = 1;
1902 case ICmpInst::ICMP_UGE:
1903 if (pred == ICmpInst::ICMP_ULT) Result = 0;
1904 if (pred == ICmpInst::ICMP_UGT || pred == ICmpInst::ICMP_UGE) Result = 1;
1906 case ICmpInst::ICMP_SGE:
1907 if (pred == ICmpInst::ICMP_SLT) Result = 0;
1908 if (pred == ICmpInst::ICMP_SGT || pred == ICmpInst::ICMP_SGE) Result = 1;
1910 case ICmpInst::ICMP_NE:
1911 if (pred == ICmpInst::ICMP_EQ) Result = 0;
1912 if (pred == ICmpInst::ICMP_NE) Result = 1;
1916 // If we evaluated the result, return it now.
1918 return ConstantInt::get(ResultTy, Result);
1920 // If the right hand side is a bitcast, try using its inverse to simplify
1921 // it by moving it to the left hand side. We can't do this if it would turn
1922 // a vector compare into a scalar compare or visa versa.
1923 if (ConstantExpr *CE2 = dyn_cast<ConstantExpr>(C2)) {
1924 Constant *CE2Op0 = CE2->getOperand(0);
1925 if (CE2->getOpcode() == Instruction::BitCast &&
1926 CE2->getType()->isVectorTy() == CE2Op0->getType()->isVectorTy()) {
1927 Constant *Inverse = ConstantExpr::getBitCast(C1, CE2Op0->getType());
1928 return ConstantExpr::getICmp(pred, Inverse, CE2Op0);
1932 // If the left hand side is an extension, try eliminating it.
1933 if (ConstantExpr *CE1 = dyn_cast<ConstantExpr>(C1)) {
1934 if ((CE1->getOpcode() == Instruction::SExt && ICmpInst::isSigned(pred)) ||
1935 (CE1->getOpcode() == Instruction::ZExt && !ICmpInst::isSigned(pred))){
1936 Constant *CE1Op0 = CE1->getOperand(0);
1937 Constant *CE1Inverse = ConstantExpr::getTrunc(CE1, CE1Op0->getType());
1938 if (CE1Inverse == CE1Op0) {
1939 // Check whether we can safely truncate the right hand side.
1940 Constant *C2Inverse = ConstantExpr::getTrunc(C2, CE1Op0->getType());
1941 if (ConstantExpr::getCast(CE1->getOpcode(), C2Inverse,
1942 C2->getType()) == C2)
1943 return ConstantExpr::getICmp(pred, CE1Inverse, C2Inverse);
1948 if ((!isa<ConstantExpr>(C1) && isa<ConstantExpr>(C2)) ||
1949 (C1->isNullValue() && !C2->isNullValue())) {
1950 // If C2 is a constant expr and C1 isn't, flip them around and fold the
1951 // other way if possible.
1952 // Also, if C1 is null and C2 isn't, flip them around.
1953 pred = ICmpInst::getSwappedPredicate((ICmpInst::Predicate)pred);
1954 return ConstantExpr::getICmp(pred, C2, C1);
1960 /// isInBoundsIndices - Test whether the given sequence of *normalized* indices
1962 template<typename IndexTy>
1963 static bool isInBoundsIndices(ArrayRef<IndexTy> Idxs) {
1964 // No indices means nothing that could be out of bounds.
1965 if (Idxs.empty()) return true;
1967 // If the first index is zero, it's in bounds.
1968 if (cast<Constant>(Idxs[0])->isNullValue()) return true;
1970 // If the first index is one and all the rest are zero, it's in bounds,
1971 // by the one-past-the-end rule.
1972 if (!cast<ConstantInt>(Idxs[0])->isOne())
1974 for (unsigned i = 1, e = Idxs.size(); i != e; ++i)
1975 if (!cast<Constant>(Idxs[i])->isNullValue())
1980 /// \brief Test whether a given ConstantInt is in-range for a SequentialType.
1981 static bool isIndexInRangeOfSequentialType(const SequentialType *STy,
1982 const ConstantInt *CI) {
1983 if (const PointerType *PTy = dyn_cast<PointerType>(STy))
1984 // Only handle pointers to sized types, not pointers to functions.
1985 return PTy->getElementType()->isSized();
1987 uint64_t NumElements = 0;
1988 // Determine the number of elements in our sequential type.
1989 if (const ArrayType *ATy = dyn_cast<ArrayType>(STy))
1990 NumElements = ATy->getNumElements();
1991 else if (const VectorType *VTy = dyn_cast<VectorType>(STy))
1992 NumElements = VTy->getNumElements();
1994 assert((isa<ArrayType>(STy) || NumElements > 0) &&
1995 "didn't expect non-array type to have zero elements!");
1997 // We cannot bounds check the index if it doesn't fit in an int64_t.
1998 if (CI->getValue().getActiveBits() > 64)
2001 // A negative index or an index past the end of our sequential type is
2002 // considered out-of-range.
