1 //===- ConstantFold.cpp - LLVM constant folder ----------------------------===//
3 // The LLVM Compiler Infrastructure
5 // This file was developed by the LLVM research group and is distributed under
6 // the University of Illinois Open Source License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file implements folding of constants for LLVM. This implements the
11 // (internal) ConstantFold.h interface, which is used by the
12 // ConstantExpr::get* methods to automatically fold constants when possible.
14 // The current constant folding implementation is implemented in two pieces: the
15 // template-based folder for simple primitive constants like ConstantInt, and
16 // the special case hackery that we use to symbolically evaluate expressions
17 // that use ConstantExprs.
19 //===----------------------------------------------------------------------===//
21 #include "ConstantFold.h"
22 #include "llvm/Constants.h"
23 #include "llvm/Instructions.h"
24 #include "llvm/DerivedTypes.h"
25 #include "llvm/Function.h"
26 #include "llvm/GlobalAlias.h"
27 #include "llvm/ADT/SmallVector.h"
28 #include "llvm/Support/Compiler.h"
29 #include "llvm/Support/GetElementPtrTypeIterator.h"
30 #include "llvm/Support/ManagedStatic.h"
31 #include "llvm/Support/MathExtras.h"
35 //===----------------------------------------------------------------------===//
36 // ConstantFold*Instruction Implementations
37 //===----------------------------------------------------------------------===//
39 /// CastConstantVector - Convert the specified ConstantVector node to the
40 /// specified vector type. At this point, we know that the elements of the
41 /// input vector constant are all simple integer or FP values.
42 static Constant *CastConstantVector(ConstantVector *CV,
43 const VectorType *DstTy) {
44 unsigned SrcNumElts = CV->getType()->getNumElements();
45 unsigned DstNumElts = DstTy->getNumElements();
46 const Type *SrcEltTy = CV->getType()->getElementType();
47 const Type *DstEltTy = DstTy->getElementType();
49 // If both vectors have the same number of elements (thus, the elements
50 // are the same size), perform the conversion now.
51 if (SrcNumElts == DstNumElts) {
52 std::vector<Constant*> Result;
54 // If the src and dest elements are both integers, or both floats, we can
55 // just BitCast each element because the elements are the same size.
56 if ((SrcEltTy->isInteger() && DstEltTy->isInteger()) ||
57 (SrcEltTy->isFloatingPoint() && DstEltTy->isFloatingPoint())) {
58 for (unsigned i = 0; i != SrcNumElts; ++i)
60 ConstantExpr::getBitCast(CV->getOperand(i), DstEltTy));
61 return ConstantVector::get(Result);
64 // If this is an int-to-fp cast ..
65 if (SrcEltTy->isInteger()) {
66 // Ensure that it is int-to-fp cast
67 assert(DstEltTy->isFloatingPoint());
68 if (DstEltTy->getTypeID() == Type::DoubleTyID) {
69 for (unsigned i = 0; i != SrcNumElts; ++i) {
70 ConstantInt *CI = cast<ConstantInt>(CV->getOperand(i));
71 double V = CI->getValue().bitsToDouble();
72 Result.push_back(ConstantFP::get(Type::DoubleTy, APFloat(V)));
74 return ConstantVector::get(Result);
76 assert(DstEltTy == Type::FloatTy && "Unknown fp type!");
77 for (unsigned i = 0; i != SrcNumElts; ++i) {
78 ConstantInt *CI = cast<ConstantInt>(CV->getOperand(i));
79 float V = CI->getValue().bitsToFloat();
80 Result.push_back(ConstantFP::get(Type::FloatTy, APFloat(V)));
82 return ConstantVector::get(Result);
85 // Otherwise, this is an fp-to-int cast.
86 assert(SrcEltTy->isFloatingPoint() && DstEltTy->isInteger());
88 if (SrcEltTy->getTypeID() == Type::DoubleTyID) {
89 for (unsigned i = 0; i != SrcNumElts; ++i) {
90 uint64_t V = cast<ConstantFP>(CV->getOperand(i))->
91 getValueAPF().convertToAPInt().getZExtValue();
92 Constant *C = ConstantInt::get(Type::Int64Ty, V);
93 Result.push_back(ConstantExpr::getBitCast(C, DstEltTy ));
95 return ConstantVector::get(Result);
98 assert(SrcEltTy->getTypeID() == Type::FloatTyID);
99 for (unsigned i = 0; i != SrcNumElts; ++i) {
100 uint32_t V = (uint32_t)cast<ConstantFP>(CV->getOperand(i))->
101 getValueAPF().convertToAPInt().getZExtValue();
102 Constant *C = ConstantInt::get(Type::Int32Ty, V);
103 Result.push_back(ConstantExpr::getBitCast(C, DstEltTy));
105 return ConstantVector::get(Result);
108 // Otherwise, this is a cast that changes element count and size. Handle
109 // casts which shrink the elements here.
111 // FIXME: We need to know endianness to do this!
116 /// This function determines which opcode to use to fold two constant cast
117 /// expressions together. It uses CastInst::isEliminableCastPair to determine
118 /// the opcode. Consequently its just a wrapper around that function.
119 /// @brief Determine if it is valid to fold a cast of a cast
121 foldConstantCastPair(
122 unsigned opc, ///< opcode of the second cast constant expression
123 const ConstantExpr*Op, ///< the first cast constant expression
124 const Type *DstTy ///< desintation type of the first cast
126 assert(Op && Op->isCast() && "Can't fold cast of cast without a cast!");
127 assert(DstTy && DstTy->isFirstClassType() && "Invalid cast destination type");
128 assert(CastInst::isCast(opc) && "Invalid cast opcode");
130 // The the types and opcodes for the two Cast constant expressions
131 const Type *SrcTy = Op->getOperand(0)->getType();
132 const Type *MidTy = Op->getType();
133 Instruction::CastOps firstOp = Instruction::CastOps(Op->getOpcode());
134 Instruction::CastOps secondOp = Instruction::CastOps(opc);
136 // Let CastInst::isEliminableCastPair do the heavy lifting.
137 return CastInst::isEliminableCastPair(firstOp, secondOp, SrcTy, MidTy, DstTy,
141 Constant *llvm::ConstantFoldCastInstruction(unsigned opc, const Constant *V,
142 const Type *DestTy) {
143 const Type *SrcTy = V->getType();
145 if (isa<UndefValue>(V)) {
146 // zext(undef) = 0, because the top bits will be zero.
147 // sext(undef) = 0, because the top bits will all be the same.
148 if (opc == Instruction::ZExt || opc == Instruction::SExt)
149 return Constant::getNullValue(DestTy);
150 return UndefValue::get(DestTy);
152 // No compile-time operations on this type yet.
153 if (V->getType() == Type::PPC_FP128Ty || DestTy == Type::PPC_FP128Ty)
156 // If the cast operand is a constant expression, there's a few things we can
157 // do to try to simplify it.
158 if (const ConstantExpr *CE = dyn_cast<ConstantExpr>(V)) {
160 // Try hard to fold cast of cast because they are often eliminable.
161 if (unsigned newOpc = foldConstantCastPair(opc, CE, DestTy))
162 return ConstantExpr::getCast(newOpc, CE->getOperand(0), DestTy);
163 } else if (CE->getOpcode() == Instruction::GetElementPtr) {
164 // If all of the indexes in the GEP are null values, there is no pointer
165 // adjustment going on. We might as well cast the source pointer.
166 bool isAllNull = true;
167 for (unsigned i = 1, e = CE->getNumOperands(); i != e; ++i)
168 if (!CE->getOperand(i)->isNullValue()) {
173 // This is casting one pointer type to another, always BitCast
174 return ConstantExpr::getPointerCast(CE->getOperand(0), DestTy);
178 // We actually have to do a cast now. Perform the cast according to the
181 case Instruction::FPTrunc:
182 case Instruction::FPExt:
183 if (const ConstantFP *FPC = dyn_cast<ConstantFP>(V)) {
184 APFloat Val = FPC->getValueAPF();
185 Val.convert(DestTy == Type::FloatTy ? APFloat::IEEEsingle :
186 DestTy == Type::DoubleTy ? APFloat::IEEEdouble :
187 DestTy == Type::X86_FP80Ty ? APFloat::x87DoubleExtended :
188 DestTy == Type::FP128Ty ? APFloat::IEEEquad :
190 APFloat::rmNearestTiesToEven);
191 return ConstantFP::get(DestTy, Val);
193 return 0; // Can't fold.
