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 packed 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) {
70 BitsToDouble(cast<ConstantInt>(CV->getOperand(i))->getZExtValue());
71 Result.push_back(ConstantFP::get(Type::DoubleTy, V));
73 return ConstantVector::get(Result);
75 assert(DstEltTy == Type::FloatTy && "Unknown fp type!");
76 for (unsigned i = 0; i != SrcNumElts; ++i) {
78 BitsToFloat(cast<ConstantInt>(CV->getOperand(i))->getZExtValue());
79 Result.push_back(ConstantFP::get(Type::FloatTy, 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))->getValue());
91 Constant *C = ConstantInt::get(Type::Int64Ty,
92 APIntOps::RoundDoubleToAPInt(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))->getValue());
101 Constant *C = ConstantInt::get(Type::Int32Ty, V);
102 Result.push_back(ConstantExpr::getBitCast(C, DstEltTy));
104 return ConstantVector::get(Result);
107 // Otherwise, this is a cast that changes element count and size. Handle
108 // casts which shrink the elements here.
110 // FIXME: We need to know endianness to do this!
115 /// This function determines which opcode to use to fold two constant cast
116 /// expressions together. It uses CastInst::isEliminableCastPair to determine
117 /// the opcode. Consequently its just a wrapper around that function.
118 /// @Determine if it is valid to fold a cast of a cast
120 foldConstantCastPair(
121 unsigned opc, ///< opcode of the second cast constant expression
122 const ConstantExpr*Op, ///< the first cast constant expression
123 const Type *DstTy ///< desintation type of the first cast
125 assert(Op && Op->isCast() && "Can't fold cast of cast without a cast!");
126 assert(DstTy && DstTy->isFirstClassType() && "Invalid cast destination type");
127 assert(CastInst::isCast(opc) && "Invalid cast opcode");
129 // The the types and opcodes for the two Cast constant expressions
130 const Type *SrcTy = Op->getOperand(0)->getType();
131 const Type *MidTy = Op->getType();
132 Instruction::CastOps firstOp = Instruction::CastOps(Op->getOpcode());
133 Instruction::CastOps secondOp = Instruction::CastOps(opc);
135 // Let CastInst::isEliminableCastPair do the heavy lifting.
136 return CastInst::isEliminableCastPair(firstOp, secondOp, SrcTy, MidTy, DstTy,
140 Constant *llvm::ConstantFoldCastInstruction(unsigned opc, const Constant *V,
141 const Type *DestTy) {
142 const Type *SrcTy = V->getType();
144 if (isa<UndefValue>(V))
145 return UndefValue::get(DestTy);
147 // If the cast operand is a constant expression, there's a few things we can
148 // do to try to simplify it.
149 if (const ConstantExpr *CE = dyn_cast<ConstantExpr>(V)) {
151 // Try hard to fold cast of cast because they are often eliminable.
152 if (unsigned newOpc = foldConstantCastPair(opc, CE, DestTy))
153 return ConstantExpr::getCast(newOpc, CE->getOperand(0), DestTy);
154 } else if (CE->getOpcode() == Instruction::GetElementPtr) {
155 // If all of the indexes in the GEP are null values, there is no pointer
156 // adjustment going on. We might as well cast the source pointer.
157 bool isAllNull = true;
158 for (unsigned i = 1, e = CE->getNumOperands(); i != e; ++i)
159 if (!CE->getOperand(i)->isNullValue()) {
164 // This is casting one pointer type to another, always BitCast
165 return ConstantExpr::getPointerCast(CE->getOperand(0), DestTy);
169 // We actually have to do a cast now. Perform the cast according to the
172 case Instruction::FPTrunc:
173 case Instruction::FPExt:
174 if (const ConstantFP *FPC = dyn_cast<ConstantFP>(V))
175 return ConstantFP::get(DestTy, FPC->getValue());
176 return 0; // Can't fold.
177 case Instruction::FPToUI:
178 if (const ConstantFP *FPC = dyn_cast<ConstantFP>(V)) {
179 uint32_t DestBitWidth = cast<IntegerType>(DestTy)->getBitWidth();
180 APInt Val(APIntOps::RoundDoubleToAPInt(FPC->getValue(), DestBitWidth));
181 return ConstantInt::get(DestTy, Val);
183 return 0; // Can't fold.
184 case Instruction::FPToSI:
185 if (const ConstantFP *FPC = dyn_cast<ConstantFP>(V)) {
186 uint32_t DestBitWidth = cast<IntegerType>(DestTy)->getBitWidth();
187 APInt Val(APIntOps::RoundDoubleToAPInt(FPC->getValue(), DestBitWidth));
188 return ConstantInt::get(DestTy, Val);
190 return 0; // Can't fold.
191 case Instruction::IntToPtr: //always treated as unsigned
192 if (V->isNullValue()) // Is it an integral null value?
193 return ConstantPointerNull::get(cast<PointerType>(DestTy));
194 return 0; // Other pointer types cannot be casted
195 case Instruction::PtrToInt: // always treated as unsigned
196 if (V->isNullValue()) // is it a null pointer value?
197 return ConstantInt::get(DestTy, 0);
198 return 0; // Other pointer types cannot be casted
199 case Instruction::UIToFP:
200 if (const ConstantInt *CI = dyn_cast<ConstantInt>(V))
201 if (CI->getType()->getBitWidth() <= APInt::APINT_BITS_PER_WORD)
202 return ConstantFP::get(DestTy, CI->getValue().roundToDouble(false));
204 case Instruction::SIToFP:
205 if (const ConstantInt *CI = dyn_cast<ConstantInt>(V))
206 if (CI->getType()->getBitWidth() <= APInt::APINT_BITS_PER_WORD)
207 return ConstantFP::get(DestTy, CI->getValue().roundToDouble(true));
209 case Instruction::ZExt:
210 if (const ConstantInt *CI = dyn_cast<ConstantInt>(V)) {
211 uint32_t BitWidth = cast<IntegerType>(DestTy)->getBitWidth();
212 APInt Result(CI->getValue());
213 Result.zext(BitWidth);
214 return ConstantInt::get(DestTy, Result);
217 case Instruction::SExt:
218 if (const ConstantInt *CI = dyn_cast<ConstantInt>(V)) {
219 uint32_t BitWidth = cast<IntegerType>(DestTy)->getBitWidth();
220 APInt Result(CI->getValue());
221 Result.sext(BitWidth);
222 return ConstantInt::get(DestTy, Result);
225 case Instruction::Trunc:
226 if (const ConstantInt *CI = dyn_cast<ConstantInt>(V)) {
227 uint32_t BitWidth = cast<IntegerType>(DestTy)->getBitWidth();
228 APInt Result(CI->getValue());
229 Result.trunc(BitWidth);
230 return ConstantInt::get(DestTy, Result);
233 case Instruction::BitCast:
235 return (Constant*)V; // no-op cast
237 // Check to see if we are casting a pointer to an aggregate to a pointer to
238 // the first element. If so, return the appropriate GEP instruction.
239 if (const PointerType *PTy = dyn_cast<PointerType>(V->getType()))
240 if (const PointerType *DPTy = dyn_cast<PointerType>(DestTy)) {
241 SmallVector<Value*, 8> IdxList;
242 IdxList.push_back(Constant::getNullValue(Type::Int32Ty));
243 const Type *ElTy = PTy->getElementType();
244 while (ElTy != DPTy->getElementType()) {
245 if (const StructType *STy = dyn_cast<StructType>(ElTy)) {
246 if (STy->getNumElements() == 0) break;
247 ElTy = STy->getElementType(0);
248 IdxList.push_back(Constant::getNullValue(Type::Int32Ty));
249 } else if (const SequentialType *STy =
250 dyn_cast<SequentialType>(ElTy)) {
251 if (isa<PointerType>(ElTy)) break; // Can't index into pointers!
