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 // [us]itofp(undef) = 0, because the result value is bounded.
179 if (opc == Instruction::ZExt || opc == Instruction::SExt ||
180 opc == Instruction::UIToFP || opc == Instruction::SIToFP)
181 return Constant::getNullValue(DestTy);
182 return UndefValue::get(DestTy);
184 // No compile-time operations on this type yet.
185 if (V->getType() == Type::PPC_FP128Ty || DestTy == Type::PPC_FP128Ty)
188 // If the cast operand is a constant expression, there's a few things we can
189 // do to try to simplify it.
190 if (const ConstantExpr *CE = dyn_cast<ConstantExpr>(V)) {
192 // Try hard to fold cast of cast because they are often eliminable.
193 if (unsigned newOpc = foldConstantCastPair(opc, CE, DestTy))
194 return ConstantExpr::getCast(newOpc, CE->getOperand(0), DestTy);
195 } else if (CE->getOpcode() == Instruction::GetElementPtr) {
196 // If all of the indexes in the GEP are null values, there is no pointer
197 // adjustment going on. We might as well cast the source pointer.
198 bool isAllNull = true;
199 for (unsigned i = 1, e = CE->getNumOperands(); i != e; ++i)
200 if (!CE->getOperand(i)->isNullValue()) {
205 // This is casting one pointer type to another, always BitCast
206 return ConstantExpr::getPointerCast(CE->getOperand(0), DestTy);
210 // We actually have to do a cast now. Perform the cast according to the
213 case Instruction::FPTrunc:
214 case Instruction::FPExt:
215 if (const ConstantFP *FPC = dyn_cast<ConstantFP>(V)) {
216 APFloat Val = FPC->getValueAPF();
217 Val.convert(DestTy == Type::FloatTy ? APFloat::IEEEsingle :
218 DestTy == Type::DoubleTy ? APFloat::IEEEdouble :
219 DestTy == Type::X86_FP80Ty ? APFloat::x87DoubleExtended :
220 DestTy == Type::FP128Ty ? APFloat::IEEEquad :
222 APFloat::rmNearestTiesToEven);
223 return ConstantFP::get(DestTy, Val);
225 return 0; // Can't fold.
226 case Instruction::FPToUI:
227 case Instruction::FPToSI:
228 if (const ConstantFP *FPC = dyn_cast<ConstantFP>(V)) {
229 const APFloat &V = FPC->getValueAPF();
231 uint32_t DestBitWidth = cast<IntegerType>(DestTy)->getBitWidth();
232 (void) V.convertToInteger(x, DestBitWidth, opc==Instruction::FPToSI,
233 APFloat::rmTowardZero);
234 APInt Val(DestBitWidth, 2, x);
235 return ConstantInt::get(Val);
237 if (const ConstantVector *CV = dyn_cast<ConstantVector>(V)) {
238 std::vector<Constant*> res;
239 const VectorType *DestVecTy = cast<VectorType>(DestTy);
240 const Type *DstEltTy = DestVecTy->getElementType();
241 for (unsigned i = 0, e = CV->getType()->getNumElements(); i != e; ++i)
242 res.push_back(ConstantFoldCastInstruction(opc, V->getOperand(i),
244 return ConstantVector::get(DestVecTy, res);
246 return 0; // Can't fold.
247 case Instruction::IntToPtr: //always treated as unsigned
248 if (V->isNullValue()) // Is it an integral null value?
249 return ConstantPointerNull::get(cast<PointerType>(DestTy));
250 return 0; // Other pointer types cannot be casted
251 case Instruction::PtrToInt: // always treated as unsigned
252 if (V->isNullValue()) // is it a null pointer value?
253 return ConstantInt::get(DestTy, 0);
254 return 0; // Other pointer types cannot be casted
255 case Instruction::UIToFP:
256 case Instruction::SIToFP:
257 if (const ConstantInt *CI = dyn_cast<ConstantInt>(V)) {
258 APInt api = CI->getValue();
259 const uint64_t zero[] = {0, 0};
260 uint32_t BitWidth = cast<IntegerType>(SrcTy)->getBitWidth();
261 APFloat apf = APFloat(APInt(DestTy->getPrimitiveSizeInBits(),
263 (void)apf.convertFromZeroExtendedInteger(api.getRawData(), BitWidth,
264 opc==Instruction::SIToFP,
265 APFloat::rmNearestTiesToEven);
266 return ConstantFP::get(DestTy, apf);
268 if (const ConstantVector *CV = dyn_cast<ConstantVector>(V)) {
269 std::vector<Constant*> res;
270 const VectorType *DestVecTy = cast<VectorType>(DestTy);
271 const Type *DstEltTy = DestVecTy->getElementType();
272 for (unsigned i = 0, e = CV->getType()->getNumElements(); i != e; ++i)
273 res.push_back(ConstantFoldCastInstruction(opc, V->getOperand(i),
275 return ConstantVector::get(DestVecTy, res);
278 case Instruction::ZExt:
279 if (const ConstantInt *CI = dyn_cast<ConstantInt>(V)) {
280 uint32_t BitWidth = cast<IntegerType>(DestTy)->getBitWidth();
281 APInt Result(CI->getValue());
282 Result.zext(BitWidth);
283 return ConstantInt::get(Result);
286 case Instruction::SExt:
287 if (const ConstantInt *CI = dyn_cast<ConstantInt>(V)) {
288 uint32_t BitWidth = cast<IntegerType>(DestTy)->getBitWidth();
289 APInt Result(CI->getValue());
290 Result.sext(BitWidth);
291 return ConstantInt::get(Result);
294 case Instruction::Trunc:
295 if (const ConstantInt *CI = dyn_cast<ConstantInt>(V)) {
296 uint32_t BitWidth = cast<IntegerType>(DestTy)->getBitWidth();
297 APInt Result(CI->getValue());
298 Result.trunc(BitWidth);
299 return ConstantInt::get(Result);
302 case Instruction::BitCast:
303 return FoldBitCast(const_cast<Constant*>(V), DestTy);
305 assert(!"Invalid CE CastInst opcode");
309 assert(0 && "Failed to cast constant expression");
313 Constant *llvm::ConstantFoldSelectInstruction(const Constant *Cond,
315 const Constant *V2) {
316 if (const ConstantInt *CB = dyn_cast<ConstantInt>(Cond))
317 return const_cast<Constant*>(CB->getZExtValue() ? V1 : V2);
319 if (isa<UndefValue>(V1)) return const_cast<Constant*>(V2);
320 if (isa<UndefValue>(V2)) return const_cast<Constant*>(V1);
321 if (isa<UndefValue>(Cond)) return const_cast<Constant*>(V1);
322 if (V1 == V2) return const_cast<Constant*>(V1);
326 Constant *llvm::ConstantFoldExtractElementInstruction(const Constant *Val,
327 const Constant *Idx) {
328 if (isa<UndefValue>(Val)) // ee(undef, x) -> undef
329 return UndefValue::get(cast<VectorType>(Val->getType())->getElementType());
330 if (Val->isNullValue()) // ee(zero, x) -> zero
331 return Constant::getNullValue(
332 cast<VectorType>(Val->getType())->getElementType());
334 if (const ConstantVector *CVal = dyn_cast<ConstantVector>(Val)) {
335 if (const ConstantInt *CIdx = dyn_cast<ConstantInt>(Idx)) {
336 return const_cast<Constant*>(CVal->getOperand(CIdx->getZExtValue()));
337 } else if (isa<UndefValue>(Idx)) {
338 // ee({w,x,y,z}, undef) -> w (an arbitrary value).