194 case Instruction::FPToUI:
195 case Instruction::FPToSI:
196 if (const ConstantFP *FPC = dyn_cast<ConstantFP>(V)) {
197 const APFloat &V = FPC->getValueAPF();
199 uint32_t DestBitWidth = cast<IntegerType>(DestTy)->getBitWidth();
200 (void) V.convertToInteger(x, DestBitWidth, opc==Instruction::FPToSI,
201 APFloat::rmTowardZero);
202 APInt Val(DestBitWidth, 2, x);
203 return ConstantInt::get(Val);
205 if (const ConstantVector *CV = dyn_cast<ConstantVector>(V)) {
206 std::vector<Constant*> res;
207 const VectorType *DestVecTy = cast<VectorType>(DestTy);
208 const Type *DstEltTy = DestVecTy->getElementType();
209 for (unsigned i = 0, e = CV->getType()->getNumElements(); i != e; ++i)
210 res.push_back(ConstantFoldCastInstruction(opc, V->getOperand(i),
212 return ConstantVector::get(DestVecTy, res);
214 return 0; // Can't fold.
215 case Instruction::IntToPtr: //always treated as unsigned
216 if (V->isNullValue()) // Is it an integral null value?
217 return ConstantPointerNull::get(cast<PointerType>(DestTy));
218 return 0; // Other pointer types cannot be casted
219 case Instruction::PtrToInt: // always treated as unsigned
220 if (V->isNullValue()) // is it a null pointer value?
221 return ConstantInt::get(DestTy, 0);
222 return 0; // Other pointer types cannot be casted
223 case Instruction::UIToFP:
224 case Instruction::SIToFP:
225 if (const ConstantInt *CI = dyn_cast<ConstantInt>(V)) {
226 APInt api = CI->getValue();
227 const uint64_t zero[] = {0, 0};
228 uint32_t BitWidth = cast<IntegerType>(SrcTy)->getBitWidth();
229 APFloat apf = APFloat(APInt(DestTy->getPrimitiveSizeInBits(),
231 (void)apf.convertFromZeroExtendedInteger(api.getRawData(), BitWidth,
232 opc==Instruction::SIToFP,
233 APFloat::rmNearestTiesToEven);
234 return ConstantFP::get(DestTy, apf);
236 if (const ConstantVector *CV = dyn_cast<ConstantVector>(V)) {
237 std::vector<Constant*> res;
238 const VectorType *DestVecTy = cast<VectorType>(DestTy);
239 const Type *DstEltTy = DestVecTy->getElementType();
240 for (unsigned i = 0, e = CV->getType()->getNumElements(); i != e; ++i)
241 res.push_back(ConstantFoldCastInstruction(opc, V->getOperand(i),
243 return ConstantVector::get(DestVecTy, res);
246 case Instruction::ZExt:
247 if (const ConstantInt *CI = dyn_cast<ConstantInt>(V)) {
248 uint32_t BitWidth = cast<IntegerType>(DestTy)->getBitWidth();
249 APInt Result(CI->getValue());
250 Result.zext(BitWidth);
251 return ConstantInt::get(Result);
254 case Instruction::SExt:
255 if (const ConstantInt *CI = dyn_cast<ConstantInt>(V)) {
256 uint32_t BitWidth = cast<IntegerType>(DestTy)->getBitWidth();
257 APInt Result(CI->getValue());
258 Result.sext(BitWidth);
259 return ConstantInt::get(Result);
262 case Instruction::Trunc:
263 if (const ConstantInt *CI = dyn_cast<ConstantInt>(V)) {
264 uint32_t BitWidth = cast<IntegerType>(DestTy)->getBitWidth();
265 APInt Result(CI->getValue());
266 Result.trunc(BitWidth);
267 return ConstantInt::get(Result);
270 case Instruction::BitCast:
272 return (Constant*)V; // no-op cast
274 // Check to see if we are casting a pointer to an aggregate to a pointer to
275 // the first element. If so, return the appropriate GEP instruction.
276 if (const PointerType *PTy = dyn_cast<PointerType>(V->getType()))
277 if (const PointerType *DPTy = dyn_cast<PointerType>(DestTy)) {
278 SmallVector<Value*, 8> IdxList;
279 IdxList.push_back(Constant::getNullValue(Type::Int32Ty));
280 const Type *ElTy = PTy->getElementType();
281 while (ElTy != DPTy->getElementType()) {
282 if (const StructType *STy = dyn_cast<StructType>(ElTy)) {
283 if (STy->getNumElements() == 0) break;
284 ElTy = STy->getElementType(0);
285 IdxList.push_back(Constant::getNullValue(Type::Int32Ty));
286 } else if (const SequentialType *STy =
287 dyn_cast<SequentialType>(ElTy)) {
288 if (isa<PointerType>(ElTy)) break; // Can't index into pointers!
289 ElTy = STy->getElementType();
290 IdxList.push_back(IdxList[0]);
296 if (ElTy == DPTy->getElementType())
297 return ConstantExpr::getGetElementPtr(
298 const_cast<Constant*>(V), &IdxList[0], IdxList.size());
301 // Handle casts from one vector constant to another. We know that the src
302 // and dest type have the same size (otherwise its an illegal cast).
303 if (const VectorType *DestPTy = dyn_cast<VectorType>(DestTy)) {
304 if (const VectorType *SrcTy = dyn_cast<VectorType>(V->getType())) {
305 assert(DestPTy->getBitWidth() == SrcTy->getBitWidth() &&
306 "Not cast between same sized vectors!");
307 // First, check for null and undef
308 if (isa<ConstantAggregateZero>(V))
309 return Constant::getNullValue(DestTy);
310 if (isa<UndefValue>(V))
311 return UndefValue::get(DestTy);
313 if (const ConstantVector *CV = dyn_cast<ConstantVector>(V)) {
314 // This is a cast from a ConstantVector of one type to a
315 // ConstantVector of another type. Check to see if all elements of
316 // the input are simple.
317 bool AllSimpleConstants = true;
318 for (unsigned i = 0, e = CV->getNumOperands(); i != e; ++i) {
319 if (!isa<ConstantInt>(CV->getOperand(i)) &&
320 !isa<ConstantFP>(CV->getOperand(i))) {
321 AllSimpleConstants = false;
326 // If all of the elements are simple constants, we can fold this.
327 if (AllSimpleConstants)
328 return CastConstantVector(const_cast<ConstantVector*>(CV), DestPTy);
333 // Finally, implement bitcast folding now. The code below doesn't handle
335 if (isa<ConstantPointerNull>(V)) // ptr->ptr cast.
336 return ConstantPointerNull::get(cast<PointerType>(DestTy));
338 // Handle integral constant input.
339 if (const ConstantInt *CI = dyn_cast<ConstantInt>(V)) {
340 if (DestTy->isInteger())
341 // Integral -> Integral. This is a no-op because the bit widths must
342 // be the same. Consequently, we just fold to V.
343 return const_cast<Constant*>(V);
345 if (DestTy->isFloatingPoint()) {
346 assert((DestTy == Type::DoubleTy || DestTy == Type::FloatTy) &&
348 return ConstantFP::get(DestTy, APFloat(CI->getValue()));
350 // Otherwise, can't fold this (vector?)
354 // Handle ConstantFP input.
355 if (const ConstantFP *FP = dyn_cast<ConstantFP>(V)) {
357 if (DestTy == Type::Int32Ty) {
358 return ConstantInt::get(FP->getValueAPF().convertToAPInt());
360 assert(DestTy == Type::Int64Ty && "only support f32/f64 for now!");
361 return ConstantInt::get(FP->getValueAPF().convertToAPInt());
366 assert(!"Invalid CE CastInst opcode");
370 assert(0 && "Failed to cast constant expression");
374 Constant *llvm::ConstantFoldSelectInstruction(const Constant *Cond,
376 const Constant *V2) {
377 if (const ConstantInt *CB = dyn_cast<ConstantInt>(Cond))
378 return const_cast<Constant*>(CB->getZExtValue() ? V1 : V2);
380 if (isa<UndefValue>(V1)) return const_cast<Constant*>(V2);
381 if (isa<UndefValue>(V2)) return const_cast<Constant*>(V1);
382 if (isa<UndefValue>(Cond)) return const_cast<Constant*>(V1);
383 if (V1 == V2) return const_cast<Constant*>(V1);
387 Constant *llvm::ConstantFoldExtractElementInstruction(const Constant *Val,
388 const Constant *Idx) {
389 if (isa<UndefValue>(Val)) // ee(undef, x) -> undef
390 return UndefValue::get(cast<VectorType>(Val->getType())->getElementType());
391 if (Val->isNullValue()) // ee(zero, x) -> zero
392 return Constant::getNullValue(
393 cast<VectorType>(Val->getType())->getElementType());
395 if (const ConstantVector *CVal = dyn_cast<ConstantVector>(Val)) {
396 if (const ConstantInt *CIdx = dyn_cast<ConstantInt>(Idx)) {
397 return const_cast<Constant*>(CVal->getOperand(CIdx->getZExtValue()));
398 } else if (isa<UndefValue>(Idx)) {
399 // ee({w,x,y,z}, undef) -> w (an arbitrary value).
