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 // Binary Operators...
35 virtual Constant *add(const Constant *V1, const Constant *V2) const = 0;
36 virtual Constant *sub(const Constant *V1, const Constant *V2) const = 0;
37 virtual Constant *mul(const Constant *V1, const Constant *V2) const = 0;
38 virtual Constant *div(const Constant *V1, const Constant *V2) const = 0;
39 virtual Constant *rem(const Constant *V1, const Constant *V2) const = 0;
40 virtual Constant *op_and(const Constant *V1, const Constant *V2) const = 0;
41 virtual Constant *op_or (const Constant *V1, const Constant *V2) const = 0;
42 virtual Constant *op_xor(const Constant *V1, const Constant *V2) const = 0;
43 virtual Constant *shl(const Constant *V1, const Constant *V2) const = 0;
44 virtual Constant *shr(const Constant *V1, const Constant *V2) const = 0;
45 virtual Constant *lessthan(const Constant *V1, const Constant *V2) const =0;
46 virtual Constant *equalto(const Constant *V1, const Constant *V2) const = 0;
49 virtual Constant *castToBool (const Constant *V) const = 0;
50 virtual Constant *castToSByte (const Constant *V) const = 0;
51 virtual Constant *castToUByte (const Constant *V) const = 0;
52 virtual Constant *castToShort (const Constant *V) const = 0;
53 virtual Constant *castToUShort(const Constant *V) const = 0;
54 virtual Constant *castToInt (const Constant *V) const = 0;
55 virtual Constant *castToUInt (const Constant *V) const = 0;
56 virtual Constant *castToLong (const Constant *V) const = 0;
57 virtual Constant *castToULong (const Constant *V) const = 0;
58 virtual Constant *castToFloat (const Constant *V) const = 0;
59 virtual Constant *castToDouble(const Constant *V) const = 0;
60 virtual Constant *castToPointer(const Constant *V,
61 const PointerType *Ty) const = 0;
63 // ConstRules::get - Return an instance of ConstRules for the specified
66 static ConstRules &get(const Constant *V1, const Constant *V2);
68 ConstRules(const ConstRules &); // Do not implement
69 ConstRules &operator=(const ConstRules &); // Do not implement
74 //===----------------------------------------------------------------------===//
75 // TemplateRules Class
76 //===----------------------------------------------------------------------===//
78 // TemplateRules - Implement a subclass of ConstRules that provides all
79 // operations as noops. All other rules classes inherit from this class so
80 // that if functionality is needed in the future, it can simply be added here
81 // and to ConstRules without changing anything else...
83 // This class also provides subclasses with typesafe implementations of methods
84 // so that don't have to do type casting.
86 template<class ArgType, class SubClassName>
87 class TemplateRules : public ConstRules {
89 //===--------------------------------------------------------------------===//
90 // Redirecting functions that cast to the appropriate types
91 //===--------------------------------------------------------------------===//
93 virtual Constant *add(const Constant *V1, const Constant *V2) const {
94 return SubClassName::Add((const ArgType *)V1, (const ArgType *)V2);
96 virtual Constant *sub(const Constant *V1, const Constant *V2) const {
97 return SubClassName::Sub((const ArgType *)V1, (const ArgType *)V2);
99 virtual Constant *mul(const Constant *V1, const Constant *V2) const {
100 return SubClassName::Mul((const ArgType *)V1, (const ArgType *)V2);
102 virtual Constant *div(const Constant *V1, const Constant *V2) const {
103 return SubClassName::Div((const ArgType *)V1, (const ArgType *)V2);
105 virtual Constant *rem(const Constant *V1, const Constant *V2) const {
106 return SubClassName::Rem((const ArgType *)V1, (const ArgType *)V2);
108 virtual Constant *op_and(const Constant *V1, const Constant *V2) const {
109 return SubClassName::And((const ArgType *)V1, (const ArgType *)V2);
111 virtual Constant *op_or(const Constant *V1, const Constant *V2) const {
112 return SubClassName::Or((const ArgType *)V1, (const ArgType *)V2);
114 virtual Constant *op_xor(const Constant *V1, const Constant *V2) const {
115 return SubClassName::Xor((const ArgType *)V1, (const ArgType *)V2);
117 virtual Constant *shl(const Constant *V1, const Constant *V2) const {
118 return SubClassName::Shl((const ArgType *)V1, (const ArgType *)V2);
120 virtual Constant *shr(const Constant *V1, const Constant *V2) const {
121 return SubClassName::Shr((const ArgType *)V1, (const ArgType *)V2);
124 virtual Constant *lessthan(const Constant *V1, const Constant *V2) const {
125 return SubClassName::LessThan((const ArgType *)V1, (const ArgType *)V2);
127 virtual Constant *equalto(const Constant *V1, const Constant *V2) const {
128 return SubClassName::EqualTo((const ArgType *)V1, (const ArgType *)V2);
131 // Casting operators. ick
132 virtual Constant *castToBool(const Constant *V) const {
133 return SubClassName::CastToBool((const ArgType*)V);
135 virtual Constant *castToSByte(const Constant *V) const {
136 return SubClassName::CastToSByte((const ArgType*)V);
138 virtual Constant *castToUByte(const Constant *V) const {
139 return SubClassName::CastToUByte((const ArgType*)V);
141 virtual Constant *castToShort(const Constant *V) const {
142 return SubClassName::CastToShort((const ArgType*)V);
144 virtual Constant *castToUShort(const Constant *V) const {
145 return SubClassName::CastToUShort((const ArgType*)V);
147 virtual Constant *castToInt(const Constant *V) const {
148 return SubClassName::CastToInt((const ArgType*)V);
150 virtual Constant *castToUInt(const Constant *V) const {
151 return SubClassName::CastToUInt((const ArgType*)V);
153 virtual Constant *castToLong(const Constant *V) const {
154 return SubClassName::CastToLong((const ArgType*)V);
156 virtual Constant *castToULong(const Constant *V) const {
157 return SubClassName::CastToULong((const ArgType*)V);
159 virtual Constant *castToFloat(const Constant *V) const {
160 return SubClassName::CastToFloat((const ArgType*)V);
162 virtual Constant *castToDouble(const Constant *V) const {
163 return SubClassName::CastToDouble((const ArgType*)V);
165 virtual Constant *castToPointer(const Constant *V,
166 const PointerType *Ty) const {
167 return SubClassName::CastToPointer((const ArgType*)V, Ty);
