LLVM API Documentation

Function.h
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00001 //===-- llvm/Function.h - Class to represent a single function --*- C++ -*-===//
00002 //
00003 //                     The LLVM Compiler Infrastructure
00004 //
00005 // This file is distributed under the University of Illinois Open Source
00006 // License. See LICENSE.TXT for details.
00007 //
00008 //===----------------------------------------------------------------------===//
00009 //
00010 // This file contains the declaration of the Function class, which represents a
00011 // single function/procedure in LLVM.
00012 //
00013 // A function basically consists of a list of basic blocks, a list of arguments,
00014 // and a symbol table.
00015 //
00016 //===----------------------------------------------------------------------===//
00017 
00018 #ifndef LLVM_IR_FUNCTION_H
00019 #define LLVM_IR_FUNCTION_H
00020 
00021 #include "llvm/ADT/iterator_range.h"
00022 #include "llvm/IR/Argument.h"
00023 #include "llvm/IR/Attributes.h"
00024 #include "llvm/IR/BasicBlock.h"
00025 #include "llvm/IR/CallingConv.h"
00026 #include "llvm/IR/GlobalObject.h"
00027 #include "llvm/Support/Compiler.h"
00028 
00029 namespace llvm {
00030 
00031 class FunctionType;
00032 class LLVMContext;
00033 
00034 // Traits for intrusive list of basic blocks...
00035 template<> struct ilist_traits<BasicBlock>
00036   : public SymbolTableListTraits<BasicBlock, Function> {
00037 
00038   // createSentinel is used to get hold of the node that marks the end of the
00039   // list... (same trick used here as in ilist_traits<Instruction>)
00040   BasicBlock *createSentinel() const {
00041     return static_cast<BasicBlock*>(&Sentinel);
00042   }
00043   static void destroySentinel(BasicBlock*) {}
00044 
00045   BasicBlock *provideInitialHead() const { return createSentinel(); }
00046   BasicBlock *ensureHead(BasicBlock*) const { return createSentinel(); }
00047   static void noteHead(BasicBlock*, BasicBlock*) {}
00048 
00049   static ValueSymbolTable *getSymTab(Function *ItemParent);
00050 private:
00051   mutable ilist_half_node<BasicBlock> Sentinel;
00052 };
00053 
00054 template<> struct ilist_traits<Argument>
00055   : public SymbolTableListTraits<Argument, Function> {
00056 
00057   Argument *createSentinel() const {
00058     return static_cast<Argument*>(&Sentinel);
00059   }
00060   static void destroySentinel(Argument*) {}
00061 
00062   Argument *provideInitialHead() const { return createSentinel(); }
00063   Argument *ensureHead(Argument*) const { return createSentinel(); }
00064   static void noteHead(Argument*, Argument*) {}
00065 
00066   static ValueSymbolTable *getSymTab(Function *ItemParent);
00067 private:
00068   mutable ilist_half_node<Argument> Sentinel;
00069 };
00070 
00071 class Function : public GlobalObject, public ilist_node<Function> {
00072 public:
00073   typedef iplist<Argument> ArgumentListType;
00074   typedef iplist<BasicBlock> BasicBlockListType;
00075 
00076   // BasicBlock iterators...
00077   typedef BasicBlockListType::iterator iterator;
00078   typedef BasicBlockListType::const_iterator const_iterator;
00079 
00080   typedef ArgumentListType::iterator arg_iterator;
00081   typedef ArgumentListType::const_iterator const_arg_iterator;
00082 
00083 private:
00084   // Important things that make up a function!
00085   BasicBlockListType  BasicBlocks;        ///< The basic blocks
00086   mutable ArgumentListType ArgumentList;  ///< The formal arguments
00087   ValueSymbolTable *SymTab;               ///< Symbol table of args/instructions
00088   AttributeSet AttributeSets;             ///< Parameter attributes
00089 
00090   /*
00091    * Value::SubclassData
00092    *
00093    * bit 0  : HasLazyArguments
00094    * bit 1  : HasPrefixData
00095    * bit 2  : HasPrologueData
00096    * bit 3-6: CallingConvention
00097    */
00098 
00099   friend class SymbolTableListTraits<Function, Module>;
00100 
00101   void setParent(Module *parent);
00102 
00103   /// hasLazyArguments/CheckLazyArguments - The argument list of a function is
00104   /// built on demand, so that the list isn't allocated until the first client
00105   /// needs it.  The hasLazyArguments predicate returns true if the arg list
00106   /// hasn't been set up yet.