400 return const_cast<Constant*>(CVal->getOperand(0));
406 Constant *llvm::ConstantFoldInsertElementInstruction(const Constant *Val,
408 const Constant *Idx) {
409 const ConstantInt *CIdx = dyn_cast<ConstantInt>(Idx);
411 APInt idxVal = CIdx->getValue();
412 if (isa<UndefValue>(Val)) {
413 // Insertion of scalar constant into vector undef
414 // Optimize away insertion of undef
415 if (isa<UndefValue>(Elt))
416 return const_cast<Constant*>(Val);
417 // Otherwise break the aggregate undef into multiple undefs and do
420 cast<VectorType>(Val->getType())->getNumElements();
421 std::vector<Constant*> Ops;
423 for (unsigned i = 0; i < numOps; ++i) {
425 (idxVal == i) ? Elt : UndefValue::get(Elt->getType());
426 Ops.push_back(const_cast<Constant*>(Op));
428 return ConstantVector::get(Ops);
430 if (isa<ConstantAggregateZero>(Val)) {
431 // Insertion of scalar constant into vector aggregate zero
432 // Optimize away insertion of zero
433 if (Elt->isNullValue())
434 return const_cast<Constant*>(Val);
435 // Otherwise break the aggregate zero into multiple zeros and do
438 cast<VectorType>(Val->getType())->getNumElements();
439 std::vector<Constant*> Ops;
441 for (unsigned i = 0; i < numOps; ++i) {
443 (idxVal == i) ? Elt : Constant::getNullValue(Elt->getType());
444 Ops.push_back(const_cast<Constant*>(Op));
446 return ConstantVector::get(Ops);
448 if (const ConstantVector *CVal = dyn_cast<ConstantVector>(Val)) {
449 // Insertion of scalar constant into vector constant
450 std::vector<Constant*> Ops;
451 Ops.reserve(CVal->getNumOperands());
452 for (unsigned i = 0; i < CVal->getNumOperands(); ++i) {
454 (idxVal == i) ? Elt : cast<Constant>(CVal->getOperand(i));
455 Ops.push_back(const_cast<Constant*>(Op));
457 return ConstantVector::get(Ops);
462 Constant *llvm::ConstantFoldShuffleVectorInstruction(const Constant *V1,
464 const Constant *Mask) {
469 /// EvalVectorOp - Given two vector constants and a function pointer, apply the
470 /// function pointer to each element pair, producing a new ConstantVector
471 /// constant. Either or both of V1 and V2 may be NULL, meaning a
472 /// ConstantAggregateZero operand.
473 static Constant *EvalVectorOp(const ConstantVector *V1,
474 const ConstantVector *V2,
475 const VectorType *VTy,
476 Constant *(*FP)(Constant*, Constant*)) {
477 std::vector<Constant*> Res;
478 const Type *EltTy = VTy->getElementType();
479 for (unsigned i = 0, e = VTy->getNumElements(); i != e; ++i) {
480 const Constant *C1 = V1 ? V1->getOperand(i) : Constant::getNullValue(EltTy);
481 const Constant *C2 = V2 ? V2->getOperand(i) : Constant::getNullValue(EltTy);
482 Res.push_back(FP(const_cast<Constant*>(C1),
483 const_cast<Constant*>(C2)));
485 return ConstantVector::get(Res);
488 Constant *llvm::ConstantFoldBinaryInstruction(unsigned Opcode,
490 const Constant *C2) {
491 // No compile-time operations on this type yet.
492 if (C1->getType() == Type::PPC_FP128Ty)
495 // Handle UndefValue up front
496 if (isa<UndefValue>(C1) || isa<UndefValue>(C2)) {
498 case Instruction::Add:
499 case Instruction::Sub:
500 case Instruction::Xor:
501 return UndefValue::get(C1->getType());
502 case Instruction::Mul:
503 case Instruction::And:
504 return Constant::getNullValue(C1->getType());
505 case Instruction::UDiv:
506 case Instruction::SDiv:
507 case Instruction::FDiv:
508 case Instruction::URem:
509 case Instruction::SRem:
510 case Instruction::FRem:
511 if (!isa<UndefValue>(C2)) // undef / X -> 0
512 return Constant::getNullValue(C1->getType());
513 return const_cast<Constant*>(C2); // X / undef -> undef
514 case Instruction::Or: // X | undef -> -1
515 if (const VectorType *PTy = dyn_cast<VectorType>(C1->getType()))
516 return ConstantVector::getAllOnesValue(PTy);
517 return ConstantInt::getAllOnesValue(C1->getType());
518 case Instruction::LShr:
519 if (isa<UndefValue>(C2) && isa<UndefValue>(C1))
520 return const_cast<Constant*>(C1); // undef lshr undef -> undef
521 return Constant::getNullValue(C1->getType()); // X lshr undef -> 0
523 case Instruction::AShr:
524 if (!isa<UndefValue>(C2))
525 return const_cast<Constant*>(C1); // undef ashr X --> undef
526 else if (isa<UndefValue>(C1))
527 return const_cast<Constant*>(C1); // undef ashr undef -> undef
529 return const_cast<Constant*>(C1); // X ashr undef --> X
530 case Instruction::Shl:
531 // undef << X -> 0 or X << undef -> 0
532 return Constant::getNullValue(C1->getType());
536 if (const ConstantExpr *CE1 = dyn_cast<ConstantExpr>(C1)) {
537 if (isa<ConstantExpr>(C2)) {
538 // There are many possible foldings we could do here. We should probably
539 // at least fold add of a pointer with an integer into the appropriate
540 // getelementptr. This will improve alias analysis a bit.
542 // Just implement a couple of simple identities.
544 case Instruction::Add:
545 if (C2->isNullValue()) return const_cast<Constant*>(C1); // X + 0 == X
547 case Instruction::Sub:
548 if (C2->isNullValue()) return const_cast<Constant*>(C1); // X - 0 == X
550 case Instruction::Mul:
551 if (C2->isNullValue()) return const_cast<Constant*>(C2); // X * 0 == 0
552 if (const ConstantInt *CI = dyn_cast<ConstantInt>(C2))
553 if (CI->equalsInt(1))
554 return const_cast<Constant*>(C1); // X * 1 == X
556 case Instruction::UDiv:
557 case Instruction::SDiv:
558 if (const ConstantInt *CI = dyn_cast<ConstantInt>(C2))
559 if (CI->equalsInt(1))
560 return const_cast<Constant*>(C1); // X / 1 == X
562 case Instruction::URem:
563 case Instruction::SRem:
564 if (const ConstantInt *CI = dyn_cast<ConstantInt>(C2))
565 if (CI->equalsInt(1))
566 return Constant::getNullValue(CI->getType()); // X % 1 == 0
568 case Instruction::And:
569 if (const ConstantInt *CI = dyn_cast<ConstantInt>(C2)) {
570 if (CI->isZero()) return const_cast<Constant*>(C2); // X & 0 == 0
571 if (CI->isAllOnesValue())
572 return const_cast<Constant*>(C1); // X & -1 == X
574 // (zext i32 to i64) & 4294967295 -> (zext i32 to i64)
575 if (CE1->getOpcode() == Instruction::ZExt) {
576 APInt PossiblySetBits
577 = cast<IntegerType>(CE1->getOperand(0)->getType())->getMask();
578 PossiblySetBits.zext(C1->getType()->getPrimitiveSizeInBits());
579 if ((PossiblySetBits & CI->getValue()) == PossiblySetBits)
580 return const_cast<Constant*>(C1);
583 if (CE1->isCast() && isa<GlobalValue>(CE1->getOperand(0))) {
584 GlobalValue *CPR = cast<GlobalValue>(CE1->getOperand(0));
586 // Functions are at least 4-byte aligned. If and'ing the address of a
587 // function with a constant < 4, fold it to zero.
588 if (const ConstantInt *CI = dyn_cast<ConstantInt>(C2))
589 if (CI->getValue().ult(APInt(CI->getType()->getBitWidth(),4)) &&
591 return Constant::getNullValue(CI->getType());
594 case Instruction::Or:
595 if (C2->isNullValue()) return const_cast<Constant*>(C1); // X | 0 == X
596 if (const ConstantInt *CI = dyn_cast<ConstantInt>(C2))
597 if (CI->isAllOnesValue())
598 return const_cast<Constant*>(C2); // X | -1 == -1
600 case Instruction::Xor:
601 if (C2->isNullValue()) return const_cast<Constant*>(C1); // X ^ 0 == X
603 case Instruction::AShr:
604 // ashr (zext C to Ty), C2 -> lshr (zext C, CSA), C2
605 if (CE1->getOpcode() == Instruction::ZExt) // Top bits known zero.
