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 // template-based folder for simple primitive constants like ConstantInt, and
16 // the special case hackery that we use to symbolically evaluate expressions
17 // that use ConstantExprs.
19 //===----------------------------------------------------------------------===//
21 #include "ConstantFold.h"
22 #include "llvm/Constants.h"
23 #include "llvm/Instructions.h"
24 #include "llvm/DerivedTypes.h"
25 #include "llvm/Function.h"
26 #include "llvm/GlobalAlias.h"
27 #include "llvm/ADT/SmallVector.h"
28 #include "llvm/Support/Compiler.h"
29 #include "llvm/Support/GetElementPtrTypeIterator.h"
30 #include "llvm/Support/ManagedStatic.h"
31 #include "llvm/Support/MathExtras.h"
35 //===----------------------------------------------------------------------===//
36 // ConstantFold*Instruction Implementations
37 //===----------------------------------------------------------------------===//
39 /// BitCastConstantVector - Convert the specified ConstantVector node to the
40 /// specified vector type. At this point, we know that the elements of the
41 /// input vector constant are all simple integer or FP values.
42 static Constant *BitCastConstantVector(ConstantVector *CV,
43 const VectorType *DstTy) {
44 // If this cast changes element count then we can't handle it here:
45 // doing so requires endianness information. This should be handled by
46 // Analysis/ConstantFolding.cpp
47 unsigned NumElts = DstTy->getNumElements();
48 if (NumElts != CV->getNumOperands())
51 // Check to verify that all elements of the input are simple.
52 for (unsigned i = 0; i != NumElts; ++i) {
53 if (!isa<ConstantInt>(CV->getOperand(i)) &&
54 !isa<ConstantFP>(CV->getOperand(i)))
58 // Bitcast each element now.
59 std::vector<Constant*> Result;
60 const Type *DstEltTy = DstTy->getElementType();
61 for (unsigned i = 0; i != NumElts; ++i)
62 Result.push_back(ConstantExpr::getBitCast(CV->getOperand(i), DstEltTy));
63 return ConstantVector::get(Result);
66 /// This function determines which opcode to use to fold two constant cast
67 /// expressions together. It uses CastInst::isEliminableCastPair to determine
68 /// the opcode. Consequently its just a wrapper around that function.
69 /// @brief Determine if it is valid to fold a cast of a cast
72 unsigned opc, ///< opcode of the second cast constant expression
73 const ConstantExpr*Op, ///< the first cast constant expression
74 const Type *DstTy ///< desintation type of the first cast
76 assert(Op && Op->isCast() && "Can't fold cast of cast without a cast!");
77 assert(DstTy && DstTy->isFirstClassType() && "Invalid cast destination type");
78 assert(CastInst::isCast(opc) && "Invalid cast opcode");
80 // The the types and opcodes for the two Cast constant expressions
81 const Type *SrcTy = Op->getOperand(0)->getType();
82 const Type *MidTy = Op->getType();
83 Instruction::CastOps firstOp = Instruction::CastOps(Op->getOpcode());
84 Instruction::CastOps secondOp = Instruction::CastOps(opc);
86 // Let CastInst::isEliminableCastPair do the heavy lifting.
87 return CastInst::isEliminableCastPair(firstOp, secondOp, SrcTy, MidTy, DstTy,
91 static Constant *FoldBitCast(Constant *V, const Type *DestTy) {
92 const Type *SrcTy = V->getType();
94 return V; // no-op cast
96 // Check to see if we are casting a pointer to an aggregate to a pointer to
97 // the first element. If so, return the appropriate GEP instruction.
98 if (const PointerType *PTy = dyn_cast<PointerType>(V->getType()))
99 if (const PointerType *DPTy = dyn_cast<PointerType>(DestTy))
100 if (PTy->getAddressSpace() == DPTy->getAddressSpace()) {
101 SmallVector<Value*, 8> IdxList;
102 IdxList.push_back(Constant::getNullValue(Type::Int32Ty));
103 const Type *ElTy = PTy->getElementType();
104 while (ElTy != DPTy->getElementType()) {
105 if (const StructType *STy = dyn_cast<StructType>(ElTy)) {
106 if (STy->getNumElements() == 0) break;
107 ElTy = STy->getElementType(0);
108 IdxList.push_back(Constant::getNullValue(Type::Int32Ty));
109 } else if (const SequentialType *STy =
110 dyn_cast<SequentialType>(ElTy)) {
111 if (isa<PointerType>(ElTy)) break; // Can't index into pointers!
112 ElTy = STy->getElementType();
113 IdxList.push_back(IdxList[0]);
119 if (ElTy == DPTy->getElementType())
120 return ConstantExpr::getGetElementPtr(V, &IdxList[0], IdxList.size());
123 // Handle casts from one vector constant to another. We know that the src
124 // and dest type have the same size (otherwise its an illegal cast).
125 if (const VectorType *DestPTy = dyn_cast<VectorType>(DestTy)) {
126 if (const VectorType *SrcTy = dyn_cast<VectorType>(V->getType())) {
127 assert(DestPTy->getBitWidth() == SrcTy->getBitWidth() &&
128 "Not cast between same sized vectors!");
129 // First, check for null. Undef is already handled.
130 if (isa<ConstantAggregateZero>(V))
131 return Constant::getNullValue(DestTy);
133 if (ConstantVector *CV = dyn_cast<ConstantVector>(V))
134 return BitCastConstantVector(CV, DestPTy);
138 // Finally, implement bitcast folding now. The code below doesn't handle
140 if (isa<ConstantPointerNull>(V)) // ptr->ptr cast.
141 return ConstantPointerNull::get(cast<PointerType>(DestTy));
143 // Handle integral constant input.
144 if (const ConstantInt *CI = dyn_cast<ConstantInt>(V)) {
145 if (DestTy->isInteger())
146 // Integral -> Integral. This is a no-op because the bit widths must
147 // be the same. Consequently, we just fold to V.
150 if (DestTy->isFloatingPoint()) {
151 assert((DestTy == Type::DoubleTy || DestTy == Type::FloatTy) &&
153 return ConstantFP::get(APFloat(CI->getValue()));
155 // Otherwise, can't fold this (vector?)
159 // Handle ConstantFP input.
160 if (const ConstantFP *FP = dyn_cast<ConstantFP>(V)) {
162 if (DestTy == Type::Int32Ty) {
163 return ConstantInt::get(FP->getValueAPF().convertToAPInt());
165 assert(DestTy == Type::Int64Ty && "only support f32/f64 for now!");
166 return ConstantInt::get(FP->getValueAPF().convertToAPInt());
173 Constant *llvm::ConstantFoldCastInstruction(unsigned opc, const Constant *V,
174 const Type *DestTy) {
175 if (isa<UndefValue>(V)) {
176 // zext(undef) = 0, because the top bits will be zero.
177 // sext(undef) = 0, because the top bits will all be the same.
178 // [us]itofp(undef) = 0, because the result value is bounded.
179 if (opc == Instruction::ZExt || opc == Instruction::SExt ||
180 opc == Instruction::UIToFP || opc == Instruction::SIToFP)
181 return Constant::getNullValue(DestTy);
182 return UndefValue::get(DestTy);
184 // No compile-time operations on this type yet.
185 if (V->getType() == Type::PPC_FP128Ty || DestTy == Type::PPC_FP128Ty)
188 // If the cast operand is a constant expression, there's a few things we can
189 // do to try to simplify it.
190 if (const ConstantExpr *CE = dyn_cast<ConstantExpr>(V)) {
192 // Try hard to fold cast of cast because they are often eliminable.
193 if (unsigned newOpc = foldConstantCastPair(opc, CE, DestTy))
194 return ConstantExpr::getCast(newOpc, CE->getOperand(0), DestTy);
195 } else if (CE->getOpcode() == Instruction::GetElementPtr) {
196 // If all of the indexes in the GEP are null values, there is no pointer
197 // adjustment going on. We might as well cast the source pointer.
198 bool isAllNull = true;
199 for (unsigned i = 1, e = CE->getNumOperands(); i != e; ++i)
200 if (!CE->getOperand(i)->isNullValue()) {
205 // This is casting one pointer type to another, always BitCast
206 return ConstantExpr::getPointerCast(CE->getOperand(0), DestTy);
210 // We actually have to do a cast now. Perform the cast according to the
213 case Instruction::FPTrunc:
214 case Instruction::FPExt:
215 if (const ConstantFP *FPC = dyn_cast<ConstantFP>(V)) {
216 APFloat Val = FPC->getValueAPF();
217 Val.convert(DestTy == Type::FloatTy ? APFloat::IEEEsingle :
218 DestTy == Type::DoubleTy ? APFloat::IEEEdouble :
219 DestTy == Type::X86_FP80Ty ? APFloat::x87DoubleExtended :
220 DestTy == Type::FP128Ty ? APFloat::IEEEquad :
222 APFloat::rmNearestTiesToEven);
223 return ConstantFP::get(Val);
225 return 0; // Can't fold.