252 ElTy = STy->getElementType();
253 IdxList.push_back(IdxList[0]);
259 if (ElTy == DPTy->getElementType())
260 return ConstantExpr::getGetElementPtr(
261 const_cast<Constant*>(V), &IdxList[0], IdxList.size());
264 // Handle casts from one packed constant to another. We know that the src
265 // and dest type have the same size (otherwise its an illegal cast).
266 if (const VectorType *DestPTy = dyn_cast<VectorType>(DestTy)) {
267 if (const VectorType *SrcTy = dyn_cast<VectorType>(V->getType())) {
268 assert(DestPTy->getBitWidth() == SrcTy->getBitWidth() &&
269 "Not cast between same sized vectors!");
270 // First, check for null and undef
271 if (isa<ConstantAggregateZero>(V))
272 return Constant::getNullValue(DestTy);
273 if (isa<UndefValue>(V))
274 return UndefValue::get(DestTy);
276 if (const ConstantVector *CV = dyn_cast<ConstantVector>(V)) {
277 // This is a cast from a ConstantVector of one type to a
278 // ConstantVector of another type. Check to see if all elements of
279 // the input are simple.
280 bool AllSimpleConstants = true;
281 for (unsigned i = 0, e = CV->getNumOperands(); i != e; ++i) {
282 if (!isa<ConstantInt>(CV->getOperand(i)) &&
283 !isa<ConstantFP>(CV->getOperand(i))) {
284 AllSimpleConstants = false;
289 // If all of the elements are simple constants, we can fold this.
290 if (AllSimpleConstants)
291 return CastConstantVector(const_cast<ConstantVector*>(CV), DestPTy);
296 // Finally, implement bitcast folding now. The code below doesn't handle
298 if (isa<ConstantPointerNull>(V)) // ptr->ptr cast.
299 return ConstantPointerNull::get(cast<PointerType>(DestTy));
301 // Handle integral constant input.
302 if (const ConstantInt *CI = dyn_cast<ConstantInt>(V)) {
303 if (DestTy->isInteger())
304 // Integral -> Integral. This is a no-op because the bit widths must
305 // be the same. Consequently, we just fold to V.
306 return const_cast<Constant*>(V);
308 if (DestTy->isFloatingPoint()) {
309 if (DestTy == Type::FloatTy)
310 return ConstantFP::get(DestTy, BitsToFloat(CI->getZExtValue()));
311 assert(DestTy == Type::DoubleTy && "Unknown FP type!");
312 return ConstantFP::get(DestTy, BitsToDouble(CI->getZExtValue()));
314 // Otherwise, can't fold this (packed?)
318 // Handle ConstantFP input.
319 if (const ConstantFP *FP = dyn_cast<ConstantFP>(V)) {
321 if (DestTy == Type::Int32Ty) {
322 return ConstantInt::get(DestTy, FloatToBits(FP->getValue()));
324 assert(DestTy == Type::Int64Ty && "only support f32/f64 for now!");
325 return ConstantInt::get(DestTy, DoubleToBits(FP->getValue()));
330 assert(!"Invalid CE CastInst opcode");
334 assert(0 && "Failed to cast constant expression");
338 Constant *llvm::ConstantFoldSelectInstruction(const Constant *Cond,
340 const Constant *V2) {
341 if (const ConstantInt *CB = dyn_cast<ConstantInt>(Cond))
342 return const_cast<Constant*>(CB->getZExtValue() ? V1 : V2);
344 if (isa<UndefValue>(V1)) return const_cast<Constant*>(V2);
345 if (isa<UndefValue>(V2)) return const_cast<Constant*>(V1);
346 if (isa<UndefValue>(Cond)) return const_cast<Constant*>(V1);
347 if (V1 == V2) return const_cast<Constant*>(V1);
351 Constant *llvm::ConstantFoldExtractElementInstruction(const Constant *Val,
352 const Constant *Idx) {
353 if (isa<UndefValue>(Val)) // ee(undef, x) -> undef
354 return UndefValue::get(cast<VectorType>(Val->getType())->getElementType());
355 if (Val->isNullValue()) // ee(zero, x) -> zero
356 return Constant::getNullValue(
357 cast<VectorType>(Val->getType())->getElementType());
359 if (const ConstantVector *CVal = dyn_cast<ConstantVector>(Val)) {
360 if (const ConstantInt *CIdx = dyn_cast<ConstantInt>(Idx)) {
361 return const_cast<Constant*>(CVal->getOperand(CIdx->getZExtValue()));
362 } else if (isa<UndefValue>(Idx)) {
363 // ee({w,x,y,z}, undef) -> w (an arbitrary value).
364 return const_cast<Constant*>(CVal->getOperand(0));
370 Constant *llvm::ConstantFoldInsertElementInstruction(const Constant *Val,
372 const Constant *Idx) {
373 const ConstantInt *CIdx = dyn_cast<ConstantInt>(Idx);
375 APInt idxVal = CIdx->getValue();
376 if (isa<UndefValue>(Val)) {
377 // Insertion of scalar constant into packed undef
378 // Optimize away insertion of undef
379 if (isa<UndefValue>(Elt))
380 return const_cast<Constant*>(Val);
381 // Otherwise break the aggregate undef into multiple undefs and do
384 cast<VectorType>(Val->getType())->getNumElements();
385 std::vector<Constant*> Ops;
387 for (unsigned i = 0; i < numOps; ++i) {
389 (idxVal == i) ? Elt : UndefValue::get(Elt->getType());
390 Ops.push_back(const_cast<Constant*>(Op));
392 return ConstantVector::get(Ops);
394 if (isa<ConstantAggregateZero>(Val)) {
395 // Insertion of scalar constant into packed aggregate zero
396 // Optimize away insertion of zero
397 if (Elt->isNullValue())
398 return const_cast<Constant*>(Val);
399 // Otherwise break the aggregate zero into multiple zeros and do
402 cast<VectorType>(Val->getType())->getNumElements();
403 std::vector<Constant*> Ops;
405 for (unsigned i = 0; i < numOps; ++i) {
407 (idxVal == i) ? Elt : Constant::getNullValue(Elt->getType());
408 Ops.push_back(const_cast<Constant*>(Op));
410 return ConstantVector::get(Ops);
412 if (const ConstantVector *CVal = dyn_cast<ConstantVector>(Val)) {
413 // Insertion of scalar constant into packed constant
414 std::vector<Constant*> Ops;
415 Ops.reserve(CVal->getNumOperands());
416 for (unsigned i = 0; i < CVal->getNumOperands(); ++i) {
418 (idxVal == i) ? Elt : cast<Constant>(CVal->getOperand(i));
419 Ops.push_back(const_cast<Constant*>(Op));
421 return ConstantVector::get(Ops);
426 Constant *llvm::ConstantFoldShuffleVectorInstruction(const Constant *V1,
428 const Constant *Mask) {
433 /// EvalVectorOp - Given two packed constants and a function pointer, apply the
434 /// function pointer to each element pair, producing a new ConstantVector
436 static Constant *EvalVectorOp(const ConstantVector *V1,
437 const ConstantVector *V2,
438 Constant *(*FP)(Constant*, Constant*)) {
439 std::vector<Constant*> Res;
440 for (unsigned i = 0, e = V1->getNumOperands(); i != e; ++i)
441 Res.push_back(FP(const_cast<Constant*>(V1->getOperand(i)),
442 const_cast<Constant*>(V2->getOperand(i))));
443 return ConstantVector::get(Res);
446 Constant *llvm::ConstantFoldBinaryInstruction(unsigned Opcode,
448 const Constant *C2) {
449 // Handle UndefValue up front
450 if (isa<UndefValue>(C1) || isa<UndefValue>(C2)) {
452 case Instruction::Add:
453 case Instruction::Sub:
454 case Instruction::Xor:
455 return UndefValue::get(C1->getType());
456 case Instruction::Mul:
457 case Instruction::And:
458 return Constant::getNullValue(C1->getType());
459 case Instruction::UDiv:
460 case Instruction::SDiv:
461 case Instruction::FDiv:
462 case Instruction::URem:
463 case Instruction::SRem:
464 case Instruction::FRem:
465 if (!isa<UndefValue>(C2)) // undef / X -> 0
466 return Constant::getNullValue(C1->getType());
467 return const_cast<Constant*>(C2); // X / undef -> undef
468 case Instruction::Or: // X | undef -> -1
469 if (const VectorType *PTy = dyn_cast<VectorType>(C1->getType()))
470 return ConstantVector::getAllOnesValue(PTy);
471 return ConstantInt::getAllOnesValue(C1->getType());
472 case Instruction::LShr:
473 if (isa<UndefValue>(C2) && isa<UndefValue>(C1))
474 return const_cast<Constant*>(C1); // undef lshr undef -> undef
475 return Constant::getNullValue(C1->getType()); // X lshr undef -> 0
477 case Instruction::AShr:
478 if (!isa<UndefValue>(C2))
479 return const_cast<Constant*>(C1); // undef ashr X --> undef
480 else if (isa<UndefValue>(C1))
481 return const_cast<Constant*>(C1); // undef ashr undef -> undef
483 return const_cast<Constant*>(C1); // X ashr undef --> X
484 case Instruction::Shl:
485 // undef << X -> 0 or X << undef -> 0
486 return Constant::getNullValue(C1->getType());
490 if (const ConstantExpr *CE1 = dyn_cast<ConstantExpr>(C1)) {
491 if (isa<ConstantExpr>(C2)) {
492 // There are many possible foldings we could do here. We should probably
493 // at least fold add of a pointer with an integer into the appropriate
494 // getelementptr. This will improve alias analysis a bit.
