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/ADT/SmallVector.h"
27 #include "llvm/Support/Compiler.h"
28 #include "llvm/Support/GetElementPtrTypeIterator.h"
29 #include "llvm/Support/ManagedStatic.h"
30 #include "llvm/Support/MathExtras.h"
34 //===----------------------------------------------------------------------===//
35 // ConstantFold*Instruction Implementations
36 //===----------------------------------------------------------------------===//
38 /// CastConstantVector - Convert the specified ConstantVector node to the
39 /// specified vector type. At this point, we know that the elements of the
40 /// input vector constant are all simple integer or FP values.
41 static Constant *CastConstantVector(ConstantVector *CV,
42 const VectorType *DstTy) {
43 unsigned SrcNumElts = CV->getType()->getNumElements();
44 unsigned DstNumElts = DstTy->getNumElements();
45 const Type *SrcEltTy = CV->getType()->getElementType();
46 const Type *DstEltTy = DstTy->getElementType();
48 // If both vectors have the same number of elements (thus, the elements
49 // are the same size), perform the conversion now.
50 if (SrcNumElts == DstNumElts) {
51 std::vector<Constant*> Result;
53 // If the src and dest elements are both integers, or both floats, we can
54 // just BitCast each element because the elements are the same size.
55 if ((SrcEltTy->isInteger() && DstEltTy->isInteger()) ||
56 (SrcEltTy->isFloatingPoint() && DstEltTy->isFloatingPoint())) {
57 for (unsigned i = 0; i != SrcNumElts; ++i)
59 ConstantExpr::getBitCast(CV->getOperand(i), DstEltTy));
60 return ConstantVector::get(Result);
63 // If this is an int-to-fp cast ..
64 if (SrcEltTy->isInteger()) {
65 // Ensure that it is int-to-fp cast
66 assert(DstEltTy->isFloatingPoint());
67 if (DstEltTy->getTypeID() == Type::DoubleTyID) {
68 for (unsigned i = 0; i != SrcNumElts; ++i) {
69 ConstantInt *CI = cast<ConstantInt>(CV->getOperand(i));
70 double V = CI->getValue().bitsToDouble();
71 Result.push_back(ConstantFP::get(Type::DoubleTy, APFloat(V)));
73 return ConstantVector::get(Result);
75 assert(DstEltTy == Type::FloatTy && "Unknown fp type!");
76 for (unsigned i = 0; i != SrcNumElts; ++i) {
77 ConstantInt *CI = cast<ConstantInt>(CV->getOperand(i));
78 float V = CI->getValue().bitsToFloat();
79 Result.push_back(ConstantFP::get(Type::FloatTy, APFloat(V)));
81 return ConstantVector::get(Result);
84 // Otherwise, this is an fp-to-int cast.
85 assert(SrcEltTy->isFloatingPoint() && DstEltTy->isInteger());
87 if (SrcEltTy->getTypeID() == Type::DoubleTyID) {
88 for (unsigned i = 0; i != SrcNumElts; ++i) {
90 DoubleToBits(cast<ConstantFP>(CV->getOperand(i))->
91 getValueAPF().convertToDouble());
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 = FloatToBits(cast<ConstantFP>(CV->getOperand(i))->
101 getValueAPF().convertToFloat());
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 if (DestTy == Type::FloatTy)
335 return ConstantFP::get(DestTy, APFloat(CI->getValue().bitsToFloat()));
336 assert(DestTy == Type::DoubleTy && "Unknown FP type!");
337 return ConstantFP::get(DestTy, APFloat(CI->getValue().bitsToDouble()));
339 // Otherwise, can't fold this (vector?)
343 // Handle ConstantFP input.
344 if (const ConstantFP *FP = dyn_cast<ConstantFP>(V)) {
346 if (DestTy == Type::Int32Ty) {
348 return ConstantInt::get(Val.floatToBits(FP->
349 getValueAPF().convertToFloat()));
351 assert(DestTy == Type::Int64Ty && "only support f32/f64 for now!");
353 return ConstantInt::get(Val.doubleToBits(FP->
354 getValueAPF().convertToDouble()));
359 assert(!"Invalid CE CastInst opcode");
363 assert(0 && "Failed to cast constant expression");
367 Constant *llvm::ConstantFoldSelectInstruction(const Constant *Cond,
369 const Constant *V2) {
370 if (const ConstantInt *CB = dyn_cast<ConstantInt>(Cond))
371 return const_cast<Constant*>(CB->getZExtValue() ? V1 : V2);
373 if (isa<UndefValue>(V1)) return const_cast<Constant*>(V2);
374 if (isa<UndefValue>(V2)) return const_cast<Constant*>(V1);
375 if (isa<UndefValue>(Cond)) return const_cast<Constant*>(V1);
376 if (V1 == V2) return const_cast<Constant*>(V1);
380 Constant *llvm::ConstantFoldExtractElementInstruction(const Constant *Val,
381 const Constant *Idx) {
382 if (isa<UndefValue>(Val)) // ee(undef, x) -> undef
383 return UndefValue::get(cast<VectorType>(Val->getType())->getElementType());
384 if (Val->isNullValue()) // ee(zero, x) -> zero
385 return Constant::getNullValue(
386 cast<VectorType>(Val->getType())->getElementType());
388 if (const ConstantVector *CVal = dyn_cast<ConstantVector>(Val)) {
389 if (const ConstantInt *CIdx = dyn_cast<ConstantInt>(Idx)) {
390 return const_cast<Constant*>(CVal->getOperand(CIdx->getZExtValue()));
391 } else if (isa<UndefValue>(Idx)) {
392 // ee({w,x,y,z}, undef) -> w (an arbitrary value).