226 case Instruction::FPToUI:
227 case Instruction::FPToSI:
228 if (const ConstantFP *FPC = dyn_cast<ConstantFP>(V)) {
229 const APFloat &V = FPC->getValueAPF();
231 uint32_t DestBitWidth = cast<IntegerType>(DestTy)->getBitWidth();
232 (void) V.convertToInteger(x, DestBitWidth, opc==Instruction::FPToSI,
233 APFloat::rmTowardZero);
234 APInt Val(DestBitWidth, 2, x);
235 return ConstantInt::get(Val);
237 if (const ConstantVector *CV = dyn_cast<ConstantVector>(V)) {
238 std::vector<Constant*> res;
239 const VectorType *DestVecTy = cast<VectorType>(DestTy);
240 const Type *DstEltTy = DestVecTy->getElementType();
241 for (unsigned i = 0, e = CV->getType()->getNumElements(); i != e; ++i)
242 res.push_back(ConstantFoldCastInstruction(opc, V->getOperand(i),
244 return ConstantVector::get(DestVecTy, res);
246 return 0; // Can't fold.
247 case Instruction::IntToPtr: //always treated as unsigned
248 if (V->isNullValue()) // Is it an integral null value?
249 return ConstantPointerNull::get(cast<PointerType>(DestTy));
250 return 0; // Other pointer types cannot be casted
251 case Instruction::PtrToInt: // always treated as unsigned
252 if (V->isNullValue()) // is it a null pointer value?
253 return ConstantInt::get(DestTy, 0);
254 return 0; // Other pointer types cannot be casted
255 case Instruction::UIToFP:
256 case Instruction::SIToFP:
257 if (const ConstantInt *CI = dyn_cast<ConstantInt>(V)) {
258 APInt api = CI->getValue();
259 const uint64_t zero[] = {0, 0};
260 APFloat apf = APFloat(APInt(DestTy->getPrimitiveSizeInBits(),
262 (void)apf.convertFromAPInt(api,
263 opc==Instruction::SIToFP,
264 APFloat::rmNearestTiesToEven);
265 return ConstantFP::get(apf);
267 if (const ConstantVector *CV = dyn_cast<ConstantVector>(V)) {
268 std::vector<Constant*> res;
269 const VectorType *DestVecTy = cast<VectorType>(DestTy);
270 const Type *DstEltTy = DestVecTy->getElementType();
271 for (unsigned i = 0, e = CV->getType()->getNumElements(); i != e; ++i)
272 res.push_back(ConstantFoldCastInstruction(opc, V->getOperand(i),
274 return ConstantVector::get(DestVecTy, res);
277 case Instruction::ZExt:
278 if (const ConstantInt *CI = dyn_cast<ConstantInt>(V)) {
279 uint32_t BitWidth = cast<IntegerType>(DestTy)->getBitWidth();
280 APInt Result(CI->getValue());
281 Result.zext(BitWidth);
282 return ConstantInt::get(Result);
285 case Instruction::SExt:
286 if (const ConstantInt *CI = dyn_cast<ConstantInt>(V)) {
287 uint32_t BitWidth = cast<IntegerType>(DestTy)->getBitWidth();
288 APInt Result(CI->getValue());
289 Result.sext(BitWidth);
290 return ConstantInt::get(Result);
293 case Instruction::Trunc:
294 if (const ConstantInt *CI = dyn_cast<ConstantInt>(V)) {
295 uint32_t BitWidth = cast<IntegerType>(DestTy)->getBitWidth();
296 APInt Result(CI->getValue());
297 Result.trunc(BitWidth);
298 return ConstantInt::get(Result);
301 case Instruction::BitCast:
302 return FoldBitCast(const_cast<Constant*>(V), DestTy);
304 assert(!"Invalid CE CastInst opcode");
308 assert(0 && "Failed to cast constant expression");
312 Constant *llvm::ConstantFoldSelectInstruction(const Constant *Cond,
314 const Constant *V2) {
315 if (const ConstantInt *CB = dyn_cast<ConstantInt>(Cond))
316 return const_cast<Constant*>(CB->getZExtValue() ? V1 : V2);
318 if (isa<UndefValue>(V1)) return const_cast<Constant*>(V2);
319 if (isa<UndefValue>(V2)) return const_cast<Constant*>(V1);
320 if (isa<UndefValue>(Cond)) return const_cast<Constant*>(V1);
321 if (V1 == V2) return const_cast<Constant*>(V1);
325 Constant *llvm::ConstantFoldExtractElementInstruction(const Constant *Val,
326 const Constant *Idx) {
327 if (isa<UndefValue>(Val)) // ee(undef, x) -> undef
328 return UndefValue::get(cast<VectorType>(Val->getType())->getElementType());
329 if (Val->isNullValue()) // ee(zero, x) -> zero
330 return Constant::getNullValue(
331 cast<VectorType>(Val->getType())->getElementType());
333 if (const ConstantVector *CVal = dyn_cast<ConstantVector>(Val)) {
334 if (const ConstantInt *CIdx = dyn_cast<ConstantInt>(Idx)) {
335 return const_cast<Constant*>(CVal->getOperand(CIdx->getZExtValue()));
336 } else if (isa<UndefValue>(Idx)) {
337 // ee({w,x,y,z}, undef) -> w (an arbitrary value).
338 return const_cast<Constant*>(CVal->getOperand(0));
344 Constant *llvm::ConstantFoldInsertElementInstruction(const Constant *Val,
346 const Constant *Idx) {
347 const ConstantInt *CIdx = dyn_cast<ConstantInt>(Idx);
349 APInt idxVal = CIdx->getValue();
350 if (isa<UndefValue>(Val)) {
351 // Insertion of scalar constant into vector undef
352 // Optimize away insertion of undef
353 if (isa<UndefValue>(Elt))
354 return const_cast<Constant*>(Val);
355 // Otherwise break the aggregate undef into multiple undefs and do
358 cast<VectorType>(Val->getType())->getNumElements();
359 std::vector<Constant*> Ops;
361 for (unsigned i = 0; i < numOps; ++i) {
363 (idxVal == i) ? Elt : UndefValue::get(Elt->getType());
364 Ops.push_back(const_cast<Constant*>(Op));
366 return ConstantVector::get(Ops);
368 if (isa<ConstantAggregateZero>(Val)) {
369 // Insertion of scalar constant into vector aggregate zero
370 // Optimize away insertion of zero
371 if (Elt->isNullValue())
372 return const_cast<Constant*>(Val);
373 // Otherwise break the aggregate zero into multiple zeros and do
376 cast<VectorType>(Val->getType())->getNumElements();
377 std::vector<Constant*> Ops;
379 for (unsigned i = 0; i < numOps; ++i) {
381 (idxVal == i) ? Elt : Constant::getNullValue(Elt->getType());
382 Ops.push_back(const_cast<Constant*>(Op));
384 return ConstantVector::get(Ops);
386 if (const ConstantVector *CVal = dyn_cast<ConstantVector>(Val)) {
387 // Insertion of scalar constant into vector constant
388 std::vector<Constant*> Ops;
389 Ops.reserve(CVal->getNumOperands());
390 for (unsigned i = 0; i < CVal->getNumOperands(); ++i) {
392 (idxVal == i) ? Elt : cast<Constant>(CVal->getOperand(i));
393 Ops.push_back(const_cast<Constant*>(Op));
395 return ConstantVector::get(Ops);
400 /// GetVectorElement - If C is a ConstantVector, ConstantAggregateZero or Undef
401 /// return the specified element value. Otherwise return null.
402 static Constant *GetVectorElement(const Constant *C, unsigned EltNo) {
403 if (const ConstantVector *CV = dyn_cast<ConstantVector>(C))
404 return const_cast<Constant*>(CV->getOperand(EltNo));
406 const Type *EltTy = cast<VectorType>(C->getType())->getElementType();
407 if (isa<ConstantAggregateZero>(C))
408 return Constant::getNullValue(EltTy);
409 if (isa<UndefValue>(C))
410 return UndefValue::get(EltTy);
414 Constant *llvm::ConstantFoldShuffleVectorInstruction(const Constant *V1,
416 const Constant *Mask) {
417 // Undefined shuffle mask -> undefined value.
