1 //===- ConstantFolding.cpp - LLVM constant folder -------------------------===//
3 // The LLVM Compiler Infrastructure
5 // This file was developed by the LLVM research group and is distributed under
6 // the University of Illinois Open Source License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file implements folding of constants for LLVM. This implements the
11 // (internal) ConstantFolding.h interface, which is used by the
12 // ConstantExpr::get* methods to automatically fold constants when possible.
14 // The current constant folding implementation is implemented in two pieces: the
15 // template-based folder for simple primitive constants like ConstantInt, and
16 // the special case hackery that we use to symbolically evaluate expressions
17 // that use ConstantExprs.
19 //===----------------------------------------------------------------------===//
21 #include "ConstantFolding.h"
22 #include "llvm/Constants.h"
23 #include "llvm/Instructions.h"
24 #include "llvm/DerivedTypes.h"
25 #include "llvm/Function.h"
26 #include "llvm/Support/GetElementPtrTypeIterator.h"
34 virtual ~ConstRules() {}
36 // Binary Operators...
37 virtual Constant *add(const Constant *V1, const Constant *V2) const = 0;
38 virtual Constant *sub(const Constant *V1, const Constant *V2) const = 0;
39 virtual Constant *mul(const Constant *V1, const Constant *V2) const = 0;
40 virtual Constant *div(const Constant *V1, const Constant *V2) const = 0;
41 virtual Constant *rem(const Constant *V1, const Constant *V2) const = 0;
42 virtual Constant *op_and(const Constant *V1, const Constant *V2) const = 0;
43 virtual Constant *op_or (const Constant *V1, const Constant *V2) const = 0;
44 virtual Constant *op_xor(const Constant *V1, const Constant *V2) const = 0;
45 virtual Constant *shl(const Constant *V1, const Constant *V2) const = 0;
46 virtual Constant *shr(const Constant *V1, const Constant *V2) const = 0;
47 virtual Constant *lessthan(const Constant *V1, const Constant *V2) const =0;
48 virtual Constant *equalto(const Constant *V1, const Constant *V2) const = 0;
51 virtual Constant *castToBool (const Constant *V) const = 0;
52 virtual Constant *castToSByte (const Constant *V) const = 0;
53 virtual Constant *castToUByte (const Constant *V) const = 0;
54 virtual Constant *castToShort (const Constant *V) const = 0;
55 virtual Constant *castToUShort(const Constant *V) const = 0;
56 virtual Constant *castToInt (const Constant *V) const = 0;
57 virtual Constant *castToUInt (const Constant *V) const = 0;
58 virtual Constant *castToLong (const Constant *V) const = 0;
59 virtual Constant *castToULong (const Constant *V) const = 0;
60 virtual Constant *castToFloat (const Constant *V) const = 0;
61 virtual Constant *castToDouble(const Constant *V) const = 0;
62 virtual Constant *castToPointer(const Constant *V,
63 const PointerType *Ty) const = 0;
65 // ConstRules::get - Return an instance of ConstRules for the specified
68 static ConstRules &get(const Constant *V1, const Constant *V2);
70 ConstRules(const ConstRules &); // Do not implement
71 ConstRules &operator=(const ConstRules &); // Do not implement
76 //===----------------------------------------------------------------------===//
77 // TemplateRules Class
78 //===----------------------------------------------------------------------===//
80 // TemplateRules - Implement a subclass of ConstRules that provides all
81 // operations as noops. All other rules classes inherit from this class so
82 // that if functionality is needed in the future, it can simply be added here
83 // and to ConstRules without changing anything else...
85 // This class also provides subclasses with typesafe implementations of methods
86 // so that don't have to do type casting.
88 template<class ArgType, class SubClassName>
89 class TemplateRules : public ConstRules {
92 //===--------------------------------------------------------------------===//
93 // Redirecting functions that cast to the appropriate types
94 //===--------------------------------------------------------------------===//
96 virtual Constant *add(const Constant *V1, const Constant *V2) const {
97 return SubClassName::Add((const ArgType *)V1, (const ArgType *)V2);
99 virtual Constant *sub(const Constant *V1, const Constant *V2) const {
100 return SubClassName::Sub((const ArgType *)V1, (const ArgType *)V2);
102 virtual Constant *mul(const Constant *V1, const Constant *V2) const {
103 return SubClassName::Mul((const ArgType *)V1, (const ArgType *)V2);
105 virtual Constant *div(const Constant *V1, const Constant *V2) const {
106 return SubClassName::Div((const ArgType *)V1, (const ArgType *)V2);
108 virtual Constant *rem(const Constant *V1, const Constant *V2) const {
109 return SubClassName::Rem((const ArgType *)V1, (const ArgType *)V2);
111 virtual Constant *op_and(const Constant *V1, const Constant *V2) const {
112 return SubClassName::And((const ArgType *)V1, (const ArgType *)V2);
114 virtual Constant *op_or(const Constant *V1, const Constant *V2) const {
115 return SubClassName::Or((const ArgType *)V1, (const ArgType *)V2);
117 virtual Constant *op_xor(const Constant *V1, const Constant *V2) const {
118 return SubClassName::Xor((const ArgType *)V1, (const ArgType *)V2);
120 virtual Constant *shl(const Constant *V1, const Constant *V2) const {
121 return SubClassName::Shl((const ArgType *)V1, (const ArgType *)V2);
123 virtual Constant *shr(const Constant *V1, const Constant *V2) const {
124 return SubClassName::Shr((const ArgType *)V1, (const ArgType *)V2);
127 virtual Constant *lessthan(const Constant *V1, const Constant *V2) const {
128 return SubClassName::LessThan((const ArgType *)V1, (const ArgType *)V2);
130 virtual Constant *equalto(const Constant *V1, const Constant *V2) const {
131 return SubClassName::EqualTo((const ArgType *)V1, (const ArgType *)V2);
134 // Casting operators. ick
135 virtual Constant *castToBool(const Constant *V) const {
136 return SubClassName::CastToBool((const ArgType*)V);
138 virtual Constant *castToSByte(const Constant *V) const {
139 return SubClassName::CastToSByte((const ArgType*)V);
141 virtual Constant *castToUByte(const Constant *V) const {
142 return SubClassName::CastToUByte((const ArgType*)V);
144 virtual Constant *castToShort(const Constant *V) const {
145 return SubClassName::CastToShort((const ArgType*)V);
147 virtual Constant *castToUShort(const Constant *V) const {
148 return SubClassName::CastToUShort((const ArgType*)V);
150 virtual Constant *castToInt(const Constant *V) const {
151 return SubClassName::CastToInt((const ArgType*)V);
153 virtual Constant *castToUInt(const Constant *V) const {
154 return SubClassName::CastToUInt((const ArgType*)V);
156 virtual Constant *castToLong(const Constant *V) const {
157 return SubClassName::CastToLong((const ArgType*)V);
159 virtual Constant *castToULong(const Constant *V) const {
160 return SubClassName::CastToULong((const ArgType*)V);
162 virtual Constant *castToFloat(const Constant *V) const {
