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, 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, 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, V);
92 Result.push_back(ConstantExpr::getBitCast(C, DstEltTy ));
94 return ConstantVector::get(Result);
97 assert(SrcEltTy->getTypeID() == Type::FloatTyID);
98 for (unsigned i = 0; i != SrcNumElts; ++i) {
99 uint32_t V = FloatToBits(cast<ConstantFP>(CV->getOperand(i))->getValue());
100 Constant *C = ConstantInt::get(Type::Int32Ty, V);
101 Result.push_back(ConstantExpr::getBitCast(C, DstEltTy));
103 return ConstantVector::get(Result);
106 // Otherwise, this is a cast that changes element count and size. Handle
107 // casts which shrink the elements here.
109 // FIXME: We need to know endianness to do this!
114 /// This function determines which opcode to use to fold two constant cast
115 /// expressions together. It uses CastInst::isEliminableCastPair to determine
116 /// the opcode. Consequently its just a wrapper around that function.
117 /// @brief Determine if it is valid to fold a cast of a cast
119 foldConstantCastPair(
120 unsigned opc, ///< opcode of the second cast constant expression
121 const ConstantExpr*Op, ///< the first cast constant expression
122 const Type *DstTy ///< desintation type of the first cast
124 assert(Op && Op->isCast() && "Can't fold cast of cast without a cast!");
125 assert(DstTy && DstTy->isFirstClassType() && "Invalid cast destination type");
126 assert(CastInst::isCast(opc) && "Invalid cast opcode");
128 // The the types and opcodes for the two Cast constant expressions
129 const Type *SrcTy = Op->getOperand(0)->getType();
130 const Type *MidTy = Op->getType();
131 Instruction::CastOps firstOp = Instruction::CastOps(Op->getOpcode());
132 Instruction::CastOps secondOp = Instruction::CastOps(opc);
134 // Let CastInst::isEliminableCastPair do the heavy lifting.
135 return CastInst::isEliminableCastPair(firstOp, secondOp, SrcTy, MidTy, DstTy,
139 Constant *llvm::ConstantFoldCastInstruction(unsigned opc, const Constant *V,
140 const Type *DestTy) {
141 const Type *SrcTy = V->getType();
143 if (isa<UndefValue>(V)) {
144 // zext(undef) = 0, because the top bits will be zero.
145 // sext(undef) = 0, because the top bits will all be the same.
146 if (opc == Instruction::ZExt || opc == Instruction::SExt)
147 return Constant::getNullValue(DestTy);
148 return UndefValue::get(DestTy);
151 // If the cast operand is a constant expression, there's a few things we can
152 // do to try to simplify it.
153 if (const ConstantExpr *CE = dyn_cast<ConstantExpr>(V)) {
155 // Try hard to fold cast of cast because they are often eliminable.
156 if (unsigned newOpc = foldConstantCastPair(opc, CE, DestTy))
157 return ConstantExpr::getCast(newOpc, CE->getOperand(0), DestTy);
158 } else if (CE->getOpcode() == Instruction::GetElementPtr) {
159 // If all of the indexes in the GEP are null values, there is no pointer
160 // adjustment going on. We might as well cast the source pointer.
161 bool isAllNull = true;
162 for (unsigned i = 1, e = CE->getNumOperands(); i != e; ++i)
163 if (!CE->getOperand(i)->isNullValue()) {
168 // This is casting one pointer type to another, always BitCast
169 return ConstantExpr::getPointerCast(CE->getOperand(0), DestTy);
173 // We actually have to do a cast now. Perform the cast according to the
176 case Instruction::FPTrunc:
177 case Instruction::FPExt:
178 if (const ConstantFP *FPC = dyn_cast<ConstantFP>(V))
179 return ConstantFP::get(DestTy, FPC->getValue());
180 return 0; // Can't fold.
181 case Instruction::FPToUI:
182 if (const ConstantFP *FPC = dyn_cast<ConstantFP>(V)) {
183 uint32_t DestBitWidth = cast<IntegerType>(DestTy)->getBitWidth();
184 APInt Val(APIntOps::RoundDoubleToAPInt(FPC->getValue(), DestBitWidth));
185 return ConstantInt::get(Val);
187 return 0; // Can't fold.
188 case Instruction::FPToSI:
189 if (const ConstantFP *FPC = dyn_cast<ConstantFP>(V)) {
190 uint32_t DestBitWidth = cast<IntegerType>(DestTy)->getBitWidth();
191 APInt Val(APIntOps::RoundDoubleToAPInt(FPC->getValue(), DestBitWidth));
192 return ConstantInt::get(Val);
194 return 0; // Can't fold.
195 case Instruction::IntToPtr: //always treated as unsigned
196 if (V->isNullValue()) // Is it an integral null value?
197 return ConstantPointerNull::get(cast<PointerType>(DestTy));
198 return 0; // Other pointer types cannot be casted
199 case Instruction::PtrToInt: // always treated as unsigned
200 if (V->isNullValue()) // is it a null pointer value?
201 return ConstantInt::get(DestTy, 0);
202 return 0; // Other pointer types cannot be casted
203 case Instruction::UIToFP:
204 if (const ConstantInt *CI = dyn_cast<ConstantInt>(V))
205 return ConstantFP::get(DestTy, CI->getValue().roundToDouble());
207 case Instruction::SIToFP:
208 if (const ConstantInt *CI = dyn_cast<ConstantInt>(V))
209 return ConstantFP::get(DestTy, CI->getValue().signedRoundToDouble());
211 case Instruction::ZExt:
212 if (const ConstantInt *CI = dyn_cast<ConstantInt>(V)) {
213 uint32_t BitWidth = cast<IntegerType>(DestTy)->getBitWidth();
214 APInt Result(CI->getValue());
215 Result.zext(BitWidth);
216 return ConstantInt::get(Result);
219 case Instruction::SExt:
220 if (const ConstantInt *CI = dyn_cast<ConstantInt>(V)) {
221 uint32_t BitWidth = cast<IntegerType>(DestTy)->getBitWidth();
222 APInt Result(CI->getValue());
223 Result.sext(BitWidth);
224 return ConstantInt::get(Result);
227 case Instruction::Trunc:
228 if (const ConstantInt *CI = dyn_cast<ConstantInt>(V)) {
229 uint32_t BitWidth = cast<IntegerType>(DestTy)->getBitWidth();
230 APInt Result(CI->getValue());
231 Result.trunc(BitWidth);
232 return ConstantInt::get(Result);
235 case Instruction::BitCast:
237 return (Constant*)V; // no-op cast
239 // Check to see if we are casting a pointer to an aggregate to a pointer to
240 // the first element. If so, return the appropriate GEP instruction.
241 if (const PointerType *PTy = dyn_cast<PointerType>(V->getType()))
242 if (const PointerType *DPTy = dyn_cast<PointerType>(DestTy)) {
243 SmallVector<Value*, 8> IdxList;
244 IdxList.push_back(Constant::getNullValue(Type::Int32Ty));
245 const Type *ElTy = PTy->getElementType();
246 while (ElTy != DPTy->getElementType()) {
247 if (const StructType *STy = dyn_cast<StructType>(ElTy)) {
248 if (STy->getNumElements() == 0) break;
249 ElTy = STy->getElementType(0);
250 IdxList.push_back(Constant::getNullValue(Type::Int32Ty));
251 } else if (const SequentialType *STy =
252 dyn_cast<SequentialType>(ElTy)) {
253 if (isa<PointerType>(ElTy)) break; // Can't index into pointers!
254 ElTy = STy->getElementType();
255 IdxList.push_back(IdxList[0]);
261 if (ElTy == DPTy->getElementType())
262 return ConstantExpr::getGetElementPtr(
263 const_cast<Constant*>(V), &IdxList[0], IdxList.size());
266 // Handle casts from one vector constant to another. We know that the src
267 // and dest type have the same size (otherwise its an illegal cast).
