1 //===- ConstantFold.cpp - LLVM constant folder ----------------------------===//
3 // The LLVM Compiler Infrastructure
5 // This file was developed by the LLVM research group and is distributed under
6 // the University of Illinois Open Source 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 /// CastConstantVector - 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 *CastConstantVector(ConstantVector *CV,
43 const VectorType *DstTy) {
44 unsigned SrcNumElts = CV->getType()->getNumElements();
45 unsigned DstNumElts = DstTy->getNumElements();
46 const Type *SrcEltTy = CV->getType()->getElementType();
47 const Type *DstEltTy = DstTy->getElementType();
49 // If both vectors have the same number of elements (thus, the elements
50 // are the same size), perform the conversion now.
51 if (SrcNumElts == DstNumElts) {
52 std::vector<Constant*> Result;
54 // If the src and dest elements are both integers, or both floats, we can
55 // just BitCast each element because the elements are the same size.
56 if ((SrcEltTy->isInteger() && DstEltTy->isInteger()) ||
57 (SrcEltTy->isFloatingPoint() && DstEltTy->isFloatingPoint())) {
58 for (unsigned i = 0; i != SrcNumElts; ++i)
60 ConstantExpr::getBitCast(CV->getOperand(i), DstEltTy));
61 return ConstantVector::get(Result);
64 // If this is an int-to-fp cast ..
65 if (SrcEltTy->isInteger()) {
66 // Ensure that it is int-to-fp cast
67 assert(DstEltTy->isFloatingPoint());
68 if (DstEltTy->getTypeID() == Type::DoubleTyID) {
69 for (unsigned i = 0; i != SrcNumElts; ++i) {
70 ConstantInt *CI = cast<ConstantInt>(CV->getOperand(i));
71 double V = CI->getValue().bitsToDouble();
72 Result.push_back(ConstantFP::get(Type::DoubleTy, APFloat(V)));
74 return ConstantVector::get(Result);
76 assert(DstEltTy == Type::FloatTy && "Unknown fp type!");
77 for (unsigned i = 0; i != SrcNumElts; ++i) {
78 ConstantInt *CI = cast<ConstantInt>(CV->getOperand(i));
79 float V = CI->getValue().bitsToFloat();
80 Result.push_back(ConstantFP::get(Type::FloatTy, APFloat(V)));
82 return ConstantVector::get(Result);
85 // Otherwise, this is an fp-to-int cast.
86 assert(SrcEltTy->isFloatingPoint() && DstEltTy->isInteger());
88 if (SrcEltTy->getTypeID() == Type::DoubleTyID) {
89 for (unsigned i = 0; i != SrcNumElts; ++i) {
90 uint64_t V = cast<ConstantFP>(CV->getOperand(i))->
91 getValueAPF().convertToAPInt().getZExtValue();
92 Constant *C = ConstantInt::get(Type::Int64Ty, V);
93 Result.push_back(ConstantExpr::getBitCast(C, DstEltTy ));
95 return ConstantVector::get(Result);
98 assert(SrcEltTy->getTypeID() == Type::FloatTyID);
99 for (unsigned i = 0; i != SrcNumElts; ++i) {
100 uint32_t V = (uint32_t)cast<ConstantFP>(CV->getOperand(i))->
101 getValueAPF().convertToAPInt().getZExtValue();
102 Constant *C = ConstantInt::get(Type::Int32Ty, V);
103 Result.push_back(ConstantExpr::getBitCast(C, DstEltTy));
105 return ConstantVector::get(Result);
108 // Otherwise, this is a cast that changes element count and size. Handle
109 // casts which shrink the elements here.
111 // FIXME: We need to know endianness to do this!
116 /// This function determines which opcode to use to fold two constant cast
117 /// expressions together. It uses CastInst::isEliminableCastPair to determine
118 /// the opcode. Consequently its just a wrapper around that function.
119 /// @brief Determine if it is valid to fold a cast of a cast
121 foldConstantCastPair(
122 unsigned opc, ///< opcode of the second cast constant expression
123 const ConstantExpr*Op, ///< the first cast constant expression
124 const Type *DstTy ///< desintation type of the first cast
126 assert(Op && Op->isCast() && "Can't fold cast of cast without a cast!");
127 assert(DstTy && DstTy->isFirstClassType() && "Invalid cast destination type");
128 assert(CastInst::isCast(opc) && "Invalid cast opcode");
130 // The the types and opcodes for the two Cast constant expressions
131 const Type *SrcTy = Op->getOperand(0)->getType();
132 const Type *MidTy = Op->getType();
133 Instruction::CastOps firstOp = Instruction::CastOps(Op->getOpcode());
134 Instruction::CastOps secondOp = Instruction::CastOps(opc);
136 // Let CastInst::isEliminableCastPair do the heavy lifting.
137 return CastInst::isEliminableCastPair(firstOp, secondOp, SrcTy, MidTy, DstTy,
141 Constant *llvm::ConstantFoldCastInstruction(unsigned opc, const Constant *V,
142 const Type *DestTy) {
143 const Type *SrcTy = V->getType();
145 if (isa<UndefValue>(V)) {
146 // zext(undef) = 0, because the top bits will be zero.
147 // sext(undef) = 0, because the top bits will all be the same.
148 if (opc == Instruction::ZExt || opc == Instruction::SExt)
149 return Constant::getNullValue(DestTy);
150 return UndefValue::get(DestTy);
152 // No compile-time operations on this type yet.
153 if (V->getType() == Type::PPC_FP128Ty || DestTy == Type::PPC_FP128Ty)
156 // If the cast operand is a constant expression, there's a few things we can
157 // do to try to simplify it.
158 if (const ConstantExpr *CE = dyn_cast<ConstantExpr>(V)) {
160 // Try hard to fold cast of cast because they are often eliminable.
161 if (unsigned newOpc = foldConstantCastPair(opc, CE, DestTy))
162 return ConstantExpr::getCast(newOpc, CE->getOperand(0), DestTy);
163 } else if (CE->getOpcode() == Instruction::GetElementPtr) {
164 // If all of the indexes in the GEP are null values, there is no pointer
165 // adjustment going on. We might as well cast the source pointer.
166 bool isAllNull = true;
167 for (unsigned i = 1, e = CE->getNumOperands(); i != e; ++i)
168 if (!CE->getOperand(i)->isNullValue()) {
173 // This is casting one pointer type to another, always BitCast
174 return ConstantExpr::getPointerCast(CE->getOperand(0), DestTy);
178 // We actually have to do a cast now. Perform the cast according to the
181 case Instruction::FPTrunc:
182 case Instruction::FPExt:
183 if (const ConstantFP *FPC = dyn_cast<ConstantFP>(V)) {
184 APFloat Val = FPC->getValueAPF();
185 Val.convert(DestTy == Type::FloatTy ? APFloat::IEEEsingle :
186 DestTy == Type::DoubleTy ? APFloat::IEEEdouble :
187 DestTy == Type::X86_FP80Ty ? APFloat::x87DoubleExtended :
188 DestTy == Type::FP128Ty ? APFloat::IEEEquad :
190 APFloat::rmNearestTiesToEven);
191 return ConstantFP::get(DestTy, Val);
193 return 0; // Can't fold.
