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/ErrorHandling.h"
32 #include "llvm/Support/ManagedStatic.h"
33 #include "llvm/Support/MathExtras.h"
35 using namespace llvm::PatternMatch;
37 //===----------------------------------------------------------------------===//
38 // ConstantFold*Instruction Implementations
39 //===----------------------------------------------------------------------===//
41 /// Convert the specified vector Constant node to the specified vector type.
42 /// At this point, we know that the elements of the input vector constant are
43 /// all simple integer or FP values.
44 static Constant *BitCastConstantVector(Constant *CV, VectorType *DstTy) {
46 if (CV->isAllOnesValue()) return Constant::getAllOnesValue(DstTy);
47 if (CV->isNullValue()) return Constant::getNullValue(DstTy);
49 // If this cast changes element count then we can't handle it here:
50 // doing so requires endianness information. This should be handled by
51 // Analysis/ConstantFolding.cpp
52 unsigned NumElts = DstTy->getNumElements();
53 if (NumElts != CV->getType()->getVectorNumElements())
56 Type *DstEltTy = DstTy->getElementType();
58 SmallVector<Constant*, 16> Result;
59 Type *Ty = IntegerType::get(CV->getContext(), 32);
60 for (unsigned i = 0; i != NumElts; ++i) {
62 ConstantExpr::getExtractElement(CV, ConstantInt::get(Ty, i));
63 C = ConstantExpr::getBitCast(C, DstEltTy);
67 return ConstantVector::get(Result);
70 /// This function determines which opcode to use to fold two constant cast
71 /// expressions together. It uses CastInst::isEliminableCastPair to determine
72 /// the opcode. Consequently its just a wrapper around that function.
73 /// @brief Determine if it is valid to fold a cast of a cast
76 unsigned opc, ///< opcode of the second cast constant expression
77 ConstantExpr *Op, ///< the first cast constant expression
78 Type *DstTy ///< destination type of the first cast
80 assert(Op && Op->isCast() && "Can't fold cast of cast without a cast!");
81 assert(DstTy && DstTy->isFirstClassType() && "Invalid cast destination type");
82 assert(CastInst::isCast(opc) && "Invalid cast opcode");
84 // The types and opcodes for the two Cast constant expressions
85 Type *SrcTy = Op->getOperand(0)->getType();
86 Type *MidTy = Op->getType();
87 Instruction::CastOps firstOp = Instruction::CastOps(Op->getOpcode());
88 Instruction::CastOps secondOp = Instruction::CastOps(opc);
90 // Assume that pointers are never more than 64 bits wide, and only use this
91 // for the middle type. Otherwise we could end up folding away illegal
92 // bitcasts between address spaces with different sizes.
93 IntegerType *FakeIntPtrTy = Type::getInt64Ty(DstTy->getContext());
95 // Let CastInst::isEliminableCastPair do the heavy lifting.
96 return CastInst::isEliminableCastPair(firstOp, secondOp, SrcTy, MidTy, DstTy,
97 nullptr, FakeIntPtrTy, nullptr);
100 static Constant *FoldBitCast(Constant *V, Type *DestTy) {
101 Type *SrcTy = V->getType();
103 return V; // no-op cast
105 // Check to see if we are casting a pointer to an aggregate to a pointer to
106 // the first element. If so, return the appropriate GEP instruction.
107 if (PointerType *PTy = dyn_cast<PointerType>(V->getType()))
108 if (PointerType *DPTy = dyn_cast<PointerType>(DestTy))
109 if (PTy->getAddressSpace() == DPTy->getAddressSpace()
110 && PTy->getElementType()->isSized()) {
111 SmallVector<Value*, 8> IdxList;
113 Constant::getNullValue(Type::getInt32Ty(DPTy->getContext()));
114 IdxList.push_back(Zero);
115 Type *ElTy = PTy->getElementType();
116 while (ElTy != DPTy->getElementType()) {
117 if (StructType *STy = dyn_cast<StructType>(ElTy)) {
118 if (STy->getNumElements() == 0) break;
119 ElTy = STy->getElementType(0);
120 IdxList.push_back(Zero);
121 } else if (SequentialType *STy =
122 dyn_cast<SequentialType>(ElTy)) {
123 ElTy = STy->getElementType();
124 IdxList.push_back(Zero);
130 if (ElTy == DPTy->getElementType())
131 // This GEP is inbounds because all indices are zero.
132 return ConstantExpr::getInBoundsGetElementPtr(PTy->getElementType(),
136 // Handle casts from one vector constant to another. We know that the src
137 // and dest type have the same size (otherwise its an illegal cast).
138 if (VectorType *DestPTy = dyn_cast<VectorType>(DestTy)) {
139 if (VectorType *SrcTy = dyn_cast<VectorType>(V->getType())) {
140 assert(DestPTy->getBitWidth() == SrcTy->getBitWidth() &&
141 "Not cast between same sized vectors!");
143 // First, check for null. Undef is already handled.
144 if (isa<ConstantAggregateZero>(V))
145 return Constant::getNullValue(DestTy);
147 // Handle ConstantVector and ConstantAggregateVector.
148 return BitCastConstantVector(V, DestPTy);
151 // Canonicalize scalar-to-vector bitcasts into vector-to-vector bitcasts
152 // This allows for other simplifications (although some of them
153 // can only be handled by Analysis/ConstantFolding.cpp).
154 if (isa<ConstantInt>(V) || isa<ConstantFP>(V))
155 return ConstantExpr::getBitCast(ConstantVector::get(V), DestPTy);
158 // Finally, implement bitcast folding now. The code below doesn't handle
160 if (isa<ConstantPointerNull>(V)) // ptr->ptr cast.
161 return ConstantPointerNull::get(cast<PointerType>(DestTy));
163 // Handle integral constant input.
164 if (ConstantInt *CI = dyn_cast<ConstantInt>(V)) {
165 if (DestTy->isIntegerTy())
166 // Integral -> Integral. This is a no-op because the bit widths must
167 // be the same. Consequently, we just fold to V.
170 // See note below regarding the PPC_FP128 restriction.
171 if (DestTy->isFloatingPointTy() && !DestTy->isPPC_FP128Ty())
172 return ConstantFP::get(DestTy->getContext(),
173 APFloat(DestTy->getFltSemantics(),
176 // Otherwise, can't fold this (vector?)
180 // Handle ConstantFP input: FP -> Integral.
181 if (ConstantFP *FP = dyn_cast<ConstantFP>(V)) {
182 // PPC_FP128 is really the sum of two consecutive doubles, where the first
183 // double is always stored first in memory, regardless of the target
184 // endianness. The memory layout of i128, however, depends on the target
185 // endianness, and so we can't fold this without target endianness
186 // information. This should instead be handled by
187 // Analysis/ConstantFolding.cpp
188 if (FP->getType()->isPPC_FP128Ty())
191 // Make sure dest type is compatible with the folded integer constant.
192 if (!DestTy->isIntegerTy())
195 return ConstantInt::get(FP->getContext(),
196 FP->getValueAPF().bitcastToAPInt());
203 /// V is an integer constant which only has a subset of its bytes used.
204 /// The bytes used are indicated by ByteStart (which is the first byte used,
205 /// counting from the least significant byte) and ByteSize, which is the number
208 /// This function analyzes the specified constant to see if the specified byte
209 /// range can be returned as a simplified constant. If so, the constant is
210 /// returned, otherwise null is returned.
211 static Constant *ExtractConstantBytes(Constant *C, unsigned ByteStart,
213 assert(C->getType()->isIntegerTy() &&
214 (cast<IntegerType>(C->getType())->getBitWidth() & 7) == 0 &&
215 "Non-byte sized integer input");
216 unsigned CSize = cast<IntegerType>(C->getType())->getBitWidth()/8;
217 assert(ByteSize && "Must be accessing some piece");
218 assert(ByteStart+ByteSize <= CSize && "Extracting invalid piece from input");
219 assert(ByteSize != CSize && "Should not extract everything");
221 // Constant Integers are simple.
222 if (ConstantInt *CI = dyn_cast<ConstantInt>(C)) {
223 APInt V = CI->getValue();
225 V = V.lshr(ByteStart*8);
226 V = V.trunc(ByteSize*8);
227 return ConstantInt::get(CI->getContext(), V);
230 // In the input is a constant expr, we might be able to recursively simplify.
231 // If not, we definitely can't do anything.
232 ConstantExpr *CE = dyn_cast<ConstantExpr>(C);
233 if (!CE) return nullptr;
235 switch (CE->getOpcode()) {
236 default: return nullptr;
237 case Instruction::Or: {
238 Constant *RHS = ExtractConstantBytes(CE->getOperand(1), ByteStart,ByteSize);
243 if (ConstantInt *RHSC = dyn_cast<ConstantInt>(RHS))
244 if (RHSC->isAllOnesValue())
247 Constant *LHS = ExtractConstantBytes(CE->getOperand(0), ByteStart,ByteSize);
250 return ConstantExpr::getOr(LHS, RHS);
252 case Instruction::And: {
253 Constant *RHS = ExtractConstantBytes(CE->getOperand(1), ByteStart,ByteSize);
258 if (RHS->isNullValue())
261 Constant *LHS = ExtractConstantBytes(CE->getOperand(0), ByteStart,ByteSize);
264 return ConstantExpr::getAnd(LHS, RHS);
266 case Instruction::LShr: {
267 ConstantInt *Amt = dyn_cast<ConstantInt>(CE->getOperand(1));
270 unsigned ShAmt = Amt->getZExtValue();
271 // Cannot analyze non-byte shifts.
272 if ((ShAmt & 7) != 0)
276 // If the extract is known to be all zeros, return zero.
277 if (ByteStart >= CSize-ShAmt)
278 return Constant::getNullValue(IntegerType::get(CE->getContext(),
280 // If the extract is known to be fully in the input, extract it.
281 if (ByteStart+ByteSize+ShAmt <= CSize)
282 return ExtractConstantBytes(CE->getOperand(0), ByteStart+ShAmt, ByteSize);
284 // TODO: Handle the 'partially zero' case.
288 case Instruction::Shl: {
289 ConstantInt *Amt = dyn_cast<ConstantInt>(CE->getOperand(1));
292 unsigned ShAmt = Amt->getZExtValue();
293 // Cannot analyze non-byte shifts.
294 if ((ShAmt & 7) != 0)
298 // If the extract is known to be all zeros, return zero.
299 if (ByteStart+ByteSize <= ShAmt)
300 return Constant::getNullValue(IntegerType::get(CE->getContext(),
302 // If the extract is known to be fully in the input, extract it.
303 if (ByteStart >= ShAmt)
304 return ExtractConstantBytes(CE->getOperand(0), ByteStart-ShAmt, ByteSize);
306 // TODO: Handle the 'partially zero' case.
310 case Instruction::ZExt: {
311 unsigned SrcBitSize =
312 cast<IntegerType>(CE->getOperand(0)->getType())->getBitWidth();
314 // If extracting something that is completely zero, return 0.
315 if (ByteStart*8 >= SrcBitSize)
316 return Constant::getNullValue(IntegerType::get(CE->getContext(),
319 // If exactly extracting the input, return it.
320 if (ByteStart == 0 && ByteSize*8 == SrcBitSize)
321 return CE->getOperand(0);
323 // If extracting something completely in the input, if if the input is a
324 // multiple of 8 bits, recurse.
325 if ((SrcBitSize&7) == 0 && (ByteStart+ByteSize)*8 <= SrcBitSize)
326 return ExtractConstantBytes(CE->getOperand(0), ByteStart, ByteSize);
328 // Otherwise, if extracting a subset of the input, which is not multiple of
329 // 8 bits, do a shift and trunc to get the bits.
