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/APSInt.h"
22 #include "llvm/ADT/SmallVector.h"
23 #include "llvm/IR/Constants.h"
24 #include "llvm/IR/DerivedTypes.h"
25 #include "llvm/IR/Function.h"
26 #include "llvm/IR/GetElementPtrTypeIterator.h"
27 #include "llvm/IR/GlobalAlias.h"
28 #include "llvm/IR/GlobalVariable.h"
29 #include "llvm/IR/Instructions.h"
30 #include "llvm/IR/Operator.h"
31 #include "llvm/IR/PatternMatch.h"
32 #include "llvm/Support/ErrorHandling.h"
33 #include "llvm/Support/ManagedStatic.h"
34 #include "llvm/Support/MathExtras.h"
36 using namespace llvm::PatternMatch;
38 //===----------------------------------------------------------------------===//
39 // ConstantFold*Instruction Implementations
40 //===----------------------------------------------------------------------===//
42 /// Convert the specified vector Constant node to the specified vector type.
43 /// At this point, we know that the elements of the input vector constant are
44 /// all simple integer or FP values.
45 static Constant *BitCastConstantVector(Constant *CV, VectorType *DstTy) {
47 if (CV->isAllOnesValue()) return Constant::getAllOnesValue(DstTy);
48 if (CV->isNullValue()) return Constant::getNullValue(DstTy);
50 // If this cast changes element count then we can't handle it here:
51 // doing so requires endianness information. This should be handled by
52 // Analysis/ConstantFolding.cpp
53 unsigned NumElts = DstTy->getNumElements();
54 if (NumElts != CV->getType()->getVectorNumElements())
57 Type *DstEltTy = DstTy->getElementType();
59 SmallVector<Constant*, 16> Result;
60 Type *Ty = IntegerType::get(CV->getContext(), 32);
61 for (unsigned i = 0; i != NumElts; ++i) {
63 ConstantExpr::getExtractElement(CV, ConstantInt::get(Ty, i));
64 C = ConstantExpr::getBitCast(C, DstEltTy);
68 return ConstantVector::get(Result);
71 /// This function determines which opcode to use to fold two constant cast
72 /// expressions together. It uses CastInst::isEliminableCastPair to determine
73 /// the opcode. Consequently its just a wrapper around that function.
74 /// @brief Determine if it is valid to fold a cast of a cast
77 unsigned opc, ///< opcode of the second cast constant expression
78 ConstantExpr *Op, ///< the first cast constant expression
79 Type *DstTy ///< destination type of the first cast
81 assert(Op && Op->isCast() && "Can't fold cast of cast without a cast!");
82 assert(DstTy && DstTy->isFirstClassType() && "Invalid cast destination type");
83 assert(CastInst::isCast(opc) && "Invalid cast opcode");
85 // The types and opcodes for the two Cast constant expressions
86 Type *SrcTy = Op->getOperand(0)->getType();
87 Type *MidTy = Op->getType();
88 Instruction::CastOps firstOp = Instruction::CastOps(Op->getOpcode());
89 Instruction::CastOps secondOp = Instruction::CastOps(opc);
91 // Assume that pointers are never more than 64 bits wide, and only use this
92 // for the middle type. Otherwise we could end up folding away illegal
93 // bitcasts between address spaces with different sizes.
94 IntegerType *FakeIntPtrTy = Type::getInt64Ty(DstTy->getContext());
96 // Let CastInst::isEliminableCastPair do the heavy lifting.
97 return CastInst::isEliminableCastPair(firstOp, secondOp, SrcTy, MidTy, DstTy,
98 nullptr, FakeIntPtrTy, nullptr);
101 static Constant *FoldBitCast(Constant *V, Type *DestTy) {
102 Type *SrcTy = V->getType();
104 return V; // no-op cast
106 // Check to see if we are casting a pointer to an aggregate to a pointer to
107 // the first element. If so, return the appropriate GEP instruction.
108 if (PointerType *PTy = dyn_cast<PointerType>(V->getType()))
109 if (PointerType *DPTy = dyn_cast<PointerType>(DestTy))
110 if (PTy->getAddressSpace() == DPTy->getAddressSpace()
111 && PTy->getElementType()->isSized()) {
112 SmallVector<Value*, 8> IdxList;
114 Constant::getNullValue(Type::getInt32Ty(DPTy->getContext()));
115 IdxList.push_back(Zero);
116 Type *ElTy = PTy->getElementType();
117 while (ElTy != DPTy->getElementType()) {
118 if (StructType *STy = dyn_cast<StructType>(ElTy)) {
119 if (STy->getNumElements() == 0) break;
120 ElTy = STy->getElementType(0);
121 IdxList.push_back(Zero);
122 } else if (SequentialType *STy =
123 dyn_cast<SequentialType>(ElTy)) {
124 ElTy = STy->getElementType();
125 IdxList.push_back(Zero);
131 if (ElTy == DPTy->getElementType())
132 // This GEP is inbounds because all indices are zero.
133 return ConstantExpr::getInBoundsGetElementPtr(PTy->getElementType(),
137 // Handle casts from one vector constant to another. We know that the src
138 // and dest type have the same size (otherwise its an illegal cast).
139 if (VectorType *DestPTy = dyn_cast<VectorType>(DestTy)) {
140 if (VectorType *SrcTy = dyn_cast<VectorType>(V->getType())) {
141 assert(DestPTy->getBitWidth() == SrcTy->getBitWidth() &&
142 "Not cast between same sized vectors!");
144 // First, check for null. Undef is already handled.
145 if (isa<ConstantAggregateZero>(V))
146 return Constant::getNullValue(DestTy);
148 // Handle ConstantVector and ConstantAggregateVector.
149 return BitCastConstantVector(V, DestPTy);
152 // Canonicalize scalar-to-vector bitcasts into vector-to-vector bitcasts
153 // This allows for other simplifications (although some of them
154 // can only be handled by Analysis/ConstantFolding.cpp).
155 if (isa<ConstantInt>(V) || isa<ConstantFP>(V))
156 return ConstantExpr::getBitCast(ConstantVector::get(V), DestPTy);
159 // Finally, implement bitcast folding now. The code below doesn't handle
161 if (isa<ConstantPointerNull>(V)) // ptr->ptr cast.
162 return ConstantPointerNull::get(cast<PointerType>(DestTy));
164 // Handle integral constant input.
165 if (ConstantInt *CI = dyn_cast<ConstantInt>(V)) {
166 if (DestTy->isIntegerTy())
167 // Integral -> Integral. This is a no-op because the bit widths must
168 // be the same. Consequently, we just fold to V.
171 // See note below regarding the PPC_FP128 restriction.
172 if (DestTy->isFloatingPointTy() && !DestTy->isPPC_FP128Ty())
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 // PPC_FP128 is really the sum of two consecutive doubles, where the first
184 // double is always stored first in memory, regardless of the target
185 // endianness. The memory layout of i128, however, depends on the target
186 // endianness, and so we can't fold this without target endianness
187 // information. This should instead be handled by
188 // Analysis/ConstantFolding.cpp
189 if (FP->getType()->isPPC_FP128Ty())
192 // Make sure dest type is compatible with the folded integer constant.
193 if (!DestTy->isIntegerTy())
196 return ConstantInt::get(FP->getContext(),
197 FP->getValueAPF().bitcastToAPInt());
204 /// V is an integer constant which only has a subset of its bytes used.
205 /// The bytes used are indicated by ByteStart (which is the first byte used,
206 /// counting from the least significant byte) and ByteSize, which is the number
209 /// This function analyzes the specified constant to see if the specified byte
210 /// range can be returned as a simplified constant. If so, the constant is
211 /// returned, otherwise null is returned.
212 static Constant *ExtractConstantBytes(Constant *C, unsigned ByteStart,
214 assert(C->getType()->isIntegerTy() &&
215 (cast<IntegerType>(C->getType())->getBitWidth() & 7) == 0 &&
216 "Non-byte sized integer input");
217 unsigned CSize = cast<IntegerType>(C->getType())->getBitWidth()/8;
218 assert(ByteSize && "Must be accessing some piece");
219 assert(ByteStart+ByteSize <= CSize && "Extracting invalid piece from input");
220 assert(ByteSize != CSize && "Should not extract everything");
222 // Constant Integers are simple.
223 if (ConstantInt *CI = dyn_cast<ConstantInt>(C)) {
224 APInt V = CI->getValue();
226 V.lshrInPlace(ByteStart*8);
227 V = V.trunc(ByteSize*8);
228 return ConstantInt::get(CI->getContext(), V);
231 // In the input is a constant expr, we might be able to recursively simplify.
232 // If not, we definitely can't do anything.
233 ConstantExpr *CE = dyn_cast<ConstantExpr>(C);
234 if (!CE) return nullptr;
236 switch (CE->getOpcode()) {
237 default: return nullptr;
238 case Instruction::Or: {
239 Constant *RHS = ExtractConstantBytes(CE->getOperand(1), ByteStart,ByteSize);
244 if (ConstantInt *RHSC = dyn_cast<ConstantInt>(RHS))
245 if (RHSC->isMinusOne())
248 Constant *LHS = ExtractConstantBytes(CE->getOperand(0), ByteStart,ByteSize);
251 return ConstantExpr::getOr(LHS, RHS);
253 case Instruction::And: {
254 Constant *RHS = ExtractConstantBytes(CE->getOperand(1), ByteStart,ByteSize);
259 if (RHS->isNullValue())
262 Constant *LHS = ExtractConstantBytes(CE->getOperand(0), ByteStart,ByteSize);
265 return ConstantExpr::getAnd(LHS, RHS);
267 case Instruction::LShr: {
268 ConstantInt *Amt = dyn_cast<ConstantInt>(CE->getOperand(1));
271 unsigned ShAmt = Amt->getZExtValue();
272 // Cannot analyze non-byte shifts.
273 if ((ShAmt & 7) != 0)
277 // If the extract is known to be all zeros, return zero.
278 if (ByteStart >= CSize-ShAmt)
279 return Constant::getNullValue(IntegerType::get(CE->getContext(),
281 // If the extract is known to be fully in the input, extract it.
282 if (ByteStart+ByteSize+ShAmt <= CSize)
283 return ExtractConstantBytes(CE->getOperand(0), ByteStart+ShAmt, ByteSize);
285 // TODO: Handle the 'partially zero' case.
289 case Instruction::Shl: {
290 ConstantInt *Amt = dyn_cast<ConstantInt>(CE->getOperand(1));
293 unsigned ShAmt = Amt->getZExtValue();
294 // Cannot analyze non-byte shifts.
295 if ((ShAmt & 7) != 0)
299 // If the extract is known to be all zeros, return zero.
300 if (ByteStart+ByteSize <= ShAmt)
301 return Constant::getNullValue(IntegerType::get(CE->getContext(),
303 // If the extract is known to be fully in the input, extract it.
304 if (ByteStart >= ShAmt)
305 return ExtractConstantBytes(CE->getOperand(0), ByteStart-ShAmt, ByteSize);
307 // TODO: Handle the 'partially zero' case.
311 case Instruction::ZExt: {
312 unsigned SrcBitSize =
313 cast<IntegerType>(CE->getOperand(0)->getType())->getBitWidth();
315 // If extracting something that is completely zero, return 0.
316 if (ByteStart*8 >= SrcBitSize)
317 return Constant::getNullValue(IntegerType::get(CE->getContext(),
320 // If exactly extracting the input, return it.
321 if (ByteStart == 0 && ByteSize*8 == SrcBitSize)
322 return CE->getOperand(0);
324 // If extracting something completely in the input, if if the input is a
325 // multiple of 8 bits, recurse.
326 if ((SrcBitSize&7) == 0 && (ByteStart+ByteSize)*8 <= SrcBitSize)
327 return ExtractConstantBytes(CE->getOperand(0), ByteStart, ByteSize);
329 // Otherwise, if extracting a subset of the input, which is not multiple of
330 // 8 bits, do a shift and trunc to get the bits.
