LLVM API Documentation
00001 //===- ConstantFolding.cpp - LLVM constant folder -------------------------===// 00002 // 00003 // The LLVM Compiler Infrastructure 00004 // 00005 // This file was developed by the LLVM research group and is distributed under 00006 // the University of Illinois Open Source License. See LICENSE.TXT for details. 00007 // 00008 //===----------------------------------------------------------------------===// 00009 // 00010 // This file implements folding of constants for LLVM. This implements the 00011 // (internal) ConstantFolding.h interface, which is used by the 00012 // ConstantExpr::get* methods to automatically fold constants when possible. 00013 // 00014 // The current constant folding implementation is implemented in two pieces: the 00015 // template-based folder for simple primitive constants like ConstantInt, and 00016 // the special case hackery that we use to symbolically evaluate expressions 00017 // that use ConstantExprs. 00018 // 00019 //===----------------------------------------------------------------------===// 00020 00021 #include "ConstantFolding.h" 00022 #include "llvm/Constants.h" 00023 #include "llvm/Instructions.h" 00024 #include "llvm/DerivedTypes.h" 00025 #include "llvm/Function.h" 00026 #include "llvm/Support/GetElementPtrTypeIterator.h" 00027 #include <cmath> 00028 using namespace llvm; 00029 00030 namespace { 00031 struct ConstRules { 00032 ConstRules() {} 00033 00034 // Binary Operators... 00035 virtual Constant *add(const Constant *V1, const Constant *V2) const = 0; 00036 virtual Constant *sub(const Constant *V1, const Constant *V2) const = 0; 00037 virtual Constant *mul(const Constant *V1, const Constant *V2) const = 0; 00038 virtual Constant *div(const Constant *V1, const Constant *V2) const = 0; 00039 virtual Constant *rem(const Constant *V1, const Constant *V2) const = 0; 00040 virtual Constant *op_and(const Constant *V1, const Constant *V2) const = 0; 00041 virtual Constant *op_or (const Constant *V1, const Constant *V2) const = 0; 00042 virtual Constant *op_xor(const Constant *V1, const Constant *V2) const = 0; 00043 virtual Constant *shl(const Constant *V1, const Constant *V2) const = 0; 00044 virtual Constant *shr(const Constant *V1, const Constant *V2) const = 0; 00045 virtual Constant *lessthan(const Constant *V1, const Constant *V2) const =0; 00046 virtual Constant *equalto(const Constant *V1, const Constant *V2) const = 0; 00047 00048 // Casting operators. 00049 virtual Constant *castToBool (const Constant *V) const = 0; 00050 virtual Constant *castToSByte (const Constant *V) const = 0; 00051 virtual Constant *castToUByte (const Constant *V) const = 0; 00052 virtual Constant *castToShort (const Constant *V) const = 0; 00053 virtual Constant *castToUShort(const Constant *V) const = 0; 00054 virtual Constant *castToInt (const Constant *V) const = 0; 00055 virtual Constant *castToUInt (const Constant *V) const = 0; 00056 virtual Constant *castToLong (const Constant *V) const = 0; 00057 virtual Constant *castToULong (const Constant *V) const = 0; 00058 virtual Constant *castToFloat (const Constant *V) const = 0; 00059 virtual Constant *castToDouble(const Constant *V) const = 0; 00060 virtual Constant *castToPointer(const Constant *V, 00061 const PointerType *Ty) const = 0; 00062 00063 // ConstRules::get - Return an instance of ConstRules for the specified 00064 // constant operands. 00065 // 00066 static ConstRules &get(const Constant *V1, const Constant *V2); 00067 private: 00068 ConstRules(const ConstRules &); // Do not implement 00069 ConstRules &operator=(const ConstRules &); // Do not implement 00070 }; 00071 } 00072 00073 00074 //===----------------------------------------------------------------------===// 00075 // TemplateRules Class 00076 //===----------------------------------------------------------------------===// 00077 // 00078 // TemplateRules - Implement a subclass of ConstRules that provides all 00079 // operations as noops. All other rules classes inherit from this class so 00080 // that if functionality is needed in the future, it can simply be added here 00081 // and to ConstRules without changing anything else... 00082 // 00083 // This class also provides subclasses with typesafe implementations of methods 00084 // so that don't have to do type casting. 00085 // 00086 template<class ArgType, class SubClassName> 00087 class TemplateRules : public ConstRules { 00088 00089 //===--------------------------------------------------------------------===// 00090 // Redirecting functions that cast to the appropriate types 00091 //===--------------------------------------------------------------------===// 00092 00093 virtual Constant *add(const Constant *V1, const Constant *V2) const { 00094 return SubClassName::Add((const ArgType *)V1, (const ArgType *)V2); 00095 } 00096 virtual Constant *sub(const Constant *V1, const Constant *V2) const { 00097 return SubClassName::Sub((const ArgType *)V1, (const ArgType *)V2); 00098 } 00099 virtual Constant *mul(const Constant *V1, const Constant *V2) const { 00100 return SubClassName::Mul((const ArgType *)V1, (const ArgType *)V2); 00101 } 00102 virtual Constant *div(const Constant *V1, const Constant *V2) const { 00103 return SubClassName::Div((const ArgType *)V1, (const ArgType *)V2); 00104 } 00105 virtual Constant *rem(const Constant *V1, const Constant *V2) const { 00106 return SubClassName::Rem((const ArgType *)V1, (const ArgType *)V2); 00107 } 00108 virtual Constant *op_and(const Constant *V1, const Constant *V2) const { 00109 return SubClassName::And((const ArgType *)V1, (const ArgType *)V2); 00110 } 00111 virtual Constant *op_or(const Constant *V1, const Constant *V2) const { 00112 return SubClassName::Or((const ArgType *)V1, (const ArgType *)V2); 00113 } 00114 virtual Constant *op_xor(const Constant *V1, const Constant *V2) const { 00115 return SubClassName::Xor((const ArgType *)V1, (const ArgType *)V2); 00116 } 00117 virtual Constant *shl(const Constant *V1, const Constant *V2) const { 00118 return SubClassName::Shl((const ArgType *)V1, (const ArgType *)V2); 00119 } 00120 virtual Constant *shr(const