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 :
184 APFloat::rmNearestTiesToEven);
185 return ConstantFP::get(DestTy, Val);
187 return 0; // Can't fold.
188 case Instruction::FPToUI:
189 if (const ConstantFP *FPC = dyn_cast<ConstantFP>(V)) {
190 APFloat V = FPC->getValueAPF();
191 bool isDouble = &V.getSemantics()==&APFloat::IEEEdouble;
192 uint32_t DestBitWidth = cast<IntegerType>(DestTy)->getBitWidth();
193 APInt Val(APIntOps::RoundDoubleToAPInt(isDouble ? V.convertToDouble() :
194 (double)V.convertToFloat(), DestBitWidth));
195 return ConstantInt::get(Val);
197 return 0; // Can't fold.
198 case Instruction::FPToSI:
199 if (const ConstantFP *FPC = dyn_cast<ConstantFP>(V)) {
200 APFloat V = FPC->getValueAPF();
201 bool isDouble = &V.getSemantics()==&APFloat::IEEEdouble;
202 uint32_t DestBitWidth = cast<IntegerType>(DestTy)->getBitWidth();
203 APInt Val(APIntOps::RoundDoubleToAPInt(isDouble ? V.convertToDouble() :
204 (double)V.convertToFloat(), DestBitWidth));
205 return ConstantInt::get(Val);
207 return 0; // Can't fold.
208 case Instruction::IntToPtr: //always treated as unsigned
209 if (V->isNullValue()) // Is it an integral null value?
210 return ConstantPointerNull::get(cast<PointerType>(DestTy));
211 return 0; // Other pointer types cannot be casted
212 case Instruction::PtrToInt: // always treated as unsigned
213 if (V->isNullValue()) // is it a null pointer value?
214 return ConstantInt::get(DestTy, 0);
215 return 0; // Other pointer types cannot be casted
216 case Instruction::UIToFP:
217 if (const ConstantInt *CI = dyn_cast<ConstantInt>(V)) {
218 if (DestTy==Type::FloatTy)
219 return ConstantFP::get(DestTy,
220 APFloat((float)CI->getValue().roundToDouble()));
222 return ConstantFP::get(DestTy, APFloat(CI->getValue().roundToDouble()));
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));
231 return ConstantFP::get(DestTy, APFloat(d));
234 case Instruction::ZExt:
235 if (const ConstantInt *CI = dyn_cast<ConstantInt>(V)) {
236 uint32_t BitWidth = cast<IntegerType>(DestTy)->getBitWidth();
237 APInt Result(CI->getValue());
238 Result.zext(BitWidth);
239 return ConstantInt::get(Result);
242 case Instruction::SExt:
243 if (const ConstantInt *CI = dyn_cast<ConstantInt>(V)) {
244 uint32_t BitWidth = cast<IntegerType>(DestTy)->getBitWidth();
245 APInt Result(CI->getValue());
246 Result.sext(BitWidth);
247 return ConstantInt::get(Result);
250 case Instruction::Trunc:
251 if (const ConstantInt *CI = dyn_cast<ConstantInt>(V)) {
252 uint32_t BitWidth = cast<IntegerType>(DestTy)->getBitWidth();
253 APInt Result(CI->getValue());
254 Result.trunc(BitWidth);
255 return ConstantInt::get(Result);
258 case Instruction::BitCast:
260 return (Constant*)V; // no-op cast
262 // Check to see if we are casting a pointer to an aggregate to a pointer to
263 // the first element. If so, return the appropriate GEP instruction.
264 if (const PointerType *PTy = dyn_cast<PointerType>(V->getType()))
265 if (const PointerType *DPTy = dyn_cast<PointerType>(DestTy)) {
266 SmallVector<Value*, 8> IdxList;
267 IdxList.push_back(Constant::getNullValue(Type::Int32Ty));
268 const Type *ElTy = PTy->getElementType();
269 while (ElTy != DPTy->getElementType()) {
270 if (const StructType *STy = dyn_cast<StructType>(ElTy)) {
271 if (STy->getNumElements() == 0) break;
272 ElTy = STy->getElementType(0);
273 IdxList.push_back(Constant::getNullValue(Type::Int32Ty));
274 } else if (const SequentialType *STy =
275 dyn_cast<SequentialType>(ElTy)) {
276 if (isa<PointerType>(ElTy)) break; // Can't index into pointers!
277 ElTy = STy->getElementType();
278 IdxList.push_back(IdxList[0]);
284 if (ElTy == DPTy->getElementType())
285 return ConstantExpr::getGetElementPtr(
286 const_cast<Constant*>(V), &IdxList[0], IdxList.size());
289 // Handle casts from one vector constant to another. We know that the src
290 // and dest type have the same size (otherwise its an illegal cast).
291 if (const VectorType *DestPTy = dyn_cast<VectorType>(DestTy)) {
292 if (const VectorType *SrcTy = dyn_cast<VectorType>(V->getType())) {
293 assert(DestPTy->getBitWidth() == SrcTy->getBitWidth() &&
294 "Not cast between same sized vectors!");
295 // First, check for null and undef
296 if (isa<ConstantAggregateZero>(V))
297 return Constant::getNullValue(DestTy);
298 if (isa<UndefValue>(V))
299 return UndefValue::get(DestTy);
301 if (const ConstantVector *CV = dyn_cast<ConstantVector>(V)) {
302 // This is a cast from a ConstantVector of one type to a
303 // ConstantVector of another type. Check to see if all elements of
304 // the input are simple.
305 bool AllSimpleConstants = true;
306 for (unsigned i = 0, e = CV->getNumOperands(); i != e; ++i) {
307 if (!isa<ConstantInt>(CV->getOperand(i)) &&
308 !isa<ConstantFP>(CV->getOperand(i))) {
309 AllSimpleConstants = false;
314 // If all of the elements are simple constants, we can fold this.
315 if (AllSimpleConstants)
316 return CastConstantVector(const_cast<ConstantVector*>(CV), DestPTy);
321 // Finally, implement bitcast folding now. The code below doesn't handle
323 if (isa<ConstantPointerNull>(V)) // ptr->ptr cast.
324 return ConstantPointerNull::get(cast<PointerType>(DestTy));
326 // Handle integral constant input.
327 if (const ConstantInt *CI = dyn_cast<ConstantInt>(V)) {
328 if (DestTy->isInteger())
329 // Integral -> Integral. This is a no-op because the bit widths must
330 // be the same. Consequently, we just fold to V.
331 return const_cast<Constant*>(V);
333 if (DestTy->isFloatingPoint()) {
334 assert((DestTy == Type::DoubleTy || DestTy == Type::FloatTy) &&
336 return ConstantFP::get(DestTy, APFloat(CI->getValue()));
338 // Otherwise, can't fold this (vector?)
342 // Handle ConstantFP input.