163 return SubClassName::CastToFloat((const ArgType*)V);
165 virtual Constant *castToDouble(const Constant *V) const {
166 return SubClassName::CastToDouble((const ArgType*)V);
168 virtual Constant *castToPointer(const Constant *V,
169 const PointerType *Ty) const {
170 return SubClassName::CastToPointer((const ArgType*)V, Ty);
173 //===--------------------------------------------------------------------===//
174 // Default "noop" implementations
175 //===--------------------------------------------------------------------===//
177 static Constant *Add(const ArgType *V1, const ArgType *V2) { return 0; }
178 static Constant *Sub(const ArgType *V1, const ArgType *V2) { return 0; }
179 static Constant *Mul(const ArgType *V1, const ArgType *V2) { return 0; }
180 static Constant *Div(const ArgType *V1, const ArgType *V2) { return 0; }
181 static Constant *Rem(const ArgType *V1, const ArgType *V2) { return 0; }
182 static Constant *And(const ArgType *V1, const ArgType *V2) { return 0; }
183 static Constant *Or (const ArgType *V1, const ArgType *V2) { return 0; }
184 static Constant *Xor(const ArgType *V1, const ArgType *V2) { return 0; }
185 static Constant *Shl(const ArgType *V1, const ArgType *V2) { return 0; }
186 static Constant *Shr(const ArgType *V1, const ArgType *V2) { return 0; }
187 static Constant *LessThan(const ArgType *V1, const ArgType *V2) {
190 static Constant *EqualTo(const ArgType *V1, const ArgType *V2) {
194 // Casting operators. ick
195 static Constant *CastToBool (const Constant *V) { return 0; }
196 static Constant *CastToSByte (const Constant *V) { return 0; }
197 static Constant *CastToUByte (const Constant *V) { return 0; }
198 static Constant *CastToShort (const Constant *V) { return 0; }
199 static Constant *CastToUShort(const Constant *V) { return 0; }
200 static Constant *CastToInt (const Constant *V) { return 0; }
201 static Constant *CastToUInt (const Constant *V) { return 0; }
202 static Constant *CastToLong (const Constant *V) { return 0; }
203 static Constant *CastToULong (const Constant *V) { return 0; }
204 static Constant *CastToFloat (const Constant *V) { return 0; }
205 static Constant *CastToDouble(const Constant *V) { return 0; }
206 static Constant *CastToPointer(const Constant *,
207 const PointerType *) {return 0;}
210 virtual ~TemplateRules() {}
215 //===----------------------------------------------------------------------===//
217 //===----------------------------------------------------------------------===//
219 // EmptyRules provides a concrete base class of ConstRules that does nothing
221 struct EmptyRules : public TemplateRules<Constant, EmptyRules> {
222 static Constant *EqualTo(const Constant *V1, const Constant *V2) {
223 if (V1 == V2) return ConstantBool::True;
230 //===----------------------------------------------------------------------===//
232 //===----------------------------------------------------------------------===//
234 // BoolRules provides a concrete base class of ConstRules for the 'bool' type.
236 struct BoolRules : public TemplateRules<ConstantBool, BoolRules> {
238 static Constant *LessThan(const ConstantBool *V1, const ConstantBool *V2) {
239 return ConstantBool::get(V1->getValue() < V2->getValue());
242 static Constant *EqualTo(const Constant *V1, const Constant *V2) {
243 return ConstantBool::get(V1 == V2);
246 static Constant *And(const ConstantBool *V1, const ConstantBool *V2) {
247 return ConstantBool::get(V1->getValue() & V2->getValue());
250 static Constant *Or(const ConstantBool *V1, const ConstantBool *V2) {
251 return ConstantBool::get(V1->getValue() | V2->getValue());
254 static Constant *Xor(const ConstantBool *V1, const ConstantBool *V2) {
255 return ConstantBool::get(V1->getValue() ^ V2->getValue());
258 // Casting operators. ick
259 #define DEF_CAST(TYPE, CLASS, CTYPE) \
260 static Constant *CastTo##TYPE (const ConstantBool *V) { \
261 return CLASS::get(Type::TYPE##Ty, (CTYPE)(bool)V->getValue()); \
264 DEF_CAST(Bool , ConstantBool, bool)
265 DEF_CAST(SByte , ConstantSInt, signed char)
266 DEF_CAST(UByte , ConstantUInt, unsigned char)
267 DEF_CAST(Short , ConstantSInt, signed short)
268 DEF_CAST(UShort, ConstantUInt, unsigned short)
269 DEF_CAST(Int , ConstantSInt, signed int)
270 DEF_CAST(UInt , ConstantUInt, unsigned int)
271 DEF_CAST(Long , ConstantSInt, int64_t)
272 DEF_CAST(ULong , ConstantUInt, uint64_t)
273 DEF_CAST(Float , ConstantFP , float)
274 DEF_CAST(Double, ConstantFP , double)
279 //===----------------------------------------------------------------------===//
280 // NullPointerRules Class
281 //===----------------------------------------------------------------------===//
283 // NullPointerRules provides a concrete base class of ConstRules for null
286 struct NullPointerRules : public TemplateRules<ConstantPointerNull,
288 static Constant *EqualTo(const Constant *V1, const Constant *V2) {
289 return ConstantBool::True; // Null pointers are always equal
291 static Constant *CastToBool(const Constant *V) {
292 return ConstantBool::False;
294 static Constant *CastToSByte (const Constant *V) {
295 return ConstantSInt::get(Type::SByteTy, 0);
297 static Constant *CastToUByte (const Constant *V) {
298 return ConstantUInt::get(Type::UByteTy, 0);
300 static Constant *CastToShort (const Constant *V) {
301 return ConstantSInt::get(Type::ShortTy, 0);
303 static Constant *CastToUShort(const Constant *V) {
304 return ConstantUInt::get(Type::UShortTy, 0);
306 static Constant *CastToInt (const Constant *V) {
307 return ConstantSInt::get(Type::IntTy, 0);
309 static Constant *CastToUInt (const Constant *V) {
310 return ConstantUInt::get(Type::UIntTy, 0);
312 static Constant *CastToLong (const Constant *V) {
313 return ConstantSInt::get(Type::LongTy, 0);
315 static Constant *CastToULong (const Constant *V) {
316 return ConstantUInt::get(Type::ULongTy, 0);
318 static Constant *CastToFloat (const Constant *V) {
319 return ConstantFP::get(Type::FloatTy, 0);
321 static Constant *CastToDouble(const Constant *V) {
322 return ConstantFP::get(Type::DoubleTy, 0);
325 static Constant *CastToPointer(const ConstantPointerNull *V,
326 const PointerType *PTy) {
327 return ConstantPointerNull::get(PTy);
331 //===----------------------------------------------------------------------===//
332 // ConstantPackedRules Class
333 //===----------------------------------------------------------------------===//
335 /// DoVectorOp - Given two packed constants and a function pointer, apply the
336 /// function pointer to each element pair, producing a new ConstantPacked
338 static Constant *EvalVectorOp(const ConstantPacked *V1,
339 const ConstantPacked *V2,
340 Constant *(*FP)(Constant*, Constant*)) {
341 std::vector<Constant*> Res;
342 for (unsigned i = 0, e = V1->getNumOperands(); i != e; ++i)
343 Res.push_back(FP(const_cast<Constant*>(V1->getOperand(i)),
344 const_cast<Constant*>(V2->getOperand(i))));
345 return ConstantPacked::get(Res);
348 /// PackedTypeRules provides a concrete base class of ConstRules for
349 /// ConstantPacked operands.