00107   bool hasLazyArguments() const {
00108     return getSubclassDataFromValue() & (1<<0);
00109   }
00110   void CheckLazyArguments() const {
00111     if (hasLazyArguments())
00112       BuildLazyArguments();
00113   }
00114   void BuildLazyArguments() const;
00115 
00116   Function(const Function&) LLVM_DELETED_FUNCTION;
00117   void operator=(const Function&) LLVM_DELETED_FUNCTION;
00118 
00119   /// Do the actual lookup of an intrinsic ID when the query could not be
00120   /// answered from the cache.
00121   unsigned lookupIntrinsicID() const LLVM_READONLY;
00122 
00123   /// Function ctor - If the (optional) Module argument is specified, the
00124   /// function is automatically inserted into the end of the function list for
00125   /// the module.
00126   ///
00127   Function(FunctionType *Ty, LinkageTypes Linkage,
00128            const Twine &N = "", Module *M = nullptr);
00129 
00130 public:
00131   static Function *Create(FunctionType *Ty, LinkageTypes Linkage,
00132                           const Twine &N = "", Module *M = nullptr) {
00133     return new(0) Function(Ty, Linkage, N, M);
00134   }
00135 
00136   ~Function();
00137 
00138   Type *getReturnType() const;           // Return the type of the ret val
00139   FunctionType *getFunctionType() const; // Return the FunctionType for me
00140 
00141   /// getContext - Return a pointer to the LLVMContext associated with this
00142   /// function, or NULL if this function is not bound to a context yet.
00143   LLVMContext &getContext() const;
00144 
00145   /// isVarArg - Return true if this function takes a variable number of
00146   /// arguments.
00147   bool isVarArg() const;
00148 
00149   bool isMaterializable() const;
00150   void setIsMaterializable(bool V);
00151 
00152   /// getIntrinsicID - This method returns the ID number of the specified
00153   /// function, or Intrinsic::not_intrinsic if the function is not an
00154   /// intrinsic, or if the pointer is null.  This value is always defined to be
00155   /// zero to allow easy checking for whether a function is intrinsic or not.
00156   /// The particular intrinsic functions which correspond to this value are
00157   /// defined in llvm/Intrinsics.h.  Results are cached in the LLVM context,
00158   /// subsequent requests for the same ID return results much faster from the
00159   /// cache.
00160   ///
00161   unsigned getIntrinsicID() const LLVM_READONLY;
00162   bool isIntrinsic() const { return getName().startswith("llvm."); }
00163 
00164   /// getCallingConv()/setCallingConv(CC) - These method get and set the
00165   /// calling convention of this function.  The enum values for the known
00166   /// calling conventions are defined in CallingConv.h.
00167   CallingConv::ID getCallingConv() const {
00168     return static_cast<CallingConv::ID>(getSubclassDataFromValue() >> 3);
00169   }
00170   void setCallingConv(CallingConv::ID CC) {
00171     setValueSubclassData((getSubclassDataFromValue() & 7) |
00172                          (static_cast<unsigned>(CC) << 3));
00173   }
00174 
00175   /// @brief Return the attribute list for this Function.
00176   AttributeSet getAttributes() const { return AttributeSets; }
00177 
00178   /// @brief Set the attribute list for this Function.
00179   void setAttributes(AttributeSet attrs) { AttributeSets = attrs; }
00180 
00181   /// @brief Add function attributes to this function.
00182   void addFnAttr(Attribute::AttrKind N) {
00183     setAttributes(AttributeSets.addAttribute(getContext(),
00184                                              AttributeSet::FunctionIndex, N));
00185   }
00186 
00187   /// @brief Remove function attributes from this function.
00188   void removeFnAttr(Attribute::AttrKind N) {
00189     setAttributes(AttributeSets.removeAttribute(
00190         getContext(), AttributeSet::FunctionIndex, N));
00191   }
00192 
00193   /// @brief Add function attributes to this function.
00194   void addFnAttr(StringRef Kind) {
00195     setAttributes(
00196       AttributeSets.addAttribute(getContext(),
00197                                  AttributeSet::FunctionIndex, Kind));
00198   }
00199   void addFnAttr(StringRef Kind, StringRef Value) {
00200     setAttributes(
00201       AttributeSets.addAttribute(getContext(),
00202                                  AttributeSet::FunctionIndex, Kind, Value));
00203   }
00204 
00205   /// @brief Return true if the function has the attribute.
