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) {
91 DoubleToBits(cast<ConstantFP>(CV->getOperand(i))->
92 getValueAPF().convertToDouble());
93 Constant *C = ConstantInt::get(Type::Int64Ty, V);
94 Result.push_back(ConstantExpr::getBitCast(C, DstEltTy ));
96 return ConstantVector::get(Result);
99 assert(SrcEltTy->getTypeID() == Type::FloatTyID);
100 for (unsigned i = 0; i != SrcNumElts; ++i) {
101 uint32_t V = FloatToBits(cast<ConstantFP>(CV->getOperand(i))->
102 getValueAPF().convertToFloat());
103 Constant *C = ConstantInt::get(Type::Int32Ty, V);
104 Result.push_back(ConstantExpr::getBitCast(C, DstEltTy));
106 return ConstantVector::get(Result);
109 // Otherwise, this is a cast that changes element count and size. Handle
110 // casts which shrink the elements here.
112 // FIXME: We need to know endianness to do this!
117 /// This function determines which opcode to use to fold two constant cast
118 /// expressions together. It uses CastInst::isEliminableCastPair to determine
119 /// the opcode. Consequently its just a wrapper around that function.
120 /// @brief Determine if it is valid to fold a cast of a cast
122 foldConstantCastPair(
123 unsigned opc, ///< opcode of the second cast constant expression
124 const ConstantExpr*Op, ///< the first cast constant expression
125 const Type *DstTy ///< desintation type of the first cast
127 assert(Op && Op->isCast() && "Can't fold cast of cast without a cast!");
128 assert(DstTy && DstTy->isFirstClassType() && "Invalid cast destination type");
129 assert(CastInst::isCast(opc) && "Invalid cast opcode");
131 // The the types and opcodes for the two Cast constant expressions
132 const Type *SrcTy = Op->getOperand(0)->getType();
133 const Type *MidTy = Op->getType();
134 Instruction::CastOps firstOp = Instruction::CastOps(Op->getOpcode());
135 Instruction::CastOps secondOp = Instruction::CastOps(opc);
137 // Let CastInst::isEliminableCastPair do the heavy lifting.
138 return CastInst::isEliminableCastPair(firstOp, secondOp, SrcTy, MidTy, DstTy,
142 Constant *llvm::ConstantFoldCastInstruction(unsigned opc, const Constant *V,
143 const Type *DestTy) {
144 const Type *SrcTy = V->getType();
146 if (isa<UndefValue>(V)) {
147 // zext(undef) = 0, because the top bits will be zero.
148 // sext(undef) = 0, because the top bits will all be the same.
149 if (opc == Instruction::ZExt || opc == Instruction::SExt)
150 return Constant::getNullValue(DestTy);
151 return UndefValue::get(DestTy);
154 // If the cast operand is a constant expression, there's a few things we can
155 // do to try to simplify it.
156 if (const ConstantExpr *CE = dyn_cast<ConstantExpr>(V)) {
158 // Try hard to fold cast of cast because they are often eliminable.
159 if (unsigned newOpc = foldConstantCastPair(opc, CE, DestTy))
160 return ConstantExpr::getCast(newOpc, CE->getOperand(0), DestTy);
161 } else if (CE->getOpcode() == Instruction::GetElementPtr) {
162 // If all of the indexes in the GEP are null values, there is no pointer
163 // adjustment going on. We might as well cast the source pointer.
164 bool isAllNull = true;
165 for (unsigned i = 1, e = CE->getNumOperands(); i != e; ++i)
166 if (!CE->getOperand(i)->isNullValue()) {
171 // This is casting one pointer type to another, always BitCast
172 return ConstantExpr::getPointerCast(CE->getOperand(0), DestTy);
176 // We actually have to do a cast now. Perform the cast according to the
179 case Instruction::FPTrunc:
180 case Instruction::FPExt:
181 if (const ConstantFP *FPC = dyn_cast<ConstantFP>(V)) {
182 APFloat Val = FPC->getValueAPF();
183 Val.convert(DestTy==Type::FloatTy ? APFloat::IEEEsingle :
185 APFloat::rmNearestTiesToEven);
186 return ConstantFP::get(DestTy, Val);
188 return 0; // Can't fold.
189 case Instruction::FPToUI:
190 if (const ConstantFP *FPC = dyn_cast<ConstantFP>(V)) {
191 APFloat V = FPC->getValueAPF();
192 bool isDouble = &V.getSemantics()==&APFloat::IEEEdouble;
193 uint32_t DestBitWidth = cast<IntegerType>(DestTy)->getBitWidth();
194 APInt Val(APIntOps::RoundDoubleToAPInt(isDouble ? V.convertToDouble() :
195 (double)V.convertToFloat(), DestBitWidth));
196 return ConstantInt::get(Val);
198 return 0; // Can't fold.
199 case Instruction::FPToSI:
200 if (const ConstantFP *FPC = dyn_cast<ConstantFP>(V)) {
201 APFloat V = FPC->getValueAPF();
202 bool isDouble = &V.getSemantics()==&APFloat::IEEEdouble;
203 uint32_t DestBitWidth = cast<IntegerType>(DestTy)->getBitWidth();
204 APInt Val(APIntOps::RoundDoubleToAPInt(isDouble ? V.convertToDouble() :
205 (double)V.convertToFloat(), DestBitWidth));
206 return ConstantInt::get(Val);
208 return 0; // Can't fold.
209 case Instruction::IntToPtr: //always treated as unsigned
210 if (V->isNullValue()) // Is it an integral null value?
211 return ConstantPointerNull::get(cast<PointerType>(DestTy));
212 return 0; // Other pointer types cannot be casted
213 case Instruction::PtrToInt: // always treated as unsigned
214 if (V->isNullValue()) // is it a null pointer value?
215 return ConstantInt::get(DestTy, 0);
216 return 0; // Other pointer types cannot be casted
217 case Instruction::UIToFP:
218 if (const ConstantInt *CI = dyn_cast<ConstantInt>(V)) {
219 if (DestTy==Type::FloatTy)
220 return ConstantFP::get(DestTy,
221 APFloat((float)CI->getValue().roundToDouble()));
223 return ConstantFP::get(DestTy, APFloat(CI->getValue().roundToDouble()));
226 case Instruction::SIToFP:
227 if (const ConstantInt *CI = dyn_cast<ConstantInt>(V)) {
228 double d = CI->getValue().signedRoundToDouble();
229 if (DestTy==Type::FloatTy)
230 return ConstantFP::get(DestTy, APFloat((float)d));
232 return ConstantFP::get(DestTy, APFloat(d));
235 case Instruction::ZExt:
236 if (const ConstantInt *CI = dyn_cast<ConstantInt>(V)) {
237 uint32_t BitWidth = cast<IntegerType>(DestTy)->getBitWidth();
238 APInt Result(CI->getValue());
239 Result.zext(BitWidth);
240 return ConstantInt::get(Result);
243 case Instruction::SExt:
244 if (const ConstantInt *CI = dyn_cast<ConstantInt>(V)) {
245 uint32_t BitWidth = cast<IntegerType>(DestTy)->getBitWidth();
246 APInt Result(CI->getValue());
247 Result.sext(BitWidth);
248 return ConstantInt::get(Result);
251 case Instruction::Trunc:
252 if (const ConstantInt *CI = dyn_cast<ConstantInt>(V)) {
253 uint32_t BitWidth = cast<IntegerType>(DestTy)->getBitWidth();
254 APInt Result(CI->getValue());
255 Result.trunc(BitWidth);
256 return ConstantInt::get(Result);
259 case Instruction::BitCast:
261 return (Constant*)V; // no-op cast
263 // Check to see if we are casting a pointer to an aggregate to a pointer to
264 // the first element. If so, return the appropriate GEP instruction.
