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 //===----------------------------------------------------------------------===//
19
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/GetElementPtrTypeIterator.h"
26 #include "llvm/IR/GlobalAlias.h"
27 #include "llvm/IR/GlobalVariable.h"
28 #include "llvm/IR/Instructions.h"
29 #include "llvm/IR/Operator.h"
30 #include "llvm/Support/Compiler.h"
31 #include "llvm/Support/ErrorHandling.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 nullptr;
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 ///< 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");
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 // 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());
94
95 // Let CastInst::isEliminableCastPair do the heavy lifting.
96 return CastInst::isEliminableCastPair(firstOp, secondOp, SrcTy, MidTy, DstTy,
97 nullptr, FakeIntPtrTy, nullptr);
98 }
99
FoldBitCast(Constant * V,Type * DestTy)100 static Constant *FoldBitCast(Constant *V, Type *DestTy) {
101 Type *SrcTy = V->getType();
102 if (SrcTy == DestTy)
103 return V; // no-op cast
104
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 }
130
131 if (ElTy == DPTy->getElementType())
132 // This GEP is inbounds because all indices are zero.
133 return ConstantExpr::getInBoundsGetElementPtr(V, IdxList);
134 }
135
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 = nullptr;
143 // First, check for null. Undef is already handled.
144 if (isa<ConstantAggregateZero>(V))
145 return Constant::getNullValue(DestTy);
146
147 // Handle ConstantVector and ConstantAggregateVector.
148 return BitCastConstantVector(V, DestPTy);
149 }
150
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 }
157
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));
162
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;
169
170 if (DestTy->isFloatingPointTy())
171 return ConstantFP::get(DestTy->getContext(),
172 APFloat(DestTy->getFltSemantics(),
173 CI->getValue()));
174
175 // Otherwise, can't fold this (vector?)
176 return nullptr;
177 }
178
179 // Handle ConstantFP input: FP -> Integral.
180 if (ConstantFP *FP = dyn_cast<ConstantFP>(V))
181 return ConstantInt::get(FP->getContext(),
182 FP->getValueAPF().bitcastToAPInt());
183
184 return nullptr;
185 }
186
187
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 ///
ExtractConstantBytes(Constant * C,unsigned ByteStart,unsigned ByteSize)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");
206
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 }
215
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) return nullptr;
220
221 switch (CE->getOpcode()) {
222 default: return nullptr;
223 case Instruction::Or: {
224 Constant *RHS = ExtractConstantBytes(CE->getOperand(1), ByteStart,ByteSize);
225 if (!RHS)
226 return nullptr;
227
228 // X | -1 -> -1.
229 if (ConstantInt *RHSC = dyn_cast<ConstantInt>(RHS))
230 if (RHSC->isAllOnesValue())
231 return RHSC;
232
233 Constant *LHS = ExtractConstantBytes(CE->getOperand(0), ByteStart,ByteSize);
234 if (!LHS)
235 return nullptr;
236 return ConstantExpr::getOr(LHS, RHS);
237 }
238 case Instruction::And: {
239 Constant *RHS = ExtractConstantBytes(CE->getOperand(1), ByteStart,ByteSize);
240 if (!RHS)
241 return nullptr;
242
243 // X & 0 -> 0.
244 if (RHS->isNullValue())
245 return RHS;
246
247 Constant *LHS = ExtractConstantBytes(CE->getOperand(0), ByteStart,ByteSize);
248 if (!LHS)
249 return nullptr;
250 return ConstantExpr::getAnd(LHS, RHS);
251 }
252 case Instruction::LShr: {
253 ConstantInt *Amt = dyn_cast<ConstantInt>(CE->getOperand(1));
254 if (!Amt)
255 return nullptr;
256 unsigned ShAmt = Amt->getZExtValue();
257 // Cannot analyze non-byte shifts.
258 if ((ShAmt & 7) != 0)
259 return nullptr;
260 ShAmt >>= 3;
261
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);
269
270 // TODO: Handle the 'partially zero' case.
271 return nullptr;
272 }
273
274 case Instruction::Shl: {
275 ConstantInt *Amt = dyn_cast<ConstantInt>(CE->getOperand(1));
276 if (!Amt)
277 return nullptr;
278 unsigned ShAmt = Amt->getZExtValue();
279 // Cannot analyze non-byte shifts.
280 if ((ShAmt & 7) != 0)
281 return nullptr;
282 ShAmt >>= 3;
283
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);
291
292 // TODO: Handle the 'partially zero' case.
293 return nullptr;
294 }
295
296 case Instruction::ZExt: {
297 unsigned SrcBitSize =
298 cast<IntegerType>(CE->getOperand(0)->getType())->getBitWidth();
299
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));
304
305 // If exactly extracting the input, return it.
306 if (ByteStart == 0 && ByteSize*8 == SrcBitSize)
307 return CE->getOperand(0);
308
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);
313
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 }
325
326 // TODO: Handle the 'partially zero' case.
327 return nullptr;
328 }
329 }
330 }
331
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 ///
getFoldedSizeOf(Type * Ty,Type * DestTy,bool Folded)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 }
344
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 }
366
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);
375
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 nullptr;
380
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 }
388
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 ///
getFoldedAlignOf(Type * Ty,Type * DestTy,bool Folded)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 }
406
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);
411
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 }
431
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);
441
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 nullptr;
446
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 }
454
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 ///
getFoldedOffsetOf(Type * Ty,Constant * FieldNo,Type * DestTy,bool Folded)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 }
470
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 nullptr;
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 }
496
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 nullptr;
501
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 }
509
ConstantFoldCastInstruction(unsigned opc,Constant * V,Type * DestTy)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 }
521
522 if (V->isNullValue() && !DestTy->isX86_MMXTy())
523 return Constant::getNullValue(DestTy);
524
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 // Do not fold addrspacecast (gep 0, .., 0). It might make the
534 // addrspacecast uncanonicalized.
535 opc != Instruction::AddrSpaceCast) {
536 // If all of the indexes in the GEP are null values, there is no pointer
537 // adjustment going on. We might as well cast the source pointer.
538 bool isAllNull = true;
539 for (unsigned i = 1, e = CE->getNumOperands(); i != e; ++i)
540 if (!CE->getOperand(i)->isNullValue()) {
541 isAllNull = false;
542 break;
543 }
544 if (isAllNull)
545 // This is casting one pointer type to another, always BitCast
546 return ConstantExpr::getPointerCast(CE->getOperand(0), DestTy);
547 }
548 }
549
550 // If the cast operand is a constant vector, perform the cast by
551 // operating on each element. In the cast of bitcasts, the element
552 // count may be mismatched; don't attempt to handle that here.
553 if ((isa<ConstantVector>(V) || isa<ConstantDataVector>(V)) &&
554 DestTy->isVectorTy() &&
555 DestTy->getVectorNumElements() == V->getType()->getVectorNumElements()) {
556 SmallVector<Constant*, 16> res;
557 VectorType *DestVecTy = cast<VectorType>(DestTy);
558 Type *DstEltTy = DestVecTy->getElementType();
559 Type *Ty = IntegerType::get(V->getContext(), 32);
560 for (unsigned i = 0, e = V->getType()->getVectorNumElements(); i != e; ++i) {
561 Constant *C =
562 ConstantExpr::getExtractElement(V, ConstantInt::get(Ty, i));
563 res.push_back(ConstantExpr::getCast(opc, C, DstEltTy));
564 }
565 return ConstantVector::get(res);
566 }
567
568 // We actually have to do a cast now. Perform the cast according to the
569 // opcode specified.
570 switch (opc) {
571 default:
572 llvm_unreachable("Failed to cast constant expression");
573 case Instruction::FPTrunc:
574 case Instruction::FPExt:
575 if (ConstantFP *FPC = dyn_cast<ConstantFP>(V)) {
576 bool ignored;
577 APFloat Val = FPC->getValueAPF();
578 Val.convert(DestTy->isHalfTy() ? APFloat::IEEEhalf :
579 DestTy->isFloatTy() ? APFloat::IEEEsingle :
580 DestTy->isDoubleTy() ? APFloat::IEEEdouble :
581 DestTy->isX86_FP80Ty() ? APFloat::x87DoubleExtended :
582 DestTy->isFP128Ty() ? APFloat::IEEEquad :
583 DestTy->isPPC_FP128Ty() ? APFloat::PPCDoubleDouble :
584 APFloat::Bogus,
585 APFloat::rmNearestTiesToEven, &ignored);
586 return ConstantFP::get(V->getContext(), Val);
587 }
588 return nullptr; // Can't fold.
589 case Instruction::FPToUI:
590 case Instruction::FPToSI:
591 if (ConstantFP *FPC = dyn_cast<ConstantFP>(V)) {
592 const APFloat &V = FPC->getValueAPF();
593 bool ignored;
594 uint64_t x[2];
595 uint32_t DestBitWidth = cast<IntegerType>(DestTy)->getBitWidth();
596 (void) V.convertToInteger(x, DestBitWidth, opc==Instruction::FPToSI,
597 APFloat::rmTowardZero, &ignored);
598 APInt Val(DestBitWidth, x);
599 return ConstantInt::get(FPC->getContext(), Val);
600 }
601 return nullptr; // Can't fold.
602 case Instruction::IntToPtr: //always treated as unsigned
603 if (V->isNullValue()) // Is it an integral null value?
604 return ConstantPointerNull::get(cast<PointerType>(DestTy));
605 return nullptr; // Other pointer types cannot be casted
606 case Instruction::PtrToInt: // always treated as unsigned
607 // Is it a null pointer value?
608 if (V->isNullValue())
609 return ConstantInt::get(DestTy, 0);
610 // If this is a sizeof-like expression, pull out multiplications by
611 // known factors to expose them to subsequent folding. If it's an
612 // alignof-like expression, factor out known factors.
613 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V))
614 if (CE->getOpcode() == Instruction::GetElementPtr &&
615 CE->getOperand(0)->isNullValue()) {
616 Type *Ty =
617 cast<PointerType>(CE->getOperand(0)->getType())->getElementType();
618 if (CE->getNumOperands() == 2) {
619 // Handle a sizeof-like expression.
620 Constant *Idx = CE->getOperand(1);
621 bool isOne = isa<ConstantInt>(Idx) && cast<ConstantInt>(Idx)->isOne();
622 if (Constant *C = getFoldedSizeOf(Ty, DestTy, !isOne)) {
623 Idx = ConstantExpr::getCast(CastInst::getCastOpcode(Idx, true,
624 DestTy, false),
625 Idx, DestTy);
626 return ConstantExpr::getMul(C, Idx);
627 }
628 } else if (CE->getNumOperands() == 3 &&
629 CE->getOperand(1)->isNullValue()) {
630 // Handle an alignof-like expression.
631 if (StructType *STy = dyn_cast<StructType>(Ty))
632 if (!STy->isPacked()) {
633 ConstantInt *CI = cast<ConstantInt>(CE->getOperand(2));
634 if (CI->isOne() &&
635 STy->getNumElements() == 2 &&
636 STy->getElementType(0)->isIntegerTy(1)) {
637 return getFoldedAlignOf(STy->getElementType(1), DestTy, false);
638 }
639 }
640 // Handle an offsetof-like expression.