393 return const_cast<Constant*>(CVal->getOperand(0));
399 Constant *llvm::ConstantFoldInsertElementInstruction(const Constant *Val,
401 const Constant *Idx) {
402 const ConstantInt *CIdx = dyn_cast<ConstantInt>(Idx);
404 APInt idxVal = CIdx->getValue();
405 if (isa<UndefValue>(Val)) {
406 // Insertion of scalar constant into vector undef
407 // Optimize away insertion of undef
408 if (isa<UndefValue>(Elt))
409 return const_cast<Constant*>(Val);
410 // Otherwise break the aggregate undef into multiple undefs and do
413 cast<VectorType>(Val->getType())->getNumElements();
414 std::vector<Constant*> Ops;
416 for (unsigned i = 0; i < numOps; ++i) {
418 (idxVal == i) ? Elt : UndefValue::get(Elt->getType());
419 Ops.push_back(const_cast<Constant*>(Op));
421 return ConstantVector::get(Ops);
423 if (isa<ConstantAggregateZero>(Val)) {
424 // Insertion of scalar constant into vector aggregate zero
425 // Optimize away insertion of zero
426 if (Elt->isNullValue())
427 return const_cast<Constant*>(Val);
428 // Otherwise break the aggregate zero into multiple zeros and do
431 cast<VectorType>(Val->getType())->getNumElements();
432 std::vector<Constant*> Ops;
434 for (unsigned i = 0; i < numOps; ++i) {
436 (idxVal == i) ? Elt : Constant::getNullValue(Elt->getType());
437 Ops.push_back(const_cast<Constant*>(Op));
439 return ConstantVector::get(Ops);
441 if (const ConstantVector *CVal = dyn_cast<ConstantVector>(Val)) {
442 // Insertion of scalar constant into vector constant
443 std::vector<Constant*> Ops;
444 Ops.reserve(CVal->getNumOperands());
445 for (unsigned i = 0; i < CVal->getNumOperands(); ++i) {
447 (idxVal == i) ? Elt : cast<Constant>(CVal->getOperand(i));
448 Ops.push_back(const_cast<Constant*>(Op));
450 return ConstantVector::get(Ops);
455 Constant *llvm::ConstantFoldShuffleVectorInstruction(const Constant *V1,
457 const Constant *Mask) {
462 /// EvalVectorOp - Given two vector constants and a function pointer, apply the
463 /// function pointer to each element pair, producing a new ConstantVector
465 static Constant *EvalVectorOp(const ConstantVector *V1,
466 const ConstantVector *V2,
467 Constant *(*FP)(Constant*, Constant*)) {
468 std::vector<Constant*> Res;
469 for (unsigned i = 0, e = V1->getNumOperands(); i != e; ++i)
470 Res.push_back(FP(const_cast<Constant*>(V1->getOperand(i)),
471 const_cast<Constant*>(V2->getOperand(i))));
472 return ConstantVector::get(Res);
475 Constant *llvm::ConstantFoldBinaryInstruction(unsigned Opcode,
477 const Constant *C2) {
478 // Handle UndefValue up front
479 if (isa<UndefValue>(C1) || isa<UndefValue>(C2)) {
481 case Instruction::Add:
482 case Instruction::Sub:
483 case Instruction::Xor:
484 return UndefValue::get(C1->getType());
485 case Instruction::Mul:
486 case Instruction::And:
487 return Constant::getNullValue(C1->getType());
488 case Instruction::UDiv:
489 case Instruction::SDiv:
490 case Instruction::FDiv:
491 case Instruction::URem:
492 case Instruction::SRem:
493 case Instruction::FRem:
494 if (!isa<UndefValue>(C2)) // undef / X -> 0
495 return Constant::getNullValue(C1->getType());
496 return const_cast<Constant*>(C2); // X / undef -> undef
497 case Instruction::Or: // X | undef -> -1
498 if (const VectorType *PTy = dyn_cast<VectorType>(C1->getType()))
499 return ConstantVector::getAllOnesValue(PTy);
500 return ConstantInt::getAllOnesValue(C1->getType());
501 case Instruction::LShr:
502 if (isa<UndefValue>(C2) && isa<UndefValue>(C1))
503 return const_cast<Constant*>(C1); // undef lshr undef -> undef
504 return Constant::getNullValue(C1->getType()); // X lshr undef -> 0
506 case Instruction::AShr:
507 if (!isa<UndefValue>(C2))
508 return const_cast<Constant*>(C1); // undef ashr X --> undef
509 else if (isa<UndefValue>(C1))
510 return const_cast<Constant*>(C1); // undef ashr undef -> undef
512 return const_cast<Constant*>(C1); // X ashr undef --> X
513 case Instruction::Shl:
514 // undef << X -> 0 or X << undef -> 0
515 return Constant::getNullValue(C1->getType());
519 if (const ConstantExpr *CE1 = dyn_cast<ConstantExpr>(C1)) {
520 if (isa<ConstantExpr>(C2)) {
521 // There are many possible foldings we could do here. We should probably
522 // at least fold add of a pointer with an integer into the appropriate
523 // getelementptr. This will improve alias analysis a bit.
525 // Just implement a couple of simple identities.
527 case Instruction::Add:
528 if (C2->isNullValue()) return const_cast<Constant*>(C1); // X + 0 == X
530 case Instruction::Sub:
531 if (C2->isNullValue()) return const_cast<Constant*>(C1); // X - 0 == X
533 case Instruction::Mul:
534 if (C2->isNullValue()) return const_cast<Constant*>(C2); // X * 0 == 0
535 if (const ConstantInt *CI = dyn_cast<ConstantInt>(C2))
536 if (CI->equalsInt(1))
537 return const_cast<Constant*>(C1); // X * 1 == X
539 case Instruction::UDiv:
540 case Instruction::SDiv:
541 if (const ConstantInt *CI = dyn_cast<ConstantInt>(C2))
542 if (CI->equalsInt(1))
543 return const_cast<Constant*>(C1); // X / 1 == X
545 case Instruction::URem:
546 case Instruction::SRem:
547 if (const ConstantInt *CI = dyn_cast<ConstantInt>(C2))
548 if (CI->equalsInt(1))
549 return Constant::getNullValue(CI->getType()); // X % 1 == 0
551 case Instruction::And:
552 if (const ConstantInt *CI = dyn_cast<ConstantInt>(C2)) {
553 if (CI->isZero()) return const_cast<Constant*>(C2); // X & 0 == 0
554 if (CI->isAllOnesValue())
555 return const_cast<Constant*>(C1); // X & -1 == X
557 // (zext i32 to i64) & 4294967295 -> (zext i32 to i64)
558 if (CE1->getOpcode() == Instruction::ZExt) {
559 APInt PossiblySetBits
560 = cast<IntegerType>(CE1->getOperand(0)->getType())->getMask();
561 PossiblySetBits.zext(C1->getType()->getPrimitiveSizeInBits());
562 if ((PossiblySetBits & CI->getValue()) == PossiblySetBits)
563 return const_cast<Constant*>(C1);
566 if (CE1->isCast() && isa<GlobalValue>(CE1->getOperand(0))) {
567 GlobalValue *CPR = cast<GlobalValue>(CE1->getOperand(0));
569 // Functions are at least 4-byte aligned. If and'ing the address of a
570 // function with a constant < 4, fold it to zero.
571 if (const ConstantInt *CI = dyn_cast<ConstantInt>(C2))
572 if (CI->getValue().ult(APInt(CI->getType()->getBitWidth(),4)) &&
574 return Constant::getNullValue(CI->getType());
577 case Instruction::Or:
578 if (C2->isNullValue()) return const_cast<Constant*>(C1); // X | 0 == X
579 if (const ConstantInt *CI = dyn_cast<ConstantInt>(C2))
580 if (CI->isAllOnesValue())
581 return const_cast<Constant*>(C2); // X | -1 == -1
583 case Instruction::Xor:
584 if (C2->isNullValue()) return const_cast<Constant*>(C1); // X ^ 0 == X
586 case Instruction::AShr:
587 // ashr (zext C to Ty), C2 -> lshr (zext C, CSA), C2
588 if (CE1->getOpcode() == Instruction::ZExt) // Top bits known zero.
589 return ConstantExpr::getLShr(const_cast<Constant*>(C1),
590 const_cast<Constant*>(C2));
594 } else if (isa<ConstantExpr>(C2)) {
595 // If C2 is a constant expr and C1 isn't, flop them around and fold the
596 // other way if possible.
598 case Instruction::Add:
599 case Instruction::Mul:
600 case Instruction::And:
601 case Instruction::Or:
602 case Instruction::Xor:
603 // No change of opcode required.