194 case Instruction::FPToUI:
195 case Instruction::FPToSI:
196 if (const ConstantFP *FPC = dyn_cast<ConstantFP>(V)) {
197 const APFloat &V = FPC->getValueAPF();
199 uint32_t DestBitWidth = cast<IntegerType>(DestTy)->getBitWidth();
200 (void) V.convertToInteger(x, DestBitWidth, opc==Instruction::FPToSI,
201 APFloat::rmTowardZero);
202 APInt Val(DestBitWidth, 2, x);
203 return ConstantInt::get(Val);
205 return 0; // Can't fold.
206 case Instruction::IntToPtr: //always treated as unsigned
207 if (V->isNullValue()) // Is it an integral null value?
208 return ConstantPointerNull::get(cast<PointerType>(DestTy));
209 return 0; // Other pointer types cannot be casted
210 case Instruction::PtrToInt: // always treated as unsigned
211 if (V->isNullValue()) // is it a null pointer value?
212 return ConstantInt::get(DestTy, 0);
213 return 0; // Other pointer types cannot be casted
214 case Instruction::UIToFP:
215 case Instruction::SIToFP:
216 if (const ConstantInt *CI = dyn_cast<ConstantInt>(V)) {
217 APInt api = CI->getValue();
218 const uint64_t zero[] = {0, 0};
219 uint32_t BitWidth = cast<IntegerType>(SrcTy)->getBitWidth();
220 APFloat apf = APFloat(APInt(DestTy->getPrimitiveSizeInBits(),
222 (void)apf.convertFromZeroExtendedInteger(api.getRawData(), BitWidth,
223 opc==Instruction::SIToFP,
224 APFloat::rmNearestTiesToEven);
225 return ConstantFP::get(DestTy, apf);
228 case Instruction::ZExt:
229 if (const ConstantInt *CI = dyn_cast<ConstantInt>(V)) {
230 uint32_t BitWidth = cast<IntegerType>(DestTy)->getBitWidth();
231 APInt Result(CI->getValue());
232 Result.zext(BitWidth);
233 return ConstantInt::get(Result);
236 case Instruction::SExt:
237 if (const ConstantInt *CI = dyn_cast<ConstantInt>(V)) {
238 uint32_t BitWidth = cast<IntegerType>(DestTy)->getBitWidth();
239 APInt Result(CI->getValue());
240 Result.sext(BitWidth);
241 return ConstantInt::get(Result);
244 case Instruction::Trunc:
245 if (const ConstantInt *CI = dyn_cast<ConstantInt>(V)) {
246 uint32_t BitWidth = cast<IntegerType>(DestTy)->getBitWidth();
247 APInt Result(CI->getValue());
248 Result.trunc(BitWidth);
249 return ConstantInt::get(Result);
252 case Instruction::BitCast:
254 return (Constant*)V; // no-op cast
256 // Check to see if we are casting a pointer to an aggregate to a pointer to
257 // the first element. If so, return the appropriate GEP instruction.
258 if (const PointerType *PTy = dyn_cast<PointerType>(V->getType()))
259 if (const PointerType *DPTy = dyn_cast<PointerType>(DestTy)) {
260 SmallVector<Value*, 8> IdxList;
261 IdxList.push_back(Constant::getNullValue(Type::Int32Ty));
262 const Type *ElTy = PTy->getElementType();
263 while (ElTy != DPTy->getElementType()) {
264 if (const StructType *STy = dyn_cast<StructType>(ElTy)) {
265 if (STy->getNumElements() == 0) break;
266 ElTy = STy->getElementType(0);
267 IdxList.push_back(Constant::getNullValue(Type::Int32Ty));
268 } else if (const SequentialType *STy =
269 dyn_cast<SequentialType>(ElTy)) {
270 if (isa<PointerType>(ElTy)) break; // Can't index into pointers!
271 ElTy = STy->getElementType();
272 IdxList.push_back(IdxList[0]);
278 if (ElTy == DPTy->getElementType())
279 return ConstantExpr::getGetElementPtr(
280 const_cast<Constant*>(V), &IdxList[0], IdxList.size());
283 // Handle casts from one vector constant to another. We know that the src
284 // and dest type have the same size (otherwise its an illegal cast).
285 if (const VectorType *DestPTy = dyn_cast<VectorType>(DestTy)) {
286 if (const VectorType *SrcTy = dyn_cast<VectorType>(V->getType())) {
287 assert(DestPTy->getBitWidth() == SrcTy->getBitWidth() &&
288 "Not cast between same sized vectors!");
289 // First, check for null and undef
290 if (isa<ConstantAggregateZero>(V))
291 return Constant::getNullValue(DestTy);
292 if (isa<UndefValue>(V))
293 return UndefValue::get(DestTy);
295 if (const ConstantVector *CV = dyn_cast<ConstantVector>(V)) {
296 // This is a cast from a ConstantVector of one type to a
297 // ConstantVector of another type. Check to see if all elements of
298 // the input are simple.
299 bool AllSimpleConstants = true;
300 for (unsigned i = 0, e = CV->getNumOperands(); i != e; ++i) {
301 if (!isa<ConstantInt>(CV->getOperand(i)) &&
302 !isa<ConstantFP>(CV->getOperand(i))) {
303 AllSimpleConstants = false;
308 // If all of the elements are simple constants, we can fold this.
309 if (AllSimpleConstants)
310 return CastConstantVector(const_cast<ConstantVector*>(CV), DestPTy);
315 // Finally, implement bitcast folding now. The code below doesn't handle
317 if (isa<ConstantPointerNull>(V)) // ptr->ptr cast.
318 return ConstantPointerNull::get(cast<PointerType>(DestTy));
320 // Handle integral constant input.
321 if (const ConstantInt *CI = dyn_cast<ConstantInt>(V)) {
322 if (DestTy->isInteger())
323 // Integral -> Integral. This is a no-op because the bit widths must
324 // be the same. Consequently, we just fold to V.
325 return const_cast<Constant*>(V);
327 if (DestTy->isFloatingPoint()) {
328 assert((DestTy == Type::DoubleTy || DestTy == Type::FloatTy) &&
330 return ConstantFP::get(DestTy, APFloat(CI->getValue()));
332 // Otherwise, can't fold this (vector?)
