1 //===- ConstantFold.cpp - LLVM constant folder ----------------------------===//
2 //
3 // The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
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.
13 //
14 // The current constant folding implementation is implemented in two pieces: the
15 // pieces that don't need DataLayout, and the pieces that do. This is to avoid
16 // a dependence in IR on Target.
17 //
18 //===----------------------------------------------------------------------===//
20 #include "ConstantFold.h"
21 #include "llvm/ADT/SmallVector.h"
22 #include "llvm/IR/Constants.h"
23 #include "llvm/IR/DerivedTypes.h"
24 #include "llvm/IR/Function.h"
25 #include "llvm/IR/GlobalAlias.h"
26 #include "llvm/IR/GlobalVariable.h"
27 #include "llvm/IR/Instructions.h"
28 #include "llvm/IR/Operator.h"
29 #include "llvm/Support/Compiler.h"
30 #include "llvm/Support/ErrorHandling.h"
31 #include "llvm/Support/GetElementPtrTypeIterator.h"
32 #include "llvm/Support/ManagedStatic.h"
33 #include "llvm/Support/MathExtras.h"
34 #include <limits>
35 using namespace llvm;
37 //===----------------------------------------------------------------------===//
38 // ConstantFold*Instruction Implementations
39 //===----------------------------------------------------------------------===//
41 /// BitCastConstantVector - Convert the specified vector Constant node to the
42 /// specified vector type. At this point, we know that the elements of the
43 /// input vector constant are all simple integer or FP values.
44 static Constant *BitCastConstantVector(Constant *CV, VectorType *DstTy) {
46 if (CV->isAllOnesValue()) return Constant::getAllOnesValue(DstTy);
47 if (CV->isNullValue()) return Constant::getNullValue(DstTy);
49 // If this cast changes element count then we can't handle it here:
50 // doing so requires endianness information. This should be handled by
51 // Analysis/ConstantFolding.cpp
52 unsigned NumElts = DstTy->getNumElements();
53 if (NumElts != CV->getType()->getVectorNumElements())
54 return 0;
56 Type *DstEltTy = DstTy->getElementType();
58 SmallVector<Constant*, 16> Result;
59 Type *Ty = IntegerType::get(CV->getContext(), 32);
60 for (unsigned i = 0; i != NumElts; ++i) {
61 Constant *C =
62 ConstantExpr::getExtractElement(CV, ConstantInt::get(Ty, i));
63 C = ConstantExpr::getBitCast(C, DstEltTy);
64 Result.push_back(C);
65 }
67 return ConstantVector::get(Result);
68 }
70 /// This function determines which opcode to use to fold two constant cast
71 /// expressions together. It uses CastInst::isEliminableCastPair to determine
72 /// the opcode. Consequently its just a wrapper around that function.
73 /// @brief Determine if it is valid to fold a cast of a cast
74 static unsigned
75 foldConstantCastPair(
76 unsigned opc, ///< opcode of the second cast constant expression
77 ConstantExpr *Op, ///< the first cast constant expression
78 Type *DstTy ///< destination type of the first cast
79 ) {
80 assert(Op && Op->isCast() && "Can't fold cast of cast without a cast!");
81 assert(DstTy && DstTy->isFirstClassType() && "Invalid cast destination type");
82 assert(CastInst::isCast(opc) && "Invalid cast opcode");
84 // The the types and opcodes for the two Cast constant expressions
85 Type *SrcTy = Op->getOperand(0)->getType();
86 Type *MidTy = Op->getType();
87 Instruction::CastOps firstOp = Instruction::CastOps(Op->getOpcode());
88 Instruction::CastOps secondOp = Instruction::CastOps(opc);
90 // Assume that pointers are never more than 64 bits wide, and only use this
91 // for the middle type. Otherwise we could end up folding away illegal
92 // bitcasts between address spaces with different sizes.
93 IntegerType *FakeIntPtrTy = Type::getInt64Ty(DstTy->getContext());
95 // Let CastInst::isEliminableCastPair do the heavy lifting.
96 return CastInst::isEliminableCastPair(firstOp, secondOp, SrcTy, MidTy, DstTy,
97 0, FakeIntPtrTy, 0);
98 }
100 static Constant *FoldBitCast(Constant *V, Type *DestTy) {
101 Type *SrcTy = V->getType();
102 if (SrcTy == DestTy)
103 return V; // no-op cast
105 // Check to see if we are casting a pointer to an aggregate to a pointer to
106 // the first element. If so, return the appropriate GEP instruction.
107 if (PointerType *PTy = dyn_cast<PointerType>(V->getType()))
108 if (PointerType *DPTy = dyn_cast<PointerType>(DestTy))
109 if (PTy->getAddressSpace() == DPTy->getAddressSpace()
110 && DPTy->getElementType()->isSized()) {
111 SmallVector<Value*, 8> IdxList;
112 Value *Zero =
113 Constant::getNullValue(Type::getInt32Ty(DPTy->getContext()));
114 IdxList.push_back(Zero);
115 Type *ElTy = PTy->getElementType();
116 while (ElTy != DPTy->getElementType()) {
117 if (StructType *STy = dyn_cast<StructType>(ElTy)) {
118 if (STy->getNumElements() == 0) break;
119 ElTy = STy->getElementType(0);
120 IdxList.push_back(Zero);
121 } else if (SequentialType *STy =
122 dyn_cast<SequentialType>(ElTy)) {
123 if (ElTy->isPointerTy()) break; // Can't index into pointers!
124 ElTy = STy->getElementType();
125 IdxList.push_back(Zero);
126 } else {
127 break;
128 }
129 }
131 if (ElTy == DPTy->getElementType())
132 // This GEP is inbounds because all indices are zero.
133 return ConstantExpr::getInBoundsGetElementPtr(V, IdxList);
134 }
136 // Handle casts from one vector constant to another. We know that the src
137 // and dest type have the same size (otherwise its an illegal cast).
138 if (VectorType *DestPTy = dyn_cast<VectorType>(DestTy)) {
139 if (VectorType *SrcTy = dyn_cast<VectorType>(V->getType())) {
140 assert(DestPTy->getBitWidth() == SrcTy->getBitWidth() &&
141 "Not cast between same sized vectors!");
142 SrcTy = NULL;
143 // First, check for null. Undef is already handled.
144 if (isa<ConstantAggregateZero>(V))
145 return Constant::getNullValue(DestTy);
147 // Handle ConstantVector and ConstantAggregateVector.
148 return BitCastConstantVector(V, DestPTy);
149 }
151 // Canonicalize scalar-to-vector bitcasts into vector-to-vector bitcasts
152 // This allows for other simplifications (although some of them
153 // can only be handled by Analysis/ConstantFolding.cpp).
154 if (isa<ConstantInt>(V) || isa<ConstantFP>(V))
155 return ConstantExpr::getBitCast(ConstantVector::get(V), DestPTy);
156 }
158 // Finally, implement bitcast folding now. The code below doesn't handle
159 // bitcast right.
160 if (isa<ConstantPointerNull>(V)) // ptr->ptr cast.
161 return ConstantPointerNull::get(cast<PointerType>(DestTy));
163 // Handle integral constant input.
164 if (ConstantInt *CI = dyn_cast<ConstantInt>(V)) {
165 if (DestTy->isIntegerTy())
166 // Integral -> Integral. This is a no-op because the bit widths must
167 // be the same. Consequently, we just fold to V.
168 return V;
170 if (DestTy->isFloatingPointTy())
171 return ConstantFP::get(DestTy->getContext(),
172 APFloat(DestTy->getFltSemantics(),
173 CI->getValue()));
175 // Otherwise, can't fold this (vector?)
176 return 0;
177 }
179 // Handle ConstantFP input: FP -> Integral.
180 if (ConstantFP *FP = dyn_cast<ConstantFP>(V))
181 return ConstantInt::get(FP->getContext(),
182 FP->getValueAPF().bitcastToAPInt());
184 return 0;
185 }
188 /// ExtractConstantBytes - V is an integer constant which only has a subset of
189 /// its bytes used. The bytes used are indicated by ByteStart (which is the
190 /// first byte used, counting from the least significant byte) and ByteSize,
191 /// which is the number of bytes used.
192 ///
193 /// This function analyzes the specified constant to see if the specified byte
194 /// range can be returned as a simplified constant. If so, the constant is
195 /// returned, otherwise null is returned.
196 ///
197 static Constant *ExtractConstantBytes(Constant *C, unsigned ByteStart,
198 unsigned ByteSize) {
199 assert(C->getType()->isIntegerTy() &&
200 (cast<IntegerType>(C->getType())->getBitWidth() & 7) == 0 &&
201 "Non-byte sized integer input");
202 unsigned CSize = cast<IntegerType>(C->getType())->getBitWidth()/8;
203 assert(ByteSize && "Must be accessing some piece");
204 assert(ByteStart+ByteSize <= CSize && "Extracting invalid piece from input");
205 assert(ByteSize != CSize && "Should not extract everything");
207 // Constant Integers are simple.
208 if (ConstantInt *CI = dyn_cast<ConstantInt>(C)) {
209 APInt V = CI->getValue();
210 if (ByteStart)
211 V = V.lshr(ByteStart*8);
212 V = V.trunc(ByteSize*8);
213 return ConstantInt::get(CI->getContext(), V);
214 }
216 // In the input is a constant expr, we might be able to recursively simplify.
217 // If not, we definitely can't do anything.
218 ConstantExpr *CE = dyn_cast<ConstantExpr>(C);
219 if (CE == 0) return 0;
221 switch (CE->getOpcode()) {
222 default: return 0;
223 case Instruction::Or: {
224 Constant *RHS = ExtractConstantBytes(CE->getOperand(1), ByteStart,ByteSize);
225 if (RHS == 0)
226 return 0;
228 // X | -1 -> -1.
229 if (ConstantInt *RHSC = dyn_cast<ConstantInt>(RHS))
230 if (RHSC->isAllOnesValue())
231 return RHSC;
233 Constant *LHS = ExtractConstantBytes(CE->getOperand(0), ByteStart,ByteSize);
234 if (LHS == 0)
235 return 0;
236 return ConstantExpr::getOr(LHS, RHS);
237 }
238 case Instruction::And: {
239 Constant *RHS = ExtractConstantBytes(CE->getOperand(1), ByteStart,ByteSize);
240 if (RHS == 0)
241 return 0;
243 // X & 0 -> 0.
244 if (RHS->isNullValue())
245 return RHS;
247 Constant *LHS = ExtractConstantBytes(CE->getOperand(0), ByteStart,ByteSize);
248 if (LHS == 0)
249 return 0;
250 return ConstantExpr::getAnd(LHS, RHS);
251 }
252 case Instruction::LShr: {
253 ConstantInt *Amt = dyn_cast<ConstantInt>(CE->getOperand(1));
254 if (Amt == 0)
255 return 0;
256 unsigned ShAmt = Amt->getZExtValue();
257 // Cannot analyze non-byte shifts.
258 if ((ShAmt & 7) != 0)
259 return 0;
260 ShAmt >>= 3;
262 // If the extract is known to be all zeros, return zero.
263 if (ByteStart >= CSize-ShAmt)
264 return Constant::getNullValue(IntegerType::get(CE->getContext(),
265 ByteSize*8));
266 // If the extract is known to be fully in the input, extract it.
267 if (ByteStart+ByteSize+ShAmt <= CSize)
268 return ExtractConstantBytes(CE->getOperand(0), ByteStart+ShAmt, ByteSize);
270 // TODO: Handle the 'partially zero' case.
271 return 0;
272 }
274 case Instruction::Shl: {
275 ConstantInt *Amt = dyn_cast<ConstantInt>(CE->getOperand(1));
276 if (Amt == 0)
277 return 0;
278 unsigned ShAmt = Amt->getZExtValue();
279 // Cannot analyze non-byte shifts.
280 if ((ShAmt & 7) != 0)
281 return 0;
282 ShAmt >>= 3;
284 // If the extract is known to be all zeros, return zero.
285 if (ByteStart+ByteSize <= ShAmt)
286 return Constant::getNullValue(IntegerType::get(CE->getContext(),
287 ByteSize*8));
288 // If the extract is known to be fully in the input, extract it.
289 if (ByteStart >= ShAmt)
290 return ExtractConstantBytes(CE->getOperand(0), ByteStart-ShAmt, ByteSize);
292 // TODO: Handle the 'partially zero' case.
293 return 0;
294 }
296 case Instruction::ZExt: {
297 unsigned SrcBitSize =
298 cast<IntegerType>(CE->getOperand(0)->getType())->getBitWidth();
300 // If extracting something that is completely zero, return 0.
301 if (ByteStart*8 >= SrcBitSize)
302 return Constant::getNullValue(IntegerType::get(CE->getContext(),
303 ByteSize*8));
305 // If exactly extracting the input, return it.