418 if (isa<UndefValue>(Mask)) return UndefValue::get(V1->getType());
420 unsigned NumElts = cast<VectorType>(V1->getType())->getNumElements();
421 const Type *EltTy = cast<VectorType>(V1->getType())->getElementType();
423 // Loop over the shuffle mask, evaluating each element.
424 SmallVector<Constant*, 32> Result;
425 for (unsigned i = 0; i != NumElts; ++i) {
426 Constant *InElt = GetVectorElement(Mask, i);
427 if (InElt == 0) return 0;
429 if (isa<UndefValue>(InElt))
430 InElt = UndefValue::get(EltTy);
431 else if (ConstantInt *CI = dyn_cast<ConstantInt>(InElt)) {
432 unsigned Elt = CI->getZExtValue();
433 if (Elt >= NumElts*2)
434 InElt = UndefValue::get(EltTy);
435 else if (Elt >= NumElts)
436 InElt = GetVectorElement(V2, Elt-NumElts);
438 InElt = GetVectorElement(V1, Elt);
439 if (InElt == 0) return 0;
444 Result.push_back(InElt);
447 return ConstantVector::get(&Result[0], Result.size());
450 /// EvalVectorOp - Given two vector constants and a function pointer, apply the
451 /// function pointer to each element pair, producing a new ConstantVector
452 /// constant. Either or both of V1 and V2 may be NULL, meaning a
453 /// ConstantAggregateZero operand.
454 static Constant *EvalVectorOp(const ConstantVector *V1,
455 const ConstantVector *V2,
456 const VectorType *VTy,
457 Constant *(*FP)(Constant*, Constant*)) {
458 std::vector<Constant*> Res;
459 const Type *EltTy = VTy->getElementType();
460 for (unsigned i = 0, e = VTy->getNumElements(); i != e; ++i) {
461 const Constant *C1 = V1 ? V1->getOperand(i) : Constant::getNullValue(EltTy);
462 const Constant *C2 = V2 ? V2->getOperand(i) : Constant::getNullValue(EltTy);
463 Res.push_back(FP(const_cast<Constant*>(C1),
464 const_cast<Constant*>(C2)));
466 return ConstantVector::get(Res);
469 Constant *llvm::ConstantFoldBinaryInstruction(unsigned Opcode,
471 const Constant *C2) {
472 // No compile-time operations on this type yet.
473 if (C1->getType() == Type::PPC_FP128Ty)
476 // Handle UndefValue up front
477 if (isa<UndefValue>(C1) || isa<UndefValue>(C2)) {
479 case Instruction::Xor:
480 if (isa<UndefValue>(C1) && isa<UndefValue>(C2))
481 // Handle undef ^ undef -> 0 special case. This is a common
483 return Constant::getNullValue(C1->getType());
485 case Instruction::Add:
486 case Instruction::Sub:
487 return UndefValue::get(C1->getType());
488 case Instruction::Mul:
489 case Instruction::And:
490 return Constant::getNullValue(C1->getType());
491 case Instruction::UDiv:
492 case Instruction::SDiv:
493 case Instruction::FDiv:
494 case Instruction::URem:
495 case Instruction::SRem:
496 case Instruction::FRem:
497 if (!isa<UndefValue>(C2)) // undef / X -> 0
498 return Constant::getNullValue(C1->getType());
499 return const_cast<Constant*>(C2); // X / undef -> undef
500 case Instruction::Or: // X | undef -> -1
501 if (const VectorType *PTy = dyn_cast<VectorType>(C1->getType()))
502 return ConstantVector::getAllOnesValue(PTy);
503 return ConstantInt::getAllOnesValue(C1->getType());
504 case Instruction::LShr:
505 if (isa<UndefValue>(C2) && isa<UndefValue>(C1))
506 return const_cast<Constant*>(C1); // undef lshr undef -> undef
507 return Constant::getNullValue(C1->getType()); // X lshr undef -> 0
509 case Instruction::AShr:
510 if (!isa<UndefValue>(C2))
511 return const_cast<Constant*>(C1); // undef ashr X --> undef
512 else if (isa<UndefValue>(C1))
513 return const_cast<Constant*>(C1); // undef ashr undef -> undef
515 return const_cast<Constant*>(C1); // X ashr undef --> X
516 case Instruction::Shl:
517 // undef << X -> 0 or X << undef -> 0
518 return Constant::getNullValue(C1->getType());
522 // Handle simplifications of the RHS when a constant int.
523 if (const ConstantInt *CI2 = dyn_cast<ConstantInt>(C2)) {
525 case Instruction::Add:
526 if (CI2->equalsInt(0)) return const_cast<Constant*>(C1); // X + 0 == X
528 case Instruction::Sub:
529 if (CI2->equalsInt(0)) return const_cast<Constant*>(C1); // X - 0 == X
531 case Instruction::Mul:
532 if (CI2->equalsInt(0)) return const_cast<Constant*>(C2); // X * 0 == 0
533 if (CI2->equalsInt(1))
534 return const_cast<Constant*>(C1); // X * 1 == X
536 case Instruction::UDiv:
537 case Instruction::SDiv:
538 if (CI2->equalsInt(1))
539 return const_cast<Constant*>(C1); // X / 1 == X
541 case Instruction::URem:
542 case Instruction::SRem:
543 if (CI2->equalsInt(1))
544 return Constant::getNullValue(CI2->getType()); // X % 1 == 0
546 case Instruction::And:
547 if (CI2->isZero()) return const_cast<Constant*>(C2); // X & 0 == 0
548 if (CI2->isAllOnesValue())
549 return const_cast<Constant*>(C1); // X & -1 == X
551 if (const ConstantExpr *CE1 = dyn_cast<ConstantExpr>(C1)) {
552 // (zext i32 to i64) & 4294967295 -> (zext i32 to i64)
553 if (CE1->getOpcode() == Instruction::ZExt) {
554 unsigned DstWidth = CI2->getType()->getBitWidth();
556 CE1->getOperand(0)->getType()->getPrimitiveSizeInBits();
557 APInt PossiblySetBits(APInt::getLowBitsSet(DstWidth, SrcWidth));
558 if ((PossiblySetBits & CI2->getValue()) == PossiblySetBits)
559 return const_cast<Constant*>(C1);
562 // If and'ing the address of a global with a constant, fold it.
563 if (CE1->getOpcode() == Instruction::PtrToInt &&
564 isa<GlobalValue>(CE1->getOperand(0))) {
565 GlobalValue *GV = cast<GlobalValue>(CE1->getOperand(0));
567 // Functions are at least 4-byte aligned.
568 unsigned GVAlign = GV->getAlignment();
569 if (isa<Function>(GV))
570 GVAlign = std::max(GVAlign, 4U);
573 unsigned DstWidth = CI2->getType()->getBitWidth();
574 unsigned SrcWidth = std::min(DstWidth, Log2_32(GVAlign));
575 APInt BitsNotSet(APInt::getLowBitsSet(DstWidth, SrcWidth));
577 // If checking bits we know are clear, return zero.
578 if ((CI2->getValue() & BitsNotSet) == CI2->getValue())
579 return Constant::getNullValue(CI2->getType());
584 case Instruction::Or:
585 if (CI2->equalsInt(0)) return const_cast<Constant*>(C1); // X | 0 == X
586 if (CI2->isAllOnesValue())
587 return const_cast<Constant*>(C2); // X | -1 == -1
589 case Instruction::Xor:
590 if (CI2->equalsInt(0)) return const_cast<Constant*>(C1); // X ^ 0 == X
592 case Instruction::AShr:
593 // ashr (zext C to Ty), C2 -> lshr (zext C, CSA), C2
594 if (const ConstantExpr *CE1 = dyn_cast<ConstantExpr>(C1))
595 if (CE1->getOpcode() == Instruction::ZExt) // Top bits known zero.
596 return ConstantExpr::getLShr(const_cast<Constant*>(C1),
597 const_cast<Constant*>(C2));
602 // At this point we know neither constant is an UndefValue.
