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 const Type *SrcTy = V->getType();
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 if (opc == Instruction::ZExt || opc == Instruction::SExt)
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 uint32_t BitWidth = cast<IntegerType>(SrcTy)->getBitWidth();
259 APFloat apf = APFloat(APInt(DestTy->getPrimitiveSizeInBits(),
261 (void)apf.convertFromZeroExtendedInteger(api.getRawData(), BitWidth,
262 opc==Instruction::SIToFP,
263 APFloat::rmNearestTiesToEven);
264 return ConstantFP::get(DestTy, apf);
266 if (const ConstantVector *CV = dyn_cast<ConstantVector>(V)) {
267 std::vector<Constant*> res;
268 const VectorType *DestVecTy = cast<VectorType>(DestTy);
269 const Type *DstEltTy = DestVecTy->getElementType();
270 for (unsigned i = 0, e = CV->getType()->getNumElements(); i != e; ++i)
271 res.push_back(ConstantFoldCastInstruction(opc, V->getOperand(i),
273 return ConstantVector::get(DestVecTy, res);
276 case Instruction::ZExt:
277 if (const ConstantInt *CI = dyn_cast<ConstantInt>(V)) {
278 uint32_t BitWidth = cast<IntegerType>(DestTy)->getBitWidth();
279 APInt Result(CI->getValue());
280 Result.zext(BitWidth);
281 return ConstantInt::get(Result);
284 case Instruction::SExt:
285 if (const ConstantInt *CI = dyn_cast<ConstantInt>(V)) {
286 uint32_t BitWidth = cast<IntegerType>(DestTy)->getBitWidth();
287 APInt Result(CI->getValue());
288 Result.sext(BitWidth);
289 return ConstantInt::get(Result);
292 case Instruction::Trunc:
293 if (const ConstantInt *CI = dyn_cast<ConstantInt>(V)) {
294 uint32_t BitWidth = cast<IntegerType>(DestTy)->getBitWidth();
295 APInt Result(CI->getValue());
296 Result.trunc(BitWidth);
297 return ConstantInt::get(Result);
300 case Instruction::BitCast:
301 return FoldBitCast(const_cast<Constant*>(V), DestTy);
303 assert(!"Invalid CE CastInst opcode");
307 assert(0 && "Failed to cast constant expression");
311 Constant *llvm::ConstantFoldSelectInstruction(const Constant *Cond,
313 const Constant *V2) {
314 if (const ConstantInt *CB = dyn_cast<ConstantInt>(Cond))
315 return const_cast<Constant*>(CB->getZExtValue() ? V1 : V2);
317 if (isa<UndefValue>(V1)) return const_cast<Constant*>(V2);
318 if (isa<UndefValue>(V2)) return const_cast<Constant*>(V1);
319 if (isa<UndefValue>(Cond)) return const_cast<Constant*>(V1);
320 if (V1 == V2) return const_cast<Constant*>(V1);
324 Constant *llvm::ConstantFoldExtractElementInstruction(const Constant *Val,
325 const Constant *Idx) {
326 if (isa<UndefValue>(Val)) // ee(undef, x) -> undef
327 return UndefValue::get(cast<VectorType>(Val->getType())->getElementType());
328 if (Val->isNullValue()) // ee(zero, x) -> zero
329 return Constant::getNullValue(
330 cast<VectorType>(Val->getType())->getElementType());
332 if (const ConstantVector *CVal = dyn_cast<ConstantVector>(Val)) {
333 if (const ConstantInt *CIdx = dyn_cast<ConstantInt>(Idx)) {
334 return const_cast<Constant*>(CVal->getOperand(CIdx->getZExtValue()));
335 } else if (isa<UndefValue>(Idx)) {
336 // ee({w,x,y,z}, undef) -> w (an arbitrary value).
337 return const_cast<Constant*>(CVal->getOperand(0));
343 Constant *llvm::ConstantFoldInsertElementInstruction(const Constant *Val,
345 const Constant *Idx) {
346 const ConstantInt *CIdx = dyn_cast<ConstantInt>(Idx);
348 APInt idxVal = CIdx->getValue();
349 if (isa<UndefValue>(Val)) {
350 // Insertion of scalar constant into vector undef
351 // Optimize away insertion of undef
352 if (isa<UndefValue>(Elt))
353 return const_cast<Constant*>(Val);
354 // Otherwise break the aggregate undef into multiple undefs and do
357 cast<VectorType>(Val->getType())->getNumElements();
358 std::vector<Constant*> Ops;
360 for (unsigned i = 0; i < numOps; ++i) {
362 (idxVal == i) ? Elt : UndefValue::get(Elt->getType());
363 Ops.push_back(const_cast<Constant*>(Op));
365 return ConstantVector::get(Ops);
367 if (isa<ConstantAggregateZero>(Val)) {
368 // Insertion of scalar constant into vector aggregate zero
369 // Optimize away insertion of zero
370 if (Elt->isNullValue())
371 return const_cast<Constant*>(Val);
372 // Otherwise break the aggregate zero into multiple zeros and do
375 cast<VectorType>(Val->getType())->getNumElements();
376 std::vector<Constant*> Ops;
378 for (unsigned i = 0; i < numOps; ++i) {
380 (idxVal == i) ? Elt : Constant::getNullValue(Elt->getType());
381 Ops.push_back(const_cast<Constant*>(Op));
383 return ConstantVector::get(Ops);
385 if (const ConstantVector *CVal = dyn_cast<ConstantVector>(Val)) {
386 // Insertion of scalar constant into vector constant
387 std::vector<Constant*> Ops;
388 Ops.reserve(CVal->getNumOperands());
389 for (unsigned i = 0; i < CVal->getNumOperands(); ++i) {
391 (idxVal == i) ? Elt : cast<Constant>(CVal->getOperand(i));
392 Ops.push_back(const_cast<Constant*>(Op));
394 return ConstantVector::get(Ops);
399 /// GetVectorElement - If C is a ConstantVector, ConstantAggregateZero or Undef
400 /// return the specified element value. Otherwise return null.
401 static Constant *GetVectorElement(const Constant *C, unsigned EltNo) {
402 if (const ConstantVector *CV = dyn_cast<ConstantVector>(C))
403 return const_cast<Constant*>(CV->getOperand(EltNo));
405 const Type *EltTy = cast<VectorType>(C->getType())->getElementType();
406 if (isa<ConstantAggregateZero>(C))
407 return Constant::getNullValue(EltTy);
408 if (isa<UndefValue>(C))
409 return UndefValue::get(EltTy);
413 Constant *llvm::ConstantFoldShuffleVectorInstruction(const Constant *V1,
415 const Constant *Mask) {
416 // Undefined shuffle mask -> undefined value.
417 if (isa<UndefValue>(Mask)) return UndefValue::get(V1->getType());
419 unsigned NumElts = cast<VectorType>(V1->getType())->getNumElements();
420 const Type *EltTy = cast<VectorType>(V1->getType())->getElementType();
422 // Loop over the shuffle mask, evaluating each element.
