src/llvm/include/llvm/IR/Value.h

   1 //===-- llvm/Value.h - Definition of the Value class ------------*- C++ -*-===//
   2 //
   3 //                     The LLVM Compiler Infrastructure
   4 //
   5 // This file is distributed under the University of Illinois Open Source
   6 // License. See LICENSE.TXT for details.
   7 //
   8 //===----------------------------------------------------------------------===//
   9 //
  10 // This file declares the Value class.
  11 //
  12 //===----------------------------------------------------------------------===//
  13
  14 #ifndef LLVM_IR_VALUE_H
  15 #define LLVM_IR_VALUE_H
  16
  17 #include "llvm-c/Core.h"
  18 #include "llvm/ADT/iterator_range.h"
  19 #include "llvm/IR/Use.h"
  20 #include "llvm/Support/CBindingWrapping.h"
  21 #include "llvm/Support/Casting.h"
  22 #include "llvm/Support/Compiler.h"
  23
  24 namespace llvm {
  25
  26 class APInt;
  27 class Argument;
  28 class AssemblyAnnotationWriter;
  29 class BasicBlock;
  30 class Constant;
  31 class DataLayout;
  32 class Function;
  33 class GlobalAlias;
  34 class GlobalObject;
  35 class GlobalValue;
  36 class GlobalVariable;
  37 class InlineAsm;
  38 class Instruction;
  39 class LLVMContext;
  40 class Module;
  41 class StringRef;
  42 class Twine;
  43 class Type;
  44 class ValueHandleBase;
  45 class ValueSymbolTable;
  46 class raw_ostream;
  47
  48 template<typename ValueTy> class StringMapEntry;
  49 typedef StringMapEntry<Value*> ValueName;
  50
  51 //===----------------------------------------------------------------------===//
  52 //                                 Value Class
  53 //===----------------------------------------------------------------------===//
  54
  55 /// \brief LLVM Value Representation
  56 ///
  57 /// This is a very important LLVM class. It is the base class of all values
  58 /// computed by a program that may be used as operands to other values. Value is
  59 /// the super class of other important classes such as Instruction and Function.
  60 /// All Values have a Type. Type is not a subclass of Value. Some values can
  61 /// have a name and they belong to some Module.  Setting the name on the Value
  62 /// automatically updates the module's symbol table.
  63 ///
  64 /// Every value has a "use list" that keeps track of which other Values are
  65 /// using this Value.  A Value can also have an arbitrary number of ValueHandle
  66 /// objects that watch it and listen to RAUW and Destroy events.  See
  67 /// llvm/IR/ValueHandle.h for details.
  68 class Value {
  69   Type *VTy;
  70   Use *UseList;
  71
  72   friend class ValueAsMetadata; // Allow access to NameAndIsUsedByMD.
  73   friend class ValueHandleBase;
  74   PointerIntPair<ValueName *, 1> NameAndIsUsedByMD;
  75
  76   const unsigned char SubclassID;   // Subclass identifier (for isa/dyn_cast)
  77   unsigned char HasValueHandle : 1; // Has a ValueHandle pointing to this?
  78 protected:
  79   /// \brief Hold subclass data that can be dropped.
  80   ///
  81   /// This member is similar to SubclassData, however it is for holding
  82   /// information which may be used to aid optimization, but which may be
  83   /// cleared to zero without affecting conservative interpretation.
  84   unsigned char SubclassOptionalData : 7;
  85
  86 private:
  87   /// \brief Hold arbitrary subclass data.
  88   ///
  89   /// This member is defined by this class, but is not used for anything.
  90   /// Subclasses can use it to hold whatever state they find useful.  This
  91   /// field is initialized to zero by the ctor.
  92   unsigned short SubclassData;
  93
  94 protected:
  95   /// \brief The number of operands in the subclass.
  96   ///
  97   /// This member is defined by this class, but not used for anything.
  98   /// Subclasses can use it to store their number of operands, if they have
  99   /// any.
 100   ///
 101   /// This is stored here to save space in User on 64-bit hosts.  Since most
 102   /// instances of Value have operands, 32-bit hosts aren't significantly
 103   /// affected.