268 if (const VectorType *DestPTy = dyn_cast<VectorType>(DestTy)) {
269 if (const VectorType *SrcTy = dyn_cast<VectorType>(V->getType())) {
270 assert(DestPTy->getBitWidth() == SrcTy->getBitWidth() &&
271 "Not cast between same sized vectors!");
272 // First, check for null and undef
273 if (isa<ConstantAggregateZero>(V))
274 return Constant::getNullValue(DestTy);
275 if (isa<UndefValue>(V))
276 return UndefValue::get(DestTy);
278 if (const ConstantVector *CV = dyn_cast<ConstantVector>(V)) {
279 // This is a cast from a ConstantVector of one type to a
280 // ConstantVector of another type. Check to see if all elements of
281 // the input are simple.
282 bool AllSimpleConstants = true;
283 for (unsigned i = 0, e = CV->getNumOperands(); i != e; ++i) {
284 if (!isa<ConstantInt>(CV->getOperand(i)) &&
285 !isa<ConstantFP>(CV->getOperand(i))) {
286 AllSimpleConstants = false;
291 // If all of the elements are simple constants, we can fold this.
292 if (AllSimpleConstants)
293 return CastConstantVector(const_cast<ConstantVector*>(CV), DestPTy);
298 // Finally, implement bitcast folding now. The code below doesn't handle
300 if (isa<ConstantPointerNull>(V)) // ptr->ptr cast.
301 return ConstantPointerNull::get(cast<PointerType>(DestTy));
303 // Handle integral constant input.
304 if (const ConstantInt *CI = dyn_cast<ConstantInt>(V)) {
305 if (DestTy->isInteger())
306 // Integral -> Integral. This is a no-op because the bit widths must
307 // be the same. Consequently, we just fold to V.
308 return const_cast<Constant*>(V);
310 if (DestTy->isFloatingPoint()) {
311 if (DestTy == Type::FloatTy)
312 return ConstantFP::get(DestTy, CI->getValue().bitsToFloat());
313 assert(DestTy == Type::DoubleTy && "Unknown FP type!");
314 return ConstantFP::get(DestTy, CI->getValue().bitsToDouble());
316 // Otherwise, can't fold this (vector?)
320 // Handle ConstantFP input.
321 if (const ConstantFP *FP = dyn_cast<ConstantFP>(V)) {
323 if (DestTy == Type::Int32Ty) {
325 return ConstantInt::get(Val.floatToBits(FP->getValue()));
327 assert(DestTy == Type::Int64Ty && "only support f32/f64 for now!");
329 return ConstantInt::get(Val.doubleToBits(FP->getValue()));
334 assert(!"Invalid CE CastInst opcode");
338 assert(0 && "Failed to cast constant expression");
342 Constant *llvm::ConstantFoldSelectInstruction(const Constant *Cond,
344 const Constant *V2) {
345 if (const ConstantInt *CB = dyn_cast<ConstantInt>(Cond))
346 return const_cast<Constant*>(CB->getZExtValue() ? V1 : V2);
348 if (isa<UndefValue>(V1)) return const_cast<Constant*>(V2);
349 if (isa<UndefValue>(V2)) return const_cast<Constant*>(V1);
350 if (isa<UndefValue>(Cond)) return const_cast<Constant*>(V1);
351 if (V1 == V2) return const_cast<Constant*>(V1);
355 Constant *llvm::ConstantFoldExtractElementInstruction(const Constant *Val,
356 const Constant *Idx) {
357 if (isa<UndefValue>(Val)) // ee(undef, x) -> undef
358 return UndefValue::get(cast<VectorType>(Val->getType())->getElementType());
359 if (Val->isNullValue()) // ee(zero, x) -> zero
360 return Constant::getNullValue(
361 cast<VectorType>(Val->getType())->getElementType());
363 if (const ConstantVector *CVal = dyn_cast<ConstantVector>(Val)) {
364 if (const ConstantInt *CIdx = dyn_cast<ConstantInt>(Idx)) {
365 return const_cast<Constant*>(CVal->getOperand(CIdx->getZExtValue()));
366 } else if (isa<UndefValue>(Idx)) {
367 // ee({w,x,y,z}, undef) -> w (an arbitrary value).
368 return const_cast<Constant*>(CVal->getOperand(0));
374 Constant *llvm::ConstantFoldInsertElementInstruction(const Constant *Val,
376 const Constant *Idx) {
377 const ConstantInt *CIdx = dyn_cast<ConstantInt>(Idx);
379 APInt idxVal = CIdx->getValue();
380 if (isa<UndefValue>(Val)) {
381 // Insertion of scalar constant into vector undef
382 // Optimize away insertion of undef
383 if (isa<UndefValue>(Elt))
384 return const_cast<Constant*>(Val);
385 // Otherwise break the aggregate undef into multiple undefs and do
388 cast<VectorType>(Val->getType())->getNumElements();
389 std::vector<Constant*> Ops;
391 for (unsigned i = 0; i < numOps; ++i) {
393 (idxVal == i) ? Elt : UndefValue::get(Elt->getType());
394 Ops.push_back(const_cast<Constant*>(Op));
396 return ConstantVector::get(Ops);
398 if (isa<ConstantAggregateZero>(Val)) {
399 // Insertion of scalar constant into vector aggregate zero
400 // Optimize away insertion of zero
401 if (Elt->isNullValue())
402 return const_cast<Constant*>(Val);
403 // Otherwise break the aggregate zero into multiple zeros and do
406 cast<VectorType>(Val->getType())->getNumElements();
407 std::vector<Constant*> Ops;
409 for (unsigned i = 0; i < numOps; ++i) {
411 (idxVal == i) ? Elt : Constant::getNullValue(Elt->getType());
412 Ops.push_back(const_cast<Constant*>(Op));
414 return ConstantVector::get(Ops);
416 if (const ConstantVector *CVal = dyn_cast<ConstantVector>(Val)) {
417 // Insertion of scalar constant into vector constant
418 std::vector<Constant*> Ops;
419 Ops.reserve(CVal->getNumOperands());
420 for (unsigned i = 0; i < CVal->getNumOperands(); ++i) {
422 (idxVal == i) ? Elt : cast<Constant>(CVal->getOperand(i));
423 Ops.push_back(const_cast<Constant*>(Op));
425 return ConstantVector::get(Ops);
430 Constant *llvm::ConstantFoldShuffleVectorInstruction(const Constant *V1,
432 const Constant *Mask) {
437 /// EvalVectorOp - Given two vector constants and a function pointer, apply the
438 /// function pointer to each element pair, producing a new ConstantVector
440 static Constant *EvalVectorOp(const ConstantVector *V1,
441 const ConstantVector *V2,
442 Constant *(*FP)(Constant*, Constant*)) {
443 std::vector<Constant*> Res;
444 for (unsigned i = 0, e = V1->getNumOperands(); i != e; ++i)
445 Res.push_back(FP(const_cast<Constant*>(V1->getOperand(i)),
446 const_cast<Constant*>(V2->getOperand(i))));
447 return ConstantVector::get(Res);
450 Constant *llvm::ConstantFoldBinaryInstruction(unsigned Opcode,
452 const Constant *C2) {
453 // Handle UndefValue up front
454 if (isa<UndefValue>(C1) || isa<UndefValue>(C2)) {
456 case Instruction::Add:
457 case Instruction::Sub:
458 case Instruction::Xor:
459 return UndefValue::get(C1->getType());
460 case Instruction::Mul:
461 case Instruction::And:
462 return Constant::getNullValue(C1->getType());
463 case Instruction::UDiv:
464 case Instruction::SDiv:
465 case Instruction::FDiv:
466 case Instruction::URem:
467 case Instruction::SRem:
468 case Instruction::FRem:
469 if (!isa<UndefValue>(C2)) // undef / X -> 0
470 return Constant::getNullValue(C1->getType());
471 return const_cast<Constant*>(C2); // X / undef -> undef
472 case Instruction::Or: // X | undef -> -1
473 if (const VectorType *PTy = dyn_cast<VectorType>(C1->getType()))
474 return ConstantVector::getAllOnesValue(PTy);
475 return ConstantInt::getAllOnesValue(C1->getType());
476 case Instruction::LShr:
477 if (isa<UndefValue>(C2) && isa<UndefValue>(C1))
478 return const_cast<Constant*>(C1); // undef lshr undef -> undef
479 return Constant::getNullValue(C1->getType()); // X lshr undef -> 0
481 case Instruction::AShr:
482 if (!isa<UndefValue>(C2))
483 return const_cast<Constant*>(C1); // undef ashr X --> undef
484 else if (isa<UndefValue>(C1))
485 return const_cast<Constant*>(C1); // undef ashr undef -> undef
487 return const_cast<Constant*>(C1); // X ashr undef --> X
488 case Instruction::Shl:
489 // undef << X -> 0 or X << undef -> 0
490 return Constant::getNullValue(C1->getType());
494 if (const ConstantExpr *CE1 = dyn_cast<ConstantExpr>(C1)) {
495 if (isa<ConstantExpr>(C2)) {
496 // There are many possible foldings we could do here. We should probably
497 // at least fold add of a pointer with an integer into the appropriate
498 // getelementptr. This will improve alias analysis a bit.