604 return ConstantFoldBinaryInstruction(Opcode, C2, C1);
606 case Instruction::Shl:
607 case Instruction::LShr:
608 case Instruction::AShr:
609 case Instruction::Sub:
610 case Instruction::SDiv:
611 case Instruction::UDiv:
612 case Instruction::FDiv:
613 case Instruction::URem:
614 case Instruction::SRem:
615 case Instruction::FRem:
616 default: // These instructions cannot be flopped around.
621 // At this point we know neither constant is an UndefValue nor a ConstantExpr
622 // so look at directly computing the value.
623 if (const ConstantInt *CI1 = dyn_cast<ConstantInt>(C1)) {
624 if (const ConstantInt *CI2 = dyn_cast<ConstantInt>(C2)) {
625 using namespace APIntOps;
626 APInt C1V = CI1->getValue();
627 APInt C2V = CI2->getValue();
631 case Instruction::Add:
632 return ConstantInt::get(C1V + C2V);
633 case Instruction::Sub:
634 return ConstantInt::get(C1V - C2V);
635 case Instruction::Mul:
636 return ConstantInt::get(C1V * C2V);
637 case Instruction::UDiv:
638 if (CI2->isNullValue())
639 return 0; // X / 0 -> can't fold
640 return ConstantInt::get(C1V.udiv(C2V));
641 case Instruction::SDiv:
642 if (CI2->isNullValue())
643 return 0; // X / 0 -> can't fold
644 if (C2V.isAllOnesValue() && C1V.isMinSignedValue())
645 return 0; // MIN_INT / -1 -> overflow
646 return ConstantInt::get(C1V.sdiv(C2V));
647 case Instruction::URem:
648 if (C2->isNullValue())
649 return 0; // X / 0 -> can't fold
650 return ConstantInt::get(C1V.urem(C2V));
651 case Instruction::SRem:
652 if (CI2->isNullValue())
653 return 0; // X % 0 -> can't fold
654 if (C2V.isAllOnesValue() && C1V.isMinSignedValue())
655 return 0; // MIN_INT % -1 -> overflow
656 return ConstantInt::get(C1V.srem(C2V));
657 case Instruction::And:
658 return ConstantInt::get(C1V & C2V);
659 case Instruction::Or:
660 return ConstantInt::get(C1V | C2V);
661 case Instruction::Xor:
662 return ConstantInt::get(C1V ^ C2V);
663 case Instruction::Shl:
664 if (uint32_t shiftAmt = C2V.getZExtValue())
665 if (shiftAmt < C1V.getBitWidth())
666 return ConstantInt::get(C1V.shl(shiftAmt));
668 return UndefValue::get(C1->getType()); // too big shift is undef
669 return const_cast<ConstantInt*>(CI1); // Zero shift is identity
670 case Instruction::LShr:
671 if (uint32_t shiftAmt = C2V.getZExtValue())
672 if (shiftAmt < C1V.getBitWidth())
673 return ConstantInt::get(C1V.lshr(shiftAmt));
675 return UndefValue::get(C1->getType()); // too big shift is undef
676 return const_cast<ConstantInt*>(CI1); // Zero shift is identity
677 case Instruction::AShr:
678 if (uint32_t shiftAmt = C2V.getZExtValue())
679 if (shiftAmt < C1V.getBitWidth())
680 return ConstantInt::get(C1V.ashr(shiftAmt));
682 return UndefValue::get(C1->getType()); // too big shift is undef
683 return const_cast<ConstantInt*>(CI1); // Zero shift is identity
686 } else if (const ConstantFP *CFP1 = dyn_cast<ConstantFP>(C1)) {
687 if (const ConstantFP *CFP2 = dyn_cast<ConstantFP>(C2)) {
688 APFloat C1V = CFP1->getValueAPF();
689 APFloat C2V = CFP2->getValueAPF();
690 APFloat C3V = C1V; // copy for modification
691 bool isDouble = CFP1->getType()==Type::DoubleTy;
695 case Instruction::Add:
696 (void)C3V.add(C2V, APFloat::rmNearestTiesToEven);
697 return ConstantFP::get(CFP1->getType(), C3V);
698 case Instruction::Sub:
699 (void)C3V.subtract(C2V, APFloat::rmNearestTiesToEven);
700 return ConstantFP::get(CFP1->getType(), C3V);
701 case Instruction::Mul:
702 (void)C3V.multiply(C2V, APFloat::rmNearestTiesToEven);
703 return ConstantFP::get(CFP1->getType(), C3V);
704 case Instruction::FDiv:
705 // FIXME better to look at the return code
708 // IEEE 754, Section 7.1, #4
709 return ConstantFP::get(CFP1->getType(), isDouble ?
710 APFloat(std::numeric_limits<double>::quiet_NaN()) :
711 APFloat(std::numeric_limits<float>::quiet_NaN()));
712 else if (C2V.isNegZero() || C1V.isNegative())
713 // IEEE 754, Section 7.2, negative infinity case
714 return ConstantFP::get(CFP1->getType(), isDouble ?
715 APFloat(-std::numeric_limits<double>::infinity()) :
716 APFloat(-std::numeric_limits<float>::infinity()));
718 // IEEE 754, Section 7.2, positive infinity case
719 return ConstantFP::get(CFP1->getType(), isDouble ?
720 APFloat(std::numeric_limits<double>::infinity()) :
721 APFloat(std::numeric_limits<float>::infinity()));
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 ConstantVector *CP1 = dyn_cast<ConstantVector>(C1)) {
735 if (const ConstantVector *CP2 = dyn_cast<ConstantVector>(C2)) {
739 case Instruction::Add:
740 return EvalVectorOp(CP1, CP2, ConstantExpr::getAdd);
741 case Instruction::Sub:
742 return EvalVectorOp(CP1, CP2, ConstantExpr::getSub);
743 case Instruction::Mul:
744 return EvalVectorOp(CP1, CP2, ConstantExpr::getMul);
745 case Instruction::UDiv:
746 return EvalVectorOp(CP1, CP2, ConstantExpr::getUDiv);
747 case Instruction::SDiv:
748 return EvalVectorOp(CP1, CP2, ConstantExpr::getSDiv);
749 case Instruction::FDiv:
750 return EvalVectorOp(CP1, CP2, ConstantExpr::getFDiv);
751 case Instruction::URem:
752 return EvalVectorOp(CP1, CP2, ConstantExpr::getURem);
753 case Instruction::SRem:
754 return EvalVectorOp(CP1, CP2, ConstantExpr::getSRem);
755 case Instruction::FRem:
756 return EvalVectorOp(CP1, CP2, ConstantExpr::getFRem);
757 case Instruction::And:
758 return EvalVectorOp(CP1, CP2, ConstantExpr::getAnd);
759 case Instruction::Or:
760 return EvalVectorOp(CP1, CP2, ConstantExpr::getOr);
761 case Instruction::Xor:
762 return EvalVectorOp(CP1, CP2, ConstantExpr::getXor);
767 // We don't know how to fold this
771 /// isZeroSizedType - This type is zero sized if its an array or structure of
772 /// zero sized types. The only leaf zero sized type is an empty structure.