170 //===--------------------------------------------------------------------===//
171 // Default "noop" implementations
172 //===--------------------------------------------------------------------===//
174 static Constant *Add(const ArgType *V1, const ArgType *V2) { return 0; }
175 static Constant *Sub(const ArgType *V1, const ArgType *V2) { return 0; }
176 static Constant *Mul(const ArgType *V1, const ArgType *V2) { return 0; }
177 static Constant *Div(const ArgType *V1, const ArgType *V2) { return 0; }
178 static Constant *Rem(const ArgType *V1, const ArgType *V2) { return 0; }
179 static Constant *And(const ArgType *V1, const ArgType *V2) { return 0; }
180 static Constant *Or (const ArgType *V1, const ArgType *V2) { return 0; }
181 static Constant *Xor(const ArgType *V1, const ArgType *V2) { return 0; }
182 static Constant *Shl(const ArgType *V1, const ArgType *V2) { return 0; }
183 static Constant *Shr(const ArgType *V1, const ArgType *V2) { return 0; }
184 static Constant *LessThan(const ArgType *V1, const ArgType *V2) {
187 static Constant *EqualTo(const ArgType *V1, const ArgType *V2) {
191 // Casting operators. ick
192 static Constant *CastToBool (const Constant *V) { return 0; }
193 static Constant *CastToSByte (const Constant *V) { return 0; }
194 static Constant *CastToUByte (const Constant *V) { return 0; }
195 static Constant *CastToShort (const Constant *V) { return 0; }
196 static Constant *CastToUShort(const Constant *V) { return 0; }
197 static Constant *CastToInt (const Constant *V) { return 0; }
198 static Constant *CastToUInt (const Constant *V) { return 0; }
199 static Constant *CastToLong (const Constant *V) { return 0; }
200 static Constant *CastToULong (const Constant *V) { return 0; }
201 static Constant *CastToFloat (const Constant *V) { return 0; }
202 static Constant *CastToDouble(const Constant *V) { return 0; }
203 static Constant *CastToPointer(const Constant *,
204 const PointerType *) {return 0;}
209 //===----------------------------------------------------------------------===//
211 //===----------------------------------------------------------------------===//
213 // EmptyRules provides a concrete base class of ConstRules that does nothing
215 struct EmptyRules : public TemplateRules<Constant, EmptyRules> {
216 static Constant *EqualTo(const Constant *V1, const Constant *V2) {
217 if (V1 == V2) return ConstantBool::True;
224 //===----------------------------------------------------------------------===//
226 //===----------------------------------------------------------------------===//
228 // BoolRules provides a concrete base class of ConstRules for the 'bool' type.
230 struct BoolRules : public TemplateRules<ConstantBool, BoolRules> {
232 static Constant *LessThan(const ConstantBool *V1, const ConstantBool *V2){
233 return ConstantBool::get(V1->getValue() < V2->getValue());
236 static Constant *EqualTo(const Constant *V1, const Constant *V2) {
237 return ConstantBool::get(V1 == V2);
240 static Constant *And(const ConstantBool *V1, const ConstantBool *V2) {
241 return ConstantBool::get(V1->getValue() & V2->getValue());
244 static Constant *Or(const ConstantBool *V1, const ConstantBool *V2) {
245 return ConstantBool::get(V1->getValue() | V2->getValue());
248 static Constant *Xor(const ConstantBool *V1, const ConstantBool *V2) {
249 return ConstantBool::get(V1->getValue() ^ V2->getValue());
252 // Casting operators. ick
253 #define DEF_CAST(TYPE, CLASS, CTYPE) \
254 static Constant *CastTo##TYPE (const ConstantBool *V) { \
255 return CLASS::get(Type::TYPE##Ty, (CTYPE)(bool)V->getValue()); \
258 DEF_CAST(Bool , ConstantBool, bool)
259 DEF_CAST(SByte , ConstantSInt, signed char)
260 DEF_CAST(UByte , ConstantUInt, unsigned char)
261 DEF_CAST(Short , ConstantSInt, signed short)
262 DEF_CAST(UShort, ConstantUInt, unsigned short)
263 DEF_CAST(Int , ConstantSInt, signed int)
264 DEF_CAST(UInt , ConstantUInt, unsigned int)
265 DEF_CAST(Long , ConstantSInt, int64_t)
266 DEF_CAST(ULong , ConstantUInt, uint64_t)
267 DEF_CAST(Float , ConstantFP , float)
268 DEF_CAST(Double, ConstantFP , double)
273 //===----------------------------------------------------------------------===//
274 // NullPointerRules Class
275 //===----------------------------------------------------------------------===//
277 // NullPointerRules provides a concrete base class of ConstRules for null
280 struct NullPointerRules : public TemplateRules<ConstantPointerNull,
282 static Constant *EqualTo(const Constant *V1, const Constant *V2) {
283 return ConstantBool::True; // Null pointers are always equal
285 static Constant *CastToBool(const Constant *V) {
286 return ConstantBool::False;
288 static Constant *CastToSByte (const Constant *V) {
289 return ConstantSInt::get(Type::SByteTy, 0);
291 static Constant *CastToUByte (const Constant *V) {
292 return ConstantUInt::get(Type::UByteTy, 0);
294 static Constant *CastToShort (const Constant *V) {
295 return ConstantSInt::get(Type::ShortTy, 0);
297 static Constant *CastToUShort(const Constant *V) {
298 return ConstantUInt::get(Type::UShortTy, 0);
300 static Constant *CastToInt (const Constant *V) {
301 return ConstantSInt::get(Type::IntTy, 0);
303 static Constant *CastToUInt (const Constant *V) {
304 return ConstantUInt::get(Type::UIntTy, 0);
306 static Constant *CastToLong (const Constant *V) {
307 return ConstantSInt::get(Type::LongTy, 0);
309 static Constant *CastToULong (const Constant *V) {
310 return ConstantUInt::get(Type::ULongTy, 0);
312 static Constant *CastToFloat (const Constant *V) {
313 return ConstantFP::get(Type::FloatTy, 0);
315 static Constant *CastToDouble(const Constant *V) {
316 return ConstantFP::get(Type::DoubleTy, 0);
319 static Constant *CastToPointer(const ConstantPointerNull *V,
320 const PointerType *PTy) {
321 return ConstantPointerNull::get(PTy);
326 //===----------------------------------------------------------------------===//
328 //===----------------------------------------------------------------------===//
330 // DirectRules provides a concrete base classes of ConstRules for a variety of
331 // different types. This allows the C++ compiler to automatically generate our
332 // constant handling operations in a typesafe and accurate manner.