Constant *V1, const Constant *V2) const { 00121 return SubClassName::Shr((const ArgType *)V1, (const ArgType *)V2); 00122 } 00123 00124 virtual Constant *lessthan(const Constant *V1, const Constant *V2) const { 00125 return SubClassName::LessThan((const ArgType *)V1, (const ArgType *)V2); 00126 } 00127 virtual Constant *equalto(const Constant *V1, const Constant *V2) const { 00128 return SubClassName::EqualTo((const ArgType *)V1, (const ArgType *)V2); 00129 } 00130 00131 // Casting operators. ick 00132 virtual Constant *castToBool(const Constant *V) const { 00133 return SubClassName::CastToBool((const ArgType*)V); 00134 } 00135 virtual Constant *castToSByte(const Constant *V) const { 00136 return SubClassName::CastToSByte((const ArgType*)V); 00137 } 00138 virtual Constant *castToUByte(const Constant *V) const { 00139 return SubClassName::CastToUByte((const ArgType*)V); 00140 } 00141 virtual Constant *castToShort(const Constant *V) const { 00142 return SubClassName::CastToShort((const ArgType*)V); 00143 } 00144 virtual Constant *castToUShort(const Constant *V) const { 00145 return SubClassName::CastToUShort((const ArgType*)V); 00146 } 00147 virtual Constant *castToInt(const Constant *V) const { 00148 return SubClassName::CastToInt((const ArgType*)V); 00149 } 00150 virtual Constant *castToUInt(const Constant *V) const { 00151 return SubClassName::CastToUInt((const ArgType*)V); 00152 } 00153 virtual Constant *castToLong(const Constant *V) const { 00154 return SubClassName::CastToLong((const ArgType*)V); 00155 } 00156 virtual Constant *castToULong(const Constant *V) const { 00157 return SubClassName::CastToULong((const ArgType*)V); 00158 } 00159 virtual Constant *castToFloat(const Constant *V) const { 00160 return SubClassName::CastToFloat((const ArgType*)V); 00161 } 00162 virtual Constant *castToDouble(const Constant *V) const { 00163 return SubClassName::CastToDouble((const ArgType*)V); 00164 } 00165 virtual Constant *castToPointer(const Constant *V, 00166 const PointerType *Ty) const { 00167 return SubClassName::CastToPointer((const ArgType*)V, Ty); 00168 } 00169 00170 //===--------------------------------------------------------------------===// 00171 // Default "noop" implementations 00172 //===--------------------------------------------------------------------===// 00173 00174 static Constant *Add(const ArgType *V1, const ArgType *V2) { return 0; } 00175 static Constant *Sub(const ArgType *V1, const ArgType *V2) { return 0; } 00176 static Constant *Mul(const ArgType *V1, const ArgType *V2) { return 0; } 00177 static Constant *Div(const ArgType *V1, const ArgType *V2) { return 0; } 00178 static Constant *Rem(const ArgType *V1, const ArgType *V2) { return 0; } 00179 static Constant *And(const ArgType *V1, const ArgType *V2) { return 0; } 00180 static Constant *Or (const ArgType *V1, const ArgType *V2) { return 0; } 00181 static Constant *Xor(const ArgType *V1, const ArgType *V2) { return 0; } 00182 static Constant *Shl(const ArgType *V1, const ArgType *V2) { return 0; } 00183 static Constant *Shr(const ArgType *V1, const ArgType *V2) { return 0; } 00184 static Constant *LessThan(const ArgType *V1, const ArgType *V2) { 00185 return 0; 00186 } 00187 static Constant *EqualTo(const ArgType *V1, const ArgType *V2) { 00188 return 0; 00189 } 00190 00191 // Casting operators. ick 00192 static Constant *CastToBool (const Constant *V) { return 0; } 00193 static Constant *CastToSByte (const Constant *V) { return 0; } 00194 static Constant *CastToUByte (const Constant *V) { return 0; } 00195 static Constant *CastToShort (const Constant *V) { return 0; } 00196 static Constant *CastToUShort(const Constant *V) { return 0; } 00197 static Constant *CastToInt (const Constant *V) { return 0; } 00198 static Constant *CastToUInt (const Constant *V) { return 0; } 00199 static Constant *CastToLong (const Constant *V) { return 0; } 00200 static Constant *CastToULong (const Constant *V) { return 0; } 00201 static Constant *CastToFloat (const Constant *V) { return 0; } 00202 static Constant *CastToDouble(const Constant *V) { return 0; } 00203 static Constant *CastToPointer(const Constant *, 00204 const PointerType *) {return 0;} 00205 }; 00206 00207 00208 00209 //===----------------------------------------------------------------------===// 00210 // EmptyRules Class 00211 //===----------------------------------------------------------------------===// 00212 // 00213 // EmptyRules provides a concrete base class of ConstRules that does nothing 00214 // 00215 struct EmptyRules : public TemplateRules<Constant, EmptyRules> { 00216 static Constant *EqualTo(const Constant *V1, const Constant *V2) { 00217 if (V1 == V2) return ConstantBool::True; 00218 return 0; 00219 } 00220 }; 00221 00222 00223 00224 //===----------------------------------------------------------------------===// 00225 // BoolRules Class 00226 //===----------------------------------------------------------------------===// 00227 // 00228 // BoolRules provides a concrete base class of ConstRules for the 'bool' type. 00229 // 00230 struct BoolRules : public TemplateRules<ConstantBool, BoolRules> { 00231 00232 static Constant *LessThan(const ConstantBool *V1, const ConstantBool *V2){ 00233 return ConstantBool::get(V1->getValue() < V2->getValue()); 00234 } 00235 00236 static Constant *EqualTo(const Constant *V1, const Constant *V2) { 00237 return ConstantBool::get(V1 == V2); 00238 } 00239 00240 static Constant *And(const ConstantBool *V1, const ConstantBool *V2) { 00241 return ConstantBool::get(V1->getValue() & V2->getValue()); 00242 } 00243 00244 static Constant *Or(const ConstantBool *V1, const ConstantBool *V2) { 00245 return ConstantBool::get(V1->getValue() | V2->getValue()); 00246 } 00247 00248 static Constant *Xor(const ConstantBool *V1, const ConstantBool *V2) { 00249 return ConstantBool::get(V1->getValue() ^ V2->getValue()); 00250 } 00251 00252 // Casting operators. ick 00253 #define DEF_CAST(TYPE, CLASS, CTYPE) \ 00254 static Constant *CastTo##TYPE (const ConstantBool *V) { \ 00255 return CLASS::get(Type::TYPE##Ty, (CTYPE)(bool)V->getValue()); \ 00256 } 00257 00258 DEF_CAST(Bool , ConstantBool, bool) 00259 DEF_CAST(SByte , ConstantSInt, signed char) 00260 DEF_CAST(UByte , ConstantUInt, unsigned char) 00261 DEF_CAST(Short , ConstantSInt, signed short) 00262 DEF_CAST(UShort, ConstantUInt, unsigned short) 00263 DEF_CAST(Int , ConstantSInt, signed int) 00264 DEF_CAST(UInt , ConstantUInt, unsigned int) 00265 DEF_CAST(Long , ConstantSInt, int64_t) 00266 DEF_CAST(ULong , ConstantUInt, uint64_t) 00267 DEF_CAST(Float , ConstantFP , float) 00268 DEF_CAST(Double, ConstantFP , double) 00269 #undef DEF_CAST 00270 }; 00271 00272 00273 //===----------------------------------------------------------------------===// 00274 // NullPointerRules Class 00275 //===----------------------------------------------------------------------===// 00276 // 00277 // NullPointerRules provides a concrete base class of ConstRules for null 00278 // pointers. 