330 if ((ByteStart+ByteSize)*8 < SrcBitSize) {
331 assert((SrcBitSize&7) && "Shouldn't get byte sized case here");
332 Constant *Res = CE->getOperand(0);
334 Res = ConstantExpr::getLShr(Res,
335 ConstantInt::get(Res->getType(), ByteStart*8));
336 return ConstantExpr::getTrunc(Res, IntegerType::get(C->getContext(),
340 // TODO: Handle the 'partially zero' case.
346 /// Return a ConstantExpr with type DestTy for sizeof on Ty, with any known
347 /// factors factored out. If Folded is false, return null if no factoring was
348 /// possible, to avoid endlessly bouncing an unfoldable expression back into the
349 /// top-level folder.
350 static Constant *getFoldedSizeOf(Type *Ty, Type *DestTy,
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,
408 // The alignment of an array is equal to the alignment of the
409 // array element. Note that this is not always true for vectors.
410 if (ArrayType *ATy = dyn_cast<ArrayType>(Ty)) {
411 Constant *C = ConstantExpr::getAlignOf(ATy->getElementType());
412 C = ConstantExpr::getCast(CastInst::getCastOpcode(C, false,
419 if (StructType *STy = dyn_cast<StructType>(Ty)) {
420 // Packed structs always have an alignment of 1.
422 return ConstantInt::get(DestTy, 1);
424 // Otherwise, struct alignment is the maximum alignment of any member.
425 // Without target data, we can't compare much, but we can check to see
426 // if all the members have the same alignment.
427 unsigned NumElems = STy->getNumElements();
428 // An empty struct has minimal alignment.
430 return ConstantInt::get(DestTy, 1);
431 // Check for a struct with all members having the same alignment.
432 Constant *MemberAlign =
433 getFoldedAlignOf(STy->getElementType(0), DestTy, true);
435 for (unsigned i = 1; i != NumElems; ++i)
436 if (MemberAlign != getFoldedAlignOf(STy->getElementType(i), DestTy, true)) {
444 // Pointer alignment doesn't depend on the pointee type, so canonicalize them
445 // to an arbitrary pointee.
446 if (PointerType *PTy = dyn_cast<PointerType>(Ty))
447 if (!PTy->getElementType()->isIntegerTy(1))
449 getFoldedAlignOf(PointerType::get(IntegerType::get(PTy->getContext(),
451 PTy->getAddressSpace()),
454 // If there's no interesting folding happening, bail so that we don't create
455 // a constant that looks like it needs folding but really doesn't.
459 // Base case: Get a regular alignof expression.
460 Constant *C = ConstantExpr::getAlignOf(Ty);
461 C = ConstantExpr::getCast(CastInst::getCastOpcode(C, false,
467 /// Return a ConstantExpr with type DestTy for offsetof on Ty and FieldNo, with
468 /// any known factors factored out. If Folded is false, return null if no
469 /// factoring was possible, to avoid endlessly bouncing an unfoldable expression
470 /// back into the top-level folder.
471 static Constant *getFoldedOffsetOf(Type *Ty, Constant *FieldNo,
474 if (ArrayType *ATy = dyn_cast<ArrayType>(Ty)) {
475 Constant *N = ConstantExpr::getCast(CastInst::getCastOpcode(FieldNo, false,
478 Constant *E = getFoldedSizeOf(ATy->getElementType(), DestTy, true);
479 return ConstantExpr::getNUWMul(E, N);
482 if (StructType *STy = dyn_cast<StructType>(Ty))
483 if (!STy->isPacked()) {
484 unsigned NumElems = STy->getNumElements();
485 // An empty struct has no members.
488 // Check for a struct with all members having the same size.
489 Constant *MemberSize =
490 getFoldedSizeOf(STy->getElementType(0), DestTy, true);
492 for (unsigned i = 1; i != NumElems; ++i)
494 getFoldedSizeOf(STy->getElementType(i), DestTy, true)) {
499 Constant *N = ConstantExpr::getCast(CastInst::getCastOpcode(FieldNo,
504 return ConstantExpr::getNUWMul(MemberSize, N);
508 // If there's no interesting folding happening, bail so that we don't create
509 // a constant that looks like it needs folding but really doesn't.
513 // Base case: Get a regular offsetof expression.
514 Constant *C = ConstantExpr::getOffsetOf(Ty, FieldNo);
515 C = ConstantExpr::getCast(CastInst::getCastOpcode(C, false,
521 Constant *llvm::ConstantFoldCastInstruction(unsigned opc, Constant *V,
523 if (isa<UndefValue>(V)) {
524 // zext(undef) = 0, because the top bits will be zero.
525 // sext(undef) = 0, because the top bits will all be the same.
526 // [us]itofp(undef) = 0, because the result value is bounded.
527 if (opc == Instruction::ZExt || opc == Instruction::SExt ||
528 opc == Instruction::UIToFP || opc == Instruction::SIToFP)
529 return Constant::getNullValue(DestTy);
530 return UndefValue::get(DestTy);
533 if (V->isNullValue() && !DestTy->isX86_MMXTy() &&
534 opc != Instruction::AddrSpaceCast)
535 return Constant::getNullValue(DestTy);
537 // If the cast operand is a constant expression, there's a few things we can
538 // do to try to simplify it.
539 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V)) {
541 // Try hard to fold cast of cast because they are often eliminable.
542 if (unsigned newOpc = foldConstantCastPair(opc, CE, DestTy))
543 return ConstantExpr::getCast(newOpc, CE->getOperand(0), DestTy);
544 } else if (CE->getOpcode() == Instruction::GetElementPtr &&
545 // Do not fold addrspacecast (gep 0, .., 0). It might make the
546 // addrspacecast uncanonicalized.
547 opc != Instruction::AddrSpaceCast &&
548 // Do not fold bitcast (gep) with inrange index, as this loses
550 !cast<GEPOperator>(CE)->getInRangeIndex().hasValue()) {
551 // If all of the indexes in the GEP are null values, there is no pointer
552 // adjustment going on. We might as well cast the source pointer.
553 bool isAllNull = true;
554 for (unsigned i = 1, e = CE->getNumOperands(); i != e; ++i)
555 if (!CE->getOperand(i)->isNullValue()) {
560 // This is casting one pointer type to another, always BitCast
561 return ConstantExpr::getPointerCast(CE->getOperand(0), DestTy);
565 // If the cast operand is a constant vector, perform the cast by
566 // operating on each element. In the cast of bitcasts, the element
567 // count may be mismatched; don't attempt to handle that here.
568 if ((isa<ConstantVector>(V) || isa<ConstantDataVector>(V)) &&
569 DestTy->isVectorTy() &&
570 DestTy->getVectorNumElements() == V->getType()->getVectorNumElements()) {
571 SmallVector<Constant*, 16> res;
572 VectorType *DestVecTy = cast<VectorType>(DestTy);
573 Type *DstEltTy = DestVecTy->getElementType();
574 Type *Ty = IntegerType::get(V->getContext(), 32);
575 for (unsigned i = 0, e = V->getType()->getVectorNumElements(); i != e; ++i) {
577 ConstantExpr::getExtractElement(V, ConstantInt::get(Ty, i));
578 res.push_back(ConstantExpr::getCast(opc, C, DstEltTy));
580 return ConstantVector::get(res);
583 // We actually have to do a cast now. Perform the cast according to the
587 llvm_unreachable("Failed to cast constant expression");
588 case Instruction::FPTrunc:
589 case Instruction::FPExt:
590 if (ConstantFP *FPC = dyn_cast<ConstantFP>(V)) {
592 APFloat Val = FPC->getValueAPF();
593 Val.convert(DestTy->isHalfTy() ? APFloat::IEEEhalf() :
594 DestTy->isFloatTy() ? APFloat::IEEEsingle() :
595 DestTy->isDoubleTy() ? APFloat::IEEEdouble() :
596 DestTy->isX86_FP80Ty() ? APFloat::x87DoubleExtended() :
597 DestTy->isFP128Ty() ? APFloat::IEEEquad() :
598 DestTy->isPPC_FP128Ty() ? APFloat::PPCDoubleDouble() :
600 APFloat::rmNearestTiesToEven, &ignored);
601 return ConstantFP::get(V->getContext(), Val);
603 return nullptr; // Can't fold.
604 case Instruction::FPToUI:
605 case Instruction::FPToSI:
606 if (ConstantFP *FPC = dyn_cast<ConstantFP>(V)) {
607 const APFloat &V = FPC->getValueAPF();
610 uint32_t DestBitWidth = cast<IntegerType>(DestTy)->getBitWidth();
611 if (APFloat::opInvalidOp ==
612 V.convertToInteger(x, DestBitWidth, opc==Instruction::FPToSI,
613 APFloat::rmTowardZero, &ignored)) {
614 // Undefined behavior invoked - the destination type can't represent
615 // the input constant.
616 return UndefValue::get(DestTy);
618 APInt Val(DestBitWidth, x);
619 return ConstantInt::get(FPC->getContext(), Val);
621 return nullptr; // Can't fold.
622 case Instruction::IntToPtr: //always treated as unsigned
623 if (V->isNullValue()) // Is it an integral null value?
624 return ConstantPointerNull::get(cast<PointerType>(DestTy));
625 return nullptr; // Other pointer types cannot be casted
626 case Instruction::PtrToInt: // always treated as unsigned
627 // Is it a null pointer value?
628 if (V->isNullValue())
629 return ConstantInt::get(DestTy, 0);
630 // If this is a sizeof-like expression, pull out multiplications by
631 // known factors to expose them to subsequent folding. If it's an
632 // alignof-like expression, factor out known factors.
633 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V))
634 if (CE->getOpcode() == Instruction::GetElementPtr &&
635 CE->getOperand(0)->isNullValue()) {
636 GEPOperator *GEPO = cast<GEPOperator>(CE);
637 Type *Ty = GEPO->getSourceElementType();
638 if (CE->getNumOperands() == 2) {
639 // Handle a sizeof-like expression.
640 Constant *Idx = CE->getOperand(1);
641 bool isOne = isa<ConstantInt>(Idx) && cast<ConstantInt>(Idx)->isOne();
642 if (Constant *C = getFoldedSizeOf(Ty, DestTy, !isOne)) {
643 Idx = ConstantExpr::getCast(CastInst::getCastOpcode(Idx, true,
646 return ConstantExpr::getMul(C, Idx);
648 } else if (CE->getNumOperands() == 3 &&
649 CE->getOperand(1)->isNullValue()) {
650 // Handle an alignof-like expression.
651 if (StructType *STy = dyn_cast<StructType>(Ty))
652 if (!STy->isPacked()) {
653 ConstantInt *CI = cast<ConstantInt>(CE->getOperand(2));
655 STy->getNumElements() == 2 &&
656 STy->getElementType(0)->isIntegerTy(1)) {
657 return getFoldedAlignOf(STy->getElementType(1), DestTy, false);
660 // Handle an offsetof-like expression.
661 if (Ty->isStructTy() || Ty->isArrayTy()) {
662 if (Constant *C = getFoldedOffsetOf(Ty, CE->getOperand(2),
668 // Other pointer types cannot be casted
670 case Instruction::UIToFP:
671 case Instruction::SIToFP:
672 if (ConstantInt *CI = dyn_cast<ConstantInt>(V)) {
673 const APInt &api = CI->getValue();
674 APFloat apf(DestTy->getFltSemantics(),
675 APInt::getNullValue(DestTy->getPrimitiveSizeInBits()));
676 if (APFloat::opOverflow &
677 apf.convertFromAPInt(api, opc==Instruction::SIToFP,
678 APFloat::rmNearestTiesToEven)) {
679 // Undefined behavior invoked - the destination type can't represent
680 // the input constant.