336 // Handle ConstantFP input.
337 if (const ConstantFP *FP = dyn_cast<ConstantFP>(V)) {
339 if (DestTy == Type::Int32Ty) {
340 return ConstantInt::get(FP->getValueAPF().convertToAPInt());
342 assert(DestTy == Type::Int64Ty && "only support f32/f64 for now!");
343 return ConstantInt::get(FP->getValueAPF().convertToAPInt());
348 assert(!"Invalid CE CastInst opcode");
352 assert(0 && "Failed to cast constant expression");
356 Constant *llvm::ConstantFoldSelectInstruction(const Constant *Cond,
358 const Constant *V2) {
359 if (const ConstantInt *CB = dyn_cast<ConstantInt>(Cond))
360 return const_cast<Constant*>(CB->getZExtValue() ? V1 : V2);
362 if (isa<UndefValue>(V1)) return const_cast<Constant*>(V2);
363 if (isa<UndefValue>(V2)) return const_cast<Constant*>(V1);
364 if (isa<UndefValue>(Cond)) return const_cast<Constant*>(V1);
365 if (V1 == V2) return const_cast<Constant*>(V1);
369 Constant *llvm::ConstantFoldExtractElementInstruction(const Constant *Val,
370 const Constant *Idx) {
371 if (isa<UndefValue>(Val)) // ee(undef, x) -> undef
372 return UndefValue::get(cast<VectorType>(Val->getType())->getElementType());
373 if (Val->isNullValue()) // ee(zero, x) -> zero
374 return Constant::getNullValue(
375 cast<VectorType>(Val->getType())->getElementType());
377 if (const ConstantVector *CVal = dyn_cast<ConstantVector>(Val)) {
378 if (const ConstantInt *CIdx = dyn_cast<ConstantInt>(Idx)) {
379 return const_cast<Constant*>(CVal->getOperand(CIdx->getZExtValue()));
380 } else if (isa<UndefValue>(Idx)) {
381 // ee({w,x,y,z}, undef) -> w (an arbitrary value).
382 return const_cast<Constant*>(CVal->getOperand(0));
388 Constant *llvm::ConstantFoldInsertElementInstruction(const Constant *Val,
390 const Constant *Idx) {
391 const ConstantInt *CIdx = dyn_cast<ConstantInt>(Idx);
393 APInt idxVal = CIdx->getValue();
394 if (isa<UndefValue>(Val)) {
395 // Insertion of scalar constant into vector undef
396 // Optimize away insertion of undef
397 if (isa<UndefValue>(Elt))
398 return const_cast<Constant*>(Val);
399 // Otherwise break the aggregate undef into multiple undefs and do
402 cast<VectorType>(Val->getType())->getNumElements();
403 std::vector<Constant*> Ops;
405 for (unsigned i = 0; i < numOps; ++i) {
407 (idxVal == i) ? Elt : UndefValue::get(Elt->getType());
408 Ops.push_back(const_cast<Constant*>(Op));
410 return ConstantVector::get(Ops);
412 if (isa<ConstantAggregateZero>(Val)) {
413 // Insertion of scalar constant into vector aggregate zero
414 // Optimize away insertion of zero
415 if (Elt->isNullValue())
416 return const_cast<Constant*>(Val);
417 // Otherwise break the aggregate zero into multiple zeros and do
420 cast<VectorType>(Val->getType())->getNumElements();
421 std::vector<Constant*> Ops;
423 for (unsigned i = 0; i < numOps; ++i) {
425 (idxVal == i) ? Elt : Constant::getNullValue(Elt->getType());
426 Ops.push_back(const_cast<Constant*>(Op));
428 return ConstantVector::get(Ops);
430 if (const ConstantVector *CVal = dyn_cast<ConstantVector>(Val)) {
431 // Insertion of scalar constant into vector constant
432 std::vector<Constant*> Ops;
433 Ops.reserve(CVal->getNumOperands());
434 for (unsigned i = 0; i < CVal->getNumOperands(); ++i) {
436 (idxVal == i) ? Elt : cast<Constant>(CVal->getOperand(i));
437 Ops.push_back(const_cast<Constant*>(Op));
439 return ConstantVector::get(Ops);
444 Constant *llvm::ConstantFoldShuffleVectorInstruction(const Constant *V1,
446 const Constant *Mask) {
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
668 return const_cast<ConstantInt*>(CI1); // Zero shift is identity
669 case Instruction::LShr:
670 if (uint32_t shiftAmt = C2V.getZExtValue())
671 if (shiftAmt < C1V.getBitWidth())
672 return ConstantInt::get(C1V.lshr(shiftAmt));
674 return UndefValue::get(C1->getType()); // too big shift is undef
675 return const_cast<ConstantInt*>(CI1); // Zero shift is identity
676 case Instruction::AShr:
677 if (uint32_t shiftAmt = C2V.getZExtValue())
678 if (shiftAmt < C1V.getBitWidth())
679 return ConstantInt::get(C1V.ashr(shiftAmt));
681 return UndefValue::get(C1->getType()); // too big shift is undef
682 return const_cast<ConstantInt*>(CI1); // Zero shift is identity
685 } else if (const ConstantFP *CFP1 = dyn_cast<ConstantFP>(C1)) {
686 if (const ConstantFP *CFP2 = dyn_cast<ConstantFP>(C2)) {
687 APFloat C1V = CFP1->getValueAPF();
688 APFloat C2V = CFP2->getValueAPF();
689 APFloat C3V = C1V; // copy for modification
690 bool isDouble = CFP1->getType()==Type::DoubleTy;
694 case Instruction::Add:
695 (void)C3V.add(C2V, APFloat::rmNearestTiesToEven);
696 return ConstantFP::get(CFP1->getType(), C3V);
697 case Instruction::Sub:
698 (void)C3V.subtract(C2V, APFloat::rmNearestTiesToEven);
699 return ConstantFP::get(CFP1->getType(), C3V);
700 case Instruction::Mul:
701 (void)C3V.multiply(C2V, APFloat::rmNearestTiesToEven);
702 return ConstantFP::get(CFP1->getType(), C3V);
703 case Instruction::FDiv:
704 (void)C3V.divide(C2V, APFloat::rmNearestTiesToEven);
705 return ConstantFP::get(CFP1->getType(), C3V);
706 case Instruction::FRem:
708 // IEEE 754, Section 7.1, #5
709 return ConstantFP::get(CFP1->getType(), isDouble ?