 104   unsigned NumOperands;
 105
 106 private:
 107   template <typename UseT> // UseT == 'Use' or 'const Use'
 108   class use_iterator_impl
 109       : public std::iterator<std::forward_iterator_tag, UseT *, ptrdiff_t> {
 110     typedef std::iterator<std::forward_iterator_tag, UseT *, ptrdiff_t> super;
 111
 112     UseT *U;
 113     explicit use_iterator_impl(UseT *u) : U(u) {}
 114     friend class Value;
 115
 116   public:
 117     typedef typename super::reference reference;
 118     typedef typename super::pointer pointer;
 119
 120     use_iterator_impl() : U() {}
 121
 122     bool operator==(const use_iterator_impl &x) const { return U == x.U; }
 123     bool operator!=(const use_iterator_impl &x) const { return !operator==(x); }
 124
 125     use_iterator_impl &operator++() { // Preincrement
 126       assert(U && "Cannot increment end iterator!");
 127       U = U->getNext();
 128       return *this;
 129     }
 130     use_iterator_impl operator++(int) { // Postincrement
 131       auto tmp = *this;
 132       ++*this;
 133       return tmp;
 134     }
 135
 136     UseT &operator*() const {
 137       assert(U && "Cannot dereference end iterator!");
 138       return *U;
 139     }
 140
 141     UseT *operator->() const { return &operator*(); }
 142
 143     operator use_iterator_impl<const UseT>() const {
 144       return use_iterator_impl<const UseT>(U);
 145     }
 146   };
 147
 148   template <typename UserTy> // UserTy == 'User' or 'const User'
 149   class user_iterator_impl
 150       : public std::iterator<std::forward_iterator_tag, UserTy *, ptrdiff_t> {
 151     typedef std::iterator<std::forward_iterator_tag, UserTy *, ptrdiff_t> super;
 152
 153     use_iterator_impl<Use> UI;
 154     explicit user_iterator_impl(Use *U) : UI(U) {}
 155     friend class Value;
 156
 157   public:
 158     typedef typename super::reference reference;
 159     typedef typename super::pointer pointer;
 160
 161     user_iterator_impl() {}
 162
 163     bool operator==(const user_iterator_impl &x) const { return UI == x.UI; }
 164     bool operator!=(const user_iterator_impl &x) const { return !operator==(x); }
 165
 166     /// \brief Returns true if this iterator is equal to user_end() on the value.
 167     bool atEnd() const { return *this == user_iterator_impl(); }
 168
 169     user_iterator_impl &operator++() { // Preincrement
 170       ++UI;
 171       return *this;
 172     }
 173     user_iterator_impl operator++(int) { // Postincrement
 174       auto tmp = *this;
 175       ++*this;
 176       return tmp;
 177     }
 178
 179     // Retrieve a pointer to the current User.
 180     UserTy *operator*() const {
 181       return UI->getUser();
 182     }
 183
 184     UserTy *operator->() const { return operator*(); }
 185
 186     operator user_iterator_impl<const UserTy>() const {
 187       return user_iterator_impl<const UserTy>(*UI);
 188     }
 189
 190     Use &getUse() const { return *UI; }
 191
 192     /// \brief Return the operand # of this use in its User.
 193     ///
 194     /// FIXME: Replace all callers with a direct call to Use::getOperandNo.
 195     unsigned getOperandNo() const { return UI->getOperandNo(); }
 196   };
 197
 198   void operator=(const Value &) LLVM_DELETED_FUNCTION;
 199   Value(const Value &) LLVM_DELETED_FUNCTION;
 200
 201 protected:
 202   Value(Type *Ty, unsigned scid);
 203 public:
 204   virtual ~Value();
 205
 206   /// \brief Support for debugging, callable in GDB: V->dump()
 207   void dump() const;
 208
 209   /// \brief Implement operator<< on Value.
 210   void print(raw_ostream &O) const;
 211
 212   /// \brief Print the name of this Value out to the specified raw_ostream.
 213   ///
 214   /// This is useful when you just want to print 'int %reg126', not the
 215   /// instruction that generated it. If you specify a Module for context, then
 216   /// even constanst get pretty-printed; for example, the type of a null
 217   /// pointer is printed symbolically.
 218   void printAsOperand(raw_ostream &O, bool PrintType = true,
 219                       const Module *M = nullptr) const;
 220
 221   /// \brief All values are typed, get the type of this value.