606 return ConstantExpr::getLShr(const_cast<Constant*>(C1),
607 const_cast<Constant*>(C2));
611 } else if (isa<ConstantExpr>(C2)) {
612 // If C2 is a constant expr and C1 isn't, flop them around and fold the
613 // other way if possible.
615 case Instruction::Add:
616 case Instruction::Mul:
617 case Instruction::And:
618 case Instruction::Or:
619 case Instruction::Xor:
620 // No change of opcode required.
621 return ConstantFoldBinaryInstruction(Opcode, C2, C1);
623 case Instruction::Shl:
624 case Instruction::LShr:
625 case Instruction::AShr:
626 case Instruction::Sub:
627 case Instruction::SDiv:
628 case Instruction::UDiv:
629 case Instruction::FDiv:
630 case Instruction::URem:
631 case Instruction::SRem:
632 case Instruction::FRem:
633 default: // These instructions cannot be flopped around.
638 // At this point we know neither constant is an UndefValue nor a ConstantExpr
639 // so look at directly computing the value.
640 if (const ConstantInt *CI1 = dyn_cast<ConstantInt>(C1)) {
641 if (const ConstantInt *CI2 = dyn_cast<ConstantInt>(C2)) {
642 using namespace APIntOps;
643 APInt C1V = CI1->getValue();
644 APInt C2V = CI2->getValue();
648 case Instruction::Add:
649 return ConstantInt::get(C1V + C2V);
650 case Instruction::Sub:
651 return ConstantInt::get(C1V - C2V);
652 case Instruction::Mul:
653 return ConstantInt::get(C1V * C2V);
654 case Instruction::UDiv:
655 if (CI2->isNullValue())
656 return 0; // X / 0 -> can't fold
657 return ConstantInt::get(C1V.udiv(C2V));
658 case Instruction::SDiv:
659 if (CI2->isNullValue())
660 return 0; // X / 0 -> can't fold
661 if (C2V.isAllOnesValue() && C1V.isMinSignedValue())
662 return 0; // MIN_INT / -1 -> overflow
663 return ConstantInt::get(C1V.sdiv(C2V));
664 case Instruction::URem:
665 if (C2->isNullValue())
666 return 0; // X / 0 -> can't fold
667 return ConstantInt::get(C1V.urem(C2V));
668 case Instruction::SRem:
669 if (CI2->isNullValue())
670 return 0; // X % 0 -> can't fold
671 if (C2V.isAllOnesValue() && C1V.isMinSignedValue())
672 return 0; // MIN_INT % -1 -> overflow
673 return ConstantInt::get(C1V.srem(C2V));
674 case Instruction::And:
675 return ConstantInt::get(C1V & C2V);
676 case Instruction::Or:
677 return ConstantInt::get(C1V | C2V);
678 case Instruction::Xor:
679 return ConstantInt::get(C1V ^ C2V);
680 case Instruction::Shl:
681 if (uint32_t shiftAmt = C2V.getZExtValue())
682 if (shiftAmt < C1V.getBitWidth())
683 return ConstantInt::get(C1V.shl(shiftAmt));
685 return UndefValue::get(C1->getType()); // too big shift is undef
686 return const_cast<ConstantInt*>(CI1); // Zero shift is identity
687 case Instruction::LShr:
688 if (uint32_t shiftAmt = C2V.getZExtValue())
689 if (shiftAmt < C1V.getBitWidth())
690 return ConstantInt::get(C1V.lshr(shiftAmt));
692 return UndefValue::get(C1->getType()); // too big shift is undef
693 return const_cast<ConstantInt*>(CI1); // Zero shift is identity
694 case Instruction::AShr:
695 if (uint32_t shiftAmt = C2V.getZExtValue())
696 if (shiftAmt < C1V.getBitWidth())
697 return ConstantInt::get(C1V.ashr(shiftAmt));
699 return UndefValue::get(C1->getType()); // too big shift is undef
700 return const_cast<ConstantInt*>(CI1); // Zero shift is identity
703 } else if (const ConstantFP *CFP1 = dyn_cast<ConstantFP>(C1)) {
704 if (const ConstantFP *CFP2 = dyn_cast<ConstantFP>(C2)) {
705 APFloat C1V = CFP1->getValueAPF();
706 APFloat C2V = CFP2->getValueAPF();
707 APFloat C3V = C1V; // copy for modification
708 bool isDouble = CFP1->getType()==Type::DoubleTy;
712 case Instruction::Add:
713 (void)C3V.add(C2V, APFloat::rmNearestTiesToEven);
714 return ConstantFP::get(CFP1->getType(), C3V);
715 case Instruction::Sub:
716 (void)C3V.subtract(C2V, APFloat::rmNearestTiesToEven);
717 return ConstantFP::get(CFP1->getType(), C3V);
718 case Instruction::Mul:
719 (void)C3V.multiply(C2V, APFloat::rmNearestTiesToEven);
720 return ConstantFP::get(CFP1->getType(), C3V);
721 case Instruction::FDiv:
722 (void)C3V.divide(C2V, APFloat::rmNearestTiesToEven);
723 return ConstantFP::get(CFP1->getType(), C3V);
724 case Instruction::FRem:
726 // IEEE 754, Section 7.1, #5
727 return ConstantFP::get(CFP1->getType(), isDouble ?
728 APFloat(std::numeric_limits<double>::quiet_NaN()) :
729 APFloat(std::numeric_limits<float>::quiet_NaN()));
730 (void)C3V.mod(C2V, APFloat::rmNearestTiesToEven);
731 return ConstantFP::get(CFP1->getType(), C3V);
734 } else if (const VectorType *VTy = dyn_cast<VectorType>(C1->getType())) {
735 const ConstantVector *CP1 = dyn_cast<ConstantVector>(C1);
736 const ConstantVector *CP2 = dyn_cast<ConstantVector>(C2);
737 if ((CP1 != NULL || isa<ConstantAggregateZero>(C1)) &&
738 (CP2 != NULL || isa<ConstantAggregateZero>(C2))) {
742 case Instruction::Add:
743 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getAdd);
744 case Instruction::Sub:
745 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getSub);
746 case Instruction::Mul:
747 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getMul);
748 case Instruction::UDiv:
749 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getUDiv);
750 case Instruction::SDiv:
751 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getSDiv);
752 case Instruction::FDiv:
753 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getFDiv);
754 case Instruction::URem:
755 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getURem);
756 case Instruction::SRem:
757 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getSRem);
758 case Instruction::FRem:
759 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getFRem);
760 case Instruction::And:
761 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getAnd);
762 case Instruction::Or:
763 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getOr);
764 case Instruction::Xor:
765 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getXor);
770 // We don't know how to fold this
774 /// isZeroSizedType - This type is zero sized if its an array or structure of
775 /// zero sized types. The only leaf zero sized type is an empty structure.
776 static bool isMaybeZeroSizedType(const Type *Ty) {
777 if (isa<OpaqueType>(Ty)) return true; // Can't say.
778 if (const StructType *STy = dyn_cast<StructType>(Ty)) {
780 // If all of elements have zero size, this does too.
781 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i)
782 if (!isMaybeZeroSizedType(STy->getElementType(i))) return false;
785 } else if (const ArrayType *ATy = dyn_cast<ArrayType>(Ty)) {
786 return isMaybeZeroSizedType(ATy->getElementType());
791 /// IdxCompare - Compare the two constants as though they were getelementptr
792 /// indices. This allows coersion of the types to be the same thing.
794 /// If the two constants are the "same" (after coersion), return 0. If the
795 /// first is less than the second, return -1, if the second is less than the
796 /// first, return 1. If the constants are not integral, return -2.
798 static int IdxCompare(Constant *C1, Constant *C2, const Type *ElTy) {
799 if (C1 == C2) return 0;
801 // Ok, we found a different index. If they are not ConstantInt, we can't do
802 // anything with them.
803 if (!isa<ConstantInt>(C1) || !isa<ConstantInt>(C2))
804 return -2; // don't know!
806 // Ok, we have two differing integer indices. Sign extend them to be the same
807 // type. Long is always big enough, so we use it.
808 if (C1->getType() != Type::Int64Ty)
809 C1 = ConstantExpr::getSExt(C1, Type::Int64Ty);
811 if (C2->getType() != Type::Int64Ty)
812 C2 = ConstantExpr::getSExt(C2, Type::Int64Ty);
814 if (C1 == C2) return 0; // They are equal
816 // If the type being indexed over is really just a zero sized type, there is
817 // no pointer difference being made here.