343 if (const ConstantFP *FP = dyn_cast<ConstantFP>(V)) {
345 if (DestTy == Type::Int32Ty) {
346 return ConstantInt::get(FP->getValueAPF().convertToAPInt());
348 assert(DestTy == Type::Int64Ty && "only support f32/f64 for now!");
349 return ConstantInt::get(FP->getValueAPF().convertToAPInt());
354 assert(!"Invalid CE CastInst opcode");
358 assert(0 && "Failed to cast constant expression");
362 Constant *llvm::ConstantFoldSelectInstruction(const Constant *Cond,
364 const Constant *V2) {
365 if (const ConstantInt *CB = dyn_cast<ConstantInt>(Cond))
366 return const_cast<Constant*>(CB->getZExtValue() ? V1 : V2);
368 if (isa<UndefValue>(V1)) return const_cast<Constant*>(V2);
369 if (isa<UndefValue>(V2)) return const_cast<Constant*>(V1);
370 if (isa<UndefValue>(Cond)) return const_cast<Constant*>(V1);
371 if (V1 == V2) return const_cast<Constant*>(V1);
375 Constant *llvm::ConstantFoldExtractElementInstruction(const Constant *Val,
376 const Constant *Idx) {
377 if (isa<UndefValue>(Val)) // ee(undef, x) -> undef
378 return UndefValue::get(cast<VectorType>(Val->getType())->getElementType());
379 if (Val->isNullValue()) // ee(zero, x) -> zero
380 return Constant::getNullValue(
381 cast<VectorType>(Val->getType())->getElementType());
383 if (const ConstantVector *CVal = dyn_cast<ConstantVector>(Val)) {
384 if (const ConstantInt *CIdx = dyn_cast<ConstantInt>(Idx)) {
385 return const_cast<Constant*>(CVal->getOperand(CIdx->getZExtValue()));
386 } else if (isa<UndefValue>(Idx)) {
387 // ee({w,x,y,z}, undef) -> w (an arbitrary value).
388 return const_cast<Constant*>(CVal->getOperand(0));
394 Constant *llvm::ConstantFoldInsertElementInstruction(const Constant *Val,
396 const Constant *Idx) {
397 const ConstantInt *CIdx = dyn_cast<ConstantInt>(Idx);
399 APInt idxVal = CIdx->getValue();
400 if (isa<UndefValue>(Val)) {
401 // Insertion of scalar constant into vector undef
402 // Optimize away insertion of undef
403 if (isa<UndefValue>(Elt))
404 return const_cast<Constant*>(Val);
405 // Otherwise break the aggregate undef into multiple undefs and do
408 cast<VectorType>(Val->getType())->getNumElements();
409 std::vector<Constant*> Ops;
411 for (unsigned i = 0; i < numOps; ++i) {
413 (idxVal == i) ? Elt : UndefValue::get(Elt->getType());
414 Ops.push_back(const_cast<Constant*>(Op));
416 return ConstantVector::get(Ops);
418 if (isa<ConstantAggregateZero>(Val)) {
419 // Insertion of scalar constant into vector aggregate zero
420 // Optimize away insertion of zero
421 if (Elt->isNullValue())
422 return const_cast<Constant*>(Val);
423 // Otherwise break the aggregate zero into multiple zeros and do
426 cast<VectorType>(Val->getType())->getNumElements();
427 std::vector<Constant*> Ops;
429 for (unsigned i = 0; i < numOps; ++i) {
431 (idxVal == i) ? Elt : Constant::getNullValue(Elt->getType());
432 Ops.push_back(const_cast<Constant*>(Op));
434 return ConstantVector::get(Ops);
436 if (const ConstantVector *CVal = dyn_cast<ConstantVector>(Val)) {
437 // Insertion of scalar constant into vector constant
438 std::vector<Constant*> Ops;
439 Ops.reserve(CVal->getNumOperands());
440 for (unsigned i = 0; i < CVal->getNumOperands(); ++i) {
442 (idxVal == i) ? Elt : cast<Constant>(CVal->getOperand(i));
443 Ops.push_back(const_cast<Constant*>(Op));
445 return ConstantVector::get(Ops);
450 Constant *llvm::ConstantFoldShuffleVectorInstruction(const Constant *V1,
452 const Constant *Mask) {
457 /// EvalVectorOp - Given two vector constants and a function pointer, apply the
458 /// function pointer to each element pair, producing a new ConstantVector
460 static Constant *EvalVectorOp(const ConstantVector *V1,
461 const ConstantVector *V2,
462 Constant *(*FP)(Constant*, Constant*)) {
463 std::vector<Constant*> Res;
464 for (unsigned i = 0, e = V1->getNumOperands(); i != e; ++i)
465 Res.push_back(FP(const_cast<Constant*>(V1->getOperand(i)),
466 const_cast<Constant*>(V2->getOperand(i))));
467 return ConstantVector::get(Res);
470 Constant *llvm::ConstantFoldBinaryInstruction(unsigned Opcode,
472 const Constant *C2) {
473 // Handle UndefValue up front
474 if (isa<UndefValue>(C1) || isa<UndefValue>(C2)) {
476 case Instruction::Add:
477 case Instruction::Sub:
478 case Instruction::Xor:
479 return UndefValue::get(C1->getType());
480 case Instruction::Mul:
481 case Instruction::And:
482 return Constant::getNullValue(C1->getType());
483 case Instruction::UDiv:
484 case Instruction::SDiv:
485 case Instruction::FDiv:
486 case Instruction::URem:
487 case Instruction::SRem:
488 case Instruction::FRem:
489 if (!isa<UndefValue>(C2)) // undef / X -> 0
490 return Constant::getNullValue(C1->getType());
491 return const_cast<Constant*>(C2); // X / undef -> undef
492 case Instruction::Or: // X | undef -> -1
493 if (const VectorType *PTy = dyn_cast<VectorType>(C1->getType()))
494 return ConstantVector::getAllOnesValue(PTy);
495 return ConstantInt::getAllOnesValue(C1->getType());
496 case Instruction::LShr:
497 if (isa<UndefValue>(C2) && isa<UndefValue>(C1))
498 return const_cast<Constant*>(C1); // undef lshr undef -> undef
499 return Constant::getNullValue(C1->getType()); // X lshr undef -> 0
501 case Instruction::AShr:
502 if (!isa<UndefValue>(C2))
503 return const_cast<Constant*>(C1); // undef ashr X --> undef
504 else if (isa<UndefValue>(C1))
505 return const_cast<Constant*>(C1); // undef ashr undef -> undef
507 return const_cast<Constant*>(C1); // X ashr undef --> X
508 case Instruction::Shl:
509 // undef << X -> 0 or X << undef -> 0
510 return Constant::getNullValue(C1->getType());
514 if (const ConstantExpr *CE1 = dyn_cast<ConstantExpr>(C1)) {
515 if (isa<ConstantExpr>(C2)) {
516 // There are many possible foldings we could do here. We should probably
517 // at least fold add of a pointer with an integer into the appropriate
518 // getelementptr. This will improve alias analysis a bit.
520 // Just implement a couple of simple identities.
522 case Instruction::Add:
523 if (C2->isNullValue()) return const_cast<Constant*>(C1); // X + 0 == X
525 case Instruction::Sub:
526 if (C2->isNullValue()) return const_cast<Constant*>(C1); // X - 0 == X
528 case Instruction::Mul:
529 if (C2->isNullValue()) return const_cast<Constant*>(C2); // X * 0 == 0
530 if (const ConstantInt *CI = dyn_cast<ConstantInt>(C2))
531 if (CI->equalsInt(1))
532 return const_cast<Constant*>(C1); // X * 1 == X
534 case Instruction::UDiv:
535 case Instruction::SDiv:
536 if (const ConstantInt *CI = dyn_cast<ConstantInt>(C2))
537 if (CI->equalsInt(1))
538 return const_cast<Constant*>(C1); // X / 1 == X
540 case Instruction::URem:
541 case Instruction::SRem:
542 if (const ConstantInt *CI = dyn_cast<ConstantInt>(C2))
543 if (CI->equalsInt(1))
544 return Constant::getNullValue(CI->getType()); // X % 1 == 0
546 case Instruction::And:
547 if (const ConstantInt *CI = dyn_cast<ConstantInt>(C2)) {
548 if (CI->isZero()) return const_cast<Constant*>(C2); // X & 0 == 0
549 if (CI->isAllOnesValue())
550 return const_cast<Constant*>(C1); // X & -1 == X
552 // (zext i32 to i64) & 4294967295 -> (zext i32 to i64)
553 if (CE1->getOpcode() == Instruction::ZExt) {
554 APInt PossiblySetBits
555 = cast<IntegerType>(CE1->getOperand(0)->getType())->getMask();
556 PossiblySetBits.zext(C1->getType()->getPrimitiveSizeInBits());
557 if ((PossiblySetBits & CI->getValue()) == PossiblySetBits)
558 return const_cast<Constant*>(C1);
561 if (CE1->isCast() && isa<GlobalValue>(CE1->getOperand(0))) {
562 GlobalValue *CPR = cast<GlobalValue>(CE1->getOperand(0));
564 // Functions are at least 4-byte aligned. If and'ing the address of a
565 // function with a constant < 4, fold it to zero.