265 if (const PointerType *PTy = dyn_cast<PointerType>(V->getType()))
266 if (const PointerType *DPTy = dyn_cast<PointerType>(DestTy)) {
267 SmallVector<Value*, 8> IdxList;
268 IdxList.push_back(Constant::getNullValue(Type::Int32Ty));
269 const Type *ElTy = PTy->getElementType();
270 while (ElTy != DPTy->getElementType()) {
271 if (const StructType *STy = dyn_cast<StructType>(ElTy)) {
272 if (STy->getNumElements() == 0) break;
273 ElTy = STy->getElementType(0);
274 IdxList.push_back(Constant::getNullValue(Type::Int32Ty));
275 } else if (const SequentialType *STy =
276 dyn_cast<SequentialType>(ElTy)) {
277 if (isa<PointerType>(ElTy)) break; // Can't index into pointers!
278 ElTy = STy->getElementType();
279 IdxList.push_back(IdxList[0]);
285 if (ElTy == DPTy->getElementType())
286 return ConstantExpr::getGetElementPtr(
287 const_cast<Constant*>(V), &IdxList[0], IdxList.size());
290 // Handle casts from one vector constant to another. We know that the src
291 // and dest type have the same size (otherwise its an illegal cast).
292 if (const VectorType *DestPTy = dyn_cast<VectorType>(DestTy)) {
293 if (const VectorType *SrcTy = dyn_cast<VectorType>(V->getType())) {
294 assert(DestPTy->getBitWidth() == SrcTy->getBitWidth() &&
295 "Not cast between same sized vectors!");
296 // First, check for null and undef
297 if (isa<ConstantAggregateZero>(V))
298 return Constant::getNullValue(DestTy);
299 if (isa<UndefValue>(V))
300 return UndefValue::get(DestTy);
302 if (const ConstantVector *CV = dyn_cast<ConstantVector>(V)) {
303 // This is a cast from a ConstantVector of one type to a
304 // ConstantVector of another type. Check to see if all elements of
305 // the input are simple.
306 bool AllSimpleConstants = true;
307 for (unsigned i = 0, e = CV->getNumOperands(); i != e; ++i) {
308 if (!isa<ConstantInt>(CV->getOperand(i)) &&
309 !isa<ConstantFP>(CV->getOperand(i))) {
310 AllSimpleConstants = false;
315 // If all of the elements are simple constants, we can fold this.
316 if (AllSimpleConstants)
317 return CastConstantVector(const_cast<ConstantVector*>(CV), DestPTy);
322 // Finally, implement bitcast folding now. The code below doesn't handle
324 if (isa<ConstantPointerNull>(V)) // ptr->ptr cast.
325 return ConstantPointerNull::get(cast<PointerType>(DestTy));
327 // Handle integral constant input.
328 if (const ConstantInt *CI = dyn_cast<ConstantInt>(V)) {
329 if (DestTy->isInteger())
330 // Integral -> Integral. This is a no-op because the bit widths must
331 // be the same. Consequently, we just fold to V.
332 return const_cast<Constant*>(V);
334 if (DestTy->isFloatingPoint()) {
335 if (DestTy == Type::FloatTy)
336 return ConstantFP::get(DestTy, APFloat(CI->getValue().bitsToFloat()));
337 assert(DestTy == Type::DoubleTy && "Unknown FP type!");
338 return ConstantFP::get(DestTy, APFloat(CI->getValue().bitsToDouble()));
340 // Otherwise, can't fold this (vector?)
344 // Handle ConstantFP input.
345 if (const ConstantFP *FP = dyn_cast<ConstantFP>(V)) {
347 if (DestTy == Type::Int32Ty) {
349 return ConstantInt::get(Val.floatToBits(FP->
350 getValueAPF().convertToFloat()));
352 assert(DestTy == Type::Int64Ty && "only support f32/f64 for now!");
354 return ConstantInt::get(Val.doubleToBits(FP->
355 getValueAPF().convertToDouble()));
360 assert(!"Invalid CE CastInst opcode");
364 assert(0 && "Failed to cast constant expression");
368 Constant *llvm::ConstantFoldSelectInstruction(const Constant *Cond,
370 const Constant *V2) {
371 if (const ConstantInt *CB = dyn_cast<ConstantInt>(Cond))
372 return const_cast<Constant*>(CB->getZExtValue() ? V1 : V2);
374 if (isa<UndefValue>(V1)) return const_cast<Constant*>(V2);
375 if (isa<UndefValue>(V2)) return const_cast<Constant*>(V1);
376 if (isa<UndefValue>(Cond)) return const_cast<Constant*>(V1);
377 if (V1 == V2) return const_cast<Constant*>(V1);
381 Constant *llvm::ConstantFoldExtractElementInstruction(const Constant *Val,
382 const Constant *Idx) {
383 if (isa<UndefValue>(Val)) // ee(undef, x) -> undef
384 return UndefValue::get(cast<VectorType>(Val->getType())->getElementType());
385 if (Val->isNullValue()) // ee(zero, x) -> zero
386 return Constant::getNullValue(
387 cast<VectorType>(Val->getType())->getElementType());
389 if (const ConstantVector *CVal = dyn_cast<ConstantVector>(Val)) {
390 if (const ConstantInt *CIdx = dyn_cast<ConstantInt>(Idx)) {
391 return const_cast<Constant*>(CVal->getOperand(CIdx->getZExtValue()));
392 } else if (isa<UndefValue>(Idx)) {
393 // ee({w,x,y,z}, undef) -> w (an arbitrary value).
394 return const_cast<Constant*>(CVal->getOperand(0));
400 Constant *llvm::ConstantFoldInsertElementInstruction(const Constant *Val,
402 const Constant *Idx) {
403 const ConstantInt *CIdx = dyn_cast<ConstantInt>(Idx);
405 APInt idxVal = CIdx->getValue();
406 if (isa<UndefValue>(Val)) {
407 // Insertion of scalar constant into vector undef
408 // Optimize away insertion of undef
409 if (isa<UndefValue>(Elt))
410 return const_cast<Constant*>(Val);
411 // Otherwise break the aggregate undef into multiple undefs and do
414 cast<VectorType>(Val->getType())->getNumElements();
415 std::vector<Constant*> Ops;
417 for (unsigned i = 0; i < numOps; ++i) {
419 (idxVal == i) ? Elt : UndefValue::get(Elt->getType());
420 Ops.push_back(const_cast<Constant*>(Op));
422 return ConstantVector::get(Ops);
424 if (isa<ConstantAggregateZero>(Val)) {
425 // Insertion of scalar constant into vector aggregate zero
426 // Optimize away insertion of zero
427 if (Elt->isNullValue())
428 return const_cast<Constant*>(Val);
429 // Otherwise break the aggregate zero into multiple zeros and do
432 cast<VectorType>(Val->getType())->getNumElements();
433 std::vector<Constant*> Ops;
435 for (unsigned i = 0; i < numOps; ++i) {
437 (idxVal == i) ? Elt : Constant::getNullValue(Elt->getType());
438 Ops.push_back(const_cast<Constant*>(Op));
440 return ConstantVector::get(Ops);
442 if (const ConstantVector *CVal = dyn_cast<ConstantVector>(Val)) {
443 // Insertion of scalar constant into vector constant
444 std::vector<Constant*> Ops;
445 Ops.reserve(CVal->getNumOperands());
446 for (unsigned i = 0; i < CVal->getNumOperands(); ++i) {
448 (idxVal == i) ? Elt : cast<Constant>(CVal->getOperand(i));
449 Ops.push_back(const_cast<Constant*>(Op));
451 return ConstantVector::get(Ops);
456 Constant *llvm::ConstantFoldShuffleVectorInstruction(const Constant *V1,
458 const Constant *Mask) {
463 /// EvalVectorOp - Given two vector constants and a function pointer, apply the
464 /// function pointer to each element pair, producing a new ConstantVector
466 static Constant *EvalVectorOp(const ConstantVector *V1,
467 const ConstantVector *V2,
468 Constant *(*FP)(Constant*, Constant*)) {
469 std::vector<Constant*> Res;
470 for (unsigned i = 0, e = V1->getNumOperands(); i != e; ++i)
471 Res.push_back(FP(const_cast<Constant*>(V1->getOperand(i)),
472 const_cast<Constant*>(V2->getOperand(i))));
473 return ConstantVector::get(Res);
476 Constant *llvm::ConstantFoldBinaryInstruction(unsigned Opcode,
478 const Constant *C2) {
479 // Handle UndefValue up front
480 if (isa<UndefValue>(C1) || isa<UndefValue>(C2)) {
482 case Instruction::Add:
483 case Instruction::Sub:
484 case Instruction::Xor:
485 return UndefValue::get(C1->getType());
486 case Instruction::Mul:
487 case Instruction::And:
488 return Constant::getNullValue(C1->getType());
489 case Instruction::UDiv:
490 case Instruction::SDiv:
491 case Instruction::FDiv:
492 case Instruction::URem:
493 case Instruction::SRem:
494 case Instruction::FRem:
495 if (!isa<UndefValue>(C2)) // undef / X -> 0
496 return Constant::getNullValue(C1->getType());
497 return const_cast<Constant*>(C2); // X / undef -> undef
498 case Instruction::Or: // X | undef -> -1
499 if (const VectorType *PTy = dyn_cast<VectorType>(C1->getType()))
500 return ConstantVector::getAllOnesValue(PTy);
501 return ConstantInt::getAllOnesValue(C1->getType());
502 case Instruction::LShr:
503 if (isa<UndefValue>(C2) && isa<UndefValue>(C1))
504 return const_cast<Constant*>(C1); // undef lshr undef -> undef
505 return Constant::getNullValue(C1->getType()); // X lshr undef -> 0
507 case Instruction::AShr:
508 if (!isa<UndefValue>(C2))
509 return const_cast<Constant*>(C1); // undef ashr X --> undef
510 else if (isa<UndefValue>(C1))
511 return const_cast<Constant*>(C1); // undef ashr undef -> undef
513 return const_cast<Constant*>(C1); // X ashr undef --> X
514 case Instruction::Shl:
515 // undef << X -> 0 or X << undef -> 0
516 return Constant::getNullValue(C1->getType());
520 if (const ConstantExpr *CE1 = dyn_cast<ConstantExpr>(C1)) {
521 if (isa<ConstantExpr>(C2)) {
522 // There are many possible foldings we could do here. We should probably
523 // at least fold add of a pointer with an integer into the appropriate
524 // getelementptr. This will improve alias analysis a bit.