500 // Just implement a couple of simple identities.
502 case Instruction::Add:
503 if (C2->isNullValue()) return const_cast<Constant*>(C1); // X + 0 == X
505 case Instruction::Sub:
506 if (C2->isNullValue()) return const_cast<Constant*>(C1); // X - 0 == X
508 case Instruction::Mul:
509 if (C2->isNullValue()) return const_cast<Constant*>(C2); // X * 0 == 0
510 if (const ConstantInt *CI = dyn_cast<ConstantInt>(C2))
511 if (CI->equalsInt(1))
512 return const_cast<Constant*>(C1); // X * 1 == X
514 case Instruction::UDiv:
515 case Instruction::SDiv:
516 if (const ConstantInt *CI = dyn_cast<ConstantInt>(C2))
517 if (CI->equalsInt(1))
518 return const_cast<Constant*>(C1); // X / 1 == X
520 case Instruction::URem:
521 case Instruction::SRem:
522 if (const ConstantInt *CI = dyn_cast<ConstantInt>(C2))
523 if (CI->equalsInt(1))
524 return Constant::getNullValue(CI->getType()); // X % 1 == 0
526 case Instruction::And:
527 if (const ConstantInt *CI = dyn_cast<ConstantInt>(C2)) {
528 if (CI->isZero()) return const_cast<Constant*>(C2); // X & 0 == 0
529 if (CI->isAllOnesValue())
530 return const_cast<Constant*>(C1); // X & -1 == X
532 // (zext i32 to i64) & 4294967295 -> (zext i32 to i64)
533 if (CE1->getOpcode() == Instruction::ZExt) {
534 APInt PossiblySetBits
535 = cast<IntegerType>(CE1->getOperand(0)->getType())->getMask();
536 PossiblySetBits.zext(C1->getType()->getPrimitiveSizeInBits());
537 if ((PossiblySetBits & CI->getValue()) == PossiblySetBits)
538 return const_cast<Constant*>(C1);
541 if (CE1->isCast() && isa<GlobalValue>(CE1->getOperand(0))) {
542 GlobalValue *CPR = cast<GlobalValue>(CE1->getOperand(0));
544 // Functions are at least 4-byte aligned. If and'ing the address of a
545 // function with a constant < 4, fold it to zero.
546 if (const ConstantInt *CI = dyn_cast<ConstantInt>(C2))
547 if (CI->getValue().ult(APInt(CI->getType()->getBitWidth(),4)) &&
549 return Constant::getNullValue(CI->getType());
552 case Instruction::Or:
553 if (C2->isNullValue()) return const_cast<Constant*>(C1); // X | 0 == X
554 if (const ConstantInt *CI = dyn_cast<ConstantInt>(C2))
555 if (CI->isAllOnesValue())
556 return const_cast<Constant*>(C2); // X | -1 == -1
558 case Instruction::Xor:
559 if (C2->isNullValue()) return const_cast<Constant*>(C1); // X ^ 0 == X
561 case Instruction::AShr:
562 // ashr (zext C to Ty), C2 -> lshr (zext C, CSA), C2
563 if (CE1->getOpcode() == Instruction::ZExt) // Top bits known zero.
564 return ConstantExpr::getLShr(const_cast<Constant*>(C1),
565 const_cast<Constant*>(C2));
569 } else if (isa<ConstantExpr>(C2)) {
570 // If C2 is a constant expr and C1 isn't, flop them around and fold the
571 // other way if possible.
573 case Instruction::Add:
574 case Instruction::Mul:
575 case Instruction::And:
576 case Instruction::Or:
577 case Instruction::Xor:
578 // No change of opcode required.
579 return ConstantFoldBinaryInstruction(Opcode, C2, C1);
581 case Instruction::Shl:
582 case Instruction::LShr:
583 case Instruction::AShr:
584 case Instruction::Sub:
585 case Instruction::SDiv:
586 case Instruction::UDiv:
587 case Instruction::FDiv:
588 case Instruction::URem:
589 case Instruction::SRem:
590 case Instruction::FRem:
591 default: // These instructions cannot be flopped around.
596 // At this point we know neither constant is an UndefValue nor a ConstantExpr
597 // so look at directly computing the value.
598 if (const ConstantInt *CI1 = dyn_cast<ConstantInt>(C1)) {
599 if (const ConstantInt *CI2 = dyn_cast<ConstantInt>(C2)) {
600 using namespace APIntOps;
601 APInt C1V = CI1->getValue();
602 APInt C2V = CI2->getValue();
606 case Instruction::Add:
607 return ConstantInt::get(C1V + C2V);
608 case Instruction::Sub:
609 return ConstantInt::get(C1V - C2V);
610 case Instruction::Mul:
611 return ConstantInt::get(C1V * C2V);
612 case Instruction::UDiv:
613 if (CI2->isNullValue())
614 return 0; // X / 0 -> can't fold
615 return ConstantInt::get(C1V.udiv(C2V));
616 case Instruction::SDiv:
617 if (CI2->isNullValue())
618 return 0; // X / 0 -> can't fold
619 if (C2V.isAllOnesValue() && C1V.isMinSignedValue())
620 return 0; // MIN_INT / -1 -> overflow
621 return ConstantInt::get(C1V.sdiv(C2V));
622 case Instruction::URem:
623 if (C2->isNullValue())
624 return 0; // X / 0 -> can't fold
625 return ConstantInt::get(C1V.urem(C2V));
626 case Instruction::SRem:
627 if (CI2->isNullValue())
628 return 0; // X % 0 -> can't fold
629 if (C2V.isAllOnesValue() && C1V.isMinSignedValue())
630 return 0; // MIN_INT % -1 -> overflow
631 return ConstantInt::get(C1V.srem(C2V));
632 case Instruction::And:
633 return ConstantInt::get(C1V & C2V);
634 case Instruction::Or:
635 return ConstantInt::get(C1V | C2V);
636 case Instruction::Xor:
637 return ConstantInt::get(C1V ^ C2V);
638 case Instruction::Shl:
639 if (uint32_t shiftAmt = C2V.getZExtValue())
640 if (shiftAmt < C1V.getBitWidth())
641 return ConstantInt::get(C1V.shl(shiftAmt));
643 return UndefValue::get(C1->getType()); // too big shift is undef
644 return const_cast<ConstantInt*>(CI1); // Zero shift is identity
645 case Instruction::LShr:
646 if (uint32_t shiftAmt = C2V.getZExtValue())
647 if (shiftAmt < C1V.getBitWidth())
648 return ConstantInt::get(C1V.lshr(shiftAmt));
650 return UndefValue::get(C1->getType()); // too big shift is undef
651 return const_cast<ConstantInt*>(CI1); // Zero shift is identity
652 case Instruction::AShr:
653 if (uint32_t shiftAmt = C2V.getZExtValue())
654 if (shiftAmt < C1V.getBitWidth())
655 return ConstantInt::get(C1V.ashr(shiftAmt));
657 return UndefValue::get(C1->getType()); // too big shift is undef
658 return const_cast<ConstantInt*>(CI1); // Zero shift is identity
661 } else if (const ConstantFP *CFP1 = dyn_cast<ConstantFP>(C1)) {
662 if (const ConstantFP *CFP2 = dyn_cast<ConstantFP>(C2)) {
663 double C1Val = CFP1->getValue();
664 double C2Val = CFP2->getValue();
668 case Instruction::Add:
669 return ConstantFP::get(CFP1->getType(), C1Val + C2Val);
670 case Instruction::Sub:
671 return ConstantFP::get(CFP1->getType(), C1Val - C2Val);
672 case Instruction::Mul:
673 return ConstantFP::get(CFP1->getType(), C1Val * C2Val);