 222   Type *getType() const { return VTy; }
 223
 224   /// \brief All values hold a context through their type.
 225   LLVMContext &getContext() const;
 226
 227   // \brief All values can potentially be named.
 228   bool hasName() const { return getValueName() != nullptr; }
 229   ValueName *getValueName() const { return NameAndIsUsedByMD.getPointer(); }
 230   void setValueName(ValueName *VN) { NameAndIsUsedByMD.setPointer(VN); }
 231
 232 private:
 233   void destroyValueName();
 234
 235 public:
 236   /// \brief Return a constant reference to the value's name.
 237   ///
 238   /// This is cheap and guaranteed to return the same reference as long as the
 239   /// value is not modified.
 240   StringRef getName() const;
 241
 242   /// \brief Change the name of the value.
 243   ///
 244   /// Choose a new unique name if the provided name is taken.
 245   ///
 246   /// \param Name The new name; or "" if the value's name should be removed.
 247   void setName(const Twine &Name);
 248
 249
 250   /// \brief Transfer the name from V to this value.
 251   ///
 252   /// After taking V's name, sets V's name to empty.
 253   ///
 254   /// \note It is an error to call V->takeName(V).
 255   void takeName(Value *V);
 256
 257   /// \brief Change all uses of this to point to a new Value.
 258   ///
 259   /// Go through the uses list for this definition and make each use point to
 260   /// "V" instead of "this".  After this completes, 'this's use list is
 261   /// guaranteed to be empty.
 262   void replaceAllUsesWith(Value *V);
 263
 264   /// replaceUsesOutsideBlock - Go through the uses list for this definition and
 265   /// make each use point to "V" instead of "this" when the use is outside the
 266   /// block. 'This's use list is expected to have at least one element.
 267   /// Unlike replaceAllUsesWith this function does not support basic block
 268   /// values or constant users.
 269   void replaceUsesOutsideBlock(Value *V, BasicBlock *BB);
 270
 271   //----------------------------------------------------------------------
 272   // Methods for handling the chain of uses of this Value.
 273   //
 274   bool               use_empty() const { return UseList == nullptr; }
 275
 276   typedef use_iterator_impl<Use>       use_iterator;
 277   typedef use_iterator_impl<const Use> const_use_iterator;
 278   use_iterator       use_begin()       { return use_iterator(UseList); }
 279   const_use_iterator use_begin() const { return const_use_iterator(UseList); }
 280   use_iterator       use_end()         { return use_iterator();   }
 281   const_use_iterator use_end()   const { return const_use_iterator();   }
 282   iterator_range<use_iterator> uses() {
 283     return iterator_range<use_iterator>(use_begin(), use_end());
 284   }
 285   iterator_range<const_use_iterator> uses() const {
 286     return iterator_range<const_use_iterator>(use_begin(), use_end());
 287   }
 288
 289   bool               user_empty() const { return UseList == nullptr; }
 290
 291   typedef user_iterator_impl<User>       user_iterator;
 292   typedef user_iterator_impl<const User> const_user_iterator;
 293   user_iterator       user_begin()       { return user_iterator(UseList); }
 294   const_user_iterator user_begin() const { return const_user_iterator(UseList); }
 295   user_iterator       user_end()         { return user_iterator();   }
 296   const_user_iterator user_end()   const { return const_user_iterator();   }
 297   User               *user_back()        { return *user_begin(); }
 298   const User         *user_back()  const { return *user_begin(); }
 299   iterator_range<user_iterator> users() {
 300     return iterator_range<user_iterator>(user_begin(), user_end());
 301   }
 302   iterator_range<const_user_iterator> users() const {
 303     return iterator_range<const_user_iterator>(user_begin(), user_end());
 304   }
 305
 306   /// \brief Return true if there is exactly one user of this value.
 307   ///
 308   /// This is specialized because it is a common request and does not require
 309   /// traversing the whole use list.
 310   bool hasOneUse() const {
 311     const_use_iterator I = use_begin(), E = use_end();
 312     if (I == E) return false;
 313     return ++I == E;
 314   }
 315
 316   /// \brief Return true if this Value has exactly N users.
 317   bool hasNUses(unsigned N) const;
 318
 319   /// \brief Return true if this value has N users or more.
 320   ///
 321   /// This is logically equivalent to getNumUses() >= N.
