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 "llvm/Support/MathExtras.h" 00028 #include <limits> 00029 #include <cmath> 00030 using namespace llvm; 00031 00032 namespace { 00033 struct ConstRules { 00034 ConstRules() {} 00035 virtual ~ConstRules() {} 00036 00037 // Binary Operators... 00038 virtual Constant *add(const Constant *V1, const Constant *V2) const = 0; 00039 virtual Constant *sub(const Constant *V1, const Constant *V2) const = 0; 00040 virtual Constant *mul(const Constant *V1, const Constant *V2) const = 0; 00041 virtual Constant *div(const Constant *V1, const Constant *V2) const = 0; 00042 virtual Constant *rem(const Constant *V1, const Constant *V2) const = 0; 00043 virtual Constant *op_and(const Constant *V1, const Constant *V2) const = 0; 00044 virtual Constant *op_or (const Constant *V1, const Constant *V2) const = 0; 00045 virtual Constant *op_xor(const Constant *V1, const Constant *V2) const = 0; 00046 virtual Constant *shl(const Constant *V1, const Constant *V2) const = 0; 00047 virtual Constant *shr(const Constant *V1, const Constant *V2) const = 0; 00048 virtual Constant *lessthan(const Constant *V1, const Constant *V2) const =0; 00049 virtual Constant *equalto(const Constant *V1, const Constant *V2) const = 0; 00050 00051 // Casting operators. 00052 virtual Constant *castToBool (const Constant *V) const = 0; 00053 virtual Constant *castToSByte (const Constant *V) const = 0; 00054 virtual Constant *castToUByte (const Constant *V) const = 0; 00055 virtual Constant *castToShort (const Constant *V) const = 0; 00056 virtual Constant *castToUShort(const Constant *V) const = 0; 00057 virtual Constant *castToInt (const Constant *V) const = 0; 00058 virtual Constant *castToUInt (const Constant *V) const = 0; 00059 virtual Constant *castToLong (const Constant *V) const = 0; 00060 virtual Constant *castToULong (const Constant *V) const = 0; 00061 virtual Constant *castToFloat (const Constant *V) const = 0; 00062 virtual Constant *castToDouble(const Constant *V) const = 0; 00063 virtual Constant *castToPointer(const Constant *V, 00064 const PointerType *Ty) const = 0; 00065 00066 // ConstRules::get - Return an instance of ConstRules for the specified 00067 // constant operands. 00068 // 00069 static ConstRules &get(const Constant *V1, const Constant *V2); 00070 private: 00071 ConstRules(const ConstRules &); // Do not implement 00072 ConstRules &operator=(const ConstRules &); // Do not implement 00073 }; 00074 } 00075 00076 00077 //===----------------------------------------------------------------------===// 00078 // TemplateRules Class 00079 //===----------------------------------------------------------------------===// 00080 // 00081 // TemplateRules - Implement a subclass of ConstRules that provides all 00082 // operations as noops. All other rules classes inherit from this class so 00083 // that if functionality is needed in the future, it can simply be added here 00084 // and to ConstRules without changing anything else... 00085 // 00086 // This class also provides subclasses with typesafe implementations of methods 00087 // so that don't have to do type casting. 00088 // 00089 template<class ArgType, class SubClassName> 00090 class TemplateRules : public ConstRules { 00091 00092 00093 //===--------------------------------------------------------------------===// 00094 // Redirecting functions that cast to the appropriate types 00095 //===--------------------------------------------------------------------===// 00096 00097 virtual Constant *add(const Constant *V1, const Constant *V2) const { 00098 return SubClassName::Add((const ArgType *)V1, (const ArgType *)V2); 00099 } 00100 virtual Constant *sub(const Constant *V1, const Constant *V2) const { 00101 return SubClassName::Sub((const ArgType *)V1, (const ArgType *)V2); 00102 } 00103 virtual Constant *mul(const Constant *V1, const Constant *V2) const { 00104 return SubClassName::Mul((const ArgType *)V1, (const ArgType *)V2); 00105 } 00106 virtual Constant *div(const Constant *V1, const Constant *V2) const { 00107 return SubClassName::Div((const ArgType *)V1, (const ArgType *)V2); 00108 } 00109 virtual Constant *rem(const Constant *V1, const Constant *V2) const { 00110 return SubClassName::Rem((const ArgType *)V1, (const ArgType *)V2); 00111 } 00112 virtual Constant *op_and(const Constant *V1, const Constant *V2) const { 00113 return SubClassName::And((const ArgType *)V1, (const ArgType *)V2); 00114 } 00115 virtual Constant *op_or(const Constant *V1, const Constant *V2) const { 00116 return SubClassName::Or((const ArgType *)V1, (const ArgType *)V2); 00117 } 00118 virtual Constant *op_xor(const Constant *V1, const Constant *V2) const { 00119 return SubClassName::Xor((const ArgType *)V1, (const ArgType *)V2); 00120 } 00121 virtual Constant *shl(const Constant *V1, const Constant *V2) const { 00122 return SubClassName::Shl((const ArgType *)V1, (const ArgType *)V2); 00123 } 00124 virtual Constant *shr(const Constant *V1, const Constant *V2) const { 00125 return SubClassName::Shr((const ArgType *)V1, (const ArgType *)V2); 00126 } 00127 00128 virtual Constant *lessthan(const Constant *V1, const Constant *V2) const { 00129 return SubClassName::LessThan((const ArgType *)V1, (const ArgType *)V2); 00130 } 00131 virtual Constant *equalto(const Constant *V1, const Constant *V2) const { 00132 return SubClassName::EqualTo((const ArgType *)V1, (const ArgType *)V2); 00133 } 00134 00135 // Casting operators. ick 00136 virtual Constant *castToBool(const Constant *V) const { 00137 return SubClassName::CastToBool((const ArgType*)V); 00138 } 00139 virtual Constant *castToSByte(const Constant *V) const { 00140 return SubClassName::CastToSByte((const ArgType*)V); 00141 } 00142 virtual Constant *castToUByte(const Constant *V) const { 00143 return SubClassName::CastToUByte((const ArgType*)V); 00144 } 00145 virtual Constant *castToShort(const Constant *V) const { 00146 return SubClassName::CastToShort((const ArgType*)V); 00147 } 00148 virtual Constant *castToUShort(const Constant *V) const { 00149 return SubClassName::CastToUShort((const ArgType*)V); 00150 } 00151 virtual Constant *castToInt(const Constant *V) const { 00152 return SubClassName::CastToInt((const ArgType*)V); 00153 } 00154 virtual Constant *castToUInt(const Constant *V) const { 00155 return SubClassName::CastToUInt((const ArgType*)V); 00156 } 00157 virtual Constant *castToLong(const Constant *V) const { 00158 return SubClassName::CastToLong((const ArgType*)V); 00159 } 00160 virtual Constant *castToULong(const Constant *V) const { 00161 return SubClassName::CastToULong((const ArgType*)V); 00162 } 00163 virtual Constant *castToFloat(const Constant *V) const { 00164 return SubClassName::CastToFloat((const ArgType*)V); 00165 } 00166 virtual Constant *castToDouble(const Constant *V) const { 00167 return SubClassName::CastToDouble((const ArgType*)V); 00168 } 00169 virtual Constant *castToPointer(const Constant *V, 00170 const PointerType *Ty) const { 00171 return SubClassName::CastToPointer((const ArgType*)V, Ty); 00172 } 00173 00174 //===--------------------------------------------------------------------===// 00175 // Default "noop" implementations 00176 //===--------------------------------------------------------------------===// 00177 00178 static Constant *Add(const ArgType *V1, const ArgType *V2) { return 0; } 00179 static Constant *Sub(const ArgType *V1, const ArgType *V2) { return 0; } 00180 static Constant *Mul(const ArgType *V1, const ArgType *V2) { return 0; } 00181 static Constant *Div(const ArgType *V1, const ArgType *V2) { return 0; } 00182 static Constant *Rem(const ArgType *V1, const ArgType *V2) { return 0; } 00183 static Constant *And(const ArgType *V1, const ArgType *V2) { return 0; } 00184 static Constant *Or (const ArgType *V1, const ArgType *V2) { return 0; } 00185 static Constant *Xor(const ArgType *V1, const ArgType *V2) { return 0; } 00186 static Constant *Shl(const ArgType *V1, const ArgType *V2) { return 0; } 00187 static Constant *Shr(const ArgType *V1, const ArgType *V2) { return 0; } 00188 static Constant *LessThan(const ArgType *V1, const ArgType *V2) { 00189 return 0; 00190 } 00191 static Constant *EqualTo(const ArgType *V1, const ArgType *V2) { 00192 return 0; 00193 } 00194 00195 // Casting operators. ick 00196 static Constant *CastToBool (const Constant *V) { return 0; } 00197 static Constant *CastToSByte (const Constant *V) { return 0; } 00198 static Constant *CastToUByte (const Constant *V) { return 0; } 00199 static Constant *CastToShort (const Constant *V) { return 0; } 00200 static Constant *CastToUShort(const Constant *V) { return 0; } 00201 static Constant *CastToInt (const Constant *V) { return 0; } 00202 static Constant *CastToUInt (const Constant *V) { return 0; } 00203 static Constant *CastToLong (const Constant *V) { return 0; } 00204 static Constant *CastToULong (const Constant *V) { return 0; } 00205 static Constant *CastToFloat (const Constant *V) { return 0; } 00206 static Constant *CastToDouble(const Constant *V) { return 0; } 00207 static Constant *CastToPointer(const Constant *, 00208 const PointerType *) {return 0;} 00209 00210 public: 00211 virtual ~TemplateRules() {} 00212 }; 00213 00214 00215 00216 //===----------------------------------------------------------------------===// 00217 // EmptyRules Class 00218 //===----------------------------------------------------------------------===// 00219 // 00220 // EmptyRules provides a concrete base class of ConstRules that does nothing 00221 // 00222 struct EmptyRules : public TemplateRules<Constant, EmptyRules> { 00223 static Constant *EqualTo(const Constant *V1, const Constant *V2) { 00224 if (V1 == V2) return ConstantBool::True; 00225 return 0; 00226 } 00227 }; 00228 00229 00230 00231 //===----------------------------------------------------------------------===// 00232 // BoolRules Class 00233 //===----------------------------------------------------------------------===// 00234 // 00235 // BoolRules provides a concrete base class of ConstRules for the 'bool' type. 00236 // 00237 struct BoolRules : public TemplateRules<ConstantBool, BoolRules> { 00238 00239 static Constant *LessThan(const ConstantBool *V1, const ConstantBool *V2) { 00240 return ConstantBool::get(V1->getValue() < V2->getValue()); 00241 } 00242 00243 static Constant *EqualTo(const Constant *V1, const Constant *V2) { 00244 return ConstantBool::get(V1 == V2); 00245 } 00246 00247 static Constant *And(const ConstantBool *V1, const ConstantBool *V2) { 00248 return ConstantBool::get(V1->getValue() & V2->getValue()); 00249 } 00250 00251 static Constant *Or(const ConstantBool *V1, const ConstantBool *V2) { 00252 return ConstantBool::get(V1->getValue() | V2->getValue()); 00253 } 00254 00255 static Constant *Xor(const ConstantBool *V1, const ConstantBool *V2) { 00256 return ConstantBool::get(V1->getValue() ^ V2->getValue()); 00257 } 00258 00259 // Casting operators. ick 00260 #define DEF_CAST(TYPE, CLASS, CTYPE) \ 00261 static Constant *CastTo##TYPE (const ConstantBool *V) { \ 00262 return CLASS::get(Type::TYPE##Ty, (CTYPE)(bool)V->getValue()); \ 00263 } 00264 00265 DEF_CAST(Bool , ConstantBool, bool) 00266 DEF_CAST(SByte , ConstantSInt, signed char) 00267 DEF_CAST(UByte , ConstantUInt, unsigned char) 00268 DEF_CAST(Short , ConstantSInt, signed short) 00269 DEF_CAST(UShort, ConstantUInt, unsigned short) 00270 DEF_CAST(Int , ConstantSInt, signed int) 00271 DEF_CAST(UInt , ConstantUInt, unsigned int) 00272 DEF_CAST(Long , ConstantSInt, int64_t) 00273 DEF_CAST(ULong , ConstantUInt, uint64_t) 00274 DEF_CAST(Float , ConstantFP , float) 00275 DEF_CAST(Double, ConstantFP , double) 00276 #undef DEF_CAST 00277 }; 00278 00279 00280 //===----------------------------------------------------------------------===// 00281 // NullPointerRules Class 00282 //===----------------------------------------------------------------------===// 00283 // 00284 // NullPointerRules provides a concrete base class of ConstRules for null 00285 // pointers. 00286 // 00287 struct NullPointerRules : public TemplateRules<ConstantPointerNull, 00288 NullPointerRules> { 00289 static Constant *EqualTo(const Constant *V1, const Constant *V2) { 00290 return ConstantBool::True; // Null pointers are always equal 00291 } 00292 static Constant *CastToBool(const Constant *V) { 00293 return ConstantBool::False; 00294 } 00295 static Constant *CastToSByte (const Constant *V) { 00296 return ConstantSInt::get(Type::SByteTy, 0); 00297 } 00298 static Constant *CastToUByte (const Constant *V) { 00299 return ConstantUInt::get(Type::UByteTy, 0); 00300 } 00301 static Constant *CastToShort (const Constant *V) { 00302 return ConstantSInt::get(Type::ShortTy, 0); 00303 } 00304 static Constant *CastToUShort(const Constant *V) { 00305 return ConstantUInt::get(Type::UShortTy, 0); 00306 } 00307 static Constant *CastToInt (const Constant *V) { 00308 return ConstantSInt::get(Type::IntTy, 0); 00309 } 00310 static Constant *CastToUInt (const Constant *V) { 00311 return ConstantUInt::get(Type::UIntTy, 0); 00312 } 00313 static Constant *CastToLong (const Constant *V) { 00314 return ConstantSInt::get(Type::LongTy, 0); 00315 } 00316 static Constant *CastToULong (const Constant *V) { 00317 return ConstantUInt::get(Type::ULongTy, 0); 00318 } 00319 static Constant *CastToFloat (const Constant *V) { 00320 return ConstantFP::get(Type::FloatTy, 0); 00321 } 00322 static Constant *CastToDouble(const Constant *V) { 00323 return ConstantFP::get(Type::DoubleTy, 0); 00324 } 00325 00326 static Constant *CastToPointer(const ConstantPointerNull *V, 00327 const PointerType *PTy) { 00328 return ConstantPointerNull::get(PTy); 00329 } 00330 }; 00331 00332 //===----------------------------------------------------------------------===// 00333 // ConstantPackedRules Class 00334 //===----------------------------------------------------------------------===// 00335 00336 /// DoVectorOp - Given two packed constants and a function pointer, apply the 00337 /// function pointer to each element pair, producing a new ConstantPacked 00338 /// constant. 00339 static Constant *EvalVectorOp(const ConstantPacked *V1, 00340 const ConstantPacked *V2, 00341 Constant *(*FP)(Constant*, Constant*)) { 00342 std::vector<Constant*> Res; 00343 for (unsigned i = 0, e = V1->getNumOperands(); i != e; ++i) 00344 Res.push_back(FP(const_cast<Constant*>(V1->getOperand(i)), 00345 const_cast<Constant*>(V2->getOperand(i)))); 00346 return ConstantPacked::get(Res); 00347 } 00348 00349 /// PackedTypeRules provides a concrete base class of ConstRules for 00350 /// ConstantPacked operands. 