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 TargetData, and the pieces that do. This is to avoid
16 // a dependence in VMCore on Target.
18 //===----------------------------------------------------------------------===//
20 #include "ConstantFold.h"
21 #include "llvm/Constants.h"
22 #include "llvm/Instructions.h"
23 #include "llvm/DerivedTypes.h"
24 #include "llvm/Function.h"
25 #include "llvm/GlobalAlias.h"
26 #include "llvm/GlobalVariable.h"
27 #include "llvm/ADT/SmallVector.h"
28 #include "llvm/Support/Compiler.h"
29 #include "llvm/Support/ErrorHandling.h"
30 #include "llvm/Support/GetElementPtrTypeIterator.h"
31 #include "llvm/Support/ManagedStatic.h"
32 #include "llvm/Support/MathExtras.h"
36 //===----------------------------------------------------------------------===//
37 // ConstantFold*Instruction Implementations
38 //===----------------------------------------------------------------------===//
40 /// BitCastConstantVector - Convert the specified ConstantVector node to the
41 /// specified vector type. At this point, we know that the elements of the
42 /// input vector constant are all simple integer or FP values.
43 static Constant *BitCastConstantVector(ConstantVector *CV,
44 const VectorType *DstTy) {
45 // If this cast changes element count then we can't handle it here:
46 // doing so requires endianness information. This should be handled by
47 // Analysis/ConstantFolding.cpp
48 unsigned NumElts = DstTy->getNumElements();
49 if (NumElts != CV->getNumOperands())
52 // Check to verify that all elements of the input are simple.
53 for (unsigned i = 0; i != NumElts; ++i) {
54 if (!isa<ConstantInt>(CV->getOperand(i)) &&
55 !isa<ConstantFP>(CV->getOperand(i)))
59 // Bitcast each element now.
60 std::vector<Constant*> Result;
61 const Type *DstEltTy = DstTy->getElementType();
62 for (unsigned i = 0; i != NumElts; ++i)
63 Result.push_back(ConstantExpr::getBitCast(CV->getOperand(i),
65 return ConstantVector::get(Result);
68 /// This function determines which opcode to use to fold two constant cast
69 /// expressions together. It uses CastInst::isEliminableCastPair to determine
70 /// the opcode. Consequently its just a wrapper around that function.
71 /// @brief Determine if it is valid to fold a cast of a cast
74 unsigned opc, ///< opcode of the second cast constant expression
75 ConstantExpr *Op, ///< the first cast constant expression
76 const Type *DstTy ///< desintation type of the first cast
78 assert(Op && Op->isCast() && "Can't fold cast of cast without a cast!");
79 assert(DstTy && DstTy->isFirstClassType() && "Invalid cast destination type");
80 assert(CastInst::isCast(opc) && "Invalid cast opcode");
82 // The the types and opcodes for the two Cast constant expressions
83 const Type *SrcTy = Op->getOperand(0)->getType();
84 const Type *MidTy = Op->getType();
85 Instruction::CastOps firstOp = Instruction::CastOps(Op->getOpcode());
86 Instruction::CastOps secondOp = Instruction::CastOps(opc);
88 // Let CastInst::isEliminableCastPair do the heavy lifting.
89 return CastInst::isEliminableCastPair(firstOp, secondOp, SrcTy, MidTy, DstTy,
90 Type::getInt64Ty(DstTy->getContext()));
93 static Constant *FoldBitCast(Constant *V, const Type *DestTy) {
94 const Type *SrcTy = V->getType();
96 return V; // no-op cast
98 // Check to see if we are casting a pointer to an aggregate to a pointer to
99 // the first element. If so, return the appropriate GEP instruction.
100 if (const PointerType *PTy = dyn_cast<PointerType>(V->getType()))
101 if (const PointerType *DPTy = dyn_cast<PointerType>(DestTy))
102 if (PTy->getAddressSpace() == DPTy->getAddressSpace()) {
103 SmallVector<Value*, 8> IdxList;
105 Constant::getNullValue(Type::getInt32Ty(DPTy->getContext()));
106 IdxList.push_back(Zero);
107 const Type *ElTy = PTy->getElementType();
108 while (ElTy != DPTy->getElementType()) {
109 if (const StructType *STy = dyn_cast<StructType>(ElTy)) {
110 if (STy->getNumElements() == 0) break;
111 ElTy = STy->getElementType(0);
112 IdxList.push_back(Zero);
113 } else if (const SequentialType *STy =
114 dyn_cast<SequentialType>(ElTy)) {
115 if (ElTy->isPointerTy()) break; // Can't index into pointers!
116 ElTy = STy->getElementType();
117 IdxList.push_back(Zero);
123 if (ElTy == DPTy->getElementType())
124 // This GEP is inbounds because all indices are zero.
125 return ConstantExpr::getInBoundsGetElementPtr(V, &IdxList[0],
129 // Handle casts from one vector constant to another. We know that the src
130 // and dest type have the same size (otherwise its an illegal cast).
131 if (const VectorType *DestPTy = dyn_cast<VectorType>(DestTy)) {
132 if (const VectorType *SrcTy = dyn_cast<VectorType>(V->getType())) {
133 assert(DestPTy->getBitWidth() == SrcTy->getBitWidth() &&
134 "Not cast between same sized vectors!");
136 // First, check for null. Undef is already handled.
137 if (isa<ConstantAggregateZero>(V))
138 return Constant::getNullValue(DestTy);
140 if (ConstantVector *CV = dyn_cast<ConstantVector>(V))
141 return BitCastConstantVector(CV, DestPTy);
144 // Canonicalize scalar-to-vector bitcasts into vector-to-vector bitcasts
145 // This allows for other simplifications (although some of them
146 // can only be handled by Analysis/ConstantFolding.cpp).
147 if (isa<ConstantInt>(V) || isa<ConstantFP>(V))
148 return ConstantExpr::getBitCast(ConstantVector::get(&V, 1), DestPTy);
151 // Finally, implement bitcast folding now. The code below doesn't handle
153 if (isa<ConstantPointerNull>(V)) // ptr->ptr cast.
154 return ConstantPointerNull::get(cast<PointerType>(DestTy));
156 // Handle integral constant input.
157 if (ConstantInt *CI = dyn_cast<ConstantInt>(V)) {
158 if (DestTy->isIntegerTy())
159 // Integral -> Integral. This is a no-op because the bit widths must
160 // be the same. Consequently, we just fold to V.
163 if (DestTy->isFloatingPointTy())
164 return ConstantFP::get(DestTy->getContext(),
165 APFloat(CI->getValue(),
166 !DestTy->isPPC_FP128Ty()));
168 // Otherwise, can't fold this (vector?)
172 // Handle ConstantFP input: FP -> Integral.
173 if (ConstantFP *FP = dyn_cast<ConstantFP>(V))
174 return ConstantInt::get(FP->getContext(),
175 FP->getValueAPF().bitcastToAPInt());
181 /// ExtractConstantBytes - V is an integer constant which only has a subset of
182 /// its bytes used. The bytes used are indicated by ByteStart (which is the
183 /// first byte used, counting from the least significant byte) and ByteSize,
184 /// which is the number of bytes used.
186 /// This function analyzes the specified constant to see if the specified byte
187 /// range can be returned as a simplified constant. If so, the constant is
188 /// returned, otherwise null is returned.
190 static Constant *ExtractConstantBytes(Constant *C, unsigned ByteStart,
192 assert(C->getType()->isIntegerTy() &&
193 (cast<IntegerType>(C->getType())->getBitWidth() & 7) == 0 &&
194 "Non-byte sized integer input");
195 unsigned CSize = cast<IntegerType>(C->getType())->getBitWidth()/8;
196 assert(ByteSize && "Must be accessing some piece");
197 assert(ByteStart+ByteSize <= CSize && "Extracting invalid piece from input");
198 assert(ByteSize != CSize && "Should not extract everything");
200 // Constant Integers are simple.
201 if (ConstantInt *CI = dyn_cast<ConstantInt>(C)) {
202 APInt V = CI->getValue();
204 V = V.lshr(ByteStart*8);
206 return ConstantInt::get(CI->getContext(), V);
209 // In the input is a constant expr, we might be able to recursively simplify.
210 // If not, we definitely can't do anything.
211 ConstantExpr *CE = dyn_cast<ConstantExpr>(C);
212 if (CE == 0) return 0;
214 switch (CE->getOpcode()) {
216 case Instruction::Or: {
217 Constant *RHS = ExtractConstantBytes(CE->getOperand(1), ByteStart,ByteSize);
222 if (ConstantInt *RHSC = dyn_cast<ConstantInt>(RHS))
223 if (RHSC->isAllOnesValue())
226 Constant *LHS = ExtractConstantBytes(CE->getOperand(0), ByteStart,ByteSize);
229 return ConstantExpr::getOr(LHS, RHS);
231 case Instruction::And: {
232 Constant *RHS = ExtractConstantBytes(CE->getOperand(1), ByteStart,ByteSize);
237 if (RHS->isNullValue())
240 Constant *LHS = ExtractConstantBytes(CE->getOperand(0), ByteStart,ByteSize);
243 return ConstantExpr::getAnd(LHS, RHS);
245 case Instruction::LShr: {
246 ConstantInt *Amt = dyn_cast<ConstantInt>(CE->getOperand(1));
249 unsigned ShAmt = Amt->getZExtValue();
250 // Cannot analyze non-byte shifts.
251 if ((ShAmt & 7) != 0)
255 // If the extract is known to be all zeros, return zero.
256 if (ByteStart >= CSize-ShAmt)
257 return Constant::getNullValue(IntegerType::get(CE->getContext(),
259 // If the extract is known to be fully in the input, extract it.
260 if (ByteStart+ByteSize+ShAmt <= CSize)
261 return ExtractConstantBytes(CE->getOperand(0), ByteStart+ShAmt, ByteSize);
263 // TODO: Handle the 'partially zero' case.
267 case Instruction::Shl: {
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+ByteSize <= 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 >= ShAmt)
283 return ExtractConstantBytes(CE->getOperand(0), ByteStart-ShAmt, ByteSize);
285 // TODO: Handle the 'partially zero' case.
289 case Instruction::ZExt: {
290 unsigned SrcBitSize =
291 cast<IntegerType>(CE->getOperand(0)->getType())->getBitWidth();
293 // If extracting something that is completely zero, return 0.
294 if (ByteStart*8 >= SrcBitSize)
295 return Constant::getNullValue(IntegerType::get(CE->getContext(),
298 // If exactly extracting the input, return it.
299 if (ByteStart == 0 && ByteSize*8 == SrcBitSize)
300 return CE->getOperand(0);
302 // If extracting something completely in the input, if if the input is a
303 // multiple of 8 bits, recurse.
304 if ((SrcBitSize&7) == 0 && (ByteStart+ByteSize)*8 <= SrcBitSize)
305 return ExtractConstantBytes(CE->getOperand(0), ByteStart, ByteSize);
307 // Otherwise, if extracting a subset of the input, which is not multiple of
308 // 8 bits, do a shift and trunc to get the bits.
309 if ((ByteStart+ByteSize)*8 < SrcBitSize) {
310 assert((SrcBitSize&7) && "Shouldn't get byte sized case here");
311 Constant *Res = CE->getOperand(0);
313 Res = ConstantExpr::getLShr(Res,
314 ConstantInt::get(Res->getType(), ByteStart*8));
315 return ConstantExpr::getTrunc(Res, IntegerType::get(C->getContext(),
319 // TODO: Handle the 'partially zero' case.
325 /// getFoldedSizeOf - Return a ConstantExpr with type DestTy for sizeof
326 /// on Ty, with any known factors factored out. If Folded is false,
327 /// return null if no factoring was possible, to avoid endlessly
328 /// bouncing an unfoldable expression back into the top-level folder.
330 static Constant *getFoldedSizeOf(const Type *Ty, const Type *DestTy,
332 if (const ArrayType *ATy = dyn_cast<ArrayType>(Ty)) {
333 Constant *N = ConstantInt::get(DestTy, ATy->getNumElements());
334 Constant *E = getFoldedSizeOf(ATy->getElementType(), DestTy, true);
335 return ConstantExpr::getNUWMul(E, N);
338 if (const StructType *STy = dyn_cast<StructType>(Ty))
339 if (!STy->isPacked()) {
340 unsigned NumElems = STy->getNumElements();
341 // An empty struct has size zero.
