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Dan Gohman947c9af2010-10-14 23:06:10 +00001//===--- CodeGenTypes.cpp - TBAA information for LLVM CodeGen -------------===//
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//
Dan Gohman5419ce62010-10-21 18:49:12 +000010// This is the code that manages TBAA information and defines the TBAA policy
11// for the optimizer to use. Relevant standards text includes:
Dan Gohmanf47df3e2010-10-15 20:54:41 +000012//
13// C99 6.5p7
14// C++ [basic.lval] (p10 in n3126, p15 in some earlier versions)
Dan Gohman947c9af2010-10-14 23:06:10 +000015//
16//===----------------------------------------------------------------------===//
17
18#include "CodeGenTBAA.h"
19#include "clang/AST/ASTContext.h"
Benjamin Kramerea70eb32012-12-01 15:09:41 +000020#include "clang/AST/Attr.h"
Peter Collingbourne0ff0b372011-01-13 18:57:25 +000021#include "clang/AST/Mangle.h"
Benjamin Kramerea70eb32012-12-01 15:09:41 +000022#include "clang/AST/RecordLayout.h"
Saleem Abdulrasool10a49722016-04-08 16:52:00 +000023#include "clang/Frontend/CodeGenOptions.h"
Manman Renc451e572013-04-04 21:53:22 +000024#include "llvm/ADT/SmallSet.h"
Chandler Carruthffd55512013-01-02 11:45:17 +000025#include "llvm/IR/Constants.h"
26#include "llvm/IR/LLVMContext.h"
27#include "llvm/IR/Metadata.h"
28#include "llvm/IR/Type.h"
Dan Gohman947c9af2010-10-14 23:06:10 +000029using namespace clang;
30using namespace CodeGen;
31
32CodeGenTBAA::CodeGenTBAA(ASTContext &Ctx, llvm::LLVMContext& VMContext,
Kostya Serebryany5dd2cfc2012-04-24 06:57:01 +000033 const CodeGenOptions &CGO,
Dan Gohman2e29eb52010-10-15 20:23:12 +000034 const LangOptions &Features, MangleContext &MContext)
Benjamin Kramerd1d76b22012-06-06 17:32:50 +000035 : Context(Ctx), CodeGenOpts(CGO), Features(Features), MContext(MContext),
Craig Topper8a13c412014-05-21 05:09:00 +000036 MDHelper(VMContext), Root(nullptr), Char(nullptr) {
Dan Gohman947c9af2010-10-14 23:06:10 +000037}
38
Angel Garcia Gomez637d1e62015-10-20 13:23:58 +000039CodeGenTBAA::~CodeGenTBAA() {
40}
Dan Gohman947c9af2010-10-14 23:06:10 +000041
Dan Gohman7dfd13c2010-10-25 21:48:30 +000042llvm::MDNode *CodeGenTBAA::getRoot() {
43 // Define the root of the tree. This identifies the tree, so that
44 // if our LLVM IR is linked with LLVM IR from a different front-end
45 // (or a different version of this front-end), their TBAA trees will
46 // remain distinct, and the optimizer will treat them conservatively.
Manman Ren37dec102016-02-11 19:19:18 +000047 if (!Root) {
48 if (Features.CPlusPlus)
49 Root = MDHelper.createTBAARoot("Simple C++ TBAA");
50 else
51 Root = MDHelper.createTBAARoot("Simple C/C++ TBAA");
52 }
Dan Gohman7dfd13c2010-10-25 21:48:30 +000053
54 return Root;
55}
56
Manman Ren4f755de2013-10-08 00:08:49 +000057// For both scalar TBAA and struct-path aware TBAA, the scalar type has the
58// same format: name, parent node, and offset.
Manman Rene1ad74e2013-04-11 23:02:56 +000059llvm::MDNode *CodeGenTBAA::createTBAAScalarType(StringRef Name,
60 llvm::MDNode *Parent) {
Manman Ren4f755de2013-10-08 00:08:49 +000061 return MDHelper.createTBAAScalarTypeNode(Name, Parent);
Manman Rene1ad74e2013-04-11 23:02:56 +000062}
63
Dan Gohman7dfd13c2010-10-25 21:48:30 +000064llvm::MDNode *CodeGenTBAA::getChar() {
65 // Define the root of the tree for user-accessible memory. C and C++
66 // give special powers to char and certain similar types. However,
67 // these special powers only cover user-accessible memory, and doesn't
68 // include things like vtables.