331 if ((ByteStart+ByteSize)*8 < SrcBitSize) {
332 assert((SrcBitSize&7) && "Shouldn't get byte sized case here");
333 Constant *Res = CE->getOperand(0);
335 Res = ConstantExpr::getLShr(Res,
336 ConstantInt::get(Res->getType(), ByteStart*8));
337 return ConstantExpr::getTrunc(Res, IntegerType::get(C->getContext(),
341 // TODO: Handle the 'partially zero' case.
347 /// Return a ConstantExpr with type DestTy for sizeof on Ty, with any known
348 /// factors factored out. If Folded is false, return null if no factoring was
349 /// possible, to avoid endlessly bouncing an unfoldable expression back into the
350 /// top-level folder.
351 static Constant *getFoldedSizeOf(Type *Ty, Type *DestTy, bool Folded) {
352 if (ArrayType *ATy = dyn_cast<ArrayType>(Ty)) {
353 Constant *N = ConstantInt::get(DestTy, ATy->getNumElements());
354 Constant *E = getFoldedSizeOf(ATy->getElementType(), DestTy, true);
355 return ConstantExpr::getNUWMul(E, N);
358 if (StructType *STy = dyn_cast<StructType>(Ty))
359 if (!STy->isPacked()) {
360 unsigned NumElems = STy->getNumElements();
361 // An empty struct has size zero.
363 return ConstantExpr::getNullValue(DestTy);
364 // Check for a struct with all members having the same size.
365 Constant *MemberSize =
366 getFoldedSizeOf(STy->getElementType(0), DestTy, true);
368 for (unsigned i = 1; i != NumElems; ++i)
370 getFoldedSizeOf(STy->getElementType(i), DestTy, true)) {
375 Constant *N = ConstantInt::get(DestTy, NumElems);
376 return ConstantExpr::getNUWMul(MemberSize, N);
380 // Pointer size doesn't depend on the pointee type, so canonicalize them
381 // to an arbitrary pointee.
382 if (PointerType *PTy = dyn_cast<PointerType>(Ty))
383 if (!PTy->getElementType()->isIntegerTy(1))
385 getFoldedSizeOf(PointerType::get(IntegerType::get(PTy->getContext(), 1),
386 PTy->getAddressSpace()),
389 // If there's no interesting folding happening, bail so that we don't create
390 // a constant that looks like it needs folding but really doesn't.
394 // Base case: Get a regular sizeof expression.
395 Constant *C = ConstantExpr::getSizeOf(Ty);
396 C = ConstantExpr::getCast(CastInst::getCastOpcode(C, false,
402 /// Return a ConstantExpr with type DestTy for alignof on Ty, with any known
403 /// factors factored out. If Folded is false, return null if no factoring was
404 /// possible, to avoid endlessly bouncing an unfoldable expression back into the
405 /// top-level folder.
406 static Constant *getFoldedAlignOf(Type *Ty, Type *DestTy, bool Folded) {
407 // The alignment of an array is equal to the alignment of the
408 // array element. Note that this is not always true for vectors.
409 if (ArrayType *ATy = dyn_cast<ArrayType>(Ty)) {
410 Constant *C = ConstantExpr::getAlignOf(ATy->getElementType());
411 C = ConstantExpr::getCast(CastInst::getCastOpcode(C, false,
418 if (StructType *STy = dyn_cast<StructType>(Ty)) {
419 // Packed structs always have an alignment of 1.
421 return ConstantInt::get(DestTy, 1);
423 // Otherwise, struct alignment is the maximum alignment of any member.
424 // Without target data, we can't compare much, but we can check to see
425 // if all the members have the same alignment.
426 unsigned NumElems = STy->getNumElements();
427 // An empty struct has minimal alignment.
429 return ConstantInt::get(DestTy, 1);
430 // Check for a struct with all members having the same alignment.
431 Constant *MemberAlign =
432 getFoldedAlignOf(STy->getElementType(0), DestTy, true);
434 for (unsigned i = 1; i != NumElems; ++i)
435 if (MemberAlign != getFoldedAlignOf(STy->getElementType(i), DestTy, true)) {
443 // Pointer alignment doesn't depend on the pointee type, so canonicalize them
444 // to an arbitrary pointee.
445 if (PointerType *PTy = dyn_cast<PointerType>(Ty))
446 if (!PTy->getElementType()->isIntegerTy(1))
448 getFoldedAlignOf(PointerType::get(IntegerType::get(PTy->getContext(),
450 PTy->getAddressSpace()),
453 // If there's no interesting folding happening, bail so that we don't create
454 // a constant that looks like it needs folding but really doesn't.
458 // Base case: Get a regular alignof expression.
459 Constant *C = ConstantExpr::getAlignOf(Ty);
460 C = ConstantExpr::getCast(CastInst::getCastOpcode(C, false,
466 /// Return a ConstantExpr with type DestTy for offsetof on Ty and FieldNo, with
467 /// any known factors factored out. If Folded is false, return null if no
468 /// factoring was possible, to avoid endlessly bouncing an unfoldable expression
469 /// back into the top-level folder.
470 static Constant *getFoldedOffsetOf(Type *Ty, Constant *FieldNo, Type *DestTy,
472 if (ArrayType *ATy = dyn_cast<ArrayType>(Ty)) {
473 Constant *N = ConstantExpr::getCast(CastInst::getCastOpcode(FieldNo, false,
476 Constant *E = getFoldedSizeOf(ATy->getElementType(), DestTy, true);
477 return ConstantExpr::getNUWMul(E, N);
480 if (StructType *STy = dyn_cast<StructType>(Ty))
481 if (!STy->isPacked()) {
482 unsigned NumElems = STy->getNumElements();
483 // An empty struct has no members.
486 // Check for a struct with all members having the same size.
487 Constant *MemberSize =
488 getFoldedSizeOf(STy->getElementType(0), DestTy, true);
490 for (unsigned i = 1; i != NumElems; ++i)
492 getFoldedSizeOf(STy->getElementType(i), DestTy, true)) {
497 Constant *N = ConstantExpr::getCast(CastInst::getCastOpcode(FieldNo,
502 return ConstantExpr::getNUWMul(MemberSize, N);
506 // If there's no interesting folding happening, bail so that we don't create
507 // a constant that looks like it needs folding but really doesn't.
511 // Base case: Get a regular offsetof expression.
512 Constant *C = ConstantExpr::getOffsetOf(Ty, FieldNo);
513 C = ConstantExpr::getCast(CastInst::getCastOpcode(C, false,
519 Constant *llvm::ConstantFoldCastInstruction(unsigned opc, Constant *V,
521 if (isa<UndefValue>(V)) {
522 // zext(undef) = 0, because the top bits will be zero.
523 // sext(undef) = 0, because the top bits will all be the same.
524 // [us]itofp(undef) = 0, because the result value is bounded.
525 if (opc == Instruction::ZExt || opc == Instruction::SExt ||
526 opc == Instruction::UIToFP || opc == Instruction::SIToFP)
527 return Constant::getNullValue(DestTy);
528 return UndefValue::get(DestTy);
531 if (V->isNullValue() && !DestTy->isX86_MMXTy() &&
532 opc != Instruction::AddrSpaceCast)
533 return Constant::getNullValue(DestTy);
535 // If the cast operand is a constant expression, there's a few things we can
536 // do to try to simplify it.
537 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V)) {
539 // Try hard to fold cast of cast because they are often eliminable.
540 if (unsigned newOpc = foldConstantCastPair(opc, CE, DestTy))
541 return ConstantExpr::getCast(newOpc, CE->getOperand(0), DestTy);
542 } else if (CE->getOpcode() == Instruction::GetElementPtr &&
543 // Do not fold addrspacecast (gep 0, .., 0). It might make the
544 // addrspacecast uncanonicalized.
545 opc != Instruction::AddrSpaceCast &&
546 // Do not fold bitcast (gep) with inrange index, as this loses
548 !cast<GEPOperator>(CE)->getInRangeIndex().hasValue()) {
549 // If all of the indexes in the GEP are null values, there is no pointer
550 // adjustment going on. We might as well cast the source pointer.
551 bool isAllNull = true;
552 for (unsigned i = 1, e = CE->getNumOperands(); i != e; ++i)
553 if (!CE->getOperand(i)->isNullValue()) {
558 // This is casting one pointer type to another, always BitCast
559 return ConstantExpr::getPointerCast(CE->getOperand(0), DestTy);
563 // If the cast operand is a constant vector, perform the cast by
564 // operating on each element. In the cast of bitcasts, the element
565 // count may be mismatched; don't attempt to handle that here.
566 if ((isa<ConstantVector>(V) || isa<ConstantDataVector>(V)) &&
567 DestTy->isVectorTy() &&
568 DestTy->getVectorNumElements() == V->getType()->getVectorNumElements()) {
569 SmallVector<Constant*, 16> res;
570 VectorType *DestVecTy = cast<VectorType>(DestTy);
571 Type *DstEltTy = DestVecTy->getElementType();
572 Type *Ty = IntegerType::get(V->getContext(), 32);
573 for (unsigned i = 0, e = V->getType()->getVectorNumElements(); i != e; ++i) {
575 ConstantExpr::getExtractElement(V, ConstantInt::get(Ty, i));
576 res.push_back(ConstantExpr::getCast(opc, C, DstEltTy));
578 return ConstantVector::get(res);
581 // We actually have to do a cast now. Perform the cast according to the
585 llvm_unreachable("Failed to cast constant expression");
586 case Instruction::FPTrunc:
587 case Instruction::FPExt:
588 if (ConstantFP *FPC = dyn_cast<ConstantFP>(V)) {
590 APFloat Val = FPC->getValueAPF();
591 Val.convert(DestTy->isHalfTy() ? APFloat::IEEEhalf() :
592 DestTy->isFloatTy() ? APFloat::IEEEsingle() :
593 DestTy->isDoubleTy() ? APFloat::IEEEdouble() :
594 DestTy->isX86_FP80Ty() ? APFloat::x87DoubleExtended() :
595 DestTy->isFP128Ty() ? APFloat::IEEEquad() :
596 DestTy->isPPC_FP128Ty() ? APFloat::PPCDoubleDouble() :
598 APFloat::rmNearestTiesToEven, &ignored);
599 return ConstantFP::get(V->getContext(), Val);
601 return nullptr; // Can't fold.
602 case Instruction::FPToUI:
603 case Instruction::FPToSI:
604 if (ConstantFP *FPC = dyn_cast<ConstantFP>(V)) {
605 const APFloat &V = FPC->getValueAPF();
607 uint32_t DestBitWidth = cast<IntegerType>(DestTy)->getBitWidth();
608 APSInt IntVal(DestBitWidth, opc == Instruction::FPToUI);
609 if (APFloat::opInvalidOp ==
610 V.convertToInteger(IntVal, APFloat::rmTowardZero, &ignored)) {
611 // Undefined behavior invoked - the destination type can't represent
612 // the input constant.
613 return UndefValue::get(DestTy);
615 return ConstantInt::get(FPC->getContext(), IntVal);
617 return nullptr; // Can't fold.
618 case Instruction::IntToPtr: //always treated as unsigned
619 if (V->isNullValue()) // Is it an integral null value?
620 return ConstantPointerNull::get(cast<PointerType>(DestTy));
621 return nullptr; // Other pointer types cannot be casted
622 case Instruction::PtrToInt: // always treated as unsigned
623 // Is it a null pointer value?
624 if (V->isNullValue())
625 return ConstantInt::get(DestTy, 0);
626 // If this is a sizeof-like expression, pull out multiplications by
627 // known factors to expose them to subsequent folding. If it's an
628 // alignof-like expression, factor out known factors.
629 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V))
630 if (CE->getOpcode() == Instruction::GetElementPtr &&
631 CE->getOperand(0)->isNullValue()) {
632 GEPOperator *GEPO = cast<GEPOperator>(CE);
633 Type *Ty = GEPO->getSourceElementType();
634 if (CE->getNumOperands() == 2) {
635 // Handle a sizeof-like expression.