339 return const_cast<Constant*>(CVal->getOperand(0));
345 Constant *llvm::ConstantFoldInsertElementInstruction(const Constant *Val,
347 const Constant *Idx) {
348 const ConstantInt *CIdx = dyn_cast<ConstantInt>(Idx);
350 APInt idxVal = CIdx->getValue();
351 if (isa<UndefValue>(Val)) {
352 // Insertion of scalar constant into vector undef
353 // Optimize away insertion of undef
354 if (isa<UndefValue>(Elt))
355 return const_cast<Constant*>(Val);
356 // Otherwise break the aggregate undef into multiple undefs and do
359 cast<VectorType>(Val->getType())->getNumElements();
360 std::vector<Constant*> Ops;
362 for (unsigned i = 0; i < numOps; ++i) {
364 (idxVal == i) ? Elt : UndefValue::get(Elt->getType());
365 Ops.push_back(const_cast<Constant*>(Op));
367 return ConstantVector::get(Ops);
369 if (isa<ConstantAggregateZero>(Val)) {
370 // Insertion of scalar constant into vector aggregate zero
371 // Optimize away insertion of zero
372 if (Elt->isNullValue())
373 return const_cast<Constant*>(Val);
374 // Otherwise break the aggregate zero into multiple zeros and do
377 cast<VectorType>(Val->getType())->getNumElements();
378 std::vector<Constant*> Ops;
380 for (unsigned i = 0; i < numOps; ++i) {
382 (idxVal == i) ? Elt : Constant::getNullValue(Elt->getType());
383 Ops.push_back(const_cast<Constant*>(Op));
385 return ConstantVector::get(Ops);
387 if (const ConstantVector *CVal = dyn_cast<ConstantVector>(Val)) {
388 // Insertion of scalar constant into vector constant
389 std::vector<Constant*> Ops;
390 Ops.reserve(CVal->getNumOperands());
391 for (unsigned i = 0; i < CVal->getNumOperands(); ++i) {
393 (idxVal == i) ? Elt : cast<Constant>(CVal->getOperand(i));
394 Ops.push_back(const_cast<Constant*>(Op));
396 return ConstantVector::get(Ops);
401 /// GetVectorElement - If C is a ConstantVector, ConstantAggregateZero or Undef
402 /// return the specified element value. Otherwise return null.
403 static Constant *GetVectorElement(const Constant *C, unsigned EltNo) {
404 if (const ConstantVector *CV = dyn_cast<ConstantVector>(C))
405 return const_cast<Constant*>(CV->getOperand(EltNo));
407 const Type *EltTy = cast<VectorType>(C->getType())->getElementType();
408 if (isa<ConstantAggregateZero>(C))
409 return Constant::getNullValue(EltTy);
410 if (isa<UndefValue>(C))
411 return UndefValue::get(EltTy);
415 Constant *llvm::ConstantFoldShuffleVectorInstruction(const Constant *V1,
417 const Constant *Mask) {
418 // Undefined shuffle mask -> undefined value.
419 if (isa<UndefValue>(Mask)) return UndefValue::get(V1->getType());
421 unsigned NumElts = cast<VectorType>(V1->getType())->getNumElements();
422 const Type *EltTy = cast<VectorType>(V1->getType())->getElementType();
424 // Loop over the shuffle mask, evaluating each element.
425 SmallVector<Constant*, 32> Result;
426 for (unsigned i = 0; i != NumElts; ++i) {
427 Constant *InElt = GetVectorElement(Mask, i);
428 if (InElt == 0) return 0;
430 if (isa<UndefValue>(InElt))
431 InElt = UndefValue::get(EltTy);
432 else if (ConstantInt *CI = dyn_cast<ConstantInt>(InElt)) {
433 unsigned Elt = CI->getZExtValue();
434 if (Elt >= NumElts*2)
435 InElt = UndefValue::get(EltTy);
436 else if (Elt >= NumElts)
437 InElt = GetVectorElement(V2, Elt-NumElts);
439 InElt = GetVectorElement(V1, Elt);
440 if (InElt == 0) return 0;
445 Result.push_back(InElt);
448 return ConstantVector::get(&Result[0], Result.size());
451 /// EvalVectorOp - Given two vector constants and a function pointer, apply the
452 /// function pointer to each element pair, producing a new ConstantVector
453 /// constant. Either or both of V1 and V2 may be NULL, meaning a
454 /// ConstantAggregateZero operand.
455 static Constant *EvalVectorOp(const ConstantVector *V1,
456 const ConstantVector *V2,
457 const VectorType *VTy,
458 Constant *(*FP)(Constant*, Constant*)) {
459 std::vector<Constant*> Res;
460 const Type *EltTy = VTy->getElementType();
461 for (unsigned i = 0, e = VTy->getNumElements(); i != e; ++i) {
462 const Constant *C1 = V1 ? V1->getOperand(i) : Constant::getNullValue(EltTy);
463 const Constant *C2 = V2 ? V2->getOperand(i) : Constant::getNullValue(EltTy);
464 Res.push_back(FP(const_cast<Constant*>(C1),
465 const_cast<Constant*>(C2)));
467 return ConstantVector::get(Res);
470 Constant *llvm::ConstantFoldBinaryInstruction(unsigned Opcode,
472 const Constant *C2) {
473 // No compile-time operations on this type yet.
474 if (C1->getType() == Type::PPC_FP128Ty)
477 // Handle UndefValue up front
478 if (isa<UndefValue>(C1) || isa<UndefValue>(C2)) {
480 case Instruction::Add:
481 case Instruction::Sub:
482 case Instruction::Xor:
483 return UndefValue::get(C1->getType());
484 case Instruction::Mul:
485 case Instruction::And:
486 return Constant::getNullValue(C1->getType());
487 case Instruction::UDiv:
488 case Instruction::SDiv:
489 case Instruction::FDiv:
490 case Instruction::URem:
491 case Instruction::SRem:
492 case Instruction::FRem:
493 if (!isa<UndefValue>(C2)) // undef / X -> 0
494 return Constant::getNullValue(C1->getType());
495 return const_cast<Constant*>(C2); // X / undef -> undef
496 case Instruction::Or: // X | undef -> -1
497 if (const VectorType *PTy = dyn_cast<VectorType>(C1->getType()))
498 return ConstantVector::getAllOnesValue(PTy);
499 return ConstantInt::getAllOnesValue(C1->getType());
500 case Instruction::LShr:
501 if (isa<UndefValue>(C2) && isa<UndefValue>(C1))
502 return const_cast<Constant*>(C1); // undef lshr undef -> undef
503 return Constant::getNullValue(C1->getType()); // X lshr undef -> 0
505 case Instruction::AShr:
506 if (!isa<UndefValue>(C2))
507 return const_cast<Constant*>(C1); // undef ashr X --> undef
508 else if (isa<UndefValue>(C1))
509 return const_cast<Constant*>(C1); // undef ashr undef -> undef
511 return const_cast<Constant*>(C1); // X ashr undef --> X
512 case Instruction::Shl:
513 // undef << X -> 0 or X << undef -> 0
514 return Constant::getNullValue(C1->getType());
518 if (const ConstantExpr *CE1 = dyn_cast<ConstantExpr>(C1)) {
519 if (isa<ConstantExpr>(C2)) {
520 // There are many possible foldings we could do here. We should probably
521 // at least fold add of a pointer with an integer into the appropriate
522 // getelementptr. This will improve alias analysis a bit.
524 // Just implement a couple of simple identities.