566 if (const ConstantInt *CI = dyn_cast<ConstantInt>(C2))
567 if (CI->getValue().ult(APInt(CI->getType()->getBitWidth(),4)) &&
569 return Constant::getNullValue(CI->getType());
572 case Instruction::Or:
573 if (C2->isNullValue()) return const_cast<Constant*>(C1); // X | 0 == X
574 if (const ConstantInt *CI = dyn_cast<ConstantInt>(C2))
575 if (CI->isAllOnesValue())
576 return const_cast<Constant*>(C2); // X | -1 == -1
578 case Instruction::Xor:
579 if (C2->isNullValue()) return const_cast<Constant*>(C1); // X ^ 0 == X
581 case Instruction::AShr:
582 // ashr (zext C to Ty), C2 -> lshr (zext C, CSA), C2
583 if (CE1->getOpcode() == Instruction::ZExt) // Top bits known zero.
584 return ConstantExpr::getLShr(const_cast<Constant*>(C1),
585 const_cast<Constant*>(C2));
589 } else if (isa<ConstantExpr>(C2)) {
590 // If C2 is a constant expr and C1 isn't, flop them around and fold the
591 // other way if possible.
593 case Instruction::Add:
594 case Instruction::Mul:
595 case Instruction::And:
596 case Instruction::Or:
597 case Instruction::Xor:
598 // No change of opcode required.
599 return ConstantFoldBinaryInstruction(Opcode, C2, C1);
601 case Instruction::Shl:
602 case Instruction::LShr:
603 case Instruction::AShr:
604 case Instruction::Sub:
605 case Instruction::SDiv:
606 case Instruction::UDiv:
607 case Instruction::FDiv:
608 case Instruction::URem:
609 case Instruction::SRem:
610 case Instruction::FRem:
611 default: // These instructions cannot be flopped around.
616 // At this point we know neither constant is an UndefValue nor a ConstantExpr
617 // so look at directly computing the value.
618 if (const ConstantInt *CI1 = dyn_cast<ConstantInt>(C1)) {
619 if (const ConstantInt *CI2 = dyn_cast<ConstantInt>(C2)) {
620 using namespace APIntOps;
621 APInt C1V = CI1->getValue();
622 APInt C2V = CI2->getValue();
626 case Instruction::Add:
627 return ConstantInt::get(C1V + C2V);
628 case Instruction::Sub:
629 return ConstantInt::get(C1V - C2V);
630 case Instruction::Mul:
631 return ConstantInt::get(C1V * C2V);
632 case Instruction::UDiv:
633 if (CI2->isNullValue())
634 return 0; // X / 0 -> can't fold
635 return ConstantInt::get(C1V.udiv(C2V));
636 case Instruction::SDiv:
637 if (CI2->isNullValue())
638 return 0; // X / 0 -> can't fold
639 if (C2V.isAllOnesValue() && C1V.isMinSignedValue())
640 return 0; // MIN_INT / -1 -> overflow
641 return ConstantInt::get(C1V.sdiv(C2V));
642 case Instruction::URem:
643 if (C2->isNullValue())
644 return 0; // X / 0 -> can't fold
645 return ConstantInt::get(C1V.urem(C2V));
646 case Instruction::SRem:
647 if (CI2->isNullValue())
648 return 0; // X % 0 -> can't fold
649 if (C2V.isAllOnesValue() && C1V.isMinSignedValue())
650 return 0; // MIN_INT % -1 -> overflow
651 return ConstantInt::get(C1V.srem(C2V));
652 case Instruction::And:
653 return ConstantInt::get(C1V & C2V);
654 case Instruction::Or:
655 return ConstantInt::get(C1V | C2V);
656 case Instruction::Xor:
657 return ConstantInt::get(C1V ^ C2V);
658 case Instruction::Shl:
659 if (uint32_t shiftAmt = C2V.getZExtValue())
660 if (shiftAmt < C1V.getBitWidth())
661 return ConstantInt::get(C1V.shl(shiftAmt));
663 return UndefValue::get(C1->getType()); // too big shift is undef
664 return const_cast<ConstantInt*>(CI1); // Zero shift is identity
665 case Instruction::LShr:
666 if (uint32_t shiftAmt = C2V.getZExtValue())
667 if (shiftAmt < C1V.getBitWidth())
668 return ConstantInt::get(C1V.lshr(shiftAmt));
670 return UndefValue::get(C1->getType()); // too big shift is undef
671 return const_cast<ConstantInt*>(CI1); // Zero shift is identity
672 case Instruction::AShr:
673 if (uint32_t shiftAmt = C2V.getZExtValue())
674 if (shiftAmt < C1V.getBitWidth())
675 return ConstantInt::get(C1V.ashr(shiftAmt));
677 return UndefValue::get(C1->getType()); // too big shift is undef
678 return const_cast<ConstantInt*>(CI1); // Zero shift is identity
681 } else if (const ConstantFP *CFP1 = dyn_cast<ConstantFP>(C1)) {
682 if (const ConstantFP *CFP2 = dyn_cast<ConstantFP>(C2)) {
683 APFloat C1V = CFP1->getValueAPF();
684 APFloat C2V = CFP2->getValueAPF();
685 APFloat C3V = C1V; // copy for modification
686 bool isDouble = CFP1->getType()==Type::DoubleTy;
690 case Instruction::Add:
691 (void)C3V.add(C2V, APFloat::rmNearestTiesToEven);
692 return ConstantFP::get(CFP1->getType(), C3V);
693 case Instruction::Sub:
694 (void)C3V.subtract(C2V, APFloat::rmNearestTiesToEven);
695 return ConstantFP::get(CFP1->getType(), C3V);
696 case Instruction::Mul:
697 (void)C3V.multiply(C2V, APFloat::rmNearestTiesToEven);
698 return ConstantFP::get(CFP1->getType(), C3V);
699 case Instruction::FDiv:
700 // FIXME better to look at the return code
703 // IEEE 754, Section 7.1, #4
704 return ConstantFP::get(CFP1->getType(), isDouble ?
705 APFloat(std::numeric_limits<double>::quiet_NaN()) :
706 APFloat(std::numeric_limits<float>::quiet_NaN()));
707 else if (C2V.isNegZero() || C1V.isNegative())
708 // IEEE 754, Section 7.2, negative infinity case
709 return ConstantFP::get(CFP1->getType(), isDouble ?
710 APFloat(-std::numeric_limits<double>::infinity()) :
711 APFloat(-std::numeric_limits<float>::infinity()));
713 // IEEE 754, Section 7.2, positive infinity case
714 return ConstantFP::get(CFP1->getType(), isDouble ?