818 if (isMaybeZeroSizedType(ElTy))
821 // If they are really different, now that they are the same type, then we
822 // found a difference!
823 if (cast<ConstantInt>(C1)->getSExtValue() <
824 cast<ConstantInt>(C2)->getSExtValue())
830 /// evaluateFCmpRelation - This function determines if there is anything we can
831 /// decide about the two constants provided. This doesn't need to handle simple
832 /// things like ConstantFP comparisons, but should instead handle ConstantExprs.
833 /// If we can determine that the two constants have a particular relation to
834 /// each other, we should return the corresponding FCmpInst predicate,
835 /// otherwise return FCmpInst::BAD_FCMP_PREDICATE. This is used below in
836 /// ConstantFoldCompareInstruction.
838 /// To simplify this code we canonicalize the relation so that the first
839 /// operand is always the most "complex" of the two. We consider ConstantFP
840 /// to be the simplest, and ConstantExprs to be the most complex.
841 static FCmpInst::Predicate evaluateFCmpRelation(const Constant *V1,
842 const Constant *V2) {
843 assert(V1->getType() == V2->getType() &&
844 "Cannot compare values of different types!");
846 // No compile-time operations on this type yet.
847 if (V1->getType() == Type::PPC_FP128Ty)
848 return FCmpInst::BAD_FCMP_PREDICATE;
850 // Handle degenerate case quickly
851 if (V1 == V2) return FCmpInst::FCMP_OEQ;
853 if (!isa<ConstantExpr>(V1)) {
854 if (!isa<ConstantExpr>(V2)) {
855 // We distilled thisUse the standard constant folder for a few cases
857 Constant *C1 = const_cast<Constant*>(V1);
858 Constant *C2 = const_cast<Constant*>(V2);
859 R = dyn_cast<ConstantInt>(
860 ConstantExpr::getFCmp(FCmpInst::FCMP_OEQ, C1, C2));
861 if (R && !R->isZero())
862 return FCmpInst::FCMP_OEQ;
863 R = dyn_cast<ConstantInt>(
864 ConstantExpr::getFCmp(FCmpInst::FCMP_OLT, C1, C2));
865 if (R && !R->isZero())
866 return FCmpInst::FCMP_OLT;
867 R = dyn_cast<ConstantInt>(
868 ConstantExpr::getFCmp(FCmpInst::FCMP_OGT, C1, C2));
869 if (R && !R->isZero())
870 return FCmpInst::FCMP_OGT;
872 // Nothing more we can do
873 return FCmpInst::BAD_FCMP_PREDICATE;
876 // If the first operand is simple and second is ConstantExpr, swap operands.
877 FCmpInst::Predicate SwappedRelation = evaluateFCmpRelation(V2, V1);
878 if (SwappedRelation != FCmpInst::BAD_FCMP_PREDICATE)
879 return FCmpInst::getSwappedPredicate(SwappedRelation);
881 // Ok, the LHS is known to be a constantexpr. The RHS can be any of a
882 // constantexpr or a simple constant.
883 const ConstantExpr *CE1 = cast<ConstantExpr>(V1);
884 switch (CE1->getOpcode()) {
885 case Instruction::FPTrunc:
886 case Instruction::FPExt:
887 case Instruction::UIToFP:
888 case Instruction::SIToFP:
889 // We might be able to do something with these but we don't right now.
895 // There are MANY other foldings that we could perform here. They will
896 // probably be added on demand, as they seem needed.
897 return FCmpInst::BAD_FCMP_PREDICATE;
900 /// evaluateICmpRelation - This function determines if there is anything we can
901 /// decide about the two constants provided. This doesn't need to handle simple
902 /// things like integer comparisons, but should instead handle ConstantExprs
903 /// and GlobalValues. If we can determine that the two constants have a
904 /// particular relation to each other, we should return the corresponding ICmp
905 /// predicate, otherwise return ICmpInst::BAD_ICMP_PREDICATE.
907 /// To simplify this code we canonicalize the relation so that the first
908 /// operand is always the most "complex" of the two. We consider simple
909 /// constants (like ConstantInt) to be the simplest, followed by
910 /// GlobalValues, followed by ConstantExpr's (the most complex).
912 static ICmpInst::Predicate evaluateICmpRelation(const Constant *V1,
915 assert(V1->getType() == V2->getType() &&
916 "Cannot compare different types of values!");
917 if (V1 == V2) return ICmpInst::ICMP_EQ;
919 if (!isa<ConstantExpr>(V1) && !isa<GlobalValue>(V1)) {
920 if (!isa<GlobalValue>(V2) && !isa<ConstantExpr>(V2)) {
921 // We distilled this down to a simple case, use the standard constant
924 Constant *C1 = const_cast<Constant*>(V1);
925 Constant *C2 = const_cast<Constant*>(V2);
926 ICmpInst::Predicate pred = ICmpInst::ICMP_EQ;
927 R = dyn_cast<ConstantInt>(ConstantExpr::getICmp(pred, C1, C2));
928 if (R && !R->isZero())
930 pred = isSigned ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT;
931 R = dyn_cast<ConstantInt>(ConstantExpr::getICmp(pred, C1, C2));
932 if (R && !R->isZero())
934 pred = isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT;
935 R = dyn_cast<ConstantInt>(ConstantExpr::getICmp(pred, C1, C2));
936 if (R && !R->isZero())
939 // If we couldn't figure it out, bail.
940 return ICmpInst::BAD_ICMP_PREDICATE;
943 // If the first operand is simple, swap operands.
944 ICmpInst::Predicate SwappedRelation =
945 evaluateICmpRelation(V2, V1, isSigned);
946 if (SwappedRelation != ICmpInst::BAD_ICMP_PREDICATE)
947 return ICmpInst::getSwappedPredicate(SwappedRelation);
949 } else if (const GlobalValue *CPR1 = dyn_cast<GlobalValue>(V1)) {
950 if (isa<ConstantExpr>(V2)) { // Swap as necessary.
951 ICmpInst::Predicate SwappedRelation =
952 evaluateICmpRelation(V2, V1, isSigned);
953 if (SwappedRelation != ICmpInst::BAD_ICMP_PREDICATE)
954 return ICmpInst::getSwappedPredicate(SwappedRelation);
956 return ICmpInst::BAD_ICMP_PREDICATE;
959 // Now we know that the RHS is a GlobalValue or simple constant,
960 // which (since the types must match) means that it's a ConstantPointerNull.
961 if (const GlobalValue *CPR2 = dyn_cast<GlobalValue>(V2)) {
962 // Don't try to decide equality of aliases.
963 if (!isa<GlobalAlias>(CPR1) && !isa<GlobalAlias>(CPR2))
964 if (!CPR1->hasExternalWeakLinkage() || !CPR2->hasExternalWeakLinkage())
965 return ICmpInst::ICMP_NE;
967 assert(isa<ConstantPointerNull>(V2) && "Canonicalization guarantee!");
968 // GlobalVals can never be null. Don't try to evaluate aliases.
969 if (!CPR1->hasExternalWeakLinkage() && !isa<GlobalAlias>(CPR1))
970 return ICmpInst::ICMP_NE;
973 // Ok, the LHS is known to be a constantexpr. The RHS can be any of a
974 // constantexpr, a CPR, or a simple constant.
975 const ConstantExpr *CE1 = cast<ConstantExpr>(V1);
976 const Constant *CE1Op0 = CE1->getOperand(0);
978 switch (CE1->getOpcode()) {
979 case Instruction::Trunc:
980 case Instruction::FPTrunc:
981 case Instruction::FPExt:
982 case Instruction::FPToUI:
983 case Instruction::FPToSI:
984 break; // We can't evaluate floating point casts or truncations.
986 case Instruction::UIToFP:
987 case Instruction::SIToFP:
988 case Instruction::IntToPtr:
989 case Instruction::BitCast:
990 case Instruction::ZExt:
991 case Instruction::SExt:
992 case Instruction::PtrToInt:
993 // If the cast is not actually changing bits, and the second operand is a
994 // null pointer, do the comparison with the pre-casted value.
995 if (V2->isNullValue() &&
996 (isa<PointerType>(CE1->getType()) || CE1->getType()->isInteger())) {
997 bool sgnd = CE1->getOpcode() == Instruction::ZExt ? false :
998 (CE1->getOpcode() == Instruction::SExt ? true :
999 (CE1->getOpcode() == Instruction::PtrToInt ? false : isSigned));
1000 return evaluateICmpRelation(
1001 CE1Op0, Constant::getNullValue(CE1Op0->getType()), sgnd);
1004 // If the dest type is a pointer type, and the RHS is a constantexpr cast
1005 // from the same type as the src of the LHS, evaluate the inputs. This is
1006 // important for things like "icmp eq (cast 4 to int*), (cast 5 to int*)",
1007 // which happens a lot in compilers with tagged integers.