636 Constant *Idx = CE->getOperand(1);
637 bool isOne = isa<ConstantInt>(Idx) && cast<ConstantInt>(Idx)->isOne();
638 if (Constant *C = getFoldedSizeOf(Ty, DestTy, !isOne)) {
639 Idx = ConstantExpr::getCast(CastInst::getCastOpcode(Idx, true,
642 return ConstantExpr::getMul(C, Idx);
644 } else if (CE->getNumOperands() == 3 &&
645 CE->getOperand(1)->isNullValue()) {
646 // Handle an alignof-like expression.
647 if (StructType *STy = dyn_cast<StructType>(Ty))
648 if (!STy->isPacked()) {
649 ConstantInt *CI = cast<ConstantInt>(CE->getOperand(2));
651 STy->getNumElements() == 2 &&
652 STy->getElementType(0)->isIntegerTy(1)) {
653 return getFoldedAlignOf(STy->getElementType(1), DestTy, false);
656 // Handle an offsetof-like expression.
657 if (Ty->isStructTy() || Ty->isArrayTy()) {
658 if (Constant *C = getFoldedOffsetOf(Ty, CE->getOperand(2),
664 // Other pointer types cannot be casted
666 case Instruction::UIToFP:
667 case Instruction::SIToFP:
668 if (ConstantInt *CI = dyn_cast<ConstantInt>(V)) {
669 const APInt &api = CI->getValue();
670 APFloat apf(DestTy->getFltSemantics(),
671 APInt::getNullValue(DestTy->getPrimitiveSizeInBits()));
672 if (APFloat::opOverflow &
673 apf.convertFromAPInt(api, opc==Instruction::SIToFP,
674 APFloat::rmNearestTiesToEven)) {
675 // Undefined behavior invoked - the destination type can't represent
676 // the input constant.
677 return UndefValue::get(DestTy);
679 return ConstantFP::get(V->getContext(), apf);
682 case Instruction::ZExt:
683 if (ConstantInt *CI = dyn_cast<ConstantInt>(V)) {
684 uint32_t BitWidth = cast<IntegerType>(DestTy)->getBitWidth();
685 return ConstantInt::get(V->getContext(),
686 CI->getValue().zext(BitWidth));
689 case Instruction::SExt:
690 if (ConstantInt *CI = dyn_cast<ConstantInt>(V)) {
691 uint32_t BitWidth = cast<IntegerType>(DestTy)->getBitWidth();
692 return ConstantInt::get(V->getContext(),
693 CI->getValue().sext(BitWidth));
696 case Instruction::Trunc: {
697 if (V->getType()->isVectorTy())
700 uint32_t DestBitWidth = cast<IntegerType>(DestTy)->getBitWidth();
701 if (ConstantInt *CI = dyn_cast<ConstantInt>(V)) {
702 return ConstantInt::get(V->getContext(),
703 CI->getValue().trunc(DestBitWidth));
706 // The input must be a constantexpr. See if we can simplify this based on
707 // the bytes we are demanding. Only do this if the source and dest are an
708 // even multiple of a byte.
709 if ((DestBitWidth & 7) == 0 &&
710 (cast<IntegerType>(V->getType())->getBitWidth() & 7) == 0)
711 if (Constant *Res = ExtractConstantBytes(V, 0, DestBitWidth / 8))
716 case Instruction::BitCast:
717 return FoldBitCast(V, DestTy);
718 case Instruction::AddrSpaceCast:
723 Constant *llvm::ConstantFoldSelectInstruction(Constant *Cond,
724 Constant *V1, Constant *V2) {
725 // Check for i1 and vector true/false conditions.
726 if (Cond->isNullValue()) return V2;
727 if (Cond->isAllOnesValue()) return V1;
729 // If the condition is a vector constant, fold the result elementwise.
730 if (ConstantVector *CondV = dyn_cast<ConstantVector>(Cond)) {
731 SmallVector<Constant*, 16> Result;
732 Type *Ty = IntegerType::get(CondV->getContext(), 32);
733 for (unsigned i = 0, e = V1->getType()->getVectorNumElements(); i != e;++i){
735 Constant *V1Element = ConstantExpr::getExtractElement(V1,
736 ConstantInt::get(Ty, i));
737 Constant *V2Element = ConstantExpr::getExtractElement(V2,
738 ConstantInt::get(Ty, i));
739 Constant *Cond = dyn_cast<Constant>(CondV->getOperand(i));
740 if (V1Element == V2Element) {
742 } else if (isa<UndefValue>(Cond)) {
743 V = isa<UndefValue>(V1Element) ? V1Element : V2Element;
745 if (!isa<ConstantInt>(Cond)) break;
746 V = Cond->isNullValue() ? V2Element : V1Element;
751 // If we were able to build the vector, return it.
752 if (Result.size() == V1->getType()->getVectorNumElements())
753 return ConstantVector::get(Result);
756 if (isa<UndefValue>(Cond)) {
757 if (isa<UndefValue>(V1)) return V1;
760 if (isa<UndefValue>(V1)) return V2;
761 if (isa<UndefValue>(V2)) return V1;
762 if (V1 == V2) return V1;
764 if (ConstantExpr *TrueVal = dyn_cast<ConstantExpr>(V1)) {
765 if (TrueVal->getOpcode() == Instruction::Select)
766 if (TrueVal->getOperand(0) == Cond)
767 return ConstantExpr::getSelect(Cond, TrueVal->getOperand(1), V2);
769 if (ConstantExpr *FalseVal = dyn_cast<ConstantExpr>(V2)) {
770 if (FalseVal->getOpcode() == Instruction::Select)
771 if (FalseVal->getOperand(0) == Cond)
772 return ConstantExpr::getSelect(Cond, V1, FalseVal->getOperand(2));
778 Constant *llvm::ConstantFoldExtractElementInstruction(Constant *Val,
780 if (isa<UndefValue>(Val)) // ee(undef, x) -> undef
781 return UndefValue::get(Val->getType()->getVectorElementType());
782 if (Val->isNullValue()) // ee(zero, x) -> zero
783 return Constant::getNullValue(Val->getType()->getVectorElementType());
784 // ee({w,x,y,z}, undef) -> undef
785 if (isa<UndefValue>(Idx))
786 return UndefValue::get(Val->getType()->getVectorElementType());
788 if (ConstantInt *CIdx = dyn_cast<ConstantInt>(Idx)) {
789 // ee({w,x,y,z}, wrong_value) -> undef
790 if (CIdx->uge(Val->getType()->getVectorNumElements()))
791 return UndefValue::get(Val->getType()->getVectorElementType());
792 return Val->getAggregateElement(CIdx->getZExtValue());
797 Constant *llvm::ConstantFoldInsertElementInstruction(Constant *Val,
800 if (isa<UndefValue>(Idx))
801 return UndefValue::get(Val->getType());
803 ConstantInt *CIdx = dyn_cast<ConstantInt>(Idx);
804 if (!CIdx) return nullptr;
806 unsigned NumElts = Val->getType()->getVectorNumElements();
807 if (CIdx->uge(NumElts))
808 return UndefValue::get(Val->getType());
810 SmallVector<Constant*, 16> Result;
811 Result.reserve(NumElts);
812 auto *Ty = Type::getInt32Ty(Val->getContext());
813 uint64_t IdxVal = CIdx->getZExtValue();
814 for (unsigned i = 0; i != NumElts; ++i) {
816 Result.push_back(Elt);
820 Constant *C = ConstantExpr::getExtractElement(Val, ConstantInt::get(Ty, i));
824 return ConstantVector::get(Result);
827 Constant *llvm::ConstantFoldShuffleVectorInstruction(Constant *V1,
830 unsigned MaskNumElts = Mask->getType()->getVectorNumElements();
831 Type *EltTy = V1->getType()->getVectorElementType();
833 // Undefined shuffle mask -> undefined value.
834 if (isa<UndefValue>(Mask))
835 return UndefValue::get(VectorType::get(EltTy, MaskNumElts));
837 // Don't break the bitcode reader hack.
838 if (isa<ConstantExpr>(Mask)) return nullptr;
840 unsigned SrcNumElts = V1->getType()->getVectorNumElements();
842 // Loop over the shuffle mask, evaluating each element.
843 SmallVector<Constant*, 32> Result;
844 for (unsigned i = 0; i != MaskNumElts; ++i) {
845 int Elt = ShuffleVectorInst::getMaskValue(Mask, i);
847 Result.push_back(UndefValue::get(EltTy));
851 if (unsigned(Elt) >= SrcNumElts*2)
852 InElt = UndefValue::get(EltTy);
853 else if (unsigned(Elt) >= SrcNumElts) {
854 Type *Ty = IntegerType::get(V2->getContext(), 32);
856 ConstantExpr::getExtractElement(V2,
857 ConstantInt::get(Ty, Elt - SrcNumElts));
859 Type *Ty = IntegerType::get(V1->getContext(), 32);
860 InElt = ConstantExpr::getExtractElement(V1, ConstantInt::get(Ty, Elt));
862 Result.push_back(InElt);
865 return ConstantVector::get(Result);
868 Constant *llvm::ConstantFoldExtractValueInstruction(Constant *Agg,
869 ArrayRef<unsigned> Idxs) {
870 // Base case: no indices, so return the entire value.
874 if (Constant *C = Agg->getAggregateElement(Idxs[0]))
875 return ConstantFoldExtractValueInstruction(C, Idxs.slice(1));
880 Constant *llvm::ConstantFoldInsertValueInstruction(Constant *Agg,
882 ArrayRef<unsigned> Idxs) {
883 // Base case: no indices, so replace the entire value.
888 if (StructType *ST = dyn_cast<StructType>(Agg->getType()))
889 NumElts = ST->getNumElements();
891 NumElts = cast<SequentialType>(Agg->getType())->getNumElements();
893 SmallVector<Constant*, 32> Result;
894 for (unsigned i = 0; i != NumElts; ++i) {
895 Constant *C = Agg->getAggregateElement(i);
896 if (!C) return nullptr;
899 C = ConstantFoldInsertValueInstruction(C, Val, Idxs.slice(1));
904 if (StructType *ST = dyn_cast<StructType>(Agg->getType()))
905 return ConstantStruct::get(ST, Result);
906 if (ArrayType *AT = dyn_cast<ArrayType>(Agg->getType()))
907 return ConstantArray::get(AT, Result);
908 return ConstantVector::get(Result);
912 Constant *llvm::ConstantFoldBinaryInstruction(unsigned Opcode,
913 Constant *C1, Constant *C2) {
914 assert(Instruction::isBinaryOp(Opcode) && "Non-binary instruction detected");
916 // Handle UndefValue up front.
917 if (isa<UndefValue>(C1) || isa<UndefValue>(C2)) {
918 switch (static_cast<Instruction::BinaryOps>(Opcode)) {
919 case Instruction::Xor:
920 if (isa<UndefValue>(C1) && isa<UndefValue>(C2))
921 // Handle undef ^ undef -> 0 special case. This is a common
923 return Constant::getNullValue(C1->getType());
925 case Instruction::Add:
926 case Instruction::Sub:
927 return UndefValue::get(C1->getType());
928 case Instruction::And:
929 if (isa<UndefValue>(C1) && isa<UndefValue>(C2)) // undef & undef -> undef
931 return Constant::getNullValue(C1->getType()); // undef & X -> 0
932 case Instruction::Mul: {
933 // undef * undef -> undef
934 if (isa<UndefValue>(C1) && isa<UndefValue>(C2))
937 // X * undef -> undef if X is odd
938 if (match(C1, m_APInt(CV)) || match(C2, m_APInt(CV)))
940 return UndefValue::get(C1->getType());
942 // X * undef -> 0 otherwise
943 return Constant::getNullValue(C1->getType());
945 case Instruction::SDiv:
946 case Instruction::UDiv:
947 // X / undef -> undef
948 if (isa<UndefValue>(C2))
950 // undef / 0 -> undef
951 // undef / 1 -> undef
952 if (match(C2, m_Zero()) || match(C2, m_One()))
954 // undef / X -> 0 otherwise
955 return Constant::getNullValue(C1->getType());
956 case Instruction::URem:
957 case Instruction::SRem:
958 // X % undef -> undef
959 if (match(C2, m_Undef()))
961 // undef % 0 -> undef
962 if (match(C2, m_Zero()))
964 // undef % X -> 0 otherwise
965 return Constant::getNullValue(C1->getType());
966 case Instruction::Or: // X | undef -> -1
967 if (isa<UndefValue>(C1) && isa<UndefValue>(C2)) // undef | undef -> undef
969 return Constant::getAllOnesValue(C1->getType()); // undef | X -> ~0
970 case Instruction::LShr:
971 // X >>l undef -> undef
972 if (isa<UndefValue>(C2))
974 // undef >>l 0 -> undef
975 if (match(C2, m_Zero()))
978 return Constant::getNullValue(C1->getType());
979 case Instruction::AShr:
980 // X >>a undef -> undef
981 if (isa<UndefValue>(C2))
983 // undef >>a 0 -> undef
984 if (match(C2, m_Zero()))
986 // TODO: undef >>a X -> undef if the shift is exact
988 return Constant::getNullValue(C1->getType());
989 case Instruction::Shl:
990 // X << undef -> undef
991 if (isa<UndefValue>(C2))
993 // undef << 0 -> undef
994 if (match(C2, m_Zero()))
997 return Constant::getNullValue(C1->getType());
998 case Instruction::FAdd:
999 case Instruction::FSub:
1000 case Instruction::FMul:
1001 case Instruction::FDiv:
1002 case Instruction::FRem:
1003 // TODO: UNDEF handling for binary float instructions.