 322   bool hasNUsesOrMore(unsigned N) const;
 323
 324   /// \brief Check if this value is used in the specified basic block.
 325   bool isUsedInBasicBlock(const BasicBlock *BB) const;
 326
 327   /// \brief This method computes the number of uses of this Value.
 328   ///
 329   /// This is a linear time operation.  Use hasOneUse, hasNUses, or
 330   /// hasNUsesOrMore to check for specific values.
 331   unsigned getNumUses() const;
 332
 333   /// \brief This method should only be used by the Use class.
 334   void addUse(Use &U) { U.addToList(&UseList); }
 335
 336   /// \brief Concrete subclass of this.
 337   ///
 338   /// An enumeration for keeping track of the concrete subclass of Value that
 339   /// is actually instantiated. Values of this enumeration are kept in the
 340   /// Value classes SubclassID field. They are used for concrete type
 341   /// identification.
 342   enum ValueTy {
 343     ArgumentVal,              // This is an instance of Argument
 344     BasicBlockVal,            // This is an instance of BasicBlock
 345     FunctionVal,              // This is an instance of Function
 346     GlobalAliasVal,           // This is an instance of GlobalAlias
 347     GlobalVariableVal,        // This is an instance of GlobalVariable
 348     UndefValueVal,            // This is an instance of UndefValue
 349     BlockAddressVal,          // This is an instance of BlockAddress
 350     ConstantExprVal,          // This is an instance of ConstantExpr
 351     ConstantAggregateZeroVal, // This is an instance of ConstantAggregateZero
 352     ConstantDataArrayVal,     // This is an instance of ConstantDataArray
 353     ConstantDataVectorVal,    // This is an instance of ConstantDataVector
 354     ConstantIntVal,           // This is an instance of ConstantInt
 355     ConstantFPVal,            // This is an instance of ConstantFP
 356     ConstantArrayVal,         // This is an instance of ConstantArray
 357     ConstantStructVal,        // This is an instance of ConstantStruct
 358     ConstantVectorVal,        // This is an instance of ConstantVector
 359     ConstantPointerNullVal,   // This is an instance of ConstantPointerNull
 360     MetadataAsValueVal,       // This is an instance of MetadataAsValue
 361     InlineAsmVal,             // This is an instance of InlineAsm
 362     InstructionVal,           // This is an instance of Instruction
 363     // Enum values starting at InstructionVal are used for Instructions;
 364     // don't add new values here!
 365
 366     // Markers:
 367     ConstantFirstVal = FunctionVal,
 368     ConstantLastVal  = ConstantPointerNullVal
 369   };
 370
 371   /// \brief Return an ID for the concrete type of this object.
 372   ///
 373   /// This is used to implement the classof checks.  This should not be used
 374   /// for any other purpose, as the values may change as LLVM evolves.  Also,
 375   /// note that for instructions, the Instruction's opcode is added to
 376   /// InstructionVal. So this means three things:
 377   /// # there is no value with code InstructionVal (no opcode==0).
 378   /// # there are more possible values for the value type than in ValueTy enum.
 379   /// # the InstructionVal enumerator must be the highest valued enumerator in
 380   ///   the ValueTy enum.
 381   unsigned getValueID() const {
 382     return SubclassID;
 383   }
 384
 385   /// \brief Return the raw optional flags value contained in this value.
 386   ///
 387   /// This should only be used when testing two Values for equivalence.
 388   unsigned getRawSubclassOptionalData() const {
 389     return SubclassOptionalData;
 390   }
 391
 392   /// \brief Clear the optional flags contained in this value.
 393   void clearSubclassOptionalData() {
 394     SubclassOptionalData = 0;
 395   }
 396
 397   /// \brief Check the optional flags for equality.
 398   bool hasSameSubclassOptionalData(const Value *V) const {
 399     return SubclassOptionalData == V->SubclassOptionalData;
 400   }
 401
 402   /// \brief Clear any optional flags not set in the given Value.
 403   void intersectOptionalDataWith(const Value *V) {
 404     SubclassOptionalData &= V->SubclassOptionalData;
 405   }
 406
 407   /// \brief Return true if there is a value handle associated with this value.
 408   bool hasValueHandle() const { return HasValueHandle; }
 409
 410   /// \brief Return true if there is metadata referencing this value.