351 struct ConstantPackedRules
352 : public TemplateRules<ConstantPacked, ConstantPackedRules> {
354 static Constant *Add(const ConstantPacked *V1, const ConstantPacked *V2) {
355 return EvalVectorOp(V1, V2, ConstantExpr::getAdd);
357 static Constant *Sub(const ConstantPacked *V1, const ConstantPacked *V2) {
358 return EvalVectorOp(V1, V2, ConstantExpr::getSub);
360 static Constant *Mul(const ConstantPacked *V1, const ConstantPacked *V2) {
361 return EvalVectorOp(V1, V2, ConstantExpr::getMul);
363 static Constant *Div(const ConstantPacked *V1, const ConstantPacked *V2) {
364 return EvalVectorOp(V1, V2, ConstantExpr::getDiv);
366 static Constant *Rem(const ConstantPacked *V1, const ConstantPacked *V2) {
367 return EvalVectorOp(V1, V2, ConstantExpr::getRem);
369 static Constant *And(const ConstantPacked *V1, const ConstantPacked *V2) {
370 return EvalVectorOp(V1, V2, ConstantExpr::getAnd);
372 static Constant *Or (const ConstantPacked *V1, const ConstantPacked *V2) {
373 return EvalVectorOp(V1, V2, ConstantExpr::getOr);
375 static Constant *Xor(const ConstantPacked *V1, const ConstantPacked *V2) {
376 return EvalVectorOp(V1, V2, ConstantExpr::getXor);
378 static Constant *Shl(const ConstantPacked *V1, const ConstantPacked *V2) {
379 return EvalVectorOp(V1, V2, ConstantExpr::getShl);
381 static Constant *Shr(const ConstantPacked *V1, const ConstantPacked *V2) {
382 return EvalVectorOp(V1, V2, ConstantExpr::getShr);
384 static Constant *LessThan(const ConstantPacked *V1, const ConstantPacked *V2){
387 static Constant *EqualTo(const ConstantPacked *V1, const ConstantPacked *V2) {
388 for (unsigned i = 0, e = V1->getNumOperands(); i != e; ++i) {
390 ConstantExpr::getSetEQ(const_cast<Constant*>(V1->getOperand(i)),
391 const_cast<Constant*>(V2->getOperand(i)));
392 if (ConstantBool *CB = dyn_cast<ConstantBool>(C))
395 // Otherwise, could not decide from any element pairs.
401 //===----------------------------------------------------------------------===//
402 // GeneralPackedRules Class
403 //===----------------------------------------------------------------------===//
405 /// GeneralPackedRules provides a concrete base class of ConstRules for
406 /// PackedType operands, where both operands are not ConstantPacked. The usual
407 /// cause for this is that one operand is a ConstantAggregateZero.
409 struct GeneralPackedRules : public TemplateRules<Constant, GeneralPackedRules> {
413 //===----------------------------------------------------------------------===//
415 //===----------------------------------------------------------------------===//
417 // DirectRules provides a concrete base classes of ConstRules for a variety of
418 // different types. This allows the C++ compiler to automatically generate our
419 // constant handling operations in a typesafe and accurate manner.
421 template<class ConstantClass, class BuiltinType, Type **Ty, class SuperClass>
422 struct DirectRules : public TemplateRules<ConstantClass, SuperClass> {
423 static Constant *Add(const ConstantClass *V1, const ConstantClass *V2) {
424 BuiltinType R = (BuiltinType)V1->getValue() + (BuiltinType)V2->getValue();
425 return ConstantClass::get(*Ty, R);
428 static Constant *Sub(const ConstantClass *V1, const ConstantClass *V2) {
429 BuiltinType R = (BuiltinType)V1->getValue() - (BuiltinType)V2->getValue();
430 return ConstantClass::get(*Ty, R);
433 static Constant *Mul(const ConstantClass *V1, const ConstantClass *V2) {
434 BuiltinType R = (BuiltinType)V1->getValue() * (BuiltinType)V2->getValue();
435 return ConstantClass::get(*Ty, R);
438 static Constant *Div(const ConstantClass *V1, const ConstantClass *V2) {
439 if (V2->isNullValue()) return 0;
440 BuiltinType R = (BuiltinType)V1->getValue() / (BuiltinType)V2->getValue();
441 return ConstantClass::get(*Ty, R);
444 static Constant *LessThan(const ConstantClass *V1, const ConstantClass *V2) {
445 bool R = (BuiltinType)V1->getValue() < (BuiltinType)V2->getValue();
446 return ConstantBool::get(R);
449 static Constant *EqualTo(const ConstantClass *V1, const ConstantClass *V2) {
450 bool R = (BuiltinType)V1->getValue() == (BuiltinType)V2->getValue();
451 return ConstantBool::get(R);
454 static Constant *CastToPointer(const ConstantClass *V,
455 const PointerType *PTy) {
456 if (V->isNullValue()) // Is it a FP or Integral null value?
457 return ConstantPointerNull::get(PTy);
458 return 0; // Can't const prop other types of pointers
461 // Casting operators. ick
462 #define DEF_CAST(TYPE, CLASS, CTYPE) \
463 static Constant *CastTo##TYPE (const ConstantClass *V) { \
464 return CLASS::get(Type::TYPE##Ty, (CTYPE)(BuiltinType)V->getValue()); \
467 DEF_CAST(Bool , ConstantBool, bool)
468 DEF_CAST(SByte , ConstantSInt, signed char)
469 DEF_CAST(UByte , ConstantUInt, unsigned char)
470 DEF_CAST(Short , ConstantSInt, signed short)
471 DEF_CAST(UShort, ConstantUInt, unsigned short)
472 DEF_CAST(Int , ConstantSInt, signed int)
473 DEF_CAST(UInt , ConstantUInt, unsigned int)
474 DEF_CAST(Long , ConstantSInt, int64_t)
475 DEF_CAST(ULong , ConstantUInt, uint64_t)
476 DEF_CAST(Float , ConstantFP , float)
477 DEF_CAST(Double, ConstantFP , double)
482 //===----------------------------------------------------------------------===//
483 // DirectIntRules Class
484 //===----------------------------------------------------------------------===//
486 // DirectIntRules provides implementations of functions that are valid on
487 // integer types, but not all types in general.
489 template <class ConstantClass, class BuiltinType, Type **Ty>
490 struct DirectIntRules
491 : public DirectRules<ConstantClass, BuiltinType, Ty,
492 DirectIntRules<ConstantClass, BuiltinType, Ty> > {
494 static Constant *Div(const ConstantClass *V1, const ConstantClass *V2) {
495 if (V2->isNullValue()) return 0;
496 if (V2->isAllOnesValue() && // MIN_INT / -1
497 (BuiltinType)V1->getValue() == -(BuiltinType)V1->getValue())
499 BuiltinType R = (BuiltinType)V1->getValue() / (BuiltinType)V2->getValue();
500 return ConstantClass::get(*Ty, R);
503 static Constant *Rem(const ConstantClass *V1,
504 const ConstantClass *V2) {
505 if (V2->isNullValue()) return 0; // X / 0
506 if (V2->isAllOnesValue() && // MIN_INT / -1
507 (BuiltinType)V1->getValue() == -(BuiltinType)V1->getValue())
509 BuiltinType R = (BuiltinType)V1->getValue() % (BuiltinType)V2->getValue();
510 return ConstantClass::get(*Ty, R);
513 static Constant *And(const ConstantClass *V1, const ConstantClass *V2) {
514 BuiltinType R = (BuiltinType)V1->getValue() & (BuiltinType)V2->getValue();
515 return ConstantClass::get(*Ty, R);
517 static Constant *Or(const ConstantClass *V1, const ConstantClass *V2) {
518 BuiltinType R = (BuiltinType)V1->getValue() | (BuiltinType)V2->getValue();
519 return ConstantClass::get(*Ty, R);
521 static Constant *Xor(const ConstantClass *V1, const ConstantClass *V2) {
522 BuiltinType R = (BuiltinType)V1->getValue() ^ (BuiltinType)V2->getValue();
523 return ConstantClass::get(*Ty, R);
526 static Constant *Shl(const ConstantClass *V1, const ConstantClass *V2) {
527 BuiltinType R = (BuiltinType)V1->getValue() << (BuiltinType)V2->getValue();
528 return ConstantClass::get(*Ty, R);
531 static Constant *Shr(const ConstantClass *V1, const ConstantClass *V2) {
532 BuiltinType R = (BuiltinType)V1->getValue() >> (BuiltinType)V2->getValue();
533 return ConstantClass::get(*Ty, R);
538 //===----------------------------------------------------------------------===//
539 // DirectFPRules Class
540 //===----------------------------------------------------------------------===//
542 /// DirectFPRules provides implementations of functions that are valid on
543 /// floating point types, but not all types in general.