715 APFloat(std::numeric_limits<double>::infinity()) :
716 APFloat(std::numeric_limits<float>::infinity()));
717 (void)C3V.divide(C2V, APFloat::rmNearestTiesToEven);
718 return ConstantFP::get(CFP1->getType(), C3V);
719 case Instruction::FRem:
721 // IEEE 754, Section 7.1, #5
722 return ConstantFP::get(CFP1->getType(), isDouble ?
723 APFloat(std::numeric_limits<double>::quiet_NaN()) :
724 APFloat(std::numeric_limits<float>::quiet_NaN()));
725 (void)C3V.mod(C2V, APFloat::rmNearestTiesToEven);
726 return ConstantFP::get(CFP1->getType(), C3V);
729 } else if (const ConstantVector *CP1 = dyn_cast<ConstantVector>(C1)) {
730 if (const ConstantVector *CP2 = dyn_cast<ConstantVector>(C2)) {
734 case Instruction::Add:
735 return EvalVectorOp(CP1, CP2, ConstantExpr::getAdd);
736 case Instruction::Sub:
737 return EvalVectorOp(CP1, CP2, ConstantExpr::getSub);
738 case Instruction::Mul:
739 return EvalVectorOp(CP1, CP2, ConstantExpr::getMul);
740 case Instruction::UDiv:
741 return EvalVectorOp(CP1, CP2, ConstantExpr::getUDiv);
742 case Instruction::SDiv:
743 return EvalVectorOp(CP1, CP2, ConstantExpr::getSDiv);
744 case Instruction::FDiv:
745 return EvalVectorOp(CP1, CP2, ConstantExpr::getFDiv);
746 case Instruction::URem:
747 return EvalVectorOp(CP1, CP2, ConstantExpr::getURem);
748 case Instruction::SRem:
749 return EvalVectorOp(CP1, CP2, ConstantExpr::getSRem);
750 case Instruction::FRem:
751 return EvalVectorOp(CP1, CP2, ConstantExpr::getFRem);
752 case Instruction::And:
753 return EvalVectorOp(CP1, CP2, ConstantExpr::getAnd);
754 case Instruction::Or:
755 return EvalVectorOp(CP1, CP2, ConstantExpr::getOr);
756 case Instruction::Xor:
757 return EvalVectorOp(CP1, CP2, ConstantExpr::getXor);
762 // We don't know how to fold this
766 /// isZeroSizedType - This type is zero sized if its an array or structure of
767 /// zero sized types. The only leaf zero sized type is an empty structure.
768 static bool isMaybeZeroSizedType(const Type *Ty) {
769 if (isa<OpaqueType>(Ty)) return true; // Can't say.
770 if (const StructType *STy = dyn_cast<StructType>(Ty)) {
772 // If all of elements have zero size, this does too.
773 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i)
774 if (!isMaybeZeroSizedType(STy->getElementType(i))) return false;
777 } else if (const ArrayType *ATy = dyn_cast<ArrayType>(Ty)) {
778 return isMaybeZeroSizedType(ATy->getElementType());
783 /// IdxCompare - Compare the two constants as though they were getelementptr
784 /// indices. This allows coersion of the types to be the same thing.
786 /// If the two constants are the "same" (after coersion), return 0. If the
787 /// first is less than the second, return -1, if the second is less than the
788 /// first, return 1. If the constants are not integral, return -2.
790 static int IdxCompare(Constant *C1, Constant *C2, const Type *ElTy) {
791 if (C1 == C2) return 0;
793 // Ok, we found a different index. If they are not ConstantInt, we can't do
794 // anything with them.
795 if (!isa<ConstantInt>(C1) || !isa<ConstantInt>(C2))
796 return -2; // don't know!
798 // Ok, we have two differing integer indices. Sign extend them to be the same
799 // type. Long is always big enough, so we use it.
800 if (C1->getType() != Type::Int64Ty)
801 C1 = ConstantExpr::getSExt(C1, Type::Int64Ty);
803 if (C2->getType() != Type::Int64Ty)
804 C2 = ConstantExpr::getSExt(C2, Type::Int64Ty);
806 if (C1 == C2) return 0; // They are equal
808 // If the type being indexed over is really just a zero sized type, there is
809 // no pointer difference being made here.
810 if (isMaybeZeroSizedType(ElTy))
813 // If they are really different, now that they are the same type, then we
814 // found a difference!
815 if (cast<ConstantInt>(C1)->getSExtValue() <
816 cast<ConstantInt>(C2)->getSExtValue())
822 /// evaluateFCmpRelation - This function determines if there is anything we can
823 /// decide about the two constants provided. This doesn't need to handle simple
824 /// things like ConstantFP comparisons, but should instead handle ConstantExprs.
825 /// If we can determine that the two constants have a particular relation to
826 /// each other, we should return the corresponding FCmpInst predicate,
827 /// otherwise return FCmpInst::BAD_FCMP_PREDICATE. This is used below in
828 /// ConstantFoldCompareInstruction.
830 /// To simplify this code we canonicalize the relation so that the first
831 /// operand is always the most "complex" of the two. We consider ConstantFP
832 /// to be the simplest, and ConstantExprs to be the most complex.
833 static FCmpInst::Predicate evaluateFCmpRelation(const Constant *V1,
834 const Constant *V2) {
835 assert(V1->getType() == V2->getType() &&
836 "Cannot compare values of different types!");
837 // Handle degenerate case quickly
838 if (V1 == V2) return FCmpInst::FCMP_OEQ;
840 if (!isa<ConstantExpr>(V1)) {
841 if (!isa<ConstantExpr>(V2)) {
842 // We distilled thisUse the standard constant folder for a few cases
844 Constant *C1 = const_cast<Constant*>(V1);
845 Constant *C2 = const_cast<Constant*>(V2);
846 R = dyn_cast<ConstantInt>(
847 ConstantExpr::getFCmp(FCmpInst::FCMP_OEQ, C1, C2));
848 if (R && !R->isZero())
849 return FCmpInst::FCMP_OEQ;
850 R = dyn_cast<ConstantInt>(
851 ConstantExpr::getFCmp(FCmpInst::FCMP_OLT, C1, C2));
852 if (R && !R->isZero())
853 return FCmpInst::FCMP_OLT;
854 R = dyn_cast<ConstantInt>(
855 ConstantExpr::getFCmp(FCmpInst::FCMP_OGT, C1, C2));
856 if (R && !R->isZero())
857 return FCmpInst::FCMP_OGT;
859 // Nothing more we can do
860 return FCmpInst::BAD_FCMP_PREDICATE;
863 // If the first operand is simple and second is ConstantExpr, swap operands.
864 FCmpInst::Predicate SwappedRelation = evaluateFCmpRelation(V2, V1);
865 if (SwappedRelation != FCmpInst::BAD_FCMP_PREDICATE)
866 return FCmpInst::getSwappedPredicate(SwappedRelation);
868 // Ok, the LHS is known to be a constantexpr. The RHS can be any of a
869 // constantexpr or a simple constant.
870 const ConstantExpr *CE1 = cast<ConstantExpr>(V1);
871 switch (CE1->getOpcode()) {
872 case Instruction::FPTrunc:
873 case Instruction::FPExt:
874 case Instruction::UIToFP:
875 case Instruction::SIToFP:
876 // We might be able to do something with these but we don't right now.
882 // There are MANY other foldings that we could perform here. They will
883 // probably be added on demand, as they seem needed.
884 return FCmpInst::BAD_FCMP_PREDICATE;
887 /// evaluateICmpRelation - This function determines if there is anything we can
888 /// decide about the two constants provided. This doesn't need to handle simple
889 /// things like integer comparisons, but should instead handle ConstantExprs
890 /// and GlobalValues. If we can determine that the two constants have a
891 /// particular relation to each other, we should return the corresponding ICmp
892 /// predicate, otherwise return ICmpInst::BAD_ICMP_PREDICATE.