306 if (ByteStart == 0 && ByteSize*8 == SrcBitSize)
307 return CE->getOperand(0);
309 // If extracting something completely in the input, if if the input is a
310 // multiple of 8 bits, recurse.
311 if ((SrcBitSize&7) == 0 && (ByteStart+ByteSize)*8 <= SrcBitSize)
312 return ExtractConstantBytes(CE->getOperand(0), ByteStart, ByteSize);
314 // Otherwise, if extracting a subset of the input, which is not multiple of
315 // 8 bits, do a shift and trunc to get the bits.
316 if ((ByteStart+ByteSize)*8 < SrcBitSize) {
317 assert((SrcBitSize&7) && "Shouldn't get byte sized case here");
318 Constant *Res = CE->getOperand(0);
319 if (ByteStart)
320 Res = ConstantExpr::getLShr(Res,
321 ConstantInt::get(Res->getType(), ByteStart*8));
322 return ConstantExpr::getTrunc(Res, IntegerType::get(C->getContext(),
323 ByteSize*8));
324 }
326 // TODO: Handle the 'partially zero' case.
327 return 0;
328 }
329 }
330 }
332 /// getFoldedSizeOf - Return a ConstantExpr with type DestTy for sizeof
333 /// on Ty, with any known factors factored out. If Folded is false,
334 /// return null if no factoring was possible, to avoid endlessly
335 /// bouncing an unfoldable expression back into the top-level folder.
336 ///
337 static Constant *getFoldedSizeOf(Type *Ty, Type *DestTy,
338 bool Folded) {
339 if (ArrayType *ATy = dyn_cast<ArrayType>(Ty)) {
340 Constant *N = ConstantInt::get(DestTy, ATy->getNumElements());
341 Constant *E = getFoldedSizeOf(ATy->getElementType(), DestTy, true);
342 return ConstantExpr::getNUWMul(E, N);
343 }
345 if (StructType *STy = dyn_cast<StructType>(Ty))
346 if (!STy->isPacked()) {
347 unsigned NumElems = STy->getNumElements();
348 // An empty struct has size zero.
349 if (NumElems == 0)
350 return ConstantExpr::getNullValue(DestTy);
351 // Check for a struct with all members having the same size.
352 Constant *MemberSize =
353 getFoldedSizeOf(STy->getElementType(0), DestTy, true);
354 bool AllSame = true;
355 for (unsigned i = 1; i != NumElems; ++i)
356 if (MemberSize !=
357 getFoldedSizeOf(STy->getElementType(i), DestTy, true)) {
358 AllSame = false;
359 break;
360 }
361 if (AllSame) {
362 Constant *N = ConstantInt::get(DestTy, NumElems);
363 return ConstantExpr::getNUWMul(MemberSize, N);
364 }
365 }
367 // Pointer size doesn't depend on the pointee type, so canonicalize them
368 // to an arbitrary pointee.
369 if (PointerType *PTy = dyn_cast<PointerType>(Ty))
370 if (!PTy->getElementType()->isIntegerTy(1))
371 return
372 getFoldedSizeOf(PointerType::get(IntegerType::get(PTy->getContext(), 1),
373 PTy->getAddressSpace()),
374 DestTy, true);
376 // If there's no interesting folding happening, bail so that we don't create
377 // a constant that looks like it needs folding but really doesn't.
378 if (!Folded)
379 return 0;
381 // Base case: Get a regular sizeof expression.
382 Constant *C = ConstantExpr::getSizeOf(Ty);
383 C = ConstantExpr::getCast(CastInst::getCastOpcode(C, false,
384 DestTy, false),
385 C, DestTy);
386 return C;
387 }
389 /// getFoldedAlignOf - Return a ConstantExpr with type DestTy for alignof
390 /// on Ty, with any known factors factored out. If Folded is false,
391 /// return null if no factoring was possible, to avoid endlessly
392 /// bouncing an unfoldable expression back into the top-level folder.
393 ///
394 static Constant *getFoldedAlignOf(Type *Ty, Type *DestTy,
395 bool Folded) {
396 // The alignment of an array is equal to the alignment of the
397 // array element. Note that this is not always true for vectors.
398 if (ArrayType *ATy = dyn_cast<ArrayType>(Ty)) {
399 Constant *C = ConstantExpr::getAlignOf(ATy->getElementType());
400 C = ConstantExpr::getCast(CastInst::getCastOpcode(C, false,
401 DestTy,
402 false),
403 C, DestTy);
404 return C;
405 }
407 if (StructType *STy = dyn_cast<StructType>(Ty)) {
408 // Packed structs always have an alignment of 1.
409 if (STy->isPacked())
410 return ConstantInt::get(DestTy, 1);
412 // Otherwise, struct alignment is the maximum alignment of any member.
413 // Without target data, we can't compare much, but we can check to see
414 // if all the members have the same alignment.
415 unsigned NumElems = STy->getNumElements();
416 // An empty struct has minimal alignment.
417 if (NumElems == 0)
418 return ConstantInt::get(DestTy, 1);
419 // Check for a struct with all members having the same alignment.
420 Constant *MemberAlign =
421 getFoldedAlignOf(STy->getElementType(0), DestTy, true);
422 bool AllSame = true;
423 for (unsigned i = 1; i != NumElems; ++i)
424 if (MemberAlign != getFoldedAlignOf(STy->getElementType(i), DestTy, true)) {
425 AllSame = false;
426 break;
427 }
428 if (AllSame)
429 return MemberAlign;
430 }
432 // Pointer alignment doesn't depend on the pointee type, so canonicalize them
433 // to an arbitrary pointee.
434 if (PointerType *PTy = dyn_cast<PointerType>(Ty))
435 if (!PTy->getElementType()->isIntegerTy(1))
436 return
437 getFoldedAlignOf(PointerType::get(IntegerType::get(PTy->getContext(),
438 1),
439 PTy->getAddressSpace()),
440 DestTy, true);
442 // If there's no interesting folding happening, bail so that we don't create
443 // a constant that looks like it needs folding but really doesn't.
444 if (!Folded)
445 return 0;
447 // Base case: Get a regular alignof expression.
448 Constant *C = ConstantExpr::getAlignOf(Ty);
449 C = ConstantExpr::getCast(CastInst::getCastOpcode(C, false,
450 DestTy, false),
451 C, DestTy);
452 return C;
453 }
455 /// getFoldedOffsetOf - Return a ConstantExpr with type DestTy for offsetof
456 /// on Ty and FieldNo, with any known factors factored out. If Folded is false,
457 /// return null if no factoring was possible, to avoid endlessly
458 /// bouncing an unfoldable expression back into the top-level folder.
459 ///
460 static Constant *getFoldedOffsetOf(Type *Ty, Constant *FieldNo,
461 Type *DestTy,
462 bool Folded) {
463 if (ArrayType *ATy = dyn_cast<ArrayType>(Ty)) {
464 Constant *N = ConstantExpr::getCast(CastInst::getCastOpcode(FieldNo, false,
465 DestTy, false),
466 FieldNo, DestTy);
467 Constant *E = getFoldedSizeOf(ATy->getElementType(), DestTy, true);
468 return ConstantExpr::getNUWMul(E, N);
469 }
471 if (StructType *STy = dyn_cast<StructType>(Ty))
472 if (!STy->isPacked()) {
473 unsigned NumElems = STy->getNumElements();
474 // An empty struct has no members.
475 if (NumElems == 0)
476 return 0;
477 // Check for a struct with all members having the same size.
478 Constant *MemberSize =
479 getFoldedSizeOf(STy->getElementType(0), DestTy, true);
480 bool AllSame = true;
481 for (unsigned i = 1; i != NumElems; ++i)
482 if (MemberSize !=
483 getFoldedSizeOf(STy->getElementType(i), DestTy, true)) {
484 AllSame = false;
485 break;
486 }
487 if (AllSame) {
488 Constant *N = ConstantExpr::getCast(CastInst::getCastOpcode(FieldNo,
489 false,
490 DestTy,
491 false),
492 FieldNo, DestTy);
493 return ConstantExpr::getNUWMul(MemberSize, N);
494 }
495 }
497 // If there's no interesting folding happening, bail so that we don't create
498 // a constant that looks like it needs folding but really doesn't.
499 if (!Folded)
500 return 0;
502 // Base case: Get a regular offsetof expression.
503 Constant *C = ConstantExpr::getOffsetOf(Ty, FieldNo);
504 C = ConstantExpr::getCast(CastInst::getCastOpcode(C, false,
505 DestTy, false),
506 C, DestTy);
507 return C;
508 }
510 Constant *llvm::ConstantFoldCastInstruction(unsigned opc, Constant *V,
511 Type *DestTy) {
512 if (isa<UndefValue>(V)) {
513 // zext(undef) = 0, because the top bits will be zero.
514 // sext(undef) = 0, because the top bits will all be the same.
515 // [us]itofp(undef) = 0, because the result value is bounded.
516 if (opc == Instruction::ZExt || opc == Instruction::SExt ||
517 opc == Instruction::UIToFP || opc == Instruction::SIToFP)
518 return Constant::getNullValue(DestTy);
519 return UndefValue::get(DestTy);
520 }
522 if (V->isNullValue() && !DestTy->isX86_MMXTy())
523 return Constant::getNullValue(DestTy);
525 // If the cast operand is a constant expression, there's a few things we can
526 // do to try to simplify it.
527 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V)) {
528 if (CE->isCast()) {
529 // Try hard to fold cast of cast because they are often eliminable.
530 if (unsigned newOpc = foldConstantCastPair(opc, CE, DestTy))
531 return ConstantExpr::getCast(newOpc, CE->getOperand(0), DestTy);
532 } else if (CE->getOpcode() == Instruction::GetElementPtr) {
533 // If all of the indexes in the GEP are null values, there is no pointer
534 // adjustment going on. We might as well cast the source pointer.
535 bool isAllNull = true;
536 for (unsigned i = 1, e = CE->getNumOperands(); i != e; ++i)
537 if (!CE->getOperand(i)->isNullValue()) {
538 isAllNull = false;
539 break;
540 }
541 if (isAllNull)
542 // This is casting one pointer type to another, always BitCast
543 return ConstantExpr::getPointerCast(CE->getOperand(0), DestTy);
544 }
545 }
547 // If the cast operand is a constant vector, perform the cast by
548 // operating on each element. In the cast of bitcasts, the element
549 // count may be mismatched; don't attempt to handle that here.
550 if ((isa<ConstantVector>(V) || isa<ConstantDataVector>(V)) &&
551 DestTy->isVectorTy() &&
552 DestTy->getVectorNumElements() == V->getType()->getVectorNumElements()) {
553 SmallVector<Constant*, 16> res;
554 VectorType *DestVecTy = cast<VectorType>(DestTy);
555 Type *DstEltTy = DestVecTy->getElementType();
556 Type *Ty = IntegerType::get(V->getContext(), 32);
557 for (unsigned i = 0, e = V->getType()->getVectorNumElements(); i != e; ++i) {
558 Constant *C =
559 ConstantExpr::getExtractElement(V, ConstantInt::get(Ty, i));
560 res.push_back(ConstantExpr::getCast(opc, C, DstEltTy));
561 }
562 return ConstantVector::get(res);
563 }
565 // We actually have to do a cast now. Perform the cast according to the
566 // opcode specified.
567 switch (opc) {
568 default:
569 llvm_unreachable("Failed to cast constant expression");
570 case Instruction::FPTrunc:
571 case Instruction::FPExt:
572 if (ConstantFP *FPC = dyn_cast<ConstantFP>(V)) {
573 bool ignored;
574 APFloat Val = FPC->getValueAPF();
575 Val.convert(DestTy->isHalfTy() ? APFloat::IEEEhalf :
576 DestTy->isFloatTy() ? APFloat::IEEEsingle :
577 DestTy->isDoubleTy() ? APFloat::IEEEdouble :
578 DestTy->isX86_FP80Ty() ? APFloat::x87DoubleExtended :
579 DestTy->isFP128Ty() ? APFloat::IEEEquad :
580 DestTy->isPPC_FP128Ty() ? APFloat::PPCDoubleDouble :
581 APFloat::Bogus,
582 APFloat::rmNearestTiesToEven, &ignored);
583 return ConstantFP::get(V->getContext(), Val);
584 }
585 return 0; // Can't fold.
586 case Instruction::FPToUI:
587 case Instruction::FPToSI:
588 if (ConstantFP *FPC = dyn_cast<ConstantFP>(V)) {
589 const APFloat &V = FPC->getValueAPF();
590 bool ignored;
591 uint64_t x[2];
592 uint32_t DestBitWidth = cast<IntegerType>(DestTy)->getBitWidth();
593 (void) V.convertToInteger(x, DestBitWidth, opc==Instruction::FPToSI,
594 APFloat::rmTowardZero, &ignored);
595 APInt Val(DestBitWidth, x);
596 return ConstantInt::get(FPC->getContext(), Val);
597 }
598 return 0; // Can't fold.
