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 TargetData, and the pieces that do. This is to avoid
16 // a dependence in VMCore on Target.
17 //
18 //===----------------------------------------------------------------------===//
19
20 #include "ConstantFold.h"
21 #include "llvm/Constants.h"
22 #include "llvm/Instructions.h"
23 #include "llvm/DerivedTypes.h"
24 #include "llvm/Function.h"
25 #include "llvm/GlobalAlias.h"
26 #include "llvm/GlobalVariable.h"
27 #include "llvm/Operator.h"
28 #include "llvm/ADT/SmallVector.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;
36
37 //===----------------------------------------------------------------------===//
38 // ConstantFold*Instruction Implementations
39 //===----------------------------------------------------------------------===//
40
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.
BitCastConstantVector(Constant * CV,VectorType * DstTy)44 static Constant *BitCastConstantVector(Constant *CV, VectorType *DstTy) {
45
46 if (CV->isAllOnesValue()) return Constant::getAllOnesValue(DstTy);
47 if (CV->isNullValue()) return Constant::getNullValue(DstTy);
48
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;
55
56 Type *DstEltTy = DstTy->getElementType();
57
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 }
66
67 return ConstantVector::get(Result);
68 }
69
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
foldConstantCastPair(unsigned opc,ConstantExpr * Op,Type * DstTy)75 foldConstantCastPair(
76 unsigned opc, ///< opcode of the second cast constant expression
77 ConstantExpr *Op, ///< the first cast constant expression
78 Type *DstTy ///< desintation 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");
83
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);
89
90 // Let CastInst::isEliminableCastPair do the heavy lifting.
91 return CastInst::isEliminableCastPair(firstOp, secondOp, SrcTy, MidTy, DstTy,
92 Type::getInt64Ty(DstTy->getContext()));
93 }
94
FoldBitCast(Constant * V,Type * DestTy)95 static Constant *FoldBitCast(Constant *V, Type *DestTy) {
96 Type *SrcTy = V->getType();
97 if (SrcTy == DestTy)
98 return V; // no-op cast
99
100 // Check to see if we are casting a pointer to an aggregate to a pointer to
101 // the first element. If so, return the appropriate GEP instruction.
102 if (PointerType *PTy = dyn_cast<PointerType>(V->getType()))
103 if (PointerType *DPTy = dyn_cast<PointerType>(DestTy))
104 if (PTy->getAddressSpace() == DPTy->getAddressSpace()
105 && DPTy->getElementType()->isSized()) {
106 SmallVector<Value*, 8> IdxList;
107 Value *Zero =
108 Constant::getNullValue(Type::getInt32Ty(DPTy->getContext()));
109 IdxList.push_back(Zero);
110 Type *ElTy = PTy->getElementType();
111 while (ElTy != DPTy->getElementType()) {
112 if (StructType *STy = dyn_cast<StructType>(ElTy)) {
113 if (STy->getNumElements() == 0) break;
114 ElTy = STy->getElementType(0);
115 IdxList.push_back(Zero);
116 } else if (SequentialType *STy =
117 dyn_cast<SequentialType>(ElTy)) {
118 if (ElTy->isPointerTy()) break; // Can't index into pointers!
119 ElTy = STy->getElementType();
120 IdxList.push_back(Zero);
121 } else {
122 break;
123 }
124 }
125
126 if (ElTy == DPTy->getElementType())
127 // This GEP is inbounds because all indices are zero.
128 return ConstantExpr::getInBoundsGetElementPtr(V, IdxList);
129 }
130
131 // Handle casts from one vector constant to another. We know that the src
132 // and dest type have the same size (otherwise its an illegal cast).
133 if (VectorType *DestPTy = dyn_cast<VectorType>(DestTy)) {
134 if (VectorType *SrcTy = dyn_cast<VectorType>(V->getType())) {
135 assert(DestPTy->getBitWidth() == SrcTy->getBitWidth() &&
136 "Not cast between same sized vectors!");
137 SrcTy = NULL;
138 // First, check for null. Undef is already handled.
139 if (isa<ConstantAggregateZero>(V))
140 return Constant::getNullValue(DestTy);
141
142 // Handle ConstantVector and ConstantAggregateVector.
143 return BitCastConstantVector(V, DestPTy);
144 }
145
146 // Canonicalize scalar-to-vector bitcasts into vector-to-vector bitcasts
147 // This allows for other simplifications (although some of them
148 // can only be handled by Analysis/ConstantFolding.cpp).
149 if (isa<ConstantInt>(V) || isa<ConstantFP>(V))
150 return ConstantExpr::getBitCast(ConstantVector::get(V), DestPTy);
151 }
152
153 // Finally, implement bitcast folding now. The code below doesn't handle
154 // bitcast right.
155 if (isa<ConstantPointerNull>(V)) // ptr->ptr cast.
156 return ConstantPointerNull::get(cast<PointerType>(DestTy));
157
158 // Handle integral constant input.
159 if (ConstantInt *CI = dyn_cast<ConstantInt>(V)) {
160 if (DestTy->isIntegerTy())
161 // Integral -> Integral. This is a no-op because the bit widths must
162 // be the same. Consequently, we just fold to V.
163 return V;
164
165 if (DestTy->isFloatingPointTy())
166 return ConstantFP::get(DestTy->getContext(),
167 APFloat(CI->getValue(),
168 !DestTy->isPPC_FP128Ty()));
169
170 // Otherwise, can't fold this (vector?)
171 return 0;
172 }
173
174 // Handle ConstantFP input: FP -> Integral.
175 if (ConstantFP *FP = dyn_cast<ConstantFP>(V))
176 return ConstantInt::get(FP->getContext(),
177 FP->getValueAPF().bitcastToAPInt());
178
179 return 0;
180 }
181
182
183 /// ExtractConstantBytes - V is an integer constant which only has a subset of
184 /// its bytes used. The bytes used are indicated by ByteStart (which is the
185 /// first byte used, counting from the least significant byte) and ByteSize,
186 /// which is the number of bytes used.
187 ///
188 /// This function analyzes the specified constant to see if the specified byte
189 /// range can be returned as a simplified constant. If so, the constant is
190 /// returned, otherwise null is returned.
191 ///
ExtractConstantBytes(Constant * C,unsigned ByteStart,unsigned ByteSize)192 static Constant *ExtractConstantBytes(Constant *C, unsigned ByteStart,
193 unsigned ByteSize) {
194 assert(C->getType()->isIntegerTy() &&
195 (cast<IntegerType>(C->getType())->getBitWidth() & 7) == 0 &&
196 "Non-byte sized integer input");
197 unsigned CSize = cast<IntegerType>(C->getType())->getBitWidth()/8;
198 assert(ByteSize && "Must be accessing some piece");
199 assert(ByteStart+ByteSize <= CSize && "Extracting invalid piece from input");
200 assert(ByteSize != CSize && "Should not extract everything");
201
202 // Constant Integers are simple.
203 if (ConstantInt *CI = dyn_cast<ConstantInt>(C)) {
204 APInt V = CI->getValue();
205 if (ByteStart)
206 V = V.lshr(ByteStart*8);
207 V = V.trunc(ByteSize*8);
208 return ConstantInt::get(CI->getContext(), V);
209 }
210
211 // In the input is a constant expr, we might be able to recursively simplify.
212 // If not, we definitely can't do anything.
213 ConstantExpr *CE = dyn_cast<ConstantExpr>(C);
214 if (CE == 0) return 0;
215
216 switch (CE->getOpcode()) {
217 default: return 0;
218 case Instruction::Or: {
219 Constant *RHS = ExtractConstantBytes(CE->getOperand(1), ByteStart,ByteSize);
220 if (RHS == 0)
221 return 0;
222
223 // X | -1 -> -1.
224 if (ConstantInt *RHSC = dyn_cast<ConstantInt>(RHS))
225 if (RHSC->isAllOnesValue())
226 return RHSC;
227
228 Constant *LHS = ExtractConstantBytes(CE->getOperand(0), ByteStart,ByteSize);
229 if (LHS == 0)
230 return 0;
231 return ConstantExpr::getOr(LHS, RHS);
232 }
233 case Instruction::And: {
234 Constant *RHS = ExtractConstantBytes(CE->getOperand(1), ByteStart,ByteSize);
235 if (RHS == 0)
236 return 0;
237
238 // X & 0 -> 0.
239 if (RHS->isNullValue())
240 return RHS;
241
242 Constant *LHS = ExtractConstantBytes(CE->getOperand(0), ByteStart,ByteSize);
243 if (LHS == 0)
244 return 0;
245 return ConstantExpr::getAnd(LHS, RHS);
246 }
247 case Instruction::LShr: {
248 ConstantInt *Amt = dyn_cast<ConstantInt>(CE->getOperand(1));
249 if (Amt == 0)
250 return 0;
251 unsigned ShAmt = Amt->getZExtValue();
252 // Cannot analyze non-byte shifts.
253 if ((ShAmt & 7) != 0)
254 return 0;
255 ShAmt >>= 3;
256
257 // If the extract is known to be all zeros, return zero.
258 if (ByteStart >= CSize-ShAmt)
259 return Constant::getNullValue(IntegerType::get(CE->getContext(),
260 ByteSize*8));
261 // If the extract is known to be fully in the input, extract it.
262 if (ByteStart+ByteSize+ShAmt <= CSize)
263 return ExtractConstantBytes(CE->getOperand(0), ByteStart+ShAmt, ByteSize);
264
265 // TODO: Handle the 'partially zero' case.
266 return 0;
267 }
268
269 case Instruction::Shl: {
270 ConstantInt *Amt = dyn_cast<ConstantInt>(CE->getOperand(1));
271 if (Amt == 0)
272 return 0;
273 unsigned ShAmt = Amt->getZExtValue();
274 // Cannot analyze non-byte shifts.
275 if ((ShAmt & 7) != 0)
276 return 0;
277 ShAmt >>= 3;
278
279 // If the extract is known to be all zeros, return zero.
280 if (ByteStart+ByteSize <= ShAmt)
281 return Constant::getNullValue(IntegerType::get(CE->getContext(),
282 ByteSize*8));
283 // If the extract is known to be fully in the input, extract it.
284 if (ByteStart >= ShAmt)
285 return ExtractConstantBytes(CE->getOperand(0), ByteStart-ShAmt, ByteSize);
286
287 // TODO: Handle the 'partially zero' case.
288 return 0;
289 }
290
291 case Instruction::ZExt: {
292 unsigned SrcBitSize =
293 cast<IntegerType>(CE->getOperand(0)->getType())->getBitWidth();
294
295 // If extracting something that is completely zero, return 0.
296 if (ByteStart*8 >= SrcBitSize)
297 return Constant::getNullValue(IntegerType::get(CE->getContext(),
298 ByteSize*8));
299
300 // If exactly extracting the input, return it.
301 if (ByteStart == 0 && ByteSize*8 == SrcBitSize)
302 return CE->getOperand(0);
303
304 // If extracting something completely in the input, if if the input is a
305 // multiple of 8 bits, recurse.
306 if ((SrcBitSize&7) == 0 && (ByteStart+ByteSize)*8 <= SrcBitSize)
307 return ExtractConstantBytes(CE->getOperand(0), ByteStart, ByteSize);
308
309 // Otherwise, if extracting a subset of the input, which is not multiple of
310 // 8 bits, do a shift and trunc to get the bits.
311 if ((ByteStart+ByteSize)*8 < SrcBitSize) {
312 assert((SrcBitSize&7) && "Shouldn't get byte sized case here");
313 Constant *Res = CE->getOperand(0);
314 if (ByteStart)
315 Res = ConstantExpr::getLShr(Res,
316 ConstantInt::get(Res->getType(), ByteStart*8));
317 return ConstantExpr::getTrunc(Res, IntegerType::get(C->getContext(),
318 ByteSize*8));
319 }
320
321 // TODO: Handle the 'partially zero' case.
322 return 0;
323 }
324 }
325 }
326
327 /// getFoldedSizeOf - Return a ConstantExpr with type DestTy for sizeof
328 /// on Ty, with any known factors factored out. If Folded is false,
329 /// return null if no factoring was possible, to avoid endlessly
330 /// bouncing an unfoldable expression back into the top-level folder.