 411   bool isUsedByMetadata() const { return NameAndIsUsedByMD.getInt(); }
 412
 413   /// \brief Strip off pointer casts, all-zero GEPs, and aliases.
 414   ///
 415   /// Returns the original uncasted value.  If this is called on a non-pointer
 416   /// value, it returns 'this'.
 417   Value *stripPointerCasts();
 418   const Value *stripPointerCasts() const {
 419     return const_cast<Value*>(this)->stripPointerCasts();
 420   }
 421
 422   /// \brief Strip off pointer casts and all-zero GEPs.
 423   ///
 424   /// Returns the original uncasted value.  If this is called on a non-pointer
 425   /// value, it returns 'this'.
 426   Value *stripPointerCastsNoFollowAliases();
 427   const Value *stripPointerCastsNoFollowAliases() const {
 428     return const_cast<Value*>(this)->stripPointerCastsNoFollowAliases();
 429   }
 430
 431   /// \brief Strip off pointer casts and all-constant inbounds GEPs.
 432   ///
 433   /// Returns the original pointer value.  If this is called on a non-pointer
 434   /// value, it returns 'this'.
 435   Value *stripInBoundsConstantOffsets();
 436   const Value *stripInBoundsConstantOffsets() const {
 437     return const_cast<Value*>(this)->stripInBoundsConstantOffsets();
 438   }
 439
 440   /// \brief Accumulate offsets from \a stripInBoundsConstantOffsets().
 441   ///
 442   /// Stores the resulting constant offset stripped into the APInt provided.
 443   /// The provided APInt will be extended or truncated as needed to be the
 444   /// correct bitwidth for an offset of this pointer type.
 445   ///
 446   /// If this is called on a non-pointer value, it returns 'this'.
 447   Value *stripAndAccumulateInBoundsConstantOffsets(const DataLayout &DL,
 448                                                    APInt &Offset);
 449   const Value *stripAndAccumulateInBoundsConstantOffsets(const DataLayout &DL,
 450                                                          APInt &Offset) const {
 451     return const_cast<Value *>(this)
 452         ->stripAndAccumulateInBoundsConstantOffsets(DL, Offset);
 453   }
 454
 455   /// \brief Strip off pointer casts and inbounds GEPs.
 456   ///
 457   /// Returns the original pointer value.  If this is called on a non-pointer
 458   /// value, it returns 'this'.
 459   Value *stripInBoundsOffsets();
 460   const Value *stripInBoundsOffsets() const {
 461     return const_cast<Value*>(this)->stripInBoundsOffsets();
 462   }
 463
 464   /// \brief Check if this is always a dereferenceable pointer.
 465   ///
 466   /// Test if this value is always a pointer to allocated and suitably aligned
 467   /// memory for a simple load or store.
 468   bool isDereferenceablePointer(const DataLayout *DL = nullptr) const;
 469
 470   /// \brief Translate PHI node to its predecessor from the given basic block.
 471   ///
 472   /// If this value is a PHI node with CurBB as its parent, return the value in
 473   /// the PHI node corresponding to PredBB.  If not, return ourself.  This is
 474   /// useful if you want to know the value something has in a predecessor
 475   /// block.
 476   Value *DoPHITranslation(const BasicBlock *CurBB, const BasicBlock *PredBB);
 477
 478   const Value *DoPHITranslation(const BasicBlock *CurBB,
 479                                 const BasicBlock *PredBB) const{
 480     return const_cast<Value*>(this)->DoPHITranslation(CurBB, PredBB);
 481   }
 482
 483   /// \brief The maximum alignment for instructions.
 484   ///
 485   /// This is the greatest alignment value supported by load, store, and alloca
 486   /// instructions, and global values.
 487   static const unsigned MaximumAlignment = 1u << 29;
 488
 489   /// \brief Mutate the type of this Value to be of the specified type.
 490   ///
 491   /// Note that this is an extremely dangerous operation which can create
 492   /// completely invalid IR very easily.  It is strongly recommended that you
 493   /// recreate IR objects with the right types instead of mutating them in
 494   /// place.
 495   void mutateType(Type *Ty) {
 496     VTy = Ty;
 497   }
 498
 499   /// \brief Sort the use-list.
 500   ///
 501   /// Sorts the Value's use-list by Cmp using a stable mergesort.  Cmp is
 502   /// expected to compare two \a Use references.