599 case Instruction::IntToPtr: //always treated as unsigned
600 if (V->isNullValue()) // Is it an integral null value?
601 return ConstantPointerNull::get(cast<PointerType>(DestTy));
602 return 0; // Other pointer types cannot be casted
603 case Instruction::PtrToInt: // always treated as unsigned
604 // Is it a null pointer value?
605 if (V->isNullValue())
606 return ConstantInt::get(DestTy, 0);
607 // If this is a sizeof-like expression, pull out multiplications by
608 // known factors to expose them to subsequent folding. If it's an
609 // alignof-like expression, factor out known factors.
610 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V))
611 if (CE->getOpcode() == Instruction::GetElementPtr &&
612 CE->getOperand(0)->isNullValue()) {
613 Type *Ty =
614 cast<PointerType>(CE->getOperand(0)->getType())->getElementType();
615 if (CE->getNumOperands() == 2) {
616 // Handle a sizeof-like expression.
617 Constant *Idx = CE->getOperand(1);
618 bool isOne = isa<ConstantInt>(Idx) && cast<ConstantInt>(Idx)->isOne();
619 if (Constant *C = getFoldedSizeOf(Ty, DestTy, !isOne)) {
620 Idx = ConstantExpr::getCast(CastInst::getCastOpcode(Idx, true,
621 DestTy, false),
622 Idx, DestTy);
623 return ConstantExpr::getMul(C, Idx);
624 }
625 } else if (CE->getNumOperands() == 3 &&
626 CE->getOperand(1)->isNullValue()) {
627 // Handle an alignof-like expression.
628 if (StructType *STy = dyn_cast<StructType>(Ty))
629 if (!STy->isPacked()) {
630 ConstantInt *CI = cast<ConstantInt>(CE->getOperand(2));
631 if (CI->isOne() &&
632 STy->getNumElements() == 2 &&
633 STy->getElementType(0)->isIntegerTy(1)) {
634 return getFoldedAlignOf(STy->getElementType(1), DestTy, false);
635 }
636 }
637 // Handle an offsetof-like expression.
638 if (Ty->isStructTy() || Ty->isArrayTy()) {
639 if (Constant *C = getFoldedOffsetOf(Ty, CE->getOperand(2),
640 DestTy, false))
641 return C;
642 }
643 }
644 }
645 // Other pointer types cannot be casted
646 return 0;
647 case Instruction::UIToFP:
648 case Instruction::SIToFP:
649 if (ConstantInt *CI = dyn_cast<ConstantInt>(V)) {
650 APInt api = CI->getValue();
651 APFloat apf(DestTy->getFltSemantics(),
652 APInt::getNullValue(DestTy->getPrimitiveSizeInBits()));
653 (void)apf.convertFromAPInt(api,
654 opc==Instruction::SIToFP,
655 APFloat::rmNearestTiesToEven);
656 return ConstantFP::get(V->getContext(), apf);
657 }
658 return 0;
659 case Instruction::ZExt:
660 if (ConstantInt *CI = dyn_cast<ConstantInt>(V)) {
661 uint32_t BitWidth = cast<IntegerType>(DestTy)->getBitWidth();
662 return ConstantInt::get(V->getContext(),
663 CI->getValue().zext(BitWidth));
664 }
665 return 0;
666 case Instruction::SExt:
667 if (ConstantInt *CI = dyn_cast<ConstantInt>(V)) {
668 uint32_t BitWidth = cast<IntegerType>(DestTy)->getBitWidth();
669 return ConstantInt::get(V->getContext(),
670 CI->getValue().sext(BitWidth));
671 }
672 return 0;
673 case Instruction::Trunc: {
674 uint32_t DestBitWidth = cast<IntegerType>(DestTy)->getBitWidth();
675 if (ConstantInt *CI = dyn_cast<ConstantInt>(V)) {
676 return ConstantInt::get(V->getContext(),
677 CI->getValue().trunc(DestBitWidth));
678 }
680 // The input must be a constantexpr. See if we can simplify this based on
681 // the bytes we are demanding. Only do this if the source and dest are an
682 // even multiple of a byte.
683 if ((DestBitWidth & 7) == 0 &&
684 (cast<IntegerType>(V->getType())->getBitWidth() & 7) == 0)
685 if (Constant *Res = ExtractConstantBytes(V, 0, DestBitWidth / 8))
686 return Res;
688 return 0;
689 }
690 case Instruction::BitCast:
691 return FoldBitCast(V, DestTy);
692 case Instruction::AddrSpaceCast:
693 return 0;
694 }
695 }
697 Constant *llvm::ConstantFoldSelectInstruction(Constant *Cond,
698 Constant *V1, Constant *V2) {
699 // Check for i1 and vector true/false conditions.
700 if (Cond->isNullValue()) return V2;
701 if (Cond->isAllOnesValue()) return V1;
703 // If the condition is a vector constant, fold the result elementwise.
704 if (ConstantVector *CondV = dyn_cast<ConstantVector>(Cond)) {
705 SmallVector<Constant*, 16> Result;
706 Type *Ty = IntegerType::get(CondV->getContext(), 32);
707 for (unsigned i = 0, e = V1->getType()->getVectorNumElements(); i != e;++i){
708 ConstantInt *Cond = dyn_cast<ConstantInt>(CondV->getOperand(i));
709 if (Cond == 0) break;
711 Constant *V = Cond->isNullValue() ? V2 : V1;
712 Constant *Res = ConstantExpr::getExtractElement(V, ConstantInt::get(Ty, i));
713 Result.push_back(Res);
714 }
716 // If we were able to build the vector, return it.
717 if (Result.size() == V1->getType()->getVectorNumElements())
718 return ConstantVector::get(Result);
719 }
721 if (isa<UndefValue>(Cond)) {
722 if (isa<UndefValue>(V1)) return V1;
723 return V2;
724 }
725 if (isa<UndefValue>(V1)) return V2;
726 if (isa<UndefValue>(V2)) return V1;
727 if (V1 == V2) return V1;
729 if (ConstantExpr *TrueVal = dyn_cast<ConstantExpr>(V1)) {
730 if (TrueVal->getOpcode() == Instruction::Select)
731 if (TrueVal->getOperand(0) == Cond)
732 return ConstantExpr::getSelect(Cond, TrueVal->getOperand(1), V2);
733 }
734 if (ConstantExpr *FalseVal = dyn_cast<ConstantExpr>(V2)) {
735 if (FalseVal->getOpcode() == Instruction::Select)
736 if (FalseVal->getOperand(0) == Cond)
737 return ConstantExpr::getSelect(Cond, V1, FalseVal->getOperand(2));
738 }
740 return 0;
741 }
743 Constant *llvm::ConstantFoldExtractElementInstruction(Constant *Val,
744 Constant *Idx) {
745 if (isa<UndefValue>(Val)) // ee(undef, x) -> undef
746 return UndefValue::get(Val->getType()->getVectorElementType());
747 if (Val->isNullValue()) // ee(zero, x) -> zero
748 return Constant::getNullValue(Val->getType()->getVectorElementType());
749 // ee({w,x,y,z}, undef) -> undef
750 if (isa<UndefValue>(Idx))
751 return UndefValue::get(Val->getType()->getVectorElementType());
753 if (ConstantInt *CIdx = dyn_cast<ConstantInt>(Idx)) {
754 uint64_t Index = CIdx->getZExtValue();
755 // ee({w,x,y,z}, wrong_value) -> undef
756 if (Index >= Val->getType()->getVectorNumElements())
757 return UndefValue::get(Val->getType()->getVectorElementType());
758 return Val->getAggregateElement(Index);
759 }
760 return 0;
761 }
763 Constant *llvm::ConstantFoldInsertElementInstruction(Constant *Val,
764 Constant *Elt,
765 Constant *Idx) {
766 ConstantInt *CIdx = dyn_cast<ConstantInt>(Idx);
767 if (!CIdx) return 0;
768 const APInt &IdxVal = CIdx->getValue();
770 SmallVector<Constant*, 16> Result;
771 Type *Ty = IntegerType::get(Val->getContext(), 32);
772 for (unsigned i = 0, e = Val->getType()->getVectorNumElements(); i != e; ++i){
773 if (i == IdxVal) {
774 Result.push_back(Elt);
775 continue;
776 }
778 Constant *C =
779 ConstantExpr::getExtractElement(Val, ConstantInt::get(Ty, i));
780 Result.push_back(C);
781 }
783 return ConstantVector::get(Result);
784 }
786 Constant *llvm::ConstantFoldShuffleVectorInstruction(Constant *V1,
787 Constant *V2,
788 Constant *Mask) {
789 unsigned MaskNumElts = Mask->getType()->getVectorNumElements();
790 Type *EltTy = V1->getType()->getVectorElementType();
792 // Undefined shuffle mask -> undefined value.
793 if (isa<UndefValue>(Mask))
794 return UndefValue::get(VectorType::get(EltTy, MaskNumElts));
796 // Don't break the bitcode reader hack.
797 if (isa<ConstantExpr>(Mask)) return 0;
799 unsigned SrcNumElts = V1->getType()->getVectorNumElements();
801 // Loop over the shuffle mask, evaluating each element.
802 SmallVector<Constant*, 32> Result;
803 for (unsigned i = 0; i != MaskNumElts; ++i) {
804 int Elt = ShuffleVectorInst::getMaskValue(Mask, i);
805 if (Elt == -1) {
806 Result.push_back(UndefValue::get(EltTy));
807 continue;
808 }
809 Constant *InElt;
810 if (unsigned(Elt) >= SrcNumElts*2)
811 InElt = UndefValue::get(EltTy);
812 else if (unsigned(Elt) >= SrcNumElts) {
813 Type *Ty = IntegerType::get(V2->getContext(), 32);
814 InElt =
815 ConstantExpr::getExtractElement(V2,
816 ConstantInt::get(Ty, Elt - SrcNumElts));
817 } else {
818 Type *Ty = IntegerType::get(V1->getContext(), 32);
819 InElt = ConstantExpr::getExtractElement(V1, ConstantInt::get(Ty, Elt));
820 }
821 Result.push_back(InElt);
822 }
824 return ConstantVector::get(Result);
825 }
827 Constant *llvm::ConstantFoldExtractValueInstruction(Constant *Agg,
828 ArrayRef<unsigned> Idxs) {
829 // Base case: no indices, so return the entire value.
830 if (Idxs.empty())
831 return Agg;
833 if (Constant *C = Agg->getAggregateElement(Idxs[0]))
834 return ConstantFoldExtractValueInstruction(C, Idxs.slice(1));
836 return 0;
837 }
839 Constant *llvm::ConstantFoldInsertValueInstruction(Constant *Agg,
840 Constant *Val,
841 ArrayRef<unsigned> Idxs) {
842 // Base case: no indices, so replace the entire value.
843 if (Idxs.empty())
844 return Val;
846 unsigned NumElts;
847 if (StructType *ST = dyn_cast<StructType>(Agg->getType()))
848 NumElts = ST->getNumElements();
849 else if (ArrayType *AT = dyn_cast<ArrayType>(Agg->getType()))
850 NumElts = AT->getNumElements();
851 else
852 NumElts = Agg->getType()->getVectorNumElements();
854 SmallVector<Constant*, 32> Result;
855 for (unsigned i = 0; i != NumElts; ++i) {
856 Constant *C = Agg->getAggregateElement(i);
857 if (C == 0) return 0;
859 if (Idxs[0] == i)
860 C = ConstantFoldInsertValueInstruction(C, Val, Idxs.slice(1));
862 Result.push_back(C);
863 }
865 if (StructType *ST = dyn_cast<StructType>(Agg->getType()))
866 return ConstantStruct::get(ST, Result);
867 if (ArrayType *AT = dyn_cast<ArrayType>(Agg->getType()))
868 return ConstantArray::get(AT, Result);
869 return ConstantVector::get(Result);
870 }
873 Constant *llvm::ConstantFoldBinaryInstruction(unsigned Opcode,
874 Constant *C1, Constant *C2) {
875 // Handle UndefValue up front.
876 if (isa<UndefValue>(C1) || isa<UndefValue>(C2)) {
877 switch (Opcode) {
878 case Instruction::Xor:
879 if (isa<UndefValue>(C1) && isa<UndefValue>(C2))
880 // Handle undef ^ undef -> 0 special case. This is a common
881 // idiom (misuse).