674 case Instruction::FDiv:
675 if (CFP2->isExactlyValue(0.0) || CFP2->isExactlyValue(-0.0))
676 if (CFP1->isExactlyValue(0.0) || CFP1->isExactlyValue(-0.0))
677 // IEEE 754, Section 7.1, #4
678 return ConstantFP::get(CFP1->getType(),
679 std::numeric_limits<double>::quiet_NaN());
680 else if (CFP2->isExactlyValue(-0.0) || C1Val < 0.0)
681 // IEEE 754, Section 7.2, negative infinity case
682 return ConstantFP::get(CFP1->getType(),
683 -std::numeric_limits<double>::infinity());
685 // IEEE 754, Section 7.2, positive infinity case
686 return ConstantFP::get(CFP1->getType(),
687 std::numeric_limits<double>::infinity());
688 return ConstantFP::get(CFP1->getType(), C1Val / C2Val);
689 case Instruction::FRem:
690 if (CFP2->isExactlyValue(0.0) || CFP2->isExactlyValue(-0.0))
691 // IEEE 754, Section 7.1, #5
692 return ConstantFP::get(CFP1->getType(),
693 std::numeric_limits<double>::quiet_NaN());
694 return ConstantFP::get(CFP1->getType(), std::fmod(C1Val, C2Val));
698 } else if (const ConstantVector *CP1 = dyn_cast<ConstantVector>(C1)) {
699 if (const ConstantVector *CP2 = dyn_cast<ConstantVector>(C2)) {
703 case Instruction::Add:
704 return EvalVectorOp(CP1, CP2, ConstantExpr::getAdd);
705 case Instruction::Sub:
706 return EvalVectorOp(CP1, CP2, ConstantExpr::getSub);
707 case Instruction::Mul:
708 return EvalVectorOp(CP1, CP2, ConstantExpr::getMul);
709 case Instruction::UDiv:
710 return EvalVectorOp(CP1, CP2, ConstantExpr::getUDiv);
711 case Instruction::SDiv:
712 return EvalVectorOp(CP1, CP2, ConstantExpr::getSDiv);
713 case Instruction::FDiv:
714 return EvalVectorOp(CP1, CP2, ConstantExpr::getFDiv);
715 case Instruction::URem:
716 return EvalVectorOp(CP1, CP2, ConstantExpr::getURem);
717 case Instruction::SRem:
718 return EvalVectorOp(CP1, CP2, ConstantExpr::getSRem);
719 case Instruction::FRem:
720 return EvalVectorOp(CP1, CP2, ConstantExpr::getFRem);
721 case Instruction::And:
722 return EvalVectorOp(CP1, CP2, ConstantExpr::getAnd);
723 case Instruction::Or:
724 return EvalVectorOp(CP1, CP2, ConstantExpr::getOr);
725 case Instruction::Xor:
726 return EvalVectorOp(CP1, CP2, ConstantExpr::getXor);
731 // We don't know how to fold this
735 /// isZeroSizedType - This type is zero sized if its an array or structure of
736 /// zero sized types. The only leaf zero sized type is an empty structure.
737 static bool isMaybeZeroSizedType(const Type *Ty) {
738 if (isa<OpaqueType>(Ty)) return true; // Can't say.
739 if (const StructType *STy = dyn_cast<StructType>(Ty)) {
741 // If all of elements have zero size, this does too.
742 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i)
743 if (!isMaybeZeroSizedType(STy->getElementType(i))) return false;
746 } else if (const ArrayType *ATy = dyn_cast<ArrayType>(Ty)) {
747 return isMaybeZeroSizedType(ATy->getElementType());
752 /// IdxCompare - Compare the two constants as though they were getelementptr
753 /// indices. This allows coersion of the types to be the same thing.
755 /// If the two constants are the "same" (after coersion), return 0. If the
756 /// first is less than the second, return -1, if the second is less than the
757 /// first, return 1. If the constants are not integral, return -2.
759 static int IdxCompare(Constant *C1, Constant *C2, const Type *ElTy) {
760 if (C1 == C2) return 0;
762 // Ok, we found a different index. If they are not ConstantInt, we can't do
763 // anything with them.
764 if (!isa<ConstantInt>(C1) || !isa<ConstantInt>(C2))
765 return -2; // don't know!
767 // Ok, we have two differing integer indices. Sign extend them to be the same
768 // type. Long is always big enough, so we use it.
769 if (C1->getType() != Type::Int64Ty)
770 C1 = ConstantExpr::getSExt(C1, Type::Int64Ty);
772 if (C2->getType() != Type::Int64Ty)
773 C2 = ConstantExpr::getSExt(C2, Type::Int64Ty);
775 if (C1 == C2) return 0; // They are equal
777 // If the type being indexed over is really just a zero sized type, there is
778 // no pointer difference being made here.
779 if (isMaybeZeroSizedType(ElTy))
782 // If they are really different, now that they are the same type, then we
783 // found a difference!
784 if (cast<ConstantInt>(C1)->getSExtValue() <
785 cast<ConstantInt>(C2)->getSExtValue())
791 /// evaluateFCmpRelation - This function determines if there is anything we can
792 /// decide about the two constants provided. This doesn't need to handle simple
793 /// things like ConstantFP comparisons, but should instead handle ConstantExprs.
794 /// If we can determine that the two constants have a particular relation to
795 /// each other, we should return the corresponding FCmpInst predicate,
796 /// otherwise return FCmpInst::BAD_FCMP_PREDICATE. This is used below in
797 /// ConstantFoldCompareInstruction.
799 /// To simplify this code we canonicalize the relation so that the first
800 /// operand is always the most "complex" of the two. We consider ConstantFP
801 /// to be the simplest, and ConstantExprs to be the most complex.
802 static FCmpInst::Predicate evaluateFCmpRelation(const Constant *V1,
803 const Constant *V2) {
804 assert(V1->getType() == V2->getType() &&
805 "Cannot compare values of different types!");
806 // Handle degenerate case quickly
807 if (V1 == V2) return FCmpInst::FCMP_OEQ;
809 if (!isa<ConstantExpr>(V1)) {
810 if (!isa<ConstantExpr>(V2)) {
811 // We distilled thisUse the standard constant folder for a few cases
813 Constant *C1 = const_cast<Constant*>(V1);
814 Constant *C2 = const_cast<Constant*>(V2);
815 R = dyn_cast<ConstantInt>(
816 ConstantExpr::getFCmp(FCmpInst::FCMP_OEQ, C1, C2));
817 if (R && !R->isZero())
818 return FCmpInst::FCMP_OEQ;
819 R = dyn_cast<ConstantInt>(
820 ConstantExpr::getFCmp(FCmpInst::FCMP_OLT, C1, C2));
821 if (R && !R->isZero())
822 return FCmpInst::FCMP_OLT;
823 R = dyn_cast<ConstantInt>(
824 ConstantExpr::getFCmp(FCmpInst::FCMP_OGT, C1, C2));
825 if (R && !R->isZero())
826 return FCmpInst::FCMP_OGT;
828 // Nothing more we can do
829 return FCmpInst::BAD_FCMP_PREDICATE;
832 // If the first operand is simple and second is ConstantExpr, swap operands.