710 APFloat(std::numeric_limits<double>::quiet_NaN()) :
711 APFloat(std::numeric_limits<float>::quiet_NaN()));
712 (void)C3V.mod(C2V, APFloat::rmNearestTiesToEven);
713 return ConstantFP::get(CFP1->getType(), C3V);
716 } else if (const VectorType *VTy = dyn_cast<VectorType>(C1->getType())) {
717 const ConstantVector *CP1 = dyn_cast<ConstantVector>(C1);
718 const ConstantVector *CP2 = dyn_cast<ConstantVector>(C2);
719 if ((CP1 != NULL || isa<ConstantAggregateZero>(C1)) &&
720 (CP2 != NULL || isa<ConstantAggregateZero>(C2))) {
724 case Instruction::Add:
725 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getAdd);
726 case Instruction::Sub:
727 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getSub);
728 case Instruction::Mul:
729 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getMul);
730 case Instruction::UDiv:
731 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getUDiv);
732 case Instruction::SDiv:
733 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getSDiv);
734 case Instruction::FDiv:
735 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getFDiv);
736 case Instruction::URem:
737 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getURem);
738 case Instruction::SRem:
739 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getSRem);
740 case Instruction::FRem:
741 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getFRem);
742 case Instruction::And:
743 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getAnd);
744 case Instruction::Or:
745 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getOr);
746 case Instruction::Xor:
747 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getXor);
752 // We don't know how to fold this
756 /// isZeroSizedType - This type is zero sized if its an array or structure of
757 /// zero sized types. The only leaf zero sized type is an empty structure.
758 static bool isMaybeZeroSizedType(const Type *Ty) {
759 if (isa<OpaqueType>(Ty)) return true; // Can't say.
760 if (const StructType *STy = dyn_cast<StructType>(Ty)) {
762 // If all of elements have zero size, this does too.
763 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i)
764 if (!isMaybeZeroSizedType(STy->getElementType(i))) return false;
767 } else if (const ArrayType *ATy = dyn_cast<ArrayType>(Ty)) {
768 return isMaybeZeroSizedType(ATy->getElementType());
773 /// IdxCompare - Compare the two constants as though they were getelementptr
774 /// indices. This allows coersion of the types to be the same thing.
776 /// If the two constants are the "same" (after coersion), return 0. If the
777 /// first is less than the second, return -1, if the second is less than the
778 /// first, return 1. If the constants are not integral, return -2.
780 static int IdxCompare(Constant *C1, Constant *C2, const Type *ElTy) {
781 if (C1 == C2) return 0;
783 // Ok, we found a different index. If they are not ConstantInt, we can't do
784 // anything with them.
785 if (!isa<ConstantInt>(C1) || !isa<ConstantInt>(C2))
786 return -2; // don't know!
788 // Ok, we have two differing integer indices. Sign extend them to be the same
789 // type. Long is always big enough, so we use it.
790 if (C1->getType() != Type::Int64Ty)
791 C1 = ConstantExpr::getSExt(C1, Type::Int64Ty);
793 if (C2->getType() != Type::Int64Ty)
794 C2 = ConstantExpr::getSExt(C2, Type::Int64Ty);
796 if (C1 == C2) return 0; // They are equal
798 // If the type being indexed over is really just a zero sized type, there is
799 // no pointer difference being made here.
800 if (isMaybeZeroSizedType(ElTy))
803 // If they are really different, now that they are the same type, then we
804 // found a difference!
805 if (cast<ConstantInt>(C1)->getSExtValue() <
806 cast<ConstantInt>(C2)->getSExtValue())
812 /// evaluateFCmpRelation - This function determines if there is anything we can
813 /// decide about the two constants provided. This doesn't need to handle simple
814 /// things like ConstantFP comparisons, but should instead handle ConstantExprs.
815 /// If we can determine that the two constants have a particular relation to
816 /// each other, we should return the corresponding FCmpInst predicate,
817 /// otherwise return FCmpInst::BAD_FCMP_PREDICATE. This is used below in
818 /// ConstantFoldCompareInstruction.
820 /// To simplify this code we canonicalize the relation so that the first
821 /// operand is always the most "complex" of the two. We consider ConstantFP
822 /// to be the simplest, and ConstantExprs to be the most complex.
823 static FCmpInst::Predicate evaluateFCmpRelation(const Constant *V1,
824 const Constant *V2) {
825 assert(V1->getType() == V2->getType() &&
826 "Cannot compare values of different types!");
828 // No compile-time operations on this type yet.
829 if (V1->getType() == Type::PPC_FP128Ty)
830 return FCmpInst::BAD_FCMP_PREDICATE;
832 // Handle degenerate case quickly
833 if (V1 == V2) return FCmpInst::FCMP_OEQ;
835 if (!isa<ConstantExpr>(V1)) {
836 if (!isa<ConstantExpr>(V2)) {
837 // We distilled thisUse the standard constant folder for a few cases
839 Constant *C1 = const_cast<Constant*>(V1);
840 Constant *C2 = const_cast<Constant*>(V2);
841 R = dyn_cast<ConstantInt>(
842 ConstantExpr::getFCmp(FCmpInst::FCMP_OEQ, C1, C2));
843 if (R && !R->isZero())
844 return FCmpInst::FCMP_OEQ;
845 R = dyn_cast<ConstantInt>(
846 ConstantExpr::getFCmp(FCmpInst::FCMP_OLT, C1, C2));
847 if (R && !R->isZero())
848 return FCmpInst::FCMP_OLT;
849 R = dyn_cast<ConstantInt>(
850 ConstantExpr::getFCmp(FCmpInst::FCMP_OGT, C1, C2));
851 if (R && !R->isZero())
852 return FCmpInst::FCMP_OGT;
854 // Nothing more we can do
855 return FCmpInst::BAD_FCMP_PREDICATE;
858 // If the first operand is simple and second is ConstantExpr, swap operands.
859 FCmpInst::Predicate SwappedRelation = evaluateFCmpRelation(V2, V1);
860 if (SwappedRelation != FCmpInst::BAD_FCMP_PREDICATE)
861 return FCmpInst::getSwappedPredicate(SwappedRelation);
863 // Ok, the LHS is known to be a constantexpr. The RHS can be any of a
864 // constantexpr or a simple constant.
865 const ConstantExpr *CE1 = cast<ConstantExpr>(V1);
866 switch (CE1->getOpcode()) {
867 case Instruction::FPTrunc:
868 case Instruction::FPExt:
869 case Instruction::UIToFP:
870 case Instruction::SIToFP:
871 // We might be able to do something with these but we don't right now.
877 // There are MANY other foldings that we could perform here. They will
878 // probably be added on demand, as they seem needed.
879 return FCmpInst::BAD_FCMP_PREDICATE;
882 /// evaluateICmpRelation - This function determines if there is anything we can
883 /// decide about the two constants provided. This doesn't need to handle simple
884 /// things like integer comparisons, but should instead handle ConstantExprs
885 /// and GlobalValues. If we can determine that the two constants have a
886 /// particular relation to each other, we should return the corresponding ICmp
887 /// predicate, otherwise return ICmpInst::BAD_ICMP_PREDICATE.