00351 /// 00352 struct ConstantPackedRules 00353 : public TemplateRules<ConstantPacked, ConstantPackedRules> { 00354 00355 static Constant *Add(const ConstantPacked *V1, const ConstantPacked *V2) { 00356 return EvalVectorOp(V1, V2, ConstantExpr::getAdd); 00357 } 00358 static Constant *Sub(const ConstantPacked *V1, const ConstantPacked *V2) { 00359 return EvalVectorOp(V1, V2, ConstantExpr::getSub); 00360 } 00361 static Constant *Mul(const ConstantPacked *V1, const ConstantPacked *V2) { 00362 return EvalVectorOp(V1, V2, ConstantExpr::getMul); 00363 } 00364 static Constant *Div(const ConstantPacked *V1, const ConstantPacked *V2) { 00365 return EvalVectorOp(V1, V2, ConstantExpr::getDiv); 00366 } 00367 static Constant *Rem(const ConstantPacked *V1, const ConstantPacked *V2) { 00368 return EvalVectorOp(V1, V2, ConstantExpr::getRem); 00369 } 00370 static Constant *And(const ConstantPacked *V1, const ConstantPacked *V2) { 00371 return EvalVectorOp(V1, V2, ConstantExpr::getAnd); 00372 } 00373 static Constant *Or (const ConstantPacked *V1, const ConstantPacked *V2) { 00374 return EvalVectorOp(V1, V2, ConstantExpr::getOr); 00375 } 00376 static Constant *Xor(const ConstantPacked *V1, const ConstantPacked *V2) { 00377 return EvalVectorOp(V1, V2, ConstantExpr::getXor); 00378 } 00379 static Constant *Shl(const ConstantPacked *V1, const ConstantPacked *V2) { 00380 return EvalVectorOp(V1, V2, ConstantExpr::getShl); 00381 } 00382 static Constant *Shr(const ConstantPacked *V1, const ConstantPacked *V2) { 00383 return EvalVectorOp(V1, V2, ConstantExpr::getShr); 00384 } 00385 static Constant *LessThan(const ConstantPacked *V1, const ConstantPacked *V2){ 00386 return 0; 00387 } 00388 static Constant *EqualTo(const ConstantPacked *V1, const ConstantPacked *V2) { 00389 for (unsigned i = 0, e = V1->getNumOperands(); i != e; ++i) { 00390 Constant *C = 00391 ConstantExpr::getSetEQ(const_cast<Constant*>(V1->getOperand(i)), 00392 const_cast<Constant*>(V2->getOperand(i))); 00393 if (ConstantBool *CB = dyn_cast<ConstantBool>(C)) 00394 return CB; 00395 } 00396 // Otherwise, could not decide from any element pairs. 00397 return 0; 00398 } 00399 }; 00400 00401 00402 //===----------------------------------------------------------------------===// 00403 // GeneralPackedRules Class 00404 //===----------------------------------------------------------------------===// 00405 00406 /// GeneralPackedRules provides a concrete base class of ConstRules for 00407 /// PackedType operands, where both operands are not ConstantPacked. The usual 00408 /// cause for this is that one operand is a ConstantAggregateZero. 00409 /// 00410 struct GeneralPackedRules : public TemplateRules<Constant, GeneralPackedRules> { 00411 }; 00412 00413 00414 //===----------------------------------------------------------------------===// 00415 // DirectRules Class 00416 //===----------------------------------------------------------------------===// 00417 // 00418 // DirectRules provides a concrete base classes of ConstRules for a variety of 00419 // different types. This allows the C++ compiler to automatically generate our 00420 // constant handling operations in a typesafe and accurate manner. 00421 // 00422 template<class ConstantClass, class BuiltinType, Type **Ty, class SuperClass> 00423 struct DirectRules : public TemplateRules<ConstantClass, SuperClass> { 00424 static Constant *Add(const ConstantClass *V1, const ConstantClass *V2) { 00425 BuiltinType R = (BuiltinType)V1->getValue() + (BuiltinType)V2->getValue(); 00426 return ConstantClass::get(*Ty, R); 00427 } 00428 00429 static Constant *Sub(const ConstantClass *V1, const ConstantClass *V2) { 00430 BuiltinType R = (BuiltinType)V1->getValue() - (BuiltinType)V2->getValue(); 00431 return ConstantClass::get(*Ty, R); 00432 } 00433 00434 static Constant *Mul(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 *Div(const ConstantClass *V1, const ConstantClass *V2) { 00440 if (V2->isNullValue()) return 0; 00441 BuiltinType R = (BuiltinType)V1->getValue() / (BuiltinType)V2->getValue(); 00442 return ConstantClass::get(*Ty, R); 00443 } 00444 00445 static Constant *LessThan(const ConstantClass *V1, const ConstantClass *V2) { 00446 bool R = (BuiltinType)V1->getValue() < (BuiltinType)V2->getValue(); 00447 return ConstantBool::get(R); 00448 } 00449 00450 static Constant *EqualTo(const ConstantClass *V1, const ConstantClass *V2) { 00451 bool R = (BuiltinType)V1->getValue() == (BuiltinType)V2->getValue(); 00452 return ConstantBool::get(R); 00453 } 00454 00455 static Constant *CastToPointer(const ConstantClass *V, 00456 const PointerType *PTy) { 00457 if (V->isNullValue()) // Is it a FP or Integral null value? 00458 return ConstantPointerNull::get(PTy); 00459 return 0; // Can't const prop other types of pointers 00460 } 00461 00462 // Casting operators. ick 00463 #define DEF_CAST(TYPE, CLASS, CTYPE) \ 00464 static Constant *CastTo##TYPE (const ConstantClass *V) { \ 00465 return CLASS::get(Type::TYPE##Ty, (CTYPE)(BuiltinType)V->getValue()); \ 00466 } 00467 00468 DEF_CAST(Bool , ConstantBool, bool) 00469 DEF_CAST(SByte , ConstantSInt, signed char) 00470 DEF_CAST(UByte , ConstantUInt, unsigned char) 00471 DEF_CAST(Short , ConstantSInt, signed short) 00472 DEF_CAST(UShort, ConstantUInt, unsigned short) 00473 DEF_CAST(Int , ConstantSInt, signed int) 00474 DEF_CAST(UInt , ConstantUInt, unsigned int) 00475 DEF_CAST(Long , ConstantSInt, int64_t) 00476 DEF_CAST(ULong , ConstantUInt, uint64_t) 00477 DEF_CAST(Float , ConstantFP , float) 00478 DEF_CAST(Double, ConstantFP , double) 00479 #undef DEF_CAST 00480 }; 00481 00482 00483 //===----------------------------------------------------------------------===// 00484 // DirectIntRules Class 00485 //===----------------------------------------------------------------------===// 00486 // 00487 // DirectIntRules provides implementations of functions that are valid on 00488 // integer types, but not all types in general. 00489 // 00490 template <class ConstantClass, class BuiltinType, Type **Ty> 00491 struct DirectIntRules 00492 : public DirectRules<ConstantClass, BuiltinType, Ty, 00493 DirectIntRules<ConstantClass, BuiltinType, Ty> > { 00494 00495 static Constant *Div(const ConstantClass *V1, const ConstantClass *V2) { 00496 if (V2->isNullValue()) return 0; 00497 if (V2->isAllOnesValue() && // MIN_INT / -1 00498 (BuiltinType)V1->getValue() == -(BuiltinType)V1->getValue()) 00499 return 0; 00500 BuiltinType R = (BuiltinType)V1->getValue() / (BuiltinType)V2->getValue(); 00501 return ConstantClass::get(*Ty, R); 00502 } 00503 00504 static Constant *Rem(const ConstantClass *V1, 00505 const ConstantClass *V2) { 00506 if (V2->isNullValue()) return 0; // X / 0 00507 if (V2->isAllOnesValue() && // MIN_INT / -1 00508 (BuiltinType)V1->getValue() == -(BuiltinType)V1->getValue()) 00509 return 0; 00510 BuiltinType R = (BuiltinType)V1->getValue() % (BuiltinType)V2->getValue(); 00511 return ConstantClass::get(*Ty, R); 00512 } 00513 00514 static Constant *And(const ConstantClass *V1, const ConstantClass *V2) { 00515 BuiltinType R = (BuiltinType)V1->getValue() & (BuiltinType)V2->getValue(); 00516 return ConstantClass::get(*Ty, R); 00517 } 00518 static Constant *Or(const ConstantClass *V1, const ConstantClass *V2) { 00519 BuiltinType R = (BuiltinType)V1->getValue() | (BuiltinType)V2->getValue(); 00520 return ConstantClass::get(*Ty, R); 00521 } 00522 static Constant *Xor(const ConstantClass *V1, const ConstantClass *V2) { 00523 BuiltinType R = (BuiltinType)V1->getValue() ^ (BuiltinType)V2->getValue(); 00524 return ConstantClass::get(*Ty, R); 00525 } 00526 00527 static Constant *Shl(const ConstantClass *V1, const ConstantClass *V2) { 00528 BuiltinType R = (BuiltinType)V1->getValue() << (BuiltinType)V2->getValue(); 00529 return ConstantClass::get(*Ty, R); 00530 } 00531 00532 static Constant *Shr(const ConstantClass *V1, const ConstantClass *V2) { 00533 BuiltinType R = (BuiltinType)V1->getValue() >> (BuiltinType)V2->getValue(); 00534 return ConstantClass::get(*Ty, R); 00535 } 00536 }; 00537 00538 00539 //===----------------------------------------------------------------------===// 00540 // DirectFPRules Class 00541 //===----------------------------------------------------------------------===// 00542 // 00543 /// DirectFPRules provides implementations of functions that are valid on 00544 /// floating point types, but not all types in general. 