2003 int64_t IndexVal = CI->getSExtValue();
2004 if (IndexVal < 0 || (NumElements > 0 && (uint64_t)IndexVal >= NumElements))
2007 // Otherwise, it is in-range.
2011 template<typename IndexTy>
2012 static Constant *ConstantFoldGetElementPtrImpl(Constant *C,
2014 ArrayRef<IndexTy> Idxs) {
2015 if (Idxs.empty()) return C;
2016 Constant *Idx0 = cast<Constant>(Idxs[0]);
2017 if ((Idxs.size() == 1 && Idx0->isNullValue()))
2020 if (isa<UndefValue>(C)) {
2021 PointerType *Ptr = cast<PointerType>(C->getType());
2022 Type *Ty = GetElementPtrInst::getIndexedType(Ptr, Idxs);
2023 assert(Ty && "Invalid indices for GEP!");
2024 return UndefValue::get(PointerType::get(Ty, Ptr->getAddressSpace()));
2027 if (C->isNullValue()) {
2029 for (unsigned i = 0, e = Idxs.size(); i != e; ++i)
2030 if (!cast<Constant>(Idxs[i])->isNullValue()) {
2035 PointerType *Ptr = cast<PointerType>(C->getType());
2036 Type *Ty = GetElementPtrInst::getIndexedType(Ptr, Idxs);
2037 assert(Ty && "Invalid indices for GEP!");
2038 return ConstantPointerNull::get(PointerType::get(Ty,
2039 Ptr->getAddressSpace()));
2043 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(C)) {
2044 // Combine Indices - If the source pointer to this getelementptr instruction
2045 // is a getelementptr instruction, combine the indices of the two
2046 // getelementptr instructions into a single instruction.
2048 if (CE->getOpcode() == Instruction::GetElementPtr) {
2049 Type *LastTy = nullptr;
2050 for (gep_type_iterator I = gep_type_begin(CE), E = gep_type_end(CE);
2054 // We cannot combine indices if doing so would take us outside of an
2055 // array or vector. Doing otherwise could trick us if we evaluated such a
2056 // GEP as part of a load.
2058 // e.g. Consider if the original GEP was:
2059 // i8* getelementptr ({ [2 x i8], i32, i8, [3 x i8] }* @main.c,
2060 // i32 0, i32 0, i64 0)
2062 // If we then tried to offset it by '8' to get to the third element,
2063 // an i8, we should *not* get:
2064 // i8* getelementptr ({ [2 x i8], i32, i8, [3 x i8] }* @main.c,
2065 // i32 0, i32 0, i64 8)
2067 // This GEP tries to index array element '8 which runs out-of-bounds.
2068 // Subsequent evaluation would get confused and produce erroneous results.
2070 // The following prohibits such a GEP from being formed by checking to see
2071 // if the index is in-range with respect to an array or vector.
2072 bool PerformFold = false;
2073 if (Idx0->isNullValue())
2075 else if (SequentialType *STy = dyn_cast_or_null<SequentialType>(LastTy))
2076 if (ConstantInt *CI = dyn_cast<ConstantInt>(Idx0))
2077 PerformFold = isIndexInRangeOfSequentialType(STy, CI);
2080 SmallVector<Value*, 16> NewIndices;
2081 NewIndices.reserve(Idxs.size() + CE->getNumOperands());
2082 NewIndices.append(CE->op_begin() + 1, CE->op_end() - 1);
2084 // Add the last index of the source with the first index of the new GEP.
2085 // Make sure to handle the case when they are actually different types.
2086 Constant *Combined = CE->getOperand(CE->getNumOperands()-1);
2087 // Otherwise it must be an array.
2088 if (!Idx0->isNullValue()) {
2089 Type *IdxTy = Combined->getType();
2090 if (IdxTy != Idx0->getType()) {
2091 unsigned CommonExtendedWidth =
2092 std::max(IdxTy->getIntegerBitWidth(),
2093 Idx0->getType()->getIntegerBitWidth());
2094 CommonExtendedWidth = std::max(CommonExtendedWidth, 64U);
2097 Type::getIntNTy(IdxTy->getContext(), CommonExtendedWidth);
2098 Constant *C1 = ConstantExpr::getSExtOrBitCast(Idx0, CommonTy);
2099 Constant *C2 = ConstantExpr::getSExtOrBitCast(Combined, CommonTy);
2100 Combined = ConstantExpr::get(Instruction::Add, C1, C2);
2103 ConstantExpr::get(Instruction::Add, Idx0, Combined);
2107 NewIndices.push_back(Combined);
2108 NewIndices.append(Idxs.begin() + 1, Idxs.end());
2110 ConstantExpr::getGetElementPtr(CE->getOperand(0), NewIndices,
2112 cast<GEPOperator>(CE)->isInBounds());
2116 // Attempt to fold casts to the same type away. For example, folding:
2118 // i32* getelementptr ([2 x i32]* bitcast ([3 x i32]* %X to [2 x i32]*),
2122 // i32* getelementptr ([3 x i32]* %X, i64 0, i64 0)
2124 // Don't fold if the cast is changing address spaces.