882 return Constant::getNullValue(C1->getType());
883 // Fallthrough
884 case Instruction::Add:
885 case Instruction::Sub:
886 return UndefValue::get(C1->getType());
887 case Instruction::And:
888 if (isa<UndefValue>(C1) && isa<UndefValue>(C2)) // undef & undef -> undef
889 return C1;
890 return Constant::getNullValue(C1->getType()); // undef & X -> 0
891 case Instruction::Mul: {
892 ConstantInt *CI;
893 // X * undef -> undef if X is odd or undef
894 if (((CI = dyn_cast<ConstantInt>(C1)) && CI->getValue()[0]) ||
895 ((CI = dyn_cast<ConstantInt>(C2)) && CI->getValue()[0]) ||
896 (isa<UndefValue>(C1) && isa<UndefValue>(C2)))
897 return UndefValue::get(C1->getType());
899 // X * undef -> 0 otherwise
900 return Constant::getNullValue(C1->getType());
901 }
902 case Instruction::UDiv:
903 case Instruction::SDiv:
904 // undef / 1 -> undef
905 if (Opcode == Instruction::UDiv || Opcode == Instruction::SDiv)
906 if (ConstantInt *CI2 = dyn_cast<ConstantInt>(C2))
907 if (CI2->isOne())
908 return C1;
909 // FALL THROUGH
910 case Instruction::URem:
911 case Instruction::SRem:
912 if (!isa<UndefValue>(C2)) // undef / X -> 0
913 return Constant::getNullValue(C1->getType());
914 return C2; // X / undef -> undef
915 case Instruction::Or: // X | undef -> -1
916 if (isa<UndefValue>(C1) && isa<UndefValue>(C2)) // undef | undef -> undef
917 return C1;
918 return Constant::getAllOnesValue(C1->getType()); // undef | X -> ~0
919 case Instruction::LShr:
920 if (isa<UndefValue>(C2) && isa<UndefValue>(C1))
921 return C1; // undef lshr undef -> undef
922 return Constant::getNullValue(C1->getType()); // X lshr undef -> 0
923 // undef lshr X -> 0
924 case Instruction::AShr:
925 if (!isa<UndefValue>(C2)) // undef ashr X --> all ones
926 return Constant::getAllOnesValue(C1->getType());
927 else if (isa<UndefValue>(C1))
928 return C1; // undef ashr undef -> undef
929 else
930 return C1; // X ashr undef --> X
931 case Instruction::Shl:
932 if (isa<UndefValue>(C2) && isa<UndefValue>(C1))
933 return C1; // undef shl undef -> undef
934 // undef << X -> 0 or X << undef -> 0
935 return Constant::getNullValue(C1->getType());
936 }
937 }
939 // Handle simplifications when the RHS is a constant int.
940 if (ConstantInt *CI2 = dyn_cast<ConstantInt>(C2)) {
941 switch (Opcode) {
942 case Instruction::Add:
943 if (CI2->equalsInt(0)) return C1; // X + 0 == X
944 break;
945 case Instruction::Sub:
946 if (CI2->equalsInt(0)) return C1; // X - 0 == X
947 break;
948 case Instruction::Mul:
949 if (CI2->equalsInt(0)) return C2; // X * 0 == 0
950 if (CI2->equalsInt(1))
951 return C1; // X * 1 == X
952 break;
953 case Instruction::UDiv:
954 case Instruction::SDiv:
955 if (CI2->equalsInt(1))
956 return C1; // X / 1 == X
957 if (CI2->equalsInt(0))
958 return UndefValue::get(CI2->getType()); // X / 0 == undef
959 break;
960 case Instruction::URem:
961 case Instruction::SRem:
962 if (CI2->equalsInt(1))
963 return Constant::getNullValue(CI2->getType()); // X % 1 == 0
964 if (CI2->equalsInt(0))
965 return UndefValue::get(CI2->getType()); // X % 0 == undef
966 break;
967 case Instruction::And:
968 if (CI2->isZero()) return C2; // X & 0 == 0
969 if (CI2->isAllOnesValue())
970 return C1; // X & -1 == X
972 if (ConstantExpr *CE1 = dyn_cast<ConstantExpr>(C1)) {
973 // (zext i32 to i64) & 4294967295 -> (zext i32 to i64)
974 if (CE1->getOpcode() == Instruction::ZExt) {
975 unsigned DstWidth = CI2->getType()->getBitWidth();
976 unsigned SrcWidth =
977 CE1->getOperand(0)->getType()->getPrimitiveSizeInBits();
978 APInt PossiblySetBits(APInt::getLowBitsSet(DstWidth, SrcWidth));
979 if ((PossiblySetBits & CI2->getValue()) == PossiblySetBits)
980 return C1;
981 }
983 // If and'ing the address of a global with a constant, fold it.
984 if (CE1->getOpcode() == Instruction::PtrToInt &&
985 isa<GlobalValue>(CE1->getOperand(0))) {
986 GlobalValue *GV = cast<GlobalValue>(CE1->getOperand(0));
988 // Functions are at least 4-byte aligned.
989 unsigned GVAlign = GV->getAlignment();
990 if (isa<Function>(GV))
991 GVAlign = std::max(GVAlign, 4U);
993 if (GVAlign > 1) {
994 unsigned DstWidth = CI2->getType()->getBitWidth();
995 unsigned SrcWidth = std::min(DstWidth, Log2_32(GVAlign));
996 APInt BitsNotSet(APInt::getLowBitsSet(DstWidth, SrcWidth));
998 // If checking bits we know are clear, return zero.
999 if ((CI2->getValue() & BitsNotSet) == CI2->getValue())
1000 return Constant::getNullValue(CI2->getType());
1001 }
1002 }
1003 }
1004 break;
1005 case Instruction::Or:
1006 if (CI2->equalsInt(0)) return C1; // X | 0 == X
1007 if (CI2->isAllOnesValue())
1008 return C2; // X | -1 == -1
1009 break;
1010 case Instruction::Xor:
1011 if (CI2->equalsInt(0)) return C1; // X ^ 0 == X
1013 if (ConstantExpr *CE1 = dyn_cast<ConstantExpr>(C1)) {
1014 switch (CE1->getOpcode()) {
1015 default: break;
1016 case Instruction::ICmp:
1017 case Instruction::FCmp:
1018 // cmp pred ^ true -> cmp !pred
1019 assert(CI2->equalsInt(1));
1020 CmpInst::Predicate pred = (CmpInst::Predicate)CE1->getPredicate();
1021 pred = CmpInst::getInversePredicate(pred);
1022 return ConstantExpr::getCompare(pred, CE1->getOperand(0),
1023 CE1->getOperand(1));
1024 }
1025 }
1026 break;
1027 case Instruction::AShr:
1028 // ashr (zext C to Ty), C2 -> lshr (zext C, CSA), C2
1029 if (ConstantExpr *CE1 = dyn_cast<ConstantExpr>(C1))
1030 if (CE1->getOpcode() == Instruction::ZExt) // Top bits known zero.
1031 return ConstantExpr::getLShr(C1, C2);
1032 break;
1033 }
1034 } else if (isa<ConstantInt>(C1)) {
1035 // If C1 is a ConstantInt and C2 is not, swap the operands.
1036 if (Instruction::isCommutative(Opcode))
1037 return ConstantExpr::get(Opcode, C2, C1);
1038 }
1040 // At this point we know neither constant is an UndefValue.
1041 if (ConstantInt *CI1 = dyn_cast<ConstantInt>(C1)) {
1042 if (ConstantInt *CI2 = dyn_cast<ConstantInt>(C2)) {
1043 const APInt &C1V = CI1->getValue();
1044 const APInt &C2V = CI2->getValue();
1045 switch (Opcode) {
1046 default:
1047 break;
1048 case Instruction::Add:
1049 return ConstantInt::get(CI1->getContext(), C1V + C2V);
1050 case Instruction::Sub:
1051 return ConstantInt::get(CI1->getContext(), C1V - C2V);
1052 case Instruction::Mul:
1053 return ConstantInt::get(CI1->getContext(), C1V * C2V);
1054 case Instruction::UDiv:
1055 assert(!CI2->isNullValue() && "Div by zero handled above");
1056 return ConstantInt::get(CI1->getContext(), C1V.udiv(C2V));
1057 case Instruction::SDiv:
1058 assert(!CI2->isNullValue() && "Div by zero handled above");
1059 if (C2V.isAllOnesValue() && C1V.isMinSignedValue())
1060 return UndefValue::get(CI1->getType()); // MIN_INT / -1 -> undef
1061 return ConstantInt::get(CI1->getContext(), C1V.sdiv(C2V));
1062 case Instruction::URem:
1063 assert(!CI2->isNullValue() && "Div by zero handled above");
1064 return ConstantInt::get(CI1->getContext(), C1V.urem(C2V));
1065 case Instruction::SRem:
1066 assert(!CI2->isNullValue() && "Div by zero handled above");
1067 if (C2V.isAllOnesValue() && C1V.isMinSignedValue())
1068 return UndefValue::get(CI1->getType()); // MIN_INT % -1 -> undef
1069 return ConstantInt::get(CI1->getContext(), C1V.srem(C2V));
1070 case Instruction::And:
1071 return ConstantInt::get(CI1->getContext(), C1V & C2V);
1072 case Instruction::Or:
1073 return ConstantInt::get(CI1->getContext(), C1V | C2V);
1074 case Instruction::Xor:
1075 return ConstantInt::get(CI1->getContext(), C1V ^ C2V);
1076 case Instruction::Shl: {
1077 uint32_t shiftAmt = C2V.getZExtValue();
1078 if (shiftAmt < C1V.getBitWidth())
1079 return ConstantInt::get(CI1->getContext(), C1V.shl(shiftAmt));
1080 else
1081 return UndefValue::get(C1->getType()); // too big shift is undef
1082 }
1083 case Instruction::LShr: {
1084 uint32_t shiftAmt = C2V.getZExtValue();
1085 if (shiftAmt < C1V.getBitWidth())
1086 return ConstantInt::get(CI1->getContext(), C1V.lshr(shiftAmt));
1087 else
1088 return UndefValue::get(C1->getType()); // too big shift is undef
1089 }
1090 case Instruction::AShr: {
1091 uint32_t shiftAmt = C2V.getZExtValue();
1092 if (shiftAmt < C1V.getBitWidth())
1093 return ConstantInt::get(CI1->getContext(), C1V.ashr(shiftAmt));
1094 else
1095 return UndefValue::get(C1->getType()); // too big shift is undef
1096 }
1097 }
1098 }
1100 switch (Opcode) {
1101 case Instruction::SDiv:
1102 case Instruction::UDiv:
1103 case Instruction::URem:
1104 case Instruction::SRem:
1105 case Instruction::LShr:
1106 case Instruction::AShr:
1107 case Instruction::Shl:
1108 if (CI1->equalsInt(0)) return C1;
1109 break;
1110 default:
1111 break;
1112 }
1113 } else if (ConstantFP *CFP1 = dyn_cast<ConstantFP>(C1)) {
1114 if (ConstantFP *CFP2 = dyn_cast<ConstantFP>(C2)) {
1115 APFloat C1V = CFP1->getValueAPF();
1116 APFloat C2V = CFP2->getValueAPF();
1117 APFloat C3V = C1V; // copy for modification
1118 switch (Opcode) {
1119 default:
1120 break;
1121 case Instruction::FAdd:
1122 (void)C3V.add(C2V, APFloat::rmNearestTiesToEven);
1123 return ConstantFP::get(C1->getContext(), C3V);
1124 case Instruction::FSub:
1125 (void)C3V.subtract(C2V, APFloat::rmNearestTiesToEven);
1126 return ConstantFP::get(C1->getContext(), C3V);
1127 case Instruction::FMul:
1128 (void)C3V.multiply(C2V, APFloat::rmNearestTiesToEven);
1129 return ConstantFP::get(C1->getContext(), C3V);
1130 case Instruction::FDiv:
1131 (void)C3V.divide(C2V, APFloat::rmNearestTiesToEven);
1132 return ConstantFP::get(C1->getContext(), C3V);
1133 case Instruction::FRem:
1134 (void)C3V.mod(C2V, APFloat::rmNearestTiesToEven);
1135 return ConstantFP::get(C1->getContext(), C3V);
1136 }
1137 }
1138 } else if (VectorType *VTy = dyn_cast<VectorType>(C1->getType())) {
1139 // Perform elementwise folding.