1005 case Instruction::BinaryOpsEnd:
1006 llvm_unreachable("Invalid BinaryOp");
1010 // At this point neither constant should be an UndefValue.
1011 assert(!isa<UndefValue>(C1) && !isa<UndefValue>(C2) &&
1012 "Unexpected UndefValue");
1014 // Handle simplifications when the RHS is a constant int.
1015 if (ConstantInt *CI2 = dyn_cast<ConstantInt>(C2)) {
1017 case Instruction::Add:
1018 if (CI2->isZero()) return C1; // X + 0 == X
1020 case Instruction::Sub:
1021 if (CI2->isZero()) return C1; // X - 0 == X
1023 case Instruction::Mul:
1024 if (CI2->isZero()) return C2; // X * 0 == 0
1026 return C1; // X * 1 == X
1028 case Instruction::UDiv:
1029 case Instruction::SDiv:
1031 return C1; // X / 1 == X
1033 return UndefValue::get(CI2->getType()); // X / 0 == undef
1035 case Instruction::URem:
1036 case Instruction::SRem:
1038 return Constant::getNullValue(CI2->getType()); // X % 1 == 0
1040 return UndefValue::get(CI2->getType()); // X % 0 == undef
1042 case Instruction::And:
1043 if (CI2->isZero()) return C2; // X & 0 == 0
1044 if (CI2->isMinusOne())
1045 return C1; // X & -1 == X
1047 if (ConstantExpr *CE1 = dyn_cast<ConstantExpr>(C1)) {
1048 // (zext i32 to i64) & 4294967295 -> (zext i32 to i64)
1049 if (CE1->getOpcode() == Instruction::ZExt) {
1050 unsigned DstWidth = CI2->getType()->getBitWidth();
1052 CE1->getOperand(0)->getType()->getPrimitiveSizeInBits();
1053 APInt PossiblySetBits(APInt::getLowBitsSet(DstWidth, SrcWidth));
1054 if ((PossiblySetBits & CI2->getValue()) == PossiblySetBits)
1058 // If and'ing the address of a global with a constant, fold it.
1059 if (CE1->getOpcode() == Instruction::PtrToInt &&
1060 isa<GlobalValue>(CE1->getOperand(0))) {
1061 GlobalValue *GV = cast<GlobalValue>(CE1->getOperand(0));
1063 // Functions are at least 4-byte aligned.
1064 unsigned GVAlign = GV->getAlignment();
1065 if (isa<Function>(GV))
1066 GVAlign = std::max(GVAlign, 4U);
1069 unsigned DstWidth = CI2->getType()->getBitWidth();
1070 unsigned SrcWidth = std::min(DstWidth, Log2_32(GVAlign));
1071 APInt BitsNotSet(APInt::getLowBitsSet(DstWidth, SrcWidth));
1073 // If checking bits we know are clear, return zero.
1074 if ((CI2->getValue() & BitsNotSet) == CI2->getValue())
1075 return Constant::getNullValue(CI2->getType());
1080 case Instruction::Or:
1081 if (CI2->isZero()) return C1; // X | 0 == X
1082 if (CI2->isMinusOne())
1083 return C2; // X | -1 == -1
1085 case Instruction::Xor:
1086 if (CI2->isZero()) return C1; // X ^ 0 == X
1088 if (ConstantExpr *CE1 = dyn_cast<ConstantExpr>(C1)) {
1089 switch (CE1->getOpcode()) {
1091 case Instruction::ICmp:
1092 case Instruction::FCmp:
1093 // cmp pred ^ true -> cmp !pred
1094 assert(CI2->isOne());
1095 CmpInst::Predicate pred = (CmpInst::Predicate)CE1->getPredicate();
1096 pred = CmpInst::getInversePredicate(pred);
1097 return ConstantExpr::getCompare(pred, CE1->getOperand(0),
1098 CE1->getOperand(1));
1102 case Instruction::AShr:
1103 // ashr (zext C to Ty), C2 -> lshr (zext C, CSA), C2
1104 if (ConstantExpr *CE1 = dyn_cast<ConstantExpr>(C1))
1105 if (CE1->getOpcode() == Instruction::ZExt) // Top bits known zero.
1106 return ConstantExpr::getLShr(C1, C2);
1109 } else if (isa<ConstantInt>(C1)) {
1110 // If C1 is a ConstantInt and C2 is not, swap the operands.
1111 if (Instruction::isCommutative(Opcode))
1112 return ConstantExpr::get(Opcode, C2, C1);
1115 if (ConstantInt *CI1 = dyn_cast<ConstantInt>(C1)) {
1116 if (ConstantInt *CI2 = dyn_cast<ConstantInt>(C2)) {
1117 const APInt &C1V = CI1->getValue();
1118 const APInt &C2V = CI2->getValue();
1122 case Instruction::Add:
1123 return ConstantInt::get(CI1->getContext(), C1V + C2V);
1124 case Instruction::Sub:
1125 return ConstantInt::get(CI1->getContext(), C1V - C2V);
1126 case Instruction::Mul:
1127 return ConstantInt::get(CI1->getContext(), C1V * C2V);
1128 case Instruction::UDiv:
1129 assert(!CI2->isZero() && "Div by zero handled above");
1130 return ConstantInt::get(CI1->getContext(), C1V.udiv(C2V));
1131 case Instruction::SDiv:
1132 assert(!CI2->isZero() && "Div by zero handled above");
1133 if (C2V.isAllOnesValue() && C1V.isMinSignedValue())
1134 return UndefValue::get(CI1->getType()); // MIN_INT / -1 -> undef
1135 return ConstantInt::get(CI1->getContext(), C1V.sdiv(C2V));
1136 case Instruction::URem:
1137 assert(!CI2->isZero() && "Div by zero handled above");
1138 return ConstantInt::get(CI1->getContext(), C1V.urem(C2V));
1139 case Instruction::SRem:
1140 assert(!CI2->isZero() && "Div by zero handled above");
1141 if (C2V.isAllOnesValue() && C1V.isMinSignedValue())
1142 return UndefValue::get(CI1->getType()); // MIN_INT % -1 -> undef
1143 return ConstantInt::get(CI1->getContext(), C1V.srem(C2V));
1144 case Instruction::And:
1145 return ConstantInt::get(CI1->getContext(), C1V & C2V);
1146 case Instruction::Or:
1147 return ConstantInt::get(CI1->getContext(), C1V | C2V);
1148 case Instruction::Xor:
1149 return ConstantInt::get(CI1->getContext(), C1V ^ C2V);
1150 case Instruction::Shl:
1151 if (C2V.ult(C1V.getBitWidth()))
1152 return ConstantInt::get(CI1->getContext(), C1V.shl(C2V));
1153 return UndefValue::get(C1->getType()); // too big shift is undef
1154 case Instruction::LShr:
1155 if (C2V.ult(C1V.getBitWidth()))
1156 return ConstantInt::get(CI1->getContext(), C1V.lshr(C2V));
1157 return UndefValue::get(C1->getType()); // too big shift is undef
1158 case Instruction::AShr:
1159 if (C2V.ult(C1V.getBitWidth()))
1160 return ConstantInt::get(CI1->getContext(), C1V.ashr(C2V));
1161 return UndefValue::get(C1->getType()); // too big shift is undef
1166 case Instruction::SDiv:
1167 case Instruction::UDiv:
1168 case Instruction::URem:
1169 case Instruction::SRem:
1170 case Instruction::LShr:
1171 case Instruction::AShr:
1172 case Instruction::Shl:
1173 if (CI1->isZero()) return C1;
1178 } else if (ConstantFP *CFP1 = dyn_cast<ConstantFP>(C1)) {
1179 if (ConstantFP *CFP2 = dyn_cast<ConstantFP>(C2)) {
1180 const APFloat &C1V = CFP1->getValueAPF();
1181 const APFloat &C2V = CFP2->getValueAPF();
1182 APFloat C3V = C1V; // copy for modification
1186 case Instruction::FAdd:
1187 (void)C3V.add(C2V, APFloat::rmNearestTiesToEven);
1188 return ConstantFP::get(C1->getContext(), C3V);
1189 case Instruction::FSub:
1190 (void)C3V.subtract(C2V, APFloat::rmNearestTiesToEven);
1191 return ConstantFP::get(C1->getContext(), C3V);
1192 case Instruction::FMul:
1193 (void)C3V.multiply(C2V, APFloat::rmNearestTiesToEven);
1194 return ConstantFP::get(C1->getContext(), C3V);
1195 case Instruction::FDiv:
1196 (void)C3V.divide(C2V, APFloat::rmNearestTiesToEven);
1197 return ConstantFP::get(C1->getContext(), C3V);
1198 case Instruction::FRem:
1200 return ConstantFP::get(C1->getContext(), C3V);
1203 } else if (VectorType *VTy = dyn_cast<VectorType>(C1->getType())) {
1204 // Perform elementwise folding.
1205 SmallVector<Constant*, 16> Result;
1206 Type *Ty = IntegerType::get(VTy->getContext(), 32);
1207 for (unsigned i = 0, e = VTy->getNumElements(); i != e; ++i) {
1208 Constant *ExtractIdx = ConstantInt::get(Ty, i);
1209 Constant *LHS = ConstantExpr::getExtractElement(C1, ExtractIdx);
1210 Constant *RHS = ConstantExpr::getExtractElement(C2, ExtractIdx);
1212 // If any element of a divisor vector is zero, the whole op is undef.
1213 if ((Opcode == Instruction::SDiv || Opcode == Instruction::UDiv ||
1214 Opcode == Instruction::SRem || Opcode == Instruction::URem) &&
1216 return UndefValue::get(VTy);
1218 Result.push_back(ConstantExpr::get(Opcode, LHS, RHS));
1221 return ConstantVector::get(Result);
1224 if (ConstantExpr *CE1 = dyn_cast<ConstantExpr>(C1)) {
1225 // There are many possible foldings we could do here. We should probably
1226 // at least fold add of a pointer with an integer into the appropriate
1227 // getelementptr. This will improve alias analysis a bit.
1229 // Given ((a + b) + c), if (b + c) folds to something interesting, return
1231 if (Instruction::isAssociative(Opcode) && CE1->getOpcode() == Opcode) {
1232 Constant *T = ConstantExpr::get(Opcode, CE1->getOperand(1), C2);
1233 if (!isa<ConstantExpr>(T) || cast<ConstantExpr>(T)->getOpcode() != Opcode)
1234 return ConstantExpr::get(Opcode, CE1->getOperand(0), T);
1236 } else if (isa<ConstantExpr>(C2)) {
1237 // If C2 is a constant expr and C1 isn't, flop them around and fold the
1238 // other way if possible.
1239 if (Instruction::isCommutative(Opcode))
1240 return ConstantFoldBinaryInstruction(Opcode, C2, C1);
1243 // i1 can be simplified in many cases.