334 template<class ConstantClass, class BuiltinType, Type **Ty, class SuperClass>
335 struct DirectRules : public TemplateRules<ConstantClass, SuperClass> {
336 static Constant *Add(const ConstantClass *V1, const ConstantClass *V2) {
337 BuiltinType R = (BuiltinType)V1->getValue() + (BuiltinType)V2->getValue();
338 return ConstantClass::get(*Ty, R);
341 static Constant *Sub(const ConstantClass *V1, const ConstantClass *V2) {
342 BuiltinType R = (BuiltinType)V1->getValue() - (BuiltinType)V2->getValue();
343 return ConstantClass::get(*Ty, R);
346 static Constant *Mul(const ConstantClass *V1, const ConstantClass *V2) {
347 BuiltinType R = (BuiltinType)V1->getValue() * (BuiltinType)V2->getValue();
348 return ConstantClass::get(*Ty, R);
351 static Constant *Div(const ConstantClass *V1, const ConstantClass *V2) {
352 if (V2->isNullValue()) return 0;
353 BuiltinType R = (BuiltinType)V1->getValue() / (BuiltinType)V2->getValue();
354 return ConstantClass::get(*Ty, R);
357 static Constant *LessThan(const ConstantClass *V1, const ConstantClass *V2) {
358 bool R = (BuiltinType)V1->getValue() < (BuiltinType)V2->getValue();
359 return ConstantBool::get(R);
362 static Constant *EqualTo(const ConstantClass *V1, const ConstantClass *V2) {
363 bool R = (BuiltinType)V1->getValue() == (BuiltinType)V2->getValue();
364 return ConstantBool::get(R);
367 static Constant *CastToPointer(const ConstantClass *V,
368 const PointerType *PTy) {
369 if (V->isNullValue()) // Is it a FP or Integral null value?
370 return ConstantPointerNull::get(PTy);
371 return 0; // Can't const prop other types of pointers
374 // Casting operators. ick
375 #define DEF_CAST(TYPE, CLASS, CTYPE) \
376 static Constant *CastTo##TYPE (const ConstantClass *V) { \
377 return CLASS::get(Type::TYPE##Ty, (CTYPE)(BuiltinType)V->getValue()); \
380 DEF_CAST(Bool , ConstantBool, bool)
381 DEF_CAST(SByte , ConstantSInt, signed char)
382 DEF_CAST(UByte , ConstantUInt, unsigned char)
383 DEF_CAST(Short , ConstantSInt, signed short)
384 DEF_CAST(UShort, ConstantUInt, unsigned short)
385 DEF_CAST(Int , ConstantSInt, signed int)
386 DEF_CAST(UInt , ConstantUInt, unsigned int)
387 DEF_CAST(Long , ConstantSInt, int64_t)
388 DEF_CAST(ULong , ConstantUInt, uint64_t)
389 DEF_CAST(Float , ConstantFP , float)
390 DEF_CAST(Double, ConstantFP , double)
395 //===----------------------------------------------------------------------===//
396 // DirectIntRules Class
397 //===----------------------------------------------------------------------===//
399 // DirectIntRules provides implementations of functions that are valid on
400 // integer types, but not all types in general.
402 template <class ConstantClass, class BuiltinType, Type **Ty>
403 struct DirectIntRules
404 : public DirectRules<ConstantClass, BuiltinType, Ty,
405 DirectIntRules<ConstantClass, BuiltinType, Ty> > {
407 static Constant *Div(const ConstantClass *V1, const ConstantClass *V2) {
408 if (V2->isNullValue()) return 0;
409 if (V2->isAllOnesValue() && // MIN_INT / -1
410 (BuiltinType)V1->getValue() == -(BuiltinType)V1->getValue())
412 BuiltinType R = (BuiltinType)V1->getValue() / (BuiltinType)V2->getValue();
413 return ConstantClass::get(*Ty, R);
416 static Constant *Rem(const ConstantClass *V1,
417 const ConstantClass *V2) {
418 if (V2->isNullValue()) return 0; // X / 0
419 if (V2->isAllOnesValue() && // MIN_INT / -1
420 (BuiltinType)V1->getValue() == -(BuiltinType)V1->getValue())
422 BuiltinType R = (BuiltinType)V1->getValue() % (BuiltinType)V2->getValue();
423 return ConstantClass::get(*Ty, R);
426 static Constant *And(const ConstantClass *V1, const ConstantClass *V2) {
427 BuiltinType R = (BuiltinType)V1->getValue() & (BuiltinType)V2->getValue();
428 return ConstantClass::get(*Ty, R);
430 static Constant *Or(const ConstantClass *V1, const ConstantClass *V2) {
431 BuiltinType R = (BuiltinType)V1->getValue() | (BuiltinType)V2->getValue();
432 return ConstantClass::get(*Ty, R);
434 static Constant *Xor(const ConstantClass *V1, const ConstantClass *V2) {
435 BuiltinType R = (BuiltinType)V1->getValue() ^ (BuiltinType)V2->getValue();
436 return ConstantClass::get(*Ty, R);
439 static Constant *Shl(const ConstantClass *V1, const ConstantClass *V2) {
440 BuiltinType R = (BuiltinType)V1->getValue() << (BuiltinType)V2->getValue();
441 return ConstantClass::get(*Ty, R);
444 static Constant *Shr(const ConstantClass *V1, const ConstantClass *V2) {
445 BuiltinType R = (BuiltinType)V1->getValue() >> (BuiltinType)V2->getValue();
446 return ConstantClass::get(*Ty, R);
451 //===----------------------------------------------------------------------===//
452 // DirectFPRules Class
453 //===----------------------------------------------------------------------===//
455 /// DirectFPRules provides implementations of functions that are valid on
456 /// floating point types, but not all types in general.