343 return ConstantExpr::getNullValue(DestTy);
344 // Check for a struct with all members having the same size.
345 Constant *MemberSize =
346 getFoldedSizeOf(STy->getElementType(0), DestTy, true);
348 for (unsigned i = 1; i != NumElems; ++i)
350 getFoldedSizeOf(STy->getElementType(i), DestTy, true)) {
355 Constant *N = ConstantInt::get(DestTy, NumElems);
356 return ConstantExpr::getNUWMul(MemberSize, N);
360 // Pointer size doesn't depend on the pointee type, so canonicalize them
361 // to an arbitrary pointee.
362 if (const PointerType *PTy = dyn_cast<PointerType>(Ty))
363 if (!PTy->getElementType()->isIntegerTy(1))
365 getFoldedSizeOf(PointerType::get(IntegerType::get(PTy->getContext(), 1),
366 PTy->getAddressSpace()),
369 // If there's no interesting folding happening, bail so that we don't create
370 // a constant that looks like it needs folding but really doesn't.
374 // Base case: Get a regular sizeof expression.
375 Constant *C = ConstantExpr::getSizeOf(Ty);
376 C = ConstantExpr::getCast(CastInst::getCastOpcode(C, false,
382 /// getFoldedAlignOf - Return a ConstantExpr with type DestTy for alignof
383 /// on Ty, with any known factors factored out. If Folded is false,
384 /// return null if no factoring was possible, to avoid endlessly
385 /// bouncing an unfoldable expression back into the top-level folder.
387 static Constant *getFoldedAlignOf(const Type *Ty, const Type *DestTy,
389 // The alignment of an array is equal to the alignment of the
390 // array element. Note that this is not always true for vectors.
391 if (const ArrayType *ATy = dyn_cast<ArrayType>(Ty)) {
392 Constant *C = ConstantExpr::getAlignOf(ATy->getElementType());
393 C = ConstantExpr::getCast(CastInst::getCastOpcode(C, false,
400 if (const StructType *STy = dyn_cast<StructType>(Ty)) {
401 // Packed structs always have an alignment of 1.
403 return ConstantInt::get(DestTy, 1);
405 // Otherwise, struct alignment is the maximum alignment of any member.
406 // Without target data, we can't compare much, but we can check to see
407 // if all the members have the same alignment.
408 unsigned NumElems = STy->getNumElements();
409 // An empty struct has minimal alignment.
411 return ConstantInt::get(DestTy, 1);
412 // Check for a struct with all members having the same alignment.
413 Constant *MemberAlign =
414 getFoldedAlignOf(STy->getElementType(0), DestTy, true);
416 for (unsigned i = 1; i != NumElems; ++i)
417 if (MemberAlign != getFoldedAlignOf(STy->getElementType(i), DestTy, true)) {
425 // Pointer alignment doesn't depend on the pointee type, so canonicalize them
426 // to an arbitrary pointee.
427 if (const PointerType *PTy = dyn_cast<PointerType>(Ty))
428 if (!PTy->getElementType()->isIntegerTy(1))
430 getFoldedAlignOf(PointerType::get(IntegerType::get(PTy->getContext(),
432 PTy->getAddressSpace()),
435 // If there's no interesting folding happening, bail so that we don't create
436 // a constant that looks like it needs folding but really doesn't.
440 // Base case: Get a regular alignof expression.
441 Constant *C = ConstantExpr::getAlignOf(Ty);
442 C = ConstantExpr::getCast(CastInst::getCastOpcode(C, false,
448 /// getFoldedOffsetOf - Return a ConstantExpr with type DestTy for offsetof
449 /// on Ty and FieldNo, with any known factors factored out. If Folded is false,
450 /// return null if no factoring was possible, to avoid endlessly
451 /// bouncing an unfoldable expression back into the top-level folder.
453 static Constant *getFoldedOffsetOf(const Type *Ty, Constant *FieldNo,
456 if (const ArrayType *ATy = dyn_cast<ArrayType>(Ty)) {
457 Constant *N = ConstantExpr::getCast(CastInst::getCastOpcode(FieldNo, false,
460 Constant *E = getFoldedSizeOf(ATy->getElementType(), DestTy, true);
461 return ConstantExpr::getNUWMul(E, N);
464 if (const StructType *STy = dyn_cast<StructType>(Ty))
465 if (!STy->isPacked()) {
466 unsigned NumElems = STy->getNumElements();
467 // An empty struct has no members.
470 // Check for a struct with all members having the same size.
471 Constant *MemberSize =
472 getFoldedSizeOf(STy->getElementType(0), DestTy, true);
474 for (unsigned i = 1; i != NumElems; ++i)
476 getFoldedSizeOf(STy->getElementType(i), DestTy, true)) {
481 Constant *N = ConstantExpr::getCast(CastInst::getCastOpcode(FieldNo,
486 return ConstantExpr::getNUWMul(MemberSize, N);
490 // If there's no interesting folding happening, bail so that we don't create
491 // a constant that looks like it needs folding but really doesn't.
495 // Base case: Get a regular offsetof expression.
496 Constant *C = ConstantExpr::getOffsetOf(Ty, FieldNo);
497 C = ConstantExpr::getCast(CastInst::getCastOpcode(C, false,
503 Constant *llvm::ConstantFoldCastInstruction(unsigned opc, Constant *V,
504 const Type *DestTy) {
505 if (isa<UndefValue>(V)) {
506 // zext(undef) = 0, because the top bits will be zero.
507 // sext(undef) = 0, because the top bits will all be the same.
508 // [us]itofp(undef) = 0, because the result value is bounded.
509 if (opc == Instruction::ZExt || opc == Instruction::SExt ||
510 opc == Instruction::UIToFP || opc == Instruction::SIToFP)
511 return Constant::getNullValue(DestTy);
512 return UndefValue::get(DestTy);
514 // No compile-time operations on this type yet.
515 if (V->getType()->isPPC_FP128Ty() || DestTy->isPPC_FP128Ty())
518 // If the cast operand is a constant expression, there's a few things we can
519 // do to try to simplify it.
520 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V)) {
522 // Try hard to fold cast of cast because they are often eliminable.
523 if (unsigned newOpc = foldConstantCastPair(opc, CE, DestTy))
524 return ConstantExpr::getCast(newOpc, CE->getOperand(0), DestTy);
525 } else if (CE->getOpcode() == Instruction::GetElementPtr) {
526 // If all of the indexes in the GEP are null values, there is no pointer
527 // adjustment going on. We might as well cast the source pointer.
528 bool isAllNull = true;
529 for (unsigned i = 1, e = CE->getNumOperands(); i != e; ++i)
530 if (!CE->getOperand(i)->isNullValue()) {
535 // This is casting one pointer type to another, always BitCast
536 return ConstantExpr::getPointerCast(CE->getOperand(0), DestTy);
540 // If the cast operand is a constant vector, perform the cast by
541 // operating on each element. In the cast of bitcasts, the element
542 // count may be mismatched; don't attempt to handle that here.
543 if (ConstantVector *CV = dyn_cast<ConstantVector>(V))
544 if (DestTy->isVectorTy() &&
545 cast<VectorType>(DestTy)->getNumElements() ==
546 CV->getType()->getNumElements()) {
547 std::vector<Constant*> res;
548 const VectorType *DestVecTy = cast<VectorType>(DestTy);
549 const Type *DstEltTy = DestVecTy->getElementType();
550 for (unsigned i = 0, e = CV->getType()->getNumElements(); i != e; ++i)
551 res.push_back(ConstantExpr::getCast(opc,
552 CV->getOperand(i), DstEltTy));
553 return ConstantVector::get(DestVecTy, res);
556 // We actually have to do a cast now. Perform the cast according to the
560 llvm_unreachable("Failed to cast constant expression");
561 case Instruction::FPTrunc:
562 case Instruction::FPExt:
563 if (ConstantFP *FPC = dyn_cast<ConstantFP>(V)) {
565 APFloat Val = FPC->getValueAPF();
566 Val.convert(DestTy->isFloatTy() ? APFloat::IEEEsingle :
567 DestTy->isDoubleTy() ? APFloat::IEEEdouble :
568 DestTy->isX86_FP80Ty() ? APFloat::x87DoubleExtended :
569 DestTy->isFP128Ty() ? APFloat::IEEEquad :
571 APFloat::rmNearestTiesToEven, &ignored);
572 return ConstantFP::get(V->getContext(), Val);
574 return 0; // Can't fold.
575 case Instruction::FPToUI:
576 case Instruction::FPToSI:
577 if (ConstantFP *FPC = dyn_cast<ConstantFP>(V)) {
578 const APFloat &V = FPC->getValueAPF();
581 uint32_t DestBitWidth = cast<IntegerType>(DestTy)->getBitWidth();
582 (void) V.convertToInteger(x, DestBitWidth, opc==Instruction::FPToSI,
583 APFloat::rmTowardZero, &ignored);
584 APInt Val(DestBitWidth, 2, x);
585 return ConstantInt::get(FPC->getContext(), Val);
587 return 0; // Can't fold.
588 case Instruction::IntToPtr: //always treated as unsigned
589 if (V->isNullValue()) // Is it an integral null value?
590 return ConstantPointerNull::get(cast<PointerType>(DestTy));
591 return 0; // Other pointer types cannot be casted
592 case Instruction::PtrToInt: // always treated as unsigned
593 // Is it a null pointer value?
594 if (V->isNullValue())
595 return ConstantInt::get(DestTy, 0);
596 // If this is a sizeof-like expression, pull out multiplications by
597 // known factors to expose them to subsequent folding. If it's an
598 // alignof-like expression, factor out known factors.
599 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V))
600 if (CE->getOpcode() == Instruction::GetElementPtr &&
601 CE->getOperand(0)->isNullValue()) {
603 cast<PointerType>(CE->getOperand(0)->getType())->getElementType();
604 if (CE->getNumOperands() == 2) {
605 // Handle a sizeof-like expression.
606 Constant *Idx = CE->getOperand(1);
607 bool isOne = isa<ConstantInt>(Idx) && cast<ConstantInt>(Idx)->isOne();
608 if (Constant *C = getFoldedSizeOf(Ty, DestTy, !isOne)) {
609 Idx = ConstantExpr::getCast(CastInst::getCastOpcode(Idx, true,
612 return ConstantExpr::getMul(C, Idx);
614 } else if (CE->getNumOperands() == 3 &&
615 CE->getOperand(1)->isNullValue()) {
616 // Handle an alignof-like expression.
617 if (const StructType *STy = dyn_cast<StructType>(Ty))
618 if (!STy->isPacked()) {
619 ConstantInt *CI = cast<ConstantInt>(CE->getOperand(2));
621 STy->getNumElements() == 2 &&
622 STy->getElementType(0)->isIntegerTy(1)) {
623 return getFoldedAlignOf(STy->getElementType(1), DestTy, false);
626 // Handle an offsetof-like expression.
627 if (Ty->isStructTy() || Ty->isArrayTy() || Ty->isVectorTy()){
628 if (Constant *C = getFoldedOffsetOf(Ty, CE->getOperand(2),
634 // Other pointer types cannot be casted
636 case Instruction::UIToFP:
637 case Instruction::SIToFP:
638 if (ConstantInt *CI = dyn_cast<ConstantInt>(V)) {
639 APInt api = CI->getValue();
640 const uint64_t zero[] = {0, 0};
641 APFloat apf = APFloat(APInt(DestTy->getPrimitiveSizeInBits(),
643 (void)apf.convertFromAPInt(api,
644 opc==Instruction::SIToFP,
645 APFloat::rmNearestTiesToEven);
646 return ConstantFP::get(V->getContext(), apf);
649 case Instruction::ZExt:
650 if (ConstantInt *CI = dyn_cast<ConstantInt>(V)) {
651 uint32_t BitWidth = cast<IntegerType>(DestTy)->getBitWidth();
652 APInt Result(CI->getValue());
653 Result.zext(BitWidth);
654 return ConstantInt::get(V->getContext(), Result);
657 case Instruction::SExt:
658 if (ConstantInt *CI = dyn_cast<ConstantInt>(V)) {
659 uint32_t BitWidth = cast<IntegerType>(DestTy)->getBitWidth();
660 APInt Result(CI->getValue());
661 Result.sext(BitWidth);
662 return ConstantInt::get(V->getContext(), Result);
665 case Instruction::Trunc: {
666 uint32_t DestBitWidth = cast<IntegerType>(DestTy)->getBitWidth();
667 if (ConstantInt *CI = dyn_cast<ConstantInt>(V)) {
668 APInt Result(CI->getValue());
669 Result.trunc(DestBitWidth);
670 return ConstantInt::get(V->getContext(), Result);
673 // The input must be a constantexpr. See if we can simplify this based on
674 // the bytes we are demanding. Only do this if the source and dest are an
675 // even multiple of a byte.