1140 SmallVector<Constant*, 16> Result;
1141 Type *Ty = IntegerType::get(VTy->getContext(), 32);
1142 for (unsigned i = 0, e = VTy->getNumElements(); i != e; ++i) {
1143 Constant *LHS =
1144 ConstantExpr::getExtractElement(C1, ConstantInt::get(Ty, i));
1145 Constant *RHS =
1146 ConstantExpr::getExtractElement(C2, ConstantInt::get(Ty, i));
1148 Result.push_back(ConstantExpr::get(Opcode, LHS, RHS));
1149 }
1151 return ConstantVector::get(Result);
1152 }
1154 if (ConstantExpr *CE1 = dyn_cast<ConstantExpr>(C1)) {
1155 // There are many possible foldings we could do here. We should probably
1156 // at least fold add of a pointer with an integer into the appropriate
1157 // getelementptr. This will improve alias analysis a bit.
1159 // Given ((a + b) + c), if (b + c) folds to something interesting, return
1160 // (a + (b + c)).
1161 if (Instruction::isAssociative(Opcode) && CE1->getOpcode() == Opcode) {
1162 Constant *T = ConstantExpr::get(Opcode, CE1->getOperand(1), C2);
1163 if (!isa<ConstantExpr>(T) || cast<ConstantExpr>(T)->getOpcode() != Opcode)
1164 return ConstantExpr::get(Opcode, CE1->getOperand(0), T);
1165 }
1166 } else if (isa<ConstantExpr>(C2)) {
1167 // If C2 is a constant expr and C1 isn't, flop them around and fold the
1168 // other way if possible.
1169 if (Instruction::isCommutative(Opcode))
1170 return ConstantFoldBinaryInstruction(Opcode, C2, C1);
1171 }
1173 // i1 can be simplified in many cases.
1174 if (C1->getType()->isIntegerTy(1)) {
1175 switch (Opcode) {
1176 case Instruction::Add:
1177 case Instruction::Sub:
1178 return ConstantExpr::getXor(C1, C2);
1179 case Instruction::Mul:
1180 return ConstantExpr::getAnd(C1, C2);
1181 case Instruction::Shl:
1182 case Instruction::LShr:
1183 case Instruction::AShr:
1184 // We can assume that C2 == 0. If it were one the result would be
1185 // undefined because the shift value is as large as the bitwidth.
1186 return C1;
1187 case Instruction::SDiv:
1188 case Instruction::UDiv:
1189 // We can assume that C2 == 1. If it were zero the result would be
1190 // undefined through division by zero.
1191 return C1;
1192 case Instruction::URem:
1193 case Instruction::SRem:
1194 // We can assume that C2 == 1. If it were zero the result would be
1195 // undefined through division by zero.
1196 return ConstantInt::getFalse(C1->getContext());
1197 default:
1198 break;
1199 }
1200 }
1202 // We don't know how to fold this.
1203 return 0;
1204 }
1206 /// isZeroSizedType - This type is zero sized if its an array or structure of
1207 /// zero sized types. The only leaf zero sized type is an empty structure.
1208 static bool isMaybeZeroSizedType(Type *Ty) {
1209 if (StructType *STy = dyn_cast<StructType>(Ty)) {
1210 if (STy->isOpaque()) return true; // Can't say.
1212 // If all of elements have zero size, this does too.
1213 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i)
1214 if (!isMaybeZeroSizedType(STy->getElementType(i))) return false;
1215 return true;
1217 } else if (ArrayType *ATy = dyn_cast<ArrayType>(Ty)) {
1218 return isMaybeZeroSizedType(ATy->getElementType());
1219 }
1220 return false;
1221 }
1223 /// IdxCompare - Compare the two constants as though they were getelementptr
1224 /// indices. This allows coersion of the types to be the same thing.
1225 ///
1226 /// If the two constants are the "same" (after coersion), return 0. If the
1227 /// first is less than the second, return -1, if the second is less than the
1228 /// first, return 1. If the constants are not integral, return -2.
1229 ///
1230 static int IdxCompare(Constant *C1, Constant *C2, Type *ElTy) {
1231 if (C1 == C2) return 0;
1233 // Ok, we found a different index. If they are not ConstantInt, we can't do
1234 // anything with them.
1235 if (!isa<ConstantInt>(C1) || !isa<ConstantInt>(C2))
1236 return -2; // don't know!
1238 // Ok, we have two differing integer indices. Sign extend them to be the same
1239 // type. Long is always big enough, so we use it.
1240 if (!C1->getType()->isIntegerTy(64))
1241 C1 = ConstantExpr::getSExt(C1, Type::getInt64Ty(C1->getContext()));
1243 if (!C2->getType()->isIntegerTy(64))
1244 C2 = ConstantExpr::getSExt(C2, Type::getInt64Ty(C1->getContext()));
1246 if (C1 == C2) return 0; // They are equal
1248 // If the type being indexed over is really just a zero sized type, there is
1249 // no pointer difference being made here.
1250 if (isMaybeZeroSizedType(ElTy))
1251 return -2; // dunno.
1253 // If they are really different, now that they are the same type, then we
1254 // found a difference!
1255 if (cast<ConstantInt>(C1)->getSExtValue() <
1256 cast<ConstantInt>(C2)->getSExtValue())
1257 return -1;
1258 else
1259 return 1;
1260 }
1262 /// evaluateFCmpRelation - This function determines if there is anything we can
1263 /// decide about the two constants provided. This doesn't need to handle simple
1264 /// things like ConstantFP comparisons, but should instead handle ConstantExprs.
1265 /// If we can determine that the two constants have a particular relation to
1266 /// each other, we should return the corresponding FCmpInst predicate,
1267 /// otherwise return FCmpInst::BAD_FCMP_PREDICATE. This is used below in
1268 /// ConstantFoldCompareInstruction.
1269 ///
1270 /// To simplify this code we canonicalize the relation so that the first
1271 /// operand is always the most "complex" of the two. We consider ConstantFP
1272 /// to be the simplest, and ConstantExprs to be the most complex.
1273 static FCmpInst::Predicate evaluateFCmpRelation(Constant *V1, Constant *V2) {
1274 assert(V1->getType() == V2->getType() &&
1275 "Cannot compare values of different types!");
1277 // Handle degenerate case quickly
1278 if (V1 == V2) return FCmpInst::FCMP_OEQ;
1280 if (!isa<ConstantExpr>(V1)) {
1281 if (!isa<ConstantExpr>(V2)) {
1282 // We distilled thisUse the standard constant folder for a few cases
1283 ConstantInt *R = 0;
1284 R = dyn_cast<ConstantInt>(
1285 ConstantExpr::getFCmp(FCmpInst::FCMP_OEQ, V1, V2));
1286 if (R && !R->isZero())
1287 return FCmpInst::FCMP_OEQ;
1288 R = dyn_cast<ConstantInt>(
1289 ConstantExpr::getFCmp(FCmpInst::FCMP_OLT, V1, V2));
1290 if (R && !R->isZero())
1291 return FCmpInst::FCMP_OLT;
1292 R = dyn_cast<ConstantInt>(
1293 ConstantExpr::getFCmp(FCmpInst::FCMP_OGT, V1, V2));
1294 if (R && !R->isZero())
1295 return FCmpInst::FCMP_OGT;
1297 // Nothing more we can do
1298 return FCmpInst::BAD_FCMP_PREDICATE;
1299 }
1301 // If the first operand is simple and second is ConstantExpr, swap operands.
1302 FCmpInst::Predicate SwappedRelation = evaluateFCmpRelation(V2, V1);
1303 if (SwappedRelation != FCmpInst::BAD_FCMP_PREDICATE)
1304 return FCmpInst::getSwappedPredicate(SwappedRelation);
1305 } else {
1306 // Ok, the LHS is known to be a constantexpr. The RHS can be any of a
1307 // constantexpr or a simple constant.
1308 ConstantExpr *CE1 = cast<ConstantExpr>(V1);
1309 switch (CE1->getOpcode()) {
1310 case Instruction::FPTrunc:
1311 case Instruction::FPExt:
1312 case Instruction::UIToFP:
1313 case Instruction::SIToFP:
1314 // We might be able to do something with these but we don't right now.
1315 break;
1316 default:
1317 break;
1318 }
1319 }
1320 // There are MANY other foldings that we could perform here. They will
1321 // probably be added on demand, as they seem needed.
1322 return FCmpInst::BAD_FCMP_PREDICATE;
1323 }
1325 /// evaluateICmpRelation - This function determines if there is anything we can
1326 /// decide about the two constants provided. This doesn't need to handle simple
1327 /// things like integer comparisons, but should instead handle ConstantExprs
1328 /// and GlobalValues. If we can determine that the two constants have a
1329 /// particular relation to each other, we should return the corresponding ICmp
1330 /// predicate, otherwise return ICmpInst::BAD_ICMP_PREDICATE.
1331 ///
1332 /// To simplify this code we canonicalize the relation so that the first
1333 /// operand is always the most "complex" of the two. We consider simple
1334 /// constants (like ConstantInt) to be the simplest, followed by
1335 /// GlobalValues, followed by ConstantExpr's (the most complex).
1336 ///
1337 static ICmpInst::Predicate evaluateICmpRelation(Constant *V1, Constant *V2,
1338 bool isSigned) {
1339 assert(V1->getType() == V2->getType() &&
1340 "Cannot compare different types of values!");
1341 if (V1 == V2) return ICmpInst::ICMP_EQ;
1343 if (!isa<ConstantExpr>(V1) && !isa<GlobalValue>(V1) &&
1344 !isa<BlockAddress>(V1)) {
1345 if (!isa<GlobalValue>(V2) && !isa<ConstantExpr>(V2) &&
1346 !isa<BlockAddress>(V2)) {
1347 // We distilled this down to a simple case, use the standard constant
1348 // folder.
1349 ConstantInt *R = 0;
1350 ICmpInst::Predicate pred = ICmpInst::ICMP_EQ;
1351 R = dyn_cast<ConstantInt>(ConstantExpr::getICmp(pred, V1, V2));
1352 if (R && !R->isZero())
1353 return pred;
1354 pred = isSigned ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT;
1355 R = dyn_cast<ConstantInt>(ConstantExpr::getICmp(pred, V1, V2));
1356 if (R && !R->isZero())
1357 return pred;
1358 pred = isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT;
1359 R = dyn_cast<ConstantInt>(ConstantExpr::getICmp(pred, V1, V2));
1360 if (R && !R->isZero())
1361 return pred;
1363 // If we couldn't figure it out, bail.
1364 return ICmpInst::BAD_ICMP_PREDICATE;
1365 }
1367 // If the first operand is simple, swap operands.
1368 ICmpInst::Predicate SwappedRelation =
1369 evaluateICmpRelation(V2, V1, isSigned);
1370 if (SwappedRelation != ICmpInst::BAD_ICMP_PREDICATE)
1371 return ICmpInst::getSwappedPredicate(SwappedRelation);
1373 } else if (const GlobalValue *GV = dyn_cast<GlobalValue>(V1)) {
1374 if (isa<ConstantExpr>(V2)) { // Swap as necessary.
1375 ICmpInst::Predicate SwappedRelation =
1376 evaluateICmpRelation(V2, V1, isSigned);
1377 if (SwappedRelation != ICmpInst::BAD_ICMP_PREDICATE)
1378 return ICmpInst::getSwappedPredicate(SwappedRelation);
1379 return ICmpInst::BAD_ICMP_PREDICATE;
1380 }
1382 // Now we know that the RHS is a GlobalValue, BlockAddress or simple
1383 // constant (which, since the types must match, means that it's a
1384 // ConstantPointerNull).
1385 if (const GlobalValue *GV2 = dyn_cast<GlobalValue>(V2)) {
1386 // Don't try to decide equality of aliases.
1387 if (!isa<GlobalAlias>(GV) && !isa<GlobalAlias>(GV2))
1388 if (!GV->hasExternalWeakLinkage() || !GV2->hasExternalWeakLinkage())
1389 return ICmpInst::ICMP_NE;
1390 } else if (isa<BlockAddress>(V2)) {
1391 return ICmpInst::ICMP_NE; // Globals never equal labels.
1392 } else {
1393 assert(isa<ConstantPointerNull>(V2) && "Canonicalization guarantee!");
1394 // GlobalVals can never be null unless they have external weak linkage.
1395 // We don't try to evaluate aliases here.
1396 if (!GV->hasExternalWeakLinkage() && !isa<GlobalAlias>(GV))
1397 return ICmpInst::ICMP_NE;
1398 }
1399 } else if (const BlockAddress *BA = dyn_cast<BlockAddress>(V1)) {
1400 if (isa<ConstantExpr>(V2)) { // Swap as necessary.
1401 ICmpInst::Predicate SwappedRelation =
1402 evaluateICmpRelation(V2, V1, isSigned);
1403 if (SwappedRelation != ICmpInst::BAD_ICMP_PREDICATE)
1404 return ICmpInst::getSwappedPredicate(SwappedRelation);
1405 return ICmpInst::BAD_ICMP_PREDICATE;
1406 }
1408 // Now we know that the RHS is a GlobalValue, BlockAddress or simple
1409 // constant (which, since the types must match, means that it is a
1410 // ConstantPointerNull).