641 if (Ty->isStructTy() || Ty->isArrayTy()) {
642 if (Constant *C = getFoldedOffsetOf(Ty, CE->getOperand(2),
643 DestTy, false))
644 return C;
645 }
646 }
647 }
648 // Other pointer types cannot be casted
649 return nullptr;
650 case Instruction::UIToFP:
651 case Instruction::SIToFP:
652 if (ConstantInt *CI = dyn_cast<ConstantInt>(V)) {
653 APInt api = CI->getValue();
654 APFloat apf(DestTy->getFltSemantics(),
655 APInt::getNullValue(DestTy->getPrimitiveSizeInBits()));
656 (void)apf.convertFromAPInt(api,
657 opc==Instruction::SIToFP,
658 APFloat::rmNearestTiesToEven);
659 return ConstantFP::get(V->getContext(), apf);
660 }
661 return nullptr;
662 case Instruction::ZExt:
663 if (ConstantInt *CI = dyn_cast<ConstantInt>(V)) {
664 uint32_t BitWidth = cast<IntegerType>(DestTy)->getBitWidth();
665 return ConstantInt::get(V->getContext(),
666 CI->getValue().zext(BitWidth));
667 }
668 return nullptr;
669 case Instruction::SExt:
670 if (ConstantInt *CI = dyn_cast<ConstantInt>(V)) {
671 uint32_t BitWidth = cast<IntegerType>(DestTy)->getBitWidth();
672 return ConstantInt::get(V->getContext(),
673 CI->getValue().sext(BitWidth));
674 }
675 return nullptr;
676 case Instruction::Trunc: {
677 uint32_t DestBitWidth = cast<IntegerType>(DestTy)->getBitWidth();
678 if (ConstantInt *CI = dyn_cast<ConstantInt>(V)) {
679 return ConstantInt::get(V->getContext(),
680 CI->getValue().trunc(DestBitWidth));
681 }
682
683 // The input must be a constantexpr. See if we can simplify this based on
684 // the bytes we are demanding. Only do this if the source and dest are an
685 // even multiple of a byte.
686 if ((DestBitWidth & 7) == 0 &&
687 (cast<IntegerType>(V->getType())->getBitWidth() & 7) == 0)
688 if (Constant *Res = ExtractConstantBytes(V, 0, DestBitWidth / 8))
689 return Res;
690
691 return nullptr;
692 }
693 case Instruction::BitCast:
694 return FoldBitCast(V, DestTy);
695 case Instruction::AddrSpaceCast:
696 return nullptr;
697 }
698 }
699
ConstantFoldSelectInstruction(Constant * Cond,Constant * V1,Constant * V2)700 Constant *llvm::ConstantFoldSelectInstruction(Constant *Cond,
701 Constant *V1, Constant *V2) {
702 // Check for i1 and vector true/false conditions.
703 if (Cond->isNullValue()) return V2;
704 if (Cond->isAllOnesValue()) return V1;
705
706 // If the condition is a vector constant, fold the result elementwise.
707 if (ConstantVector *CondV = dyn_cast<ConstantVector>(Cond)) {
708 SmallVector<Constant*, 16> Result;
709 Type *Ty = IntegerType::get(CondV->getContext(), 32);
710 for (unsigned i = 0, e = V1->getType()->getVectorNumElements(); i != e;++i){
711 Constant *V;
712 Constant *V1Element = ConstantExpr::getExtractElement(V1,
713 ConstantInt::get(Ty, i));
714 Constant *V2Element = ConstantExpr::getExtractElement(V2,
715 ConstantInt::get(Ty, i));
716 Constant *Cond = dyn_cast<Constant>(CondV->getOperand(i));
717 if (V1Element == V2Element) {
718 V = V1Element;
719 } else if (isa<UndefValue>(Cond)) {
720 V = isa<UndefValue>(V1Element) ? V1Element : V2Element;
721 } else {
722 if (!isa<ConstantInt>(Cond)) break;
723 V = Cond->isNullValue() ? V2Element : V1Element;
724 }
725 Result.push_back(V);
726 }
727
728 // If we were able to build the vector, return it.
729 if (Result.size() == V1->getType()->getVectorNumElements())
730 return ConstantVector::get(Result);
731 }
732
733 if (isa<UndefValue>(Cond)) {
734 if (isa<UndefValue>(V1)) return V1;
735 return V2;
736 }
737 if (isa<UndefValue>(V1)) return V2;
738 if (isa<UndefValue>(V2)) return V1;
739 if (V1 == V2) return V1;
740
741 if (ConstantExpr *TrueVal = dyn_cast<ConstantExpr>(V1)) {
742 if (TrueVal->getOpcode() == Instruction::Select)
743 if (TrueVal->getOperand(0) == Cond)
744 return ConstantExpr::getSelect(Cond, TrueVal->getOperand(1), V2);
745 }
746 if (ConstantExpr *FalseVal = dyn_cast<ConstantExpr>(V2)) {
747 if (FalseVal->getOpcode() == Instruction::Select)
748 if (FalseVal->getOperand(0) == Cond)
749 return ConstantExpr::getSelect(Cond, V1, FalseVal->getOperand(2));
750 }
751
752 return nullptr;
753 }
754
ConstantFoldExtractElementInstruction(Constant * Val,Constant * Idx)755 Constant *llvm::ConstantFoldExtractElementInstruction(Constant *Val,
756 Constant *Idx) {
757 if (isa<UndefValue>(Val)) // ee(undef, x) -> undef
758 return UndefValue::get(Val->getType()->getVectorElementType());
759 if (Val->isNullValue()) // ee(zero, x) -> zero
760 return Constant::getNullValue(Val->getType()->getVectorElementType());
761 // ee({w,x,y,z}, undef) -> undef
762 if (isa<UndefValue>(Idx))
763 return UndefValue::get(Val->getType()->getVectorElementType());
764
765 if (ConstantInt *CIdx = dyn_cast<ConstantInt>(Idx)) {
766 uint64_t Index = CIdx->getZExtValue();
767 // ee({w,x,y,z}, wrong_value) -> undef
768 if (Index >= Val->getType()->getVectorNumElements())
769 return UndefValue::get(Val->getType()->getVectorElementType());
770 return Val->getAggregateElement(Index);
771 }
772 return nullptr;
773 }
774
ConstantFoldInsertElementInstruction(Constant * Val,Constant * Elt,Constant * Idx)775 Constant *llvm::ConstantFoldInsertElementInstruction(Constant *Val,
776 Constant *Elt,
777 Constant *Idx) {
778 ConstantInt *CIdx = dyn_cast<ConstantInt>(Idx);
779 if (!CIdx) return nullptr;
780 const APInt &IdxVal = CIdx->getValue();
781
782 SmallVector<Constant*, 16> Result;
783 Type *Ty = IntegerType::get(Val->getContext(), 32);
784 for (unsigned i = 0, e = Val->getType()->getVectorNumElements(); i != e; ++i){
785 if (i == IdxVal) {
786 Result.push_back(Elt);
787 continue;
788 }
789
790 Constant *C =
791 ConstantExpr::getExtractElement(Val, ConstantInt::get(Ty, i));
792 Result.push_back(C);
793 }
794
795 return ConstantVector::get(Result);
796 }
797
ConstantFoldShuffleVectorInstruction(Constant * V1,Constant * V2,Constant * Mask)798 Constant *llvm::ConstantFoldShuffleVectorInstruction(Constant *V1,
799 Constant *V2,
800 Constant *Mask) {
801 unsigned MaskNumElts = Mask->getType()->getVectorNumElements();
802 Type *EltTy = V1->getType()->getVectorElementType();
803
804 // Undefined shuffle mask -> undefined value.
805 if (isa<UndefValue>(Mask))
806 return UndefValue::get(VectorType::get(EltTy, MaskNumElts));
807
808 // Don't break the bitcode reader hack.
809 if (isa<ConstantExpr>(Mask)) return nullptr;
810
811 unsigned SrcNumElts = V1->getType()->getVectorNumElements();
812
813 // Loop over the shuffle mask, evaluating each element.
814 SmallVector<Constant*, 32> Result;
815 for (unsigned i = 0; i != MaskNumElts; ++i) {
816 int Elt = ShuffleVectorInst::getMaskValue(Mask, i);
817 if (Elt == -1) {
818 Result.push_back(UndefValue::get(EltTy));
819 continue;
820 }
821 Constant *InElt;
822 if (unsigned(Elt) >= SrcNumElts*2)
823 InElt = UndefValue::get(EltTy);
824 else if (unsigned(Elt) >= SrcNumElts) {
825 Type *Ty = IntegerType::get(V2->getContext(), 32);
826 InElt =
827 ConstantExpr::getExtractElement(V2,
828 ConstantInt::get(Ty, Elt - SrcNumElts));
829 } else {
830 Type *Ty = IntegerType::get(V1->getContext(), 32);
831 InElt = ConstantExpr::getExtractElement(V1, ConstantInt::get(Ty, Elt));
832 }
833 Result.push_back(InElt);
834 }
835
836 return ConstantVector::get(Result);
837 }
838
ConstantFoldExtractValueInstruction(Constant * Agg,ArrayRef<unsigned> Idxs)839 Constant *llvm::ConstantFoldExtractValueInstruction(Constant *Agg,
840 ArrayRef<unsigned> Idxs) {
841 // Base case: no indices, so return the entire value.
842 if (Idxs.empty())
843 return Agg;
844
845 if (Constant *C = Agg->getAggregateElement(Idxs[0]))
846 return ConstantFoldExtractValueInstruction(C, Idxs.slice(1));
847
848 return nullptr;
849 }
850
ConstantFoldInsertValueInstruction(Constant * Agg,Constant * Val,ArrayRef<unsigned> Idxs)851 Constant *llvm::ConstantFoldInsertValueInstruction(Constant *Agg,
852 Constant *Val,
853 ArrayRef<unsigned> Idxs) {
854 // Base case: no indices, so replace the entire value.
855 if (Idxs.empty())
856 return Val;
857
858 unsigned NumElts;
859 if (StructType *ST = dyn_cast<StructType>(Agg->getType()))
860 NumElts = ST->getNumElements();
861 else if (ArrayType *AT = dyn_cast<ArrayType>(Agg->getType()))
862 NumElts = AT->getNumElements();
863 else
864 NumElts = Agg->getType()->getVectorNumElements();
865
866 SmallVector<Constant*, 32> Result;
867 for (unsigned i = 0; i != NumElts; ++i) {
868 Constant *C = Agg->getAggregateElement(i);
869 if (!C) return nullptr;
870
871 if (Idxs[0] == i)
872 C = ConstantFoldInsertValueInstruction(C, Val, Idxs.slice(1));
873
874 Result.push_back(C);
875 }
876
877 if (StructType *ST = dyn_cast<StructType>(Agg->getType()))
878 return ConstantStruct::get(ST, Result);
879 if (ArrayType *AT = dyn_cast<ArrayType>(Agg->getType()))
880 return ConstantArray::get(AT, Result);
881 return ConstantVector::get(Result);
882 }
883
884
ConstantFoldBinaryInstruction(unsigned Opcode,Constant * C1,Constant * C2)885 Constant *llvm::ConstantFoldBinaryInstruction(unsigned Opcode,
886 Constant *C1, Constant *C2) {
887 // Handle UndefValue up front.