458 template <class ConstantClass, class BuiltinType, Type **Ty>
460 : public DirectRules<ConstantClass, BuiltinType, Ty,
461 DirectFPRules<ConstantClass, BuiltinType, Ty> > {
462 static Constant *Rem(const ConstantClass *V1, const ConstantClass *V2) {
463 if (V2->isNullValue()) return 0;
464 BuiltinType Result = std::fmod((BuiltinType)V1->getValue(),
465 (BuiltinType)V2->getValue());
466 return ConstantClass::get(*Ty, Result);
471 /// ConstRules::get - This method returns the constant rules implementation that
472 /// implements the semantics of the two specified constants.
473 ConstRules &ConstRules::get(const Constant *V1, const Constant *V2) {
474 static EmptyRules EmptyR;
475 static BoolRules BoolR;
476 static NullPointerRules NullPointerR;
477 static DirectIntRules<ConstantSInt, signed char , &Type::SByteTy> SByteR;
478 static DirectIntRules<ConstantUInt, unsigned char , &Type::UByteTy> UByteR;
479 static DirectIntRules<ConstantSInt, signed short, &Type::ShortTy> ShortR;
480 static DirectIntRules<ConstantUInt, unsigned short, &Type::UShortTy> UShortR;
481 static DirectIntRules<ConstantSInt, signed int , &Type::IntTy> IntR;
482 static DirectIntRules<ConstantUInt, unsigned int , &Type::UIntTy> UIntR;
483 static DirectIntRules<ConstantSInt, int64_t , &Type::LongTy> LongR;
484 static DirectIntRules<ConstantUInt, uint64_t , &Type::ULongTy> ULongR;
485 static DirectFPRules <ConstantFP , float , &Type::FloatTy> FloatR;
486 static DirectFPRules <ConstantFP , double , &Type::DoubleTy> DoubleR;
488 if (isa<ConstantExpr>(V1) || isa<ConstantExpr>(V2) ||
489 isa<GlobalValue>(V1) || isa<GlobalValue>(V2) ||
490 isa<UndefValue>(V1) || isa<UndefValue>(V2))
493 switch (V1->getType()->getTypeID()) {
494 default: assert(0 && "Unknown value type for constant folding!");
495 case Type::BoolTyID: return BoolR;
496 case Type::PointerTyID: return NullPointerR;
497 case Type::SByteTyID: return SByteR;
498 case Type::UByteTyID: return UByteR;
499 case Type::ShortTyID: return ShortR;
500 case Type::UShortTyID: return UShortR;
501 case Type::IntTyID: return IntR;
502 case Type::UIntTyID: return UIntR;
503 case Type::LongTyID: return LongR;
504 case Type::ULongTyID: return ULongR;
505 case Type::FloatTyID: return FloatR;
506 case Type::DoubleTyID: return DoubleR;
511 //===----------------------------------------------------------------------===//
512 // ConstantFold*Instruction Implementations
513 //===----------------------------------------------------------------------===//
515 // These methods contain the special case hackery required to symbolically
516 // evaluate some constant expression cases, and use the ConstantRules class to
517 // evaluate normal constants.
519 static unsigned getSize(const Type *Ty) {
520 unsigned S = Ty->getPrimitiveSize();
521 return S ? S : 8; // Treat pointers at 8 bytes
524 Constant *llvm::ConstantFoldCastInstruction(const Constant *V,
525 const Type *DestTy) {
526 if (V->getType() == DestTy) return (Constant*)V;
528 // Cast of a global address to boolean is always true.
529 if (const GlobalValue *GV = dyn_cast<GlobalValue>(V)) {
530 if (DestTy == Type::BoolTy)
531 // FIXME: When we support 'external weak' references, we have to prevent
532 // this transformation from happening. This code will need to be updated
533 // to ignore external weak symbols when we support it.
534 return ConstantBool::True;
535 } else if (const ConstantExpr *CE = dyn_cast<ConstantExpr>(V)) {
536 if (CE->getOpcode() == Instruction::Cast) {
537 Constant *Op = const_cast<Constant*>(CE->getOperand(0));
538 // Try to not produce a cast of a cast, which is almost always redundant.
539 if (!Op->getType()->isFloatingPoint() &&
540 !CE->getType()->isFloatingPoint() &&
541 !DestTy->isFloatingPoint()) {
542 unsigned S1 = getSize(Op->getType()), S2 = getSize(CE->getType());
543 unsigned S3 = getSize(DestTy);
544 if (Op->getType() == DestTy && S3 >= S2)
546 if (S1 >= S2 && S2 >= S3)
547 return ConstantExpr::getCast(Op, DestTy);
548 if (S1 <= S2 && S2 >= S3 && S1 <= S3)
549 return ConstantExpr::getCast(Op, DestTy);
551 } else if (CE->getOpcode() == Instruction::GetElementPtr) {
552 // If all of the indexes in the GEP are null values, there is no pointer
553 // adjustment going on. We might as well cast the source pointer.
554 bool isAllNull = true;
555 for (unsigned i = 1, e = CE->getNumOperands(); i != e; ++i)
556 if (!CE->getOperand(i)->isNullValue()) {
561 return ConstantExpr::getCast(CE->getOperand(0), DestTy);
563 } else if (isa<UndefValue>(V)) {
564 return UndefValue::get(DestTy);
567 // Check to see if we are casting an pointer to an aggregate to a pointer to
568 // the first element. If so, return the appropriate GEP instruction.
569 if (const PointerType *PTy = dyn_cast<PointerType>(V->getType()))
570 if (const PointerType *DPTy = dyn_cast<PointerType>(DestTy)) {
571 std::vector<Value*> IdxList;
572 IdxList.push_back(Constant::getNullValue(Type::IntTy));
573 const Type *ElTy = PTy->getElementType();
574 while (ElTy != DPTy->getElementType()) {
575 if (const StructType *STy = dyn_cast<StructType>(ElTy)) {
576 if (STy->getNumElements() == 0) break;
577 ElTy = STy->getElementType(0);
578 IdxList.push_back(Constant::getNullValue(Type::UIntTy));
579 } else if (const SequentialType *STy = dyn_cast<SequentialType>(ElTy)) {
580 if (isa<PointerType>(ElTy)) break; // Can't index into pointers!
