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(DestTy, 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(DestTy, 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(DestTy, 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 // (zext i32 to i64) & 4294967295 -> (zext i32 to i64)
552 if (const ConstantExpr *CE1 = dyn_cast<ConstantExpr>(C1)) {
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 (CE1->getOpcode() == Instruction::PtrToInt &&
563 isa<GlobalValue>(CE1->getOperand(0))) {
564 GlobalValue *CPR = cast<GlobalValue>(CE1->getOperand(0));
566 // Functions are at least 4-byte aligned. If and'ing the address of a
567 // function with a constant < 4, fold it to zero.
568 if (const ConstantInt *CI = dyn_cast<ConstantInt>(C2))
569 if (CI->getValue().ult(APInt(CI->getType()->getBitWidth(),4)) &&
571 return Constant::getNullValue(CI->getType());
575 case Instruction::Or:
576 if (CI2->equalsInt(0)) return const_cast<Constant*>(C1); // X | 0 == X
577 if (CI2->isAllOnesValue())
578 return const_cast<Constant*>(C2); // X | -1 == -1
580 case Instruction::Xor:
581 if (CI2->equalsInt(0)) return const_cast<Constant*>(C1); // X ^ 0 == X
583 case Instruction::AShr:
584 // ashr (zext C to Ty), C2 -> lshr (zext C, CSA), C2
585 if (const ConstantExpr *CE1 = dyn_cast<ConstantExpr>(C1))
586 if (CE1->getOpcode() == Instruction::ZExt) // Top bits known zero.
587 return ConstantExpr::getLShr(const_cast<Constant*>(C1),
588 const_cast<Constant*>(C2));
593 if (isa<ConstantExpr>(C1)) {
594 // There are many possible foldings we could do here. We should probably
595 // at least fold add of a pointer with an integer into the appropriate
596 // getelementptr. This will improve alias analysis a bit.
597 } else if (isa<ConstantExpr>(C2)) {
598 // If C2 is a constant expr and C1 isn't, flop them around and fold the
599 // other way if possible.
601 case Instruction::Add:
602 case Instruction::Mul:
603 case Instruction::And:
604 case Instruction::Or:
605 case Instruction::Xor:
606 // No change of opcode required.
607 return ConstantFoldBinaryInstruction(Opcode, C2, C1);
609 case Instruction::Shl:
610 case Instruction::LShr:
611 case Instruction::AShr:
612 case Instruction::Sub:
613 case Instruction::SDiv:
614 case Instruction::UDiv:
615 case Instruction::FDiv:
616 case Instruction::URem:
617 case Instruction::SRem:
618 case Instruction::FRem:
619 default: // These instructions cannot be flopped around.
624 // At this point we know neither constant is an UndefValue nor a ConstantExpr
625 // so look at directly computing the value.
626 if (const ConstantInt *CI1 = dyn_cast<ConstantInt>(C1)) {
627 if (const ConstantInt *CI2 = dyn_cast<ConstantInt>(C2)) {
628 using namespace APIntOps;
629 APInt C1V = CI1->getValue();
630 APInt C2V = CI2->getValue();
634 case Instruction::Add:
635 return ConstantInt::get(C1V + C2V);
636 case Instruction::Sub:
637 return ConstantInt::get(C1V - C2V);
638 case Instruction::Mul:
639 return ConstantInt::get(C1V * C2V);
640 case Instruction::UDiv:
641 if (CI2->isNullValue())
642 return 0; // X / 0 -> can't fold
643 return ConstantInt::get(C1V.udiv(C2V));
644 case Instruction::SDiv:
645 if (CI2->isNullValue())
646 return 0; // X / 0 -> can't fold
647 if (C2V.isAllOnesValue() && C1V.isMinSignedValue())
648 return 0; // MIN_INT / -1 -> overflow
649 return ConstantInt::get(C1V.sdiv(C2V));
650 case Instruction::URem:
651 if (C2->isNullValue())
652 return 0; // X / 0 -> can't fold
653 return ConstantInt::get(C1V.urem(C2V));
654 case Instruction::SRem:
655 if (CI2->isNullValue())
656 return 0; // X % 0 -> can't fold
657 if (C2V.isAllOnesValue() && C1V.isMinSignedValue())
658 return 0; // MIN_INT % -1 -> overflow
659 return ConstantInt::get(C1V.srem(C2V));
660 case Instruction::And:
661 return ConstantInt::get(C1V & C2V);
662 case Instruction::Or:
663 return ConstantInt::get(C1V | C2V);
664 case Instruction::Xor:
665 return ConstantInt::get(C1V ^ C2V);
666 case Instruction::Shl:
667 if (uint32_t shiftAmt = C2V.getZExtValue()) {
668 if (shiftAmt < C1V.getBitWidth())
669 return ConstantInt::get(C1V.shl(shiftAmt));
671 return UndefValue::get(C1->getType()); // too big shift is undef
673 return const_cast<ConstantInt*>(CI1); // Zero shift is identity
674 case Instruction::LShr:
675 if (uint32_t shiftAmt = C2V.getZExtValue()) {
676 if (shiftAmt < C1V.getBitWidth())
677 return ConstantInt::get(C1V.lshr(shiftAmt));
679 return UndefValue::get(C1->getType()); // too big shift is undef
681 return const_cast<ConstantInt*>(CI1); // Zero shift is identity
682 case Instruction::AShr:
683 if (uint32_t shiftAmt = C2V.getZExtValue()) {
684 if (shiftAmt < C1V.getBitWidth())
685 return ConstantInt::get(C1V.ashr(shiftAmt));
687 return UndefValue::get(C1->getType()); // too big shift is undef
689 return const_cast<ConstantInt*>(CI1); // Zero shift is identity
692 } else if (const ConstantFP *CFP1 = dyn_cast<ConstantFP>(C1)) {
693 if (const ConstantFP *CFP2 = dyn_cast<ConstantFP>(C2)) {
694 APFloat C1V = CFP1->getValueAPF();
695 APFloat C2V = CFP2->getValueAPF();
696 APFloat C3V = C1V; // copy for modification
697 bool isDouble = CFP1->getType()==Type::DoubleTy;
701 case Instruction::Add:
702 (void)C3V.add(C2V, APFloat::rmNearestTiesToEven);
703 return ConstantFP::get(CFP1->getType(), C3V);
704 case Instruction::Sub:
705 (void)C3V.subtract(C2V, APFloat::rmNearestTiesToEven);
706 return ConstantFP::get(CFP1->getType(), C3V);
707 case Instruction::Mul:
708 (void)C3V.multiply(C2V, APFloat::rmNearestTiesToEven);
709 return ConstantFP::get(CFP1->getType(), C3V);
710 case Instruction::FDiv:
711 (void)C3V.divide(C2V, APFloat::rmNearestTiesToEven);
712 return ConstantFP::get(CFP1->getType(), C3V);
713 case Instruction::FRem:
715 // IEEE 754, Section 7.1, #5
716 return ConstantFP::get(CFP1->getType(), isDouble ?