888 if (isa<UndefValue>(C1) || isa<UndefValue>(C2)) {
889 switch (Opcode) {
890 case Instruction::Xor:
891 if (isa<UndefValue>(C1) && isa<UndefValue>(C2))
892 // Handle undef ^ undef -> 0 special case. This is a common
893 // idiom (misuse).
894 return Constant::getNullValue(C1->getType());
895 // Fallthrough
896 case Instruction::Add:
897 case Instruction::Sub:
898 return UndefValue::get(C1->getType());
899 case Instruction::And:
900 if (isa<UndefValue>(C1) && isa<UndefValue>(C2)) // undef & undef -> undef
901 return C1;
902 return Constant::getNullValue(C1->getType()); // undef & X -> 0
903 case Instruction::Mul: {
904 ConstantInt *CI;
905 // X * undef -> undef if X is odd or undef
906 if (((CI = dyn_cast<ConstantInt>(C1)) && CI->getValue()[0]) ||
907 ((CI = dyn_cast<ConstantInt>(C2)) && CI->getValue()[0]) ||
908 (isa<UndefValue>(C1) && isa<UndefValue>(C2)))
909 return UndefValue::get(C1->getType());
910
911 // X * undef -> 0 otherwise
912 return Constant::getNullValue(C1->getType());
913 }
914 case Instruction::UDiv:
915 case Instruction::SDiv:
916 // undef / 1 -> undef
917 if (Opcode == Instruction::UDiv || Opcode == Instruction::SDiv)
918 if (ConstantInt *CI2 = dyn_cast<ConstantInt>(C2))
919 if (CI2->isOne())
920 return C1;
921 // FALL THROUGH
922 case Instruction::URem:
923 case Instruction::SRem:
924 if (!isa<UndefValue>(C2)) // undef / X -> 0
925 return Constant::getNullValue(C1->getType());
926 return C2; // X / undef -> undef
927 case Instruction::Or: // X | undef -> -1
928 if (isa<UndefValue>(C1) && isa<UndefValue>(C2)) // undef | undef -> undef
929 return C1;
930 return Constant::getAllOnesValue(C1->getType()); // undef | X -> ~0
931 case Instruction::LShr:
932 if (isa<UndefValue>(C2) && isa<UndefValue>(C1))
933 return C1; // undef lshr undef -> undef
934 return Constant::getNullValue(C1->getType()); // X lshr undef -> 0
935 // undef lshr X -> 0
936 case Instruction::AShr:
937 if (!isa<UndefValue>(C2)) // undef ashr X --> all ones
938 return Constant::getAllOnesValue(C1->getType());
939 else if (isa<UndefValue>(C1))
940 return C1; // undef ashr undef -> undef
941 else
942 return C1; // X ashr undef --> X
943 case Instruction::Shl:
944 if (isa<UndefValue>(C2) && isa<UndefValue>(C1))
945 return C1; // undef shl undef -> undef
946 // undef << X -> 0 or X << undef -> 0
947 return Constant::getNullValue(C1->getType());
948 }
949 }
950
951 // Handle simplifications when the RHS is a constant int.
952 if (ConstantInt *CI2 = dyn_cast<ConstantInt>(C2)) {
953 switch (Opcode) {
954 case Instruction::Add:
955 if (CI2->equalsInt(0)) return C1; // X + 0 == X
956 break;
957 case Instruction::Sub:
958 if (CI2->equalsInt(0)) return C1; // X - 0 == X
959 break;
960 case Instruction::Mul:
961 if (CI2->equalsInt(0)) return C2; // X * 0 == 0
962 if (CI2->equalsInt(1))
963 return C1; // X * 1 == X
964 break;
965 case Instruction::UDiv:
966 case Instruction::SDiv:
967 if (CI2->equalsInt(1))
968 return C1; // X / 1 == X
969 if (CI2->equalsInt(0))
970 return UndefValue::get(CI2->getType()); // X / 0 == undef
971 break;
972 case Instruction::URem:
973 case Instruction::SRem:
974 if (CI2->equalsInt(1))
975 return Constant::getNullValue(CI2->getType()); // X % 1 == 0
976 if (CI2->equalsInt(0))
977 return UndefValue::get(CI2->getType()); // X % 0 == undef
978 break;
979 case Instruction::And:
980 if (CI2->isZero()) return C2; // X & 0 == 0
981 if (CI2->isAllOnesValue())
982 return C1; // X & -1 == X
983
984 if (ConstantExpr *CE1 = dyn_cast<ConstantExpr>(C1)) {
985 // (zext i32 to i64) & 4294967295 -> (zext i32 to i64)
986 if (CE1->getOpcode() == Instruction::ZExt) {
987 unsigned DstWidth = CI2->getType()->getBitWidth();
988 unsigned SrcWidth =
989 CE1->getOperand(0)->getType()->getPrimitiveSizeInBits();
990 APInt PossiblySetBits(APInt::getLowBitsSet(DstWidth, SrcWidth));
991 if ((PossiblySetBits & CI2->getValue()) == PossiblySetBits)
992 return C1;
993 }
994
995 // If and'ing the address of a global with a constant, fold it.
996 if (CE1->getOpcode() == Instruction::PtrToInt &&
997 isa<GlobalValue>(CE1->getOperand(0))) {
998 GlobalValue *GV = cast<GlobalValue>(CE1->getOperand(0));
999
1000 // Functions are at least 4-byte aligned.
1001 unsigned GVAlign = GV->getAlignment();
1002 if (isa<Function>(GV))
1003 GVAlign = std::max(GVAlign, 4U);
1004
1005 if (GVAlign > 1) {
1006 unsigned DstWidth = CI2->getType()->getBitWidth();
1007 unsigned SrcWidth = std::min(DstWidth, Log2_32(GVAlign));
1008 APInt BitsNotSet(APInt::getLowBitsSet(DstWidth, SrcWidth));
1009
1010 // If checking bits we know are clear, return zero.
1011 if ((CI2->getValue() & BitsNotSet) == CI2->getValue())
1012 return Constant::getNullValue(CI2->getType());
1013 }
1014 }
1015 }
1016 break;
1017 case Instruction::Or:
1018 if (CI2->equalsInt(0)) return C1; // X | 0 == X
1019 if (CI2->isAllOnesValue())
1020 return C2; // X | -1 == -1
1021 break;
1022 case Instruction::Xor:
1023 if (CI2->equalsInt(0)) return C1; // X ^ 0 == X
1024
1025 if (ConstantExpr *CE1 = dyn_cast<ConstantExpr>(C1)) {
1026 switch (CE1->getOpcode()) {
1027 default: break;
1028 case Instruction::ICmp:
1029 case Instruction::FCmp:
1030 // cmp pred ^ true -> cmp !pred
1031 assert(CI2->equalsInt(1));
1032 CmpInst::Predicate pred = (CmpInst::Predicate)CE1->getPredicate();
1033 pred = CmpInst::getInversePredicate(pred);
1034 return ConstantExpr::getCompare(pred, CE1->getOperand(0),
1035 CE1->getOperand(1));
1036 }
1037 }
1038 break;
1039 case Instruction::AShr:
1040 // ashr (zext C to Ty), C2 -> lshr (zext C, CSA), C2
1041 if (ConstantExpr *CE1 = dyn_cast<ConstantExpr>(C1))
1042 if (CE1->getOpcode() == Instruction::ZExt) // Top bits known zero.
1043 return ConstantExpr::getLShr(C1, C2);
1044 break;
1045 }
1046 } else if (isa<ConstantInt>(C1)) {
1047 // If C1 is a ConstantInt and C2 is not, swap the operands.
1048 if (Instruction::isCommutative(Opcode))
1049 return ConstantExpr::get(Opcode, C2, C1);
1050 }
1051
1052 // At this point we know neither constant is an UndefValue.
1053 if (ConstantInt *CI1 = dyn_cast<ConstantInt>(C1)) {
1054 if (ConstantInt *CI2 = dyn_cast<ConstantInt>(C2)) {
1055 const APInt &C1V = CI1->getValue();
1056 const APInt &C2V = CI2->getValue();
1057 switch (Opcode) {
1058 default:
1059 break;
1060 case Instruction::Add:
1061 return ConstantInt::get(CI1->getContext(), C1V + C2V);
1062 case Instruction::Sub:
1063 return ConstantInt::get(CI1->getContext(), C1V - C2V);
1064 case Instruction::Mul:
1065 return ConstantInt::get(CI1->getContext(), C1V * C2V);
1066 case Instruction::UDiv:
1067 assert(!CI2->isNullValue() && "Div by zero handled above");
1068 return ConstantInt::get(CI1->getContext(), C1V.udiv(C2V));
1069 case Instruction::SDiv:
1070 assert(!CI2->isNullValue() && "Div by zero handled above");
1071 if (C2V.isAllOnesValue() && C1V.isMinSignedValue())
1072 return UndefValue::get(CI1->getType()); // MIN_INT / -1 -> undef
1073 return ConstantInt::get(CI1->getContext(), C1V.sdiv(C2V));
1074 case Instruction::URem:
1075 assert(!CI2->isNullValue() && "Div by zero handled above");
1076 return ConstantInt::get(CI1->getContext(), C1V.urem(C2V));
1077 case Instruction::SRem:
1078 assert(!CI2->isNullValue() && "Div by zero handled above");
1079 if (C2V.isAllOnesValue() && C1V.isMinSignedValue())
1080 return UndefValue::get(CI1->getType()); // MIN_INT % -1 -> undef
1081 return ConstantInt::get(CI1->getContext(), C1V.srem(C2V));
1082 case Instruction::And:
1083 return ConstantInt::get(CI1->getContext(), C1V & C2V);
1084 case Instruction::Or:
1085 return ConstantInt::get(CI1->getContext(), C1V | C2V);
1086 case Instruction::Xor:
1087 return ConstantInt::get(CI1->getContext(), C1V ^ C2V);
1088 case Instruction::Shl: {
1089 uint32_t shiftAmt = C2V.getZExtValue();
1090 if (shiftAmt < C1V.getBitWidth())
1091 return ConstantInt::get(CI1->getContext(), C1V.shl(shiftAmt));
1092 else
1093 return UndefValue::get(C1->getType()); // too big shift is undef
1094 }
1095 case Instruction::LShr: {
1096 uint32_t shiftAmt = C2V.getZExtValue();
1097 if (shiftAmt < C1V.getBitWidth())
1098 return ConstantInt::get(CI1->getContext(), C1V.lshr(shiftAmt));
1099 else
1100 return UndefValue::get(C1->getType()); // too big shift is undef
1101 }
1102 case Instruction::AShr: {
1103 uint32_t shiftAmt = C2V.getZExtValue();
1104 if (shiftAmt < C1V.getBitWidth())
1105 return ConstantInt::get(CI1->getContext(), C1V.ashr(shiftAmt));
1106 else
1107 return UndefValue::get(C1->getType()); // too big shift is undef
1108 }
1109 }
1110 }
1111
1112 switch (Opcode) {
1113 case Instruction::SDiv:
1114 case Instruction::UDiv:
1115 case Instruction::URem:
1116 case Instruction::SRem:
1117 case Instruction::LShr:
1118 case Instruction::AShr:
1119 case Instruction::Shl:
1120 if (CI1->equalsInt(0)) return C1;
1121 break;
1122 default:
1123 break;
1124 }
1125 } else if (ConstantFP *CFP1 = dyn_cast<ConstantFP>(C1)) {
1126 if (ConstantFP *CFP2 = dyn_cast<ConstantFP>(C2)) {
1127 APFloat C1V = CFP1->getValueAPF();
1128 APFloat C2V = CFP2->getValueAPF();
1129 APFloat C3V = C1V; // copy for modification
1130 switch (Opcode) {
1131 default:
1132 break;
1133 case Instruction::FAdd:
1134 (void)C3V.add(C2V, APFloat::rmNearestTiesToEven);
1135 return ConstantFP::get(C1->getContext(), C3V);
1136 case Instruction::FSub:
1137 (void)C3V.subtract(C2V, APFloat::rmNearestTiesToEven);
1138 return ConstantFP::get(C1->getContext(), C3V);
1139 case Instruction::FMul:
1140 (void)C3V.multiply(C2V, APFloat::rmNearestTiesToEven);
1141 return ConstantFP::get(C1->getContext(), C3V);
1142 case Instruction::FDiv:
1143 (void)C3V.divide(C2V, APFloat::rmNearestTiesToEven);
1144 return ConstantFP::get(C1->getContext(), C3V);
1145 case Instruction::FRem:
1146 (void)C3V.mod(C2V, APFloat::rmNearestTiesToEven);
1147 return ConstantFP::get(C1->getContext(), C3V);
1148 }
1149 }
1150 } else if (VectorType *VTy = dyn_cast<VectorType>(C1->getType())) {
1151 // Perform elementwise folding.