69 if (!Char)
Manman Rene1ad74e2013-04-11 23:02:56 +000070 Char = createTBAAScalarType("omnipotent char", getRoot());
Dan Gohman7dfd13c2010-10-25 21:48:30 +000071
72 return Char;
73}
74
Dan Gohmanc2897692010-12-13 23:51:08 +000075static bool TypeHasMayAlias(QualType QTy) {
76 // Tagged types have declarations, and therefore may have attributes.
77 if (const TagType *TTy = dyn_cast<TagType>(QTy))
78 return TTy->getDecl()->hasAttr<MayAliasAttr>();
79
80 // Typedef types have declarations, and therefore may have attributes.
81 if (const TypedefType *TTy = dyn_cast<TypedefType>(QTy)) {
82 if (TTy->getDecl()->hasAttr<MayAliasAttr>())
83 return true;
84 // Also, their underlying types may have relevant attributes.
85 return TypeHasMayAlias(TTy->desugar());
86 }
87
88 return false;
89}
90
Dan Gohman947c9af2010-10-14 23:06:10 +000091llvm::MDNode *
92CodeGenTBAA::getTBAAInfo(QualType QTy) {
Manman Ren4f755de2013-10-08 00:08:49 +000093 // At -O0 or relaxed aliasing, TBAA is not emitted for regular types.
Kostya Serebryany5dd2cfc2012-04-24 06:57:01 +000094 if (CodeGenOpts.OptimizationLevel == 0 || CodeGenOpts.RelaxedAliasing)
Craig Topper8a13c412014-05-21 05:09:00 +000095 return nullptr;
Kostya Serebryany5dd2cfc2012-04-24 06:57:01 +000096
Dan Gohmanc2897692010-12-13 23:51:08 +000097 // If the type has the may_alias attribute (even on a typedef), it is
98 // effectively in the general char alias class.
99 if (TypeHasMayAlias(QTy))
100 return getChar();
101
John McCall424cec92011-01-19 06:33:43 +0000102 const Type *Ty = Context.getCanonicalType(QTy).getTypePtr();
Dan Gohman947c9af2010-10-14 23:06:10 +0000103
104 if (llvm::MDNode *N = MetadataCache[Ty])
105 return N;
106
Dan Gohman5419ce62010-10-21 18:49:12 +0000107 // Handle builtin types.
Dan Gohman3f1cf0f2010-10-14 23:39:00 +0000108 if (const BuiltinType *BTy = dyn_cast<BuiltinType>(Ty)) {
Dan Gohman947c9af2010-10-14 23:06:10 +0000109 switch (BTy->getKind()) {
Dan Gohmanf5c5e072010-10-15 17:52:03 +0000110 // Character types are special and can alias anything.
111 // In C++, this technically only includes "char" and "unsigned char",
112 // and not "signed char". In C, it includes all three. For now,
Dan Gohman4a3b1b32010-10-15 20:24:10 +0000113 // the risk of exploiting this detail in C++ seems likely to outweigh
Dan Gohmanf5c5e072010-10-15 17:52:03 +0000114 // the benefit.
Dan Gohman947c9af2010-10-14 23:06:10 +0000115 case BuiltinType::Char_U:
116 case BuiltinType::Char_S:
117 case BuiltinType::UChar:
118 case BuiltinType::SChar:
Dan Gohman7dfd13c2010-10-25 21:48:30 +0000119 return getChar();
Dan Gohman3f1cf0f2010-10-14 23:39:00 +0000120
121 // Unsigned types can alias their corresponding signed types.
122 case BuiltinType::UShort:
123 return getTBAAInfo(Context.ShortTy);
124 case BuiltinType::UInt:
125 return getTBAAInfo(Context.IntTy);
126 case BuiltinType::ULong:
127 return getTBAAInfo(Context.LongTy);
128 case BuiltinType::ULongLong:
129 return getTBAAInfo(Context.LongLongTy);
130 case BuiltinType::UInt128:
131 return getTBAAInfo(Context.Int128Ty);
132
Dan Gohman2d0a3c72010-10-15 20:24:53 +0000133 // Treat all other builtin types as distinct types. This includes
134 // treating wchar_t, char16_t, and char32_t as distinct from their
135 // "underlying types".