773 static bool isMaybeZeroSizedType(const Type *Ty) {
774 if (isa<OpaqueType>(Ty)) return true; // Can't say.
775 if (const StructType *STy = dyn_cast<StructType>(Ty)) {
777 // If all of elements have zero size, this does too.
778 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i)
779 if (!isMaybeZeroSizedType(STy->getElementType(i))) return false;
782 } else if (const ArrayType *ATy = dyn_cast<ArrayType>(Ty)) {
783 return isMaybeZeroSizedType(ATy->getElementType());
788 /// IdxCompare - Compare the two constants as though they were getelementptr
789 /// indices. This allows coersion of the types to be the same thing.
791 /// If the two constants are the "same" (after coersion), return 0. If the
792 /// first is less than the second, return -1, if the second is less than the
793 /// first, return 1. If the constants are not integral, return -2.
795 static int IdxCompare(Constant *C1, Constant *C2, const Type *ElTy) {
796 if (C1 == C2) return 0;
798 // Ok, we found a different index. If they are not ConstantInt, we can't do
799 // anything with them.
800 if (!isa<ConstantInt>(C1) || !isa<ConstantInt>(C2))
801 return -2; // don't know!
803 // Ok, we have two differing integer indices. Sign extend them to be the same
804 // type. Long is always big enough, so we use it.
805 if (C1->getType() != Type::Int64Ty)
806 C1 = ConstantExpr::getSExt(C1, Type::Int64Ty);
808 if (C2->getType() != Type::Int64Ty)
809 C2 = ConstantExpr::getSExt(C2, Type::Int64Ty);
811 if (C1 == C2) return 0; // They are equal
813 // If the type being indexed over is really just a zero sized type, there is
814 // no pointer difference being made here.
815 if (isMaybeZeroSizedType(ElTy))
818 // If they are really different, now that they are the same type, then we
819 // found a difference!
820 if (cast<ConstantInt>(C1)->getSExtValue() <
821 cast<ConstantInt>(C2)->getSExtValue())
827 /// evaluateFCmpRelation - This function determines if there is anything we can
828 /// decide about the two constants provided. This doesn't need to handle simple
829 /// things like ConstantFP comparisons, but should instead handle ConstantExprs.
830 /// If we can determine that the two constants have a particular relation to
831 /// each other, we should return the corresponding FCmpInst predicate,
832 /// otherwise return FCmpInst::BAD_FCMP_PREDICATE. This is used below in
833 /// ConstantFoldCompareInstruction.
835 /// To simplify this code we canonicalize the relation so that the first
836 /// operand is always the most "complex" of the two. We consider ConstantFP
837 /// to be the simplest, and ConstantExprs to be the most complex.
838 static FCmpInst::Predicate evaluateFCmpRelation(const Constant *V1,
839 const Constant *V2) {
840 assert(V1->getType() == V2->getType() &&
841 "Cannot compare values of different types!");
842 // Handle degenerate case quickly
843 if (V1 == V2) return FCmpInst::FCMP_OEQ;
845 if (!isa<ConstantExpr>(V1)) {
846 if (!isa<ConstantExpr>(V2)) {
847 // We distilled thisUse the standard constant folder for a few cases
849 Constant *C1 = const_cast<Constant*>(V1);
850 Constant *C2 = const_cast<Constant*>(V2);
851 R = dyn_cast<ConstantInt>(
852 ConstantExpr::getFCmp(FCmpInst::FCMP_OEQ, C1, C2));
853 if (R && !R->isZero())
854 return FCmpInst::FCMP_OEQ;
855 R = dyn_cast<ConstantInt>(
856 ConstantExpr::getFCmp(FCmpInst::FCMP_OLT, C1, C2));
857 if (R && !R->isZero())
858 return FCmpInst::FCMP_OLT;
859 R = dyn_cast<ConstantInt>(
860 ConstantExpr::getFCmp(FCmpInst::FCMP_OGT, C1, C2));
861 if (R && !R->isZero())
862 return FCmpInst::FCMP_OGT;
864 // Nothing more we can do
865 return FCmpInst::BAD_FCMP_PREDICATE;
868 // If the first operand is simple and second is ConstantExpr, swap operands.
869 FCmpInst::Predicate SwappedRelation = evaluateFCmpRelation(V2, V1);
870 if (SwappedRelation != FCmpInst::BAD_FCMP_PREDICATE)
871 return FCmpInst::getSwappedPredicate(SwappedRelation);
873 // Ok, the LHS is known to be a constantexpr. The RHS can be any of a
874 // constantexpr or a simple constant.
875 const ConstantExpr *CE1 = cast<ConstantExpr>(V1);
876 switch (CE1->getOpcode()) {
877 case Instruction::FPTrunc:
878 case Instruction::FPExt:
879 case Instruction::UIToFP:
880 case Instruction::SIToFP:
881 // We might be able to do something with these but we don't right now.
887 // There are MANY other foldings that we could perform here. They will
888 // probably be added on demand, as they seem needed.
889 return FCmpInst::BAD_FCMP_PREDICATE;
892 /// evaluateICmpRelation - This function determines if there is anything we can
893 /// decide about the two constants provided. This doesn't need to handle simple
894 /// things like integer comparisons, but should instead handle ConstantExprs
895 /// and GlobalValues. If we can determine that the two constants have a
896 /// particular relation to each other, we should return the corresponding ICmp
897 /// predicate, otherwise return ICmpInst::BAD_ICMP_PREDICATE.
899 /// To simplify this code we canonicalize the relation so that the first
900 /// operand is always the most "complex" of the two. We consider simple
901 /// constants (like ConstantInt) to be the simplest, followed by
902 /// GlobalValues, followed by ConstantExpr's (the most complex).
904 static ICmpInst::Predicate evaluateICmpRelation(const Constant *V1,
907 assert(V1->getType() == V2->getType() &&
908 "Cannot compare different types of values!");
909 if (V1 == V2) return ICmpInst::ICMP_EQ;
911 if (!isa<ConstantExpr>(V1) && !isa<GlobalValue>(V1)) {
912 if (!isa<GlobalValue>(V2) && !isa<ConstantExpr>(V2)) {
913 // We distilled this down to a simple case, use the standard constant
916 Constant *C1 = const_cast<Constant*>(V1);
917 Constant *C2 = const_cast<Constant*>(V2);
918 ICmpInst::Predicate pred = ICmpInst::ICMP_EQ;
919 R = dyn_cast<ConstantInt>(ConstantExpr::getICmp(pred, C1, C2));
920 if (R && !R->isZero())
922 pred = isSigned ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT;
923 R = dyn_cast<ConstantInt>(ConstantExpr::getICmp(pred, C1, C2));
924 if (R && !R->isZero())
926 pred = isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT;
927 R = dyn_cast<ConstantInt>(ConstantExpr::getICmp(pred, C1, C2));
928 if (R && !R->isZero())
931 // If we couldn't figure it out, bail.
932 return ICmpInst::BAD_ICMP_PREDICATE;
935 // If the first operand is simple, swap operands.