545 template <class ConstantClass, class BuiltinType, Type **Ty>
547 : public DirectRules<ConstantClass, BuiltinType, Ty,
548 DirectFPRules<ConstantClass, BuiltinType, Ty> > {
549 static Constant *Rem(const ConstantClass *V1, const ConstantClass *V2) {
550 if (V2->isNullValue()) return 0;
551 BuiltinType Result = std::fmod((BuiltinType)V1->getValue(),
552 (BuiltinType)V2->getValue());
553 return ConstantClass::get(*Ty, Result);
555 static Constant *Div(const ConstantClass *V1, const ConstantClass *V2) {
556 BuiltinType inf = std::numeric_limits<BuiltinType>::infinity();
557 if (V2->isExactlyValue(0.0)) return ConstantClass::get(*Ty, inf);
558 if (V2->isExactlyValue(-0.0)) return ConstantClass::get(*Ty, -inf);
559 BuiltinType R = (BuiltinType)V1->getValue() / (BuiltinType)V2->getValue();
560 return ConstantClass::get(*Ty, R);
565 /// ConstRules::get - This method returns the constant rules implementation that
566 /// implements the semantics of the two specified constants.
567 ConstRules &ConstRules::get(const Constant *V1, const Constant *V2) {
568 static EmptyRules EmptyR;
569 static BoolRules BoolR;
570 static NullPointerRules NullPointerR;
571 static ConstantPackedRules ConstantPackedR;
572 static GeneralPackedRules GeneralPackedR;
573 static DirectIntRules<ConstantSInt, signed char , &Type::SByteTy> SByteR;
574 static DirectIntRules<ConstantUInt, unsigned char , &Type::UByteTy> UByteR;
575 static DirectIntRules<ConstantSInt, signed short, &Type::ShortTy> ShortR;
576 static DirectIntRules<ConstantUInt, unsigned short, &Type::UShortTy> UShortR;
577 static DirectIntRules<ConstantSInt, signed int , &Type::IntTy> IntR;
578 static DirectIntRules<ConstantUInt, unsigned int , &Type::UIntTy> UIntR;
579 static DirectIntRules<ConstantSInt, int64_t , &Type::LongTy> LongR;
580 static DirectIntRules<ConstantUInt, uint64_t , &Type::ULongTy> ULongR;
581 static DirectFPRules <ConstantFP , float , &Type::FloatTy> FloatR;
582 static DirectFPRules <ConstantFP , double , &Type::DoubleTy> DoubleR;
584 if (isa<ConstantExpr>(V1) || isa<ConstantExpr>(V2) ||
585 isa<GlobalValue>(V1) || isa<GlobalValue>(V2) ||
586 isa<UndefValue>(V1) || isa<UndefValue>(V2))
589 switch (V1->getType()->getTypeID()) {
590 default: assert(0 && "Unknown value type for constant folding!");
591 case Type::BoolTyID: return BoolR;
592 case Type::PointerTyID: return NullPointerR;
593 case Type::SByteTyID: return SByteR;
594 case Type::UByteTyID: return UByteR;
595 case Type::ShortTyID: return ShortR;
596 case Type::UShortTyID: return UShortR;
597 case Type::IntTyID: return IntR;
598 case Type::UIntTyID: return UIntR;
599 case Type::LongTyID: return LongR;
600 case Type::ULongTyID: return ULongR;
601 case Type::FloatTyID: return FloatR;
602 case Type::DoubleTyID: return DoubleR;
603 case Type::PackedTyID:
604 if (isa<ConstantPacked>(V1) && isa<ConstantPacked>(V2))
605 return ConstantPackedR;
606 return GeneralPackedR; // Constant folding rules for ConstantAggregateZero.
611 //===----------------------------------------------------------------------===//
612 // ConstantFold*Instruction Implementations
613 //===----------------------------------------------------------------------===//
615 // These methods contain the special case hackery required to symbolically
616 // evaluate some constant expression cases, and use the ConstantRules class to
617 // evaluate normal constants.
619 static unsigned getSize(const Type *Ty) {
620 unsigned S = Ty->getPrimitiveSize();
621 return S ? S : 8; // Treat pointers at 8 bytes
624 Constant *llvm::ConstantFoldCastInstruction(const Constant *V,
625 const Type *DestTy) {
626 if (V->getType() == DestTy) return (Constant*)V;
628 // Cast of a global address to boolean is always true.
629 if (const GlobalValue *GV = dyn_cast<GlobalValue>(V)) {
630 if (DestTy == Type::BoolTy)
631 // FIXME: When we support 'external weak' references, we have to prevent
632 // this transformation from happening. This code will need to be updated
633 // to ignore external weak symbols when we support it.
634 return ConstantBool::True;
635 } else if (const ConstantExpr *CE = dyn_cast<ConstantExpr>(V)) {
636 if (CE->getOpcode() == Instruction::Cast) {
637 Constant *Op = const_cast<Constant*>(CE->getOperand(0));
638 // Try to not produce a cast of a cast, which is almost always redundant.
639 if (!Op->getType()->isFloatingPoint() &&
640 !CE->getType()->isFloatingPoint() &&
641 !DestTy->isFloatingPoint()) {
642 unsigned S1 = getSize(Op->getType()), S2 = getSize(CE->getType());
643 unsigned S3 = getSize(DestTy);
644 if (Op->getType() == DestTy && S3 >= S2)
646 if (S1 >= S2 && S2 >= S3)
647 return ConstantExpr::getCast(Op, DestTy);
648 if (S1 <= S2 && S2 >= S3 && S1 <= S3)
649 return ConstantExpr::getCast(Op, DestTy);
651 } else if (CE->getOpcode() == Instruction::GetElementPtr) {
652 // If all of the indexes in the GEP are null values, there is no pointer
653 // adjustment going on. We might as well cast the source pointer.
654 bool isAllNull = true;
655 for (unsigned i = 1, e = CE->getNumOperands(); i != e; ++i)
656 if (!CE->getOperand(i)->isNullValue()) {
661 return ConstantExpr::getCast(CE->getOperand(0), DestTy);
663 } else if (isa<UndefValue>(V)) {
664 return UndefValue::get(DestTy);
667 // Check to see if we are casting an pointer to an aggregate to a pointer to
668 // the first element. If so, return the appropriate GEP instruction.