00206   bool hasFnAttribute(Attribute::AttrKind Kind) const {
00207     return AttributeSets.hasAttribute(AttributeSet::FunctionIndex, Kind);
00208   }
00209   bool hasFnAttribute(StringRef Kind) const {
00210     return AttributeSets.hasAttribute(AttributeSet::FunctionIndex, Kind);
00211   }
00212 
00213   /// @brief Return the attribute for the given attribute kind.
00214   Attribute getFnAttribute(Attribute::AttrKind Kind) const {
00215     return AttributeSets.getAttribute(AttributeSet::FunctionIndex, Kind);
00216   }
00217   Attribute getFnAttribute(StringRef Kind) const {
00218     return AttributeSets.getAttribute(AttributeSet::FunctionIndex, Kind);
00219   }
00220 
00221   /// hasGC/getGC/setGC/clearGC - The name of the garbage collection algorithm
00222   ///                             to use during code generation.
00223   bool hasGC() const;
00224   const char *getGC() const;
00225   void setGC(const char *Str);
00226   void clearGC();
00227 
00228   /// @brief adds the attribute to the list of attributes.
00229   void addAttribute(unsigned i, Attribute::AttrKind attr);
00230 
00231   /// @brief adds the attributes to the list of attributes.
00232   void addAttributes(unsigned i, AttributeSet attrs);
00233 
00234   /// @brief removes the attributes from the list of attributes.
00235   void removeAttributes(unsigned i, AttributeSet attr);
00236 
00237   /// @brief Extract the alignment for a call or parameter (0=unknown).
00238   unsigned getParamAlignment(unsigned i) const {
00239     return AttributeSets.getParamAlignment(i);
00240   }
00241 
00242   /// @brief Extract the number of dereferenceable bytes for a call or
00243   /// parameter (0=unknown).
00244   uint64_t getDereferenceableBytes(unsigned i) const {
00245     return AttributeSets.getDereferenceableBytes(i);
00246   }
00247 
00248   /// @brief Determine if the function does not access memory.
00249   bool doesNotAccessMemory() const {
00250     return AttributeSets.hasAttribute(AttributeSet::FunctionIndex,
00251                                       Attribute::ReadNone);
00252   }
00253   void setDoesNotAccessMemory() {
00254     addFnAttr(Attribute::ReadNone);
00255   }
00256 
00257   /// @brief Determine if the function does not access or only reads memory.
00258   bool onlyReadsMemory() const {
00259     return doesNotAccessMemory() ||
00260       AttributeSets.hasAttribute(AttributeSet::FunctionIndex,
00261                                  Attribute::ReadOnly);
00262   }
00263   void setOnlyReadsMemory() {
00264     addFnAttr(Attribute::ReadOnly);
00265   }
00266 
00267   /// @brief Determine if the function cannot return.
00268   bool doesNotReturn() const {
00269     return AttributeSets.hasAttribute(AttributeSet::FunctionIndex,
00270                                       Attribute::NoReturn);
00271   }
00272   void setDoesNotReturn() {
00273     addFnAttr(Attribute::NoReturn);
00274   }
00275 
00276   /// @brief Determine if the function cannot unwind.
00277   bool doesNotThrow() const {
00278     return AttributeSets.hasAttribute(AttributeSet::FunctionIndex,
00279                                       Attribute::NoUnwind);
00280   }
00281   void setDoesNotThrow() {
00282     addFnAttr(Attribute::NoUnwind);
00283   }
00284 
00285   /// @brief Determine if the call cannot be duplicated.
00286   bool cannotDuplicate() const {
00287     return AttributeSets.hasAttribute(AttributeSet::FunctionIndex,
00288                                       Attribute::NoDuplicate);
00289   }
00290   void setCannotDuplicate() {
00291     addFnAttr(Attribute::NoDuplicate);
00292   }
00293 
00294   /// @brief True if the ABI mandates (or the user requested) that this
00295   /// function be in a unwind table.
00296   bool hasUWTable() const {
00297     return AttributeSets.hasAttribute(AttributeSet::FunctionIndex,
00298                                       Attribute::UWTable);
00299   }
00300   void setHasUWTable() {
00301     addFnAttr(Attribute::UWTable);
00302   }
00303 
00304   /// @brief True if this function needs an unwind table.
00305   bool needsUnwindTableEntry() const {
00306     return hasUWTable() || !doesNotThrow();
00307   }
00308 
00309   /// @brief Determine if the function returns a structure through first
00310   /// pointer argument.
00311   bool hasStructRetAttr() const {
00312     return AttributeSets.hasAttribute(1, Attribute::StructRet) ||
00313            AttributeSets.hasAttribute(2, Attribute::StructRet);
00314   }
00315 
00316   /// @brief Determine if the parameter does not alias other parameters.
