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 SmallVector<Value*, 8> IdxList;
101 IdxList.push_back(Constant::getNullValue(Type::Int32Ty));
102 const Type *ElTy = PTy->getElementType();
103 while (ElTy != DPTy->getElementType()) {
104 if (const StructType *STy = dyn_cast<StructType>(ElTy)) {
105 if (STy->getNumElements() == 0) break;
106 ElTy = STy->getElementType(0);
107 IdxList.push_back(Constant::getNullValue(Type::Int32Ty));
108 } else if (const SequentialType *STy = dyn_cast<SequentialType>(ElTy)) {
109 if (isa<PointerType>(ElTy)) break; // Can't index into pointers!
110 ElTy = STy->getElementType();
111 IdxList.push_back(IdxList[0]);
117 if (ElTy == DPTy->getElementType())
118 return ConstantExpr::getGetElementPtr(V, &IdxList[0], IdxList.size());
121 // Handle casts from one vector constant to another. We know that the src
122 // and dest type have the same size (otherwise its an illegal cast).
123 if (const VectorType *DestPTy = dyn_cast<VectorType>(DestTy)) {
124 if (const VectorType *SrcTy = dyn_cast<VectorType>(V->getType())) {
125 assert(DestPTy->getBitWidth() == SrcTy->getBitWidth() &&
126 "Not cast between same sized vectors!");
127 // First, check for null. Undef is already handled.
128 if (isa<ConstantAggregateZero>(V))
129 return Constant::getNullValue(DestTy);
131 if (ConstantVector *CV = dyn_cast<ConstantVector>(V))
132 return BitCastConstantVector(CV, DestPTy);
136 // Finally, implement bitcast folding now. The code below doesn't handle
138 if (isa<ConstantPointerNull>(V)) // ptr->ptr cast.
139 return ConstantPointerNull::get(cast<PointerType>(DestTy));
141 // Handle integral constant input.
142 if (const ConstantInt *CI = dyn_cast<ConstantInt>(V)) {
143 if (DestTy->isInteger())
144 // Integral -> Integral. This is a no-op because the bit widths must
145 // be the same. Consequently, we just fold to V.
148 if (DestTy->isFloatingPoint()) {
149 assert((DestTy == Type::DoubleTy || DestTy == Type::FloatTy) &&
151 return ConstantFP::get(DestTy, APFloat(CI->getValue()));
153 // Otherwise, can't fold this (vector?)
157 // Handle ConstantFP input.
158 if (const ConstantFP *FP = dyn_cast<ConstantFP>(V)) {
160 if (DestTy == Type::Int32Ty) {
161 return ConstantInt::get(FP->getValueAPF().convertToAPInt());
163 assert(DestTy == Type::Int64Ty && "only support f32/f64 for now!");
164 return ConstantInt::get(FP->getValueAPF().convertToAPInt());
171 Constant *llvm::ConstantFoldCastInstruction(unsigned opc, const Constant *V,
172 const Type *DestTy) {
173 if (isa<UndefValue>(V)) {
174 // zext(undef) = 0, because the top bits will be zero.
175 // sext(undef) = 0, because the top bits will all be the same.
176 // [us]itofp(undef) = 0, because the result value is bounded.
177 if (opc == Instruction::ZExt || opc == Instruction::SExt ||
178 opc == Instruction::UIToFP || opc == Instruction::SIToFP)
179 return Constant::getNullValue(DestTy);
180 return UndefValue::get(DestTy);
182 // No compile-time operations on this type yet.
183 if (V->getType() == Type::PPC_FP128Ty || DestTy == Type::PPC_FP128Ty)
186 // If the cast operand is a constant expression, there's a few things we can
187 // do to try to simplify it.
188 if (const ConstantExpr *CE = dyn_cast<ConstantExpr>(V)) {
190 // Try hard to fold cast of cast because they are often eliminable.
191 if (unsigned newOpc = foldConstantCastPair(opc, CE, DestTy))
192 return ConstantExpr::getCast(newOpc, CE->getOperand(0), DestTy);
193 } else if (CE->getOpcode() == Instruction::GetElementPtr) {
194 // If all of the indexes in the GEP are null values, there is no pointer
195 // adjustment going on. We might as well cast the source pointer.
196 bool isAllNull = true;
197 for (unsigned i = 1, e = CE->getNumOperands(); i != e; ++i)
198 if (!CE->getOperand(i)->isNullValue()) {
203 // This is casting one pointer type to another, always BitCast
204 return ConstantExpr::getPointerCast(CE->getOperand(0), DestTy);
208 // We actually have to do a cast now. Perform the cast according to the
211 case Instruction::FPTrunc:
212 case Instruction::FPExt:
213 if (const ConstantFP *FPC = dyn_cast<ConstantFP>(V)) {
214 APFloat Val = FPC->getValueAPF();
215 Val.convert(DestTy == Type::FloatTy ? APFloat::IEEEsingle :
216 DestTy == Type::DoubleTy ? APFloat::IEEEdouble :
217 DestTy == Type::X86_FP80Ty ? APFloat::x87DoubleExtended :
218 DestTy == Type::FP128Ty ? APFloat::IEEEquad :
220 APFloat::rmNearestTiesToEven);
221 return ConstantFP::get(DestTy, Val);
223 return 0; // Can't fold.
224 case Instruction::FPToUI:
225 case Instruction::FPToSI:
226 if (const ConstantFP *FPC = dyn_cast<ConstantFP>(V)) {
227 const APFloat &V = FPC->getValueAPF();
229 uint32_t DestBitWidth = cast<IntegerType>(DestTy)->getBitWidth();
230 (void) V.convertToInteger(x, DestBitWidth, opc==Instruction::FPToSI,
231 APFloat::rmTowardZero);
232 APInt Val(DestBitWidth, 2, x);
233 return ConstantInt::get(Val);
235 if (const ConstantVector *CV = dyn_cast<ConstantVector>(V)) {
236 std::vector<Constant*> res;
237 const VectorType *DestVecTy = cast<VectorType>(DestTy);
238 const Type *DstEltTy = DestVecTy->getElementType();
239 for (unsigned i = 0, e = CV->getType()->getNumElements(); i != e; ++i)
240 res.push_back(ConstantFoldCastInstruction(opc, V->getOperand(i),
242 return ConstantVector::get(DestVecTy, res);
244 return 0; // Can't fold.
245 case Instruction::IntToPtr: //always treated as unsigned
246 if (V->isNullValue()) // Is it an integral null value?
247 return ConstantPointerNull::get(cast<PointerType>(DestTy));
248 return 0; // Other pointer types cannot be casted
249 case Instruction::PtrToInt: // always treated as unsigned
250 if (V->isNullValue()) // is it a null pointer value?