833 FCmpInst::Predicate SwappedRelation = evaluateFCmpRelation(V2, V1);
834 if (SwappedRelation != FCmpInst::BAD_FCMP_PREDICATE)
835 return FCmpInst::getSwappedPredicate(SwappedRelation);
837 // Ok, the LHS is known to be a constantexpr. The RHS can be any of a
838 // constantexpr or a simple constant.
839 const ConstantExpr *CE1 = cast<ConstantExpr>(V1);
840 switch (CE1->getOpcode()) {
841 case Instruction::FPTrunc:
842 case Instruction::FPExt:
843 case Instruction::UIToFP:
844 case Instruction::SIToFP:
845 // We might be able to do something with these but we don't right now.
851 // There are MANY other foldings that we could perform here. They will
852 // probably be added on demand, as they seem needed.
853 return FCmpInst::BAD_FCMP_PREDICATE;
856 /// evaluateICmpRelation - This function determines if there is anything we can
857 /// decide about the two constants provided. This doesn't need to handle simple
858 /// things like integer comparisons, but should instead handle ConstantExprs
859 /// and GlobalValues. If we can determine that the two constants have a
860 /// particular relation to each other, we should return the corresponding ICmp
861 /// predicate, otherwise return ICmpInst::BAD_ICMP_PREDICATE.
863 /// To simplify this code we canonicalize the relation so that the first
864 /// operand is always the most "complex" of the two. We consider simple
865 /// constants (like ConstantInt) to be the simplest, followed by
866 /// GlobalValues, followed by ConstantExpr's (the most complex).
868 static ICmpInst::Predicate evaluateICmpRelation(const Constant *V1,
871 assert(V1->getType() == V2->getType() &&
872 "Cannot compare different types of values!");
873 if (V1 == V2) return ICmpInst::ICMP_EQ;
875 if (!isa<ConstantExpr>(V1) && !isa<GlobalValue>(V1)) {
876 if (!isa<GlobalValue>(V2) && !isa<ConstantExpr>(V2)) {
877 // We distilled this down to a simple case, use the standard constant
880 Constant *C1 = const_cast<Constant*>(V1);
881 Constant *C2 = const_cast<Constant*>(V2);
882 ICmpInst::Predicate pred = ICmpInst::ICMP_EQ;
883 R = dyn_cast<ConstantInt>(ConstantExpr::getICmp(pred, C1, C2));
884 if (R && !R->isZero())
886 pred = isSigned ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT;
887 R = dyn_cast<ConstantInt>(ConstantExpr::getICmp(pred, C1, C2));
888 if (R && !R->isZero())
890 pred = isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT;
891 R = dyn_cast<ConstantInt>(ConstantExpr::getICmp(pred, C1, C2));
892 if (R && !R->isZero())
895 // If we couldn't figure it out, bail.
896 return ICmpInst::BAD_ICMP_PREDICATE;
899 // If the first operand is simple, swap operands.
900 ICmpInst::Predicate SwappedRelation =
901 evaluateICmpRelation(V2, V1, isSigned);
902 if (SwappedRelation != ICmpInst::BAD_ICMP_PREDICATE)
903 return ICmpInst::getSwappedPredicate(SwappedRelation);
905 } else if (const GlobalValue *CPR1 = dyn_cast<GlobalValue>(V1)) {
906 if (isa<ConstantExpr>(V2)) { // Swap as necessary.
907 ICmpInst::Predicate SwappedRelation =
908 evaluateICmpRelation(V2, V1, isSigned);
909 if (SwappedRelation != ICmpInst::BAD_ICMP_PREDICATE)
910 return ICmpInst::getSwappedPredicate(SwappedRelation);
912 return ICmpInst::BAD_ICMP_PREDICATE;
915 // Now we know that the RHS is a GlobalValue or simple constant,
916 // which (since the types must match) means that it's a ConstantPointerNull.
917 if (const GlobalValue *CPR2 = dyn_cast<GlobalValue>(V2)) {
918 if (!CPR1->hasExternalWeakLinkage() || !CPR2->hasExternalWeakLinkage())
919 return ICmpInst::ICMP_NE;
921 // GlobalVals can never be null.
922 assert(isa<ConstantPointerNull>(V2) && "Canonicalization guarantee!");
923 if (!CPR1->hasExternalWeakLinkage())
924 return ICmpInst::ICMP_NE;
927 // Ok, the LHS is known to be a constantexpr. The RHS can be any of a
928 // constantexpr, a CPR, or a simple constant.
929 const ConstantExpr *CE1 = cast<ConstantExpr>(V1);
930 const Constant *CE1Op0 = CE1->getOperand(0);
932 switch (CE1->getOpcode()) {
933 case Instruction::Trunc:
934 case Instruction::FPTrunc:
935 case Instruction::FPExt:
936 case Instruction::FPToUI:
937 case Instruction::FPToSI:
938 break; // We can't evaluate floating point casts or truncations.
940 case Instruction::UIToFP:
941 case Instruction::SIToFP:
942 case Instruction::IntToPtr:
943 case Instruction::BitCast:
944 case Instruction::ZExt:
945 case Instruction::SExt:
946 case Instruction::PtrToInt:
947 // If the cast is not actually changing bits, and the second operand is a
948 // null pointer, do the comparison with the pre-casted value.
949 if (V2->isNullValue() &&
950 (isa<PointerType>(CE1->getType()) || CE1->getType()->isInteger())) {
951 bool sgnd = CE1->getOpcode() == Instruction::ZExt ? false :
952 (CE1->getOpcode() == Instruction::SExt ? true :
953 (CE1->getOpcode() == Instruction::PtrToInt ? false : isSigned));
954 return evaluateICmpRelation(
955 CE1Op0, Constant::getNullValue(CE1Op0->getType()), sgnd);
958 // If the dest type is a pointer type, and the RHS is a constantexpr cast
959 // from the same type as the src of the LHS, evaluate the inputs. This is
960 // important for things like "icmp eq (cast 4 to int*), (cast 5 to int*)",
961 // which happens a lot in compilers with tagged integers.
962 if (const ConstantExpr *CE2 = dyn_cast<ConstantExpr>(V2))
963 if (CE2->isCast() && isa<PointerType>(CE1->getType()) &&
964 CE1->getOperand(0)->getType() == CE2->getOperand(0)->getType() &&
965 CE1->getOperand(0)->getType()->isInteger()) {
966 bool sgnd = CE1->getOpcode() == Instruction::ZExt ? false :
967 (CE1->getOpcode() == Instruction::SExt ? true :
968 (CE1->getOpcode() == Instruction::PtrToInt ? false : isSigned));
969 return evaluateICmpRelation(CE1->getOperand(0), CE2->getOperand(0),
974 case Instruction::GetElementPtr:
975 // Ok, since this is a getelementptr, we know that the constant has a
976 // pointer type. Check the various cases.
977 if (isa<ConstantPointerNull>(V2)) {
978 // If we are comparing a GEP to a null pointer, check to see if the base
979 // of the GEP equals the null pointer.
980 if (const GlobalValue *GV = dyn_cast<GlobalValue>(CE1Op0)) {
981 if (GV->hasExternalWeakLinkage())
982 // Weak linkage GVals could be zero or not. We're comparing that
983 // to null pointer so its greater-or-equal
984 return isSigned ? ICmpInst::ICMP_SGE : ICmpInst::ICMP_UGE;
986 // If its not weak linkage, the GVal must have a non-zero address
987 // so the result is greater-than
988 return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT;
989 } else if (isa<ConstantPointerNull>(CE1Op0)) {
990 // If we are indexing from a null pointer, check to see if we have any
992 for (unsigned i = 1, e = CE1->getNumOperands(); i != e; ++i)
993 if (!CE1->getOperand(i)->isNullValue())
994 // Offsetting from null, must not be equal.