681 return UndefValue::get(DestTy);
683 return ConstantFP::get(V->getContext(), apf);
686 case Instruction::ZExt:
687 if (ConstantInt *CI = dyn_cast<ConstantInt>(V)) {
688 uint32_t BitWidth = cast<IntegerType>(DestTy)->getBitWidth();
689 return ConstantInt::get(V->getContext(),
690 CI->getValue().zext(BitWidth));
693 case Instruction::SExt:
694 if (ConstantInt *CI = dyn_cast<ConstantInt>(V)) {
695 uint32_t BitWidth = cast<IntegerType>(DestTy)->getBitWidth();
696 return ConstantInt::get(V->getContext(),
697 CI->getValue().sext(BitWidth));
700 case Instruction::Trunc: {
701 if (V->getType()->isVectorTy())
704 uint32_t DestBitWidth = cast<IntegerType>(DestTy)->getBitWidth();
705 if (ConstantInt *CI = dyn_cast<ConstantInt>(V)) {
706 return ConstantInt::get(V->getContext(),
707 CI->getValue().trunc(DestBitWidth));
710 // The input must be a constantexpr. See if we can simplify this based on
711 // the bytes we are demanding. Only do this if the source and dest are an
712 // even multiple of a byte.
713 if ((DestBitWidth & 7) == 0 &&
714 (cast<IntegerType>(V->getType())->getBitWidth() & 7) == 0)
715 if (Constant *Res = ExtractConstantBytes(V, 0, DestBitWidth / 8))
720 case Instruction::BitCast:
721 return FoldBitCast(V, DestTy);
722 case Instruction::AddrSpaceCast:
727 Constant *llvm::ConstantFoldSelectInstruction(Constant *Cond,
728 Constant *V1, Constant *V2) {
729 // Check for i1 and vector true/false conditions.
730 if (Cond->isNullValue()) return V2;
731 if (Cond->isAllOnesValue()) return V1;
733 // If the condition is a vector constant, fold the result elementwise.
734 if (ConstantVector *CondV = dyn_cast<ConstantVector>(Cond)) {
735 SmallVector<Constant*, 16> Result;
736 Type *Ty = IntegerType::get(CondV->getContext(), 32);
737 for (unsigned i = 0, e = V1->getType()->getVectorNumElements(); i != e;++i){
739 Constant *V1Element = ConstantExpr::getExtractElement(V1,
740 ConstantInt::get(Ty, i));
741 Constant *V2Element = ConstantExpr::getExtractElement(V2,
742 ConstantInt::get(Ty, i));
743 Constant *Cond = dyn_cast<Constant>(CondV->getOperand(i));
744 if (V1Element == V2Element) {
746 } else if (isa<UndefValue>(Cond)) {
747 V = isa<UndefValue>(V1Element) ? V1Element : V2Element;
749 if (!isa<ConstantInt>(Cond)) break;
750 V = Cond->isNullValue() ? V2Element : V1Element;
755 // If we were able to build the vector, return it.
756 if (Result.size() == V1->getType()->getVectorNumElements())
757 return ConstantVector::get(Result);
760 if (isa<UndefValue>(Cond)) {
761 if (isa<UndefValue>(V1)) return V1;
764 if (isa<UndefValue>(V1)) return V2;
765 if (isa<UndefValue>(V2)) return V1;
766 if (V1 == V2) return V1;
768 if (ConstantExpr *TrueVal = dyn_cast<ConstantExpr>(V1)) {
769 if (TrueVal->getOpcode() == Instruction::Select)
770 if (TrueVal->getOperand(0) == Cond)
771 return ConstantExpr::getSelect(Cond, TrueVal->getOperand(1), V2);
773 if (ConstantExpr *FalseVal = dyn_cast<ConstantExpr>(V2)) {
774 if (FalseVal->getOpcode() == Instruction::Select)
775 if (FalseVal->getOperand(0) == Cond)
776 return ConstantExpr::getSelect(Cond, V1, FalseVal->getOperand(2));
782 Constant *llvm::ConstantFoldExtractElementInstruction(Constant *Val,
784 if (isa<UndefValue>(Val)) // ee(undef, x) -> undef
785 return UndefValue::get(Val->getType()->getVectorElementType());
786 if (Val->isNullValue()) // ee(zero, x) -> zero
787 return Constant::getNullValue(Val->getType()->getVectorElementType());
788 // ee({w,x,y,z}, undef) -> undef
789 if (isa<UndefValue>(Idx))
790 return UndefValue::get(Val->getType()->getVectorElementType());
792 if (ConstantInt *CIdx = dyn_cast<ConstantInt>(Idx)) {
793 // ee({w,x,y,z}, wrong_value) -> undef
794 if (CIdx->uge(Val->getType()->getVectorNumElements()))
795 return UndefValue::get(Val->getType()->getVectorElementType());
796 return Val->getAggregateElement(CIdx->getZExtValue());
801 Constant *llvm::ConstantFoldInsertElementInstruction(Constant *Val,
804 if (isa<UndefValue>(Idx))
805 return UndefValue::get(Val->getType());
807 ConstantInt *CIdx = dyn_cast<ConstantInt>(Idx);
808 if (!CIdx) return nullptr;
810 unsigned NumElts = Val->getType()->getVectorNumElements();
811 if (CIdx->uge(NumElts))
812 return UndefValue::get(Val->getType());
814 SmallVector<Constant*, 16> Result;
815 Result.reserve(NumElts);
816 auto *Ty = Type::getInt32Ty(Val->getContext());
817 uint64_t IdxVal = CIdx->getZExtValue();
818 for (unsigned i = 0; i != NumElts; ++i) {
820 Result.push_back(Elt);
824 Constant *C = ConstantExpr::getExtractElement(Val, ConstantInt::get(Ty, i));
828 return ConstantVector::get(Result);
831 Constant *llvm::ConstantFoldShuffleVectorInstruction(Constant *V1,
834 unsigned MaskNumElts = Mask->getType()->getVectorNumElements();
835 Type *EltTy = V1->getType()->getVectorElementType();
837 // Undefined shuffle mask -> undefined value.
838 if (isa<UndefValue>(Mask))
839 return UndefValue::get(VectorType::get(EltTy, MaskNumElts));
841 // Don't break the bitcode reader hack.
842 if (isa<ConstantExpr>(Mask)) return nullptr;
844 unsigned SrcNumElts = V1->getType()->getVectorNumElements();
846 // Loop over the shuffle mask, evaluating each element.
847 SmallVector<Constant*, 32> Result;
848 for (unsigned i = 0; i != MaskNumElts; ++i) {
849 int Elt = ShuffleVectorInst::getMaskValue(Mask, i);
851 Result.push_back(UndefValue::get(EltTy));
855 if (unsigned(Elt) >= SrcNumElts*2)
856 InElt = UndefValue::get(EltTy);
857 else if (unsigned(Elt) >= SrcNumElts) {
858 Type *Ty = IntegerType::get(V2->getContext(), 32);
860 ConstantExpr::getExtractElement(V2,
861 ConstantInt::get(Ty, Elt - SrcNumElts));
863 Type *Ty = IntegerType::get(V1->getContext(), 32);
864 InElt = ConstantExpr::getExtractElement(V1, ConstantInt::get(Ty, Elt));
866 Result.push_back(InElt);
869 return ConstantVector::get(Result);
872 Constant *llvm::ConstantFoldExtractValueInstruction(Constant *Agg,
873 ArrayRef<unsigned> Idxs) {
874 // Base case: no indices, so return the entire value.
878 if (Constant *C = Agg->getAggregateElement(Idxs[0]))
879 return ConstantFoldExtractValueInstruction(C, Idxs.slice(1));
884 Constant *llvm::ConstantFoldInsertValueInstruction(Constant *Agg,
886 ArrayRef<unsigned> Idxs) {
887 // Base case: no indices, so replace the entire value.
892 if (StructType *ST = dyn_cast<StructType>(Agg->getType()))
893 NumElts = ST->getNumElements();
895 NumElts = cast<SequentialType>(Agg->getType())->getNumElements();
897 SmallVector<Constant*, 32> Result;
898 for (unsigned i = 0; i != NumElts; ++i) {
899 Constant *C = Agg->getAggregateElement(i);
900 if (!C) return nullptr;
903 C = ConstantFoldInsertValueInstruction(C, Val, Idxs.slice(1));
908 if (StructType *ST = dyn_cast<StructType>(Agg->getType()))
909 return ConstantStruct::get(ST, Result);
910 if (ArrayType *AT = dyn_cast<ArrayType>(Agg->getType()))
911 return ConstantArray::get(AT, Result);
912 return ConstantVector::get(Result);
916 Constant *llvm::ConstantFoldBinaryInstruction(unsigned Opcode,
917 Constant *C1, Constant *C2) {
918 assert(Instruction::isBinaryOp(Opcode) && "Non-binary instruction detected");
920 // Handle UndefValue up front.
921 if (isa<UndefValue>(C1) || isa<UndefValue>(C2)) {
922 switch (static_cast<Instruction::BinaryOps>(Opcode)) {
923 case Instruction::Xor:
924 if (isa<UndefValue>(C1) && isa<UndefValue>(C2))
925 // Handle undef ^ undef -> 0 special case. This is a common
927 return Constant::getNullValue(C1->getType());
929 case Instruction::Add:
930 case Instruction::Sub:
931 return UndefValue::get(C1->getType());
932 case Instruction::And:
933 if (isa<UndefValue>(C1) && isa<UndefValue>(C2)) // undef & undef -> undef
935 return Constant::getNullValue(C1->getType()); // undef & X -> 0
936 case Instruction::Mul: {
937 // undef * undef -> undef
938 if (isa<UndefValue>(C1) && isa<UndefValue>(C2))
941 // X * undef -> undef if X is odd
942 if (match(C1, m_APInt(CV)) || match(C2, m_APInt(CV)))
944 return UndefValue::get(C1->getType());
946 // X * undef -> 0 otherwise
947 return Constant::getNullValue(C1->getType());
949 case Instruction::SDiv:
950 case Instruction::UDiv:
951 // X / undef -> undef
952 if (isa<UndefValue>(C2))
954 // undef / 0 -> undef
955 // undef / 1 -> undef
956 if (match(C2, m_Zero()) || match(C2, m_One()))
958 // undef / X -> 0 otherwise
959 return Constant::getNullValue(C1->getType());
960 case Instruction::URem:
961 case Instruction::SRem:
962 // X % undef -> undef
963 if (match(C2, m_Undef()))
965 // undef % 0 -> undef
966 if (match(C2, m_Zero()))
968 // undef % X -> 0 otherwise
969 return Constant::getNullValue(C1->getType());
970 case Instruction::Or: // X | undef -> -1
971 if (isa<UndefValue>(C1) && isa<UndefValue>(C2)) // undef | undef -> undef
973 return Constant::getAllOnesValue(C1->getType()); // undef | X -> ~0
974 case Instruction::LShr:
975 // X >>l undef -> undef
976 if (isa<UndefValue>(C2))
978 // undef >>l 0 -> undef
979 if (match(C2, m_Zero()))
982 return Constant::getNullValue(C1->getType());
983 case Instruction::AShr:
984 // X >>a undef -> undef
985 if (isa<UndefValue>(C2))
987 // undef >>a 0 -> undef
988 if (match(C2, m_Zero()))
990 // TODO: undef >>a X -> undef if the shift is exact
992 return Constant::getNullValue(C1->getType());
993 case Instruction::Shl:
994 // X << undef -> undef
995 if (isa<UndefValue>(C2))
997 // undef << 0 -> undef
998 if (match(C2, m_Zero()))
1001 return Constant::getNullValue(C1->getType());
1002 case Instruction::FAdd:
1003 case Instruction::FSub:
1004 case Instruction::FMul:
1005 case Instruction::FDiv:
1006 case Instruction::FRem:
1007 // TODO: UNDEF handling for binary float instructions.
1009 case Instruction::BinaryOpsEnd:
1010 llvm_unreachable("Invalid BinaryOp");
1014 // At this point neither constant should be an UndefValue.
1015 assert(!isa<UndefValue>(C1) && !isa<UndefValue>(C2) &&
1016 "Unexpected UndefValue");
1018 // Handle simplifications when the RHS is a constant int.