526 // Just implement a couple of simple identities.
528 case Instruction::Add:
529 if (C2->isNullValue()) return const_cast<Constant*>(C1); // X + 0 == X
531 case Instruction::Sub:
532 if (C2->isNullValue()) return const_cast<Constant*>(C1); // X - 0 == X
534 case Instruction::Mul:
535 if (C2->isNullValue()) return const_cast<Constant*>(C2); // X * 0 == 0
536 if (const ConstantInt *CI = dyn_cast<ConstantInt>(C2))
537 if (CI->equalsInt(1))
538 return const_cast<Constant*>(C1); // X * 1 == X
540 case Instruction::UDiv:
541 case Instruction::SDiv:
542 if (const ConstantInt *CI = dyn_cast<ConstantInt>(C2))
543 if (CI->equalsInt(1))
544 return const_cast<Constant*>(C1); // X / 1 == X
546 case Instruction::URem:
547 case Instruction::SRem:
548 if (const ConstantInt *CI = dyn_cast<ConstantInt>(C2))
549 if (CI->equalsInt(1))
550 return Constant::getNullValue(CI->getType()); // X % 1 == 0
552 case Instruction::And:
553 if (const ConstantInt *CI = dyn_cast<ConstantInt>(C2)) {
554 if (CI->isZero()) return const_cast<Constant*>(C2); // X & 0 == 0
555 if (CI->isAllOnesValue())
556 return const_cast<Constant*>(C1); // X & -1 == X
558 // (zext i32 to i64) & 4294967295 -> (zext i32 to i64)
559 if (CE1->getOpcode() == Instruction::ZExt) {
560 APInt PossiblySetBits
561 = cast<IntegerType>(CE1->getOperand(0)->getType())->getMask();
562 PossiblySetBits.zext(C1->getType()->getPrimitiveSizeInBits());
563 if ((PossiblySetBits & CI->getValue()) == PossiblySetBits)
564 return const_cast<Constant*>(C1);
567 if (CE1->isCast() && isa<GlobalValue>(CE1->getOperand(0))) {
568 GlobalValue *CPR = cast<GlobalValue>(CE1->getOperand(0));
570 // Functions are at least 4-byte aligned. If and'ing the address of a
571 // function with a constant < 4, fold it to zero.
572 if (const ConstantInt *CI = dyn_cast<ConstantInt>(C2))
573 if (CI->getValue().ult(APInt(CI->getType()->getBitWidth(),4)) &&
575 return Constant::getNullValue(CI->getType());
578 case Instruction::Or:
579 if (C2->isNullValue()) return const_cast<Constant*>(C1); // X | 0 == X
580 if (const ConstantInt *CI = dyn_cast<ConstantInt>(C2))
581 if (CI->isAllOnesValue())
582 return const_cast<Constant*>(C2); // X | -1 == -1
584 case Instruction::Xor:
585 if (C2->isNullValue()) return const_cast<Constant*>(C1); // X ^ 0 == X
587 case Instruction::AShr:
588 // ashr (zext C to Ty), C2 -> lshr (zext C, CSA), C2
589 if (CE1->getOpcode() == Instruction::ZExt) // Top bits known zero.
590 return ConstantExpr::getLShr(const_cast<Constant*>(C1),
591 const_cast<Constant*>(C2));
595 } else if (isa<ConstantExpr>(C2)) {
596 // If C2 is a constant expr and C1 isn't, flop them around and fold the
597 // other way if possible.
599 case Instruction::Add:
600 case Instruction::Mul:
601 case Instruction::And:
602 case Instruction::Or:
603 case Instruction::Xor:
604 // No change of opcode required.
605 return ConstantFoldBinaryInstruction(Opcode, C2, C1);
607 case Instruction::Shl:
608 case Instruction::LShr:
609 case Instruction::AShr:
610 case Instruction::Sub:
611 case Instruction::SDiv:
612 case Instruction::UDiv:
613 case Instruction::FDiv:
614 case Instruction::URem:
615 case Instruction::SRem:
616 case Instruction::FRem:
617 default: // These instructions cannot be flopped around.
622 // At this point we know neither constant is an UndefValue nor a ConstantExpr
623 // so look at directly computing the value.
624 if (const ConstantInt *CI1 = dyn_cast<ConstantInt>(C1)) {
625 if (const ConstantInt *CI2 = dyn_cast<ConstantInt>(C2)) {
626 using namespace APIntOps;
627 APInt C1V = CI1->getValue();
628 APInt C2V = CI2->getValue();
632 case Instruction::Add:
633 return ConstantInt::get(C1V + C2V);
634 case Instruction::Sub:
635 return ConstantInt::get(C1V - C2V);
636 case Instruction::Mul:
637 return ConstantInt::get(C1V * C2V);
638 case Instruction::UDiv:
639 if (CI2->isNullValue())
640 return 0; // X / 0 -> can't fold
641 return ConstantInt::get(C1V.udiv(C2V));
642 case Instruction::SDiv:
643 if (CI2->isNullValue())
644 return 0; // X / 0 -> can't fold
645 if (C2V.isAllOnesValue() && C1V.isMinSignedValue())
646 return 0; // MIN_INT / -1 -> overflow
647 return ConstantInt::get(C1V.sdiv(C2V));
648 case Instruction::URem:
649 if (C2->isNullValue())
650 return 0; // X / 0 -> can't fold
651 return ConstantInt::get(C1V.urem(C2V));
652 case Instruction::SRem:
653 if (CI2->isNullValue())
654 return 0; // X % 0 -> can't fold
655 if (C2V.isAllOnesValue() && C1V.isMinSignedValue())
656 return 0; // MIN_INT % -1 -> overflow
657 return ConstantInt::get(C1V.srem(C2V));
658 case Instruction::And:
659 return ConstantInt::get(C1V & C2V);
660 case Instruction::Or:
661 return ConstantInt::get(C1V | C2V);
662 case Instruction::Xor:
663 return ConstantInt::get(C1V ^ C2V);
664 case Instruction::Shl:
665 if (uint32_t shiftAmt = C2V.getZExtValue())
666 if (shiftAmt < C1V.getBitWidth())
667 return ConstantInt::get(C1V.shl(shiftAmt));
669 return UndefValue::get(C1->getType()); // too big shift is undef
670 return const_cast<ConstantInt*>(CI1); // Zero shift is identity
671 case Instruction::LShr:
672 if (uint32_t shiftAmt = C2V.getZExtValue())
673 if (shiftAmt < C1V.getBitWidth())
674 return ConstantInt::get(C1V.lshr(shiftAmt));
676 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
684 return const_cast<ConstantInt*>(CI1); // Zero shift is identity
687 } else if (const ConstantFP *CFP1 = dyn_cast<ConstantFP>(C1)) {
688 if (const ConstantFP *CFP2 = dyn_cast<ConstantFP>(C2)) {
689 APFloat C1V = CFP1->getValueAPF();
690 APFloat C2V = CFP2->getValueAPF();
691 APFloat C3V = C1V; // copy for modification
692 bool isDouble = CFP1->getType()==Type::DoubleTy;
696 case Instruction::Add:
697 (void)C3V.add(C2V, APFloat::rmNearestTiesToEven);
698 return ConstantFP::get(CFP1->getType(), C3V);
699 case Instruction::Sub:
700 (void)C3V.subtract(C2V, APFloat::rmNearestTiesToEven);
701 return ConstantFP::get(CFP1->getType(), C3V);
702 case Instruction::Mul:
703 (void)C3V.multiply(C2V, APFloat::rmNearestTiesToEven);
704 return ConstantFP::get(CFP1->getType(), C3V);
705 case Instruction::FDiv:
706 // FIXME better to look at the return code
709 // IEEE 754, Section 7.1, #4
710 return ConstantFP::get(CFP1->getType(), isDouble ?