 503   template <class Compare> void sortUseList(Compare Cmp);
 504
 505   /// \brief Reverse the use-list.
 506   void reverseUseList();
 507
 508 private:
 509   /// \brief Merge two lists together.
 510   ///
 511   /// Merges \c L and \c R using \c Cmp.  To enable stable sorts, always pushes
 512   /// "equal" items from L before items from R.
 513   ///
 514   /// \return the first element in the list.
 515   ///
 516   /// \note Completely ignores \a Use::Prev (doesn't read, doesn't update).
 517   template <class Compare>
 518   static Use *mergeUseLists(Use *L, Use *R, Compare Cmp) {
 519     Use *Merged;
 520     mergeUseListsImpl(L, R, &Merged, Cmp);
 521     return Merged;
 522   }
 523
 524   /// \brief Tail-recursive helper for \a mergeUseLists().
 525   ///
 526   /// \param[out] Next the first element in the list.
 527   template <class Compare>
 528   static void mergeUseListsImpl(Use *L, Use *R, Use **Next, Compare Cmp);
 529
 530 protected:
 531   unsigned short getSubclassDataFromValue() const { return SubclassData; }
 532   void setValueSubclassData(unsigned short D) { SubclassData = D; }
 533 };
 534
 535 inline raw_ostream &operator<<(raw_ostream &OS, const Value &V) {
 536   V.print(OS);
 537   return OS;
 538 }
 539
 540 void Use::set(Value *V) {
 541   if (Val) removeFromList();
 542   Val = V;
 543   if (V) V->addUse(*this);
 544 }
 545
 546 template <class Compare> void Value::sortUseList(Compare Cmp) {
 547   if (!UseList || !UseList->Next)
 548     // No need to sort 0 or 1 uses.
 549     return;
 550
 551   // Note: this function completely ignores Prev pointers until the end when
 552   // they're fixed en masse.
 553
 554   // Create a binomial vector of sorted lists, visiting uses one at a time and
 555   // merging lists as necessary.
 556   const unsigned MaxSlots = 32;
 557   Use *Slots[MaxSlots];
 558
 559   // Collect the first use, turning it into a single-item list.
 560   Use *Next = UseList->Next;
 561   UseList->Next = nullptr;
 562   unsigned NumSlots = 1;
 563   Slots[0] = UseList;
 564
 565   // Collect all but the last use.
 566   while (Next->Next) {
 567     Use *Current = Next;
 568     Next = Current->Next;
 569
 570     // Turn Current into a single-item list.
 571     Current->Next = nullptr;
 572
 573     // Save Current in the first available slot, merging on collisions.
 574     unsigned I;
 575     for (I = 0; I < NumSlots; ++I) {
 576       if (!Slots[I])
 577         break;
 578
 579       // Merge two lists, doubling the size of Current and emptying slot I.
 580       //
 581       // Since the uses in Slots[I] originally preceded those in Current, send
 582       // Slots[I] in as the left parameter to maintain a stable sort.
 583       Current = mergeUseLists(Slots[I], Current, Cmp);
 584       Slots[I] = nullptr;
 585     }
 586     // Check if this is a new slot.
 587     if (I == NumSlots) {
 588       ++NumSlots;
 589       assert(NumSlots <= MaxSlots && "Use list bigger than 2^32");
 590     }
 591
 592     // Found an open slot.
 593     Slots[I] = Current;
 594   }
 595
 596   // Merge all the lists together.
 597   assert(Next && "Expected one more Use");
 598   assert(!Next->Next && "Expected only one Use");
 599   UseList = Next;
 600   for (unsigned I = 0; I < NumSlots; ++I)
 601     if (Slots[I])
 602       // Since the uses in Slots[I] originally preceded those in UseList, send
 603       // Slots[I] in as the left parameter to maintain a stable sort.
 604       UseList = mergeUseLists(Slots[I], UseList, Cmp);
 605
 606   // Fix the Prev pointers.