1019 if (ConstantInt *CI2 = dyn_cast<ConstantInt>(C2)) {
1021 case Instruction::Add:
1022 if (CI2->equalsInt(0)) return C1; // X + 0 == X
1024 case Instruction::Sub:
1025 if (CI2->equalsInt(0)) return C1; // X - 0 == X
1027 case Instruction::Mul:
1028 if (CI2->equalsInt(0)) return C2; // X * 0 == 0
1029 if (CI2->equalsInt(1))
1030 return C1; // X * 1 == X
1032 case Instruction::UDiv:
1033 case Instruction::SDiv:
1034 if (CI2->equalsInt(1))
1035 return C1; // X / 1 == X
1036 if (CI2->equalsInt(0))
1037 return UndefValue::get(CI2->getType()); // X / 0 == undef
1039 case Instruction::URem:
1040 case Instruction::SRem:
1041 if (CI2->equalsInt(1))
1042 return Constant::getNullValue(CI2->getType()); // X % 1 == 0
1043 if (CI2->equalsInt(0))
1044 return UndefValue::get(CI2->getType()); // X % 0 == undef
1046 case Instruction::And:
1047 if (CI2->isZero()) return C2; // X & 0 == 0
1048 if (CI2->isAllOnesValue())
1049 return C1; // X & -1 == X
1051 if (ConstantExpr *CE1 = dyn_cast<ConstantExpr>(C1)) {
1052 // (zext i32 to i64) & 4294967295 -> (zext i32 to i64)
1053 if (CE1->getOpcode() == Instruction::ZExt) {
1054 unsigned DstWidth = CI2->getType()->getBitWidth();
1056 CE1->getOperand(0)->getType()->getPrimitiveSizeInBits();
1057 APInt PossiblySetBits(APInt::getLowBitsSet(DstWidth, SrcWidth));
1058 if ((PossiblySetBits & CI2->getValue()) == PossiblySetBits)
1062 // If and'ing the address of a global with a constant, fold it.
1063 if (CE1->getOpcode() == Instruction::PtrToInt &&
1064 isa<GlobalValue>(CE1->getOperand(0))) {
1065 GlobalValue *GV = cast<GlobalValue>(CE1->getOperand(0));
1067 // Functions are at least 4-byte aligned.
1068 unsigned GVAlign = GV->getAlignment();
1069 if (isa<Function>(GV))
1070 GVAlign = std::max(GVAlign, 4U);
1073 unsigned DstWidth = CI2->getType()->getBitWidth();
1074 unsigned SrcWidth = std::min(DstWidth, Log2_32(GVAlign));
1075 APInt BitsNotSet(APInt::getLowBitsSet(DstWidth, SrcWidth));
1077 // If checking bits we know are clear, return zero.
1078 if ((CI2->getValue() & BitsNotSet) == CI2->getValue())
1079 return Constant::getNullValue(CI2->getType());
1084 case Instruction::Or:
1085 if (CI2->equalsInt(0)) return C1; // X | 0 == X
1086 if (CI2->isAllOnesValue())
1087 return C2; // X | -1 == -1
1089 case Instruction::Xor:
1090 if (CI2->equalsInt(0)) return C1; // X ^ 0 == X
1092 if (ConstantExpr *CE1 = dyn_cast<ConstantExpr>(C1)) {
1093 switch (CE1->getOpcode()) {
1095 case Instruction::ICmp:
1096 case Instruction::FCmp:
1097 // cmp pred ^ true -> cmp !pred
1098 assert(CI2->equalsInt(1));
1099 CmpInst::Predicate pred = (CmpInst::Predicate)CE1->getPredicate();
1100 pred = CmpInst::getInversePredicate(pred);
1101 return ConstantExpr::getCompare(pred, CE1->getOperand(0),
1102 CE1->getOperand(1));
1106 case Instruction::AShr:
1107 // ashr (zext C to Ty), C2 -> lshr (zext C, CSA), C2
1108 if (ConstantExpr *CE1 = dyn_cast<ConstantExpr>(C1))
1109 if (CE1->getOpcode() == Instruction::ZExt) // Top bits known zero.
1110 return ConstantExpr::getLShr(C1, C2);
1113 } else if (isa<ConstantInt>(C1)) {
1114 // If C1 is a ConstantInt and C2 is not, swap the operands.
1115 if (Instruction::isCommutative(Opcode))
1116 return ConstantExpr::get(Opcode, C2, C1);
1119 if (ConstantInt *CI1 = dyn_cast<ConstantInt>(C1)) {
1120 if (ConstantInt *CI2 = dyn_cast<ConstantInt>(C2)) {
1121 const APInt &C1V = CI1->getValue();
1122 const APInt &C2V = CI2->getValue();
1126 case Instruction::Add:
1127 return ConstantInt::get(CI1->getContext(), C1V + C2V);
1128 case Instruction::Sub:
1129 return ConstantInt::get(CI1->getContext(), C1V - C2V);
1130 case Instruction::Mul:
1131 return ConstantInt::get(CI1->getContext(), C1V * C2V);
1132 case Instruction::UDiv:
1133 assert(!CI2->isNullValue() && "Div by zero handled above");
1134 return ConstantInt::get(CI1->getContext(), C1V.udiv(C2V));
1135 case Instruction::SDiv:
1136 assert(!CI2->isNullValue() && "Div by zero handled above");
1137 if (C2V.isAllOnesValue() && C1V.isMinSignedValue())
1138 return UndefValue::get(CI1->getType()); // MIN_INT / -1 -> undef
1139 return ConstantInt::get(CI1->getContext(), C1V.sdiv(C2V));
1140 case Instruction::URem:
1141 assert(!CI2->isNullValue() && "Div by zero handled above");
1142 return ConstantInt::get(CI1->getContext(), C1V.urem(C2V));
1143 case Instruction::SRem:
1144 assert(!CI2->isNullValue() && "Div by zero handled above");
1145 if (C2V.isAllOnesValue() && C1V.isMinSignedValue())
1146 return UndefValue::get(CI1->getType()); // MIN_INT % -1 -> undef
1147 return ConstantInt::get(CI1->getContext(), C1V.srem(C2V));
1148 case Instruction::And:
1149 return ConstantInt::get(CI1->getContext(), C1V & C2V);
1150 case Instruction::Or:
1151 return ConstantInt::get(CI1->getContext(), C1V | C2V);
1152 case Instruction::Xor:
1153 return ConstantInt::get(CI1->getContext(), C1V ^ C2V);
1154 case Instruction::Shl:
1155 if (C2V.ult(C1V.getBitWidth()))
1156 return ConstantInt::get(CI1->getContext(), C1V.shl(C2V));
1157 return UndefValue::get(C1->getType()); // too big shift is undef
1158 case Instruction::LShr:
1159 if (C2V.ult(C1V.getBitWidth()))
1160 return ConstantInt::get(CI1->getContext(), C1V.lshr(C2V));
1161 return UndefValue::get(C1->getType()); // too big shift is undef
1162 case Instruction::AShr:
1163 if (C2V.ult(C1V.getBitWidth()))
1164 return ConstantInt::get(CI1->getContext(), C1V.ashr(C2V));
1165 return UndefValue::get(C1->getType()); // too big shift is undef
1170 case Instruction::SDiv:
1171 case Instruction::UDiv:
1172 case Instruction::URem:
1173 case Instruction::SRem:
1174 case Instruction::LShr:
1175 case Instruction::AShr:
1176 case Instruction::Shl:
1177 if (CI1->equalsInt(0)) return C1;
1182 } else if (ConstantFP *CFP1 = dyn_cast<ConstantFP>(C1)) {
1183 if (ConstantFP *CFP2 = dyn_cast<ConstantFP>(C2)) {
1184 const APFloat &C1V = CFP1->getValueAPF();
1185 const APFloat &C2V = CFP2->getValueAPF();
1186 APFloat C3V = C1V; // copy for modification
1190 case Instruction::FAdd:
1191 (void)C3V.add(C2V, APFloat::rmNearestTiesToEven);
1192 return ConstantFP::get(C1->getContext(), C3V);
1193 case Instruction::FSub:
1194 (void)C3V.subtract(C2V, APFloat::rmNearestTiesToEven);
1195 return ConstantFP::get(C1->getContext(), C3V);
1196 case Instruction::FMul:
1197 (void)C3V.multiply(C2V, APFloat::rmNearestTiesToEven);
1198 return ConstantFP::get(C1->getContext(), C3V);
1199 case Instruction::FDiv:
1200 (void)C3V.divide(C2V, APFloat::rmNearestTiesToEven);
1201 return ConstantFP::get(C1->getContext(), C3V);
1202 case Instruction::FRem:
1204 return ConstantFP::get(C1->getContext(), C3V);
1207 } else if (VectorType *VTy = dyn_cast<VectorType>(C1->getType())) {
1208 // Perform elementwise folding.
1209 SmallVector<Constant*, 16> Result;
1210 Type *Ty = IntegerType::get(VTy->getContext(), 32);
1211 for (unsigned i = 0, e = VTy->getNumElements(); i != e; ++i) {
1213 ConstantExpr::getExtractElement(C1, ConstantInt::get(Ty, i));
1215 ConstantExpr::getExtractElement(C2, ConstantInt::get(Ty, i));
1217 Result.push_back(ConstantExpr::get(Opcode, LHS, RHS));
1220 return ConstantVector::get(Result);
1223 if (ConstantExpr *CE1 = dyn_cast<ConstantExpr>(C1)) {
1224 // There are many possible foldings we could do here. We should probably
1225 // at least fold add of a pointer with an integer into the appropriate
1226 // getelementptr. This will improve alias analysis a bit.
1228 // Given ((a + b) + c), if (b + c) folds to something interesting, return
1230 if (Instruction::isAssociative(Opcode) && CE1->getOpcode() == Opcode) {
1231 Constant *T = ConstantExpr::get(Opcode, CE1->getOperand(1), C2);
1232 if (!isa<ConstantExpr>(T) || cast<ConstantExpr>(T)->getOpcode() != Opcode)
1233 return ConstantExpr::get(Opcode, CE1->getOperand(0), T);
1235 } else if (isa<ConstantExpr>(C2)) {
1236 // If C2 is a constant expr and C1 isn't, flop them around and fold the
1237 // other way if possible.
1238 if (Instruction::isCommutative(Opcode))
1239 return ConstantFoldBinaryInstruction(Opcode, C2, C1);
1242 // i1 can be simplified in many cases.
1243 if (C1->getType()->isIntegerTy(1)) {
1245 case Instruction::Add:
1246 case Instruction::Sub:
1247 return ConstantExpr::getXor(C1, C2);
1248 case Instruction::Mul:
1249 return ConstantExpr::getAnd(C1, C2);
1250 case Instruction::Shl:
1251 case Instruction::LShr:
1252 case Instruction::AShr:
1253 // We can assume that C2 == 0. If it were one the result would be
1254 // undefined because the shift value is as large as the bitwidth.
1256 case Instruction::SDiv:
1257 case Instruction::UDiv:
1258 // We can assume that C2 == 1. If it were zero the result would be
1259 // undefined through division by zero.
1261 case Instruction::URem:
1262 case Instruction::SRem:
1263 // We can assume that C2 == 1. If it were zero the result would be
1264 // undefined through division by zero.
1265 return ConstantInt::getFalse(C1->getContext());
1271 // We don't know how to fold this.
1275 /// This type is zero-sized if it's an array or structure of zero-sized types.
1276 /// The only leaf zero-sized type is an empty structure.
1277 static bool isMaybeZeroSizedType(Type *Ty) {
1278 if (StructType *STy = dyn_cast<StructType>(Ty)) {
1279 if (STy->isOpaque()) return true; // Can't say.
1281 // If all of elements have zero size, this does too.