331 ///
getFoldedSizeOf(Type * Ty,Type * DestTy,bool Folded)332 static Constant *getFoldedSizeOf(Type *Ty, Type *DestTy,
333 bool Folded) {
334 if (ArrayType *ATy = dyn_cast<ArrayType>(Ty)) {
335 Constant *N = ConstantInt::get(DestTy, ATy->getNumElements());
336 Constant *E = getFoldedSizeOf(ATy->getElementType(), DestTy, true);
337 return ConstantExpr::getNUWMul(E, N);
338 }
339
340 if (StructType *STy = dyn_cast<StructType>(Ty))
341 if (!STy->isPacked()) {
342 unsigned NumElems = STy->getNumElements();
343 // An empty struct has size zero.
344 if (NumElems == 0)
345 return ConstantExpr::getNullValue(DestTy);
346 // Check for a struct with all members having the same size.
347 Constant *MemberSize =
348 getFoldedSizeOf(STy->getElementType(0), DestTy, true);
349 bool AllSame = true;
350 for (unsigned i = 1; i != NumElems; ++i)
351 if (MemberSize !=
352 getFoldedSizeOf(STy->getElementType(i), DestTy, true)) {
353 AllSame = false;
354 break;
355 }
356 if (AllSame) {
357 Constant *N = ConstantInt::get(DestTy, NumElems);
358 return ConstantExpr::getNUWMul(MemberSize, N);
359 }
360 }
361
362 // Pointer size doesn't depend on the pointee type, so canonicalize them
363 // to an arbitrary pointee.
364 if (PointerType *PTy = dyn_cast<PointerType>(Ty))
365 if (!PTy->getElementType()->isIntegerTy(1))
366 return
367 getFoldedSizeOf(PointerType::get(IntegerType::get(PTy->getContext(), 1),
368 PTy->getAddressSpace()),
369 DestTy, true);
370
371 // If there's no interesting folding happening, bail so that we don't create
372 // a constant that looks like it needs folding but really doesn't.
373 if (!Folded)
374 return 0;
375
376 // Base case: Get a regular sizeof expression.
377 Constant *C = ConstantExpr::getSizeOf(Ty);
378 C = ConstantExpr::getCast(CastInst::getCastOpcode(C, false,
379 DestTy, false),
380 C, DestTy);
381 return C;
382 }
383
384 /// getFoldedAlignOf - Return a ConstantExpr with type DestTy for alignof
385 /// on Ty, with any known factors factored out. If Folded is false,
386 /// return null if no factoring was possible, to avoid endlessly
387 /// bouncing an unfoldable expression back into the top-level folder.
388 ///
getFoldedAlignOf(Type * Ty,Type * DestTy,bool Folded)389 static Constant *getFoldedAlignOf(Type *Ty, Type *DestTy,
390 bool Folded) {
391 // The alignment of an array is equal to the alignment of the
392 // array element. Note that this is not always true for vectors.
393 if (ArrayType *ATy = dyn_cast<ArrayType>(Ty)) {
394 Constant *C = ConstantExpr::getAlignOf(ATy->getElementType());
395 C = ConstantExpr::getCast(CastInst::getCastOpcode(C, false,
396 DestTy,
397 false),
398 C, DestTy);
399 return C;
400 }
401
402 if (StructType *STy = dyn_cast<StructType>(Ty)) {
403 // Packed structs always have an alignment of 1.
404 if (STy->isPacked())
405 return ConstantInt::get(DestTy, 1);
406
407 // Otherwise, struct alignment is the maximum alignment of any member.
408 // Without target data, we can't compare much, but we can check to see
409 // if all the members have the same alignment.
410 unsigned NumElems = STy->getNumElements();
411 // An empty struct has minimal alignment.
412 if (NumElems == 0)
413 return ConstantInt::get(DestTy, 1);
414 // Check for a struct with all members having the same alignment.
415 Constant *MemberAlign =
416 getFoldedAlignOf(STy->getElementType(0), DestTy, true);
417 bool AllSame = true;
418 for (unsigned i = 1; i != NumElems; ++i)
419 if (MemberAlign != getFoldedAlignOf(STy->getElementType(i), DestTy, true)) {
420 AllSame = false;
421 break;
422 }
423 if (AllSame)
424 return MemberAlign;
425 }
426
427 // Pointer alignment doesn't depend on the pointee type, so canonicalize them
428 // to an arbitrary pointee.
429 if (PointerType *PTy = dyn_cast<PointerType>(Ty))
430 if (!PTy->getElementType()->isIntegerTy(1))
431 return
432 getFoldedAlignOf(PointerType::get(IntegerType::get(PTy->getContext(),
433 1),
434 PTy->getAddressSpace()),
435 DestTy, true);
436
437 // If there's no interesting folding happening, bail so that we don't create
438 // a constant that looks like it needs folding but really doesn't.
439 if (!Folded)
440 return 0;
441
442 // Base case: Get a regular alignof expression.
443 Constant *C = ConstantExpr::getAlignOf(Ty);
444 C = ConstantExpr::getCast(CastInst::getCastOpcode(C, false,
445 DestTy, false),
446 C, DestTy);
447 return C;
448 }
449
450 /// getFoldedOffsetOf - Return a ConstantExpr with type DestTy for offsetof
451 /// on Ty and FieldNo, with any known factors factored out. If Folded is false,
452 /// return null if no factoring was possible, to avoid endlessly
453 /// bouncing an unfoldable expression back into the top-level folder.
454 ///
getFoldedOffsetOf(Type * Ty,Constant * FieldNo,Type * DestTy,bool Folded)455 static Constant *getFoldedOffsetOf(Type *Ty, Constant *FieldNo,
456 Type *DestTy,
457 bool Folded) {
458 if (ArrayType *ATy = dyn_cast<ArrayType>(Ty)) {
459 Constant *N = ConstantExpr::getCast(CastInst::getCastOpcode(FieldNo, false,
460 DestTy, false),
461 FieldNo, DestTy);
462 Constant *E = getFoldedSizeOf(ATy->getElementType(), DestTy, true);
463 return ConstantExpr::getNUWMul(E, N);
464 }
465
466 if (StructType *STy = dyn_cast<StructType>(Ty))
467 if (!STy->isPacked()) {
468 unsigned NumElems = STy->getNumElements();
469 // An empty struct has no members.
470 if (NumElems == 0)
471 return 0;
472 // Check for a struct with all members having the same size.
473 Constant *MemberSize =
474 getFoldedSizeOf(STy->getElementType(0), DestTy, true);
475 bool AllSame = true;
476 for (unsigned i = 1; i != NumElems; ++i)
477 if (MemberSize !=
478 getFoldedSizeOf(STy->getElementType(i), DestTy, true)) {
479 AllSame = false;
480 break;
481 }
482 if (AllSame) {
483 Constant *N = ConstantExpr::getCast(CastInst::getCastOpcode(FieldNo,
484 false,
485 DestTy,
486 false),
487 FieldNo, DestTy);
488 return ConstantExpr::getNUWMul(MemberSize, N);
489 }
490 }
491
492 // If there's no interesting folding happening, bail so that we don't create
493 // a constant that looks like it needs folding but really doesn't.
494 if (!Folded)
495 return 0;
496
497 // Base case: Get a regular offsetof expression.
498 Constant *C = ConstantExpr::getOffsetOf(Ty, FieldNo);
499 C = ConstantExpr::getCast(CastInst::getCastOpcode(C, false,
500 DestTy, false),
501 C, DestTy);
502 return C;
503 }
504
ConstantFoldCastInstruction(unsigned opc,Constant * V,Type * DestTy)505 Constant *llvm::ConstantFoldCastInstruction(unsigned opc, Constant *V,
506 Type *DestTy) {
507 if (isa<UndefValue>(V)) {
508 // zext(undef) = 0, because the top bits will be zero.
509 // sext(undef) = 0, because the top bits will all be the same.
510 // [us]itofp(undef) = 0, because the result value is bounded.
511 if (opc == Instruction::ZExt || opc == Instruction::SExt ||
512 opc == Instruction::UIToFP || opc == Instruction::SIToFP)
513 return Constant::getNullValue(DestTy);
514 return UndefValue::get(DestTy);
515 }
516
517 // No compile-time operations on this type yet.
518 if (V->getType()->isPPC_FP128Ty() || DestTy->isPPC_FP128Ty())
519 return 0;
520
521 if (V->isNullValue() && !DestTy->isX86_MMXTy())
522 return Constant::getNullValue(DestTy);
523
524 // If the cast operand is a constant expression, there's a few things we can
525 // do to try to simplify it.
526 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V)) {
527 if (CE->isCast()) {
528 // Try hard to fold cast of cast because they are often eliminable.
529 if (unsigned newOpc = foldConstantCastPair(opc, CE, DestTy))
530 return ConstantExpr::getCast(newOpc, CE->getOperand(0), DestTy);
531 } else if (CE->getOpcode() == Instruction::GetElementPtr) {
532 // If all of the indexes in the GEP are null values, there is no pointer
533 // adjustment going on. We might as well cast the source pointer.
534 bool isAllNull = true;
535 for (unsigned i = 1, e = CE->getNumOperands(); i != e; ++i)
536 if (!CE->getOperand(i)->isNullValue()) {
537 isAllNull = false;
538 break;
539 }
540 if (isAllNull)
541 // This is casting one pointer type to another, always BitCast
542 return ConstantExpr::getPointerCast(CE->getOperand(0), DestTy);
543 }
544 }
545
546 // If the cast operand is a constant vector, perform the cast by
547 // operating on each element. In the cast of bitcasts, the element
548 // count may be mismatched; don't attempt to handle that here.
549 if ((isa<ConstantVector>(V) || isa<ConstantDataVector>(V)) &&
550 DestTy->isVectorTy() &&
551 DestTy->getVectorNumElements() == V->getType()->getVectorNumElements()) {
552 SmallVector<Constant*, 16> res;
553 VectorType *DestVecTy = cast<VectorType>(DestTy);
554 Type *DstEltTy = DestVecTy->getElementType();
555 Type *Ty = IntegerType::get(V->getContext(), 32);
556 for (unsigned i = 0, e = V->getType()->getVectorNumElements(); i != e; ++i) {
557 Constant *C =
558 ConstantExpr::getExtractElement(V, ConstantInt::get(Ty, i));
559 res.push_back(ConstantExpr::getCast(opc, C, DstEltTy));
560 }
561 return ConstantVector::get(res);
562 }
563
564 // We actually have to do a cast now. Perform the cast according to the
565 // opcode specified.
566 switch (opc) {
567 default:
568 llvm_unreachable("Failed to cast constant expression");
569 case Instruction::FPTrunc:
570 case Instruction::FPExt:
571 if (ConstantFP *FPC = dyn_cast<ConstantFP>(V)) {
572 bool ignored;
573 APFloat Val = FPC->getValueAPF();
574 Val.convert(DestTy->isHalfTy() ? APFloat::IEEEhalf :
575 DestTy->isFloatTy() ? APFloat::IEEEsingle :
576 DestTy->isDoubleTy() ? APFloat::IEEEdouble :
577 DestTy->isX86_FP80Ty() ? APFloat::x87DoubleExtended :
578 DestTy->isFP128Ty() ? APFloat::IEEEquad :
579 APFloat::Bogus,
580 APFloat::rmNearestTiesToEven, &ignored);
581 return ConstantFP::get(V->getContext(), Val);
582 }
583 return 0; // Can't fold.
584 case Instruction::FPToUI:
585 case Instruction::FPToSI:
586 if (ConstantFP *FPC = dyn_cast<ConstantFP>(V)) {
587 const APFloat &V = FPC->getValueAPF();
588 bool ignored;
589 uint64_t x[2];
590 uint32_t DestBitWidth = cast<IntegerType>(DestTy)->getBitWidth();
591 (void) V.convertToInteger(x, DestBitWidth, opc==Instruction::FPToSI,
592 APFloat::rmTowardZero, &ignored);
593 APInt Val(DestBitWidth, x);
594 return ConstantInt::get(FPC->getContext(), Val);
595 }
596 return 0; // Can't fold.
597 case Instruction::IntToPtr: //always treated as unsigned
598 if (V->isNullValue()) // Is it an integral null value?
599 return ConstantPointerNull::get(cast<PointerType>(DestTy));
600 return 0; // Other pointer types cannot be casted
601 case Instruction::PtrToInt: // always treated as unsigned
602 // Is it a null pointer value?
603 if (V->isNullValue())
604 return ConstantInt::get(DestTy, 0);
605 // If this is a sizeof-like expression, pull out multiplications by
606 // known factors to expose them to subsequent folding. If it's an
607 // alignof-like expression, factor out known factors.