936 ICmpInst::Predicate SwappedRelation =
937 evaluateICmpRelation(V2, V1, isSigned);
938 if (SwappedRelation != ICmpInst::BAD_ICMP_PREDICATE)
939 return ICmpInst::getSwappedPredicate(SwappedRelation);
941 } else if (const GlobalValue *CPR1 = dyn_cast<GlobalValue>(V1)) {
942 if (isa<ConstantExpr>(V2)) { // Swap as necessary.
943 ICmpInst::Predicate SwappedRelation =
944 evaluateICmpRelation(V2, V1, isSigned);
945 if (SwappedRelation != ICmpInst::BAD_ICMP_PREDICATE)
946 return ICmpInst::getSwappedPredicate(SwappedRelation);
948 return ICmpInst::BAD_ICMP_PREDICATE;
951 // Now we know that the RHS is a GlobalValue or simple constant,
952 // which (since the types must match) means that it's a ConstantPointerNull.
953 if (const GlobalValue *CPR2 = dyn_cast<GlobalValue>(V2)) {
954 if (!CPR1->hasExternalWeakLinkage() || !CPR2->hasExternalWeakLinkage())
955 return ICmpInst::ICMP_NE;
957 // GlobalVals can never be null.
958 assert(isa<ConstantPointerNull>(V2) && "Canonicalization guarantee!");
959 if (!CPR1->hasExternalWeakLinkage())
960 return ICmpInst::ICMP_NE;
963 // Ok, the LHS is known to be a constantexpr. The RHS can be any of a
964 // constantexpr, a CPR, or a simple constant.
965 const ConstantExpr *CE1 = cast<ConstantExpr>(V1);
966 const Constant *CE1Op0 = CE1->getOperand(0);
968 switch (CE1->getOpcode()) {
969 case Instruction::Trunc:
970 case Instruction::FPTrunc:
971 case Instruction::FPExt:
972 case Instruction::FPToUI:
973 case Instruction::FPToSI:
974 break; // We can't evaluate floating point casts or truncations.
976 case Instruction::UIToFP:
977 case Instruction::SIToFP:
978 case Instruction::IntToPtr:
979 case Instruction::BitCast:
980 case Instruction::ZExt:
981 case Instruction::SExt:
982 case Instruction::PtrToInt:
983 // If the cast is not actually changing bits, and the second operand is a
984 // null pointer, do the comparison with the pre-casted value.
985 if (V2->isNullValue() &&
986 (isa<PointerType>(CE1->getType()) || CE1->getType()->isInteger())) {
987 bool sgnd = CE1->getOpcode() == Instruction::ZExt ? false :
988 (CE1->getOpcode() == Instruction::SExt ? true :
989 (CE1->getOpcode() == Instruction::PtrToInt ? false : isSigned));
990 return evaluateICmpRelation(
991 CE1Op0, Constant::getNullValue(CE1Op0->getType()), sgnd);
994 // If the dest type is a pointer type, and the RHS is a constantexpr cast
995 // from the same type as the src of the LHS, evaluate the inputs. This is
996 // important for things like "icmp eq (cast 4 to int*), (cast 5 to int*)",
997 // which happens a lot in compilers with tagged integers.
998 if (const ConstantExpr *CE2 = dyn_cast<ConstantExpr>(V2))
999 if (CE2->isCast() && isa<PointerType>(CE1->getType()) &&
1000 CE1->getOperand(0)->getType() == CE2->getOperand(0)->getType() &&
1001 CE1->getOperand(0)->getType()->isInteger()) {
1002 bool sgnd = CE1->getOpcode() == Instruction::ZExt ? false :
1003 (CE1->getOpcode() == Instruction::SExt ? true :
1004 (CE1->getOpcode() == Instruction::PtrToInt ? false : isSigned));
1005 return evaluateICmpRelation(CE1->getOperand(0), CE2->getOperand(0),
1010 case Instruction::GetElementPtr:
1011 // Ok, since this is a getelementptr, we know that the constant has a
1012 // pointer type. Check the various cases.
1013 if (isa<ConstantPointerNull>(V2)) {
1014 // If we are comparing a GEP to a null pointer, check to see if the base
1015 // of the GEP equals the null pointer.
1016 if (const GlobalValue *GV = dyn_cast<GlobalValue>(CE1Op0)) {
1017 if (GV->hasExternalWeakLinkage())
1018 // Weak linkage GVals could be zero or not. We're comparing that
1019 // to null pointer so its greater-or-equal
1020 return isSigned ? ICmpInst::ICMP_SGE : ICmpInst::ICMP_UGE;
1022 // If its not weak linkage, the GVal must have a non-zero address
1023 // so the result is greater-than
1024 return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT;
1025 } else if (isa<ConstantPointerNull>(CE1Op0)) {
1026 // If we are indexing from a null pointer, check to see if we have any
1027 // non-zero indices.
1028 for (unsigned i = 1, e = CE1->getNumOperands(); i != e; ++i)
1029 if (!CE1->getOperand(i)->isNullValue())
1030 // Offsetting from null, must not be equal.
1031 return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT;
1032 // Only zero indexes from null, must still be zero.
1033 return ICmpInst::ICMP_EQ;
1035 // Otherwise, we can't really say if the first operand is null or not.
1036 } else if (const GlobalValue *CPR2 = dyn_cast<GlobalValue>(V2)) {
1037 if (isa<ConstantPointerNull>(CE1Op0)) {
1038 if (CPR2->hasExternalWeakLinkage())
1039 // Weak linkage GVals could be zero or not. We're comparing it to
1040 // a null pointer, so its less-or-equal
1041 return isSigned ? ICmpInst::ICMP_SLE : ICmpInst::ICMP_ULE;
1043 // If its not weak linkage, the GVal must have a non-zero address
1044 // so the result is less-than
1045 return isSigned ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT;
1046 } else if (const GlobalValue *CPR1 = dyn_cast<GlobalValue>(CE1Op0)) {
1048 // If this is a getelementptr of the same global, then it must be
1049 // different. Because the types must match, the getelementptr could
1050 // only have at most one index, and because we fold getelementptr's
1051 // with a single zero index, it must be nonzero.
1052 assert(CE1->getNumOperands() == 2 &&
1053 !CE1->getOperand(1)->isNullValue() &&
1054 "Suprising getelementptr!");
1055 return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT;
1057 // If they are different globals, we don't know what the value is,
1058 // but they can't be equal.
1059 return ICmpInst::ICMP_NE;
1063 const ConstantExpr *CE2 = cast<ConstantExpr>(V2);
1064 const Constant *CE2Op0 = CE2->getOperand(0);
1066 // There are MANY other foldings that we could perform here. They will
1067 // probably be added on demand, as they seem needed.
1068 switch (CE2->getOpcode()) {
1070 case Instruction::GetElementPtr:
1071 // By far the most common case to handle is when the base pointers are
1072 // obviously to the same or different globals.
1073 if (isa<GlobalValue>(CE1Op0) && isa<GlobalValue>(CE2Op0)) {
1074 if (CE1Op0 != CE2Op0) // Don't know relative ordering, but not equal
1075 return ICmpInst::ICMP_NE;
1076 // Ok, we know that both getelementptr instructions are based on the
1077 // same global. From this, we can precisely determine the relative
1078 // ordering of the resultant pointers.