1152 SmallVector<Constant*, 16> Result;
1153 Type *Ty = IntegerType::get(VTy->getContext(), 32);
1154 for (unsigned i = 0, e = VTy->getNumElements(); i != e; ++i) {
1155 Constant *LHS =
1156 ConstantExpr::getExtractElement(C1, ConstantInt::get(Ty, i));
1157 Constant *RHS =
1158 ConstantExpr::getExtractElement(C2, ConstantInt::get(Ty, i));
1159
1160 Result.push_back(ConstantExpr::get(Opcode, LHS, RHS));
1161 }
1162
1163 return ConstantVector::get(Result);
1164 }
1165
1166 if (ConstantExpr *CE1 = dyn_cast<ConstantExpr>(C1)) {
1167 // There are many possible foldings we could do here. We should probably
1168 // at least fold add of a pointer with an integer into the appropriate
1169 // getelementptr. This will improve alias analysis a bit.
1170
1171 // Given ((a + b) + c), if (b + c) folds to something interesting, return
1172 // (a + (b + c)).
1173 if (Instruction::isAssociative(Opcode) && CE1->getOpcode() == Opcode) {
1174 Constant *T = ConstantExpr::get(Opcode, CE1->getOperand(1), C2);
1175 if (!isa<ConstantExpr>(T) || cast<ConstantExpr>(T)->getOpcode() != Opcode)
1176 return ConstantExpr::get(Opcode, CE1->getOperand(0), T);
1177 }
1178 } else if (isa<ConstantExpr>(C2)) {
1179 // If C2 is a constant expr and C1 isn't, flop them around and fold the
1180 // other way if possible.
1181 if (Instruction::isCommutative(Opcode))
1182 return ConstantFoldBinaryInstruction(Opcode, C2, C1);
1183 }
1184
1185 // i1 can be simplified in many cases.
1186 if (C1->getType()->isIntegerTy(1)) {
1187 switch (Opcode) {
1188 case Instruction::Add:
1189 case Instruction::Sub:
1190 return ConstantExpr::getXor(C1, C2);
1191 case Instruction::Mul:
1192 return ConstantExpr::getAnd(C1, C2);
1193 case Instruction::Shl:
1194 case Instruction::LShr:
1195 case Instruction::AShr:
1196 // We can assume that C2 == 0. If it were one the result would be
1197 // undefined because the shift value is as large as the bitwidth.
1198 return C1;
1199 case Instruction::SDiv:
1200 case Instruction::UDiv:
1201 // We can assume that C2 == 1. If it were zero the result would be
1202 // undefined through division by zero.
1203 return C1;
1204 case Instruction::URem:
1205 case Instruction::SRem:
1206 // We can assume that C2 == 1. If it were zero the result would be
1207 // undefined through division by zero.
1208 return ConstantInt::getFalse(C1->getContext());
1209 default:
1210 break;
1211 }
1212 }
1213
1214 // We don't know how to fold this.
1215 return nullptr;
1216 }
1217
1218 /// isZeroSizedType - This type is zero sized if its an array or structure of
1219 /// zero sized types. The only leaf zero sized type is an empty structure.
isMaybeZeroSizedType(Type * Ty)1220 static bool isMaybeZeroSizedType(Type *Ty) {
1221 if (StructType *STy = dyn_cast<StructType>(Ty)) {
1222 if (STy->isOpaque()) return true; // Can't say.
1223
1224 // If all of elements have zero size, this does too.
1225 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i)
1226 if (!isMaybeZeroSizedType(STy->getElementType(i))) return false;
1227 return true;
1228
1229 } else if (ArrayType *ATy = dyn_cast<ArrayType>(Ty)) {
1230 return isMaybeZeroSizedType(ATy->getElementType());
1231 }
1232 return false;
1233 }
1234
1235 /// IdxCompare - Compare the two constants as though they were getelementptr
1236 /// indices. This allows coersion of the types to be the same thing.
1237 ///
1238 /// If the two constants are the "same" (after coersion), return 0. If the
1239 /// first is less than the second, return -1, if the second is less than the
1240 /// first, return 1. If the constants are not integral, return -2.
1241 ///
IdxCompare(Constant * C1,Constant * C2,Type * ElTy)1242 static int IdxCompare(Constant *C1, Constant *C2, Type *ElTy) {
1243 if (C1 == C2) return 0;
1244
1245 // Ok, we found a different index. If they are not ConstantInt, we can't do
1246 // anything with them.
1247 if (!isa<ConstantInt>(C1) || !isa<ConstantInt>(C2))
1248 return -2; // don't know!
1249
1250 // Ok, we have two differing integer indices. Sign extend them to be the same
1251 // type. Long is always big enough, so we use it.
1252 if (!C1->getType()->isIntegerTy(64))
1253 C1 = ConstantExpr::getSExt(C1, Type::getInt64Ty(C1->getContext()));
1254
1255 if (!C2->getType()->isIntegerTy(64))
1256 C2 = ConstantExpr::getSExt(C2, Type::getInt64Ty(C1->getContext()));
1257
1258 if (C1 == C2) return 0; // They are equal
1259
1260 // If the type being indexed over is really just a zero sized type, there is
1261 // no pointer difference being made here.
1262 if (isMaybeZeroSizedType(ElTy))
1263 return -2; // dunno.
1264
1265 // If they are really different, now that they are the same type, then we
1266 // found a difference!
1267 if (cast<ConstantInt>(C1)->getSExtValue() <
1268 cast<ConstantInt>(C2)->getSExtValue())
1269 return -1;
1270 else
1271 return 1;
1272 }
1273
1274 /// evaluateFCmpRelation - This function determines if there is anything we can
1275 /// decide about the two constants provided. This doesn't need to handle simple
1276 /// things like ConstantFP comparisons, but should instead handle ConstantExprs.
1277 /// If we can determine that the two constants have a particular relation to
1278 /// each other, we should return the corresponding FCmpInst predicate,
1279 /// otherwise return FCmpInst::BAD_FCMP_PREDICATE. This is used below in
1280 /// ConstantFoldCompareInstruction.
1281 ///
1282 /// To simplify this code we canonicalize the relation so that the first
1283 /// operand is always the most "complex" of the two. We consider ConstantFP
1284 /// to be the simplest, and ConstantExprs to be the most complex.
evaluateFCmpRelation(Constant * V1,Constant * V2)1285 static FCmpInst::Predicate evaluateFCmpRelation(Constant *V1, Constant *V2) {
1286 assert(V1->getType() == V2->getType() &&
1287 "Cannot compare values of different types!");
1288
1289 // Handle degenerate case quickly
1290 if (V1 == V2) return FCmpInst::FCMP_OEQ;
1291
1292 if (!isa<ConstantExpr>(V1)) {
1293 if (!isa<ConstantExpr>(V2)) {
1294 // We distilled thisUse the standard constant folder for a few cases
1295 ConstantInt *R = nullptr;
1296 R = dyn_cast<ConstantInt>(
1297 ConstantExpr::getFCmp(FCmpInst::FCMP_OEQ, V1, V2));
1298 if (R && !R->isZero())
1299 return FCmpInst::FCMP_OEQ;
1300 R = dyn_cast<ConstantInt>(
1301 ConstantExpr::getFCmp(FCmpInst::FCMP_OLT, V1, V2));
1302 if (R && !R->isZero())
1303 return FCmpInst::FCMP_OLT;
1304 R = dyn_cast<ConstantInt>(
1305 ConstantExpr::getFCmp(FCmpInst::FCMP_OGT, V1, V2));
1306 if (R && !R->isZero())
1307 return FCmpInst::FCMP_OGT;
1308
1309 // Nothing more we can do
1310 return FCmpInst::BAD_FCMP_PREDICATE;
1311 }
1312
1313 // If the first operand is simple and second is ConstantExpr, swap operands.
1314 FCmpInst::Predicate SwappedRelation = evaluateFCmpRelation(V2, V1);
1315 if (SwappedRelation != FCmpInst::BAD_FCMP_PREDICATE)
1316 return FCmpInst::getSwappedPredicate(SwappedRelation);
1317 } else {
1318 // Ok, the LHS is known to be a constantexpr. The RHS can be any of a
1319 // constantexpr or a simple constant.
1320 ConstantExpr *CE1 = cast<ConstantExpr>(V1);
1321 switch (CE1->getOpcode()) {
1322 case Instruction::FPTrunc:
1323 case Instruction::FPExt:
1324 case Instruction::UIToFP:
1325 case Instruction::SIToFP:
1326 // We might be able to do something with these but we don't right now.
1327 break;
1328 default:
1329 break;
1330 }
1331 }
1332 // There are MANY other foldings that we could perform here. They will
1333 // probably be added on demand, as they seem needed.
1334 return FCmpInst::BAD_FCMP_PREDICATE;
1335 }
1336
areGlobalsPotentiallyEqual(const GlobalValue * GV1,const GlobalValue * GV2)1337 static ICmpInst::Predicate areGlobalsPotentiallyEqual(const GlobalValue *GV1,
1338 const GlobalValue *GV2) {
1339 // Don't try to decide equality of aliases.