1282 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i)
1283 if (!isMaybeZeroSizedType(STy->getElementType(i))) return false;
1286 } else if (ArrayType *ATy = dyn_cast<ArrayType>(Ty)) {
1287 return isMaybeZeroSizedType(ATy->getElementType());
1292 /// Compare the two constants as though they were getelementptr indices.
1293 /// This allows coercion of the types to be the same thing.
1295 /// If the two constants are the "same" (after coercion), return 0. If the
1296 /// first is less than the second, return -1, if the second is less than the
1297 /// first, return 1. If the constants are not integral, return -2.
1299 static int IdxCompare(Constant *C1, Constant *C2, Type *ElTy) {
1300 if (C1 == C2) return 0;
1302 // Ok, we found a different index. If they are not ConstantInt, we can't do
1303 // anything with them.
1304 if (!isa<ConstantInt>(C1) || !isa<ConstantInt>(C2))
1305 return -2; // don't know!
1307 // We cannot compare the indices if they don't fit in an int64_t.
1308 if (cast<ConstantInt>(C1)->getValue().getActiveBits() > 64 ||
1309 cast<ConstantInt>(C2)->getValue().getActiveBits() > 64)
1310 return -2; // don't know!
1312 // Ok, we have two differing integer indices. Sign extend them to be the same
1314 int64_t C1Val = cast<ConstantInt>(C1)->getSExtValue();
1315 int64_t C2Val = cast<ConstantInt>(C2)->getSExtValue();
1317 if (C1Val == C2Val) return 0; // They are equal
1319 // If the type being indexed over is really just a zero sized type, there is
1320 // no pointer difference being made here.
1321 if (isMaybeZeroSizedType(ElTy))
1322 return -2; // dunno.
1324 // If they are really different, now that they are the same type, then we
1325 // found a difference!
1332 /// This function determines if there is anything we can decide about the two
1333 /// constants provided. This doesn't need to handle simple things like
1334 /// ConstantFP comparisons, but should instead handle ConstantExprs.
1335 /// If we can determine that the two constants have a particular relation to
1336 /// each other, we should return the corresponding FCmpInst predicate,
1337 /// otherwise return FCmpInst::BAD_FCMP_PREDICATE. This is used below in
1338 /// ConstantFoldCompareInstruction.
1340 /// To simplify this code we canonicalize the relation so that the first
1341 /// operand is always the most "complex" of the two. We consider ConstantFP
1342 /// to be the simplest, and ConstantExprs to be the most complex.
1343 static FCmpInst::Predicate evaluateFCmpRelation(Constant *V1, Constant *V2) {
1344 assert(V1->getType() == V2->getType() &&
1345 "Cannot compare values of different types!");
1347 // Handle degenerate case quickly
1348 if (V1 == V2) return FCmpInst::FCMP_OEQ;
1350 if (!isa<ConstantExpr>(V1)) {
1351 if (!isa<ConstantExpr>(V2)) {
1352 // Simple case, use the standard constant folder.
1353 ConstantInt *R = nullptr;
1354 R = dyn_cast<ConstantInt>(
1355 ConstantExpr::getFCmp(FCmpInst::FCMP_OEQ, V1, V2));
1356 if (R && !R->isZero())
1357 return FCmpInst::FCMP_OEQ;
1358 R = dyn_cast<ConstantInt>(
1359 ConstantExpr::getFCmp(FCmpInst::FCMP_OLT, V1, V2));
1360 if (R && !R->isZero())
1361 return FCmpInst::FCMP_OLT;
1362 R = dyn_cast<ConstantInt>(
1363 ConstantExpr::getFCmp(FCmpInst::FCMP_OGT, V1, V2));
1364 if (R && !R->isZero())
1365 return FCmpInst::FCMP_OGT;
1367 // Nothing more we can do
1368 return FCmpInst::BAD_FCMP_PREDICATE;
1371 // If the first operand is simple and second is ConstantExpr, swap operands.
1372 FCmpInst::Predicate SwappedRelation = evaluateFCmpRelation(V2, V1);
1373 if (SwappedRelation != FCmpInst::BAD_FCMP_PREDICATE)
1374 return FCmpInst::getSwappedPredicate(SwappedRelation);
1376 // Ok, the LHS is known to be a constantexpr. The RHS can be any of a
1377 // constantexpr or a simple constant.
1378 ConstantExpr *CE1 = cast<ConstantExpr>(V1);
1379 switch (CE1->getOpcode()) {
1380 case Instruction::FPTrunc:
1381 case Instruction::FPExt:
1382 case Instruction::UIToFP:
1383 case Instruction::SIToFP:
1384 // We might be able to do something with these but we don't right now.
1390 // There are MANY other foldings that we could perform here. They will
1391 // probably be added on demand, as they seem needed.
1392 return FCmpInst::BAD_FCMP_PREDICATE;
1395 static ICmpInst::Predicate areGlobalsPotentiallyEqual(const GlobalValue *GV1,
1396 const GlobalValue *GV2) {
1397 auto isGlobalUnsafeForEquality = [](const GlobalValue *GV) {
1398 if (GV->hasExternalWeakLinkage() || GV->hasWeakAnyLinkage())
1400 if (const auto *GVar = dyn_cast<GlobalVariable>(GV)) {
1401 Type *Ty = GVar->getValueType();
1402 // A global with opaque type might end up being zero sized.
1405 // A global with an empty type might lie at the address of any other
1407 if (Ty->isEmptyTy())
1412 // Don't try to decide equality of aliases.
1413 if (!isa<GlobalAlias>(GV1) && !isa<GlobalAlias>(GV2))
1414 if (!isGlobalUnsafeForEquality(GV1) && !isGlobalUnsafeForEquality(GV2))
1415 return ICmpInst::ICMP_NE;
1416 return ICmpInst::BAD_ICMP_PREDICATE;
1419 /// This function determines if there is anything we can decide about the two
1420 /// constants provided. This doesn't need to handle simple things like integer
1421 /// comparisons, but should instead handle ConstantExprs and GlobalValues.
1422 /// If we can determine that the two constants have a particular relation to
1423 /// each other, we should return the corresponding ICmp predicate, otherwise
1424 /// return ICmpInst::BAD_ICMP_PREDICATE.
1426 /// To simplify this code we canonicalize the relation so that the first
1427 /// operand is always the most "complex" of the two. We consider simple
1428 /// constants (like ConstantInt) to be the simplest, followed by
1429 /// GlobalValues, followed by ConstantExpr's (the most complex).
1431 static ICmpInst::Predicate evaluateICmpRelation(Constant *V1, Constant *V2,
1433 assert(V1->getType() == V2->getType() &&
1434 "Cannot compare different types of values!");
1435 if (V1 == V2) return ICmpInst::ICMP_EQ;
1437 if (!isa<ConstantExpr>(V1) && !isa<GlobalValue>(V1) &&
1438 !isa<BlockAddress>(V1)) {
1439 if (!isa<GlobalValue>(V2) && !isa<ConstantExpr>(V2) &&
1440 !isa<BlockAddress>(V2)) {
1441 // We distilled this down to a simple case, use the standard constant
1443 ConstantInt *R = nullptr;
1444 ICmpInst::Predicate pred = ICmpInst::ICMP_EQ;
1445 R = dyn_cast<ConstantInt>(ConstantExpr::getICmp(pred, V1, V2));
1446 if (R && !R->isZero())
1448 pred = isSigned ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT;
1449 R = dyn_cast<ConstantInt>(ConstantExpr::getICmp(pred, V1, V2));
1450 if (R && !R->isZero())
1452 pred = isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT;
1453 R = dyn_cast<ConstantInt>(ConstantExpr::getICmp(pred, V1, V2));
1454 if (R && !R->isZero())
1457 // If we couldn't figure it out, bail.
1458 return ICmpInst::BAD_ICMP_PREDICATE;
1461 // If the first operand is simple, swap operands.
1462 ICmpInst::Predicate SwappedRelation =
1463 evaluateICmpRelation(V2, V1, isSigned);
1464 if (SwappedRelation != ICmpInst::BAD_ICMP_PREDICATE)
1465 return ICmpInst::getSwappedPredicate(SwappedRelation);
1467 } else if (const GlobalValue *GV = dyn_cast<GlobalValue>(V1)) {
1468 if (isa<ConstantExpr>(V2)) { // Swap as necessary.
1469 ICmpInst::Predicate SwappedRelation =
1470 evaluateICmpRelation(V2, V1, isSigned);
1471 if (SwappedRelation != ICmpInst::BAD_ICMP_PREDICATE)
1472 return ICmpInst::getSwappedPredicate(SwappedRelation);
1473 return ICmpInst::BAD_ICMP_PREDICATE;
1476 // Now we know that the RHS is a GlobalValue, BlockAddress or simple
1477 // constant (which, since the types must match, means that it's a
1478 // ConstantPointerNull).
1479 if (const GlobalValue *GV2 = dyn_cast<GlobalValue>(V2)) {
1480 return areGlobalsPotentiallyEqual(GV, GV2);
1481 } else if (isa<BlockAddress>(V2)) {
1482 return ICmpInst::ICMP_NE; // Globals never equal labels.
1484 assert(isa<ConstantPointerNull>(V2) && "Canonicalization guarantee!");
1485 // GlobalVals can never be null unless they have external weak linkage.
1486 // We don't try to evaluate aliases here.
1487 if (!GV->hasExternalWeakLinkage() && !isa<GlobalAlias>(GV))
1488 return ICmpInst::ICMP_NE;
1490 } else if (const BlockAddress *BA = dyn_cast<BlockAddress>(V1)) {
1491 if (isa<ConstantExpr>(V2)) { // Swap as necessary.
1492 ICmpInst::Predicate SwappedRelation =
1493 evaluateICmpRelation(V2, V1, isSigned);
1494 if (SwappedRelation != ICmpInst::BAD_ICMP_PREDICATE)
1495 return ICmpInst::getSwappedPredicate(SwappedRelation);
1496 return ICmpInst::BAD_ICMP_PREDICATE;
1499 // Now we know that the RHS is a GlobalValue, BlockAddress or simple
1500 // constant (which, since the types must match, means that it is a
1501 // ConstantPointerNull).
1502 if (const BlockAddress *BA2 = dyn_cast<BlockAddress>(V2)) {
1503 // Block address in another function can't equal this one, but block
1504 // addresses in the current function might be the same if blocks are
1506 if (BA2->getFunction() != BA->getFunction())
1507 return ICmpInst::ICMP_NE;
1509 // Block addresses aren't null, don't equal the address of globals.
1510 assert((isa<ConstantPointerNull>(V2) || isa<GlobalValue>(V2)) &&
1511 "Canonicalization guarantee!");
1512 return ICmpInst::ICMP_NE;
1515 // Ok, the LHS is known to be a constantexpr. The RHS can be any of a
1516 // constantexpr, a global, block address, or a simple constant.
1517 ConstantExpr *CE1 = cast<ConstantExpr>(V1);
1518 Constant *CE1Op0 = CE1->getOperand(0);
1520 switch (CE1->getOpcode()) {
1521 case Instruction::Trunc:
1522 case Instruction::FPTrunc:
1523 case Instruction::FPExt:
1524 case Instruction::FPToUI:
1525 case Instruction::FPToSI:
1526 break; // We can't evaluate floating point casts or truncations.
1528 case Instruction::UIToFP:
1529 case Instruction::SIToFP:
1530 case Instruction::BitCast:
1531 case Instruction::ZExt:
1532 case Instruction::SExt:
1533 // We can't evaluate floating point casts or truncations.
1534 if (CE1Op0->getType()->isFloatingPointTy())
1537 // If the cast is not actually changing bits, and the second operand is a
1538 // null pointer, do the comparison with the pre-casted value.
