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