251 return ConstantInt::get(DestTy, 0);
252 return 0; // Other pointer types cannot be casted
253 case Instruction::UIToFP:
254 case Instruction::SIToFP:
255 if (const ConstantInt *CI = dyn_cast<ConstantInt>(V)) {
256 APInt api = CI->getValue();
257 const uint64_t zero[] = {0, 0};
258 APFloat apf = APFloat(APInt(DestTy->getPrimitiveSizeInBits(),
260 (void)apf.convertFromAPInt(api,
261 opc==Instruction::SIToFP,
262 APFloat::rmNearestTiesToEven);
263 return ConstantFP::get(DestTy, apf);
265 if (const ConstantVector *CV = dyn_cast<ConstantVector>(V)) {
266 std::vector<Constant*> res;
267 const VectorType *DestVecTy = cast<VectorType>(DestTy);
268 const Type *DstEltTy = DestVecTy->getElementType();
269 for (unsigned i = 0, e = CV->getType()->getNumElements(); i != e; ++i)
270 res.push_back(ConstantFoldCastInstruction(opc, V->getOperand(i),
272 return ConstantVector::get(DestVecTy, res);
275 case Instruction::ZExt:
276 if (const ConstantInt *CI = dyn_cast<ConstantInt>(V)) {
277 uint32_t BitWidth = cast<IntegerType>(DestTy)->getBitWidth();
278 APInt Result(CI->getValue());
279 Result.zext(BitWidth);
280 return ConstantInt::get(Result);
283 case Instruction::SExt:
284 if (const ConstantInt *CI = dyn_cast<ConstantInt>(V)) {
285 uint32_t BitWidth = cast<IntegerType>(DestTy)->getBitWidth();
286 APInt Result(CI->getValue());
287 Result.sext(BitWidth);
288 return ConstantInt::get(Result);
291 case Instruction::Trunc:
292 if (const ConstantInt *CI = dyn_cast<ConstantInt>(V)) {
293 uint32_t BitWidth = cast<IntegerType>(DestTy)->getBitWidth();
294 APInt Result(CI->getValue());
295 Result.trunc(BitWidth);
296 return ConstantInt::get(Result);
299 case Instruction::BitCast:
300 return FoldBitCast(const_cast<Constant*>(V), DestTy);
302 assert(!"Invalid CE CastInst opcode");
306 assert(0 && "Failed to cast constant expression");
310 Constant *llvm::ConstantFoldSelectInstruction(const Constant *Cond,
312 const Constant *V2) {
313 if (const ConstantInt *CB = dyn_cast<ConstantInt>(Cond))
314 return const_cast<Constant*>(CB->getZExtValue() ? V1 : V2);
316 if (isa<UndefValue>(V1)) return const_cast<Constant*>(V2);
317 if (isa<UndefValue>(V2)) return const_cast<Constant*>(V1);
318 if (isa<UndefValue>(Cond)) return const_cast<Constant*>(V1);
319 if (V1 == V2) return const_cast<Constant*>(V1);
323 Constant *llvm::ConstantFoldExtractElementInstruction(const Constant *Val,
324 const Constant *Idx) {
325 if (isa<UndefValue>(Val)) // ee(undef, x) -> undef
326 return UndefValue::get(cast<VectorType>(Val->getType())->getElementType());
327 if (Val->isNullValue()) // ee(zero, x) -> zero
328 return Constant::getNullValue(
329 cast<VectorType>(Val->getType())->getElementType());
331 if (const ConstantVector *CVal = dyn_cast<ConstantVector>(Val)) {
332 if (const ConstantInt *CIdx = dyn_cast<ConstantInt>(Idx)) {
333 return const_cast<Constant*>(CVal->getOperand(CIdx->getZExtValue()));
334 } else if (isa<UndefValue>(Idx)) {
335 // ee({w,x,y,z}, undef) -> w (an arbitrary value).
336 return const_cast<Constant*>(CVal->getOperand(0));
342 Constant *llvm::ConstantFoldInsertElementInstruction(const Constant *Val,
344 const Constant *Idx) {
345 const ConstantInt *CIdx = dyn_cast<ConstantInt>(Idx);
347 APInt idxVal = CIdx->getValue();
348 if (isa<UndefValue>(Val)) {
349 // Insertion of scalar constant into vector undef
350 // Optimize away insertion of undef
351 if (isa<UndefValue>(Elt))
352 return const_cast<Constant*>(Val);
353 // Otherwise break the aggregate undef into multiple undefs and do
356 cast<VectorType>(Val->getType())->getNumElements();
357 std::vector<Constant*> Ops;
359 for (unsigned i = 0; i < numOps; ++i) {
361 (idxVal == i) ? Elt : UndefValue::get(Elt->getType());
362 Ops.push_back(const_cast<Constant*>(Op));
364 return ConstantVector::get(Ops);
366 if (isa<ConstantAggregateZero>(Val)) {
367 // Insertion of scalar constant into vector aggregate zero
368 // Optimize away insertion of zero
369 if (Elt->isNullValue())
370 return const_cast<Constant*>(Val);
371 // Otherwise break the aggregate zero into multiple zeros and do
374 cast<VectorType>(Val->getType())->getNumElements();
375 std::vector<Constant*> Ops;
377 for (unsigned i = 0; i < numOps; ++i) {
379 (idxVal == i) ? Elt : Constant::getNullValue(Elt->getType());
380 Ops.push_back(const_cast<Constant*>(Op));
382 return ConstantVector::get(Ops);
384 if (const ConstantVector *CVal = dyn_cast<ConstantVector>(Val)) {
385 // Insertion of scalar constant into vector constant
386 std::vector<Constant*> Ops;
387 Ops.reserve(CVal->getNumOperands());
388 for (unsigned i = 0; i < CVal->getNumOperands(); ++i) {
390 (idxVal == i) ? Elt : cast<Constant>(CVal->getOperand(i));
391 Ops.push_back(const_cast<Constant*>(Op));
393 return ConstantVector::get(Ops);
398 /// GetVectorElement - If C is a ConstantVector, ConstantAggregateZero or Undef
399 /// return the specified element value. Otherwise return null.
400 static Constant *GetVectorElement(const Constant *C, unsigned EltNo) {
401 if (const ConstantVector *CV = dyn_cast<ConstantVector>(C))
402 return const_cast<Constant*>(CV->getOperand(EltNo));
404 const Type *EltTy = cast<VectorType>(C->getType())->getElementType();
405 if (isa<ConstantAggregateZero>(C))
406 return Constant::getNullValue(EltTy);
407 if (isa<UndefValue>(C))
408 return UndefValue::get(EltTy);
412 Constant *llvm::ConstantFoldShuffleVectorInstruction(const Constant *V1,
414 const Constant *Mask) {
415 // Undefined shuffle mask -> undefined value.
416 if (isa<UndefValue>(Mask)) return UndefValue::get(V1->getType());
418 unsigned NumElts = cast<VectorType>(V1->getType())->getNumElements();
419 const Type *EltTy = cast<VectorType>(V1->getType())->getElementType();
421 // Loop over the shuffle mask, evaluating each element.
422 SmallVector<Constant*, 32> Result;
423 for (unsigned i = 0; i != NumElts; ++i) {
424 Constant *InElt = GetVectorElement(Mask, i);
425 if (InElt == 0) return 0;
427 if (isa<UndefValue>(InElt))
428 InElt = UndefValue::get(EltTy);
429 else if (ConstantInt *CI = dyn_cast<ConstantInt>(InElt)) {
430 unsigned Elt = CI->getZExtValue();
431 if (Elt >= NumElts*2)
432 InElt = UndefValue::get(EltTy);
433 else if (Elt >= NumElts)
434 InElt = GetVectorElement(V2, Elt-NumElts);
436 InElt = GetVectorElement(V1, Elt);
437 if (InElt == 0) return 0;
442 Result.push_back(InElt);
445 return ConstantVector::get(&Result[0], Result.size());
448 /// EvalVectorOp - Given two vector constants and a function pointer, apply the
449 /// function pointer to each element pair, producing a new ConstantVector
450 /// constant. Either or both of V1 and V2 may be NULL, meaning a
451 /// ConstantAggregateZero operand.
452 static Constant *EvalVectorOp(const ConstantVector *V1,
453 const ConstantVector *V2,
454 const VectorType *VTy,
455 Constant *(*FP)(Constant*, Constant*)) {
456 std::vector<Constant*> Res;
457 const Type *EltTy = VTy->getElementType();
458 for (unsigned i = 0, e = VTy->getNumElements(); i != e; ++i) {
459 const Constant *C1 = V1 ? V1->getOperand(i) : Constant::getNullValue(EltTy);
460 const Constant *C2 = V2 ? V2->getOperand(i) : Constant::getNullValue(EltTy);
461 Res.push_back(FP(const_cast<Constant*>(C1),
462 const_cast<Constant*>(C2)));
464 return ConstantVector::get(Res);
467 Constant *llvm::ConstantFoldBinaryInstruction(unsigned Opcode,
469 const Constant *C2) {
470 // No compile-time operations on this type yet.