00545 /// 00546 template <class ConstantClass, class BuiltinType, Type **Ty> 00547 struct DirectFPRules 00548 : public DirectRules<ConstantClass, BuiltinType, Ty, 00549 DirectFPRules<ConstantClass, BuiltinType, Ty> > { 00550 static Constant *Rem(const ConstantClass *V1, const ConstantClass *V2) { 00551 if (V2->isNullValue()) return 0; 00552 BuiltinType Result = std::fmod((BuiltinType)V1->getValue(), 00553 (BuiltinType)V2->getValue()); 00554 return ConstantClass::get(*Ty, Result); 00555 } 00556 static Constant *Div(const ConstantClass *V1, const ConstantClass *V2) { 00557 BuiltinType inf = std::numeric_limits<BuiltinType>::infinity(); 00558 if (V2->isExactlyValue(0.0)) return ConstantClass::get(*Ty, inf); 00559 if (V2->isExactlyValue(-0.0)) return ConstantClass::get(*Ty, -inf); 00560 BuiltinType R = (BuiltinType)V1->getValue() / (BuiltinType)V2->getValue(); 00561 return ConstantClass::get(*Ty, R); 00562 } 00563 }; 00564 00565 00566 /// ConstRules::get - This method returns the constant rules implementation that 00567 /// implements the semantics of the two specified constants. 00568 ConstRules &ConstRules::get(const Constant *V1, const Constant *V2) { 00569 static EmptyRules EmptyR; 00570 static BoolRules BoolR; 00571 static NullPointerRules NullPointerR; 00572 static ConstantPackedRules ConstantPackedR; 00573 static GeneralPackedRules GeneralPackedR; 00574 static DirectIntRules<ConstantSInt, signed char , &Type::SByteTy> SByteR; 00575 static DirectIntRules<ConstantUInt, unsigned char , &Type::UByteTy> UByteR; 00576 static DirectIntRules<ConstantSInt, signed short, &Type::ShortTy> ShortR; 00577 static DirectIntRules<ConstantUInt, unsigned short, &Type::UShortTy> UShortR; 00578 static DirectIntRules<ConstantSInt, signed int , &Type::IntTy> IntR; 00579 static DirectIntRules<ConstantUInt, unsigned int , &Type::UIntTy> UIntR; 00580 static DirectIntRules<ConstantSInt, int64_t , &Type::LongTy> LongR; 00581 static DirectIntRules<ConstantUInt, uint64_t , &Type::ULongTy> ULongR; 00582 static DirectFPRules <ConstantFP , float , &Type::FloatTy> FloatR; 00583 static DirectFPRules <ConstantFP , double , &Type::DoubleTy> DoubleR; 00584 00585 if (isa<ConstantExpr>(V1) || isa<ConstantExpr>(V2) || 00586 isa<GlobalValue>(V1) || isa<GlobalValue>(V2) || 00587 isa<UndefValue>(V1) || isa<UndefValue>(V2)) 00588 return EmptyR; 00589 00590 switch (V1->getType()->getTypeID()) { 00591 default: assert(0 && "Unknown value type for constant folding!"); 00592 case Type::BoolTyID: return BoolR; 00593 case Type::PointerTyID: return NullPointerR; 00594 case Type::SByteTyID: return SByteR; 00595 case Type::UByteTyID: return UByteR; 00596 case Type::ShortTyID: return ShortR; 00597 case Type::UShortTyID: return UShortR; 00598 case Type::IntTyID: return IntR; 00599 case Type::UIntTyID: return UIntR; 00600 case Type::LongTyID: return LongR; 00601 case Type::ULongTyID: return ULongR; 00602 case Type::FloatTyID: return FloatR; 00603 case Type::DoubleTyID: return DoubleR; 00604 case Type::PackedTyID: 00605 if (isa<ConstantPacked>(V1) && isa<ConstantPacked>(V2)) 00606 return ConstantPackedR; 00607 return GeneralPackedR; // Constant folding rules for ConstantAggregateZero. 00608 } 00609 } 00610 00611 00612 //===----------------------------------------------------------------------===// 00613 // ConstantFold*Instruction Implementations 00614 //===----------------------------------------------------------------------===// 00615 // 00616 // These methods contain the special case hackery required to symbolically 00617 // evaluate some constant expression cases, and use the ConstantRules class to 00618 // evaluate normal constants. 00619 // 00620 static unsigned getSize(const Type *Ty) { 00621 unsigned S = Ty->getPrimitiveSize(); 00622 return S ? S : 8; // Treat pointers at 8 bytes 00623 } 00624 00625 /// CastConstantPacked - Convert the specified ConstantPacked node to the 00626 /// specified packed type. At this point, we know that the elements of the 00627 /// input packed constant are all simple integer or FP values. 00628 static Constant *CastConstantPacked(ConstantPacked *CP, 00629 const PackedType *DstTy) { 00630 unsigned SrcNumElts = CP->getType()->getNumElements(); 00631 unsigned DstNumElts = DstTy->getNumElements(); 00632 const Type *SrcEltTy = CP->getType()->getElementType(); 00633 const Type *DstEltTy = DstTy->getElementType(); 00634 00635 // If both vectors have the same number of elements (thus, the elements 00636 // are the same size), perform the conversion now. 00637 if (SrcNumElts == DstNumElts) { 00638 std::vector<Constant*> Result; 00639 00640 // If the src and dest elements are both integers, just cast each one 00641 // which will do the appropriate bit-convert. 00642 if (SrcEltTy->isIntegral() && DstEltTy->isIntegral()) { 00643 for (unsigned i = 0; i != SrcNumElts; ++i) 00644 Result.push_back(ConstantExpr::getCast(CP->getOperand(i), 00645 DstEltTy)); 00646 return ConstantPacked::get(Result); 00647 } 00648 00649 if (SrcEltTy->isIntegral()) { 00650 // Otherwise, this is an int-to-fp cast. 00651 assert(DstEltTy->isFloatingPoint()); 00652 if (DstEltTy->getTypeID() == Type::DoubleTyID) { 00653 for (unsigned i = 0; i != SrcNumElts; ++i) { 00654 double V = 00655 BitsToDouble(cast<ConstantInt>(CP->getOperand(i))->getRawValue()); 00656 Result.push_back(ConstantFP::get(Type::DoubleTy, V)); 00657 } 00658 return ConstantPacked::get(Result); 00659 } 00660 assert(DstEltTy == Type::FloatTy && "Unknown fp type!"); 00661 for (unsigned i = 0; i != SrcNumElts; ++i) { 00662 float V = 00663 BitsToFloat(cast<ConstantInt>(CP->getOperand(i))->getRawValue()); 00664 Result.push_back(ConstantFP::get(Type::FloatTy, V)); 00665 } 00666 return ConstantPacked::get(Result); 00667 } 00668 00669 // Otherwise, this is an fp-to-int cast. 00670 assert(SrcEltTy->isFloatingPoint() && DstEltTy->isIntegral()); 00671 00672 if (SrcEltTy->getTypeID() == Type::DoubleTyID) { 00673 for (unsigned i = 0; i != SrcNumElts; ++i) { 00674 uint64_t V = 00675 DoubleToBits(cast<ConstantFP>(CP->getOperand(i))->getValue()); 00676 Constant *C = ConstantUInt::get(Type::ULongTy, V); 00677 Result.push_back(ConstantExpr::getCast(C, DstEltTy)); 00678 } 00679 return ConstantPacked::get(Result); 00680 } 00681 00682 assert(SrcEltTy->getTypeID() == Type::FloatTyID); 00683 for (unsigned i = 0; i != SrcNumElts; ++i) { 00684 unsigned V = FloatToBits(cast<ConstantFP>(CP->getOperand(i))->getValue()); 00685 Constant *C = ConstantUInt::get(Type::UIntTy, V); 00686 Result.push_back(ConstantExpr::getCast(C, DstEltTy)); 00687 } 00688 return ConstantPacked::get(Result); 00689 } 00690 00691 // Otherwise, this is a cast that changes element count and size. Handle 00692 // casts which shrink the elements here. 00693 00694 // FIXME: We need to know endianness to do this! 00695 00696 return 0; 00697 } 00698 00699 00700 Constant *llvm::ConstantFoldCastInstruction(const Constant *V, 00701 const Type *DestTy) { 00702 if (V->getType() == DestTy) return (Constant*)V; 00703 00704 // Cast of a global address to boolean is always true. 00705 if (const GlobalValue *GV = dyn_cast<GlobalValue>(V)) { 00706 if (DestTy == Type::BoolTy) 00707 // FIXME: When we support 'external weak' references, we have to prevent 00708 // this transformation from happening. This code will need to be updated 00709 // to ignore external weak symbols when we support it. 00710 return ConstantBool::True; 00711 } else if (const ConstantExpr *CE = dyn_cast<ConstantExpr>(V)) { 00712 if (CE->getOpcode() == Instruction::Cast) { 00713 Constant *Op = const_cast<Constant*>(CE->getOperand(0)); 00714 // Try to not produce a cast of a cast, which is almost always redundant. 00715 if (!Op->getType()->isFloatingPoint() && 00716 !CE->getType()->isFloatingPoint() && 00717 !DestTy->isFloatingPoint()) { 00718 unsigned S1 = getSize(Op->getType()), S2 = getSize(CE->getType()); 00719 unsigned S3 = getSize(DestTy); 00720 if (Op->getType() == DestTy && S3 >= S2) 00721 return Op; 00722 if (S1 >= S2 && S2 >= S3) 00723 return ConstantExpr::getCast(Op, DestTy); 00724 if (S1 <= S2 && S2 >= S3 && S1 <= S3) 00725 return ConstantExpr::getCast(Op, DestTy); 00726 } 00727 } else if (CE->getOpcode() == Instruction::GetElementPtr) { 00728 // If all of the indexes in the GEP are null values, there is no pointer 00729 // adjustment going on. We might as well cast the source pointer. 