608 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V))
609 if (CE->getOpcode() == Instruction::GetElementPtr &&
610 CE->getOperand(0)->isNullValue()) {
611 Type *Ty =
612 cast<PointerType>(CE->getOperand(0)->getType())->getElementType();
613 if (CE->getNumOperands() == 2) {
614 // Handle a sizeof-like expression.
615 Constant *Idx = CE->getOperand(1);
616 bool isOne = isa<ConstantInt>(Idx) && cast<ConstantInt>(Idx)->isOne();
617 if (Constant *C = getFoldedSizeOf(Ty, DestTy, !isOne)) {
618 Idx = ConstantExpr::getCast(CastInst::getCastOpcode(Idx, true,
619 DestTy, false),
620 Idx, DestTy);
621 return ConstantExpr::getMul(C, Idx);
622 }
623 } else if (CE->getNumOperands() == 3 &&
624 CE->getOperand(1)->isNullValue()) {
625 // Handle an alignof-like expression.
626 if (StructType *STy = dyn_cast<StructType>(Ty))
627 if (!STy->isPacked()) {
628 ConstantInt *CI = cast<ConstantInt>(CE->getOperand(2));
629 if (CI->isOne() &&
630 STy->getNumElements() == 2 &&
631 STy->getElementType(0)->isIntegerTy(1)) {
632 return getFoldedAlignOf(STy->getElementType(1), DestTy, false);
633 }
634 }
635 // Handle an offsetof-like expression.
636 if (Ty->isStructTy() || Ty->isArrayTy()) {
637 if (Constant *C = getFoldedOffsetOf(Ty, CE->getOperand(2),
638 DestTy, false))
639 return C;
640 }
641 }
642 }
643 // Other pointer types cannot be casted
644 return 0;
645 case Instruction::UIToFP:
646 case Instruction::SIToFP:
647 if (ConstantInt *CI = dyn_cast<ConstantInt>(V)) {
648 APInt api = CI->getValue();
649 APFloat apf(APInt::getNullValue(DestTy->getPrimitiveSizeInBits()), true);
650 (void)apf.convertFromAPInt(api,
651 opc==Instruction::SIToFP,
652 APFloat::rmNearestTiesToEven);
653 return ConstantFP::get(V->getContext(), apf);
654 }
655 return 0;
656 case Instruction::ZExt:
657 if (ConstantInt *CI = dyn_cast<ConstantInt>(V)) {
658 uint32_t BitWidth = cast<IntegerType>(DestTy)->getBitWidth();
659 return ConstantInt::get(V->getContext(),
660 CI->getValue().zext(BitWidth));
661 }
662 return 0;
663 case Instruction::SExt:
664 if (ConstantInt *CI = dyn_cast<ConstantInt>(V)) {
665 uint32_t BitWidth = cast<IntegerType>(DestTy)->getBitWidth();
666 return ConstantInt::get(V->getContext(),
667 CI->getValue().sext(BitWidth));
668 }
669 return 0;
670 case Instruction::Trunc: {
671 uint32_t DestBitWidth = cast<IntegerType>(DestTy)->getBitWidth();
672 if (ConstantInt *CI = dyn_cast<ConstantInt>(V)) {
673 return ConstantInt::get(V->getContext(),
674 CI->getValue().trunc(DestBitWidth));
675 }
676
677 // The input must be a constantexpr. See if we can simplify this based on
678 // the bytes we are demanding. Only do this if the source and dest are an
679 // even multiple of a byte.
680 if ((DestBitWidth & 7) == 0 &&
681 (cast<IntegerType>(V->getType())->getBitWidth() & 7) == 0)
682 if (Constant *Res = ExtractConstantBytes(V, 0, DestBitWidth / 8))
683 return Res;
684
685 return 0;
686 }
687 case Instruction::BitCast:
688 return FoldBitCast(V, DestTy);
689 }
690 }
691
ConstantFoldSelectInstruction(Constant * Cond,Constant * V1,Constant * V2)692 Constant *llvm::ConstantFoldSelectInstruction(Constant *Cond,
693 Constant *V1, Constant *V2) {
694 // Check for i1 and vector true/false conditions.
695 if (Cond->isNullValue()) return V2;
696 if (Cond->isAllOnesValue()) return V1;
697
698 // If the condition is a vector constant, fold the result elementwise.
699 if (ConstantVector *CondV = dyn_cast<ConstantVector>(Cond)) {
700 SmallVector<Constant*, 16> Result;
701 Type *Ty = IntegerType::get(CondV->getContext(), 32);
702 for (unsigned i = 0, e = V1->getType()->getVectorNumElements(); i != e;++i){
703 ConstantInt *Cond = dyn_cast<ConstantInt>(CondV->getOperand(i));
704 if (Cond == 0) break;
705
706 Constant *V = Cond->isNullValue() ? V2 : V1;
707 Constant *Res = ConstantExpr::getExtractElement(V, ConstantInt::get(Ty, i));
708 Result.push_back(Res);
709 }
710
711 // If we were able to build the vector, return it.
712 if (Result.size() == V1->getType()->getVectorNumElements())
713 return ConstantVector::get(Result);
714 }
715
716 if (isa<UndefValue>(Cond)) {
717 if (isa<UndefValue>(V1)) return V1;
718 return V2;
719 }
720 if (isa<UndefValue>(V1)) return V2;
721 if (isa<UndefValue>(V2)) return V1;
722 if (V1 == V2) return V1;
723
724 if (ConstantExpr *TrueVal = dyn_cast<ConstantExpr>(V1)) {
725 if (TrueVal->getOpcode() == Instruction::Select)
726 if (TrueVal->getOperand(0) == Cond)
727 return ConstantExpr::getSelect(Cond, TrueVal->getOperand(1), V2);
728 }
729 if (ConstantExpr *FalseVal = dyn_cast<ConstantExpr>(V2)) {
730 if (FalseVal->getOpcode() == Instruction::Select)
731 if (FalseVal->getOperand(0) == Cond)
732 return ConstantExpr::getSelect(Cond, V1, FalseVal->getOperand(2));
733 }
734
735 return 0;
736 }
737
ConstantFoldExtractElementInstruction(Constant * Val,Constant * Idx)738 Constant *llvm::ConstantFoldExtractElementInstruction(Constant *Val,
739 Constant *Idx) {
740 if (isa<UndefValue>(Val)) // ee(undef, x) -> undef
741 return UndefValue::get(Val->getType()->getVectorElementType());
742 if (Val->isNullValue()) // ee(zero, x) -> zero
743 return Constant::getNullValue(Val->getType()->getVectorElementType());
744 // ee({w,x,y,z}, undef) -> undef
745 if (isa<UndefValue>(Idx))
746 return UndefValue::get(Val->getType()->getVectorElementType());
747
748 if (ConstantInt *CIdx = dyn_cast<ConstantInt>(Idx)) {
749 uint64_t Index = CIdx->getZExtValue();
750 // ee({w,x,y,z}, wrong_value) -> undef
751 if (Index >= Val->getType()->getVectorNumElements())
752 return UndefValue::get(Val->getType()->getVectorElementType());
753 return Val->getAggregateElement(Index);
754 }
755 return 0;
756 }
757
ConstantFoldInsertElementInstruction(Constant * Val,Constant * Elt,Constant * Idx)758 Constant *llvm::ConstantFoldInsertElementInstruction(Constant *Val,
759 Constant *Elt,
760 Constant *Idx) {
761 ConstantInt *CIdx = dyn_cast<ConstantInt>(Idx);
762 if (!CIdx) return 0;
763 const APInt &IdxVal = CIdx->getValue();
764
765 SmallVector<Constant*, 16> Result;
766 Type *Ty = IntegerType::get(Val->getContext(), 32);
767 for (unsigned i = 0, e = Val->getType()->getVectorNumElements(); i != e; ++i){
768 if (i == IdxVal) {
769 Result.push_back(Elt);
770 continue;
771 }
772
773 Constant *C =
774 ConstantExpr::getExtractElement(Val, ConstantInt::get(Ty, i));
775 Result.push_back(C);
776 }
777
778 return ConstantVector::get(Result);
779 }
780
ConstantFoldShuffleVectorInstruction(Constant * V1,Constant * V2,Constant * Mask)781 Constant *llvm::ConstantFoldShuffleVectorInstruction(Constant *V1,
782 Constant *V2,
783 Constant *Mask) {
784 unsigned MaskNumElts = Mask->getType()->getVectorNumElements();
785 Type *EltTy = V1->getType()->getVectorElementType();
786
787 // Undefined shuffle mask -> undefined value.
788 if (isa<UndefValue>(Mask))
789 return UndefValue::get(VectorType::get(EltTy, MaskNumElts));
790
791 // Don't break the bitcode reader hack.
792 if (isa<ConstantExpr>(Mask)) return 0;
793
794 unsigned SrcNumElts = V1->getType()->getVectorNumElements();
795
796 // Loop over the shuffle mask, evaluating each element.
797 SmallVector<Constant*, 32> Result;
798 for (unsigned i = 0; i != MaskNumElts; ++i) {
799 int Elt = ShuffleVectorInst::getMaskValue(Mask, i);
800 if (Elt == -1) {
801 Result.push_back(UndefValue::get(EltTy));
802 continue;
803 }
804 Constant *InElt;
805 if (unsigned(Elt) >= SrcNumElts*2)
806 InElt = UndefValue::get(EltTy);
807 else if (unsigned(Elt) >= SrcNumElts) {
808 Type *Ty = IntegerType::get(V2->getContext(), 32);
809 InElt =
810 ConstantExpr::getExtractElement(V2,
811 ConstantInt::get(Ty, Elt - SrcNumElts));
812 } else {
813 Type *Ty = IntegerType::get(V1->getContext(), 32);
814 InElt = ConstantExpr::getExtractElement(V1, ConstantInt::get(Ty, Elt));
815 }
816 Result.push_back(InElt);
817 }
818
819 return ConstantVector::get(Result);
820 }
821
ConstantFoldExtractValueInstruction(Constant * Agg,ArrayRef<unsigned> Idxs)822 Constant *llvm::ConstantFoldExtractValueInstruction(Constant *Agg,
823 ArrayRef<unsigned> Idxs) {
824 // Base case: no indices, so return the entire value.
825 if (Idxs.empty())
826 return Agg;
827
828 if (Constant *C = Agg->getAggregateElement(Idxs[0]))
829 return ConstantFoldExtractValueInstruction(C, Idxs.slice(1));
830
831 return 0;
832 }
833
ConstantFoldInsertValueInstruction(Constant * Agg,Constant * Val,ArrayRef<unsigned> Idxs)834 Constant *llvm::ConstantFoldInsertValueInstruction(Constant *Agg,
835 Constant *Val,
836 ArrayRef<unsigned> Idxs) {
837 // Base case: no indices, so replace the entire value.
838 if (Idxs.empty())
839 return Val;
840
841 unsigned NumElts;
842 if (StructType *ST = dyn_cast<StructType>(Agg->getType()))
843 NumElts = ST->getNumElements();
844 else if (ArrayType *AT = dyn_cast<ArrayType>(Agg->getType()))
845 NumElts = AT->getNumElements();
846 else
847 NumElts = AT->getVectorNumElements();
848
849 SmallVector<Constant*, 32> Result;
850 for (unsigned i = 0; i != NumElts; ++i) {
851 Constant *C = Agg->getAggregateElement(i);
852 if (C == 0) return 0;
853
854 if (Idxs[0] == i)
855 C = ConstantFoldInsertValueInstruction(C, Val, Idxs.slice(1));
856
857 Result.push_back(C);
858 }
859
860 if (StructType *ST = dyn_cast<StructType>(Agg->getType()))
861 return ConstantStruct::get(ST, Result);
862 if (ArrayType *AT = dyn_cast<ArrayType>(Agg->getType()))
863 return ConstantArray::get(AT, Result);
864 return ConstantVector::get(Result);
865 }
866
867
ConstantFoldBinaryInstruction(unsigned Opcode,Constant * C1,Constant * C2)868 Constant *llvm::ConstantFoldBinaryInstruction(unsigned Opcode,
869 Constant *C1, Constant *C2) {
870 // No compile-time operations on this type yet.
871 if (C1->getType()->isPPC_FP128Ty())
872 return 0;
873
874 // Handle UndefValue up front.
875 if (isa<UndefValue>(C1) || isa<UndefValue>(C2)) {
876 switch (Opcode) {
877 case Instruction::Xor:
878 if (isa<UndefValue>(C1) && isa<UndefValue>(C2))
879 // Handle undef ^ undef -> 0 special case. This is a common
880 // idiom (misuse).