894 /// To simplify this code we canonicalize the relation so that the first
895 /// operand is always the most "complex" of the two. We consider simple
896 /// constants (like ConstantInt) to be the simplest, followed by
897 /// GlobalValues, followed by ConstantExpr's (the most complex).
899 static ICmpInst::Predicate evaluateICmpRelation(const Constant *V1,
902 assert(V1->getType() == V2->getType() &&
903 "Cannot compare different types of values!");
904 if (V1 == V2) return ICmpInst::ICMP_EQ;
906 if (!isa<ConstantExpr>(V1) && !isa<GlobalValue>(V1)) {
907 if (!isa<GlobalValue>(V2) && !isa<ConstantExpr>(V2)) {
908 // We distilled this down to a simple case, use the standard constant
911 Constant *C1 = const_cast<Constant*>(V1);
912 Constant *C2 = const_cast<Constant*>(V2);
913 ICmpInst::Predicate pred = ICmpInst::ICMP_EQ;
914 R = dyn_cast<ConstantInt>(ConstantExpr::getICmp(pred, C1, C2));
915 if (R && !R->isZero())
917 pred = isSigned ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT;
918 R = dyn_cast<ConstantInt>(ConstantExpr::getICmp(pred, C1, C2));
919 if (R && !R->isZero())
921 pred = isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT;
922 R = dyn_cast<ConstantInt>(ConstantExpr::getICmp(pred, C1, C2));
923 if (R && !R->isZero())
926 // If we couldn't figure it out, bail.
927 return ICmpInst::BAD_ICMP_PREDICATE;
930 // If the first operand is simple, swap operands.
931 ICmpInst::Predicate SwappedRelation =
932 evaluateICmpRelation(V2, V1, isSigned);
933 if (SwappedRelation != ICmpInst::BAD_ICMP_PREDICATE)
934 return ICmpInst::getSwappedPredicate(SwappedRelation);
936 } else if (const GlobalValue *CPR1 = dyn_cast<GlobalValue>(V1)) {
937 if (isa<ConstantExpr>(V2)) { // Swap as necessary.
938 ICmpInst::Predicate SwappedRelation =
939 evaluateICmpRelation(V2, V1, isSigned);
940 if (SwappedRelation != ICmpInst::BAD_ICMP_PREDICATE)
941 return ICmpInst::getSwappedPredicate(SwappedRelation);
943 return ICmpInst::BAD_ICMP_PREDICATE;
946 // Now we know that the RHS is a GlobalValue or simple constant,
947 // which (since the types must match) means that it's a ConstantPointerNull.
948 if (const GlobalValue *CPR2 = dyn_cast<GlobalValue>(V2)) {
949 // Don't try to decide equality of aliases.
950 if (!isa<GlobalAlias>(CPR1) && !isa<GlobalAlias>(CPR2))
951 if (!CPR1->hasExternalWeakLinkage() || !CPR2->hasExternalWeakLinkage())
952 return ICmpInst::ICMP_NE;
954 assert(isa<ConstantPointerNull>(V2) && "Canonicalization guarantee!");
955 // GlobalVals can never be null. Don't try to evaluate aliases.
956 if (!CPR1->hasExternalWeakLinkage() && !isa<GlobalAlias>(CPR1))
957 return ICmpInst::ICMP_NE;
960 // Ok, the LHS is known to be a constantexpr. The RHS can be any of a
961 // constantexpr, a CPR, or a simple constant.
962 const ConstantExpr *CE1 = cast<ConstantExpr>(V1);
963 const Constant *CE1Op0 = CE1->getOperand(0);
965 switch (CE1->getOpcode()) {
966 case Instruction::Trunc:
967 case Instruction::FPTrunc:
968 case Instruction::FPExt:
969 case Instruction::FPToUI:
970 case Instruction::FPToSI:
971 break; // We can't evaluate floating point casts or truncations.
973 case Instruction::UIToFP:
974 case Instruction::SIToFP:
975 case Instruction::IntToPtr:
976 case Instruction::BitCast:
977 case Instruction::ZExt:
978 case Instruction::SExt:
979 case Instruction::PtrToInt:
980 // If the cast is not actually changing bits, and the second operand is a
981 // null pointer, do the comparison with the pre-casted value.
982 if (V2->isNullValue() &&
983 (isa<PointerType>(CE1->getType()) || CE1->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(
988 CE1Op0, Constant::getNullValue(CE1Op0->getType()), sgnd);
991 // If the dest type is a pointer type, and the RHS is a constantexpr cast
992 // from the same type as the src of the LHS, evaluate the inputs. This is
993 // important for things like "icmp eq (cast 4 to int*), (cast 5 to int*)",
994 // which happens a lot in compilers with tagged integers.
995 if (const ConstantExpr *CE2 = dyn_cast<ConstantExpr>(V2))
996 if (CE2->isCast() && isa<PointerType>(CE1->getType()) &&
997 CE1->getOperand(0)->getType() == CE2->getOperand(0)->getType() &&
998 CE1->getOperand(0)->getType()->isInteger()) {
999 bool sgnd = CE1->getOpcode() == Instruction::ZExt ? false :
1000 (CE1->getOpcode() == Instruction::SExt ? true :
1001 (CE1->getOpcode() == Instruction::PtrToInt ? false : isSigned));
1002 return evaluateICmpRelation(CE1->getOperand(0), CE2->getOperand(0),
1007 case Instruction::GetElementPtr:
1008 // Ok, since this is a getelementptr, we know that the constant has a
1009 // pointer type. Check the various cases.
1010 if (isa<ConstantPointerNull>(V2)) {
1011 // If we are comparing a GEP to a null pointer, check to see if the base
1012 // of the GEP equals the null pointer.
1013 if (const GlobalValue *GV = dyn_cast<GlobalValue>(CE1Op0)) {
1014 if (GV->hasExternalWeakLinkage())
1015 // Weak linkage GVals could be zero or not. We're comparing that
1016 // to null pointer so its greater-or-equal
1017 return isSigned ? ICmpInst::ICMP_SGE : ICmpInst::ICMP_UGE;
1019 // If its not weak linkage, the GVal must have a non-zero address
1020 // so the result is greater-than
1021 return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT;
1022 } else if (isa<ConstantPointerNull>(CE1Op0)) {
1023 // If we are indexing from a null pointer, check to see if we have any
1024 // non-zero indices.
1025 for (unsigned i = 1, e = CE1->getNumOperands(); i != e; ++i)
1026 if (!CE1->getOperand(i)->isNullValue())
1027 // Offsetting from null, must not be equal.
1028 return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT;
1029 // Only zero indexes from null, must still be zero.
1030 return ICmpInst::ICMP_EQ;
1032 // Otherwise, we can't really say if the first operand is null or not.
1033 } else if (const GlobalValue *CPR2 = dyn_cast<GlobalValue>(V2)) {
1034 if (isa<ConstantPointerNull>(CE1Op0)) {
1035 if (CPR2->hasExternalWeakLinkage())
1036 // Weak linkage GVals could be zero or not. We're comparing it to
1037 // a null pointer, so its less-or-equal
1038 return isSigned ? ICmpInst::ICMP_SLE : ICmpInst::ICMP_ULE;
1040 // If its not weak linkage, the GVal must have a non-zero address
1041 // so the result is less-than
1042 return isSigned ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT;
1043 } else if (const GlobalValue *CPR1 = dyn_cast<GlobalValue>(CE1Op0)) {
1045 // If this is a getelementptr of the same global, then it must be
1046 // different. Because the types must match, the getelementptr could
1047 // only have at most one index, and because we fold getelementptr's
1048 // with a single zero index, it must be nonzero.