1411 if (const BlockAddress *BA2 = dyn_cast<BlockAddress>(V2)) {
1412 // Block address in another function can't equal this one, but block
1413 // addresses in the current function might be the same if blocks are
1414 // empty.
1415 if (BA2->getFunction() != BA->getFunction())
1416 return ICmpInst::ICMP_NE;
1417 } else {
1418 // Block addresses aren't null, don't equal the address of globals.
1419 assert((isa<ConstantPointerNull>(V2) || isa<GlobalValue>(V2)) &&
1420 "Canonicalization guarantee!");
1421 return ICmpInst::ICMP_NE;
1422 }
1423 } else {
1424 // Ok, the LHS is known to be a constantexpr. The RHS can be any of a
1425 // constantexpr, a global, block address, or a simple constant.
1426 ConstantExpr *CE1 = cast<ConstantExpr>(V1);
1427 Constant *CE1Op0 = CE1->getOperand(0);
1429 switch (CE1->getOpcode()) {
1430 case Instruction::Trunc:
1431 case Instruction::FPTrunc:
1432 case Instruction::FPExt:
1433 case Instruction::FPToUI:
1434 case Instruction::FPToSI:
1435 break; // We can't evaluate floating point casts or truncations.
1437 case Instruction::UIToFP:
1438 case Instruction::SIToFP:
1439 case Instruction::BitCast:
1440 case Instruction::ZExt:
1441 case Instruction::SExt:
1442 // If the cast is not actually changing bits, and the second operand is a
1443 // null pointer, do the comparison with the pre-casted value.
1444 if (V2->isNullValue() &&
1445 (CE1->getType()->isPointerTy() || CE1->getType()->isIntegerTy())) {
1446 if (CE1->getOpcode() == Instruction::ZExt) isSigned = false;
1447 if (CE1->getOpcode() == Instruction::SExt) isSigned = true;
1448 return evaluateICmpRelation(CE1Op0,
1449 Constant::getNullValue(CE1Op0->getType()),
1450 isSigned);
1451 }
1452 break;
1454 case Instruction::GetElementPtr:
1455 // Ok, since this is a getelementptr, we know that the constant has a
1456 // pointer type. Check the various cases.
1457 if (isa<ConstantPointerNull>(V2)) {
1458 // If we are comparing a GEP to a null pointer, check to see if the base
1459 // of the GEP equals the null pointer.
1460 if (const GlobalValue *GV = dyn_cast<GlobalValue>(CE1Op0)) {
1461 if (GV->hasExternalWeakLinkage())
1462 // Weak linkage GVals could be zero or not. We're comparing that
1463 // to null pointer so its greater-or-equal
1464 return isSigned ? ICmpInst::ICMP_SGE : ICmpInst::ICMP_UGE;
1465 else
1466 // If its not weak linkage, the GVal must have a non-zero address
1467 // so the result is greater-than
1468 return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT;
1469 } else if (isa<ConstantPointerNull>(CE1Op0)) {
1470 // If we are indexing from a null pointer, check to see if we have any
1471 // non-zero indices.
1472 for (unsigned i = 1, e = CE1->getNumOperands(); i != e; ++i)
1473 if (!CE1->getOperand(i)->isNullValue())
1474 // Offsetting from null, must not be equal.
1475 return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT;
1476 // Only zero indexes from null, must still be zero.
1477 return ICmpInst::ICMP_EQ;
1478 }
1479 // Otherwise, we can't really say if the first operand is null or not.
1480 } else if (const GlobalValue *GV2 = dyn_cast<GlobalValue>(V2)) {
1481 if (isa<ConstantPointerNull>(CE1Op0)) {
1482 if (GV2->hasExternalWeakLinkage())
1483 // Weak linkage GVals could be zero or not. We're comparing it to
1484 // a null pointer, so its less-or-equal
1485 return isSigned ? ICmpInst::ICMP_SLE : ICmpInst::ICMP_ULE;
1486 else
1487 // If its not weak linkage, the GVal must have a non-zero address
1488 // so the result is less-than
1489 return isSigned ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT;
1490 } else if (const GlobalValue *GV = dyn_cast<GlobalValue>(CE1Op0)) {
1491 if (GV == GV2) {
1492 // If this is a getelementptr of the same global, then it must be
1493 // different. Because the types must match, the getelementptr could
1494 // only have at most one index, and because we fold getelementptr's
1495 // with a single zero index, it must be nonzero.
1496 assert(CE1->getNumOperands() == 2 &&
1497 !CE1->getOperand(1)->isNullValue() &&
1498 "Surprising getelementptr!");
1499 return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT;
1500 } else {
1501 // If they are different globals, we don't know what the value is.
1502 return ICmpInst::BAD_ICMP_PREDICATE;
1503 }
1504 }
1505 } else {
1506 ConstantExpr *CE2 = cast<ConstantExpr>(V2);
1507 Constant *CE2Op0 = CE2->getOperand(0);
1509 // There are MANY other foldings that we could perform here. They will
1510 // probably be added on demand, as they seem needed.
1511 switch (CE2->getOpcode()) {
1512 default: break;
1513 case Instruction::GetElementPtr:
1514 // By far the most common case to handle is when the base pointers are
1515 // obviously to the same global.
1516 if (isa<GlobalValue>(CE1Op0) && isa<GlobalValue>(CE2Op0)) {
1517 if (CE1Op0 != CE2Op0) // Don't know relative ordering.
1518 return ICmpInst::BAD_ICMP_PREDICATE;
1519 // Ok, we know that both getelementptr instructions are based on the
1520 // same global. From this, we can precisely determine the relative
1521 // ordering of the resultant pointers.
1522 unsigned i = 1;
1524 // The logic below assumes that the result of the comparison
1525 // can be determined by finding the first index that differs.
1526 // This doesn't work if there is over-indexing in any
1527 // subsequent indices, so check for that case first.
1528 if (!CE1->isGEPWithNoNotionalOverIndexing() ||
1529 !CE2->isGEPWithNoNotionalOverIndexing())
1530 return ICmpInst::BAD_ICMP_PREDICATE; // Might be equal.
1532 // Compare all of the operands the GEP's have in common.
1533 gep_type_iterator GTI = gep_type_begin(CE1);
1534 for (;i != CE1->getNumOperands() && i != CE2->getNumOperands();
1535 ++i, ++GTI)
1536 switch (IdxCompare(CE1->getOperand(i),
1537 CE2->getOperand(i), GTI.getIndexedType())) {
1538 case -1: return isSigned ? ICmpInst::ICMP_SLT:ICmpInst::ICMP_ULT;
1539 case 1: return isSigned ? ICmpInst::ICMP_SGT:ICmpInst::ICMP_UGT;
1540 case -2: return ICmpInst::BAD_ICMP_PREDICATE;
1541 }
1543 // Ok, we ran out of things they have in common. If any leftovers
1544 // are non-zero then we have a difference, otherwise we are equal.
1545 for (; i < CE1->getNumOperands(); ++i)
1546 if (!CE1->getOperand(i)->isNullValue()) {
1547 if (isa<ConstantInt>(CE1->getOperand(i)))
1548 return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT;
1549 else
1550 return ICmpInst::BAD_ICMP_PREDICATE; // Might be equal.
1551 }
1553 for (; i < CE2->getNumOperands(); ++i)
1554 if (!CE2->getOperand(i)->isNullValue()) {
1555 if (isa<ConstantInt>(CE2->getOperand(i)))
1556 return isSigned ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT;
1557 else
1558 return ICmpInst::BAD_ICMP_PREDICATE; // Might be equal.
1559 }
1560 return ICmpInst::ICMP_EQ;
1561 }
1562 }
1563 }
1564 default:
1565 break;
1566 }
1567 }
1569 return ICmpInst::BAD_ICMP_PREDICATE;
1570 }
1572 Constant *llvm::ConstantFoldCompareInstruction(unsigned short pred,
1573 Constant *C1, Constant *C2) {
1574 Type *ResultTy;
1575 if (VectorType *VT = dyn_cast<VectorType>(C1->getType()))
1576 ResultTy = VectorType::get(Type::getInt1Ty(C1->getContext()),
1577 VT->getNumElements());
1578 else
1579 ResultTy = Type::getInt1Ty(C1->getContext());
1581 // Fold FCMP_FALSE/FCMP_TRUE unconditionally.
1582 if (pred == FCmpInst::FCMP_FALSE)
1583 return Constant::getNullValue(ResultTy);
1585 if (pred == FCmpInst::FCMP_TRUE)
1586 return Constant::getAllOnesValue(ResultTy);
1588 // Handle some degenerate cases first
1589 if (isa<UndefValue>(C1) || isa<UndefValue>(C2)) {
1590 // For EQ and NE, we can always pick a value for the undef to make the
1591 // predicate pass or fail, so we can return undef.
1592 // Also, if both operands are undef, we can return undef.
1593 if (ICmpInst::isEquality(ICmpInst::Predicate(pred)) ||
1594 (isa<UndefValue>(C1) && isa<UndefValue>(C2)))
1595 return UndefValue::get(ResultTy);
1596 // Otherwise, pick the same value as the non-undef operand, and fold
1597 // it to true or false.
1598 return ConstantInt::get(ResultTy, CmpInst::isTrueWhenEqual(pred));
1599 }
1601 // icmp eq/ne(null,GV) -> false/true
1602 if (C1->isNullValue()) {
1603 if (const GlobalValue *GV = dyn_cast<GlobalValue>(C2))
1604 // Don't try to evaluate aliases. External weak GV can be null.
1605 if (!isa<GlobalAlias>(GV) && !GV->hasExternalWeakLinkage()) {
1606 if (pred == ICmpInst::ICMP_EQ)
1607 return ConstantInt::getFalse(C1->getContext());
1608 else if (pred == ICmpInst::ICMP_NE)
1609 return ConstantInt::getTrue(C1->getContext());
1610 }
1611 // icmp eq/ne(GV,null) -> false/true
1612 } else if (C2->isNullValue()) {
1613 if (const GlobalValue *GV = dyn_cast<GlobalValue>(C1))
1614 // Don't try to evaluate aliases. External weak GV can be null.
1615 if (!isa<GlobalAlias>(GV) && !GV->hasExternalWeakLinkage()) {
1616 if (pred == ICmpInst::ICMP_EQ)
1617 return ConstantInt::getFalse(C1->getContext());
1618 else if (pred == ICmpInst::ICMP_NE)
1619 return ConstantInt::getTrue(C1->getContext());
1620 }
1621 }
1623 // If the comparison is a comparison between two i1's, simplify it.