881 return Constant::getNullValue(C1->getType());
882 // Fallthrough
883 case Instruction::Add:
884 case Instruction::Sub:
885 return UndefValue::get(C1->getType());
886 case Instruction::And:
887 if (isa<UndefValue>(C1) && isa<UndefValue>(C2)) // undef & undef -> undef
888 return C1;
889 return Constant::getNullValue(C1->getType()); // undef & X -> 0
890 case Instruction::Mul: {
891 ConstantInt *CI;
892 // X * undef -> undef if X is odd or undef
893 if (((CI = dyn_cast<ConstantInt>(C1)) && CI->getValue()[0]) ||
894 ((CI = dyn_cast<ConstantInt>(C2)) && CI->getValue()[0]) ||
895 (isa<UndefValue>(C1) && isa<UndefValue>(C2)))
896 return UndefValue::get(C1->getType());
897
898 // X * undef -> 0 otherwise
899 return Constant::getNullValue(C1->getType());
900 }
901 case Instruction::UDiv:
902 case Instruction::SDiv:
903 // undef / 1 -> undef
904 if (Opcode == Instruction::UDiv || Opcode == Instruction::SDiv)
905 if (ConstantInt *CI2 = dyn_cast<ConstantInt>(C2))
906 if (CI2->isOne())
907 return C1;
908 // FALL THROUGH
909 case Instruction::URem:
910 case Instruction::SRem:
911 if (!isa<UndefValue>(C2)) // undef / X -> 0
912 return Constant::getNullValue(C1->getType());
913 return C2; // X / undef -> undef
914 case Instruction::Or: // X | undef -> -1
915 if (isa<UndefValue>(C1) && isa<UndefValue>(C2)) // undef | undef -> undef
916 return C1;
917 return Constant::getAllOnesValue(C1->getType()); // undef | X -> ~0
918 case Instruction::LShr:
919 if (isa<UndefValue>(C2) && isa<UndefValue>(C1))
920 return C1; // undef lshr undef -> undef
921 return Constant::getNullValue(C1->getType()); // X lshr undef -> 0
922 // undef lshr X -> 0
923 case Instruction::AShr:
924 if (!isa<UndefValue>(C2)) // undef ashr X --> all ones
925 return Constant::getAllOnesValue(C1->getType());
926 else if (isa<UndefValue>(C1))
927 return C1; // undef ashr undef -> undef
928 else
929 return C1; // X ashr undef --> X
930 case Instruction::Shl:
931 if (isa<UndefValue>(C2) && isa<UndefValue>(C1))
932 return C1; // undef shl undef -> undef
933 // undef << X -> 0 or X << undef -> 0
934 return Constant::getNullValue(C1->getType());
935 }
936 }
937
938 // Handle simplifications when the RHS is a constant int.
939 if (ConstantInt *CI2 = dyn_cast<ConstantInt>(C2)) {
940 switch (Opcode) {
941 case Instruction::Add:
942 if (CI2->equalsInt(0)) return C1; // X + 0 == X
943 break;
944 case Instruction::Sub:
945 if (CI2->equalsInt(0)) return C1; // X - 0 == X
946 break;
947 case Instruction::Mul:
948 if (CI2->equalsInt(0)) return C2; // X * 0 == 0
949 if (CI2->equalsInt(1))
950 return C1; // X * 1 == X
951 break;
952 case Instruction::UDiv:
953 case Instruction::SDiv:
954 if (CI2->equalsInt(1))
955 return C1; // X / 1 == X
956 if (CI2->equalsInt(0))
957 return UndefValue::get(CI2->getType()); // X / 0 == undef
958 break;
959 case Instruction::URem:
960 case Instruction::SRem:
961 if (CI2->equalsInt(1))
962 return Constant::getNullValue(CI2->getType()); // X % 1 == 0
963 if (CI2->equalsInt(0))
964 return UndefValue::get(CI2->getType()); // X % 0 == undef
965 break;
966 case Instruction::And:
967 if (CI2->isZero()) return C2; // X & 0 == 0
968 if (CI2->isAllOnesValue())
969 return C1; // X & -1 == X
970
971 if (ConstantExpr *CE1 = dyn_cast<ConstantExpr>(C1)) {
972 // (zext i32 to i64) & 4294967295 -> (zext i32 to i64)
973 if (CE1->getOpcode() == Instruction::ZExt) {
974 unsigned DstWidth = CI2->getType()->getBitWidth();
975 unsigned SrcWidth =
976 CE1->getOperand(0)->getType()->getPrimitiveSizeInBits();
977 APInt PossiblySetBits(APInt::getLowBitsSet(DstWidth, SrcWidth));
978 if ((PossiblySetBits & CI2->getValue()) == PossiblySetBits)
979 return C1;
980 }
981
982 // If and'ing the address of a global with a constant, fold it.
983 if (CE1->getOpcode() == Instruction::PtrToInt &&
984 isa<GlobalValue>(CE1->getOperand(0))) {
985 GlobalValue *GV = cast<GlobalValue>(CE1->getOperand(0));
986
987 // Functions are at least 4-byte aligned.
988 unsigned GVAlign = GV->getAlignment();
989 if (isa<Function>(GV))
990 GVAlign = std::max(GVAlign, 4U);
991
992 if (GVAlign > 1) {
993 unsigned DstWidth = CI2->getType()->getBitWidth();
994 unsigned SrcWidth = std::min(DstWidth, Log2_32(GVAlign));
995 APInt BitsNotSet(APInt::getLowBitsSet(DstWidth, SrcWidth));
996
997 // If checking bits we know are clear, return zero.
998 if ((CI2->getValue() & BitsNotSet) == CI2->getValue())
999 return Constant::getNullValue(CI2->getType());
1000 }
1001 }
1002 }
1003 break;
1004 case Instruction::Or:
1005 if (CI2->equalsInt(0)) return C1; // X | 0 == X
1006 if (CI2->isAllOnesValue())
1007 return C2; // X | -1 == -1
1008 break;
1009 case Instruction::Xor:
1010 if (CI2->equalsInt(0)) return C1; // X ^ 0 == X
1011
1012 if (ConstantExpr *CE1 = dyn_cast<ConstantExpr>(C1)) {
1013 switch (CE1->getOpcode()) {
1014 default: break;
1015 case Instruction::ICmp:
1016 case Instruction::FCmp:
1017 // cmp pred ^ true -> cmp !pred
1018 assert(CI2->equalsInt(1));
1019 CmpInst::Predicate pred = (CmpInst::Predicate)CE1->getPredicate();
1020 pred = CmpInst::getInversePredicate(pred);
1021 return ConstantExpr::getCompare(pred, CE1->getOperand(0),
1022 CE1->getOperand(1));
1023 }
1024 }
1025 break;
1026 case Instruction::AShr:
1027 // ashr (zext C to Ty), C2 -> lshr (zext C, CSA), C2
1028 if (ConstantExpr *CE1 = dyn_cast<ConstantExpr>(C1))
1029 if (CE1->getOpcode() == Instruction::ZExt) // Top bits known zero.
1030 return ConstantExpr::getLShr(C1, C2);
1031 break;
1032 }
1033 } else if (isa<ConstantInt>(C1)) {
1034 // If C1 is a ConstantInt and C2 is not, swap the operands.
1035 if (Instruction::isCommutative(Opcode))
1036 return ConstantExpr::get(Opcode, C2, C1);
1037 }
1038
1039 // At this point we know neither constant is an UndefValue.
1040 if (ConstantInt *CI1 = dyn_cast<ConstantInt>(C1)) {
1041 if (ConstantInt *CI2 = dyn_cast<ConstantInt>(C2)) {
1042 const APInt &C1V = CI1->getValue();
1043 const APInt &C2V = CI2->getValue();
1044 switch (Opcode) {
1045 default:
1046 break;
1047 case Instruction::Add:
1048 return ConstantInt::get(CI1->getContext(), C1V + C2V);
1049 case Instruction::Sub:
1050 return ConstantInt::get(CI1->getContext(), C1V - C2V);
1051 case Instruction::Mul:
1052 return ConstantInt::get(CI1->getContext(), C1V * C2V);
1053 case Instruction::UDiv:
1054 assert(!CI2->isNullValue() && "Div by zero handled above");
1055 return ConstantInt::get(CI1->getContext(), C1V.udiv(C2V));
1056 case Instruction::SDiv:
1057 assert(!CI2->isNullValue() && "Div by zero handled above");
1058 if (C2V.isAllOnesValue() && C1V.isMinSignedValue())
1059 return UndefValue::get(CI1->getType()); // MIN_INT / -1 -> undef
1060 return ConstantInt::get(CI1->getContext(), C1V.sdiv(C2V));
1061 case Instruction::URem:
1062 assert(!CI2->isNullValue() && "Div by zero handled above");
1063 return ConstantInt::get(CI1->getContext(), C1V.urem(C2V));
1064 case Instruction::SRem:
1065 assert(!CI2->isNullValue() && "Div by zero handled above");
1066 if (C2V.isAllOnesValue() && C1V.isMinSignedValue())
1067 return UndefValue::get(CI1->getType()); // MIN_INT % -1 -> undef
1068 return ConstantInt::get(CI1->getContext(), C1V.srem(C2V));
1069 case Instruction::And:
1070 return ConstantInt::get(CI1->getContext(), C1V & C2V);
1071 case Instruction::Or:
1072 return ConstantInt::get(CI1->getContext(), C1V | C2V);
1073 case Instruction::Xor:
1074 return ConstantInt::get(CI1->getContext(), C1V ^ C2V);
1075 case Instruction::Shl: {
1076 uint32_t shiftAmt = C2V.getZExtValue();
1077 if (shiftAmt < C1V.getBitWidth())
1078 return ConstantInt::get(CI1->getContext(), C1V.shl(shiftAmt));
1079 else
1080 return UndefValue::get(C1->getType()); // too big shift is undef
1081 }
1082 case Instruction::LShr: {
1083 uint32_t shiftAmt = C2V.getZExtValue();
1084 if (shiftAmt < C1V.getBitWidth())
1085 return ConstantInt::get(CI1->getContext(), C1V.lshr(shiftAmt));
1086 else
1087 return UndefValue::get(C1->getType()); // too big shift is undef
1088 }
1089 case Instruction::AShr: {
1090 uint32_t shiftAmt = C2V.getZExtValue();
1091 if (shiftAmt < C1V.getBitWidth())
1092 return ConstantInt::get(CI1->getContext(), C1V.ashr(shiftAmt));
1093 else
1094 return UndefValue::get(C1->getType()); // too big shift is undef
1095 }
1096 }
1097 }
1098
1099 switch (Opcode) {
1100 case Instruction::SDiv:
1101 case Instruction::UDiv:
1102 case Instruction::URem:
1103 case Instruction::SRem:
1104 case Instruction::LShr:
1105 case Instruction::AShr:
1106 case Instruction::Shl:
1107 if (CI1->equalsInt(0)) return C1;
1108 break;
1109 default:
1110 break;
1111 }
1112 } else if (ConstantFP *CFP1 = dyn_cast<ConstantFP>(C1)) {
1113 if (ConstantFP *CFP2 = dyn_cast<ConstantFP>(C2)) {
1114 APFloat C1V = CFP1->getValueAPF();
1115 APFloat C2V = CFP2->getValueAPF();
1116 APFloat C3V = C1V; // copy for modification
1117 switch (Opcode) {
1118 default:
1119 break;
1120 case Instruction::FAdd:
1121 (void)C3V.add(C2V, APFloat::rmNearestTiesToEven);
1122 return ConstantFP::get(C1->getContext(), C3V);
1123 case Instruction::FSub:
1124 (void)C3V.subtract(C2V, APFloat::rmNearestTiesToEven);
1125 return ConstantFP::get(C1->getContext(), C3V);
1126 case Instruction::FMul:
1127 (void)C3V.multiply(C2V, APFloat::rmNearestTiesToEven);
1128 return ConstantFP::get(C1->getContext(), C3V);
1129 case Instruction::FDiv:
1130 (void)C3V.divide(C2V, APFloat::rmNearestTiesToEven);
1131 return ConstantFP::get(C1->getContext(), C3V);
1132 case Instruction::FRem:
1133 (void)C3V.mod(C2V, APFloat::rmNearestTiesToEven);
1134 return ConstantFP::get(C1->getContext(), C3V);
1135 }
1136 }
1137 } else if (VectorType *VTy = dyn_cast<VectorType>(C1->getType())) {
1138 // Perform elementwise folding.