496 // Just implement a couple of simple identities.
498 case Instruction::Add:
499 if (C2->isNullValue()) return const_cast<Constant*>(C1); // X + 0 == X
501 case Instruction::Sub:
502 if (C2->isNullValue()) return const_cast<Constant*>(C1); // X - 0 == X
504 case Instruction::Mul:
505 if (C2->isNullValue()) return const_cast<Constant*>(C2); // X * 0 == 0
506 if (const ConstantInt *CI = dyn_cast<ConstantInt>(C2))
507 if (CI->equalsInt(1))
508 return const_cast<Constant*>(C1); // X * 1 == X
510 case Instruction::UDiv:
511 case Instruction::SDiv:
512 if (const ConstantInt *CI = dyn_cast<ConstantInt>(C2))
513 if (CI->equalsInt(1))
514 return const_cast<Constant*>(C1); // X / 1 == X
516 case Instruction::URem:
517 case Instruction::SRem:
518 if (const ConstantInt *CI = dyn_cast<ConstantInt>(C2))
519 if (CI->equalsInt(1))
520 return Constant::getNullValue(CI->getType()); // X % 1 == 0
522 case Instruction::And:
523 if (const ConstantInt *CI = dyn_cast<ConstantInt>(C2))
524 if (CI->isAllOnesValue())
525 return const_cast<Constant*>(C1); // X & -1 == X
526 if (C2->isNullValue()) return const_cast<Constant*>(C2); // X & 0 == 0
527 if (CE1->isCast() && isa<GlobalValue>(CE1->getOperand(0))) {
528 GlobalValue *CPR = cast<GlobalValue>(CE1->getOperand(0));
530 // Functions are at least 4-byte aligned. If and'ing the address of a
531 // function with a constant < 4, fold it to zero.
532 if (const ConstantInt *CI = dyn_cast<ConstantInt>(C2))
533 if (CI->getValue().ult(APInt(CI->getType()->getBitWidth(),4)) &&
535 return Constant::getNullValue(CI->getType());
538 case Instruction::Or:
539 if (C2->isNullValue()) return const_cast<Constant*>(C1); // X | 0 == X
540 if (const ConstantInt *CI = dyn_cast<ConstantInt>(C2))
541 if (CI->isAllOnesValue())
542 return const_cast<Constant*>(C2); // X | -1 == -1
544 case Instruction::Xor:
545 if (C2->isNullValue()) return const_cast<Constant*>(C1); // X ^ 0 == X
549 } else if (isa<ConstantExpr>(C2)) {
550 // If C2 is a constant expr and C1 isn't, flop them around and fold the
551 // other way if possible.
553 case Instruction::Add:
554 case Instruction::Mul:
555 case Instruction::And:
556 case Instruction::Or:
557 case Instruction::Xor:
558 // No change of opcode required.
559 return ConstantFoldBinaryInstruction(Opcode, C2, C1);
561 case Instruction::Shl:
562 case Instruction::LShr:
563 case Instruction::AShr:
564 case Instruction::Sub:
565 case Instruction::SDiv:
566 case Instruction::UDiv:
567 case Instruction::FDiv:
568 case Instruction::URem:
569 case Instruction::SRem:
570 case Instruction::FRem:
571 default: // These instructions cannot be flopped around.
576 // At this point we know neither constant is an UndefValue nor a ConstantExpr
577 // so look at directly computing the value.