526 case Instruction::Add:
527 if (C2->isNullValue()) return const_cast<Constant*>(C1); // X + 0 == X
529 case Instruction::Sub:
530 if (C2->isNullValue()) return const_cast<Constant*>(C1); // X - 0 == X
532 case Instruction::Mul:
533 if (C2->isNullValue()) return const_cast<Constant*>(C2); // X * 0 == 0
534 if (const ConstantInt *CI = dyn_cast<ConstantInt>(C2))
535 if (CI->equalsInt(1))
536 return const_cast<Constant*>(C1); // X * 1 == X
538 case Instruction::UDiv:
539 case Instruction::SDiv:
540 if (const ConstantInt *CI = dyn_cast<ConstantInt>(C2))
541 if (CI->equalsInt(1))
542 return const_cast<Constant*>(C1); // X / 1 == X
544 case Instruction::URem:
545 case Instruction::SRem:
546 if (const ConstantInt *CI = dyn_cast<ConstantInt>(C2))
547 if (CI->equalsInt(1))
548 return Constant::getNullValue(CI->getType()); // X % 1 == 0
550 case Instruction::And:
551 if (const ConstantInt *CI = dyn_cast<ConstantInt>(C2)) {
552 if (CI->isZero()) return const_cast<Constant*>(C2); // X & 0 == 0
553 if (CI->isAllOnesValue())
554 return const_cast<Constant*>(C1); // X & -1 == X
556 // (zext i32 to i64) & 4294967295 -> (zext i32 to i64)
557 if (CE1->getOpcode() == Instruction::ZExt) {
558 APInt PossiblySetBits
559 = cast<IntegerType>(CE1->getOperand(0)->getType())->getMask();
560 PossiblySetBits.zext(C1->getType()->getPrimitiveSizeInBits());
561 if ((PossiblySetBits & CI->getValue()) == PossiblySetBits)
562 return const_cast<Constant*>(C1);
565 if (CE1->isCast() && isa<GlobalValue>(CE1->getOperand(0))) {
566 GlobalValue *CPR = cast<GlobalValue>(CE1->getOperand(0));
568 // Functions are at least 4-byte aligned. If and'ing the address of a
569 // function with a constant < 4, fold it to zero.
570 if (const ConstantInt *CI = dyn_cast<ConstantInt>(C2))
571 if (CI->getValue().ult(APInt(CI->getType()->getBitWidth(),4)) &&
573 return Constant::getNullValue(CI->getType());
576 case Instruction::Or:
577 if (C2->isNullValue()) return const_cast<Constant*>(C1); // X | 0 == X
578 if (const ConstantInt *CI = dyn_cast<ConstantInt>(C2))
579 if (CI->isAllOnesValue())
580 return const_cast<Constant*>(C2); // X | -1 == -1
582 case Instruction::Xor:
583 if (C2->isNullValue()) return const_cast<Constant*>(C1); // X ^ 0 == X
585 case Instruction::AShr:
586 // ashr (zext C to Ty), C2 -> lshr (zext C, CSA), C2
587 if (CE1->getOpcode() == Instruction::ZExt) // Top bits known zero.
588 return ConstantExpr::getLShr(const_cast<Constant*>(C1),
589 const_cast<Constant*>(C2));
593 } else if (isa<ConstantExpr>(C2)) {
594 // If C2 is a constant expr and C1 isn't, flop them around and fold the
595 // other way if possible.
597 case Instruction::Add:
598 case Instruction::Mul:
599 case Instruction::And:
600 case Instruction::Or:
601 case Instruction::Xor:
602 // No change of opcode required.
603 return ConstantFoldBinaryInstruction(Opcode, C2, C1);
605 case Instruction::Shl:
606 case Instruction::LShr:
607 case Instruction::AShr:
608 case Instruction::Sub:
609 case Instruction::SDiv:
610 case Instruction::UDiv:
611 case Instruction::FDiv:
612 case Instruction::URem:
613 case Instruction::SRem:
614 case Instruction::FRem:
615 default: // These instructions cannot be flopped around.
620 // At this point we know neither constant is an UndefValue nor a ConstantExpr
621 // so look at directly computing the value.
622 if (const ConstantInt *CI1 = dyn_cast<ConstantInt>(C1)) {
623 if (const ConstantInt *CI2 = dyn_cast<ConstantInt>(C2)) {
624 using namespace APIntOps;
625 APInt C1V = CI1->getValue();
626 APInt C2V = CI2->getValue();
630 case Instruction::Add:
631 return ConstantInt::get(C1V + C2V);
632 case Instruction::Sub:
633 return ConstantInt::get(C1V - C2V);
634 case Instruction::Mul:
635 return ConstantInt::get(C1V * C2V);
636 case Instruction::UDiv:
637 if (CI2->isNullValue())
638 return 0; // X / 0 -> can't fold
639 return ConstantInt::get(C1V.udiv(C2V));
640 case Instruction::SDiv:
641 if (CI2->isNullValue())
642 return 0; // X / 0 -> can't fold
643 if (C2V.isAllOnesValue() && C1V.isMinSignedValue())
644 return 0; // MIN_INT / -1 -> overflow
645 return ConstantInt::get(C1V.sdiv(C2V));
646 case Instruction::URem:
647 if (C2->isNullValue())
648 return 0; // X / 0 -> can't fold
649 return ConstantInt::get(C1V.urem(C2V));
650 case Instruction::SRem:
651 if (CI2->isNullValue())
652 return 0; // X % 0 -> can't fold
653 if (C2V.isAllOnesValue() && C1V.isMinSignedValue())
654 return 0; // MIN_INT % -1 -> overflow
655 return ConstantInt::get(C1V.srem(C2V));
656 case Instruction::And:
657 return ConstantInt::get(C1V & C2V);
658 case Instruction::Or:
659 return ConstantInt::get(C1V | C2V);
660 case Instruction::Xor:
661 return ConstantInt::get(C1V ^ C2V);
662 case Instruction::Shl:
663 if (uint32_t shiftAmt = C2V.getZExtValue()) {
664 if (shiftAmt < C1V.getBitWidth())
665 return ConstantInt::get(C1V.shl(shiftAmt));
667 return UndefValue::get(C1->getType()); // too big shift is undef
669 return const_cast<ConstantInt*>(CI1); // Zero shift is identity
670 case Instruction::LShr:
671 if (uint32_t shiftAmt = C2V.getZExtValue()) {
672 if (shiftAmt < C1V.getBitWidth())
673 return ConstantInt::get(C1V.lshr(shiftAmt));
675 return UndefValue::get(C1->getType()); // too big shift is undef
677 return const_cast<ConstantInt*>(CI1); // Zero shift is identity
678 case Instruction::AShr:
679 if (uint32_t shiftAmt = C2V.getZExtValue()) {
680 if (shiftAmt < C1V.getBitWidth())
681 return ConstantInt::get(C1V.ashr(shiftAmt));
683 return UndefValue::get(C1->getType()); // too big shift is undef
685 return const_cast<ConstantInt*>(CI1); // Zero shift is identity
688 } else if (const ConstantFP *CFP1 = dyn_cast<ConstantFP>(C1)) {
689 if (const ConstantFP *CFP2 = dyn_cast<ConstantFP>(C2)) {
690 APFloat C1V = CFP1->getValueAPF();
691 APFloat C2V = CFP2->getValueAPF();
692 APFloat C3V = C1V; // copy for modification
693 bool isDouble = CFP1->getType()==Type::DoubleTy;
697 case Instruction::Add:
698 (void)C3V.add(C2V, APFloat::rmNearestTiesToEven);
699 return ConstantFP::get(CFP1->getType(), C3V);
700 case Instruction::Sub:
701 (void)C3V.subtract(C2V, APFloat::rmNearestTiesToEven);
702 return ConstantFP::get(CFP1->getType(), C3V);
703 case Instruction::Mul:
704 (void)C3V.multiply(C2V, APFloat::rmNearestTiesToEven);
705 return ConstantFP::get(CFP1->getType(), C3V);
706 case Instruction::FDiv:
707 (void)C3V.divide(C2V, APFloat::rmNearestTiesToEven);
708 return ConstantFP::get(CFP1->getType(), C3V);
709 case Instruction::FRem:
711 // IEEE 754, Section 7.1, #5
712 return ConstantFP::get(CFP1->getType(), isDouble ?