423 SmallVector<Constant*, 32> Result;
424 for (unsigned i = 0; i != NumElts; ++i) {
425 Constant *InElt = GetVectorElement(Mask, i);
426 if (InElt == 0) return 0;
428 if (isa<UndefValue>(InElt))
429 InElt = UndefValue::get(EltTy);
430 else if (ConstantInt *CI = dyn_cast<ConstantInt>(InElt)) {
431 unsigned Elt = CI->getZExtValue();
432 if (Elt >= NumElts*2)
433 InElt = UndefValue::get(EltTy);
434 else if (Elt >= NumElts)
435 InElt = GetVectorElement(V2, Elt-NumElts);
437 InElt = GetVectorElement(V1, Elt);
438 if (InElt == 0) return 0;
443 Result.push_back(InElt);
446 return ConstantVector::get(&Result[0], Result.size());
449 /// EvalVectorOp - Given two vector constants and a function pointer, apply the
450 /// function pointer to each element pair, producing a new ConstantVector
451 /// constant. Either or both of V1 and V2 may be NULL, meaning a
452 /// ConstantAggregateZero operand.
453 static Constant *EvalVectorOp(const ConstantVector *V1,
454 const ConstantVector *V2,
455 const VectorType *VTy,
456 Constant *(*FP)(Constant*, Constant*)) {
457 std::vector<Constant*> Res;
458 const Type *EltTy = VTy->getElementType();
459 for (unsigned i = 0, e = VTy->getNumElements(); i != e; ++i) {
460 const Constant *C1 = V1 ? V1->getOperand(i) : Constant::getNullValue(EltTy);
461 const Constant *C2 = V2 ? V2->getOperand(i) : Constant::getNullValue(EltTy);
462 Res.push_back(FP(const_cast<Constant*>(C1),
463 const_cast<Constant*>(C2)));
465 return ConstantVector::get(Res);
468 Constant *llvm::ConstantFoldBinaryInstruction(unsigned Opcode,
470 const Constant *C2) {
471 // No compile-time operations on this type yet.
472 if (C1->getType() == Type::PPC_FP128Ty)
475 // Handle UndefValue up front
476 if (isa<UndefValue>(C1) || isa<UndefValue>(C2)) {
478 case Instruction::Add:
479 case Instruction::Sub:
480 case Instruction::Xor:
481 return UndefValue::get(C1->getType());
482 case Instruction::Mul:
483 case Instruction::And:
484 return Constant::getNullValue(C1->getType());
485 case Instruction::UDiv:
486 case Instruction::SDiv:
487 case Instruction::FDiv:
488 case Instruction::URem:
489 case Instruction::SRem:
490 case Instruction::FRem:
491 if (!isa<UndefValue>(C2)) // undef / X -> 0
492 return Constant::getNullValue(C1->getType());
493 return const_cast<Constant*>(C2); // X / undef -> undef
494 case Instruction::Or: // X | undef -> -1
495 if (const VectorType *PTy = dyn_cast<VectorType>(C1->getType()))
496 return ConstantVector::getAllOnesValue(PTy);
497 return ConstantInt::getAllOnesValue(C1->getType());
498 case Instruction::LShr:
499 if (isa<UndefValue>(C2) && isa<UndefValue>(C1))
500 return const_cast<Constant*>(C1); // undef lshr undef -> undef
501 return Constant::getNullValue(C1->getType()); // X lshr undef -> 0
503 case Instruction::AShr:
504 if (!isa<UndefValue>(C2))
505 return const_cast<Constant*>(C1); // undef ashr X --> undef
506 else if (isa<UndefValue>(C1))
507 return const_cast<Constant*>(C1); // undef ashr undef -> undef
509 return const_cast<Constant*>(C1); // X ashr undef --> X
510 case Instruction::Shl:
511 // undef << X -> 0 or X << undef -> 0
512 return Constant::getNullValue(C1->getType());
516 if (const ConstantExpr *CE1 = dyn_cast<ConstantExpr>(C1)) {
517 if (isa<ConstantExpr>(C2)) {
518 // There are many possible foldings we could do here. We should probably
519 // at least fold add of a pointer with an integer into the appropriate
520 // getelementptr. This will improve alias analysis a bit.
522 // Just implement a couple of simple identities.
524 case Instruction::Add:
525 if (C2->isNullValue()) return const_cast<Constant*>(C1); // X + 0 == X
527 case Instruction::Sub:
528 if (C2->isNullValue()) return const_cast<Constant*>(C1); // X - 0 == X
530 case Instruction::Mul:
531 if (C2->isNullValue()) return const_cast<Constant*>(C2); // X * 0 == 0
532 if (const ConstantInt *CI = dyn_cast<ConstantInt>(C2))
533 if (CI->equalsInt(1))
534 return const_cast<Constant*>(C1); // X * 1 == X
536 case Instruction::UDiv:
537 case Instruction::SDiv:
538 if (const ConstantInt *CI = dyn_cast<ConstantInt>(C2))
539 if (CI->equalsInt(1))
540 return const_cast<Constant*>(C1); // X / 1 == X
542 case Instruction::URem:
543 case Instruction::SRem:
544 if (const ConstantInt *CI = dyn_cast<ConstantInt>(C2))
545 if (CI->equalsInt(1))
546 return Constant::getNullValue(CI->getType()); // X % 1 == 0
548 case Instruction::And:
549 if (const ConstantInt *CI = dyn_cast<ConstantInt>(C2)) {
550 if (CI->isZero()) return const_cast<Constant*>(C2); // X & 0 == 0
551 if (CI->isAllOnesValue())
552 return const_cast<Constant*>(C1); // X & -1 == X
554 // (zext i32 to i64) & 4294967295 -> (zext i32 to i64)
555 if (CE1->getOpcode() == Instruction::ZExt) {
556 APInt PossiblySetBits
557 = cast<IntegerType>(CE1->getOperand(0)->getType())->getMask();
558 PossiblySetBits.zext(C1->getType()->getPrimitiveSizeInBits());
559 if ((PossiblySetBits & CI->getValue()) == PossiblySetBits)
560 return const_cast<Constant*>(C1);
563 if (CE1->isCast() && 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());
574 case Instruction::Or:
575 if (C2->isNullValue()) return const_cast<Constant*>(C1); // X | 0 == X
576 if (const ConstantInt *CI = dyn_cast<ConstantInt>(C2))
577 if (CI->isAllOnesValue())
578 return const_cast<Constant*>(C2); // X | -1 == -1
580 case Instruction::Xor:
581 if (C2->isNullValue()) 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 (CE1->getOpcode() == Instruction::ZExt) // Top bits known zero.
586 return ConstantExpr::getLShr(const_cast<Constant*>(C1),
587 const_cast<Constant*>(C2));
591 } else if (isa<ConstantExpr>(C2)) {
592 // If C2 is a constant expr and C1 isn't, flop them around and fold the
593 // other way if possible.
595 case Instruction::Add:
596 case Instruction::Mul:
597 case Instruction::And:
598 case Instruction::Or:
599 case Instruction::Xor:
600 // No change of opcode required.
