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);
153 // If the cast operand is a constant expression, there's a few things we can
154 // do to try to simplify it.
155 if (const ConstantExpr *CE = dyn_cast<ConstantExpr>(V)) {
157 // Try hard to fold cast of cast because they are often eliminable.
158 if (unsigned newOpc = foldConstantCastPair(opc, CE, DestTy))
159 return ConstantExpr::getCast(newOpc, CE->getOperand(0), DestTy);
160 } else if (CE->getOpcode() == Instruction::GetElementPtr) {
161 // If all of the indexes in the GEP are null values, there is no pointer
162 // adjustment going on. We might as well cast the source pointer.
163 bool isAllNull = true;
164 for (unsigned i = 1, e = CE->getNumOperands(); i != e; ++i)
165 if (!CE->getOperand(i)->isNullValue()) {
170 // This is casting one pointer type to another, always BitCast
171 return ConstantExpr::getPointerCast(CE->getOperand(0), DestTy);
175 // We actually have to do a cast now. Perform the cast according to the
178 case Instruction::FPTrunc:
179 case Instruction::FPExt:
180 if (const ConstantFP *FPC = dyn_cast<ConstantFP>(V)) {
181 APFloat Val = FPC->getValueAPF();
182 Val.convert(DestTy == Type::FloatTy ? APFloat::IEEEsingle :
183 DestTy == Type::DoubleTy ? APFloat::IEEEdouble :
184 DestTy == Type::X86_FP80Ty ? APFloat::x87DoubleExtended :
185 DestTy == Type::FP128Ty ? APFloat::IEEEquad :
187 APFloat::rmNearestTiesToEven);
188 return ConstantFP::get(DestTy, Val);
190 return 0; // Can't fold.
191 case Instruction::FPToUI:
192 case Instruction::FPToSI:
193 if (const ConstantFP *FPC = dyn_cast<ConstantFP>(V)) {
194 APFloat V = FPC->getValueAPF();
196 uint32_t DestBitWidth = cast<IntegerType>(DestTy)->getBitWidth();
197 APFloat::opStatus status = V.convertToInteger(x, DestBitWidth,
198 opc==Instruction::FPToSI,
199 APFloat::rmNearestTiesToEven);
200 if (status!=APFloat::opOK && status!=APFloat::opInexact)
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 if (const ConstantInt *CI = dyn_cast<ConstantInt>(V)) {
216 double d = CI->getValue().roundToDouble();
217 if (DestTy==Type::FloatTy)
218 return ConstantFP::get(DestTy, APFloat((float)d));
219 else if (DestTy==Type::DoubleTy)
220 return ConstantFP::get(DestTy, APFloat(d));
222 return 0; // FIXME do this for long double
225 case Instruction::SIToFP:
226 if (const ConstantInt *CI = dyn_cast<ConstantInt>(V)) {
227 double d = CI->getValue().signedRoundToDouble();
228 if (DestTy==Type::FloatTy)
229 return ConstantFP::get(DestTy, APFloat((float)d));
230 else if (DestTy==Type::DoubleTy)
231 return ConstantFP::get(DestTy, APFloat(d));
233 return 0; // FIXME do this for long double
236 case Instruction::ZExt:
237 if (const ConstantInt *CI = dyn_cast<ConstantInt>(V)) {
238 uint32_t BitWidth = cast<IntegerType>(DestTy)->getBitWidth();
239 APInt Result(CI->getValue());
240 Result.zext(BitWidth);
241 return ConstantInt::get(Result);
244 case Instruction::SExt:
245 if (const ConstantInt *CI = dyn_cast<ConstantInt>(V)) {
246 uint32_t BitWidth = cast<IntegerType>(DestTy)->getBitWidth();
247 APInt Result(CI->getValue());
248 Result.sext(BitWidth);
249 return ConstantInt::get(Result);
252 case Instruction::Trunc:
253 if (const ConstantInt *CI = dyn_cast<ConstantInt>(V)) {
254 uint32_t BitWidth = cast<IntegerType>(DestTy)->getBitWidth();
255 APInt Result(CI->getValue());
256 Result.trunc(BitWidth);
257 return ConstantInt::get(Result);
260 case Instruction::BitCast:
262 return (Constant*)V; // no-op cast
264 // Check to see if we are casting a pointer to an aggregate to a pointer to
265 // the first element. If so, return the appropriate GEP instruction.
266 if (const PointerType *PTy = dyn_cast<PointerType>(V->getType()))
267 if (const PointerType *DPTy = dyn_cast<PointerType>(DestTy)) {
268 SmallVector<Value*, 8> IdxList;
269 IdxList.push_back(Constant::getNullValue(Type::Int32Ty));
270 const Type *ElTy = PTy->getElementType();
271 while (ElTy != DPTy->getElementType()) {
272 if (const StructType *STy = dyn_cast<StructType>(ElTy)) {
273 if (STy->getNumElements() == 0) break;
274 ElTy = STy->getElementType(0);
275 IdxList.push_back(Constant::getNullValue(Type::Int32Ty));
276 } else if (const SequentialType *STy =
277 dyn_cast<SequentialType>(ElTy)) {
278 if (isa<PointerType>(ElTy)) break; // Can't index into pointers!
279 ElTy = STy->getElementType();
280 IdxList.push_back(IdxList[0]);
286 if (ElTy == DPTy->getElementType())
287 return ConstantExpr::getGetElementPtr(
288 const_cast<Constant*>(V), &IdxList[0], IdxList.size());
291 // Handle casts from one vector constant to another. We know that the src
292 // and dest type have the same size (otherwise its an illegal cast).
293 if (const VectorType *DestPTy = dyn_cast<VectorType>(DestTy)) {
294 if (const VectorType *SrcTy = dyn_cast<VectorType>(V->getType())) {
295 assert(DestPTy->getBitWidth() == SrcTy->getBitWidth() &&
296 "Not cast between same sized vectors!");
297 // First, check for null and undef
298 if (isa<ConstantAggregateZero>(V))
299 return Constant::getNullValue(DestTy);
300 if (isa<UndefValue>(V))
301 return UndefValue::get(DestTy);
303 if (const ConstantVector *CV = dyn_cast<ConstantVector>(V)) {
304 // This is a cast from a ConstantVector of one type to a
305 // ConstantVector of another type. Check to see if all elements of
306 // the input are simple.
307 bool AllSimpleConstants = true;
308 for (unsigned i = 0, e = CV->getNumOperands(); i != e; ++i) {
309 if (!isa<ConstantInt>(CV->getOperand(i)) &&
310 !isa<ConstantFP>(CV->getOperand(i))) {
311 AllSimpleConstants = false;
316 // If all of the elements are simple constants, we can fold this.
317 if (AllSimpleConstants)
318 return CastConstantVector(const_cast<ConstantVector*>(CV), DestPTy);
323 // Finally, implement bitcast folding now. The code below doesn't handle
325 if (isa<ConstantPointerNull>(V)) // ptr->ptr cast.
326 return ConstantPointerNull::get(cast<PointerType>(DestTy));
328 // Handle integral constant input.
329 if (const ConstantInt *CI = dyn_cast<ConstantInt>(V)) {
330 if (DestTy->isInteger())
331 // Integral -> Integral. This is a no-op because the bit widths must
332 // be the same. Consequently, we just fold to V.