1340 if (!isa<GlobalAlias>(GV1) && !isa<GlobalAlias>(GV2))
1341 if (!GV1->hasExternalWeakLinkage() || !GV2->hasExternalWeakLinkage())
1342 return ICmpInst::ICMP_NE;
1343 return ICmpInst::BAD_ICMP_PREDICATE;
1344 }
1345
1346 /// evaluateICmpRelation - This function determines if there is anything we can
1347 /// decide about the two constants provided. This doesn't need to handle simple
1348 /// things like integer comparisons, but should instead handle ConstantExprs
1349 /// and GlobalValues. If we can determine that the two constants have a
1350 /// particular relation to each other, we should return the corresponding ICmp
1351 /// predicate, otherwise return ICmpInst::BAD_ICMP_PREDICATE.
1352 ///
1353 /// To simplify this code we canonicalize the relation so that the first
1354 /// operand is always the most "complex" of the two. We consider simple
1355 /// constants (like ConstantInt) to be the simplest, followed by
1356 /// GlobalValues, followed by ConstantExpr's (the most complex).
1357 ///
evaluateICmpRelation(Constant * V1,Constant * V2,bool isSigned)1358 static ICmpInst::Predicate evaluateICmpRelation(Constant *V1, Constant *V2,
1359 bool isSigned) {
1360 assert(V1->getType() == V2->getType() &&
1361 "Cannot compare different types of values!");
1362 if (V1 == V2) return ICmpInst::ICMP_EQ;
1363
1364 if (!isa<ConstantExpr>(V1) && !isa<GlobalValue>(V1) &&
1365 !isa<BlockAddress>(V1)) {
1366 if (!isa<GlobalValue>(V2) && !isa<ConstantExpr>(V2) &&
1367 !isa<BlockAddress>(V2)) {
1368 // We distilled this down to a simple case, use the standard constant
1369 // folder.
1370 ConstantInt *R = nullptr;
1371 ICmpInst::Predicate pred = ICmpInst::ICMP_EQ;
1372 R = dyn_cast<ConstantInt>(ConstantExpr::getICmp(pred, V1, V2));
1373 if (R && !R->isZero())
1374 return pred;
1375 pred = isSigned ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT;
1376 R = dyn_cast<ConstantInt>(ConstantExpr::getICmp(pred, V1, V2));
1377 if (R && !R->isZero())
1378 return pred;
1379 pred = isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT;
1380 R = dyn_cast<ConstantInt>(ConstantExpr::getICmp(pred, V1, V2));
1381 if (R && !R->isZero())
1382 return pred;
1383
1384 // If we couldn't figure it out, bail.
1385 return ICmpInst::BAD_ICMP_PREDICATE;
1386 }
1387
1388 // If the first operand is simple, swap operands.
1389 ICmpInst::Predicate SwappedRelation =
1390 evaluateICmpRelation(V2, V1, isSigned);
1391 if (SwappedRelation != ICmpInst::BAD_ICMP_PREDICATE)
1392 return ICmpInst::getSwappedPredicate(SwappedRelation);
1393
1394 } else if (const GlobalValue *GV = dyn_cast<GlobalValue>(V1)) {
1395 if (isa<ConstantExpr>(V2)) { // Swap as necessary.
1396 ICmpInst::Predicate SwappedRelation =
1397 evaluateICmpRelation(V2, V1, isSigned);
1398 if (SwappedRelation != ICmpInst::BAD_ICMP_PREDICATE)
1399 return ICmpInst::getSwappedPredicate(SwappedRelation);
1400 return ICmpInst::BAD_ICMP_PREDICATE;
1401 }
1402
1403 // Now we know that the RHS is a GlobalValue, BlockAddress or simple
1404 // constant (which, since the types must match, means that it's a
1405 // ConstantPointerNull).
1406 if (const GlobalValue *GV2 = dyn_cast<GlobalValue>(V2)) {
1407 return areGlobalsPotentiallyEqual(GV, GV2);
1408 } else if (isa<BlockAddress>(V2)) {
1409 return ICmpInst::ICMP_NE; // Globals never equal labels.
1410 } else {
1411 assert(isa<ConstantPointerNull>(V2) && "Canonicalization guarantee!");
1412 // GlobalVals can never be null unless they have external weak linkage.
1413 // We don't try to evaluate aliases here.
1414 if (!GV->hasExternalWeakLinkage() && !isa<GlobalAlias>(GV))
1415 return ICmpInst::ICMP_NE;
1416 }
1417 } else if (const BlockAddress *BA = dyn_cast<BlockAddress>(V1)) {
1418 if (isa<ConstantExpr>(V2)) { // Swap as necessary.
1419 ICmpInst::Predicate SwappedRelation =
1420 evaluateICmpRelation(V2, V1, isSigned);
1421 if (SwappedRelation != ICmpInst::BAD_ICMP_PREDICATE)
1422 return ICmpInst::getSwappedPredicate(SwappedRelation);
1423 return ICmpInst::BAD_ICMP_PREDICATE;
1424 }
1425
1426 // Now we know that the RHS is a GlobalValue, BlockAddress or simple
1427 // constant (which, since the types must match, means that it is a
1428 // ConstantPointerNull).
1429 if (const BlockAddress *BA2 = dyn_cast<BlockAddress>(V2)) {
1430 // Block address in another function can't equal this one, but block
1431 // addresses in the current function might be the same if blocks are
1432 // empty.
1433 if (BA2->getFunction() != BA->getFunction())
1434 return ICmpInst::ICMP_NE;
1435 } else {
1436 // Block addresses aren't null, don't equal the address of globals.
1437 assert((isa<ConstantPointerNull>(V2) || isa<GlobalValue>(V2)) &&
1438 "Canonicalization guarantee!");
1439 return ICmpInst::ICMP_NE;
1440 }
1441 } else {
1442 // Ok, the LHS is known to be a constantexpr. The RHS can be any of a
1443 // constantexpr, a global, block address, or a simple constant.
1444 ConstantExpr *CE1 = cast<ConstantExpr>(V1);
1445 Constant *CE1Op0 = CE1->getOperand(0);
1446
1447 switch (CE1->getOpcode()) {
1448 case Instruction::Trunc:
1449 case Instruction::FPTrunc:
1450 case Instruction::FPExt:
1451 case Instruction::FPToUI:
1452 case Instruction::FPToSI:
1453 break; // We can't evaluate floating point casts or truncations.
1454
1455 case Instruction::UIToFP:
1456 case Instruction::SIToFP:
1457 case Instruction::BitCast:
1458 case Instruction::ZExt:
1459 case Instruction::SExt:
1460 // If the cast is not actually changing bits, and the second operand is a
1461 // null pointer, do the comparison with the pre-casted value.
1462 if (V2->isNullValue() &&
1463 (CE1->getType()->isPointerTy() || CE1->getType()->isIntegerTy())) {
1464 if (CE1->getOpcode() == Instruction::ZExt) isSigned = false;
1465 if (CE1->getOpcode() == Instruction::SExt) isSigned = true;
1466 return evaluateICmpRelation(CE1Op0,
1467 Constant::getNullValue(CE1Op0->getType()),
1468 isSigned);
1469 }
1470 break;
1471
1472 case Instruction::GetElementPtr: {
1473 GEPOperator *CE1GEP = cast<GEPOperator>(CE1);
1474 // Ok, since this is a getelementptr, we know that the constant has a
1475 // pointer type. Check the various cases.
1476 if (isa<ConstantPointerNull>(V2)) {
1477 // If we are comparing a GEP to a null pointer, check to see if the base
1478 // of the GEP equals the null pointer.
1479 if (const GlobalValue *GV = dyn_cast<GlobalValue>(CE1Op0)) {
1480 if (GV->hasExternalWeakLinkage())
1481 // Weak linkage GVals could be zero or not. We're comparing that
1482 // to null pointer so its greater-or-equal
1483 return isSigned ? ICmpInst::ICMP_SGE : ICmpInst::ICMP_UGE;
1484 else
1485 // If its not weak linkage, the GVal must have a non-zero address
1486 // so the result is greater-than
1487 return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT;
1488 } else if (isa<ConstantPointerNull>(CE1Op0)) {
1489 // If we are indexing from a null pointer, check to see if we have any
1490 // non-zero indices.
1491 for (unsigned i = 1, e = CE1->getNumOperands(); i != e; ++i)
1492 if (!CE1->getOperand(i)->isNullValue())
1493 // Offsetting from null, must not be equal.
1494 return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT;
1495 // Only zero indexes from null, must still be zero.
1496 return ICmpInst::ICMP_EQ;
1497 }
1498 // Otherwise, we can't really say if the first operand is null or not.
1499 } else if (const GlobalValue *GV2 = dyn_cast<GlobalValue>(V2)) {
1500 if (isa<ConstantPointerNull>(CE1Op0)) {
1501 if (GV2->hasExternalWeakLinkage())
1502 // Weak linkage GVals could be zero or not. We're comparing it to
1503 // a null pointer, so its less-or-equal
1504 return isSigned ? ICmpInst::ICMP_SLE : ICmpInst::ICMP_ULE;
1505 else
1506 // If its not weak linkage, the GVal must have a non-zero address
1507 // so the result is less-than
1508 return isSigned ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT;
1509 } else if (const GlobalValue *GV = dyn_cast<GlobalValue>(CE1Op0)) {
1510 if (GV == GV2) {
1511 // If this is a getelementptr of the same global, then it must be
1512 // different. Because the types must match, the getelementptr could
1513 // only have at most one index, and because we fold getelementptr's
1514 // with a single zero index, it must be nonzero.
1515 assert(CE1->getNumOperands() == 2 &&
1516 !CE1->getOperand(1)->isNullValue() &&
1517 "Surprising getelementptr!");
1518 return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT;
1519 } else {
1520 if (CE1GEP->hasAllZeroIndices())
1521 return areGlobalsPotentiallyEqual(GV, GV2);
1522 return ICmpInst::BAD_ICMP_PREDICATE;
1523 }
1524 }
1525 } else {
1526 ConstantExpr *CE2 = cast<ConstantExpr>(V2);
1527 Constant *CE2Op0 = CE2->getOperand(0);
1528
1529 // There are MANY other foldings that we could perform here. They will
1530 // probably be added on demand, as they seem needed.
1531 switch (CE2->getOpcode()) {
1532 default: break;
1533 case Instruction::GetElementPtr:
1534 // By far the most common case to handle is when the base pointers are
1535 // obviously to the same global.
1536 if (isa<GlobalValue>(CE1Op0) && isa<GlobalValue>(CE2Op0)) {
1537 // Don't know relative ordering, but check for inequality.
1538 if (CE1Op0 != CE2Op0) {
1539 GEPOperator *CE2GEP = cast<GEPOperator>(CE2);
1540 if (CE1GEP->hasAllZeroIndices() && CE2GEP->hasAllZeroIndices())
1541 return areGlobalsPotentiallyEqual(cast<GlobalValue>(CE1Op0),
1542 cast<GlobalValue>(CE2Op0));
1543 return ICmpInst::BAD_ICMP_PREDICATE;
1544 }
1545 // Ok, we know that both getelementptr instructions are based on the
1546 // same global. From this, we can precisely determine the relative
1547 // ordering of the resultant pointers.
1548 unsigned i = 1;
1549
1550 // The logic below assumes that the result of the comparison
1551 // can be determined by finding the first index that differs.