717 APFloat(std::numeric_limits<double>::quiet_NaN()) :
718 APFloat(std::numeric_limits<float>::quiet_NaN()));
719 (void)C3V.mod(C2V, APFloat::rmNearestTiesToEven);
720 return ConstantFP::get(CFP1->getType(), C3V);
723 } else if (const VectorType *VTy = dyn_cast<VectorType>(C1->getType())) {
724 const ConstantVector *CP1 = dyn_cast<ConstantVector>(C1);
725 const ConstantVector *CP2 = dyn_cast<ConstantVector>(C2);
726 if ((CP1 != NULL || isa<ConstantAggregateZero>(C1)) &&
727 (CP2 != NULL || isa<ConstantAggregateZero>(C2))) {
731 case Instruction::Add:
732 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getAdd);
733 case Instruction::Sub:
734 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getSub);
735 case Instruction::Mul:
736 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getMul);
737 case Instruction::UDiv:
738 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getUDiv);
739 case Instruction::SDiv:
740 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getSDiv);
741 case Instruction::FDiv:
742 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getFDiv);
743 case Instruction::URem:
744 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getURem);
745 case Instruction::SRem:
746 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getSRem);
747 case Instruction::FRem:
748 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getFRem);
749 case Instruction::And:
750 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getAnd);
751 case Instruction::Or:
752 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getOr);
753 case Instruction::Xor:
754 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getXor);
759 // We don't know how to fold this
763 /// isZeroSizedType - This type is zero sized if its an array or structure of
764 /// zero sized types. The only leaf zero sized type is an empty structure.
765 static bool isMaybeZeroSizedType(const Type *Ty) {
766 if (isa<OpaqueType>(Ty)) return true; // Can't say.
767 if (const StructType *STy = dyn_cast<StructType>(Ty)) {
769 // If all of elements have zero size, this does too.
770 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i)
771 if (!isMaybeZeroSizedType(STy->getElementType(i))) return false;
774 } else if (const ArrayType *ATy = dyn_cast<ArrayType>(Ty)) {
775 return isMaybeZeroSizedType(ATy->getElementType());
780 /// IdxCompare - Compare the two constants as though they were getelementptr
781 /// indices. This allows coersion of the types to be the same thing.
783 /// If the two constants are the "same" (after coersion), return 0. If the
784 /// first is less than the second, return -1, if the second is less than the
785 /// first, return 1. If the constants are not integral, return -2.
787 static int IdxCompare(Constant *C1, Constant *C2, const Type *ElTy) {
788 if (C1 == C2) return 0;
790 // Ok, we found a different index. If they are not ConstantInt, we can't do
791 // anything with them.
792 if (!isa<ConstantInt>(C1) || !isa<ConstantInt>(C2))
793 return -2; // don't know!
795 // Ok, we have two differing integer indices. Sign extend them to be the same
796 // type. Long is always big enough, so we use it.
797 if (C1->getType() != Type::Int64Ty)
798 C1 = ConstantExpr::getSExt(C1, Type::Int64Ty);
800 if (C2->getType() != Type::Int64Ty)
801 C2 = ConstantExpr::getSExt(C2, Type::Int64Ty);
803 if (C1 == C2) return 0; // They are equal
805 // If the type being indexed over is really just a zero sized type, there is
806 // no pointer difference being made here.
807 if (isMaybeZeroSizedType(ElTy))
810 // If they are really different, now that they are the same type, then we
811 // found a difference!
812 if (cast<ConstantInt>(C1)->getSExtValue() <
813 cast<ConstantInt>(C2)->getSExtValue())
819 /// evaluateFCmpRelation - This function determines if there is anything we can
820 /// decide about the two constants provided. This doesn't need to handle simple
821 /// things like ConstantFP comparisons, but should instead handle ConstantExprs.
822 /// If we can determine that the two constants have a particular relation to
823 /// each other, we should return the corresponding FCmpInst predicate,
824 /// otherwise return FCmpInst::BAD_FCMP_PREDICATE. This is used below in
825 /// ConstantFoldCompareInstruction.
827 /// To simplify this code we canonicalize the relation so that the first
828 /// operand is always the most "complex" of the two. We consider ConstantFP
829 /// to be the simplest, and ConstantExprs to be the most complex.