471 if (C1->getType() == Type::PPC_FP128Ty)
474 // Handle UndefValue up front
475 if (isa<UndefValue>(C1) || isa<UndefValue>(C2)) {
477 case Instruction::Xor:
478 if (isa<UndefValue>(C1) && isa<UndefValue>(C2))
479 // Handle undef ^ undef -> 0 special case. This is a common
481 return Constant::getNullValue(C1->getType());
483 case Instruction::Add:
484 case Instruction::Sub:
485 return UndefValue::get(C1->getType());
486 case Instruction::Mul:
487 case Instruction::And:
488 return Constant::getNullValue(C1->getType());
489 case Instruction::UDiv:
490 case Instruction::SDiv:
491 case Instruction::FDiv:
492 case Instruction::URem:
493 case Instruction::SRem:
494 case Instruction::FRem:
495 if (!isa<UndefValue>(C2)) // undef / X -> 0
496 return Constant::getNullValue(C1->getType());
497 return const_cast<Constant*>(C2); // X / undef -> undef
498 case Instruction::Or: // X | undef -> -1
499 if (const VectorType *PTy = dyn_cast<VectorType>(C1->getType()))
500 return ConstantVector::getAllOnesValue(PTy);
501 return ConstantInt::getAllOnesValue(C1->getType());
502 case Instruction::LShr:
503 if (isa<UndefValue>(C2) && isa<UndefValue>(C1))
504 return const_cast<Constant*>(C1); // undef lshr undef -> undef
505 return Constant::getNullValue(C1->getType()); // X lshr undef -> 0
507 case Instruction::AShr:
508 if (!isa<UndefValue>(C2))
509 return const_cast<Constant*>(C1); // undef ashr X --> undef
510 else if (isa<UndefValue>(C1))
511 return const_cast<Constant*>(C1); // undef ashr undef -> undef
513 return const_cast<Constant*>(C1); // X ashr undef --> X
514 case Instruction::Shl:
515 // undef << X -> 0 or X << undef -> 0
516 return Constant::getNullValue(C1->getType());
520 if (const ConstantExpr *CE1 = dyn_cast<ConstantExpr>(C1)) {
521 if (isa<ConstantExpr>(C2)) {
522 // There are many possible foldings we could do here. We should probably
523 // at least fold add of a pointer with an integer into the appropriate
524 // getelementptr. This will improve alias analysis a bit.
526 // Just implement a couple of simple identities.
528 case Instruction::Add:
529 if (C2->isNullValue()) return const_cast<Constant*>(C1); // X + 0 == X
531 case Instruction::Sub:
532 if (C2->isNullValue()) return const_cast<Constant*>(C1); // X - 0 == X
534 case Instruction::Mul:
535 if (C2->isNullValue()) return const_cast<Constant*>(C2); // X * 0 == 0
536 if (const ConstantInt *CI = dyn_cast<ConstantInt>(C2))
537 if (CI->equalsInt(1))
538 return const_cast<Constant*>(C1); // X * 1 == X
540 case Instruction::UDiv:
541 case Instruction::SDiv:
542 if (const ConstantInt *CI = dyn_cast<ConstantInt>(C2))
543 if (CI->equalsInt(1))
544 return const_cast<Constant*>(C1); // X / 1 == X
546 case Instruction::URem:
547 case Instruction::SRem:
548 if (const ConstantInt *CI = dyn_cast<ConstantInt>(C2))
549 if (CI->equalsInt(1))
550 return Constant::getNullValue(CI->getType()); // X % 1 == 0
552 case Instruction::And:
553 if (const ConstantInt *CI = dyn_cast<ConstantInt>(C2)) {
554 if (CI->isZero()) return const_cast<Constant*>(C2); // X & 0 == 0
555 if (CI->isAllOnesValue())
556 return const_cast<Constant*>(C1); // X & -1 == X
558 // (zext i32 to i64) & 4294967295 -> (zext i32 to i64)
559 if (CE1->getOpcode() == Instruction::ZExt) {
560 APInt PossiblySetBits
561 = cast<IntegerType>(CE1->getOperand(0)->getType())->getMask();
562 PossiblySetBits.zext(C1->getType()->getPrimitiveSizeInBits());
563 if ((PossiblySetBits & CI->getValue()) == PossiblySetBits)
564 return const_cast<Constant*>(C1);
567 if (CE1->isCast() && isa<GlobalValue>(CE1->getOperand(0))) {
568 GlobalValue *CPR = cast<GlobalValue>(CE1->getOperand(0));
570 // Functions are at least 4-byte aligned. If and'ing the address of a
571 // function with a constant < 4, fold it to zero.
572 if (const ConstantInt *CI = dyn_cast<ConstantInt>(C2))
573 if (CI->getValue().ult(APInt(CI->getType()->getBitWidth(),4)) &&
575 return Constant::getNullValue(CI->getType());
578 case Instruction::Or:
579 if (C2->isNullValue()) return const_cast<Constant*>(C1); // X | 0 == X
580 if (const ConstantInt *CI = dyn_cast<ConstantInt>(C2))
581 if (CI->isAllOnesValue())
582 return const_cast<Constant*>(C2); // X | -1 == -1
584 case Instruction::Xor:
585 if (C2->isNullValue()) return const_cast<Constant*>(C1); // X ^ 0 == X
587 case Instruction::AShr:
588 // ashr (zext C to Ty), C2 -> lshr (zext C, CSA), C2
589 if (CE1->getOpcode() == Instruction::ZExt) // Top bits known zero.
590 return ConstantExpr::getLShr(const_cast<Constant*>(C1),
591 const_cast<Constant*>(C2));
595 } else if (isa<ConstantExpr>(C2)) {
596 // If C2 is a constant expr and C1 isn't, flop them around and fold the
597 // other way if possible.
599 case Instruction::Add:
600 case Instruction::Mul:
601 case Instruction::And:
602 case Instruction::Or:
603 case Instruction::Xor:
604 // No change of opcode required.
605 return ConstantFoldBinaryInstruction(Opcode, C2, C1);
607 case Instruction::Shl:
608 case Instruction::LShr:
609 case Instruction::AShr:
610 case Instruction::Sub:
611 case Instruction::SDiv:
612 case Instruction::UDiv:
613 case Instruction::FDiv:
614 case Instruction::URem:
615 case Instruction::SRem:
616 case Instruction::FRem:
617 default: // These instructions cannot be flopped around.
622 // At this point we know neither constant is an UndefValue nor a ConstantExpr
623 // so look at directly computing the value.