1008 if (const ConstantExpr *CE2 = dyn_cast<ConstantExpr>(V2))
1009 if (CE2->isCast() && isa<PointerType>(CE1->getType()) &&
1010 CE1->getOperand(0)->getType() == CE2->getOperand(0)->getType() &&
1011 CE1->getOperand(0)->getType()->isInteger()) {
1012 bool sgnd = CE1->getOpcode() == Instruction::ZExt ? false :
1013 (CE1->getOpcode() == Instruction::SExt ? true :
1014 (CE1->getOpcode() == Instruction::PtrToInt ? false : isSigned));
1015 return evaluateICmpRelation(CE1->getOperand(0), CE2->getOperand(0),
1020 case Instruction::GetElementPtr:
1021 // Ok, since this is a getelementptr, we know that the constant has a
1022 // pointer type. Check the various cases.
1023 if (isa<ConstantPointerNull>(V2)) {
1024 // If we are comparing a GEP to a null pointer, check to see if the base
1025 // of the GEP equals the null pointer.
1026 if (const GlobalValue *GV = dyn_cast<GlobalValue>(CE1Op0)) {
1027 if (GV->hasExternalWeakLinkage())
1028 // Weak linkage GVals could be zero or not. We're comparing that
1029 // to null pointer so its greater-or-equal
1030 return isSigned ? ICmpInst::ICMP_SGE : ICmpInst::ICMP_UGE;
1032 // If its not weak linkage, the GVal must have a non-zero address
1033 // so the result is greater-than
1034 return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT;
1035 } else if (isa<ConstantPointerNull>(CE1Op0)) {
1036 // If we are indexing from a null pointer, check to see if we have any
1037 // non-zero indices.
1038 for (unsigned i = 1, e = CE1->getNumOperands(); i != e; ++i)
1039 if (!CE1->getOperand(i)->isNullValue())
1040 // Offsetting from null, must not be equal.
1041 return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT;
1042 // Only zero indexes from null, must still be zero.
1043 return ICmpInst::ICMP_EQ;
1045 // Otherwise, we can't really say if the first operand is null or not.
1046 } else if (const GlobalValue *CPR2 = dyn_cast<GlobalValue>(V2)) {
1047 if (isa<ConstantPointerNull>(CE1Op0)) {
1048 if (CPR2->hasExternalWeakLinkage())
1049 // Weak linkage GVals could be zero or not. We're comparing it to
1050 // a null pointer, so its less-or-equal
1051 return isSigned ? ICmpInst::ICMP_SLE : ICmpInst::ICMP_ULE;
1053 // If its not weak linkage, the GVal must have a non-zero address
1054 // so the result is less-than
1055 return isSigned ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT;
1056 } else if (const GlobalValue *CPR1 = dyn_cast<GlobalValue>(CE1Op0)) {
1058 // If this is a getelementptr of the same global, then it must be
1059 // different. Because the types must match, the getelementptr could
1060 // only have at most one index, and because we fold getelementptr's
1061 // with a single zero index, it must be nonzero.
1062 assert(CE1->getNumOperands() == 2 &&
1063 !CE1->getOperand(1)->isNullValue() &&
1064 "Suprising getelementptr!");
1065 return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT;
1067 // If they are different globals, we don't know what the value is,
1068 // but they can't be equal.
1069 return ICmpInst::ICMP_NE;
1073 const ConstantExpr *CE2 = cast<ConstantExpr>(V2);
1074 const Constant *CE2Op0 = CE2->getOperand(0);
1076 // There are MANY other foldings that we could perform here. They will
1077 // probably be added on demand, as they seem needed.
1078 switch (CE2->getOpcode()) {
1080 case Instruction::GetElementPtr:
1081 // By far the most common case to handle is when the base pointers are
1082 // obviously to the same or different globals.
1083 if (isa<GlobalValue>(CE1Op0) && isa<GlobalValue>(CE2Op0)) {
1084 if (CE1Op0 != CE2Op0) // Don't know relative ordering, but not equal
1085 return ICmpInst::ICMP_NE;
1086 // Ok, we know that both getelementptr instructions are based on the
1087 // same global. From this, we can precisely determine the relative
1088 // ordering of the resultant pointers.
1091 // Compare all of the operands the GEP's have in common.
1092 gep_type_iterator GTI = gep_type_begin(CE1);
1093 for (;i != CE1->getNumOperands() && i != CE2->getNumOperands();
1095 switch (IdxCompare(CE1->getOperand(i), CE2->getOperand(i),
1096 GTI.getIndexedType())) {
1097 case -1: return isSigned ? ICmpInst::ICMP_SLT:ICmpInst::ICMP_ULT;
1098 case 1: return isSigned ? ICmpInst::ICMP_SGT:ICmpInst::ICMP_UGT;
1099 case -2: return ICmpInst::BAD_ICMP_PREDICATE;
1102 // Ok, we ran out of things they have in common. If any leftovers
1103 // are non-zero then we have a difference, otherwise we are equal.
1104 for (; i < CE1->getNumOperands(); ++i)
1105 if (!CE1->getOperand(i)->isNullValue())
1106 if (isa<ConstantInt>(CE1->getOperand(i)))
1107 return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT;
1109 return ICmpInst::BAD_ICMP_PREDICATE; // Might be equal.
1111 for (; i < CE2->getNumOperands(); ++i)
1112 if (!CE2->getOperand(i)->isNullValue())
1113 if (isa<ConstantInt>(CE2->getOperand(i)))
1114 return isSigned ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT;
1116 return ICmpInst::BAD_ICMP_PREDICATE; // Might be equal.
1117 return ICmpInst::ICMP_EQ;
1126 return ICmpInst::BAD_ICMP_PREDICATE;
1129 Constant *llvm::ConstantFoldCompareInstruction(unsigned short pred,
1131 const Constant *C2) {
1133 // Handle some degenerate cases first
1134 if (isa<UndefValue>(C1) || isa<UndefValue>(C2))
1135 return UndefValue::get(Type::Int1Ty);
1137 // No compile-time operations on this type yet.
1138 if (C1->getType() == Type::PPC_FP128Ty)
1141 // icmp eq/ne(null,GV) -> false/true
1142 if (C1->isNullValue()) {
1143 if (const GlobalValue *GV = dyn_cast<GlobalValue>(C2))
1144 // Don't try to evaluate aliases. External weak GV can be null.
1145 if (!isa<GlobalAlias>(GV) && !GV->hasExternalWeakLinkage())
1146 if (pred == ICmpInst::ICMP_EQ)
1147 return ConstantInt::getFalse();
1148 else if (pred == ICmpInst::ICMP_NE)
1149 return ConstantInt::getTrue();
1150 // icmp eq/ne(GV,null) -> false/true
1151 } else if (C2->isNullValue()) {
1152 if (const GlobalValue *GV = dyn_cast<GlobalValue>(C1))
1153 // Don't try to evaluate aliases. External weak GV can be null.