578 if (const ConstantInt *CI1 = dyn_cast<ConstantInt>(C1)) {
579 if (const ConstantInt *CI2 = dyn_cast<ConstantInt>(C2)) {
580 using namespace APIntOps;
581 APInt C1V = CI1->getValue();
582 APInt C2V = CI2->getValue();
586 case Instruction::Add:
587 return ConstantInt::get(C1->getType(), C1V + C2V);
588 case Instruction::Sub:
589 return ConstantInt::get(C1->getType(), C1V - C2V);
590 case Instruction::Mul:
591 return ConstantInt::get(C1->getType(), C1V * C2V);
592 case Instruction::UDiv:
593 if (CI2->isNullValue())
594 return 0; // X / 0 -> can't fold
595 return ConstantInt::get(C1->getType(), C1V.udiv(C2V));
596 case Instruction::SDiv:
597 if (CI2->isNullValue())
598 return 0; // X / 0 -> can't fold
599 if (C2V.isAllOnesValue() && C1V.isMinSignedValue())
600 return 0; // MIN_INT / -1 -> overflow
601 return ConstantInt::get(C1->getType(), C1V.sdiv(C2V));
602 case Instruction::URem:
603 if (C2->isNullValue())
604 return 0; // X / 0 -> can't fold
605 return ConstantInt::get(C1->getType(), C1V.urem(C2V));
606 case Instruction::SRem:
607 if (CI2->isNullValue())
608 return 0; // X % 0 -> can't fold
609 if (C2V.isAllOnesValue() && C1V.isMinSignedValue())
610 return 0; // MIN_INT % -1 -> overflow
611 return ConstantInt::get(C1->getType(), C1V.srem(C2V));
612 case Instruction::And:
613 return ConstantInt::get(C1->getType(), C1V & C2V);
614 case Instruction::Or:
615 return ConstantInt::get(C1->getType(), C1V | C2V);
616 case Instruction::Xor:
617 return ConstantInt::get(C1->getType(), C1V ^ C2V);
618 case Instruction::Shl:
619 if (uint32_t shiftAmt = C2V.getZExtValue())
620 if (shiftAmt < C1V.getBitWidth())
621 return ConstantInt::get(C1->getType(), C1V.shl(shiftAmt));
623 return UndefValue::get(C1->getType()); // too big shift is undef
624 return const_cast<ConstantInt*>(CI1); // Zero shift is identity
625 case Instruction::LShr:
626 if (uint32_t shiftAmt = C2V.getZExtValue())
627 if (shiftAmt < C1V.getBitWidth())
628 return ConstantInt::get(C1->getType(), C1V.lshr(shiftAmt));
630 return UndefValue::get(C1->getType()); // too big shift is undef
631 return const_cast<ConstantInt*>(CI1); // Zero shift is identity
632 case Instruction::AShr:
633 if (uint32_t shiftAmt = C2V.getZExtValue())
634 if (shiftAmt < C1V.getBitWidth())
635 return ConstantInt::get(C1->getType(), C1V.ashr(shiftAmt));
637 return UndefValue::get(C1->getType()); // too big shift is undef
638 return const_cast<ConstantInt*>(CI1); // Zero shift is identity
641 } else if (const ConstantFP *CFP1 = dyn_cast<ConstantFP>(C1)) {
642 if (const ConstantFP *CFP2 = dyn_cast<ConstantFP>(C2)) {
643 double C1Val = CFP1->getValue();
644 double C2Val = CFP2->getValue();
648 case Instruction::Add:
649 return ConstantFP::get(CFP1->getType(), C1Val + C2Val);
650 case Instruction::Sub:
651 return ConstantFP::get(CFP1->getType(), C1Val - C2Val);
652 case Instruction::Mul:
653 return ConstantFP::get(CFP1->getType(), C1Val * C2Val);
654 case Instruction::FDiv:
655 if (CFP2->isExactlyValue(0.0))
656 return ConstantFP::get(CFP1->getType(),
657 std::numeric_limits<double>::infinity());
658 if (CFP2->isExactlyValue(-0.0))
659 return ConstantFP::get(CFP1->getType(),
660 -std::numeric_limits<double>::infinity());
661 return ConstantFP::get(CFP1->getType(), C1Val / C2Val);
662 case Instruction::FRem:
663 if (CFP2->isNullValue())
665 return ConstantFP::get(CFP1->getType(), std::fmod(C1Val, C2Val));
668 } else if (const ConstantVector *CP1 = dyn_cast<ConstantVector>(C1)) {
669 if (const ConstantVector *CP2 = dyn_cast<ConstantVector>(C2)) {
673 case Instruction::Add:
674 return EvalVectorOp(CP1, CP2, ConstantExpr::getAdd);
675 case Instruction::Sub:
676 return EvalVectorOp(CP1, CP2, ConstantExpr::getSub);
677 case Instruction::Mul:
678 return EvalVectorOp(CP1, CP2, ConstantExpr::getMul);
679 case Instruction::UDiv:
680 return EvalVectorOp(CP1, CP2, ConstantExpr::getUDiv);
681 case Instruction::SDiv:
682 return EvalVectorOp(CP1, CP2, ConstantExpr::getSDiv);
683 case Instruction::FDiv:
684 return EvalVectorOp(CP1, CP2, ConstantExpr::getFDiv);
685 case Instruction::URem:
686 return EvalVectorOp(CP1, CP2, ConstantExpr::getURem);
687 case Instruction::SRem:
688 return EvalVectorOp(CP1, CP2, ConstantExpr::getSRem);
689 case Instruction::FRem:
690 return EvalVectorOp(CP1, CP2, ConstantExpr::getFRem);
691 case Instruction::And:
692 return EvalVectorOp(CP1, CP2, ConstantExpr::getAnd);
693 case Instruction::Or:
694 return EvalVectorOp(CP1, CP2, ConstantExpr::getOr);
695 case Instruction::Xor:
696 return EvalVectorOp(CP1, CP2, ConstantExpr::getXor);
701 // We don't know how to fold this
705 /// isZeroSizedType - This type is zero sized if its an array or structure of
706 /// zero sized types. The only leaf zero sized type is an empty structure.
707 static bool isMaybeZeroSizedType(const Type *Ty) {
708 if (isa<OpaqueType>(Ty)) return true; // Can't say.
709 if (const StructType *STy = dyn_cast<StructType>(Ty)) {
711 // If all of elements have zero size, this does too.
712 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i)
713 if (!isMaybeZeroSizedType(STy->getElementType(i))) return false;
716 } else if (const ArrayType *ATy = dyn_cast<ArrayType>(Ty)) {
717 return isMaybeZeroSizedType(ATy->getElementType());
722 /// IdxCompare - Compare the two constants as though they were getelementptr
723 /// indices. This allows coersion of the types to be the same thing.
725 /// If the two constants are the "same" (after coersion), return 0. If the
726 /// first is less than the second, return -1, if the second is less than the
727 /// first, return 1. If the constants are not integral, return -2.
729 static int IdxCompare(Constant *C1, Constant *C2, const Type *ElTy) {
730 if (C1 == C2) return 0;
732 // Ok, we found a different index. If they are not ConstantInt, we can't do
733 // anything with them.
734 if (!isa<ConstantInt>(C1) || !isa<ConstantInt>(C2))
735 return -2; // don't know!
737 // Ok, we have two differing integer indices. Sign extend them to be the same
738 // type. Long is always big enough, so we use it.
739 if (C1->getType() != Type::Int64Ty)
740 C1 = ConstantExpr::getSExt(C1, Type::Int64Ty);
742 if (C2->getType() != Type::Int64Ty)
743 C2 = ConstantExpr::getSExt(C2, Type::Int64Ty);
745 if (C1 == C2) return 0; // They are equal
747 // If the type being indexed over is really just a zero sized type, there is
748 // no pointer difference being made here.
749 if (isMaybeZeroSizedType(ElTy))
752 // If they are really different, now that they are the same type, then we
753 // found a difference!
754 if (cast<ConstantInt>(C1)->getSExtValue() <
755 cast<ConstantInt>(C2)->getSExtValue())
761 /// evaluateFCmpRelation - This function determines if there is anything we can
762 /// decide about the two constants provided. This doesn't need to handle simple
763 /// things like ConstantFP comparisons, but should instead handle ConstantExprs.
764 /// If we can determine that the two constants have a particular relation to
765 /// each other, we should return the corresponding FCmpInst predicate,
766 /// otherwise return FCmpInst::BAD_FCMP_PREDICATE. This is used below in
767 /// ConstantFoldCompareInstruction.
769 /// To simplify this code we canonicalize the relation so that the first
770 /// operand is always the most "complex" of the two. We consider ConstantFP
771 /// to be the simplest, and ConstantExprs to be the most complex.
772 static FCmpInst::Predicate evaluateFCmpRelation(const Constant *V1,
773 const Constant *V2) {
774 assert(V1->getType() == V2->getType() &&
775 "Cannot compare values of different types!");
776 // Handle degenerate case quickly
777 if (V1 == V2) return FCmpInst::FCMP_OEQ;
779 if (!isa<ConstantExpr>(V1)) {
780 if (!isa<ConstantExpr>(V2)) {
781 // We distilled thisUse the standard constant folder for a few cases
783 Constant *C1 = const_cast<Constant*>(V1);
784 Constant *C2 = const_cast<Constant*>(V2);
785 R = dyn_cast<ConstantInt>(
786 ConstantExpr::getFCmp(FCmpInst::FCMP_OEQ, C1, C2));
787 if (R && !R->isNullValue())
788 return FCmpInst::FCMP_OEQ;
789 R = dyn_cast<ConstantInt>(
790 ConstantExpr::getFCmp(FCmpInst::FCMP_OLT, C1, C2));
791 if (R && !R->isNullValue())
792 return FCmpInst::FCMP_OLT;
793 R = dyn_cast<ConstantInt>(
794 ConstantExpr::getFCmp(FCmpInst::FCMP_OGT, C1, C2));
795 if (R && !R->isNullValue())
796 return FCmpInst::FCMP_OGT;
798 // Nothing more we can do
799 return FCmpInst::BAD_FCMP_PREDICATE;
802 // If the first operand is simple and second is ConstantExpr, swap operands.