 607   for (Use *I = UseList, **Prev = &UseList; I; I = I->Next) {
 608     I->setPrev(Prev);
 609     Prev = &I->Next;
 610   }
 611 }
 612
 613 template <class Compare>
 614 void Value::mergeUseListsImpl(Use *L, Use *R, Use **Next, Compare Cmp) {
 615   if (!L) {
 616     *Next = R;
 617     return;
 618   }
 619   if (!R) {
 620     *Next = L;
 621     return;
 622   }
 623   if (Cmp(*R, *L)) {
 624     *Next = R;
 625     mergeUseListsImpl(L, R->Next, &R->Next, Cmp);
 626     return;
 627   }
 628   *Next = L;
 629   mergeUseListsImpl(L->Next, R, &L->Next, Cmp);
 630 }
 631
 632 // isa - Provide some specializations of isa so that we don't have to include
 633 // the subtype header files to test to see if the value is a subclass...
 634 //
 635 template <> struct isa_impl<Constant, Value> {
 636   static inline bool doit(const Value &Val) {
 637     return Val.getValueID() >= Value::ConstantFirstVal &&
 638       Val.getValueID() <= Value::ConstantLastVal;
 639   }
 640 };
 641
 642 template <> struct isa_impl<Argument, Value> {
 643   static inline bool doit (const Value &Val) {
 644     return Val.getValueID() == Value::ArgumentVal;
 645   }
 646 };
 647
 648 template <> struct isa_impl<InlineAsm, Value> {
 649   static inline bool doit(const Value &Val) {
 650     return Val.getValueID() == Value::InlineAsmVal;
 651   }
 652 };
 653
 654 template <> struct isa_impl<Instruction, Value> {
 655   static inline bool doit(const Value &Val) {
 656     return Val.getValueID() >= Value::InstructionVal;
 657   }
 658 };
 659
 660 template <> struct isa_impl<BasicBlock, Value> {
 661   static inline bool doit(const Value &Val) {
 662     return Val.getValueID() == Value::BasicBlockVal;
 663   }
 664 };
 665
 666 template <> struct isa_impl<Function, Value> {
 667   static inline bool doit(const Value &Val) {
 668     return Val.getValueID() == Value::FunctionVal;
 669   }
 670 };
 671
 672 template <> struct isa_impl<GlobalVariable, Value> {
 673   static inline bool doit(const Value &Val) {
 674     return Val.getValueID() == Value::GlobalVariableVal;
 675   }
 676 };
 677
 678 template <> struct isa_impl<GlobalAlias, Value> {
 679   static inline bool doit(const Value &Val) {
 680     return Val.getValueID() == Value::GlobalAliasVal;
 681   }
 682 };
 683
 684 template <> struct isa_impl<GlobalValue, Value> {
 685   static inline bool doit(const Value &Val) {
 686     return isa<GlobalObject>(Val) || isa<GlobalAlias>(Val);
 687   }
 688 };
 689
 690 template <> struct isa_impl<GlobalObject, Value> {
 691   static inline bool doit(const Value &Val) {
 692     return isa<GlobalVariable>(Val) || isa<Function>(Val);
 693   }
 694 };
 695
 696 // Value* is only 4-byte aligned.
 697 template<>
 698 class PointerLikeTypeTraits<Value*> {
 699   typedef Value* PT;
 700 public:
 701   static inline void *getAsVoidPointer(PT P) { return P; }
 702   static inline PT getFromVoidPointer(void *P) {
 703     return static_cast<PT>(P);
 704   }
 705   enum { NumLowBitsAvailable = 2 };
 706 };
 707
 708 // Create wrappers for C Binding types (see CBindingWrapping.h).
 709 DEFINE_ISA_CONVERSION_FUNCTIONS(Value, LLVMValueRef)
 710
 711 /* Specialized opaque value conversions.
 712  */
 713 inline Value **unwrap(LLVMValueRef *Vals) {
 714   return reinterpret_cast<Value**>(Vals);
 715 }
 716
 717 template<typename T>
 718 inline T **unwrap(LLVMValueRef *Vals, unsigned Length) {
 719 #ifdef DEBUG
 720   for (LLVMValueRef *I = Vals, *E = Vals + Length; I != E; ++I)
 721     cast<T>(*I);
 722 #endif
 723   (void)Length;
 724   return reinterpret_cast<T**>(Vals);
 725 }
 726
 727 inline LLVMValueRef *wrap(const Value **Vals) {
 728   return reinterpret_cast<LLVMValueRef*>(const_cast<Value**>(Vals));
 729 }
 730
 731 } // End llvm namespace
 732
 733 #endif