601 return ConstantFoldBinaryInstruction(Opcode, C2, C1);
603 case Instruction::Shl:
604 case Instruction::LShr:
605 case Instruction::AShr:
606 case Instruction::Sub:
607 case Instruction::SDiv:
608 case Instruction::UDiv:
609 case Instruction::FDiv:
610 case Instruction::URem:
611 case Instruction::SRem:
612 case Instruction::FRem:
613 default: // These instructions cannot be flopped around.
618 // At this point we know neither constant is an UndefValue nor a ConstantExpr
619 // so look at directly computing the value.
620 if (const ConstantInt *CI1 = dyn_cast<ConstantInt>(C1)) {
621 if (const ConstantInt *CI2 = dyn_cast<ConstantInt>(C2)) {
622 using namespace APIntOps;
623 APInt C1V = CI1->getValue();
624 APInt C2V = CI2->getValue();
628 case Instruction::Add:
629 return ConstantInt::get(C1V + C2V);
630 case Instruction::Sub:
631 return ConstantInt::get(C1V - C2V);
632 case Instruction::Mul:
633 return ConstantInt::get(C1V * C2V);
634 case Instruction::UDiv:
635 if (CI2->isNullValue())
636 return 0; // X / 0 -> can't fold
637 return ConstantInt::get(C1V.udiv(C2V));
638 case Instruction::SDiv:
639 if (CI2->isNullValue())
640 return 0; // X / 0 -> can't fold
641 if (C2V.isAllOnesValue() && C1V.isMinSignedValue())
642 return 0; // MIN_INT / -1 -> overflow
643 return ConstantInt::get(C1V.sdiv(C2V));
644 case Instruction::URem:
645 if (C2->isNullValue())
646 return 0; // X / 0 -> can't fold
647 return ConstantInt::get(C1V.urem(C2V));
648 case Instruction::SRem:
649 if (CI2->isNullValue())
650 return 0; // X % 0 -> can't fold
651 if (C2V.isAllOnesValue() && C1V.isMinSignedValue())
652 return 0; // MIN_INT % -1 -> overflow
653 return ConstantInt::get(C1V.srem(C2V));
654 case Instruction::And:
655 return ConstantInt::get(C1V & C2V);
656 case Instruction::Or:
657 return ConstantInt::get(C1V | C2V);
658 case Instruction::Xor:
659 return ConstantInt::get(C1V ^ C2V);
660 case Instruction::Shl:
661 if (uint32_t shiftAmt = C2V.getZExtValue())
662 if (shiftAmt < C1V.getBitWidth())
663 return ConstantInt::get(C1V.shl(shiftAmt));
665 return UndefValue::get(C1->getType()); // too big shift is undef
666 return const_cast<ConstantInt*>(CI1); // Zero shift is identity
667 case Instruction::LShr:
668 if (uint32_t shiftAmt = C2V.getZExtValue())
669 if (shiftAmt < C1V.getBitWidth())
670 return ConstantInt::get(C1V.lshr(shiftAmt));
672 return UndefValue::get(C1->getType()); // too big shift is undef
673 return const_cast<ConstantInt*>(CI1); // Zero shift is identity
674 case Instruction::AShr:
675 if (uint32_t shiftAmt = C2V.getZExtValue())
676 if (shiftAmt < C1V.getBitWidth())
677 return ConstantInt::get(C1V.ashr(shiftAmt));
679 return UndefValue::get(C1->getType()); // too big shift is undef
680 return const_cast<ConstantInt*>(CI1); // Zero shift is identity
683 } else if (const ConstantFP *CFP1 = dyn_cast<ConstantFP>(C1)) {
684 if (const ConstantFP *CFP2 = dyn_cast<ConstantFP>(C2)) {
685 APFloat C1V = CFP1->getValueAPF();
686 APFloat C2V = CFP2->getValueAPF();
687 APFloat C3V = C1V; // copy for modification
688 bool isDouble = CFP1->getType()==Type::DoubleTy;
692 case Instruction::Add:
693 (void)C3V.add(C2V, APFloat::rmNearestTiesToEven);
694 return ConstantFP::get(CFP1->getType(), C3V);
695 case Instruction::Sub:
696 (void)C3V.subtract(C2V, APFloat::rmNearestTiesToEven);
697 return ConstantFP::get(CFP1->getType(), C3V);
698 case Instruction::Mul:
699 (void)C3V.multiply(C2V, APFloat::rmNearestTiesToEven);
700 return ConstantFP::get(CFP1->getType(), C3V);
701 case Instruction::FDiv:
702 (void)C3V.divide(C2V, APFloat::rmNearestTiesToEven);
703 return ConstantFP::get(CFP1->getType(), C3V);
704 case Instruction::FRem:
706 // IEEE 754, Section 7.1, #5
707 return ConstantFP::get(CFP1->getType(), isDouble ?
708 APFloat(std::numeric_limits<double>::quiet_NaN()) :
709 APFloat(std::numeric_limits<float>::quiet_NaN()));
710 (void)C3V.mod(C2V, APFloat::rmNearestTiesToEven);
711 return ConstantFP::get(CFP1->getType(), C3V);
714 } else if (const VectorType *VTy = dyn_cast<VectorType>(C1->getType())) {
715 const ConstantVector *CP1 = dyn_cast<ConstantVector>(C1);
716 const ConstantVector *CP2 = dyn_cast<ConstantVector>(C2);
717 if ((CP1 != NULL || isa<ConstantAggregateZero>(C1)) &&
718 (CP2 != NULL || isa<ConstantAggregateZero>(C2))) {
722 case Instruction::Add:
723 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getAdd);
724 case Instruction::Sub:
725 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getSub);
726 case Instruction::Mul:
727 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getMul);
728 case Instruction::UDiv:
729 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getUDiv);
730 case Instruction::SDiv:
731 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getSDiv);
732 case Instruction::FDiv:
733 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getFDiv);
734 case Instruction::URem:
735 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getURem);
736 case Instruction::SRem:
737 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getSRem);
738 case Instruction::FRem:
739 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getFRem);
740 case Instruction::And:
741 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getAnd);
742 case Instruction::Or:
743 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getOr);
744 case Instruction::Xor:
745 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getXor);
750 // We don't know how to fold this
754 /// isZeroSizedType - This type is zero sized if its an array or structure of
755 /// zero sized types. The only leaf zero sized type is an empty structure.
756 static bool isMaybeZeroSizedType(const Type *Ty) {
757 if (isa<OpaqueType>(Ty)) return true; // Can't say.
758 if (const StructType *STy = dyn_cast<StructType>(Ty)) {
760 // If all of elements have zero size, this does too.
761 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i)
762 if (!isMaybeZeroSizedType(STy->getElementType(i))) return false;
765 } else if (const ArrayType *ATy = dyn_cast<ArrayType>(Ty)) {
766 return isMaybeZeroSizedType(ATy->getElementType());
771 /// IdxCompare - Compare the two constants as though they were getelementptr
772 /// indices. This allows coersion of the types to be the same thing.