1539 if (V2->isNullValue() &&
1540 (CE1->getType()->isPointerTy() || CE1->getType()->isIntegerTy())) {
1541 if (CE1->getOpcode() == Instruction::ZExt) isSigned = false;
1542 if (CE1->getOpcode() == Instruction::SExt) isSigned = true;
1543 return evaluateICmpRelation(CE1Op0,
1544 Constant::getNullValue(CE1Op0->getType()),
1549 case Instruction::GetElementPtr: {
1550 GEPOperator *CE1GEP = cast<GEPOperator>(CE1);
1551 // Ok, since this is a getelementptr, we know that the constant has a
1552 // pointer type. Check the various cases.
1553 if (isa<ConstantPointerNull>(V2)) {
1554 // If we are comparing a GEP to a null pointer, check to see if the base
1555 // of the GEP equals the null pointer.
1556 if (const GlobalValue *GV = dyn_cast<GlobalValue>(CE1Op0)) {
1557 if (GV->hasExternalWeakLinkage())
1558 // Weak linkage GVals could be zero or not. We're comparing that
1559 // to null pointer so its greater-or-equal
1560 return isSigned ? ICmpInst::ICMP_SGE : ICmpInst::ICMP_UGE;
1562 // If its not weak linkage, the GVal must have a non-zero address
1563 // so the result is greater-than
1564 return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT;
1565 } else if (isa<ConstantPointerNull>(CE1Op0)) {
1566 // If we are indexing from a null pointer, check to see if we have any
1567 // non-zero indices.
1568 for (unsigned i = 1, e = CE1->getNumOperands(); i != e; ++i)
1569 if (!CE1->getOperand(i)->isNullValue())
1570 // Offsetting from null, must not be equal.
1571 return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT;
1572 // Only zero indexes from null, must still be zero.
1573 return ICmpInst::ICMP_EQ;
1575 // Otherwise, we can't really say if the first operand is null or not.
1576 } else if (const GlobalValue *GV2 = dyn_cast<GlobalValue>(V2)) {
1577 if (isa<ConstantPointerNull>(CE1Op0)) {
1578 if (GV2->hasExternalWeakLinkage())
1579 // Weak linkage GVals could be zero or not. We're comparing it to
1580 // a null pointer, so its less-or-equal
1581 return isSigned ? ICmpInst::ICMP_SLE : ICmpInst::ICMP_ULE;
1583 // If its not weak linkage, the GVal must have a non-zero address
1584 // so the result is less-than
1585 return isSigned ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT;
1586 } else if (const GlobalValue *GV = dyn_cast<GlobalValue>(CE1Op0)) {
1588 // If this is a getelementptr of the same global, then it must be
1589 // different. Because the types must match, the getelementptr could
1590 // only have at most one index, and because we fold getelementptr's
1591 // with a single zero index, it must be nonzero.
1592 assert(CE1->getNumOperands() == 2 &&
1593 !CE1->getOperand(1)->isNullValue() &&
1594 "Surprising getelementptr!");
1595 return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT;
1597 if (CE1GEP->hasAllZeroIndices())
1598 return areGlobalsPotentiallyEqual(GV, GV2);
1599 return ICmpInst::BAD_ICMP_PREDICATE;
1603 ConstantExpr *CE2 = cast<ConstantExpr>(V2);
1604 Constant *CE2Op0 = CE2->getOperand(0);
1606 // There are MANY other foldings that we could perform here. They will
1607 // probably be added on demand, as they seem needed.
1608 switch (CE2->getOpcode()) {
1610 case Instruction::GetElementPtr:
1611 // By far the most common case to handle is when the base pointers are
1612 // obviously to the same global.
1613 if (isa<GlobalValue>(CE1Op0) && isa<GlobalValue>(CE2Op0)) {
1614 // Don't know relative ordering, but check for inequality.
1615 if (CE1Op0 != CE2Op0) {
1616 GEPOperator *CE2GEP = cast<GEPOperator>(CE2);
1617 if (CE1GEP->hasAllZeroIndices() && CE2GEP->hasAllZeroIndices())
1618 return areGlobalsPotentiallyEqual(cast<GlobalValue>(CE1Op0),
1619 cast<GlobalValue>(CE2Op0));
1620 return ICmpInst::BAD_ICMP_PREDICATE;
1622 // Ok, we know that both getelementptr instructions are based on the
1623 // same global. From this, we can precisely determine the relative
1624 // ordering of the resultant pointers.
1627 // The logic below assumes that the result of the comparison
1628 // can be determined by finding the first index that differs.
1629 // This doesn't work if there is over-indexing in any
1630 // subsequent indices, so check for that case first.
1631 if (!CE1->isGEPWithNoNotionalOverIndexing() ||
1632 !CE2->isGEPWithNoNotionalOverIndexing())
1633 return ICmpInst::BAD_ICMP_PREDICATE; // Might be equal.
1635 // Compare all of the operands the GEP's have in common.
1636 gep_type_iterator GTI = gep_type_begin(CE1);
1637 for (;i != CE1->getNumOperands() && i != CE2->getNumOperands();
1639 switch (IdxCompare(CE1->getOperand(i),
1640 CE2->getOperand(i), GTI.getIndexedType())) {
1641 case -1: return isSigned ? ICmpInst::ICMP_SLT:ICmpInst::ICMP_ULT;
1642 case 1: return isSigned ? ICmpInst::ICMP_SGT:ICmpInst::ICMP_UGT;
1643 case -2: return ICmpInst::BAD_ICMP_PREDICATE;
1646 // Ok, we ran out of things they have in common. If any leftovers
1647 // are non-zero then we have a difference, otherwise we are equal.
1648 for (; i < CE1->getNumOperands(); ++i)
1649 if (!CE1->getOperand(i)->isNullValue()) {
1650 if (isa<ConstantInt>(CE1->getOperand(i)))
1651 return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT;
1653 return ICmpInst::BAD_ICMP_PREDICATE; // Might be equal.
1656 for (; i < CE2->getNumOperands(); ++i)
1657 if (!CE2->getOperand(i)->isNullValue()) {
1658 if (isa<ConstantInt>(CE2->getOperand(i)))
1659 return isSigned ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT;
1661 return ICmpInst::BAD_ICMP_PREDICATE; // Might be equal.
1663 return ICmpInst::ICMP_EQ;
1673 return ICmpInst::BAD_ICMP_PREDICATE;
1676 Constant *llvm::ConstantFoldCompareInstruction(unsigned short pred,
1677 Constant *C1, Constant *C2) {
1679 if (VectorType *VT = dyn_cast<VectorType>(C1->getType()))
1680 ResultTy = VectorType::get(Type::getInt1Ty(C1->getContext()),
1681 VT->getNumElements());
1683 ResultTy = Type::getInt1Ty(C1->getContext());
1685 // Fold FCMP_FALSE/FCMP_TRUE unconditionally.
1686 if (pred == FCmpInst::FCMP_FALSE)
1687 return Constant::getNullValue(ResultTy);
1689 if (pred == FCmpInst::FCMP_TRUE)
1690 return Constant::getAllOnesValue(ResultTy);
1692 // Handle some degenerate cases first
1693 if (isa<UndefValue>(C1) || isa<UndefValue>(C2)) {
1694 CmpInst::Predicate Predicate = CmpInst::Predicate(pred);
1695 bool isIntegerPredicate = ICmpInst::isIntPredicate(Predicate);
1696 // For EQ and NE, we can always pick a value for the undef to make the
1697 // predicate pass or fail, so we can return undef.
1698 // Also, if both operands are undef, we can return undef for int comparison.
1699 if (ICmpInst::isEquality(Predicate) || (isIntegerPredicate && C1 == C2))
1700 return UndefValue::get(ResultTy);
1702 // Otherwise, for integer compare, pick the same value as the non-undef
1703 // operand, and fold it to true or false.
1704 if (isIntegerPredicate)
1705 return ConstantInt::get(ResultTy, CmpInst::isTrueWhenEqual(Predicate));
1707 // Choosing NaN for the undef will always make unordered comparison succeed
1708 // and ordered comparison fails.
1709 return ConstantInt::get(ResultTy, CmpInst::isUnordered(Predicate));
1712 // icmp eq/ne(null,GV) -> false/true
1713 if (C1->isNullValue()) {
1714 if (const GlobalValue *GV = dyn_cast<GlobalValue>(C2))
1715 // Don't try to evaluate aliases. External weak GV can be null.
1716 if (!isa<GlobalAlias>(GV) && !GV->hasExternalWeakLinkage()) {
1717 if (pred == ICmpInst::ICMP_EQ)
1718 return ConstantInt::getFalse(C1->getContext());
1719 else if (pred == ICmpInst::ICMP_NE)
1720 return ConstantInt::getTrue(C1->getContext());
1722 // icmp eq/ne(GV,null) -> false/true
1723 } else if (C2->isNullValue()) {
1724 if (const GlobalValue *GV = dyn_cast<GlobalValue>(C1))
1725 // Don't try to evaluate aliases. External weak GV can be null.
1726 if (!isa<GlobalAlias>(GV) && !GV->hasExternalWeakLinkage()) {
1727 if (pred == ICmpInst::ICMP_EQ)
1728 return ConstantInt::getFalse(C1->getContext());
1729 else if (pred == ICmpInst::ICMP_NE)
1730 return ConstantInt::getTrue(C1->getContext());
1734 // If the comparison is a comparison between two i1's, simplify it.
1735 if (C1->getType()->isIntegerTy(1)) {
1737 case ICmpInst::ICMP_EQ:
1738 if (isa<ConstantInt>(C2))
1739 return ConstantExpr::getXor(C1, ConstantExpr::getNot(C2));
1740 return ConstantExpr::getXor(ConstantExpr::getNot(C1), C2);
1741 case ICmpInst::ICMP_NE:
1742 return ConstantExpr::getXor(C1, C2);
1748 if (isa<ConstantInt>(C1) && isa<ConstantInt>(C2)) {
1749 const APInt &V1 = cast<ConstantInt>(C1)->getValue();
1750 const APInt &V2 = cast<ConstantInt>(C2)->getValue();
1752 default: llvm_unreachable("Invalid ICmp Predicate");
1753 case ICmpInst::ICMP_EQ: return ConstantInt::get(ResultTy, V1 == V2);
1754 case ICmpInst::ICMP_NE: return ConstantInt::get(ResultTy, V1 != V2);
1755 case ICmpInst::ICMP_SLT: return ConstantInt::get(ResultTy, V1.slt(V2));
1756 case ICmpInst::ICMP_SGT: return ConstantInt::get(ResultTy, V1.sgt(V2));
1757 case ICmpInst::ICMP_SLE: return ConstantInt::get(ResultTy, V1.sle(V2));
1758 case ICmpInst::ICMP_SGE: return ConstantInt::get(ResultTy, V1.sge(V2));
1759 case ICmpInst::ICMP_ULT: return ConstantInt::get(ResultTy, V1.ult(V2));
1760 case ICmpInst::ICMP_UGT: return ConstantInt::get(ResultTy, V1.ugt(V2));
1761 case ICmpInst::ICMP_ULE: return ConstantInt::get(ResultTy, V1.ule(V2));
1762 case ICmpInst::ICMP_UGE: return ConstantInt::get(ResultTy, V1.uge(V2));
1764 } else if (isa<ConstantFP>(C1) && isa<ConstantFP>(C2)) {
1765 const APFloat &C1V = cast<ConstantFP>(C1)->getValueAPF();
1766 const APFloat &C2V = cast<ConstantFP>(C2)->getValueAPF();
1767 APFloat::cmpResult R = C1V.compare(C2V);
1769 default: llvm_unreachable("Invalid FCmp Predicate");
1770 case FCmpInst::FCMP_FALSE: return Constant::getNullValue(ResultTy);
1771 case FCmpInst::FCMP_TRUE: return Constant::getAllOnesValue(ResultTy);
1772 case FCmpInst::FCMP_UNO:
1773 return ConstantInt::get(ResultTy, R==APFloat::cmpUnordered);
1774 case FCmpInst::FCMP_ORD:
1775 return ConstantInt::get(ResultTy, R!=APFloat::cmpUnordered);
1776 case FCmpInst::FCMP_UEQ:
1777 return ConstantInt::get(ResultTy, R==APFloat::cmpUnordered ||
1778 R==APFloat::cmpEqual);
1779 case FCmpInst::FCMP_OEQ:
1780 return ConstantInt::get(ResultTy, R==APFloat::cmpEqual);
1781 case FCmpInst::FCMP_UNE:
1782 return ConstantInt::get(ResultTy, R!=APFloat::cmpEqual);
1783 case FCmpInst::FCMP_ONE:
1784 return ConstantInt::get(ResultTy, R==APFloat::cmpLessThan ||
1785 R==APFloat::cmpGreaterThan);
1786 case FCmpInst::FCMP_ULT:
1787 return ConstantInt::get(ResultTy, R==APFloat::cmpUnordered ||
1788 R==APFloat::cmpLessThan);
1789 case FCmpInst::FCMP_OLT:
1790 return ConstantInt::get(ResultTy, R==APFloat::cmpLessThan);
1791 case FCmpInst::FCMP_UGT:
1792 return ConstantInt::get(ResultTy, R==APFloat::cmpUnordered ||
1793 R==APFloat::cmpGreaterThan);
1794 case FCmpInst::FCMP_OGT:
1795 return ConstantInt::get(ResultTy, R==APFloat::cmpGreaterThan);
1796 case FCmpInst::FCMP_ULE:
1797 return ConstantInt::get(ResultTy, R!=APFloat::cmpGreaterThan);
1798 case FCmpInst::FCMP_OLE:
1799 return ConstantInt::get(ResultTy, R==APFloat::cmpLessThan ||
1800 R==APFloat::cmpEqual);
1801 case FCmpInst::FCMP_UGE:
1802 return ConstantInt::get(ResultTy, R!=APFloat::cmpLessThan);
1803 case FCmpInst::FCMP_OGE:
1804 return ConstantInt::get(ResultTy, R==APFloat::cmpGreaterThan ||
1805 R==APFloat::cmpEqual);
1807 } else if (C1->getType()->isVectorTy()) {
1808 // If we can constant fold the comparison of each element, constant fold
1809 // the whole vector comparison.