1552 // This doesn't work if there is over-indexing in any
1553 // subsequent indices, so check for that case first.
1554 if (!CE1->isGEPWithNoNotionalOverIndexing() ||
1555 !CE2->isGEPWithNoNotionalOverIndexing())
1556 return ICmpInst::BAD_ICMP_PREDICATE; // Might be equal.
1557
1558 // Compare all of the operands the GEP's have in common.
1559 gep_type_iterator GTI = gep_type_begin(CE1);
1560 for (;i != CE1->getNumOperands() && i != CE2->getNumOperands();
1561 ++i, ++GTI)
1562 switch (IdxCompare(CE1->getOperand(i),
1563 CE2->getOperand(i), GTI.getIndexedType())) {
1564 case -1: return isSigned ? ICmpInst::ICMP_SLT:ICmpInst::ICMP_ULT;
1565 case 1: return isSigned ? ICmpInst::ICMP_SGT:ICmpInst::ICMP_UGT;
1566 case -2: return ICmpInst::BAD_ICMP_PREDICATE;
1567 }
1568
1569 // Ok, we ran out of things they have in common. If any leftovers
1570 // are non-zero then we have a difference, otherwise we are equal.
1571 for (; i < CE1->getNumOperands(); ++i)
1572 if (!CE1->getOperand(i)->isNullValue()) {
1573 if (isa<ConstantInt>(CE1->getOperand(i)))
1574 return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT;
1575 else
1576 return ICmpInst::BAD_ICMP_PREDICATE; // Might be equal.
1577 }
1578
1579 for (; i < CE2->getNumOperands(); ++i)
1580 if (!CE2->getOperand(i)->isNullValue()) {
1581 if (isa<ConstantInt>(CE2->getOperand(i)))
1582 return isSigned ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT;
1583 else
1584 return ICmpInst::BAD_ICMP_PREDICATE; // Might be equal.
1585 }
1586 return ICmpInst::ICMP_EQ;
1587 }
1588 }
1589 }
1590 }
1591 default:
1592 break;
1593 }
1594 }
1595
1596 return ICmpInst::BAD_ICMP_PREDICATE;
1597 }
1598
ConstantFoldCompareInstruction(unsigned short pred,Constant * C1,Constant * C2)1599 Constant *llvm::ConstantFoldCompareInstruction(unsigned short pred,
1600 Constant *C1, Constant *C2) {
1601 Type *ResultTy;
1602 if (VectorType *VT = dyn_cast<VectorType>(C1->getType()))
1603 ResultTy = VectorType::get(Type::getInt1Ty(C1->getContext()),
1604 VT->getNumElements());
1605 else
1606 ResultTy = Type::getInt1Ty(C1->getContext());
1607
1608 // Fold FCMP_FALSE/FCMP_TRUE unconditionally.
1609 if (pred == FCmpInst::FCMP_FALSE)
1610 return Constant::getNullValue(ResultTy);
1611
1612 if (pred == FCmpInst::FCMP_TRUE)
1613 return Constant::getAllOnesValue(ResultTy);
1614
1615 // Handle some degenerate cases first
1616 if (isa<UndefValue>(C1) || isa<UndefValue>(C2)) {
1617 // For EQ and NE, we can always pick a value for the undef to make the
1618 // predicate pass or fail, so we can return undef.
1619 // Also, if both operands are undef, we can return undef.
1620 if (ICmpInst::isEquality(ICmpInst::Predicate(pred)) ||
1621 (isa<UndefValue>(C1) && isa<UndefValue>(C2)))
1622 return UndefValue::get(ResultTy);
1623 // Otherwise, pick the same value as the non-undef operand, and fold
1624 // it to true or false.
1625 return ConstantInt::get(ResultTy, CmpInst::isTrueWhenEqual(pred));
1626 }
1627
1628 // icmp eq/ne(null,GV) -> false/true
1629 if (C1->isNullValue()) {
1630 if (const GlobalValue *GV = dyn_cast<GlobalValue>(C2))
1631 // Don't try to evaluate aliases. External weak GV can be null.
1632 if (!isa<GlobalAlias>(GV) && !GV->hasExternalWeakLinkage()) {
1633 if (pred == ICmpInst::ICMP_EQ)
1634 return ConstantInt::getFalse(C1->getContext());
1635 else if (pred == ICmpInst::ICMP_NE)
1636 return ConstantInt::getTrue(C1->getContext());
1637 }
1638 // icmp eq/ne(GV,null) -> false/true
1639 } else if (C2->isNullValue()) {
1640 if (const GlobalValue *GV = dyn_cast<GlobalValue>(C1))
1641 // Don't try to evaluate aliases. External weak GV can be null.
1642 if (!isa<GlobalAlias>(GV) && !GV->hasExternalWeakLinkage()) {
1643 if (pred == ICmpInst::ICMP_EQ)
1644 return ConstantInt::getFalse(C1->getContext());
1645 else if (pred == ICmpInst::ICMP_NE)
1646 return ConstantInt::getTrue(C1->getContext());
1647 }
1648 }
1649
1650 // If the comparison is a comparison between two i1's, simplify it.
1651 if (C1->getType()->isIntegerTy(1)) {
1652 switch(pred) {
1653 case ICmpInst::ICMP_EQ:
1654 if (isa<ConstantInt>(C2))
1655 return ConstantExpr::getXor(C1, ConstantExpr::getNot(C2));
1656 return ConstantExpr::getXor(ConstantExpr::getNot(C1), C2);
1657 case ICmpInst::ICMP_NE:
1658 return ConstantExpr::getXor(C1, C2);
1659 default:
1660 break;
1661 }
1662 }
1663
1664 if (isa<ConstantInt>(C1) && isa<ConstantInt>(C2)) {
1665 APInt V1 = cast<ConstantInt>(C1)->getValue();
1666 APInt V2 = cast<ConstantInt>(C2)->getValue();
1667 switch (pred) {
1668 default: llvm_unreachable("Invalid ICmp Predicate");
1669 case ICmpInst::ICMP_EQ: return ConstantInt::get(ResultTy, V1 == V2);
1670 case ICmpInst::ICMP_NE: return ConstantInt::get(ResultTy, V1 != V2);
1671 case ICmpInst::ICMP_SLT: return ConstantInt::get(ResultTy, V1.slt(V2));
1672 case ICmpInst::ICMP_SGT: return ConstantInt::get(ResultTy, V1.sgt(V2));
1673 case ICmpInst::ICMP_SLE: return ConstantInt::get(ResultTy, V1.sle(V2));
1674 case ICmpInst::ICMP_SGE: return ConstantInt::get(ResultTy, V1.sge(V2));
1675 case ICmpInst::ICMP_ULT: return ConstantInt::get(ResultTy, V1.ult(V2));
1676 case ICmpInst::ICMP_UGT: return ConstantInt::get(ResultTy, V1.ugt(V2));
1677 case ICmpInst::ICMP_ULE: return ConstantInt::get(ResultTy, V1.ule(V2));
1678 case ICmpInst::ICMP_UGE: return ConstantInt::get(ResultTy, V1.uge(V2));
1679 }
1680 } else if (isa<ConstantFP>(C1) && isa<ConstantFP>(C2)) {
1681 APFloat C1V = cast<ConstantFP>(C1)->getValueAPF();
1682 APFloat C2V = cast<ConstantFP>(C2)->getValueAPF();
1683 APFloat::cmpResult R = C1V.compare(C2V);
1684 switch (pred) {
1685 default: llvm_unreachable("Invalid FCmp Predicate");
1686 case FCmpInst::FCMP_FALSE: return Constant::getNullValue(ResultTy);
1687 case FCmpInst::FCMP_TRUE: return Constant::getAllOnesValue(ResultTy);
1688 case FCmpInst::FCMP_UNO:
1689 return ConstantInt::get(ResultTy, R==APFloat::cmpUnordered);
1690 case FCmpInst::FCMP_ORD:
1691 return ConstantInt::get(ResultTy, R!=APFloat::cmpUnordered);
1692 case FCmpInst::FCMP_UEQ:
1693 return ConstantInt::get(ResultTy, R==APFloat::cmpUnordered ||
1694 R==APFloat::cmpEqual);
1695 case FCmpInst::FCMP_OEQ:
1696 return ConstantInt::get(ResultTy, R==APFloat::cmpEqual);
1697 case FCmpInst::FCMP_UNE:
1698 return ConstantInt::get(ResultTy, R!=APFloat::cmpEqual);
1699 case FCmpInst::FCMP_ONE:
1700 return ConstantInt::get(ResultTy, R==APFloat::cmpLessThan ||
1701 R==APFloat::cmpGreaterThan);
1702 case FCmpInst::FCMP_ULT:
1703 return ConstantInt::get(ResultTy, R==APFloat::cmpUnordered ||
1704 R==APFloat::cmpLessThan);
1705 case FCmpInst::FCMP_OLT:
1706 return ConstantInt::get(ResultTy, R==APFloat::cmpLessThan);
1707 case FCmpInst::FCMP_UGT:
1708 return ConstantInt::get(ResultTy, R==APFloat::cmpUnordered ||
1709 R==APFloat::cmpGreaterThan);
1710 case FCmpInst::FCMP_OGT:
1711 return ConstantInt::get(ResultTy, R==APFloat::cmpGreaterThan);
1712 case FCmpInst::FCMP_ULE:
1713 return ConstantInt::get(ResultTy, R!=APFloat::cmpGreaterThan);
1714 case FCmpInst::FCMP_OLE:
1715 return ConstantInt::get(ResultTy, R==APFloat::cmpLessThan ||
1716 R==APFloat::cmpEqual);
1717 case FCmpInst::FCMP_UGE:
1718 return ConstantInt::get(ResultTy, R!=APFloat::cmpLessThan);
1719 case FCmpInst::FCMP_OGE:
1720 return ConstantInt::get(ResultTy, R==APFloat::cmpGreaterThan ||
1721 R==APFloat::cmpEqual);
1722 }
1723 } else if (C1->getType()->isVectorTy()) {
1724 // If we can constant fold the comparison of each element, constant fold
1725 // the whole vector comparison.
1726 SmallVector<Constant*, 4> ResElts;
1727 Type *Ty = IntegerType::get(C1->getContext(), 32);
1728 // Compare the elements, producing an i1 result or constant expr.
1729 for (unsigned i = 0, e = C1->getType()->getVectorNumElements(); i != e;++i){
1730 Constant *C1E =
1731 ConstantExpr::getExtractElement(C1, ConstantInt::get(Ty, i));
1732 Constant *C2E =
1733 ConstantExpr::getExtractElement(C2, ConstantInt::get(Ty, i));
1734
1735 ResElts.push_back(ConstantExpr::getCompare(pred, C1E, C2E));
1736 }
1737
1738 return ConstantVector::get(ResElts);
1739 }
1740
1741 if (C1->getType()->isFloatingPointTy()) {
1742 int Result = -1; // -1 = unknown, 0 = known false, 1 = known true.