713 APFloat(std::numeric_limits<double>::quiet_NaN()) :
714 APFloat(std::numeric_limits<float>::quiet_NaN()));
715 (void)C3V.mod(C2V, APFloat::rmNearestTiesToEven);
716 return ConstantFP::get(CFP1->getType(), C3V);
719 } else if (const VectorType *VTy = dyn_cast<VectorType>(C1->getType())) {
720 const ConstantVector *CP1 = dyn_cast<ConstantVector>(C1);
721 const ConstantVector *CP2 = dyn_cast<ConstantVector>(C2);
722 if ((CP1 != NULL || isa<ConstantAggregateZero>(C1)) &&
723 (CP2 != NULL || isa<ConstantAggregateZero>(C2))) {
727 case Instruction::Add:
728 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getAdd);
729 case Instruction::Sub:
730 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getSub);
731 case Instruction::Mul:
732 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getMul);
733 case Instruction::UDiv:
734 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getUDiv);
735 case Instruction::SDiv:
736 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getSDiv);
737 case Instruction::FDiv:
738 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getFDiv);
739 case Instruction::URem:
740 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getURem);
741 case Instruction::SRem:
742 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getSRem);
743 case Instruction::FRem:
744 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getFRem);
745 case Instruction::And:
746 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getAnd);
747 case Instruction::Or:
748 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getOr);
749 case Instruction::Xor:
750 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getXor);
755 // We don't know how to fold this
759 /// isZeroSizedType - This type is zero sized if its an array or structure of
760 /// zero sized types. The only leaf zero sized type is an empty structure.
761 static bool isMaybeZeroSizedType(const Type *Ty) {
762 if (isa<OpaqueType>(Ty)) return true; // Can't say.
763 if (const StructType *STy = dyn_cast<StructType>(Ty)) {
765 // If all of elements have zero size, this does too.
766 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i)
767 if (!isMaybeZeroSizedType(STy->getElementType(i))) return false;
770 } else if (const ArrayType *ATy = dyn_cast<ArrayType>(Ty)) {
771 return isMaybeZeroSizedType(ATy->getElementType());
776 /// IdxCompare - Compare the two constants as though they were getelementptr
777 /// indices. This allows coersion of the types to be the same thing.
779 /// If the two constants are the "same" (after coersion), return 0. If the
780 /// first is less than the second, return -1, if the second is less than the
781 /// first, return 1. If the constants are not integral, return -2.
783 static int IdxCompare(Constant *C1, Constant *C2, const Type *ElTy) {
784 if (C1 == C2) return 0;
786 // Ok, we found a different index. If they are not ConstantInt, we can't do
787 // anything with them.
788 if (!isa<ConstantInt>(C1) || !isa<ConstantInt>(C2))
789 return -2; // don't know!
791 // Ok, we have two differing integer indices. Sign extend them to be the same
792 // type. Long is always big enough, so we use it.
793 if (C1->getType() != Type::Int64Ty)
794 C1 = ConstantExpr::getSExt(C1, Type::Int64Ty);
796 if (C2->getType() != Type::Int64Ty)
797 C2 = ConstantExpr::getSExt(C2, Type::Int64Ty);
799 if (C1 == C2) return 0; // They are equal
801 // If the type being indexed over is really just a zero sized type, there is
802 // no pointer difference being made here.
803 if (isMaybeZeroSizedType(ElTy))
806 // If they are really different, now that they are the same type, then we
807 // found a difference!
808 if (cast<ConstantInt>(C1)->getSExtValue() <
809 cast<ConstantInt>(C2)->getSExtValue())
815 /// evaluateFCmpRelation - This function determines if there is anything we can
816 /// decide about the two constants provided. This doesn't need to handle simple
817 /// things like ConstantFP comparisons, but should instead handle ConstantExprs.
818 /// If we can determine that the two constants have a particular relation to
819 /// each other, we should return the corresponding FCmpInst predicate,
820 /// otherwise return FCmpInst::BAD_FCMP_PREDICATE. This is used below in
821 /// ConstantFoldCompareInstruction.
823 /// To simplify this code we canonicalize the relation so that the first
824 /// operand is always the most "complex" of the two. We consider ConstantFP
825 /// to be the simplest, and ConstantExprs to be the most complex.
826 static FCmpInst::Predicate evaluateFCmpRelation(const Constant *V1,
827 const Constant *V2) {
828 assert(V1->getType() == V2->getType() &&
829 "Cannot compare values of different types!");
831 // No compile-time operations on this type yet.
832 if (V1->getType() == Type::PPC_FP128Ty)
833 return FCmpInst::BAD_FCMP_PREDICATE;
835 // Handle degenerate case quickly
836 if (V1 == V2) return FCmpInst::FCMP_OEQ;
838 if (!isa<ConstantExpr>(V1)) {
839 if (!isa<ConstantExpr>(V2)) {
840 // We distilled thisUse the standard constant folder for a few cases
842 Constant *C1 = const_cast<Constant*>(V1);
843 Constant *C2 = const_cast<Constant*>(V2);
844 R = dyn_cast<ConstantInt>(
845 ConstantExpr::getFCmp(FCmpInst::FCMP_OEQ, C1, C2));
846 if (R && !R->isZero())
847 return FCmpInst::FCMP_OEQ;
848 R = dyn_cast<ConstantInt>(
849 ConstantExpr::getFCmp(FCmpInst::FCMP_OLT, C1, C2));
850 if (R && !R->isZero())
851 return FCmpInst::FCMP_OLT;
852 R = dyn_cast<ConstantInt>(
853 ConstantExpr::getFCmp(FCmpInst::FCMP_OGT, C1, C2));
854 if (R && !R->isZero())
855 return FCmpInst::FCMP_OGT;
857 // Nothing more we can do
858 return FCmpInst::BAD_FCMP_PREDICATE;
861 // If the first operand is simple and second is ConstantExpr, swap operands.
862 FCmpInst::Predicate SwappedRelation = evaluateFCmpRelation(V2, V1);
863 if (SwappedRelation != FCmpInst::BAD_FCMP_PREDICATE)
864 return FCmpInst::getSwappedPredicate(SwappedRelation);
866 // Ok, the LHS is known to be a constantexpr. The RHS can be any of a
867 // constantexpr or a simple constant.
868 const ConstantExpr *CE1 = cast<ConstantExpr>(V1);
869 switch (CE1->getOpcode()) {
870 case Instruction::FPTrunc:
871 case Instruction::FPExt:
872 case Instruction::UIToFP:
873 case Instruction::SIToFP:
874 // We might be able to do something with these but we don't right now.
880 // There are MANY other foldings that we could perform here. They will
881 // probably be added on demand, as they seem needed.
882 return FCmpInst::BAD_FCMP_PREDICATE;
885 /// evaluateICmpRelation - This function determines if there is anything we can
886 /// decide about the two constants provided. This doesn't need to handle simple
887 /// things like integer comparisons, but should instead handle ConstantExprs
888 /// and GlobalValues. If we can determine that the two constants have a
889 /// particular relation to each other, we should return the corresponding ICmp
890 /// predicate, otherwise return ICmpInst::BAD_ICMP_PREDICATE.