995 return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT;
996 // Only zero indexes from null, must still be zero.
997 return ICmpInst::ICMP_EQ;
999 // Otherwise, we can't really say if the first operand is null or not.
1000 } else if (const GlobalValue *CPR2 = dyn_cast<GlobalValue>(V2)) {
1001 if (isa<ConstantPointerNull>(CE1Op0)) {
1002 if (CPR2->hasExternalWeakLinkage())
1003 // Weak linkage GVals could be zero or not. We're comparing it to
1004 // a null pointer, so its less-or-equal
1005 return isSigned ? ICmpInst::ICMP_SLE : ICmpInst::ICMP_ULE;
1007 // If its not weak linkage, the GVal must have a non-zero address
1008 // so the result is less-than
1009 return isSigned ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT;
1010 } else if (const GlobalValue *CPR1 = dyn_cast<GlobalValue>(CE1Op0)) {
1012 // If this is a getelementptr of the same global, then it must be
1013 // different. Because the types must match, the getelementptr could
1014 // only have at most one index, and because we fold getelementptr's
1015 // with a single zero index, it must be nonzero.
1016 assert(CE1->getNumOperands() == 2 &&
1017 !CE1->getOperand(1)->isNullValue() &&
1018 "Suprising getelementptr!");
1019 return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT;
1021 // If they are different globals, we don't know what the value is,
1022 // but they can't be equal.
1023 return ICmpInst::ICMP_NE;
1027 const ConstantExpr *CE2 = cast<ConstantExpr>(V2);
1028 const Constant *CE2Op0 = CE2->getOperand(0);
1030 // There are MANY other foldings that we could perform here. They will
1031 // probably be added on demand, as they seem needed.
1032 switch (CE2->getOpcode()) {
1034 case Instruction::GetElementPtr:
1035 // By far the most common case to handle is when the base pointers are
1036 // obviously to the same or different globals.
1037 if (isa<GlobalValue>(CE1Op0) && isa<GlobalValue>(CE2Op0)) {
1038 if (CE1Op0 != CE2Op0) // Don't know relative ordering, but not equal
1039 return ICmpInst::ICMP_NE;
1040 // Ok, we know that both getelementptr instructions are based on the
1041 // same global. From this, we can precisely determine the relative
1042 // ordering of the resultant pointers.
1045 // Compare all of the operands the GEP's have in common.
1046 gep_type_iterator GTI = gep_type_begin(CE1);
1047 for (;i != CE1->getNumOperands() && i != CE2->getNumOperands();
1049 switch (IdxCompare(CE1->getOperand(i), CE2->getOperand(i),
1050 GTI.getIndexedType())) {
1051 case -1: return isSigned ? ICmpInst::ICMP_SLT:ICmpInst::ICMP_ULT;
1052 case 1: return isSigned ? ICmpInst::ICMP_SGT:ICmpInst::ICMP_UGT;
1053 case -2: return ICmpInst::BAD_ICMP_PREDICATE;
1056 // Ok, we ran out of things they have in common. If any leftovers
1057 // are non-zero then we have a difference, otherwise we are equal.
1058 for (; i < CE1->getNumOperands(); ++i)
1059 if (!CE1->getOperand(i)->isNullValue())
1060 if (isa<ConstantInt>(CE1->getOperand(i)))
1061 return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT;
1063 return ICmpInst::BAD_ICMP_PREDICATE; // Might be equal.
1065 for (; i < CE2->getNumOperands(); ++i)
1066 if (!CE2->getOperand(i)->isNullValue())
1067 if (isa<ConstantInt>(CE2->getOperand(i)))
1068 return isSigned ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT;
1070 return ICmpInst::BAD_ICMP_PREDICATE; // Might be equal.
1071 return ICmpInst::ICMP_EQ;
1080 return ICmpInst::BAD_ICMP_PREDICATE;
1083 Constant *llvm::ConstantFoldCompareInstruction(unsigned short pred,
1085 const Constant *C2) {
1087 // Handle some degenerate cases first
1088 if (isa<UndefValue>(C1) || isa<UndefValue>(C2))
1089 return UndefValue::get(Type::Int1Ty);
1091 // icmp eq/ne(null,GV) -> false/true
1092 if (C1->isNullValue()) {
1093 if (const GlobalValue *GV = dyn_cast<GlobalValue>(C2))
1094 if (!GV->hasExternalWeakLinkage()) // External weak GV can be null
1095 if (pred == ICmpInst::ICMP_EQ)
1096 return ConstantInt::getFalse();
1097 else if (pred == ICmpInst::ICMP_NE)
1098 return ConstantInt::getTrue();
1099 // icmp eq/ne(GV,null) -> false/true
1100 } else if (C2->isNullValue()) {
1101 if (const GlobalValue *GV = dyn_cast<GlobalValue>(C1))
1102 if (!GV->hasExternalWeakLinkage()) // External weak GV can be null
1103 if (pred == ICmpInst::ICMP_EQ)
1104 return ConstantInt::getFalse();
1105 else if (pred == ICmpInst::ICMP_NE)
1106 return ConstantInt::getTrue();
1109 if (isa<ConstantInt>(C1) && isa<ConstantInt>(C2)) {
1110 APInt V1 = cast<ConstantInt>(C1)->getValue();
1111 APInt V2 = cast<ConstantInt>(C2)->getValue();
1113 default: assert(0 && "Invalid ICmp Predicate"); return 0;
1114 case ICmpInst::ICMP_EQ: return ConstantInt::get(Type::Int1Ty, V1 == V2);
1115 case ICmpInst::ICMP_NE: return ConstantInt::get(Type::Int1Ty, V1 != V2);
1116 case ICmpInst::ICMP_SLT:return ConstantInt::get(Type::Int1Ty, V1.slt(V2));
1117 case ICmpInst::ICMP_SGT:return ConstantInt::get(Type::Int1Ty, V1.sgt(V2));
1118 case ICmpInst::ICMP_SLE:return ConstantInt::get(Type::Int1Ty, V1.sle(V2));
1119 case ICmpInst::ICMP_SGE:return ConstantInt::get(Type::Int1Ty, V1.sge(V2));
1120 case ICmpInst::ICMP_ULT:return ConstantInt::get(Type::Int1Ty, V1.ult(V2));
1121 case ICmpInst::ICMP_UGT:return ConstantInt::get(Type::Int1Ty, V1.ugt(V2));
1122 case ICmpInst::ICMP_ULE:return ConstantInt::get(Type::Int1Ty, V1.ule(V2));
1123 case ICmpInst::ICMP_UGE:return ConstantInt::get(Type::Int1Ty, V1.uge(V2));
1125 } else if (isa<ConstantFP>(C1) && isa<ConstantFP>(C2)) {
1126 double C1Val = cast<ConstantFP>(C1)->getValue();
1127 double C2Val = cast<ConstantFP>(C2)->getValue();
1129 default: assert(0 && "Invalid FCmp Predicate"); return 0;
1130 case FCmpInst::FCMP_FALSE: return ConstantInt::getFalse();
1131 case FCmpInst::FCMP_TRUE: return ConstantInt::getTrue();
1132 case FCmpInst::FCMP_UNO:
1133 return ConstantInt::get(Type::Int1Ty, C1Val != C1Val || C2Val != C2Val);
1134 case FCmpInst::FCMP_ORD:
1135 return ConstantInt::get(Type::Int1Ty, C1Val == C1Val && C2Val == C2Val);
1136 case FCmpInst::FCMP_UEQ:
1137 if (C1Val != C1Val || C2Val != C2Val)
1138 return ConstantInt::getTrue();
1140 case FCmpInst::FCMP_OEQ:
1141 return ConstantInt::get(Type::Int1Ty, C1Val == C2Val);
1142 case FCmpInst::FCMP_UNE:
1143 if (C1Val != C1Val || C2Val != C2Val)
1144 return ConstantInt::getTrue();
1146 case FCmpInst::FCMP_ONE:
1147 return ConstantInt::get(Type::Int1Ty, C1Val != C2Val);
1148 case FCmpInst::FCMP_ULT:
1149 if (C1Val != C1Val || C2Val != C2Val)
1150 return ConstantInt::getTrue();
1152 case FCmpInst::FCMP_OLT:
1153 return ConstantInt::get(Type::Int1Ty, C1Val < C2Val);
1154 case FCmpInst::FCMP_UGT:
1155 if (C1Val != C1Val || C2Val != C2Val)
1156 return ConstantInt::getTrue();
1158 case FCmpInst::FCMP_OGT:
1159 return ConstantInt::get(Type::Int1Ty, C1Val > C2Val);
1160 case FCmpInst::FCMP_ULE:
1161 if (C1Val != C1Val || C2Val != C2Val)
1162 return ConstantInt::getTrue();
1164 case FCmpInst::FCMP_OLE:
1165 return ConstantInt::get(Type::Int1Ty, C1Val <= C2Val);
1166 case FCmpInst::FCMP_UGE:
1167 if (C1Val != C1Val || C2Val != C2Val)
1168 return ConstantInt::getTrue();
1170 case FCmpInst::FCMP_OGE:
1171 return ConstantInt::get(Type::Int1Ty, C1Val >= C2Val);
1173 } else if (const ConstantVector *CP1 = dyn_cast<ConstantVector>(C1)) {
1174 if (const ConstantVector *CP2 = dyn_cast<ConstantVector>(C2)) {
1175 if (pred == FCmpInst::FCMP_OEQ || pred == FCmpInst::FCMP_UEQ) {
1176 for (unsigned i = 0, e = CP1->getNumOperands(); i != e; ++i) {
1177 Constant *C= ConstantExpr::getFCmp(FCmpInst::FCMP_OEQ,
1178 const_cast<Constant*>(CP1->getOperand(i)),
1179 const_cast<Constant*>(CP2->getOperand(i)));
1180 if (ConstantInt *CB = dyn_cast<ConstantInt>(C))
1183 // Otherwise, could not decide from any element pairs.