889 /// To simplify this code we canonicalize the relation so that the first
890 /// operand is always the most "complex" of the two. We consider simple
891 /// constants (like ConstantInt) to be the simplest, followed by
892 /// GlobalValues, followed by ConstantExpr's (the most complex).
894 static ICmpInst::Predicate evaluateICmpRelation(const Constant *V1,
897 assert(V1->getType() == V2->getType() &&
898 "Cannot compare different types of values!");
899 if (V1 == V2) return ICmpInst::ICMP_EQ;
901 if (!isa<ConstantExpr>(V1) && !isa<GlobalValue>(V1)) {
902 if (!isa<GlobalValue>(V2) && !isa<ConstantExpr>(V2)) {
903 // We distilled this down to a simple case, use the standard constant
906 Constant *C1 = const_cast<Constant*>(V1);
907 Constant *C2 = const_cast<Constant*>(V2);
908 ICmpInst::Predicate pred = ICmpInst::ICMP_EQ;
909 R = dyn_cast<ConstantInt>(ConstantExpr::getICmp(pred, C1, C2));
910 if (R && !R->isZero())
912 pred = isSigned ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT;
913 R = dyn_cast<ConstantInt>(ConstantExpr::getICmp(pred, C1, C2));
914 if (R && !R->isZero())
916 pred = isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT;
917 R = dyn_cast<ConstantInt>(ConstantExpr::getICmp(pred, C1, C2));
918 if (R && !R->isZero())
921 // If we couldn't figure it out, bail.
922 return ICmpInst::BAD_ICMP_PREDICATE;
925 // If the first operand is simple, swap operands.
926 ICmpInst::Predicate SwappedRelation =
927 evaluateICmpRelation(V2, V1, isSigned);
928 if (SwappedRelation != ICmpInst::BAD_ICMP_PREDICATE)
929 return ICmpInst::getSwappedPredicate(SwappedRelation);
931 } else if (const GlobalValue *CPR1 = dyn_cast<GlobalValue>(V1)) {
932 if (isa<ConstantExpr>(V2)) { // Swap as necessary.
933 ICmpInst::Predicate SwappedRelation =
934 evaluateICmpRelation(V2, V1, isSigned);
935 if (SwappedRelation != ICmpInst::BAD_ICMP_PREDICATE)
936 return ICmpInst::getSwappedPredicate(SwappedRelation);
938 return ICmpInst::BAD_ICMP_PREDICATE;
941 // Now we know that the RHS is a GlobalValue or simple constant,
942 // which (since the types must match) means that it's a ConstantPointerNull.
943 if (const GlobalValue *CPR2 = dyn_cast<GlobalValue>(V2)) {
944 // Don't try to decide equality of aliases.
945 if (!isa<GlobalAlias>(CPR1) && !isa<GlobalAlias>(CPR2))
946 if (!CPR1->hasExternalWeakLinkage() || !CPR2->hasExternalWeakLinkage())
947 return ICmpInst::ICMP_NE;
949 assert(isa<ConstantPointerNull>(V2) && "Canonicalization guarantee!");
950 // GlobalVals can never be null. Don't try to evaluate aliases.
951 if (!CPR1->hasExternalWeakLinkage() && !isa<GlobalAlias>(CPR1))
952 return ICmpInst::ICMP_NE;
955 // Ok, the LHS is known to be a constantexpr. The RHS can be any of a
956 // constantexpr, a CPR, or a simple constant.
957 const ConstantExpr *CE1 = cast<ConstantExpr>(V1);
958 const Constant *CE1Op0 = CE1->getOperand(0);
960 switch (CE1->getOpcode()) {
961 case Instruction::Trunc:
962 case Instruction::FPTrunc:
963 case Instruction::FPExt:
964 case Instruction::FPToUI:
965 case Instruction::FPToSI:
966 break; // We can't evaluate floating point casts or truncations.
968 case Instruction::UIToFP:
969 case Instruction::SIToFP:
970 case Instruction::IntToPtr:
971 case Instruction::BitCast:
972 case Instruction::ZExt:
973 case Instruction::SExt:
974 case Instruction::PtrToInt:
975 // If the cast is not actually changing bits, and the second operand is a
976 // null pointer, do the comparison with the pre-casted value.
977 if (V2->isNullValue() &&
978 (isa<PointerType>(CE1->getType()) || CE1->getType()->isInteger())) {
979 bool sgnd = CE1->getOpcode() == Instruction::ZExt ? false :
980 (CE1->getOpcode() == Instruction::SExt ? true :
981 (CE1->getOpcode() == Instruction::PtrToInt ? false : isSigned));
982 return evaluateICmpRelation(
983 CE1Op0, Constant::getNullValue(CE1Op0->getType()), sgnd);
986 // If the dest type is a pointer type, and the RHS is a constantexpr cast
987 // from the same type as the src of the LHS, evaluate the inputs. This is
988 // important for things like "icmp eq (cast 4 to int*), (cast 5 to int*)",
989 // which happens a lot in compilers with tagged integers.
990 if (const ConstantExpr *CE2 = dyn_cast<ConstantExpr>(V2))
991 if (CE2->isCast() && isa<PointerType>(CE1->getType()) &&
992 CE1->getOperand(0)->getType() == CE2->getOperand(0)->getType() &&
993 CE1->getOperand(0)->getType()->isInteger()) {
994 bool sgnd = CE1->getOpcode() == Instruction::ZExt ? false :
995 (CE1->getOpcode() == Instruction::SExt ? true :
996 (CE1->getOpcode() == Instruction::PtrToInt ? false : isSigned));
997 return evaluateICmpRelation(CE1->getOperand(0), CE2->getOperand(0),
1002 case Instruction::GetElementPtr:
1003 // Ok, since this is a getelementptr, we know that the constant has a
1004 // pointer type. Check the various cases.
1005 if (isa<ConstantPointerNull>(V2)) {
1006 // If we are comparing a GEP to a null pointer, check to see if the base
1007 // of the GEP equals the null pointer.
1008 if (const GlobalValue *GV = dyn_cast<GlobalValue>(CE1Op0)) {
1009 if (GV->hasExternalWeakLinkage())
1010 // Weak linkage GVals could be zero or not. We're comparing that
1011 // to null pointer so its greater-or-equal
1012 return isSigned ? ICmpInst::ICMP_SGE : ICmpInst::ICMP_UGE;
1014 // If its not weak linkage, the GVal must have a non-zero address
1015 // so the result is greater-than
1016 return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT;
1017 } else if (isa<ConstantPointerNull>(CE1Op0)) {
1018 // If we are indexing from a null pointer, check to see if we have any
1019 // non-zero indices.