711 APFloat(std::numeric_limits<double>::quiet_NaN()) :
712 APFloat(std::numeric_limits<float>::quiet_NaN()));
713 else if (C2V.isNegZero() || C1V.isNegative())
714 // IEEE 754, Section 7.2, negative infinity case
715 return ConstantFP::get(CFP1->getType(), isDouble ?
716 APFloat(-std::numeric_limits<double>::infinity()) :
717 APFloat(-std::numeric_limits<float>::infinity()));
719 // IEEE 754, Section 7.2, positive infinity case
720 return ConstantFP::get(CFP1->getType(), isDouble ?
721 APFloat(std::numeric_limits<double>::infinity()) :
722 APFloat(std::numeric_limits<float>::infinity()));
723 (void)C3V.divide(C2V, APFloat::rmNearestTiesToEven);
724 return ConstantFP::get(CFP1->getType(), C3V);
725 case Instruction::FRem:
727 // IEEE 754, Section 7.1, #5
728 return ConstantFP::get(CFP1->getType(), isDouble ?
729 APFloat(std::numeric_limits<double>::quiet_NaN()) :
730 APFloat(std::numeric_limits<float>::quiet_NaN()));
731 (void)C3V.mod(C2V, APFloat::rmNearestTiesToEven);
732 return ConstantFP::get(CFP1->getType(), C3V);
735 } else if (const ConstantVector *CP1 = dyn_cast<ConstantVector>(C1)) {
736 if (const ConstantVector *CP2 = dyn_cast<ConstantVector>(C2)) {
740 case Instruction::Add:
741 return EvalVectorOp(CP1, CP2, ConstantExpr::getAdd);
742 case Instruction::Sub:
743 return EvalVectorOp(CP1, CP2, ConstantExpr::getSub);
744 case Instruction::Mul:
745 return EvalVectorOp(CP1, CP2, ConstantExpr::getMul);
746 case Instruction::UDiv:
747 return EvalVectorOp(CP1, CP2, ConstantExpr::getUDiv);
748 case Instruction::SDiv:
749 return EvalVectorOp(CP1, CP2, ConstantExpr::getSDiv);
750 case Instruction::FDiv:
751 return EvalVectorOp(CP1, CP2, ConstantExpr::getFDiv);
752 case Instruction::URem:
753 return EvalVectorOp(CP1, CP2, ConstantExpr::getURem);
754 case Instruction::SRem:
755 return EvalVectorOp(CP1, CP2, ConstantExpr::getSRem);
756 case Instruction::FRem:
757 return EvalVectorOp(CP1, CP2, ConstantExpr::getFRem);
758 case Instruction::And:
759 return EvalVectorOp(CP1, CP2, ConstantExpr::getAnd);
760 case Instruction::Or:
761 return EvalVectorOp(CP1, CP2, ConstantExpr::getOr);
762 case Instruction::Xor:
763 return EvalVectorOp(CP1, CP2, ConstantExpr::getXor);
768 // We don't know how to fold this
772 /// isZeroSizedType - This type is zero sized if its an array or structure of
773 /// zero sized types. The only leaf zero sized type is an empty structure.
774 static bool isMaybeZeroSizedType(const Type *Ty) {
775 if (isa<OpaqueType>(Ty)) return true; // Can't say.
776 if (const StructType *STy = dyn_cast<StructType>(Ty)) {
778 // If all of elements have zero size, this does too.
779 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i)
780 if (!isMaybeZeroSizedType(STy->getElementType(i))) return false;
783 } else if (const ArrayType *ATy = dyn_cast<ArrayType>(Ty)) {
784 return isMaybeZeroSizedType(ATy->getElementType());
789 /// IdxCompare - Compare the two constants as though they were getelementptr
790 /// indices. This allows coersion of the types to be the same thing.
792 /// If the two constants are the "same" (after coersion), return 0. If the
793 /// first is less than the second, return -1, if the second is less than the
794 /// first, return 1. If the constants are not integral, return -2.
796 static int IdxCompare(Constant *C1, Constant *C2, const Type *ElTy) {
797 if (C1 == C2) return 0;
799 // Ok, we found a different index. If they are not ConstantInt, we can't do
800 // anything with them.
801 if (!isa<ConstantInt>(C1) || !isa<ConstantInt>(C2))
802 return -2; // don't know!
804 // Ok, we have two differing integer indices. Sign extend them to be the same
805 // type. Long is always big enough, so we use it.
806 if (C1->getType() != Type::Int64Ty)
807 C1 = ConstantExpr::getSExt(C1, Type::Int64Ty);
809 if (C2->getType() != Type::Int64Ty)
810 C2 = ConstantExpr::getSExt(C2, Type::Int64Ty);
812 if (C1 == C2) return 0; // They are equal
814 // If the type being indexed over is really just a zero sized type, there is
815 // no pointer difference being made here.
816 if (isMaybeZeroSizedType(ElTy))
819 // If they are really different, now that they are the same type, then we
820 // found a difference!
821 if (cast<ConstantInt>(C1)->getSExtValue() <
822 cast<ConstantInt>(C2)->getSExtValue())
828 /// evaluateFCmpRelation - This function determines if there is anything we can
829 /// decide about the two constants provided. This doesn't need to handle simple
830 /// things like ConstantFP comparisons, but should instead handle ConstantExprs.
831 /// If we can determine that the two constants have a particular relation to
832 /// each other, we should return the corresponding FCmpInst predicate,
833 /// otherwise return FCmpInst::BAD_FCMP_PREDICATE. This is used below in
834 /// ConstantFoldCompareInstruction.
836 /// To simplify this code we canonicalize the relation so that the first
837 /// operand is always the most "complex" of the two. We consider ConstantFP
838 /// to be the simplest, and ConstantExprs to be the most complex.