676 if ((DestBitWidth & 7) == 0 &&
677 (cast<IntegerType>(V->getType())->getBitWidth() & 7) == 0)
678 if (Constant *Res = ExtractConstantBytes(V, 0, DestBitWidth / 8))
683 case Instruction::BitCast:
684 return FoldBitCast(V, DestTy);
688 Constant *llvm::ConstantFoldSelectInstruction(Constant *Cond,
689 Constant *V1, Constant *V2) {
690 if (ConstantInt *CB = dyn_cast<ConstantInt>(Cond))
691 return CB->getZExtValue() ? V1 : V2;
693 if (isa<UndefValue>(V1)) return V2;
694 if (isa<UndefValue>(V2)) return V1;
695 if (isa<UndefValue>(Cond)) return V1;
696 if (V1 == V2) return V1;
700 Constant *llvm::ConstantFoldExtractElementInstruction(Constant *Val,
702 if (isa<UndefValue>(Val)) // ee(undef, x) -> undef
703 return UndefValue::get(cast<VectorType>(Val->getType())->getElementType());
704 if (Val->isNullValue()) // ee(zero, x) -> zero
705 return Constant::getNullValue(
706 cast<VectorType>(Val->getType())->getElementType());
708 if (ConstantVector *CVal = dyn_cast<ConstantVector>(Val)) {
709 if (ConstantInt *CIdx = dyn_cast<ConstantInt>(Idx)) {
710 return CVal->getOperand(CIdx->getZExtValue());
711 } else if (isa<UndefValue>(Idx)) {
712 // ee({w,x,y,z}, undef) -> w (an arbitrary value).
713 return CVal->getOperand(0);
719 Constant *llvm::ConstantFoldInsertElementInstruction(Constant *Val,
722 ConstantInt *CIdx = dyn_cast<ConstantInt>(Idx);
724 APInt idxVal = CIdx->getValue();
725 if (isa<UndefValue>(Val)) {
726 // Insertion of scalar constant into vector undef
727 // Optimize away insertion of undef
728 if (isa<UndefValue>(Elt))
730 // Otherwise break the aggregate undef into multiple undefs and do
733 cast<VectorType>(Val->getType())->getNumElements();
734 std::vector<Constant*> Ops;
736 for (unsigned i = 0; i < numOps; ++i) {
738 (idxVal == i) ? Elt : UndefValue::get(Elt->getType());
741 return ConstantVector::get(Ops);
743 if (isa<ConstantAggregateZero>(Val)) {
744 // Insertion of scalar constant into vector aggregate zero
745 // Optimize away insertion of zero
746 if (Elt->isNullValue())
748 // Otherwise break the aggregate zero into multiple zeros and do
751 cast<VectorType>(Val->getType())->getNumElements();
752 std::vector<Constant*> Ops;
754 for (unsigned i = 0; i < numOps; ++i) {
756 (idxVal == i) ? Elt : Constant::getNullValue(Elt->getType());
759 return ConstantVector::get(Ops);
761 if (ConstantVector *CVal = dyn_cast<ConstantVector>(Val)) {
762 // Insertion of scalar constant into vector constant
763 std::vector<Constant*> Ops;
764 Ops.reserve(CVal->getNumOperands());
765 for (unsigned i = 0; i < CVal->getNumOperands(); ++i) {
767 (idxVal == i) ? Elt : cast<Constant>(CVal->getOperand(i));
770 return ConstantVector::get(Ops);
776 /// GetVectorElement - If C is a ConstantVector, ConstantAggregateZero or Undef
777 /// return the specified element value. Otherwise return null.
778 static Constant *GetVectorElement(Constant *C, unsigned EltNo) {
779 if (ConstantVector *CV = dyn_cast<ConstantVector>(C))
780 return CV->getOperand(EltNo);
782 const Type *EltTy = cast<VectorType>(C->getType())->getElementType();
783 if (isa<ConstantAggregateZero>(C))
784 return Constant::getNullValue(EltTy);
785 if (isa<UndefValue>(C))
786 return UndefValue::get(EltTy);
790 Constant *llvm::ConstantFoldShuffleVectorInstruction(Constant *V1,
793 // Undefined shuffle mask -> undefined value.
794 if (isa<UndefValue>(Mask)) return UndefValue::get(V1->getType());
796 unsigned MaskNumElts = cast<VectorType>(Mask->getType())->getNumElements();
797 unsigned SrcNumElts = cast<VectorType>(V1->getType())->getNumElements();
798 const Type *EltTy = cast<VectorType>(V1->getType())->getElementType();
800 // Loop over the shuffle mask, evaluating each element.
801 SmallVector<Constant*, 32> Result;
802 for (unsigned i = 0; i != MaskNumElts; ++i) {
803 Constant *InElt = GetVectorElement(Mask, i);
804 if (InElt == 0) return 0;
806 if (isa<UndefValue>(InElt))
807 InElt = UndefValue::get(EltTy);
808 else if (ConstantInt *CI = dyn_cast<ConstantInt>(InElt)) {
809 unsigned Elt = CI->getZExtValue();
810 if (Elt >= SrcNumElts*2)
811 InElt = UndefValue::get(EltTy);
812 else if (Elt >= SrcNumElts)
813 InElt = GetVectorElement(V2, Elt - SrcNumElts);
815 InElt = GetVectorElement(V1, Elt);
816 if (InElt == 0) return 0;
821 Result.push_back(InElt);
824 return ConstantVector::get(&Result[0], Result.size());
827 Constant *llvm::ConstantFoldExtractValueInstruction(Constant *Agg,
828 const unsigned *Idxs,
830 // Base case: no indices, so return the entire value.
834 if (isa<UndefValue>(Agg)) // ev(undef, x) -> undef
835 return UndefValue::get(ExtractValueInst::getIndexedType(Agg->getType(),
839 if (isa<ConstantAggregateZero>(Agg)) // ev(0, x) -> 0
841 Constant::getNullValue(ExtractValueInst::getIndexedType(Agg->getType(),
845 // Otherwise recurse.
846 if (ConstantStruct *CS = dyn_cast<ConstantStruct>(Agg))
847 return ConstantFoldExtractValueInstruction(CS->getOperand(*Idxs),
850 if (ConstantArray *CA = dyn_cast<ConstantArray>(Agg))
851 return ConstantFoldExtractValueInstruction(CA->getOperand(*Idxs),
853 ConstantVector *CV = cast<ConstantVector>(Agg);
854 return ConstantFoldExtractValueInstruction(CV->getOperand(*Idxs),
858 Constant *llvm::ConstantFoldInsertValueInstruction(Constant *Agg,
860 const unsigned *Idxs,
862 // Base case: no indices, so replace the entire value.
866 if (isa<UndefValue>(Agg)) {
867 // Insertion of constant into aggregate undef
868 // Optimize away insertion of undef.
869 if (isa<UndefValue>(Val))
872 // Otherwise break the aggregate undef into multiple undefs and do
874 const CompositeType *AggTy = cast<CompositeType>(Agg->getType());
876 if (const ArrayType *AR = dyn_cast<ArrayType>(AggTy))
877 numOps = AR->getNumElements();
878 else if (AggTy->isUnionTy())
881 numOps = cast<StructType>(AggTy)->getNumElements();
883 std::vector<Constant*> Ops(numOps);
884 for (unsigned i = 0; i < numOps; ++i) {
885 const Type *MemberTy = AggTy->getTypeAtIndex(i);
888 ConstantFoldInsertValueInstruction(UndefValue::get(MemberTy),
889 Val, Idxs+1, NumIdx-1) :
890 UndefValue::get(MemberTy);
894 if (const StructType* ST = dyn_cast<StructType>(AggTy))
895 return ConstantStruct::get(ST->getContext(), Ops, ST->isPacked());
896 if (const UnionType* UT = dyn_cast<UnionType>(AggTy)) {
897 assert(Ops.size() == 1 && "Union can only contain a single value!");
898 return ConstantUnion::get(UT, Ops[0]);
900 return ConstantArray::get(cast<ArrayType>(AggTy), Ops);
903 if (isa<ConstantAggregateZero>(Agg)) {
904 // Insertion of constant into aggregate zero
905 // Optimize away insertion of zero.
906 if (Val->isNullValue())
909 // Otherwise break the aggregate zero into multiple zeros and do
911 const CompositeType *AggTy = cast<CompositeType>(Agg->getType());
913 if (const ArrayType *AR = dyn_cast<ArrayType>(AggTy))
914 numOps = AR->getNumElements();
916 numOps = cast<StructType>(AggTy)->getNumElements();
918 std::vector<Constant*> Ops(numOps);
919 for (unsigned i = 0; i < numOps; ++i) {
920 const Type *MemberTy = AggTy->getTypeAtIndex(i);
923 ConstantFoldInsertValueInstruction(Constant::getNullValue(MemberTy),
924 Val, Idxs+1, NumIdx-1) :
925 Constant::getNullValue(MemberTy);
929 if (const StructType *ST = dyn_cast<StructType>(AggTy))
930 return ConstantStruct::get(ST->getContext(), Ops, ST->isPacked());
931 return ConstantArray::get(cast<ArrayType>(AggTy), Ops);
934 if (isa<ConstantStruct>(Agg) || isa<ConstantArray>(Agg)) {
935 // Insertion of constant into aggregate constant.
936 std::vector<Constant*> Ops(Agg->getNumOperands());
937 for (unsigned i = 0; i < Agg->getNumOperands(); ++i) {
938 Constant *Op = cast<Constant>(Agg->getOperand(i));
940 Op = ConstantFoldInsertValueInstruction(Op, Val, Idxs+1, NumIdx-1);
944 if (const StructType* ST = dyn_cast<StructType>(Agg->getType()))
945 return ConstantStruct::get(ST->getContext(), Ops, ST->isPacked());
946 return ConstantArray::get(cast<ArrayType>(Agg->getType()), Ops);
953 Constant *llvm::ConstantFoldBinaryInstruction(unsigned Opcode,
954 Constant *C1, Constant *C2) {
955 // No compile-time operations on this type yet.
956 if (C1->getType()->isPPC_FP128Ty())
959 // Handle UndefValue up front.
960 if (isa<UndefValue>(C1) || isa<UndefValue>(C2)) {
962 case Instruction::Xor:
963 if (isa<UndefValue>(C1) && isa<UndefValue>(C2))
964 // Handle undef ^ undef -> 0 special case. This is a common
966 return Constant::getNullValue(C1->getType());
968 case Instruction::Add:
969 case Instruction::Sub:
970 return UndefValue::get(C1->getType());
971 case Instruction::Mul:
972 case Instruction::And:
973 return Constant::getNullValue(C1->getType());
974 case Instruction::UDiv:
975 case Instruction::SDiv:
976 case Instruction::URem:
977 case Instruction::SRem:
978 if (!isa<UndefValue>(C2)) // undef / X -> 0
979 return Constant::getNullValue(C1->getType());
980 return C2; // X / undef -> undef
981 case Instruction::Or: // X | undef -> -1
982 if (const VectorType *PTy = dyn_cast<VectorType>(C1->getType()))
983 return Constant::getAllOnesValue(PTy);
984 return Constant::getAllOnesValue(C1->getType());
985 case Instruction::LShr:
986 if (isa<UndefValue>(C2) && isa<UndefValue>(C1))
987 return C1; // undef lshr undef -> undef
988 return Constant::getNullValue(C1->getType()); // X lshr undef -> 0
990 case Instruction::AShr:
991 if (!isa<UndefValue>(C2))
992 return C1; // undef ashr X --> undef
993 else if (isa<UndefValue>(C1))
994 return C1; // undef ashr undef -> undef
996 return C1; // X ashr undef --> X
997 case Instruction::Shl:
998 // undef << X -> 0 or X << undef -> 0
999 return Constant::getNullValue(C1->getType());
1003 // Handle simplifications when the RHS is a constant int.