774 /// If the two constants are the "same" (after coersion), return 0. If the
775 /// first is less than the second, return -1, if the second is less than the
776 /// first, return 1. If the constants are not integral, return -2.
778 static int IdxCompare(Constant *C1, Constant *C2, const Type *ElTy) {
779 if (C1 == C2) return 0;
781 // Ok, we found a different index. If they are not ConstantInt, we can't do
782 // anything with them.
783 if (!isa<ConstantInt>(C1) || !isa<ConstantInt>(C2))
784 return -2; // don't know!
786 // Ok, we have two differing integer indices. Sign extend them to be the same
787 // type. Long is always big enough, so we use it.
788 if (C1->getType() != Type::Int64Ty)
789 C1 = ConstantExpr::getSExt(C1, Type::Int64Ty);
791 if (C2->getType() != Type::Int64Ty)
792 C2 = ConstantExpr::getSExt(C2, Type::Int64Ty);
794 if (C1 == C2) return 0; // They are equal
796 // If the type being indexed over is really just a zero sized type, there is
797 // no pointer difference being made here.
798 if (isMaybeZeroSizedType(ElTy))
801 // If they are really different, now that they are the same type, then we
802 // found a difference!
803 if (cast<ConstantInt>(C1)->getSExtValue() <
804 cast<ConstantInt>(C2)->getSExtValue())
810 /// evaluateFCmpRelation - This function determines if there is anything we can
811 /// decide about the two constants provided. This doesn't need to handle simple
812 /// things like ConstantFP comparisons, but should instead handle ConstantExprs.
813 /// If we can determine that the two constants have a particular relation to
814 /// each other, we should return the corresponding FCmpInst predicate,
815 /// otherwise return FCmpInst::BAD_FCMP_PREDICATE. This is used below in
816 /// ConstantFoldCompareInstruction.
818 /// To simplify this code we canonicalize the relation so that the first
819 /// operand is always the most "complex" of the two. We consider ConstantFP
820 /// to be the simplest, and ConstantExprs to be the most complex.
821 static FCmpInst::Predicate evaluateFCmpRelation(const Constant *V1,
822 const Constant *V2) {
823 assert(V1->getType() == V2->getType() &&
824 "Cannot compare values of different types!");
826 // No compile-time operations on this type yet.
827 if (V1->getType() == Type::PPC_FP128Ty)
828 return FCmpInst::BAD_FCMP_PREDICATE;
830 // Handle degenerate case quickly
831 if (V1 == V2) return FCmpInst::FCMP_OEQ;
833 if (!isa<ConstantExpr>(V1)) {
834 if (!isa<ConstantExpr>(V2)) {
835 // We distilled thisUse the standard constant folder for a few cases
837 Constant *C1 = const_cast<Constant*>(V1);
838 Constant *C2 = const_cast<Constant*>(V2);
839 R = dyn_cast<ConstantInt>(
840 ConstantExpr::getFCmp(FCmpInst::FCMP_OEQ, C1, C2));
841 if (R && !R->isZero())
842 return FCmpInst::FCMP_OEQ;
843 R = dyn_cast<ConstantInt>(
844 ConstantExpr::getFCmp(FCmpInst::FCMP_OLT, C1, C2));
845 if (R && !R->isZero())
846 return FCmpInst::FCMP_OLT;
847 R = dyn_cast<ConstantInt>(
848 ConstantExpr::getFCmp(FCmpInst::FCMP_OGT, C1, C2));
849 if (R && !R->isZero())
850 return FCmpInst::FCMP_OGT;
852 // Nothing more we can do
853 return FCmpInst::BAD_FCMP_PREDICATE;
856 // If the first operand is simple and second is ConstantExpr, swap operands.
857 FCmpInst::Predicate SwappedRelation = evaluateFCmpRelation(V2, V1);
858 if (SwappedRelation != FCmpInst::BAD_FCMP_PREDICATE)
859 return FCmpInst::getSwappedPredicate(SwappedRelation);
861 // Ok, the LHS is known to be a constantexpr. The RHS can be any of a
862 // constantexpr or a simple constant.
863 const ConstantExpr *CE1 = cast<ConstantExpr>(V1);
864 switch (CE1->getOpcode()) {
865 case Instruction::FPTrunc:
866 case Instruction::FPExt:
867 case Instruction::UIToFP:
868 case Instruction::SIToFP:
869 // We might be able to do something with these but we don't right now.
875 // There are MANY other foldings that we could perform here. They will
876 // probably be added on demand, as they seem needed.
877 return FCmpInst::BAD_FCMP_PREDICATE;
880 /// evaluateICmpRelation - This function determines if there is anything we can
881 /// decide about the two constants provided. This doesn't need to handle simple
882 /// things like integer comparisons, but should instead handle ConstantExprs
883 /// and GlobalValues. If we can determine that the two constants have a
884 /// particular relation to each other, we should return the corresponding ICmp
885 /// predicate, otherwise return ICmpInst::BAD_ICMP_PREDICATE.
887 /// To simplify this code we canonicalize the relation so that the first
888 /// operand is always the most "complex" of the two. We consider simple
889 /// constants (like ConstantInt) to be the simplest, followed by
890 /// GlobalValues, followed by ConstantExpr's (the most complex).
892 static ICmpInst::Predicate evaluateICmpRelation(const Constant *V1,
895 assert(V1->getType() == V2->getType() &&
896 "Cannot compare different types of values!");
897 if (V1 == V2) return ICmpInst::ICMP_EQ;
899 if (!isa<ConstantExpr>(V1) && !isa<GlobalValue>(V1)) {
900 if (!isa<GlobalValue>(V2) && !isa<ConstantExpr>(V2)) {
901 // We distilled this down to a simple case, use the standard constant
904 Constant *C1 = const_cast<Constant*>(V1);
905 Constant *C2 = const_cast<Constant*>(V2);
906 ICmpInst::Predicate pred = ICmpInst::ICMP_EQ;
907 R = dyn_cast<ConstantInt>(ConstantExpr::getICmp(pred, C1, C2));
908 if (R && !R->isZero())
910 pred = isSigned ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT;
911 R = dyn_cast<ConstantInt>(ConstantExpr::getICmp(pred, C1, C2));
912 if (R && !R->isZero())
914 pred = isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT;
915 R = dyn_cast<ConstantInt>(ConstantExpr::getICmp(pred, C1, C2));
916 if (R && !R->isZero())
919 // If we couldn't figure it out, bail.
920 return ICmpInst::BAD_ICMP_PREDICATE;
923 // If the first operand is simple, swap operands.
924 ICmpInst::Predicate SwappedRelation =
925 evaluateICmpRelation(V2, V1, isSigned);
926 if (SwappedRelation != ICmpInst::BAD_ICMP_PREDICATE)
927 return ICmpInst::getSwappedPredicate(SwappedRelation);
929 } else if (const GlobalValue *CPR1 = dyn_cast<GlobalValue>(V1)) {
930 if (isa<ConstantExpr>(V2)) { // Swap as necessary.