830 static FCmpInst::Predicate evaluateFCmpRelation(const Constant *V1,
831 const Constant *V2) {
832 assert(V1->getType() == V2->getType() &&
833 "Cannot compare values of different types!");
835 // No compile-time operations on this type yet.
836 if (V1->getType() == Type::PPC_FP128Ty)
837 return FCmpInst::BAD_FCMP_PREDICATE;
839 // Handle degenerate case quickly
840 if (V1 == V2) return FCmpInst::FCMP_OEQ;
842 if (!isa<ConstantExpr>(V1)) {
843 if (!isa<ConstantExpr>(V2)) {
844 // We distilled thisUse the standard constant folder for a few cases
846 Constant *C1 = const_cast<Constant*>(V1);
847 Constant *C2 = const_cast<Constant*>(V2);
848 R = dyn_cast<ConstantInt>(
849 ConstantExpr::getFCmp(FCmpInst::FCMP_OEQ, C1, C2));
850 if (R && !R->isZero())
851 return FCmpInst::FCMP_OEQ;
852 R = dyn_cast<ConstantInt>(
853 ConstantExpr::getFCmp(FCmpInst::FCMP_OLT, C1, C2));
854 if (R && !R->isZero())
855 return FCmpInst::FCMP_OLT;
856 R = dyn_cast<ConstantInt>(
857 ConstantExpr::getFCmp(FCmpInst::FCMP_OGT, C1, C2));
858 if (R && !R->isZero())
859 return FCmpInst::FCMP_OGT;
861 // Nothing more we can do
862 return FCmpInst::BAD_FCMP_PREDICATE;
865 // If the first operand is simple and second is ConstantExpr, swap operands.
866 FCmpInst::Predicate SwappedRelation = evaluateFCmpRelation(V2, V1);
867 if (SwappedRelation != FCmpInst::BAD_FCMP_PREDICATE)
868 return FCmpInst::getSwappedPredicate(SwappedRelation);
870 // Ok, the LHS is known to be a constantexpr. The RHS can be any of a
871 // constantexpr or a simple constant.
872 const ConstantExpr *CE1 = cast<ConstantExpr>(V1);
873 switch (CE1->getOpcode()) {
874 case Instruction::FPTrunc:
875 case Instruction::FPExt:
876 case Instruction::UIToFP:
877 case Instruction::SIToFP:
878 // We might be able to do something with these but we don't right now.
884 // There are MANY other foldings that we could perform here. They will
885 // probably be added on demand, as they seem needed.
886 return FCmpInst::BAD_FCMP_PREDICATE;
889 /// evaluateICmpRelation - This function determines if there is anything we can
890 /// decide about the two constants provided. This doesn't need to handle simple
891 /// things like integer comparisons, but should instead handle ConstantExprs
892 /// and GlobalValues. If we can determine that the two constants have a
893 /// particular relation to each other, we should return the corresponding ICmp
894 /// predicate, otherwise return ICmpInst::BAD_ICMP_PREDICATE.
896 /// To simplify this code we canonicalize the relation so that the first
897 /// operand is always the most "complex" of the two. We consider simple
898 /// constants (like ConstantInt) to be the simplest, followed by
899 /// GlobalValues, followed by ConstantExpr's (the most complex).
901 static ICmpInst::Predicate evaluateICmpRelation(const Constant *V1,
904 assert(V1->getType() == V2->getType() &&
905 "Cannot compare different types of values!");
906 if (V1 == V2) return ICmpInst::ICMP_EQ;
908 if (!isa<ConstantExpr>(V1) && !isa<GlobalValue>(V1)) {
909 if (!isa<GlobalValue>(V2) && !isa<ConstantExpr>(V2)) {
910 // We distilled this down to a simple case, use the standard constant
913 Constant *C1 = const_cast<Constant*>(V1);
914 Constant *C2 = const_cast<Constant*>(V2);
915 ICmpInst::Predicate pred = ICmpInst::ICMP_EQ;
916 R = dyn_cast<ConstantInt>(ConstantExpr::getICmp(pred, C1, C2));
917 if (R && !R->isZero())
919 pred = isSigned ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT;
920 R = dyn_cast<ConstantInt>(ConstantExpr::getICmp(pred, C1, C2));
921 if (R && !R->isZero())
923 pred = isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT;
924 R = dyn_cast<ConstantInt>(ConstantExpr::getICmp(pred, C1, C2));
925 if (R && !R->isZero())
928 // If we couldn't figure it out, bail.
929 return ICmpInst::BAD_ICMP_PREDICATE;
932 // If the first operand is simple, swap operands.
933 ICmpInst::Predicate SwappedRelation =
934 evaluateICmpRelation(V2, V1, isSigned);
935 if (SwappedRelation != ICmpInst::BAD_ICMP_PREDICATE)
936 return ICmpInst::getSwappedPredicate(SwappedRelation);
938 } else if (const GlobalValue *CPR1 = dyn_cast<GlobalValue>(V1)) {
939 if (isa<ConstantExpr>(V2)) { // Swap as necessary.
940 ICmpInst::Predicate SwappedRelation =
941 evaluateICmpRelation(V2, V1, isSigned);
942 if (SwappedRelation != ICmpInst::BAD_ICMP_PREDICATE)
943 return ICmpInst::getSwappedPredicate(SwappedRelation);
945 return ICmpInst::BAD_ICMP_PREDICATE;
948 // Now we know that the RHS is a GlobalValue or simple constant,
949 // which (since the types must match) means that it's a ConstantPointerNull.
950 if (const GlobalValue *CPR2 = dyn_cast<GlobalValue>(V2)) {
951 // Don't try to decide equality of aliases.