00317   /// @param n The parameter to check. 1 is the first parameter, 0 is the return
00318   bool doesNotAlias(unsigned n) const {
00319     return AttributeSets.hasAttribute(n, Attribute::NoAlias);
00320   }
00321   void setDoesNotAlias(unsigned n) {
00322     addAttribute(n, Attribute::NoAlias);
00323   }
00324 
00325   /// @brief Determine if the parameter can be captured.
00326   /// @param n The parameter to check. 1 is the first parameter, 0 is the return
00327   bool doesNotCapture(unsigned n) const {
00328     return AttributeSets.hasAttribute(n, Attribute::NoCapture);
00329   }
00330   void setDoesNotCapture(unsigned n) {
00331     addAttribute(n, Attribute::NoCapture);
00332   }
00333 
00334   bool doesNotAccessMemory(unsigned n) const {
00335     return AttributeSets.hasAttribute(n, Attribute::ReadNone);
00336   }
00337   void setDoesNotAccessMemory(unsigned n) {
00338     addAttribute(n, Attribute::ReadNone);
00339   }
00340 
00341   bool onlyReadsMemory(unsigned n) const {
00342     return doesNotAccessMemory(n) ||
00343       AttributeSets.hasAttribute(n, Attribute::ReadOnly);
00344   }
00345   void setOnlyReadsMemory(unsigned n) {
00346     addAttribute(n, Attribute::ReadOnly);
00347   }
00348 
00349   /// copyAttributesFrom - copy all additional attributes (those not needed to
00350   /// create a Function) from the Function Src to this one.
00351   void copyAttributesFrom(const GlobalValue *Src) override;
00352 
00353   /// deleteBody - This method deletes the body of the function, and converts
00354   /// the linkage to external.
00355   ///
00356   void deleteBody() {
00357     dropAllReferences();
00358     setLinkage(ExternalLinkage);
00359   }
00360 
00361   /// removeFromParent - This method unlinks 'this' from the containing module,
00362   /// but does not delete it.
00363   ///
00364   void removeFromParent() override;
00365 
00366   /// eraseFromParent - This method unlinks 'this' from the containing module
00367   /// and deletes it.
00368   ///
00369   void eraseFromParent() override;
00370 
00371 
00372   /// Get the underlying elements of the Function... the basic block list is
00373   /// empty for external functions.
00374   ///
00375   const ArgumentListType &getArgumentList() const {
00376     CheckLazyArguments();
00377     return ArgumentList;
00378   }
00379   ArgumentListType &getArgumentList() {
00380     CheckLazyArguments();
00381     return ArgumentList;
00382   }
00383   static iplist<Argument> Function::*getSublistAccess(Argument*) {
00384     return &Function::ArgumentList;
00385   }
00386 
00387   const BasicBlockListType &getBasicBlockList() const { return BasicBlocks; }
00388         BasicBlockListType &getBasicBlockList()       { return BasicBlocks; }
00389   static iplist<BasicBlock> Function::*getSublistAccess(BasicBlock*) {
00390     return &Function::BasicBlocks;
00391   }
00392 
00393   const BasicBlock       &getEntryBlock() const   { return front(); }
00394         BasicBlock       &getEntryBlock()         { return front(); }
00395 
00396   //===--------------------------------------------------------------------===//
00397   // Symbol Table Accessing functions...
00398 
00399   /// getSymbolTable() - Return the symbol table...