892 /// To simplify this code we canonicalize the relation so that the first
893 /// operand is always the most "complex" of the two. We consider simple
894 /// constants (like ConstantInt) to be the simplest, followed by
895 /// GlobalValues, followed by ConstantExpr's (the most complex).
897 static ICmpInst::Predicate evaluateICmpRelation(const Constant *V1,
900 assert(V1->getType() == V2->getType() &&
901 "Cannot compare different types of values!");
902 if (V1 == V2) return ICmpInst::ICMP_EQ;
904 if (!isa<ConstantExpr>(V1) && !isa<GlobalValue>(V1)) {
905 if (!isa<GlobalValue>(V2) && !isa<ConstantExpr>(V2)) {
906 // We distilled this down to a simple case, use the standard constant
909 Constant *C1 = const_cast<Constant*>(V1);
910 Constant *C2 = const_cast<Constant*>(V2);
911 ICmpInst::Predicate pred = ICmpInst::ICMP_EQ;
912 R = dyn_cast<ConstantInt>(ConstantExpr::getICmp(pred, C1, C2));
913 if (R && !R->isZero())
915 pred = isSigned ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT;
916 R = dyn_cast<ConstantInt>(ConstantExpr::getICmp(pred, C1, C2));
917 if (R && !R->isZero())
919 pred = isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT;
920 R = dyn_cast<ConstantInt>(ConstantExpr::getICmp(pred, C1, C2));
921 if (R && !R->isZero())
924 // If we couldn't figure it out, bail.
925 return ICmpInst::BAD_ICMP_PREDICATE;
928 // If the first operand is simple, swap operands.
929 ICmpInst::Predicate SwappedRelation =
930 evaluateICmpRelation(V2, V1, isSigned);
931 if (SwappedRelation != ICmpInst::BAD_ICMP_PREDICATE)
932 return ICmpInst::getSwappedPredicate(SwappedRelation);
934 } else if (const GlobalValue *CPR1 = dyn_cast<GlobalValue>(V1)) {
935 if (isa<ConstantExpr>(V2)) { // Swap as necessary.
936 ICmpInst::Predicate SwappedRelation =
937 evaluateICmpRelation(V2, V1, isSigned);
938 if (SwappedRelation != ICmpInst::BAD_ICMP_PREDICATE)
939 return ICmpInst::getSwappedPredicate(SwappedRelation);
941 return ICmpInst::BAD_ICMP_PREDICATE;
944 // Now we know that the RHS is a GlobalValue or simple constant,
945 // which (since the types must match) means that it's a ConstantPointerNull.
946 if (const GlobalValue *CPR2 = dyn_cast<GlobalValue>(V2)) {
947 // Don't try to decide equality of aliases.
948 if (!isa<GlobalAlias>(CPR1) && !isa<GlobalAlias>(CPR2))
949 if (!CPR1->hasExternalWeakLinkage() || !CPR2->hasExternalWeakLinkage())
950 return ICmpInst::ICMP_NE;
952 assert(isa<ConstantPointerNull>(V2) && "Canonicalization guarantee!");
953 // GlobalVals can never be null. Don't try to evaluate aliases.
954 if (!CPR1->hasExternalWeakLinkage() && !isa<GlobalAlias>(CPR1))
955 return ICmpInst::ICMP_NE;
958 // Ok, the LHS is known to be a constantexpr. The RHS can be any of a
959 // constantexpr, a CPR, or a simple constant.
960 const ConstantExpr *CE1 = cast<ConstantExpr>(V1);
961 const Constant *CE1Op0 = CE1->getOperand(0);
963 switch (CE1->getOpcode()) {
964 case Instruction::Trunc:
965 case Instruction::FPTrunc:
966 case Instruction::FPExt:
967 case Instruction::FPToUI:
968 case Instruction::FPToSI:
969 break; // We can't evaluate floating point casts or truncations.
971 case Instruction::UIToFP:
972 case Instruction::SIToFP:
973 case Instruction::BitCast:
974 case Instruction::ZExt:
975 case Instruction::SExt:
976 // If the cast is not actually changing bits, and the second operand is a
977 // null pointer, do the comparison with the pre-casted value.
978 if (V2->isNullValue() &&
979 (isa<PointerType>(CE1->getType()) || CE1->getType()->isInteger())) {
980 bool sgnd = isSigned;
981 if (CE1->getOpcode() == Instruction::ZExt) isSigned = false;
982 if (CE1->getOpcode() == Instruction::SExt) isSigned = true;
983 return evaluateICmpRelation(CE1Op0,
984 Constant::getNullValue(CE1Op0->getType()),
988 // If the dest type is a pointer type, and the RHS is a constantexpr cast
989 // from the same type as the src of the LHS, evaluate the inputs. This is
990 // important for things like "icmp eq (cast 4 to int*), (cast 5 to int*)",
991 // which happens a lot in compilers with tagged integers.
992 if (const ConstantExpr *CE2 = dyn_cast<ConstantExpr>(V2))
993 if (CE2->isCast() && isa<PointerType>(CE1->getType()) &&
994 CE1->getOperand(0)->getType() == CE2->getOperand(0)->getType() &&
995 CE1->getOperand(0)->getType()->isInteger()) {
996 bool sgnd = isSigned;
997 if (CE1->getOpcode() == Instruction::ZExt) isSigned = false;
998 if (CE1->getOpcode() == Instruction::SExt) isSigned = true;
999 return evaluateICmpRelation(CE1->getOperand(0), CE2->getOperand(0),
1004 case Instruction::GetElementPtr:
1005 // Ok, since this is a getelementptr, we know that the constant has a
1006 // pointer type. Check the various cases.
1007 if (isa<ConstantPointerNull>(V2)) {
1008 // If we are comparing a GEP to a null pointer, check to see if the base
1009 // of the GEP equals the null pointer.
1010 if (const GlobalValue *GV = dyn_cast<GlobalValue>(CE1Op0)) {
1011 if (GV->hasExternalWeakLinkage())
1012 // Weak linkage GVals could be zero or not. We're comparing that
1013 // to null pointer so its greater-or-equal
1014 return isSigned ? ICmpInst::ICMP_SGE : ICmpInst::ICMP_UGE;
1016 // If its not weak linkage, the GVal must have a non-zero address
1017 // so the result is greater-than
1018 return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT;
1019 } else if (isa<ConstantPointerNull>(CE1Op0)) {
1020 // If we are indexing from a null pointer, check to see if we have any
1021 // non-zero indices.
1022 for (unsigned i = 1, e = CE1->getNumOperands(); i != e; ++i)
1023 if (!CE1->getOperand(i)->isNullValue())
1024 // Offsetting from null, must not be equal.
1025 return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT;
1026 // Only zero indexes from null, must still be zero.
1027 return ICmpInst::ICMP_EQ;
1029 // Otherwise, we can't really say if the first operand is null or not.
1030 } else if (const GlobalValue *CPR2 = dyn_cast<GlobalValue>(V2)) {
1031 if (isa<ConstantPointerNull>(CE1Op0)) {
1032 if (CPR2->hasExternalWeakLinkage())
1033 // Weak linkage GVals could be zero or not. We're comparing it to
1034 // a null pointer, so its less-or-equal
1035 return isSigned ? ICmpInst::ICMP_SLE : ICmpInst::ICMP_ULE;
1037 // If its not weak linkage, the GVal must have a non-zero address
1038 // so the result is less-than
1039 return isSigned ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT;
1040 } else if (const GlobalValue *CPR1 = dyn_cast<GlobalValue>(CE1Op0)) {
1042 // If this is a getelementptr of the same global, then it must be
1043 // different. Because the types must match, the getelementptr could
1044 // only have at most one index, and because we fold getelementptr's
1045 // with a single zero index, it must be nonzero.