1004 if (ConstantInt *CI2 = dyn_cast<ConstantInt>(C2)) {
1006 case Instruction::Add:
1007 if (CI2->equalsInt(0)) return C1; // X + 0 == X
1009 case Instruction::Sub:
1010 if (CI2->equalsInt(0)) return C1; // X - 0 == X
1012 case Instruction::Mul:
1013 if (CI2->equalsInt(0)) return C2; // X * 0 == 0
1014 if (CI2->equalsInt(1))
1015 return C1; // X * 1 == X
1017 case Instruction::UDiv:
1018 case Instruction::SDiv:
1019 if (CI2->equalsInt(1))
1020 return C1; // X / 1 == X
1021 if (CI2->equalsInt(0))
1022 return UndefValue::get(CI2->getType()); // X / 0 == undef
1024 case Instruction::URem:
1025 case Instruction::SRem:
1026 if (CI2->equalsInt(1))
1027 return Constant::getNullValue(CI2->getType()); // X % 1 == 0
1028 if (CI2->equalsInt(0))
1029 return UndefValue::get(CI2->getType()); // X % 0 == undef
1031 case Instruction::And:
1032 if (CI2->isZero()) return C2; // X & 0 == 0
1033 if (CI2->isAllOnesValue())
1034 return C1; // X & -1 == X
1036 if (ConstantExpr *CE1 = dyn_cast<ConstantExpr>(C1)) {
1037 // (zext i32 to i64) & 4294967295 -> (zext i32 to i64)
1038 if (CE1->getOpcode() == Instruction::ZExt) {
1039 unsigned DstWidth = CI2->getType()->getBitWidth();
1041 CE1->getOperand(0)->getType()->getPrimitiveSizeInBits();
1042 APInt PossiblySetBits(APInt::getLowBitsSet(DstWidth, SrcWidth));
1043 if ((PossiblySetBits & CI2->getValue()) == PossiblySetBits)
1047 // If and'ing the address of a global with a constant, fold it.
1048 if (CE1->getOpcode() == Instruction::PtrToInt &&
1049 isa<GlobalValue>(CE1->getOperand(0))) {
1050 GlobalValue *GV = cast<GlobalValue>(CE1->getOperand(0));
1052 // Functions are at least 4-byte aligned.
1053 unsigned GVAlign = GV->getAlignment();
1054 if (isa<Function>(GV))
1055 GVAlign = std::max(GVAlign, 4U);
1058 unsigned DstWidth = CI2->getType()->getBitWidth();
1059 unsigned SrcWidth = std::min(DstWidth, Log2_32(GVAlign));
1060 APInt BitsNotSet(APInt::getLowBitsSet(DstWidth, SrcWidth));
1062 // If checking bits we know are clear, return zero.
1063 if ((CI2->getValue() & BitsNotSet) == CI2->getValue())
1064 return Constant::getNullValue(CI2->getType());
1069 case Instruction::Or:
1070 if (CI2->equalsInt(0)) return C1; // X | 0 == X
1071 if (CI2->isAllOnesValue())
1072 return C2; // X | -1 == -1
1074 case Instruction::Xor:
1075 if (CI2->equalsInt(0)) return C1; // X ^ 0 == X
1077 if (ConstantExpr *CE1 = dyn_cast<ConstantExpr>(C1)) {
1078 switch (CE1->getOpcode()) {
1080 case Instruction::ICmp:
1081 case Instruction::FCmp:
1082 // cmp pred ^ true -> cmp !pred
1083 assert(CI2->equalsInt(1));
1084 CmpInst::Predicate pred = (CmpInst::Predicate)CE1->getPredicate();
1085 pred = CmpInst::getInversePredicate(pred);
1086 return ConstantExpr::getCompare(pred, CE1->getOperand(0),
1087 CE1->getOperand(1));
1091 case Instruction::AShr:
1092 // ashr (zext C to Ty), C2 -> lshr (zext C, CSA), C2
1093 if (ConstantExpr *CE1 = dyn_cast<ConstantExpr>(C1))
1094 if (CE1->getOpcode() == Instruction::ZExt) // Top bits known zero.
1095 return ConstantExpr::getLShr(C1, C2);
1098 } else if (isa<ConstantInt>(C1)) {
1099 // If C1 is a ConstantInt and C2 is not, swap the operands.
1100 if (Instruction::isCommutative(Opcode))
1101 return ConstantExpr::get(Opcode, C2, C1);
1104 // At this point we know neither constant is an UndefValue.
1105 if (ConstantInt *CI1 = dyn_cast<ConstantInt>(C1)) {
1106 if (ConstantInt *CI2 = dyn_cast<ConstantInt>(C2)) {
1107 using namespace APIntOps;
1108 const APInt &C1V = CI1->getValue();
1109 const APInt &C2V = CI2->getValue();
1113 case Instruction::Add:
1114 return ConstantInt::get(CI1->getContext(), C1V + C2V);
1115 case Instruction::Sub:
1116 return ConstantInt::get(CI1->getContext(), C1V - C2V);
1117 case Instruction::Mul:
1118 return ConstantInt::get(CI1->getContext(), C1V * C2V);
1119 case Instruction::UDiv:
1120 assert(!CI2->isNullValue() && "Div by zero handled above");
1121 return ConstantInt::get(CI1->getContext(), C1V.udiv(C2V));
1122 case Instruction::SDiv:
1123 assert(!CI2->isNullValue() && "Div by zero handled above");
1124 if (C2V.isAllOnesValue() && C1V.isMinSignedValue())
1125 return UndefValue::get(CI1->getType()); // MIN_INT / -1 -> undef
1126 return ConstantInt::get(CI1->getContext(), C1V.sdiv(C2V));
1127 case Instruction::URem:
1128 assert(!CI2->isNullValue() && "Div by zero handled above");
1129 return ConstantInt::get(CI1->getContext(), C1V.urem(C2V));
1130 case Instruction::SRem:
1131 assert(!CI2->isNullValue() && "Div by zero handled above");
1132 if (C2V.isAllOnesValue() && C1V.isMinSignedValue())
1133 return UndefValue::get(CI1->getType()); // MIN_INT % -1 -> undef
1134 return ConstantInt::get(CI1->getContext(), C1V.srem(C2V));
1135 case Instruction::And:
1136 return ConstantInt::get(CI1->getContext(), C1V & C2V);
1137 case Instruction::Or:
1138 return ConstantInt::get(CI1->getContext(), C1V | C2V);
1139 case Instruction::Xor:
1140 return ConstantInt::get(CI1->getContext(), C1V ^ C2V);
1141 case Instruction::Shl: {
1142 uint32_t shiftAmt = C2V.getZExtValue();
1143 if (shiftAmt < C1V.getBitWidth())
1144 return ConstantInt::get(CI1->getContext(), C1V.shl(shiftAmt));
1146 return UndefValue::get(C1->getType()); // too big shift is undef
1148 case Instruction::LShr: {
1149 uint32_t shiftAmt = C2V.getZExtValue();
1150 if (shiftAmt < C1V.getBitWidth())
1151 return ConstantInt::get(CI1->getContext(), C1V.lshr(shiftAmt));
1153 return UndefValue::get(C1->getType()); // too big shift is undef
1155 case Instruction::AShr: {
1156 uint32_t shiftAmt = C2V.getZExtValue();
1157 if (shiftAmt < C1V.getBitWidth())
1158 return ConstantInt::get(CI1->getContext(), C1V.ashr(shiftAmt));
1160 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->equalsInt(0)) return C1;
1178 } else if (ConstantFP *CFP1 = dyn_cast<ConstantFP>(C1)) {
1179 if (ConstantFP *CFP2 = dyn_cast<ConstantFP>(C2)) {
1180 APFloat C1V = CFP1->getValueAPF();
1181 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:
1199 (void)C3V.mod(C2V, APFloat::rmNearestTiesToEven);
1200 return ConstantFP::get(C1->getContext(), C3V);
1203 } else if (const VectorType *VTy = dyn_cast<VectorType>(C1->getType())) {
1204 ConstantVector *CP1 = dyn_cast<ConstantVector>(C1);
1205 ConstantVector *CP2 = dyn_cast<ConstantVector>(C2);
1206 if ((CP1 != NULL || isa<ConstantAggregateZero>(C1)) &&
1207 (CP2 != NULL || isa<ConstantAggregateZero>(C2))) {
1208 std::vector<Constant*> Res;
1209 const Type* EltTy = VTy->getElementType();
1215 case Instruction::Add:
1216 for (unsigned i = 0, e = VTy->getNumElements(); i != e; ++i) {
1217 C1 = CP1 ? CP1->getOperand(i) : Constant::getNullValue(EltTy);
1218 C2 = CP2 ? CP2->getOperand(i) : Constant::getNullValue(EltTy);
1219 Res.push_back(ConstantExpr::getAdd(C1, C2));
1221 return ConstantVector::get(Res);
1222 case Instruction::FAdd:
1223 for (unsigned i = 0, e = VTy->getNumElements(); i != e; ++i) {
1224 C1 = CP1 ? CP1->getOperand(i) : Constant::getNullValue(EltTy);
1225 C2 = CP2 ? CP2->getOperand(i) : Constant::getNullValue(EltTy);
1226 Res.push_back(ConstantExpr::getFAdd(C1, C2));
1228 return ConstantVector::get(Res);
1229 case Instruction::Sub:
1230 for (unsigned i = 0, e = VTy->getNumElements(); i != e; ++i) {
1231 C1 = CP1 ? CP1->getOperand(i) : Constant::getNullValue(EltTy);
1232 C2 = CP2 ? CP2->getOperand(i) : Constant::getNullValue(EltTy);
1233 Res.push_back(ConstantExpr::getSub(C1, C2));
1235 return ConstantVector::get(Res);
1236 case Instruction::FSub:
1237 for (unsigned i = 0, e = VTy->getNumElements(); i != e; ++i) {
1238 C1 = CP1 ? CP1->getOperand(i) : Constant::getNullValue(EltTy);
1239 C2 = CP2 ? CP2->getOperand(i) : Constant::getNullValue(EltTy);
1240 Res.push_back(ConstantExpr::getFSub(C1, C2));
1242 return ConstantVector::get(Res);
1243 case Instruction::Mul:
1244 for (unsigned i = 0, e = VTy->getNumElements(); i != e; ++i) {
1245 C1 = CP1 ? CP1->getOperand(i) : Constant::getNullValue(EltTy);
1246 C2 = CP2 ? CP2->getOperand(i) : Constant::getNullValue(EltTy);
1247 Res.push_back(ConstantExpr::getMul(C1, C2));
1249 return ConstantVector::get(Res);
1250 case Instruction::FMul:
1251 for (unsigned i = 0, e = VTy->getNumElements(); i != e; ++i) {
1252 C1 = CP1 ? CP1->getOperand(i) : Constant::getNullValue(EltTy);
1253 C2 = CP2 ? CP2->getOperand(i) : Constant::getNullValue(EltTy);
1254 Res.push_back(ConstantExpr::getFMul(C1, C2));
1256 return ConstantVector::get(Res);
1257 case Instruction::UDiv:
1258 for (unsigned i = 0, e = VTy->getNumElements(); i != e; ++i) {
1259 C1 = CP1 ? CP1->getOperand(i) : Constant::getNullValue(EltTy);
1260 C2 = CP2 ? CP2->getOperand(i) : Constant::getNullValue(EltTy);
1261 Res.push_back(ConstantExpr::getUDiv(C1, C2));
1263 return ConstantVector::get(Res);
1264 case Instruction::SDiv:
1265 for (unsigned i = 0, e = VTy->getNumElements(); i != e; ++i) {
1266 C1 = CP1 ? CP1->getOperand(i) : Constant::getNullValue(EltTy);
1267 C2 = CP2 ? CP2->getOperand(i) : Constant::getNullValue(EltTy);
1268 Res.push_back(ConstantExpr::getSDiv(C1, C2));
1270 return ConstantVector::get(Res);
1271 case Instruction::FDiv:
1272 for (unsigned i = 0, e = VTy->getNumElements(); i != e; ++i) {
1273 C1 = CP1 ? CP1->getOperand(i) : Constant::getNullValue(EltTy);
1274 C2 = CP2 ? CP2->getOperand(i) : Constant::getNullValue(EltTy);
1275 Res.push_back(ConstantExpr::getFDiv(C1, C2));
1277 return ConstantVector::get(Res);
1278 case Instruction::URem:
1279 for (unsigned i = 0, e = VTy->getNumElements(); i != e; ++i) {