603 if (const ConstantInt *CI1 = dyn_cast<ConstantInt>(C1)) {
604 if (const ConstantInt *CI2 = dyn_cast<ConstantInt>(C2)) {
605 using namespace APIntOps;
606 const APInt &C1V = CI1->getValue();
607 const APInt &C2V = CI2->getValue();
611 case Instruction::Add:
612 return ConstantInt::get(C1V + C2V);
613 case Instruction::Sub:
614 return ConstantInt::get(C1V - C2V);
615 case Instruction::Mul:
616 return ConstantInt::get(C1V * C2V);
617 case Instruction::UDiv:
618 if (CI2->isNullValue())
619 return 0; // X / 0 -> can't fold
620 return ConstantInt::get(C1V.udiv(C2V));
621 case Instruction::SDiv:
622 if (CI2->isNullValue())
623 return 0; // X / 0 -> can't fold
624 if (C2V.isAllOnesValue() && C1V.isMinSignedValue())
625 return 0; // MIN_INT / -1 -> overflow
626 return ConstantInt::get(C1V.sdiv(C2V));
627 case Instruction::URem:
628 if (C2->isNullValue())
629 return 0; // X / 0 -> can't fold
630 return ConstantInt::get(C1V.urem(C2V));
631 case Instruction::SRem:
632 if (CI2->isNullValue())
633 return 0; // X % 0 -> can't fold
634 if (C2V.isAllOnesValue() && C1V.isMinSignedValue())
635 return 0; // MIN_INT % -1 -> overflow
636 return ConstantInt::get(C1V.srem(C2V));
637 case Instruction::And:
638 return ConstantInt::get(C1V & C2V);
639 case Instruction::Or:
640 return ConstantInt::get(C1V | C2V);
641 case Instruction::Xor:
642 return ConstantInt::get(C1V ^ C2V);
643 case Instruction::Shl: {
644 uint32_t shiftAmt = C2V.getZExtValue();
645 if (shiftAmt < C1V.getBitWidth())
646 return ConstantInt::get(C1V.shl(shiftAmt));
648 return UndefValue::get(C1->getType()); // too big shift is undef
650 case Instruction::LShr: {
651 uint32_t shiftAmt = C2V.getZExtValue();
652 if (shiftAmt < C1V.getBitWidth())
653 return ConstantInt::get(C1V.lshr(shiftAmt));
655 return UndefValue::get(C1->getType()); // too big shift is undef
657 case Instruction::AShr: {
658 uint32_t shiftAmt = C2V.getZExtValue();
659 if (shiftAmt < C1V.getBitWidth())
660 return ConstantInt::get(C1V.ashr(shiftAmt));
662 return UndefValue::get(C1->getType()); // too big shift is undef
666 } else if (const ConstantFP *CFP1 = dyn_cast<ConstantFP>(C1)) {
667 if (const ConstantFP *CFP2 = dyn_cast<ConstantFP>(C2)) {
668 APFloat C1V = CFP1->getValueAPF();
669 APFloat C2V = CFP2->getValueAPF();
670 APFloat C3V = C1V; // copy for modification
674 case Instruction::Add:
675 (void)C3V.add(C2V, APFloat::rmNearestTiesToEven);
676 return ConstantFP::get(C3V);
677 case Instruction::Sub:
678 (void)C3V.subtract(C2V, APFloat::rmNearestTiesToEven);
679 return ConstantFP::get(C3V);
680 case Instruction::Mul:
681 (void)C3V.multiply(C2V, APFloat::rmNearestTiesToEven);
682 return ConstantFP::get(C3V);
683 case Instruction::FDiv:
684 (void)C3V.divide(C2V, APFloat::rmNearestTiesToEven);
685 return ConstantFP::get(C3V);
686 case Instruction::FRem:
688 // IEEE 754, Section 7.1, #5
689 if (CFP1->getType() == Type::DoubleTy)
690 return ConstantFP::get(APFloat(std::numeric_limits<double>::
692 if (CFP1->getType() == Type::FloatTy)
693 return ConstantFP::get(APFloat(std::numeric_limits<float>::
697 (void)C3V.mod(C2V, APFloat::rmNearestTiesToEven);
698 return ConstantFP::get(C3V);
701 } else if (const VectorType *VTy = dyn_cast<VectorType>(C1->getType())) {
702 const ConstantVector *CP1 = dyn_cast<ConstantVector>(C1);
703 const ConstantVector *CP2 = dyn_cast<ConstantVector>(C2);
704 if ((CP1 != NULL || isa<ConstantAggregateZero>(C1)) &&
705 (CP2 != NULL || isa<ConstantAggregateZero>(C2))) {
709 case Instruction::Add:
710 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getAdd);
711 case Instruction::Sub:
712 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getSub);
713 case Instruction::Mul:
714 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getMul);
715 case Instruction::UDiv:
716 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getUDiv);
717 case Instruction::SDiv:
718 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getSDiv);
719 case Instruction::FDiv:
720 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getFDiv);
721 case Instruction::URem:
722 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getURem);
723 case Instruction::SRem:
724 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getSRem);
725 case Instruction::FRem:
726 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getFRem);
727 case Instruction::And:
728 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getAnd);
729 case Instruction::Or:
730 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getOr);
731 case Instruction::Xor:
732 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getXor);
737 if (isa<ConstantExpr>(C1)) {
738 // There are many possible foldings we could do here. We should probably
739 // at least fold add of a pointer with an integer into the appropriate
740 // getelementptr. This will improve alias analysis a bit.
741 } else if (isa<ConstantExpr>(C2)) {
742 // If C2 is a constant expr and C1 isn't, flop them around and fold the
743 // other way if possible.
745 case Instruction::Add:
746 case Instruction::Mul:
747 case Instruction::And:
748 case Instruction::Or:
749 case Instruction::Xor:
750 // No change of opcode required.
751 return ConstantFoldBinaryInstruction(Opcode, C2, C1);
753 case Instruction::Shl:
754 case Instruction::LShr:
755 case Instruction::AShr:
756 case Instruction::Sub:
757 case Instruction::SDiv:
758 case Instruction::UDiv:
759 case Instruction::FDiv:
760 case Instruction::URem:
761 case Instruction::SRem:
762 case Instruction::FRem:
763 default: // These instructions cannot be flopped around.
768 // We don't know how to fold this.
772 /// isZeroSizedType - This type is zero sized if its an array or structure of
773 /// zero sized types. The only leaf zero sized type is an empty structure.
774 static bool isMaybeZeroSizedType(const Type *Ty) {
775 if (isa<OpaqueType>(Ty)) return true; // Can't say.
776 if (const StructType *STy = dyn_cast<StructType>(Ty)) {
778 // If all of elements have zero size, this does too.
779 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i)
780 if (!isMaybeZeroSizedType(STy->getElementType(i))) return false;
783 } else if (const ArrayType *ATy = dyn_cast<ArrayType>(Ty)) {
784 return isMaybeZeroSizedType(ATy->getElementType());
789 /// IdxCompare - Compare the two constants as though they were getelementptr
790 /// indices. This allows coersion of the types to be the same thing.
792 /// If the two constants are the "same" (after coersion), return 0. If the
793 /// first is less than the second, return -1, if the second is less than the
794 /// first, return 1. If the constants are not integral, return -2.
796 static int IdxCompare(Constant *C1, Constant *C2, const Type *ElTy) {
797 if (C1 == C2) return 0;
799 // Ok, we found a different index. If they are not ConstantInt, we can't do
800 // anything with them.
801 if (!isa<ConstantInt>(C1) || !isa<ConstantInt>(C2))
802 return -2; // don't know!
804 // Ok, we have two differing integer indices. Sign extend them to be the same
805 // type. Long is always big enough, so we use it.
806 if (C1->getType() != Type::Int64Ty)
807 C1 = ConstantExpr::getSExt(C1, Type::Int64Ty);
809 if (C2->getType() != Type::Int64Ty)
810 C2 = ConstantExpr::getSExt(C2, Type::Int64Ty);
812 if (C1 == C2) return 0; // They are equal
814 // If the type being indexed over is really just a zero sized type, there is
815 // no pointer difference being made here.
816 if (isMaybeZeroSizedType(ElTy))
819 // If they are really different, now that they are the same type, then we
820 // found a difference!
821 if (cast<ConstantInt>(C1)->getSExtValue() <
822 cast<ConstantInt>(C2)->getSExtValue())
828 /// evaluateFCmpRelation - This function determines if there is anything we can
829 /// decide about the two constants provided. This doesn't need to handle simple
830 /// things like ConstantFP comparisons, but should instead handle ConstantExprs.
831 /// If we can determine that the two constants have a particular relation to
832 /// each other, we should return the corresponding FCmpInst predicate,
833 /// otherwise return FCmpInst::BAD_FCMP_PREDICATE. This is used below in
834 /// ConstantFoldCompareInstruction.