00279 // 00280 struct NullPointerRules : public TemplateRules<ConstantPointerNull, 00281 NullPointerRules> { 00282 static Constant *EqualTo(const Constant *V1, const Constant *V2) { 00283 return ConstantBool::True; // Null pointers are always equal 00284 } 00285 static Constant *CastToBool(const Constant *V) { 00286 return ConstantBool::False; 00287 } 00288 static Constant *CastToSByte (const Constant *V) { 00289 return ConstantSInt::get(Type::SByteTy, 0); 00290 } 00291 static Constant *CastToUByte (const Constant *V) { 00292 return ConstantUInt::get(Type::UByteTy, 0); 00293 } 00294 static Constant *CastToShort (const Constant *V) { 00295 return ConstantSInt::get(Type::ShortTy, 0); 00296 } 00297 static Constant *CastToUShort(const Constant *V) { 00298 return ConstantUInt::get(Type::UShortTy, 0); 00299 } 00300 static Constant *CastToInt (const Constant *V) { 00301 return ConstantSInt::get(Type::IntTy, 0); 00302 } 00303 static Constant *CastToUInt (const Constant *V) { 00304 return ConstantUInt::get(Type::UIntTy, 0); 00305 } 00306 static Constant *CastToLong (const Constant *V) { 00307 return ConstantSInt::get(Type::LongTy, 0); 00308 } 00309 static Constant *CastToULong (const Constant *V) { 00310 return ConstantUInt::get(Type::ULongTy, 0); 00311 } 00312 static Constant *CastToFloat (const Constant *V) { 00313 return ConstantFP::get(Type::FloatTy, 0); 00314 } 00315 static Constant *CastToDouble(const Constant *V) { 00316 return ConstantFP::get(Type::DoubleTy, 0); 00317 } 00318 00319 static Constant *CastToPointer(const ConstantPointerNull *V, 00320 const PointerType *PTy) { 00321 return ConstantPointerNull::get(PTy); 00322 } 00323 }; 00324 00325 00326 //===----------------------------------------------------------------------===// 00327 // DirectRules Class 00328 //===----------------------------------------------------------------------===// 00329 // 00330 // DirectRules provides a concrete base classes of ConstRules for a variety of 00331 // different types. This allows the C++ compiler to automatically generate our 00332 // constant handling operations in a typesafe and accurate manner. 00333 // 00334 template<class ConstantClass, class BuiltinType, Type **Ty, class SuperClass> 00335 struct DirectRules : public TemplateRules<ConstantClass, SuperClass> { 00336 static Constant *Add(const ConstantClass *V1, const ConstantClass *V2) { 00337 BuiltinType R = (BuiltinType)V1->getValue() + (BuiltinType)V2->getValue(); 00338 return ConstantClass::get(*Ty, R); 00339 } 00340 00341 static Constant *Sub(const ConstantClass *V1, const ConstantClass *V2) { 00342 BuiltinType R = (BuiltinType)V1->getValue() - (BuiltinType)V2->getValue(); 00343 return ConstantClass::get(*Ty, R); 00344 } 00345 00346 static Constant *Mul(const ConstantClass *V1, const ConstantClass *V2) { 00347 BuiltinType R = (BuiltinType)V1->getValue() * (BuiltinType)V2->getValue(); 00348 return ConstantClass::get(*Ty, R); 00349 } 00350 00351 static Constant *Div(const ConstantClass *V1, const ConstantClass *V2) { 00352 if (V2->isNullValue()) return 0; 00353 BuiltinType R = (BuiltinType)V1->getValue() / (BuiltinType)V2->getValue(); 00354 return ConstantClass::get(*Ty, R); 00355 } 00356 00357 static Constant *LessThan(const ConstantClass *V1, const ConstantClass *V2) { 00358 bool R = (BuiltinType)V1->getValue() < (BuiltinType)V2->getValue(); 00359 return ConstantBool::get(R); 00360 } 00361 00362 static Constant *EqualTo(const ConstantClass *V1, const ConstantClass *V2) { 00363 bool R = (BuiltinType)V1->getValue() == (BuiltinType)V2->getValue(); 00364 return ConstantBool::get(R); 00365 } 00366 00367 static Constant *CastToPointer(const ConstantClass *V, 00368 const PointerType *PTy) { 00369 if (V->isNullValue()) // Is it a FP or Integral null value? 00370 return ConstantPointerNull::get(PTy); 00371 return 0; // Can't const prop other types of pointers 00372 } 00373 00374 // Casting operators. ick 00375 #define DEF_CAST(TYPE, CLASS, CTYPE) \ 00376 static Constant *CastTo##TYPE (const ConstantClass *V) { \ 00377 return CLASS::get(Type::TYPE##Ty, (CTYPE)(BuiltinType)V->getValue()); \ 00378 } 00379 00380 DEF_CAST(Bool , ConstantBool, bool) 00381 DEF_CAST(SByte , ConstantSInt, signed char) 00382 DEF_CAST(UByte , ConstantUInt, unsigned char) 00383 DEF_CAST(Short , ConstantSInt, signed short) 00384 DEF_CAST(UShort, ConstantUInt, unsigned short) 00385 DEF_CAST(Int , ConstantSInt, signed int) 00386 DEF_CAST(UInt , ConstantUInt, unsigned int) 00387 DEF_CAST(Long , ConstantSInt, int64_t) 00388 DEF_CAST(ULong , ConstantUInt, uint64_t) 00389 DEF_CAST(Float , ConstantFP , float) 00390 DEF_CAST(Double, ConstantFP , double) 00391 #undef DEF_CAST 00392 }; 00393 00394 00395 //===----------------------------------------------------------------------===// 00396 // DirectIntRules Class 00397 //===----------------------------------------------------------------------===// 00398 // 00399 // DirectIntRules provides implementations of functions that are valid on 00400 // integer types, but not all types in general. 