Dan Gohman947c9af2010-10-14 23:06:10 +0000136 default:
137 return MetadataCache[Ty] =
Manman Rene1ad74e2013-04-11 23:02:56 +0000138 createTBAAScalarType(BTy->getName(Features), getChar());
Dan Gohman947c9af2010-10-14 23:06:10 +0000139 }
140 }
141
Dan Gohman5419ce62010-10-21 18:49:12 +0000142 // Handle pointers.
Dan Gohmanc44fd642010-10-15 20:26:20 +0000143 // TODO: Implement C++'s type "similarity" and consider dis-"similar"
144 // pointers distinct.
Dan Gohmand65c1962010-10-15 00:01:39 +0000145 if (Ty->isPointerType())
Manman Rene1ad74e2013-04-11 23:02:56 +0000146 return MetadataCache[Ty] = createTBAAScalarType("any pointer",
147 getChar());
Dan Gohmand65c1962010-10-15 00:01:39 +0000148
Dan Gohman2e29eb52010-10-15 20:23:12 +0000149 // Enum types are distinct types. In C++ they have "underlying types",
150 // however they aren't related for TBAA.
151 if (const EnumType *ETy = dyn_cast<EnumType>(Ty)) {
Dan Gohman2e29eb52010-10-15 20:23:12 +0000152 // In C++ mode, types have linkage, so we can rely on the ODR and
153 // on their mangled names, if they're external.
154 // TODO: Is there a way to get a program-wide unique name for a
155 // decl with local linkage or no linkage?
Eli Friedmaneecc09a2013-07-05 20:27:40 +0000156 if (!Features.CPlusPlus || !ETy->getDecl()->isExternallyVisible())
Dan Gohman7dfd13c2010-10-25 21:48:30 +0000157 return MetadataCache[Ty] = getChar();
Dan Gohman2e29eb52010-10-15 20:23:12 +0000158
Dylan Noblesmith2c1dd272012-02-05 02:13:05 +0000159 SmallString<256> OutName;
Rafael Espindola3968cd02011-02-11 02:52:17 +0000160 llvm::raw_svector_ostream Out(OutName);
Reid Klecknercc99e262013-11-19 23:23:00 +0000161 MContext.mangleTypeName(QualType(ETy, 0), Out);
Manman Rene1ad74e2013-04-11 23:02:56 +0000162 return MetadataCache[Ty] = createTBAAScalarType(OutName, getChar());
Dan Gohman2e29eb52010-10-15 20:23:12 +0000163 }
164
Dan Gohman3f1cf0f2010-10-14 23:39:00 +0000165 // For now, handle any other kind of type conservatively.
Dan Gohman7dfd13c2010-10-25 21:48:30 +0000166 return MetadataCache[Ty] = getChar();
Dan Gohman947c9af2010-10-14 23:06:10 +0000167}
Kostya Serebryany141e46f2012-03-26 17:03:51 +0000168
169llvm::MDNode *CodeGenTBAA::getTBAAInfoForVTablePtr() {
Manman Rene1ad74e2013-04-11 23:02:56 +0000170 return createTBAAScalarType("vtable pointer", getRoot());
Kostya Serebryany141e46f2012-03-26 17:03:51 +0000171}
Dan Gohman22695fc2012-09-28 21:58:29 +0000172
173bool
174CodeGenTBAA::CollectFields(uint64_t BaseOffset,
175 QualType QTy,
176 SmallVectorImpl<llvm::MDBuilder::TBAAStructField> &
177 Fields,
178 bool MayAlias) {
179 /* Things not handled yet include: C++ base classes, bitfields, */
180
181 if (const RecordType *TTy = QTy->getAs<RecordType>()) {
182 const RecordDecl *RD = TTy->getDecl()->getDefinition();
183 if (RD->hasFlexibleArrayMember())
184 return false;
185
186 // TODO: Handle C++ base classes.