1046 assert(CE1->getNumOperands() == 2 &&
1047 !CE1->getOperand(1)->isNullValue() &&
1048 "Suprising getelementptr!");
1049 return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT;
1051 // If they are different globals, we don't know what the value is,
1052 // but they can't be equal.
1053 return ICmpInst::ICMP_NE;
1057 const ConstantExpr *CE2 = cast<ConstantExpr>(V2);
1058 const Constant *CE2Op0 = CE2->getOperand(0);
1060 // There are MANY other foldings that we could perform here. They will
1061 // probably be added on demand, as they seem needed.
1062 switch (CE2->getOpcode()) {
1064 case Instruction::GetElementPtr:
1065 // By far the most common case to handle is when the base pointers are
1066 // obviously to the same or different globals.
1067 if (isa<GlobalValue>(CE1Op0) && isa<GlobalValue>(CE2Op0)) {
1068 if (CE1Op0 != CE2Op0) // Don't know relative ordering, but not equal
1069 return ICmpInst::ICMP_NE;
1070 // Ok, we know that both getelementptr instructions are based on the
1071 // same global. From this, we can precisely determine the relative
1072 // ordering of the resultant pointers.
1075 // Compare all of the operands the GEP's have in common.
1076 gep_type_iterator GTI = gep_type_begin(CE1);
1077 for (;i != CE1->getNumOperands() && i != CE2->getNumOperands();
1079 switch (IdxCompare(CE1->getOperand(i), CE2->getOperand(i),
1080 GTI.getIndexedType())) {
1081 case -1: return isSigned ? ICmpInst::ICMP_SLT:ICmpInst::ICMP_ULT;
1082 case 1: return isSigned ? ICmpInst::ICMP_SGT:ICmpInst::ICMP_UGT;
1083 case -2: return ICmpInst::BAD_ICMP_PREDICATE;
1086 // Ok, we ran out of things they have in common. If any leftovers
1087 // are non-zero then we have a difference, otherwise we are equal.
1088 for (; i < CE1->getNumOperands(); ++i)
1089 if (!CE1->getOperand(i)->isNullValue()) {
1090 if (isa<ConstantInt>(CE1->getOperand(i)))
1091 return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT;
1093 return ICmpInst::BAD_ICMP_PREDICATE; // Might be equal.
1096 for (; i < CE2->getNumOperands(); ++i)
1097 if (!CE2->getOperand(i)->isNullValue()) {
1098 if (isa<ConstantInt>(CE2->getOperand(i)))
1099 return isSigned ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT;
1101 return ICmpInst::BAD_ICMP_PREDICATE; // Might be equal.
1103 return ICmpInst::ICMP_EQ;
1112 return ICmpInst::BAD_ICMP_PREDICATE;
1115 Constant *llvm::ConstantFoldCompareInstruction(unsigned short pred,
1117 const Constant *C2) {
1119 // Handle some degenerate cases first
1120 if (isa<UndefValue>(C1) || isa<UndefValue>(C2))
1121 return UndefValue::get(Type::Int1Ty);
1123 // No compile-time operations on this type yet.
1124 if (C1->getType() == Type::PPC_FP128Ty)
1127 // icmp eq/ne(null,GV) -> false/true
1128 if (C1->isNullValue()) {
1129 if (const GlobalValue *GV = dyn_cast<GlobalValue>(C2))
1130 // Don't try to evaluate aliases. External weak GV can be null.
1131 if (!isa<GlobalAlias>(GV) && !GV->hasExternalWeakLinkage()) {
1132 if (pred == ICmpInst::ICMP_EQ)
1133 return ConstantInt::getFalse();
1134 else if (pred == ICmpInst::ICMP_NE)
1135 return ConstantInt::getTrue();
1137 // icmp eq/ne(GV,null) -> false/true
1138 } else if (C2->isNullValue()) {
1139 if (const GlobalValue *GV = dyn_cast<GlobalValue>(C1))
1140 // Don't try to evaluate aliases. External weak GV can be null.
1141 if (!isa<GlobalAlias>(GV) && !GV->hasExternalWeakLinkage()) {
1142 if (pred == ICmpInst::ICMP_EQ)
1143 return ConstantInt::getFalse();
1144 else if (pred == ICmpInst::ICMP_NE)
1145 return ConstantInt::getTrue();
1149 if (isa<ConstantInt>(C1) && isa<ConstantInt>(C2)) {
1150 APInt V1 = cast<ConstantInt>(C1)->getValue();
1151 APInt V2 = cast<ConstantInt>(C2)->getValue();
1153 default: assert(0 && "Invalid ICmp Predicate"); return 0;
1154 case ICmpInst::ICMP_EQ: return ConstantInt::get(Type::Int1Ty, V1 == V2);
1155 case ICmpInst::ICMP_NE: return ConstantInt::get(Type::Int1Ty, V1 != V2);
1156 case ICmpInst::ICMP_SLT:return ConstantInt::get(Type::Int1Ty, V1.slt(V2));
1157 case ICmpInst::ICMP_SGT:return ConstantInt::get(Type::Int1Ty, V1.sgt(V2));
1158 case ICmpInst::ICMP_SLE:return ConstantInt::get(Type::Int1Ty, V1.sle(V2));
1159 case ICmpInst::ICMP_SGE:return ConstantInt::get(Type::Int1Ty, V1.sge(V2));
1160 case ICmpInst::ICMP_ULT:return ConstantInt::get(Type::Int1Ty, V1.ult(V2));
1161 case ICmpInst::ICMP_UGT:return ConstantInt::get(Type::Int1Ty, V1.ugt(V2));
1162 case ICmpInst::ICMP_ULE:return ConstantInt::get(Type::Int1Ty, V1.ule(V2));
1163 case ICmpInst::ICMP_UGE:return ConstantInt::get(Type::Int1Ty, V1.uge(V2));
1165 } else if (isa<ConstantFP>(C1) && isa<ConstantFP>(C2)) {
1166 APFloat C1V = cast<ConstantFP>(C1)->getValueAPF();
1167 APFloat C2V = cast<ConstantFP>(C2)->getValueAPF();
1168 APFloat::cmpResult R = C1V.compare(C2V);
1170 default: assert(0 && "Invalid FCmp Predicate"); return 0;
1171 case FCmpInst::FCMP_FALSE: return ConstantInt::getFalse();
1172 case FCmpInst::FCMP_TRUE: return ConstantInt::getTrue();
1173 case FCmpInst::FCMP_UNO:
1174 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpUnordered);
1175 case FCmpInst::FCMP_ORD:
1176 return ConstantInt::get(Type::Int1Ty, R!=APFloat::cmpUnordered);
1177 case FCmpInst::FCMP_UEQ:
1178 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpUnordered ||
1179 R==APFloat::cmpEqual);
1180 case FCmpInst::FCMP_OEQ:
1181 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpEqual);
1182 case FCmpInst::FCMP_UNE:
1183 return ConstantInt::get(Type::Int1Ty, R!=APFloat::cmpEqual);
1184 case FCmpInst::FCMP_ONE:
1185 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpLessThan ||
1186 R==APFloat::cmpGreaterThan);
1187 case FCmpInst::FCMP_ULT:
1188 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpUnordered ||
1189 R==APFloat::cmpLessThan);
1190 case FCmpInst::FCMP_OLT:
1191 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpLessThan);
1192 case FCmpInst::FCMP_UGT:
1193 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpUnordered ||
1194 R==APFloat::cmpGreaterThan);
1195 case FCmpInst::FCMP_OGT:
1196 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpGreaterThan);
1197 case FCmpInst::FCMP_ULE:
1198 return ConstantInt::get(Type::Int1Ty, R!=APFloat::cmpGreaterThan);
1199 case FCmpInst::FCMP_OLE:
1200 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpLessThan ||
1201 R==APFloat::cmpEqual);
1202 case FCmpInst::FCMP_UGE:
1203 return ConstantInt::get(Type::Int1Ty, R!=APFloat::cmpLessThan);
1204 case FCmpInst::FCMP_OGE:
1205 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpGreaterThan ||
1206 R==APFloat::cmpEqual);
1208 } else if (const ConstantVector *CP1 = dyn_cast<ConstantVector>(C1)) {
1209 if (const ConstantVector *CP2 = dyn_cast<ConstantVector>(C2)) {
1210 if (pred == FCmpInst::FCMP_OEQ || pred == FCmpInst::FCMP_UEQ) {
1211 for (unsigned i = 0, e = CP1->getNumOperands(); i != e; ++i) {
1212 Constant *C= ConstantExpr::getFCmp(FCmpInst::FCMP_OEQ,
1213 const_cast<Constant*>(CP1->getOperand(i)),
1214 const_cast<Constant*>(CP2->getOperand(i)));
1215 if (ConstantInt *CB = dyn_cast<ConstantInt>(C))
1218 // Otherwise, could not decide from any element pairs.