1020 for (unsigned i = 1, e = CE1->getNumOperands(); i != e; ++i)
1021 if (!CE1->getOperand(i)->isNullValue())
1022 // Offsetting from null, must not be equal.
1023 return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT;
1024 // Only zero indexes from null, must still be zero.
1025 return ICmpInst::ICMP_EQ;
1027 // Otherwise, we can't really say if the first operand is null or not.
1028 } else if (const GlobalValue *CPR2 = dyn_cast<GlobalValue>(V2)) {
1029 if (isa<ConstantPointerNull>(CE1Op0)) {
1030 if (CPR2->hasExternalWeakLinkage())
1031 // Weak linkage GVals could be zero or not. We're comparing it to
1032 // a null pointer, so its less-or-equal
1033 return isSigned ? ICmpInst::ICMP_SLE : ICmpInst::ICMP_ULE;
1035 // If its not weak linkage, the GVal must have a non-zero address
1036 // so the result is less-than
1037 return isSigned ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT;
1038 } else if (const GlobalValue *CPR1 = dyn_cast<GlobalValue>(CE1Op0)) {
1040 // If this is a getelementptr of the same global, then it must be
1041 // different. Because the types must match, the getelementptr could
1042 // only have at most one index, and because we fold getelementptr's
1043 // with a single zero index, it must be nonzero.
1044 assert(CE1->getNumOperands() == 2 &&
1045 !CE1->getOperand(1)->isNullValue() &&
1046 "Suprising getelementptr!");
1047 return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT;
1049 // If they are different globals, we don't know what the value is,
1050 // but they can't be equal.
1051 return ICmpInst::ICMP_NE;
1055 const ConstantExpr *CE2 = cast<ConstantExpr>(V2);
1056 const Constant *CE2Op0 = CE2->getOperand(0);
1058 // There are MANY other foldings that we could perform here. They will
1059 // probably be added on demand, as they seem needed.
1060 switch (CE2->getOpcode()) {
1062 case Instruction::GetElementPtr:
1063 // By far the most common case to handle is when the base pointers are
1064 // obviously to the same or different globals.
1065 if (isa<GlobalValue>(CE1Op0) && isa<GlobalValue>(CE2Op0)) {
1066 if (CE1Op0 != CE2Op0) // Don't know relative ordering, but not equal
1067 return ICmpInst::ICMP_NE;
1068 // Ok, we know that both getelementptr instructions are based on the
1069 // same global. From this, we can precisely determine the relative
1070 // ordering of the resultant pointers.
1073 // Compare all of the operands the GEP's have in common.
1074 gep_type_iterator GTI = gep_type_begin(CE1);
1075 for (;i != CE1->getNumOperands() && i != CE2->getNumOperands();
1077 switch (IdxCompare(CE1->getOperand(i), CE2->getOperand(i),
1078 GTI.getIndexedType())) {
1079 case -1: return isSigned ? ICmpInst::ICMP_SLT:ICmpInst::ICMP_ULT;
1080 case 1: return isSigned ? ICmpInst::ICMP_SGT:ICmpInst::ICMP_UGT;
1081 case -2: return ICmpInst::BAD_ICMP_PREDICATE;
1084 // Ok, we ran out of things they have in common. If any leftovers
1085 // are non-zero then we have a difference, otherwise we are equal.
1086 for (; i < CE1->getNumOperands(); ++i)
1087 if (!CE1->getOperand(i)->isNullValue())
1088 if (isa<ConstantInt>(CE1->getOperand(i)))
1089 return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT;
1091 return ICmpInst::BAD_ICMP_PREDICATE; // Might be equal.
1093 for (; i < CE2->getNumOperands(); ++i)
1094 if (!CE2->getOperand(i)->isNullValue())
1095 if (isa<ConstantInt>(CE2->getOperand(i)))
1096 return isSigned ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT;
1098 return ICmpInst::BAD_ICMP_PREDICATE; // Might be equal.
1099 return ICmpInst::ICMP_EQ;
1108 return ICmpInst::BAD_ICMP_PREDICATE;
1111 Constant *llvm::ConstantFoldCompareInstruction(unsigned short pred,
1113 const Constant *C2) {
1115 // Handle some degenerate cases first
1116 if (isa<UndefValue>(C1) || isa<UndefValue>(C2))
1117 return UndefValue::get(Type::Int1Ty);
1119 // No compile-time operations on this type yet.
1120 if (C1->getType() == Type::PPC_FP128Ty)
1123 // icmp eq/ne(null,GV) -> false/true
1124 if (C1->isNullValue()) {
1125 if (const GlobalValue *GV = dyn_cast<GlobalValue>(C2))
1126 // Don't try to evaluate aliases. External weak GV can be null.
1127 if (!isa<GlobalAlias>(GV) && !GV->hasExternalWeakLinkage())
1128 if (pred == ICmpInst::ICMP_EQ)
1129 return ConstantInt::getFalse();
1130 else if (pred == ICmpInst::ICMP_NE)
1131 return ConstantInt::getTrue();
1132 // icmp eq/ne(GV,null) -> false/true
1133 } else if (C2->isNullValue()) {
1134 if (const GlobalValue *GV = dyn_cast<GlobalValue>(C1))
1135 // Don't try to evaluate aliases. External weak GV can be null.