333 return const_cast<Constant*>(V);
335 if (DestTy->isFloatingPoint()) {
336 assert((DestTy == Type::DoubleTy || DestTy == Type::FloatTy) &&
338 return ConstantFP::get(DestTy, APFloat(CI->getValue()));
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) {
348 return ConstantInt::get(FP->getValueAPF().convertToAPInt());
350 assert(DestTy == Type::Int64Ty && "only support f32/f64 for now!");
351 return ConstantInt::get(FP->getValueAPF().convertToAPInt());
356 assert(!"Invalid CE CastInst opcode");
360 assert(0 && "Failed to cast constant expression");
364 Constant *llvm::ConstantFoldSelectInstruction(const Constant *Cond,
366 const Constant *V2) {
367 if (const ConstantInt *CB = dyn_cast<ConstantInt>(Cond))
368 return const_cast<Constant*>(CB->getZExtValue() ? V1 : V2);
370 if (isa<UndefValue>(V1)) return const_cast<Constant*>(V2);
371 if (isa<UndefValue>(V2)) return const_cast<Constant*>(V1);
372 if (isa<UndefValue>(Cond)) return const_cast<Constant*>(V1);
373 if (V1 == V2) return const_cast<Constant*>(V1);
377 Constant *llvm::ConstantFoldExtractElementInstruction(const Constant *Val,
378 const Constant *Idx) {
379 if (isa<UndefValue>(Val)) // ee(undef, x) -> undef
380 return UndefValue::get(cast<VectorType>(Val->getType())->getElementType());
381 if (Val->isNullValue()) // ee(zero, x) -> zero
382 return Constant::getNullValue(
383 cast<VectorType>(Val->getType())->getElementType());
385 if (const ConstantVector *CVal = dyn_cast<ConstantVector>(Val)) {
386 if (const ConstantInt *CIdx = dyn_cast<ConstantInt>(Idx)) {
387 return const_cast<Constant*>(CVal->getOperand(CIdx->getZExtValue()));
388 } else if (isa<UndefValue>(Idx)) {
389 // ee({w,x,y,z}, undef) -> w (an arbitrary value).
390 return const_cast<Constant*>(CVal->getOperand(0));
396 Constant *llvm::ConstantFoldInsertElementInstruction(const Constant *Val,
398 const Constant *Idx) {
399 const ConstantInt *CIdx = dyn_cast<ConstantInt>(Idx);
401 APInt idxVal = CIdx->getValue();
402 if (isa<UndefValue>(Val)) {
403 // Insertion of scalar constant into vector undef
404 // Optimize away insertion of undef
405 if (isa<UndefValue>(Elt))
406 return const_cast<Constant*>(Val);
407 // Otherwise break the aggregate undef into multiple undefs and do
410 cast<VectorType>(Val->getType())->getNumElements();
411 std::vector<Constant*> Ops;
413 for (unsigned i = 0; i < numOps; ++i) {
415 (idxVal == i) ? Elt : UndefValue::get(Elt->getType());
416 Ops.push_back(const_cast<Constant*>(Op));
418 return ConstantVector::get(Ops);
420 if (isa<ConstantAggregateZero>(Val)) {
421 // Insertion of scalar constant into vector aggregate zero
422 // Optimize away insertion of zero
423 if (Elt->isNullValue())
424 return const_cast<Constant*>(Val);
425 // Otherwise break the aggregate zero into multiple zeros and do
428 cast<VectorType>(Val->getType())->getNumElements();
429 std::vector<Constant*> Ops;
431 for (unsigned i = 0; i < numOps; ++i) {
433 (idxVal == i) ? Elt : Constant::getNullValue(Elt->getType());
434 Ops.push_back(const_cast<Constant*>(Op));
436 return ConstantVector::get(Ops);
438 if (const ConstantVector *CVal = dyn_cast<ConstantVector>(Val)) {
439 // Insertion of scalar constant into vector constant
440 std::vector<Constant*> Ops;
441 Ops.reserve(CVal->getNumOperands());
442 for (unsigned i = 0; i < CVal->getNumOperands(); ++i) {
444 (idxVal == i) ? Elt : cast<Constant>(CVal->getOperand(i));
445 Ops.push_back(const_cast<Constant*>(Op));
447 return ConstantVector::get(Ops);
452 Constant *llvm::ConstantFoldShuffleVectorInstruction(const Constant *V1,
454 const Constant *Mask) {
459 /// EvalVectorOp - Given two vector constants and a function pointer, apply the
460 /// function pointer to each element pair, producing a new ConstantVector
462 static Constant *EvalVectorOp(const ConstantVector *V1,
463 const ConstantVector *V2,
464 Constant *(*FP)(Constant*, Constant*)) {
465 std::vector<Constant*> Res;
466 for (unsigned i = 0, e = V1->getNumOperands(); i != e; ++i)
467 Res.push_back(FP(const_cast<Constant*>(V1->getOperand(i)),
468 const_cast<Constant*>(V2->getOperand(i))));
469 return ConstantVector::get(Res);
472 Constant *llvm::ConstantFoldBinaryInstruction(unsigned Opcode,
474 const Constant *C2) {
475 // Handle UndefValue up front
476 if (isa<UndefValue>(C1) || isa<UndefValue>(C2)) {
478 case Instruction::Add:
479 case Instruction::Sub:
480 case Instruction::Xor:
481 return UndefValue::get(C1->getType());
482 case Instruction::Mul:
483 case Instruction::And:
484 return Constant::getNullValue(C1->getType());
485 case Instruction::UDiv:
486 case Instruction::SDiv:
487 case Instruction::FDiv:
488 case Instruction::URem:
489 case Instruction::SRem:
490 case Instruction::FRem:
491 if (!isa<UndefValue>(C2)) // undef / X -> 0
492 return Constant::getNullValue(C1->getType());
493 return const_cast<Constant*>(C2); // X / undef -> undef
494 case Instruction::Or: // X | undef -> -1
495 if (const VectorType *PTy = dyn_cast<VectorType>(C1->getType()))
496 return ConstantVector::getAllOnesValue(PTy);
497 return ConstantInt::getAllOnesValue(C1->getType());
498 case Instruction::LShr:
499 if (isa<UndefValue>(C2) && isa<UndefValue>(C1))
500 return const_cast<Constant*>(C1); // undef lshr undef -> undef
501 return Constant::getNullValue(C1->getType()); // X lshr undef -> 0
503 case Instruction::AShr:
504 if (!isa<UndefValue>(C2))
505 return const_cast<Constant*>(C1); // undef ashr X --> undef
506 else if (isa<UndefValue>(C1))
507 return const_cast<Constant*>(C1); // undef ashr undef -> undef
509 return const_cast<Constant*>(C1); // X ashr undef --> X
510 case Instruction::Shl:
511 // undef << X -> 0 or X << undef -> 0
512 return Constant::getNullValue(C1->getType());
516 if (const ConstantExpr *CE1 = dyn_cast<ConstantExpr>(C1)) {
517 if (isa<ConstantExpr>(C2)) {
518 // There are many possible foldings we could do here. We should probably
519 // at least fold add of a pointer with an integer into the appropriate
520 // getelementptr. This will improve alias analysis a bit.
522 // Just implement a couple of simple identities.