624 if (const ConstantInt *CI1 = dyn_cast<ConstantInt>(C1)) {
625 if (const ConstantInt *CI2 = dyn_cast<ConstantInt>(C2)) {
626 using namespace APIntOps;
627 APInt C1V = CI1->getValue();
628 APInt C2V = CI2->getValue();
632 case Instruction::Add:
633 return ConstantInt::get(C1V + C2V);
634 case Instruction::Sub:
635 return ConstantInt::get(C1V - C2V);
636 case Instruction::Mul:
637 return ConstantInt::get(C1V * C2V);
638 case Instruction::UDiv:
639 if (CI2->isNullValue())
640 return 0; // X / 0 -> can't fold
641 return ConstantInt::get(C1V.udiv(C2V));
642 case Instruction::SDiv:
643 if (CI2->isNullValue())
644 return 0; // X / 0 -> can't fold
645 if (C2V.isAllOnesValue() && C1V.isMinSignedValue())
646 return 0; // MIN_INT / -1 -> overflow
647 return ConstantInt::get(C1V.sdiv(C2V));
648 case Instruction::URem:
649 if (C2->isNullValue())
650 return 0; // X / 0 -> can't fold
651 return ConstantInt::get(C1V.urem(C2V));
652 case Instruction::SRem:
653 if (CI2->isNullValue())
654 return 0; // X % 0 -> can't fold
655 if (C2V.isAllOnesValue() && C1V.isMinSignedValue())
656 return 0; // MIN_INT % -1 -> overflow
657 return ConstantInt::get(C1V.srem(C2V));
658 case Instruction::And:
659 return ConstantInt::get(C1V & C2V);
660 case Instruction::Or:
661 return ConstantInt::get(C1V | C2V);
662 case Instruction::Xor:
663 return ConstantInt::get(C1V ^ C2V);
664 case Instruction::Shl:
665 if (uint32_t shiftAmt = C2V.getZExtValue()) {
666 if (shiftAmt < C1V.getBitWidth())
667 return ConstantInt::get(C1V.shl(shiftAmt));
669 return UndefValue::get(C1->getType()); // too big shift is undef
671 return const_cast<ConstantInt*>(CI1); // Zero shift is identity
672 case Instruction::LShr:
673 if (uint32_t shiftAmt = C2V.getZExtValue()) {
674 if (shiftAmt < C1V.getBitWidth())
675 return ConstantInt::get(C1V.lshr(shiftAmt));
677 return UndefValue::get(C1->getType()); // too big shift is undef
679 return const_cast<ConstantInt*>(CI1); // Zero shift is identity
680 case Instruction::AShr:
681 if (uint32_t shiftAmt = C2V.getZExtValue()) {
682 if (shiftAmt < C1V.getBitWidth())
683 return ConstantInt::get(C1V.ashr(shiftAmt));
685 return UndefValue::get(C1->getType()); // too big shift is undef
687 return const_cast<ConstantInt*>(CI1); // Zero shift is identity
690 } else if (const ConstantFP *CFP1 = dyn_cast<ConstantFP>(C1)) {
691 if (const ConstantFP *CFP2 = dyn_cast<ConstantFP>(C2)) {
692 APFloat C1V = CFP1->getValueAPF();
693 APFloat C2V = CFP2->getValueAPF();
694 APFloat C3V = C1V; // copy for modification
695 bool isDouble = CFP1->getType()==Type::DoubleTy;
699 case Instruction::Add:
700 (void)C3V.add(C2V, APFloat::rmNearestTiesToEven);
701 return ConstantFP::get(CFP1->getType(), C3V);
702 case Instruction::Sub:
703 (void)C3V.subtract(C2V, APFloat::rmNearestTiesToEven);
704 return ConstantFP::get(CFP1->getType(), C3V);
705 case Instruction::Mul:
706 (void)C3V.multiply(C2V, APFloat::rmNearestTiesToEven);
707 return ConstantFP::get(CFP1->getType(), C3V);
708 case Instruction::FDiv:
709 (void)C3V.divide(C2V, APFloat::rmNearestTiesToEven);
710 return ConstantFP::get(CFP1->getType(), C3V);
711 case Instruction::FRem:
713 // IEEE 754, Section 7.1, #5
714 return ConstantFP::get(CFP1->getType(), isDouble ?
715 APFloat(std::numeric_limits<double>::quiet_NaN()) :
716 APFloat(std::numeric_limits<float>::quiet_NaN()));
717 (void)C3V.mod(C2V, APFloat::rmNearestTiesToEven);
718 return ConstantFP::get(CFP1->getType(), C3V);
721 } else if (const VectorType *VTy = dyn_cast<VectorType>(C1->getType())) {
722 const ConstantVector *CP1 = dyn_cast<ConstantVector>(C1);
723 const ConstantVector *CP2 = dyn_cast<ConstantVector>(C2);
724 if ((CP1 != NULL || isa<ConstantAggregateZero>(C1)) &&
725 (CP2 != NULL || isa<ConstantAggregateZero>(C2))) {
729 case Instruction::Add:
730 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getAdd);
731 case Instruction::Sub:
732 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getSub);
733 case Instruction::Mul:
734 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getMul);
735 case Instruction::UDiv:
736 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getUDiv);
737 case Instruction::SDiv:
738 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getSDiv);
739 case Instruction::FDiv:
740 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getFDiv);
741 case Instruction::URem:
742 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getURem);
743 case Instruction::SRem:
744 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getSRem);
745 case Instruction::FRem:
746 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getFRem);
747 case Instruction::And:
748 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getAnd);
749 case Instruction::Or:
750 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getOr);
751 case Instruction::Xor:
752 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getXor);
757 // We don't know how to fold this
761 /// isZeroSizedType - This type is zero sized if its an array or structure of
762 /// zero sized types. The only leaf zero sized type is an empty structure.
763 static bool isMaybeZeroSizedType(const Type *Ty) {
764 if (isa<OpaqueType>(Ty)) return true; // Can't say.
765 if (const StructType *STy = dyn_cast<StructType>(Ty)) {
767 // If all of elements have zero size, this does too.
768 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i)
769 if (!isMaybeZeroSizedType(STy->getElementType(i))) return false;
772 } else if (const ArrayType *ATy = dyn_cast<ArrayType>(Ty)) {
773 return isMaybeZeroSizedType(ATy->getElementType());
778 /// IdxCompare - Compare the two constants as though they were getelementptr
779 /// indices. This allows coersion of the types to be the same thing.
781 /// If the two constants are the "same" (after coersion), return 0. If the
782 /// first is less than the second, return -1, if the second is less than the
783 /// first, return 1. If the constants are not integral, return -2.
785 static int IdxCompare(Constant *C1, Constant *C2, const Type *ElTy) {
786 if (C1 == C2) return 0;
788 // Ok, we found a different index. If they are not ConstantInt, we can't do
789 // anything with them.
790 if (!isa<ConstantInt>(C1) || !isa<ConstantInt>(C2))
791 return -2; // don't know!
793 // Ok, we have two differing integer indices. Sign extend them to be the same
794 // type. Long is always big enough, so we use it.
795 if (C1->getType() != Type::Int64Ty)
796 C1 = ConstantExpr::getSExt(C1, Type::Int64Ty);
798 if (C2->getType() != Type::Int64Ty)
799 C2 = ConstantExpr::getSExt(C2, Type::Int64Ty);
801 if (C1 == C2) return 0; // They are equal
803 // If the type being indexed over is really just a zero sized type, there is
804 // no pointer difference being made here.
805 if (isMaybeZeroSizedType(ElTy))
808 // If they are really different, now that they are the same type, then we
809 // found a difference!
810 if (cast<ConstantInt>(C1)->getSExtValue() <
811 cast<ConstantInt>(C2)->getSExtValue())
817 /// evaluateFCmpRelation - This function determines if there is anything we can
818 /// decide about the two constants provided. This doesn't need to handle simple
819 /// things like ConstantFP comparisons, but should instead handle ConstantExprs.
820 /// If we can determine that the two constants have a particular relation to
821 /// each other, we should return the corresponding FCmpInst predicate,
822 /// otherwise return FCmpInst::BAD_FCMP_PREDICATE. This is used below in
823 /// ConstantFoldCompareInstruction.
825 /// To simplify this code we canonicalize the relation so that the first
826 /// operand is always the most "complex" of the two. We consider ConstantFP
827 /// to be the simplest, and ConstantExprs to be the most complex.
828 static FCmpInst::Predicate evaluateFCmpRelation(const Constant *V1,
829 const Constant *V2) {
830 assert(V1->getType() == V2->getType() &&
831 "Cannot compare values of different types!");
833 // No compile-time operations on this type yet.
834 if (V1->getType() == Type::PPC_FP128Ty)
835 return FCmpInst::BAD_FCMP_PREDICATE;
837 // Handle degenerate case quickly
838 if (V1 == V2) return FCmpInst::FCMP_OEQ;
840 if (!isa<ConstantExpr>(V1)) {
841 if (!isa<ConstantExpr>(V2)) {
842 // We distilled thisUse the standard constant folder for a few cases
844 Constant *C1 = const_cast<Constant*>(V1);
845 Constant *C2 = const_cast<Constant*>(V2);
846 R = dyn_cast<ConstantInt>(
847 ConstantExpr::getFCmp(FCmpInst::FCMP_OEQ, C1, C2));
848 if (R && !R->isZero())
849 return FCmpInst::FCMP_OEQ;
850 R = dyn_cast<ConstantInt>(
851 ConstantExpr::getFCmp(FCmpInst::FCMP_OLT, C1, C2));
852 if (R && !R->isZero())
853 return FCmpInst::FCMP_OLT;
854 R = dyn_cast<ConstantInt>(
855 ConstantExpr::getFCmp(FCmpInst::FCMP_OGT, C1, C2));
856 if (R && !R->isZero())
857 return FCmpInst::FCMP_OGT;
859 // Nothing more we can do
860 return FCmpInst::BAD_FCMP_PREDICATE;
863 // If the first operand is simple and second is ConstantExpr, swap operands.