1185 } else if (pred == ICmpInst::ICMP_EQ) {
1186 for (unsigned i = 0, e = CP1->getNumOperands(); i != e; ++i) {
1187 Constant *C = ConstantExpr::getICmp(ICmpInst::ICMP_EQ,
1188 const_cast<Constant*>(CP1->getOperand(i)),
1189 const_cast<Constant*>(CP2->getOperand(i)));
1190 if (ConstantInt *CB = dyn_cast<ConstantInt>(C))
1193 // Otherwise, could not decide from any element pairs.
1199 if (C1->getType()->isFloatingPoint()) {
1200 switch (evaluateFCmpRelation(C1, C2)) {
1201 default: assert(0 && "Unknown relation!");
1202 case FCmpInst::FCMP_UNO:
1203 case FCmpInst::FCMP_ORD:
1204 case FCmpInst::FCMP_UEQ:
1205 case FCmpInst::FCMP_UNE:
1206 case FCmpInst::FCMP_ULT:
1207 case FCmpInst::FCMP_UGT:
1208 case FCmpInst::FCMP_ULE:
1209 case FCmpInst::FCMP_UGE:
1210 case FCmpInst::FCMP_TRUE:
1211 case FCmpInst::FCMP_FALSE:
1212 case FCmpInst::BAD_FCMP_PREDICATE:
1213 break; // Couldn't determine anything about these constants.
1214 case FCmpInst::FCMP_OEQ: // We know that C1 == C2
1215 return ConstantInt::get(Type::Int1Ty,
1216 pred == FCmpInst::FCMP_UEQ || pred == FCmpInst::FCMP_OEQ ||
1217 pred == FCmpInst::FCMP_ULE || pred == FCmpInst::FCMP_OLE ||
1218 pred == FCmpInst::FCMP_UGE || pred == FCmpInst::FCMP_OGE);
1219 case FCmpInst::FCMP_OLT: // We know that C1 < C2
1220 return ConstantInt::get(Type::Int1Ty,
1221 pred == FCmpInst::FCMP_UNE || pred == FCmpInst::FCMP_ONE ||
1222 pred == FCmpInst::FCMP_ULT || pred == FCmpInst::FCMP_OLT ||
1223 pred == FCmpInst::FCMP_ULE || pred == FCmpInst::FCMP_OLE);
1224 case FCmpInst::FCMP_OGT: // We know that C1 > C2
1225 return ConstantInt::get(Type::Int1Ty,
1226 pred == FCmpInst::FCMP_UNE || pred == FCmpInst::FCMP_ONE ||
1227 pred == FCmpInst::FCMP_UGT || pred == FCmpInst::FCMP_OGT ||
1228 pred == FCmpInst::FCMP_UGE || pred == FCmpInst::FCMP_OGE);
1229 case FCmpInst::FCMP_OLE: // We know that C1 <= C2
1230 // We can only partially decide this relation.
1231 if (pred == FCmpInst::FCMP_UGT || pred == FCmpInst::FCMP_OGT)
1232 return ConstantInt::getFalse();
1233 if (pred == FCmpInst::FCMP_ULT || pred == FCmpInst::FCMP_OLT)
1234 return ConstantInt::getTrue();
1236 case FCmpInst::FCMP_OGE: // We known that C1 >= C2
1237 // We can only partially decide this relation.
1238 if (pred == FCmpInst::FCMP_ULT || pred == FCmpInst::FCMP_OLT)
1239 return ConstantInt::getFalse();
1240 if (pred == FCmpInst::FCMP_UGT || pred == FCmpInst::FCMP_OGT)
1241 return ConstantInt::getTrue();
1243 case ICmpInst::ICMP_NE: // We know that C1 != C2
1244 // We can only partially decide this relation.
1245 if (pred == FCmpInst::FCMP_OEQ || pred == FCmpInst::FCMP_UEQ)
1246 return ConstantInt::getFalse();
1247 if (pred == FCmpInst::FCMP_ONE || pred == FCmpInst::FCMP_UNE)
1248 return ConstantInt::getTrue();
1252 // Evaluate the relation between the two constants, per the predicate.
1253 switch (evaluateICmpRelation(C1, C2, CmpInst::isSigned(pred))) {
1254 default: assert(0 && "Unknown relational!");
1255 case ICmpInst::BAD_ICMP_PREDICATE:
1256 break; // Couldn't determine anything about these constants.
1257 case ICmpInst::ICMP_EQ: // We know the constants are equal!
1258 // If we know the constants are equal, we can decide the result of this
1259 // computation precisely.
1260 return ConstantInt::get(Type::Int1Ty,
1261 pred == ICmpInst::ICMP_EQ ||
1262 pred == ICmpInst::ICMP_ULE ||
1263 pred == ICmpInst::ICMP_SLE ||
1264 pred == ICmpInst::ICMP_UGE ||
1265 pred == ICmpInst::ICMP_SGE);
1266 case ICmpInst::ICMP_ULT:
1267 // If we know that C1 < C2, we can decide the result of this computation
1269 return ConstantInt::get(Type::Int1Ty,
1270 pred == ICmpInst::ICMP_ULT ||
1271 pred == ICmpInst::ICMP_NE ||
1272 pred == ICmpInst::ICMP_ULE);
1273 case ICmpInst::ICMP_SLT:
1274 // If we know that C1 < C2, we can decide the result of this computation
1276 return ConstantInt::get(Type::Int1Ty,
1277 pred == ICmpInst::ICMP_SLT ||
1278 pred == ICmpInst::ICMP_NE ||
1279 pred == ICmpInst::ICMP_SLE);
1280 case ICmpInst::ICMP_UGT:
1281 // If we know that C1 > C2, we can decide the result of this computation
1283 return ConstantInt::get(Type::Int1Ty,
1284 pred == ICmpInst::ICMP_UGT ||
1285 pred == ICmpInst::ICMP_NE ||
1286 pred == ICmpInst::ICMP_UGE);
1287 case ICmpInst::ICMP_SGT:
1288 // If we know that C1 > C2, we can decide the result of this computation
1290 return ConstantInt::get(Type::Int1Ty,
1291 pred == ICmpInst::ICMP_SGT ||
1292 pred == ICmpInst::ICMP_NE ||
1293 pred == ICmpInst::ICMP_SGE);
1294 case ICmpInst::ICMP_ULE:
1295 // If we know that C1 <= C2, we can only partially decide this relation.