839 static FCmpInst::Predicate evaluateFCmpRelation(const Constant *V1,
840 const Constant *V2) {
841 assert(V1->getType() == V2->getType() &&
842 "Cannot compare values of different types!");
843 // Handle degenerate case quickly
844 if (V1 == V2) return FCmpInst::FCMP_OEQ;
846 if (!isa<ConstantExpr>(V1)) {
847 if (!isa<ConstantExpr>(V2)) {
848 // We distilled thisUse the standard constant folder for a few cases
850 Constant *C1 = const_cast<Constant*>(V1);
851 Constant *C2 = const_cast<Constant*>(V2);
852 R = dyn_cast<ConstantInt>(
853 ConstantExpr::getFCmp(FCmpInst::FCMP_OEQ, C1, C2));
854 if (R && !R->isZero())
855 return FCmpInst::FCMP_OEQ;
856 R = dyn_cast<ConstantInt>(
857 ConstantExpr::getFCmp(FCmpInst::FCMP_OLT, C1, C2));
858 if (R && !R->isZero())
859 return FCmpInst::FCMP_OLT;
860 R = dyn_cast<ConstantInt>(
861 ConstantExpr::getFCmp(FCmpInst::FCMP_OGT, C1, C2));
862 if (R && !R->isZero())
863 return FCmpInst::FCMP_OGT;
865 // Nothing more we can do
866 return FCmpInst::BAD_FCMP_PREDICATE;
869 // If the first operand is simple and second is ConstantExpr, swap operands.
870 FCmpInst::Predicate SwappedRelation = evaluateFCmpRelation(V2, V1);
871 if (SwappedRelation != FCmpInst::BAD_FCMP_PREDICATE)
872 return FCmpInst::getSwappedPredicate(SwappedRelation);
874 // Ok, the LHS is known to be a constantexpr. The RHS can be any of a
875 // constantexpr or a simple constant.
876 const ConstantExpr *CE1 = cast<ConstantExpr>(V1);
877 switch (CE1->getOpcode()) {
878 case Instruction::FPTrunc:
879 case Instruction::FPExt:
880 case Instruction::UIToFP:
881 case Instruction::SIToFP:
882 // We might be able to do something with these but we don't right now.
888 // There are MANY other foldings that we could perform here. They will
889 // probably be added on demand, as they seem needed.
890 return FCmpInst::BAD_FCMP_PREDICATE;
893 /// evaluateICmpRelation - This function determines if there is anything we can
894 /// decide about the two constants provided. This doesn't need to handle simple
895 /// things like integer comparisons, but should instead handle ConstantExprs
896 /// and GlobalValues. If we can determine that the two constants have a
897 /// particular relation to each other, we should return the corresponding ICmp
898 /// predicate, otherwise return ICmpInst::BAD_ICMP_PREDICATE.
900 /// To simplify this code we canonicalize the relation so that the first
901 /// operand is always the most "complex" of the two. We consider simple
902 /// constants (like ConstantInt) to be the simplest, followed by
903 /// GlobalValues, followed by ConstantExpr's (the most complex).
905 static ICmpInst::Predicate evaluateICmpRelation(const Constant *V1,
908 assert(V1->getType() == V2->getType() &&
909 "Cannot compare different types of values!");
910 if (V1 == V2) return ICmpInst::ICMP_EQ;
912 if (!isa<ConstantExpr>(V1) && !isa<GlobalValue>(V1)) {
913 if (!isa<GlobalValue>(V2) && !isa<ConstantExpr>(V2)) {
914 // We distilled this down to a simple case, use the standard constant
917 Constant *C1 = const_cast<Constant*>(V1);
918 Constant *C2 = const_cast<Constant*>(V2);
919 ICmpInst::Predicate pred = ICmpInst::ICMP_EQ;
920 R = dyn_cast<ConstantInt>(ConstantExpr::getICmp(pred, C1, C2));
921 if (R && !R->isZero())
923 pred = isSigned ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT;
924 R = dyn_cast<ConstantInt>(ConstantExpr::getICmp(pred, C1, C2));
925 if (R && !R->isZero())
927 pred = isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT;
928 R = dyn_cast<ConstantInt>(ConstantExpr::getICmp(pred, C1, C2));
929 if (R && !R->isZero())
932 // If we couldn't figure it out, bail.
933 return ICmpInst::BAD_ICMP_PREDICATE;
936 // If the first operand is simple, swap operands.
937 ICmpInst::Predicate SwappedRelation =
938 evaluateICmpRelation(V2, V1, isSigned);
939 if (SwappedRelation != ICmpInst::BAD_ICMP_PREDICATE)
940 return ICmpInst::getSwappedPredicate(SwappedRelation);
942 } else if (const GlobalValue *CPR1 = dyn_cast<GlobalValue>(V1)) {
943 if (isa<ConstantExpr>(V2)) { // Swap as necessary.
944 ICmpInst::Predicate SwappedRelation =
945 evaluateICmpRelation(V2, V1, isSigned);
946 if (SwappedRelation != ICmpInst::BAD_ICMP_PREDICATE)
947 return ICmpInst::getSwappedPredicate(SwappedRelation);
949 return ICmpInst::BAD_ICMP_PREDICATE;
952 // Now we know that the RHS is a GlobalValue or simple constant,
953 // which (since the types must match) means that it's a ConstantPointerNull.
954 if (const GlobalValue *CPR2 = dyn_cast<GlobalValue>(V2)) {
955 // Don't try to decide equality of aliases.
956 if (!isa<GlobalAlias>(CPR1) && !isa<GlobalAlias>(CPR2))
957 if (!CPR1->hasExternalWeakLinkage() || !CPR2->hasExternalWeakLinkage())
958 return ICmpInst::ICMP_NE;
960 assert(isa<ConstantPointerNull>(V2) && "Canonicalization guarantee!");
961 // GlobalVals can never be null. Don't try to evaluate aliases.
962 if (!CPR1->hasExternalWeakLinkage() && !isa<GlobalAlias>(CPR1))
963 return ICmpInst::ICMP_NE;
966 // Ok, the LHS is known to be a constantexpr. The RHS can be any of a
967 // constantexpr, a CPR, or a simple constant.
968 const ConstantExpr *CE1 = cast<ConstantExpr>(V1);
969 const Constant *CE1Op0 = CE1->getOperand(0);
971 switch (CE1->getOpcode()) {
972 case Instruction::Trunc:
973 case Instruction::FPTrunc:
974 case Instruction::FPExt:
975 case Instruction::FPToUI:
976 case Instruction::FPToSI:
977 break; // We can't evaluate floating point casts or truncations.
979 case Instruction::UIToFP:
980 case Instruction::SIToFP:
981 case Instruction::IntToPtr:
982 case Instruction::BitCast:
983 case Instruction::ZExt:
984 case Instruction::SExt:
985 case Instruction::PtrToInt:
986 // If the cast is not actually changing bits, and the second operand is a
987 // null pointer, do the comparison with the pre-casted value.
988 if (V2->isNullValue() &&
989 (isa<PointerType>(CE1->getType()) || CE1->getType()->isInteger())) {
990 bool sgnd = CE1->getOpcode() == Instruction::ZExt ? false :
991 (CE1->getOpcode() == Instruction::SExt ? true :
992 (CE1->getOpcode() == Instruction::PtrToInt ? false : isSigned));
993 return evaluateICmpRelation(
994 CE1Op0, Constant::getNullValue(CE1Op0->getType()), sgnd);
997 // If the dest type is a pointer type, and the RHS is a constantexpr cast
998 // from the same type as the src of the LHS, evaluate the inputs. This is
999 // important for things like "icmp eq (cast 4 to int*), (cast 5 to int*)",
1000 // which happens a lot in compilers with tagged integers.
1001 if (const ConstantExpr *CE2 = dyn_cast<ConstantExpr>(V2))
1002 if (CE2->isCast() && isa<PointerType>(CE1->getType()) &&
1003 CE1->getOperand(0)->getType() == CE2->getOperand(0)->getType() &&
1004 CE1->getOperand(0)->getType()->isInteger()) {
1005 bool sgnd = CE1->getOpcode() == Instruction::ZExt ? false :
1006 (CE1->getOpcode() == Instruction::SExt ? true :
1007 (CE1->getOpcode() == Instruction::PtrToInt ? false : isSigned));
1008 return evaluateICmpRelation(CE1->getOperand(0), CE2->getOperand(0),
1013 case Instruction::GetElementPtr:
1014 // Ok, since this is a getelementptr, we know that the constant has a
1015 // pointer type. Check the various cases.
1016 if (isa<ConstantPointerNull>(V2)) {
1017 // If we are comparing a GEP to a null pointer, check to see if the base
1018 // of the GEP equals the null pointer.