1244 if (C1->getType()->isIntegerTy(1)) {
1246 case Instruction::Add:
1247 case Instruction::Sub:
1248 return ConstantExpr::getXor(C1, C2);
1249 case Instruction::Mul:
1250 return ConstantExpr::getAnd(C1, C2);
1251 case Instruction::Shl:
1252 case Instruction::LShr:
1253 case Instruction::AShr:
1254 // We can assume that C2 == 0. If it were one the result would be
1255 // undefined because the shift value is as large as the bitwidth.
1257 case Instruction::SDiv:
1258 case Instruction::UDiv:
1259 // We can assume that C2 == 1. If it were zero the result would be
1260 // undefined through division by zero.
1262 case Instruction::URem:
1263 case Instruction::SRem:
1264 // We can assume that C2 == 1. If it were zero the result would be
1265 // undefined through division by zero.
1266 return ConstantInt::getFalse(C1->getContext());
1272 // We don't know how to fold this.
1276 /// This type is zero-sized if it's an array or structure of zero-sized types.
1277 /// The only leaf zero-sized type is an empty structure.
1278 static bool isMaybeZeroSizedType(Type *Ty) {
1279 if (StructType *STy = dyn_cast<StructType>(Ty)) {
1280 if (STy->isOpaque()) return true; // Can't say.
1282 // If all of elements have zero size, this does too.
1283 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i)
1284 if (!isMaybeZeroSizedType(STy->getElementType(i))) return false;
1287 } else if (ArrayType *ATy = dyn_cast<ArrayType>(Ty)) {
1288 return isMaybeZeroSizedType(ATy->getElementType());
1293 /// Compare the two constants as though they were getelementptr indices.
1294 /// This allows coercion of the types to be the same thing.
1296 /// If the two constants are the "same" (after coercion), return 0. If the
1297 /// first is less than the second, return -1, if the second is less than the
1298 /// first, return 1. If the constants are not integral, return -2.
1300 static int IdxCompare(Constant *C1, Constant *C2, Type *ElTy) {
1301 if (C1 == C2) return 0;
1303 // Ok, we found a different index. If they are not ConstantInt, we can't do
1304 // anything with them.
1305 if (!isa<ConstantInt>(C1) || !isa<ConstantInt>(C2))
1306 return -2; // don't know!
1308 // We cannot compare the indices if they don't fit in an int64_t.
1309 if (cast<ConstantInt>(C1)->getValue().getActiveBits() > 64 ||
1310 cast<ConstantInt>(C2)->getValue().getActiveBits() > 64)
1311 return -2; // don't know!
1313 // Ok, we have two differing integer indices. Sign extend them to be the same
1315 int64_t C1Val = cast<ConstantInt>(C1)->getSExtValue();
1316 int64_t C2Val = cast<ConstantInt>(C2)->getSExtValue();
1318 if (C1Val == C2Val) return 0; // They are equal
1320 // If the type being indexed over is really just a zero sized type, there is
1321 // no pointer difference being made here.
1322 if (isMaybeZeroSizedType(ElTy))
1323 return -2; // dunno.
1325 // If they are really different, now that they are the same type, then we
1326 // found a difference!
1333 /// This function determines if there is anything we can decide about the two
1334 /// constants provided. This doesn't need to handle simple things like
1335 /// ConstantFP comparisons, but should instead handle ConstantExprs.
1336 /// If we can determine that the two constants have a particular relation to
1337 /// each other, we should return the corresponding FCmpInst predicate,
1338 /// otherwise return FCmpInst::BAD_FCMP_PREDICATE. This is used below in
1339 /// ConstantFoldCompareInstruction.
1341 /// To simplify this code we canonicalize the relation so that the first
1342 /// operand is always the most "complex" of the two. We consider ConstantFP
1343 /// to be the simplest, and ConstantExprs to be the most complex.
1344 static FCmpInst::Predicate evaluateFCmpRelation(Constant *V1, Constant *V2) {
1345 assert(V1->getType() == V2->getType() &&
1346 "Cannot compare values of different types!");
1348 // Handle degenerate case quickly
1349 if (V1 == V2) return FCmpInst::FCMP_OEQ;
1351 if (!isa<ConstantExpr>(V1)) {
1352 if (!isa<ConstantExpr>(V2)) {
1353 // Simple case, use the standard constant folder.
1354 ConstantInt *R = nullptr;
1355 R = dyn_cast<ConstantInt>(
1356 ConstantExpr::getFCmp(FCmpInst::FCMP_OEQ, V1, V2));
1357 if (R && !R->isZero())
1358 return FCmpInst::FCMP_OEQ;
1359 R = dyn_cast<ConstantInt>(
1360 ConstantExpr::getFCmp(FCmpInst::FCMP_OLT, V1, V2));
1361 if (R && !R->isZero())
1362 return FCmpInst::FCMP_OLT;
1363 R = dyn_cast<ConstantInt>(
1364 ConstantExpr::getFCmp(FCmpInst::FCMP_OGT, V1, V2));
1365 if (R && !R->isZero())
1366 return FCmpInst::FCMP_OGT;
1368 // Nothing more we can do
1369 return FCmpInst::BAD_FCMP_PREDICATE;
1372 // If the first operand is simple and second is ConstantExpr, swap operands.
1373 FCmpInst::Predicate SwappedRelation = evaluateFCmpRelation(V2, V1);
1374 if (SwappedRelation != FCmpInst::BAD_FCMP_PREDICATE)
1375 return FCmpInst::getSwappedPredicate(SwappedRelation);
1377 // Ok, the LHS is known to be a constantexpr. The RHS can be any of a
1378 // constantexpr or a simple constant.
1379 ConstantExpr *CE1 = cast<ConstantExpr>(V1);
1380 switch (CE1->getOpcode()) {
1381 case Instruction::FPTrunc:
1382 case Instruction::FPExt:
1383 case Instruction::UIToFP:
1384 case Instruction::SIToFP:
1385 // We might be able to do something with these but we don't right now.
1391 // There are MANY other foldings that we could perform here. They will
1392 // probably be added on demand, as they seem needed.
1393 return FCmpInst::BAD_FCMP_PREDICATE;
1396 static ICmpInst::Predicate areGlobalsPotentiallyEqual(const GlobalValue *GV1,
1397 const GlobalValue *GV2) {
1398 auto isGlobalUnsafeForEquality = [](const GlobalValue *GV) {
1399 if (GV->hasExternalWeakLinkage() || GV->hasWeakAnyLinkage())
1401 if (const auto *GVar = dyn_cast<GlobalVariable>(GV)) {
1402 Type *Ty = GVar->getValueType();
1403 // A global with opaque type might end up being zero sized.
1406 // A global with an empty type might lie at the address of any other
1408 if (Ty->isEmptyTy())
1413 // Don't try to decide equality of aliases.
1414 if (!isa<GlobalAlias>(GV1) && !isa<GlobalAlias>(GV2))
1415 if (!isGlobalUnsafeForEquality(GV1) && !isGlobalUnsafeForEquality(GV2))
1416 return ICmpInst::ICMP_NE;
1417 return ICmpInst::BAD_ICMP_PREDICATE;
1420 /// This function determines if there is anything we can decide about the two
1421 /// constants provided. This doesn't need to handle simple things like integer
1422 /// comparisons, but should instead handle ConstantExprs and GlobalValues.
1423 /// If we can determine that the two constants have a particular relation to
1424 /// each other, we should return the corresponding ICmp predicate, otherwise
1425 /// return ICmpInst::BAD_ICMP_PREDICATE.
1427 /// To simplify this code we canonicalize the relation so that the first
1428 /// operand is always the most "complex" of the two. We consider simple
1429 /// constants (like ConstantInt) to be the simplest, followed by
1430 /// GlobalValues, followed by ConstantExpr's (the most complex).
1432 static ICmpInst::Predicate evaluateICmpRelation(Constant *V1, Constant *V2,
1434 assert(V1->getType() == V2->getType() &&
1435 "Cannot compare different types of values!");
1436 if (V1 == V2) return ICmpInst::ICMP_EQ;
1438 if (!isa<ConstantExpr>(V1) && !isa<GlobalValue>(V1) &&
1439 !isa<BlockAddress>(V1)) {
1440 if (!isa<GlobalValue>(V2) && !isa<ConstantExpr>(V2) &&
1441 !isa<BlockAddress>(V2)) {
1442 // We distilled this down to a simple case, use the standard constant
1444 ConstantInt *R = nullptr;
1445 ICmpInst::Predicate pred = ICmpInst::ICMP_EQ;
1446 R = dyn_cast<ConstantInt>(ConstantExpr::getICmp(pred, V1, V2));
1447 if (R && !R->isZero())
1449 pred = isSigned ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT;
1450 R = dyn_cast<ConstantInt>(ConstantExpr::getICmp(pred, V1, V2));
1451 if (R && !R->isZero())
1453 pred = isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT;
1454 R = dyn_cast<ConstantInt>(ConstantExpr::getICmp(pred, V1, V2));
1455 if (R && !R->isZero())
1458 // If we couldn't figure it out, bail.
1459 return ICmpInst::BAD_ICMP_PREDICATE;
1462 // If the first operand is simple, swap operands.
1463 ICmpInst::Predicate SwappedRelation =
1464 evaluateICmpRelation(V2, V1, isSigned);
1465 if (SwappedRelation != ICmpInst::BAD_ICMP_PREDICATE)
1466 return ICmpInst::getSwappedPredicate(SwappedRelation);
1468 } else if (const GlobalValue *GV = dyn_cast<GlobalValue>(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's a
1479 // ConstantPointerNull).
1480 if (const GlobalValue *GV2 = dyn_cast<GlobalValue>(V2)) {
1481 return areGlobalsPotentiallyEqual(GV, GV2);
1482 } else if (isa<BlockAddress>(V2)) {
1483 return ICmpInst::ICMP_NE; // Globals never equal labels.
1485 assert(isa<ConstantPointerNull>(V2) && "Canonicalization guarantee!");
1486 // GlobalVals can never be null unless they have external weak linkage.
1487 // We don't try to evaluate aliases here.
1488 if (!GV->hasExternalWeakLinkage() && !isa<GlobalAlias>(GV))
1489 return ICmpInst::ICMP_NE;
1491 } else if (const BlockAddress *BA = dyn_cast<BlockAddress>(V1)) {
1492 if (isa<ConstantExpr>(V2)) { // Swap as necessary.
1493 ICmpInst::Predicate SwappedRelation =
1494 evaluateICmpRelation(V2, V1, isSigned);
1495 if (SwappedRelation != ICmpInst::BAD_ICMP_PREDICATE)
1496 return ICmpInst::getSwappedPredicate(SwappedRelation);
1497 return ICmpInst::BAD_ICMP_PREDICATE;
1500 // Now we know that the RHS is a GlobalValue, BlockAddress or simple
1501 // constant (which, since the types must match, means that it is a
1502 // ConstantPointerNull).
1503 if (const BlockAddress *BA2 = dyn_cast<BlockAddress>(V2)) {
1504 // Block address in another function can't equal this one, but block
1505 // addresses in the current function might be the same if blocks are
1507 if (BA2->getFunction() != BA->getFunction())
1508 return ICmpInst::ICMP_NE;
1510 // Block addresses aren't null, don't equal the address of globals.
1511 assert((isa<ConstantPointerNull>(V2) || isa<GlobalValue>(V2)) &&
1512 "Canonicalization guarantee!");
1513 return ICmpInst::ICMP_NE;
1516 // Ok, the LHS is known to be a constantexpr. The RHS can be any of a
1517 // constantexpr, a global, block address, or a simple constant.
1518 ConstantExpr *CE1 = cast<ConstantExpr>(V1);
1519 Constant *CE1Op0 = CE1->getOperand(0);
1521 switch (CE1->getOpcode()) {
1522 case Instruction::Trunc:
1523 case Instruction::FPTrunc:
1524 case Instruction::FPExt:
1525 case Instruction::FPToUI:
1526 case Instruction::FPToSI:
1527 break; // We can't evaluate floating point casts or truncations.