524 case Instruction::Add:
525 if (C2->isNullValue()) return const_cast<Constant*>(C1); // X + 0 == X
527 case Instruction::Sub:
528 if (C2->isNullValue()) return const_cast<Constant*>(C1); // X - 0 == X
530 case Instruction::Mul:
531 if (C2->isNullValue()) return const_cast<Constant*>(C2); // X * 0 == 0
532 if (const ConstantInt *CI = dyn_cast<ConstantInt>(C2))
533 if (CI->equalsInt(1))
534 return const_cast<Constant*>(C1); // X * 1 == X
536 case Instruction::UDiv:
537 case Instruction::SDiv:
538 if (const ConstantInt *CI = dyn_cast<ConstantInt>(C2))
539 if (CI->equalsInt(1))
540 return const_cast<Constant*>(C1); // X / 1 == X
542 case Instruction::URem:
543 case Instruction::SRem:
544 if (const ConstantInt *CI = dyn_cast<ConstantInt>(C2))
545 if (CI->equalsInt(1))
546 return Constant::getNullValue(CI->getType()); // X % 1 == 0
548 case Instruction::And:
549 if (const ConstantInt *CI = dyn_cast<ConstantInt>(C2)) {
550 if (CI->isZero()) return const_cast<Constant*>(C2); // X & 0 == 0
551 if (CI->isAllOnesValue())
552 return const_cast<Constant*>(C1); // X & -1 == X
554 // (zext i32 to i64) & 4294967295 -> (zext i32 to i64)
555 if (CE1->getOpcode() == Instruction::ZExt) {
556 APInt PossiblySetBits
557 = cast<IntegerType>(CE1->getOperand(0)->getType())->getMask();
558 PossiblySetBits.zext(C1->getType()->getPrimitiveSizeInBits());
559 if ((PossiblySetBits & CI->getValue()) == PossiblySetBits)
560 return const_cast<Constant*>(C1);
563 if (CE1->isCast() && isa<GlobalValue>(CE1->getOperand(0))) {
564 GlobalValue *CPR = cast<GlobalValue>(CE1->getOperand(0));
566 // Functions are at least 4-byte aligned. If and'ing the address of a
567 // function with a constant < 4, fold it to zero.
568 if (const ConstantInt *CI = dyn_cast<ConstantInt>(C2))
569 if (CI->getValue().ult(APInt(CI->getType()->getBitWidth(),4)) &&
571 return Constant::getNullValue(CI->getType());
574 case Instruction::Or:
575 if (C2->isNullValue()) return const_cast<Constant*>(C1); // X | 0 == X
576 if (const ConstantInt *CI = dyn_cast<ConstantInt>(C2))
577 if (CI->isAllOnesValue())
578 return const_cast<Constant*>(C2); // X | -1 == -1
580 case Instruction::Xor:
581 if (C2->isNullValue()) return const_cast<Constant*>(C1); // X ^ 0 == X
583 case Instruction::AShr:
584 // ashr (zext C to Ty), C2 -> lshr (zext C, CSA), C2
585 if (CE1->getOpcode() == Instruction::ZExt) // Top bits known zero.
586 return ConstantExpr::getLShr(const_cast<Constant*>(C1),
587 const_cast<Constant*>(C2));
591 } else if (isa<ConstantExpr>(C2)) {
592 // If C2 is a constant expr and C1 isn't, flop them around and fold the
593 // other way if possible.
595 case Instruction::Add:
596 case Instruction::Mul:
597 case Instruction::And:
598 case Instruction::Or:
599 case Instruction::Xor:
600 // No change of opcode required.
601 return ConstantFoldBinaryInstruction(Opcode, C2, C1);
603 case Instruction::Shl:
604 case Instruction::LShr:
605 case Instruction::AShr:
606 case Instruction::Sub:
607 case Instruction::SDiv:
608 case Instruction::UDiv:
609 case Instruction::FDiv:
610 case Instruction::URem:
611 case Instruction::SRem:
612 case Instruction::FRem:
613 default: // These instructions cannot be flopped around.
618 // At this point we know neither constant is an UndefValue nor a ConstantExpr
619 // so look at directly computing the value.
620 if (const ConstantInt *CI1 = dyn_cast<ConstantInt>(C1)) {
621 if (const ConstantInt *CI2 = dyn_cast<ConstantInt>(C2)) {
622 using namespace APIntOps;
623 APInt C1V = CI1->getValue();
624 APInt C2V = CI2->getValue();
628 case Instruction::Add:
629 return ConstantInt::get(C1V + C2V);
630 case Instruction::Sub:
631 return ConstantInt::get(C1V - C2V);
632 case Instruction::Mul:
633 return ConstantInt::get(C1V * C2V);
634 case Instruction::UDiv:
635 if (CI2->isNullValue())
636 return 0; // X / 0 -> can't fold
637 return ConstantInt::get(C1V.udiv(C2V));
638 case Instruction::SDiv:
639 if (CI2->isNullValue())
640 return 0; // X / 0 -> can't fold
641 if (C2V.isAllOnesValue() && C1V.isMinSignedValue())
642 return 0; // MIN_INT / -1 -> overflow
643 return ConstantInt::get(C1V.sdiv(C2V));
644 case Instruction::URem:
645 if (C2->isNullValue())
646 return 0; // X / 0 -> can't fold
647 return ConstantInt::get(C1V.urem(C2V));
648 case Instruction::SRem:
649 if (CI2->isNullValue())
650 return 0; // X % 0 -> can't fold
651 if (C2V.isAllOnesValue() && C1V.isMinSignedValue())
652 return 0; // MIN_INT % -1 -> overflow
653 return ConstantInt::get(C1V.srem(C2V));
654 case Instruction::And:
655 return ConstantInt::get(C1V & C2V);
656 case Instruction::Or:
657 return ConstantInt::get(C1V | C2V);
658 case Instruction::Xor:
659 return ConstantInt::get(C1V ^ C2V);
660 case Instruction::Shl:
661 if (uint32_t shiftAmt = C2V.getZExtValue())
662 if (shiftAmt < C1V.getBitWidth())
663 return ConstantInt::get(C1V.shl(shiftAmt));
665 return UndefValue::get(C1->getType()); // too big shift is undef
666 return const_cast<ConstantInt*>(CI1); // Zero shift is identity
667 case Instruction::LShr:
668 if (uint32_t shiftAmt = C2V.getZExtValue())
669 if (shiftAmt < C1V.getBitWidth())
670 return ConstantInt::get(C1V.lshr(shiftAmt));
672 return UndefValue::get(C1->getType()); // too big shift is undef
673 return const_cast<ConstantInt*>(CI1); // Zero shift is identity
674 case Instruction::AShr:
675 if (uint32_t shiftAmt = C2V.getZExtValue())
676 if (shiftAmt < C1V.getBitWidth())
677 return ConstantInt::get(C1V.ashr(shiftAmt));
679 return UndefValue::get(C1->getType()); // too big shift is undef
680 return const_cast<ConstantInt*>(CI1); // Zero shift is identity
683 } else if (const ConstantFP *CFP1 = dyn_cast<ConstantFP>(C1)) {
684 if (const ConstantFP *CFP2 = dyn_cast<ConstantFP>(C2)) {
685 APFloat C1V = CFP1->getValueAPF();
686 APFloat C2V = CFP2->getValueAPF();
687 APFloat C3V = C1V; // copy for modification
688 bool isDouble = CFP1->getType()==Type::DoubleTy;
692 case Instruction::Add:
693 (void)C3V.add(C2V, APFloat::rmNearestTiesToEven);
694 return ConstantFP::get(CFP1->getType(), C3V);
695 case Instruction::Sub:
696 (void)C3V.subtract(C2V, APFloat::rmNearestTiesToEven);
697 return ConstantFP::get(CFP1->getType(), C3V);
698 case Instruction::Mul:
699 (void)C3V.multiply(C2V, APFloat::rmNearestTiesToEven);
700 return ConstantFP::get(CFP1->getType(), C3V);
701 case Instruction::FDiv:
702 (void)C3V.divide(C2V, APFloat::rmNearestTiesToEven);
703 return ConstantFP::get(CFP1->getType(), C3V);
704 case Instruction::FRem:
706 // IEEE 754, Section 7.1, #5
707 return ConstantFP::get(CFP1->getType(), isDouble ?