1624 if (C1->getType()->isIntegerTy(1)) {
1625 switch(pred) {
1626 case ICmpInst::ICMP_EQ:
1627 if (isa<ConstantInt>(C2))
1628 return ConstantExpr::getXor(C1, ConstantExpr::getNot(C2));
1629 return ConstantExpr::getXor(ConstantExpr::getNot(C1), C2);
1630 case ICmpInst::ICMP_NE:
1631 return ConstantExpr::getXor(C1, C2);
1632 default:
1633 break;
1634 }
1635 }
1637 if (isa<ConstantInt>(C1) && isa<ConstantInt>(C2)) {
1638 APInt V1 = cast<ConstantInt>(C1)->getValue();
1639 APInt V2 = cast<ConstantInt>(C2)->getValue();
1640 switch (pred) {
1641 default: llvm_unreachable("Invalid ICmp Predicate");
1642 case ICmpInst::ICMP_EQ: return ConstantInt::get(ResultTy, V1 == V2);
1643 case ICmpInst::ICMP_NE: return ConstantInt::get(ResultTy, V1 != V2);
1644 case ICmpInst::ICMP_SLT: return ConstantInt::get(ResultTy, V1.slt(V2));
1645 case ICmpInst::ICMP_SGT: return ConstantInt::get(ResultTy, V1.sgt(V2));
1646 case ICmpInst::ICMP_SLE: return ConstantInt::get(ResultTy, V1.sle(V2));
1647 case ICmpInst::ICMP_SGE: return ConstantInt::get(ResultTy, V1.sge(V2));
1648 case ICmpInst::ICMP_ULT: return ConstantInt::get(ResultTy, V1.ult(V2));
1649 case ICmpInst::ICMP_UGT: return ConstantInt::get(ResultTy, V1.ugt(V2));
1650 case ICmpInst::ICMP_ULE: return ConstantInt::get(ResultTy, V1.ule(V2));
1651 case ICmpInst::ICMP_UGE: return ConstantInt::get(ResultTy, V1.uge(V2));
1652 }
1653 } else if (isa<ConstantFP>(C1) && isa<ConstantFP>(C2)) {
1654 APFloat C1V = cast<ConstantFP>(C1)->getValueAPF();
1655 APFloat C2V = cast<ConstantFP>(C2)->getValueAPF();
1656 APFloat::cmpResult R = C1V.compare(C2V);
1657 switch (pred) {
1658 default: llvm_unreachable("Invalid FCmp Predicate");
1659 case FCmpInst::FCMP_FALSE: return Constant::getNullValue(ResultTy);
1660 case FCmpInst::FCMP_TRUE: return Constant::getAllOnesValue(ResultTy);
1661 case FCmpInst::FCMP_UNO:
1662 return ConstantInt::get(ResultTy, R==APFloat::cmpUnordered);
1663 case FCmpInst::FCMP_ORD:
1664 return ConstantInt::get(ResultTy, R!=APFloat::cmpUnordered);
1665 case FCmpInst::FCMP_UEQ:
1666 return ConstantInt::get(ResultTy, R==APFloat::cmpUnordered ||
1667 R==APFloat::cmpEqual);
1668 case FCmpInst::FCMP_OEQ:
1669 return ConstantInt::get(ResultTy, R==APFloat::cmpEqual);
1670 case FCmpInst::FCMP_UNE:
1671 return ConstantInt::get(ResultTy, R!=APFloat::cmpEqual);
1672 case FCmpInst::FCMP_ONE:
1673 return ConstantInt::get(ResultTy, R==APFloat::cmpLessThan ||
1674 R==APFloat::cmpGreaterThan);
1675 case FCmpInst::FCMP_ULT:
1676 return ConstantInt::get(ResultTy, R==APFloat::cmpUnordered ||
1677 R==APFloat::cmpLessThan);
1678 case FCmpInst::FCMP_OLT:
1679 return ConstantInt::get(ResultTy, R==APFloat::cmpLessThan);
1680 case FCmpInst::FCMP_UGT:
1681 return ConstantInt::get(ResultTy, R==APFloat::cmpUnordered ||
1682 R==APFloat::cmpGreaterThan);
1683 case FCmpInst::FCMP_OGT:
1684 return ConstantInt::get(ResultTy, R==APFloat::cmpGreaterThan);
1685 case FCmpInst::FCMP_ULE:
1686 return ConstantInt::get(ResultTy, R!=APFloat::cmpGreaterThan);
1687 case FCmpInst::FCMP_OLE:
1688 return ConstantInt::get(ResultTy, R==APFloat::cmpLessThan ||
1689 R==APFloat::cmpEqual);
1690 case FCmpInst::FCMP_UGE:
1691 return ConstantInt::get(ResultTy, R!=APFloat::cmpLessThan);
1692 case FCmpInst::FCMP_OGE:
1693 return ConstantInt::get(ResultTy, R==APFloat::cmpGreaterThan ||
1694 R==APFloat::cmpEqual);
1695 }
1696 } else if (C1->getType()->isVectorTy()) {
1697 // If we can constant fold the comparison of each element, constant fold
1698 // the whole vector comparison.
1699 SmallVector<Constant*, 4> ResElts;
1700 Type *Ty = IntegerType::get(C1->getContext(), 32);
1701 // Compare the elements, producing an i1 result or constant expr.
1702 for (unsigned i = 0, e = C1->getType()->getVectorNumElements(); i != e;++i){
1703 Constant *C1E =
1704 ConstantExpr::getExtractElement(C1, ConstantInt::get(Ty, i));
1705 Constant *C2E =
1706 ConstantExpr::getExtractElement(C2, ConstantInt::get(Ty, i));
1708 ResElts.push_back(ConstantExpr::getCompare(pred, C1E, C2E));
1709 }
1711 return ConstantVector::get(ResElts);
1712 }
1714 if (C1->getType()->isFloatingPointTy()) {
1715 int Result = -1; // -1 = unknown, 0 = known false, 1 = known true.
1716 switch (evaluateFCmpRelation(C1, C2)) {
1717 default: llvm_unreachable("Unknown relation!");
1718 case FCmpInst::FCMP_UNO:
1719 case FCmpInst::FCMP_ORD:
1720 case FCmpInst::FCMP_UEQ:
1721 case FCmpInst::FCMP_UNE:
1722 case FCmpInst::FCMP_ULT:
1723 case FCmpInst::FCMP_UGT:
1724 case FCmpInst::FCMP_ULE:
1725 case FCmpInst::FCMP_UGE:
1726 case FCmpInst::FCMP_TRUE:
1727 case FCmpInst::FCMP_FALSE:
1728 case FCmpInst::BAD_FCMP_PREDICATE:
1729 break; // Couldn't determine anything about these constants.
1730 case FCmpInst::FCMP_OEQ: // We know that C1 == C2
1731 Result = (pred == FCmpInst::FCMP_UEQ || pred == FCmpInst::FCMP_OEQ ||
1732 pred == FCmpInst::FCMP_ULE || pred == FCmpInst::FCMP_OLE ||
1733 pred == FCmpInst::FCMP_UGE || pred == FCmpInst::FCMP_OGE);
1734 break;
1735 case FCmpInst::FCMP_OLT: // We know that C1 < C2
1736 Result = (pred == FCmpInst::FCMP_UNE || pred == FCmpInst::FCMP_ONE ||
1737 pred == FCmpInst::FCMP_ULT || pred == FCmpInst::FCMP_OLT ||
1738 pred == FCmpInst::FCMP_ULE || pred == FCmpInst::FCMP_OLE);
1739 break;
1740 case FCmpInst::FCMP_OGT: // We know that C1 > C2
1741 Result = (pred == FCmpInst::FCMP_UNE || pred == FCmpInst::FCMP_ONE ||
1742 pred == FCmpInst::FCMP_UGT || pred == FCmpInst::FCMP_OGT ||
1743 pred == FCmpInst::FCMP_UGE || pred == FCmpInst::FCMP_OGE);
1744 break;
1745 case FCmpInst::FCMP_OLE: // We know that C1 <= C2
1746 // We can only partially decide this relation.
1747 if (pred == FCmpInst::FCMP_UGT || pred == FCmpInst::FCMP_OGT)
1748 Result = 0;
1749 else if (pred == FCmpInst::FCMP_ULT || pred == FCmpInst::FCMP_OLT)
1750 Result = 1;
1751 break;
1752 case FCmpInst::FCMP_OGE: // We known that C1 >= C2
1753 // We can only partially decide this relation.
1754 if (pred == FCmpInst::FCMP_ULT || pred == FCmpInst::FCMP_OLT)
1755 Result = 0;
1756 else if (pred == FCmpInst::FCMP_UGT || pred == FCmpInst::FCMP_OGT)
1757 Result = 1;
1758 break;
1759 case FCmpInst::FCMP_ONE: // We know that C1 != C2
1760 // We can only partially decide this relation.
1761 if (pred == FCmpInst::FCMP_OEQ || pred == FCmpInst::FCMP_UEQ)
1762 Result = 0;
1763 else if (pred == FCmpInst::FCMP_ONE || pred == FCmpInst::FCMP_UNE)
1764 Result = 1;
1765 break;
1766 }
1768 // If we evaluated the result, return it now.
1769 if (Result != -1)
1770 return ConstantInt::get(ResultTy, Result);
1772 } else {
1773 // Evaluate the relation between the two constants, per the predicate.
1774 int Result = -1; // -1 = unknown, 0 = known false, 1 = known true.
1775 switch (evaluateICmpRelation(C1, C2, CmpInst::isSigned(pred))) {
1776 default: llvm_unreachable("Unknown relational!");
1777 case ICmpInst::BAD_ICMP_PREDICATE:
1778 break; // Couldn't determine anything about these constants.
1779 case ICmpInst::ICMP_EQ: // We know the constants are equal!
1780 // If we know the constants are equal, we can decide the result of this
1781 // computation precisely.
1782 Result = ICmpInst::isTrueWhenEqual((ICmpInst::Predicate)pred);
1783 break;
1784 case ICmpInst::ICMP_ULT:
1785 switch (pred) {
1786 case ICmpInst::ICMP_ULT: case ICmpInst::ICMP_NE: case ICmpInst::ICMP_ULE:
1787 Result = 1; break;
1788 case ICmpInst::ICMP_UGT: case ICmpInst::ICMP_EQ: case ICmpInst::ICMP_UGE:
1789 Result = 0; break;
1790 }
1791 break;
1792 case ICmpInst::ICMP_SLT:
1793 switch (pred) {
1794 case ICmpInst::ICMP_SLT: case ICmpInst::ICMP_NE: case ICmpInst::ICMP_SLE:
1795 Result = 1; break;
1796 case ICmpInst::ICMP_SGT: case ICmpInst::ICMP_EQ: case ICmpInst::ICMP_SGE:
1797 Result = 0; break;
1798 }
1799 break;
1800 case ICmpInst::ICMP_UGT:
1801 switch (pred) {
1802 case ICmpInst::ICMP_UGT: case ICmpInst::ICMP_NE: case ICmpInst::ICMP_UGE:
1803 Result = 1; break;
1804 case ICmpInst::ICMP_ULT: case ICmpInst::ICMP_EQ: case ICmpInst::ICMP_ULE:
1805 Result = 0; break;
1806 }
1807 break;
1808 case ICmpInst::ICMP_SGT:
1809 switch (pred) {
1810 case ICmpInst::ICMP_SGT: case ICmpInst::ICMP_NE: case ICmpInst::ICMP_SGE:
1811 Result = 1; break;
1812 case ICmpInst::ICMP_SLT: case ICmpInst::ICMP_EQ: case ICmpInst::ICMP_SLE:
1813 Result = 0; break;
1814 }
1815 break;
1816 case ICmpInst::ICMP_ULE:
1817 if (pred == ICmpInst::ICMP_UGT) Result = 0;
1818 if (pred == ICmpInst::ICMP_ULT || pred == ICmpInst::ICMP_ULE) Result = 1;
1819 break;
1820 case ICmpInst::ICMP_SLE:
1821 if (pred == ICmpInst::ICMP_SGT) Result = 0;
1822 if (pred == ICmpInst::ICMP_SLT || pred == ICmpInst::ICMP_SLE) Result = 1;
1823 break;
1824 case ICmpInst::ICMP_UGE:
1825 if (pred == ICmpInst::ICMP_ULT) Result = 0;
1826 if (pred == ICmpInst::ICMP_UGT || pred == ICmpInst::ICMP_UGE) Result = 1;
1827 break;
1828 case ICmpInst::ICMP_SGE:
1829 if (pred == ICmpInst::ICMP_SLT) Result = 0;
1830 if (pred == ICmpInst::ICMP_SGT || pred == ICmpInst::ICMP_SGE) Result = 1;
1831 break;
1832 case ICmpInst::ICMP_NE:
1833 if (pred == ICmpInst::ICMP_EQ) Result = 0;
1834 if (pred == ICmpInst::ICMP_NE) Result = 1;
1835 break;
1836 }
1838 // If we evaluated the result, return it now.
1839 if (Result != -1)
1840 return ConstantInt::get(ResultTy, Result);
1842 // If the right hand side is a bitcast, try using its inverse to simplify
1843 // it by moving it to the left hand side. We can't do this if it would turn
1844 // a vector compare into a scalar compare or visa versa.
1845 if (ConstantExpr *CE2 = dyn_cast<ConstantExpr>(C2)) {
1846 Constant *CE2Op0 = CE2->getOperand(0);
1847 if (CE2->getOpcode() == Instruction::BitCast &&
1848 CE2->getType()->isVectorTy() == CE2Op0->getType()->isVectorTy()) {
1849 Constant *Inverse = ConstantExpr::getBitCast(C1, CE2Op0->getType());
1850 return ConstantExpr::getICmp(pred, Inverse, CE2Op0);
1851 }
1852 }
1854 // If the left hand side is an extension, try eliminating it.
1855 if (ConstantExpr *CE1 = dyn_cast<ConstantExpr>(C1)) {
1856 if ((CE1->getOpcode() == Instruction::SExt && ICmpInst::isSigned(pred)) ||
1857 (CE1->getOpcode() == Instruction::ZExt && !ICmpInst::isSigned(pred))){
1858 Constant *CE1Op0 = CE1->getOperand(0);
1859 Constant *CE1Inverse = ConstantExpr::getTrunc(CE1, CE1Op0->getType());
1860 if (CE1Inverse == CE1Op0) {
1861 // Check whether we can safely truncate the right hand side.
1862 Constant *C2Inverse = ConstantExpr::getTrunc(C2, CE1Op0->getType());
1863 if (ConstantExpr::getCast(CE1->getOpcode(), C2Inverse,
1864 C2->getType()) == C2)
1865 return ConstantExpr::getICmp(pred, CE1Inverse, C2Inverse);
1866 }
1867 }
1868 }
1870 if ((!isa<ConstantExpr>(C1) && isa<ConstantExpr>(C2)) ||
1871 (C1->isNullValue() && !C2->isNullValue())) {
1872 // If C2 is a constant expr and C1 isn't, flip them around and fold the
1873 // other way if possible.