1081 // Compare all of the operands the GEP's have in common.
1082 gep_type_iterator GTI = gep_type_begin(CE1);
1083 for (;i != CE1->getNumOperands() && i != CE2->getNumOperands();
1085 switch (IdxCompare(CE1->getOperand(i), CE2->getOperand(i),
1086 GTI.getIndexedType())) {
1087 case -1: return isSigned ? ICmpInst::ICMP_SLT:ICmpInst::ICMP_ULT;
1088 case 1: return isSigned ? ICmpInst::ICMP_SGT:ICmpInst::ICMP_UGT;
1089 case -2: return ICmpInst::BAD_ICMP_PREDICATE;
1092 // Ok, we ran out of things they have in common. If any leftovers
1093 // are non-zero then we have a difference, otherwise we are equal.
1094 for (; i < CE1->getNumOperands(); ++i)
1095 if (!CE1->getOperand(i)->isNullValue())
1096 if (isa<ConstantInt>(CE1->getOperand(i)))
1097 return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT;
1099 return ICmpInst::BAD_ICMP_PREDICATE; // Might be equal.
1101 for (; i < CE2->getNumOperands(); ++i)
1102 if (!CE2->getOperand(i)->isNullValue())
1103 if (isa<ConstantInt>(CE2->getOperand(i)))
1104 return isSigned ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT;
1106 return ICmpInst::BAD_ICMP_PREDICATE; // Might be equal.
1107 return ICmpInst::ICMP_EQ;
1116 return ICmpInst::BAD_ICMP_PREDICATE;
1119 Constant *llvm::ConstantFoldCompareInstruction(unsigned short pred,
1121 const Constant *C2) {
1123 // Handle some degenerate cases first
1124 if (isa<UndefValue>(C1) || isa<UndefValue>(C2))
1125 return UndefValue::get(Type::Int1Ty);
1127 // icmp eq/ne(null,GV) -> false/true
1128 if (C1->isNullValue()) {
1129 if (const GlobalValue *GV = dyn_cast<GlobalValue>(C2))
1130 if (!GV->hasExternalWeakLinkage()) // External weak GV can be null
1131 if (pred == ICmpInst::ICMP_EQ)
1132 return ConstantInt::getFalse();
1133 else if (pred == ICmpInst::ICMP_NE)
1134 return ConstantInt::getTrue();
1135 // icmp eq/ne(GV,null) -> false/true
1136 } else if (C2->isNullValue()) {
1137 if (const GlobalValue *GV = dyn_cast<GlobalValue>(C1))
1138 if (!GV->hasExternalWeakLinkage()) // External weak GV can be null
1139 if (pred == ICmpInst::ICMP_EQ)
1140 return ConstantInt::getFalse();
1141 else if (pred == ICmpInst::ICMP_NE)
1142 return ConstantInt::getTrue();
1145 if (isa<ConstantInt>(C1) && isa<ConstantInt>(C2)) {
1146 APInt V1 = cast<ConstantInt>(C1)->getValue();
1147 APInt V2 = cast<ConstantInt>(C2)->getValue();
1149 default: assert(0 && "Invalid ICmp Predicate"); return 0;
1150 case ICmpInst::ICMP_EQ: return ConstantInt::get(Type::Int1Ty, V1 == V2);
1151 case ICmpInst::ICMP_NE: return ConstantInt::get(Type::Int1Ty, V1 != V2);
1152 case ICmpInst::ICMP_SLT:return ConstantInt::get(Type::Int1Ty, V1.slt(V2));
1153 case ICmpInst::ICMP_SGT:return ConstantInt::get(Type::Int1Ty, V1.sgt(V2));
1154 case ICmpInst::ICMP_SLE:return ConstantInt::get(Type::Int1Ty, V1.sle(V2));
1155 case ICmpInst::ICMP_SGE:return ConstantInt::get(Type::Int1Ty, V1.sge(V2));
1156 case ICmpInst::ICMP_ULT:return ConstantInt::get(Type::Int1Ty, V1.ult(V2));
1157 case ICmpInst::ICMP_UGT:return ConstantInt::get(Type::Int1Ty, V1.ugt(V2));
1158 case ICmpInst::ICMP_ULE:return ConstantInt::get(Type::Int1Ty, V1.ule(V2));
1159 case ICmpInst::ICMP_UGE:return ConstantInt::get(Type::Int1Ty, V1.uge(V2));
1161 } else if (isa<ConstantFP>(C1) && isa<ConstantFP>(C2)) {
1162 APFloat C1V = cast<ConstantFP>(C1)->getValueAPF();
1163 APFloat C2V = cast<ConstantFP>(C2)->getValueAPF();
1164 APFloat::cmpResult R = C1V.compare(C2V);
1166 default: assert(0 && "Invalid FCmp Predicate"); return 0;
1167 case FCmpInst::FCMP_FALSE: return ConstantInt::getFalse();
1168 case FCmpInst::FCMP_TRUE: return ConstantInt::getTrue();
1169 case FCmpInst::FCMP_UNO:
1170 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpUnordered);
1171 case FCmpInst::FCMP_ORD:
1172 return ConstantInt::get(Type::Int1Ty, R!=APFloat::cmpUnordered);
1173 case FCmpInst::FCMP_UEQ:
1174 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpUnordered ||
1175 R==APFloat::cmpEqual);
1176 case FCmpInst::FCMP_OEQ:
1177 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpEqual);
1178 case FCmpInst::FCMP_UNE:
1179 return ConstantInt::get(Type::Int1Ty, R!=APFloat::cmpEqual);
1180 case FCmpInst::FCMP_ONE:
1181 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpLessThan ||
1182 R==APFloat::cmpGreaterThan);
1183 case FCmpInst::FCMP_ULT:
1184 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpUnordered ||
1185 R==APFloat::cmpLessThan);
1186 case FCmpInst::FCMP_OLT:
1187 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpLessThan);
1188 case FCmpInst::FCMP_UGT:
1189 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpUnordered ||
1190 R==APFloat::cmpGreaterThan);
1191 case FCmpInst::FCMP_OGT:
1192 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpGreaterThan);
1193 case FCmpInst::FCMP_ULE:
1194 return ConstantInt::get(Type::Int1Ty, R!=APFloat::cmpGreaterThan);
1195 case FCmpInst::FCMP_OLE:
1196 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpLessThan ||
1197 R==APFloat::cmpEqual);
1198 case FCmpInst::FCMP_UGE:
1199 return ConstantInt::get(Type::Int1Ty, R!=APFloat::cmpLessThan);
1200 case FCmpInst::FCMP_OGE:
1201 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpGreaterThan ||
1202 R==APFloat::cmpEqual);
1204 } else if (const ConstantVector *CP1 = dyn_cast<ConstantVector>(C1)) {
1205 if (const ConstantVector *CP2 = dyn_cast<ConstantVector>(C2)) {
1206 if (pred == FCmpInst::FCMP_OEQ || pred == FCmpInst::FCMP_UEQ) {
1207 for (unsigned i = 0, e = CP1->getNumOperands(); i != e; ++i) {
1208 Constant *C= ConstantExpr::getFCmp(FCmpInst::FCMP_OEQ,
1209 const_cast<Constant*>(CP1->getOperand(i)),
1210 const_cast<Constant*>(CP2->getOperand(i)));
1211 if (ConstantInt *CB = dyn_cast<ConstantInt>(C))
1214 // Otherwise, could not decide from any element pairs.