1139 SmallVector<Constant*, 16> Result;
1140 Type *Ty = IntegerType::get(VTy->getContext(), 32);
1141 for (unsigned i = 0, e = VTy->getNumElements(); i != e; ++i) {
1142 Constant *LHS =
1143 ConstantExpr::getExtractElement(C1, ConstantInt::get(Ty, i));
1144 Constant *RHS =
1145 ConstantExpr::getExtractElement(C2, ConstantInt::get(Ty, i));
1146
1147 Result.push_back(ConstantExpr::get(Opcode, LHS, RHS));
1148 }
1149
1150 return ConstantVector::get(Result);
1151 }
1152
1153 if (ConstantExpr *CE1 = dyn_cast<ConstantExpr>(C1)) {
1154 // There are many possible foldings we could do here. We should probably
1155 // at least fold add of a pointer with an integer into the appropriate
1156 // getelementptr. This will improve alias analysis a bit.
1157
1158 // Given ((a + b) + c), if (b + c) folds to something interesting, return
1159 // (a + (b + c)).
1160 if (Instruction::isAssociative(Opcode) && CE1->getOpcode() == Opcode) {
1161 Constant *T = ConstantExpr::get(Opcode, CE1->getOperand(1), C2);
1162 if (!isa<ConstantExpr>(T) || cast<ConstantExpr>(T)->getOpcode() != Opcode)
1163 return ConstantExpr::get(Opcode, CE1->getOperand(0), T);
1164 }
1165 } else if (isa<ConstantExpr>(C2)) {
1166 // If C2 is a constant expr and C1 isn't, flop them around and fold the
1167 // other way if possible.
1168 if (Instruction::isCommutative(Opcode))
1169 return ConstantFoldBinaryInstruction(Opcode, C2, C1);
1170 }
1171
1172 // i1 can be simplified in many cases.
1173 if (C1->getType()->isIntegerTy(1)) {
1174 switch (Opcode) {
1175 case Instruction::Add:
1176 case Instruction::Sub:
1177 return ConstantExpr::getXor(C1, C2);
1178 case Instruction::Mul:
1179 return ConstantExpr::getAnd(C1, C2);
1180 case Instruction::Shl:
1181 case Instruction::LShr:
1182 case Instruction::AShr:
1183 // We can assume that C2 == 0. If it were one the result would be
1184 // undefined because the shift value is as large as the bitwidth.
1185 return C1;
1186 case Instruction::SDiv:
1187 case Instruction::UDiv:
1188 // We can assume that C2 == 1. If it were zero the result would be
1189 // undefined through division by zero.
1190 return C1;
1191 case Instruction::URem:
1192 case Instruction::SRem:
1193 // We can assume that C2 == 1. If it were zero the result would be
1194 // undefined through division by zero.
1195 return ConstantInt::getFalse(C1->getContext());
1196 default:
1197 break;
1198 }
1199 }
1200
1201 // We don't know how to fold this.
1202 return 0;
1203 }
1204
1205 /// isZeroSizedType - This type is zero sized if its an array or structure of
1206 /// zero sized types. The only leaf zero sized type is an empty structure.
isMaybeZeroSizedType(Type * Ty)1207 static bool isMaybeZeroSizedType(Type *Ty) {
1208 if (StructType *STy = dyn_cast<StructType>(Ty)) {
1209 if (STy->isOpaque()) return true; // Can't say.
1210
1211 // If all of elements have zero size, this does too.
1212 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i)
1213 if (!isMaybeZeroSizedType(STy->getElementType(i))) return false;
1214 return true;
1215
1216 } else if (ArrayType *ATy = dyn_cast<ArrayType>(Ty)) {
1217 return isMaybeZeroSizedType(ATy->getElementType());
1218 }
1219 return false;
1220 }
1221
1222 /// IdxCompare - Compare the two constants as though they were getelementptr
1223 /// indices. This allows coersion of the types to be the same thing.
1224 ///
1225 /// If the two constants are the "same" (after coersion), return 0. If the
1226 /// first is less than the second, return -1, if the second is less than the
1227 /// first, return 1. If the constants are not integral, return -2.
1228 ///
IdxCompare(Constant * C1,Constant * C2,Type * ElTy)1229 static int IdxCompare(Constant *C1, Constant *C2, Type *ElTy) {
1230 if (C1 == C2) return 0;
1231
1232 // Ok, we found a different index. If they are not ConstantInt, we can't do
1233 // anything with them.
1234 if (!isa<ConstantInt>(C1) || !isa<ConstantInt>(C2))
1235 return -2; // don't know!
1236
1237 // Ok, we have two differing integer indices. Sign extend them to be the same
1238 // type. Long is always big enough, so we use it.
1239 if (!C1->getType()->isIntegerTy(64))
1240 C1 = ConstantExpr::getSExt(C1, Type::getInt64Ty(C1->getContext()));
1241
1242 if (!C2->getType()->isIntegerTy(64))
1243 C2 = ConstantExpr::getSExt(C2, Type::getInt64Ty(C1->getContext()));
1244
1245 if (C1 == C2) return 0; // They are equal
1246
1247 // If the type being indexed over is really just a zero sized type, there is
1248 // no pointer difference being made here.
1249 if (isMaybeZeroSizedType(ElTy))
1250 return -2; // dunno.
1251
1252 // If they are really different, now that they are the same type, then we
1253 // found a difference!
1254 if (cast<ConstantInt>(C1)->getSExtValue() <
1255 cast<ConstantInt>(C2)->getSExtValue())
1256 return -1;
1257 else
1258 return 1;
1259 }
1260
1261 /// evaluateFCmpRelation - This function determines if there is anything we can
1262 /// decide about the two constants provided. This doesn't need to handle simple
1263 /// things like ConstantFP comparisons, but should instead handle ConstantExprs.
1264 /// If we can determine that the two constants have a particular relation to
1265 /// each other, we should return the corresponding FCmpInst predicate,
1266 /// otherwise return FCmpInst::BAD_FCMP_PREDICATE. This is used below in
1267 /// ConstantFoldCompareInstruction.
1268 ///
1269 /// To simplify this code we canonicalize the relation so that the first
1270 /// operand is always the most "complex" of the two. We consider ConstantFP
1271 /// to be the simplest, and ConstantExprs to be the most complex.
evaluateFCmpRelation(Constant * V1,Constant * V2)1272 static FCmpInst::Predicate evaluateFCmpRelation(Constant *V1, Constant *V2) {
1273 assert(V1->getType() == V2->getType() &&
1274 "Cannot compare values of different types!");
1275
1276 // No compile-time operations on this type yet.
1277 if (V1->getType()->isPPC_FP128Ty())
1278 return FCmpInst::BAD_FCMP_PREDICATE;
1279
1280 // Handle degenerate case quickly
1281 if (V1 == V2) return FCmpInst::FCMP_OEQ;
1282
1283 if (!isa<ConstantExpr>(V1)) {
1284 if (!isa<ConstantExpr>(V2)) {
1285 // We distilled thisUse the standard constant folder for a few cases
1286 ConstantInt *R = 0;
1287 R = dyn_cast<ConstantInt>(
1288 ConstantExpr::getFCmp(FCmpInst::FCMP_OEQ, V1, V2));
1289 if (R && !R->isZero())
1290 return FCmpInst::FCMP_OEQ;
1291 R = dyn_cast<ConstantInt>(
1292 ConstantExpr::getFCmp(FCmpInst::FCMP_OLT, V1, V2));
1293 if (R && !R->isZero())
1294 return FCmpInst::FCMP_OLT;
1295 R = dyn_cast<ConstantInt>(
1296 ConstantExpr::getFCmp(FCmpInst::FCMP_OGT, V1, V2));
1297 if (R && !R->isZero())
1298 return FCmpInst::FCMP_OGT;
1299
1300 // Nothing more we can do
1301 return FCmpInst::BAD_FCMP_PREDICATE;
1302 }
1303
1304 // If the first operand is simple and second is ConstantExpr, swap operands.
1305 FCmpInst::Predicate SwappedRelation = evaluateFCmpRelation(V2, V1);
1306 if (SwappedRelation != FCmpInst::BAD_FCMP_PREDICATE)
1307 return FCmpInst::getSwappedPredicate(SwappedRelation);
1308 } else {
1309 // Ok, the LHS is known to be a constantexpr. The RHS can be any of a
1310 // constantexpr or a simple constant.
1311 ConstantExpr *CE1 = cast<ConstantExpr>(V1);
1312 switch (CE1->getOpcode()) {
1313 case Instruction::FPTrunc:
1314 case Instruction::FPExt:
1315 case Instruction::UIToFP:
1316 case Instruction::SIToFP:
1317 // We might be able to do something with these but we don't right now.
1318 break;
1319 default:
1320 break;
1321 }
1322 }
1323 // There are MANY other foldings that we could perform here. They will
1324 // probably be added on demand, as they seem needed.
1325 return FCmpInst::BAD_FCMP_PREDICATE;
1326 }
1327
1328 /// evaluateICmpRelation - This function determines if there is anything we can
1329 /// decide about the two constants provided. This doesn't need to handle simple
1330 /// things like integer comparisons, but should instead handle ConstantExprs
1331 /// and GlobalValues. If we can determine that the two constants have a
1332 /// particular relation to each other, we should return the corresponding ICmp
1333 /// predicate, otherwise return ICmpInst::BAD_ICMP_PREDICATE.
1334 ///
1335 /// To simplify this code we canonicalize the relation so that the first
1336 /// operand is always the most "complex" of the two. We consider simple
1337 /// constants (like ConstantInt) to be the simplest, followed by
1338 /// GlobalValues, followed by ConstantExpr's (the most complex).
1339 ///
evaluateICmpRelation(Constant * V1,Constant * V2,bool isSigned)1340 static ICmpInst::Predicate evaluateICmpRelation(Constant *V1, Constant *V2,
1341 bool isSigned) {
1342 assert(V1->getType() == V2->getType() &&
1343 "Cannot compare different types of values!");
1344 if (V1 == V2) return ICmpInst::ICMP_EQ;
1345
1346 if (!isa<ConstantExpr>(V1) && !isa<GlobalValue>(V1) &&
1347 !isa<BlockAddress>(V1)) {
1348 if (!isa<GlobalValue>(V2) && !isa<ConstantExpr>(V2) &&
1349 !isa<BlockAddress>(V2)) {
1350 // We distilled this down to a simple case, use the standard constant
1351 // folder.
1352 ConstantInt *R = 0;
1353 ICmpInst::Predicate pred = ICmpInst::ICMP_EQ;
1354 R = dyn_cast<ConstantInt>(ConstantExpr::getICmp(pred, V1, V2));
1355 if (R && !R->isZero())
1356 return pred;
1357 pred = isSigned ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT;
1358 R = dyn_cast<ConstantInt>(ConstantExpr::getICmp(pred, V1, V2));
1359 if (R && !R->isZero())
1360 return pred;
1361 pred = isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT;
1362 R = dyn_cast<ConstantInt>(ConstantExpr::getICmp(pred, V1, V2));
1363 if (R && !R->isZero())
1364 return pred;
1365
1366 // If we couldn't figure it out, bail.
1367 return ICmpInst::BAD_ICMP_PREDICATE;
1368 }
1369
1370 // If the first operand is simple, swap operands.
1371 ICmpInst::Predicate SwappedRelation =
1372 evaluateICmpRelation(V2, V1, isSigned);
1373 if (SwappedRelation != ICmpInst::BAD_ICMP_PREDICATE)
1374 return ICmpInst::getSwappedPredicate(SwappedRelation);
1375
1376 } else if (const GlobalValue *GV = dyn_cast<GlobalValue>(V1)) {
1377 if (isa<ConstantExpr>(V2)) { // Swap as necessary.
1378 ICmpInst::Predicate SwappedRelation =
1379 evaluateICmpRelation(V2, V1, isSigned);
1380 if (SwappedRelation != ICmpInst::BAD_ICMP_PREDICATE)
1381 return ICmpInst::getSwappedPredicate(SwappedRelation);
1382 return ICmpInst::BAD_ICMP_PREDICATE;
1383 }
1384
1385 // Now we know that the RHS is a GlobalValue, BlockAddress or simple
1386 // constant (which, since the types must match, means that it's a
1387 // ConstantPointerNull).