1019 if (const GlobalValue *GV = dyn_cast<GlobalValue>(CE1Op0)) {
1020 if (GV->hasExternalWeakLinkage())
1021 // Weak linkage GVals could be zero or not. We're comparing that
1022 // to null pointer so its greater-or-equal
1023 return isSigned ? ICmpInst::ICMP_SGE : ICmpInst::ICMP_UGE;
1025 // If its not weak linkage, the GVal must have a non-zero address
1026 // so the result is greater-than
1027 return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT;
1028 } else if (isa<ConstantPointerNull>(CE1Op0)) {
1029 // If we are indexing from a null pointer, check to see if we have any
1030 // non-zero indices.
1031 for (unsigned i = 1, e = CE1->getNumOperands(); i != e; ++i)
1032 if (!CE1->getOperand(i)->isNullValue())
1033 // Offsetting from null, must not be equal.
1034 return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT;
1035 // Only zero indexes from null, must still be zero.
1036 return ICmpInst::ICMP_EQ;
1038 // Otherwise, we can't really say if the first operand is null or not.
1039 } else if (const GlobalValue *CPR2 = dyn_cast<GlobalValue>(V2)) {
1040 if (isa<ConstantPointerNull>(CE1Op0)) {
1041 if (CPR2->hasExternalWeakLinkage())
1042 // Weak linkage GVals could be zero or not. We're comparing it to
1043 // a null pointer, so its less-or-equal
1044 return isSigned ? ICmpInst::ICMP_SLE : ICmpInst::ICMP_ULE;
1046 // If its not weak linkage, the GVal must have a non-zero address
1047 // so the result is less-than
1048 return isSigned ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT;
1049 } else if (const GlobalValue *CPR1 = dyn_cast<GlobalValue>(CE1Op0)) {
1051 // If this is a getelementptr of the same global, then it must be
1052 // different. Because the types must match, the getelementptr could
1053 // only have at most one index, and because we fold getelementptr's
1054 // with a single zero index, it must be nonzero.
1055 assert(CE1->getNumOperands() == 2 &&
1056 !CE1->getOperand(1)->isNullValue() &&
1057 "Suprising getelementptr!");
1058 return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT;
1060 // If they are different globals, we don't know what the value is,
1061 // but they can't be equal.
1062 return ICmpInst::ICMP_NE;
1066 const ConstantExpr *CE2 = cast<ConstantExpr>(V2);
1067 const Constant *CE2Op0 = CE2->getOperand(0);
1069 // There are MANY other foldings that we could perform here. They will
1070 // probably be added on demand, as they seem needed.
1071 switch (CE2->getOpcode()) {
1073 case Instruction::GetElementPtr:
1074 // By far the most common case to handle is when the base pointers are
1075 // obviously to the same or different globals.
1076 if (isa<GlobalValue>(CE1Op0) && isa<GlobalValue>(CE2Op0)) {
1077 if (CE1Op0 != CE2Op0) // Don't know relative ordering, but not equal
1078 return ICmpInst::ICMP_NE;
1079 // Ok, we know that both getelementptr instructions are based on the
1080 // same global. From this, we can precisely determine the relative
1081 // ordering of the resultant pointers.
1084 // Compare all of the operands the GEP's have in common.
1085 gep_type_iterator GTI = gep_type_begin(CE1);
1086 for (;i != CE1->getNumOperands() && i != CE2->getNumOperands();
1088 switch (IdxCompare(CE1->getOperand(i), CE2->getOperand(i),
1089 GTI.getIndexedType())) {
1090 case -1: return isSigned ? ICmpInst::ICMP_SLT:ICmpInst::ICMP_ULT;
1091 case 1: return isSigned ? ICmpInst::ICMP_SGT:ICmpInst::ICMP_UGT;
1092 case -2: return ICmpInst::BAD_ICMP_PREDICATE;
1095 // Ok, we ran out of things they have in common. If any leftovers
1096 // are non-zero then we have a difference, otherwise we are equal.
1097 for (; i < CE1->getNumOperands(); ++i)
1098 if (!CE1->getOperand(i)->isNullValue())
1099 if (isa<ConstantInt>(CE1->getOperand(i)))
1100 return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT;
1102 return ICmpInst::BAD_ICMP_PREDICATE; // Might be equal.
1104 for (; i < CE2->getNumOperands(); ++i)
1105 if (!CE2->getOperand(i)->isNullValue())
1106 if (isa<ConstantInt>(CE2->getOperand(i)))
1107 return isSigned ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT;
1109 return ICmpInst::BAD_ICMP_PREDICATE; // Might be equal.
1110 return ICmpInst::ICMP_EQ;
1119 return ICmpInst::BAD_ICMP_PREDICATE;
1122 Constant *llvm::ConstantFoldCompareInstruction(unsigned short pred,
1124 const Constant *C2) {
1126 // Handle some degenerate cases first
1127 if (isa<UndefValue>(C1) || isa<UndefValue>(C2))
1128 return UndefValue::get(Type::Int1Ty);
1130 // icmp eq/ne(null,GV) -> false/true
1131 if (C1->isNullValue()) {
1132 if (const GlobalValue *GV = dyn_cast<GlobalValue>(C2))
1133 if (!GV->hasExternalWeakLinkage()) // External weak GV can be null
1134 if (pred == ICmpInst::ICMP_EQ)
1135 return ConstantInt::getFalse();
1136 else if (pred == ICmpInst::ICMP_NE)
1137 return ConstantInt::getTrue();
1138 // icmp eq/ne(GV,null) -> false/true
1139 } else if (C2->isNullValue()) {
1140 if (const GlobalValue *GV = dyn_cast<GlobalValue>(C1))
1141 if (!GV->hasExternalWeakLinkage()) // External weak GV can be null
1142 if (pred == ICmpInst::ICMP_EQ)
1143 return ConstantInt::getFalse();
1144 else if (pred == ICmpInst::ICMP_NE)
1145 return ConstantInt::getTrue();
1148 if (isa<ConstantInt>(C1) && isa<ConstantInt>(C2)) {
1149 APInt V1 = cast<ConstantInt>(C1)->getValue();
1150 APInt V2 = cast<ConstantInt>(C2)->getValue();
1152 default: assert(0 && "Invalid ICmp Predicate"); return 0;
1153 case ICmpInst::ICMP_EQ: return ConstantInt::get(Type::Int1Ty, V1 == V2);
1154 case ICmpInst::ICMP_NE: return ConstantInt::get(Type::Int1Ty, V1 != V2);
1155 case ICmpInst::ICMP_SLT:return ConstantInt::get(Type::Int1Ty, V1.slt(V2));
1156 case ICmpInst::ICMP_SGT:return ConstantInt::get(Type::Int1Ty, V1.sgt(V2));
1157 case ICmpInst::ICMP_SLE:return ConstantInt::get(Type::Int1Ty, V1.sle(V2));
1158 case ICmpInst::ICMP_SGE:return ConstantInt::get(Type::Int1Ty, V1.sge(V2));
1159 case ICmpInst::ICMP_ULT:return ConstantInt::get(Type::Int1Ty, V1.ult(V2));
1160 case ICmpInst::ICMP_UGT:return ConstantInt::get(Type::Int1Ty, V1.ugt(V2));
1161 case ICmpInst::ICMP_ULE:return ConstantInt::get(Type::Int1Ty, V1.ule(V2));
1162 case ICmpInst::ICMP_UGE:return ConstantInt::get(Type::Int1Ty, V1.uge(V2));
1164 } else if (isa<ConstantFP>(C1) && isa<ConstantFP>(C2)) {
1165 APFloat C1V = cast<ConstantFP>(C1)->getValueAPF();
1166 APFloat C2V = cast<ConstantFP>(C2)->getValueAPF();
1167 APFloat::cmpResult R = C1V.compare(C2V);
1169 default: assert(0 && "Invalid FCmp Predicate"); return 0;
1170 case FCmpInst::FCMP_FALSE: return ConstantInt::getFalse();
1171 case FCmpInst::FCMP_TRUE: return ConstantInt::getTrue();
1172 case FCmpInst::FCMP_UNO:
1173 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpUnordered);
1174 case FCmpInst::FCMP_ORD:
1175 return ConstantInt::get(Type::Int1Ty, R!=APFloat::cmpUnordered);
1176 case FCmpInst::FCMP_UEQ:
1177 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpUnordered ||
1178 R==APFloat::cmpEqual);
1179 case FCmpInst::FCMP_OEQ:
1180 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpEqual);
1181 case FCmpInst::FCMP_UNE:
1182 return ConstantInt::get(Type::Int1Ty, R!=APFloat::cmpEqual);
1183 case FCmpInst::FCMP_ONE:
1184 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpLessThan ||
1185 R==APFloat::cmpGreaterThan);
1186 case FCmpInst::FCMP_ULT:
1187 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpUnordered ||
1188 R==APFloat::cmpLessThan);
1189 case FCmpInst::FCMP_OLT:
1190 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpLessThan);
1191 case FCmpInst::FCMP_UGT:
1192 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpUnordered ||
1193 R==APFloat::cmpGreaterThan);
1194 case FCmpInst::FCMP_OGT:
1195 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpGreaterThan);
1196 case FCmpInst::FCMP_ULE:
1197 return ConstantInt::get(Type::Int1Ty, R!=APFloat::cmpGreaterThan);
1198 case FCmpInst::FCMP_OLE:
1199 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpLessThan ||
1200 R==APFloat::cmpEqual);
1201 case FCmpInst::FCMP_UGE:
1202 return ConstantInt::get(Type::Int1Ty, R!=APFloat::cmpLessThan);
1203 case FCmpInst::FCMP_OGE:
1204 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpGreaterThan ||
1205 R==APFloat::cmpEqual);
1207 } else if (const ConstantVector *CP1 = dyn_cast<ConstantVector>(C1)) {
1208 if (const ConstantVector *CP2 = dyn_cast<ConstantVector>(C2)) {
1209 if (pred == FCmpInst::FCMP_OEQ || pred == FCmpInst::FCMP_UEQ) {
1210 for (unsigned i = 0, e = CP1->getNumOperands(); i != e; ++i) {
1211 Constant *C= ConstantExpr::getFCmp(FCmpInst::FCMP_OEQ,
1212 const_cast<Constant*>(CP1->getOperand(i)),
1213 const_cast<Constant*>(CP2->getOperand(i)));
1214 if (ConstantInt *CB = dyn_cast<ConstantInt>(C))
1217 // Otherwise, could not decide from any element pairs.