931 ICmpInst::Predicate SwappedRelation =
932 evaluateICmpRelation(V2, V1, isSigned);
933 if (SwappedRelation != ICmpInst::BAD_ICMP_PREDICATE)
934 return ICmpInst::getSwappedPredicate(SwappedRelation);
936 return ICmpInst::BAD_ICMP_PREDICATE;
939 // Now we know that the RHS is a GlobalValue or simple constant,
940 // which (since the types must match) means that it's a ConstantPointerNull.
941 if (const GlobalValue *CPR2 = dyn_cast<GlobalValue>(V2)) {
942 // Don't try to decide equality of aliases.
943 if (!isa<GlobalAlias>(CPR1) && !isa<GlobalAlias>(CPR2))
944 if (!CPR1->hasExternalWeakLinkage() || !CPR2->hasExternalWeakLinkage())
945 return ICmpInst::ICMP_NE;
947 assert(isa<ConstantPointerNull>(V2) && "Canonicalization guarantee!");
948 // GlobalVals can never be null. Don't try to evaluate aliases.
949 if (!CPR1->hasExternalWeakLinkage() && !isa<GlobalAlias>(CPR1))
950 return ICmpInst::ICMP_NE;
953 // Ok, the LHS is known to be a constantexpr. The RHS can be any of a
954 // constantexpr, a CPR, or a simple constant.
955 const ConstantExpr *CE1 = cast<ConstantExpr>(V1);
956 const Constant *CE1Op0 = CE1->getOperand(0);
958 switch (CE1->getOpcode()) {
959 case Instruction::Trunc:
960 case Instruction::FPTrunc:
961 case Instruction::FPExt:
962 case Instruction::FPToUI:
963 case Instruction::FPToSI:
964 break; // We can't evaluate floating point casts or truncations.
966 case Instruction::UIToFP:
967 case Instruction::SIToFP:
968 case Instruction::BitCast:
969 case Instruction::ZExt:
970 case Instruction::SExt:
971 // If the cast is not actually changing bits, and the second operand is a
972 // null pointer, do the comparison with the pre-casted value.
973 if (V2->isNullValue() &&
974 (isa<PointerType>(CE1->getType()) || CE1->getType()->isInteger())) {
975 bool sgnd = isSigned;
976 if (CE1->getOpcode() == Instruction::ZExt) isSigned = false;
977 if (CE1->getOpcode() == Instruction::SExt) isSigned = true;
978 return evaluateICmpRelation(CE1Op0,
979 Constant::getNullValue(CE1Op0->getType()),
983 // If the dest type is a pointer type, and the RHS is a constantexpr cast
984 // from the same type as the src of the LHS, evaluate the inputs. This is
985 // important for things like "icmp eq (cast 4 to int*), (cast 5 to int*)",
986 // which happens a lot in compilers with tagged integers.
987 if (const ConstantExpr *CE2 = dyn_cast<ConstantExpr>(V2))
988 if (CE2->isCast() && isa<PointerType>(CE1->getType()) &&
989 CE1->getOperand(0)->getType() == CE2->getOperand(0)->getType() &&
990 CE1->getOperand(0)->getType()->isInteger()) {
991 bool sgnd = isSigned;
992 if (CE1->getOpcode() == Instruction::ZExt) isSigned = false;
993 if (CE1->getOpcode() == Instruction::SExt) isSigned = true;
994 return evaluateICmpRelation(CE1->getOperand(0), CE2->getOperand(0),
999 case Instruction::GetElementPtr:
1000 // Ok, since this is a getelementptr, we know that the constant has a
1001 // pointer type. Check the various cases.
1002 if (isa<ConstantPointerNull>(V2)) {
1003 // If we are comparing a GEP to a null pointer, check to see if the base
1004 // of the GEP equals the null pointer.
1005 if (const GlobalValue *GV = dyn_cast<GlobalValue>(CE1Op0)) {
1006 if (GV->hasExternalWeakLinkage())
1007 // Weak linkage GVals could be zero or not. We're comparing that
1008 // to null pointer so its greater-or-equal
1009 return isSigned ? ICmpInst::ICMP_SGE : ICmpInst::ICMP_UGE;
1011 // If its not weak linkage, the GVal must have a non-zero address
1012 // so the result is greater-than
1013 return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT;
1014 } else if (isa<ConstantPointerNull>(CE1Op0)) {
1015 // If we are indexing from a null pointer, check to see if we have any
1016 // non-zero indices.
1017 for (unsigned i = 1, e = CE1->getNumOperands(); i != e; ++i)
1018 if (!CE1->getOperand(i)->isNullValue())
1019 // Offsetting from null, must not be equal.
1020 return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT;
1021 // Only zero indexes from null, must still be zero.
1022 return ICmpInst::ICMP_EQ;
1024 // Otherwise, we can't really say if the first operand is null or not.
1025 } else if (const GlobalValue *CPR2 = dyn_cast<GlobalValue>(V2)) {
1026 if (isa<ConstantPointerNull>(CE1Op0)) {
1027 if (CPR2->hasExternalWeakLinkage())
1028 // Weak linkage GVals could be zero or not. We're comparing it to
1029 // a null pointer, so its less-or-equal
1030 return isSigned ? ICmpInst::ICMP_SLE : ICmpInst::ICMP_ULE;
1032 // If its not weak linkage, the GVal must have a non-zero address
1033 // so the result is less-than
1034 return isSigned ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT;
1035 } else if (const GlobalValue *CPR1 = dyn_cast<GlobalValue>(CE1Op0)) {
1037 // If this is a getelementptr of the same global, then it must be
1038 // different. Because the types must match, the getelementptr could
1039 // only have at most one index, and because we fold getelementptr's
1040 // with a single zero index, it must be nonzero.
1041 assert(CE1->getNumOperands() == 2 &&
1042 !CE1->getOperand(1)->isNullValue() &&
1043 "Suprising getelementptr!");
1044 return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT;
1046 // If they are different globals, we don't know what the value is,
1047 // but they can't be equal.
1048 return ICmpInst::ICMP_NE;
1052 const ConstantExpr *CE2 = cast<ConstantExpr>(V2);
1053 const Constant *CE2Op0 = CE2->getOperand(0);
1055 // There are MANY other foldings that we could perform here. They will
1056 // probably be added on demand, as they seem needed.
1057 switch (CE2->getOpcode()) {
1059 case Instruction::GetElementPtr:
1060 // By far the most common case to handle is when the base pointers are
1061 // obviously to the same or different globals.
1062 if (isa<GlobalValue>(CE1Op0) && isa<GlobalValue>(CE2Op0)) {
1063 if (CE1Op0 != CE2Op0) // Don't know relative ordering, but not equal
1064 return ICmpInst::ICMP_NE;
1065 // Ok, we know that both getelementptr instructions are based on the
1066 // same global. From this, we can precisely determine the relative
1067 // ordering of the resultant pointers.
1070 // Compare all of the operands the GEP's have in common.