00730 bool isAllNull = true; 00731 for (unsigned i = 1, e = CE->getNumOperands(); i != e; ++i) 00732 if (!CE->getOperand(i)->isNullValue()) { 00733 isAllNull = false; 00734 break; 00735 } 00736 if (isAllNull) 00737 return ConstantExpr::getCast(CE->getOperand(0), DestTy); 00738 } 00739 } else if (isa<UndefValue>(V)) { 00740 return UndefValue::get(DestTy); 00741 } 00742 00743 // Check to see if we are casting an pointer to an aggregate to a pointer to 00744 // the first element. If so, return the appropriate GEP instruction. 00745 if (const PointerType *PTy = dyn_cast<PointerType>(V->getType())) 00746 if (const PointerType *DPTy = dyn_cast<PointerType>(DestTy)) { 00747 std::vector<Value*> IdxList; 00748 IdxList.push_back(Constant::getNullValue(Type::IntTy)); 00749 const Type *ElTy = PTy->getElementType(); 00750 while (ElTy != DPTy->getElementType()) { 00751 if (const StructType *STy = dyn_cast<StructType>(ElTy)) { 00752 if (STy->getNumElements() == 0) break; 00753 ElTy = STy->getElementType(0); 00754 IdxList.push_back(Constant::getNullValue(Type::UIntTy)); 00755 } else if (const SequentialType *STy = dyn_cast<SequentialType>(ElTy)) { 00756 if (isa<PointerType>(ElTy)) break; // Can't index into pointers! 00757 ElTy = STy->getElementType(); 00758 IdxList.push_back(IdxList[0]); 00759 } else { 00760 break; 00761 } 00762 } 00763 00764 if (ElTy == DPTy->getElementType()) 00765 return ConstantExpr::getGetElementPtr(const_cast<Constant*>(V),IdxList); 00766 } 00767 00768 // Handle casts from one packed constant to another. We know that the src and 00769 // dest type have the same size. 00770 if (const PackedType *DestPTy = dyn_cast<PackedType>(DestTy)) { 00771 if (const PackedType *SrcTy = dyn_cast<PackedType>(V->getType())) { 00772 assert(DestPTy->getElementType()->getPrimitiveSizeInBits() * 00773 DestPTy->getNumElements() == 00774 SrcTy->getElementType()->getPrimitiveSizeInBits() * 00775 SrcTy->getNumElements() && "Not cast between same sized vectors!"); 00776 if (isa<ConstantAggregateZero>(V)) 00777 return Constant::getNullValue(DestTy); 00778 if (isa<UndefValue>(V)) 00779 return UndefValue::get(DestTy); 00780 if (const ConstantPacked *CP = dyn_cast<ConstantPacked>(V)) { 00781 // This is a cast from a ConstantPacked of one type to a ConstantPacked 00782 // of another type. Check to see if all elements of the input are 00783 // simple. 00784 bool AllSimpleConstants = true; 00785 for (unsigned i = 0, e = CP->getNumOperands(); i != e; ++i) { 00786 if (!isa<ConstantInt>(CP->getOperand(i)) && 00787 !isa<ConstantFP>(CP->getOperand(i))) { 00788 AllSimpleConstants = false; 00789 break; 00790 } 00791 } 00792 00793 // If all of the elements are simple constants, we can fold this. 00794 if (AllSimpleConstants) 00795 return CastConstantPacked(const_cast<ConstantPacked*>(CP), DestPTy); 00796 } 00797 } 00798 } 00799 00800 ConstRules &Rules = ConstRules::get(V, V); 00801 00802 switch (DestTy->getTypeID()) { 00803 case Type::BoolTyID: return Rules.castToBool(V); 00804 case Type::UByteTyID: return Rules.castToUByte(V); 00805 case Type::SByteTyID: return Rules.castToSByte(V); 00806 case Type::UShortTyID: return Rules.castToUShort(V); 00807 case Type::ShortTyID: return Rules.castToShort(V); 00808 case Type::UIntTyID: return Rules.castToUInt(V); 00809 case Type::IntTyID: return Rules.castToInt(V); 00810 case Type::ULongTyID: return Rules.castToULong(V); 00811 case Type::LongTyID: return Rules.castToLong(V); 00812 case Type::FloatTyID: return Rules.castToFloat(V); 00813 case Type::DoubleTyID: return Rules.castToDouble(V); 00814 case Type::PointerTyID: 00815 return Rules.castToPointer(V, cast<PointerType>(DestTy)); 00816 default: return 0; 00817 } 00818 } 00819 00820 Constant *llvm::ConstantFoldSelectInstruction(const Constant *Cond, 00821 const Constant *V1, 00822 const Constant *V2) { 00823 if (Cond == ConstantBool::True) 00824 return const_cast<Constant*>(V1); 00825 else if (Cond == ConstantBool::False) 00826 return const_cast<Constant*>(V2); 00827 00828 if (isa<UndefValue>(V1)) return const_cast<Constant*>(V2); 00829 if (isa<UndefValue>(V2)) return const_cast<Constant*>(V1); 00830 if (isa<UndefValue>(Cond)) return const_cast<Constant*>(V1); 00831 if (V1 == V2) return const_cast<Constant*>(V1); 00832 return 0; 00833 } 00834 00835 Constant *llvm::ConstantFoldExtractElementInstruction(const Constant *Val, 00836 const Constant *Idx) { 00837 if (isa<UndefValue>(Val)) // ee(undef, x) -> undef 00838 return UndefValue::get(cast<PackedType>(Val->getType())->getElementType()); 00839 if (Val->isNullValue()) // ee(zero, x) -> zero 00840 return Constant::getNullValue( 00841 cast<PackedType>(Val->getType())->getElementType()); 00842 00843 if (const ConstantPacked *CVal = dyn_cast<ConstantPacked>(Val)) { 00844 if (const ConstantUInt *CIdx = dyn_cast<ConstantUInt>(Idx)) { 00845 return const_cast<Constant*>(CVal->getOperand(CIdx->getValue())); 00846 } else if (isa<UndefValue>(Idx)) { 00847 // ee({w,x,y,z}, undef) -> w (an arbitrary value). 00848 return const_cast<Constant*>(CVal->getOperand(0)); 00849 } 00850 } 00851 return 0; 00852 } 00853 00854 Constant *llvm::ConstantFoldInsertElementInstruction(const Constant *Val, 00855 const Constant *Elt, 00856 const Constant *Idx) { 00857 const ConstantUInt *CIdx = dyn_cast<ConstantUInt>(Idx); 00858 if (!CIdx) return 0; 00859 unsigned idxVal = CIdx->getValue(); 00860 if (const UndefValue *UVal = dyn_cast<UndefValue>(Val)) { 00861 // Insertion of scalar constant into packed undef 00862 // Optimize away insertion of undef 00863 if (isa<UndefValue>(Elt)) 00864 return const_cast<Constant*>(Val); 00865 // Otherwise break the aggregate undef into multiple undefs and do 00866 // the insertion 00867 unsigned numOps = 00868 cast<PackedType>(Val->getType())->getNumElements(); 00869 std::vector<Constant*> Ops; 00870 Ops.reserve(numOps); 00871 for (unsigned i = 0; i < numOps; ++i) { 00872 const Constant *Op = 00873 (i == idxVal) ? Elt : UndefValue::get(Elt->getType()); 00874 Ops.push_back(const_cast<Constant*>(Op)); 00875 } 00876 return ConstantPacked::get(Ops); 00877 } 00878 if (const ConstantAggregateZero *CVal = 00879 dyn_cast<ConstantAggregateZero>(Val)) { 00880 // Insertion of scalar constant into packed aggregate zero 00881 // Optimize away insertion of zero 00882 if (Elt->isNullValue()) 00883 return const_cast<Constant*>(Val); 00884 // Otherwise break the aggregate zero into multiple zeros and do 00885 // the insertion 00886 unsigned numOps = 00887 cast<PackedType>(Val->getType())->getNumElements(); 00888 std::vector<Constant*> Ops; 00889 Ops.reserve(numOps); 00890 for (unsigned i = 0; i < numOps; ++i) { 00891 const Constant *Op = 00892 (i == idxVal) ? Elt : Constant::getNullValue(Elt->getType()); 00893 Ops.push_back(const_cast<Constant*>(Op)); 00894 } 00895 return ConstantPacked::get(Ops); 00896 } 00897 if (const ConstantPacked *CVal = dyn_cast<ConstantPacked>(Val)) { 00898 // Insertion of scalar constant into packed constant 00899 std::vector<Constant*> Ops; 00900 Ops.reserve(CVal->getNumOperands()); 00901 for (unsigned i = 0; i < CVal->getNumOperands(); ++i) { 00902 const Constant *Op = 00903 (i == idxVal) ? Elt : cast<Constant>(CVal->getOperand(i)); 00904 Ops.push_back(const_cast<Constant*>(Op)); 00905 } 00906 return ConstantPacked::get(Ops); 00907 } 00908 return 0; 00909 } 00910 00911 Constant *llvm::ConstantFoldShuffleVectorInstruction(const Constant *V1, 00912 const Constant *V2, 00913 const Constant *Mask) { 00914 // TODO: 00915 return 0; 00916 } 00917 00918 00919 /// isZeroSizedType - This type is zero sized if its an array or structure of 00920 /// zero sized types. The only leaf zero sized type is an empty structure. 