1743 switch (evaluateFCmpRelation(C1, C2)) {
1744 default: llvm_unreachable("Unknown relation!");
1745 case FCmpInst::FCMP_UNO:
1746 case FCmpInst::FCMP_ORD:
1747 case FCmpInst::FCMP_UEQ:
1748 case FCmpInst::FCMP_UNE:
1749 case FCmpInst::FCMP_ULT:
1750 case FCmpInst::FCMP_UGT:
1751 case FCmpInst::FCMP_ULE:
1752 case FCmpInst::FCMP_UGE:
1753 case FCmpInst::FCMP_TRUE:
1754 case FCmpInst::FCMP_FALSE:
1755 case FCmpInst::BAD_FCMP_PREDICATE:
1756 break; // Couldn't determine anything about these constants.
1757 case FCmpInst::FCMP_OEQ: // We know that C1 == C2
1758 Result = (pred == FCmpInst::FCMP_UEQ || pred == FCmpInst::FCMP_OEQ ||
1759 pred == FCmpInst::FCMP_ULE || pred == FCmpInst::FCMP_OLE ||
1760 pred == FCmpInst::FCMP_UGE || pred == FCmpInst::FCMP_OGE);
1761 break;
1762 case FCmpInst::FCMP_OLT: // We know that C1 < C2
1763 Result = (pred == FCmpInst::FCMP_UNE || pred == FCmpInst::FCMP_ONE ||
1764 pred == FCmpInst::FCMP_ULT || pred == FCmpInst::FCMP_OLT ||
1765 pred == FCmpInst::FCMP_ULE || pred == FCmpInst::FCMP_OLE);
1766 break;
1767 case FCmpInst::FCMP_OGT: // We know that C1 > C2
1768 Result = (pred == FCmpInst::FCMP_UNE || pred == FCmpInst::FCMP_ONE ||
1769 pred == FCmpInst::FCMP_UGT || pred == FCmpInst::FCMP_OGT ||
1770 pred == FCmpInst::FCMP_UGE || pred == FCmpInst::FCMP_OGE);
1771 break;
1772 case FCmpInst::FCMP_OLE: // We know that C1 <= C2
1773 // We can only partially decide this relation.
1774 if (pred == FCmpInst::FCMP_UGT || pred == FCmpInst::FCMP_OGT)
1775 Result = 0;
1776 else if (pred == FCmpInst::FCMP_ULT || pred == FCmpInst::FCMP_OLT)
1777 Result = 1;
1778 break;
1779 case FCmpInst::FCMP_OGE: // We known that C1 >= C2
1780 // We can only partially decide this relation.
1781 if (pred == FCmpInst::FCMP_ULT || pred == FCmpInst::FCMP_OLT)
1782 Result = 0;
1783 else if (pred == FCmpInst::FCMP_UGT || pred == FCmpInst::FCMP_OGT)
1784 Result = 1;
1785 break;
1786 case FCmpInst::FCMP_ONE: // We know that C1 != C2
1787 // We can only partially decide this relation.
1788 if (pred == FCmpInst::FCMP_OEQ || pred == FCmpInst::FCMP_UEQ)
1789 Result = 0;
1790 else if (pred == FCmpInst::FCMP_ONE || pred == FCmpInst::FCMP_UNE)
1791 Result = 1;
1792 break;
1793 }
1794
1795 // If we evaluated the result, return it now.
1796 if (Result != -1)
1797 return ConstantInt::get(ResultTy, Result);
1798
1799 } else {
1800 // Evaluate the relation between the two constants, per the predicate.
1801 int Result = -1; // -1 = unknown, 0 = known false, 1 = known true.
1802 switch (evaluateICmpRelation(C1, C2, CmpInst::isSigned(pred))) {
1803 default: llvm_unreachable("Unknown relational!");
1804 case ICmpInst::BAD_ICMP_PREDICATE:
1805 break; // Couldn't determine anything about these constants.
1806 case ICmpInst::ICMP_EQ: // We know the constants are equal!
1807 // If we know the constants are equal, we can decide the result of this
1808 // computation precisely.
1809 Result = ICmpInst::isTrueWhenEqual((ICmpInst::Predicate)pred);
1810 break;
1811 case ICmpInst::ICMP_ULT:
1812 switch (pred) {
1813 case ICmpInst::ICMP_ULT: case ICmpInst::ICMP_NE: case ICmpInst::ICMP_ULE:
1814 Result = 1; break;
1815 case ICmpInst::ICMP_UGT: case ICmpInst::ICMP_EQ: case ICmpInst::ICMP_UGE:
1816 Result = 0; break;
1817 }
1818 break;
1819 case ICmpInst::ICMP_SLT:
1820 switch (pred) {
1821 case ICmpInst::ICMP_SLT: case ICmpInst::ICMP_NE: case ICmpInst::ICMP_SLE:
1822 Result = 1; break;
1823 case ICmpInst::ICMP_SGT: case ICmpInst::ICMP_EQ: case ICmpInst::ICMP_SGE:
1824 Result = 0; break;
1825 }
1826 break;
1827 case ICmpInst::ICMP_UGT:
1828 switch (pred) {
1829 case ICmpInst::ICMP_UGT: case ICmpInst::ICMP_NE: case ICmpInst::ICMP_UGE:
1830 Result = 1; break;
1831 case ICmpInst::ICMP_ULT: case ICmpInst::ICMP_EQ: case ICmpInst::ICMP_ULE:
1832 Result = 0; break;
1833 }
1834 break;
1835 case ICmpInst::ICMP_SGT:
1836 switch (pred) {
1837 case ICmpInst::ICMP_SGT: case ICmpInst::ICMP_NE: case ICmpInst::ICMP_SGE:
1838 Result = 1; break;
1839 case ICmpInst::ICMP_SLT: case ICmpInst::ICMP_EQ: case ICmpInst::ICMP_SLE:
1840 Result = 0; break;
1841 }
1842 break;
1843 case ICmpInst::ICMP_ULE:
1844 if (pred == ICmpInst::ICMP_UGT) Result = 0;
1845 if (pred == ICmpInst::ICMP_ULT || pred == ICmpInst::ICMP_ULE) Result = 1;
1846 break;
1847 case ICmpInst::ICMP_SLE:
1848 if (pred == ICmpInst::ICMP_SGT) Result = 0;
1849 if (pred == ICmpInst::ICMP_SLT || pred == ICmpInst::ICMP_SLE) Result = 1;
1850 break;
1851 case ICmpInst::ICMP_UGE:
1852 if (pred == ICmpInst::ICMP_ULT) Result = 0;
1853 if (pred == ICmpInst::ICMP_UGT || pred == ICmpInst::ICMP_UGE) Result = 1;
1854 break;
1855 case ICmpInst::ICMP_SGE:
1856 if (pred == ICmpInst::ICMP_SLT) Result = 0;
1857 if (pred == ICmpInst::ICMP_SGT || pred == ICmpInst::ICMP_SGE) Result = 1;
1858 break;
1859 case ICmpInst::ICMP_NE:
1860 if (pred == ICmpInst::ICMP_EQ) Result = 0;
1861 if (pred == ICmpInst::ICMP_NE) Result = 1;
1862 break;
1863 }
1864
1865 // If we evaluated the result, return it now.
1866 if (Result != -1)
1867 return ConstantInt::get(ResultTy, Result);
1868
1869 // If the right hand side is a bitcast, try using its inverse to simplify
1870 // it by moving it to the left hand side. We can't do this if it would turn
1871 // a vector compare into a scalar compare or visa versa.
1872 if (ConstantExpr *CE2 = dyn_cast<ConstantExpr>(C2)) {
1873 Constant *CE2Op0 = CE2->getOperand(0);
1874 if (CE2->getOpcode() == Instruction::BitCast &&
1875 CE2->getType()->isVectorTy() == CE2Op0->getType()->isVectorTy()) {
1876 Constant *Inverse = ConstantExpr::getBitCast(C1, CE2Op0->getType());
1877 return ConstantExpr::getICmp(pred, Inverse, CE2Op0);
1878 }
1879 }
1880
1881 // If the left hand side is an extension, try eliminating it.
1882 if (ConstantExpr *CE1 = dyn_cast<ConstantExpr>(C1)) {
1883 if ((CE1->getOpcode() == Instruction::SExt && ICmpInst::isSigned(pred)) ||
1884 (CE1->getOpcode() == Instruction::ZExt && !ICmpInst::isSigned(pred))){
1885 Constant *CE1Op0 = CE1->getOperand(0);
1886 Constant *CE1Inverse = ConstantExpr::getTrunc(CE1, CE1Op0->getType());
1887 if (CE1Inverse == CE1Op0) {
1888 // Check whether we can safely truncate the right hand side.
1889 Constant *C2Inverse = ConstantExpr::getTrunc(C2, CE1Op0->getType());
1890 if (ConstantExpr::getCast(CE1->getOpcode(), C2Inverse,
1891 C2->getType()) == C2)
1892 return ConstantExpr::getICmp(pred, CE1Inverse, C2Inverse);
1893 }
1894 }
1895 }
1896
1897 if ((!isa<ConstantExpr>(C1) && isa<ConstantExpr>(C2)) ||
1898 (C1->isNullValue() && !C2->isNullValue())) {
1899 // If C2 is a constant expr and C1 isn't, flip them around and fold the
1900 // other way if possible.
1901 // Also, if C1 is null and C2 isn't, flip them around.
1902 pred = ICmpInst::getSwappedPredicate((ICmpInst::Predicate)pred);
1903 return ConstantExpr::getICmp(pred, C2, C1);
1904 }
1905 }
1906 return nullptr;
1907 }
1908
1909 /// isInBoundsIndices - Test whether the given sequence of *normalized* indices
1910 /// is "inbounds".
1911 template<typename IndexTy>
isInBoundsIndices(ArrayRef<IndexTy> Idxs)1912 static bool isInBoundsIndices(ArrayRef<IndexTy> Idxs) {
1913 // No indices means nothing that could be out of bounds.
1914 if (Idxs.empty()) return true;
1915
1916 // If the first index is zero, it's in bounds.
1917 if (cast<Constant>(Idxs[0])->isNullValue()) return true;
1918
1919 // If the first index is one and all the rest are zero, it's in bounds,
1920 // by the one-past-the-end rule.
1921 if (!cast<ConstantInt>(Idxs[0])->isOne())
1922 return false;
1923 for (unsigned i = 1, e = Idxs.size(); i != e; ++i)
1924 if (!cast<Constant>(Idxs[i])->isNullValue())
1925 return false;
1926 return true;
1927 }
1928
1929 /// \brief Test whether a given ConstantInt is in-range for a SequentialType.
isIndexInRangeOfSequentialType(const SequentialType * STy,const ConstantInt * CI)1930 static bool isIndexInRangeOfSequentialType(const SequentialType *STy,
1931 const ConstantInt *CI) {
1932 if (const PointerType *PTy = dyn_cast<PointerType>(STy))
1933 // Only handle pointers to sized types, not pointers to functions.
1934 return PTy->getElementType()->isSized();
1935
1936 uint64_t NumElements = 0;
1937 // Determine the number of elements in our sequential type.