1071 gep_type_iterator GTI = gep_type_begin(CE1);
1072 for (;i != CE1->getNumOperands() && i != CE2->getNumOperands();
1074 switch (IdxCompare(CE1->getOperand(i), CE2->getOperand(i),
1075 GTI.getIndexedType())) {
1076 case -1: return isSigned ? ICmpInst::ICMP_SLT:ICmpInst::ICMP_ULT;
1077 case 1: return isSigned ? ICmpInst::ICMP_SGT:ICmpInst::ICMP_UGT;
1078 case -2: return ICmpInst::BAD_ICMP_PREDICATE;
1081 // Ok, we ran out of things they have in common. If any leftovers
1082 // are non-zero then we have a difference, otherwise we are equal.
1083 for (; i < CE1->getNumOperands(); ++i)
1084 if (!CE1->getOperand(i)->isNullValue())
1085 if (isa<ConstantInt>(CE1->getOperand(i)))
1086 return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT;
1088 return ICmpInst::BAD_ICMP_PREDICATE; // Might be equal.
1090 for (; i < CE2->getNumOperands(); ++i)
1091 if (!CE2->getOperand(i)->isNullValue())
1092 if (isa<ConstantInt>(CE2->getOperand(i)))
1093 return isSigned ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT;
1095 return ICmpInst::BAD_ICMP_PREDICATE; // Might be equal.
1096 return ICmpInst::ICMP_EQ;
1105 return ICmpInst::BAD_ICMP_PREDICATE;
1108 Constant *llvm::ConstantFoldCompareInstruction(unsigned short pred,
1110 const Constant *C2) {
1112 // Handle some degenerate cases first
1113 if (isa<UndefValue>(C1) || isa<UndefValue>(C2))
1114 return UndefValue::get(Type::Int1Ty);
1116 // No compile-time operations on this type yet.
1117 if (C1->getType() == Type::PPC_FP128Ty)
1120 // icmp eq/ne(null,GV) -> false/true
1121 if (C1->isNullValue()) {
1122 if (const GlobalValue *GV = dyn_cast<GlobalValue>(C2))
1123 // Don't try to evaluate aliases. External weak GV can be null.
1124 if (!isa<GlobalAlias>(GV) && !GV->hasExternalWeakLinkage())
1125 if (pred == ICmpInst::ICMP_EQ)
1126 return ConstantInt::getFalse();
1127 else if (pred == ICmpInst::ICMP_NE)
1128 return ConstantInt::getTrue();
1129 // icmp eq/ne(GV,null) -> false/true
1130 } else if (C2->isNullValue()) {
1131 if (const GlobalValue *GV = dyn_cast<GlobalValue>(C1))
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();
1140 if (isa<ConstantInt>(C1) && isa<ConstantInt>(C2)) {
1141 APInt V1 = cast<ConstantInt>(C1)->getValue();
1142 APInt V2 = cast<ConstantInt>(C2)->getValue();
1144 default: assert(0 && "Invalid ICmp Predicate"); return 0;
1145 case ICmpInst::ICMP_EQ: return ConstantInt::get(Type::Int1Ty, V1 == V2);
1146 case ICmpInst::ICMP_NE: return ConstantInt::get(Type::Int1Ty, V1 != V2);
1147 case ICmpInst::ICMP_SLT:return ConstantInt::get(Type::Int1Ty, V1.slt(V2));
1148 case ICmpInst::ICMP_SGT:return ConstantInt::get(Type::Int1Ty, V1.sgt(V2));
1149 case ICmpInst::ICMP_SLE:return ConstantInt::get(Type::Int1Ty, V1.sle(V2));
1150 case ICmpInst::ICMP_SGE:return ConstantInt::get(Type::Int1Ty, V1.sge(V2));
1151 case ICmpInst::ICMP_ULT:return ConstantInt::get(Type::Int1Ty, V1.ult(V2));
1152 case ICmpInst::ICMP_UGT:return ConstantInt::get(Type::Int1Ty, V1.ugt(V2));
1153 case ICmpInst::ICMP_ULE:return ConstantInt::get(Type::Int1Ty, V1.ule(V2));
1154 case ICmpInst::ICMP_UGE:return ConstantInt::get(Type::Int1Ty, V1.uge(V2));
1156 } else if (isa<ConstantFP>(C1) && isa<ConstantFP>(C2)) {
1157 APFloat C1V = cast<ConstantFP>(C1)->getValueAPF();
1158 APFloat C2V = cast<ConstantFP>(C2)->getValueAPF();
1159 APFloat::cmpResult R = C1V.compare(C2V);
1161 default: assert(0 && "Invalid FCmp Predicate"); return 0;
1162 case FCmpInst::FCMP_FALSE: return ConstantInt::getFalse();
1163 case FCmpInst::FCMP_TRUE: return ConstantInt::getTrue();
1164 case FCmpInst::FCMP_UNO:
1165 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpUnordered);
1166 case FCmpInst::FCMP_ORD:
1167 return ConstantInt::get(Type::Int1Ty, R!=APFloat::cmpUnordered);
1168 case FCmpInst::FCMP_UEQ:
1169 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpUnordered ||
1170 R==APFloat::cmpEqual);
1171 case FCmpInst::FCMP_OEQ:
1172 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpEqual);
1173 case FCmpInst::FCMP_UNE:
1174 return ConstantInt::get(Type::Int1Ty, R!=APFloat::cmpEqual);
1175 case FCmpInst::FCMP_ONE:
1176 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpLessThan ||
1177 R==APFloat::cmpGreaterThan);
1178 case FCmpInst::FCMP_ULT:
1179 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpUnordered ||
1180 R==APFloat::cmpLessThan);
1181 case FCmpInst::FCMP_OLT:
1182 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpLessThan);
1183 case FCmpInst::FCMP_UGT:
1184 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpUnordered ||
1185 R==APFloat::cmpGreaterThan);
1186 case FCmpInst::FCMP_OGT:
1187 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpGreaterThan);
1188 case FCmpInst::FCMP_ULE:
1189 return ConstantInt::get(Type::Int1Ty, R!=APFloat::cmpGreaterThan);
1190 case FCmpInst::FCMP_OLE:
1191 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpLessThan ||
1192 R==APFloat::cmpEqual);
1193 case FCmpInst::FCMP_UGE:
1194 return ConstantInt::get(Type::Int1Ty, R!=APFloat::cmpLessThan);
1195 case FCmpInst::FCMP_OGE:
1196 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpGreaterThan ||
1197 R==APFloat::cmpEqual);
1199 } else if (const ConstantVector *CP1 = dyn_cast<ConstantVector>(C1)) {
1200 if (const ConstantVector *CP2 = dyn_cast<ConstantVector>(C2)) {
1201 if (pred == FCmpInst::FCMP_OEQ || pred == FCmpInst::FCMP_UEQ) {
1202 for (unsigned i = 0, e = CP1->getNumOperands(); i != e; ++i) {
1203 Constant *C= ConstantExpr::getFCmp(FCmpInst::FCMP_OEQ,
1204 const_cast<Constant*>(CP1->getOperand(i)),
1205 const_cast<Constant*>(CP2->getOperand(i)));
1206 if (ConstantInt *CB = dyn_cast<ConstantInt>(C))
1209 // Otherwise, could not decide from any element pairs.