1216 } else if (pred == ICmpInst::ICMP_EQ) {
1217 for (unsigned i = 0, e = CP1->getNumOperands(); i != e; ++i) {
1218 Constant *C = ConstantExpr::getICmp(ICmpInst::ICMP_EQ,
1219 const_cast<Constant*>(CP1->getOperand(i)),
1220 const_cast<Constant*>(CP2->getOperand(i)));
1221 if (ConstantInt *CB = dyn_cast<ConstantInt>(C))
1224 // Otherwise, could not decide from any element pairs.
1230 if (C1->getType()->isFloatingPoint()) {
1231 switch (evaluateFCmpRelation(C1, C2)) {
1232 default: assert(0 && "Unknown relation!");
1233 case FCmpInst::FCMP_UNO:
1234 case FCmpInst::FCMP_ORD:
1235 case FCmpInst::FCMP_UEQ:
1236 case FCmpInst::FCMP_UNE:
1237 case FCmpInst::FCMP_ULT:
1238 case FCmpInst::FCMP_UGT:
1239 case FCmpInst::FCMP_ULE:
1240 case FCmpInst::FCMP_UGE:
1241 case FCmpInst::FCMP_TRUE:
1242 case FCmpInst::FCMP_FALSE:
1243 case FCmpInst::BAD_FCMP_PREDICATE:
1244 break; // Couldn't determine anything about these constants.
1245 case FCmpInst::FCMP_OEQ: // We know that C1 == C2
1246 return ConstantInt::get(Type::Int1Ty,
1247 pred == FCmpInst::FCMP_UEQ || pred == FCmpInst::FCMP_OEQ ||
1248 pred == FCmpInst::FCMP_ULE || pred == FCmpInst::FCMP_OLE ||
1249 pred == FCmpInst::FCMP_UGE || pred == FCmpInst::FCMP_OGE);
1250 case FCmpInst::FCMP_OLT: // We know that C1 < C2
1251 return ConstantInt::get(Type::Int1Ty,
1252 pred == FCmpInst::FCMP_UNE || pred == FCmpInst::FCMP_ONE ||
1253 pred == FCmpInst::FCMP_ULT || pred == FCmpInst::FCMP_OLT ||
1254 pred == FCmpInst::FCMP_ULE || pred == FCmpInst::FCMP_OLE);
1255 case FCmpInst::FCMP_OGT: // We know that C1 > C2
1256 return ConstantInt::get(Type::Int1Ty,
1257 pred == FCmpInst::FCMP_UNE || pred == FCmpInst::FCMP_ONE ||
1258 pred == FCmpInst::FCMP_UGT || pred == FCmpInst::FCMP_OGT ||
1259 pred == FCmpInst::FCMP_UGE || pred == FCmpInst::FCMP_OGE);
1260 case FCmpInst::FCMP_OLE: // We know that C1 <= C2
1261 // We can only partially decide this relation.
1262 if (pred == FCmpInst::FCMP_UGT || pred == FCmpInst::FCMP_OGT)
1263 return ConstantInt::getFalse();
1264 if (pred == FCmpInst::FCMP_ULT || pred == FCmpInst::FCMP_OLT)
1265 return ConstantInt::getTrue();
1267 case FCmpInst::FCMP_OGE: // We known that C1 >= C2
1268 // We can only partially decide this relation.
1269 if (pred == FCmpInst::FCMP_ULT || pred == FCmpInst::FCMP_OLT)
1270 return ConstantInt::getFalse();
1271 if (pred == FCmpInst::FCMP_UGT || pred == FCmpInst::FCMP_OGT)
1272 return ConstantInt::getTrue();
1274 case ICmpInst::ICMP_NE: // We know that C1 != C2
1275 // We can only partially decide this relation.
1276 if (pred == FCmpInst::FCMP_OEQ || pred == FCmpInst::FCMP_UEQ)
1277 return ConstantInt::getFalse();
1278 if (pred == FCmpInst::FCMP_ONE || pred == FCmpInst::FCMP_UNE)
1279 return ConstantInt::getTrue();
1283 // Evaluate the relation between the two constants, per the predicate.
1284 switch (evaluateICmpRelation(C1, C2, CmpInst::isSigned(pred))) {
1285 default: assert(0 && "Unknown relational!");
1286 case ICmpInst::BAD_ICMP_PREDICATE:
1287 break; // Couldn't determine anything about these constants.
1288 case ICmpInst::ICMP_EQ: // We know the constants are equal!
1289 // If we know the constants are equal, we can decide the result of this
1290 // computation precisely.
1291 return ConstantInt::get(Type::Int1Ty,
1292 pred == ICmpInst::ICMP_EQ ||
1293 pred == ICmpInst::ICMP_ULE ||
1294 pred == ICmpInst::ICMP_SLE ||
1295 pred == ICmpInst::ICMP_UGE ||
1296 pred == ICmpInst::ICMP_SGE);
1297 case ICmpInst::ICMP_ULT:
1298 // If we know that C1 < C2, we can decide the result of this computation
1300 return ConstantInt::get(Type::Int1Ty,
1301 pred == ICmpInst::ICMP_ULT ||
1302 pred == ICmpInst::ICMP_NE ||
1303 pred == ICmpInst::ICMP_ULE);
1304 case ICmpInst::ICMP_SLT:
1305 // If we know that C1 < C2, we can decide the result of this computation
1307 return ConstantInt::get(Type::Int1Ty,
1308 pred == ICmpInst::ICMP_SLT ||
1309 pred == ICmpInst::ICMP_NE ||
1310 pred == ICmpInst::ICMP_SLE);
1311 case ICmpInst::ICMP_UGT:
1312 // If we know that C1 > C2, we can decide the result of this computation
1314 return ConstantInt::get(Type::Int1Ty,
1315 pred == ICmpInst::ICMP_UGT ||
1316 pred == ICmpInst::ICMP_NE ||
1317 pred == ICmpInst::ICMP_UGE);
1318 case ICmpInst::ICMP_SGT:
1319 // If we know that C1 > C2, we can decide the result of this computation
1321 return ConstantInt::get(Type::Int1Ty,
1322 pred == ICmpInst::ICMP_SGT ||
1323 pred == ICmpInst::ICMP_NE ||
1324 pred == ICmpInst::ICMP_SGE);
1325 case ICmpInst::ICMP_ULE:
1326 // If we know that C1 <= C2, we can only partially decide this relation.
1327 if (pred == ICmpInst::ICMP_UGT) return ConstantInt::getFalse();
1328 if (pred == ICmpInst::ICMP_ULT) return ConstantInt::getTrue();
1330 case ICmpInst::ICMP_SLE:
1331 // If we know that C1 <= C2, we can only partially decide this relation.