1136 if (!isa<GlobalAlias>(GV) && !GV->hasExternalWeakLinkage())
1137 if (pred == ICmpInst::ICMP_EQ)
1138 return ConstantInt::getFalse();
1139 else if (pred == ICmpInst::ICMP_NE)
1140 return ConstantInt::getTrue();
1143 if (isa<ConstantInt>(C1) && isa<ConstantInt>(C2)) {
1144 APInt V1 = cast<ConstantInt>(C1)->getValue();
1145 APInt V2 = cast<ConstantInt>(C2)->getValue();
1147 default: assert(0 && "Invalid ICmp Predicate"); return 0;
1148 case ICmpInst::ICMP_EQ: return ConstantInt::get(Type::Int1Ty, V1 == V2);
1149 case ICmpInst::ICMP_NE: return ConstantInt::get(Type::Int1Ty, V1 != V2);
1150 case ICmpInst::ICMP_SLT:return ConstantInt::get(Type::Int1Ty, V1.slt(V2));
1151 case ICmpInst::ICMP_SGT:return ConstantInt::get(Type::Int1Ty, V1.sgt(V2));
1152 case ICmpInst::ICMP_SLE:return ConstantInt::get(Type::Int1Ty, V1.sle(V2));
1153 case ICmpInst::ICMP_SGE:return ConstantInt::get(Type::Int1Ty, V1.sge(V2));
1154 case ICmpInst::ICMP_ULT:return ConstantInt::get(Type::Int1Ty, V1.ult(V2));
1155 case ICmpInst::ICMP_UGT:return ConstantInt::get(Type::Int1Ty, V1.ugt(V2));
1156 case ICmpInst::ICMP_ULE:return ConstantInt::get(Type::Int1Ty, V1.ule(V2));
1157 case ICmpInst::ICMP_UGE:return ConstantInt::get(Type::Int1Ty, V1.uge(V2));
1159 } else if (isa<ConstantFP>(C1) && isa<ConstantFP>(C2)) {
1160 APFloat C1V = cast<ConstantFP>(C1)->getValueAPF();
1161 APFloat C2V = cast<ConstantFP>(C2)->getValueAPF();
1162 APFloat::cmpResult R = C1V.compare(C2V);
1164 default: assert(0 && "Invalid FCmp Predicate"); return 0;
1165 case FCmpInst::FCMP_FALSE: return ConstantInt::getFalse();
1166 case FCmpInst::FCMP_TRUE: return ConstantInt::getTrue();
1167 case FCmpInst::FCMP_UNO:
1168 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpUnordered);
1169 case FCmpInst::FCMP_ORD:
1170 return ConstantInt::get(Type::Int1Ty, R!=APFloat::cmpUnordered);
1171 case FCmpInst::FCMP_UEQ:
1172 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpUnordered ||
1173 R==APFloat::cmpEqual);
1174 case FCmpInst::FCMP_OEQ:
1175 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpEqual);
1176 case FCmpInst::FCMP_UNE:
1177 return ConstantInt::get(Type::Int1Ty, R!=APFloat::cmpEqual);
1178 case FCmpInst::FCMP_ONE:
1179 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpLessThan ||
1180 R==APFloat::cmpGreaterThan);
1181 case FCmpInst::FCMP_ULT:
1182 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpUnordered ||
1183 R==APFloat::cmpLessThan);
1184 case FCmpInst::FCMP_OLT:
1185 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpLessThan);
1186 case FCmpInst::FCMP_UGT:
1187 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpUnordered ||
1188 R==APFloat::cmpGreaterThan);
1189 case FCmpInst::FCMP_OGT:
1190 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpGreaterThan);
1191 case FCmpInst::FCMP_ULE:
1192 return ConstantInt::get(Type::Int1Ty, R!=APFloat::cmpGreaterThan);
1193 case FCmpInst::FCMP_OLE:
1194 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpLessThan ||
1195 R==APFloat::cmpEqual);
1196 case FCmpInst::FCMP_UGE:
1197 return ConstantInt::get(Type::Int1Ty, R!=APFloat::cmpLessThan);
1198 case FCmpInst::FCMP_OGE:
1199 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpGreaterThan ||
1200 R==APFloat::cmpEqual);
1202 } else if (const ConstantVector *CP1 = dyn_cast<ConstantVector>(C1)) {
1203 if (const ConstantVector *CP2 = dyn_cast<ConstantVector>(C2)) {
1204 if (pred == FCmpInst::FCMP_OEQ || pred == FCmpInst::FCMP_UEQ) {
1205 for (unsigned i = 0, e = CP1->getNumOperands(); i != e; ++i) {
1206 Constant *C= ConstantExpr::getFCmp(FCmpInst::FCMP_OEQ,
1207 const_cast<Constant*>(CP1->getOperand(i)),
1208 const_cast<Constant*>(CP2->getOperand(i)));
1209 if (ConstantInt *CB = dyn_cast<ConstantInt>(C))
1212 // Otherwise, could not decide from any element pairs.
1214 } else if (pred == ICmpInst::ICMP_EQ) {
1215 for (unsigned i = 0, e = CP1->getNumOperands(); i != e; ++i) {
1216 Constant *C = ConstantExpr::getICmp(ICmpInst::ICMP_EQ,
1217 const_cast<Constant*>(CP1->getOperand(i)),
1218 const_cast<Constant*>(CP2->getOperand(i)));
1219 if (ConstantInt *CB = dyn_cast<ConstantInt>(C))
1222 // Otherwise, could not decide from any element pairs.
1228 if (C1->getType()->isFloatingPoint()) {
1229 switch (evaluateFCmpRelation(C1, C2)) {
1230 default: assert(0 && "Unknown relation!");
1231 case FCmpInst::FCMP_UNO:
1232 case FCmpInst::FCMP_ORD:
1233 case FCmpInst::FCMP_UEQ:
1234 case FCmpInst::FCMP_UNE:
1235 case FCmpInst::FCMP_ULT:
1236 case FCmpInst::FCMP_UGT:
1237 case FCmpInst::FCMP_ULE:
1238 case FCmpInst::FCMP_UGE:
1239 case FCmpInst::FCMP_TRUE:
1240 case FCmpInst::FCMP_FALSE:
1241 case FCmpInst::BAD_FCMP_PREDICATE:
1242 break; // Couldn't determine anything about these constants.
1243 case FCmpInst::FCMP_OEQ: // We know that C1 == C2
1244 return ConstantInt::get(Type::Int1Ty,
1245 pred == FCmpInst::FCMP_UEQ || pred == FCmpInst::FCMP_OEQ ||
1246 pred == FCmpInst::FCMP_ULE || pred == FCmpInst::FCMP_OLE ||
1247 pred == FCmpInst::FCMP_UGE || pred == FCmpInst::FCMP_OGE);
1248 case FCmpInst::FCMP_OLT: // We know that C1 < C2
1249 return ConstantInt::get(Type::Int1Ty,
1250 pred == FCmpInst::FCMP_UNE || pred == FCmpInst::FCMP_ONE ||
1251 pred == FCmpInst::FCMP_ULT || pred == FCmpInst::FCMP_OLT ||
1252 pred == FCmpInst::FCMP_ULE || pred == FCmpInst::FCMP_OLE);
1253 case FCmpInst::FCMP_OGT: // We know that C1 > C2
1254 return ConstantInt::get(Type::Int1Ty,
1255 pred == FCmpInst::FCMP_UNE || pred == FCmpInst::FCMP_ONE ||
1256 pred == FCmpInst::FCMP_UGT || pred == FCmpInst::FCMP_OGT ||
1257 pred == FCmpInst::FCMP_UGE || pred == FCmpInst::FCMP_OGE);
1258 case FCmpInst::FCMP_OLE: // We know that C1 <= C2
1259 // We can only partially decide this relation.
1260 if (pred == FCmpInst::FCMP_UGT || pred == FCmpInst::FCMP_OGT)
1261 return ConstantInt::getFalse();
1262 if (pred == FCmpInst::FCMP_ULT || pred == FCmpInst::FCMP_OLT)
1263 return ConstantInt::getTrue();
1265 case FCmpInst::FCMP_OGE: // We known that C1 >= C2
1266 // We can only partially decide this relation.