187 if (const CXXRecordDecl *Decl = dyn_cast<CXXRecordDecl>(RD))
188 if (Decl->bases_begin() != Decl->bases_end())
189 return false;
190
191 const ASTRecordLayout &Layout = Context.getASTRecordLayout(RD);
192
193 unsigned idx = 0;
194 for (RecordDecl::field_iterator i = RD->field_begin(),
195 e = RD->field_end(); i != e; ++i, ++idx) {
196 uint64_t Offset = BaseOffset +
197 Layout.getFieldOffset(idx) / Context.getCharWidth();
198 QualType FieldQTy = i->getType();
199 if (!CollectFields(Offset, FieldQTy, Fields,
200 MayAlias || TypeHasMayAlias(FieldQTy)))
201 return false;
202 }
203 return true;
204 }
205
206 /* Otherwise, treat whatever it is as a field. */
207 uint64_t Offset = BaseOffset;
208 uint64_t Size = Context.getTypeSizeInChars(QTy).getQuantity();
209 llvm::MDNode *TBAAInfo = MayAlias ? getChar() : getTBAAInfo(QTy);
Manman Ren4f755de2013-10-08 00:08:49 +0000210 llvm::MDNode *TBAATag = getTBAAScalarTagInfo(TBAAInfo);
Manman Ren09a39122013-04-22 19:50:07 +0000211 Fields.push_back(llvm::MDBuilder::TBAAStructField(Offset, Size, TBAATag));
Dan Gohman22695fc2012-09-28 21:58:29 +0000212 return true;
213}
214
215llvm::MDNode *
216CodeGenTBAA::getTBAAStructInfo(QualType QTy) {
217 const Type *Ty = Context.getCanonicalType(QTy).getTypePtr();
218
219 if (llvm::MDNode *N = StructMetadataCache[Ty])
220 return N;
221
222 SmallVector<llvm::MDBuilder::TBAAStructField, 4> Fields;
223 if (CollectFields(0, QTy, Fields, TypeHasMayAlias(QTy)))
224 return MDHelper.createTBAAStructNode(Fields);
225
226 // For now, handle any other kind of type conservatively.
Craig Topper8a13c412014-05-21 05:09:00 +0000227 return StructMetadataCache[Ty] = nullptr;
Dan Gohman22695fc2012-09-28 21:58:29 +0000228}
Manman Renc451e572013-04-04 21:53:22 +0000229
230/// Check if the given type can be handled by path-aware TBAA.
231static bool isTBAAPathStruct(QualType QTy) {
232 if (const RecordType *TTy = QTy->getAs<RecordType>()) {
233 const RecordDecl *RD = TTy->getDecl()->getDefinition();
Manman Rene36d3412013-04-30 17:38:09 +0000234 if (RD->hasFlexibleArrayMember())
235 return false;
Manman Renc451e572013-04-04 21:53:22 +0000236 // RD can be struct, union, class, interface or enum.
Manman Rene36d3412013-04-30 17:38:09 +0000237 // For now, we only handle struct and class.
238 if (RD->isStruct() || RD->isClass())
Manman Renc451e572013-04-04 21:53:22 +0000239 return true;
240 }
241 return false;
242}
243
244llvm::MDNode *
245CodeGenTBAA::getTBAAStructTypeInfo(QualType QTy) {
246 const Type *Ty = Context.getCanonicalType(QTy).getTypePtr();
247 assert(isTBAAPathStruct(QTy));
248
249 if (llvm::MDNode *N = StructTypeMetadataCache[Ty])
250 return N;
251
252 if (const RecordType *TTy = QTy->getAs<RecordType>()) {
253 const RecordDecl *RD = TTy->getDecl()->getDefinition();
254
255 const ASTRecordLayout &Layout = Context.getASTRecordLayout(RD);
Manman Rena6b73032013-04-27 00:26:07 +0000256 SmallVector <std::pair<llvm::MDNode*, uint64_t>, 4> Fields;
Manman Renc451e572013-04-04 21:53:22 +0000257 unsigned idx = 0;
258 for (RecordDecl::field_iterator i = RD->field_begin(),
259 e = RD->field_end(); i != e; ++i, ++idx) {
260 QualType FieldQTy = i->getType();
261 llvm::MDNode *FieldNode;
262 if (isTBAAPathStruct(FieldQTy))
263 FieldNode = getTBAAStructTypeInfo(FieldQTy);
Manman Rene1ad74e2013-04-11 23:02:56 +0000264 else
Manman Renc451e572013-04-04 21:53:22 +0000265 FieldNode = getTBAAInfo(FieldQTy);
Manman Renc451e572013-04-04 21:53:22 +0000266 if (!FieldNode)
Craig Topper8a13c412014-05-21 05:09:00 +0000267 return StructTypeMetadataCache[Ty] = nullptr;
Manman Renc451e572013-04-04 21:53:22 +0000268 Fields.push_back(std::make_pair(
Manman Rena6b73032013-04-27 00:26:07 +0000269 FieldNode, Layout.getFieldOffset(idx) / Context.getCharWidth()));
Manman Renc451e572013-04-04 21:53:22 +0000270 }
271
Manman Renc451e572013-04-04 21:53:22 +0000272 SmallString<256> OutName;
Manman Ren879ce882013-08-21 20:58:45 +0000273 if (Features.CPlusPlus) {
Reid Klecknercc99e262013-11-19 23:23:00 +0000274 // Don't use the mangler for C code.