1388 if (const GlobalValue *GV2 = dyn_cast<GlobalValue>(V2)) {
1389 // Don't try to decide equality of aliases.
1390 if (!isa<GlobalAlias>(GV) && !isa<GlobalAlias>(GV2))
1391 if (!GV->hasExternalWeakLinkage() || !GV2->hasExternalWeakLinkage())
1392 return ICmpInst::ICMP_NE;
1393 } else if (isa<BlockAddress>(V2)) {
1394 return ICmpInst::ICMP_NE; // Globals never equal labels.
1395 } else {
1396 assert(isa<ConstantPointerNull>(V2) && "Canonicalization guarantee!");
1397 // GlobalVals can never be null unless they have external weak linkage.
1398 // We don't try to evaluate aliases here.
1399 if (!GV->hasExternalWeakLinkage() && !isa<GlobalAlias>(GV))
1400 return ICmpInst::ICMP_NE;
1401 }
1402 } else if (const BlockAddress *BA = dyn_cast<BlockAddress>(V1)) {
1403 if (isa<ConstantExpr>(V2)) { // Swap as necessary.
1404 ICmpInst::Predicate SwappedRelation =
1405 evaluateICmpRelation(V2, V1, isSigned);
1406 if (SwappedRelation != ICmpInst::BAD_ICMP_PREDICATE)
1407 return ICmpInst::getSwappedPredicate(SwappedRelation);
1408 return ICmpInst::BAD_ICMP_PREDICATE;
1409 }
1410
1411 // Now we know that the RHS is a GlobalValue, BlockAddress or simple
1412 // constant (which, since the types must match, means that it is a
1413 // ConstantPointerNull).
1414 if (const BlockAddress *BA2 = dyn_cast<BlockAddress>(V2)) {
1415 // Block address in another function can't equal this one, but block
1416 // addresses in the current function might be the same if blocks are
1417 // empty.
1418 if (BA2->getFunction() != BA->getFunction())
1419 return ICmpInst::ICMP_NE;
1420 } else {
1421 // Block addresses aren't null, don't equal the address of globals.
1422 assert((isa<ConstantPointerNull>(V2) || isa<GlobalValue>(V2)) &&
1423 "Canonicalization guarantee!");
1424 return ICmpInst::ICMP_NE;
1425 }
1426 } else {
1427 // Ok, the LHS is known to be a constantexpr. The RHS can be any of a
1428 // constantexpr, a global, block address, or a simple constant.
1429 ConstantExpr *CE1 = cast<ConstantExpr>(V1);
1430 Constant *CE1Op0 = CE1->getOperand(0);
1431
1432 switch (CE1->getOpcode()) {
1433 case Instruction::Trunc:
1434 case Instruction::FPTrunc:
1435 case Instruction::FPExt:
1436 case Instruction::FPToUI:
1437 case Instruction::FPToSI:
1438 break; // We can't evaluate floating point casts or truncations.
1439
1440 case Instruction::UIToFP:
1441 case Instruction::SIToFP:
1442 case Instruction::BitCast:
1443 case Instruction::ZExt:
1444 case Instruction::SExt:
1445 // If the cast is not actually changing bits, and the second operand is a
1446 // null pointer, do the comparison with the pre-casted value.
1447 if (V2->isNullValue() &&
1448 (CE1->getType()->isPointerTy() || CE1->getType()->isIntegerTy())) {
1449 if (CE1->getOpcode() == Instruction::ZExt) isSigned = false;
1450 if (CE1->getOpcode() == Instruction::SExt) isSigned = true;
1451 return evaluateICmpRelation(CE1Op0,
1452 Constant::getNullValue(CE1Op0->getType()),
1453 isSigned);
1454 }
1455 break;
1456
1457 case Instruction::GetElementPtr:
1458 // Ok, since this is a getelementptr, we know that the constant has a
1459 // pointer type. Check the various cases.
1460 if (isa<ConstantPointerNull>(V2)) {
1461 // If we are comparing a GEP to a null pointer, check to see if the base
1462 // of the GEP equals the null pointer.
1463 if (const GlobalValue *GV = dyn_cast<GlobalValue>(CE1Op0)) {
1464 if (GV->hasExternalWeakLinkage())
1465 // Weak linkage GVals could be zero or not. We're comparing that
1466 // to null pointer so its greater-or-equal
1467 return isSigned ? ICmpInst::ICMP_SGE : ICmpInst::ICMP_UGE;
1468 else
1469 // If its not weak linkage, the GVal must have a non-zero address
1470 // so the result is greater-than
1471 return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT;
1472 } else if (isa<ConstantPointerNull>(CE1Op0)) {
1473 // If we are indexing from a null pointer, check to see if we have any
1474 // non-zero indices.
1475 for (unsigned i = 1, e = CE1->getNumOperands(); i != e; ++i)
1476 if (!CE1->getOperand(i)->isNullValue())
1477 // Offsetting from null, must not be equal.
1478 return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT;
1479 // Only zero indexes from null, must still be zero.
1480 return ICmpInst::ICMP_EQ;
1481 }
1482 // Otherwise, we can't really say if the first operand is null or not.
1483 } else if (const GlobalValue *GV2 = dyn_cast<GlobalValue>(V2)) {
1484 if (isa<ConstantPointerNull>(CE1Op0)) {
1485 if (GV2->hasExternalWeakLinkage())
1486 // Weak linkage GVals could be zero or not. We're comparing it to
1487 // a null pointer, so its less-or-equal
1488 return isSigned ? ICmpInst::ICMP_SLE : ICmpInst::ICMP_ULE;
1489 else
1490 // If its not weak linkage, the GVal must have a non-zero address
1491 // so the result is less-than
1492 return isSigned ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT;
1493 } else if (const GlobalValue *GV = dyn_cast<GlobalValue>(CE1Op0)) {
1494 if (GV == GV2) {
1495 // If this is a getelementptr of the same global, then it must be
1496 // different. Because the types must match, the getelementptr could
1497 // only have at most one index, and because we fold getelementptr's
1498 // with a single zero index, it must be nonzero.
1499 assert(CE1->getNumOperands() == 2 &&
1500 !CE1->getOperand(1)->isNullValue() &&
1501 "Surprising getelementptr!");
1502 return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT;
1503 } else {
1504 // If they are different globals, we don't know what the value is,
1505 // but they can't be equal.
1506 return ICmpInst::ICMP_NE;
1507 }
1508 }
1509 } else {
1510 ConstantExpr *CE2 = cast<ConstantExpr>(V2);
1511 Constant *CE2Op0 = CE2->getOperand(0);
1512
1513 // There are MANY other foldings that we could perform here. They will
1514 // probably be added on demand, as they seem needed.
1515 switch (CE2->getOpcode()) {
1516 default: break;
1517 case Instruction::GetElementPtr:
1518 // By far the most common case to handle is when the base pointers are
1519 // obviously to the same or different globals.
1520 if (isa<GlobalValue>(CE1Op0) && isa<GlobalValue>(CE2Op0)) {
1521 if (CE1Op0 != CE2Op0) // Don't know relative ordering, but not equal
1522 return ICmpInst::ICMP_NE;
1523 // Ok, we know that both getelementptr instructions are based on the
1524 // same global. From this, we can precisely determine the relative
1525 // ordering of the resultant pointers.
1526 unsigned i = 1;
1527
1528 // The logic below assumes that the result of the comparison
1529 // can be determined by finding the first index that differs.
1530 // This doesn't work if there is over-indexing in any
1531 // subsequent indices, so check for that case first.
1532 if (!CE1->isGEPWithNoNotionalOverIndexing() ||
1533 !CE2->isGEPWithNoNotionalOverIndexing())
1534 return ICmpInst::BAD_ICMP_PREDICATE; // Might be equal.
1535
1536 // Compare all of the operands the GEP's have in common.
1537 gep_type_iterator GTI = gep_type_begin(CE1);
1538 for (;i != CE1->getNumOperands() && i != CE2->getNumOperands();
1539 ++i, ++GTI)
1540 switch (IdxCompare(CE1->getOperand(i),
1541 CE2->getOperand(i), GTI.getIndexedType())) {
1542 case -1: return isSigned ? ICmpInst::ICMP_SLT:ICmpInst::ICMP_ULT;
1543 case 1: return isSigned ? ICmpInst::ICMP_SGT:ICmpInst::ICMP_UGT;
1544 case -2: return ICmpInst::BAD_ICMP_PREDICATE;
1545 }
1546
1547 // Ok, we ran out of things they have in common. If any leftovers
1548 // are non-zero then we have a difference, otherwise we are equal.
1549 for (; i < CE1->getNumOperands(); ++i)
1550 if (!CE1->getOperand(i)->isNullValue()) {
1551 if (isa<ConstantInt>(CE1->getOperand(i)))
1552 return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT;
1553 else
1554 return ICmpInst::BAD_ICMP_PREDICATE; // Might be equal.
1555 }
1556
1557 for (; i < CE2->getNumOperands(); ++i)
1558 if (!CE2->getOperand(i)->isNullValue()) {
1559 if (isa<ConstantInt>(CE2->getOperand(i)))
1560 return isSigned ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT;
1561 else
1562 return ICmpInst::BAD_ICMP_PREDICATE; // Might be equal.
1563 }
1564 return ICmpInst::ICMP_EQ;
1565 }
1566 }
1567 }
1568 default:
1569 break;
1570 }
1571 }
1572
1573 return ICmpInst::BAD_ICMP_PREDICATE;
1574 }
1575
ConstantFoldCompareInstruction(unsigned short pred,Constant * C1,Constant * C2)1576 Constant *llvm::ConstantFoldCompareInstruction(unsigned short pred,
1577 Constant *C1, Constant *C2) {
1578 Type *ResultTy;
1579 if (VectorType *VT = dyn_cast<VectorType>(C1->getType()))
1580 ResultTy = VectorType::get(Type::getInt1Ty(C1->getContext()),
1581 VT->getNumElements());
1582 else
1583 ResultTy = Type::getInt1Ty(C1->getContext());
1584
1585 // Fold FCMP_FALSE/FCMP_TRUE unconditionally.
1586 if (pred == FCmpInst::FCMP_FALSE)
1587 return Constant::getNullValue(ResultTy);
1588
1589 if (pred == FCmpInst::FCMP_TRUE)
1590 return Constant::getAllOnesValue(ResultTy);
1591
1592 // Handle some degenerate cases first
1593 if (isa<UndefValue>(C1) || isa<UndefValue>(C2)) {
1594 // For EQ and NE, we can always pick a value for the undef to make the
1595 // predicate pass or fail, so we can return undef.
1596 // Also, if both operands are undef, we can return undef.
1597 if (ICmpInst::isEquality(ICmpInst::Predicate(pred)) ||
1598 (isa<UndefValue>(C1) && isa<UndefValue>(C2)))
1599 return UndefValue::get(ResultTy);
1600 // Otherwise, pick the same value as the non-undef operand, and fold
1601 // it to true or false.
1602 return ConstantInt::get(ResultTy, CmpInst::isTrueWhenEqual(pred));
1603 }
1604
1605 // No compile-time operations on this type yet.
1606 if (C1->getType()->isPPC_FP128Ty())
1607 return 0;
1608
1609 // icmp eq/ne(null,GV) -> false/true
1610 if (C1->isNullValue()) {
1611 if (const GlobalValue *GV = dyn_cast<GlobalValue>(C2))
1612 // Don't try to evaluate aliases. External weak GV can be null.
1613 if (!isa<GlobalAlias>(GV) && !GV->hasExternalWeakLinkage()) {
1614 if (pred == ICmpInst::ICMP_EQ)
1615 return ConstantInt::getFalse(C1->getContext());
1616 else if (pred == ICmpInst::ICMP_NE)
1617 return ConstantInt::getTrue(C1->getContext());
1618 }
1619 // icmp eq/ne(GV,null) -> false/true
1620 } else if (C2->isNullValue()) {
1621 if (const GlobalValue *GV = dyn_cast<GlobalValue>(C1))
1622 // Don't try to evaluate aliases. External weak GV can be null.
1623 if (!isa<GlobalAlias>(GV) && !GV->hasExternalWeakLinkage()) {
1624 if (pred == ICmpInst::ICMP_EQ)
1625 return ConstantInt::getFalse(C1->getContext());
1626 else if (pred == ICmpInst::ICMP_NE)
1627 return ConstantInt::getTrue(C1->getContext());
1628 }
1629 }
1630
1631 // If the comparison is a comparison between two i1's, simplify it.