669 if (const PointerType *PTy = dyn_cast<PointerType>(V->getType()))
670 if (const PointerType *DPTy = dyn_cast<PointerType>(DestTy)) {
671 std::vector<Value*> IdxList;
672 IdxList.push_back(Constant::getNullValue(Type::IntTy));
673 const Type *ElTy = PTy->getElementType();
674 while (ElTy != DPTy->getElementType()) {
675 if (const StructType *STy = dyn_cast<StructType>(ElTy)) {
676 if (STy->getNumElements() == 0) break;
677 ElTy = STy->getElementType(0);
678 IdxList.push_back(Constant::getNullValue(Type::UIntTy));
679 } else if (const SequentialType *STy = dyn_cast<SequentialType>(ElTy)) {
680 if (isa<PointerType>(ElTy)) break; // Can't index into pointers!
681 ElTy = STy->getElementType();
682 IdxList.push_back(IdxList[0]);
688 if (ElTy == DPTy->getElementType())
689 return ConstantExpr::getGetElementPtr(const_cast<Constant*>(V),IdxList);
692 ConstRules &Rules = ConstRules::get(V, V);
694 switch (DestTy->getTypeID()) {
695 case Type::BoolTyID: return Rules.castToBool(V);
696 case Type::UByteTyID: return Rules.castToUByte(V);
697 case Type::SByteTyID: return Rules.castToSByte(V);
698 case Type::UShortTyID: return Rules.castToUShort(V);
699 case Type::ShortTyID: return Rules.castToShort(V);
700 case Type::UIntTyID: return Rules.castToUInt(V);
701 case Type::IntTyID: return Rules.castToInt(V);
702 case Type::ULongTyID: return Rules.castToULong(V);
703 case Type::LongTyID: return Rules.castToLong(V);
704 case Type::FloatTyID: return Rules.castToFloat(V);
705 case Type::DoubleTyID: return Rules.castToDouble(V);
706 case Type::PointerTyID:
707 return Rules.castToPointer(V, cast<PointerType>(DestTy));
712 Constant *llvm::ConstantFoldSelectInstruction(const Constant *Cond,
714 const Constant *V2) {
715 if (Cond == ConstantBool::True)
716 return const_cast<Constant*>(V1);
717 else if (Cond == ConstantBool::False)
718 return const_cast<Constant*>(V2);
720 if (isa<UndefValue>(V1)) return const_cast<Constant*>(V2);
721 if (isa<UndefValue>(V2)) return const_cast<Constant*>(V1);
722 if (isa<UndefValue>(Cond)) return const_cast<Constant*>(V1);
723 if (V1 == V2) return const_cast<Constant*>(V1);
727 Constant *llvm::ConstantFoldExtractElementInstruction(const Constant *Val,
728 const Constant *Idx) {
729 if (const ConstantPacked *CVal = dyn_cast<ConstantPacked>(Val)) {
730 if (const ConstantUInt *CIdx = dyn_cast<ConstantUInt>(Idx)) {
731 return const_cast<Constant*>(CVal->getOperand(CIdx->getValue()));
737 Constant *llvm::ConstantFoldInsertElementInstruction(const Constant *Val,
739 const Constant *Idx) {
740 const ConstantUInt *CIdx = dyn_cast<ConstantUInt>(Idx);
742 unsigned idxVal = CIdx->getValue();
743 if (const UndefValue *UVal = dyn_cast<UndefValue>(Val)) {
744 // Insertion of scalar constant into packed undef
745 // Optimize away insertion of undef
746 if (isa<UndefValue>(Elt))
747 return const_cast<Constant*>(Val);
748 // Otherwise break the aggregate undef into multiple undefs and do
751 cast<PackedType>(Val->getType())->getNumElements();
752 std::vector<Constant*> Ops;
754 for (unsigned i = 0; i < numOps; ++i) {
756 (i == idxVal) ? Elt : UndefValue::get(Elt->getType());
757 Ops.push_back(const_cast<Constant*>(Op));
759 return ConstantPacked::get(Ops);
761 if (const ConstantAggregateZero *CVal =
762 dyn_cast<ConstantAggregateZero>(Val)) {
763 // Insertion of scalar constant into packed aggregate zero
764 // Optimize away insertion of zero
765 if (Elt->isNullValue())
766 return const_cast<Constant*>(Val);
767 // Otherwise break the aggregate zero into multiple zeros and do
770 cast<PackedType>(Val->getType())->getNumElements();
771 std::vector<Constant*> Ops;
773 for (unsigned i = 0; i < numOps; ++i) {
775 (i == idxVal) ? Elt : Constant::getNullValue(Elt->getType());
776 Ops.push_back(const_cast<Constant*>(Op));
778 return ConstantPacked::get(Ops);
780 if (const ConstantPacked *CVal = dyn_cast<ConstantPacked>(Val)) {
781 // Insertion of scalar constant into packed constant
782 std::vector<Constant*> Ops;
783 Ops.reserve(CVal->getNumOperands());
784 for (unsigned i = 0; i < CVal->getNumOperands(); ++i) {
786 (i == idxVal) ? Elt : cast<Constant>(CVal->getOperand(i));
787 Ops.push_back(const_cast<Constant*>(Op));
789 return ConstantPacked::get(Ops);
794 /// isZeroSizedType - This type is zero sized if its an array or structure of
795 /// zero sized types. The only leaf zero sized type is an empty structure.
796 static bool isMaybeZeroSizedType(const Type *Ty) {
797 if (isa<OpaqueType>(Ty)) return true; // Can't say.
798 if (const StructType *STy = dyn_cast<StructType>(Ty)) {
800 // If all of elements have zero size, this does too.
801 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i)
802 if (!isMaybeZeroSizedType(STy->getElementType(i))) return false;
805 } else if (const ArrayType *ATy = dyn_cast<ArrayType>(Ty)) {
806 return isMaybeZeroSizedType(ATy->getElementType());
811 /// IdxCompare - Compare the two constants as though they were getelementptr
812 /// indices. This allows coersion of the types to be the same thing.
814 /// If the two constants are the "same" (after coersion), return 0. If the
815 /// first is less than the second, return -1, if the second is less than the
816 /// first, return 1. If the constants are not integral, return -2.
818 static int IdxCompare(Constant *C1, Constant *C2, const Type *ElTy) {
819 if (C1 == C2) return 0;
821 // Ok, we found a different index. Are either of the operands
822 // ConstantExprs? If so, we can't do anything with them.
823 if (!isa<ConstantInt>(C1) || !isa<ConstantInt>(C2))
824 return -2; // don't know!
826 // Ok, we have two differing integer indices. Sign extend them to be the same
827 // type. Long is always big enough, so we use it.
828 C1 = ConstantExpr::getSignExtend(C1, Type::LongTy);
829 C2 = ConstantExpr::getSignExtend(C2, Type::LongTy);
830 if (C1 == C2) return 0; // Are they just differing types?
832 // If the type being indexed over is really just a zero sized type, there is
833 // no pointer difference being made here.
834 if (isMaybeZeroSizedType(ElTy))
837 // If they are really different, now that they are the same type, then we
838 // found a difference!
839 if (cast<ConstantSInt>(C1)->getValue() < cast<ConstantSInt>(C2)->getValue())
845 /// evaluateRelation - This function determines if there is anything we can
846 /// decide about the two constants provided. This doesn't need to handle simple
847 /// things like integer comparisons, but should instead handle ConstantExprs
848 /// and GlobalValuess. If we can determine that the two constants have a
849 /// particular relation to each other, we should return the corresponding SetCC
850 /// code, otherwise return Instruction::BinaryOpsEnd.