836 /// To simplify this code we canonicalize the relation so that the first
837 /// operand is always the most "complex" of the two. We consider ConstantFP
838 /// to be the simplest, and ConstantExprs to be the most complex.
839 static FCmpInst::Predicate evaluateFCmpRelation(const Constant *V1,
840 const Constant *V2) {
841 assert(V1->getType() == V2->getType() &&
842 "Cannot compare values of different types!");
844 // No compile-time operations on this type yet.
845 if (V1->getType() == Type::PPC_FP128Ty)
846 return FCmpInst::BAD_FCMP_PREDICATE;
848 // Handle degenerate case quickly
849 if (V1 == V2) return FCmpInst::FCMP_OEQ;
851 if (!isa<ConstantExpr>(V1)) {
852 if (!isa<ConstantExpr>(V2)) {
853 // We distilled thisUse the standard constant folder for a few cases
855 Constant *C1 = const_cast<Constant*>(V1);
856 Constant *C2 = const_cast<Constant*>(V2);
857 R = dyn_cast<ConstantInt>(
858 ConstantExpr::getFCmp(FCmpInst::FCMP_OEQ, C1, C2));
859 if (R && !R->isZero())
860 return FCmpInst::FCMP_OEQ;
861 R = dyn_cast<ConstantInt>(
862 ConstantExpr::getFCmp(FCmpInst::FCMP_OLT, C1, C2));
863 if (R && !R->isZero())
864 return FCmpInst::FCMP_OLT;
865 R = dyn_cast<ConstantInt>(
866 ConstantExpr::getFCmp(FCmpInst::FCMP_OGT, C1, C2));
867 if (R && !R->isZero())
868 return FCmpInst::FCMP_OGT;
870 // Nothing more we can do
871 return FCmpInst::BAD_FCMP_PREDICATE;
874 // If the first operand is simple and second is ConstantExpr, swap operands.
875 FCmpInst::Predicate SwappedRelation = evaluateFCmpRelation(V2, V1);
876 if (SwappedRelation != FCmpInst::BAD_FCMP_PREDICATE)
877 return FCmpInst::getSwappedPredicate(SwappedRelation);
879 // Ok, the LHS is known to be a constantexpr. The RHS can be any of a
880 // constantexpr or a simple constant.
881 const ConstantExpr *CE1 = cast<ConstantExpr>(V1);
882 switch (CE1->getOpcode()) {
883 case Instruction::FPTrunc:
884 case Instruction::FPExt:
885 case Instruction::UIToFP:
886 case Instruction::SIToFP:
887 // We might be able to do something with these but we don't right now.
893 // There are MANY other foldings that we could perform here. They will
894 // probably be added on demand, as they seem needed.
895 return FCmpInst::BAD_FCMP_PREDICATE;
898 /// evaluateICmpRelation - This function determines if there is anything we can
899 /// decide about the two constants provided. This doesn't need to handle simple
900 /// things like integer comparisons, but should instead handle ConstantExprs
901 /// and GlobalValues. If we can determine that the two constants have a
902 /// particular relation to each other, we should return the corresponding ICmp
903 /// predicate, otherwise return ICmpInst::BAD_ICMP_PREDICATE.
905 /// To simplify this code we canonicalize the relation so that the first
906 /// operand is always the most "complex" of the two. We consider simple
907 /// constants (like ConstantInt) to be the simplest, followed by
908 /// GlobalValues, followed by ConstantExpr's (the most complex).
910 static ICmpInst::Predicate evaluateICmpRelation(const Constant *V1,
913 assert(V1->getType() == V2->getType() &&
914 "Cannot compare different types of values!");
915 if (V1 == V2) return ICmpInst::ICMP_EQ;
917 if (!isa<ConstantExpr>(V1) && !isa<GlobalValue>(V1)) {
918 if (!isa<GlobalValue>(V2) && !isa<ConstantExpr>(V2)) {
919 // We distilled this down to a simple case, use the standard constant
922 Constant *C1 = const_cast<Constant*>(V1);
923 Constant *C2 = const_cast<Constant*>(V2);
924 ICmpInst::Predicate pred = ICmpInst::ICMP_EQ;
925 R = dyn_cast<ConstantInt>(ConstantExpr::getICmp(pred, C1, C2));
926 if (R && !R->isZero())
928 pred = isSigned ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT;
929 R = dyn_cast<ConstantInt>(ConstantExpr::getICmp(pred, C1, C2));
930 if (R && !R->isZero())
932 pred = isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT;
933 R = dyn_cast<ConstantInt>(ConstantExpr::getICmp(pred, C1, C2));
934 if (R && !R->isZero())
937 // If we couldn't figure it out, bail.
938 return ICmpInst::BAD_ICMP_PREDICATE;
941 // If the first operand is simple, swap operands.
942 ICmpInst::Predicate SwappedRelation =
943 evaluateICmpRelation(V2, V1, isSigned);
944 if (SwappedRelation != ICmpInst::BAD_ICMP_PREDICATE)
945 return ICmpInst::getSwappedPredicate(SwappedRelation);
947 } else if (const GlobalValue *CPR1 = dyn_cast<GlobalValue>(V1)) {
948 if (isa<ConstantExpr>(V2)) { // Swap as necessary.
949 ICmpInst::Predicate SwappedRelation =
950 evaluateICmpRelation(V2, V1, isSigned);
951 if (SwappedRelation != ICmpInst::BAD_ICMP_PREDICATE)
952 return ICmpInst::getSwappedPredicate(SwappedRelation);
954 return ICmpInst::BAD_ICMP_PREDICATE;
957 // Now we know that the RHS is a GlobalValue or simple constant,
958 // which (since the types must match) means that it's a ConstantPointerNull.
959 if (const GlobalValue *CPR2 = dyn_cast<GlobalValue>(V2)) {
960 // Don't try to decide equality of aliases.
961 if (!isa<GlobalAlias>(CPR1) && !isa<GlobalAlias>(CPR2))
962 if (!CPR1->hasExternalWeakLinkage() || !CPR2->hasExternalWeakLinkage())
963 return ICmpInst::ICMP_NE;
965 assert(isa<ConstantPointerNull>(V2) && "Canonicalization guarantee!");
966 // GlobalVals can never be null. Don't try to evaluate aliases.
967 if (!CPR1->hasExternalWeakLinkage() && !isa<GlobalAlias>(CPR1))
968 return ICmpInst::ICMP_NE;
971 // Ok, the LHS is known to be a constantexpr. The RHS can be any of a
972 // constantexpr, a CPR, or a simple constant.
973 const ConstantExpr *CE1 = cast<ConstantExpr>(V1);
974 const Constant *CE1Op0 = CE1->getOperand(0);
976 switch (CE1->getOpcode()) {
977 case Instruction::Trunc:
978 case Instruction::FPTrunc:
979 case Instruction::FPExt:
980 case Instruction::FPToUI:
981 case Instruction::FPToSI:
982 break; // We can't evaluate floating point casts or truncations.
984 case Instruction::UIToFP:
985 case Instruction::SIToFP:
986 case Instruction::BitCast:
987 case Instruction::ZExt:
988 case Instruction::SExt:
989 // If the cast is not actually changing bits, and the second operand is a
990 // null pointer, do the comparison with the pre-casted value.
991 if (V2->isNullValue() &&
992 (isa<PointerType>(CE1->getType()) || CE1->getType()->isInteger())) {
993 bool sgnd = isSigned;
994 if (CE1->getOpcode() == Instruction::ZExt) isSigned = false;
995 if (CE1->getOpcode() == Instruction::SExt) isSigned = true;
996 return evaluateICmpRelation(CE1Op0,
997 Constant::getNullValue(CE1Op0->getType()),
1001 // If the dest type is a pointer type, and the RHS is a constantexpr cast
1002 // from the same type as the src of the LHS, evaluate the inputs. This is
1003 // important for things like "icmp eq (cast 4 to int*), (cast 5 to int*)",
1004 // which happens a lot in compilers with tagged integers.
1005 if (const ConstantExpr *CE2 = dyn_cast<ConstantExpr>(V2))
1006 if (CE2->isCast() && isa<PointerType>(CE1->getType()) &&
1007 CE1->getOperand(0)->getType() == CE2->getOperand(0)->getType() &&
1008 CE1->getOperand(0)->getType()->isInteger()) {
1009 bool sgnd = isSigned;
1010 if (CE1->getOpcode() == Instruction::ZExt) isSigned = false;
1011 if (CE1->getOpcode() == Instruction::SExt) isSigned = true;
1012 return evaluateICmpRelation(CE1->getOperand(0), CE2->getOperand(0),
1017 case Instruction::GetElementPtr:
1018 // Ok, since this is a getelementptr, we know that the constant has a
1019 // pointer type. Check the various cases.