952 if (!isa<GlobalAlias>(CPR1) && !isa<GlobalAlias>(CPR2))
953 if (!CPR1->hasExternalWeakLinkage() || !CPR2->hasExternalWeakLinkage())
954 return ICmpInst::ICMP_NE;
956 assert(isa<ConstantPointerNull>(V2) && "Canonicalization guarantee!");
957 // GlobalVals can never be null. Don't try to evaluate aliases.
958 if (!CPR1->hasExternalWeakLinkage() && !isa<GlobalAlias>(CPR1))
959 return ICmpInst::ICMP_NE;
962 // Ok, the LHS is known to be a constantexpr. The RHS can be any of a
963 // constantexpr, a CPR, or a simple constant.
964 const ConstantExpr *CE1 = cast<ConstantExpr>(V1);
965 const Constant *CE1Op0 = CE1->getOperand(0);
967 switch (CE1->getOpcode()) {
968 case Instruction::Trunc:
969 case Instruction::FPTrunc:
970 case Instruction::FPExt:
971 case Instruction::FPToUI:
972 case Instruction::FPToSI:
973 break; // We can't evaluate floating point casts or truncations.
975 case Instruction::UIToFP:
976 case Instruction::SIToFP:
977 case Instruction::BitCast:
978 case Instruction::ZExt:
979 case Instruction::SExt:
980 // If the cast is not actually changing bits, and the second operand is a
981 // null pointer, do the comparison with the pre-casted value.
982 if (V2->isNullValue() &&
983 (isa<PointerType>(CE1->getType()) || CE1->getType()->isInteger())) {
984 bool sgnd = isSigned;
985 if (CE1->getOpcode() == Instruction::ZExt) isSigned = false;
986 if (CE1->getOpcode() == Instruction::SExt) isSigned = true;
987 return evaluateICmpRelation(CE1Op0,
988 Constant::getNullValue(CE1Op0->getType()),
992 // If the dest type is a pointer type, and the RHS is a constantexpr cast
993 // from the same type as the src of the LHS, evaluate the inputs. This is
994 // important for things like "icmp eq (cast 4 to int*), (cast 5 to int*)",
995 // which happens a lot in compilers with tagged integers.
996 if (const ConstantExpr *CE2 = dyn_cast<ConstantExpr>(V2))
997 if (CE2->isCast() && isa<PointerType>(CE1->getType()) &&
998 CE1->getOperand(0)->getType() == CE2->getOperand(0)->getType() &&
999 CE1->getOperand(0)->getType()->isInteger()) {
1000 bool sgnd = isSigned;
1001 if (CE1->getOpcode() == Instruction::ZExt) isSigned = false;
1002 if (CE1->getOpcode() == Instruction::SExt) isSigned = true;
1003 return evaluateICmpRelation(CE1->getOperand(0), CE2->getOperand(0),
1008 case Instruction::GetElementPtr:
1009 // Ok, since this is a getelementptr, we know that the constant has a
1010 // pointer type. Check the various cases.
1011 if (isa<ConstantPointerNull>(V2)) {
1012 // If we are comparing a GEP to a null pointer, check to see if the base
1013 // of the GEP equals the null pointer.
1014 if (const GlobalValue *GV = dyn_cast<GlobalValue>(CE1Op0)) {
1015 if (GV->hasExternalWeakLinkage())
1016 // Weak linkage GVals could be zero or not. We're comparing that
1017 // to null pointer so its greater-or-equal
1018 return isSigned ? ICmpInst::ICMP_SGE : ICmpInst::ICMP_UGE;
1020 // If its not weak linkage, the GVal must have a non-zero address
1021 // so the result is greater-than
1022 return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT;
1023 } else if (isa<ConstantPointerNull>(CE1Op0)) {
1024 // If we are indexing from a null pointer, check to see if we have any
1025 // non-zero indices.
1026 for (unsigned i = 1, e = CE1->getNumOperands(); i != e; ++i)
1027 if (!CE1->getOperand(i)->isNullValue())
1028 // Offsetting from null, must not be equal.
1029 return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT;
1030 // Only zero indexes from null, must still be zero.
1031 return ICmpInst::ICMP_EQ;
1033 // Otherwise, we can't really say if the first operand is null or not.
1034 } else if (const GlobalValue *CPR2 = dyn_cast<GlobalValue>(V2)) {
1035 if (isa<ConstantPointerNull>(CE1Op0)) {
1036 if (CPR2->hasExternalWeakLinkage())
1037 // Weak linkage GVals could be zero or not. We're comparing it to
1038 // a null pointer, so its less-or-equal
1039 return isSigned ? ICmpInst::ICMP_SLE : ICmpInst::ICMP_ULE;
1041 // If its not weak linkage, the GVal must have a non-zero address
1042 // so the result is less-than
1043 return isSigned ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT;
1044 } else if (const GlobalValue *CPR1 = dyn_cast<GlobalValue>(CE1Op0)) {
1046 // If this is a getelementptr of the same global, then it must be
1047 // different. Because the types must match, the getelementptr could
1048 // only have at most one index, and because we fold getelementptr's
1049 // with a single zero index, it must be nonzero.
1050 assert(CE1->getNumOperands() == 2 &&
1051 !CE1->getOperand(1)->isNullValue() &&
1052 "Suprising getelementptr!");
1053 return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT;
1055 // If they are different globals, we don't know what the value is,
1056 // but they can't be equal.
1057 return ICmpInst::ICMP_NE;
1061 const ConstantExpr *CE2 = cast<ConstantExpr>(V2);
1062 const Constant *CE2Op0 = CE2->getOperand(0);
1064 // There are MANY other foldings that we could perform here. They will
1065 // probably be added on demand, as they seem needed.