708 APFloat(std::numeric_limits<double>::quiet_NaN()) :
709 APFloat(std::numeric_limits<float>::quiet_NaN()));
710 (void)C3V.mod(C2V, APFloat::rmNearestTiesToEven);
711 return ConstantFP::get(CFP1->getType(), C3V);
714 } else if (const ConstantVector *CP1 = dyn_cast<ConstantVector>(C1)) {
715 if (const ConstantVector *CP2 = dyn_cast<ConstantVector>(C2)) {
719 case Instruction::Add:
720 return EvalVectorOp(CP1, CP2, ConstantExpr::getAdd);
721 case Instruction::Sub:
722 return EvalVectorOp(CP1, CP2, ConstantExpr::getSub);
723 case Instruction::Mul:
724 return EvalVectorOp(CP1, CP2, ConstantExpr::getMul);
725 case Instruction::UDiv:
726 return EvalVectorOp(CP1, CP2, ConstantExpr::getUDiv);
727 case Instruction::SDiv:
728 return EvalVectorOp(CP1, CP2, ConstantExpr::getSDiv);
729 case Instruction::FDiv:
730 return EvalVectorOp(CP1, CP2, ConstantExpr::getFDiv);
731 case Instruction::URem:
732 return EvalVectorOp(CP1, CP2, ConstantExpr::getURem);
733 case Instruction::SRem:
734 return EvalVectorOp(CP1, CP2, ConstantExpr::getSRem);
735 case Instruction::FRem:
736 return EvalVectorOp(CP1, CP2, ConstantExpr::getFRem);
737 case Instruction::And:
738 return EvalVectorOp(CP1, CP2, ConstantExpr::getAnd);
739 case Instruction::Or:
740 return EvalVectorOp(CP1, CP2, ConstantExpr::getOr);
741 case Instruction::Xor:
742 return EvalVectorOp(CP1, CP2, ConstantExpr::getXor);
747 // We don't know how to fold this
751 /// isZeroSizedType - This type is zero sized if its an array or structure of
752 /// zero sized types. The only leaf zero sized type is an empty structure.
753 static bool isMaybeZeroSizedType(const Type *Ty) {
754 if (isa<OpaqueType>(Ty)) return true; // Can't say.
755 if (const StructType *STy = dyn_cast<StructType>(Ty)) {
757 // If all of elements have zero size, this does too.
758 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i)
759 if (!isMaybeZeroSizedType(STy->getElementType(i))) return false;
762 } else if (const ArrayType *ATy = dyn_cast<ArrayType>(Ty)) {
763 return isMaybeZeroSizedType(ATy->getElementType());
768 /// IdxCompare - Compare the two constants as though they were getelementptr
769 /// indices. This allows coersion of the types to be the same thing.
771 /// If the two constants are the "same" (after coersion), return 0. If the
772 /// first is less than the second, return -1, if the second is less than the
773 /// first, return 1. If the constants are not integral, return -2.
775 static int IdxCompare(Constant *C1, Constant *C2, const Type *ElTy) {
776 if (C1 == C2) return 0;
778 // Ok, we found a different index. If they are not ConstantInt, we can't do
779 // anything with them.
780 if (!isa<ConstantInt>(C1) || !isa<ConstantInt>(C2))
781 return -2; // don't know!
783 // Ok, we have two differing integer indices. Sign extend them to be the same
784 // type. Long is always big enough, so we use it.
785 if (C1->getType() != Type::Int64Ty)
786 C1 = ConstantExpr::getSExt(C1, Type::Int64Ty);
788 if (C2->getType() != Type::Int64Ty)
789 C2 = ConstantExpr::getSExt(C2, Type::Int64Ty);
791 if (C1 == C2) return 0; // They are equal
793 // If the type being indexed over is really just a zero sized type, there is
794 // no pointer difference being made here.
795 if (isMaybeZeroSizedType(ElTy))
798 // If they are really different, now that they are the same type, then we
799 // found a difference!
800 if (cast<ConstantInt>(C1)->getSExtValue() <
801 cast<ConstantInt>(C2)->getSExtValue())
807 /// evaluateFCmpRelation - This function determines if there is anything we can
808 /// decide about the two constants provided. This doesn't need to handle simple
809 /// things like ConstantFP comparisons, but should instead handle ConstantExprs.
810 /// If we can determine that the two constants have a particular relation to
811 /// each other, we should return the corresponding FCmpInst predicate,
812 /// otherwise return FCmpInst::BAD_FCMP_PREDICATE. This is used below in
813 /// ConstantFoldCompareInstruction.
815 /// To simplify this code we canonicalize the relation so that the first
816 /// operand is always the most "complex" of the two. We consider ConstantFP
817 /// to be the simplest, and ConstantExprs to be the most complex.
818 static FCmpInst::Predicate evaluateFCmpRelation(const Constant *V1,
819 const Constant *V2) {
820 assert(V1->getType() == V2->getType() &&
821 "Cannot compare values of different types!");
822 // Handle degenerate case quickly
823 if (V1 == V2) return FCmpInst::FCMP_OEQ;
825 if (!isa<ConstantExpr>(V1)) {
826 if (!isa<ConstantExpr>(V2)) {
827 // We distilled thisUse the standard constant folder for a few cases
829 Constant *C1 = const_cast<Constant*>(V1);
830 Constant *C2 = const_cast<Constant*>(V2);
831 R = dyn_cast<ConstantInt>(
832 ConstantExpr::getFCmp(FCmpInst::FCMP_OEQ, C1, C2));
833 if (R && !R->isZero())
834 return FCmpInst::FCMP_OEQ;
835 R = dyn_cast<ConstantInt>(
836 ConstantExpr::getFCmp(FCmpInst::FCMP_OLT, C1, C2));
837 if (R && !R->isZero())
838 return FCmpInst::FCMP_OLT;
839 R = dyn_cast<ConstantInt>(
840 ConstantExpr::getFCmp(FCmpInst::FCMP_OGT, C1, C2));
841 if (R && !R->isZero())
842 return FCmpInst::FCMP_OGT;
844 // Nothing more we can do
845 return FCmpInst::BAD_FCMP_PREDICATE;
848 // If the first operand is simple and second is ConstantExpr, swap operands.
849 FCmpInst::Predicate SwappedRelation = evaluateFCmpRelation(V2, V1);
850 if (SwappedRelation != FCmpInst::BAD_FCMP_PREDICATE)
851 return FCmpInst::getSwappedPredicate(SwappedRelation);
853 // Ok, the LHS is known to be a constantexpr. The RHS can be any of a
854 // constantexpr or a simple constant.
855 const ConstantExpr *CE1 = cast<ConstantExpr>(V1);
856 switch (CE1->getOpcode()) {
857 case Instruction::FPTrunc:
858 case Instruction::FPExt:
859 case Instruction::UIToFP:
860 case Instruction::SIToFP:
861 // We might be able to do something with these but we don't right now.
867 // There are MANY other foldings that we could perform here. They will
868 // probably be added on demand, as they seem needed.
869 return FCmpInst::BAD_FCMP_PREDICATE;
872 /// evaluateICmpRelation - This function determines if there is anything we can
873 /// decide about the two constants provided. This doesn't need to handle simple
874 /// things like integer comparisons, but should instead handle ConstantExprs
875 /// and GlobalValues. If we can determine that the two constants have a
876 /// particular relation to each other, we should return the corresponding ICmp
877 /// predicate, otherwise return ICmpInst::BAD_ICMP_PREDICATE.