1332 if (pred == ICmpInst::ICMP_SGT) return ConstantInt::getFalse();
1333 if (pred == ICmpInst::ICMP_SLT) return ConstantInt::getTrue();
1336 case ICmpInst::ICMP_UGE:
1337 // If we know that C1 >= C2, we can only partially decide this relation.
1338 if (pred == ICmpInst::ICMP_ULT) return ConstantInt::getFalse();
1339 if (pred == ICmpInst::ICMP_UGT) return ConstantInt::getTrue();
1341 case ICmpInst::ICMP_SGE:
1342 // If we know that C1 >= C2, we can only partially decide this relation.
1343 if (pred == ICmpInst::ICMP_SLT) return ConstantInt::getFalse();
1344 if (pred == ICmpInst::ICMP_SGT) return ConstantInt::getTrue();
1347 case ICmpInst::ICMP_NE:
1348 // If we know that C1 != C2, we can only partially decide this relation.
1349 if (pred == ICmpInst::ICMP_EQ) return ConstantInt::getFalse();
1350 if (pred == ICmpInst::ICMP_NE) return ConstantInt::getTrue();
1354 if (!isa<ConstantExpr>(C1) && isa<ConstantExpr>(C2)) {
1355 // If C2 is a constant expr and C1 isn't, flop them around and fold the
1356 // other way if possible.
1358 case ICmpInst::ICMP_EQ:
1359 case ICmpInst::ICMP_NE:
1360 // No change of predicate required.
1361 return ConstantFoldCompareInstruction(pred, C2, C1);
1363 case ICmpInst::ICMP_ULT:
1364 case ICmpInst::ICMP_SLT:
1365 case ICmpInst::ICMP_UGT:
1366 case ICmpInst::ICMP_SGT:
1367 case ICmpInst::ICMP_ULE:
1368 case ICmpInst::ICMP_SLE:
1369 case ICmpInst::ICMP_UGE:
1370 case ICmpInst::ICMP_SGE:
1371 // Change the predicate as necessary to swap the operands.
1372 pred = ICmpInst::getSwappedPredicate((ICmpInst::Predicate)pred);
1373 return ConstantFoldCompareInstruction(pred, C2, C1);
1375 default: // These predicates cannot be flopped around.
1383 Constant *llvm::ConstantFoldGetElementPtr(const Constant *C,
1384 Constant* const *Idxs,
1387 (NumIdx == 1 && Idxs[0]->isNullValue()))
1388 return const_cast<Constant*>(C);
1390 if (isa<UndefValue>(C)) {
1391 const Type *Ty = GetElementPtrInst::getIndexedType(C->getType(),
1393 (Value **)Idxs+NumIdx,
1395 assert(Ty != 0 && "Invalid indices for GEP!");
1396 return UndefValue::get(PointerType::get(Ty));
1399 Constant *Idx0 = Idxs[0];
1400 if (C->isNullValue()) {
1402 for (unsigned i = 0, e = NumIdx; i != e; ++i)
1403 if (!Idxs[i]->isNullValue()) {
1408 const Type *Ty = GetElementPtrInst::getIndexedType(C->getType(),
1410 (Value**)Idxs+NumIdx,
1412 assert(Ty != 0 && "Invalid indices for GEP!");
1413 return ConstantPointerNull::get(PointerType::get(Ty));
1417 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(const_cast<Constant*>(C))) {
1418 // Combine Indices - If the source pointer to this getelementptr instruction
1419 // is a getelementptr instruction, combine the indices of the two
1420 // getelementptr instructions into a single instruction.
1422 if (CE->getOpcode() == Instruction::GetElementPtr) {
1423 const Type *LastTy = 0;
1424 for (gep_type_iterator I = gep_type_begin(CE), E = gep_type_end(CE);
1428 if ((LastTy && isa<ArrayType>(LastTy)) || Idx0->isNullValue()) {
1429 SmallVector<Value*, 16> NewIndices;
1430 NewIndices.reserve(NumIdx + CE->getNumOperands());
1431 for (unsigned i = 1, e = CE->getNumOperands()-1; i != e; ++i)
1432 NewIndices.push_back(CE->getOperand(i));
1434 // Add the last index of the source with the first index of the new GEP.
1435 // Make sure to handle the case when they are actually different types.
1436 Constant *Combined = CE->getOperand(CE->getNumOperands()-1);
1437 // Otherwise it must be an array.
1438 if (!Idx0->isNullValue()) {
1439 const Type *IdxTy = Combined->getType();
1440 if (IdxTy != Idx0->getType()) {
1441 Constant *C1 = ConstantExpr::getSExtOrBitCast(Idx0, Type::Int64Ty);
1442 Constant *C2 = ConstantExpr::getSExtOrBitCast(Combined,
1444 Combined = ConstantExpr::get(Instruction::Add, C1, C2);
1447 ConstantExpr::get(Instruction::Add, Idx0, Combined);
1451 NewIndices.push_back(Combined);
1452 NewIndices.insert(NewIndices.end(), Idxs+1, Idxs+NumIdx);
1453 return ConstantExpr::getGetElementPtr(CE->getOperand(0), &NewIndices[0],
1458 // Implement folding of:
1459 // int* getelementptr ([2 x int]* cast ([3 x int]* %X to [2 x int]*),
1461 // To: int* getelementptr ([3 x int]* %X, long 0, long 0)
1463 if (CE->isCast() && NumIdx > 1 && Idx0->isNullValue()) {
1464 if (const PointerType *SPT =
1465 dyn_cast<PointerType>(CE->getOperand(0)->getType()))
1466 if (const ArrayType *SAT = dyn_cast<ArrayType>(SPT->getElementType()))
1467 if (const ArrayType *CAT =
1468 dyn_cast<ArrayType>(cast<PointerType>(C->getType())->getElementType()))
1469 if (CAT->getElementType() == SAT->getElementType())
1470 return ConstantExpr::getGetElementPtr(
1471 (Constant*)CE->getOperand(0), Idxs, NumIdx);
1474 // Fold: getelementptr (i8* inttoptr (i64 1 to i8*), i32 -1)
1475 // Into: inttoptr (i64 0 to i8*)
1476 // This happens with pointers to member functions in C++.
1477 if (CE->getOpcode() == Instruction::IntToPtr && NumIdx == 1 &&
1478 isa<ConstantInt>(CE->getOperand(0)) && isa<ConstantInt>(Idxs[0]) &&
1479 cast<PointerType>(CE->getType())->getElementType() == Type::Int8Ty) {
1480 Constant *Base = CE->getOperand(0);
1481 Constant *Offset = Idxs[0];
1483 // Convert the smaller integer to the larger type.
1484 if (Offset->getType()->getPrimitiveSizeInBits() <
1485 Base->getType()->getPrimitiveSizeInBits())
1486 Offset = ConstantExpr::getSExt(Offset, Base->getType());
1487 else if (Base->getType()->getPrimitiveSizeInBits() <
1488 Offset->getType()->getPrimitiveSizeInBits())
1489 Base = ConstantExpr::getZExt(Base, Base->getType());
1491 Base = ConstantExpr::getAdd(Base, Offset);
1492 return ConstantExpr::getIntToPtr(Base, CE->getType());