1020 if (isa<ConstantPointerNull>(V2)) {
1021 // If we are comparing a GEP to a null pointer, check to see if the base
1022 // of the GEP equals the null pointer.
1023 if (const GlobalValue *GV = dyn_cast<GlobalValue>(CE1Op0)) {
1024 if (GV->hasExternalWeakLinkage())
1025 // Weak linkage GVals could be zero or not. We're comparing that
1026 // to null pointer so its greater-or-equal
1027 return isSigned ? ICmpInst::ICMP_SGE : ICmpInst::ICMP_UGE;
1029 // If its not weak linkage, the GVal must have a non-zero address
1030 // so the result is greater-than
1031 return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT;
1032 } else if (isa<ConstantPointerNull>(CE1Op0)) {
1033 // If we are indexing from a null pointer, check to see if we have any
1034 // non-zero indices.
1035 for (unsigned i = 1, e = CE1->getNumOperands(); i != e; ++i)
1036 if (!CE1->getOperand(i)->isNullValue())
1037 // Offsetting from null, must not be equal.
1038 return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT;
1039 // Only zero indexes from null, must still be zero.
1040 return ICmpInst::ICMP_EQ;
1042 // Otherwise, we can't really say if the first operand is null or not.
1043 } else if (const GlobalValue *CPR2 = dyn_cast<GlobalValue>(V2)) {
1044 if (isa<ConstantPointerNull>(CE1Op0)) {
1045 if (CPR2->hasExternalWeakLinkage())
1046 // Weak linkage GVals could be zero or not. We're comparing it to
1047 // a null pointer, so its less-or-equal
1048 return isSigned ? ICmpInst::ICMP_SLE : ICmpInst::ICMP_ULE;
1050 // If its not weak linkage, the GVal must have a non-zero address
1051 // so the result is less-than
1052 return isSigned ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT;
1053 } else if (const GlobalValue *CPR1 = dyn_cast<GlobalValue>(CE1Op0)) {
1055 // If this is a getelementptr of the same global, then it must be
1056 // different. Because the types must match, the getelementptr could
1057 // only have at most one index, and because we fold getelementptr's
1058 // with a single zero index, it must be nonzero.
1059 assert(CE1->getNumOperands() == 2 &&
1060 !CE1->getOperand(1)->isNullValue() &&
1061 "Suprising getelementptr!");
1062 return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT;
1064 // If they are different globals, we don't know what the value is,
1065 // but they can't be equal.
1066 return ICmpInst::ICMP_NE;
1070 const ConstantExpr *CE2 = cast<ConstantExpr>(V2);
1071 const Constant *CE2Op0 = CE2->getOperand(0);
1073 // There are MANY other foldings that we could perform here. They will
1074 // probably be added on demand, as they seem needed.
1075 switch (CE2->getOpcode()) {
1077 case Instruction::GetElementPtr:
1078 // By far the most common case to handle is when the base pointers are
1079 // obviously to the same or different globals.
1080 if (isa<GlobalValue>(CE1Op0) && isa<GlobalValue>(CE2Op0)) {
1081 if (CE1Op0 != CE2Op0) // Don't know relative ordering, but not equal
1082 return ICmpInst::ICMP_NE;
1083 // Ok, we know that both getelementptr instructions are based on the
1084 // same global. From this, we can precisely determine the relative
1085 // ordering of the resultant pointers.
1088 // Compare all of the operands the GEP's have in common.
1089 gep_type_iterator GTI = gep_type_begin(CE1);
1090 for (;i != CE1->getNumOperands() && i != CE2->getNumOperands();
1092 switch (IdxCompare(CE1->getOperand(i), CE2->getOperand(i),
1093 GTI.getIndexedType())) {
1094 case -1: return isSigned ? ICmpInst::ICMP_SLT:ICmpInst::ICMP_ULT;
1095 case 1: return isSigned ? ICmpInst::ICMP_SGT:ICmpInst::ICMP_UGT;
1096 case -2: return ICmpInst::BAD_ICMP_PREDICATE;
1099 // Ok, we ran out of things they have in common. If any leftovers
1100 // are non-zero then we have a difference, otherwise we are equal.
1101 for (; i < CE1->getNumOperands(); ++i)
1102 if (!CE1->getOperand(i)->isNullValue()) {
1103 if (isa<ConstantInt>(CE1->getOperand(i)))
1104 return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT;
1106 return ICmpInst::BAD_ICMP_PREDICATE; // Might be equal.
1109 for (; i < CE2->getNumOperands(); ++i)
1110 if (!CE2->getOperand(i)->isNullValue()) {
1111 if (isa<ConstantInt>(CE2->getOperand(i)))
1112 return isSigned ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT;
1114 return ICmpInst::BAD_ICMP_PREDICATE; // Might be equal.
1116 return ICmpInst::ICMP_EQ;
1125 return ICmpInst::BAD_ICMP_PREDICATE;
1128 Constant *llvm::ConstantFoldCompareInstruction(unsigned short pred,
1130 const Constant *C2) {
1132 // Handle some degenerate cases first
1133 if (isa<UndefValue>(C1) || isa<UndefValue>(C2))
1134 return UndefValue::get(Type::Int1Ty);
1136 // No compile-time operations on this type yet.
1137 if (C1->getType() == Type::PPC_FP128Ty)
1140 // icmp eq/ne(null,GV) -> false/true
1141 if (C1->isNullValue()) {
1142 if (const GlobalValue *GV = dyn_cast<GlobalValue>(C2))
1143 // Don't try to evaluate aliases. External weak GV can be null.
1144 if (!isa<GlobalAlias>(GV) && !GV->hasExternalWeakLinkage()) {
1145 if (pred == ICmpInst::ICMP_EQ)
1146 return ConstantInt::getFalse();
1147 else if (pred == ICmpInst::ICMP_NE)
1148 return ConstantInt::getTrue();
1150 // icmp eq/ne(GV,null) -> false/true
1151 } else if (C2->isNullValue()) {
1152 if (const GlobalValue *GV = dyn_cast<GlobalValue>(C1))
1153 // Don't try to evaluate aliases. External weak GV can be null.