852 /// To simplify this code we canonicalize the relation so that the first
853 /// operand is always the most "complex" of the two. We consider simple
854 /// constants (like ConstantInt) to be the simplest, followed by
855 /// GlobalValues, followed by ConstantExpr's (the most complex).
857 static Instruction::BinaryOps evaluateRelation(Constant *V1, Constant *V2) {
858 assert(V1->getType() == V2->getType() &&
859 "Cannot compare different types of values!");
860 if (V1 == V2) return Instruction::SetEQ;
862 if (!isa<ConstantExpr>(V1) && !isa<GlobalValue>(V1)) {
863 if (!isa<GlobalValue>(V2) && !isa<ConstantExpr>(V2)) {
864 // We distilled this down to a simple case, use the standard constant
866 ConstantBool *R = dyn_cast<ConstantBool>(ConstantExpr::getSetEQ(V1, V2));
867 if (R == ConstantBool::True) return Instruction::SetEQ;
868 R = dyn_cast<ConstantBool>(ConstantExpr::getSetLT(V1, V2));
869 if (R == ConstantBool::True) return Instruction::SetLT;
870 R = dyn_cast<ConstantBool>(ConstantExpr::getSetGT(V1, V2));
871 if (R == ConstantBool::True) return Instruction::SetGT;
873 // If we couldn't figure it out, bail.
874 return Instruction::BinaryOpsEnd;
877 // If the first operand is simple, swap operands.
878 Instruction::BinaryOps SwappedRelation = evaluateRelation(V2, V1);
879 if (SwappedRelation != Instruction::BinaryOpsEnd)
880 return SetCondInst::getSwappedCondition(SwappedRelation);
882 } else if (const GlobalValue *CPR1 = dyn_cast<GlobalValue>(V1)) {
883 if (isa<ConstantExpr>(V2)) { // Swap as necessary.
884 Instruction::BinaryOps SwappedRelation = evaluateRelation(V2, V1);
885 if (SwappedRelation != Instruction::BinaryOpsEnd)
886 return SetCondInst::getSwappedCondition(SwappedRelation);
888 return Instruction::BinaryOpsEnd;
891 // Now we know that the RHS is a GlobalValue or simple constant,
892 // which (since the types must match) means that it's a ConstantPointerNull.
893 if (const GlobalValue *CPR2 = dyn_cast<GlobalValue>(V2)) {
894 assert(CPR1 != CPR2 &&
895 "GVs for the same value exist at different addresses??");
896 // FIXME: If both globals are external weak, they might both be null!
897 return Instruction::SetNE;
899 assert(isa<ConstantPointerNull>(V2) && "Canonicalization guarantee!");
900 // Global can never be null. FIXME: if we implement external weak
901 // linkage, this is not necessarily true!
902 return Instruction::SetNE;
906 // Ok, the LHS is known to be a constantexpr. The RHS can be any of a
907 // constantexpr, a CPR, or a simple constant.
908 ConstantExpr *CE1 = cast<ConstantExpr>(V1);
909 Constant *CE1Op0 = CE1->getOperand(0);
911 switch (CE1->getOpcode()) {
912 case Instruction::Cast:
913 // If the cast is not actually changing bits, and the second operand is a
914 // null pointer, do the comparison with the pre-casted value.
915 if (V2->isNullValue() &&
916 (isa<PointerType>(CE1->getType()) || CE1->getType()->isIntegral()))
917 return evaluateRelation(CE1Op0,
918 Constant::getNullValue(CE1Op0->getType()));
920 // If the dest type is a pointer type, and the RHS is a constantexpr cast
921 // from the same type as the src of the LHS, evaluate the inputs. This is
922 // important for things like "seteq (cast 4 to int*), (cast 5 to int*)",
923 // which happens a lot in compilers with tagged integers.
924 if (ConstantExpr *CE2 = dyn_cast<ConstantExpr>(V2))
925 if (isa<PointerType>(CE1->getType()) &&
926 CE2->getOpcode() == Instruction::Cast &&
927 CE1->getOperand(0)->getType() == CE2->getOperand(0)->getType() &&
928 CE1->getOperand(0)->getType()->isIntegral()) {
929 return evaluateRelation(CE1->getOperand(0), CE2->getOperand(0));
933 case Instruction::GetElementPtr:
934 // Ok, since this is a getelementptr, we know that the constant has a
935 // pointer type. Check the various cases.
936 if (isa<ConstantPointerNull>(V2)) {
937 // If we are comparing a GEP to a null pointer, check to see if the base
938 // of the GEP equals the null pointer.
939 if (isa<GlobalValue>(CE1Op0)) {
940 // FIXME: this is not true when we have external weak references!
941 // No offset can go from a global to a null pointer.
942 return Instruction::SetGT;
943 } else if (isa<ConstantPointerNull>(CE1Op0)) {
944 // If we are indexing from a null pointer, check to see if we have any
946 for (unsigned i = 1, e = CE1->getNumOperands(); i != e; ++i)
947 if (!CE1->getOperand(i)->isNullValue())
948 // Offsetting from null, must not be equal.
949 return Instruction::SetGT;
950 // Only zero indexes from null, must still be zero.
951 return Instruction::SetEQ;
953 // Otherwise, we can't really say if the first operand is null or not.
954 } else if (const GlobalValue *CPR2 = dyn_cast<GlobalValue>(V2)) {
955 if (isa<ConstantPointerNull>(CE1Op0)) {
956 // FIXME: This is not true with external weak references.
957 return Instruction::SetLT;
958 } else if (const GlobalValue *CPR1 = dyn_cast<GlobalValue>(CE1Op0)) {
960 // If this is a getelementptr of the same global, then it must be
961 // different. Because the types must match, the getelementptr could
962 // only have at most one index, and because we fold getelementptr's
963 // with a single zero index, it must be nonzero.
964 assert(CE1->getNumOperands() == 2 &&
965 !CE1->getOperand(1)->isNullValue() &&
966 "Suprising getelementptr!");
967 return Instruction::SetGT;
969 // If they are different globals, we don't know what the value is,
970 // but they can't be equal.
971 return Instruction::SetNE;
975 const ConstantExpr *CE2 = cast<ConstantExpr>(V2);
976 const Constant *CE2Op0 = CE2->getOperand(0);
978 // There are MANY other foldings that we could perform here. They will
979 // probably be added on demand, as they seem needed.
980 switch (CE2->getOpcode()) {
982 case Instruction::GetElementPtr:
983 // By far the most common case to handle is when the base pointers are
984 // obviously to the same or different globals.
985 if (isa<GlobalValue>(CE1Op0) && isa<GlobalValue>(CE2Op0)) {
986 if (CE1Op0 != CE2Op0) // Don't know relative ordering, but not equal
987 return Instruction::SetNE;
988 // Ok, we know that both getelementptr instructions are based on the
989 // same global. From this, we can precisely determine the relative
990 // ordering of the resultant pointers.
993 // Compare all of the operands the GEP's have in common.
994 gep_type_iterator GTI = gep_type_begin(CE1);
995 for (;i != CE1->getNumOperands() && i != CE2->getNumOperands();
997 switch (IdxCompare(CE1->getOperand(i), CE2->getOperand(i),
998 GTI.getIndexedType())) {
999 case -1: return Instruction::SetLT;
1000 case 1: return Instruction::SetGT;
1001 case -2: return Instruction::BinaryOpsEnd;
1004 // Ok, we ran out of things they have in common. If any leftovers
1005 // are non-zero then we have a difference, otherwise we are equal.