1154 if (!isa<GlobalAlias>(GV) && !GV->hasExternalWeakLinkage())
1155 if (pred == ICmpInst::ICMP_EQ)
1156 return ConstantInt::getFalse();
1157 else if (pred == ICmpInst::ICMP_NE)
1158 return ConstantInt::getTrue();
1161 if (isa<ConstantInt>(C1) && isa<ConstantInt>(C2)) {
1162 APInt V1 = cast<ConstantInt>(C1)->getValue();
1163 APInt V2 = cast<ConstantInt>(C2)->getValue();
1165 default: assert(0 && "Invalid ICmp Predicate"); return 0;
1166 case ICmpInst::ICMP_EQ: return ConstantInt::get(Type::Int1Ty, V1 == V2);
1167 case ICmpInst::ICMP_NE: return ConstantInt::get(Type::Int1Ty, V1 != V2);
1168 case ICmpInst::ICMP_SLT:return ConstantInt::get(Type::Int1Ty, V1.slt(V2));
1169 case ICmpInst::ICMP_SGT:return ConstantInt::get(Type::Int1Ty, V1.sgt(V2));
1170 case ICmpInst::ICMP_SLE:return ConstantInt::get(Type::Int1Ty, V1.sle(V2));
1171 case ICmpInst::ICMP_SGE:return ConstantInt::get(Type::Int1Ty, V1.sge(V2));
1172 case ICmpInst::ICMP_ULT:return ConstantInt::get(Type::Int1Ty, V1.ult(V2));
1173 case ICmpInst::ICMP_UGT:return ConstantInt::get(Type::Int1Ty, V1.ugt(V2));
1174 case ICmpInst::ICMP_ULE:return ConstantInt::get(Type::Int1Ty, V1.ule(V2));
1175 case ICmpInst::ICMP_UGE:return ConstantInt::get(Type::Int1Ty, V1.uge(V2));
1177 } else if (isa<ConstantFP>(C1) && isa<ConstantFP>(C2)) {
1178 APFloat C1V = cast<ConstantFP>(C1)->getValueAPF();
1179 APFloat C2V = cast<ConstantFP>(C2)->getValueAPF();
1180 APFloat::cmpResult R = C1V.compare(C2V);
1182 default: assert(0 && "Invalid FCmp Predicate"); return 0;
1183 case FCmpInst::FCMP_FALSE: return ConstantInt::getFalse();
1184 case FCmpInst::FCMP_TRUE: return ConstantInt::getTrue();
1185 case FCmpInst::FCMP_UNO:
1186 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpUnordered);
1187 case FCmpInst::FCMP_ORD:
1188 return ConstantInt::get(Type::Int1Ty, R!=APFloat::cmpUnordered);
1189 case FCmpInst::FCMP_UEQ:
1190 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpUnordered ||
1191 R==APFloat::cmpEqual);
1192 case FCmpInst::FCMP_OEQ:
1193 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpEqual);
1194 case FCmpInst::FCMP_UNE:
1195 return ConstantInt::get(Type::Int1Ty, R!=APFloat::cmpEqual);
1196 case FCmpInst::FCMP_ONE:
1197 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpLessThan ||
1198 R==APFloat::cmpGreaterThan);
1199 case FCmpInst::FCMP_ULT:
1200 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpUnordered ||
1201 R==APFloat::cmpLessThan);
1202 case FCmpInst::FCMP_OLT:
1203 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpLessThan);
1204 case FCmpInst::FCMP_UGT:
1205 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpUnordered ||
1206 R==APFloat::cmpGreaterThan);
1207 case FCmpInst::FCMP_OGT:
1208 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpGreaterThan);
1209 case FCmpInst::FCMP_ULE:
1210 return ConstantInt::get(Type::Int1Ty, R!=APFloat::cmpGreaterThan);
1211 case FCmpInst::FCMP_OLE:
1212 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpLessThan ||
1213 R==APFloat::cmpEqual);
1214 case FCmpInst::FCMP_UGE:
1215 return ConstantInt::get(Type::Int1Ty, R!=APFloat::cmpLessThan);
1216 case FCmpInst::FCMP_OGE:
1217 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpGreaterThan ||
1218 R==APFloat::cmpEqual);
1220 } else if (const ConstantVector *CP1 = dyn_cast<ConstantVector>(C1)) {
1221 if (const ConstantVector *CP2 = dyn_cast<ConstantVector>(C2)) {
1222 if (pred == FCmpInst::FCMP_OEQ || pred == FCmpInst::FCMP_UEQ) {
1223 for (unsigned i = 0, e = CP1->getNumOperands(); i != e; ++i) {
1224 Constant *C= ConstantExpr::getFCmp(FCmpInst::FCMP_OEQ,
1225 const_cast<Constant*>(CP1->getOperand(i)),
1226 const_cast<Constant*>(CP2->getOperand(i)));
1227 if (ConstantInt *CB = dyn_cast<ConstantInt>(C))
1230 // Otherwise, could not decide from any element pairs.
1232 } else if (pred == ICmpInst::ICMP_EQ) {
1233 for (unsigned i = 0, e = CP1->getNumOperands(); i != e; ++i) {
1234 Constant *C = ConstantExpr::getICmp(ICmpInst::ICMP_EQ,
1235 const_cast<Constant*>(CP1->getOperand(i)),
1236 const_cast<Constant*>(CP2->getOperand(i)));
1237 if (ConstantInt *CB = dyn_cast<ConstantInt>(C))
1240 // Otherwise, could not decide from any element pairs.
1246 if (C1->getType()->isFloatingPoint()) {
1247 switch (evaluateFCmpRelation(C1, C2)) {
1248 default: assert(0 && "Unknown relation!");
1249 case FCmpInst::FCMP_UNO:
1250 case FCmpInst::FCMP_ORD:
1251 case FCmpInst::FCMP_UEQ:
1252 case FCmpInst::FCMP_UNE:
1253 case FCmpInst::FCMP_ULT:
1254 case FCmpInst::FCMP_UGT:
1255 case FCmpInst::FCMP_ULE:
1256 case FCmpInst::FCMP_UGE:
1257 case FCmpInst::FCMP_TRUE:
1258 case FCmpInst::FCMP_FALSE:
1259 case FCmpInst::BAD_FCMP_PREDICATE:
1260 break; // Couldn't determine anything about these constants.
1261 case FCmpInst::FCMP_OEQ: // We know that C1 == C2
1262 return ConstantInt::get(Type::Int1Ty,
1263 pred == FCmpInst::FCMP_UEQ || pred == FCmpInst::FCMP_OEQ ||
1264 pred == FCmpInst::FCMP_ULE || pred == FCmpInst::FCMP_OLE ||
1265 pred == FCmpInst::FCMP_UGE || pred == FCmpInst::FCMP_OGE);
1266 case FCmpInst::FCMP_OLT: // We know that C1 < C2
1267 return ConstantInt::get(Type::Int1Ty,
1268 pred == FCmpInst::FCMP_UNE || pred == FCmpInst::FCMP_ONE ||
1269 pred == FCmpInst::FCMP_ULT || pred == FCmpInst::FCMP_OLT ||
1270 pred == FCmpInst::FCMP_ULE || pred == FCmpInst::FCMP_OLE);
1271 case FCmpInst::FCMP_OGT: // We know that C1 > C2
1272 return ConstantInt::get(Type::Int1Ty,
1273 pred == FCmpInst::FCMP_UNE || pred == FCmpInst::FCMP_ONE ||
1274 pred == FCmpInst::FCMP_UGT || pred == FCmpInst::FCMP_OGT ||
1275 pred == FCmpInst::FCMP_UGE || pred == FCmpInst::FCMP_OGE);
1276 case FCmpInst::FCMP_OLE: // We know that C1 <= C2
1277 // We can only partially decide this relation.
1278 if (pred == FCmpInst::FCMP_UGT || pred == FCmpInst::FCMP_OGT)
1279 return ConstantInt::getFalse();
1280 if (pred == FCmpInst::FCMP_ULT || pred == FCmpInst::FCMP_OLT)
1281 return ConstantInt::getTrue();
1283 case FCmpInst::FCMP_OGE: // We known that C1 >= C2
1284 // We can only partially decide this relation.
1285 if (pred == FCmpInst::FCMP_ULT || pred == FCmpInst::FCMP_OLT)
1286 return ConstantInt::getFalse();
1287 if (pred == FCmpInst::FCMP_UGT || pred == FCmpInst::FCMP_OGT)
1288 return ConstantInt::getTrue();
1290 case ICmpInst::ICMP_NE: // We know that C1 != C2
1291 // We can only partially decide this relation.
1292 if (pred == FCmpInst::FCMP_OEQ || pred == FCmpInst::FCMP_UEQ)
1293 return ConstantInt::getFalse();
1294 if (pred == FCmpInst::FCMP_ONE || pred == FCmpInst::FCMP_UNE)
1295 return ConstantInt::getTrue();
1299 // Evaluate the relation between the two constants, per the predicate.
1300 switch (evaluateICmpRelation(C1, C2, CmpInst::isSigned(pred))) {
1301 default: assert(0 && "Unknown relational!");
1302 case ICmpInst::BAD_ICMP_PREDICATE:
1303 break; // Couldn't determine anything about these constants.
1304 case ICmpInst::ICMP_EQ: // We know the constants are equal!
1305 // If we know the constants are equal, we can decide the result of this
1306 // computation precisely.