1529 case Instruction::UIToFP:
1530 case Instruction::SIToFP:
1531 case Instruction::BitCast:
1532 case Instruction::ZExt:
1533 case Instruction::SExt:
1534 // We can't evaluate floating point casts or truncations.
1535 if (CE1Op0->getType()->isFloatingPointTy())
1538 // If the cast is not actually changing bits, and the second operand is a
1539 // null pointer, do the comparison with the pre-casted value.
1540 if (V2->isNullValue() &&
1541 (CE1->getType()->isPointerTy() || CE1->getType()->isIntegerTy())) {
1542 if (CE1->getOpcode() == Instruction::ZExt) isSigned = false;
1543 if (CE1->getOpcode() == Instruction::SExt) isSigned = true;
1544 return evaluateICmpRelation(CE1Op0,
1545 Constant::getNullValue(CE1Op0->getType()),
1550 case Instruction::GetElementPtr: {
1551 GEPOperator *CE1GEP = cast<GEPOperator>(CE1);
1552 // Ok, since this is a getelementptr, we know that the constant has a
1553 // pointer type. Check the various cases.
1554 if (isa<ConstantPointerNull>(V2)) {
1555 // If we are comparing a GEP to a null pointer, check to see if the base
1556 // of the GEP equals the null pointer.
1557 if (const GlobalValue *GV = dyn_cast<GlobalValue>(CE1Op0)) {
1558 if (GV->hasExternalWeakLinkage())
1559 // Weak linkage GVals could be zero or not. We're comparing that
1560 // to null pointer so its greater-or-equal
1561 return isSigned ? ICmpInst::ICMP_SGE : ICmpInst::ICMP_UGE;
1563 // If its not weak linkage, the GVal must have a non-zero address
1564 // so the result is greater-than
1565 return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT;
1566 } else if (isa<ConstantPointerNull>(CE1Op0)) {
1567 // If we are indexing from a null pointer, check to see if we have any
1568 // non-zero indices.
1569 for (unsigned i = 1, e = CE1->getNumOperands(); i != e; ++i)
1570 if (!CE1->getOperand(i)->isNullValue())
1571 // Offsetting from null, must not be equal.
1572 return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT;
1573 // Only zero indexes from null, must still be zero.
1574 return ICmpInst::ICMP_EQ;
1576 // Otherwise, we can't really say if the first operand is null or not.
1577 } else if (const GlobalValue *GV2 = dyn_cast<GlobalValue>(V2)) {
1578 if (isa<ConstantPointerNull>(CE1Op0)) {
1579 if (GV2->hasExternalWeakLinkage())
1580 // Weak linkage GVals could be zero or not. We're comparing it to
1581 // a null pointer, so its less-or-equal
1582 return isSigned ? ICmpInst::ICMP_SLE : ICmpInst::ICMP_ULE;
1584 // If its not weak linkage, the GVal must have a non-zero address
1585 // so the result is less-than
1586 return isSigned ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT;
1587 } else if (const GlobalValue *GV = dyn_cast<GlobalValue>(CE1Op0)) {
1589 // If this is a getelementptr of the same global, then it must be
1590 // different. Because the types must match, the getelementptr could
1591 // only have at most one index, and because we fold getelementptr's
1592 // with a single zero index, it must be nonzero.
1593 assert(CE1->getNumOperands() == 2 &&
1594 !CE1->getOperand(1)->isNullValue() &&
1595 "Surprising getelementptr!");
1596 return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT;
1598 if (CE1GEP->hasAllZeroIndices())
1599 return areGlobalsPotentiallyEqual(GV, GV2);
1600 return ICmpInst::BAD_ICMP_PREDICATE;
1604 ConstantExpr *CE2 = cast<ConstantExpr>(V2);
1605 Constant *CE2Op0 = CE2->getOperand(0);
1607 // There are MANY other foldings that we could perform here. They will
1608 // probably be added on demand, as they seem needed.
1609 switch (CE2->getOpcode()) {
1611 case Instruction::GetElementPtr:
1612 // By far the most common case to handle is when the base pointers are
1613 // obviously to the same global.
1614 if (isa<GlobalValue>(CE1Op0) && isa<GlobalValue>(CE2Op0)) {
1615 // Don't know relative ordering, but check for inequality.
1616 if (CE1Op0 != CE2Op0) {
1617 GEPOperator *CE2GEP = cast<GEPOperator>(CE2);
1618 if (CE1GEP->hasAllZeroIndices() && CE2GEP->hasAllZeroIndices())
1619 return areGlobalsPotentiallyEqual(cast<GlobalValue>(CE1Op0),
1620 cast<GlobalValue>(CE2Op0));
1621 return ICmpInst::BAD_ICMP_PREDICATE;
1623 // Ok, we know that both getelementptr instructions are based on the
1624 // same global. From this, we can precisely determine the relative
1625 // ordering of the resultant pointers.
1628 // The logic below assumes that the result of the comparison
1629 // can be determined by finding the first index that differs.
1630 // This doesn't work if there is over-indexing in any
1631 // subsequent indices, so check for that case first.
1632 if (!CE1->isGEPWithNoNotionalOverIndexing() ||
1633 !CE2->isGEPWithNoNotionalOverIndexing())
1634 return ICmpInst::BAD_ICMP_PREDICATE; // Might be equal.
1636 // Compare all of the operands the GEP's have in common.
1637 gep_type_iterator GTI = gep_type_begin(CE1);
1638 for (;i != CE1->getNumOperands() && i != CE2->getNumOperands();
1640 switch (IdxCompare(CE1->getOperand(i),
1641 CE2->getOperand(i), GTI.getIndexedType())) {
1642 case -1: return isSigned ? ICmpInst::ICMP_SLT:ICmpInst::ICMP_ULT;
1643 case 1: return isSigned ? ICmpInst::ICMP_SGT:ICmpInst::ICMP_UGT;
1644 case -2: return ICmpInst::BAD_ICMP_PREDICATE;
1647 // Ok, we ran out of things they have in common. If any leftovers
1648 // are non-zero then we have a difference, otherwise we are equal.
1649 for (; i < CE1->getNumOperands(); ++i)
1650 if (!CE1->getOperand(i)->isNullValue()) {
1651 if (isa<ConstantInt>(CE1->getOperand(i)))
1652 return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT;
1654 return ICmpInst::BAD_ICMP_PREDICATE; // Might be equal.
1657 for (; i < CE2->getNumOperands(); ++i)
1658 if (!CE2->getOperand(i)->isNullValue()) {
1659 if (isa<ConstantInt>(CE2->getOperand(i)))
1660 return isSigned ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT;
1662 return ICmpInst::BAD_ICMP_PREDICATE; // Might be equal.
1664 return ICmpInst::ICMP_EQ;
1674 return ICmpInst::BAD_ICMP_PREDICATE;
1677 Constant *llvm::ConstantFoldCompareInstruction(unsigned short pred,
1678 Constant *C1, Constant *C2) {
1680 if (VectorType *VT = dyn_cast<VectorType>(C1->getType()))
1681 ResultTy = VectorType::get(Type::getInt1Ty(C1->getContext()),
1682 VT->getNumElements());
1684 ResultTy = Type::getInt1Ty(C1->getContext());
1686 // Fold FCMP_FALSE/FCMP_TRUE unconditionally.
1687 if (pred == FCmpInst::FCMP_FALSE)
1688 return Constant::getNullValue(ResultTy);
1690 if (pred == FCmpInst::FCMP_TRUE)
1691 return Constant::getAllOnesValue(ResultTy);
1693 // Handle some degenerate cases first
1694 if (isa<UndefValue>(C1) || isa<UndefValue>(C2)) {
1695 CmpInst::Predicate Predicate = CmpInst::Predicate(pred);
1696 bool isIntegerPredicate = ICmpInst::isIntPredicate(Predicate);
1697 // For EQ and NE, we can always pick a value for the undef to make the
1698 // predicate pass or fail, so we can return undef.
1699 // Also, if both operands are undef, we can return undef for int comparison.
1700 if (ICmpInst::isEquality(Predicate) || (isIntegerPredicate && C1 == C2))
1701 return UndefValue::get(ResultTy);
1703 // Otherwise, for integer compare, pick the same value as the non-undef
1704 // operand, and fold it to true or false.
1705 if (isIntegerPredicate)
1706 return ConstantInt::get(ResultTy, CmpInst::isTrueWhenEqual(Predicate));
1708 // Choosing NaN for the undef will always make unordered comparison succeed
1709 // and ordered comparison fails.
1710 return ConstantInt::get(ResultTy, CmpInst::isUnordered(Predicate));
1713 // icmp eq/ne(null,GV) -> false/true
1714 if (C1->isNullValue()) {
1715 if (const GlobalValue *GV = dyn_cast<GlobalValue>(C2))
1716 // Don't try to evaluate aliases. External weak GV can be null.
1717 if (!isa<GlobalAlias>(GV) && !GV->hasExternalWeakLinkage()) {
1718 if (pred == ICmpInst::ICMP_EQ)
1719 return ConstantInt::getFalse(C1->getContext());
1720 else if (pred == ICmpInst::ICMP_NE)
1721 return ConstantInt::getTrue(C1->getContext());
1723 // icmp eq/ne(GV,null) -> false/true
1724 } else if (C2->isNullValue()) {
1725 if (const GlobalValue *GV = dyn_cast<GlobalValue>(C1))
1726 // Don't try to evaluate aliases. External weak GV can be null.
1727 if (!isa<GlobalAlias>(GV) && !GV->hasExternalWeakLinkage()) {
1728 if (pred == ICmpInst::ICMP_EQ)
1729 return ConstantInt::getFalse(C1->getContext());
1730 else if (pred == ICmpInst::ICMP_NE)
1731 return ConstantInt::getTrue(C1->getContext());
1735 // If the comparison is a comparison between two i1's, simplify it.