581 ElTy = STy->getElementType();
582 IdxList.push_back(IdxList[0]);
588 if (ElTy == DPTy->getElementType())
589 return ConstantExpr::getGetElementPtr(const_cast<Constant*>(V),IdxList);
592 ConstRules &Rules = ConstRules::get(V, V);
594 switch (DestTy->getTypeID()) {
595 case Type::BoolTyID: return Rules.castToBool(V);
596 case Type::UByteTyID: return Rules.castToUByte(V);
597 case Type::SByteTyID: return Rules.castToSByte(V);
598 case Type::UShortTyID: return Rules.castToUShort(V);
599 case Type::ShortTyID: return Rules.castToShort(V);
600 case Type::UIntTyID: return Rules.castToUInt(V);
601 case Type::IntTyID: return Rules.castToInt(V);
602 case Type::ULongTyID: return Rules.castToULong(V);
603 case Type::LongTyID: return Rules.castToLong(V);
604 case Type::FloatTyID: return Rules.castToFloat(V);
605 case Type::DoubleTyID: return Rules.castToDouble(V);
606 case Type::PointerTyID:
607 return Rules.castToPointer(V, cast<PointerType>(DestTy));
612 Constant *llvm::ConstantFoldSelectInstruction(const Constant *Cond,
614 const Constant *V2) {
615 if (Cond == ConstantBool::True)
616 return const_cast<Constant*>(V1);
617 else if (Cond == ConstantBool::False)
618 return const_cast<Constant*>(V2);
620 if (isa<UndefValue>(V1)) return const_cast<Constant*>(V2);
621 if (isa<UndefValue>(V2)) return const_cast<Constant*>(V1);
622 if (isa<UndefValue>(Cond)) return const_cast<Constant*>(V1);
626 /// isZeroSizedType - This type is zero sized if its an array or structure of
627 /// zero sized types. The only leaf zero sized type is an empty structure.
628 static bool isMaybeZeroSizedType(const Type *Ty) {
629 if (isa<OpaqueType>(Ty)) return true; // Can't say.
630 if (const StructType *STy = dyn_cast<StructType>(Ty)) {
632 // If all of elements have zero size, this does too.
633 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i)
634 if (!isMaybeZeroSizedType(STy->getElementType(i))) return false;
637 } else if (const ArrayType *ATy = dyn_cast<ArrayType>(Ty)) {
638 return isMaybeZeroSizedType(ATy->getElementType());
643 /// IdxCompare - Compare the two constants as though they were getelementptr
644 /// indices. This allows coersion of the types to be the same thing.
646 /// If the two constants are the "same" (after coersion), return 0. If the
647 /// first is less than the second, return -1, if the second is less than the
648 /// first, return 1. If the constants are not integral, return -2.
650 static int IdxCompare(Constant *C1, Constant *C2, const Type *ElTy) {
651 if (C1 == C2) return 0;
653 // Ok, we found a different index. Are either of the operands
654 // ConstantExprs? If so, we can't do anything with them.
655 if (!isa<ConstantInt>(C1) || !isa<ConstantInt>(C2))
656 return -2; // don't know!
658 // Ok, we have two differing integer indices. Sign extend them to be the same
659 // type. Long is always big enough, so we use it.
660 C1 = ConstantExpr::getSignExtend(C1, Type::LongTy);
661 C2 = ConstantExpr::getSignExtend(C2, Type::LongTy);
662 if (C1 == C2) return 0; // Are they just differing types?
664 // If the type being indexed over is really just a zero sized type, there is
665 // no pointer difference being made here.
666 if (isMaybeZeroSizedType(ElTy))
669 // If they are really different, now that they are the same type, then we
670 // found a difference!
671 if (cast<ConstantSInt>(C1)->getValue() < cast<ConstantSInt>(C2)->getValue())
677 /// evaluateRelation - This function determines if there is anything we can
678 /// decide about the two constants provided. This doesn't need to handle simple
679 /// things like integer comparisons, but should instead handle ConstantExprs
680 /// and GlobalValuess. If we can determine that the two constants have a
681 /// particular relation to each other, we should return the corresponding SetCC
682 /// code, otherwise return Instruction::BinaryOpsEnd.
684 /// To simplify this code we canonicalize the relation so that the first
685 /// operand is always the most "complex" of the two. We consider simple
686 /// constants (like ConstantInt) to be the simplest, followed by
687 /// GlobalValues, followed by ConstantExpr's (the most complex).
689 static Instruction::BinaryOps evaluateRelation(const Constant *V1,
690 const Constant *V2) {
691 assert(V1->getType() == V2->getType() &&
692 "Cannot compare different types of values!");
693 if (V1 == V2) return Instruction::SetEQ;
695 if (!isa<ConstantExpr>(V1) && !isa<GlobalValue>(V1)) {
696 // If the first operand is simple, swap operands.
697 assert((isa<GlobalValue>(V2) || isa<ConstantExpr>(V2)) &&
698 "Simple cases should have been handled by caller!");
699 Instruction::BinaryOps SwappedRelation = evaluateRelation(V2, V1);
700 if (SwappedRelation != Instruction::BinaryOpsEnd)
701 return SetCondInst::getSwappedCondition(SwappedRelation);
703 } else if (const GlobalValue *CPR1 = dyn_cast<GlobalValue>(V1)){
704 if (isa<ConstantExpr>(V2)) { // Swap as necessary.
705 Instruction::BinaryOps SwappedRelation = evaluateRelation(V2, V1);
706 if (SwappedRelation != Instruction::BinaryOpsEnd)
707 return SetCondInst::getSwappedCondition(SwappedRelation);
709 return Instruction::BinaryOpsEnd;
712 // Now we know that the RHS is a GlobalValue or simple constant,
713 // which (since the types must match) means that it's a ConstantPointerNull.
714 if (const GlobalValue *CPR2 = dyn_cast<GlobalValue>(V2)) {
715 assert(CPR1 != CPR2 &&
716 "GVs for the same value exist at different addresses??");
717 // FIXME: If both globals are external weak, they might both be null!