00400   ///
00401   inline       ValueSymbolTable &getValueSymbolTable()       { return *SymTab; }
00402   inline const ValueSymbolTable &getValueSymbolTable() const { return *SymTab; }
00403 
00404 
00405   //===--------------------------------------------------------------------===//
00406   // BasicBlock iterator forwarding functions
00407   //
00408   iterator                begin()       { return BasicBlocks.begin(); }
00409   const_iterator          begin() const { return BasicBlocks.begin(); }
00410   iterator                end  ()       { return BasicBlocks.end();   }
00411   const_iterator          end  () const { return BasicBlocks.end();   }
00412 
00413   size_t                   size() const { return BasicBlocks.size();  }
00414   bool                    empty() const { return BasicBlocks.empty(); }
00415   const BasicBlock       &front() const { return BasicBlocks.front(); }
00416         BasicBlock       &front()       { return BasicBlocks.front(); }
00417   const BasicBlock        &back() const { return BasicBlocks.back();  }
00418         BasicBlock        &back()       { return BasicBlocks.back();  }
00419 
00420 /// @name Function Argument Iteration
00421 /// @{
00422 
00423   arg_iterator arg_begin() {
00424     CheckLazyArguments();
00425     return ArgumentList.begin();
00426   }
00427   const_arg_iterator arg_begin() const {
00428     CheckLazyArguments();
00429     return ArgumentList.begin();
00430   }
00431   arg_iterator arg_end() {
00432     CheckLazyArguments();
00433     return ArgumentList.end();
00434   }
00435   const_arg_iterator arg_end() const {
00436     CheckLazyArguments();
00437     return ArgumentList.end();
00438   }
00439 
00440   iterator_range<arg_iterator> args() {
00441     return iterator_range<arg_iterator>(arg_begin(), arg_end());
00442   }
00443 
00444   iterator_range<const_arg_iterator> args() const {
00445     return iterator_range<const_arg_iterator>(arg_begin(), arg_end());
00446   }
00447 
00448 /// @}
00449 
00450   size_t arg_size() const;
00451   bool arg_empty() const;
00452 
00453   bool hasPrefixData() const {
00454     return getSubclassDataFromValue() & (1<<1);
00455   }
00456 
00457   Constant *getPrefixData() const;
00458   void setPrefixData(Constant *PrefixData);
00459 
00460   bool hasPrologueData() const {
00461     return getSubclassDataFromValue() & (1<<2);
00462   }
00463 
00464   Constant *getPrologueData() const;
00465   void setPrologueData(Constant *PrologueData);
00466 
00467   /// viewCFG - This function is meant for use from the debugger.  You can just
00468   /// say 'call F->viewCFG()' and a ghostview window should pop up from the
00469   /// program, displaying the CFG of the current function with the code for each
00470   /// basic block inside.  This depends on there being a 'dot' and 'gv' program
00471   /// in your path.
00472   ///
00473   void viewCFG() const;
00474 
00475   /// viewCFGOnly - This function is meant for use from the debugger.  It works
00476   /// just like viewCFG, but it does not include the contents of basic blocks
00477   /// into the nodes, just the label.  If you are only interested in the CFG
00478   /// this can make the graph smaller.
00479   ///
00480   void viewCFGOnly() const;
00481 
00482   /// Methods for support type inquiry through isa, cast, and dyn_cast:
00483   static inline bool classof(const Value *V) {
00484     return V->getValueID() == Value::FunctionVal;
00485   }
00486 
00487   /// dropAllReferences() - This method causes all the subinstructions to "let
00488   /// go" of all references that they are maintaining.  This allows one to
00489   /// 'delete' a whole module at a time, even though there may be circular
00490   /// references... first all references are dropped, and all use counts go to
00491   /// zero.  Then everything is deleted for real.  Note that no operations are
00492   /// valid on an object that has "dropped all references", except operator
00493   /// delete.
00494   ///
00495   /// Since no other object in the module can have references into the body of a
00496   /// function, dropping all references deletes the entire body of the function,
00497   /// including any contained basic blocks.
00498   ///
00499   void dropAllReferences();
00500 
00501   /// hasAddressTaken - returns true if there are any uses of this function
00502   /// other than direct calls or invokes to it, or blockaddress expressions.
00503   /// Optionally passes back an offending user for diagnostic purposes.
00504   ///
00505   bool hasAddressTaken(const User** = nullptr) const;
00506 
00507   /// isDefTriviallyDead - Return true if it is trivially safe to remove
00508   /// this function definition from the module (because it isn't externally
00509   /// visible, does not have its address taken, and has no callers).  To make
00510   /// this more accurate, call removeDeadConstantUsers first.
00511   bool isDefTriviallyDead() const;
00512 
00513   /// callsFunctionThatReturnsTwice - Return true if the function has a call to
00514   /// setjmp or other function that gcc recognizes as "returning twice".
00515   bool callsFunctionThatReturnsTwice() const;
00516 
00517 private:
00518   // Shadow Value::setValueSubclassData with a private forwarding method so that
00519   // subclasses cannot accidentally use it.
00520   void setValueSubclassData(unsigned short D) {
00521     Value::setValueSubclassData(D);
00522   }
00523 };
00524 
00525 inline ValueSymbolTable *
00526 ilist_traits<BasicBlock>::getSymTab(Function *F) {
00527   return F ? &F->getValueSymbolTable() : nullptr;
00528 }
00529 
00530 inline ValueSymbolTable *
00531 ilist_traits<Argument>::getSymTab(Function *F) {
00532   return F ? &F->getValueSymbolTable() : nullptr;
00533 }
00534 
00535 } // End llvm namespace
00536 
00537 #endif