00401 // 00402 template <class ConstantClass, class BuiltinType, Type **Ty> 00403 struct DirectIntRules 00404 : public DirectRules<ConstantClass, BuiltinType, Ty, 00405 DirectIntRules<ConstantClass, BuiltinType, Ty> > { 00406 00407 static Constant *Div(const ConstantClass *V1, const ConstantClass *V2) { 00408 if (V2->isNullValue()) return 0; 00409 if (V2->isAllOnesValue() && // MIN_INT / -1 00410 (BuiltinType)V1->getValue() == -(BuiltinType)V1->getValue()) 00411 return 0; 00412 BuiltinType R = (BuiltinType)V1->getValue() / (BuiltinType)V2->getValue(); 00413 return ConstantClass::get(*Ty, R); 00414 } 00415 00416 static Constant *Rem(const ConstantClass *V1, 00417 const ConstantClass *V2) { 00418 if (V2->isNullValue()) return 0; // X / 0 00419 if (V2->isAllOnesValue() && // MIN_INT / -1 00420 (BuiltinType)V1->getValue() == -(BuiltinType)V1->getValue()) 00421 return 0; 00422 BuiltinType R = (BuiltinType)V1->getValue() % (BuiltinType)V2->getValue(); 00423 return ConstantClass::get(*Ty, R); 00424 } 00425 00426 static Constant *And(const ConstantClass *V1, const ConstantClass *V2) { 00427 BuiltinType R = (BuiltinType)V1->getValue() & (BuiltinType)V2->getValue(); 00428 return ConstantClass::get(*Ty, R); 00429 } 00430 static Constant *Or(const ConstantClass *V1, const ConstantClass *V2) { 00431 BuiltinType R = (BuiltinType)V1->getValue() | (BuiltinType)V2->getValue(); 00432 return ConstantClass::get(*Ty, R); 00433 } 00434 static Constant *Xor(const ConstantClass *V1, const ConstantClass *V2) { 00435 BuiltinType R = (BuiltinType)V1->getValue() ^ (BuiltinType)V2->getValue(); 00436 return ConstantClass::get(*Ty, R); 00437 } 00438 00439 static Constant *Shl(const ConstantClass *V1, const ConstantClass *V2) { 00440 BuiltinType R = (BuiltinType)V1->getValue() << (BuiltinType)V2->getValue(); 00441 return ConstantClass::get(*Ty, R); 00442 } 00443 00444 static Constant *Shr(const ConstantClass *V1, const ConstantClass *V2) { 00445 BuiltinType R = (BuiltinType)V1->getValue() >> (BuiltinType)V2->getValue(); 00446 return ConstantClass::get(*Ty, R); 00447 } 00448 }; 00449 00450 00451 //===----------------------------------------------------------------------===// 00452 // DirectFPRules Class 00453 //===----------------------------------------------------------------------===// 00454 // 00455 /// DirectFPRules provides implementations of functions that are valid on 00456 /// floating point types, but not all types in general. 00457 /// 00458 template <class ConstantClass, class BuiltinType, Type **Ty> 00459 struct DirectFPRules 00460 : public DirectRules<ConstantClass, BuiltinType, Ty, 00461 DirectFPRules<ConstantClass, BuiltinType, Ty> > { 00462 static Constant *Rem(const ConstantClass *V1, const ConstantClass *V2) { 00463 if (V2->isNullValue()) return 0; 00464 BuiltinType Result = std::fmod((BuiltinType)V1->getValue(), 00465 (BuiltinType)V2->getValue()); 00466 return ConstantClass::get(*Ty, Result); 00467 } 00468 }; 00469 00470 00471 /// ConstRules::get - This method returns the constant rules implementation that 00472 /// implements the semantics of the two specified constants. 00473 ConstRules &ConstRules::get(const Constant *V1, const Constant *V2) { 00474 static EmptyRules EmptyR; 00475 static BoolRules BoolR; 00476 static NullPointerRules NullPointerR; 00477 static DirectIntRules<ConstantSInt, signed char , &Type::SByteTy> SByteR; 00478 static DirectIntRules<ConstantUInt, unsigned char , &Type::UByteTy> UByteR; 00479 static DirectIntRules<ConstantSInt, signed short, &Type::ShortTy> ShortR; 00480 static DirectIntRules<ConstantUInt, unsigned short, &Type::UShortTy> UShortR; 00481 static DirectIntRules<ConstantSInt, signed int , &Type::IntTy> IntR; 00482 static DirectIntRules<ConstantUInt, unsigned int , &Type::UIntTy> UIntR; 00483 static DirectIntRules<ConstantSInt, int64_t , &Type::LongTy> LongR; 00484 static DirectIntRules<ConstantUInt, uint64_t , &Type::ULongTy> ULongR; 00485 static DirectFPRules <ConstantFP , float , &Type::FloatTy> FloatR; 00486 static DirectFPRules <ConstantFP , double , &Type::DoubleTy> DoubleR; 00487 00488 if (isa<ConstantExpr>(V1) || isa<ConstantExpr>(V2) || 00489 isa<GlobalValue>(V1) || isa<GlobalValue>(V2) || 00490 isa<UndefValue>(V1) || isa<UndefValue>(V2)) 00491 return EmptyR; 00492 00493 switch (V1->getType()->getTypeID()) { 00494 default: assert(0 && "Unknown value type for constant folding!"); 00495 case Type::BoolTyID: return BoolR; 00496 case Type::PointerTyID: return NullPointerR; 00497 case Type::SByteTyID: return SByteR; 00498 case Type::UByteTyID: return UByteR; 00499 case Type::ShortTyID: return ShortR; 00500 case Type::UShortTyID: return UShortR; 00501 case Type::IntTyID: return IntR; 00502 case Type::UIntTyID: return UIntR; 00503 case Type::LongTyID: return LongR; 00504 case Type::ULongTyID: return ULongR; 00505 case Type::FloatTyID: return FloatR; 00506 case Type::DoubleTyID: return DoubleR; 00507 } 00508 } 00509 00510 00511 //===----------------------------------------------------------------------===// 00512 // ConstantFold*Instruction Implementations 00513 //===----------------------------------------------------------------------===// 00514 // 00515 // These methods contain the special case hackery required to symbolically 00516 // evaluate some constant expression cases, and use the ConstantRules class to 00517 // evaluate normal constants. 00518 // 00519 static unsigned getSize(const Type *Ty) { 00520 unsigned S = Ty->getPrimitiveSize(); 00521 return S ? S : 8; // Treat pointers at 8 bytes 00522 } 00523 00524 Constant *llvm::ConstantFoldCastInstruction(const Constant *V, 00525 const Type *DestTy) { 00526 if (V->getType() == DestTy) return (Constant*)V; 00527 00528 // Cast of a global address to boolean is always true. 00529 if (const GlobalValue *GV = dyn_cast<GlobalValue>(V)) { 00530 if (DestTy == Type::BoolTy) 00531 // FIXME: When we support 'external weak' references, we have to prevent 00532 // this transformation from happening. In the meantime we avoid folding 00533 // any cast of an external symbol. 00534 if (!GV->isExternal()) 00535 return ConstantBool::True; 00536 } else if (const ConstantExpr *CE = dyn_cast<ConstantExpr>(V)) { 00537 if (CE->getOpcode() == Instruction::Cast) { 00538 Constant *Op = const_cast<Constant*>(CE->getOperand(0)); 00539 // Try to not produce a cast of a cast, which is almost always redundant. 