803 FCmpInst::Predicate SwappedRelation = evaluateFCmpRelation(V2, V1);
804 if (SwappedRelation != FCmpInst::BAD_FCMP_PREDICATE)
805 return FCmpInst::getSwappedPredicate(SwappedRelation);
807 // Ok, the LHS is known to be a constantexpr. The RHS can be any of a
808 // constantexpr or a simple constant.
809 const ConstantExpr *CE1 = cast<ConstantExpr>(V1);
810 switch (CE1->getOpcode()) {
811 case Instruction::FPTrunc:
812 case Instruction::FPExt:
813 case Instruction::UIToFP:
814 case Instruction::SIToFP:
815 // We might be able to do something with these but we don't right now.
821 // There are MANY other foldings that we could perform here. They will
822 // probably be added on demand, as they seem needed.
823 return FCmpInst::BAD_FCMP_PREDICATE;
826 /// evaluateICmpRelation - This function determines if there is anything we can
827 /// decide about the two constants provided. This doesn't need to handle simple
828 /// things like integer comparisons, but should instead handle ConstantExprs
829 /// and GlobalValues. If we can determine that the two constants have a
830 /// particular relation to each other, we should return the corresponding ICmp
831 /// predicate, otherwise return ICmpInst::BAD_ICMP_PREDICATE.
833 /// To simplify this code we canonicalize the relation so that the first
834 /// operand is always the most "complex" of the two. We consider simple
835 /// constants (like ConstantInt) to be the simplest, followed by
836 /// GlobalValues, followed by ConstantExpr's (the most complex).
838 static ICmpInst::Predicate evaluateICmpRelation(const Constant *V1,
841 assert(V1->getType() == V2->getType() &&
842 "Cannot compare different types of values!");
843 if (V1 == V2) return ICmpInst::ICMP_EQ;
845 if (!isa<ConstantExpr>(V1) && !isa<GlobalValue>(V1)) {
846 if (!isa<GlobalValue>(V2) && !isa<ConstantExpr>(V2)) {
847 // We distilled this down to a simple case, use the standard constant
850 Constant *C1 = const_cast<Constant*>(V1);
851 Constant *C2 = const_cast<Constant*>(V2);
852 ICmpInst::Predicate pred = ICmpInst::ICMP_EQ;
853 R = dyn_cast<ConstantInt>(ConstantExpr::getICmp(pred, C1, C2));
854 if (R && !R->isNullValue())
856 pred = isSigned ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT;
857 R = dyn_cast<ConstantInt>(ConstantExpr::getICmp(pred, C1, C2));
858 if (R && !R->isNullValue())
860 pred = isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT;
861 R = dyn_cast<ConstantInt>(ConstantExpr::getICmp(pred, C1, C2));
862 if (R && !R->isNullValue())
865 // If we couldn't figure it out, bail.
866 return ICmpInst::BAD_ICMP_PREDICATE;
869 // If the first operand is simple, swap operands.
870 ICmpInst::Predicate SwappedRelation =
871 evaluateICmpRelation(V2, V1, isSigned);
872 if (SwappedRelation != ICmpInst::BAD_ICMP_PREDICATE)
873 return ICmpInst::getSwappedPredicate(SwappedRelation);
875 } else if (const GlobalValue *CPR1 = dyn_cast<GlobalValue>(V1)) {
876 if (isa<ConstantExpr>(V2)) { // Swap as necessary.
877 ICmpInst::Predicate SwappedRelation =
878 evaluateICmpRelation(V2, V1, isSigned);
879 if (SwappedRelation != ICmpInst::BAD_ICMP_PREDICATE)
880 return ICmpInst::getSwappedPredicate(SwappedRelation);
882 return ICmpInst::BAD_ICMP_PREDICATE;
885 // Now we know that the RHS is a GlobalValue or simple constant,
886 // which (since the types must match) means that it's a ConstantPointerNull.
887 if (const GlobalValue *CPR2 = dyn_cast<GlobalValue>(V2)) {
888 if (!CPR1->hasExternalWeakLinkage() || !CPR2->hasExternalWeakLinkage())
889 return ICmpInst::ICMP_NE;
891 // GlobalVals can never be null.
892 assert(isa<ConstantPointerNull>(V2) && "Canonicalization guarantee!");
893 if (!CPR1->hasExternalWeakLinkage())
894 return ICmpInst::ICMP_NE;
897 // Ok, the LHS is known to be a constantexpr. The RHS can be any of a
898 // constantexpr, a CPR, or a simple constant.
899 const ConstantExpr *CE1 = cast<ConstantExpr>(V1);
900 const Constant *CE1Op0 = CE1->getOperand(0);
902 switch (CE1->getOpcode()) {
903 case Instruction::Trunc:
904 case Instruction::FPTrunc:
905 case Instruction::FPExt:
906 case Instruction::FPToUI:
907 case Instruction::FPToSI:
908 break; // We can't evaluate floating point casts or truncations.
910 case Instruction::UIToFP:
911 case Instruction::SIToFP:
912 case Instruction::IntToPtr:
913 case Instruction::BitCast:
914 case Instruction::ZExt:
915 case Instruction::SExt:
916 case Instruction::PtrToInt:
917 // If the cast is not actually changing bits, and the second operand is a
918 // null pointer, do the comparison with the pre-casted value.
919 if (V2->isNullValue() &&
920 (isa<PointerType>(CE1->getType()) || CE1->getType()->isInteger())) {
921 bool sgnd = CE1->getOpcode() == Instruction::ZExt ? false :
922 (CE1->getOpcode() == Instruction::SExt ? true :
923 (CE1->getOpcode() == Instruction::PtrToInt ? false : isSigned));
924 return evaluateICmpRelation(
925 CE1Op0, Constant::getNullValue(CE1Op0->getType()), sgnd);
928 // If the dest type is a pointer type, and the RHS is a constantexpr cast
929 // from the same type as the src of the LHS, evaluate the inputs. This is
930 // important for things like "icmp eq (cast 4 to int*), (cast 5 to int*)",
931 // which happens a lot in compilers with tagged integers.
932 if (const ConstantExpr *CE2 = dyn_cast<ConstantExpr>(V2))
933 if (CE2->isCast() && isa<PointerType>(CE1->getType()) &&
934 CE1->getOperand(0)->getType() == CE2->getOperand(0)->getType() &&
935 CE1->getOperand(0)->getType()->isInteger()) {
936 bool sgnd = CE1->getOpcode() == Instruction::ZExt ? false :
937 (CE1->getOpcode() == Instruction::SExt ? true :
938 (CE1->getOpcode() == Instruction::PtrToInt ? false : isSigned));
939 return evaluateICmpRelation(CE1->getOperand(0), CE2->getOperand(0),
944 case Instruction::GetElementPtr:
945 // Ok, since this is a getelementptr, we know that the constant has a
946 // pointer type. Check the various cases.
947 if (isa<ConstantPointerNull>(V2)) {
948 // If we are comparing a GEP to a null pointer, check to see if the base
949 // of the GEP equals the null pointer.