864 FCmpInst::Predicate SwappedRelation = evaluateFCmpRelation(V2, V1);
865 if (SwappedRelation != FCmpInst::BAD_FCMP_PREDICATE)
866 return FCmpInst::getSwappedPredicate(SwappedRelation);
868 // Ok, the LHS is known to be a constantexpr. The RHS can be any of a
869 // constantexpr or a simple constant.
870 const ConstantExpr *CE1 = cast<ConstantExpr>(V1);
871 switch (CE1->getOpcode()) {
872 case Instruction::FPTrunc:
873 case Instruction::FPExt:
874 case Instruction::UIToFP:
875 case Instruction::SIToFP:
876 // We might be able to do something with these but we don't right now.
882 // There are MANY other foldings that we could perform here. They will
883 // probably be added on demand, as they seem needed.
884 return FCmpInst::BAD_FCMP_PREDICATE;
887 /// evaluateICmpRelation - This function determines if there is anything we can
888 /// decide about the two constants provided. This doesn't need to handle simple
889 /// things like integer comparisons, but should instead handle ConstantExprs
890 /// and GlobalValues. If we can determine that the two constants have a
891 /// particular relation to each other, we should return the corresponding ICmp
892 /// predicate, otherwise return ICmpInst::BAD_ICMP_PREDICATE.
894 /// To simplify this code we canonicalize the relation so that the first
895 /// operand is always the most "complex" of the two. We consider simple
896 /// constants (like ConstantInt) to be the simplest, followed by
897 /// GlobalValues, followed by ConstantExpr's (the most complex).
899 static ICmpInst::Predicate evaluateICmpRelation(const Constant *V1,
902 assert(V1->getType() == V2->getType() &&
903 "Cannot compare different types of values!");
904 if (V1 == V2) return ICmpInst::ICMP_EQ;
906 if (!isa<ConstantExpr>(V1) && !isa<GlobalValue>(V1)) {
907 if (!isa<GlobalValue>(V2) && !isa<ConstantExpr>(V2)) {
908 // We distilled this down to a simple case, use the standard constant
911 Constant *C1 = const_cast<Constant*>(V1);
912 Constant *C2 = const_cast<Constant*>(V2);
913 ICmpInst::Predicate pred = ICmpInst::ICMP_EQ;
914 R = dyn_cast<ConstantInt>(ConstantExpr::getICmp(pred, C1, C2));
915 if (R && !R->isZero())
917 pred = isSigned ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT;
918 R = dyn_cast<ConstantInt>(ConstantExpr::getICmp(pred, C1, C2));
919 if (R && !R->isZero())
921 pred = isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT;
922 R = dyn_cast<ConstantInt>(ConstantExpr::getICmp(pred, C1, C2));
923 if (R && !R->isZero())
926 // If we couldn't figure it out, bail.
927 return ICmpInst::BAD_ICMP_PREDICATE;
930 // If the first operand is simple, swap operands.
931 ICmpInst::Predicate SwappedRelation =
932 evaluateICmpRelation(V2, V1, isSigned);
933 if (SwappedRelation != ICmpInst::BAD_ICMP_PREDICATE)
934 return ICmpInst::getSwappedPredicate(SwappedRelation);
936 } else if (const GlobalValue *CPR1 = dyn_cast<GlobalValue>(V1)) {
937 if (isa<ConstantExpr>(V2)) { // Swap as necessary.
938 ICmpInst::Predicate SwappedRelation =
939 evaluateICmpRelation(V2, V1, isSigned);
940 if (SwappedRelation != ICmpInst::BAD_ICMP_PREDICATE)
941 return ICmpInst::getSwappedPredicate(SwappedRelation);
943 return ICmpInst::BAD_ICMP_PREDICATE;
946 // Now we know that the RHS is a GlobalValue or simple constant,
947 // which (since the types must match) means that it's a ConstantPointerNull.
948 if (const GlobalValue *CPR2 = dyn_cast<GlobalValue>(V2)) {
949 // Don't try to decide equality of aliases.
950 if (!isa<GlobalAlias>(CPR1) && !isa<GlobalAlias>(CPR2))
951 if (!CPR1->hasExternalWeakLinkage() || !CPR2->hasExternalWeakLinkage())
952 return ICmpInst::ICMP_NE;
954 assert(isa<ConstantPointerNull>(V2) && "Canonicalization guarantee!");
955 // GlobalVals can never be null. Don't try to evaluate aliases.
956 if (!CPR1->hasExternalWeakLinkage() && !isa<GlobalAlias>(CPR1))
957 return ICmpInst::ICMP_NE;
960 // Ok, the LHS is known to be a constantexpr. The RHS can be any of a
961 // constantexpr, a CPR, or a simple constant.
962 const ConstantExpr *CE1 = cast<ConstantExpr>(V1);
963 const Constant *CE1Op0 = CE1->getOperand(0);
965 switch (CE1->getOpcode()) {
966 case Instruction::Trunc:
967 case Instruction::FPTrunc:
968 case Instruction::FPExt:
969 case Instruction::FPToUI:
970 case Instruction::FPToSI:
971 break; // We can't evaluate floating point casts or truncations.
973 case Instruction::UIToFP:
974 case Instruction::SIToFP:
975 case Instruction::BitCast:
976 case Instruction::ZExt:
977 case Instruction::SExt:
978 // If the cast is not actually changing bits, and the second operand is a
979 // null pointer, do the comparison with the pre-casted value.
980 if (V2->isNullValue() &&
981 (isa<PointerType>(CE1->getType()) || CE1->getType()->isInteger())) {
982 bool sgnd = isSigned;
983 if (CE1->getOpcode() == Instruction::ZExt) isSigned = false;
984 if (CE1->getOpcode() == Instruction::SExt) isSigned = true;
985 return evaluateICmpRelation(CE1Op0,
986 Constant::getNullValue(CE1Op0->getType()),
990 // If the dest type is a pointer type, and the RHS is a constantexpr cast
991 // from the same type as the src of the LHS, evaluate the inputs. This is
992 // important for things like "icmp eq (cast 4 to int*), (cast 5 to int*)",
993 // which happens a lot in compilers with tagged integers.
994 if (const ConstantExpr *CE2 = dyn_cast<ConstantExpr>(V2))
995 if (CE2->isCast() && isa<PointerType>(CE1->getType()) &&
996 CE1->getOperand(0)->getType() == CE2->getOperand(0)->getType() &&
997 CE1->getOperand(0)->getType()->isInteger()) {
998 bool sgnd = isSigned;
999 if (CE1->getOpcode() == Instruction::ZExt) isSigned = false;
1000 if (CE1->getOpcode() == Instruction::SExt) isSigned = true;
1001 return evaluateICmpRelation(CE1->getOperand(0), CE2->getOperand(0),
1006 case Instruction::GetElementPtr:
1007 // Ok, since this is a getelementptr, we know that the constant has a
1008 // pointer type. Check the various cases.
1009 if (isa<ConstantPointerNull>(V2)) {
1010 // If we are comparing a GEP to a null pointer, check to see if the base
1011 // of the GEP equals the null pointer.
1012 if (const GlobalValue *GV = dyn_cast<GlobalValue>(CE1Op0)) {
1013 if (GV->hasExternalWeakLinkage())
1014 // Weak linkage GVals could be zero or not. We're comparing that
1015 // to null pointer so its greater-or-equal
1016 return isSigned ? ICmpInst::ICMP_SGE : ICmpInst::ICMP_UGE;
1018 // If its not weak linkage, the GVal must have a non-zero address
1019 // so the result is greater-than
1020 return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT;
1021 } else if (isa<ConstantPointerNull>(CE1Op0)) {
1022 // If we are indexing from a null pointer, check to see if we have any
1023 // non-zero indices.
1024 for (unsigned i = 1, e = CE1->getNumOperands(); i != e; ++i)
1025 if (!CE1->getOperand(i)->isNullValue())
1026 // Offsetting from null, must not be equal.