1154 if (!isa<GlobalAlias>(GV) && !GV->hasExternalWeakLinkage()) {
1155 if (pred == ICmpInst::ICMP_EQ)
1156 return ConstantInt::getFalse();
1157 else if (pred == ICmpInst::ICMP_NE)
1158 return ConstantInt::getTrue();
1162 if (isa<ConstantInt>(C1) && isa<ConstantInt>(C2)) {
1163 APInt V1 = cast<ConstantInt>(C1)->getValue();
1164 APInt V2 = cast<ConstantInt>(C2)->getValue();
1166 default: assert(0 && "Invalid ICmp Predicate"); return 0;
1167 case ICmpInst::ICMP_EQ: return ConstantInt::get(Type::Int1Ty, V1 == V2);
1168 case ICmpInst::ICMP_NE: return ConstantInt::get(Type::Int1Ty, V1 != V2);
1169 case ICmpInst::ICMP_SLT:return ConstantInt::get(Type::Int1Ty, V1.slt(V2));
1170 case ICmpInst::ICMP_SGT:return ConstantInt::get(Type::Int1Ty, V1.sgt(V2));
1171 case ICmpInst::ICMP_SLE:return ConstantInt::get(Type::Int1Ty, V1.sle(V2));
1172 case ICmpInst::ICMP_SGE:return ConstantInt::get(Type::Int1Ty, V1.sge(V2));
1173 case ICmpInst::ICMP_ULT:return ConstantInt::get(Type::Int1Ty, V1.ult(V2));
1174 case ICmpInst::ICMP_UGT:return ConstantInt::get(Type::Int1Ty, V1.ugt(V2));
1175 case ICmpInst::ICMP_ULE:return ConstantInt::get(Type::Int1Ty, V1.ule(V2));
1176 case ICmpInst::ICMP_UGE:return ConstantInt::get(Type::Int1Ty, V1.uge(V2));
1178 } else if (isa<ConstantFP>(C1) && isa<ConstantFP>(C2)) {
1179 APFloat C1V = cast<ConstantFP>(C1)->getValueAPF();
1180 APFloat C2V = cast<ConstantFP>(C2)->getValueAPF();
1181 APFloat::cmpResult R = C1V.compare(C2V);
1183 default: assert(0 && "Invalid FCmp Predicate"); return 0;
1184 case FCmpInst::FCMP_FALSE: return ConstantInt::getFalse();
1185 case FCmpInst::FCMP_TRUE: return ConstantInt::getTrue();
1186 case FCmpInst::FCMP_UNO:
1187 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpUnordered);
1188 case FCmpInst::FCMP_ORD:
1189 return ConstantInt::get(Type::Int1Ty, R!=APFloat::cmpUnordered);
1190 case FCmpInst::FCMP_UEQ:
1191 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpUnordered ||
1192 R==APFloat::cmpEqual);
1193 case FCmpInst::FCMP_OEQ:
1194 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpEqual);
1195 case FCmpInst::FCMP_UNE:
1196 return ConstantInt::get(Type::Int1Ty, R!=APFloat::cmpEqual);
1197 case FCmpInst::FCMP_ONE:
1198 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpLessThan ||
1199 R==APFloat::cmpGreaterThan);
1200 case FCmpInst::FCMP_ULT:
1201 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpUnordered ||
1202 R==APFloat::cmpLessThan);
1203 case FCmpInst::FCMP_OLT:
1204 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpLessThan);
1205 case FCmpInst::FCMP_UGT:
1206 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpUnordered ||
1207 R==APFloat::cmpGreaterThan);
1208 case FCmpInst::FCMP_OGT:
1209 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpGreaterThan);
1210 case FCmpInst::FCMP_ULE:
1211 return ConstantInt::get(Type::Int1Ty, R!=APFloat::cmpGreaterThan);
1212 case FCmpInst::FCMP_OLE:
1213 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpLessThan ||
1214 R==APFloat::cmpEqual);
1215 case FCmpInst::FCMP_UGE:
1216 return ConstantInt::get(Type::Int1Ty, R!=APFloat::cmpLessThan);
1217 case FCmpInst::FCMP_OGE:
1218 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpGreaterThan ||
1219 R==APFloat::cmpEqual);
1221 } else if (const ConstantVector *CP1 = dyn_cast<ConstantVector>(C1)) {
1222 if (const ConstantVector *CP2 = dyn_cast<ConstantVector>(C2)) {
1223 if (pred == FCmpInst::FCMP_OEQ || pred == FCmpInst::FCMP_UEQ) {
1224 for (unsigned i = 0, e = CP1->getNumOperands(); i != e; ++i) {
1225 Constant *C= ConstantExpr::getFCmp(FCmpInst::FCMP_OEQ,
1226 const_cast<Constant*>(CP1->getOperand(i)),
1227 const_cast<Constant*>(CP2->getOperand(i)));
1228 if (ConstantInt *CB = dyn_cast<ConstantInt>(C))
1231 // Otherwise, could not decide from any element pairs.
1233 } else if (pred == ICmpInst::ICMP_EQ) {
1234 for (unsigned i = 0, e = CP1->getNumOperands(); i != e; ++i) {
1235 Constant *C = ConstantExpr::getICmp(ICmpInst::ICMP_EQ,
1236 const_cast<Constant*>(CP1->getOperand(i)),
1237 const_cast<Constant*>(CP2->getOperand(i)));
1238 if (ConstantInt *CB = dyn_cast<ConstantInt>(C))
1241 // Otherwise, could not decide from any element pairs.
1247 if (C1->getType()->isFloatingPoint()) {
1248 switch (evaluateFCmpRelation(C1, C2)) {
1249 default: assert(0 && "Unknown relation!");
1250 case FCmpInst::FCMP_UNO:
1251 case FCmpInst::FCMP_ORD:
1252 case FCmpInst::FCMP_UEQ:
1253 case FCmpInst::FCMP_UNE:
1254 case FCmpInst::FCMP_ULT:
1255 case FCmpInst::FCMP_UGT:
1256 case FCmpInst::FCMP_ULE:
1257 case FCmpInst::FCMP_UGE:
1258 case FCmpInst::FCMP_TRUE:
1259 case FCmpInst::FCMP_FALSE:
1260 case FCmpInst::BAD_FCMP_PREDICATE:
1261 break; // Couldn't determine anything about these constants.
1262 case FCmpInst::FCMP_OEQ: // We know that C1 == C2
1263 return ConstantInt::get(Type::Int1Ty,
1264 pred == FCmpInst::FCMP_UEQ || pred == FCmpInst::FCMP_OEQ ||
1265 pred == FCmpInst::FCMP_ULE || pred == FCmpInst::FCMP_OLE ||
1266 pred == FCmpInst::FCMP_UGE || pred == FCmpInst::FCMP_OGE);
1267 case FCmpInst::FCMP_OLT: // We know that C1 < C2
1268 return ConstantInt::get(Type::Int1Ty,
1269 pred == FCmpInst::FCMP_UNE || pred == FCmpInst::FCMP_ONE ||
1270 pred == FCmpInst::FCMP_ULT || pred == FCmpInst::FCMP_OLT ||
1271 pred == FCmpInst::FCMP_ULE || pred == FCmpInst::FCMP_OLE);
1272 case FCmpInst::FCMP_OGT: // We know that C1 > C2
1273 return ConstantInt::get(Type::Int1Ty,
1274 pred == FCmpInst::FCMP_UNE || pred == FCmpInst::FCMP_ONE ||
1275 pred == FCmpInst::FCMP_UGT || pred == FCmpInst::FCMP_OGT ||
1276 pred == FCmpInst::FCMP_UGE || pred == FCmpInst::FCMP_OGE);
1277 case FCmpInst::FCMP_OLE: // We know that C1 <= C2
1278 // We can only partially decide this relation.
1279 if (pred == FCmpInst::FCMP_UGT || pred == FCmpInst::FCMP_OGT)
1280 return ConstantInt::getFalse();
1281 if (pred == FCmpInst::FCMP_ULT || pred == FCmpInst::FCMP_OLT)
1282 return ConstantInt::getTrue();
1284 case FCmpInst::FCMP_OGE: // We known that C1 >= C2
1285 // We can only partially decide this relation.
1286 if (pred == FCmpInst::FCMP_ULT || pred == FCmpInst::FCMP_OLT)
1287 return ConstantInt::getFalse();
1288 if (pred == FCmpInst::FCMP_UGT || pred == FCmpInst::FCMP_OGT)
1289 return ConstantInt::getTrue();
1291 case ICmpInst::ICMP_NE: // We know that C1 != C2
1292 // We can only partially decide this relation.
1293 if (pred == FCmpInst::FCMP_OEQ || pred == FCmpInst::FCMP_UEQ)
1294 return ConstantInt::getFalse();
1295 if (pred == FCmpInst::FCMP_ONE || pred == FCmpInst::FCMP_UNE)
1296 return ConstantInt::getTrue();
1300 // Evaluate the relation between the two constants, per the predicate.
1301 switch (evaluateICmpRelation(C1, C2, CmpInst::isSigned(pred))) {
1302 default: assert(0 && "Unknown relational!");
1303 case ICmpInst::BAD_ICMP_PREDICATE:
1304 break; // Couldn't determine anything about these constants.
1305 case ICmpInst::ICMP_EQ: // We know the constants are equal!
1306 // If we know the constants are equal, we can decide the result of this
1307 // computation precisely.
1308 return ConstantInt::get(Type::Int1Ty,
1309 pred == ICmpInst::ICMP_EQ ||
1310 pred == ICmpInst::ICMP_ULE ||
1311 pred == ICmpInst::ICMP_SLE ||
1312 pred == ICmpInst::ICMP_UGE ||
1313 pred == ICmpInst::ICMP_SGE);
1314 case ICmpInst::ICMP_ULT:
1315 // If we know that C1 < C2, we can decide the result of this computation
1317 return ConstantInt::get(Type::Int1Ty,
1318 pred == ICmpInst::ICMP_ULT ||
1319 pred == ICmpInst::ICMP_NE ||
1320 pred == ICmpInst::ICMP_ULE);
1321 case ICmpInst::ICMP_SLT:
1322 // If we know that C1 < C2, we can decide the result of this computation
1324 return ConstantInt::get(Type::Int1Ty,
1325 pred == ICmpInst::ICMP_SLT ||
1326 pred == ICmpInst::ICMP_NE ||
1327 pred == ICmpInst::ICMP_SLE);
1328 case ICmpInst::ICMP_UGT:
1329 // If we know that C1 > C2, we can decide the result of this computation
1331 return ConstantInt::get(Type::Int1Ty,
1332 pred == ICmpInst::ICMP_UGT ||
1333 pred == ICmpInst::ICMP_NE ||
1334 pred == ICmpInst::ICMP_UGE);
1335 case ICmpInst::ICMP_SGT:
1336 // If we know that C1 > C2, we can decide the result of this computation
1338 return ConstantInt::get(Type::Int1Ty,
1339 pred == ICmpInst::ICMP_SGT ||
1340 pred == ICmpInst::ICMP_NE ||
1341 pred == ICmpInst::ICMP_SGE);
1342 case ICmpInst::ICMP_ULE:
1343 // If we know that C1 <= C2, we can only partially decide this relation.