2125 if (CE->isCast() && Idxs.size() > 1 && Idx0->isNullValue()) {
2126 PointerType *SrcPtrTy =
2127 dyn_cast<PointerType>(CE->getOperand(0)->getType());
2128 PointerType *DstPtrTy = dyn_cast<PointerType>(CE->getType());
2129 if (SrcPtrTy && DstPtrTy) {
2130 ArrayType *SrcArrayTy =
2131 dyn_cast<ArrayType>(SrcPtrTy->getElementType());
2132 ArrayType *DstArrayTy =
2133 dyn_cast<ArrayType>(DstPtrTy->getElementType());
2134 if (SrcArrayTy && DstArrayTy
2135 && SrcArrayTy->getElementType() == DstArrayTy->getElementType()
2136 && SrcPtrTy->getAddressSpace() == DstPtrTy->getAddressSpace())
2137 return ConstantExpr::getGetElementPtr((Constant*)CE->getOperand(0),
2143 // Check to see if any array indices are not within the corresponding
2144 // notional array or vector bounds. If so, try to determine if they can be
2145 // factored out into preceding dimensions.
2146 bool Unknown = false;
2147 SmallVector<Constant *, 8> NewIdxs;
2148 Type *Ty = C->getType();
2149 Type *Prev = nullptr;
2150 for (unsigned i = 0, e = Idxs.size(); i != e;
2151 Prev = Ty, Ty = cast<CompositeType>(Ty)->getTypeAtIndex(Idxs[i]), ++i) {
2152 if (ConstantInt *CI = dyn_cast<ConstantInt>(Idxs[i])) {
2153 if (isa<ArrayType>(Ty) || isa<VectorType>(Ty))
2154 if (CI->getSExtValue() > 0 &&
2155 !isIndexInRangeOfSequentialType(cast<SequentialType>(Ty), CI)) {
2156 if (isa<SequentialType>(Prev)) {
2157 // It's out of range, but we can factor it into the prior
2159 NewIdxs.resize(Idxs.size());
2160 uint64_t NumElements = 0;
2161 if (const ArrayType *ATy = dyn_cast<ArrayType>(Ty))
2162 NumElements = ATy->getNumElements();
2164 NumElements = cast<VectorType>(Ty)->getNumElements();
2166 ConstantInt *Factor = ConstantInt::get(CI->getType(), NumElements);
2167 NewIdxs[i] = ConstantExpr::getSRem(CI, Factor);
2169 Constant *PrevIdx = cast<Constant>(Idxs[i-1]);
2170 Constant *Div = ConstantExpr::getSDiv(CI, Factor);
2172 unsigned CommonExtendedWidth =
2173 std::max(PrevIdx->getType()->getIntegerBitWidth(),
2174 Div->getType()->getIntegerBitWidth());
2175 CommonExtendedWidth = std::max(CommonExtendedWidth, 64U);
2177 // Before adding, extend both operands to i64 to avoid
2178 // overflow trouble.
2179 if (!PrevIdx->getType()->isIntegerTy(CommonExtendedWidth))
2180 PrevIdx = ConstantExpr::getSExt(
2182 Type::getIntNTy(Div->getContext(), CommonExtendedWidth));
2183 if (!Div->getType()->isIntegerTy(CommonExtendedWidth))
2184 Div = ConstantExpr::getSExt(
2185 Div, Type::getIntNTy(Div->getContext(), CommonExtendedWidth));
2187 NewIdxs[i-1] = ConstantExpr::getAdd(PrevIdx, Div);
2189 // It's out of range, but the prior dimension is a struct
2190 // so we can't do anything about it.
2195 // We don't know if it's in range or not.
2200 // If we did any factoring, start over with the adjusted indices.
2201 if (!NewIdxs.empty()) {
2202 for (unsigned i = 0, e = Idxs.size(); i != e; ++i)
2203 if (!NewIdxs[i]) NewIdxs[i] = cast<Constant>(Idxs[i]);
2204 return ConstantExpr::getGetElementPtr(C, NewIdxs, inBounds);
2207 // If all indices are known integers and normalized, we can do a simple
2208 // check for the "inbounds" property.
2209 if (!Unknown && !inBounds)
2210 if (auto *GV = dyn_cast<GlobalVariable>(C))
2211 if (!GV->hasExternalWeakLinkage() && isInBoundsIndices(Idxs))
2212 return ConstantExpr::getInBoundsGetElementPtr(C, Idxs);
2217 Constant *llvm::ConstantFoldGetElementPtr(Constant *C,
2219 ArrayRef<Constant *> Idxs) {
2220 return ConstantFoldGetElementPtrImpl(C, inBounds, Idxs);
2223 Constant *llvm::ConstantFoldGetElementPtr(Constant *C,
2225 ArrayRef<Value *> Idxs) {
2226 return ConstantFoldGetElementPtrImpl(C, inBounds, Idxs);