1219 } else if (pred == ICmpInst::ICMP_EQ) {
1220 for (unsigned i = 0, e = CP1->getNumOperands(); i != e; ++i) {
1221 Constant *C = ConstantExpr::getICmp(ICmpInst::ICMP_EQ,
1222 const_cast<Constant*>(CP1->getOperand(i)),
1223 const_cast<Constant*>(CP2->getOperand(i)));
1224 if (ConstantInt *CB = dyn_cast<ConstantInt>(C))
1227 // Otherwise, could not decide from any element pairs.
1233 if (C1->getType()->isFloatingPoint()) {
1234 switch (evaluateFCmpRelation(C1, C2)) {
1235 default: assert(0 && "Unknown relation!");
1236 case FCmpInst::FCMP_UNO:
1237 case FCmpInst::FCMP_ORD:
1238 case FCmpInst::FCMP_UEQ:
1239 case FCmpInst::FCMP_UNE:
1240 case FCmpInst::FCMP_ULT:
1241 case FCmpInst::FCMP_UGT:
1242 case FCmpInst::FCMP_ULE:
1243 case FCmpInst::FCMP_UGE:
1244 case FCmpInst::FCMP_TRUE:
1245 case FCmpInst::FCMP_FALSE:
1246 case FCmpInst::BAD_FCMP_PREDICATE:
1247 break; // Couldn't determine anything about these constants.
1248 case FCmpInst::FCMP_OEQ: // We know that C1 == C2
1249 return ConstantInt::get(Type::Int1Ty,
1250 pred == FCmpInst::FCMP_UEQ || pred == FCmpInst::FCMP_OEQ ||
1251 pred == FCmpInst::FCMP_ULE || pred == FCmpInst::FCMP_OLE ||
1252 pred == FCmpInst::FCMP_UGE || pred == FCmpInst::FCMP_OGE);
1253 case FCmpInst::FCMP_OLT: // We know that C1 < C2
1254 return ConstantInt::get(Type::Int1Ty,
1255 pred == FCmpInst::FCMP_UNE || pred == FCmpInst::FCMP_ONE ||
1256 pred == FCmpInst::FCMP_ULT || pred == FCmpInst::FCMP_OLT ||
1257 pred == FCmpInst::FCMP_ULE || pred == FCmpInst::FCMP_OLE);
1258 case FCmpInst::FCMP_OGT: // We know that C1 > C2
1259 return ConstantInt::get(Type::Int1Ty,
1260 pred == FCmpInst::FCMP_UNE || pred == FCmpInst::FCMP_ONE ||
1261 pred == FCmpInst::FCMP_UGT || pred == FCmpInst::FCMP_OGT ||
1262 pred == FCmpInst::FCMP_UGE || pred == FCmpInst::FCMP_OGE);
1263 case FCmpInst::FCMP_OLE: // We know that C1 <= C2
1264 // We can only partially decide this relation.
1265 if (pred == FCmpInst::FCMP_UGT || pred == FCmpInst::FCMP_OGT)
1266 return ConstantInt::getFalse();
1267 if (pred == FCmpInst::FCMP_ULT || pred == FCmpInst::FCMP_OLT)
1268 return ConstantInt::getTrue();
1270 case FCmpInst::FCMP_OGE: // We known that C1 >= C2
1271 // We can only partially decide this relation.
1272 if (pred == FCmpInst::FCMP_ULT || pred == FCmpInst::FCMP_OLT)
1273 return ConstantInt::getFalse();
1274 if (pred == FCmpInst::FCMP_UGT || pred == FCmpInst::FCMP_OGT)
1275 return ConstantInt::getTrue();
1277 case ICmpInst::ICMP_NE: // We know that C1 != C2
1278 // We can only partially decide this relation.
1279 if (pred == FCmpInst::FCMP_OEQ || pred == FCmpInst::FCMP_UEQ)
1280 return ConstantInt::getFalse();
1281 if (pred == FCmpInst::FCMP_ONE || pred == FCmpInst::FCMP_UNE)
1282 return ConstantInt::getTrue();
1286 // Evaluate the relation between the two constants, per the predicate.
1287 switch (evaluateICmpRelation(C1, C2, CmpInst::isSigned(pred))) {
1288 default: assert(0 && "Unknown relational!");
1289 case ICmpInst::BAD_ICMP_PREDICATE:
1290 break; // Couldn't determine anything about these constants.
1291 case ICmpInst::ICMP_EQ: // We know the constants are equal!
1292 // If we know the constants are equal, we can decide the result of this
1293 // computation precisely.
1294 return ConstantInt::get(Type::Int1Ty,
1295 pred == ICmpInst::ICMP_EQ ||
1296 pred == ICmpInst::ICMP_ULE ||
1297 pred == ICmpInst::ICMP_SLE ||
1298 pred == ICmpInst::ICMP_UGE ||
1299 pred == ICmpInst::ICMP_SGE);
1300 case ICmpInst::ICMP_ULT:
1301 // If we know that C1 < C2, we can decide the result of this computation
1303 return ConstantInt::get(Type::Int1Ty,
1304 pred == ICmpInst::ICMP_ULT ||
1305 pred == ICmpInst::ICMP_NE ||
1306 pred == ICmpInst::ICMP_ULE);
1307 case ICmpInst::ICMP_SLT:
1308 // If we know that C1 < C2, we can decide the result of this computation
1310 return ConstantInt::get(Type::Int1Ty,
1311 pred == ICmpInst::ICMP_SLT ||
1312 pred == ICmpInst::ICMP_NE ||
1313 pred == ICmpInst::ICMP_SLE);
1314 case ICmpInst::ICMP_UGT:
1315 // If we know that C1 > C2, we can decide the result of this computation
1317 return ConstantInt::get(Type::Int1Ty,
1318 pred == ICmpInst::ICMP_UGT ||
1319 pred == ICmpInst::ICMP_NE ||
1320 pred == ICmpInst::ICMP_UGE);
1321 case ICmpInst::ICMP_SGT:
1322 // If we know that C1 > C2, we can decide the result of this computation
1324 return ConstantInt::get(Type::Int1Ty,
1325 pred == ICmpInst::ICMP_SGT ||
1326 pred == ICmpInst::ICMP_NE ||
1327 pred == ICmpInst::ICMP_SGE);
1328 case ICmpInst::ICMP_ULE:
1329 // If we know that C1 <= C2, we can only partially decide this relation.