1066 switch (CE2->getOpcode()) {
1068 case Instruction::GetElementPtr:
1069 // By far the most common case to handle is when the base pointers are
1070 // obviously to the same or different globals.
1071 if (isa<GlobalValue>(CE1Op0) && isa<GlobalValue>(CE2Op0)) {
1072 if (CE1Op0 != CE2Op0) // Don't know relative ordering, but not equal
1073 return ICmpInst::ICMP_NE;
1074 // Ok, we know that both getelementptr instructions are based on the
1075 // same global. From this, we can precisely determine the relative
1076 // ordering of the resultant pointers.
1079 // Compare all of the operands the GEP's have in common.
1080 gep_type_iterator GTI = gep_type_begin(CE1);
1081 for (;i != CE1->getNumOperands() && i != CE2->getNumOperands();
1083 switch (IdxCompare(CE1->getOperand(i), CE2->getOperand(i),
1084 GTI.getIndexedType())) {
1085 case -1: return isSigned ? ICmpInst::ICMP_SLT:ICmpInst::ICMP_ULT;
1086 case 1: return isSigned ? ICmpInst::ICMP_SGT:ICmpInst::ICMP_UGT;
1087 case -2: return ICmpInst::BAD_ICMP_PREDICATE;
1090 // Ok, we ran out of things they have in common. If any leftovers
1091 // are non-zero then we have a difference, otherwise we are equal.
1092 for (; i < CE1->getNumOperands(); ++i)
1093 if (!CE1->getOperand(i)->isNullValue()) {
1094 if (isa<ConstantInt>(CE1->getOperand(i)))
1095 return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT;
1097 return ICmpInst::BAD_ICMP_PREDICATE; // Might be equal.
1100 for (; i < CE2->getNumOperands(); ++i)
1101 if (!CE2->getOperand(i)->isNullValue()) {
1102 if (isa<ConstantInt>(CE2->getOperand(i)))
1103 return isSigned ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT;
1105 return ICmpInst::BAD_ICMP_PREDICATE; // Might be equal.
1107 return ICmpInst::ICMP_EQ;
1116 return ICmpInst::BAD_ICMP_PREDICATE;
1119 Constant *llvm::ConstantFoldCompareInstruction(unsigned short pred,
1121 const Constant *C2) {
1123 // Handle some degenerate cases first
1124 if (isa<UndefValue>(C1) || isa<UndefValue>(C2))
1125 return UndefValue::get(Type::Int1Ty);
1127 // No compile-time operations on this type yet.
1128 if (C1->getType() == Type::PPC_FP128Ty)
1131 // icmp eq/ne(null,GV) -> false/true
1132 if (C1->isNullValue()) {
1133 if (const GlobalValue *GV = dyn_cast<GlobalValue>(C2))
1134 // Don't try to evaluate aliases. External weak GV can be null.
1135 if (!isa<GlobalAlias>(GV) && !GV->hasExternalWeakLinkage()) {
1136 if (pred == ICmpInst::ICMP_EQ)
1137 return ConstantInt::getFalse();
1138 else if (pred == ICmpInst::ICMP_NE)
1139 return ConstantInt::getTrue();
1141 // icmp eq/ne(GV,null) -> false/true
1142 } else if (C2->isNullValue()) {
1143 if (const GlobalValue *GV = dyn_cast<GlobalValue>(C1))
1144 // Don't try to evaluate aliases. External weak GV can be null.
1145 if (!isa<GlobalAlias>(GV) && !GV->hasExternalWeakLinkage()) {
1146 if (pred == ICmpInst::ICMP_EQ)
1147 return ConstantInt::getFalse();
1148 else if (pred == ICmpInst::ICMP_NE)
1149 return ConstantInt::getTrue();
1153 if (isa<ConstantInt>(C1) && isa<ConstantInt>(C2)) {
1154 APInt V1 = cast<ConstantInt>(C1)->getValue();
1155 APInt V2 = cast<ConstantInt>(C2)->getValue();
1157 default: assert(0 && "Invalid ICmp Predicate"); return 0;
1158 case ICmpInst::ICMP_EQ: return ConstantInt::get(Type::Int1Ty, V1 == V2);
1159 case ICmpInst::ICMP_NE: return ConstantInt::get(Type::Int1Ty, V1 != V2);
1160 case ICmpInst::ICMP_SLT:return ConstantInt::get(Type::Int1Ty, V1.slt(V2));
1161 case ICmpInst::ICMP_SGT:return ConstantInt::get(Type::Int1Ty, V1.sgt(V2));
1162 case ICmpInst::ICMP_SLE:return ConstantInt::get(Type::Int1Ty, V1.sle(V2));
1163 case ICmpInst::ICMP_SGE:return ConstantInt::get(Type::Int1Ty, V1.sge(V2));
1164 case ICmpInst::ICMP_ULT:return ConstantInt::get(Type::Int1Ty, V1.ult(V2));
1165 case ICmpInst::ICMP_UGT:return ConstantInt::get(Type::Int1Ty, V1.ugt(V2));
1166 case ICmpInst::ICMP_ULE:return ConstantInt::get(Type::Int1Ty, V1.ule(V2));
1167 case ICmpInst::ICMP_UGE:return ConstantInt::get(Type::Int1Ty, V1.uge(V2));
1169 } else if (isa<ConstantFP>(C1) && isa<ConstantFP>(C2)) {
1170 APFloat C1V = cast<ConstantFP>(C1)->getValueAPF();
1171 APFloat C2V = cast<ConstantFP>(C2)->getValueAPF();
1172 APFloat::cmpResult R = C1V.compare(C2V);