00921 static bool isMaybeZeroSizedType(const Type *Ty) { 00922 if (isa<OpaqueType>(Ty)) return true; // Can't say. 00923 if (const StructType *STy = dyn_cast<StructType>(Ty)) { 00924 00925 // If all of elements have zero size, this does too. 00926 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) 00927 if (!isMaybeZeroSizedType(STy->getElementType(i))) return false; 00928 return true; 00929 00930 } else if (const ArrayType *ATy = dyn_cast<ArrayType>(Ty)) { 00931 return isMaybeZeroSizedType(ATy->getElementType()); 00932 } 00933 return false; 00934 } 00935 00936 /// IdxCompare - Compare the two constants as though they were getelementptr 00937 /// indices. This allows coersion of the types to be the same thing. 00938 /// 00939 /// If the two constants are the "same" (after coersion), return 0. If the 00940 /// first is less than the second, return -1, if the second is less than the 00941 /// first, return 1. If the constants are not integral, return -2. 00942 /// 00943 static int IdxCompare(Constant *C1, Constant *C2, const Type *ElTy) { 00944 if (C1 == C2) return 0; 00945 00946 // Ok, we found a different index. Are either of the operands 00947 // ConstantExprs? If so, we can't do anything with them. 00948 if (!isa<ConstantInt>(C1) || !isa<ConstantInt>(C2)) 00949 return -2; // don't know! 00950 00951 // Ok, we have two differing integer indices. Sign extend them to be the same 00952 // type. Long is always big enough, so we use it. 00953 C1 = ConstantExpr::getSignExtend(C1, Type::LongTy); 00954 C2 = ConstantExpr::getSignExtend(C2, Type::LongTy); 00955 if (C1 == C2) return 0; // Are they just differing types? 00956 00957 // If the type being indexed over is really just a zero sized type, there is 00958 // no pointer difference being made here. 00959 if (isMaybeZeroSizedType(ElTy)) 00960 return -2; // dunno. 00961 00962 // If they are really different, now that they are the same type, then we 00963 // found a difference! 00964 if (cast<ConstantSInt>(C1)->getValue() < cast<ConstantSInt>(C2)->getValue()) 00965 return -1; 00966 else 00967 return 1; 00968 } 00969 00970 /// evaluateRelation - This function determines if there is anything we can 00971 /// decide about the two constants provided. This doesn't need to handle simple 00972 /// things like integer comparisons, but should instead handle ConstantExprs 00973 /// and GlobalValuess. If we can determine that the two constants have a 00974 /// particular relation to each other, we should return the corresponding SetCC 00975 /// code, otherwise return Instruction::BinaryOpsEnd. 00976 /// 00977 /// To simplify this code we canonicalize the relation so that the first 00978 /// operand is always the most "complex" of the two. We consider simple 00979 /// constants (like ConstantInt) to be the simplest, followed by 00980 /// GlobalValues, followed by ConstantExpr's (the most complex). 00981 /// 00982 static Instruction::BinaryOps evaluateRelation(Constant *V1, Constant *V2) { 00983 assert(V1->getType() == V2->getType() && 00984 "Cannot compare different types of values!"); 00985 if (V1 == V2) return Instruction::SetEQ; 00986 00987 if (!isa<ConstantExpr>(V1) && !isa<GlobalValue>(V1)) { 00988 if (!isa<GlobalValue>(V2) && !isa<ConstantExpr>(V2)) { 00989 // We distilled this down to a simple case, use the standard constant 00990 // folder. 00991 ConstantBool *R = dyn_cast<ConstantBool>(ConstantExpr::getSetEQ(V1, V2)); 00992 if (R == ConstantBool::True) return Instruction::SetEQ; 00993 R = dyn_cast<ConstantBool>(ConstantExpr::getSetLT(V1, V2)); 00994 if (R == ConstantBool::True) return Instruction::SetLT; 00995 R = dyn_cast<ConstantBool>(ConstantExpr::getSetGT(V1, V2)); 00996 if (R == ConstantBool::True) return Instruction::SetGT; 00997 00998 // If we couldn't figure it out, bail. 00999 return Instruction::BinaryOpsEnd; 01000 } 01001 01002 // If the first operand is simple, swap operands. 01003 Instruction::BinaryOps SwappedRelation = evaluateRelation(V2, V1); 01004 if (SwappedRelation != Instruction::BinaryOpsEnd) 01005 return SetCondInst::getSwappedCondition(SwappedRelation); 01006 01007 } else if (const GlobalValue *CPR1 = dyn_cast<GlobalValue>(V1)) { 01008 if (isa<ConstantExpr>(V2)) { // Swap as necessary. 01009 Instruction::BinaryOps SwappedRelation = evaluateRelation(V2, V1); 01010 if (SwappedRelation != Instruction::BinaryOpsEnd) 01011 return SetCondInst::getSwappedCondition(SwappedRelation); 01012 else 01013 return Instruction::BinaryOpsEnd; 01014 } 01015 01016 // Now we know that the RHS is a GlobalValue or simple constant, 01017 // which (since the types must match) means that it's a ConstantPointerNull. 01018 if (const GlobalValue *CPR2 = dyn_cast<GlobalValue>(V2)) { 01019 assert(CPR1 != CPR2 && 01020 "GVs for the same value exist at different addresses??"); 01021 // FIXME: If both globals are external weak, they might both be null! 01022 return Instruction::SetNE; 01023 } else { 01024 assert(isa<ConstantPointerNull>(V2) && "Canonicalization guarantee!"); 01025 // Global can never be null. FIXME: if we implement external weak 01026 // linkage, this is not necessarily true! 01027 return Instruction::SetNE; 01028 } 01029 01030 } else { 01031 // Ok, the LHS is known to be a constantexpr. The RHS can be any of a 01032 // constantexpr, a CPR, or a simple constant. 01033 ConstantExpr *CE1 = cast<ConstantExpr>(V1); 01034 Constant *CE1Op0 = CE1->getOperand(0); 01035 01036 switch (CE1->getOpcode()) { 01037 case Instruction::Cast: 01038 // If the cast is not actually changing bits, and the second operand is a 01039 // null pointer, do the comparison with the pre-casted value. 01040 if (V2->isNullValue() && 01041 (isa<PointerType>(CE1->getType()) || CE1->getType()->isIntegral())) 01042 return evaluateRelation(CE1Op0, 01043 Constant::getNullValue(CE1Op0->getType())); 01044 01045 // If the dest type is a pointer type, and the RHS is a constantexpr cast 01046 // from the same type as the src of the LHS, evaluate the inputs. This is 01047 // important for things like "seteq (cast 4 to int*), (cast 5 to int*)", 01048 // which happens a lot in compilers with tagged integers. 01049 if (ConstantExpr *CE2 = dyn_cast<ConstantExpr>(V2)) 01050 if (isa<PointerType>(CE1->getType()) && 01051 CE2->getOpcode() == Instruction::Cast && 01052 CE1->getOperand(0)->getType() == CE2->getOperand(0)->getType() && 01053 CE1->getOperand(0)->getType()->isIntegral()) { 01054 return evaluateRelation(CE1->getOperand(0), CE2->getOperand(0)); 01055 } 01056 break; 01057 01058 case Instruction::GetElementPtr: 01059 // Ok, since this is a getelementptr, we know that the constant has a 01060 // pointer type. Check the various cases. 01061 if (isa<ConstantPointerNull>(V2)) { 01062 // If we are comparing a GEP to a null pointer, check to see if the base 01063 // of the GEP equals the null pointer. 01064 if (isa<GlobalValue>(CE1Op0)) { 01065 // FIXME: this is not true when we have external weak references! 01066 // No offset can go from a global to a null pointer. 01067 return Instruction::SetGT; 01068 } else if (isa<ConstantPointerNull>(CE1Op0)) { 01069 // If we are indexing from a null pointer, check to see if we have any 01070 // non-zero indices. 01071 for (unsigned i = 1, e = CE1->getNumOperands(); i != e; ++i) 01072 if (!CE1->getOperand(i)->isNullValue()) 01073 // Offsetting from null, must not be equal. 01074 return Instruction::SetGT; 01075 // Only zero indexes from null, must still be zero. 01076 return Instruction::SetEQ; 01077 } 01078 // Otherwise, we can't really say if the first operand is null or not. 01079 } else if (const GlobalValue *CPR2 = dyn_cast<GlobalValue>(V2)) { 01080 if (isa<ConstantPointerNull>(CE1Op0)) { 01081 // FIXME: This is not true with external weak references. 