1632 if (C1->getType()->isIntegerTy(1)) {
1633 switch(pred) {
1634 case ICmpInst::ICMP_EQ:
1635 if (isa<ConstantInt>(C2))
1636 return ConstantExpr::getXor(C1, ConstantExpr::getNot(C2));
1637 return ConstantExpr::getXor(ConstantExpr::getNot(C1), C2);
1638 case ICmpInst::ICMP_NE:
1639 return ConstantExpr::getXor(C1, C2);
1640 default:
1641 break;
1642 }
1643 }
1644
1645 if (isa<ConstantInt>(C1) && isa<ConstantInt>(C2)) {
1646 APInt V1 = cast<ConstantInt>(C1)->getValue();
1647 APInt V2 = cast<ConstantInt>(C2)->getValue();
1648 switch (pred) {
1649 default: llvm_unreachable("Invalid ICmp Predicate");
1650 case ICmpInst::ICMP_EQ: return ConstantInt::get(ResultTy, V1 == V2);
1651 case ICmpInst::ICMP_NE: return ConstantInt::get(ResultTy, V1 != V2);
1652 case ICmpInst::ICMP_SLT: return ConstantInt::get(ResultTy, V1.slt(V2));
1653 case ICmpInst::ICMP_SGT: return ConstantInt::get(ResultTy, V1.sgt(V2));
1654 case ICmpInst::ICMP_SLE: return ConstantInt::get(ResultTy, V1.sle(V2));
1655 case ICmpInst::ICMP_SGE: return ConstantInt::get(ResultTy, V1.sge(V2));
1656 case ICmpInst::ICMP_ULT: return ConstantInt::get(ResultTy, V1.ult(V2));
1657 case ICmpInst::ICMP_UGT: return ConstantInt::get(ResultTy, V1.ugt(V2));
1658 case ICmpInst::ICMP_ULE: return ConstantInt::get(ResultTy, V1.ule(V2));
1659 case ICmpInst::ICMP_UGE: return ConstantInt::get(ResultTy, V1.uge(V2));
1660 }
1661 } else if (isa<ConstantFP>(C1) && isa<ConstantFP>(C2)) {
1662 APFloat C1V = cast<ConstantFP>(C1)->getValueAPF();
1663 APFloat C2V = cast<ConstantFP>(C2)->getValueAPF();
1664 APFloat::cmpResult R = C1V.compare(C2V);
1665 switch (pred) {
1666 default: llvm_unreachable("Invalid FCmp Predicate");
1667 case FCmpInst::FCMP_FALSE: return Constant::getNullValue(ResultTy);
1668 case FCmpInst::FCMP_TRUE: return Constant::getAllOnesValue(ResultTy);
1669 case FCmpInst::FCMP_UNO:
1670 return ConstantInt::get(ResultTy, R==APFloat::cmpUnordered);
1671 case FCmpInst::FCMP_ORD:
1672 return ConstantInt::get(ResultTy, R!=APFloat::cmpUnordered);
1673 case FCmpInst::FCMP_UEQ:
1674 return ConstantInt::get(ResultTy, R==APFloat::cmpUnordered ||
1675 R==APFloat::cmpEqual);
1676 case FCmpInst::FCMP_OEQ:
1677 return ConstantInt::get(ResultTy, R==APFloat::cmpEqual);
1678 case FCmpInst::FCMP_UNE:
1679 return ConstantInt::get(ResultTy, R!=APFloat::cmpEqual);
1680 case FCmpInst::FCMP_ONE:
1681 return ConstantInt::get(ResultTy, R==APFloat::cmpLessThan ||
1682 R==APFloat::cmpGreaterThan);
1683 case FCmpInst::FCMP_ULT:
1684 return ConstantInt::get(ResultTy, R==APFloat::cmpUnordered ||
1685 R==APFloat::cmpLessThan);
1686 case FCmpInst::FCMP_OLT:
1687 return ConstantInt::get(ResultTy, R==APFloat::cmpLessThan);
1688 case FCmpInst::FCMP_UGT:
1689 return ConstantInt::get(ResultTy, R==APFloat::cmpUnordered ||
1690 R==APFloat::cmpGreaterThan);
1691 case FCmpInst::FCMP_OGT:
1692 return ConstantInt::get(ResultTy, R==APFloat::cmpGreaterThan);
1693 case FCmpInst::FCMP_ULE:
1694 return ConstantInt::get(ResultTy, R!=APFloat::cmpGreaterThan);
1695 case FCmpInst::FCMP_OLE:
1696 return ConstantInt::get(ResultTy, R==APFloat::cmpLessThan ||
1697 R==APFloat::cmpEqual);
1698 case FCmpInst::FCMP_UGE:
1699 return ConstantInt::get(ResultTy, R!=APFloat::cmpLessThan);
1700 case FCmpInst::FCMP_OGE:
1701 return ConstantInt::get(ResultTy, R==APFloat::cmpGreaterThan ||
1702 R==APFloat::cmpEqual);
1703 }
1704 } else if (C1->getType()->isVectorTy()) {
1705 // If we can constant fold the comparison of each element, constant fold
1706 // the whole vector comparison.
1707 SmallVector<Constant*, 4> ResElts;
1708 Type *Ty = IntegerType::get(C1->getContext(), 32);
1709 // Compare the elements, producing an i1 result or constant expr.
1710 for (unsigned i = 0, e = C1->getType()->getVectorNumElements(); i != e;++i){
1711 Constant *C1E =
1712 ConstantExpr::getExtractElement(C1, ConstantInt::get(Ty, i));
1713 Constant *C2E =
1714 ConstantExpr::getExtractElement(C2, ConstantInt::get(Ty, i));
1715
1716 ResElts.push_back(ConstantExpr::getCompare(pred, C1E, C2E));
1717 }
1718
1719 return ConstantVector::get(ResElts);
1720 }
1721
1722 if (C1->getType()->isFloatingPointTy()) {
1723 int Result = -1; // -1 = unknown, 0 = known false, 1 = known true.
1724 switch (evaluateFCmpRelation(C1, C2)) {
1725 default: llvm_unreachable("Unknown relation!");
1726 case FCmpInst::FCMP_UNO:
1727 case FCmpInst::FCMP_ORD:
1728 case FCmpInst::FCMP_UEQ:
1729 case FCmpInst::FCMP_UNE:
1730 case FCmpInst::FCMP_ULT:
1731 case FCmpInst::FCMP_UGT:
1732 case FCmpInst::FCMP_ULE:
1733 case FCmpInst::FCMP_UGE:
1734 case FCmpInst::FCMP_TRUE:
1735 case FCmpInst::FCMP_FALSE:
1736 case FCmpInst::BAD_FCMP_PREDICATE:
1737 break; // Couldn't determine anything about these constants.
1738 case FCmpInst::FCMP_OEQ: // We know that C1 == C2
1739 Result = (pred == FCmpInst::FCMP_UEQ || pred == FCmpInst::FCMP_OEQ ||
1740 pred == FCmpInst::FCMP_ULE || pred == FCmpInst::FCMP_OLE ||
1741 pred == FCmpInst::FCMP_UGE || pred == FCmpInst::FCMP_OGE);
1742 break;
1743 case FCmpInst::FCMP_OLT: // We know that C1 < C2
1744 Result = (pred == FCmpInst::FCMP_UNE || pred == FCmpInst::FCMP_ONE ||
1745 pred == FCmpInst::FCMP_ULT || pred == FCmpInst::FCMP_OLT ||
1746 pred == FCmpInst::FCMP_ULE || pred == FCmpInst::FCMP_OLE);
1747 break;
1748 case FCmpInst::FCMP_OGT: // We know that C1 > C2
1749 Result = (pred == FCmpInst::FCMP_UNE || pred == FCmpInst::FCMP_ONE ||
1750 pred == FCmpInst::FCMP_UGT || pred == FCmpInst::FCMP_OGT ||
1751 pred == FCmpInst::FCMP_UGE || pred == FCmpInst::FCMP_OGE);
1752 break;
1753 case FCmpInst::FCMP_OLE: // We know that C1 <= C2
1754 // We can only partially decide this relation.
1755 if (pred == FCmpInst::FCMP_UGT || pred == FCmpInst::FCMP_OGT)
1756 Result = 0;
1757 else if (pred == FCmpInst::FCMP_ULT || pred == FCmpInst::FCMP_OLT)
1758 Result = 1;
1759 break;
1760 case FCmpInst::FCMP_OGE: // We known that C1 >= C2
1761 // We can only partially decide this relation.
1762 if (pred == FCmpInst::FCMP_ULT || pred == FCmpInst::FCMP_OLT)
1763 Result = 0;
1764 else if (pred == FCmpInst::FCMP_UGT || pred == FCmpInst::FCMP_OGT)
1765 Result = 1;
1766 break;
1767 case FCmpInst::FCMP_ONE: // We know that C1 != C2
1768 // We can only partially decide this relation.
1769 if (pred == FCmpInst::FCMP_OEQ || pred == FCmpInst::FCMP_UEQ)
1770 Result = 0;
1771 else if (pred == FCmpInst::FCMP_ONE || pred == FCmpInst::FCMP_UNE)
1772 Result = 1;
1773 break;
1774 }
1775
1776 // If we evaluated the result, return it now.
1777 if (Result != -1)
1778 return ConstantInt::get(ResultTy, Result);
1779
1780 } else {
1781 // Evaluate the relation between the two constants, per the predicate.
1782 int Result = -1; // -1 = unknown, 0 = known false, 1 = known true.
1783 switch (evaluateICmpRelation(C1, C2, CmpInst::isSigned(pred))) {
1784 default: llvm_unreachable("Unknown relational!");
1785 case ICmpInst::BAD_ICMP_PREDICATE:
1786 break; // Couldn't determine anything about these constants.
1787 case ICmpInst::ICMP_EQ: // We know the constants are equal!
1788 // If we know the constants are equal, we can decide the result of this
1789 // computation precisely.
1790 Result = ICmpInst::isTrueWhenEqual((ICmpInst::Predicate)pred);
1791 break;
1792 case ICmpInst::ICMP_ULT:
1793 switch (pred) {
1794 case ICmpInst::ICMP_ULT: case ICmpInst::ICMP_NE: case ICmpInst::ICMP_ULE:
1795 Result = 1; break;
1796 case ICmpInst::ICMP_UGT: case ICmpInst::ICMP_EQ: case ICmpInst::ICMP_UGE:
1797 Result = 0; break;
1798 }
1799 break;
1800 case ICmpInst::ICMP_SLT:
1801 switch (pred) {
1802 case ICmpInst::ICMP_SLT: case ICmpInst::ICMP_NE: case ICmpInst::ICMP_SLE:
1803 Result = 1; break;
1804 case ICmpInst::ICMP_SGT: case ICmpInst::ICMP_EQ: case ICmpInst::ICMP_SGE:
1805 Result = 0; break;
1806 }
1807 break;
1808 case ICmpInst::ICMP_UGT:
1809 switch (pred) {
1810 case ICmpInst::ICMP_UGT: case ICmpInst::ICMP_NE: case ICmpInst::ICMP_UGE:
1811 Result = 1; break;
1812 case ICmpInst::ICMP_ULT: case ICmpInst::ICMP_EQ: case ICmpInst::ICMP_ULE:
1813 Result = 0; break;
1814 }
1815 break;
1816 case ICmpInst::ICMP_SGT:
1817 switch (pred) {
1818 case ICmpInst::ICMP_SGT: case ICmpInst::ICMP_NE: case ICmpInst::ICMP_SGE:
1819 Result = 1; break;
1820 case ICmpInst::ICMP_SLT: case ICmpInst::ICMP_EQ: case ICmpInst::ICMP_SLE:
1821 Result = 0; break;
1822 }
1823 break;
1824 case ICmpInst::ICMP_ULE:
1825 if (pred == ICmpInst::ICMP_UGT) Result = 0;
1826 if (pred == ICmpInst::ICMP_ULT || pred == ICmpInst::ICMP_ULE) Result = 1;
1827 break;
1828 case ICmpInst::ICMP_SLE:
1829 if (pred == ICmpInst::ICMP_SGT) Result = 0;
1830 if (pred == ICmpInst::ICMP_SLT || pred == ICmpInst::ICMP_SLE) Result = 1;
1831 break;
1832 case ICmpInst::ICMP_UGE:
1833 if (pred == ICmpInst::ICMP_ULT) Result = 0;
1834 if (pred == ICmpInst::ICMP_UGT || pred == ICmpInst::ICMP_UGE) Result = 1;
1835 break;
1836 case ICmpInst::ICMP_SGE:
1837 if (pred == ICmpInst::ICMP_SLT) Result = 0;
1838 if (pred == ICmpInst::ICMP_SGT || pred == ICmpInst::ICMP_SGE) Result = 1;
1839 break;
1840 case ICmpInst::ICMP_NE:
1841 if (pred == ICmpInst::ICMP_EQ) Result = 0;
1842 if (pred == ICmpInst::ICMP_NE) Result = 1;
1843 break;
1844 }
1845
1846 // If we evaluated the result, return it now.