00540 if (!Op->getType()->isFloatingPoint() && 00541 !CE->getType()->isFloatingPoint() && 00542 !DestTy->isFloatingPoint()) { 00543 unsigned S1 = getSize(Op->getType()), S2 = getSize(CE->getType()); 00544 unsigned S3 = getSize(DestTy); 00545 if (Op->getType() == DestTy && S3 >= S2) 00546 return Op; 00547 if (S1 >= S2 && S2 >= S3) 00548 return ConstantExpr::getCast(Op, DestTy); 00549 if (S1 <= S2 && S2 >= S3 && S1 <= S3) 00550 return ConstantExpr::getCast(Op, DestTy); 00551 } 00552 } else if (CE->getOpcode() == Instruction::GetElementPtr) { 00553 // If all of the indexes in the GEP are null values, there is no pointer 00554 // adjustment going on. We might as well cast the source pointer. 00555 bool isAllNull = true; 00556 for (unsigned i = 1, e = CE->getNumOperands(); i != e; ++i) 00557 if (!CE->getOperand(i)->isNullValue()) { 00558 isAllNull = false; 00559 break; 00560 } 00561 if (isAllNull) 00562 return ConstantExpr::getCast(CE->getOperand(0), DestTy); 00563 } 00564 } else if (isa<UndefValue>(V)) { 00565 return UndefValue::get(DestTy); 00566 } 00567 00568 // Check to see if we are casting an pointer to an aggregate to a pointer to 00569 // the first element. If so, return the appropriate GEP instruction. 00570 if (const PointerType *PTy = dyn_cast<PointerType>(V->getType())) 00571 if (const PointerType *DPTy = dyn_cast<PointerType>(DestTy)) { 00572 std::vector<Value*> IdxList; 00573 IdxList.push_back(Constant::getNullValue(Type::IntTy)); 00574 const Type *ElTy = PTy->getElementType(); 00575 while (ElTy != DPTy->getElementType()) { 00576 if (const StructType *STy = dyn_cast<StructType>(ElTy)) { 00577 if (STy->getNumElements() == 0) break; 00578 ElTy = STy->getElementType(0); 00579 IdxList.push_back(Constant::getNullValue(Type::UIntTy)); 00580 } else if (const SequentialType *STy = dyn_cast<SequentialType>(ElTy)) { 00581 if (isa<PointerType>(ElTy)) break; // Can't index into pointers! 00582 ElTy = STy->getElementType(); 00583 IdxList.push_back(IdxList[0]); 00584 } else { 00585 break; 00586 } 00587 } 00588 00589 if (ElTy == DPTy->getElementType()) 00590 return ConstantExpr::getGetElementPtr(const_cast<Constant*>(V),IdxList); 00591 } 00592 00593 ConstRules &Rules = ConstRules::get(V, V); 00594 00595 switch (DestTy->getTypeID()) { 00596 case Type::BoolTyID: return Rules.castToBool(V); 00597 case Type::UByteTyID: return Rules.castToUByte(V); 00598 case Type::SByteTyID: return Rules.castToSByte(V); 00599 case Type::UShortTyID: return Rules.castToUShort(V); 00600 case Type::ShortTyID: return Rules.castToShort(V); 00601 case Type::UIntTyID: return Rules.castToUInt(V); 00602 case Type::IntTyID: return Rules.castToInt(V); 00603 case Type::ULongTyID: return Rules.castToULong(V); 00604 case Type::LongTyID: return Rules.castToLong(V); 00605 case Type::FloatTyID: return Rules.castToFloat(V); 00606 case Type::DoubleTyID: return Rules.castToDouble(V); 00607 case Type::PointerTyID: 00608 return Rules.castToPointer(V, cast<PointerType>(DestTy)); 00609 default: return 0; 00610 } 00611 } 00612 00613 Constant *llvm::ConstantFoldSelectInstruction(const Constant *Cond, 00614 const Constant *V1, 00615 const Constant *V2) { 00616 if (Cond == ConstantBool::True) 00617 return const_cast<Constant*>(V1); 00618 else if (Cond == ConstantBool::False) 00619 return const_cast<Constant*>(V2); 00620 00621 if (isa<UndefValue>(V1)) return const_cast<Constant*>(V2); 00622 if (isa<UndefValue>(V2)) return const_cast<Constant*>(V1); 00623 if (isa<UndefValue>(Cond)) return const_cast<Constant*>(V1); 00624 return 0; 00625 } 00626 00627 00628 /// IdxCompare - Compare the two constants as though they were getelementptr 00629 /// indices. This allows coersion of the types to be the same thing. 00630 /// 00631 /// If the two constants are the "same" (after coersion), return 0. If the 00632 /// first is less than the second, return -1, if the second is less than the 00633 /// first, return 1. If the constants are not integral, return -2. 00634 /// 00635 static int IdxCompare(Constant *C1, Constant *C2) { 00636 if (C1 == C2) return 0; 00637 00638 // Ok, we found a different index. Are either of the operands 00639 // ConstantExprs? If so, we can't do anything with them. 00640 if (!isa<ConstantInt>(C1) || !isa<ConstantInt>(C2)) 00641 return -2; // don't know! 00642 00643 // Ok, we have two differing integer indices. Sign extend them to be the same 00644 // type. Long is always big enough, so we use it. 00645 C1 = ConstantExpr::getSignExtend(C1, Type::LongTy); 00646 C2 = ConstantExpr::getSignExtend(C2, Type::LongTy); 00647 if (C1 == C2) return 0; // Are they just differing types? 00648 00649 // If they are really different, now that they are the same type, then we 00650 // found a difference! 00651 if (cast<ConstantSInt>(C1)->getValue() < cast<ConstantSInt>(C2)->getValue()) 00652 return -1; 00653 else 00654 return 1; 00655 } 00656 00657 /// evaluateRelation - This function determines if there is anything we can 00658 /// decide about the two constants provided. This doesn't need to handle simple 00659 /// things like integer comparisons, but should instead handle ConstantExprs 00660 /// and GlobalValuess. If we can determine that the two constants have a 00661 /// particular relation to each other, we should return the corresponding SetCC 00662 /// code, otherwise return Instruction::BinaryOpsEnd. 00663 /// 00664 /// To simplify this code we canonicalize the relation so that the first 00665 /// operand is always the most "complex" of the two. We consider simple 00666 /// constants (like ConstantInt) to be the simplest, followed by 00667 /// GlobalValues, followed by ConstantExpr's (the most complex). 00668 /// 00669 static Instruction::BinaryOps evaluateRelation(const Constant *V1, 00670 const Constant *V2) { 00671 assert(V1->getType() == V2->getType() && 00672 "Cannot compare different types of values!"); 00673 if (V1 == V2) return Instruction::SetEQ; 00674 00675 if (!isa<ConstantExpr>(V1) && !isa<GlobalValue>(V1)) { 00676 // If the first operand is simple, swap operands. 