1810 SmallVector<Constant*, 4> ResElts;
1811 Type *Ty = IntegerType::get(C1->getContext(), 32);
1812 // Compare the elements, producing an i1 result or constant expr.
1813 for (unsigned i = 0, e = C1->getType()->getVectorNumElements(); i != e;++i){
1815 ConstantExpr::getExtractElement(C1, ConstantInt::get(Ty, i));
1817 ConstantExpr::getExtractElement(C2, ConstantInt::get(Ty, i));
1819 ResElts.push_back(ConstantExpr::getCompare(pred, C1E, C2E));
1822 return ConstantVector::get(ResElts);
1825 if (C1->getType()->isFloatingPointTy() &&
1826 // Only call evaluateFCmpRelation if we have a constant expr to avoid
1827 // infinite recursive loop
1828 (isa<ConstantExpr>(C1) || isa<ConstantExpr>(C2))) {
1829 int Result = -1; // -1 = unknown, 0 = known false, 1 = known true.
1830 switch (evaluateFCmpRelation(C1, C2)) {
1831 default: llvm_unreachable("Unknown relation!");
1832 case FCmpInst::FCMP_UNO:
1833 case FCmpInst::FCMP_ORD:
1834 case FCmpInst::FCMP_UEQ:
1835 case FCmpInst::FCMP_UNE:
1836 case FCmpInst::FCMP_ULT:
1837 case FCmpInst::FCMP_UGT:
1838 case FCmpInst::FCMP_ULE:
1839 case FCmpInst::FCMP_UGE:
1840 case FCmpInst::FCMP_TRUE:
1841 case FCmpInst::FCMP_FALSE:
1842 case FCmpInst::BAD_FCMP_PREDICATE:
1843 break; // Couldn't determine anything about these constants.
1844 case FCmpInst::FCMP_OEQ: // We know that C1 == C2
1845 Result = (pred == FCmpInst::FCMP_UEQ || pred == FCmpInst::FCMP_OEQ ||
1846 pred == FCmpInst::FCMP_ULE || pred == FCmpInst::FCMP_OLE ||
1847 pred == FCmpInst::FCMP_UGE || pred == FCmpInst::FCMP_OGE);
1849 case FCmpInst::FCMP_OLT: // We know that C1 < C2
1850 Result = (pred == FCmpInst::FCMP_UNE || pred == FCmpInst::FCMP_ONE ||
1851 pred == FCmpInst::FCMP_ULT || pred == FCmpInst::FCMP_OLT ||
1852 pred == FCmpInst::FCMP_ULE || pred == FCmpInst::FCMP_OLE);
1854 case FCmpInst::FCMP_OGT: // We know that C1 > C2
1855 Result = (pred == FCmpInst::FCMP_UNE || pred == FCmpInst::FCMP_ONE ||
1856 pred == FCmpInst::FCMP_UGT || pred == FCmpInst::FCMP_OGT ||
1857 pred == FCmpInst::FCMP_UGE || pred == FCmpInst::FCMP_OGE);
1859 case FCmpInst::FCMP_OLE: // We know that C1 <= C2
1860 // We can only partially decide this relation.
1861 if (pred == FCmpInst::FCMP_UGT || pred == FCmpInst::FCMP_OGT)
1863 else if (pred == FCmpInst::FCMP_ULT || pred == FCmpInst::FCMP_OLT)
1866 case FCmpInst::FCMP_OGE: // We known that C1 >= C2
1867 // We can only partially decide this relation.
1868 if (pred == FCmpInst::FCMP_ULT || pred == FCmpInst::FCMP_OLT)
1870 else if (pred == FCmpInst::FCMP_UGT || pred == FCmpInst::FCMP_OGT)
1873 case FCmpInst::FCMP_ONE: // We know that C1 != C2
1874 // We can only partially decide this relation.
1875 if (pred == FCmpInst::FCMP_OEQ || pred == FCmpInst::FCMP_UEQ)
1877 else if (pred == FCmpInst::FCMP_ONE || pred == FCmpInst::FCMP_UNE)
1882 // If we evaluated the result, return it now.
1884 return ConstantInt::get(ResultTy, Result);
1887 // Evaluate the relation between the two constants, per the predicate.
1888 int Result = -1; // -1 = unknown, 0 = known false, 1 = known true.
1889 switch (evaluateICmpRelation(C1, C2,
1890 CmpInst::isSigned((CmpInst::Predicate)pred))) {
1891 default: llvm_unreachable("Unknown relational!");
1892 case ICmpInst::BAD_ICMP_PREDICATE:
1893 break; // Couldn't determine anything about these constants.
1894 case ICmpInst::ICMP_EQ: // We know the constants are equal!
1895 // If we know the constants are equal, we can decide the result of this
1896 // computation precisely.
1897 Result = ICmpInst::isTrueWhenEqual((ICmpInst::Predicate)pred);
1899 case ICmpInst::ICMP_ULT:
1901 case ICmpInst::ICMP_ULT: case ICmpInst::ICMP_NE: case ICmpInst::ICMP_ULE:
1903 case ICmpInst::ICMP_UGT: case ICmpInst::ICMP_EQ: case ICmpInst::ICMP_UGE:
1907 case ICmpInst::ICMP_SLT:
1909 case ICmpInst::ICMP_SLT: case ICmpInst::ICMP_NE: case ICmpInst::ICMP_SLE:
1911 case ICmpInst::ICMP_SGT: case ICmpInst::ICMP_EQ: case ICmpInst::ICMP_SGE:
1915 case ICmpInst::ICMP_UGT:
1917 case ICmpInst::ICMP_UGT: case ICmpInst::ICMP_NE: case ICmpInst::ICMP_UGE:
1919 case ICmpInst::ICMP_ULT: case ICmpInst::ICMP_EQ: case ICmpInst::ICMP_ULE:
1923 case ICmpInst::ICMP_SGT:
1925 case ICmpInst::ICMP_SGT: case ICmpInst::ICMP_NE: case ICmpInst::ICMP_SGE:
1927 case ICmpInst::ICMP_SLT: case ICmpInst::ICMP_EQ: case ICmpInst::ICMP_SLE:
1931 case ICmpInst::ICMP_ULE:
1932 if (pred == ICmpInst::ICMP_UGT) Result = 0;
1933 if (pred == ICmpInst::ICMP_ULT || pred == ICmpInst::ICMP_ULE) Result = 1;
1935 case ICmpInst::ICMP_SLE:
1936 if (pred == ICmpInst::ICMP_SGT) Result = 0;
1937 if (pred == ICmpInst::ICMP_SLT || pred == ICmpInst::ICMP_SLE) Result = 1;
1939 case ICmpInst::ICMP_UGE:
1940 if (pred == ICmpInst::ICMP_ULT) Result = 0;
1941 if (pred == ICmpInst::ICMP_UGT || pred == ICmpInst::ICMP_UGE) Result = 1;
1943 case ICmpInst::ICMP_SGE:
1944 if (pred == ICmpInst::ICMP_SLT) Result = 0;
1945 if (pred == ICmpInst::ICMP_SGT || pred == ICmpInst::ICMP_SGE) Result = 1;
1947 case ICmpInst::ICMP_NE:
1948 if (pred == ICmpInst::ICMP_EQ) Result = 0;
1949 if (pred == ICmpInst::ICMP_NE) Result = 1;
1953 // If we evaluated the result, return it now.
1955 return ConstantInt::get(ResultTy, Result);
1957 // If the right hand side is a bitcast, try using its inverse to simplify
1958 // it by moving it to the left hand side. We can't do this if it would turn
1959 // a vector compare into a scalar compare or visa versa.
1960 if (ConstantExpr *CE2 = dyn_cast<ConstantExpr>(C2)) {
1961 Constant *CE2Op0 = CE2->getOperand(0);
1962 if (CE2->getOpcode() == Instruction::BitCast &&
1963 CE2->getType()->isVectorTy() == CE2Op0->getType()->isVectorTy()) {
1964 Constant *Inverse = ConstantExpr::getBitCast(C1, CE2Op0->getType());
1965 return ConstantExpr::getICmp(pred, Inverse, CE2Op0);
1969 // If the left hand side is an extension, try eliminating it.
1970 if (ConstantExpr *CE1 = dyn_cast<ConstantExpr>(C1)) {
1971 if ((CE1->getOpcode() == Instruction::SExt &&
1972 ICmpInst::isSigned((ICmpInst::Predicate)pred)) ||
1973 (CE1->getOpcode() == Instruction::ZExt &&
1974 !ICmpInst::isSigned((ICmpInst::Predicate)pred))){
1975 Constant *CE1Op0 = CE1->getOperand(0);
1976 Constant *CE1Inverse = ConstantExpr::getTrunc(CE1, CE1Op0->getType());
1977 if (CE1Inverse == CE1Op0) {
1978 // Check whether we can safely truncate the right hand side.
1979 Constant *C2Inverse = ConstantExpr::getTrunc(C2, CE1Op0->getType());
1980 if (ConstantExpr::getCast(CE1->getOpcode(), C2Inverse,
1981 C2->getType()) == C2)
1982 return ConstantExpr::getICmp(pred, CE1Inverse, C2Inverse);
1987 if ((!isa<ConstantExpr>(C1) && isa<ConstantExpr>(C2)) ||
1988 (C1->isNullValue() && !C2->isNullValue())) {
1989 // If C2 is a constant expr and C1 isn't, flip them around and fold the
1990 // other way if possible.
1991 // Also, if C1 is null and C2 isn't, flip them around.