1049 assert(CE1->getNumOperands() == 2 &&
1050 !CE1->getOperand(1)->isNullValue() &&
1051 "Suprising getelementptr!");
1052 return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT;
1054 // If they are different globals, we don't know what the value is,
1055 // but they can't be equal.
1056 return ICmpInst::ICMP_NE;
1060 const ConstantExpr *CE2 = cast<ConstantExpr>(V2);
1061 const Constant *CE2Op0 = CE2->getOperand(0);
1063 // There are MANY other foldings that we could perform here. They will
1064 // probably be added on demand, as they seem needed.
1065 switch (CE2->getOpcode()) {
1067 case Instruction::GetElementPtr:
1068 // By far the most common case to handle is when the base pointers are
1069 // obviously to the same or different globals.
1070 if (isa<GlobalValue>(CE1Op0) && isa<GlobalValue>(CE2Op0)) {
1071 if (CE1Op0 != CE2Op0) // Don't know relative ordering, but not equal
1072 return ICmpInst::ICMP_NE;
1073 // Ok, we know that both getelementptr instructions are based on the
1074 // same global. From this, we can precisely determine the relative
1075 // ordering of the resultant pointers.
1078 // Compare all of the operands the GEP's have in common.
1079 gep_type_iterator GTI = gep_type_begin(CE1);
1080 for (;i != CE1->getNumOperands() && i != CE2->getNumOperands();
1082 switch (IdxCompare(CE1->getOperand(i), CE2->getOperand(i),
1083 GTI.getIndexedType())) {
1084 case -1: return isSigned ? ICmpInst::ICMP_SLT:ICmpInst::ICMP_ULT;
1085 case 1: return isSigned ? ICmpInst::ICMP_SGT:ICmpInst::ICMP_UGT;
1086 case -2: return ICmpInst::BAD_ICMP_PREDICATE;
1089 // Ok, we ran out of things they have in common. If any leftovers
1090 // are non-zero then we have a difference, otherwise we are equal.
1091 for (; i < CE1->getNumOperands(); ++i)
1092 if (!CE1->getOperand(i)->isNullValue())
1093 if (isa<ConstantInt>(CE1->getOperand(i)))
1094 return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT;
1096 return ICmpInst::BAD_ICMP_PREDICATE; // Might be equal.
1098 for (; i < CE2->getNumOperands(); ++i)
1099 if (!CE2->getOperand(i)->isNullValue())
1100 if (isa<ConstantInt>(CE2->getOperand(i)))
1101 return isSigned ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT;
1103 return ICmpInst::BAD_ICMP_PREDICATE; // Might be equal.
1104 return ICmpInst::ICMP_EQ;
1113 return ICmpInst::BAD_ICMP_PREDICATE;
1116 Constant *llvm::ConstantFoldCompareInstruction(unsigned short pred,
1118 const Constant *C2) {
1120 // Handle some degenerate cases first
1121 if (isa<UndefValue>(C1) || isa<UndefValue>(C2))
1122 return UndefValue::get(Type::Int1Ty);
1124 // icmp eq/ne(null,GV) -> false/true
1125 if (C1->isNullValue()) {
1126 if (const GlobalValue *GV = dyn_cast<GlobalValue>(C2))
1127 // Don't try to evaluate aliases. External weak GV can be null.
1128 if (!isa<GlobalAlias>(GV) && !GV->hasExternalWeakLinkage())
1129 if (pred == ICmpInst::ICMP_EQ)
1130 return ConstantInt::getFalse();
1131 else if (pred == ICmpInst::ICMP_NE)
1132 return ConstantInt::getTrue();
1133 // icmp eq/ne(GV,null) -> false/true
1134 } else if (C2->isNullValue()) {
1135 if (const GlobalValue *GV = dyn_cast<GlobalValue>(C1))
1136 // Don't try to evaluate aliases. External weak GV can be null.
1137 if (!isa<GlobalAlias>(GV) && !GV->hasExternalWeakLinkage())
1138 if (pred == ICmpInst::ICMP_EQ)
1139 return ConstantInt::getFalse();
1140 else if (pred == ICmpInst::ICMP_NE)
1141 return ConstantInt::getTrue();
1144 if (isa<ConstantInt>(C1) && isa<ConstantInt>(C2)) {
1145 APInt V1 = cast<ConstantInt>(C1)->getValue();
1146 APInt V2 = cast<ConstantInt>(C2)->getValue();
1148 default: assert(0 && "Invalid ICmp Predicate"); return 0;
1149 case ICmpInst::ICMP_EQ: return ConstantInt::get(Type::Int1Ty, V1 == V2);
1150 case ICmpInst::ICMP_NE: return ConstantInt::get(Type::Int1Ty, V1 != V2);
1151 case ICmpInst::ICMP_SLT:return ConstantInt::get(Type::Int1Ty, V1.slt(V2));
1152 case ICmpInst::ICMP_SGT:return ConstantInt::get(Type::Int1Ty, V1.sgt(V2));
1153 case ICmpInst::ICMP_SLE:return ConstantInt::get(Type::Int1Ty, V1.sle(V2));
1154 case ICmpInst::ICMP_SGE:return ConstantInt::get(Type::Int1Ty, V1.sge(V2));
1155 case ICmpInst::ICMP_ULT:return ConstantInt::get(Type::Int1Ty, V1.ult(V2));
1156 case ICmpInst::ICMP_UGT:return ConstantInt::get(Type::Int1Ty, V1.ugt(V2));
1157 case ICmpInst::ICMP_ULE:return ConstantInt::get(Type::Int1Ty, V1.ule(V2));
1158 case ICmpInst::ICMP_UGE:return ConstantInt::get(Type::Int1Ty, V1.uge(V2));
1160 } else if (isa<ConstantFP>(C1) && isa<ConstantFP>(C2)) {
1161 APFloat C1V = cast<ConstantFP>(C1)->getValueAPF();
1162 APFloat C2V = cast<ConstantFP>(C2)->getValueAPF();
1163 APFloat::cmpResult R = C1V.compare(C2V);
1165 default: assert(0 && "Invalid FCmp Predicate"); return 0;
1166 case FCmpInst::FCMP_FALSE: return ConstantInt::getFalse();
1167 case FCmpInst::FCMP_TRUE: return ConstantInt::getTrue();
1168 case FCmpInst::FCMP_UNO:
1169 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpUnordered);
1170 case FCmpInst::FCMP_ORD:
1171 return ConstantInt::get(Type::Int1Ty, R!=APFloat::cmpUnordered);
1172 case FCmpInst::FCMP_UEQ:
1173 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpUnordered ||
1174 R==APFloat::cmpEqual);
1175 case FCmpInst::FCMP_OEQ:
1176 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpEqual);
1177 case FCmpInst::FCMP_UNE:
1178 return ConstantInt::get(Type::Int1Ty, R!=APFloat::cmpEqual);
1179 case FCmpInst::FCMP_ONE:
1180 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpLessThan ||
1181 R==APFloat::cmpGreaterThan);
1182 case FCmpInst::FCMP_ULT:
1183 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpUnordered ||
1184 R==APFloat::cmpLessThan);
1185 case FCmpInst::FCMP_OLT:
1186 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpLessThan);
1187 case FCmpInst::FCMP_UGT:
1188 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpUnordered ||
1189 R==APFloat::cmpGreaterThan);
1190 case FCmpInst::FCMP_OGT:
1191 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpGreaterThan);
1192 case FCmpInst::FCMP_ULE:
1193 return ConstantInt::get(Type::Int1Ty, R!=APFloat::cmpGreaterThan);
1194 case FCmpInst::FCMP_OLE:
1195 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpLessThan ||
1196 R==APFloat::cmpEqual);
1197 case FCmpInst::FCMP_UGE:
1198 return ConstantInt::get(Type::Int1Ty, R!=APFloat::cmpLessThan);
1199 case FCmpInst::FCMP_OGE:
1200 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpGreaterThan ||
1201 R==APFloat::cmpEqual);
1203 } else if (const ConstantVector *CP1 = dyn_cast<ConstantVector>(C1)) {
1204 if (const ConstantVector *CP2 = dyn_cast<ConstantVector>(C2)) {
1205 if (pred == FCmpInst::FCMP_OEQ || pred == FCmpInst::FCMP_UEQ) {
1206 for (unsigned i = 0, e = CP1->getNumOperands(); i != e; ++i) {
1207 Constant *C= ConstantExpr::getFCmp(FCmpInst::FCMP_OEQ,
1208 const_cast<Constant*>(CP1->getOperand(i)),
1209 const_cast<Constant*>(CP2->getOperand(i)));
1210 if (ConstantInt *CB = dyn_cast<ConstantInt>(C))
1213 // Otherwise, could not decide from any element pairs.