1027 return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT;
1028 // Only zero indexes from null, must still be zero.
1029 return ICmpInst::ICMP_EQ;
1031 // Otherwise, we can't really say if the first operand is null or not.
1032 } else if (const GlobalValue *CPR2 = dyn_cast<GlobalValue>(V2)) {
1033 if (isa<ConstantPointerNull>(CE1Op0)) {
1034 if (CPR2->hasExternalWeakLinkage())
1035 // Weak linkage GVals could be zero or not. We're comparing it to
1036 // a null pointer, so its less-or-equal
1037 return isSigned ? ICmpInst::ICMP_SLE : ICmpInst::ICMP_ULE;
1039 // If its not weak linkage, the GVal must have a non-zero address
1040 // so the result is less-than
1041 return isSigned ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT;
1042 } else if (const GlobalValue *CPR1 = dyn_cast<GlobalValue>(CE1Op0)) {
1044 // If this is a getelementptr of the same global, then it must be
1045 // different. Because the types must match, the getelementptr could
1046 // only have at most one index, and because we fold getelementptr's
1047 // with a single zero index, it must be nonzero.
1048 assert(CE1->getNumOperands() == 2 &&
1049 !CE1->getOperand(1)->isNullValue() &&
1050 "Suprising getelementptr!");
1051 return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT;
1053 // If they are different globals, we don't know what the value is,
1054 // but they can't be equal.
1055 return ICmpInst::ICMP_NE;
1059 const ConstantExpr *CE2 = cast<ConstantExpr>(V2);
1060 const Constant *CE2Op0 = CE2->getOperand(0);
1062 // There are MANY other foldings that we could perform here. They will
1063 // probably be added on demand, as they seem needed.
1064 switch (CE2->getOpcode()) {
1066 case Instruction::GetElementPtr:
1067 // By far the most common case to handle is when the base pointers are
1068 // obviously to the same or different globals.
1069 if (isa<GlobalValue>(CE1Op0) && isa<GlobalValue>(CE2Op0)) {
1070 if (CE1Op0 != CE2Op0) // Don't know relative ordering, but not equal
1071 return ICmpInst::ICMP_NE;
1072 // Ok, we know that both getelementptr instructions are based on the
1073 // same global. From this, we can precisely determine the relative
1074 // ordering of the resultant pointers.
1077 // Compare all of the operands the GEP's have in common.
1078 gep_type_iterator GTI = gep_type_begin(CE1);
1079 for (;i != CE1->getNumOperands() && i != CE2->getNumOperands();
1081 switch (IdxCompare(CE1->getOperand(i), CE2->getOperand(i),
1082 GTI.getIndexedType())) {
1083 case -1: return isSigned ? ICmpInst::ICMP_SLT:ICmpInst::ICMP_ULT;
1084 case 1: return isSigned ? ICmpInst::ICMP_SGT:ICmpInst::ICMP_UGT;
1085 case -2: return ICmpInst::BAD_ICMP_PREDICATE;
1088 // Ok, we ran out of things they have in common. If any leftovers
1089 // are non-zero then we have a difference, otherwise we are equal.
1090 for (; i < CE1->getNumOperands(); ++i)
1091 if (!CE1->getOperand(i)->isNullValue()) {
1092 if (isa<ConstantInt>(CE1->getOperand(i)))
1093 return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT;
1095 return ICmpInst::BAD_ICMP_PREDICATE; // Might be equal.
1098 for (; i < CE2->getNumOperands(); ++i)
1099 if (!CE2->getOperand(i)->isNullValue()) {
1100 if (isa<ConstantInt>(CE2->getOperand(i)))
1101 return isSigned ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT;
1103 return ICmpInst::BAD_ICMP_PREDICATE; // Might be equal.
1105 return ICmpInst::ICMP_EQ;
1114 return ICmpInst::BAD_ICMP_PREDICATE;
1117 Constant *llvm::ConstantFoldCompareInstruction(unsigned short pred,
1119 const Constant *C2) {
1121 // Handle some degenerate cases first
1122 if (isa<UndefValue>(C1) || isa<UndefValue>(C2))
1123 return UndefValue::get(Type::Int1Ty);
1125 // No compile-time operations on this type yet.
1126 if (C1->getType() == Type::PPC_FP128Ty)
1129 // icmp eq/ne(null,GV) -> false/true
1130 if (C1->isNullValue()) {
1131 if (const GlobalValue *GV = dyn_cast<GlobalValue>(C2))
1132 // Don't try to evaluate aliases. External weak GV can be null.
1133 if (!isa<GlobalAlias>(GV) && !GV->hasExternalWeakLinkage()) {
1134 if (pred == ICmpInst::ICMP_EQ)
1135 return ConstantInt::getFalse();
1136 else if (pred == ICmpInst::ICMP_NE)
1137 return ConstantInt::getTrue();
1139 // icmp eq/ne(GV,null) -> false/true
1140 } else if (C2->isNullValue()) {
1141 if (const GlobalValue *GV = dyn_cast<GlobalValue>(C1))
1142 // Don't try to evaluate aliases. External weak GV can be null.
1143 if (!isa<GlobalAlias>(GV) && !GV->hasExternalWeakLinkage()) {
1144 if (pred == ICmpInst::ICMP_EQ)
1145 return ConstantInt::getFalse();
1146 else if (pred == ICmpInst::ICMP_NE)
1147 return ConstantInt::getTrue();
1151 if (isa<ConstantInt>(C1) && isa<ConstantInt>(C2)) {
1152 APInt V1 = cast<ConstantInt>(C1)->getValue();
1153 APInt V2 = cast<ConstantInt>(C2)->getValue();
1155 default: assert(0 && "Invalid ICmp Predicate"); return 0;
1156 case ICmpInst::ICMP_EQ: return ConstantInt::get(Type::Int1Ty, V1 == V2);
1157 case ICmpInst::ICMP_NE: return ConstantInt::get(Type::Int1Ty, V1 != V2);
1158 case ICmpInst::ICMP_SLT:return ConstantInt::get(Type::Int1Ty, V1.slt(V2));
1159 case ICmpInst::ICMP_SGT:return ConstantInt::get(Type::Int1Ty, V1.sgt(V2));
1160 case ICmpInst::ICMP_SLE:return ConstantInt::get(Type::Int1Ty, V1.sle(V2));
1161 case ICmpInst::ICMP_SGE:return ConstantInt::get(Type::Int1Ty, V1.sge(V2));
1162 case ICmpInst::ICMP_ULT:return ConstantInt::get(Type::Int1Ty, V1.ult(V2));
1163 case ICmpInst::ICMP_UGT:return ConstantInt::get(Type::Int1Ty, V1.ugt(V2));
1164 case ICmpInst::ICMP_ULE:return ConstantInt::get(Type::Int1Ty, V1.ule(V2));
1165 case ICmpInst::ICMP_UGE:return ConstantInt::get(Type::Int1Ty, V1.uge(V2));
1167 } else if (isa<ConstantFP>(C1) && isa<ConstantFP>(C2)) {
1168 APFloat C1V = cast<ConstantFP>(C1)->getValueAPF();
1169 APFloat C2V = cast<ConstantFP>(C2)->getValueAPF();
1170 APFloat::cmpResult R = C1V.compare(C2V);
1172 default: assert(0 && "Invalid FCmp Predicate"); return 0;
1173 case FCmpInst::FCMP_FALSE: return ConstantInt::getFalse();
1174 case FCmpInst::FCMP_TRUE: return ConstantInt::getTrue();
1175 case FCmpInst::FCMP_UNO:
1176 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpUnordered);
1177 case FCmpInst::FCMP_ORD:
1178 return ConstantInt::get(Type::Int1Ty, R!=APFloat::cmpUnordered);
1179 case FCmpInst::FCMP_UEQ:
1180 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpUnordered ||
1181 R==APFloat::cmpEqual);
1182 case FCmpInst::FCMP_OEQ:
1183 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpEqual);
1184 case FCmpInst::FCMP_UNE:
1185 return ConstantInt::get(Type::Int1Ty, R!=APFloat::cmpEqual);
1186 case FCmpInst::FCMP_ONE:
1187 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpLessThan ||
1188 R==APFloat::cmpGreaterThan);
1189 case FCmpInst::FCMP_ULT:
1190 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpUnordered ||
1191 R==APFloat::cmpLessThan);
1192 case FCmpInst::FCMP_OLT:
1193 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpLessThan);
1194 case FCmpInst::FCMP_UGT:
1195 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpUnordered ||
1196 R==APFloat::cmpGreaterThan);
1197 case FCmpInst::FCMP_OGT:
1198 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpGreaterThan);
1199 case FCmpInst::FCMP_ULE:
1200 return ConstantInt::get(Type::Int1Ty, R!=APFloat::cmpGreaterThan);
1201 case FCmpInst::FCMP_OLE:
1202 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpLessThan ||
1203 R==APFloat::cmpEqual);
1204 case FCmpInst::FCMP_UGE:
1205 return ConstantInt::get(Type::Int1Ty, R!=APFloat::cmpLessThan);
1206 case FCmpInst::FCMP_OGE:
1207 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpGreaterThan ||
1208 R==APFloat::cmpEqual);
1210 } else if (const ConstantVector *CP1 = dyn_cast<ConstantVector>(C1)) {
1211 if (const ConstantVector *CP2 = dyn_cast<ConstantVector>(C2)) {
1212 if (pred == FCmpInst::FCMP_OEQ || pred == FCmpInst::FCMP_UEQ) {
1213 for (unsigned i = 0, e = CP1->getNumOperands(); i != e; ++i) {
1214 Constant *C= ConstantExpr::getFCmp(FCmpInst::FCMP_OEQ,
1215 const_cast<Constant*>(CP1->getOperand(i)),
1216 const_cast<Constant*>(CP2->getOperand(i)));
1217 if (ConstantInt *CB = dyn_cast<ConstantInt>(C))
1220 // Otherwise, could not decide from any element pairs.