1992 pred = ICmpInst::getSwappedPredicate((ICmpInst::Predicate)pred);
1993 return ConstantExpr::getICmp(pred, C2, C1);
1999 /// Test whether the given sequence of *normalized* indices is "inbounds".
2000 template<typename IndexTy>
2001 static bool isInBoundsIndices(ArrayRef<IndexTy> Idxs) {
2002 // No indices means nothing that could be out of bounds.
2003 if (Idxs.empty()) return true;
2005 // If the first index is zero, it's in bounds.
2006 if (cast<Constant>(Idxs[0])->isNullValue()) return true;
2008 // If the first index is one and all the rest are zero, it's in bounds,
2009 // by the one-past-the-end rule.
2010 if (!cast<ConstantInt>(Idxs[0])->isOne())
2012 for (unsigned i = 1, e = Idxs.size(); i != e; ++i)
2013 if (!cast<Constant>(Idxs[i])->isNullValue())
2018 /// Test whether a given ConstantInt is in-range for a SequentialType.
2019 static bool isIndexInRangeOfArrayType(uint64_t NumElements,
2020 const ConstantInt *CI) {
2021 // We cannot bounds check the index if it doesn't fit in an int64_t.
2022 if (CI->getValue().getActiveBits() > 64)
2025 // A negative index or an index past the end of our sequential type is
2026 // considered out-of-range.
2027 int64_t IndexVal = CI->getSExtValue();
2028 if (IndexVal < 0 || (NumElements > 0 && (uint64_t)IndexVal >= NumElements))
2031 // Otherwise, it is in-range.
2035 Constant *llvm::ConstantFoldGetElementPtr(Type *PointeeTy, Constant *C,
2037 Optional<unsigned> InRangeIndex,
2038 ArrayRef<Value *> Idxs) {
2039 if (Idxs.empty()) return C;
2040 Constant *Idx0 = cast<Constant>(Idxs[0]);
2041 if ((Idxs.size() == 1 && Idx0->isNullValue()))
2044 if (isa<UndefValue>(C)) {
2045 Type *GEPTy = GetElementPtrInst::getGEPReturnType(
2046 C, makeArrayRef((Value * const *)Idxs.data(), Idxs.size()));
2047 return UndefValue::get(GEPTy);
2050 if (C->isNullValue()) {
2052 for (unsigned i = 0, e = Idxs.size(); i != e; ++i)
2053 if (!cast<Constant>(Idxs[i])->isNullValue()) {
2058 PointerType *PtrTy = cast<PointerType>(C->getType()->getScalarType());
2059 Type *Ty = GetElementPtrInst::getIndexedType(PointeeTy, Idxs);
2061 assert(Ty && "Invalid indices for GEP!");
2062 Type *GEPTy = PointerType::get(Ty, PtrTy->getAddressSpace());
2063 if (VectorType *VT = dyn_cast<VectorType>(C->getType()))
2064 GEPTy = VectorType::get(GEPTy, VT->getNumElements());
2065 return Constant::getNullValue(GEPTy);
2069 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(C)) {
2070 // Combine Indices - If the source pointer to this getelementptr instruction
2071 // is a getelementptr instruction, combine the indices of the two
2072 // getelementptr instructions into a single instruction.
2074 if (CE->getOpcode() == Instruction::GetElementPtr) {
2075 gep_type_iterator LastI = gep_type_end(CE);
2076 for (gep_type_iterator I = gep_type_begin(CE), E = gep_type_end(CE);
2080 // We cannot combine indices if doing so would take us outside of an
2081 // array or vector. Doing otherwise could trick us if we evaluated such a
2082 // GEP as part of a load.
2084 // e.g. Consider if the original GEP was:
2085 // i8* getelementptr ({ [2 x i8], i32, i8, [3 x i8] }* @main.c,
2086 // i32 0, i32 0, i64 0)
2088 // If we then tried to offset it by '8' to get to the third element,
2089 // an i8, we should *not* get:
2090 // i8* getelementptr ({ [2 x i8], i32, i8, [3 x i8] }* @main.c,
2091 // i32 0, i32 0, i64 8)
2093 // This GEP tries to index array element '8 which runs out-of-bounds.
2094 // Subsequent evaluation would get confused and produce erroneous results.
2096 // The following prohibits such a GEP from being formed by checking to see
2097 // if the index is in-range with respect to an array or vector.
2098 bool PerformFold = false;
2099 if (Idx0->isNullValue())
2101 else if (LastI.isSequential())
2102 if (ConstantInt *CI = dyn_cast<ConstantInt>(Idx0))
2104 !LastI.isBoundedSequential() ||
2105 isIndexInRangeOfArrayType(LastI.getSequentialNumElements(), CI);
2108 SmallVector<Value*, 16> NewIndices;
2109 NewIndices.reserve(Idxs.size() + CE->getNumOperands());
2110 NewIndices.append(CE->op_begin() + 1, CE->op_end() - 1);
2112 // Add the last index of the source with the first index of the new GEP.
2113 // Make sure to handle the case when they are actually different types.
2114 Constant *Combined = CE->getOperand(CE->getNumOperands()-1);
2115 // Otherwise it must be an array.
2116 if (!Idx0->isNullValue()) {
2117 Type *IdxTy = Combined->getType();
2118 if (IdxTy != Idx0->getType()) {
2119 unsigned CommonExtendedWidth =
2120 std::max(IdxTy->getIntegerBitWidth(),
2121 Idx0->getType()->getIntegerBitWidth());
2122 CommonExtendedWidth = std::max(CommonExtendedWidth, 64U);
2125 Type::getIntNTy(IdxTy->getContext(), CommonExtendedWidth);
2126 Constant *C1 = ConstantExpr::getSExtOrBitCast(Idx0, CommonTy);
2127 Constant *C2 = ConstantExpr::getSExtOrBitCast(Combined, CommonTy);
2128 Combined = ConstantExpr::get(Instruction::Add, C1, C2);
2131 ConstantExpr::get(Instruction::Add, Idx0, Combined);
2135 NewIndices.push_back(Combined);
2136 NewIndices.append(Idxs.begin() + 1, Idxs.end());
2138 // The combined GEP normally inherits its index inrange attribute from
2139 // the inner GEP, but if the inner GEP's last index was adjusted by the
2140 // outer GEP, any inbounds attribute on that index is invalidated.
2141 Optional<unsigned> IRIndex = cast<GEPOperator>(CE)->getInRangeIndex();
2142 if (IRIndex && *IRIndex == CE->getNumOperands() - 2 && !Idx0->isNullValue())
2145 return ConstantExpr::getGetElementPtr(
2146 cast<GEPOperator>(CE)->getSourceElementType(), CE->getOperand(0),
2147 NewIndices, InBounds && cast<GEPOperator>(CE)->isInBounds(),
2152 // Attempt to fold casts to the same type away. For example, folding:
2154 // i32* getelementptr ([2 x i32]* bitcast ([3 x i32]* %X to [2 x i32]*),
2158 // i32* getelementptr ([3 x i32]* %X, i64 0, i64 0)
2160 // Don't fold if the cast is changing address spaces.
2161 if (CE->isCast() && Idxs.size() > 1 && Idx0->isNullValue()) {
2162 PointerType *SrcPtrTy =
2163 dyn_cast<PointerType>(CE->getOperand(0)->getType());
2164 PointerType *DstPtrTy = dyn_cast<PointerType>(CE->getType());
2165 if (SrcPtrTy && DstPtrTy) {
2166 ArrayType *SrcArrayTy =
2167 dyn_cast<ArrayType>(SrcPtrTy->getElementType());
2168 ArrayType *DstArrayTy =
2169 dyn_cast<ArrayType>(DstPtrTy->getElementType());
2170 if (SrcArrayTy && DstArrayTy
2171 && SrcArrayTy->getElementType() == DstArrayTy->getElementType()
2172 && SrcPtrTy->getAddressSpace() == DstPtrTy->getAddressSpace())
2173 return ConstantExpr::getGetElementPtr(SrcArrayTy,
2174 (Constant *)CE->getOperand(0),
2175 Idxs, InBounds, InRangeIndex);
2180 // Check to see if any array indices are not within the corresponding
2181 // notional array or vector bounds. If so, try to determine if they can be
2182 // factored out into preceding dimensions.
2183 SmallVector<Constant *, 8> NewIdxs;
2184 Type *Ty = PointeeTy;
2185 Type *Prev = C->getType();
2186 bool Unknown = !isa<ConstantInt>(Idxs[0]);
2187 for (unsigned i = 1, e = Idxs.size(); i != e;
2188 Prev = Ty, Ty = cast<CompositeType>(Ty)->getTypeAtIndex(Idxs[i]), ++i) {
2189 auto *CI = dyn_cast<ConstantInt>(Idxs[i]);
2191 // We don't know if it's in range or not.
2195 if (InRangeIndex && i == *InRangeIndex + 1) {
2196 // If an index is marked inrange, we cannot apply this canonicalization to
2197 // the following index, as that will cause the inrange index to point to
2198 // the wrong element.
2201 if (isa<StructType>(Ty)) {
2202 // The verify makes sure that GEPs into a struct are in range.
2205 auto *STy = cast<SequentialType>(Ty);
2206 if (isa<VectorType>(STy)) {
2207 // There can be awkward padding in after a non-power of two vector.
2211 if (isIndexInRangeOfArrayType(STy->getNumElements(), CI))
2212 // It's in range, skip to the next index.
2214 if (isa<StructType>(Prev)) {
2215 // It's out of range, but the prior dimension is a struct
2216 // so we can't do anything about it.
2220 if (CI->getSExtValue() < 0) {
2221 // It's out of range and negative, don't try to factor it.
2225 // It's out of range, but we can factor it into the prior
2227 NewIdxs.resize(Idxs.size());
2228 // Determine the number of elements in our sequential type.
2229 uint64_t NumElements = STy->getArrayNumElements();
2231 ConstantInt *Factor = ConstantInt::get(CI->getType(), NumElements);
2232 NewIdxs[i] = ConstantExpr::getSRem(CI, Factor);
2234 Constant *PrevIdx = cast<Constant>(Idxs[i - 1]);
2235 Constant *Div = ConstantExpr::getSDiv(CI, Factor);
2237 unsigned CommonExtendedWidth =
2238 std::max(PrevIdx->getType()->getIntegerBitWidth(),
2239 Div->getType()->getIntegerBitWidth());
2240 CommonExtendedWidth = std::max(CommonExtendedWidth, 64U);
2242 // Before adding, extend both operands to i64 to avoid
2243 // overflow trouble.
2244 if (!PrevIdx->getType()->isIntegerTy(CommonExtendedWidth))
2245 PrevIdx = ConstantExpr::getSExt(
2246 PrevIdx, Type::getIntNTy(Div->getContext(), CommonExtendedWidth));
2247 if (!Div->getType()->isIntegerTy(CommonExtendedWidth))
2248 Div = ConstantExpr::getSExt(
2249 Div, Type::getIntNTy(Div->getContext(), CommonExtendedWidth));
2251 NewIdxs[i - 1] = ConstantExpr::getAdd(PrevIdx, Div);
2254 // If we did any factoring, start over with the adjusted indices.
2255 if (!NewIdxs.empty()) {
2256 for (unsigned i = 0, e = Idxs.size(); i != e; ++i)
2257 if (!NewIdxs[i]) NewIdxs[i] = cast<Constant>(Idxs[i]);
2258 return ConstantExpr::getGetElementPtr(PointeeTy, C, NewIdxs, InBounds,
2262 // If all indices are known integers and normalized, we can do a simple
2263 // check for the "inbounds" property.
2264 if (!Unknown && !InBounds)
2265 if (auto *GV = dyn_cast<GlobalVariable>(C))
2266 if (!GV->hasExternalWeakLinkage() && isInBoundsIndices(Idxs))
2267 return ConstantExpr::getGetElementPtr(PointeeTy, C, Idxs,
2268 /*InBounds=*/true, InRangeIndex);