1736 if (C1->getType()->isIntegerTy(1)) {
1738 case ICmpInst::ICMP_EQ:
1739 if (isa<ConstantInt>(C2))
1740 return ConstantExpr::getXor(C1, ConstantExpr::getNot(C2));
1741 return ConstantExpr::getXor(ConstantExpr::getNot(C1), C2);
1742 case ICmpInst::ICMP_NE:
1743 return ConstantExpr::getXor(C1, C2);
1749 if (isa<ConstantInt>(C1) && isa<ConstantInt>(C2)) {
1750 const APInt &V1 = cast<ConstantInt>(C1)->getValue();
1751 const APInt &V2 = cast<ConstantInt>(C2)->getValue();
1753 default: llvm_unreachable("Invalid ICmp Predicate");
1754 case ICmpInst::ICMP_EQ: return ConstantInt::get(ResultTy, V1 == V2);
1755 case ICmpInst::ICMP_NE: return ConstantInt::get(ResultTy, V1 != V2);
1756 case ICmpInst::ICMP_SLT: return ConstantInt::get(ResultTy, V1.slt(V2));
1757 case ICmpInst::ICMP_SGT: return ConstantInt::get(ResultTy, V1.sgt(V2));
1758 case ICmpInst::ICMP_SLE: return ConstantInt::get(ResultTy, V1.sle(V2));
1759 case ICmpInst::ICMP_SGE: return ConstantInt::get(ResultTy, V1.sge(V2));
1760 case ICmpInst::ICMP_ULT: return ConstantInt::get(ResultTy, V1.ult(V2));
1761 case ICmpInst::ICMP_UGT: return ConstantInt::get(ResultTy, V1.ugt(V2));
1762 case ICmpInst::ICMP_ULE: return ConstantInt::get(ResultTy, V1.ule(V2));
1763 case ICmpInst::ICMP_UGE: return ConstantInt::get(ResultTy, V1.uge(V2));
1765 } else if (isa<ConstantFP>(C1) && isa<ConstantFP>(C2)) {
1766 const APFloat &C1V = cast<ConstantFP>(C1)->getValueAPF();
1767 const APFloat &C2V = cast<ConstantFP>(C2)->getValueAPF();
1768 APFloat::cmpResult R = C1V.compare(C2V);
1770 default: llvm_unreachable("Invalid FCmp Predicate");
1771 case FCmpInst::FCMP_FALSE: return Constant::getNullValue(ResultTy);
1772 case FCmpInst::FCMP_TRUE: return Constant::getAllOnesValue(ResultTy);
1773 case FCmpInst::FCMP_UNO:
1774 return ConstantInt::get(ResultTy, R==APFloat::cmpUnordered);
1775 case FCmpInst::FCMP_ORD:
1776 return ConstantInt::get(ResultTy, R!=APFloat::cmpUnordered);
1777 case FCmpInst::FCMP_UEQ:
1778 return ConstantInt::get(ResultTy, R==APFloat::cmpUnordered ||
1779 R==APFloat::cmpEqual);
1780 case FCmpInst::FCMP_OEQ:
1781 return ConstantInt::get(ResultTy, R==APFloat::cmpEqual);
1782 case FCmpInst::FCMP_UNE:
1783 return ConstantInt::get(ResultTy, R!=APFloat::cmpEqual);
1784 case FCmpInst::FCMP_ONE:
1785 return ConstantInt::get(ResultTy, R==APFloat::cmpLessThan ||
1786 R==APFloat::cmpGreaterThan);
1787 case FCmpInst::FCMP_ULT:
1788 return ConstantInt::get(ResultTy, R==APFloat::cmpUnordered ||
1789 R==APFloat::cmpLessThan);
1790 case FCmpInst::FCMP_OLT:
1791 return ConstantInt::get(ResultTy, R==APFloat::cmpLessThan);
1792 case FCmpInst::FCMP_UGT:
1793 return ConstantInt::get(ResultTy, R==APFloat::cmpUnordered ||
1794 R==APFloat::cmpGreaterThan);
1795 case FCmpInst::FCMP_OGT:
1796 return ConstantInt::get(ResultTy, R==APFloat::cmpGreaterThan);
1797 case FCmpInst::FCMP_ULE:
1798 return ConstantInt::get(ResultTy, R!=APFloat::cmpGreaterThan);
1799 case FCmpInst::FCMP_OLE:
1800 return ConstantInt::get(ResultTy, R==APFloat::cmpLessThan ||
1801 R==APFloat::cmpEqual);
1802 case FCmpInst::FCMP_UGE:
1803 return ConstantInt::get(ResultTy, R!=APFloat::cmpLessThan);
1804 case FCmpInst::FCMP_OGE:
1805 return ConstantInt::get(ResultTy, R==APFloat::cmpGreaterThan ||
1806 R==APFloat::cmpEqual);
1808 } else if (C1->getType()->isVectorTy()) {
1809 // If we can constant fold the comparison of each element, constant fold
1810 // the whole vector comparison.
1811 SmallVector<Constant*, 4> ResElts;
1812 Type *Ty = IntegerType::get(C1->getContext(), 32);
1813 // Compare the elements, producing an i1 result or constant expr.
1814 for (unsigned i = 0, e = C1->getType()->getVectorNumElements(); i != e;++i){
1816 ConstantExpr::getExtractElement(C1, ConstantInt::get(Ty, i));
1818 ConstantExpr::getExtractElement(C2, ConstantInt::get(Ty, i));
1820 ResElts.push_back(ConstantExpr::getCompare(pred, C1E, C2E));
1823 return ConstantVector::get(ResElts);
1826 if (C1->getType()->isFloatingPointTy() &&
1827 // Only call evaluateFCmpRelation if we have a constant expr to avoid
1828 // infinite recursive loop
1829 (isa<ConstantExpr>(C1) || isa<ConstantExpr>(C2))) {
1830 int Result = -1; // -1 = unknown, 0 = known false, 1 = known true.
1831 switch (evaluateFCmpRelation(C1, C2)) {
1832 default: llvm_unreachable("Unknown relation!");
1833 case FCmpInst::FCMP_UNO:
1834 case FCmpInst::FCMP_ORD:
1835 case FCmpInst::FCMP_UEQ:
1836 case FCmpInst::FCMP_UNE:
1837 case FCmpInst::FCMP_ULT:
1838 case FCmpInst::FCMP_UGT:
1839 case FCmpInst::FCMP_ULE:
1840 case FCmpInst::FCMP_UGE:
1841 case FCmpInst::FCMP_TRUE:
1842 case FCmpInst::FCMP_FALSE:
1843 case FCmpInst::BAD_FCMP_PREDICATE:
1844 break; // Couldn't determine anything about these constants.
1845 case FCmpInst::FCMP_OEQ: // We know that C1 == C2
1846 Result = (pred == FCmpInst::FCMP_UEQ || pred == FCmpInst::FCMP_OEQ ||
1847 pred == FCmpInst::FCMP_ULE || pred == FCmpInst::FCMP_OLE ||
1848 pred == FCmpInst::FCMP_UGE || pred == FCmpInst::FCMP_OGE);
1850 case FCmpInst::FCMP_OLT: // We know that C1 < C2
1851 Result = (pred == FCmpInst::FCMP_UNE || pred == FCmpInst::FCMP_ONE ||
1852 pred == FCmpInst::FCMP_ULT || pred == FCmpInst::FCMP_OLT ||
1853 pred == FCmpInst::FCMP_ULE || pred == FCmpInst::FCMP_OLE);
1855 case FCmpInst::FCMP_OGT: // We know that C1 > C2
1856 Result = (pred == FCmpInst::FCMP_UNE || pred == FCmpInst::FCMP_ONE ||
1857 pred == FCmpInst::FCMP_UGT || pred == FCmpInst::FCMP_OGT ||
1858 pred == FCmpInst::FCMP_UGE || pred == FCmpInst::FCMP_OGE);
1860 case FCmpInst::FCMP_OLE: // We know that C1 <= C2
1861 // We can only partially decide this relation.
1862 if (pred == FCmpInst::FCMP_UGT || pred == FCmpInst::FCMP_OGT)
1864 else if (pred == FCmpInst::FCMP_ULT || pred == FCmpInst::FCMP_OLT)
1867 case FCmpInst::FCMP_OGE: // We known that C1 >= C2
1868 // We can only partially decide this relation.
1869 if (pred == FCmpInst::FCMP_ULT || pred == FCmpInst::FCMP_OLT)
1871 else if (pred == FCmpInst::FCMP_UGT || pred == FCmpInst::FCMP_OGT)
1874 case FCmpInst::FCMP_ONE: // We know that C1 != C2
1875 // We can only partially decide this relation.
1876 if (pred == FCmpInst::FCMP_OEQ || pred == FCmpInst::FCMP_UEQ)
1878 else if (pred == FCmpInst::FCMP_ONE || pred == FCmpInst::FCMP_UNE)
1883 // If we evaluated the result, return it now.
1885 return ConstantInt::get(ResultTy, Result);
1888 // Evaluate the relation between the two constants, per the predicate.
1889 int Result = -1; // -1 = unknown, 0 = known false, 1 = known true.
1890 switch (evaluateICmpRelation(C1, C2,
1891 CmpInst::isSigned((CmpInst::Predicate)pred))) {
1892 default: llvm_unreachable("Unknown relational!");
1893 case ICmpInst::BAD_ICMP_PREDICATE:
1894 break; // Couldn't determine anything about these constants.
1895 case ICmpInst::ICMP_EQ: // We know the constants are equal!
1896 // If we know the constants are equal, we can decide the result of this
1897 // computation precisely.
1898 Result = ICmpInst::isTrueWhenEqual((ICmpInst::Predicate)pred);
1900 case ICmpInst::ICMP_ULT:
1902 case ICmpInst::ICMP_ULT: case ICmpInst::ICMP_NE: case ICmpInst::ICMP_ULE:
1904 case ICmpInst::ICMP_UGT: case ICmpInst::ICMP_EQ: case ICmpInst::ICMP_UGE:
1908 case ICmpInst::ICMP_SLT:
1910 case ICmpInst::ICMP_SLT: case ICmpInst::ICMP_NE: case ICmpInst::ICMP_SLE:
1912 case ICmpInst::ICMP_SGT: case ICmpInst::ICMP_EQ: case ICmpInst::ICMP_SGE:
1916 case ICmpInst::ICMP_UGT:
1918 case ICmpInst::ICMP_UGT: case ICmpInst::ICMP_NE: case ICmpInst::ICMP_UGE:
1920 case ICmpInst::ICMP_ULT: case ICmpInst::ICMP_EQ: case ICmpInst::ICMP_ULE:
1924 case ICmpInst::ICMP_SGT:
1926 case ICmpInst::ICMP_SGT: case ICmpInst::ICMP_NE: case ICmpInst::ICMP_SGE:
1928 case ICmpInst::ICMP_SLT: case ICmpInst::ICMP_EQ: case ICmpInst::ICMP_SLE:
1932 case ICmpInst::ICMP_ULE:
1933 if (pred == ICmpInst::ICMP_UGT) Result = 0;
1934 if (pred == ICmpInst::ICMP_ULT || pred == ICmpInst::ICMP_ULE) Result = 1;
1936 case ICmpInst::ICMP_SLE:
1937 if (pred == ICmpInst::ICMP_SGT) Result = 0;
1938 if (pred == ICmpInst::ICMP_SLT || pred == ICmpInst::ICMP_SLE) Result = 1;
1940 case ICmpInst::ICMP_UGE:
1941 if (pred == ICmpInst::ICMP_ULT) Result = 0;
1942 if (pred == ICmpInst::ICMP_UGT || pred == ICmpInst::ICMP_UGE) Result = 1;
1944 case ICmpInst::ICMP_SGE:
1945 if (pred == ICmpInst::ICMP_SLT) Result = 0;
1946 if (pred == ICmpInst::ICMP_SGT || pred == ICmpInst::ICMP_SGE) Result = 1;
1948 case ICmpInst::ICMP_NE:
1949 if (pred == ICmpInst::ICMP_EQ) Result = 0;
1950 if (pred == ICmpInst::ICMP_NE) Result = 1;
1954 // If we evaluated the result, return it now.
1956 return ConstantInt::get(ResultTy, Result);
1958 // If the right hand side is a bitcast, try using its inverse to simplify
1959 // it by moving it to the left hand side. We can't do this if it would turn
1960 // a vector compare into a scalar compare or visa versa.
1961 if (ConstantExpr *CE2 = dyn_cast<ConstantExpr>(C2)) {
1962 Constant *CE2Op0 = CE2->getOperand(0);
1963 if (CE2->getOpcode() == Instruction::BitCast &&
1964 CE2->getType()->isVectorTy() == CE2Op0->getType()->isVectorTy()) {
1965 Constant *Inverse = ConstantExpr::getBitCast(C1, CE2Op0->getType());
1966 return ConstantExpr::getICmp(pred, Inverse, CE2Op0);
1970 // If the left hand side is an extension, try eliminating it.
1971 if (ConstantExpr *CE1 = dyn_cast<ConstantExpr>(C1)) {
1972 if ((CE1->getOpcode() == Instruction::SExt &&
1973 ICmpInst::isSigned((ICmpInst::Predicate)pred)) ||
1974 (CE1->getOpcode() == Instruction::ZExt &&
1975 !ICmpInst::isSigned((ICmpInst::Predicate)pred))){
1976 Constant *CE1Op0 = CE1->getOperand(0);
1977 Constant *CE1Inverse = ConstantExpr::getTrunc(CE1, CE1Op0->getType());
1978 if (CE1Inverse == CE1Op0) {
1979 // Check whether we can safely truncate the right hand side.
1980 Constant *C2Inverse = ConstantExpr::getTrunc(C2, CE1Op0->getType());
1981 if (ConstantExpr::getCast(CE1->getOpcode(), C2Inverse,
1982 C2->getType()) == C2)
1983 return ConstantExpr::getICmp(pred, CE1Inverse, C2Inverse);
1988 if ((!isa<ConstantExpr>(C1) && isa<ConstantExpr>(C2)) ||
1989 (C1->isNullValue() && !C2->isNullValue())) {
1990 // If C2 is a constant expr and C1 isn't, flip them around and fold the
1991 // other way if possible.
1992 // Also, if C1 is null and C2 isn't, flip them around.
1993 pred = ICmpInst::getSwappedPredicate((ICmpInst::Predicate)pred);
1994 return ConstantExpr::getICmp(pred, C2, C1);
2000 /// Test whether the given sequence of *normalized* indices is "inbounds".