718 return Instruction::SetNE;
720 assert(isa<ConstantPointerNull>(V2) && "Canonicalization guarantee!");
721 // Global can never be null. FIXME: if we implement external weak
722 // linkage, this is not necessarily true!
723 return Instruction::SetNE;
727 // Ok, the LHS is known to be a constantexpr. The RHS can be any of a
728 // constantexpr, a CPR, or a simple constant.
729 const ConstantExpr *CE1 = cast<ConstantExpr>(V1);
730 Constant *CE1Op0 = CE1->getOperand(0);
732 switch (CE1->getOpcode()) {
733 case Instruction::Cast:
734 // If the cast is not actually changing bits, and the second operand is a
735 // null pointer, do the comparison with the pre-casted value.
736 if (V2->isNullValue() &&
737 CE1->getType()->isLosslesslyConvertibleTo(CE1Op0->getType()))
738 return evaluateRelation(CE1Op0,
739 Constant::getNullValue(CE1Op0->getType()));
742 case Instruction::GetElementPtr:
743 // Ok, since this is a getelementptr, we know that the constant has a
744 // pointer type. Check the various cases.
745 if (isa<ConstantPointerNull>(V2)) {
746 // If we are comparing a GEP to a null pointer, check to see if the base
747 // of the GEP equals the null pointer.
748 if (isa<GlobalValue>(CE1Op0)) {
749 // FIXME: this is not true when we have external weak references!
750 // No offset can go from a global to a null pointer.
751 return Instruction::SetGT;
752 } else if (isa<ConstantPointerNull>(CE1Op0)) {
753 // If we are indexing from a null pointer, check to see if we have any
755 for (unsigned i = 1, e = CE1->getNumOperands(); i != e; ++i)
756 if (!CE1->getOperand(i)->isNullValue())
757 // Offsetting from null, must not be equal.
758 return Instruction::SetGT;
759 // Only zero indexes from null, must still be zero.
760 return Instruction::SetEQ;
762 // Otherwise, we can't really say if the first operand is null or not.
763 } else if (const GlobalValue *CPR2 = dyn_cast<GlobalValue>(V2)) {
764 if (isa<ConstantPointerNull>(CE1Op0)) {
765 // FIXME: This is not true with external weak references.
766 return Instruction::SetLT;
767 } else if (const GlobalValue *CPR1 = dyn_cast<GlobalValue>(CE1Op0)) {
769 // If this is a getelementptr of the same global, then it must be
770 // different. Because the types must match, the getelementptr could
771 // only have at most one index, and because we fold getelementptr's
772 // with a single zero index, it must be nonzero.
773 assert(CE1->getNumOperands() == 2 &&
774 !CE1->getOperand(1)->isNullValue() &&
775 "Suprising getelementptr!");
776 return Instruction::SetGT;
778 // If they are different globals, we don't know what the value is,
779 // but they can't be equal.
780 return Instruction::SetNE;
784 const ConstantExpr *CE2 = cast<ConstantExpr>(V2);
785 const Constant *CE2Op0 = CE2->getOperand(0);
787 // There are MANY other foldings that we could perform here. They will
788 // probably be added on demand, as they seem needed.
789 switch (CE2->getOpcode()) {
791 case Instruction::GetElementPtr:
792 // By far the most common case to handle is when the base pointers are
793 // obviously to the same or different globals.
794 if (isa<GlobalValue>(CE1Op0) && isa<GlobalValue>(CE2Op0)) {
795 if (CE1Op0 != CE2Op0) // Don't know relative ordering, but not equal
796 return Instruction::SetNE;
797 // Ok, we know that both getelementptr instructions are based on the
798 // same global. From this, we can precisely determine the relative
799 // ordering of the resultant pointers.
802 // Compare all of the operands the GEP's have in common.
803 gep_type_iterator GTI = gep_type_begin(CE1);
804 for (;i != CE1->getNumOperands() && i != CE2->getNumOperands();
806 switch (IdxCompare(CE1->getOperand(i), CE2->getOperand(i),
807 GTI.getIndexedType())) {
808 case -1: return Instruction::SetLT;
809 case 1: return Instruction::SetGT;
810 case -2: return Instruction::BinaryOpsEnd;
813 // Ok, we ran out of things they have in common. If any leftovers
814 // are non-zero then we have a difference, otherwise we are equal.
815 for (; i < CE1->getNumOperands(); ++i)
816 if (!CE1->getOperand(i)->isNullValue())
817 if (isa<ConstantIntegral>(CE1->getOperand(i)))
818 return Instruction::SetGT;
820 return Instruction::BinaryOpsEnd; // Might be equal.
822 for (; i < CE2->getNumOperands(); ++i)
823 if (!CE2->getOperand(i)->isNullValue())
824 if (isa<ConstantIntegral>(CE2->getOperand(i)))
825 return Instruction::SetLT;
827 return Instruction::BinaryOpsEnd; // Might be equal.
828 return Instruction::SetEQ;
838 return Instruction::BinaryOpsEnd;
841 Constant *llvm::ConstantFoldBinaryInstruction(unsigned Opcode,
843 const Constant *V2) {
847 case Instruction::Add: C = ConstRules::get(V1, V2).add(V1, V2); break;
848 case Instruction::Sub: C = ConstRules::get(V1, V2).sub(V1, V2); break;
849 case Instruction::Mul: C = ConstRules::get(V1, V2).mul(V1, V2); break;
850 case Instruction::Div: C = ConstRules::get(V1, V2).div(V1, V2); break;
851 case Instruction::Rem: C = ConstRules::get(V1, V2).rem(V1, V2); break;
852 case Instruction::And: C = ConstRules::get(V1, V2).op_and(V1, V2); break;
853 case Instruction::Or: C = ConstRules::get(V1, V2).op_or (V1, V2); break;
854 case Instruction::Xor: C = ConstRules::get(V1, V2).op_xor(V1, V2); break;
855 case Instruction::Shl: C = ConstRules::get(V1, V2).shl(V1, V2); break;
856 case Instruction::Shr: C = ConstRules::get(V1, V2).shr(V1, V2); break;
857 case Instruction::SetEQ: C = ConstRules::get(V1, V2).equalto(V1, V2); break;
858 case Instruction::SetLT: C = ConstRules::get(V1, V2).lessthan(V1, V2);break;
859 case Instruction::SetGT: C = ConstRules::get(V1, V2).lessthan(V2, V1);break;
860 case Instruction::SetNE: // V1 != V2 === !(V1 == V2)
861 C = ConstRules::get(V1, V2).equalto(V1, V2);
862 if (C) return ConstantExpr::get(Instruction::Xor, C, ConstantBool::True);
864 case Instruction::SetLE: // V1 <= V2 === !(V2 < V1)
865 C = ConstRules::get(V1, V2).lessthan(V2, V1);
866 if (C) return ConstantExpr::get(Instruction::Xor, C, ConstantBool::True);
868 case Instruction::SetGE: // V1 >= V2 === !(V1 < V2)
869 C = ConstRules::get(V1, V2).lessthan(V1, V2);
870 if (C) return ConstantExpr::get(Instruction::Xor, C, ConstantBool::True);
874 // If we successfully folded the expression, return it now.