1280 C1 = CP1 ? CP1->getOperand(i) : Constant::getNullValue(EltTy);
1281 C2 = CP2 ? CP2->getOperand(i) : Constant::getNullValue(EltTy);
1282 Res.push_back(ConstantExpr::getURem(C1, C2));
1284 return ConstantVector::get(Res);
1285 case Instruction::SRem:
1286 for (unsigned i = 0, e = VTy->getNumElements(); i != e; ++i) {
1287 C1 = CP1 ? CP1->getOperand(i) : Constant::getNullValue(EltTy);
1288 C2 = CP2 ? CP2->getOperand(i) : Constant::getNullValue(EltTy);
1289 Res.push_back(ConstantExpr::getSRem(C1, C2));
1291 return ConstantVector::get(Res);
1292 case Instruction::FRem:
1293 for (unsigned i = 0, e = VTy->getNumElements(); i != e; ++i) {
1294 C1 = CP1 ? CP1->getOperand(i) : Constant::getNullValue(EltTy);
1295 C2 = CP2 ? CP2->getOperand(i) : Constant::getNullValue(EltTy);
1296 Res.push_back(ConstantExpr::getFRem(C1, C2));
1298 return ConstantVector::get(Res);
1299 case Instruction::And:
1300 for (unsigned i = 0, e = VTy->getNumElements(); i != e; ++i) {
1301 C1 = CP1 ? CP1->getOperand(i) : Constant::getNullValue(EltTy);
1302 C2 = CP2 ? CP2->getOperand(i) : Constant::getNullValue(EltTy);
1303 Res.push_back(ConstantExpr::getAnd(C1, C2));
1305 return ConstantVector::get(Res);
1306 case Instruction::Or:
1307 for (unsigned i = 0, e = VTy->getNumElements(); i != e; ++i) {
1308 C1 = CP1 ? CP1->getOperand(i) : Constant::getNullValue(EltTy);
1309 C2 = CP2 ? CP2->getOperand(i) : Constant::getNullValue(EltTy);
1310 Res.push_back(ConstantExpr::getOr(C1, C2));
1312 return ConstantVector::get(Res);
1313 case Instruction::Xor:
1314 for (unsigned i = 0, e = VTy->getNumElements(); i != e; ++i) {
1315 C1 = CP1 ? CP1->getOperand(i) : Constant::getNullValue(EltTy);
1316 C2 = CP2 ? CP2->getOperand(i) : Constant::getNullValue(EltTy);
1317 Res.push_back(ConstantExpr::getXor(C1, C2));
1319 return ConstantVector::get(Res);
1320 case Instruction::LShr:
1321 for (unsigned i = 0, e = VTy->getNumElements(); i != e; ++i) {
1322 C1 = CP1 ? CP1->getOperand(i) : Constant::getNullValue(EltTy);
1323 C2 = CP2 ? CP2->getOperand(i) : Constant::getNullValue(EltTy);
1324 Res.push_back(ConstantExpr::getLShr(C1, C2));
1326 return ConstantVector::get(Res);
1327 case Instruction::AShr:
1328 for (unsigned i = 0, e = VTy->getNumElements(); i != e; ++i) {
1329 C1 = CP1 ? CP1->getOperand(i) : Constant::getNullValue(EltTy);
1330 C2 = CP2 ? CP2->getOperand(i) : Constant::getNullValue(EltTy);
1331 Res.push_back(ConstantExpr::getAShr(C1, C2));
1333 return ConstantVector::get(Res);
1334 case Instruction::Shl:
1335 for (unsigned i = 0, e = VTy->getNumElements(); i != e; ++i) {
1336 C1 = CP1 ? CP1->getOperand(i) : Constant::getNullValue(EltTy);
1337 C2 = CP2 ? CP2->getOperand(i) : Constant::getNullValue(EltTy);
1338 Res.push_back(ConstantExpr::getShl(C1, C2));
1340 return ConstantVector::get(Res);
1345 if (ConstantExpr *CE1 = dyn_cast<ConstantExpr>(C1)) {
1346 // There are many possible foldings we could do here. We should probably
1347 // at least fold add of a pointer with an integer into the appropriate
1348 // getelementptr. This will improve alias analysis a bit.
1350 // Given ((a + b) + c), if (b + c) folds to something interesting, return
1352 if (Instruction::isAssociative(Opcode, C1->getType()) &&
1353 CE1->getOpcode() == Opcode) {
1354 Constant *T = ConstantExpr::get(Opcode, CE1->getOperand(1), C2);
1355 if (!isa<ConstantExpr>(T) || cast<ConstantExpr>(T)->getOpcode() != Opcode)
1356 return ConstantExpr::get(Opcode, CE1->getOperand(0), T);
1358 } else if (isa<ConstantExpr>(C2)) {
1359 // If C2 is a constant expr and C1 isn't, flop them around and fold the
1360 // other way if possible.
1361 if (Instruction::isCommutative(Opcode))
1362 return ConstantFoldBinaryInstruction(Opcode, C2, C1);
1365 // i1 can be simplified in many cases.
1366 if (C1->getType()->isIntegerTy(1)) {
1368 case Instruction::Add:
1369 case Instruction::Sub:
1370 return ConstantExpr::getXor(C1, C2);
1371 case Instruction::Mul:
1372 return ConstantExpr::getAnd(C1, C2);
1373 case Instruction::Shl:
1374 case Instruction::LShr:
1375 case Instruction::AShr:
1376 // We can assume that C2 == 0. If it were one the result would be
1377 // undefined because the shift value is as large as the bitwidth.
1379 case Instruction::SDiv:
1380 case Instruction::UDiv:
1381 // We can assume that C2 == 1. If it were zero the result would be
1382 // undefined through division by zero.
1384 case Instruction::URem:
1385 case Instruction::SRem:
1386 // We can assume that C2 == 1. If it were zero the result would be
1387 // undefined through division by zero.
1388 return ConstantInt::getFalse(C1->getContext());
1394 // We don't know how to fold this.
1398 /// isZeroSizedType - This type is zero sized if its an array or structure of
1399 /// zero sized types. The only leaf zero sized type is an empty structure.
1400 static bool isMaybeZeroSizedType(const Type *Ty) {
1401 if (Ty->isOpaqueTy()) return true; // Can't say.
1402 if (const StructType *STy = dyn_cast<StructType>(Ty)) {
1404 // If all of elements have zero size, this does too.
1405 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i)
1406 if (!isMaybeZeroSizedType(STy->getElementType(i))) return false;
1409 } else if (const ArrayType *ATy = dyn_cast<ArrayType>(Ty)) {
1410 return isMaybeZeroSizedType(ATy->getElementType());
1415 /// IdxCompare - Compare the two constants as though they were getelementptr
1416 /// indices. This allows coersion of the types to be the same thing.
1418 /// If the two constants are the "same" (after coersion), return 0. If the
1419 /// first is less than the second, return -1, if the second is less than the
1420 /// first, return 1. If the constants are not integral, return -2.
1422 static int IdxCompare(Constant *C1, Constant *C2, const Type *ElTy) {
1423 if (C1 == C2) return 0;
1425 // Ok, we found a different index. If they are not ConstantInt, we can't do
1426 // anything with them.
1427 if (!isa<ConstantInt>(C1) || !isa<ConstantInt>(C2))
1428 return -2; // don't know!
1430 // Ok, we have two differing integer indices. Sign extend them to be the same
1431 // type. Long is always big enough, so we use it.
1432 if (!C1->getType()->isIntegerTy(64))
1433 C1 = ConstantExpr::getSExt(C1, Type::getInt64Ty(C1->getContext()));
1435 if (!C2->getType()->isIntegerTy(64))
1436 C2 = ConstantExpr::getSExt(C2, Type::getInt64Ty(C1->getContext()));
1438 if (C1 == C2) return 0; // They are equal
1440 // If the type being indexed over is really just a zero sized type, there is
1441 // no pointer difference being made here.
1442 if (isMaybeZeroSizedType(ElTy))
1443 return -2; // dunno.
1445 // If they are really different, now that they are the same type, then we
1446 // found a difference!
1447 if (cast<ConstantInt>(C1)->getSExtValue() <
1448 cast<ConstantInt>(C2)->getSExtValue())
1454 /// evaluateFCmpRelation - This function determines if there is anything we can
1455 /// decide about the two constants provided. This doesn't need to handle simple
1456 /// things like ConstantFP comparisons, but should instead handle ConstantExprs.
1457 /// If we can determine that the two constants have a particular relation to
1458 /// each other, we should return the corresponding FCmpInst predicate,
1459 /// otherwise return FCmpInst::BAD_FCMP_PREDICATE. This is used below in
1460 /// ConstantFoldCompareInstruction.
1462 /// To simplify this code we canonicalize the relation so that the first
1463 /// operand is always the most "complex" of the two. We consider ConstantFP
1464 /// to be the simplest, and ConstantExprs to be the most complex.
1465 static FCmpInst::Predicate evaluateFCmpRelation(Constant *V1, Constant *V2) {
1466 assert(V1->getType() == V2->getType() &&
1467 "Cannot compare values of different types!");
1469 // No compile-time operations on this type yet.
1470 if (V1->getType()->isPPC_FP128Ty())
1471 return FCmpInst::BAD_FCMP_PREDICATE;
1473 // Handle degenerate case quickly
1474 if (V1 == V2) return FCmpInst::FCMP_OEQ;
1476 if (!isa<ConstantExpr>(V1)) {
1477 if (!isa<ConstantExpr>(V2)) {
1478 // We distilled thisUse the standard constant folder for a few cases
1480 R = dyn_cast<ConstantInt>(
1481 ConstantExpr::getFCmp(FCmpInst::FCMP_OEQ, V1, V2));
1482 if (R && !R->isZero())
1483 return FCmpInst::FCMP_OEQ;
1484 R = dyn_cast<ConstantInt>(
1485 ConstantExpr::getFCmp(FCmpInst::FCMP_OLT, V1, V2));
1486 if (R && !R->isZero())
1487 return FCmpInst::FCMP_OLT;
1488 R = dyn_cast<ConstantInt>(
1489 ConstantExpr::getFCmp(FCmpInst::FCMP_OGT, V1, V2));
1490 if (R && !R->isZero())
1491 return FCmpInst::FCMP_OGT;
1493 // Nothing more we can do
1494 return FCmpInst::BAD_FCMP_PREDICATE;
1497 // If the first operand is simple and second is ConstantExpr, swap operands.
1498 FCmpInst::Predicate SwappedRelation = evaluateFCmpRelation(V2, V1);
1499 if (SwappedRelation != FCmpInst::BAD_FCMP_PREDICATE)
1500 return FCmpInst::getSwappedPredicate(SwappedRelation);
1502 // Ok, the LHS is known to be a constantexpr. The RHS can be any of a
1503 // constantexpr or a simple constant.
1504 ConstantExpr *CE1 = cast<ConstantExpr>(V1);
1505 switch (CE1->getOpcode()) {
1506 case Instruction::FPTrunc:
1507 case Instruction::FPExt:
1508 case Instruction::UIToFP:
1509 case Instruction::SIToFP:
1510 // We might be able to do something with these but we don't right now.
1516 // There are MANY other foldings that we could perform here. They will
1517 // probably be added on demand, as they seem needed.