1344 if (pred == ICmpInst::ICMP_UGT) return ConstantInt::getFalse();
1345 if (pred == ICmpInst::ICMP_ULT) return ConstantInt::getTrue();
1347 case ICmpInst::ICMP_SLE:
1348 // If we know that C1 <= C2, we can only partially decide this relation.
1349 if (pred == ICmpInst::ICMP_SGT) return ConstantInt::getFalse();
1350 if (pred == ICmpInst::ICMP_SLT) return ConstantInt::getTrue();
1353 case ICmpInst::ICMP_UGE:
1354 // If we know that C1 >= C2, we can only partially decide this relation.
1355 if (pred == ICmpInst::ICMP_ULT) return ConstantInt::getFalse();
1356 if (pred == ICmpInst::ICMP_UGT) return ConstantInt::getTrue();
1358 case ICmpInst::ICMP_SGE:
1359 // If we know that C1 >= C2, we can only partially decide this relation.
1360 if (pred == ICmpInst::ICMP_SLT) return ConstantInt::getFalse();
1361 if (pred == ICmpInst::ICMP_SGT) return ConstantInt::getTrue();
1364 case ICmpInst::ICMP_NE:
1365 // If we know that C1 != C2, we can only partially decide this relation.
1366 if (pred == ICmpInst::ICMP_EQ) return ConstantInt::getFalse();
1367 if (pred == ICmpInst::ICMP_NE) return ConstantInt::getTrue();
1371 if (!isa<ConstantExpr>(C1) && isa<ConstantExpr>(C2)) {
1372 // If C2 is a constant expr and C1 isn't, flop them around and fold the
1373 // other way if possible.
1375 case ICmpInst::ICMP_EQ:
1376 case ICmpInst::ICMP_NE:
1377 // No change of predicate required.
1378 return ConstantFoldCompareInstruction(pred, C2, C1);
1380 case ICmpInst::ICMP_ULT:
1381 case ICmpInst::ICMP_SLT:
1382 case ICmpInst::ICMP_UGT:
1383 case ICmpInst::ICMP_SGT:
1384 case ICmpInst::ICMP_ULE:
1385 case ICmpInst::ICMP_SLE:
1386 case ICmpInst::ICMP_UGE:
1387 case ICmpInst::ICMP_SGE:
1388 // Change the predicate as necessary to swap the operands.
1389 pred = ICmpInst::getSwappedPredicate((ICmpInst::Predicate)pred);
1390 return ConstantFoldCompareInstruction(pred, C2, C1);
1392 default: // These predicates cannot be flopped around.
1400 Constant *llvm::ConstantFoldGetElementPtr(const Constant *C,
1401 Constant* const *Idxs,
1404 (NumIdx == 1 && Idxs[0]->isNullValue()))
1405 return const_cast<Constant*>(C);
1407 if (isa<UndefValue>(C)) {
1408 const PointerType *Ptr = cast<PointerType>(C->getType());
1409 const Type *Ty = GetElementPtrInst::getIndexedType(Ptr,
1411 (Value **)Idxs+NumIdx,
1413 assert(Ty != 0 && "Invalid indices for GEP!");
1414 return UndefValue::get(PointerType::get(Ty, Ptr->getAddressSpace()));
1417 Constant *Idx0 = Idxs[0];
1418 if (C->isNullValue()) {
1420 for (unsigned i = 0, e = NumIdx; i != e; ++i)
1421 if (!Idxs[i]->isNullValue()) {
1426 const PointerType *Ptr = cast<PointerType>(C->getType());
1427 const Type *Ty = GetElementPtrInst::getIndexedType(Ptr,
1429 (Value**)Idxs+NumIdx,
1431 assert(Ty != 0 && "Invalid indices for GEP!");
1433 ConstantPointerNull::get(PointerType::get(Ty,Ptr->getAddressSpace()));
1437 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(const_cast<Constant*>(C))) {
1438 // Combine Indices - If the source pointer to this getelementptr instruction
1439 // is a getelementptr instruction, combine the indices of the two
1440 // getelementptr instructions into a single instruction.
1442 if (CE->getOpcode() == Instruction::GetElementPtr) {
1443 const Type *LastTy = 0;
1444 for (gep_type_iterator I = gep_type_begin(CE), E = gep_type_end(CE);
1448 if ((LastTy && isa<ArrayType>(LastTy)) || Idx0->isNullValue()) {
1449 SmallVector<Value*, 16> NewIndices;
1450 NewIndices.reserve(NumIdx + CE->getNumOperands());
1451 for (unsigned i = 1, e = CE->getNumOperands()-1; i != e; ++i)
1452 NewIndices.push_back(CE->getOperand(i));
1454 // Add the last index of the source with the first index of the new GEP.
1455 // Make sure to handle the case when they are actually different types.
1456 Constant *Combined = CE->getOperand(CE->getNumOperands()-1);
1457 // Otherwise it must be an array.
1458 if (!Idx0->isNullValue()) {
1459 const Type *IdxTy = Combined->getType();
1460 if (IdxTy != Idx0->getType()) {
1461 Constant *C1 = ConstantExpr::getSExtOrBitCast(Idx0, Type::Int64Ty);
1462 Constant *C2 = ConstantExpr::getSExtOrBitCast(Combined,
1464 Combined = ConstantExpr::get(Instruction::Add, C1, C2);
1467 ConstantExpr::get(Instruction::Add, Idx0, Combined);
1471 NewIndices.push_back(Combined);
1472 NewIndices.insert(NewIndices.end(), Idxs+1, Idxs+NumIdx);
1473 return ConstantExpr::getGetElementPtr(CE->getOperand(0), &NewIndices[0],
1478 // Implement folding of:
1479 // int* getelementptr ([2 x int]* cast ([3 x int]* %X to [2 x int]*),
1481 // To: int* getelementptr ([3 x int]* %X, long 0, long 0)
1483 if (CE->isCast() && NumIdx > 1 && Idx0->isNullValue()) {
1484 if (const PointerType *SPT =
1485 dyn_cast<PointerType>(CE->getOperand(0)->getType()))
1486 if (const ArrayType *SAT = dyn_cast<ArrayType>(SPT->getElementType()))
1487 if (const ArrayType *CAT =
1488 dyn_cast<ArrayType>(cast<PointerType>(C->getType())->getElementType()))
1489 if (CAT->getElementType() == SAT->getElementType())
1490 return ConstantExpr::getGetElementPtr(
1491 (Constant*)CE->getOperand(0), Idxs, NumIdx);
1494 // Fold: getelementptr (i8* inttoptr (i64 1 to i8*), i32 -1)
1495 // Into: inttoptr (i64 0 to i8*)
1496 // This happens with pointers to member functions in C++.
1497 if (CE->getOpcode() == Instruction::IntToPtr && NumIdx == 1 &&
1498 isa<ConstantInt>(CE->getOperand(0)) && isa<ConstantInt>(Idxs[0]) &&
1499 cast<PointerType>(CE->getType())->getElementType() == Type::Int8Ty) {
1500 Constant *Base = CE->getOperand(0);
1501 Constant *Offset = Idxs[0];
1503 // Convert the smaller integer to the larger type.
1504 if (Offset->getType()->getPrimitiveSizeInBits() <
1505 Base->getType()->getPrimitiveSizeInBits())
1506 Offset = ConstantExpr::getSExt(Offset, Base->getType());
1507 else if (Base->getType()->getPrimitiveSizeInBits() <
1508 Offset->getType()->getPrimitiveSizeInBits())
1509 Base = ConstantExpr::getZExt(Base, Base->getType());
1511 Base = ConstantExpr::getAdd(Base, Offset);
1512 return ConstantExpr::getIntToPtr(Base, CE->getType());