879 /// To simplify this code we canonicalize the relation so that the first
880 /// operand is always the most "complex" of the two. We consider simple
881 /// constants (like ConstantInt) to be the simplest, followed by
882 /// GlobalValues, followed by ConstantExpr's (the most complex).
884 static ICmpInst::Predicate evaluateICmpRelation(const Constant *V1,
887 assert(V1->getType() == V2->getType() &&
888 "Cannot compare different types of values!");
889 if (V1 == V2) return ICmpInst::ICMP_EQ;
891 if (!isa<ConstantExpr>(V1) && !isa<GlobalValue>(V1)) {
892 if (!isa<GlobalValue>(V2) && !isa<ConstantExpr>(V2)) {
893 // We distilled this down to a simple case, use the standard constant
896 Constant *C1 = const_cast<Constant*>(V1);
897 Constant *C2 = const_cast<Constant*>(V2);
898 ICmpInst::Predicate pred = ICmpInst::ICMP_EQ;
899 R = dyn_cast<ConstantInt>(ConstantExpr::getICmp(pred, C1, C2));
900 if (R && !R->isZero())
902 pred = isSigned ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT;
903 R = dyn_cast<ConstantInt>(ConstantExpr::getICmp(pred, C1, C2));
904 if (R && !R->isZero())
906 pred = isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT;
907 R = dyn_cast<ConstantInt>(ConstantExpr::getICmp(pred, C1, C2));
908 if (R && !R->isZero())
911 // If we couldn't figure it out, bail.
912 return ICmpInst::BAD_ICMP_PREDICATE;
915 // If the first operand is simple, swap operands.
916 ICmpInst::Predicate SwappedRelation =
917 evaluateICmpRelation(V2, V1, isSigned);
918 if (SwappedRelation != ICmpInst::BAD_ICMP_PREDICATE)
919 return ICmpInst::getSwappedPredicate(SwappedRelation);
921 } else if (const GlobalValue *CPR1 = dyn_cast<GlobalValue>(V1)) {
922 if (isa<ConstantExpr>(V2)) { // Swap as necessary.
923 ICmpInst::Predicate SwappedRelation =
924 evaluateICmpRelation(V2, V1, isSigned);
925 if (SwappedRelation != ICmpInst::BAD_ICMP_PREDICATE)
926 return ICmpInst::getSwappedPredicate(SwappedRelation);
928 return ICmpInst::BAD_ICMP_PREDICATE;
931 // Now we know that the RHS is a GlobalValue or simple constant,
932 // which (since the types must match) means that it's a ConstantPointerNull.
933 if (const GlobalValue *CPR2 = dyn_cast<GlobalValue>(V2)) {
934 // Don't try to decide equality of aliases.
935 if (!isa<GlobalAlias>(CPR1) && !isa<GlobalAlias>(CPR2))
936 if (!CPR1->hasExternalWeakLinkage() || !CPR2->hasExternalWeakLinkage())
937 return ICmpInst::ICMP_NE;
939 assert(isa<ConstantPointerNull>(V2) && "Canonicalization guarantee!");
940 // GlobalVals can never be null. Don't try to evaluate aliases.
941 if (!CPR1->hasExternalWeakLinkage() && !isa<GlobalAlias>(CPR1))
942 return ICmpInst::ICMP_NE;
945 // Ok, the LHS is known to be a constantexpr. The RHS can be any of a
946 // constantexpr, a CPR, or a simple constant.
947 const ConstantExpr *CE1 = cast<ConstantExpr>(V1);
948 const Constant *CE1Op0 = CE1->getOperand(0);
950 switch (CE1->getOpcode()) {
951 case Instruction::Trunc:
952 case Instruction::FPTrunc:
953 case Instruction::FPExt:
954 case Instruction::FPToUI:
955 case Instruction::FPToSI:
956 break; // We can't evaluate floating point casts or truncations.
958 case Instruction::UIToFP:
959 case Instruction::SIToFP:
960 case Instruction::IntToPtr:
961 case Instruction::BitCast:
962 case Instruction::ZExt:
963 case Instruction::SExt:
964 case Instruction::PtrToInt:
965 // If the cast is not actually changing bits, and the second operand is a
966 // null pointer, do the comparison with the pre-casted value.
967 if (V2->isNullValue() &&
968 (isa<PointerType>(CE1->getType()) || CE1->getType()->isInteger())) {
969 bool sgnd = CE1->getOpcode() == Instruction::ZExt ? false :
970 (CE1->getOpcode() == Instruction::SExt ? true :
971 (CE1->getOpcode() == Instruction::PtrToInt ? false : isSigned));
972 return evaluateICmpRelation(
973 CE1Op0, Constant::getNullValue(CE1Op0->getType()), sgnd);
976 // If the dest type is a pointer type, and the RHS is a constantexpr cast
977 // from the same type as the src of the LHS, evaluate the inputs. This is
978 // important for things like "icmp eq (cast 4 to int*), (cast 5 to int*)",
979 // which happens a lot in compilers with tagged integers.
980 if (const ConstantExpr *CE2 = dyn_cast<ConstantExpr>(V2))
981 if (CE2->isCast() && isa<PointerType>(CE1->getType()) &&
982 CE1->getOperand(0)->getType() == CE2->getOperand(0)->getType() &&
983 CE1->getOperand(0)->getType()->isInteger()) {
984 bool sgnd = CE1->getOpcode() == Instruction::ZExt ? false :
985 (CE1->getOpcode() == Instruction::SExt ? true :
986 (CE1->getOpcode() == Instruction::PtrToInt ? false : isSigned));
987 return evaluateICmpRelation(CE1->getOperand(0), CE2->getOperand(0),
992 case Instruction::GetElementPtr:
993 // Ok, since this is a getelementptr, we know that the constant has a
994 // pointer type. Check the various cases.
995 if (isa<ConstantPointerNull>(V2)) {
996 // If we are comparing a GEP to a null pointer, check to see if the base
997 // of the GEP equals the null pointer.
998 if (const GlobalValue *GV = dyn_cast<GlobalValue>(CE1Op0)) {
999 if (GV->hasExternalWeakLinkage())
1000 // Weak linkage GVals could be zero or not. We're comparing that
1001 // to null pointer so its greater-or-equal
1002 return isSigned ? ICmpInst::ICMP_SGE : ICmpInst::ICMP_UGE;
1004 // If its not weak linkage, the GVal must have a non-zero address
1005 // so the result is greater-than
1006 return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT;
1007 } else if (isa<ConstantPointerNull>(CE1Op0)) {
1008 // If we are indexing from a null pointer, check to see if we have any
1009 // non-zero indices.
1010 for (unsigned i = 1, e = CE1->getNumOperands(); i != e; ++i)
1011 if (!CE1->getOperand(i)->isNullValue())
1012 // Offsetting from null, must not be equal.
1013 return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT;
1014 // Only zero indexes from null, must still be zero.
1015 return ICmpInst::ICMP_EQ;
1017 // Otherwise, we can't really say if the first operand is null or not.
1018 } else if (const GlobalValue *CPR2 = dyn_cast<GlobalValue>(V2)) {
1019 if (isa<ConstantPointerNull>(CE1Op0)) {
1020 if (CPR2->hasExternalWeakLinkage())
1021 // Weak linkage GVals could be zero or not. We're comparing it to
1022 // a null pointer, so its less-or-equal
1023 return isSigned ? ICmpInst::ICMP_SLE : ICmpInst::ICMP_ULE;
1025 // If its not weak linkage, the GVal must have a non-zero address
1026 // so the result is less-than
1027 return isSigned ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT;
1028 } else if (const GlobalValue *CPR1 = dyn_cast<GlobalValue>(CE1Op0)) {
1030 // If this is a getelementptr of the same global, then it must be
1031 // different. Because the types must match, the getelementptr could
1032 // only have at most one index, and because we fold getelementptr's
1033 // with a single zero index, it must be nonzero.