1006 for (; i < CE1->getNumOperands(); ++i)
1007 if (!CE1->getOperand(i)->isNullValue())
1008 if (isa<ConstantIntegral>(CE1->getOperand(i)))
1009 return Instruction::SetGT;
1011 return Instruction::BinaryOpsEnd; // Might be equal.
1013 for (; i < CE2->getNumOperands(); ++i)
1014 if (!CE2->getOperand(i)->isNullValue())
1015 if (isa<ConstantIntegral>(CE2->getOperand(i)))
1016 return Instruction::SetLT;
1018 return Instruction::BinaryOpsEnd; // Might be equal.
1019 return Instruction::SetEQ;
1029 return Instruction::BinaryOpsEnd;
1032 Constant *llvm::ConstantFoldBinaryInstruction(unsigned Opcode,
1034 const Constant *V2) {
1038 case Instruction::Add: C = ConstRules::get(V1, V2).add(V1, V2); break;
1039 case Instruction::Sub: C = ConstRules::get(V1, V2).sub(V1, V2); break;
1040 case Instruction::Mul: C = ConstRules::get(V1, V2).mul(V1, V2); break;
1041 case Instruction::Div: C = ConstRules::get(V1, V2).div(V1, V2); break;
1042 case Instruction::Rem: C = ConstRules::get(V1, V2).rem(V1, V2); break;
1043 case Instruction::And: C = ConstRules::get(V1, V2).op_and(V1, V2); break;
1044 case Instruction::Or: C = ConstRules::get(V1, V2).op_or (V1, V2); break;
1045 case Instruction::Xor: C = ConstRules::get(V1, V2).op_xor(V1, V2); break;
1046 case Instruction::Shl: C = ConstRules::get(V1, V2).shl(V1, V2); break;
1047 case Instruction::Shr: C = ConstRules::get(V1, V2).shr(V1, V2); break;
1048 case Instruction::SetEQ: C = ConstRules::get(V1, V2).equalto(V1, V2); break;
1049 case Instruction::SetLT: C = ConstRules::get(V1, V2).lessthan(V1, V2);break;
1050 case Instruction::SetGT: C = ConstRules::get(V1, V2).lessthan(V2, V1);break;
1051 case Instruction::SetNE: // V1 != V2 === !(V1 == V2)
1052 C = ConstRules::get(V1, V2).equalto(V1, V2);
1053 if (C) return ConstantExpr::getNot(C);
1055 case Instruction::SetLE: // V1 <= V2 === !(V2 < V1)
1056 C = ConstRules::get(V1, V2).lessthan(V2, V1);
1057 if (C) return ConstantExpr::getNot(C);
1059 case Instruction::SetGE: // V1 >= V2 === !(V1 < V2)
1060 C = ConstRules::get(V1, V2).lessthan(V1, V2);
1061 if (C) return ConstantExpr::getNot(C);
1065 // If we successfully folded the expression, return it now.
1068 if (SetCondInst::isRelational(Opcode)) {
1069 if (isa<UndefValue>(V1) || isa<UndefValue>(V2))
1070 return UndefValue::get(Type::BoolTy);
1071 switch (evaluateRelation(const_cast<Constant*>(V1),
1072 const_cast<Constant*>(V2))) {
1073 default: assert(0 && "Unknown relational!");
1074 case Instruction::BinaryOpsEnd:
1075 break; // Couldn't determine anything about these constants.
1076 case Instruction::SetEQ: // We know the constants are equal!
1077 // If we know the constants are equal, we can decide the result of this
1078 // computation precisely.
1079 return ConstantBool::get(Opcode == Instruction::SetEQ ||
1080 Opcode == Instruction::SetLE ||
1081 Opcode == Instruction::SetGE);
1082 case Instruction::SetLT:
1083 // If we know that V1 < V2, we can decide the result of this computation
1085 return ConstantBool::get(Opcode == Instruction::SetLT ||
1086 Opcode == Instruction::SetNE ||
1087 Opcode == Instruction::SetLE);
1088 case Instruction::SetGT:
1089 // If we know that V1 > V2, we can decide the result of this computation
1091 return ConstantBool::get(Opcode == Instruction::SetGT ||
1092 Opcode == Instruction::SetNE ||
1093 Opcode == Instruction::SetGE);
1094 case Instruction::SetLE:
1095 // If we know that V1 <= V2, we can only partially decide this relation.
1096 if (Opcode == Instruction::SetGT) return ConstantBool::False;
1097 if (Opcode == Instruction::SetLT) return ConstantBool::True;
1100 case Instruction::SetGE:
1101 // If we know that V1 >= V2, we can only partially decide this relation.
1102 if (Opcode == Instruction::SetLT) return ConstantBool::False;
1103 if (Opcode == Instruction::SetGT) return ConstantBool::True;
1106 case Instruction::SetNE:
1107 // If we know that V1 != V2, we can only partially decide this relation.
1108 if (Opcode == Instruction::SetEQ) return ConstantBool::False;
1109 if (Opcode == Instruction::SetNE) return ConstantBool::True;
1114 if (isa<UndefValue>(V1) || isa<UndefValue>(V2)) {
1116 case Instruction::Add:
1117 case Instruction::Sub:
1118 case Instruction::Xor:
1119 return UndefValue::get(V1->getType());
1121 case Instruction::Mul:
1122 case Instruction::And:
1123 return Constant::getNullValue(V1->getType());
1124 case Instruction::Div:
1125 case Instruction::Rem:
1126 if (!isa<UndefValue>(V2)) // undef/X -> 0
1127 return Constant::getNullValue(V1->getType());
1128 return const_cast<Constant*>(V2); // X/undef -> undef
1129 case Instruction::Or: // X|undef -> -1
1130 return ConstantInt::getAllOnesValue(V1->getType());
1131 case Instruction::Shr:
1132 if (!isa<UndefValue>(V2)) {
1133 if (V1->getType()->isSigned())
1134 return const_cast<Constant*>(V1); // undef >>s X -> undef
1136 } else if (isa<UndefValue>(V1)) {
1137 return const_cast<Constant*>(V1); // undef >> undef -> undef
1139 if (V1->getType()->isSigned())
1140 return const_cast<Constant*>(V1); // X >>s undef -> X
1143 return Constant::getNullValue(V1->getType());
1145 case Instruction::Shl:
1146 // undef << X -> 0 X << undef -> 0
1147 return Constant::getNullValue(V1->getType());
1151 if (const ConstantExpr *CE1 = dyn_cast<ConstantExpr>(V1)) {
1152 if (const ConstantExpr *CE2 = dyn_cast<ConstantExpr>(V2)) {
1153 // There are many possible foldings we could do here. We should probably
1154 // at least fold add of a pointer with an integer into the appropriate
1155 // getelementptr. This will improve alias analysis a bit.
1161 // Just implement a couple of simple identities.
