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      1 //===--- CodeGenTBAA.h - TBAA information for LLVM CodeGen ------*- 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 is the code that manages TBAA information and defines the TBAA policy
     11 // for the optimizer to use.
     12 //
     13 //===----------------------------------------------------------------------===//
     14 
     15 #ifndef CLANG_CODEGEN_CODEGENTBAA_H
     16 #define CLANG_CODEGEN_CODEGENTBAA_H
     17 
     18 #include "clang/Basic/LLVM.h"
     19 #include "llvm/ADT/DenseMap.h"
     20 #include "llvm/IR/MDBuilder.h"
     21 
     22 namespace llvm {
     23   class LLVMContext;
     24   class MDNode;
     25 }
     26 
     27 namespace clang {
     28   class ASTContext;
     29   class CodeGenOptions;
     30   class LangOptions;
     31   class MangleContext;
     32   class QualType;
     33   class Type;
     34 
     35 namespace CodeGen {
     36   class CGRecordLayout;
     37 
     38   struct TBAAPathTag {
     39     TBAAPathTag(const Type *B, const llvm::MDNode *A, uint64_t O)
     40       : BaseT(B), AccessN(A), Offset(O) {}
     41     const Type *BaseT;
     42     const llvm::MDNode *AccessN;
     43     uint64_t Offset;
     44   };
     45 
     46 /// CodeGenTBAA - This class organizes the cross-module state that is used
     47 /// while lowering AST types to LLVM types.
     48 class CodeGenTBAA {
     49   ASTContext &Context;
     50   const CodeGenOptions &CodeGenOpts;
     51   const LangOptions &Features;
     52   MangleContext &MContext;
     53 
     54   // MDHelper - Helper for creating metadata.
     55   llvm::MDBuilder MDHelper;
     56 
     57   /// MetadataCache - This maps clang::Types to scalar llvm::MDNodes describing
     58   /// them.
     59   llvm::DenseMap<const Type *, llvm::MDNode *> MetadataCache;
     60   /// This maps clang::Types to a struct node in the type DAG.
     61   llvm::DenseMap<const Type *, llvm::MDNode *> StructTypeMetadataCache;
     62   /// This maps TBAAPathTags to a tag node.
     63   llvm::DenseMap<TBAAPathTag, llvm::MDNode *> StructTagMetadataCache;
     64   /// This maps a scalar type to a scalar tag node.
     65   llvm::DenseMap<const llvm::MDNode *, llvm::MDNode *> ScalarTagMetadataCache;
     66 
     67   /// StructMetadataCache - This maps clang::Types to llvm::MDNodes describing
     68   /// them for struct assignments.
     69   llvm::DenseMap<const Type *, llvm::MDNode *> StructMetadataCache;
     70 
     71   llvm::MDNode *Root;
     72   llvm::MDNode *Char;
     73 
     74   /// getRoot - This is the mdnode for the root of the metadata type graph
     75   /// for this translation unit.
     76   llvm::MDNode *getRoot();
     77 
     78   /// getChar - This is the mdnode for "char", which is special, and any types
     79   /// considered to be equivalent to it.
     80   llvm::MDNode *getChar();
     81 
     82   /// CollectFields - Collect information about the fields of a type for
     83   /// !tbaa.struct metadata formation. Return false for an unsupported type.
     84   bool CollectFields(uint64_t BaseOffset,
     85                      QualType Ty,
     86                      SmallVectorImpl<llvm::MDBuilder::TBAAStructField> &Fields,
     87                      bool MayAlias);
     88 
     89   /// A wrapper function to create a scalar type. For struct-path aware TBAA,
     90   /// the scalar type has the same format as the struct type: name, offset,
     91   /// pointer to another node in the type DAG.
     92   llvm::MDNode *createTBAAScalarType(StringRef Name, llvm::MDNode *Parent);
     93 
     94 public:
     95   CodeGenTBAA(ASTContext &Ctx, llvm::LLVMContext &VMContext,
     96               const CodeGenOptions &CGO,
     97               const LangOptions &Features,
     98               MangleContext &MContext);
     99   ~CodeGenTBAA();
    100 
    101   /// getTBAAInfo - Get the TBAA MDNode to be used for a dereference
    102   /// of the given type.
    103   llvm::MDNode *getTBAAInfo(QualType QTy);
    104 
    105   /// getTBAAInfoForVTablePtr - Get the TBAA MDNode to be used for a
    106   /// dereference of a vtable pointer.
    107   llvm::MDNode *getTBAAInfoForVTablePtr();
    108 
    109   /// getTBAAStructInfo - Get the TBAAStruct MDNode to be used for a memcpy of
    110   /// the given type.
    111   llvm::MDNode *getTBAAStructInfo(QualType QTy);
    112 
    113   /// Get the MDNode in the type DAG for given struct type QType.
    114   llvm::MDNode *getTBAAStructTypeInfo(QualType QType);
    115   /// Get the tag MDNode for a given base type, the actual scalar access MDNode
    116   /// and offset into the base type.
    117   llvm::MDNode *getTBAAStructTagInfo(QualType BaseQType,
    118                                      llvm::MDNode *AccessNode, uint64_t Offset);
    119 
    120   /// Get the scalar tag MDNode for a given scalar type.
    121   llvm::MDNode *getTBAAScalarTagInfo(llvm::MDNode *AccessNode);
    122 };
    123 
    124 }  // end namespace CodeGen
    125 }  // end namespace clang
    126 
    127 namespace llvm {
    128 
    129 template<> struct DenseMapInfo<clang::CodeGen::TBAAPathTag> {
    130   static clang::CodeGen::TBAAPathTag getEmptyKey() {
    131     return clang::CodeGen::TBAAPathTag(
    132       DenseMapInfo<const clang::Type *>::getEmptyKey(),
    133       DenseMapInfo<const MDNode *>::getEmptyKey(),
    134       DenseMapInfo<uint64_t>::getEmptyKey());
    135   }
    136 
    137   static clang::CodeGen::TBAAPathTag getTombstoneKey() {
    138     return clang::CodeGen::TBAAPathTag(
    139       DenseMapInfo<const clang::Type *>::getTombstoneKey(),
    140       DenseMapInfo<const MDNode *>::getTombstoneKey(),
    141       DenseMapInfo<uint64_t>::getTombstoneKey());
    142   }
    143 
    144   static unsigned getHashValue(const clang::CodeGen::TBAAPathTag &Val) {
    145     return DenseMapInfo<const clang::Type *>::getHashValue(Val.BaseT) ^
    146            DenseMapInfo<const MDNode *>::getHashValue(Val.AccessN) ^
    147            DenseMapInfo<uint64_t>::getHashValue(Val.Offset);
    148   }
    149 
    150   static bool isEqual(const clang::CodeGen::TBAAPathTag &LHS,
    151                       const clang::CodeGen::TBAAPathTag &RHS) {
    152     return LHS.BaseT == RHS.BaseT &&
    153            LHS.AccessN == RHS.AccessN &&
    154            LHS.Offset == RHS.Offset;
    155   }
    156 };
    157 
    158 }  // end namespace llvm
    159 
    160 #endif
    161