1174 default: assert(0 && "Invalid FCmp Predicate"); return 0;
1175 case FCmpInst::FCMP_FALSE: return ConstantInt::getFalse();
1176 case FCmpInst::FCMP_TRUE: return ConstantInt::getTrue();
1177 case FCmpInst::FCMP_UNO:
1178 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpUnordered);
1179 case FCmpInst::FCMP_ORD:
1180 return ConstantInt::get(Type::Int1Ty, R!=APFloat::cmpUnordered);
1181 case FCmpInst::FCMP_UEQ:
1182 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpUnordered ||
1183 R==APFloat::cmpEqual);
1184 case FCmpInst::FCMP_OEQ:
1185 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpEqual);
1186 case FCmpInst::FCMP_UNE:
1187 return ConstantInt::get(Type::Int1Ty, R!=APFloat::cmpEqual);
1188 case FCmpInst::FCMP_ONE:
1189 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpLessThan ||
1190 R==APFloat::cmpGreaterThan);
1191 case FCmpInst::FCMP_ULT:
1192 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpUnordered ||
1193 R==APFloat::cmpLessThan);
1194 case FCmpInst::FCMP_OLT:
1195 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpLessThan);
1196 case FCmpInst::FCMP_UGT:
1197 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpUnordered ||
1198 R==APFloat::cmpGreaterThan);
1199 case FCmpInst::FCMP_OGT:
1200 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpGreaterThan);
1201 case FCmpInst::FCMP_ULE:
1202 return ConstantInt::get(Type::Int1Ty, R!=APFloat::cmpGreaterThan);
1203 case FCmpInst::FCMP_OLE:
1204 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpLessThan ||
1205 R==APFloat::cmpEqual);
1206 case FCmpInst::FCMP_UGE:
1207 return ConstantInt::get(Type::Int1Ty, R!=APFloat::cmpLessThan);
1208 case FCmpInst::FCMP_OGE:
1209 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpGreaterThan ||
1210 R==APFloat::cmpEqual);
1212 } else if (const ConstantVector *CP1 = dyn_cast<ConstantVector>(C1)) {
1213 if (const ConstantVector *CP2 = dyn_cast<ConstantVector>(C2)) {
1214 if (pred == FCmpInst::FCMP_OEQ || pred == FCmpInst::FCMP_UEQ) {
1215 for (unsigned i = 0, e = CP1->getNumOperands(); i != e; ++i) {
1216 Constant *C= ConstantExpr::getFCmp(FCmpInst::FCMP_OEQ,
1217 const_cast<Constant*>(CP1->getOperand(i)),
1218 const_cast<Constant*>(CP2->getOperand(i)));
1219 if (ConstantInt *CB = dyn_cast<ConstantInt>(C))
1222 // Otherwise, could not decide from any element pairs.
1224 } else if (pred == ICmpInst::ICMP_EQ) {
1225 for (unsigned i = 0, e = CP1->getNumOperands(); i != e; ++i) {
1226 Constant *C = ConstantExpr::getICmp(ICmpInst::ICMP_EQ,
1227 const_cast<Constant*>(CP1->getOperand(i)),
1228 const_cast<Constant*>(CP2->getOperand(i)));
1229 if (ConstantInt *CB = dyn_cast<ConstantInt>(C))
1232 // Otherwise, could not decide from any element pairs.
1238 if (C1->getType()->isFloatingPoint()) {
1239 switch (evaluateFCmpRelation(C1, C2)) {
1240 default: assert(0 && "Unknown relation!");
1241 case FCmpInst::FCMP_UNO:
1242 case FCmpInst::FCMP_ORD:
1243 case FCmpInst::FCMP_UEQ:
1244 case FCmpInst::FCMP_UNE:
1245 case FCmpInst::FCMP_ULT:
1246 case FCmpInst::FCMP_UGT:
1247 case FCmpInst::FCMP_ULE:
1248 case FCmpInst::FCMP_UGE:
1249 case FCmpInst::FCMP_TRUE:
1250 case FCmpInst::FCMP_FALSE:
1251 case FCmpInst::BAD_FCMP_PREDICATE:
1252 break; // Couldn't determine anything about these constants.
1253 case FCmpInst::FCMP_OEQ: // We know that C1 == C2
1254 return ConstantInt::get(Type::Int1Ty,
1255 pred == FCmpInst::FCMP_UEQ || pred == FCmpInst::FCMP_OEQ ||
1256 pred == FCmpInst::FCMP_ULE || pred == FCmpInst::FCMP_OLE ||
1257 pred == FCmpInst::FCMP_UGE || pred == FCmpInst::FCMP_OGE);
1258 case FCmpInst::FCMP_OLT: // We know that C1 < C2
1259 return ConstantInt::get(Type::Int1Ty,
1260 pred == FCmpInst::FCMP_UNE || pred == FCmpInst::FCMP_ONE ||
1261 pred == FCmpInst::FCMP_ULT || pred == FCmpInst::FCMP_OLT ||
1262 pred == FCmpInst::FCMP_ULE || pred == FCmpInst::FCMP_OLE);
1263 case FCmpInst::FCMP_OGT: // We know that C1 > C2
1264 return ConstantInt::get(Type::Int1Ty,
1265 pred == FCmpInst::FCMP_UNE || pred == FCmpInst::FCMP_ONE ||
1266 pred == FCmpInst::FCMP_UGT || pred == FCmpInst::FCMP_OGT ||
1267 pred == FCmpInst::FCMP_UGE || pred == FCmpInst::FCMP_OGE);
1268 case FCmpInst::FCMP_OLE: // We know that C1 <= C2
1269 // We can only partially decide this relation.