1307 return ConstantInt::get(Type::Int1Ty,
1308 pred == ICmpInst::ICMP_EQ ||
1309 pred == ICmpInst::ICMP_ULE ||
1310 pred == ICmpInst::ICMP_SLE ||
1311 pred == ICmpInst::ICMP_UGE ||
1312 pred == ICmpInst::ICMP_SGE);
1313 case ICmpInst::ICMP_ULT:
1314 // If we know that C1 < C2, we can decide the result of this computation
1316 return ConstantInt::get(Type::Int1Ty,
1317 pred == ICmpInst::ICMP_ULT ||
1318 pred == ICmpInst::ICMP_NE ||
1319 pred == ICmpInst::ICMP_ULE);
1320 case ICmpInst::ICMP_SLT:
1321 // If we know that C1 < C2, we can decide the result of this computation
1323 return ConstantInt::get(Type::Int1Ty,
1324 pred == ICmpInst::ICMP_SLT ||
1325 pred == ICmpInst::ICMP_NE ||
1326 pred == ICmpInst::ICMP_SLE);
1327 case ICmpInst::ICMP_UGT:
1328 // If we know that C1 > C2, we can decide the result of this computation
1330 return ConstantInt::get(Type::Int1Ty,
1331 pred == ICmpInst::ICMP_UGT ||
1332 pred == ICmpInst::ICMP_NE ||
1333 pred == ICmpInst::ICMP_UGE);
1334 case ICmpInst::ICMP_SGT:
1335 // If we know that C1 > C2, we can decide the result of this computation
1337 return ConstantInt::get(Type::Int1Ty,
1338 pred == ICmpInst::ICMP_SGT ||
1339 pred == ICmpInst::ICMP_NE ||
1340 pred == ICmpInst::ICMP_SGE);
1341 case ICmpInst::ICMP_ULE:
1342 // If we know that C1 <= C2, we can only partially decide this relation.
1343 if (pred == ICmpInst::ICMP_UGT) return ConstantInt::getFalse();
1344 if (pred == ICmpInst::ICMP_ULT) return ConstantInt::getTrue();
1346 case ICmpInst::ICMP_SLE:
1347 // If we know that C1 <= C2, we can only partially decide this relation.
1348 if (pred == ICmpInst::ICMP_SGT) return ConstantInt::getFalse();
1349 if (pred == ICmpInst::ICMP_SLT) return ConstantInt::getTrue();
1352 case ICmpInst::ICMP_UGE:
1353 // If we know that C1 >= C2, we can only partially decide this relation.
1354 if (pred == ICmpInst::ICMP_ULT) return ConstantInt::getFalse();
1355 if (pred == ICmpInst::ICMP_UGT) return ConstantInt::getTrue();
1357 case ICmpInst::ICMP_SGE:
1358 // If we know that C1 >= C2, we can only partially decide this relation.
1359 if (pred == ICmpInst::ICMP_SLT) return ConstantInt::getFalse();
1360 if (pred == ICmpInst::ICMP_SGT) return ConstantInt::getTrue();
1363 case ICmpInst::ICMP_NE:
1364 // If we know that C1 != C2, we can only partially decide this relation.
1365 if (pred == ICmpInst::ICMP_EQ) return ConstantInt::getFalse();
1366 if (pred == ICmpInst::ICMP_NE) return ConstantInt::getTrue();
1370 if (!isa<ConstantExpr>(C1) && isa<ConstantExpr>(C2)) {
1371 // If C2 is a constant expr and C1 isn't, flop them around and fold the
1372 // other way if possible.
1374 case ICmpInst::ICMP_EQ:
1375 case ICmpInst::ICMP_NE:
1376 // No change of predicate required.
1377 return ConstantFoldCompareInstruction(pred, C2, C1);
1379 case ICmpInst::ICMP_ULT:
1380 case ICmpInst::ICMP_SLT:
1381 case ICmpInst::ICMP_UGT:
1382 case ICmpInst::ICMP_SGT:
1383 case ICmpInst::ICMP_ULE:
1384 case ICmpInst::ICMP_SLE:
1385 case ICmpInst::ICMP_UGE:
1386 case ICmpInst::ICMP_SGE:
1387 // Change the predicate as necessary to swap the operands.
1388 pred = ICmpInst::getSwappedPredicate((ICmpInst::Predicate)pred);
1389 return ConstantFoldCompareInstruction(pred, C2, C1);
1391 default: // These predicates cannot be flopped around.
1399 Constant *llvm::ConstantFoldGetElementPtr(const Constant *C,
1400 Constant* const *Idxs,
1403 (NumIdx == 1 && Idxs[0]->isNullValue()))
1404 return const_cast<Constant*>(C);
1406 if (isa<UndefValue>(C)) {
1407 const Type *Ty = GetElementPtrInst::getIndexedType(C->getType(),
1409 (Value **)Idxs+NumIdx,
1411 assert(Ty != 0 && "Invalid indices for GEP!");
1412 return UndefValue::get(PointerType::get(Ty));
1415 Constant *Idx0 = Idxs[0];
1416 if (C->isNullValue()) {
1418 for (unsigned i = 0, e = NumIdx; i != e; ++i)
1419 if (!Idxs[i]->isNullValue()) {
1424 const Type *Ty = GetElementPtrInst::getIndexedType(C->getType(),
1426 (Value**)Idxs+NumIdx,
1428 assert(Ty != 0 && "Invalid indices for GEP!");
1429 return ConstantPointerNull::get(PointerType::get(Ty));
1433 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(const_cast<Constant*>(C))) {
1434 // Combine Indices - If the source pointer to this getelementptr instruction
1435 // is a getelementptr instruction, combine the indices of the two
1436 // getelementptr instructions into a single instruction.
1438 if (CE->getOpcode() == Instruction::GetElementPtr) {
1439 const Type *LastTy = 0;
1440 for (gep_type_iterator I = gep_type_begin(CE), E = gep_type_end(CE);
1444 if ((LastTy && isa<ArrayType>(LastTy)) || Idx0->isNullValue()) {
1445 SmallVector<Value*, 16> NewIndices;
1446 NewIndices.reserve(NumIdx + CE->getNumOperands());
1447 for (unsigned i = 1, e = CE->getNumOperands()-1; i != e; ++i)
1448 NewIndices.push_back(CE->getOperand(i));
1450 // Add the last index of the source with the first index of the new GEP.
1451 // Make sure to handle the case when they are actually different types.
1452 Constant *Combined = CE->getOperand(CE->getNumOperands()-1);
1453 // Otherwise it must be an array.
1454 if (!Idx0->isNullValue()) {
1455 const Type *IdxTy = Combined->getType();
1456 if (IdxTy != Idx0->getType()) {
1457 Constant *C1 = ConstantExpr::getSExtOrBitCast(Idx0, Type::Int64Ty);
1458 Constant *C2 = ConstantExpr::getSExtOrBitCast(Combined,
1460 Combined = ConstantExpr::get(Instruction::Add, C1, C2);
1463 ConstantExpr::get(Instruction::Add, Idx0, Combined);
1467 NewIndices.push_back(Combined);
1468 NewIndices.insert(NewIndices.end(), Idxs+1, Idxs+NumIdx);
1469 return ConstantExpr::getGetElementPtr(CE->getOperand(0), &NewIndices[0],
1474 // Implement folding of:
1475 // int* getelementptr ([2 x int]* cast ([3 x int]* %X to [2 x int]*),
1477 // To: int* getelementptr ([3 x int]* %X, long 0, long 0)
1479 if (CE->isCast() && NumIdx > 1 && Idx0->isNullValue()) {
1480 if (const PointerType *SPT =
1481 dyn_cast<PointerType>(CE->getOperand(0)->getType()))
1482 if (const ArrayType *SAT = dyn_cast<ArrayType>(SPT->getElementType()))
1483 if (const ArrayType *CAT =
1484 dyn_cast<ArrayType>(cast<PointerType>(C->getType())->getElementType()))
1485 if (CAT->getElementType() == SAT->getElementType())
1486 return ConstantExpr::getGetElementPtr(
1487 (Constant*)CE->getOperand(0), Idxs, NumIdx);
1490 // Fold: getelementptr (i8* inttoptr (i64 1 to i8*), i32 -1)
1491 // Into: inttoptr (i64 0 to i8*)
1492 // This happens with pointers to member functions in C++.
1493 if (CE->getOpcode() == Instruction::IntToPtr && NumIdx == 1 &&
1494 isa<ConstantInt>(CE->getOperand(0)) && isa<ConstantInt>(Idxs[0]) &&
1495 cast<PointerType>(CE->getType())->getElementType() == Type::Int8Ty) {
1496 Constant *Base = CE->getOperand(0);
1497 Constant *Offset = Idxs[0];
1499 // Convert the smaller integer to the larger type.
1500 if (Offset->getType()->getPrimitiveSizeInBits() <
1501 Base->getType()->getPrimitiveSizeInBits())
1502 Offset = ConstantExpr::getSExt(Offset, Base->getType());
1503 else if (Base->getType()->getPrimitiveSizeInBits() <
1504 Offset->getType()->getPrimitiveSizeInBits())
1505 Base = ConstantExpr::getZExt(Base, Base->getType());
1507 Base = ConstantExpr::getAdd(Base, Offset);
1508 return ConstantExpr::getIntToPtr(Base, CE->getType());