950 if (const GlobalValue *GV = dyn_cast<GlobalValue>(CE1Op0)) {
951 if (GV->hasExternalWeakLinkage())
952 // Weak linkage GVals could be zero or not. We're comparing that
953 // to null pointer so its greater-or-equal
954 return isSigned ? ICmpInst::ICMP_SGE : ICmpInst::ICMP_UGE;
956 // If its not weak linkage, the GVal must have a non-zero address
957 // so the result is greater-than
958 return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT;
959 } else if (isa<ConstantPointerNull>(CE1Op0)) {
960 // If we are indexing from a null pointer, check to see if we have any
962 for (unsigned i = 1, e = CE1->getNumOperands(); i != e; ++i)
963 if (!CE1->getOperand(i)->isNullValue())
964 // Offsetting from null, must not be equal.
965 return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT;
966 // Only zero indexes from null, must still be zero.
967 return ICmpInst::ICMP_EQ;
969 // Otherwise, we can't really say if the first operand is null or not.
970 } else if (const GlobalValue *CPR2 = dyn_cast<GlobalValue>(V2)) {
971 if (isa<ConstantPointerNull>(CE1Op0)) {
972 if (CPR2->hasExternalWeakLinkage())
973 // Weak linkage GVals could be zero or not. We're comparing it to
974 // a null pointer, so its less-or-equal
975 return isSigned ? ICmpInst::ICMP_SLE : ICmpInst::ICMP_ULE;
977 // If its not weak linkage, the GVal must have a non-zero address
978 // so the result is less-than
979 return isSigned ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT;
980 } else if (const GlobalValue *CPR1 = dyn_cast<GlobalValue>(CE1Op0)) {
982 // If this is a getelementptr of the same global, then it must be
983 // different. Because the types must match, the getelementptr could
984 // only have at most one index, and because we fold getelementptr's
985 // with a single zero index, it must be nonzero.
986 assert(CE1->getNumOperands() == 2 &&
987 !CE1->getOperand(1)->isNullValue() &&
988 "Suprising getelementptr!");
989 return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT;
991 // If they are different globals, we don't know what the value is,
992 // but they can't be equal.
993 return ICmpInst::ICMP_NE;
997 const ConstantExpr *CE2 = cast<ConstantExpr>(V2);
998 const Constant *CE2Op0 = CE2->getOperand(0);
1000 // There are MANY other foldings that we could perform here. They will
1001 // probably be added on demand, as they seem needed.
1002 switch (CE2->getOpcode()) {
1004 case Instruction::GetElementPtr:
1005 // By far the most common case to handle is when the base pointers are
1006 // obviously to the same or different globals.
1007 if (isa<GlobalValue>(CE1Op0) && isa<GlobalValue>(CE2Op0)) {
1008 if (CE1Op0 != CE2Op0) // Don't know relative ordering, but not equal
1009 return ICmpInst::ICMP_NE;
1010 // Ok, we know that both getelementptr instructions are based on the
1011 // same global. From this, we can precisely determine the relative
1012 // ordering of the resultant pointers.
1015 // Compare all of the operands the GEP's have in common.
1016 gep_type_iterator GTI = gep_type_begin(CE1);
1017 for (;i != CE1->getNumOperands() && i != CE2->getNumOperands();
1019 switch (IdxCompare(CE1->getOperand(i), CE2->getOperand(i),
1020 GTI.getIndexedType())) {
1021 case -1: return isSigned ? ICmpInst::ICMP_SLT:ICmpInst::ICMP_ULT;
1022 case 1: return isSigned ? ICmpInst::ICMP_SGT:ICmpInst::ICMP_UGT;
1023 case -2: return ICmpInst::BAD_ICMP_PREDICATE;
1026 // Ok, we ran out of things they have in common. If any leftovers
1027 // are non-zero then we have a difference, otherwise we are equal.
1028 for (; i < CE1->getNumOperands(); ++i)
1029 if (!CE1->getOperand(i)->isNullValue())
1030 if (isa<ConstantInt>(CE1->getOperand(i)))
1031 return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT;
1033 return ICmpInst::BAD_ICMP_PREDICATE; // Might be equal.
1035 for (; i < CE2->getNumOperands(); ++i)
1036 if (!CE2->getOperand(i)->isNullValue())
1037 if (isa<ConstantInt>(CE2->getOperand(i)))
1038 return isSigned ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT;
1040 return ICmpInst::BAD_ICMP_PREDICATE; // Might be equal.
1041 return ICmpInst::ICMP_EQ;
1050 return ICmpInst::BAD_ICMP_PREDICATE;
1053 Constant *llvm::ConstantFoldCompareInstruction(unsigned short pred,
1055 const Constant *C2) {
1057 // Handle some degenerate cases first
1058 if (isa<UndefValue>(C1) || isa<UndefValue>(C2))
1059 return UndefValue::get(Type::Int1Ty);
1061 // icmp eq/ne(null,GV) -> false/true
1062 if (C1->isNullValue()) {
1063 if (const GlobalValue *GV = dyn_cast<GlobalValue>(C2))
1064 if (!GV->hasExternalWeakLinkage()) // External weak GV can be null
1065 if (pred == ICmpInst::ICMP_EQ)
1066 return ConstantInt::getFalse();
1067 else if (pred == ICmpInst::ICMP_NE)
1068 return ConstantInt::getTrue();
1069 // icmp eq/ne(GV,null) -> false/true
1070 } else if (C2->isNullValue()) {
1071 if (const GlobalValue *GV = dyn_cast<GlobalValue>(C1))
1072 if (!GV->hasExternalWeakLinkage()) // External weak GV can be null
1073 if (pred == ICmpInst::ICMP_EQ)
1074 return ConstantInt::getFalse();
1075 else if (pred == ICmpInst::ICMP_NE)
1076 return ConstantInt::getTrue();
1079 if (isa<ConstantInt>(C1) && isa<ConstantInt>(C2)) {
1080 APInt V1 = cast<ConstantInt>(C1)->getValue();
1081 APInt V2 = cast<ConstantInt>(C2)->getValue();
1083 default: assert(0 && "Invalid ICmp Predicate"); return 0;
1084 case ICmpInst::ICMP_EQ: return ConstantInt::get(Type::Int1Ty, V1 == V2);
1085 case ICmpInst::ICMP_NE: return ConstantInt::get(Type::Int1Ty, V1 != V2);
1086 case ICmpInst::ICMP_SLT:return ConstantInt::get(Type::Int1Ty, V1.slt(V2));
1087 case ICmpInst::ICMP_SGT:return ConstantInt::get(Type::Int1Ty, V1.sgt(V2));
1088 case ICmpInst::ICMP_SLE:return ConstantInt::get(Type::Int1Ty, V1.sle(V2));
1089 case ICmpInst::ICMP_SGE:return ConstantInt::get(Type::Int1Ty, V1.sge(V2));