1215 } else if (pred == ICmpInst::ICMP_EQ) {
1216 for (unsigned i = 0, e = CP1->getNumOperands(); i != e; ++i) {
1217 Constant *C = ConstantExpr::getICmp(ICmpInst::ICMP_EQ,
1218 const_cast<Constant*>(CP1->getOperand(i)),
1219 const_cast<Constant*>(CP2->getOperand(i)));
1220 if (ConstantInt *CB = dyn_cast<ConstantInt>(C))
1223 // Otherwise, could not decide from any element pairs.
1229 if (C1->getType()->isFloatingPoint()) {
1230 switch (evaluateFCmpRelation(C1, C2)) {
1231 default: assert(0 && "Unknown relation!");
1232 case FCmpInst::FCMP_UNO:
1233 case FCmpInst::FCMP_ORD:
1234 case FCmpInst::FCMP_UEQ:
1235 case FCmpInst::FCMP_UNE:
1236 case FCmpInst::FCMP_ULT:
1237 case FCmpInst::FCMP_UGT:
1238 case FCmpInst::FCMP_ULE:
1239 case FCmpInst::FCMP_UGE:
1240 case FCmpInst::FCMP_TRUE:
1241 case FCmpInst::FCMP_FALSE:
1242 case FCmpInst::BAD_FCMP_PREDICATE:
1243 break; // Couldn't determine anything about these constants.
1244 case FCmpInst::FCMP_OEQ: // We know that C1 == C2
1245 return ConstantInt::get(Type::Int1Ty,
1246 pred == FCmpInst::FCMP_UEQ || pred == FCmpInst::FCMP_OEQ ||
1247 pred == FCmpInst::FCMP_ULE || pred == FCmpInst::FCMP_OLE ||
1248 pred == FCmpInst::FCMP_UGE || pred == FCmpInst::FCMP_OGE);
1249 case FCmpInst::FCMP_OLT: // We know that C1 < C2
1250 return ConstantInt::get(Type::Int1Ty,
1251 pred == FCmpInst::FCMP_UNE || pred == FCmpInst::FCMP_ONE ||
1252 pred == FCmpInst::FCMP_ULT || pred == FCmpInst::FCMP_OLT ||
1253 pred == FCmpInst::FCMP_ULE || pred == FCmpInst::FCMP_OLE);
1254 case FCmpInst::FCMP_OGT: // We know that C1 > C2
1255 return ConstantInt::get(Type::Int1Ty,
1256 pred == FCmpInst::FCMP_UNE || pred == FCmpInst::FCMP_ONE ||
1257 pred == FCmpInst::FCMP_UGT || pred == FCmpInst::FCMP_OGT ||
1258 pred == FCmpInst::FCMP_UGE || pred == FCmpInst::FCMP_OGE);
1259 case FCmpInst::FCMP_OLE: // We know that C1 <= C2
1260 // We can only partially decide this relation.
1261 if (pred == FCmpInst::FCMP_UGT || pred == FCmpInst::FCMP_OGT)
1262 return ConstantInt::getFalse();
1263 if (pred == FCmpInst::FCMP_ULT || pred == FCmpInst::FCMP_OLT)
1264 return ConstantInt::getTrue();
1266 case FCmpInst::FCMP_OGE: // We known that C1 >= C2
1267 // We can only partially decide this relation.
1268 if (pred == FCmpInst::FCMP_ULT || pred == FCmpInst::FCMP_OLT)
1269 return ConstantInt::getFalse();
1270 if (pred == FCmpInst::FCMP_UGT || pred == FCmpInst::FCMP_OGT)
1271 return ConstantInt::getTrue();
1273 case ICmpInst::ICMP_NE: // We know that C1 != C2
1274 // We can only partially decide this relation.
1275 if (pred == FCmpInst::FCMP_OEQ || pred == FCmpInst::FCMP_UEQ)
1276 return ConstantInt::getFalse();
1277 if (pred == FCmpInst::FCMP_ONE || pred == FCmpInst::FCMP_UNE)
1278 return ConstantInt::getTrue();
1282 // Evaluate the relation between the two constants, per the predicate.
1283 switch (evaluateICmpRelation(C1, C2, CmpInst::isSigned(pred))) {
1284 default: assert(0 && "Unknown relational!");
1285 case ICmpInst::BAD_ICMP_PREDICATE:
1286 break; // Couldn't determine anything about these constants.
1287 case ICmpInst::ICMP_EQ: // We know the constants are equal!
1288 // If we know the constants are equal, we can decide the result of this
1289 // computation precisely.
1290 return ConstantInt::get(Type::Int1Ty,
1291 pred == ICmpInst::ICMP_EQ ||
1292 pred == ICmpInst::ICMP_ULE ||
1293 pred == ICmpInst::ICMP_SLE ||
1294 pred == ICmpInst::ICMP_UGE ||
1295 pred == ICmpInst::ICMP_SGE);
1296 case ICmpInst::ICMP_ULT:
1297 // If we know that C1 < C2, we can decide the result of this computation
1299 return ConstantInt::get(Type::Int1Ty,
1300 pred == ICmpInst::ICMP_ULT ||
1301 pred == ICmpInst::ICMP_NE ||
1302 pred == ICmpInst::ICMP_ULE);
1303 case ICmpInst::ICMP_SLT:
1304 // If we know that C1 < C2, we can decide the result of this computation
1306 return ConstantInt::get(Type::Int1Ty,
1307 pred == ICmpInst::ICMP_SLT ||
1308 pred == ICmpInst::ICMP_NE ||
1309 pred == ICmpInst::ICMP_SLE);
1310 case ICmpInst::ICMP_UGT:
1311 // If we know that C1 > C2, we can decide the result of this computation
1313 return ConstantInt::get(Type::Int1Ty,
1314 pred == ICmpInst::ICMP_UGT ||
1315 pred == ICmpInst::ICMP_NE ||
1316 pred == ICmpInst::ICMP_UGE);
1317 case ICmpInst::ICMP_SGT:
1318 // If we know that C1 > C2, we can decide the result of this computation
1320 return ConstantInt::get(Type::Int1Ty,
1321 pred == ICmpInst::ICMP_SGT ||
1322 pred == ICmpInst::ICMP_NE ||
1323 pred == ICmpInst::ICMP_SGE);
1324 case ICmpInst::ICMP_ULE:
1325 // If we know that C1 <= C2, we can only partially decide this relation.