1938 if (const ArrayType *ATy = dyn_cast<ArrayType>(STy))
1939 NumElements = ATy->getNumElements();
1940 else if (const VectorType *VTy = dyn_cast<VectorType>(STy))
1941 NumElements = VTy->getNumElements();
1942
1943 assert((isa<ArrayType>(STy) || NumElements > 0) &&
1944 "didn't expect non-array type to have zero elements!");
1945
1946 // We cannot bounds check the index if it doesn't fit in an int64_t.
1947 if (CI->getValue().getActiveBits() > 64)
1948 return false;
1949
1950 // A negative index or an index past the end of our sequential type is
1951 // considered out-of-range.
1952 int64_t IndexVal = CI->getSExtValue();
1953 if (IndexVal < 0 || (NumElements > 0 && (uint64_t)IndexVal >= NumElements))
1954 return false;
1955
1956 // Otherwise, it is in-range.
1957 return true;
1958 }
1959
1960 template<typename IndexTy>
ConstantFoldGetElementPtrImpl(Constant * C,bool inBounds,ArrayRef<IndexTy> Idxs)1961 static Constant *ConstantFoldGetElementPtrImpl(Constant *C,
1962 bool inBounds,
1963 ArrayRef<IndexTy> Idxs) {
1964 if (Idxs.empty()) return C;
1965 Constant *Idx0 = cast<Constant>(Idxs[0]);
1966 if ((Idxs.size() == 1 && Idx0->isNullValue()))
1967 return C;
1968
1969 if (isa<UndefValue>(C)) {
1970 PointerType *Ptr = cast<PointerType>(C->getType());
1971 Type *Ty = GetElementPtrInst::getIndexedType(Ptr, Idxs);
1972 assert(Ty && "Invalid indices for GEP!");
1973 return UndefValue::get(PointerType::get(Ty, Ptr->getAddressSpace()));
1974 }
1975
1976 if (C->isNullValue()) {
1977 bool isNull = true;
1978 for (unsigned i = 0, e = Idxs.size(); i != e; ++i)
1979 if (!cast<Constant>(Idxs[i])->isNullValue()) {
1980 isNull = false;
1981 break;
1982 }
1983 if (isNull) {
1984 PointerType *Ptr = cast<PointerType>(C->getType());
1985 Type *Ty = GetElementPtrInst::getIndexedType(Ptr, Idxs);
1986 assert(Ty && "Invalid indices for GEP!");
1987 return ConstantPointerNull::get(PointerType::get(Ty,
1988 Ptr->getAddressSpace()));
1989 }
1990 }
1991
1992 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(C)) {
1993 // Combine Indices - If the source pointer to this getelementptr instruction
1994 // is a getelementptr instruction, combine the indices of the two
1995 // getelementptr instructions into a single instruction.
1996 //
1997 if (CE->getOpcode() == Instruction::GetElementPtr) {
1998 Type *LastTy = nullptr;
1999 for (gep_type_iterator I = gep_type_begin(CE), E = gep_type_end(CE);
2000 I != E; ++I)
2001 LastTy = *I;
2002
2003 // We cannot combine indices if doing so would take us outside of an
2004 // array or vector. Doing otherwise could trick us if we evaluated such a
2005 // GEP as part of a load.
2006 //
2007 // e.g. Consider if the original GEP was:
2008 // i8* getelementptr ({ [2 x i8], i32, i8, [3 x i8] }* @main.c,
2009 // i32 0, i32 0, i64 0)
2010 //
2011 // If we then tried to offset it by '8' to get to the third element,
2012 // an i8, we should *not* get:
2013 // i8* getelementptr ({ [2 x i8], i32, i8, [3 x i8] }* @main.c,
2014 // i32 0, i32 0, i64 8)
2015 //
2016 // This GEP tries to index array element '8 which runs out-of-bounds.
2017 // Subsequent evaluation would get confused and produce erroneous results.
2018 //
2019 // The following prohibits such a GEP from being formed by checking to see
2020 // if the index is in-range with respect to an array or vector.
2021 bool PerformFold = false;
2022 if (Idx0->isNullValue())
2023 PerformFold = true;
2024 else if (SequentialType *STy = dyn_cast_or_null<SequentialType>(LastTy))
2025 if (ConstantInt *CI = dyn_cast<ConstantInt>(Idx0))
2026 PerformFold = isIndexInRangeOfSequentialType(STy, CI);
2027
2028 if (PerformFold) {
2029 SmallVector<Value*, 16> NewIndices;
2030 NewIndices.reserve(Idxs.size() + CE->getNumOperands());
2031 for (unsigned i = 1, e = CE->getNumOperands()-1; i != e; ++i)
2032 NewIndices.push_back(CE->getOperand(i));
2033
2034 // Add the last index of the source with the first index of the new GEP.
2035 // Make sure to handle the case when they are actually different types.
2036 Constant *Combined = CE->getOperand(CE->getNumOperands()-1);
2037 // Otherwise it must be an array.
2038 if (!Idx0->isNullValue()) {
2039 Type *IdxTy = Combined->getType();
2040 if (IdxTy != Idx0->getType()) {
2041 Type *Int64Ty = Type::getInt64Ty(IdxTy->getContext());
2042 Constant *C1 = ConstantExpr::getSExtOrBitCast(Idx0, Int64Ty);
2043 Constant *C2 = ConstantExpr::getSExtOrBitCast(Combined, Int64Ty);
2044 Combined = ConstantExpr::get(Instruction::Add, C1, C2);
2045 } else {
2046 Combined =
2047 ConstantExpr::get(Instruction::Add, Idx0, Combined);
2048 }
2049 }
2050
2051 NewIndices.push_back(Combined);
2052 NewIndices.append(Idxs.begin() + 1, Idxs.end());
2053 return
2054 ConstantExpr::getGetElementPtr(CE->getOperand(0), NewIndices,
2055 inBounds &&
2056 cast<GEPOperator>(CE)->isInBounds());
2057 }
2058 }
2059
2060 // Attempt to fold casts to the same type away. For example, folding:
2061 //
2062 // i32* getelementptr ([2 x i32]* bitcast ([3 x i32]* %X to [2 x i32]*),
2063 // i64 0, i64 0)
2064 // into:
2065 //
2066 // i32* getelementptr ([3 x i32]* %X, i64 0, i64 0)
2067 //
2068 // Don't fold if the cast is changing address spaces.
2069 if (CE->isCast() && Idxs.size() > 1 && Idx0->isNullValue()) {
2070 PointerType *SrcPtrTy =
2071 dyn_cast<PointerType>(CE->getOperand(0)->getType());
2072 PointerType *DstPtrTy = dyn_cast<PointerType>(CE->getType());
2073 if (SrcPtrTy && DstPtrTy) {
2074 ArrayType *SrcArrayTy =
2075 dyn_cast<ArrayType>(SrcPtrTy->getElementType());
2076 ArrayType *DstArrayTy =
2077 dyn_cast<ArrayType>(DstPtrTy->getElementType());
2078 if (SrcArrayTy && DstArrayTy
2079 && SrcArrayTy->getElementType() == DstArrayTy->getElementType()
2080 && SrcPtrTy->getAddressSpace() == DstPtrTy->getAddressSpace())
2081 return ConstantExpr::getGetElementPtr((Constant*)CE->getOperand(0),
2082 Idxs, inBounds);
2083 }
2084 }
2085 }
2086
2087 // Check to see if any array indices are not within the corresponding
2088 // notional array or vector bounds. If so, try to determine if they can be
2089 // factored out into preceding dimensions.
2090 bool Unknown = false;
2091 SmallVector<Constant *, 8> NewIdxs;
2092 Type *Ty = C->getType();
2093 Type *Prev = nullptr;
2094 for (unsigned i = 0, e = Idxs.size(); i != e;
2095 Prev = Ty, Ty = cast<CompositeType>(Ty)->getTypeAtIndex(Idxs[i]), ++i) {
2096 if (ConstantInt *CI = dyn_cast<ConstantInt>(Idxs[i])) {
2097 if (isa<ArrayType>(Ty) || isa<VectorType>(Ty))
2098 if (CI->getSExtValue() > 0 &&
2099 !isIndexInRangeOfSequentialType(cast<SequentialType>(Ty), CI)) {
2100 if (isa<SequentialType>(Prev)) {
2101 // It's out of range, but we can factor it into the prior
2102 // dimension.
2103 NewIdxs.resize(Idxs.size());
2104 uint64_t NumElements = 0;
2105 if (const ArrayType *ATy = dyn_cast<ArrayType>(Ty))
2106 NumElements = ATy->getNumElements();
2107 else
2108 NumElements = cast<VectorType>(Ty)->getNumElements();
2109
2110 ConstantInt *Factor = ConstantInt::get(CI->getType(), NumElements);
2111 NewIdxs[i] = ConstantExpr::getSRem(CI, Factor);
2112
2113 Constant *PrevIdx = cast<Constant>(Idxs[i-1]);
2114 Constant *Div = ConstantExpr::getSDiv(CI, Factor);
2115
2116 // Before adding, extend both operands to i64 to avoid
2117 // overflow trouble.
2118 if (!PrevIdx->getType()->isIntegerTy(64))
2119 PrevIdx = ConstantExpr::getSExt(PrevIdx,
2120 Type::getInt64Ty(Div->getContext()));
2121 if (!Div->getType()->isIntegerTy(64))
2122 Div = ConstantExpr::getSExt(Div,
2123 Type::getInt64Ty(Div->getContext()));
2124
2125 NewIdxs[i-1] = ConstantExpr::getAdd(PrevIdx, Div);
2126 } else {
2127 // It's out of range, but the prior dimension is a struct
2128 // so we can't do anything about it.
2129 Unknown = true;
2130 }
2131 }
2132 } else {
2133 // We don't know if it's in range or not.
2134 Unknown = true;
2135 }
2136 }
2137
2138 // If we did any factoring, start over with the adjusted indices.
2139 if (!NewIdxs.empty()) {
2140 for (unsigned i = 0, e = Idxs.size(); i != e; ++i)
2141 if (!NewIdxs[i]) NewIdxs[i] = cast<Constant>(Idxs[i]);
2142 return ConstantExpr::getGetElementPtr(C, NewIdxs, inBounds);
2143 }
2144
2145 // If all indices are known integers and normalized, we can do a simple
2146 // check for the "inbounds" property.
2147 if (!Unknown && !inBounds &&
2148 isa<GlobalVariable>(C) && isInBoundsIndices(Idxs))
2149 return ConstantExpr::getInBoundsGetElementPtr(C, Idxs);
2150
2151 return nullptr;
2152 }
2153
ConstantFoldGetElementPtr(Constant * C,bool inBounds,ArrayRef<Constant * > Idxs)2154 Constant *llvm::ConstantFoldGetElementPtr(Constant *C,
2155 bool inBounds,
2156 ArrayRef<Constant *> Idxs) {
2157 return ConstantFoldGetElementPtrImpl(C, inBounds, Idxs);
2158 }
2159
ConstantFoldGetElementPtr(Constant * C,bool inBounds,ArrayRef<Value * > Idxs)2160 Constant *llvm::ConstantFoldGetElementPtr(Constant *C,
2161 bool inBounds,
2162 ArrayRef<Value *> Idxs) {
2163 return ConstantFoldGetElementPtrImpl(C, inBounds, Idxs);
2164 }
2165