1090 case ICmpInst::ICMP_ULT:return ConstantInt::get(Type::Int1Ty, V1.ult(V2));
1091 case ICmpInst::ICMP_UGT:return ConstantInt::get(Type::Int1Ty, V1.ugt(V2));
1092 case ICmpInst::ICMP_ULE:return ConstantInt::get(Type::Int1Ty, V1.ule(V2));
1093 case ICmpInst::ICMP_UGE:return ConstantInt::get(Type::Int1Ty, V1.uge(V2));
1095 } else if (isa<ConstantFP>(C1) && isa<ConstantFP>(C2)) {
1096 double C1Val = cast<ConstantFP>(C1)->getValue();
1097 double C2Val = cast<ConstantFP>(C2)->getValue();
1099 default: assert(0 && "Invalid FCmp Predicate"); return 0;
1100 case FCmpInst::FCMP_FALSE: return ConstantInt::getFalse();
1101 case FCmpInst::FCMP_TRUE: return ConstantInt::getTrue();
1102 case FCmpInst::FCMP_UNO:
1103 return ConstantInt::get(Type::Int1Ty, C1Val != C1Val || C2Val != C2Val);
1104 case FCmpInst::FCMP_ORD:
1105 return ConstantInt::get(Type::Int1Ty, C1Val == C1Val && C2Val == C2Val);
1106 case FCmpInst::FCMP_UEQ:
1107 if (C1Val != C1Val || C2Val != C2Val)
1108 return ConstantInt::getTrue();
1110 case FCmpInst::FCMP_OEQ:
1111 return ConstantInt::get(Type::Int1Ty, C1Val == C2Val);
1112 case FCmpInst::FCMP_UNE:
1113 if (C1Val != C1Val || C2Val != C2Val)
1114 return ConstantInt::getTrue();
1116 case FCmpInst::FCMP_ONE:
1117 return ConstantInt::get(Type::Int1Ty, C1Val != C2Val);
1118 case FCmpInst::FCMP_ULT:
1119 if (C1Val != C1Val || C2Val != C2Val)
1120 return ConstantInt::getTrue();
1122 case FCmpInst::FCMP_OLT:
1123 return ConstantInt::get(Type::Int1Ty, C1Val < C2Val);
1124 case FCmpInst::FCMP_UGT:
1125 if (C1Val != C1Val || C2Val != C2Val)
1126 return ConstantInt::getTrue();
1128 case FCmpInst::FCMP_OGT:
1129 return ConstantInt::get(Type::Int1Ty, C1Val > C2Val);
1130 case FCmpInst::FCMP_ULE:
1131 if (C1Val != C1Val || C2Val != C2Val)
1132 return ConstantInt::getTrue();
1134 case FCmpInst::FCMP_OLE:
1135 return ConstantInt::get(Type::Int1Ty, C1Val <= C2Val);
1136 case FCmpInst::FCMP_UGE:
1137 if (C1Val != C1Val || C2Val != C2Val)
1138 return ConstantInt::getTrue();
1140 case FCmpInst::FCMP_OGE:
1141 return ConstantInt::get(Type::Int1Ty, C1Val >= C2Val);
1143 } else if (const ConstantVector *CP1 = dyn_cast<ConstantVector>(C1)) {
1144 if (const ConstantVector *CP2 = dyn_cast<ConstantVector>(C2)) {
1145 if (pred == FCmpInst::FCMP_OEQ || pred == FCmpInst::FCMP_UEQ) {
1146 for (unsigned i = 0, e = CP1->getNumOperands(); i != e; ++i) {
1147 Constant *C= ConstantExpr::getFCmp(FCmpInst::FCMP_OEQ,
1148 const_cast<Constant*>(CP1->getOperand(i)),
1149 const_cast<Constant*>(CP2->getOperand(i)));
1150 if (ConstantInt *CB = dyn_cast<ConstantInt>(C))
1153 // Otherwise, could not decide from any element pairs.
1155 } else if (pred == ICmpInst::ICMP_EQ) {
1156 for (unsigned i = 0, e = CP1->getNumOperands(); i != e; ++i) {
1157 Constant *C = ConstantExpr::getICmp(ICmpInst::ICMP_EQ,
1158 const_cast<Constant*>(CP1->getOperand(i)),
1159 const_cast<Constant*>(CP2->getOperand(i)));
1160 if (ConstantInt *CB = dyn_cast<ConstantInt>(C))
1163 // Otherwise, could not decide from any element pairs.
1169 if (C1->getType()->isFloatingPoint()) {
1170 switch (evaluateFCmpRelation(C1, C2)) {
1171 default: assert(0 && "Unknown relation!");
1172 case FCmpInst::FCMP_UNO:
1173 case FCmpInst::FCMP_ORD:
1174 case FCmpInst::FCMP_UEQ:
1175 case FCmpInst::FCMP_UNE:
1176 case FCmpInst::FCMP_ULT:
1177 case FCmpInst::FCMP_UGT:
1178 case FCmpInst::FCMP_ULE:
1179 case FCmpInst::FCMP_UGE:
1180 case FCmpInst::FCMP_TRUE:
1181 case FCmpInst::FCMP_FALSE:
1182 case FCmpInst::BAD_FCMP_PREDICATE:
1183 break; // Couldn't determine anything about these constants.
1184 case FCmpInst::FCMP_OEQ: // We know that C1 == C2
1185 return ConstantInt::get(Type::Int1Ty,
1186 pred == FCmpInst::FCMP_UEQ || pred == FCmpInst::FCMP_OEQ ||
1187 pred == FCmpInst::FCMP_ULE || pred == FCmpInst::FCMP_OLE ||
1188 pred == FCmpInst::FCMP_UGE || pred == FCmpInst::FCMP_OGE);
1189 case FCmpInst::FCMP_OLT: // We know that C1 < C2
1190 return ConstantInt::get(Type::Int1Ty,
1191 pred == FCmpInst::FCMP_UNE || pred == FCmpInst::FCMP_ONE ||
1192 pred == FCmpInst::FCMP_ULT || pred == FCmpInst::FCMP_OLT ||
1193 pred == FCmpInst::FCMP_ULE || pred == FCmpInst::FCMP_OLE);
1194 case FCmpInst::FCMP_OGT: // We know that C1 > C2
1195 return ConstantInt::get(Type::Int1Ty,
1196 pred == FCmpInst::FCMP_UNE || pred == FCmpInst::FCMP_ONE ||
1197 pred == FCmpInst::FCMP_UGT || pred == FCmpInst::FCMP_OGT ||
1198 pred == FCmpInst::FCMP_UGE || pred == FCmpInst::FCMP_OGE);
1199 case FCmpInst::FCMP_OLE: // We know that C1 <= C2
1200 // We can only partially decide this relation.
1201 if (pred == FCmpInst::FCMP_UGT || pred == FCmpInst::FCMP_OGT)
1202 return ConstantInt::getFalse();
1203 if (pred == FCmpInst::FCMP_ULT || pred == FCmpInst::FCMP_OLT)
1204 return ConstantInt::getTrue();
1206 case FCmpInst::FCMP_OGE: // We known that C1 >= C2
1207 // We can only partially decide this relation.
1208 if (pred == FCmpInst::FCMP_ULT || pred == FCmpInst::FCMP_OLT)
1209 return ConstantInt::getFalse();
1210 if (pred == FCmpInst::FCMP_UGT || pred == FCmpInst::FCMP_OGT)
1211 return ConstantInt::getTrue();
1213 case ICmpInst::ICMP_NE: // We know that C1 != C2
1214 // We can only partially decide this relation.
1215 if (pred == FCmpInst::FCMP_OEQ || pred == FCmpInst::FCMP_UEQ)
1216 return ConstantInt::getFalse();
1217 if (pred == FCmpInst::FCMP_ONE || pred == FCmpInst::FCMP_UNE)
1218 return ConstantInt::getTrue();
1222 // Evaluate the relation between the two constants, per the predicate.
1223 switch (evaluateICmpRelation(C1, C2, CmpInst::isSigned(pred))) {
1224 default: assert(0 && "Unknown relational!");
1225 case ICmpInst::BAD_ICMP_PREDICATE:
1226 break; // Couldn't determine anything about these constants.
1227 case ICmpInst::ICMP_EQ: // We know the constants are equal!
1228 // If we know the constants are equal, we can decide the result of this
1229 // computation precisely.
