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