1034 assert(CE1->getNumOperands() == 2 &&
1035 !CE1->getOperand(1)->isNullValue() &&
1036 "Suprising getelementptr!");
1037 return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT;
1039 // If they are different globals, we don't know what the value is,
1040 // but they can't be equal.
1041 return ICmpInst::ICMP_NE;
1045 const ConstantExpr *CE2 = cast<ConstantExpr>(V2);
1046 const Constant *CE2Op0 = CE2->getOperand(0);
1048 // There are MANY other foldings that we could perform here. They will
1049 // probably be added on demand, as they seem needed.
1050 switch (CE2->getOpcode()) {
1052 case Instruction::GetElementPtr:
1053 // By far the most common case to handle is when the base pointers are
1054 // obviously to the same or different globals.
1055 if (isa<GlobalValue>(CE1Op0) && isa<GlobalValue>(CE2Op0)) {
1056 if (CE1Op0 != CE2Op0) // Don't know relative ordering, but not equal
1057 return ICmpInst::ICMP_NE;
1058 // Ok, we know that both getelementptr instructions are based on the
1059 // same global. From this, we can precisely determine the relative
1060 // ordering of the resultant pointers.
1063 // Compare all of the operands the GEP's have in common.
1064 gep_type_iterator GTI = gep_type_begin(CE1);
1065 for (;i != CE1->getNumOperands() && i != CE2->getNumOperands();
1067 switch (IdxCompare(CE1->getOperand(i), CE2->getOperand(i),
1068 GTI.getIndexedType())) {
1069 case -1: return isSigned ? ICmpInst::ICMP_SLT:ICmpInst::ICMP_ULT;
1070 case 1: return isSigned ? ICmpInst::ICMP_SGT:ICmpInst::ICMP_UGT;
1071 case -2: return ICmpInst::BAD_ICMP_PREDICATE;
1074 // Ok, we ran out of things they have in common. If any leftovers
1075 // are non-zero then we have a difference, otherwise we are equal.
1076 for (; i < CE1->getNumOperands(); ++i)
1077 if (!CE1->getOperand(i)->isNullValue())
1078 if (isa<ConstantInt>(CE1->getOperand(i)))
1079 return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT;
1081 return ICmpInst::BAD_ICMP_PREDICATE; // Might be equal.
1083 for (; i < CE2->getNumOperands(); ++i)
1084 if (!CE2->getOperand(i)->isNullValue())
1085 if (isa<ConstantInt>(CE2->getOperand(i)))
1086 return isSigned ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT;
1088 return ICmpInst::BAD_ICMP_PREDICATE; // Might be equal.
1089 return ICmpInst::ICMP_EQ;
1098 return ICmpInst::BAD_ICMP_PREDICATE;
1101 Constant *llvm::ConstantFoldCompareInstruction(unsigned short pred,
1103 const Constant *C2) {
1105 // Handle some degenerate cases first
1106 if (isa<UndefValue>(C1) || isa<UndefValue>(C2))
1107 return UndefValue::get(Type::Int1Ty);
1109 // icmp eq/ne(null,GV) -> false/true
1110 if (C1->isNullValue()) {
1111 if (const GlobalValue *GV = dyn_cast<GlobalValue>(C2))
1112 // Don't try to evaluate aliases. External weak GV can be null.
1113 if (!isa<GlobalAlias>(GV) && !GV->hasExternalWeakLinkage())
1114 if (pred == ICmpInst::ICMP_EQ)
1115 return ConstantInt::getFalse();
1116 else if (pred == ICmpInst::ICMP_NE)
1117 return ConstantInt::getTrue();
1118 // icmp eq/ne(GV,null) -> false/true
1119 } else if (C2->isNullValue()) {
1120 if (const GlobalValue *GV = dyn_cast<GlobalValue>(C1))
1121 // Don't try to evaluate aliases. External weak GV can be null.
1122 if (!isa<GlobalAlias>(GV) && !GV->hasExternalWeakLinkage())
1123 if (pred == ICmpInst::ICMP_EQ)
1124 return ConstantInt::getFalse();
1125 else if (pred == ICmpInst::ICMP_NE)
1126 return ConstantInt::getTrue();
1129 if (isa<ConstantInt>(C1) && isa<ConstantInt>(C2)) {
1130 APInt V1 = cast<ConstantInt>(C1)->getValue();
1131 APInt V2 = cast<ConstantInt>(C2)->getValue();
1133 default: assert(0 && "Invalid ICmp Predicate"); return 0;
1134 case ICmpInst::ICMP_EQ: return ConstantInt::get(Type::Int1Ty, V1 == V2);
1135 case ICmpInst::ICMP_NE: return ConstantInt::get(Type::Int1Ty, V1 != V2);
1136 case ICmpInst::ICMP_SLT:return ConstantInt::get(Type::Int1Ty, V1.slt(V2));
1137 case ICmpInst::ICMP_SGT:return ConstantInt::get(Type::Int1Ty, V1.sgt(V2));
1138 case ICmpInst::ICMP_SLE:return ConstantInt::get(Type::Int1Ty, V1.sle(V2));
1139 case ICmpInst::ICMP_SGE:return ConstantInt::get(Type::Int1Ty, V1.sge(V2));
1140 case ICmpInst::ICMP_ULT:return ConstantInt::get(Type::Int1Ty, V1.ult(V2));
1141 case ICmpInst::ICMP_UGT:return ConstantInt::get(Type::Int1Ty, V1.ugt(V2));
1142 case ICmpInst::ICMP_ULE:return ConstantInt::get(Type::Int1Ty, V1.ule(V2));
1143 case ICmpInst::ICMP_UGE:return ConstantInt::get(Type::Int1Ty, V1.uge(V2));
1145 } else if (isa<ConstantFP>(C1) && isa<ConstantFP>(C2)) {
1146 APFloat C1V = cast<ConstantFP>(C1)->getValueAPF();
1147 APFloat C2V = cast<ConstantFP>(C2)->getValueAPF();
1148 APFloat::cmpResult R = C1V.compare(C2V);
1150 default: assert(0 && "Invalid FCmp Predicate"); return 0;
1151 case FCmpInst::FCMP_FALSE: return ConstantInt::getFalse();
1152 case FCmpInst::FCMP_TRUE: return ConstantInt::getTrue();
1153 case FCmpInst::FCMP_UNO:
1154 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpUnordered);
1155 case FCmpInst::FCMP_ORD:
1156 return ConstantInt::get(Type::Int1Ty, R!=APFloat::cmpUnordered);
1157 case FCmpInst::FCMP_UEQ:
1158 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpUnordered ||
1159 R==APFloat::cmpEqual);
1160 case FCmpInst::FCMP_OEQ:
1161 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpEqual);
1162 case FCmpInst::FCMP_UNE:
1163 return ConstantInt::get(Type::Int1Ty, R!=APFloat::cmpEqual);
1164 case FCmpInst::FCMP_ONE:
1165 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpLessThan ||
1166 R==APFloat::cmpGreaterThan);
1167 case FCmpInst::FCMP_ULT:
1168 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpUnordered ||
1169 R==APFloat::cmpLessThan);
1170 case FCmpInst::FCMP_OLT:
1171 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpLessThan);
1172 case FCmpInst::FCMP_UGT:
1173 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpUnordered ||
1174 R==APFloat::cmpGreaterThan);
1175 case FCmpInst::FCMP_OGT:
1176 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpGreaterThan);
1177 case FCmpInst::FCMP_ULE:
1178 return ConstantInt::get(Type::Int1Ty, R!=APFloat::cmpGreaterThan);
1179 case FCmpInst::FCMP_OLE:
1180 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpLessThan ||
1181 R==APFloat::cmpEqual);
1182 case FCmpInst::FCMP_UGE:
1183 return ConstantInt::get(Type::Int1Ty, R!=APFloat::cmpLessThan);
1184 case FCmpInst::FCMP_OGE:
1185 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpGreaterThan ||
1186 R==APFloat::cmpEqual);
1188 } else if (const ConstantVector *CP1 = dyn_cast<ConstantVector>(C1)) {
1189 if (const ConstantVector *CP2 = dyn_cast<ConstantVector>(C2)) {
1190 if (pred == FCmpInst::FCMP_OEQ || pred == FCmpInst::FCMP_UEQ) {
1191 for (unsigned i = 0, e = CP1->getNumOperands(); i != e; ++i) {
1192 Constant *C= ConstantExpr::getFCmp(FCmpInst::FCMP_OEQ,
1193 const_cast<Constant*>(CP1->getOperand(i)),
1194 const_cast<Constant*>(CP2->getOperand(i)));
1195 if (ConstantInt *CB = dyn_cast<ConstantInt>(C))
1198 // Otherwise, could not decide from any element pairs.