00677 assert((isa<GlobalValue>(V2) || isa<ConstantExpr>(V2)) && 00678 "Simple cases should have been handled by caller!"); 00679 Instruction::BinaryOps SwappedRelation = evaluateRelation(V2, V1); 00680 if (SwappedRelation != Instruction::BinaryOpsEnd) 00681 return SetCondInst::getSwappedCondition(SwappedRelation); 00682 00683 } else if (const GlobalValue *CPR1 = dyn_cast<GlobalValue>(V1)){ 00684 if (isa<ConstantExpr>(V2)) { // Swap as necessary. 00685 Instruction::BinaryOps SwappedRelation = evaluateRelation(V2, V1); 00686 if (SwappedRelation != Instruction::BinaryOpsEnd) 00687 return SetCondInst::getSwappedCondition(SwappedRelation); 00688 else 00689 return Instruction::BinaryOpsEnd; 00690 } 00691 00692 // Now we know that the RHS is a GlobalValue or simple constant, 00693 // which (since the types must match) means that it's a ConstantPointerNull. 00694 if (const GlobalValue *CPR2 = dyn_cast<GlobalValue>(V2)) { 00695 assert(CPR1 != CPR2 && 00696 "GVs for the same value exist at different addresses??"); 00697 // FIXME: If both globals are external weak, they might both be null! 00698 return Instruction::SetNE; 00699 } else { 00700 assert(isa<ConstantPointerNull>(V2) && "Canonicalization guarantee!"); 00701 // Global can never be null. FIXME: if we implement external weak 00702 // linkage, this is not necessarily true! 00703 return Instruction::SetNE; 00704 } 00705 00706 } else { 00707 // Ok, the LHS is known to be a constantexpr. The RHS can be any of a 00708 // constantexpr, a CPR, or a simple constant. 00709 const ConstantExpr *CE1 = cast<ConstantExpr>(V1); 00710 Constant *CE1Op0 = CE1->getOperand(0); 00711 00712 switch (CE1->getOpcode()) { 00713 case Instruction::Cast: 00714 // If the cast is not actually changing bits, and the second operand is a 00715 // null pointer, do the comparison with the pre-casted value. 00716 if (V2->isNullValue() && 00717 CE1->getType()->isLosslesslyConvertibleTo(CE1Op0->getType())) 00718 return evaluateRelation(CE1Op0, 00719 Constant::getNullValue(CE1Op0->getType())); 00720 break; 00721 00722 case Instruction::GetElementPtr: 00723 // Ok, since this is a getelementptr, we know that the constant has a 00724 // pointer type. Check the various cases. 00725 if (isa<ConstantPointerNull>(V2)) { 00726 // If we are comparing a GEP to a null pointer, check to see if the base 00727 // of the GEP equals the null pointer. 00728 if (isa<GlobalValue>(CE1Op0)) { 00729 // FIXME: this is not true when we have external weak references! 00730 // No offset can go from a global to a null pointer. 00731 return Instruction::SetGT; 00732 } else if (isa<ConstantPointerNull>(CE1Op0)) { 00733 // If we are indexing from a null pointer, check to see if we have any 00734 // non-zero indices. 00735 for (unsigned i = 1, e = CE1->getNumOperands(); i != e; ++i) 00736 if (!CE1->getOperand(i)->isNullValue()) 00737 // Offsetting from null, must not be equal. 00738 return Instruction::SetGT; 00739 // Only zero indexes from null, must still be zero. 00740 return Instruction::SetEQ; 00741 } 00742 // Otherwise, we can't really say if the first operand is null or not. 00743 } else if (const GlobalValue *CPR2 = dyn_cast<GlobalValue>(V2)) { 00744 if (isa<ConstantPointerNull>(CE1Op0)) { 00745 // FIXME: This is not true with external weak references. 00746 return Instruction::SetLT; 00747 } else if (const GlobalValue *CPR1 = dyn_cast<GlobalValue>(CE1Op0)) { 00748 if (CPR1 == CPR2) { 00749 // If this is a getelementptr of the same global, then it must be 00750 // different. Because the types must match, the getelementptr could 00751 // only have at most one index, and because we fold getelementptr's 00752 // with a single zero index, it must be nonzero. 00753 assert(CE1->getNumOperands() == 2 && 00754 !CE1->getOperand(1)->isNullValue() && 00755 "Suprising getelementptr!"); 00756 return Instruction::SetGT; 00757 } else { 00758 // If they are different globals, we don't know what the value is, 00759 // but they can't be equal. 00760 return Instruction::SetNE; 00761 } 00762 } 00763 } else { 00764 const ConstantExpr *CE2 = cast<ConstantExpr>(V2); 00765 const Constant *CE2Op0 = CE2->getOperand(0); 00766 00767 // There are MANY other foldings that we could perform here. They will 00768 // probably be added on demand, as they seem needed. 00769 switch (CE2->getOpcode()) { 00770 default: break; 00771 case Instruction::GetElementPtr: 00772 // By far the most common case to handle is when the base pointers are 00773 // obviously to the same or different globals. 00774 if (isa<GlobalValue>(CE1Op0) && isa<GlobalValue>(CE2Op0)) { 00775 if (CE1Op0 != CE2Op0) // Don't know relative ordering, but not equal 00776 return Instruction::SetNE; 00777 // Ok, we know that both getelementptr instructions are based on the 00778 // same global. From this, we can precisely determine the relative 00779 // ordering of the resultant pointers. 00780 unsigned i = 1; 00781 00782 // Compare all of the operands the GEP's have in common. 00783 for (;i != CE1->getNumOperands() && i != CE2->getNumOperands(); ++i) 00784 switch (IdxCompare(CE1->getOperand(i), CE2->getOperand(i))) { 00785 case -1: return Instruction::SetLT; 00786 case 1: return Instruction::SetGT; 00787 case -2: return Instruction::BinaryOpsEnd; 00788 } 00789 00790 // Ok, we ran out of things they have in common. If any leftovers 00791 // are non-zero then we have a difference, otherwise we are equal. 