1222 } else if (pred == ICmpInst::ICMP_EQ) {
1223 for (unsigned i = 0, e = CP1->getNumOperands(); i != e; ++i) {
1224 Constant *C = ConstantExpr::getICmp(ICmpInst::ICMP_EQ,
1225 const_cast<Constant*>(CP1->getOperand(i)),
1226 const_cast<Constant*>(CP2->getOperand(i)));
1227 if (ConstantInt *CB = dyn_cast<ConstantInt>(C))
1230 // Otherwise, could not decide from any element pairs.
1236 if (C1->getType()->isFloatingPoint()) {
1237 switch (evaluateFCmpRelation(C1, C2)) {
1238 default: assert(0 && "Unknown relation!");
1239 case FCmpInst::FCMP_UNO:
1240 case FCmpInst::FCMP_ORD:
1241 case FCmpInst::FCMP_UEQ:
1242 case FCmpInst::FCMP_UNE:
1243 case FCmpInst::FCMP_ULT:
1244 case FCmpInst::FCMP_UGT:
1245 case FCmpInst::FCMP_ULE:
1246 case FCmpInst::FCMP_UGE:
1247 case FCmpInst::FCMP_TRUE:
1248 case FCmpInst::FCMP_FALSE:
1249 case FCmpInst::BAD_FCMP_PREDICATE:
1250 break; // Couldn't determine anything about these constants.
1251 case FCmpInst::FCMP_OEQ: // We know that C1 == C2
1252 return ConstantInt::get(Type::Int1Ty,
1253 pred == FCmpInst::FCMP_UEQ || pred == FCmpInst::FCMP_OEQ ||
1254 pred == FCmpInst::FCMP_ULE || pred == FCmpInst::FCMP_OLE ||
1255 pred == FCmpInst::FCMP_UGE || pred == FCmpInst::FCMP_OGE);
1256 case FCmpInst::FCMP_OLT: // We know that C1 < C2
1257 return ConstantInt::get(Type::Int1Ty,
1258 pred == FCmpInst::FCMP_UNE || pred == FCmpInst::FCMP_ONE ||
1259 pred == FCmpInst::FCMP_ULT || pred == FCmpInst::FCMP_OLT ||
1260 pred == FCmpInst::FCMP_ULE || pred == FCmpInst::FCMP_OLE);
1261 case FCmpInst::FCMP_OGT: // We know that C1 > C2
1262 return ConstantInt::get(Type::Int1Ty,
1263 pred == FCmpInst::FCMP_UNE || pred == FCmpInst::FCMP_ONE ||
1264 pred == FCmpInst::FCMP_UGT || pred == FCmpInst::FCMP_OGT ||
1265 pred == FCmpInst::FCMP_UGE || pred == FCmpInst::FCMP_OGE);
1266 case FCmpInst::FCMP_OLE: // We know that C1 <= C2
1267 // We can only partially decide this relation.
1268 if (pred == FCmpInst::FCMP_UGT || pred == FCmpInst::FCMP_OGT)
1269 return ConstantInt::getFalse();
1270 if (pred == FCmpInst::FCMP_ULT || pred == FCmpInst::FCMP_OLT)
1271 return ConstantInt::getTrue();
1273 case FCmpInst::FCMP_OGE: // We known that C1 >= C2
1274 // We can only partially decide this relation.
1275 if (pred == FCmpInst::FCMP_ULT || pred == FCmpInst::FCMP_OLT)
1276 return ConstantInt::getFalse();
1277 if (pred == FCmpInst::FCMP_UGT || pred == FCmpInst::FCMP_OGT)
1278 return ConstantInt::getTrue();
1280 case ICmpInst::ICMP_NE: // We know that C1 != C2
1281 // We can only partially decide this relation.
1282 if (pred == FCmpInst::FCMP_OEQ || pred == FCmpInst::FCMP_UEQ)
1283 return ConstantInt::getFalse();
1284 if (pred == FCmpInst::FCMP_ONE || pred == FCmpInst::FCMP_UNE)
1285 return ConstantInt::getTrue();
1289 // Evaluate the relation between the two constants, per the predicate.
1290 switch (evaluateICmpRelation(C1, C2, CmpInst::isSigned(pred))) {
1291 default: assert(0 && "Unknown relational!");
1292 case ICmpInst::BAD_ICMP_PREDICATE:
1293 break; // Couldn't determine anything about these constants.
1294 case ICmpInst::ICMP_EQ: // We know the constants are equal!
1295 // If we know the constants are equal, we can decide the result of this
1296 // computation precisely.
1297 return ConstantInt::get(Type::Int1Ty,
1298 pred == ICmpInst::ICMP_EQ ||
1299 pred == ICmpInst::ICMP_ULE ||
1300 pred == ICmpInst::ICMP_SLE ||
1301 pred == ICmpInst::ICMP_UGE ||
1302 pred == ICmpInst::ICMP_SGE);
1303 case ICmpInst::ICMP_ULT:
1304 // If we know that C1 < C2, we can decide the result of this computation
1306 return ConstantInt::get(Type::Int1Ty,
1307 pred == ICmpInst::ICMP_ULT ||
1308 pred == ICmpInst::ICMP_NE ||
1309 pred == ICmpInst::ICMP_ULE);
1310 case ICmpInst::ICMP_SLT:
1311 // If we know that C1 < C2, we can decide the result of this computation
1313 return ConstantInt::get(Type::Int1Ty,
1314 pred == ICmpInst::ICMP_SLT ||
1315 pred == ICmpInst::ICMP_NE ||
1316 pred == ICmpInst::ICMP_SLE);
1317 case ICmpInst::ICMP_UGT:
1318 // If we know that C1 > C2, we can decide the result of this computation
1320 return ConstantInt::get(Type::Int1Ty,
1321 pred == ICmpInst::ICMP_UGT ||
1322 pred == ICmpInst::ICMP_NE ||
1323 pred == ICmpInst::ICMP_UGE);
1324 case ICmpInst::ICMP_SGT:
1325 // If we know that C1 > C2, we can decide the result of this computation
1327 return ConstantInt::get(Type::Int1Ty,
1328 pred == ICmpInst::ICMP_SGT ||
1329 pred == ICmpInst::ICMP_NE ||
1330 pred == ICmpInst::ICMP_SGE);
1331 case ICmpInst::ICMP_ULE:
1332 // If we know that C1 <= C2, we can only partially decide this relation.