1200 } else if (pred == ICmpInst::ICMP_EQ) {
1201 for (unsigned i = 0, e = CP1->getNumOperands(); i != e; ++i) {
1202 Constant *C = ConstantExpr::getICmp(ICmpInst::ICMP_EQ,
1203 const_cast<Constant*>(CP1->getOperand(i)),
1204 const_cast<Constant*>(CP2->getOperand(i)));
1205 if (ConstantInt *CB = dyn_cast<ConstantInt>(C))
1208 // Otherwise, could not decide from any element pairs.
1214 if (C1->getType()->isFloatingPoint()) {
1215 switch (evaluateFCmpRelation(C1, C2)) {
1216 default: assert(0 && "Unknown relation!");
1217 case FCmpInst::FCMP_UNO:
1218 case FCmpInst::FCMP_ORD:
1219 case FCmpInst::FCMP_UEQ:
1220 case FCmpInst::FCMP_UNE:
1221 case FCmpInst::FCMP_ULT:
1222 case FCmpInst::FCMP_UGT:
1223 case FCmpInst::FCMP_ULE:
1224 case FCmpInst::FCMP_UGE:
1225 case FCmpInst::FCMP_TRUE:
1226 case FCmpInst::FCMP_FALSE:
1227 case FCmpInst::BAD_FCMP_PREDICATE:
1228 break; // Couldn't determine anything about these constants.
1229 case FCmpInst::FCMP_OEQ: // We know that C1 == C2
1230 return ConstantInt::get(Type::Int1Ty,
1231 pred == FCmpInst::FCMP_UEQ || pred == FCmpInst::FCMP_OEQ ||
1232 pred == FCmpInst::FCMP_ULE || pred == FCmpInst::FCMP_OLE ||
1233 pred == FCmpInst::FCMP_UGE || pred == FCmpInst::FCMP_OGE);
1234 case FCmpInst::FCMP_OLT: // We know that C1 < C2
1235 return ConstantInt::get(Type::Int1Ty,
1236 pred == FCmpInst::FCMP_UNE || pred == FCmpInst::FCMP_ONE ||
1237 pred == FCmpInst::FCMP_ULT || pred == FCmpInst::FCMP_OLT ||
1238 pred == FCmpInst::FCMP_ULE || pred == FCmpInst::FCMP_OLE);
1239 case FCmpInst::FCMP_OGT: // We know that C1 > C2
1240 return ConstantInt::get(Type::Int1Ty,
1241 pred == FCmpInst::FCMP_UNE || pred == FCmpInst::FCMP_ONE ||
1242 pred == FCmpInst::FCMP_UGT || pred == FCmpInst::FCMP_OGT ||
1243 pred == FCmpInst::FCMP_UGE || pred == FCmpInst::FCMP_OGE);
1244 case FCmpInst::FCMP_OLE: // We know that C1 <= C2
1245 // We can only partially decide this relation.
1246 if (pred == FCmpInst::FCMP_UGT || pred == FCmpInst::FCMP_OGT)
1247 return ConstantInt::getFalse();
1248 if (pred == FCmpInst::FCMP_ULT || pred == FCmpInst::FCMP_OLT)
1249 return ConstantInt::getTrue();
1251 case FCmpInst::FCMP_OGE: // We known that C1 >= C2
1252 // We can only partially decide this relation.
1253 if (pred == FCmpInst::FCMP_ULT || pred == FCmpInst::FCMP_OLT)
1254 return ConstantInt::getFalse();
1255 if (pred == FCmpInst::FCMP_UGT || pred == FCmpInst::FCMP_OGT)
1256 return ConstantInt::getTrue();
1258 case ICmpInst::ICMP_NE: // We know that C1 != C2
1259 // We can only partially decide this relation.
1260 if (pred == FCmpInst::FCMP_OEQ || pred == FCmpInst::FCMP_UEQ)
1261 return ConstantInt::getFalse();
1262 if (pred == FCmpInst::FCMP_ONE || pred == FCmpInst::FCMP_UNE)
1263 return ConstantInt::getTrue();
1267 // Evaluate the relation between the two constants, per the predicate.
1268 switch (evaluateICmpRelation(C1, C2, CmpInst::isSigned(pred))) {
1269 default: assert(0 && "Unknown relational!");
1270 case ICmpInst::BAD_ICMP_PREDICATE:
1271 break; // Couldn't determine anything about these constants.
1272 case ICmpInst::ICMP_EQ: // We know the constants are equal!
1273 // If we know the constants are equal, we can decide the result of this
1274 // computation precisely.
1275 return ConstantInt::get(Type::Int1Ty,
1276 pred == ICmpInst::ICMP_EQ ||
1277 pred == ICmpInst::ICMP_ULE ||
1278 pred == ICmpInst::ICMP_SLE ||
1279 pred == ICmpInst::ICMP_UGE ||
1280 pred == ICmpInst::ICMP_SGE);
1281 case ICmpInst::ICMP_ULT:
1282 // If we know that C1 < C2, we can decide the result of this computation
1284 return ConstantInt::get(Type::Int1Ty,
1285 pred == ICmpInst::ICMP_ULT ||
1286 pred == ICmpInst::ICMP_NE ||
1287 pred == ICmpInst::ICMP_ULE);
1288 case ICmpInst::ICMP_SLT:
1289 // If we know that C1 < C2, we can decide the result of this computation
1291 return ConstantInt::get(Type::Int1Ty,
1292 pred == ICmpInst::ICMP_SLT ||
1293 pred == ICmpInst::ICMP_NE ||
1294 pred == ICmpInst::ICMP_SLE);
1295 case ICmpInst::ICMP_UGT:
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_UGT ||
1300 pred == ICmpInst::ICMP_NE ||
1301 pred == ICmpInst::ICMP_UGE);
1302 case ICmpInst::ICMP_SGT:
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_SGT ||
1307 pred == ICmpInst::ICMP_NE ||
1308 pred == ICmpInst::ICMP_SGE);
1309 case ICmpInst::ICMP_ULE:
1310 // If we know that C1 <= C2, we can only partially decide this relation.