1270 if (pred == FCmpInst::FCMP_UGT || pred == FCmpInst::FCMP_OGT)
1271 return ConstantInt::getFalse();
1272 if (pred == FCmpInst::FCMP_ULT || pred == FCmpInst::FCMP_OLT)
1273 return ConstantInt::getTrue();
1275 case FCmpInst::FCMP_OGE: // We known that C1 >= C2
1276 // We can only partially decide this relation.
1277 if (pred == FCmpInst::FCMP_ULT || pred == FCmpInst::FCMP_OLT)
1278 return ConstantInt::getFalse();
1279 if (pred == FCmpInst::FCMP_UGT || pred == FCmpInst::FCMP_OGT)
1280 return ConstantInt::getTrue();
1282 case ICmpInst::ICMP_NE: // We know that C1 != C2
1283 // We can only partially decide this relation.
1284 if (pred == FCmpInst::FCMP_OEQ || pred == FCmpInst::FCMP_UEQ)
1285 return ConstantInt::getFalse();
1286 if (pred == FCmpInst::FCMP_ONE || pred == FCmpInst::FCMP_UNE)
1287 return ConstantInt::getTrue();
1291 // Evaluate the relation between the two constants, per the predicate.
1292 switch (evaluateICmpRelation(C1, C2, CmpInst::isSigned(pred))) {
1293 default: assert(0 && "Unknown relational!");
1294 case ICmpInst::BAD_ICMP_PREDICATE:
1295 break; // Couldn't determine anything about these constants.
1296 case ICmpInst::ICMP_EQ: // We know the constants are equal!
1297 // If we know the constants are equal, we can decide the result of this
1298 // computation precisely.
1299 return ConstantInt::get(Type::Int1Ty,
1300 pred == ICmpInst::ICMP_EQ ||
1301 pred == ICmpInst::ICMP_ULE ||
1302 pred == ICmpInst::ICMP_SLE ||
1303 pred == ICmpInst::ICMP_UGE ||
1304 pred == ICmpInst::ICMP_SGE);
1305 case ICmpInst::ICMP_ULT:
1306 // If we know that C1 < C2, we can decide the result of this computation
1308 return ConstantInt::get(Type::Int1Ty,
1309 pred == ICmpInst::ICMP_ULT ||
1310 pred == ICmpInst::ICMP_NE ||
1311 pred == ICmpInst::ICMP_ULE);
1312 case ICmpInst::ICMP_SLT:
1313 // If we know that C1 < C2, we can decide the result of this computation
1315 return ConstantInt::get(Type::Int1Ty,
1316 pred == ICmpInst::ICMP_SLT ||
1317 pred == ICmpInst::ICMP_NE ||
1318 pred == ICmpInst::ICMP_SLE);
1319 case ICmpInst::ICMP_UGT:
1320 // If we know that C1 > C2, we can decide the result of this computation
1322 return ConstantInt::get(Type::Int1Ty,
1323 pred == ICmpInst::ICMP_UGT ||
1324 pred == ICmpInst::ICMP_NE ||
1325 pred == ICmpInst::ICMP_UGE);
1326 case ICmpInst::ICMP_SGT:
1327 // If we know that C1 > C2, we can decide the result of this computation
1329 return ConstantInt::get(Type::Int1Ty,
1330 pred == ICmpInst::ICMP_SGT ||
1331 pred == ICmpInst::ICMP_NE ||
1332 pred == ICmpInst::ICMP_SGE);
1333 case ICmpInst::ICMP_ULE:
1334 // If we know that C1 <= C2, we can only partially decide this relation.
1335 if (pred == ICmpInst::ICMP_UGT) return ConstantInt::getFalse();
1336 if (pred == ICmpInst::ICMP_ULT) return ConstantInt::getTrue();
1338 case ICmpInst::ICMP_SLE:
1339 // If we know that C1 <= C2, we can only partially decide this relation.
1340 if (pred == ICmpInst::ICMP_SGT) return ConstantInt::getFalse();
1341 if (pred == ICmpInst::ICMP_SLT) return ConstantInt::getTrue();
1344 case ICmpInst::ICMP_UGE:
1345 // If we know that C1 >= C2, we can only partially decide this relation.
1346 if (pred == ICmpInst::ICMP_ULT) return ConstantInt::getFalse();
1347 if (pred == ICmpInst::ICMP_UGT) return ConstantInt::getTrue();
1349 case ICmpInst::ICMP_SGE:
1350 // If we know that C1 >= C2, we can only partially decide this relation.
1351 if (pred == ICmpInst::ICMP_SLT) return ConstantInt::getFalse();
1352 if (pred == ICmpInst::ICMP_SGT) return ConstantInt::getTrue();
1355 case ICmpInst::ICMP_NE:
1356 // If we know that C1 != C2, we can only partially decide this relation.
1357 if (pred == ICmpInst::ICMP_EQ) return ConstantInt::getFalse();
1358 if (pred == ICmpInst::ICMP_NE) return ConstantInt::getTrue();
1362 if (!isa<ConstantExpr>(C1) && isa<ConstantExpr>(C2)) {
1363 // If C2 is a constant expr and C1 isn't, flop them around and fold the
1364 // other way if possible.
1366 case ICmpInst::ICMP_EQ:
1367 case ICmpInst::ICMP_NE:
1368 // No change of predicate required.
1369 return ConstantFoldCompareInstruction(pred, C2, C1);
1371 case ICmpInst::ICMP_ULT:
1372 case ICmpInst::ICMP_SLT:
1373 case ICmpInst::ICMP_UGT:
1374 case ICmpInst::ICMP_SGT:
1375 case ICmpInst::ICMP_ULE:
1376 case ICmpInst::ICMP_SLE:
1377 case ICmpInst::ICMP_UGE:
1378 case ICmpInst::ICMP_SGE:
1379 // Change the predicate as necessary to swap the operands.