2001 template<typename IndexTy>
2002 static bool isInBoundsIndices(ArrayRef<IndexTy> Idxs) {
2003 // No indices means nothing that could be out of bounds.
2004 if (Idxs.empty()) return true;
2006 // If the first index is zero, it's in bounds.
2007 if (cast<Constant>(Idxs[0])->isNullValue()) return true;
2009 // If the first index is one and all the rest are zero, it's in bounds,
2010 // by the one-past-the-end rule.
2011 if (!cast<ConstantInt>(Idxs[0])->isOne())
2013 for (unsigned i = 1, e = Idxs.size(); i != e; ++i)
2014 if (!cast<Constant>(Idxs[i])->isNullValue())
2019 /// Test whether a given ConstantInt is in-range for a SequentialType.
2020 static bool isIndexInRangeOfArrayType(uint64_t NumElements,
2021 const ConstantInt *CI) {
2022 // We cannot bounds check the index if it doesn't fit in an int64_t.
2023 if (CI->getValue().getActiveBits() > 64)
2026 // A negative index or an index past the end of our sequential type is
2027 // considered out-of-range.
2028 int64_t IndexVal = CI->getSExtValue();
2029 if (IndexVal < 0 || (NumElements > 0 && (uint64_t)IndexVal >= NumElements))
2032 // Otherwise, it is in-range.
2036 Constant *llvm::ConstantFoldGetElementPtr(Type *PointeeTy, Constant *C,
2038 Optional<unsigned> InRangeIndex,
2039 ArrayRef<Value *> Idxs) {
2040 if (Idxs.empty()) return C;
2042 if (isa<UndefValue>(C)) {
2043 Type *GEPTy = GetElementPtrInst::getGEPReturnType(
2044 C, makeArrayRef((Value * const *)Idxs.data(), Idxs.size()));
2045 return UndefValue::get(GEPTy);
2048 Constant *Idx0 = cast<Constant>(Idxs[0]);
2049 if (Idxs.size() == 1 && (Idx0->isNullValue() || isa<UndefValue>(Idx0)))
2052 if (C->isNullValue()) {
2054 for (unsigned i = 0, e = Idxs.size(); i != e; ++i)
2055 if (!isa<UndefValue>(Idxs[i]) &&
2056 !cast<Constant>(Idxs[i])->isNullValue()) {
2061 PointerType *PtrTy = cast<PointerType>(C->getType()->getScalarType());
2062 Type *Ty = GetElementPtrInst::getIndexedType(PointeeTy, Idxs);
2064 assert(Ty && "Invalid indices for GEP!");
2065 Type *GEPTy = PointerType::get(Ty, PtrTy->getAddressSpace());
2066 if (VectorType *VT = dyn_cast<VectorType>(C->getType()))
2067 GEPTy = VectorType::get(GEPTy, VT->getNumElements());
2068 return Constant::getNullValue(GEPTy);
2072 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(C)) {
2073 // Combine Indices - If the source pointer to this getelementptr instruction
2074 // is a getelementptr instruction, combine the indices of the two
2075 // getelementptr instructions into a single instruction.
2077 if (CE->getOpcode() == Instruction::GetElementPtr) {
2078 gep_type_iterator LastI = gep_type_end(CE);
2079 for (gep_type_iterator I = gep_type_begin(CE), E = gep_type_end(CE);
2083 // We cannot combine indices if doing so would take us outside of an
2084 // array or vector. Doing otherwise could trick us if we evaluated such a
2085 // GEP as part of a load.
2087 // e.g. Consider if the original GEP was:
2088 // i8* getelementptr ({ [2 x i8], i32, i8, [3 x i8] }* @main.c,
2089 // i32 0, i32 0, i64 0)
2091 // If we then tried to offset it by '8' to get to the third element,
2092 // an i8, we should *not* get:
2093 // i8* getelementptr ({ [2 x i8], i32, i8, [3 x i8] }* @main.c,
2094 // i32 0, i32 0, i64 8)
2096 // This GEP tries to index array element '8 which runs out-of-bounds.
2097 // Subsequent evaluation would get confused and produce erroneous results.
2099 // The following prohibits such a GEP from being formed by checking to see
2100 // if the index is in-range with respect to an array.
2101 // TODO: This code may be extended to handle vectors as well.
2102 bool PerformFold = false;
2103 if (Idx0->isNullValue())
2105 else if (LastI.isSequential())
2106 if (ConstantInt *CI = dyn_cast<ConstantInt>(Idx0))
2107 PerformFold = (!LastI.isBoundedSequential() ||
2108 isIndexInRangeOfArrayType(
2109 LastI.getSequentialNumElements(), CI)) &&
2110 !CE->getOperand(CE->getNumOperands() - 1)
2115 SmallVector<Value*, 16> NewIndices;
2116 NewIndices.reserve(Idxs.size() + CE->getNumOperands());
2117 NewIndices.append(CE->op_begin() + 1, CE->op_end() - 1);
2119 // Add the last index of the source with the first index of the new GEP.
2120 // Make sure to handle the case when they are actually different types.
2121 Constant *Combined = CE->getOperand(CE->getNumOperands()-1);
2122 // Otherwise it must be an array.
2123 if (!Idx0->isNullValue()) {
2124 Type *IdxTy = Combined->getType();
2125 if (IdxTy != Idx0->getType()) {
2126 unsigned CommonExtendedWidth =
2127 std::max(IdxTy->getIntegerBitWidth(),
2128 Idx0->getType()->getIntegerBitWidth());
2129 CommonExtendedWidth = std::max(CommonExtendedWidth, 64U);
2132 Type::getIntNTy(IdxTy->getContext(), CommonExtendedWidth);
2133 Constant *C1 = ConstantExpr::getSExtOrBitCast(Idx0, CommonTy);
2134 Constant *C2 = ConstantExpr::getSExtOrBitCast(Combined, CommonTy);
2135 Combined = ConstantExpr::get(Instruction::Add, C1, C2);
2138 ConstantExpr::get(Instruction::Add, Idx0, Combined);
2142 NewIndices.push_back(Combined);
2143 NewIndices.append(Idxs.begin() + 1, Idxs.end());
2145 // The combined GEP normally inherits its index inrange attribute from
2146 // the inner GEP, but if the inner GEP's last index was adjusted by the
2147 // outer GEP, any inbounds attribute on that index is invalidated.
2148 Optional<unsigned> IRIndex = cast<GEPOperator>(CE)->getInRangeIndex();
2149 if (IRIndex && *IRIndex == CE->getNumOperands() - 2 && !Idx0->isNullValue())
2152 return ConstantExpr::getGetElementPtr(
2153 cast<GEPOperator>(CE)->getSourceElementType(), CE->getOperand(0),
2154 NewIndices, InBounds && cast<GEPOperator>(CE)->isInBounds(),
2159 // Attempt to fold casts to the same type away. For example, folding:
2161 // i32* getelementptr ([2 x i32]* bitcast ([3 x i32]* %X to [2 x i32]*),
2165 // i32* getelementptr ([3 x i32]* %X, i64 0, i64 0)
2167 // Don't fold if the cast is changing address spaces.
2168 if (CE->isCast() && Idxs.size() > 1 && Idx0->isNullValue()) {
2169 PointerType *SrcPtrTy =
2170 dyn_cast<PointerType>(CE->getOperand(0)->getType());
2171 PointerType *DstPtrTy = dyn_cast<PointerType>(CE->getType());
2172 if (SrcPtrTy && DstPtrTy) {
2173 ArrayType *SrcArrayTy =
2174 dyn_cast<ArrayType>(SrcPtrTy->getElementType());
2175 ArrayType *DstArrayTy =
2176 dyn_cast<ArrayType>(DstPtrTy->getElementType());
2177 if (SrcArrayTy && DstArrayTy
2178 && SrcArrayTy->getElementType() == DstArrayTy->getElementType()
2179 && SrcPtrTy->getAddressSpace() == DstPtrTy->getAddressSpace())
2180 return ConstantExpr::getGetElementPtr(SrcArrayTy,
2181 (Constant *)CE->getOperand(0),
2182 Idxs, InBounds, InRangeIndex);
2187 // Check to see if any array indices are not within the corresponding
2188 // notional array or vector bounds. If so, try to determine if they can be
2189 // factored out into preceding dimensions.
2190 SmallVector<Constant *, 8> NewIdxs;
2191 Type *Ty = PointeeTy;
2192 Type *Prev = C->getType();
2193 bool Unknown = !isa<ConstantInt>(Idxs[0]);
2194 for (unsigned i = 1, e = Idxs.size(); i != e;
2195 Prev = Ty, Ty = cast<CompositeType>(Ty)->getTypeAtIndex(Idxs[i]), ++i) {
2196 auto *CI = dyn_cast<ConstantInt>(Idxs[i]);
2198 // We don't know if it's in range or not.
2202 if (InRangeIndex && i == *InRangeIndex + 1) {
2203 // If an index is marked inrange, we cannot apply this canonicalization to
2204 // the following index, as that will cause the inrange index to point to
2205 // the wrong element.
2208 if (isa<StructType>(Ty)) {
2209 // The verify makes sure that GEPs into a struct are in range.
2212 auto *STy = cast<SequentialType>(Ty);
2213 if (isa<VectorType>(STy)) {
2214 // There can be awkward padding in after a non-power of two vector.
2218 if (isIndexInRangeOfArrayType(STy->getNumElements(), CI))
2219 // It's in range, skip to the next index.
2221 if (isa<StructType>(Prev)) {
2222 // It's out of range, but the prior dimension is a struct
2223 // so we can't do anything about it.
2227 if (CI->getSExtValue() < 0) {
2228 // It's out of range and negative, don't try to factor it.
2232 // It's out of range, but we can factor it into the prior
2234 NewIdxs.resize(Idxs.size());
2235 // Determine the number of elements in our sequential type.
2236 uint64_t NumElements = STy->getArrayNumElements();
2238 ConstantInt *Factor = ConstantInt::get(CI->getType(), NumElements);
2239 NewIdxs[i] = ConstantExpr::getSRem(CI, Factor);
2241 Constant *PrevIdx = NewIdxs[i-1] ? NewIdxs[i-1] :
2242 cast<Constant>(Idxs[i - 1]);
2243 Constant *Div = ConstantExpr::getSDiv(CI, Factor);
2245 unsigned CommonExtendedWidth =
2246 std::max(PrevIdx->getType()->getIntegerBitWidth(),
2247 Div->getType()->getIntegerBitWidth());
2248 CommonExtendedWidth = std::max(CommonExtendedWidth, 64U);
2250 // Before adding, extend both operands to i64 to avoid
2251 // overflow trouble.
2252 if (!PrevIdx->getType()->isIntegerTy(CommonExtendedWidth))
2253 PrevIdx = ConstantExpr::getSExt(
2254 PrevIdx, Type::getIntNTy(Div->getContext(), CommonExtendedWidth));
2255 if (!Div->getType()->isIntegerTy(CommonExtendedWidth))
2256 Div = ConstantExpr::getSExt(
2257 Div, Type::getIntNTy(Div->getContext(), CommonExtendedWidth));
2259 NewIdxs[i - 1] = ConstantExpr::getAdd(PrevIdx, Div);
2262 // If we did any factoring, start over with the adjusted indices.
2263 if (!NewIdxs.empty()) {
2264 for (unsigned i = 0, e = Idxs.size(); i != e; ++i)
2265 if (!NewIdxs[i]) NewIdxs[i] = cast<Constant>(Idxs[i]);
2266 return ConstantExpr::getGetElementPtr(PointeeTy, C, NewIdxs, InBounds,
2270 // If all indices are known integers and normalized, we can do a simple
2271 // check for the "inbounds" property.
2272 if (!Unknown && !InBounds)
2273 if (auto *GV = dyn_cast<GlobalVariable>(C))
2274 if (!GV->hasExternalWeakLinkage() && isInBoundsIndices(Idxs))
2275 return ConstantExpr::getGetElementPtr(PointeeTy, C, Idxs,
2276 /*InBounds=*/true, InRangeIndex);