00792 for (; i < CE1->getNumOperands(); ++i) 00793 if (!CE1->getOperand(i)->isNullValue()) 00794 return Instruction::SetGT; 00795 for (; i < CE2->getNumOperands(); ++i) 00796 if (!CE2->getOperand(i)->isNullValue()) 00797 return Instruction::SetLT; 00798 return Instruction::SetEQ; 00799 } 00800 } 00801 } 00802 00803 default: 00804 break; 00805 } 00806 } 00807 00808 return Instruction::BinaryOpsEnd; 00809 } 00810 00811 Constant *llvm::ConstantFoldBinaryInstruction(unsigned Opcode, 00812 const Constant *V1, 00813 const Constant *V2) { 00814 Constant *C = 0; 00815 switch (Opcode) { 00816 default: break; 00817 case Instruction::Add: C = ConstRules::get(V1, V2).add(V1, V2); break; 00818 case Instruction::Sub: C = ConstRules::get(V1, V2).sub(V1, V2); break; 00819 case Instruction::Mul: C = ConstRules::get(V1, V2).mul(V1, V2); break; 00820 case Instruction::Div: C = ConstRules::get(V1, V2).div(V1, V2); break; 00821 case Instruction::Rem: C = ConstRules::get(V1, V2).rem(V1, V2); break; 00822 case Instruction::And: C = ConstRules::get(V1, V2).op_and(V1, V2); break; 00823 case Instruction::Or: C = ConstRules::get(V1, V2).op_or (V1, V2); break; 00824 case Instruction::Xor: C = ConstRules::get(V1, V2).op_xor(V1, V2); break; 00825 case Instruction::Shl: C = ConstRules::get(V1, V2).shl(V1, V2); break; 00826 case Instruction::Shr: C = ConstRules::get(V1, V2).shr(V1, V2); break; 00827 case Instruction::SetEQ: C = ConstRules::get(V1, V2).equalto(V1, V2); break; 00828 case Instruction::SetLT: C = ConstRules::get(V1, V2).lessthan(V1, V2);break; 00829 case Instruction::SetGT: C = ConstRules::get(V1, V2).lessthan(V2, V1);break; 00830 case Instruction::SetNE: // V1 != V2 === !(V1 == V2) 00831 C = ConstRules::get(V1, V2).equalto(V1, V2); 00832 if (C) return ConstantExpr::get(Instruction::Xor, C, ConstantBool::True); 00833 break; 00834 case Instruction::SetLE: // V1 <= V2 === !(V2 < V1) 00835 C = ConstRules::get(V1, V2).lessthan(V2, V1); 00836 if (C) return ConstantExpr::get(Instruction::Xor, C, ConstantBool::True); 00837 break; 00838 case Instruction::SetGE: // V1 >= V2 === !(V1 < V2) 00839 C = ConstRules::get(V1, V2).lessthan(V1, V2); 00840 if (C) return ConstantExpr::get(Instruction::Xor, C, ConstantBool::True); 00841 break; 00842 } 00843 00844 // If we successfully folded the expression, return it now. 00845 if (C) return C; 00846 00847 if (SetCondInst::isRelational(Opcode)) { 00848 if (isa<UndefValue>(V1) || isa<UndefValue>(V2)) 00849 return UndefValue::get(Type::BoolTy); 00850 switch (evaluateRelation(V1, V2)) { 00851 default: assert(0 && "Unknown relational!"); 00852 case Instruction::BinaryOpsEnd: 00853 break; // Couldn't determine anything about these constants. 00854 case Instruction::SetEQ: // We know the constants are equal! 00855 // If we know the constants are equal, we can decide the result of this 00856 // computation precisely. 00857 return ConstantBool::get(Opcode == Instruction::SetEQ || 00858 Opcode == Instruction::SetLE || 00859 Opcode == Instruction::SetGE); 00860 case Instruction::SetLT: 00861 // If we know that V1 < V2, we can decide the result of this computation 00862 // precisely. 00863 return ConstantBool::get(Opcode == Instruction::SetLT || 00864 Opcode == Instruction::SetNE || 00865 Opcode == Instruction::SetLE); 00866 case Instruction::SetGT: 00867 // If we know that V1 > V2, we can decide the result of this computation 00868 // precisely. 00869 return ConstantBool::get(Opcode == Instruction::SetGT || 00870 Opcode == Instruction::SetNE || 00871 Opcode == Instruction::SetGE); 00872 case Instruction::SetLE: 00873 // If we know that V1 <= V2, we can only partially decide this relation. 00874 if (Opcode == Instruction::SetGT) return ConstantBool::False; 00875 if (Opcode == Instruction::SetLT) return ConstantBool::True; 00876 break; 00877 00878 case Instruction::SetGE: 00879 // If we know that V1 >= V2, we can only partially decide this relation. 00880 if (Opcode == Instruction::SetLT) return ConstantBool::False; 00881 if (Opcode == Instruction::SetGT) return ConstantBool::True; 00882 break; 00883 00884 case Instruction::SetNE: 00885 // If we know that V1 != V2, we can only partially decide this relation. 00886 if (Opcode == Instruction::SetEQ) return ConstantBool::False; 00887 if (Opcode == Instruction::SetNE) return ConstantBool::True; 00888 break; 00889 } 00890 } 00891 00892 if (isa<UndefValue>(V1) || isa<UndefValue>(V2)) { 00893 switch (Opcode) { 00894 case Instruction::Add: 00895 case Instruction::Sub: 00896 case Instruction::Xor: 00897 return UndefValue::get(V1->getType()); 00898 00899 case Instruction::Mul: 00900 case Instruction::And: 00901 return Constant::getNullValue(V1->getType()); 00902 case Instruction::Div: 00903 case Instruction::Rem: 00904 if (!isa<UndefValue>(V2)) // undef/X -> 0 00905 return Constant::getNullValue(V1->getType()); 00906 return const_cast<Constant*>(V2); // X/undef -> undef 00907 case Instruction::Or: // X|undef -> -1 00908 return ConstantInt::getAllOnesValue(V1->getType()); 00909 case Instruction::Shr: 00910 if (!isa<UndefValue>(V2)) { 00911 if (V1->getType()->isSigned()) 00912 return const_cast<Constant*>(V1); // undef >>s X -> undef 00913 // undef >>u X -> 0 00914 } else if (isa<UndefValue>(V1)) { 00915 return const_cast<Constant*>(V1); // undef >> undef -> undef 00916 } else { 00917 if (V1->getType()->isSigned()) 00918 return const_cast<Constant*>(V1); // X >>s undef -> X 00919 // X >>u undef -> 0 00920 } 00921 return Constant::getNullValue(V1->getType()); 00922 00923 case Instruction::Shl: 00924 // undef << X -> 0 X << undef -> 0 00925 return Constant::getNullValue(V1->getType()); 00926 } 00927 } 00928 00929 if (const ConstantExpr *CE1 = dyn_cast<ConstantExpr>(V1)) { 00930 if (const ConstantExpr *CE2 = dyn_cast<ConstantExpr>(V2)) { 00931 // There are many possible foldings we could do here. We should probably 00932 // at least fold add of a pointer with an integer into the appropriate 00933 // getelementptr. This will improve alias analysis a bit. 00934 00935 00936 00937 00938 } else { 00939 // Just implement a couple of simple identities. 