Manman Ren879ce882013-08-21 20:58:45 +0000275 llvm::raw_svector_ostream Out(OutName);
Reid Klecknercc99e262013-11-19 23:23:00 +0000276 MContext.mangleTypeName(QualType(Ty, 0), Out);
Manman Ren879ce882013-08-21 20:58:45 +0000277 } else {
278 OutName = RD->getName();
279 }
Manman Renc451e572013-04-04 21:53:22 +0000280 // Create the struct type node with a vector of pairs (offset, type).
281 return StructTypeMetadataCache[Ty] =
282 MDHelper.createTBAAStructTypeNode(OutName, Fields);
283 }
284
Craig Topper8a13c412014-05-21 05:09:00 +0000285 return StructMetadataCache[Ty] = nullptr;
Manman Renc451e572013-04-04 21:53:22 +0000286}
287
Manman Ren4f755de2013-10-08 00:08:49 +0000288/// Return a TBAA tag node for both scalar TBAA and struct-path aware TBAA.
Manman Renc451e572013-04-04 21:53:22 +0000289llvm::MDNode *
290CodeGenTBAA::getTBAAStructTagInfo(QualType BaseQTy, llvm::MDNode *AccessNode,
291 uint64_t Offset) {
Manman Ren4f755de2013-10-08 00:08:49 +0000292 if (!AccessNode)
Craig Topper8a13c412014-05-21 05:09:00 +0000293 return nullptr;
Manman Ren4f755de2013-10-08 00:08:49 +0000294
Manman Renc451e572013-04-04 21:53:22 +0000295 if (!CodeGenOpts.StructPathTBAA)
Manman Ren4f755de2013-10-08 00:08:49 +0000296 return getTBAAScalarTagInfo(AccessNode);
Manman Renc451e572013-04-04 21:53:22 +0000297
298 const Type *BTy = Context.getCanonicalType(BaseQTy).getTypePtr();
299 TBAAPathTag PathTag = TBAAPathTag(BTy, AccessNode, Offset);
300 if (llvm::MDNode *N = StructTagMetadataCache[PathTag])
301 return N;
302
Craig Topper8a13c412014-05-21 05:09:00 +0000303 llvm::MDNode *BNode = nullptr;
Manman Renc451e572013-04-04 21:53:22 +0000304 if (isTBAAPathStruct(BaseQTy))
305 BNode = getTBAAStructTypeInfo(BaseQTy);
306 if (!BNode)
Manman Rene1ad74e2013-04-11 23:02:56 +0000307 return StructTagMetadataCache[PathTag] =
308 MDHelper.createTBAAStructTagNode(AccessNode, AccessNode, 0);
Manman Renc451e572013-04-04 21:53:22 +0000309
310 return StructTagMetadataCache[PathTag] =
311 MDHelper.createTBAAStructTagNode(BNode, AccessNode, Offset);
312}
Manman Rene1ad74e2013-04-11 23:02:56 +0000313
314llvm::MDNode *
315CodeGenTBAA::getTBAAScalarTagInfo(llvm::MDNode *AccessNode) {
Manman Ren4f755de2013-10-08 00:08:49 +0000316 if (!AccessNode)
Craig Topper8a13c412014-05-21 05:09:00 +0000317 return nullptr;
Manman Rene1ad74e2013-04-11 23:02:56 +0000318 if (llvm::MDNode *N = ScalarTagMetadataCache[AccessNode])
319 return N;
320
321 return ScalarTagMetadataCache[AccessNode] =
322 MDHelper.createTBAAStructTagNode(AccessNode, AccessNode, 0);
323}