1220 } else if (pred == ICmpInst::ICMP_EQ) {
1221 for (unsigned i = 0, e = CP1->getNumOperands(); i != e; ++i) {
1222 Constant *C = ConstantExpr::getICmp(ICmpInst::ICMP_EQ,
1223 const_cast<Constant*>(CP1->getOperand(i)),
1224 const_cast<Constant*>(CP2->getOperand(i)));
1225 if (ConstantInt *CB = dyn_cast<ConstantInt>(C))
1228 // Otherwise, could not decide from any element pairs.
1234 if (C1->getType()->isFloatingPoint()) {
1235 switch (evaluateFCmpRelation(C1, C2)) {
1236 default: assert(0 && "Unknown relation!");
1237 case FCmpInst::FCMP_UNO:
1238 case FCmpInst::FCMP_ORD:
1239 case FCmpInst::FCMP_UEQ:
1240 case FCmpInst::FCMP_UNE:
1241 case FCmpInst::FCMP_ULT:
1242 case FCmpInst::FCMP_UGT:
1243 case FCmpInst::FCMP_ULE:
1244 case FCmpInst::FCMP_UGE:
1245 case FCmpInst::FCMP_TRUE:
1246 case FCmpInst::FCMP_FALSE:
1247 case FCmpInst::BAD_FCMP_PREDICATE:
1248 break; // Couldn't determine anything about these constants.
1249 case FCmpInst::FCMP_OEQ: // We know that C1 == C2
1250 return ConstantInt::get(Type::Int1Ty,
1251 pred == FCmpInst::FCMP_UEQ || pred == FCmpInst::FCMP_OEQ ||
1252 pred == FCmpInst::FCMP_ULE || pred == FCmpInst::FCMP_OLE ||
1253 pred == FCmpInst::FCMP_UGE || pred == FCmpInst::FCMP_OGE);
1254 case FCmpInst::FCMP_OLT: // We know that C1 < C2
1255 return ConstantInt::get(Type::Int1Ty,
1256 pred == FCmpInst::FCMP_UNE || pred == FCmpInst::FCMP_ONE ||
1257 pred == FCmpInst::FCMP_ULT || pred == FCmpInst::FCMP_OLT ||
1258 pred == FCmpInst::FCMP_ULE || pred == FCmpInst::FCMP_OLE);
1259 case FCmpInst::FCMP_OGT: // We know that C1 > C2
1260 return ConstantInt::get(Type::Int1Ty,
1261 pred == FCmpInst::FCMP_UNE || pred == FCmpInst::FCMP_ONE ||
1262 pred == FCmpInst::FCMP_UGT || pred == FCmpInst::FCMP_OGT ||
1263 pred == FCmpInst::FCMP_UGE || pred == FCmpInst::FCMP_OGE);
1264 case FCmpInst::FCMP_OLE: // We know that C1 <= C2
1265 // We can only partially decide this relation.
1266 if (pred == FCmpInst::FCMP_UGT || pred == FCmpInst::FCMP_OGT)
1267 return ConstantInt::getFalse();
1268 if (pred == FCmpInst::FCMP_ULT || pred == FCmpInst::FCMP_OLT)
1269 return ConstantInt::getTrue();
1271 case FCmpInst::FCMP_OGE: // We known that C1 >= C2
1272 // We can only partially decide this relation.
1273 if (pred == FCmpInst::FCMP_ULT || pred == FCmpInst::FCMP_OLT)
1274 return ConstantInt::getFalse();
1275 if (pred == FCmpInst::FCMP_UGT || pred == FCmpInst::FCMP_OGT)
1276 return ConstantInt::getTrue();
1278 case ICmpInst::ICMP_NE: // We know that C1 != C2
1279 // We can only partially decide this relation.
1280 if (pred == FCmpInst::FCMP_OEQ || pred == FCmpInst::FCMP_UEQ)
1281 return ConstantInt::getFalse();
1282 if (pred == FCmpInst::FCMP_ONE || pred == FCmpInst::FCMP_UNE)
1283 return ConstantInt::getTrue();
1287 // Evaluate the relation between the two constants, per the predicate.
1288 switch (evaluateICmpRelation(C1, C2, CmpInst::isSigned(pred))) {
1289 default: assert(0 && "Unknown relational!");
1290 case ICmpInst::BAD_ICMP_PREDICATE:
1291 break; // Couldn't determine anything about these constants.
1292 case ICmpInst::ICMP_EQ: // We know the constants are equal!
1293 // If we know the constants are equal, we can decide the result of this
1294 // computation precisely.
1295 return ConstantInt::get(Type::Int1Ty,
1296 pred == ICmpInst::ICMP_EQ ||
1297 pred == ICmpInst::ICMP_ULE ||
1298 pred == ICmpInst::ICMP_SLE ||
1299 pred == ICmpInst::ICMP_UGE ||
1300 pred == ICmpInst::ICMP_SGE);
1301 case ICmpInst::ICMP_ULT:
1302 // If we know that C1 < C2, we can decide the result of this computation
1304 return ConstantInt::get(Type::Int1Ty,
1305 pred == ICmpInst::ICMP_ULT ||
1306 pred == ICmpInst::ICMP_NE ||
1307 pred == ICmpInst::ICMP_ULE);
1308 case ICmpInst::ICMP_SLT:
1309 // If we know that C1 < C2, we can decide the result of this computation
1311 return ConstantInt::get(Type::Int1Ty,
1312 pred == ICmpInst::ICMP_SLT ||
1313 pred == ICmpInst::ICMP_NE ||
1314 pred == ICmpInst::ICMP_SLE);
1315 case ICmpInst::ICMP_UGT:
1316 // If we know that C1 > C2, we can decide the result of this computation
1318 return ConstantInt::get(Type::Int1Ty,
1319 pred == ICmpInst::ICMP_UGT ||
1320 pred == ICmpInst::ICMP_NE ||
1321 pred == ICmpInst::ICMP_UGE);
1322 case ICmpInst::ICMP_SGT:
1323 // If we know that C1 > C2, we can decide the result of this computation
1325 return ConstantInt::get(Type::Int1Ty,
1326 pred == ICmpInst::ICMP_SGT ||
1327 pred == ICmpInst::ICMP_NE ||
1328 pred == ICmpInst::ICMP_SGE);
1329 case ICmpInst::ICMP_ULE:
1330 // If we know that C1 <= C2, we can only partially decide this relation.