00940 switch (Opcode) { 00941 case Instruction::Add: 00942 if (V2->isNullValue()) return const_cast<Constant*>(V1); // X + 0 == X 00943 break; 00944 case Instruction::Sub: 00945 if (V2->isNullValue()) return const_cast<Constant*>(V1); // X - 0 == X 00946 break; 00947 case Instruction::Mul: 00948 if (V2->isNullValue()) return const_cast<Constant*>(V2); // X * 0 == 0 00949 if (const ConstantInt *CI = dyn_cast<ConstantInt>(V2)) 00950 if (CI->getRawValue() == 1) 00951 return const_cast<Constant*>(V1); // X * 1 == X 00952 break; 00953 case Instruction::Div: 00954 if (const ConstantInt *CI = dyn_cast<ConstantInt>(V2)) 00955 if (CI->getRawValue() == 1) 00956 return const_cast<Constant*>(V1); // X / 1 == X 00957 break; 00958 case Instruction::Rem: 00959 if (const ConstantInt *CI = dyn_cast<ConstantInt>(V2)) 00960 if (CI->getRawValue() == 1) 00961 return Constant::getNullValue(CI->getType()); // X % 1 == 0 00962 break; 00963 case Instruction::And: 00964 if (cast<ConstantIntegral>(V2)->isAllOnesValue()) 00965 return const_cast<Constant*>(V1); // X & -1 == X 00966 if (V2->isNullValue()) return const_cast<Constant*>(V2); // X & 0 == 0 00967 if (CE1->getOpcode() == Instruction::Cast && 00968 isa<GlobalValue>(CE1->getOperand(0))) { 00969 GlobalValue *CPR = cast<GlobalValue>(CE1->getOperand(0)); 00970 00971 // Functions are at least 4-byte aligned. If and'ing the address of a 00972 // function with a constant < 4, fold it to zero. 00973 if (const ConstantInt *CI = dyn_cast<ConstantInt>(V2)) 00974 if (CI->getRawValue() < 4 && isa<Function>(CPR)) 00975 return Constant::getNullValue(CI->getType()); 00976 } 00977 break; 00978 case Instruction::Or: 00979 if (V2->isNullValue()) return const_cast<Constant*>(V1); // X | 0 == X 00980 if (cast<ConstantIntegral>(V2)->isAllOnesValue()) 00981 return const_cast<Constant*>(V2); // X | -1 == -1 00982 break; 00983 case Instruction::Xor: 00984 if (V2->isNullValue()) return const_cast<Constant*>(V1); // X ^ 0 == X 00985 break; 00986 } 00987 } 00988 00989 } else if (const ConstantExpr *CE2 = dyn_cast<ConstantExpr>(V2)) { 00990 // If V2 is a constant expr and V1 isn't, flop them around and fold the 00991 // other way if possible. 00992 switch (Opcode) { 00993 case Instruction::Add: 00994 case Instruction::Mul: 00995 case Instruction::And: 00996 case Instruction::Or: 00997 case Instruction::Xor: 00998 case Instruction::SetEQ: 00999 case Instruction::SetNE: 01000 // No change of opcode required. 01001 return ConstantFoldBinaryInstruction(Opcode, V2, V1); 01002 01003 case Instruction::SetLT: 01004 case Instruction::SetGT: 01005 case Instruction::SetLE: 01006 case Instruction::SetGE: 01007 // Change the opcode as necessary to swap the operands. 01008 Opcode = SetCondInst::getSwappedCondition((Instruction::BinaryOps)Opcode); 01009 return ConstantFoldBinaryInstruction(Opcode, V2, V1); 01010 01011 case Instruction::Shl: 01012 case Instruction::Shr: 01013 case Instruction::Sub: 01014 case Instruction::Div: 01015 case Instruction::Rem: 01016 default: // These instructions cannot be flopped around. 01017 break; 01018 } 01019 } 01020 return 0; 01021 } 01022 01023 Constant *llvm::ConstantFoldGetElementPtr(const Constant *C, 01024 const std::vector<Value*> &IdxList) { 01025 if (IdxList.size() == 0 || 01026 (IdxList.size() == 1 && cast<Constant>(IdxList[0])->isNullValue())) 01027 return const_cast<Constant*>(C); 01028 01029 if (isa<UndefValue>(C)) { 01030 const Type *Ty = GetElementPtrInst::getIndexedType(C->getType(), IdxList, 01031 true); 01032 assert(Ty != 0 && "Invalid indices for GEP!"); 01033 return UndefValue::get(PointerType::get(Ty)); 01034 } 01035 01036 Constant *Idx0 = cast<Constant>(IdxList[0]); 01037 if (C->isNullValue()) { 01038 bool isNull = true; 01039 for (unsigned i = 0, e = IdxList.size(); i != e; ++i) 01040 if (!cast<Constant>(IdxList[i])->isNullValue()) { 01041 isNull = false; 01042 break; 01043 } 01044 if (isNull) { 01045 const Type *Ty = GetElementPtrInst::getIndexedType(C->getType(), IdxList, 01046 true); 01047 assert(Ty != 0 && "Invalid indices for GEP!"); 01048 return ConstantPointerNull::get(PointerType::get(Ty)); 01049 } 01050 01051 if (IdxList.size() == 1) { 01052 const Type *ElTy = cast<PointerType>(C->getType())->getElementType(); 01053 if (unsigned ElSize = ElTy->getPrimitiveSize()) { 01054 // gep null, C is equal to C*sizeof(nullty). If nullty is a known llvm 01055 // type, we can statically fold this. 01056 Constant *R = ConstantUInt::get(Type::UIntTy, ElSize); 01057 R = ConstantExpr::getCast(R, Idx0->getType()); 01058 R = ConstantExpr::getMul(R, Idx0); 01059 return ConstantExpr::getCast(R, C->getType()); 01060 } 01061 } 01062 } 01063 01064 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(const_cast<Constant*>(C))) { 01065 // Combine Indices - If the source pointer to this getelementptr instruction 01066 // is a getelementptr instruction, combine the indices of the two 01067 // getelementptr instructions into a single instruction. 01068 // 01069 if (CE->getOpcode() == Instruction::GetElementPtr) { 01070 const Type *LastTy = 0; 01071 for (gep_type_iterator I = gep_type_begin(CE), E = gep_type_end(CE); 01072 I != E; ++I) 01073 LastTy = *I; 01074 01075 if ((LastTy && isa<ArrayType>(LastTy)) || Idx0->isNullValue()) { 01076 std::vector<Value*> NewIndices; 01077 NewIndices.reserve(IdxList.size() + CE->getNumOperands()); 01078 for (unsigned i = 1, e = CE->getNumOperands()-1; i != e; ++i) 01079 NewIndices.push_back(CE->getOperand(i)); 01080 01081 // Add the last index of the source with the first index of the new GEP. 01082 // Make sure to handle the case when they are actually different types. 01083 Constant *Combined = CE->getOperand(CE->getNumOperands()-1); 01084 // Otherwise it must be an array. 01085 if (!Idx0->isNullValue()) { 01086 const Type *IdxTy = Combined->getType(); 01087 if (IdxTy != Idx0->getType()) IdxTy = Type::LongTy; 01088 Combined = 01089 ConstantExpr::get(Instruction::Add, 01090 ConstantExpr::getCast(Idx0, IdxTy), 01091 ConstantExpr::getCast(Combined, IdxTy)); 01092 } 01093 01094 NewIndices.push_back(Combined); 01095 NewIndices.insert(NewIndices.end(), IdxList.begin()+1, IdxList.end()); 01096 return ConstantExpr::getGetElementPtr(CE->getOperand(0), NewIndices); 01097 } 01098 } 01099 01100 // Implement folding of: 01101 // int* getelementptr ([2 x int]* cast ([3 x int]* %X to [2 x int]*), 01102 // long 0, long 0) 01103 // To: int* getelementptr ([3 x int]* %X, long 0, long 0) 01104 // 01105 if (CE->getOpcode() == Instruction::Cast && IdxList.size() > 1 && 01106 Idx0->isNullValue()) 01107 if (const PointerType *SPT = 01108 dyn_cast<PointerType>(CE->getOperand(0)->getType())) 01109 if (const ArrayType *SAT = dyn_cast<ArrayType>(SPT->getElementType())) 01110 if (const ArrayType *CAT = 01111 dyn_cast<ArrayType>(cast<PointerType>(C->getType())->getElementType())) 01112 if (CAT->getElementType() == SAT->getElementType()) 01113 return ConstantExpr::getGetElementPtr( 01114 (Constant*)CE->getOperand(0), IdxList); 01115 } 01116 return 0; 01117 } 01118