1311 if (pred == ICmpInst::ICMP_UGT) return ConstantInt::getFalse();
1312 if (pred == ICmpInst::ICMP_ULT) return ConstantInt::getTrue();
1314 case ICmpInst::ICMP_SLE:
1315 // If we know that C1 <= C2, we can only partially decide this relation.
1316 if (pred == ICmpInst::ICMP_SGT) return ConstantInt::getFalse();
1317 if (pred == ICmpInst::ICMP_SLT) return ConstantInt::getTrue();
1320 case ICmpInst::ICMP_UGE:
1321 // If we know that C1 >= C2, we can only partially decide this relation.
1322 if (pred == ICmpInst::ICMP_ULT) return ConstantInt::getFalse();
1323 if (pred == ICmpInst::ICMP_UGT) return ConstantInt::getTrue();
1325 case ICmpInst::ICMP_SGE:
1326 // If we know that C1 >= C2, we can only partially decide this relation.
1327 if (pred == ICmpInst::ICMP_SLT) return ConstantInt::getFalse();
1328 if (pred == ICmpInst::ICMP_SGT) return ConstantInt::getTrue();
1331 case ICmpInst::ICMP_NE:
1332 // If we know that C1 != C2, we can only partially decide this relation.
1333 if (pred == ICmpInst::ICMP_EQ) return ConstantInt::getFalse();
1334 if (pred == ICmpInst::ICMP_NE) return ConstantInt::getTrue();
1338 if (!isa<ConstantExpr>(C1) && isa<ConstantExpr>(C2)) {
1339 // If C2 is a constant expr and C1 isn't, flop them around and fold the
1340 // other way if possible.
1342 case ICmpInst::ICMP_EQ:
1343 case ICmpInst::ICMP_NE:
1344 // No change of predicate required.
1345 return ConstantFoldCompareInstruction(pred, C2, C1);
1347 case ICmpInst::ICMP_ULT:
1348 case ICmpInst::ICMP_SLT:
1349 case ICmpInst::ICMP_UGT:
1350 case ICmpInst::ICMP_SGT:
1351 case ICmpInst::ICMP_ULE:
1352 case ICmpInst::ICMP_SLE:
1353 case ICmpInst::ICMP_UGE:
1354 case ICmpInst::ICMP_SGE:
1355 // Change the predicate as necessary to swap the operands.
1356 pred = ICmpInst::getSwappedPredicate((ICmpInst::Predicate)pred);
1357 return ConstantFoldCompareInstruction(pred, C2, C1);
1359 default: // These predicates cannot be flopped around.
1367 Constant *llvm::ConstantFoldGetElementPtr(const Constant *C,
1368 Constant* const *Idxs,
1371 (NumIdx == 1 && Idxs[0]->isNullValue()))
1372 return const_cast<Constant*>(C);
1374 if (isa<UndefValue>(C)) {
1375 const Type *Ty = GetElementPtrInst::getIndexedType(C->getType(),
1377 (Value **)Idxs+NumIdx,
1379 assert(Ty != 0 && "Invalid indices for GEP!");
1380 return UndefValue::get(PointerType::get(Ty));
1383 Constant *Idx0 = Idxs[0];
1384 if (C->isNullValue()) {
1386 for (unsigned i = 0, e = NumIdx; i != e; ++i)
1387 if (!Idxs[i]->isNullValue()) {
1392 const Type *Ty = GetElementPtrInst::getIndexedType(C->getType(),
1394 (Value**)Idxs+NumIdx,
1396 assert(Ty != 0 && "Invalid indices for GEP!");
1397 return ConstantPointerNull::get(PointerType::get(Ty));
1401 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(const_cast<Constant*>(C))) {
1402 // Combine Indices - If the source pointer to this getelementptr instruction
1403 // is a getelementptr instruction, combine the indices of the two
1404 // getelementptr instructions into a single instruction.
1406 if (CE->getOpcode() == Instruction::GetElementPtr) {
1407 const Type *LastTy = 0;
1408 for (gep_type_iterator I = gep_type_begin(CE), E = gep_type_end(CE);
1412 if ((LastTy && isa<ArrayType>(LastTy)) || Idx0->isNullValue()) {
1413 SmallVector<Value*, 16> NewIndices;
1414 NewIndices.reserve(NumIdx + CE->getNumOperands());
1415 for (unsigned i = 1, e = CE->getNumOperands()-1; i != e; ++i)
1416 NewIndices.push_back(CE->getOperand(i));
1418 // Add the last index of the source with the first index of the new GEP.
1419 // Make sure to handle the case when they are actually different types.
1420 Constant *Combined = CE->getOperand(CE->getNumOperands()-1);
1421 // Otherwise it must be an array.
1422 if (!Idx0->isNullValue()) {
1423 const Type *IdxTy = Combined->getType();
1424 if (IdxTy != Idx0->getType()) {
1425 Constant *C1 = ConstantExpr::getSExtOrBitCast(Idx0, Type::Int64Ty);
1426 Constant *C2 = ConstantExpr::getSExtOrBitCast(Combined,
1428 Combined = ConstantExpr::get(Instruction::Add, C1, C2);
1431 ConstantExpr::get(Instruction::Add, Idx0, Combined);
1435 NewIndices.push_back(Combined);
1436 NewIndices.insert(NewIndices.end(), Idxs+1, Idxs+NumIdx);
1437 return ConstantExpr::getGetElementPtr(CE->getOperand(0), &NewIndices[0],
1442 // Implement folding of:
1443 // int* getelementptr ([2 x int]* cast ([3 x int]* %X to [2 x int]*),
1445 // To: int* getelementptr ([3 x int]* %X, long 0, long 0)
1447 if (CE->isCast() && NumIdx > 1 && Idx0->isNullValue()) {
1448 if (const PointerType *SPT =
1449 dyn_cast<PointerType>(CE->getOperand(0)->getType()))
1450 if (const ArrayType *SAT = dyn_cast<ArrayType>(SPT->getElementType()))
1451 if (const ArrayType *CAT =
1452 dyn_cast<ArrayType>(cast<PointerType>(C->getType())->getElementType()))
1453 if (CAT->getElementType() == SAT->getElementType())
1454 return ConstantExpr::getGetElementPtr(
1455 (Constant*)CE->getOperand(0), Idxs, NumIdx);
1458 // Fold: getelementptr (i8* inttoptr (i64 1 to i8*), i32 -1)
1459 // Into: inttoptr (i64 0 to i8*)
1460 // This happens with pointers to member functions in C++.
1461 if (CE->getOpcode() == Instruction::IntToPtr && NumIdx == 1 &&
1462 isa<ConstantInt>(CE->getOperand(0)) && isa<ConstantInt>(Idxs[0]) &&
1463 cast<PointerType>(CE->getType())->getElementType() == Type::Int8Ty) {
1464 Constant *Base = CE->getOperand(0);
1465 Constant *Offset = Idxs[0];
1467 // Convert the smaller integer to the larger type.
1468 if (Offset->getType()->getPrimitiveSizeInBits() <
1469 Base->getType()->getPrimitiveSizeInBits())
1470 Offset = ConstantExpr::getSExt(Offset, Base->getType());
1471 else if (Base->getType()->getPrimitiveSizeInBits() <
1472 Offset->getType()->getPrimitiveSizeInBits())
1473 Base = ConstantExpr::getZExt(Base, Base->getType());
1475 Base = ConstantExpr::getAdd(Base, Offset);
1476 return ConstantExpr::getIntToPtr(Base, CE->getType());