1518 return FCmpInst::BAD_FCMP_PREDICATE;
1521 /// evaluateICmpRelation - This function determines if there is anything we can
1522 /// decide about the two constants provided. This doesn't need to handle simple
1523 /// things like integer comparisons, but should instead handle ConstantExprs
1524 /// and GlobalValues. If we can determine that the two constants have a
1525 /// particular relation to each other, we should return the corresponding ICmp
1526 /// predicate, otherwise return ICmpInst::BAD_ICMP_PREDICATE.
1528 /// To simplify this code we canonicalize the relation so that the first
1529 /// operand is always the most "complex" of the two. We consider simple
1530 /// constants (like ConstantInt) to be the simplest, followed by
1531 /// GlobalValues, followed by ConstantExpr's (the most complex).
1533 static ICmpInst::Predicate evaluateICmpRelation(Constant *V1, Constant *V2,
1535 assert(V1->getType() == V2->getType() &&
1536 "Cannot compare different types of values!");
1537 if (V1 == V2) return ICmpInst::ICMP_EQ;
1539 if (!isa<ConstantExpr>(V1) && !isa<GlobalValue>(V1) &&
1540 !isa<BlockAddress>(V1)) {
1541 if (!isa<GlobalValue>(V2) && !isa<ConstantExpr>(V2) &&
1542 !isa<BlockAddress>(V2)) {
1543 // We distilled this down to a simple case, use the standard constant
1546 ICmpInst::Predicate pred = ICmpInst::ICMP_EQ;
1547 R = dyn_cast<ConstantInt>(ConstantExpr::getICmp(pred, V1, V2));
1548 if (R && !R->isZero())
1550 pred = isSigned ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT;
1551 R = dyn_cast<ConstantInt>(ConstantExpr::getICmp(pred, V1, V2));
1552 if (R && !R->isZero())
1554 pred = isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT;
1555 R = dyn_cast<ConstantInt>(ConstantExpr::getICmp(pred, V1, V2));
1556 if (R && !R->isZero())
1559 // If we couldn't figure it out, bail.
1560 return ICmpInst::BAD_ICMP_PREDICATE;
1563 // If the first operand is simple, swap operands.
1564 ICmpInst::Predicate SwappedRelation =
1565 evaluateICmpRelation(V2, V1, isSigned);
1566 if (SwappedRelation != ICmpInst::BAD_ICMP_PREDICATE)
1567 return ICmpInst::getSwappedPredicate(SwappedRelation);
1569 } else if (const GlobalValue *GV = dyn_cast<GlobalValue>(V1)) {
1570 if (isa<ConstantExpr>(V2)) { // Swap as necessary.
1571 ICmpInst::Predicate SwappedRelation =
1572 evaluateICmpRelation(V2, V1, isSigned);
1573 if (SwappedRelation != ICmpInst::BAD_ICMP_PREDICATE)
1574 return ICmpInst::getSwappedPredicate(SwappedRelation);
1575 return ICmpInst::BAD_ICMP_PREDICATE;
1578 // Now we know that the RHS is a GlobalValue, BlockAddress or simple
1579 // constant (which, since the types must match, means that it's a
1580 // ConstantPointerNull).
1581 if (const GlobalValue *GV2 = dyn_cast<GlobalValue>(V2)) {
1582 // Don't try to decide equality of aliases.
1583 if (!isa<GlobalAlias>(GV) && !isa<GlobalAlias>(GV2))
1584 if (!GV->hasExternalWeakLinkage() || !GV2->hasExternalWeakLinkage())
1585 return ICmpInst::ICMP_NE;
1586 } else if (isa<BlockAddress>(V2)) {
1587 return ICmpInst::ICMP_NE; // Globals never equal labels.
1589 assert(isa<ConstantPointerNull>(V2) && "Canonicalization guarantee!");
1590 // GlobalVals can never be null unless they have external weak linkage.
1591 // We don't try to evaluate aliases here.
1592 if (!GV->hasExternalWeakLinkage() && !isa<GlobalAlias>(GV))
1593 return ICmpInst::ICMP_NE;
1595 } else if (const BlockAddress *BA = dyn_cast<BlockAddress>(V1)) {
1596 if (isa<ConstantExpr>(V2)) { // Swap as necessary.
1597 ICmpInst::Predicate SwappedRelation =
1598 evaluateICmpRelation(V2, V1, isSigned);
1599 if (SwappedRelation != ICmpInst::BAD_ICMP_PREDICATE)
1600 return ICmpInst::getSwappedPredicate(SwappedRelation);
1601 return ICmpInst::BAD_ICMP_PREDICATE;
1604 // Now we know that the RHS is a GlobalValue, BlockAddress or simple
1605 // constant (which, since the types must match, means that it is a
1606 // ConstantPointerNull).
1607 if (const BlockAddress *BA2 = dyn_cast<BlockAddress>(V2)) {
1608 // Block address in another function can't equal this one, but block
1609 // addresses in the current function might be the same if blocks are
1611 if (BA2->getFunction() != BA->getFunction())
1612 return ICmpInst::ICMP_NE;
1614 // Block addresses aren't null, don't equal the address of globals.
1615 assert((isa<ConstantPointerNull>(V2) || isa<GlobalValue>(V2)) &&
1616 "Canonicalization guarantee!");
1617 return ICmpInst::ICMP_NE;
1620 // Ok, the LHS is known to be a constantexpr. The RHS can be any of a
1621 // constantexpr, a global, block address, or a simple constant.
1622 ConstantExpr *CE1 = cast<ConstantExpr>(V1);
1623 Constant *CE1Op0 = CE1->getOperand(0);
1625 switch (CE1->getOpcode()) {
1626 case Instruction::Trunc:
1627 case Instruction::FPTrunc:
1628 case Instruction::FPExt:
1629 case Instruction::FPToUI:
1630 case Instruction::FPToSI:
1631 break; // We can't evaluate floating point casts or truncations.
1633 case Instruction::UIToFP:
1634 case Instruction::SIToFP:
1635 case Instruction::BitCast:
1636 case Instruction::ZExt:
1637 case Instruction::SExt:
1638 // If the cast is not actually changing bits, and the second operand is a
1639 // null pointer, do the comparison with the pre-casted value.
1640 if (V2->isNullValue() &&
1641 (CE1->getType()->isPointerTy() || CE1->getType()->isIntegerTy())) {
1642 if (CE1->getOpcode() == Instruction::ZExt) isSigned = false;
1643 if (CE1->getOpcode() == Instruction::SExt) isSigned = true;
1644 return evaluateICmpRelation(CE1Op0,
1645 Constant::getNullValue(CE1Op0->getType()),
1650 case Instruction::GetElementPtr:
1651 // Ok, since this is a getelementptr, we know that the constant has a
1652 // pointer type. Check the various cases.
1653 if (isa<ConstantPointerNull>(V2)) {
1654 // If we are comparing a GEP to a null pointer, check to see if the base
1655 // of the GEP equals the null pointer.
1656 if (const GlobalValue *GV = dyn_cast<GlobalValue>(CE1Op0)) {
1657 if (GV->hasExternalWeakLinkage())
1658 // Weak linkage GVals could be zero or not. We're comparing that
1659 // to null pointer so its greater-or-equal
1660 return isSigned ? ICmpInst::ICMP_SGE : ICmpInst::ICMP_UGE;
1662 // If its not weak linkage, the GVal must have a non-zero address
1663 // so the result is greater-than
1664 return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT;
1665 } else if (isa<ConstantPointerNull>(CE1Op0)) {
1666 // If we are indexing from a null pointer, check to see if we have any
1667 // non-zero indices.
1668 for (unsigned i = 1, e = CE1->getNumOperands(); i != e; ++i)
1669 if (!CE1->getOperand(i)->isNullValue())
1670 // Offsetting from null, must not be equal.
1671 return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT;
1672 // Only zero indexes from null, must still be zero.
1673 return ICmpInst::ICMP_EQ;
1675 // Otherwise, we can't really say if the first operand is null or not.
1676 } else if (const GlobalValue *GV2 = dyn_cast<GlobalValue>(V2)) {
1677 if (isa<ConstantPointerNull>(CE1Op0)) {
1678 if (GV2->hasExternalWeakLinkage())
1679 // Weak linkage GVals could be zero or not. We're comparing it to
1680 // a null pointer, so its less-or-equal
1681 return isSigned ? ICmpInst::ICMP_SLE : ICmpInst::ICMP_ULE;
1683 // If its not weak linkage, the GVal must have a non-zero address
1684 // so the result is less-than
1685 return isSigned ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT;
1686 } else if (const GlobalValue *GV = dyn_cast<GlobalValue>(CE1Op0)) {
1688 // If this is a getelementptr of the same global, then it must be
1689 // different. Because the types must match, the getelementptr could
1690 // only have at most one index, and because we fold getelementptr's
1691 // with a single zero index, it must be nonzero.
1692 assert(CE1->getNumOperands() == 2 &&
1693 !CE1->getOperand(1)->isNullValue() &&
1694 "Suprising getelementptr!");
1695 return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT;
1697 // If they are different globals, we don't know what the value is,
1698 // but they can't be equal.
1699 return ICmpInst::ICMP_NE;
1703 ConstantExpr *CE2 = cast<ConstantExpr>(V2);
1704 Constant *CE2Op0 = CE2->getOperand(0);
1706 // There are MANY other foldings that we could perform here. They will
1707 // probably be added on demand, as they seem needed.
1708 switch (CE2->getOpcode()) {
1710 case Instruction::GetElementPtr:
1711 // By far the most common case to handle is when the base pointers are
1712 // obviously to the same or different globals.
1713 if (isa<GlobalValue>(CE1Op0) && isa<GlobalValue>(CE2Op0)) {
1714 if (CE1Op0 != CE2Op0) // Don't know relative ordering, but not equal
1715 return ICmpInst::ICMP_NE;
1716 // Ok, we know that both getelementptr instructions are based on the
1717 // same global. From this, we can precisely determine the relative
1718 // ordering of the resultant pointers.
1721 // The logic below assumes that the result of the comparison
1722 // can be determined by finding the first index that differs.
1723 // This doesn't work if there is over-indexing in any
1724 // subsequent indices, so check for that case first.
1725 if (!CE1->isGEPWithNoNotionalOverIndexing() ||
1726 !CE2->isGEPWithNoNotionalOverIndexing())
1727 return ICmpInst::BAD_ICMP_PREDICATE; // Might be equal.
1729 // Compare all of the operands the GEP's have in common.
1730 gep_type_iterator GTI = gep_type_begin(CE1);
1731 for (;i != CE1->getNumOperands() && i != CE2->getNumOperands();
1733 switch (IdxCompare(CE1->getOperand(i),
1734 CE2->getOperand(i), GTI.getIndexedType())) {
1735 case -1: return isSigned ? ICmpInst::ICMP_SLT:ICmpInst::ICMP_ULT;
1736 case 1: return isSigned ? ICmpInst::ICMP_SGT:ICmpInst::ICMP_UGT;
1737 case -2: return ICmpInst::BAD_ICMP_PREDICATE;
1740 // Ok, we ran out of things they have in common. If any leftovers
1741 // are non-zero then we have a difference, otherwise we are equal.
1742 for (; i < CE1->getNumOperands(); ++i)
1743 if (!CE1->getOperand(i)->isNullValue()) {
1744 if (isa<ConstantInt>(CE1->getOperand(i)))
1745 return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT;
1747 return ICmpInst::BAD_ICMP_PREDICATE; // Might be equal.
1750 for (; i < CE2->getNumOperands(); ++i)
1751 if (!CE2->getOperand(i)->isNullValue()) {
1752 if (isa<ConstantInt>(CE2->getOperand(i)))
1753 return isSigned ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT;
1755 return ICmpInst::BAD_ICMP_PREDICATE; // Might be equal.
1757 return ICmpInst::ICMP_EQ;
1766 return ICmpInst::BAD_ICMP_PREDICATE;
1769 Constant *llvm::ConstantFoldCompareInstruction(unsigned short pred,
1770 Constant *C1, Constant *C2) {
1771 const Type *ResultTy;
1772 if (const VectorType *VT = dyn_cast<VectorType>(C1->getType()))
1773 ResultTy = VectorType::get(Type::getInt1Ty(C1->getContext()),
1774 VT->getNumElements());
1776 ResultTy = Type::getInt1Ty(C1->getContext());
1778 // Fold FCMP_FALSE/FCMP_TRUE unconditionally.