1333 if (pred == ICmpInst::ICMP_UGT) return ConstantInt::getFalse();
1334 if (pred == ICmpInst::ICMP_ULT) return ConstantInt::getTrue();
1336 case ICmpInst::ICMP_SLE:
1337 // If we know that C1 <= C2, we can only partially decide this relation.
1338 if (pred == ICmpInst::ICMP_SGT) return ConstantInt::getFalse();
1339 if (pred == ICmpInst::ICMP_SLT) return ConstantInt::getTrue();
1342 case ICmpInst::ICMP_UGE:
1343 // If we know that C1 >= C2, we can only partially decide this relation.
1344 if (pred == ICmpInst::ICMP_ULT) return ConstantInt::getFalse();
1345 if (pred == ICmpInst::ICMP_UGT) return ConstantInt::getTrue();
1347 case ICmpInst::ICMP_SGE:
1348 // If we know that C1 >= C2, we can only partially decide this relation.
1349 if (pred == ICmpInst::ICMP_SLT) return ConstantInt::getFalse();
1350 if (pred == ICmpInst::ICMP_SGT) return ConstantInt::getTrue();
1353 case ICmpInst::ICMP_NE:
1354 // If we know that C1 != C2, we can only partially decide this relation.
1355 if (pred == ICmpInst::ICMP_EQ) return ConstantInt::getFalse();
1356 if (pred == ICmpInst::ICMP_NE) return ConstantInt::getTrue();
1360 if (!isa<ConstantExpr>(C1) && isa<ConstantExpr>(C2)) {
1361 // If C2 is a constant expr and C1 isn't, flop them around and fold the
1362 // other way if possible.
1364 case ICmpInst::ICMP_EQ:
1365 case ICmpInst::ICMP_NE:
1366 // No change of predicate required.
1367 return ConstantFoldCompareInstruction(pred, C2, C1);
1369 case ICmpInst::ICMP_ULT:
1370 case ICmpInst::ICMP_SLT:
1371 case ICmpInst::ICMP_UGT:
1372 case ICmpInst::ICMP_SGT:
1373 case ICmpInst::ICMP_ULE:
1374 case ICmpInst::ICMP_SLE:
1375 case ICmpInst::ICMP_UGE:
1376 case ICmpInst::ICMP_SGE:
1377 // Change the predicate as necessary to swap the operands.
1378 pred = ICmpInst::getSwappedPredicate((ICmpInst::Predicate)pred);
1379 return ConstantFoldCompareInstruction(pred, C2, C1);
1381 default: // These predicates cannot be flopped around.
1389 Constant *llvm::ConstantFoldGetElementPtr(const Constant *C,
1390 Constant* const *Idxs,
1393 (NumIdx == 1 && Idxs[0]->isNullValue()))
1394 return const_cast<Constant*>(C);
1396 if (isa<UndefValue>(C)) {
1397 const PointerType *Ptr = cast<PointerType>(C->getType());
1398 const Type *Ty = GetElementPtrInst::getIndexedType(Ptr,
1400 (Value **)Idxs+NumIdx,
1402 assert(Ty != 0 && "Invalid indices for GEP!");
1403 return UndefValue::get(PointerType::get(Ty, Ptr->getAddressSpace()));
1406 Constant *Idx0 = Idxs[0];
1407 if (C->isNullValue()) {
1409 for (unsigned i = 0, e = NumIdx; i != e; ++i)
1410 if (!Idxs[i]->isNullValue()) {
1415 const PointerType *Ptr = cast<PointerType>(C->getType());
1416 const Type *Ty = GetElementPtrInst::getIndexedType(Ptr,
1418 (Value**)Idxs+NumIdx,
1420 assert(Ty != 0 && "Invalid indices for GEP!");
1422 ConstantPointerNull::get(PointerType::get(Ty,Ptr->getAddressSpace()));
1426 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(const_cast<Constant*>(C))) {
1427 // Combine Indices - If the source pointer to this getelementptr instruction
1428 // is a getelementptr instruction, combine the indices of the two
1429 // getelementptr instructions into a single instruction.
1431 if (CE->getOpcode() == Instruction::GetElementPtr) {
1432 const Type *LastTy = 0;
1433 for (gep_type_iterator I = gep_type_begin(CE), E = gep_type_end(CE);
1437 if ((LastTy && isa<ArrayType>(LastTy)) || Idx0->isNullValue()) {
1438 SmallVector<Value*, 16> NewIndices;
1439 NewIndices.reserve(NumIdx + CE->getNumOperands());
1440 for (unsigned i = 1, e = CE->getNumOperands()-1; i != e; ++i)
1441 NewIndices.push_back(CE->getOperand(i));
1443 // Add the last index of the source with the first index of the new GEP.
1444 // Make sure to handle the case when they are actually different types.
1445 Constant *Combined = CE->getOperand(CE->getNumOperands()-1);
1446 // Otherwise it must be an array.
1447 if (!Idx0->isNullValue()) {
1448 const Type *IdxTy = Combined->getType();
1449 if (IdxTy != Idx0->getType()) {
1450 Constant *C1 = ConstantExpr::getSExtOrBitCast(Idx0, Type::Int64Ty);
1451 Constant *C2 = ConstantExpr::getSExtOrBitCast(Combined,
1453 Combined = ConstantExpr::get(Instruction::Add, C1, C2);
1456 ConstantExpr::get(Instruction::Add, Idx0, Combined);
1460 NewIndices.push_back(Combined);
1461 NewIndices.insert(NewIndices.end(), Idxs+1, Idxs+NumIdx);
1462 return ConstantExpr::getGetElementPtr(CE->getOperand(0), &NewIndices[0],
1467 // Implement folding of:
1468 // int* getelementptr ([2 x int]* cast ([3 x int]* %X to [2 x int]*),
1470 // To: int* getelementptr ([3 x int]* %X, long 0, long 0)
1472 if (CE->isCast() && NumIdx > 1 && Idx0->isNullValue()) {
1473 if (const PointerType *SPT =
1474 dyn_cast<PointerType>(CE->getOperand(0)->getType()))
1475 if (const ArrayType *SAT = dyn_cast<ArrayType>(SPT->getElementType()))
1476 if (const ArrayType *CAT =
1477 dyn_cast<ArrayType>(cast<PointerType>(C->getType())->getElementType()))
1478 if (CAT->getElementType() == SAT->getElementType())
1479 return ConstantExpr::getGetElementPtr(
1480 (Constant*)CE->getOperand(0), Idxs, NumIdx);
1483 // Fold: getelementptr (i8* inttoptr (i64 1 to i8*), i32 -1)
1484 // Into: inttoptr (i64 0 to i8*)
1485 // This happens with pointers to member functions in C++.
1486 if (CE->getOpcode() == Instruction::IntToPtr && NumIdx == 1 &&
1487 isa<ConstantInt>(CE->getOperand(0)) && isa<ConstantInt>(Idxs[0]) &&
1488 cast<PointerType>(CE->getType())->getElementType() == Type::Int8Ty) {
1489 Constant *Base = CE->getOperand(0);
1490 Constant *Offset = Idxs[0];
1492 // Convert the smaller integer to the larger type.
1493 if (Offset->getType()->getPrimitiveSizeInBits() <
1494 Base->getType()->getPrimitiveSizeInBits())
1495 Offset = ConstantExpr::getSExt(Offset, Base->getType());
1496 else if (Base->getType()->getPrimitiveSizeInBits() <
1497 Offset->getType()->getPrimitiveSizeInBits())
1498 Base = ConstantExpr::getZExt(Base, Base->getType());
1500 Base = ConstantExpr::getAdd(Base, Offset);
1501 return ConstantExpr::getIntToPtr(Base, CE->getType());