1380 pred = ICmpInst::getSwappedPredicate((ICmpInst::Predicate)pred);
1381 return ConstantFoldCompareInstruction(pred, C2, C1);
1383 default: // These predicates cannot be flopped around.
1391 Constant *llvm::ConstantFoldGetElementPtr(const Constant *C,
1392 Constant* const *Idxs,
1395 (NumIdx == 1 && Idxs[0]->isNullValue()))
1396 return const_cast<Constant*>(C);
1398 if (isa<UndefValue>(C)) {
1399 const PointerType *Ptr = cast<PointerType>(C->getType());
1400 const Type *Ty = GetElementPtrInst::getIndexedType(Ptr,
1402 (Value **)Idxs+NumIdx,
1404 assert(Ty != 0 && "Invalid indices for GEP!");
1405 return UndefValue::get(PointerType::get(Ty, Ptr->getAddressSpace()));
1408 Constant *Idx0 = Idxs[0];
1409 if (C->isNullValue()) {
1411 for (unsigned i = 0, e = NumIdx; i != e; ++i)
1412 if (!Idxs[i]->isNullValue()) {
1417 const PointerType *Ptr = cast<PointerType>(C->getType());
1418 const Type *Ty = GetElementPtrInst::getIndexedType(Ptr,
1420 (Value**)Idxs+NumIdx,
1422 assert(Ty != 0 && "Invalid indices for GEP!");
1424 ConstantPointerNull::get(PointerType::get(Ty,Ptr->getAddressSpace()));
1428 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(const_cast<Constant*>(C))) {
1429 // Combine Indices - If the source pointer to this getelementptr instruction
1430 // is a getelementptr instruction, combine the indices of the two
1431 // getelementptr instructions into a single instruction.
1433 if (CE->getOpcode() == Instruction::GetElementPtr) {
1434 const Type *LastTy = 0;
1435 for (gep_type_iterator I = gep_type_begin(CE), E = gep_type_end(CE);
1439 if ((LastTy && isa<ArrayType>(LastTy)) || Idx0->isNullValue()) {
1440 SmallVector<Value*, 16> NewIndices;
1441 NewIndices.reserve(NumIdx + CE->getNumOperands());
1442 for (unsigned i = 1, e = CE->getNumOperands()-1; i != e; ++i)
1443 NewIndices.push_back(CE->getOperand(i));
1445 // Add the last index of the source with the first index of the new GEP.
1446 // Make sure to handle the case when they are actually different types.
1447 Constant *Combined = CE->getOperand(CE->getNumOperands()-1);
1448 // Otherwise it must be an array.
1449 if (!Idx0->isNullValue()) {
1450 const Type *IdxTy = Combined->getType();
1451 if (IdxTy != Idx0->getType()) {
1452 Constant *C1 = ConstantExpr::getSExtOrBitCast(Idx0, Type::Int64Ty);
1453 Constant *C2 = ConstantExpr::getSExtOrBitCast(Combined,
1455 Combined = ConstantExpr::get(Instruction::Add, C1, C2);
1458 ConstantExpr::get(Instruction::Add, Idx0, Combined);
1462 NewIndices.push_back(Combined);
1463 NewIndices.insert(NewIndices.end(), Idxs+1, Idxs+NumIdx);
1464 return ConstantExpr::getGetElementPtr(CE->getOperand(0), &NewIndices[0],
1469 // Implement folding of:
1470 // int* getelementptr ([2 x int]* cast ([3 x int]* %X to [2 x int]*),
1472 // To: int* getelementptr ([3 x int]* %X, long 0, long 0)
1474 if (CE->isCast() && NumIdx > 1 && Idx0->isNullValue()) {
1475 if (const PointerType *SPT =
1476 dyn_cast<PointerType>(CE->getOperand(0)->getType()))
1477 if (const ArrayType *SAT = dyn_cast<ArrayType>(SPT->getElementType()))
1478 if (const ArrayType *CAT =
1479 dyn_cast<ArrayType>(cast<PointerType>(C->getType())->getElementType()))
1480 if (CAT->getElementType() == SAT->getElementType())
1481 return ConstantExpr::getGetElementPtr(
1482 (Constant*)CE->getOperand(0), Idxs, NumIdx);
1485 // Fold: getelementptr (i8* inttoptr (i64 1 to i8*), i32 -1)
1486 // Into: inttoptr (i64 0 to i8*)
1487 // This happens with pointers to member functions in C++.
1488 if (CE->getOpcode() == Instruction::IntToPtr && NumIdx == 1 &&
1489 isa<ConstantInt>(CE->getOperand(0)) && isa<ConstantInt>(Idxs[0]) &&
1490 cast<PointerType>(CE->getType())->getElementType() == Type::Int8Ty) {
1491 Constant *Base = CE->getOperand(0);
1492 Constant *Offset = Idxs[0];
1494 // Convert the smaller integer to the larger type.
1495 if (Offset->getType()->getPrimitiveSizeInBits() <
1496 Base->getType()->getPrimitiveSizeInBits())
1497 Offset = ConstantExpr::getSExt(Offset, Base->getType());
1498 else if (Base->getType()->getPrimitiveSizeInBits() <
1499 Offset->getType()->getPrimitiveSizeInBits())
1500 Base = ConstantExpr::getZExt(Base, Base->getType());
1502 Base = ConstantExpr::getAdd(Base, Offset);
1503 return ConstantExpr::getIntToPtr(Base, CE->getType());