877 if (SetCondInst::isRelational(Opcode)) {
878 if (isa<UndefValue>(V1) || isa<UndefValue>(V2))
879 return UndefValue::get(Type::BoolTy);
880 switch (evaluateRelation(V1, V2)) {
881 default: assert(0 && "Unknown relational!");
882 case Instruction::BinaryOpsEnd:
883 break; // Couldn't determine anything about these constants.
884 case Instruction::SetEQ: // We know the constants are equal!
885 // If we know the constants are equal, we can decide the result of this
886 // computation precisely.
887 return ConstantBool::get(Opcode == Instruction::SetEQ ||
888 Opcode == Instruction::SetLE ||
889 Opcode == Instruction::SetGE);
890 case Instruction::SetLT:
891 // If we know that V1 < V2, we can decide the result of this computation
893 return ConstantBool::get(Opcode == Instruction::SetLT ||
894 Opcode == Instruction::SetNE ||
895 Opcode == Instruction::SetLE);
896 case Instruction::SetGT:
897 // If we know that V1 > V2, we can decide the result of this computation
899 return ConstantBool::get(Opcode == Instruction::SetGT ||
900 Opcode == Instruction::SetNE ||
901 Opcode == Instruction::SetGE);
902 case Instruction::SetLE:
903 // If we know that V1 <= V2, we can only partially decide this relation.
904 if (Opcode == Instruction::SetGT) return ConstantBool::False;
905 if (Opcode == Instruction::SetLT) return ConstantBool::True;
908 case Instruction::SetGE:
909 // If we know that V1 >= V2, we can only partially decide this relation.
910 if (Opcode == Instruction::SetLT) return ConstantBool::False;
911 if (Opcode == Instruction::SetGT) return ConstantBool::True;
914 case Instruction::SetNE:
915 // If we know that V1 != V2, we can only partially decide this relation.
916 if (Opcode == Instruction::SetEQ) return ConstantBool::False;
917 if (Opcode == Instruction::SetNE) return ConstantBool::True;
922 if (isa<UndefValue>(V1) || isa<UndefValue>(V2)) {
924 case Instruction::Add:
925 case Instruction::Sub:
926 case Instruction::Xor:
927 return UndefValue::get(V1->getType());
929 case Instruction::Mul:
930 case Instruction::And:
931 return Constant::getNullValue(V1->getType());
932 case Instruction::Div:
933 case Instruction::Rem:
934 if (!isa<UndefValue>(V2)) // undef/X -> 0
935 return Constant::getNullValue(V1->getType());
936 return const_cast<Constant*>(V2); // X/undef -> undef
937 case Instruction::Or: // X|undef -> -1
938 return ConstantInt::getAllOnesValue(V1->getType());
939 case Instruction::Shr:
940 if (!isa<UndefValue>(V2)) {
941 if (V1->getType()->isSigned())
942 return const_cast<Constant*>(V1); // undef >>s X -> undef
944 } else if (isa<UndefValue>(V1)) {
945 return const_cast<Constant*>(V1); // undef >> undef -> undef
947 if (V1->getType()->isSigned())
948 return const_cast<Constant*>(V1); // X >>s undef -> X
951 return Constant::getNullValue(V1->getType());
953 case Instruction::Shl:
954 // undef << X -> 0 X << undef -> 0
955 return Constant::getNullValue(V1->getType());
959 if (const ConstantExpr *CE1 = dyn_cast<ConstantExpr>(V1)) {
960 if (const ConstantExpr *CE2 = dyn_cast<ConstantExpr>(V2)) {
961 // There are many possible foldings we could do here. We should probably
962 // at least fold add of a pointer with an integer into the appropriate
963 // getelementptr. This will improve alias analysis a bit.
969 // Just implement a couple of simple identities.
971 case Instruction::Add:
972 if (V2->isNullValue()) return const_cast<Constant*>(V1); // X + 0 == X
974 case Instruction::Sub:
975 if (V2->isNullValue()) return const_cast<Constant*>(V1); // X - 0 == X
977 case Instruction::Mul:
978 if (V2->isNullValue()) return const_cast<Constant*>(V2); // X * 0 == 0
979 if (const ConstantInt *CI = dyn_cast<ConstantInt>(V2))
980 if (CI->getRawValue() == 1)
981 return const_cast<Constant*>(V1); // X * 1 == X
983 case Instruction::Div:
984 if (const ConstantInt *CI = dyn_cast<ConstantInt>(V2))
985 if (CI->getRawValue() == 1)
986 return const_cast<Constant*>(V1); // X / 1 == X
988 case Instruction::Rem:
989 if (const ConstantInt *CI = dyn_cast<ConstantInt>(V2))
990 if (CI->getRawValue() == 1)
991 return Constant::getNullValue(CI->getType()); // X % 1 == 0
993 case Instruction::And:
994 if (cast<ConstantIntegral>(V2)->isAllOnesValue())
995 return const_cast<Constant*>(V1); // X & -1 == X
996 if (V2->isNullValue()) return const_cast<Constant*>(V2); // X & 0 == 0
997 if (CE1->getOpcode() == Instruction::Cast &&
998 isa<GlobalValue>(CE1->getOperand(0))) {
999 GlobalValue *CPR = cast<GlobalValue>(CE1->getOperand(0));
1001 // Functions are at least 4-byte aligned. If and'ing the address of a
1002 // function with a constant < 4, fold it to zero.