1326 if (pred == ICmpInst::ICMP_UGT) return ConstantInt::getFalse();
1327 if (pred == ICmpInst::ICMP_ULT) return ConstantInt::getTrue();
1329 case ICmpInst::ICMP_SLE:
1330 // If we know that C1 <= C2, we can only partially decide this relation.
1331 if (pred == ICmpInst::ICMP_SGT) return ConstantInt::getFalse();
1332 if (pred == ICmpInst::ICMP_SLT) return ConstantInt::getTrue();
1335 case ICmpInst::ICMP_UGE:
1336 // If we know that C1 >= C2, we can only partially decide this relation.
1337 if (pred == ICmpInst::ICMP_ULT) return ConstantInt::getFalse();
1338 if (pred == ICmpInst::ICMP_UGT) return ConstantInt::getTrue();
1340 case ICmpInst::ICMP_SGE:
1341 // If we know that C1 >= C2, we can only partially decide this relation.
1342 if (pred == ICmpInst::ICMP_SLT) return ConstantInt::getFalse();
1343 if (pred == ICmpInst::ICMP_SGT) return ConstantInt::getTrue();
1346 case ICmpInst::ICMP_NE:
1347 // If we know that C1 != C2, we can only partially decide this relation.
1348 if (pred == ICmpInst::ICMP_EQ) return ConstantInt::getFalse();
1349 if (pred == ICmpInst::ICMP_NE) return ConstantInt::getTrue();
1353 if (!isa<ConstantExpr>(C1) && isa<ConstantExpr>(C2)) {
1354 // If C2 is a constant expr and C1 isn't, flop them around and fold the
1355 // other way if possible.
1357 case ICmpInst::ICMP_EQ:
1358 case ICmpInst::ICMP_NE:
1359 // No change of predicate required.
1360 return ConstantFoldCompareInstruction(pred, C2, C1);
1362 case ICmpInst::ICMP_ULT:
1363 case ICmpInst::ICMP_SLT:
1364 case ICmpInst::ICMP_UGT:
1365 case ICmpInst::ICMP_SGT:
1366 case ICmpInst::ICMP_ULE:
1367 case ICmpInst::ICMP_SLE:
1368 case ICmpInst::ICMP_UGE:
1369 case ICmpInst::ICMP_SGE:
1370 // Change the predicate as necessary to swap the operands.
1371 pred = ICmpInst::getSwappedPredicate((ICmpInst::Predicate)pred);
1372 return ConstantFoldCompareInstruction(pred, C2, C1);
1374 default: // These predicates cannot be flopped around.
1382 Constant *llvm::ConstantFoldGetElementPtr(const Constant *C,
1383 Constant* const *Idxs,
1386 (NumIdx == 1 && Idxs[0]->isNullValue()))
1387 return const_cast<Constant*>(C);
1389 if (isa<UndefValue>(C)) {
1390 const Type *Ty = GetElementPtrInst::getIndexedType(C->getType(),
1392 (Value **)Idxs+NumIdx,
1394 assert(Ty != 0 && "Invalid indices for GEP!");
1395 return UndefValue::get(PointerType::get(Ty));
1398 Constant *Idx0 = Idxs[0];
1399 if (C->isNullValue()) {
1401 for (unsigned i = 0, e = NumIdx; i != e; ++i)
1402 if (!Idxs[i]->isNullValue()) {
1407 const Type *Ty = GetElementPtrInst::getIndexedType(C->getType(),
1409 (Value**)Idxs+NumIdx,
1411 assert(Ty != 0 && "Invalid indices for GEP!");
1412 return ConstantPointerNull::get(PointerType::get(Ty));
1416 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(const_cast<Constant*>(C))) {
1417 // Combine Indices - If the source pointer to this getelementptr instruction
1418 // is a getelementptr instruction, combine the indices of the two
1419 // getelementptr instructions into a single instruction.
1421 if (CE->getOpcode() == Instruction::GetElementPtr) {
1422 const Type *LastTy = 0;
1423 for (gep_type_iterator I = gep_type_begin(CE), E = gep_type_end(CE);
1427 if ((LastTy && isa<ArrayType>(LastTy)) || Idx0->isNullValue()) {
1428 SmallVector<Value*, 16> NewIndices;
1429 NewIndices.reserve(NumIdx + CE->getNumOperands());
1430 for (unsigned i = 1, e = CE->getNumOperands()-1; i != e; ++i)
1431 NewIndices.push_back(CE->getOperand(i));
1433 // Add the last index of the source with the first index of the new GEP.
1434 // Make sure to handle the case when they are actually different types.
1435 Constant *Combined = CE->getOperand(CE->getNumOperands()-1);
1436 // Otherwise it must be an array.
1437 if (!Idx0->isNullValue()) {
1438 const Type *IdxTy = Combined->getType();
1439 if (IdxTy != Idx0->getType()) {
1440 Constant *C1 = ConstantExpr::getSExtOrBitCast(Idx0, Type::Int64Ty);
1441 Constant *C2 = ConstantExpr::getSExtOrBitCast(Combined,
1443 Combined = ConstantExpr::get(Instruction::Add, C1, C2);
1446 ConstantExpr::get(Instruction::Add, Idx0, Combined);
1450 NewIndices.push_back(Combined);
1451 NewIndices.insert(NewIndices.end(), Idxs+1, Idxs+NumIdx);
1452 return ConstantExpr::getGetElementPtr(CE->getOperand(0), &NewIndices[0],
1457 // Implement folding of:
1458 // int* getelementptr ([2 x int]* cast ([3 x int]* %X to [2 x int]*),
1460 // To: int* getelementptr ([3 x int]* %X, long 0, long 0)
1462 if (CE->isCast() && NumIdx > 1 && Idx0->isNullValue()) {
1463 if (const PointerType *SPT =
1464 dyn_cast<PointerType>(CE->getOperand(0)->getType()))
1465 if (const ArrayType *SAT = dyn_cast<ArrayType>(SPT->getElementType()))
1466 if (const ArrayType *CAT =
1467 dyn_cast<ArrayType>(cast<PointerType>(C->getType())->getElementType()))
1468 if (CAT->getElementType() == SAT->getElementType())
1469 return ConstantExpr::getGetElementPtr(
1470 (Constant*)CE->getOperand(0), Idxs, NumIdx);
1473 // Fold: getelementptr (i8* inttoptr (i64 1 to i8*), i32 -1)
1474 // Into: inttoptr (i64 0 to i8*)
1475 // This happens with pointers to member functions in C++.
1476 if (CE->getOpcode() == Instruction::IntToPtr && NumIdx == 1 &&
1477 isa<ConstantInt>(CE->getOperand(0)) && isa<ConstantInt>(Idxs[0]) &&
1478 cast<PointerType>(CE->getType())->getElementType() == Type::Int8Ty) {
1479 Constant *Base = CE->getOperand(0);
1480 Constant *Offset = Idxs[0];
1482 // Convert the smaller integer to the larger type.
1483 if (Offset->getType()->getPrimitiveSizeInBits() <
1484 Base->getType()->getPrimitiveSizeInBits())
1485 Offset = ConstantExpr::getSExt(Offset, Base->getType());
1486 else if (Base->getType()->getPrimitiveSizeInBits() <
1487 Offset->getType()->getPrimitiveSizeInBits())
1488 Base = ConstantExpr::getZExt(Base, Base->getType());
1490 Base = ConstantExpr::getAdd(Base, Offset);
1491 return ConstantExpr::getIntToPtr(Base, CE->getType());