1330 if (pred == ICmpInst::ICMP_UGT) return ConstantInt::getFalse();
1331 if (pred == ICmpInst::ICMP_ULT) return ConstantInt::getTrue();
1333 case ICmpInst::ICMP_SLE:
1334 // If we know that C1 <= C2, we can only partially decide this relation.
1335 if (pred == ICmpInst::ICMP_SGT) return ConstantInt::getFalse();
1336 if (pred == ICmpInst::ICMP_SLT) return ConstantInt::getTrue();
1339 case ICmpInst::ICMP_UGE:
1340 // If we know that C1 >= C2, we can only partially decide this relation.
1341 if (pred == ICmpInst::ICMP_ULT) return ConstantInt::getFalse();
1342 if (pred == ICmpInst::ICMP_UGT) return ConstantInt::getTrue();
1344 case ICmpInst::ICMP_SGE:
1345 // If we know that C1 >= C2, we can only partially decide this relation.
1346 if (pred == ICmpInst::ICMP_SLT) return ConstantInt::getFalse();
1347 if (pred == ICmpInst::ICMP_SGT) return ConstantInt::getTrue();
1350 case ICmpInst::ICMP_NE:
1351 // If we know that C1 != C2, we can only partially decide this relation.
1352 if (pred == ICmpInst::ICMP_EQ) return ConstantInt::getFalse();
1353 if (pred == ICmpInst::ICMP_NE) return ConstantInt::getTrue();
1357 if (!isa<ConstantExpr>(C1) && isa<ConstantExpr>(C2)) {
1358 // If C2 is a constant expr and C1 isn't, flop them around and fold the
1359 // other way if possible.
1361 case ICmpInst::ICMP_EQ:
1362 case ICmpInst::ICMP_NE:
1363 // No change of predicate required.
1364 return ConstantFoldCompareInstruction(pred, C2, C1);
1366 case ICmpInst::ICMP_ULT:
1367 case ICmpInst::ICMP_SLT:
1368 case ICmpInst::ICMP_UGT:
1369 case ICmpInst::ICMP_SGT:
1370 case ICmpInst::ICMP_ULE:
1371 case ICmpInst::ICMP_SLE:
1372 case ICmpInst::ICMP_UGE:
1373 case ICmpInst::ICMP_SGE:
1374 // Change the predicate as necessary to swap the operands.
1375 pred = ICmpInst::getSwappedPredicate((ICmpInst::Predicate)pred);
1376 return ConstantFoldCompareInstruction(pred, C2, C1);
1378 default: // These predicates cannot be flopped around.
1386 Constant *llvm::ConstantFoldGetElementPtr(const Constant *C,
1387 Constant* const *Idxs,
1390 (NumIdx == 1 && Idxs[0]->isNullValue()))
1391 return const_cast<Constant*>(C);
1393 if (isa<UndefValue>(C)) {
1394 const Type *Ty = GetElementPtrInst::getIndexedType(C->getType(),
1396 (Value **)Idxs+NumIdx,
1398 assert(Ty != 0 && "Invalid indices for GEP!");
1399 return UndefValue::get(PointerType::get(Ty));
1402 Constant *Idx0 = Idxs[0];
1403 if (C->isNullValue()) {
1405 for (unsigned i = 0, e = NumIdx; i != e; ++i)
1406 if (!Idxs[i]->isNullValue()) {
1411 const Type *Ty = GetElementPtrInst::getIndexedType(C->getType(),
1413 (Value**)Idxs+NumIdx,
1415 assert(Ty != 0 && "Invalid indices for GEP!");
1416 return ConstantPointerNull::get(PointerType::get(Ty));
1420 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(const_cast<Constant*>(C))) {
1421 // Combine Indices - If the source pointer to this getelementptr instruction
1422 // is a getelementptr instruction, combine the indices of the two
1423 // getelementptr instructions into a single instruction.
1425 if (CE->getOpcode() == Instruction::GetElementPtr) {
1426 const Type *LastTy = 0;
1427 for (gep_type_iterator I = gep_type_begin(CE), E = gep_type_end(CE);
1431 if ((LastTy && isa<ArrayType>(LastTy)) || Idx0->isNullValue()) {
1432 SmallVector<Value*, 16> NewIndices;
1433 NewIndices.reserve(NumIdx + CE->getNumOperands());
1434 for (unsigned i = 1, e = CE->getNumOperands()-1; i != e; ++i)
1435 NewIndices.push_back(CE->getOperand(i));
1437 // Add the last index of the source with the first index of the new GEP.
1438 // Make sure to handle the case when they are actually different types.
1439 Constant *Combined = CE->getOperand(CE->getNumOperands()-1);
1440 // Otherwise it must be an array.
1441 if (!Idx0->isNullValue()) {
1442 const Type *IdxTy = Combined->getType();
1443 if (IdxTy != Idx0->getType()) {
1444 Constant *C1 = ConstantExpr::getSExtOrBitCast(Idx0, Type::Int64Ty);
1445 Constant *C2 = ConstantExpr::getSExtOrBitCast(Combined,
1447 Combined = ConstantExpr::get(Instruction::Add, C1, C2);
1450 ConstantExpr::get(Instruction::Add, Idx0, Combined);
1454 NewIndices.push_back(Combined);
1455 NewIndices.insert(NewIndices.end(), Idxs+1, Idxs+NumIdx);
1456 return ConstantExpr::getGetElementPtr(CE->getOperand(0), &NewIndices[0],
1461 // Implement folding of:
1462 // int* getelementptr ([2 x int]* cast ([3 x int]* %X to [2 x int]*),
1464 // To: int* getelementptr ([3 x int]* %X, long 0, long 0)
1466 if (CE->isCast() && NumIdx > 1 && Idx0->isNullValue()) {
1467 if (const PointerType *SPT =
1468 dyn_cast<PointerType>(CE->getOperand(0)->getType()))
1469 if (const ArrayType *SAT = dyn_cast<ArrayType>(SPT->getElementType()))
1470 if (const ArrayType *CAT =
1471 dyn_cast<ArrayType>(cast<PointerType>(C->getType())->getElementType()))
1472 if (CAT->getElementType() == SAT->getElementType())
1473 return ConstantExpr::getGetElementPtr(
1474 (Constant*)CE->getOperand(0), Idxs, NumIdx);
1477 // Fold: getelementptr (i8* inttoptr (i64 1 to i8*), i32 -1)
1478 // Into: inttoptr (i64 0 to i8*)
1479 // This happens with pointers to member functions in C++.
1480 if (CE->getOpcode() == Instruction::IntToPtr && NumIdx == 1 &&
1481 isa<ConstantInt>(CE->getOperand(0)) && isa<ConstantInt>(Idxs[0]) &&
1482 cast<PointerType>(CE->getType())->getElementType() == Type::Int8Ty) {
1483 Constant *Base = CE->getOperand(0);
1484 Constant *Offset = Idxs[0];
1486 // Convert the smaller integer to the larger type.
1487 if (Offset->getType()->getPrimitiveSizeInBits() <
1488 Base->getType()->getPrimitiveSizeInBits())
1489 Offset = ConstantExpr::getSExt(Offset, Base->getType());
1490 else if (Base->getType()->getPrimitiveSizeInBits() <
1491 Offset->getType()->getPrimitiveSizeInBits())
1492 Base = ConstantExpr::getZExt(Base, Base->getType());
1494 Base = ConstantExpr::getAdd(Base, Offset);
1495 return ConstantExpr::getIntToPtr(Base, CE->getType());