1779 if (pred == FCmpInst::FCMP_FALSE)
1780 return Constant::getNullValue(ResultTy);
1782 if (pred == FCmpInst::FCMP_TRUE)
1783 return Constant::getAllOnesValue(ResultTy);
1785 // Handle some degenerate cases first
1786 if (isa<UndefValue>(C1) || isa<UndefValue>(C2))
1787 return UndefValue::get(ResultTy);
1789 // No compile-time operations on this type yet.
1790 if (C1->getType()->isPPC_FP128Ty())
1793 // icmp eq/ne(null,GV) -> false/true
1794 if (C1->isNullValue()) {
1795 if (const GlobalValue *GV = dyn_cast<GlobalValue>(C2))
1796 // Don't try to evaluate aliases. External weak GV can be null.
1797 if (!isa<GlobalAlias>(GV) && !GV->hasExternalWeakLinkage()) {
1798 if (pred == ICmpInst::ICMP_EQ)
1799 return ConstantInt::getFalse(C1->getContext());
1800 else if (pred == ICmpInst::ICMP_NE)
1801 return ConstantInt::getTrue(C1->getContext());
1803 // icmp eq/ne(GV,null) -> false/true
1804 } else if (C2->isNullValue()) {
1805 if (const GlobalValue *GV = dyn_cast<GlobalValue>(C1))
1806 // Don't try to evaluate aliases. External weak GV can be null.
1807 if (!isa<GlobalAlias>(GV) && !GV->hasExternalWeakLinkage()) {
1808 if (pred == ICmpInst::ICMP_EQ)
1809 return ConstantInt::getFalse(C1->getContext());
1810 else if (pred == ICmpInst::ICMP_NE)
1811 return ConstantInt::getTrue(C1->getContext());
1815 // If the comparison is a comparison between two i1's, simplify it.
1816 if (C1->getType()->isIntegerTy(1)) {
1818 case ICmpInst::ICMP_EQ:
1819 if (isa<ConstantInt>(C2))
1820 return ConstantExpr::getXor(C1, ConstantExpr::getNot(C2));
1821 return ConstantExpr::getXor(ConstantExpr::getNot(C1), C2);
1822 case ICmpInst::ICMP_NE:
1823 return ConstantExpr::getXor(C1, C2);
1829 if (isa<ConstantInt>(C1) && isa<ConstantInt>(C2)) {
1830 APInt V1 = cast<ConstantInt>(C1)->getValue();
1831 APInt V2 = cast<ConstantInt>(C2)->getValue();
1833 default: llvm_unreachable("Invalid ICmp Predicate"); return 0;
1834 case ICmpInst::ICMP_EQ: return ConstantInt::get(ResultTy, V1 == V2);
1835 case ICmpInst::ICMP_NE: return ConstantInt::get(ResultTy, V1 != V2);
1836 case ICmpInst::ICMP_SLT: return ConstantInt::get(ResultTy, V1.slt(V2));
1837 case ICmpInst::ICMP_SGT: return ConstantInt::get(ResultTy, V1.sgt(V2));
1838 case ICmpInst::ICMP_SLE: return ConstantInt::get(ResultTy, V1.sle(V2));
1839 case ICmpInst::ICMP_SGE: return ConstantInt::get(ResultTy, V1.sge(V2));
1840 case ICmpInst::ICMP_ULT: return ConstantInt::get(ResultTy, V1.ult(V2));
1841 case ICmpInst::ICMP_UGT: return ConstantInt::get(ResultTy, V1.ugt(V2));
1842 case ICmpInst::ICMP_ULE: return ConstantInt::get(ResultTy, V1.ule(V2));
1843 case ICmpInst::ICMP_UGE: return ConstantInt::get(ResultTy, V1.uge(V2));
1845 } else if (isa<ConstantFP>(C1) && isa<ConstantFP>(C2)) {
1846 APFloat C1V = cast<ConstantFP>(C1)->getValueAPF();
1847 APFloat C2V = cast<ConstantFP>(C2)->getValueAPF();
1848 APFloat::cmpResult R = C1V.compare(C2V);
1850 default: llvm_unreachable("Invalid FCmp Predicate"); return 0;
1851 case FCmpInst::FCMP_FALSE: return Constant::getNullValue(ResultTy);
1852 case FCmpInst::FCMP_TRUE: return Constant::getAllOnesValue(ResultTy);
1853 case FCmpInst::FCMP_UNO:
1854 return ConstantInt::get(ResultTy, R==APFloat::cmpUnordered);
1855 case FCmpInst::FCMP_ORD:
1856 return ConstantInt::get(ResultTy, R!=APFloat::cmpUnordered);
1857 case FCmpInst::FCMP_UEQ:
1858 return ConstantInt::get(ResultTy, R==APFloat::cmpUnordered ||
1859 R==APFloat::cmpEqual);
1860 case FCmpInst::FCMP_OEQ:
1861 return ConstantInt::get(ResultTy, R==APFloat::cmpEqual);
1862 case FCmpInst::FCMP_UNE:
1863 return ConstantInt::get(ResultTy, R!=APFloat::cmpEqual);
1864 case FCmpInst::FCMP_ONE:
1865 return ConstantInt::get(ResultTy, R==APFloat::cmpLessThan ||
1866 R==APFloat::cmpGreaterThan);
1867 case FCmpInst::FCMP_ULT:
1868 return ConstantInt::get(ResultTy, R==APFloat::cmpUnordered ||
1869 R==APFloat::cmpLessThan);
1870 case FCmpInst::FCMP_OLT:
1871 return ConstantInt::get(ResultTy, R==APFloat::cmpLessThan);
1872 case FCmpInst::FCMP_UGT:
1873 return ConstantInt::get(ResultTy, R==APFloat::cmpUnordered ||
1874 R==APFloat::cmpGreaterThan);
1875 case FCmpInst::FCMP_OGT:
1876 return ConstantInt::get(ResultTy, R==APFloat::cmpGreaterThan);
1877 case FCmpInst::FCMP_ULE:
1878 return ConstantInt::get(ResultTy, R!=APFloat::cmpGreaterThan);
1879 case FCmpInst::FCMP_OLE:
1880 return ConstantInt::get(ResultTy, R==APFloat::cmpLessThan ||
1881 R==APFloat::cmpEqual);
1882 case FCmpInst::FCMP_UGE:
1883 return ConstantInt::get(ResultTy, R!=APFloat::cmpLessThan);
1884 case FCmpInst::FCMP_OGE:
1885 return ConstantInt::get(ResultTy, R==APFloat::cmpGreaterThan ||
1886 R==APFloat::cmpEqual);
1888 } else if (C1->getType()->isVectorTy()) {
1889 SmallVector<Constant*, 16> C1Elts, C2Elts;
1890 C1->getVectorElements(C1Elts);
1891 C2->getVectorElements(C2Elts);
1892 if (C1Elts.empty() || C2Elts.empty())
1895 // If we can constant fold the comparison of each element, constant fold
1896 // the whole vector comparison.
1897 SmallVector<Constant*, 4> ResElts;
1898 for (unsigned i = 0, e = C1Elts.size(); i != e; ++i) {
1899 // Compare the elements, producing an i1 result or constant expr.
1900 ResElts.push_back(ConstantExpr::getCompare(pred, C1Elts[i], C2Elts[i]));
1902 return ConstantVector::get(&ResElts[0], ResElts.size());
1905 if (C1->getType()->isFloatingPointTy()) {
1906 int Result = -1; // -1 = unknown, 0 = known false, 1 = known true.
1907 switch (evaluateFCmpRelation(C1, C2)) {
1908 default: llvm_unreachable("Unknown relation!");
1909 case FCmpInst::FCMP_UNO:
1910 case FCmpInst::FCMP_ORD:
1911 case FCmpInst::FCMP_UEQ:
1912 case FCmpInst::FCMP_UNE:
1913 case FCmpInst::FCMP_ULT:
1914 case FCmpInst::FCMP_UGT:
1915 case FCmpInst::FCMP_ULE:
1916 case FCmpInst::FCMP_UGE:
1917 case FCmpInst::FCMP_TRUE:
1918 case FCmpInst::FCMP_FALSE:
1919 case FCmpInst::BAD_FCMP_PREDICATE:
1920 break; // Couldn't determine anything about these constants.
1921 case FCmpInst::FCMP_OEQ: // We know that C1 == C2
1922 Result = (pred == FCmpInst::FCMP_UEQ || pred == FCmpInst::FCMP_OEQ ||
1923 pred == FCmpInst::FCMP_ULE || pred == FCmpInst::FCMP_OLE ||
1924 pred == FCmpInst::FCMP_UGE || pred == FCmpInst::FCMP_OGE);
1926 case FCmpInst::FCMP_OLT: // We know that C1 < C2
1927 Result = (pred == FCmpInst::FCMP_UNE || pred == FCmpInst::FCMP_ONE ||
1928 pred == FCmpInst::FCMP_ULT || pred == FCmpInst::FCMP_OLT ||
1929 pred == FCmpInst::FCMP_ULE || pred == FCmpInst::FCMP_OLE);
1931 case FCmpInst::FCMP_OGT: // We know that C1 > C2
1932 Result = (pred == FCmpInst::FCMP_UNE || pred == FCmpInst::FCMP_ONE ||
1933 pred == FCmpInst::FCMP_UGT || pred == FCmpInst::FCMP_OGT ||
1934 pred == FCmpInst::FCMP_UGE || pred == FCmpInst::FCMP_OGE);
1936 case FCmpInst::FCMP_OLE: // We know that C1 <= C2
1937 // We can only partially decide this relation.
1938 if (pred == FCmpInst::FCMP_UGT || pred == FCmpInst::FCMP_OGT)
1940 else if (pred == FCmpInst::FCMP_ULT || pred == FCmpInst::FCMP_OLT)
1943 case FCmpInst::FCMP_OGE: // We known that C1 >= C2
1944 // We can only partially decide this relation.
1945 if (pred == FCmpInst::FCMP_ULT || pred == FCmpInst::FCMP_OLT)
1947 else if (pred == FCmpInst::FCMP_UGT || pred == FCmpInst::FCMP_OGT)
1950 case ICmpInst::ICMP_NE: // We know that C1 != C2
1951 // We can only partially decide this relation.
1952 if (pred == FCmpInst::FCMP_OEQ || pred == FCmpInst::FCMP_UEQ)
1954 else if (pred == FCmpInst::FCMP_ONE || pred == FCmpInst::FCMP_UNE)
1959 // If we evaluated the result, return it now.
1961 return ConstantInt::get(ResultTy, Result);
1964 // Evaluate the relation between the two constants, per the predicate.
1965 int Result = -1; // -1 = unknown, 0 = known false, 1 = known true.
1966 switch (evaluateICmpRelation(C1, C2, CmpInst::isSigned(pred))) {
1967 default: llvm_unreachable("Unknown relational!");
1968 case ICmpInst::BAD_ICMP_PREDICATE:
1969 break; // Couldn't determine anything about these constants.
1970 case ICmpInst::ICMP_EQ: // We know the constants are equal!
1971 // If we know the constants are equal, we can decide the result of this
1972 // computation precisely.