1230 return ConstantInt::get(Type::Int1Ty,
1231 pred == ICmpInst::ICMP_EQ ||
1232 pred == ICmpInst::ICMP_ULE ||
1233 pred == ICmpInst::ICMP_SLE ||
1234 pred == ICmpInst::ICMP_UGE ||
1235 pred == ICmpInst::ICMP_SGE);
1236 case ICmpInst::ICMP_ULT:
1237 // If we know that C1 < C2, we can decide the result of this computation
1239 return ConstantInt::get(Type::Int1Ty,
1240 pred == ICmpInst::ICMP_ULT ||
1241 pred == ICmpInst::ICMP_NE ||
1242 pred == ICmpInst::ICMP_ULE);
1243 case ICmpInst::ICMP_SLT:
1244 // If we know that C1 < C2, we can decide the result of this computation
1246 return ConstantInt::get(Type::Int1Ty,
1247 pred == ICmpInst::ICMP_SLT ||
1248 pred == ICmpInst::ICMP_NE ||
1249 pred == ICmpInst::ICMP_SLE);
1250 case ICmpInst::ICMP_UGT:
1251 // If we know that C1 > C2, we can decide the result of this computation
1253 return ConstantInt::get(Type::Int1Ty,
1254 pred == ICmpInst::ICMP_UGT ||
1255 pred == ICmpInst::ICMP_NE ||
1256 pred == ICmpInst::ICMP_UGE);
1257 case ICmpInst::ICMP_SGT:
1258 // If we know that C1 > C2, we can decide the result of this computation
1260 return ConstantInt::get(Type::Int1Ty,
1261 pred == ICmpInst::ICMP_SGT ||
1262 pred == ICmpInst::ICMP_NE ||
1263 pred == ICmpInst::ICMP_SGE);
1264 case ICmpInst::ICMP_ULE:
1265 // If we know that C1 <= C2, we can only partially decide this relation.
1266 if (pred == ICmpInst::ICMP_UGT) return ConstantInt::getFalse();
1267 if (pred == ICmpInst::ICMP_ULT) return ConstantInt::getTrue();
1269 case ICmpInst::ICMP_SLE:
1270 // If we know that C1 <= C2, we can only partially decide this relation.
1271 if (pred == ICmpInst::ICMP_SGT) return ConstantInt::getFalse();
1272 if (pred == ICmpInst::ICMP_SLT) return ConstantInt::getTrue();
1275 case ICmpInst::ICMP_UGE:
1276 // If we know that C1 >= C2, we can only partially decide this relation.
1277 if (pred == ICmpInst::ICMP_ULT) return ConstantInt::getFalse();
1278 if (pred == ICmpInst::ICMP_UGT) return ConstantInt::getTrue();
1280 case ICmpInst::ICMP_SGE:
1281 // If we know that C1 >= C2, we can only partially decide this relation.
1282 if (pred == ICmpInst::ICMP_SLT) return ConstantInt::getFalse();
1283 if (pred == ICmpInst::ICMP_SGT) return ConstantInt::getTrue();
1286 case ICmpInst::ICMP_NE:
1287 // If we know that C1 != C2, we can only partially decide this relation.
1288 if (pred == ICmpInst::ICMP_EQ) return ConstantInt::getFalse();
1289 if (pred == ICmpInst::ICMP_NE) return ConstantInt::getTrue();
1293 if (!isa<ConstantExpr>(C1) && isa<ConstantExpr>(C2)) {
1294 // If C2 is a constant expr and C1 isn't, flop them around and fold the
1295 // other way if possible.
1297 case ICmpInst::ICMP_EQ:
1298 case ICmpInst::ICMP_NE:
1299 // No change of predicate required.
1300 return ConstantFoldCompareInstruction(pred, C2, C1);
1302 case ICmpInst::ICMP_ULT:
1303 case ICmpInst::ICMP_SLT:
1304 case ICmpInst::ICMP_UGT:
1305 case ICmpInst::ICMP_SGT:
1306 case ICmpInst::ICMP_ULE:
1307 case ICmpInst::ICMP_SLE:
1308 case ICmpInst::ICMP_UGE:
1309 case ICmpInst::ICMP_SGE:
1310 // Change the predicate as necessary to swap the operands.
1311 pred = ICmpInst::getSwappedPredicate((ICmpInst::Predicate)pred);
1312 return ConstantFoldCompareInstruction(pred, C2, C1);
1314 default: // These predicates cannot be flopped around.
1322 Constant *llvm::ConstantFoldGetElementPtr(const Constant *C,
1323 Constant* const *Idxs,
1326 (NumIdx == 1 && Idxs[0]->isNullValue()))
1327 return const_cast<Constant*>(C);
1329 if (isa<UndefValue>(C)) {
1330 const Type *Ty = GetElementPtrInst::getIndexedType(C->getType(),
1331 (Value**)Idxs, NumIdx,
1333 assert(Ty != 0 && "Invalid indices for GEP!");
1334 return UndefValue::get(PointerType::get(Ty));
1337 Constant *Idx0 = Idxs[0];
1338 if (C->isNullValue()) {
1340 for (unsigned i = 0, e = NumIdx; i != e; ++i)
1341 if (!Idxs[i]->isNullValue()) {
1346 const Type *Ty = GetElementPtrInst::getIndexedType(C->getType(),
1347 (Value**)Idxs, NumIdx,
1349 assert(Ty != 0 && "Invalid indices for GEP!");
1350 return ConstantPointerNull::get(PointerType::get(Ty));
1354 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(const_cast<Constant*>(C))) {
1355 // Combine Indices - If the source pointer to this getelementptr instruction
1356 // is a getelementptr instruction, combine the indices of the two
1357 // getelementptr instructions into a single instruction.
1359 if (CE->getOpcode() == Instruction::GetElementPtr) {
1360 const Type *LastTy = 0;
1361 for (gep_type_iterator I = gep_type_begin(CE), E = gep_type_end(CE);
1365 if ((LastTy && isa<ArrayType>(LastTy)) || Idx0->isNullValue()) {
1366 SmallVector<Value*, 16> NewIndices;
1367 NewIndices.reserve(NumIdx + CE->getNumOperands());
1368 for (unsigned i = 1, e = CE->getNumOperands()-1; i != e; ++i)
1369 NewIndices.push_back(CE->getOperand(i));
1371 // Add the last index of the source with the first index of the new GEP.
1372 // Make sure to handle the case when they are actually different types.
1373 Constant *Combined = CE->getOperand(CE->getNumOperands()-1);
1374 // Otherwise it must be an array.
1375 if (!Idx0->isNullValue()) {
1376 const Type *IdxTy = Combined->getType();
1377 if (IdxTy != Idx0->getType()) {
1378 Constant *C1 = ConstantExpr::getSExtOrBitCast(Idx0, Type::Int64Ty);
1379 Constant *C2 = ConstantExpr::getSExtOrBitCast(Combined,
1381 Combined = ConstantExpr::get(Instruction::Add, C1, C2);
1384 ConstantExpr::get(Instruction::Add, Idx0, Combined);
1388 NewIndices.push_back(Combined);
1389 NewIndices.insert(NewIndices.end(), Idxs+1, Idxs+NumIdx);
1390 return ConstantExpr::getGetElementPtr(CE->getOperand(0), &NewIndices[0],
1395 // Implement folding of:
1396 // int* getelementptr ([2 x int]* cast ([3 x int]* %X to [2 x int]*),
1398 // To: int* getelementptr ([3 x int]* %X, long 0, long 0)
1400 if (CE->isCast() && NumIdx > 1 && Idx0->isNullValue())
1401 if (const PointerType *SPT =
1402 dyn_cast<PointerType>(CE->getOperand(0)->getType()))
1403 if (const ArrayType *SAT = dyn_cast<ArrayType>(SPT->getElementType()))
1404 if (const ArrayType *CAT =
1405 dyn_cast<ArrayType>(cast<PointerType>(C->getType())->getElementType()))
1406 if (CAT->getElementType() == SAT->getElementType())
1407 return ConstantExpr::getGetElementPtr(
1408 (Constant*)CE->getOperand(0), Idxs, NumIdx);