1003 if (const ConstantInt *CI = dyn_cast<ConstantInt>(V2))
1004 if (CI->getRawValue() < 4 && isa<Function>(CPR))
1005 return Constant::getNullValue(CI->getType());
1008 case Instruction::Or:
1009 if (V2->isNullValue()) return const_cast<Constant*>(V1); // X | 0 == X
1010 if (cast<ConstantIntegral>(V2)->isAllOnesValue())
1011 return const_cast<Constant*>(V2); // X | -1 == -1
1013 case Instruction::Xor:
1014 if (V2->isNullValue()) return const_cast<Constant*>(V1); // X ^ 0 == X
1019 } else if (const ConstantExpr *CE2 = dyn_cast<ConstantExpr>(V2)) {
1020 // If V2 is a constant expr and V1 isn't, flop them around and fold the
1021 // other way if possible.
1023 case Instruction::Add:
1024 case Instruction::Mul:
1025 case Instruction::And:
1026 case Instruction::Or:
1027 case Instruction::Xor:
1028 case Instruction::SetEQ:
1029 case Instruction::SetNE:
1030 // No change of opcode required.
1031 return ConstantFoldBinaryInstruction(Opcode, V2, V1);
1033 case Instruction::SetLT:
1034 case Instruction::SetGT:
1035 case Instruction::SetLE:
1036 case Instruction::SetGE:
1037 // Change the opcode as necessary to swap the operands.
1038 Opcode = SetCondInst::getSwappedCondition((Instruction::BinaryOps)Opcode);
1039 return ConstantFoldBinaryInstruction(Opcode, V2, V1);
1041 case Instruction::Shl:
1042 case Instruction::Shr:
1043 case Instruction::Sub:
1044 case Instruction::Div:
1045 case Instruction::Rem:
1046 default: // These instructions cannot be flopped around.
1053 Constant *llvm::ConstantFoldGetElementPtr(const Constant *C,
1054 const std::vector<Value*> &IdxList) {
1055 if (IdxList.size() == 0 ||
1056 (IdxList.size() == 1 && cast<Constant>(IdxList[0])->isNullValue()))
1057 return const_cast<Constant*>(C);
1059 if (isa<UndefValue>(C)) {
1060 const Type *Ty = GetElementPtrInst::getIndexedType(C->getType(), IdxList,
1062 assert(Ty != 0 && "Invalid indices for GEP!");
1063 return UndefValue::get(PointerType::get(Ty));
1066 Constant *Idx0 = cast<Constant>(IdxList[0]);
1067 if (C->isNullValue()) {
1069 for (unsigned i = 0, e = IdxList.size(); i != e; ++i)
1070 if (!cast<Constant>(IdxList[i])->isNullValue()) {
1075 const Type *Ty = GetElementPtrInst::getIndexedType(C->getType(), IdxList,
1077 assert(Ty != 0 && "Invalid indices for GEP!");
1078 return ConstantPointerNull::get(PointerType::get(Ty));
1081 if (IdxList.size() == 1) {
1082 const Type *ElTy = cast<PointerType>(C->getType())->getElementType();
1083 if (unsigned ElSize = ElTy->getPrimitiveSize()) {
1084 // gep null, C is equal to C*sizeof(nullty). If nullty is a known llvm
1085 // type, we can statically fold this.
1086 Constant *R = ConstantUInt::get(Type::UIntTy, ElSize);
1087 R = ConstantExpr::getCast(R, Idx0->getType());
1088 R = ConstantExpr::getMul(R, Idx0);
1089 return ConstantExpr::getCast(R, C->getType());
1094 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(const_cast<Constant*>(C))) {
1095 // Combine Indices - If the source pointer to this getelementptr instruction
1096 // is a getelementptr instruction, combine the indices of the two
1097 // getelementptr instructions into a single instruction.
1099 if (CE->getOpcode() == Instruction::GetElementPtr) {
1100 const Type *LastTy = 0;
1101 for (gep_type_iterator I = gep_type_begin(CE), E = gep_type_end(CE);
1105 if ((LastTy && isa<ArrayType>(LastTy)) || Idx0->isNullValue()) {
1106 std::vector<Value*> NewIndices;
1107 NewIndices.reserve(IdxList.size() + CE->getNumOperands());
1108 for (unsigned i = 1, e = CE->getNumOperands()-1; i != e; ++i)
1109 NewIndices.push_back(CE->getOperand(i));
1111 // Add the last index of the source with the first index of the new GEP.
1112 // Make sure to handle the case when they are actually different types.
1113 Constant *Combined = CE->getOperand(CE->getNumOperands()-1);
1114 // Otherwise it must be an array.
1115 if (!Idx0->isNullValue()) {
1116 const Type *IdxTy = Combined->getType();
1117 if (IdxTy != Idx0->getType()) IdxTy = Type::LongTy;
1119 ConstantExpr::get(Instruction::Add,
1120 ConstantExpr::getCast(Idx0, IdxTy),
1121 ConstantExpr::getCast(Combined, IdxTy));
1124 NewIndices.push_back(Combined);
1125 NewIndices.insert(NewIndices.end(), IdxList.begin()+1, IdxList.end());
1126 return ConstantExpr::getGetElementPtr(CE->getOperand(0), NewIndices);
1130 // Implement folding of:
1131 // int* getelementptr ([2 x int]* cast ([3 x int]* %X to [2 x int]*),
1133 // To: int* getelementptr ([3 x int]* %X, long 0, long 0)
1135 if (CE->getOpcode() == Instruction::Cast && IdxList.size() > 1 &&
1136 Idx0->isNullValue())
1137 if (const PointerType *SPT =
1138 dyn_cast<PointerType>(CE->getOperand(0)->getType()))
1139 if (const ArrayType *SAT = dyn_cast<ArrayType>(SPT->getElementType()))
1140 if (const ArrayType *CAT =
1141 dyn_cast<ArrayType>(cast<PointerType>(C->getType())->getElementType()))
1142 if (CAT->getElementType() == SAT->getElementType())
1143 return ConstantExpr::getGetElementPtr(
1144 (Constant*)CE->getOperand(0), IdxList);