1973 Result = ICmpInst::isTrueWhenEqual((ICmpInst::Predicate)pred);
1975 case ICmpInst::ICMP_ULT:
1977 case ICmpInst::ICMP_ULT: case ICmpInst::ICMP_NE: case ICmpInst::ICMP_ULE:
1979 case ICmpInst::ICMP_UGT: case ICmpInst::ICMP_EQ: case ICmpInst::ICMP_UGE:
1983 case ICmpInst::ICMP_SLT:
1985 case ICmpInst::ICMP_SLT: case ICmpInst::ICMP_NE: case ICmpInst::ICMP_SLE:
1987 case ICmpInst::ICMP_SGT: case ICmpInst::ICMP_EQ: case ICmpInst::ICMP_SGE:
1991 case ICmpInst::ICMP_UGT:
1993 case ICmpInst::ICMP_UGT: case ICmpInst::ICMP_NE: case ICmpInst::ICMP_UGE:
1995 case ICmpInst::ICMP_ULT: case ICmpInst::ICMP_EQ: case ICmpInst::ICMP_ULE:
1999 case ICmpInst::ICMP_SGT:
2001 case ICmpInst::ICMP_SGT: case ICmpInst::ICMP_NE: case ICmpInst::ICMP_SGE:
2003 case ICmpInst::ICMP_SLT: case ICmpInst::ICMP_EQ: case ICmpInst::ICMP_SLE:
2007 case ICmpInst::ICMP_ULE:
2008 if (pred == ICmpInst::ICMP_UGT) Result = 0;
2009 if (pred == ICmpInst::ICMP_ULT || pred == ICmpInst::ICMP_ULE) Result = 1;
2011 case ICmpInst::ICMP_SLE:
2012 if (pred == ICmpInst::ICMP_SGT) Result = 0;
2013 if (pred == ICmpInst::ICMP_SLT || pred == ICmpInst::ICMP_SLE) Result = 1;
2015 case ICmpInst::ICMP_UGE:
2016 if (pred == ICmpInst::ICMP_ULT) Result = 0;
2017 if (pred == ICmpInst::ICMP_UGT || pred == ICmpInst::ICMP_UGE) Result = 1;
2019 case ICmpInst::ICMP_SGE:
2020 if (pred == ICmpInst::ICMP_SLT) Result = 0;
2021 if (pred == ICmpInst::ICMP_SGT || pred == ICmpInst::ICMP_SGE) Result = 1;
2023 case ICmpInst::ICMP_NE:
2024 if (pred == ICmpInst::ICMP_EQ) Result = 0;
2025 if (pred == ICmpInst::ICMP_NE) Result = 1;
2029 // If we evaluated the result, return it now.
2031 return ConstantInt::get(ResultTy, Result);
2033 // If the right hand side is a bitcast, try using its inverse to simplify
2034 // it by moving it to the left hand side. We can't do this if it would turn
2035 // a vector compare into a scalar compare or visa versa.
2036 if (ConstantExpr *CE2 = dyn_cast<ConstantExpr>(C2)) {
2037 Constant *CE2Op0 = CE2->getOperand(0);
2038 if (CE2->getOpcode() == Instruction::BitCast &&
2039 CE2->getType()->isVectorTy()==CE2Op0->getType()->isVectorTy()) {
2040 Constant *Inverse = ConstantExpr::getBitCast(C1, CE2Op0->getType());
2041 return ConstantExpr::getICmp(pred, Inverse, CE2Op0);
2045 // If the left hand side is an extension, try eliminating it.
2046 if (ConstantExpr *CE1 = dyn_cast<ConstantExpr>(C1)) {
2047 if (CE1->getOpcode() == Instruction::SExt ||
2048 CE1->getOpcode() == Instruction::ZExt) {
2049 Constant *CE1Op0 = CE1->getOperand(0);
2050 Constant *CE1Inverse = ConstantExpr::getTrunc(CE1, CE1Op0->getType());
2051 if (CE1Inverse == CE1Op0) {
2052 // Check whether we can safely truncate the right hand side.
2053 Constant *C2Inverse = ConstantExpr::getTrunc(C2, CE1Op0->getType());
2054 if (ConstantExpr::getZExt(C2Inverse, C2->getType()) == C2) {
2055 return ConstantExpr::getICmp(pred, CE1Inverse, C2Inverse);
2061 if ((!isa<ConstantExpr>(C1) && isa<ConstantExpr>(C2)) ||
2062 (C1->isNullValue() && !C2->isNullValue())) {
2063 // If C2 is a constant expr and C1 isn't, flip them around and fold the
2064 // other way if possible.
2065 // Also, if C1 is null and C2 isn't, flip them around.
2067 case ICmpInst::ICMP_EQ:
2068 case ICmpInst::ICMP_NE:
2069 // No change of predicate required.
2070 return ConstantExpr::getICmp(pred, C2, C1);
2072 case ICmpInst::ICMP_ULT:
2073 case ICmpInst::ICMP_SLT:
2074 case ICmpInst::ICMP_UGT:
2075 case ICmpInst::ICMP_SGT:
2076 case ICmpInst::ICMP_ULE:
2077 case ICmpInst::ICMP_SLE:
2078 case ICmpInst::ICMP_UGE:
2079 case ICmpInst::ICMP_SGE:
2080 // Change the predicate as necessary to swap the operands.
2081 pred = ICmpInst::getSwappedPredicate((ICmpInst::Predicate)pred);
2082 return ConstantExpr::getICmp(pred, C2, C1);
2084 default: // These predicates cannot be flopped around.
2092 /// isInBoundsIndices - Test whether the given sequence of *normalized* indices
2094 static bool isInBoundsIndices(Constant *const *Idxs, size_t NumIdx) {
2095 // No indices means nothing that could be out of bounds.
2096 if (NumIdx == 0) return true;
2098 // If the first index is zero, it's in bounds.
2099 if (Idxs[0]->isNullValue()) return true;
2101 // If the first index is one and all the rest are zero, it's in bounds,
2102 // by the one-past-the-end rule.
2103 if (!cast<ConstantInt>(Idxs[0])->isOne())
2105 for (unsigned i = 1, e = NumIdx; i != e; ++i)
2106 if (!Idxs[i]->isNullValue())
2111 Constant *llvm::ConstantFoldGetElementPtr(Constant *C,
2113 Constant* const *Idxs,
2116 (NumIdx == 1 && Idxs[0]->isNullValue()))
2119 if (isa<UndefValue>(C)) {
2120 const PointerType *Ptr = cast<PointerType>(C->getType());
2121 const Type *Ty = GetElementPtrInst::getIndexedType(Ptr,
2123 (Value **)Idxs+NumIdx);
2124 assert(Ty != 0 && "Invalid indices for GEP!");
2125 return UndefValue::get(PointerType::get(Ty, Ptr->getAddressSpace()));
2128 Constant *Idx0 = Idxs[0];
2129 if (C->isNullValue()) {
2131 for (unsigned i = 0, e = NumIdx; i != e; ++i)
2132 if (!Idxs[i]->isNullValue()) {
2137 const PointerType *Ptr = cast<PointerType>(C->getType());
2138 const Type *Ty = GetElementPtrInst::getIndexedType(Ptr,
2140 (Value**)Idxs+NumIdx);
2141 assert(Ty != 0 && "Invalid indices for GEP!");
2142 return ConstantPointerNull::get(
2143 PointerType::get(Ty,Ptr->getAddressSpace()));
2147 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(C)) {
2148 // Combine Indices - If the source pointer to this getelementptr instruction
2149 // is a getelementptr instruction, combine the indices of the two
2150 // getelementptr instructions into a single instruction.
2152 if (CE->getOpcode() == Instruction::GetElementPtr) {
2153 const Type *LastTy = 0;
2154 for (gep_type_iterator I = gep_type_begin(CE), E = gep_type_end(CE);
2158 if ((LastTy && LastTy->isArrayTy()) || Idx0->isNullValue()) {
2159 SmallVector<Value*, 16> NewIndices;
2160 NewIndices.reserve(NumIdx + CE->getNumOperands());
2161 for (unsigned i = 1, e = CE->getNumOperands()-1; i != e; ++i)
2162 NewIndices.push_back(CE->getOperand(i));
2164 // Add the last index of the source with the first index of the new GEP.
2165 // Make sure to handle the case when they are actually different types.
2166 Constant *Combined = CE->getOperand(CE->getNumOperands()-1);
2167 // Otherwise it must be an array.
2168 if (!Idx0->isNullValue()) {
2169 const Type *IdxTy = Combined->getType();
2170 if (IdxTy != Idx0->getType()) {
2171 const Type *Int64Ty = Type::getInt64Ty(IdxTy->getContext());
2172 Constant *C1 = ConstantExpr::getSExtOrBitCast(Idx0, Int64Ty);
2173 Constant *C2 = ConstantExpr::getSExtOrBitCast(Combined, Int64Ty);
2174 Combined = ConstantExpr::get(Instruction::Add, C1, C2);
2177 ConstantExpr::get(Instruction::Add, Idx0, Combined);
2181 NewIndices.push_back(Combined);
2182 NewIndices.insert(NewIndices.end(), Idxs+1, Idxs+NumIdx);
2183 return (inBounds && cast<GEPOperator>(CE)->isInBounds()) ?
2184 ConstantExpr::getInBoundsGetElementPtr(CE->getOperand(0),
2186 NewIndices.size()) :
2187 ConstantExpr::getGetElementPtr(CE->getOperand(0),
2193 // Implement folding of:
2194 // int* getelementptr ([2 x int]* bitcast ([3 x int]* %X to [2 x int]*),
2196 // To: int* getelementptr ([3 x int]* %X, long 0, long 0)
2198 if (CE->isCast() && NumIdx > 1 && Idx0->isNullValue()) {
2199 if (const PointerType *SPT =
2200 dyn_cast<PointerType>(CE->getOperand(0)->getType()))
2201 if (const ArrayType *SAT = dyn_cast<ArrayType>(SPT->getElementType()))
2202 if (const ArrayType *CAT =
2203 dyn_cast<ArrayType>(cast<PointerType>(C->getType())->getElementType()))
2204 if (CAT->getElementType() == SAT->getElementType())
2206 ConstantExpr::getInBoundsGetElementPtr(
2207 (Constant*)CE->getOperand(0), Idxs, NumIdx) :
2208 ConstantExpr::getGetElementPtr(
2209 (Constant*)CE->getOperand(0), Idxs, NumIdx);
2213 // Check to see if any array indices are not within the corresponding
2214 // notional array bounds. If so, try to determine if they can be factored
2215 // out into preceding dimensions.
2216 bool Unknown = false;
2217 SmallVector<Constant *, 8> NewIdxs;
2218 const Type *Ty = C->getType();
2219 const Type *Prev = 0;
2220 for (unsigned i = 0; i != NumIdx;
2221 Prev = Ty, Ty = cast<CompositeType>(Ty)->getTypeAtIndex(Idxs[i]), ++i) {
2222 if (ConstantInt *CI = dyn_cast<ConstantInt>(Idxs[i])) {
2223 if (const ArrayType *ATy = dyn_cast<ArrayType>(Ty))
2224 if (ATy->getNumElements() <= INT64_MAX &&
2225 ATy->getNumElements() != 0 &&
2226 CI->getSExtValue() >= (int64_t)ATy->getNumElements()) {
2227 if (isa<SequentialType>(Prev)) {
2228 // It's out of range, but we can factor it into the prior
2230 NewIdxs.resize(NumIdx);
2231 ConstantInt *Factor = ConstantInt::get(CI->getType(),
2232 ATy->getNumElements());
2233 NewIdxs[i] = ConstantExpr::getSRem(CI, Factor);
2235 Constant *PrevIdx = Idxs[i-1];
2236 Constant *Div = ConstantExpr::getSDiv(CI, Factor);
2238 // Before adding, extend both operands to i64 to avoid
2239 // overflow trouble.
2240 if (!PrevIdx->getType()->isIntegerTy(64))
2241 PrevIdx = ConstantExpr::getSExt(PrevIdx,
2242 Type::getInt64Ty(Div->getContext()));
2243 if (!Div->getType()->isIntegerTy(64))
2244 Div = ConstantExpr::getSExt(Div,
2245 Type::getInt64Ty(Div->getContext()));
2247 NewIdxs[i-1] = ConstantExpr::getAdd(PrevIdx, Div);
2249 // It's out of range, but the prior dimension is a struct
2250 // so we can't do anything about it.
2255 // We don't know if it's in range or not.
2260 // If we did any factoring, start over with the adjusted indices.
2261 if (!NewIdxs.empty()) {
2262 for (unsigned i = 0; i != NumIdx; ++i)
2263 if (!NewIdxs[i]) NewIdxs[i] = Idxs[i];
2265 ConstantExpr::getInBoundsGetElementPtr(C, NewIdxs.data(),
2267 ConstantExpr::getGetElementPtr(C, NewIdxs.data(), NewIdxs.size());
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 isa<GlobalVariable>(C) && isInBoundsIndices(Idxs, NumIdx))
2274 return ConstantExpr::getInBoundsGetElementPtr(C, Idxs, NumIdx);