1163 case Instruction::Add:
1164 if (V2->isNullValue()) return const_cast<Constant*>(V1); // X + 0 == X
1166 case Instruction::Sub:
1167 if (V2->isNullValue()) return const_cast<Constant*>(V1); // X - 0 == X
1169 case Instruction::Mul:
1170 if (V2->isNullValue()) return const_cast<Constant*>(V2); // X * 0 == 0
1171 if (const ConstantInt *CI = dyn_cast<ConstantInt>(V2))
1172 if (CI->getRawValue() == 1)
1173 return const_cast<Constant*>(V1); // X * 1 == X
1175 case Instruction::Div:
1176 if (const ConstantInt *CI = dyn_cast<ConstantInt>(V2))
1177 if (CI->getRawValue() == 1)
1178 return const_cast<Constant*>(V1); // X / 1 == X
1180 case Instruction::Rem:
1181 if (const ConstantInt *CI = dyn_cast<ConstantInt>(V2))
1182 if (CI->getRawValue() == 1)
1183 return Constant::getNullValue(CI->getType()); // X % 1 == 0
1185 case Instruction::And:
1186 if (cast<ConstantIntegral>(V2)->isAllOnesValue())
1187 return const_cast<Constant*>(V1); // X & -1 == X
1188 if (V2->isNullValue()) return const_cast<Constant*>(V2); // X & 0 == 0
1189 if (CE1->getOpcode() == Instruction::Cast &&
1190 isa<GlobalValue>(CE1->getOperand(0))) {
1191 GlobalValue *CPR = cast<GlobalValue>(CE1->getOperand(0));
1193 // Functions are at least 4-byte aligned. If and'ing the address of a
1194 // function with a constant < 4, fold it to zero.
1195 if (const ConstantInt *CI = dyn_cast<ConstantInt>(V2))
1196 if (CI->getRawValue() < 4 && isa<Function>(CPR))
1197 return Constant::getNullValue(CI->getType());
1200 case Instruction::Or:
1201 if (V2->isNullValue()) return const_cast<Constant*>(V1); // X | 0 == X
1202 if (cast<ConstantIntegral>(V2)->isAllOnesValue())
1203 return const_cast<Constant*>(V2); // X | -1 == -1
1205 case Instruction::Xor:
1206 if (V2->isNullValue()) return const_cast<Constant*>(V1); // X ^ 0 == X
1211 } else if (const ConstantExpr *CE2 = dyn_cast<ConstantExpr>(V2)) {
1212 // If V2 is a constant expr and V1 isn't, flop them around and fold the
1213 // other way if possible.
1215 case Instruction::Add:
1216 case Instruction::Mul:
1217 case Instruction::And:
1218 case Instruction::Or:
1219 case Instruction::Xor:
1220 case Instruction::SetEQ:
1221 case Instruction::SetNE:
1222 // No change of opcode required.
1223 return ConstantFoldBinaryInstruction(Opcode, V2, V1);
1225 case Instruction::SetLT:
1226 case Instruction::SetGT:
1227 case Instruction::SetLE:
1228 case Instruction::SetGE:
1229 // Change the opcode as necessary to swap the operands.
1230 Opcode = SetCondInst::getSwappedCondition((Instruction::BinaryOps)Opcode);
1231 return ConstantFoldBinaryInstruction(Opcode, V2, V1);
1233 case Instruction::Shl:
1234 case Instruction::Shr:
1235 case Instruction::Sub:
1236 case Instruction::Div:
1237 case Instruction::Rem:
1238 default: // These instructions cannot be flopped around.
1245 Constant *llvm::ConstantFoldGetElementPtr(const Constant *C,
1246 const std::vector<Value*> &IdxList) {
1247 if (IdxList.size() == 0 ||
1248 (IdxList.size() == 1 && cast<Constant>(IdxList[0])->isNullValue()))
1249 return const_cast<Constant*>(C);
1251 if (isa<UndefValue>(C)) {
1252 const Type *Ty = GetElementPtrInst::getIndexedType(C->getType(), IdxList,
1254 assert(Ty != 0 && "Invalid indices for GEP!");
1255 return UndefValue::get(PointerType::get(Ty));
1258 Constant *Idx0 = cast<Constant>(IdxList[0]);
1259 if (C->isNullValue()) {
1261 for (unsigned i = 0, e = IdxList.size(); i != e; ++i)
1262 if (!cast<Constant>(IdxList[i])->isNullValue()) {
1267 const Type *Ty = GetElementPtrInst::getIndexedType(C->getType(), IdxList,
1269 assert(Ty != 0 && "Invalid indices for GEP!");
1270 return ConstantPointerNull::get(PointerType::get(Ty));
1273 if (IdxList.size() == 1) {
1274 const Type *ElTy = cast<PointerType>(C->getType())->getElementType();
1275 if (unsigned ElSize = ElTy->getPrimitiveSize()) {
1276 // gep null, C is equal to C*sizeof(nullty). If nullty is a known llvm
1277 // type, we can statically fold this.
1278 Constant *R = ConstantUInt::get(Type::UIntTy, ElSize);
1279 R = ConstantExpr::getCast(R, Idx0->getType());
1280 R = ConstantExpr::getMul(R, Idx0);
1281 return ConstantExpr::getCast(R, C->getType());
1286 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(const_cast<Constant*>(C))) {
1287 // Combine Indices - If the source pointer to this getelementptr instruction
1288 // is a getelementptr instruction, combine the indices of the two
1289 // getelementptr instructions into a single instruction.
1291 if (CE->getOpcode() == Instruction::GetElementPtr) {
1292 const Type *LastTy = 0;
1293 for (gep_type_iterator I = gep_type_begin(CE), E = gep_type_end(CE);
1297 if ((LastTy && isa<ArrayType>(LastTy)) || Idx0->isNullValue()) {
1298 std::vector<Value*> NewIndices;
1299 NewIndices.reserve(IdxList.size() + CE->getNumOperands());
1300 for (unsigned i = 1, e = CE->getNumOperands()-1; i != e; ++i)
1301 NewIndices.push_back(CE->getOperand(i));
1303 // Add the last index of the source with the first index of the new GEP.
1304 // Make sure to handle the case when they are actually different types.
1305 Constant *Combined = CE->getOperand(CE->getNumOperands()-1);
1306 // Otherwise it must be an array.
1307 if (!Idx0->isNullValue()) {
1308 const Type *IdxTy = Combined->getType();
1309 if (IdxTy != Idx0->getType()) IdxTy = Type::LongTy;
1311 ConstantExpr::get(Instruction::Add,
1312 ConstantExpr::getCast(Idx0, IdxTy),
1313 ConstantExpr::getCast(Combined, IdxTy));
1316 NewIndices.push_back(Combined);
1317 NewIndices.insert(NewIndices.end(), IdxList.begin()+1, IdxList.end());
1318 return ConstantExpr::getGetElementPtr(CE->getOperand(0), NewIndices);
1322 // Implement folding of:
1323 // int* getelementptr ([2 x int]* cast ([3 x int]* %X to [2 x int]*),
1325 // To: int* getelementptr ([3 x int]* %X, long 0, long 0)
1327 if (CE->getOpcode() == Instruction::Cast && IdxList.size() > 1 &&
1328 Idx0->isNullValue())
1329 if (const PointerType *SPT =
1330 dyn_cast<PointerType>(CE->getOperand(0)->getType()))
1331 if (const ArrayType *SAT = dyn_cast<ArrayType>(SPT->getElementType()))
1332 if (const ArrayType *CAT =
1333 dyn_cast<ArrayType>(cast<PointerType>(C->getType())->getElementType()))
1334 if (CAT->getElementType() == SAT->getElementType())
1335 return ConstantExpr::getGetElementPtr(
1336 (Constant*)CE->getOperand(0), IdxList);