01082 return Instruction::SetLT; 01083 } else if (const GlobalValue *CPR1 = dyn_cast<GlobalValue>(CE1Op0)) { 01084 if (CPR1 == CPR2) { 01085 // If this is a getelementptr of the same global, then it must be 01086 // different. Because the types must match, the getelementptr could 01087 // only have at most one index, and because we fold getelementptr's 01088 // with a single zero index, it must be nonzero. 01089 assert(CE1->getNumOperands() == 2 && 01090 !CE1->getOperand(1)->isNullValue() && 01091 "Suprising getelementptr!"); 01092 return Instruction::SetGT; 01093 } else { 01094 // If they are different globals, we don't know what the value is, 01095 // but they can't be equal. 01096 return Instruction::SetNE; 01097 } 01098 } 01099 } else { 01100 const ConstantExpr *CE2 = cast<ConstantExpr>(V2); 01101 const Constant *CE2Op0 = CE2->getOperand(0); 01102 01103 // There are MANY other foldings that we could perform here. They will 01104 // probably be added on demand, as they seem needed. 01105 switch (CE2->getOpcode()) { 01106 default: break; 01107 case Instruction::GetElementPtr: 01108 // By far the most common case to handle is when the base pointers are 01109 // obviously to the same or different globals. 01110 if (isa<GlobalValue>(CE1Op0) && isa<GlobalValue>(CE2Op0)) { 01111 if (CE1Op0 != CE2Op0) // Don't know relative ordering, but not equal 01112 return Instruction::SetNE; 01113 // Ok, we know that both getelementptr instructions are based on the 01114 // same global. From this, we can precisely determine the relative 01115 // ordering of the resultant pointers. 01116 unsigned i = 1; 01117 01118 // Compare all of the operands the GEP's have in common. 01119 gep_type_iterator GTI = gep_type_begin(CE1); 01120 for (;i != CE1->getNumOperands() && i != CE2->getNumOperands(); 01121 ++i, ++GTI) 01122 switch (IdxCompare(CE1->getOperand(i), CE2->getOperand(i), 01123 GTI.getIndexedType())) { 01124 case -1: return Instruction::SetLT; 01125 case 1: return Instruction::SetGT; 01126 case -2: return Instruction::BinaryOpsEnd; 01127 } 01128 01129 // Ok, we ran out of things they have in common. If any leftovers 01130 // are non-zero then we have a difference, otherwise we are equal. 01131 for (; i < CE1->getNumOperands(); ++i) 01132 if (!CE1->getOperand(i)->isNullValue()) 01133 if (isa<ConstantIntegral>(CE1->getOperand(i))) 01134 return Instruction::SetGT; 01135 else 01136 return Instruction::BinaryOpsEnd; // Might be equal. 01137 01138 for (; i < CE2->getNumOperands(); ++i) 01139 if (!CE2->getOperand(i)->isNullValue()) 01140 if (isa<ConstantIntegral>(CE2->getOperand(i))) 01141 return Instruction::SetLT; 01142 else 01143 return Instruction::BinaryOpsEnd; // Might be equal. 01144 return Instruction::SetEQ; 01145 } 01146 } 01147 } 01148 01149 default: 01150 break; 01151 } 01152 } 01153 01154 return Instruction::BinaryOpsEnd; 01155 } 01156 01157 Constant *llvm::ConstantFoldBinaryInstruction(unsigned Opcode, 01158 const Constant *V1, 01159 const Constant *V2) { 01160 Constant *C = 0; 01161 switch (Opcode) { 01162 default: break; 01163 case Instruction::Add: C = ConstRules::get(V1, V2).add(V1, V2); break; 01164 case Instruction::Sub: C = ConstRules::get(V1, V2).sub(V1, V2); break; 01165 case Instruction::Mul: C = ConstRules::get(V1, V2).mul(V1, V2); break; 01166 case Instruction::Div: C = ConstRules::get(V1, V2).div(V1, V2); break; 01167 case Instruction::Rem: C = ConstRules::get(V1, V2).rem(V1, V2); break; 01168 case Instruction::And: C = ConstRules::get(V1, V2).op_and(V1, V2); break; 01169 case Instruction::Or: C = ConstRules::get(V1, V2).op_or (V1, V2); break; 01170 case Instruction::Xor: C = ConstRules::get(V1, V2).op_xor(V1, V2); break; 01171 case Instruction::Shl: C = ConstRules::get(V1, V2).shl(V1, V2); break; 01172 case Instruction::Shr: C = ConstRules::get(V1, V2).shr(V1, V2); break; 01173 case Instruction::SetEQ: C = ConstRules::get(V1, V2).equalto(V1, V2); break; 01174 case Instruction::SetLT: C = ConstRules::get(V1, V2).lessthan(V1, V2);break; 01175 case Instruction::SetGT: C = ConstRules::get(V1, V2).lessthan(V2, V1);break; 01176 case Instruction::SetNE: // V1 != V2 === !(V1 == V2) 01177 C = ConstRules::get(V1, V2).equalto(V1, V2); 01178 if (C) return ConstantExpr::getNot(C); 01179 break; 01180 case Instruction::SetLE: // V1 <= V2 === !(V2 < V1) 01181 C = ConstRules::get(V1, V2).lessthan(V2, V1); 01182 if (C) return ConstantExpr::getNot(C); 01183 break; 01184 case Instruction::SetGE: // V1 >= V2 === !(V1 < V2) 01185 C = ConstRules::get(V1, V2).lessthan(V1, V2); 01186 if (C) return ConstantExpr::getNot(C); 01187 break; 01188 } 01189 01190 // If we successfully folded the expression, return it now. 01191 if (C) return C; 01192 01193 if (SetCondInst::isRelational(Opcode)) { 01194 if (isa<UndefValue>(V1) || isa<UndefValue>(V2)) 01195 return UndefValue::get(Type::BoolTy); 01196 switch (evaluateRelation(const_cast<Constant*>(V1), 01197 const_cast<Constant*>(V2))) { 01198 default: assert(0 && "Unknown relational!"); 01199 case Instruction::BinaryOpsEnd: 01200 break; // Couldn't determine anything about these constants. 01201 case Instruction::SetEQ: // We know the constants are equal! 01202 // If we know the constants are equal, we can decide the result of this 01203 // computation precisely. 01204 return ConstantBool::get(Opcode == Instruction::SetEQ || 01205 Opcode == Instruction::SetLE || 01206 Opcode == Instruction::SetGE); 01207 case Instruction::SetLT: 01208 // If we know that V1 < V2, we can decide the result of this computation 01209 // precisely. 01210 return ConstantBool::get(Opcode == Instruction::SetLT || 01211 Opcode == Instruction::SetNE || 01212 Opcode == Instruction::SetLE); 01213 case Instruction::SetGT: 01214 // If we know that V1 > V2, we can decide the result of this computation 01215 // precisely. 01216 return ConstantBool::get(Opcode == Instruction::SetGT || 01217 Opcode == Instruction::SetNE || 01218 Opcode == Instruction::SetGE); 01219 case Instruction::SetLE: 01220 // If we know that V1 <= V2, we can only partially decide this relation. 01221 if (Opcode == Instruction::SetGT) return ConstantBool::False; 01222 if (Opcode == Instruction::SetLT) return ConstantBool::True; 01223 break; 01224 01225 case Instruction::SetGE: 01226 // If we know that V1 >= V2, we can only partially decide this relation. 01227 if (Opcode == Instruction::SetLT) return ConstantBool::False; 01228 if (Opcode == Instruction::SetGT) return ConstantBool::True; 01229 break; 01230 01231 case Instruction::SetNE: 01232 // If we know that V1 != V2, we can only partially decide this relation. 01233 if (Opcode == Instruction::SetEQ) return ConstantBool::False; 01234 if (Opcode == Instruction::SetNE) return ConstantBool::True; 01235 break; 01236 } 01237 } 01238 01239 if (isa<UndefValue>(V1) || isa<UndefValue>(V2)) { 01240 switch (Opcode) { 01241 case Instruction::Add: 01242 case Instruction::Sub: 01243 case Instruction::Xor: 01244 return UndefValue::get(V1->getType()); 01245 01246 case Instruction::Mul: 01247 case Instruction::And: 01248 return Constant::getNullValue(V1->getType()); 01249 case Instruction::Div: 01250 case Instruction::Rem: 01251 if (!isa<UndefValue>(V2)) // undef/X -> 0 01252 return Constant::getNullValue(V1->getType()); 01253 return const_cast<Constant*>(V2); // X/undef -> undef 01254 case Instruction::Or: // X|undef -> -1 01255 return ConstantInt::getAllOnesValue(V1->getType()); 01256 case Instruction::Shr: 01257 if (!isa<UndefValue>(V2)) { 01258 if (V1->getType()->isSigned()) 01259 return const_cast<Constant*>(V1); // undef >>s X -> undef 01260 // undef >>u X -> 0 01261 } else if (isa<UndefValue>(V1)) { 01262 return const_cast<Constant*>(V1); // undef >> undef -> undef 01263 } else { 01264 if (V1->getType()->isSigned()) 01265 return const_cast<Constant*>(V1); // X >>s undef -> X 01266 // X >>u undef -> 0 01267 } 01268 return Constant::getNullValue(V1->getType()); 01269 01270 case Instruction::Shl: 01271 // undef << X -> 0 X << undef -> 0 01272 return Constant::getNullValue(V1->getType()); 01273 } 01274 } 01275 01276 if (const ConstantExpr *CE1 = dyn_cast<ConstantExpr>(V1)) { 01277 if (const ConstantExpr *CE2 = dyn_cast<ConstantExpr>(V2)) { 01278 // There are many possible foldings we could do here. We should probably 01279 // at least fold add of a pointer with an integer into the appropriate 01280 // getelementptr. This will improve alias analysis a bit. 01281 01282 01283 01284 01285 } else { 01286 // Just implement a couple of simple identities. 