1296 if (pred == ICmpInst::ICMP_UGT) return ConstantInt::getFalse();
1297 if (pred == ICmpInst::ICMP_ULT) return ConstantInt::getTrue();
1299 case ICmpInst::ICMP_SLE:
1300 // If we know that C1 <= C2, we can only partially decide this relation.
1301 if (pred == ICmpInst::ICMP_SGT) return ConstantInt::getFalse();
1302 if (pred == ICmpInst::ICMP_SLT) return ConstantInt::getTrue();
1305 case ICmpInst::ICMP_UGE:
1306 // If we know that C1 >= C2, we can only partially decide this relation.
1307 if (pred == ICmpInst::ICMP_ULT) return ConstantInt::getFalse();
1308 if (pred == ICmpInst::ICMP_UGT) return ConstantInt::getTrue();
1310 case ICmpInst::ICMP_SGE:
1311 // If we know that C1 >= C2, we can only partially decide this relation.
1312 if (pred == ICmpInst::ICMP_SLT) return ConstantInt::getFalse();
1313 if (pred == ICmpInst::ICMP_SGT) return ConstantInt::getTrue();
1316 case ICmpInst::ICMP_NE:
1317 // If we know that C1 != C2, we can only partially decide this relation.
1318 if (pred == ICmpInst::ICMP_EQ) return ConstantInt::getFalse();
1319 if (pred == ICmpInst::ICMP_NE) return ConstantInt::getTrue();
1323 if (!isa<ConstantExpr>(C1) && isa<ConstantExpr>(C2)) {
1324 // If C2 is a constant expr and C1 isn't, flop them around and fold the
1325 // other way if possible.
1327 case ICmpInst::ICMP_EQ:
1328 case ICmpInst::ICMP_NE:
1329 // No change of predicate required.
1330 return ConstantFoldCompareInstruction(pred, C2, C1);
1332 case ICmpInst::ICMP_ULT:
1333 case ICmpInst::ICMP_SLT:
1334 case ICmpInst::ICMP_UGT:
1335 case ICmpInst::ICMP_SGT:
1336 case ICmpInst::ICMP_ULE:
1337 case ICmpInst::ICMP_SLE:
1338 case ICmpInst::ICMP_UGE:
1339 case ICmpInst::ICMP_SGE:
1340 // Change the predicate as necessary to swap the operands.
1341 pred = ICmpInst::getSwappedPredicate((ICmpInst::Predicate)pred);
1342 return ConstantFoldCompareInstruction(pred, C2, C1);
1344 default: // These predicates cannot be flopped around.
1352 Constant *llvm::ConstantFoldGetElementPtr(const Constant *C,
1353 Constant* const *Idxs,
1356 (NumIdx == 1 && Idxs[0]->isNullValue()))
1357 return const_cast<Constant*>(C);
1359 if (isa<UndefValue>(C)) {
1360 const Type *Ty = GetElementPtrInst::getIndexedType(C->getType(),
1361 (Value**)Idxs, NumIdx,
1363 assert(Ty != 0 && "Invalid indices for GEP!");
1364 return UndefValue::get(PointerType::get(Ty));
1367 Constant *Idx0 = Idxs[0];
1368 if (C->isNullValue()) {
1370 for (unsigned i = 0, e = NumIdx; i != e; ++i)
1371 if (!Idxs[i]->isNullValue()) {
1376 const Type *Ty = GetElementPtrInst::getIndexedType(C->getType(),
1377 (Value**)Idxs, NumIdx,
1379 assert(Ty != 0 && "Invalid indices for GEP!");
1380 return ConstantPointerNull::get(PointerType::get(Ty));
1384 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(const_cast<Constant*>(C))) {
1385 // Combine Indices - If the source pointer to this getelementptr instruction
1386 // is a getelementptr instruction, combine the indices of the two
1387 // getelementptr instructions into a single instruction.
1389 if (CE->getOpcode() == Instruction::GetElementPtr) {
1390 const Type *LastTy = 0;
1391 for (gep_type_iterator I = gep_type_begin(CE), E = gep_type_end(CE);
1395 if ((LastTy && isa<ArrayType>(LastTy)) || Idx0->isNullValue()) {
1396 SmallVector<Value*, 16> NewIndices;
1397 NewIndices.reserve(NumIdx + CE->getNumOperands());
1398 for (unsigned i = 1, e = CE->getNumOperands()-1; i != e; ++i)
1399 NewIndices.push_back(CE->getOperand(i));
1401 // Add the last index of the source with the first index of the new GEP.
1402 // Make sure to handle the case when they are actually different types.
1403 Constant *Combined = CE->getOperand(CE->getNumOperands()-1);
1404 // Otherwise it must be an array.
1405 if (!Idx0->isNullValue()) {
1406 const Type *IdxTy = Combined->getType();
1407 if (IdxTy != Idx0->getType()) {
1408 Constant *C1 = ConstantExpr::getSExtOrBitCast(Idx0, Type::Int64Ty);
1409 Constant *C2 = ConstantExpr::getSExtOrBitCast(Combined,
1411 Combined = ConstantExpr::get(Instruction::Add, C1, C2);
1414 ConstantExpr::get(Instruction::Add, Idx0, Combined);
1418 NewIndices.push_back(Combined);
1419 NewIndices.insert(NewIndices.end(), Idxs+1, Idxs+NumIdx);
1420 return ConstantExpr::getGetElementPtr(CE->getOperand(0), &NewIndices[0],
1425 // Implement folding of:
1426 // int* getelementptr ([2 x int]* cast ([3 x int]* %X to [2 x int]*),
1428 // To: int* getelementptr ([3 x int]* %X, long 0, long 0)
1430 if (CE->isCast() && NumIdx > 1 && Idx0->isNullValue()) {
1431 if (const PointerType *SPT =
1432 dyn_cast<PointerType>(CE->getOperand(0)->getType()))
1433 if (const ArrayType *SAT = dyn_cast<ArrayType>(SPT->getElementType()))
1434 if (const ArrayType *CAT =
1435 dyn_cast<ArrayType>(cast<PointerType>(C->getType())->getElementType()))
1436 if (CAT->getElementType() == SAT->getElementType())
1437 return ConstantExpr::getGetElementPtr(
1438 (Constant*)CE->getOperand(0), Idxs, NumIdx);
1441 // Fold: getelementptr (i8* inttoptr (i64 1 to i8*), i32 -1)
1442 // Into: inttoptr (i64 0 to i8*)
1443 // This happens with pointers to member functions in C++.
1444 if (CE->getOpcode() == Instruction::IntToPtr && NumIdx == 1 &&
1445 isa<ConstantInt>(CE->getOperand(0)) && isa<ConstantInt>(Idxs[0]) &&
1446 cast<PointerType>(CE->getType())->getElementType() == Type::Int8Ty) {
1447 Constant *Base = CE->getOperand(0);
1448 Constant *Offset = Idxs[0];
1450 // Convert the smaller integer to the larger type.
1451 if (Offset->getType()->getPrimitiveSizeInBits() <
1452 Base->getType()->getPrimitiveSizeInBits())
1453 Offset = ConstantExpr::getSExt(Offset, Base->getType());
1454 else if (Base->getType()->getPrimitiveSizeInBits() <
1455 Offset->getType()->getPrimitiveSizeInBits())
1456 Base = ConstantExpr::getZExt(Base, Base->getType());
1458 Base = ConstantExpr::getAdd(Base, Offset);
1459 return ConstantExpr::getIntToPtr(Base, CE->getType());