1211 } else if (pred == ICmpInst::ICMP_EQ) {
1212 for (unsigned i = 0, e = CP1->getNumOperands(); i != e; ++i) {
1213 Constant *C = ConstantExpr::getICmp(ICmpInst::ICMP_EQ,
1214 const_cast<Constant*>(CP1->getOperand(i)),
1215 const_cast<Constant*>(CP2->getOperand(i)));
1216 if (ConstantInt *CB = dyn_cast<ConstantInt>(C))
1219 // Otherwise, could not decide from any element pairs.
1225 if (C1->getType()->isFloatingPoint()) {
1226 switch (evaluateFCmpRelation(C1, C2)) {
1227 default: assert(0 && "Unknown relation!");
1228 case FCmpInst::FCMP_UNO:
1229 case FCmpInst::FCMP_ORD:
1230 case FCmpInst::FCMP_UEQ:
1231 case FCmpInst::FCMP_UNE:
1232 case FCmpInst::FCMP_ULT:
1233 case FCmpInst::FCMP_UGT:
1234 case FCmpInst::FCMP_ULE:
1235 case FCmpInst::FCMP_UGE:
1236 case FCmpInst::FCMP_TRUE:
1237 case FCmpInst::FCMP_FALSE:
1238 case FCmpInst::BAD_FCMP_PREDICATE:
1239 break; // Couldn't determine anything about these constants.
1240 case FCmpInst::FCMP_OEQ: // We know that C1 == C2
1241 return ConstantInt::get(Type::Int1Ty,
1242 pred == FCmpInst::FCMP_UEQ || pred == FCmpInst::FCMP_OEQ ||
1243 pred == FCmpInst::FCMP_ULE || pred == FCmpInst::FCMP_OLE ||
1244 pred == FCmpInst::FCMP_UGE || pred == FCmpInst::FCMP_OGE);
1245 case FCmpInst::FCMP_OLT: // We know that C1 < C2
1246 return ConstantInt::get(Type::Int1Ty,
1247 pred == FCmpInst::FCMP_UNE || pred == FCmpInst::FCMP_ONE ||
1248 pred == FCmpInst::FCMP_ULT || pred == FCmpInst::FCMP_OLT ||
1249 pred == FCmpInst::FCMP_ULE || pred == FCmpInst::FCMP_OLE);
1250 case FCmpInst::FCMP_OGT: // We know that C1 > C2
1251 return ConstantInt::get(Type::Int1Ty,
1252 pred == FCmpInst::FCMP_UNE || pred == FCmpInst::FCMP_ONE ||
1253 pred == FCmpInst::FCMP_UGT || pred == FCmpInst::FCMP_OGT ||
1254 pred == FCmpInst::FCMP_UGE || pred == FCmpInst::FCMP_OGE);
1255 case FCmpInst::FCMP_OLE: // We know that C1 <= C2
1256 // We can only partially decide this relation.
1257 if (pred == FCmpInst::FCMP_UGT || pred == FCmpInst::FCMP_OGT)
1258 return ConstantInt::getFalse();
1259 if (pred == FCmpInst::FCMP_ULT || pred == FCmpInst::FCMP_OLT)
1260 return ConstantInt::getTrue();
1262 case FCmpInst::FCMP_OGE: // We known that C1 >= C2
1263 // We can only partially decide this relation.
1264 if (pred == FCmpInst::FCMP_ULT || pred == FCmpInst::FCMP_OLT)
1265 return ConstantInt::getFalse();
1266 if (pred == FCmpInst::FCMP_UGT || pred == FCmpInst::FCMP_OGT)
1267 return ConstantInt::getTrue();
1269 case ICmpInst::ICMP_NE: // We know that C1 != C2
1270 // We can only partially decide this relation.
1271 if (pred == FCmpInst::FCMP_OEQ || pred == FCmpInst::FCMP_UEQ)
1272 return ConstantInt::getFalse();
1273 if (pred == FCmpInst::FCMP_ONE || pred == FCmpInst::FCMP_UNE)
1274 return ConstantInt::getTrue();
1278 // Evaluate the relation between the two constants, per the predicate.
1279 switch (evaluateICmpRelation(C1, C2, CmpInst::isSigned(pred))) {
1280 default: assert(0 && "Unknown relational!");
1281 case ICmpInst::BAD_ICMP_PREDICATE:
1282 break; // Couldn't determine anything about these constants.
1283 case ICmpInst::ICMP_EQ: // We know the constants are equal!
1284 // If we know the constants are equal, we can decide the result of this
1285 // computation precisely.
1286 return ConstantInt::get(Type::Int1Ty,
1287 pred == ICmpInst::ICMP_EQ ||
1288 pred == ICmpInst::ICMP_ULE ||
1289 pred == ICmpInst::ICMP_SLE ||
1290 pred == ICmpInst::ICMP_UGE ||
1291 pred == ICmpInst::ICMP_SGE);
1292 case ICmpInst::ICMP_ULT:
1293 // If we know that C1 < C2, we can decide the result of this computation
1295 return ConstantInt::get(Type::Int1Ty,
1296 pred == ICmpInst::ICMP_ULT ||
1297 pred == ICmpInst::ICMP_NE ||
1298 pred == ICmpInst::ICMP_ULE);
1299 case ICmpInst::ICMP_SLT:
1300 // If we know that C1 < C2, we can decide the result of this computation
1302 return ConstantInt::get(Type::Int1Ty,
1303 pred == ICmpInst::ICMP_SLT ||
1304 pred == ICmpInst::ICMP_NE ||
1305 pred == ICmpInst::ICMP_SLE);
1306 case ICmpInst::ICMP_UGT:
1307 // If we know that C1 > C2, we can decide the result of this computation
1309 return ConstantInt::get(Type::Int1Ty,
1310 pred == ICmpInst::ICMP_UGT ||
1311 pred == ICmpInst::ICMP_NE ||
1312 pred == ICmpInst::ICMP_UGE);
1313 case ICmpInst::ICMP_SGT:
1314 // If we know that C1 > C2, we can decide the result of this computation
1316 return ConstantInt::get(Type::Int1Ty,
1317 pred == ICmpInst::ICMP_SGT ||
1318 pred == ICmpInst::ICMP_NE ||
1319 pred == ICmpInst::ICMP_SGE);
1320 case ICmpInst::ICMP_ULE:
1321 // If we know that C1 <= C2, we can only partially decide this relation.
1322 if (pred == ICmpInst::ICMP_UGT) return ConstantInt::getFalse();
1323 if (pred == ICmpInst::ICMP_ULT) return ConstantInt::getTrue();
1325 case ICmpInst::ICMP_SLE:
1326 // If we know that C1 <= C2, we can only partially decide this relation.
1327 if (pred == ICmpInst::ICMP_SGT) return ConstantInt::getFalse();
1328 if (pred == ICmpInst::ICMP_SLT) return ConstantInt::getTrue();
1331 case ICmpInst::ICMP_UGE:
1332 // If we know that C1 >= C2, we can only partially decide this relation.