1267 if (pred == FCmpInst::FCMP_ULT || pred == FCmpInst::FCMP_OLT)
1268 return ConstantInt::getFalse();
1269 if (pred == FCmpInst::FCMP_UGT || pred == FCmpInst::FCMP_OGT)
1270 return ConstantInt::getTrue();
1272 case ICmpInst::ICMP_NE: // We know that C1 != C2
1273 // We can only partially decide this relation.
1274 if (pred == FCmpInst::FCMP_OEQ || pred == FCmpInst::FCMP_UEQ)
1275 return ConstantInt::getFalse();
1276 if (pred == FCmpInst::FCMP_ONE || pred == FCmpInst::FCMP_UNE)
1277 return ConstantInt::getTrue();
1281 // Evaluate the relation between the two constants, per the predicate.
1282 switch (evaluateICmpRelation(C1, C2, CmpInst::isSigned(pred))) {
1283 default: assert(0 && "Unknown relational!");
1284 case ICmpInst::BAD_ICMP_PREDICATE:
1285 break; // Couldn't determine anything about these constants.
1286 case ICmpInst::ICMP_EQ: // We know the constants are equal!
1287 // If we know the constants are equal, we can decide the result of this
1288 // computation precisely.
1289 return ConstantInt::get(Type::Int1Ty,
1290 pred == ICmpInst::ICMP_EQ ||
1291 pred == ICmpInst::ICMP_ULE ||
1292 pred == ICmpInst::ICMP_SLE ||
1293 pred == ICmpInst::ICMP_UGE ||
1294 pred == ICmpInst::ICMP_SGE);
1295 case ICmpInst::ICMP_ULT:
1296 // If we know that C1 < C2, we can decide the result of this computation
1298 return ConstantInt::get(Type::Int1Ty,
1299 pred == ICmpInst::ICMP_ULT ||
1300 pred == ICmpInst::ICMP_NE ||
1301 pred == ICmpInst::ICMP_ULE);
1302 case ICmpInst::ICMP_SLT:
1303 // If we know that C1 < C2, we can decide the result of this computation
1305 return ConstantInt::get(Type::Int1Ty,
1306 pred == ICmpInst::ICMP_SLT ||
1307 pred == ICmpInst::ICMP_NE ||
1308 pred == ICmpInst::ICMP_SLE);
1309 case ICmpInst::ICMP_UGT:
1310 // If we know that C1 > C2, we can decide the result of this computation
1312 return ConstantInt::get(Type::Int1Ty,
1313 pred == ICmpInst::ICMP_UGT ||
1314 pred == ICmpInst::ICMP_NE ||
1315 pred == ICmpInst::ICMP_UGE);
1316 case ICmpInst::ICMP_SGT:
1317 // If we know that C1 > C2, we can decide the result of this computation
1319 return ConstantInt::get(Type::Int1Ty,
1320 pred == ICmpInst::ICMP_SGT ||
1321 pred == ICmpInst::ICMP_NE ||
1322 pred == ICmpInst::ICMP_SGE);
1323 case ICmpInst::ICMP_ULE:
1324 // If we know that C1 <= C2, we can only partially decide this relation.
1325 if (pred == ICmpInst::ICMP_UGT) return ConstantInt::getFalse();
1326 if (pred == ICmpInst::ICMP_ULT) return ConstantInt::getTrue();
1328 case ICmpInst::ICMP_SLE:
1329 // If we know that C1 <= C2, we can only partially decide this relation.
1330 if (pred == ICmpInst::ICMP_SGT) return ConstantInt::getFalse();
1331 if (pred == ICmpInst::ICMP_SLT) return ConstantInt::getTrue();
1334 case ICmpInst::ICMP_UGE:
1335 // If we know that C1 >= C2, we can only partially decide this relation.
1336 if (pred == ICmpInst::ICMP_ULT) return ConstantInt::getFalse();
1337 if (pred == ICmpInst::ICMP_UGT) return ConstantInt::getTrue();
1339 case ICmpInst::ICMP_SGE:
1340 // If we know that C1 >= C2, we can only partially decide this relation.
1341 if (pred == ICmpInst::ICMP_SLT) return ConstantInt::getFalse();
1342 if (pred == ICmpInst::ICMP_SGT) return ConstantInt::getTrue();
1345 case ICmpInst::ICMP_NE:
1346 // If we know that C1 != C2, we can only partially decide this relation.
1347 if (pred == ICmpInst::ICMP_EQ) return ConstantInt::getFalse();
1348 if (pred == ICmpInst::ICMP_NE) return ConstantInt::getTrue();
1352 if (!isa<ConstantExpr>(C1) && isa<ConstantExpr>(C2)) {
1353 // If C2 is a constant expr and C1 isn't, flop them around and fold the
1354 // other way if possible.
1356 case ICmpInst::ICMP_EQ:
1357 case ICmpInst::ICMP_NE:
1358 // No change of predicate required.
1359 return ConstantFoldCompareInstruction(pred, C2, C1);
1361 case ICmpInst::ICMP_ULT:
1362 case ICmpInst::ICMP_SLT:
1363 case ICmpInst::ICMP_UGT:
1364 case ICmpInst::ICMP_SGT:
1365 case ICmpInst::ICMP_ULE:
1366 case ICmpInst::ICMP_SLE:
1367 case ICmpInst::ICMP_UGE:
1368 case ICmpInst::ICMP_SGE:
1369 // Change the predicate as necessary to swap the operands.
1370 pred = ICmpInst::getSwappedPredicate((ICmpInst::Predicate)pred);
1371 return ConstantFoldCompareInstruction(pred, C2, C1);
1373 default: // These predicates cannot be flopped around.
1381 Constant *llvm::ConstantFoldGetElementPtr(const Constant *C,
1382 Constant* const *Idxs,
1385 (NumIdx == 1 && Idxs[0]->isNullValue()))
1386 return const_cast<Constant*>(C);
1388 if (isa<UndefValue>(C)) {
1389 const Type *Ty = GetElementPtrInst::getIndexedType(C->getType(),
1391 (Value **)Idxs+NumIdx,
1393 assert(Ty != 0 && "Invalid indices for GEP!");
1394 return UndefValue::get(PointerType::get(Ty));
1397 Constant *Idx0 = Idxs[0];
1398 if (C->isNullValue()) {
1400 for (unsigned i = 0, e = NumIdx; i != e; ++i)
1401 if (!Idxs[i]->isNullValue()) {
1406 const Type *Ty = GetElementPtrInst::getIndexedType(C->getType(),
1408 (Value**)Idxs+NumIdx,
1410 assert(Ty != 0 && "Invalid indices for GEP!");
1411 return ConstantPointerNull::get(PointerType::get(Ty));
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());