1//===--- CodeGenTBAA.h - TBAA information for LLVM CodeGen ------*- C++ -*-===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8//
9// This is the code that manages TBAA information and defines the TBAA policy
10// for the optimizer to use.
11//
12//===----------------------------------------------------------------------===//
13
14#ifndef LLVM_CLANG_LIB_CODEGEN_CODEGENTBAA_H
15#define LLVM_CLANG_LIB_CODEGEN_CODEGENTBAA_H
16
17#include "clang/AST/Type.h"
18#include "clang/Basic/LLVM.h"
19#include "llvm/ADT/DenseMap.h"
20#include "llvm/IR/MDBuilder.h"
21#include "llvm/IR/Metadata.h"
22
23namespace clang {
24  class ASTContext;
25  class CodeGenOptions;
26  class LangOptions;
27  class MangleContext;
28  class QualType;
29  class Type;
30
31namespace CodeGen {
32class CGRecordLayout;
33
34// TBAAAccessKind - A kind of TBAA memory access descriptor.
35enum class TBAAAccessKind : unsigned {
36  Ordinary,
37  MayAlias,
38  Incomplete,
39};
40
41// TBAAAccessInfo - Describes a memory access in terms of TBAA.
42struct TBAAAccessInfo {
43  TBAAAccessInfo(TBAAAccessKind Kind, llvm::MDNode *BaseType,
44                 llvm::MDNode *AccessType, uint64_t Offset, uint64_t Size)
45    : Kind(Kind), BaseType(BaseType), AccessType(AccessType),
46      Offset(Offset), Size(Size)
47  {}
48
49  TBAAAccessInfo(llvm::MDNode *BaseType, llvm::MDNode *AccessType,
50                 uint64_t Offset, uint64_t Size)
51    : TBAAAccessInfo(TBAAAccessKind::Ordinary, BaseType, AccessType,
52                     Offset, Size)
53  {}
54
55  explicit TBAAAccessInfo(llvm::MDNode *AccessType, uint64_t Size)
56    : TBAAAccessInfo(/* BaseType= */ nullptr, AccessType, /* Offset= */ 0, Size)
57  {}
58
59  TBAAAccessInfo()
60    : TBAAAccessInfo(/* AccessType= */ nullptr, /* Size= */ 0)
61  {}
62
63  static TBAAAccessInfo getMayAliasInfo() {
64    return TBAAAccessInfo(TBAAAccessKind::MayAlias,
65                          /* BaseType= */ nullptr, /* AccessType= */ nullptr,
66                          /* Offset= */ 0, /* Size= */ 0);
67  }
68
69  bool isMayAlias() const { return Kind == TBAAAccessKind::MayAlias; }
70
71  static TBAAAccessInfo getIncompleteInfo() {
72    return TBAAAccessInfo(TBAAAccessKind::Incomplete,
73                          /* BaseType= */ nullptr, /* AccessType= */ nullptr,
74                          /* Offset= */ 0, /* Size= */ 0);
75  }
76
77  bool isIncomplete() const { return Kind == TBAAAccessKind::Incomplete; }
78
79  bool operator==(const TBAAAccessInfo &Other) const {
80    return Kind == Other.Kind &&
81           BaseType == Other.BaseType &&
82           AccessType == Other.AccessType &&
83           Offset == Other.Offset &&
84           Size == Other.Size;
85  }
86
87  bool operator!=(const TBAAAccessInfo &Other) const {
88    return !(*this == Other);
89  }
90
91  explicit operator bool() const {
92    return *this != TBAAAccessInfo();
93  }
94
95  /// Kind - The kind of the access descriptor.
96  TBAAAccessKind Kind;
97
98  /// BaseType - The base/leading access type. May be null if this access
99  /// descriptor represents an access that is not considered to be an access
100  /// to an aggregate or union member.
101  llvm::MDNode *BaseType;
102
103  /// AccessType - The final access type. May be null if there is no TBAA
104  /// information available about this access.
105  llvm::MDNode *AccessType;
106
107  /// Offset - The byte offset of the final access within the base one. Must be
108  /// zero if the base access type is not specified.
109  uint64_t Offset;
110
111  /// Size - The size of access, in bytes.
112  uint64_t Size;
113};
114
115/// CodeGenTBAA - This class organizes the cross-module state that is used
116/// while lowering AST types to LLVM types.
117class CodeGenTBAA {
118  ASTContext &Context;
119  llvm::Module &Module;
120  const CodeGenOptions &CodeGenOpts;
121  const LangOptions &Features;
122  MangleContext &MContext;
123
124  // MDHelper - Helper for creating metadata.
125  llvm::MDBuilder MDHelper;
126
127  /// MetadataCache - This maps clang::Types to scalar llvm::MDNodes describing
128  /// them.
129  llvm::DenseMap<const Type *, llvm::MDNode *> MetadataCache;
130  /// This maps clang::Types to a base access type in the type DAG.
131  llvm::DenseMap<const Type *, llvm::MDNode *> BaseTypeMetadataCache;
132  /// This maps TBAA access descriptors to tag nodes.
133  llvm::DenseMap<TBAAAccessInfo, llvm::MDNode *> AccessTagMetadataCache;
134
135  /// StructMetadataCache - This maps clang::Types to llvm::MDNodes describing
136  /// them for struct assignments.
137  llvm::DenseMap<const Type *, llvm::MDNode *> StructMetadataCache;
138
139  llvm::MDNode *Root;
140  llvm::MDNode *Char;
141
142  /// getRoot - This is the mdnode for the root of the metadata type graph
143  /// for this translation unit.
144  llvm::MDNode *getRoot();
145
146  /// getChar - This is the mdnode for "char", which is special, and any types
147  /// considered to be equivalent to it.