1847 if (Result != -1)
1848 return ConstantInt::get(ResultTy, Result);
1849
1850 // If the right hand side is a bitcast, try using its inverse to simplify
1851 // it by moving it to the left hand side. We can't do this if it would turn
1852 // a vector compare into a scalar compare or visa versa.
1853 if (ConstantExpr *CE2 = dyn_cast<ConstantExpr>(C2)) {
1854 Constant *CE2Op0 = CE2->getOperand(0);
1855 if (CE2->getOpcode() == Instruction::BitCast &&
1856 CE2->getType()->isVectorTy() == CE2Op0->getType()->isVectorTy()) {
1857 Constant *Inverse = ConstantExpr::getBitCast(C1, CE2Op0->getType());
1858 return ConstantExpr::getICmp(pred, Inverse, CE2Op0);
1859 }
1860 }
1861
1862 // If the left hand side is an extension, try eliminating it.
1863 if (ConstantExpr *CE1 = dyn_cast<ConstantExpr>(C1)) {
1864 if ((CE1->getOpcode() == Instruction::SExt && ICmpInst::isSigned(pred)) ||
1865 (CE1->getOpcode() == Instruction::ZExt && !ICmpInst::isSigned(pred))){
1866 Constant *CE1Op0 = CE1->getOperand(0);
1867 Constant *CE1Inverse = ConstantExpr::getTrunc(CE1, CE1Op0->getType());
1868 if (CE1Inverse == CE1Op0) {
1869 // Check whether we can safely truncate the right hand side.
1870 Constant *C2Inverse = ConstantExpr::getTrunc(C2, CE1Op0->getType());
1871 if (ConstantExpr::getZExt(C2Inverse, C2->getType()) == C2) {
1872 return ConstantExpr::getICmp(pred, CE1Inverse, C2Inverse);
1873 }
1874 }
1875 }
1876 }
1877
1878 if ((!isa<ConstantExpr>(C1) && isa<ConstantExpr>(C2)) ||
1879 (C1->isNullValue() && !C2->isNullValue())) {
1880 // If C2 is a constant expr and C1 isn't, flip them around and fold the
1881 // other way if possible.
1882 // Also, if C1 is null and C2 isn't, flip them around.
1883 pred = ICmpInst::getSwappedPredicate((ICmpInst::Predicate)pred);
1884 return ConstantExpr::getICmp(pred, C2, C1);
1885 }
1886 }
1887 return 0;
1888 }
1889
1890 /// isInBoundsIndices - Test whether the given sequence of *normalized* indices
1891 /// is "inbounds".
1892 template<typename IndexTy>
isInBoundsIndices(ArrayRef<IndexTy> Idxs)1893 static bool isInBoundsIndices(ArrayRef<IndexTy> Idxs) {
1894 // No indices means nothing that could be out of bounds.
1895 if (Idxs.empty()) return true;
1896
1897 // If the first index is zero, it's in bounds.
1898 if (cast<Constant>(Idxs[0])->isNullValue()) return true;
1899
1900 // If the first index is one and all the rest are zero, it's in bounds,
1901 // by the one-past-the-end rule.
1902 if (!cast<ConstantInt>(Idxs[0])->isOne())
1903 return false;
1904 for (unsigned i = 1, e = Idxs.size(); i != e; ++i)
1905 if (!cast<Constant>(Idxs[i])->isNullValue())
1906 return false;
1907 return true;
1908 }
1909
1910 template<typename IndexTy>
ConstantFoldGetElementPtrImpl(Constant * C,bool inBounds,ArrayRef<IndexTy> Idxs)1911 static Constant *ConstantFoldGetElementPtrImpl(Constant *C,
1912 bool inBounds,
1913 ArrayRef<IndexTy> Idxs) {
1914 if (Idxs.empty()) return C;
1915 Constant *Idx0 = cast<Constant>(Idxs[0]);
1916 if ((Idxs.size() == 1 && Idx0->isNullValue()))
1917 return C;
1918
1919 if (isa<UndefValue>(C)) {
1920 PointerType *Ptr = cast<PointerType>(C->getType());
1921 Type *Ty = GetElementPtrInst::getIndexedType(Ptr, Idxs);
1922 assert(Ty != 0 && "Invalid indices for GEP!");
1923 return UndefValue::get(PointerType::get(Ty, Ptr->getAddressSpace()));
1924 }
1925
1926 if (C->isNullValue()) {
1927 bool isNull = true;
1928 for (unsigned i = 0, e = Idxs.size(); i != e; ++i)
1929 if (!cast<Constant>(Idxs[i])->isNullValue()) {
1930 isNull = false;
1931 break;
1932 }
1933 if (isNull) {
1934 PointerType *Ptr = cast<PointerType>(C->getType());
1935 Type *Ty = GetElementPtrInst::getIndexedType(Ptr, Idxs);
1936 assert(Ty != 0 && "Invalid indices for GEP!");
1937 return ConstantPointerNull::get(PointerType::get(Ty,
1938 Ptr->getAddressSpace()));
1939 }
1940 }
1941
1942 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(C)) {
1943 // Combine Indices - If the source pointer to this getelementptr instruction
1944 // is a getelementptr instruction, combine the indices of the two
1945 // getelementptr instructions into a single instruction.
1946 //
1947 if (CE->getOpcode() == Instruction::GetElementPtr) {
1948 Type *LastTy = 0;
1949 for (gep_type_iterator I = gep_type_begin(CE), E = gep_type_end(CE);
1950 I != E; ++I)
1951 LastTy = *I;
1952
1953 if ((LastTy && isa<SequentialType>(LastTy)) || Idx0->isNullValue()) {
1954 SmallVector<Value*, 16> NewIndices;
1955 NewIndices.reserve(Idxs.size() + CE->getNumOperands());
1956 for (unsigned i = 1, e = CE->getNumOperands()-1; i != e; ++i)
1957 NewIndices.push_back(CE->getOperand(i));
1958
1959 // Add the last index of the source with the first index of the new GEP.
1960 // Make sure to handle the case when they are actually different types.
1961 Constant *Combined = CE->getOperand(CE->getNumOperands()-1);
1962 // Otherwise it must be an array.
1963 if (!Idx0->isNullValue()) {
1964 Type *IdxTy = Combined->getType();
1965 if (IdxTy != Idx0->getType()) {
1966 Type *Int64Ty = Type::getInt64Ty(IdxTy->getContext());
1967 Constant *C1 = ConstantExpr::getSExtOrBitCast(Idx0, Int64Ty);
1968 Constant *C2 = ConstantExpr::getSExtOrBitCast(Combined, Int64Ty);
1969 Combined = ConstantExpr::get(Instruction::Add, C1, C2);
1970 } else {
1971 Combined =
1972 ConstantExpr::get(Instruction::Add, Idx0, Combined);
1973 }
1974 }
1975
1976 NewIndices.push_back(Combined);
1977 NewIndices.append(Idxs.begin() + 1, Idxs.end());
1978 return
1979 ConstantExpr::getGetElementPtr(CE->getOperand(0), NewIndices,
1980 inBounds &&
1981 cast<GEPOperator>(CE)->isInBounds());
1982 }
1983 }
1984
1985 // Implement folding of:
1986 // i32* getelementptr ([2 x i32]* bitcast ([3 x i32]* %X to [2 x i32]*),
1987 // i64 0, i64 0)
1988 // To: i32* getelementptr ([3 x i32]* %X, i64 0, i64 0)
1989 //
1990 if (CE->isCast() && Idxs.size() > 1 && Idx0->isNullValue()) {
1991 if (PointerType *SPT =
1992 dyn_cast<PointerType>(CE->getOperand(0)->getType()))
1993 if (ArrayType *SAT = dyn_cast<ArrayType>(SPT->getElementType()))
1994 if (ArrayType *CAT =
1995 dyn_cast<ArrayType>(cast<PointerType>(C->getType())->getElementType()))
1996 if (CAT->getElementType() == SAT->getElementType())
1997 return
1998 ConstantExpr::getGetElementPtr((Constant*)CE->getOperand(0),
1999 Idxs, inBounds);
2000 }
2001 }
2002
2003 // Check to see if any array indices are not within the corresponding
2004 // notional array bounds. If so, try to determine if they can be factored
2005 // out into preceding dimensions.
2006 bool Unknown = false;
2007 SmallVector<Constant *, 8> NewIdxs;
2008 Type *Ty = C->getType();
2009 Type *Prev = 0;
2010 for (unsigned i = 0, e = Idxs.size(); i != e;
2011 Prev = Ty, Ty = cast<CompositeType>(Ty)->getTypeAtIndex(Idxs[i]), ++i) {
2012 if (ConstantInt *CI = dyn_cast<ConstantInt>(Idxs[i])) {
2013 if (ArrayType *ATy = dyn_cast<ArrayType>(Ty))
2014 if (ATy->getNumElements() <= INT64_MAX &&
2015 ATy->getNumElements() != 0 &&
2016 CI->getSExtValue() >= (int64_t)ATy->getNumElements()) {
2017 if (isa<SequentialType>(Prev)) {
2018 // It's out of range, but we can factor it into the prior
2019 // dimension.
2020 NewIdxs.resize(Idxs.size());
2021 ConstantInt *Factor = ConstantInt::get(CI->getType(),
2022 ATy->getNumElements());
2023 NewIdxs[i] = ConstantExpr::getSRem(CI, Factor);
2024
2025 Constant *PrevIdx = cast<Constant>(Idxs[i-1]);
2026 Constant *Div = ConstantExpr::getSDiv(CI, Factor);
2027
2028 // Before adding, extend both operands to i64 to avoid
2029 // overflow trouble.
2030 if (!PrevIdx->getType()->isIntegerTy(64))
2031 PrevIdx = ConstantExpr::getSExt(PrevIdx,
2032 Type::getInt64Ty(Div->getContext()));
2033 if (!Div->getType()->isIntegerTy(64))
2034 Div = ConstantExpr::getSExt(Div,
2035 Type::getInt64Ty(Div->getContext()));
2036
2037 NewIdxs[i-1] = ConstantExpr::getAdd(PrevIdx, Div);
2038 } else {
2039 // It's out of range, but the prior dimension is a struct
2040 // so we can't do anything about it.
2041 Unknown = true;
2042 }
2043 }
2044 } else {
2045 // We don't know if it's in range or not.
2046 Unknown = true;
2047 }
2048 }
2049
2050 // If we did any factoring, start over with the adjusted indices.
2051 if (!NewIdxs.empty()) {
2052 for (unsigned i = 0, e = Idxs.size(); i != e; ++i)
2053 if (!NewIdxs[i]) NewIdxs[i] = cast<Constant>(Idxs[i]);
2054 return ConstantExpr::getGetElementPtr(C, NewIdxs, inBounds);
2055 }
2056
2057 // If all indices are known integers and normalized, we can do a simple
2058 // check for the "inbounds" property.
2059 if (!Unknown && !inBounds &&
2060 isa<GlobalVariable>(C) && isInBoundsIndices(Idxs))
2061 return ConstantExpr::getInBoundsGetElementPtr(C, Idxs);
2062
2063 return 0;
2064 }
2065
ConstantFoldGetElementPtr(Constant * C,bool inBounds,ArrayRef<Constant * > Idxs)2066 Constant *llvm::ConstantFoldGetElementPtr(Constant *C,
2067 bool inBounds,
2068 ArrayRef<Constant *> Idxs) {
2069 return ConstantFoldGetElementPtrImpl(C, inBounds, Idxs);
2070 }
2071
ConstantFoldGetElementPtr(Constant * C,bool inBounds,ArrayRef<Value * > Idxs)2072 Constant *llvm::ConstantFoldGetElementPtr(Constant *C,
2073 bool inBounds,
2074 ArrayRef<Value *> Idxs) {
2075 return ConstantFoldGetElementPtrImpl(C, inBounds, Idxs);
2076 }
2077