1874 // Also, if C1 is null and C2 isn't, flip them around.
1875 pred = ICmpInst::getSwappedPredicate((ICmpInst::Predicate)pred);
1876 return ConstantExpr::getICmp(pred, C2, C1);
1877 }
1878 }
1879 return 0;
1880 }
1882 /// isInBoundsIndices - Test whether the given sequence of *normalized* indices
1883 /// is "inbounds".
1884 template<typename IndexTy>
1885 static bool isInBoundsIndices(ArrayRef<IndexTy> Idxs) {
1886 // No indices means nothing that could be out of bounds.
1887 if (Idxs.empty()) return true;
1889 // If the first index is zero, it's in bounds.
1890 if (cast<Constant>(Idxs[0])->isNullValue()) return true;
1892 // If the first index is one and all the rest are zero, it's in bounds,
1893 // by the one-past-the-end rule.
1894 if (!cast<ConstantInt>(Idxs[0])->isOne())
1895 return false;
1896 for (unsigned i = 1, e = Idxs.size(); i != e; ++i)
1897 if (!cast<Constant>(Idxs[i])->isNullValue())
1898 return false;
1899 return true;
1900 }
1902 /// \brief Test whether a given ConstantInt is in-range for a SequentialType.
1903 static bool isIndexInRangeOfSequentialType(const SequentialType *STy,
1904 const ConstantInt *CI) {
1905 if (const PointerType *PTy = dyn_cast<PointerType>(STy))
1906 // Only handle pointers to sized types, not pointers to functions.
1907 return PTy->getElementType()->isSized();
1909 uint64_t NumElements = 0;
1910 // Determine the number of elements in our sequential type.
1911 if (const ArrayType *ATy = dyn_cast<ArrayType>(STy))
1912 NumElements = ATy->getNumElements();
1913 else if (const VectorType *VTy = dyn_cast<VectorType>(STy))
1914 NumElements = VTy->getNumElements();
1916 assert((isa<ArrayType>(STy) || NumElements > 0) &&
1917 "didn't expect non-array type to have zero elements!");
1919 // We cannot bounds check the index if it doesn't fit in an int64_t.
1920 if (CI->getValue().getActiveBits() > 64)
1921 return false;
1923 // A negative index or an index past the end of our sequential type is
1924 // considered out-of-range.
1925 int64_t IndexVal = CI->getSExtValue();
1926 if (IndexVal < 0 || (NumElements > 0 && (uint64_t)IndexVal >= NumElements))
1927 return false;
1929 // Otherwise, it is in-range.
1930 return true;
1931 }
1933 template<typename IndexTy>
1934 static Constant *ConstantFoldGetElementPtrImpl(Constant *C,
1935 bool inBounds,
1936 ArrayRef<IndexTy> Idxs) {
1937 if (Idxs.empty()) return C;
1938 Constant *Idx0 = cast<Constant>(Idxs[0]);
1939 if ((Idxs.size() == 1 && Idx0->isNullValue()))
1940 return C;
1942 if (isa<UndefValue>(C)) {
1943 PointerType *Ptr = cast<PointerType>(C->getType());
1944 Type *Ty = GetElementPtrInst::getIndexedType(Ptr, Idxs);
1945 assert(Ty != 0 && "Invalid indices for GEP!");
1946 return UndefValue::get(PointerType::get(Ty, Ptr->getAddressSpace()));
1947 }
1949 if (C->isNullValue()) {
1950 bool isNull = true;
1951 for (unsigned i = 0, e = Idxs.size(); i != e; ++i)
1952 if (!cast<Constant>(Idxs[i])->isNullValue()) {
1953 isNull = false;
1954 break;
1955 }
1956 if (isNull) {
1957 PointerType *Ptr = cast<PointerType>(C->getType());
1958 Type *Ty = GetElementPtrInst::getIndexedType(Ptr, Idxs);
1959 assert(Ty != 0 && "Invalid indices for GEP!");
1960 return ConstantPointerNull::get(PointerType::get(Ty,
1961 Ptr->getAddressSpace()));
1962 }
1963 }
1965 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(C)) {
1966 // Combine Indices - If the source pointer to this getelementptr instruction
1967 // is a getelementptr instruction, combine the indices of the two
1968 // getelementptr instructions into a single instruction.
1969 //
1970 if (CE->getOpcode() == Instruction::GetElementPtr) {
1971 Type *LastTy = 0;
1972 for (gep_type_iterator I = gep_type_begin(CE), E = gep_type_end(CE);
1973 I != E; ++I)
1974 LastTy = *I;
1976 // We cannot combine indices if doing so would take us outside of an
1977 // array or vector. Doing otherwise could trick us if we evaluated such a
1978 // GEP as part of a load.
1979 //
1980 // e.g. Consider if the original GEP was:
1981 // i8* getelementptr ({ [2 x i8], i32, i8, [3 x i8] }* @main.c,
1982 // i32 0, i32 0, i64 0)
1983 //
1984 // If we then tried to offset it by '8' to get to the third element,
1985 // an i8, we should *not* get:
1986 // i8* getelementptr ({ [2 x i8], i32, i8, [3 x i8] }* @main.c,
1987 // i32 0, i32 0, i64 8)
1988 //
1989 // This GEP tries to index array element '8 which runs out-of-bounds.
1990 // Subsequent evaluation would get confused and produce erroneous results.
1991 //
1992 // The following prohibits such a GEP from being formed by checking to see
1993 // if the index is in-range with respect to an array or vector.
1994 bool PerformFold = false;
1995 if (Idx0->isNullValue())
1996 PerformFold = true;
1997 else if (SequentialType *STy = dyn_cast_or_null<SequentialType>(LastTy))
1998 if (ConstantInt *CI = dyn_cast<ConstantInt>(Idx0))
1999 PerformFold = isIndexInRangeOfSequentialType(STy, CI);
2001 if (PerformFold) {
2002 SmallVector<Value*, 16> NewIndices;
2003 NewIndices.reserve(Idxs.size() + CE->getNumOperands());
2004 for (unsigned i = 1, e = CE->getNumOperands()-1; i != e; ++i)
2005 NewIndices.push_back(CE->getOperand(i));
2007 // Add the last index of the source with the first index of the new GEP.
2008 // Make sure to handle the case when they are actually different types.
2009 Constant *Combined = CE->getOperand(CE->getNumOperands()-1);
2010 // Otherwise it must be an array.
2011 if (!Idx0->isNullValue()) {
2012 Type *IdxTy = Combined->getType();
2013 if (IdxTy != Idx0->getType()) {
2014 Type *Int64Ty = Type::getInt64Ty(IdxTy->getContext());
2015 Constant *C1 = ConstantExpr::getSExtOrBitCast(Idx0, Int64Ty);
2016 Constant *C2 = ConstantExpr::getSExtOrBitCast(Combined, Int64Ty);
2017 Combined = ConstantExpr::get(Instruction::Add, C1, C2);
2018 } else {
2019 Combined =
2020 ConstantExpr::get(Instruction::Add, Idx0, Combined);
2021 }
2022 }
2024 NewIndices.push_back(Combined);
2025 NewIndices.append(Idxs.begin() + 1, Idxs.end());
2026 return
2027 ConstantExpr::getGetElementPtr(CE->getOperand(0), NewIndices,
2028 inBounds &&
2029 cast<GEPOperator>(CE)->isInBounds());
2030 }
2031 }
2033 // Attempt to fold casts to the same type away. For example, folding:
2034 //
2035 // i32* getelementptr ([2 x i32]* bitcast ([3 x i32]* %X to [2 x i32]*),
2036 // i64 0, i64 0)
2037 // into:
2038 //
2039 // i32* getelementptr ([3 x i32]* %X, i64 0, i64 0)
2040 //
2041 // Don't fold if the cast is changing address spaces.
2042 if (CE->isCast() && Idxs.size() > 1 && Idx0->isNullValue()) {
2043 PointerType *SrcPtrTy =
2044 dyn_cast<PointerType>(CE->getOperand(0)->getType());
2045 PointerType *DstPtrTy = dyn_cast<PointerType>(CE->getType());
2046 if (SrcPtrTy && DstPtrTy) {
2047 ArrayType *SrcArrayTy =
2048 dyn_cast<ArrayType>(SrcPtrTy->getElementType());
2049 ArrayType *DstArrayTy =
2050 dyn_cast<ArrayType>(DstPtrTy->getElementType());
2051 if (SrcArrayTy && DstArrayTy
2052 && SrcArrayTy->getElementType() == DstArrayTy->getElementType()
2053 && SrcPtrTy->getAddressSpace() == DstPtrTy->getAddressSpace())
2054 return ConstantExpr::getGetElementPtr((Constant*)CE->getOperand(0),
2055 Idxs, inBounds);
2056 }
2057 }
2058 }
2060 // Check to see if any array indices are not within the corresponding
2061 // notional array or vector bounds. If so, try to determine if they can be
2062 // factored out into preceding dimensions.
2063 bool Unknown = false;
2064 SmallVector<Constant *, 8> NewIdxs;
2065 Type *Ty = C->getType();
2066 Type *Prev = 0;
2067 for (unsigned i = 0, e = Idxs.size(); i != e;
2068 Prev = Ty, Ty = cast<CompositeType>(Ty)->getTypeAtIndex(Idxs[i]), ++i) {
2069 if (ConstantInt *CI = dyn_cast<ConstantInt>(Idxs[i])) {
2070 if (isa<ArrayType>(Ty) || isa<VectorType>(Ty))
2071 if (CI->getSExtValue() > 0 &&
2072 !isIndexInRangeOfSequentialType(cast<SequentialType>(Ty), CI)) {
2073 if (isa<SequentialType>(Prev)) {
2074 // It's out of range, but we can factor it into the prior
2075 // dimension.
2076 NewIdxs.resize(Idxs.size());
2077 uint64_t NumElements = 0;
2078 if (const ArrayType *ATy = dyn_cast<ArrayType>(Ty))
2079 NumElements = ATy->getNumElements();
2080 else
2081 NumElements = cast<VectorType>(Ty)->getNumElements();
2083 ConstantInt *Factor = ConstantInt::get(CI->getType(), NumElements);
2084 NewIdxs[i] = ConstantExpr::getSRem(CI, Factor);
2086 Constant *PrevIdx = cast<Constant>(Idxs[i-1]);
2087 Constant *Div = ConstantExpr::getSDiv(CI, Factor);
2089 // Before adding, extend both operands to i64 to avoid
2090 // overflow trouble.
2091 if (!PrevIdx->getType()->isIntegerTy(64))
2092 PrevIdx = ConstantExpr::getSExt(PrevIdx,
2093 Type::getInt64Ty(Div->getContext()));
2094 if (!Div->getType()->isIntegerTy(64))
2095 Div = ConstantExpr::getSExt(Div,
2096 Type::getInt64Ty(Div->getContext()));
2098 NewIdxs[i-1] = ConstantExpr::getAdd(PrevIdx, Div);
2099 } else {
2100 // It's out of range, but the prior dimension is a struct
2101 // so we can't do anything about it.
2102 Unknown = true;
2103 }
2104 }
2105 } else {
2106 // We don't know if it's in range or not.
2107 Unknown = true;
2108 }
2109 }
2111 // If we did any factoring, start over with the adjusted indices.
2112 if (!NewIdxs.empty()) {
2113 for (unsigned i = 0, e = Idxs.size(); i != e; ++i)
2114 if (!NewIdxs[i]) NewIdxs[i] = cast<Constant>(Idxs[i]);
2115 return ConstantExpr::getGetElementPtr(C, NewIdxs, inBounds);
2116 }
2118 // If all indices are known integers and normalized, we can do a simple
2119 // check for the "inbounds" property.
2120 if (!Unknown && !inBounds &&
2121 isa<GlobalVariable>(C) && isInBoundsIndices(Idxs))
2122 return ConstantExpr::getInBoundsGetElementPtr(C, Idxs);
2124 return 0;
2125 }
2127 Constant *llvm::ConstantFoldGetElementPtr(Constant *C,
2128 bool inBounds,
2129 ArrayRef<Constant *> Idxs) {
2130 return ConstantFoldGetElementPtrImpl(C, inBounds, Idxs);
2131 }
2133 Constant *llvm::ConstantFoldGetElementPtr(Constant *C,
2134 bool inBounds,
2135 ArrayRef<Value *> Idxs) {
2136 return ConstantFoldGetElementPtrImpl(C, inBounds, Idxs);
2137 }