148  llvm::MDNode *getChar();
149
150  /// CollectFields - Collect information about the fields of a type for
151  /// !tbaa.struct metadata formation. Return false for an unsupported type.
152  bool CollectFields(uint64_t BaseOffset,
153                     QualType Ty,
154                     SmallVectorImpl<llvm::MDBuilder::TBAAStructField> &Fields,
155                     bool MayAlias);
156
157  /// createScalarTypeNode - A wrapper function to create a metadata node
158  /// describing a scalar type.
159  llvm::MDNode *createScalarTypeNode(StringRef Name, llvm::MDNode *Parent,
160                                     uint64_t Size);
161
162  /// getTypeInfoHelper - An internal helper function to generate metadata used
163  /// to describe accesses to objects of the given type.
164  llvm::MDNode *getTypeInfoHelper(const Type *Ty);
165
166  /// getBaseTypeInfoHelper - An internal helper function to generate metadata
167  /// used to describe accesses to objects of the given base type.
168  llvm::MDNode *getBaseTypeInfoHelper(const Type *Ty);
169
170public:
171  CodeGenTBAA(ASTContext &Ctx, llvm::Module &M, const CodeGenOptions &CGO,
172              const LangOptions &Features, MangleContext &MContext);
173  ~CodeGenTBAA();
174
175  /// getTypeInfo - Get metadata used to describe accesses to objects of the
176  /// given type.
177  llvm::MDNode *getTypeInfo(QualType QTy);
178
179  /// getAccessInfo - Get TBAA information that describes an access to
180  /// an object of the given type.
181  TBAAAccessInfo getAccessInfo(QualType AccessType);
182
183  /// getVTablePtrAccessInfo - Get the TBAA information that describes an
184  /// access to a virtual table pointer.
185  TBAAAccessInfo getVTablePtrAccessInfo(llvm::Type *VTablePtrType);
186
187  /// getTBAAStructInfo - Get the TBAAStruct MDNode to be used for a memcpy of
188  /// the given type.
189  llvm::MDNode *getTBAAStructInfo(QualType QTy);
190
191  /// getBaseTypeInfo - Get metadata that describes the given base access type.
192  /// Return null if the type is not suitable for use in TBAA access tags.
193  llvm::MDNode *getBaseTypeInfo(QualType QTy);
194
195  /// getAccessTagInfo - Get TBAA tag for a given memory access.
196  llvm::MDNode *getAccessTagInfo(TBAAAccessInfo Info);
197
198  /// mergeTBAAInfoForCast - Get merged TBAA information for the purpose of
199  /// type casts.
200  TBAAAccessInfo mergeTBAAInfoForCast(TBAAAccessInfo SourceInfo,
201                                      TBAAAccessInfo TargetInfo);
202
203  /// mergeTBAAInfoForConditionalOperator - Get merged TBAA information for the
204  /// purpose of conditional operator.
205  TBAAAccessInfo mergeTBAAInfoForConditionalOperator(TBAAAccessInfo InfoA,
206                                                     TBAAAccessInfo InfoB);
207
208  /// mergeTBAAInfoForMemoryTransfer - Get merged TBAA information for the
209  /// purpose of memory transfer calls.
210  TBAAAccessInfo mergeTBAAInfoForMemoryTransfer(TBAAAccessInfo DestInfo,
211                                                TBAAAccessInfo SrcInfo);
212};
213
214}  // end namespace CodeGen
215}  // end namespace clang
216
217namespace llvm {
218
219template<> struct DenseMapInfo<clang::CodeGen::TBAAAccessInfo> {
220  static clang::CodeGen::TBAAAccessInfo getEmptyKey() {
221    unsigned UnsignedKey = DenseMapInfo<unsigned>::getEmptyKey();
222    return clang::CodeGen::TBAAAccessInfo(
223      static_cast<clang::CodeGen::TBAAAccessKind>(UnsignedKey),
224      DenseMapInfo<MDNode *>::getEmptyKey(),
225      DenseMapInfo<MDNode *>::getEmptyKey(),
226      DenseMapInfo<uint64_t>::getEmptyKey(),
227      DenseMapInfo<uint64_t>::getEmptyKey());
228  }
229
230  static clang::CodeGen::TBAAAccessInfo getTombstoneKey() {
231    unsigned UnsignedKey = DenseMapInfo<unsigned>::getTombstoneKey();
232    return clang::CodeGen::TBAAAccessInfo(
233      static_cast<clang::CodeGen::TBAAAccessKind>(UnsignedKey),
234      DenseMapInfo<MDNode *>::getTombstoneKey(),
235      DenseMapInfo<MDNode *>::getTombstoneKey(),
236      DenseMapInfo<uint64_t>::getTombstoneKey(),
237      DenseMapInfo<uint64_t>::getTombstoneKey());
238  }
239
240  static unsigned getHashValue(const clang::CodeGen::TBAAAccessInfo &Val) {
241    auto KindValue = static_cast<unsigned>(Val.Kind);
242    return DenseMapInfo<unsigned>::getHashValue(KindValue) ^
243           DenseMapInfo<MDNode *>::getHashValue(Val.BaseType) ^
244           DenseMapInfo<MDNode *>::getHashValue(Val.AccessType) ^
245           DenseMapInfo<uint64_t>::getHashValue(Val.Offset) ^
246           DenseMapInfo<uint64_t>::getHashValue(Val.Size);
247  }
248
249  static bool isEqual(const clang::CodeGen::TBAAAccessInfo &LHS,
250                      const clang::CodeGen::TBAAAccessInfo &RHS) {
251    return LHS == RHS;
252  }
253};
254
255}  // end namespace llvm
256
257#endif
258