1331 if (pred == ICmpInst::ICMP_UGT) return ConstantInt::getFalse();
1332 if (pred == ICmpInst::ICMP_ULT) return ConstantInt::getTrue();
1334 case ICmpInst::ICMP_SLE:
1335 // If we know that C1 <= C2, we can only partially decide this relation.
1336 if (pred == ICmpInst::ICMP_SGT) return ConstantInt::getFalse();
1337 if (pred == ICmpInst::ICMP_SLT) return ConstantInt::getTrue();
1340 case ICmpInst::ICMP_UGE:
1341 // If we know that C1 >= C2, we can only partially decide this relation.
1342 if (pred == ICmpInst::ICMP_ULT) return ConstantInt::getFalse();
1343 if (pred == ICmpInst::ICMP_UGT) return ConstantInt::getTrue();
1345 case ICmpInst::ICMP_SGE:
1346 // If we know that C1 >= C2, we can only partially decide this relation.
1347 if (pred == ICmpInst::ICMP_SLT) return ConstantInt::getFalse();
1348 if (pred == ICmpInst::ICMP_SGT) return ConstantInt::getTrue();
1351 case ICmpInst::ICMP_NE:
1352 // If we know that C1 != C2, we can only partially decide this relation.
1353 if (pred == ICmpInst::ICMP_EQ) return ConstantInt::getFalse();
1354 if (pred == ICmpInst::ICMP_NE) return ConstantInt::getTrue();
1358 if (!isa<ConstantExpr>(C1) && isa<ConstantExpr>(C2)) {
1359 // If C2 is a constant expr and C1 isn't, flop them around and fold the
1360 // other way if possible.
1362 case ICmpInst::ICMP_EQ:
1363 case ICmpInst::ICMP_NE:
1364 // No change of predicate required.
1365 return ConstantFoldCompareInstruction(pred, C2, C1);
1367 case ICmpInst::ICMP_ULT:
1368 case ICmpInst::ICMP_SLT:
1369 case ICmpInst::ICMP_UGT:
1370 case ICmpInst::ICMP_SGT:
1371 case ICmpInst::ICMP_ULE:
1372 case ICmpInst::ICMP_SLE:
1373 case ICmpInst::ICMP_UGE:
1374 case ICmpInst::ICMP_SGE:
1375 // Change the predicate as necessary to swap the operands.
1376 pred = ICmpInst::getSwappedPredicate((ICmpInst::Predicate)pred);
1377 return ConstantFoldCompareInstruction(pred, C2, C1);
1379 default: // These predicates cannot be flopped around.
1387 Constant *llvm::ConstantFoldGetElementPtr(const Constant *C,
1388 Constant* const *Idxs,
1391 (NumIdx == 1 && Idxs[0]->isNullValue()))
1392 return const_cast<Constant*>(C);
1394 if (isa<UndefValue>(C)) {
1395 const PointerType *Ptr = cast<PointerType>(C->getType());
1396 const Type *Ty = GetElementPtrInst::getIndexedType(Ptr,
1398 (Value **)Idxs+NumIdx,
1400 assert(Ty != 0 && "Invalid indices for GEP!");
1401 return UndefValue::get(PointerType::get(Ty, Ptr->getAddressSpace()));
1404 Constant *Idx0 = Idxs[0];
1405 if (C->isNullValue()) {
1407 for (unsigned i = 0, e = NumIdx; i != e; ++i)
1408 if (!Idxs[i]->isNullValue()) {
1413 const PointerType *Ptr = cast<PointerType>(C->getType());
1414 const Type *Ty = GetElementPtrInst::getIndexedType(Ptr,
1416 (Value**)Idxs+NumIdx,
1418 assert(Ty != 0 && "Invalid indices for GEP!");
1420 ConstantPointerNull::get(PointerType::get(Ty,Ptr->getAddressSpace()));
1424 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(const_cast<Constant*>(C))) {
1425 // Combine Indices - If the source pointer to this getelementptr instruction
1426 // is a getelementptr instruction, combine the indices of the two
1427 // getelementptr instructions into a single instruction.
1429 if (CE->getOpcode() == Instruction::GetElementPtr) {
1430 const Type *LastTy = 0;
1431 for (gep_type_iterator I = gep_type_begin(CE), E = gep_type_end(CE);
1435 if ((LastTy && isa<ArrayType>(LastTy)) || Idx0->isNullValue()) {
1436 SmallVector<Value*, 16> NewIndices;
1437 NewIndices.reserve(NumIdx + CE->getNumOperands());
1438 for (unsigned i = 1, e = CE->getNumOperands()-1; i != e; ++i)
1439 NewIndices.push_back(CE->getOperand(i));
1441 // Add the last index of the source with the first index of the new GEP.
1442 // Make sure to handle the case when they are actually different types.
1443 Constant *Combined = CE->getOperand(CE->getNumOperands()-1);
1444 // Otherwise it must be an array.
1445 if (!Idx0->isNullValue()) {
1446 const Type *IdxTy = Combined->getType();
1447 if (IdxTy != Idx0->getType()) {
1448 Constant *C1 = ConstantExpr::getSExtOrBitCast(Idx0, Type::Int64Ty);
1449 Constant *C2 = ConstantExpr::getSExtOrBitCast(Combined,
1451 Combined = ConstantExpr::get(Instruction::Add, C1, C2);
1454 ConstantExpr::get(Instruction::Add, Idx0, Combined);
1458 NewIndices.push_back(Combined);
1459 NewIndices.insert(NewIndices.end(), Idxs+1, Idxs+NumIdx);
1460 return ConstantExpr::getGetElementPtr(CE->getOperand(0), &NewIndices[0],
1465 // Implement folding of:
1466 // int* getelementptr ([2 x int]* cast ([3 x int]* %X to [2 x int]*),
1468 // To: int* getelementptr ([3 x int]* %X, long 0, long 0)
1470 if (CE->isCast() && NumIdx > 1 && Idx0->isNullValue()) {
1471 if (const PointerType *SPT =
1472 dyn_cast<PointerType>(CE->getOperand(0)->getType()))
1473 if (const ArrayType *SAT = dyn_cast<ArrayType>(SPT->getElementType()))
1474 if (const ArrayType *CAT =
1475 dyn_cast<ArrayType>(cast<PointerType>(C->getType())->getElementType()))
1476 if (CAT->getElementType() == SAT->getElementType())
1477 return ConstantExpr::getGetElementPtr(
1478 (Constant*)CE->getOperand(0), Idxs, NumIdx);
1481 // Fold: getelementptr (i8* inttoptr (i64 1 to i8*), i32 -1)
1482 // Into: inttoptr (i64 0 to i8*)
1483 // This happens with pointers to member functions in C++.
1484 if (CE->getOpcode() == Instruction::IntToPtr && NumIdx == 1 &&
1485 isa<ConstantInt>(CE->getOperand(0)) && isa<ConstantInt>(Idxs[0]) &&
1486 cast<PointerType>(CE->getType())->getElementType() == Type::Int8Ty) {
1487 Constant *Base = CE->getOperand(0);
1488 Constant *Offset = Idxs[0];
1490 // Convert the smaller integer to the larger type.
1491 if (Offset->getType()->getPrimitiveSizeInBits() <
1492 Base->getType()->getPrimitiveSizeInBits())
1493 Offset = ConstantExpr::getSExt(Offset, Base->getType());
1494 else if (Base->getType()->getPrimitiveSizeInBits() <
1495 Offset->getType()->getPrimitiveSizeInBits())
1496 Base = ConstantExpr::getZExt(Base, Base->getType());
1498 Base = ConstantExpr::getAdd(Base, Offset);
1499 return ConstantExpr::getIntToPtr(Base, CE->getType());