1333 if (pred == ICmpInst::ICMP_ULT) return ConstantInt::getFalse();
1334 if (pred == ICmpInst::ICMP_UGT) return ConstantInt::getTrue();
1336 case ICmpInst::ICMP_SGE:
1337 // If we know that C1 >= C2, we can only partially decide this relation.
1338 if (pred == ICmpInst::ICMP_SLT) return ConstantInt::getFalse();
1339 if (pred == ICmpInst::ICMP_SGT) return ConstantInt::getTrue();
1342 case ICmpInst::ICMP_NE:
1343 // If we know that C1 != C2, we can only partially decide this relation.
1344 if (pred == ICmpInst::ICMP_EQ) return ConstantInt::getFalse();
1345 if (pred == ICmpInst::ICMP_NE) return ConstantInt::getTrue();
1349 if (!isa<ConstantExpr>(C1) && isa<ConstantExpr>(C2)) {
1350 // If C2 is a constant expr and C1 isn't, flop them around and fold the
1351 // other way if possible.
1353 case ICmpInst::ICMP_EQ:
1354 case ICmpInst::ICMP_NE:
1355 // No change of predicate required.
1356 return ConstantFoldCompareInstruction(pred, C2, C1);
1358 case ICmpInst::ICMP_ULT:
1359 case ICmpInst::ICMP_SLT:
1360 case ICmpInst::ICMP_UGT:
1361 case ICmpInst::ICMP_SGT:
1362 case ICmpInst::ICMP_ULE:
1363 case ICmpInst::ICMP_SLE:
1364 case ICmpInst::ICMP_UGE:
1365 case ICmpInst::ICMP_SGE:
1366 // Change the predicate as necessary to swap the operands.
1367 pred = ICmpInst::getSwappedPredicate((ICmpInst::Predicate)pred);
1368 return ConstantFoldCompareInstruction(pred, C2, C1);
1370 default: // These predicates cannot be flopped around.
1378 Constant *llvm::ConstantFoldGetElementPtr(const Constant *C,
1379 Constant* const *Idxs,
1382 (NumIdx == 1 && Idxs[0]->isNullValue()))
1383 return const_cast<Constant*>(C);
1385 if (isa<UndefValue>(C)) {
1386 const PointerType *Ptr = cast<PointerType>(C->getType());
1387 const Type *Ty = GetElementPtrInst::getIndexedType(Ptr,
1389 (Value **)Idxs+NumIdx,
1391 assert(Ty != 0 && "Invalid indices for GEP!");
1392 return UndefValue::get(PointerType::get(Ty, Ptr->getAddressSpace()));
1395 Constant *Idx0 = Idxs[0];
1396 if (C->isNullValue()) {
1398 for (unsigned i = 0, e = NumIdx; i != e; ++i)
1399 if (!Idxs[i]->isNullValue()) {
1404 const PointerType *Ptr = cast<PointerType>(C->getType());
1405 const Type *Ty = GetElementPtrInst::getIndexedType(Ptr,
1407 (Value**)Idxs+NumIdx,
1409 assert(Ty != 0 && "Invalid indices for GEP!");
1411 ConstantPointerNull::get(PointerType::get(Ty,Ptr->getAddressSpace()));
1415 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(const_cast<Constant*>(C))) {
1416 // Combine Indices - If the source pointer to this getelementptr instruction
1417 // is a getelementptr instruction, combine the indices of the two
1418 // getelementptr instructions into a single instruction.
1420 if (CE->getOpcode() == Instruction::GetElementPtr) {
1421 const Type *LastTy = 0;
1422 for (gep_type_iterator I = gep_type_begin(CE), E = gep_type_end(CE);
1426 if ((LastTy && isa<ArrayType>(LastTy)) || Idx0->isNullValue()) {
1427 SmallVector<Value*, 16> NewIndices;
1428 NewIndices.reserve(NumIdx + CE->getNumOperands());
1429 for (unsigned i = 1, e = CE->getNumOperands()-1; i != e; ++i)
1430 NewIndices.push_back(CE->getOperand(i));
1432 // Add the last index of the source with the first index of the new GEP.
1433 // Make sure to handle the case when they are actually different types.
1434 Constant *Combined = CE->getOperand(CE->getNumOperands()-1);
1435 // Otherwise it must be an array.
1436 if (!Idx0->isNullValue()) {
1437 const Type *IdxTy = Combined->getType();
1438 if (IdxTy != Idx0->getType()) {
1439 Constant *C1 = ConstantExpr::getSExtOrBitCast(Idx0, Type::Int64Ty);
1440 Constant *C2 = ConstantExpr::getSExtOrBitCast(Combined,
1442 Combined = ConstantExpr::get(Instruction::Add, C1, C2);
1445 ConstantExpr::get(Instruction::Add, Idx0, Combined);
1449 NewIndices.push_back(Combined);
1450 NewIndices.insert(NewIndices.end(), Idxs+1, Idxs+NumIdx);
1451 return ConstantExpr::getGetElementPtr(CE->getOperand(0), &NewIndices[0],
1456 // Implement folding of:
1457 // int* getelementptr ([2 x int]* cast ([3 x int]* %X to [2 x int]*),
1459 // To: int* getelementptr ([3 x int]* %X, long 0, long 0)
1461 if (CE->isCast() && NumIdx > 1 && Idx0->isNullValue()) {
1462 if (const PointerType *SPT =
1463 dyn_cast<PointerType>(CE->getOperand(0)->getType()))
1464 if (const ArrayType *SAT = dyn_cast<ArrayType>(SPT->getElementType()))
1465 if (const ArrayType *CAT =
1466 dyn_cast<ArrayType>(cast<PointerType>(C->getType())->getElementType()))
1467 if (CAT->getElementType() == SAT->getElementType())
1468 return ConstantExpr::getGetElementPtr(
1469 (Constant*)CE->getOperand(0), Idxs, NumIdx);
1472 // Fold: getelementptr (i8* inttoptr (i64 1 to i8*), i32 -1)
1473 // Into: inttoptr (i64 0 to i8*)
1474 // This happens with pointers to member functions in C++.
1475 if (CE->getOpcode() == Instruction::IntToPtr && NumIdx == 1 &&
1476 isa<ConstantInt>(CE->getOperand(0)) && isa<ConstantInt>(Idxs[0]) &&
1477 cast<PointerType>(CE->getType())->getElementType() == Type::Int8Ty) {
1478 Constant *Base = CE->getOperand(0);
1479 Constant *Offset = Idxs[0];
1481 // Convert the smaller integer to the larger type.
1482 if (Offset->getType()->getPrimitiveSizeInBits() <
1483 Base->getType()->getPrimitiveSizeInBits())
1484 Offset = ConstantExpr::getSExt(Offset, Base->getType());
1485 else if (Base->getType()->getPrimitiveSizeInBits() <
1486 Offset->getType()->getPrimitiveSizeInBits())
1487 Base = ConstantExpr::getZExt(Base, Base->getType());
1489 Base = ConstantExpr::getAdd(Base, Offset);
1490 return ConstantExpr::getIntToPtr(Base, CE->getType());