01287 switch (Opcode) { 01288 case Instruction::Add: 01289 if (V2->isNullValue()) return const_cast<Constant*>(V1); // X + 0 == X 01290 break; 01291 case Instruction::Sub: 01292 if (V2->isNullValue()) return const_cast<Constant*>(V1); // X - 0 == X 01293 break; 01294 case Instruction::Mul: 01295 if (V2->isNullValue()) return const_cast<Constant*>(V2); // X * 0 == 0 01296 if (const ConstantInt *CI = dyn_cast<ConstantInt>(V2)) 01297 if (CI->getRawValue() == 1) 01298 return const_cast<Constant*>(V1); // X * 1 == X 01299 break; 01300 case Instruction::Div: 01301 if (const ConstantInt *CI = dyn_cast<ConstantInt>(V2)) 01302 if (CI->getRawValue() == 1) 01303 return const_cast<Constant*>(V1); // X / 1 == X 01304 break; 01305 case Instruction::Rem: 01306 if (const ConstantInt *CI = dyn_cast<ConstantInt>(V2)) 01307 if (CI->getRawValue() == 1) 01308 return Constant::getNullValue(CI->getType()); // X % 1 == 0 01309 break; 01310 case Instruction::And: 01311 if (cast<ConstantIntegral>(V2)->isAllOnesValue()) 01312 return const_cast<Constant*>(V1); // X & -1 == X 01313 if (V2->isNullValue()) return const_cast<Constant*>(V2); // X & 0 == 0 01314 if (CE1->getOpcode() == Instruction::Cast && 01315 isa<GlobalValue>(CE1->getOperand(0))) { 01316 GlobalValue *CPR = cast<GlobalValue>(CE1->getOperand(0)); 01317 01318 // Functions are at least 4-byte aligned. If and'ing the address of a 01319 // function with a constant < 4, fold it to zero. 01320 if (const ConstantInt *CI = dyn_cast<ConstantInt>(V2)) 01321 if (CI->getRawValue() < 4 && isa<Function>(CPR)) 01322 return Constant::getNullValue(CI->getType()); 01323 } 01324 break; 01325 case Instruction::Or: 01326 if (V2->isNullValue()) return const_cast<Constant*>(V1); // X | 0 == X 01327 if (cast<ConstantIntegral>(V2)->isAllOnesValue()) 01328 return const_cast<Constant*>(V2); // X | -1 == -1 01329 break; 01330 case Instruction::Xor: 01331 if (V2->isNullValue()) return const_cast<Constant*>(V1); // X ^ 0 == X 01332 break; 01333 } 01334 } 01335 01336 } else if (const ConstantExpr *CE2 = dyn_cast<ConstantExpr>(V2)) { 01337 // If V2 is a constant expr and V1 isn't, flop them around and fold the 01338 // other way if possible. 01339 switch (Opcode) { 01340 case Instruction::Add: 01341 case Instruction::Mul: 01342 case Instruction::And: 01343 case Instruction::Or: 01344 case Instruction::Xor: 01345 case Instruction::SetEQ: 01346 case Instruction::SetNE: 01347 // No change of opcode required. 01348 return ConstantFoldBinaryInstruction(Opcode, V2, V1); 01349 01350 case Instruction::SetLT: 01351 case Instruction::SetGT: 01352 case Instruction::SetLE: 01353 case Instruction::SetGE: 01354 // Change the opcode as necessary to swap the operands. 01355 Opcode = SetCondInst::getSwappedCondition((Instruction::BinaryOps)Opcode); 01356 return ConstantFoldBinaryInstruction(Opcode, V2, V1); 01357 01358 case Instruction::Shl: 01359 case Instruction::Shr: 01360 case Instruction::Sub: 01361 case Instruction::Div: 01362 case Instruction::Rem: 01363 default: // These instructions cannot be flopped around. 01364 break; 01365 } 01366 } 01367 return 0; 01368 } 01369 01370 Constant *llvm::ConstantFoldGetElementPtr(const Constant *C, 01371 const std::vector<Value*> &IdxList) { 01372 if (IdxList.size() == 0 || 01373 (IdxList.size() == 1 && cast<Constant>(IdxList[0])->isNullValue())) 01374 return const_cast<Constant*>(C); 01375 01376 if (isa<UndefValue>(C)) { 01377 const Type *Ty = GetElementPtrInst::getIndexedType(C->getType(), IdxList, 01378 true); 01379 assert(Ty != 0 && "Invalid indices for GEP!"); 01380 return UndefValue::get(PointerType::get(Ty)); 01381 } 01382 01383 Constant *Idx0 = cast<Constant>(IdxList[0]); 01384 if (C->isNullValue()) { 01385 bool isNull = true; 01386 for (unsigned i = 0, e = IdxList.size(); i != e; ++i) 01387 if (!cast<Constant>(IdxList[i])->isNullValue()) { 01388 isNull = false; 01389 break; 01390 } 01391 if (isNull) { 01392 const Type *Ty = GetElementPtrInst::getIndexedType(C->getType(), IdxList, 01393 true); 01394 assert(Ty != 0 && "Invalid indices for GEP!"); 01395 return ConstantPointerNull::get(PointerType::get(Ty)); 01396 } 01397 01398 if (IdxList.size() == 1) { 01399 const Type *ElTy = cast<PointerType>(C->getType())->getElementType(); 01400 if (unsigned ElSize = ElTy->getPrimitiveSize()) { 01401 // gep null, C is equal to C*sizeof(nullty). If nullty is a known llvm 01402 // type, we can statically fold this. 01403 Constant *R = ConstantUInt::get(Type::UIntTy, ElSize); 01404 R = ConstantExpr::getCast(R, Idx0->getType()); 01405 R = ConstantExpr::getMul(R, Idx0); 01406 return ConstantExpr::getCast(R, C->getType()); 01407 } 01408 } 01409 } 01410 01411 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(const_cast<Constant*>(C))) { 01412 // Combine Indices - If the source pointer to this getelementptr instruction 01413 // is a getelementptr instruction, combine the indices of the two 01414 // getelementptr instructions into a single instruction. 01415 // 01416 if (CE->getOpcode() == Instruction::GetElementPtr) { 01417 const Type *LastTy = 0; 01418 for (gep_type_iterator I = gep_type_begin(CE), E = gep_type_end(CE); 01419 I != E; ++I) 01420 LastTy = *I; 01421 01422 if ((LastTy && isa<ArrayType>(LastTy)) || Idx0->isNullValue()) { 01423 std::vector<Value*> NewIndices; 01424 NewIndices.reserve(IdxList.size() + CE->getNumOperands()); 01425 for (unsigned i = 1, e = CE->getNumOperands()-1; i != e; ++i) 01426 NewIndices.push_back(CE->getOperand(i)); 01427 01428 // Add the last index of the source with the first index of the new GEP. 01429 // Make sure to handle the case when they are actually different types. 01430 Constant *Combined = CE->getOperand(CE->getNumOperands()-1); 01431 // Otherwise it must be an array. 01432 if (!Idx0->isNullValue()) { 01433 const Type *IdxTy = Combined->getType(); 01434 if (IdxTy != Idx0->getType()) IdxTy = Type::LongTy; 01435 Combined = 01436 ConstantExpr::get(Instruction::Add, 01437 ConstantExpr::getCast(Idx0, IdxTy), 01438 ConstantExpr::getCast(Combined, IdxTy)); 01439 } 01440 01441 NewIndices.push_back(Combined); 01442 NewIndices.insert(NewIndices.end(), IdxList.begin()+1, IdxList.end()); 01443 return ConstantExpr::getGetElementPtr(CE->getOperand(0), NewIndices); 01444 } 01445 } 01446 01447 // Implement folding of: 01448 // int* getelementptr ([2 x int]* cast ([3 x int]* %X to [2 x int]*), 01449 // long 0, long 0) 01450 // To: int* getelementptr ([3 x int]* %X, long 0, long 0) 01451 // 01452 if (CE->getOpcode() == Instruction::Cast && IdxList.size() > 1 && 01453 Idx0->isNullValue()) 01454 if (const PointerType *SPT = 01455 dyn_cast<PointerType>(CE->getOperand(0)->getType())) 01456 if (const ArrayType *SAT = dyn_cast<ArrayType>(SPT->getElementType())) 01457 if (const ArrayType *CAT = 01458 dyn_cast<ArrayType>(cast<PointerType>(C->getType())->getElementType())) 01459 if (CAT->getElementType() == SAT->getElementType()) 01460 return ConstantExpr::getGetElementPtr( 01461 (Constant*)CE->getOperand(0), IdxList); 01462 } 01463 return 0; 01464 } 01465