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Diffstat (limited to 'contrib/llvm/tools/clang/lib/CodeGen/CodeGenTBAA.cpp')
| -rw-r--r-- | contrib/llvm/tools/clang/lib/CodeGen/CodeGenTBAA.cpp | 321 |
1 files changed, 321 insertions, 0 deletions
diff --git a/contrib/llvm/tools/clang/lib/CodeGen/CodeGenTBAA.cpp b/contrib/llvm/tools/clang/lib/CodeGen/CodeGenTBAA.cpp new file mode 100644 index 0000000..699cc2e --- /dev/null +++ b/contrib/llvm/tools/clang/lib/CodeGen/CodeGenTBAA.cpp @@ -0,0 +1,321 @@ +//===--- CodeGenTypes.cpp - TBAA information for LLVM CodeGen -------------===// +// +// The LLVM Compiler Infrastructure +// +// This file is distributed under the University of Illinois Open Source +// License. See LICENSE.TXT for details. +// +//===----------------------------------------------------------------------===// +// +// This is the code that manages TBAA information and defines the TBAA policy +// for the optimizer to use. Relevant standards text includes: +// +// C99 6.5p7 +// C++ [basic.lval] (p10 in n3126, p15 in some earlier versions) +// +//===----------------------------------------------------------------------===// + +#include "CodeGenTBAA.h" +#include "clang/AST/ASTContext.h" +#include "clang/AST/Attr.h" +#include "clang/AST/Mangle.h" +#include "clang/AST/RecordLayout.h" +#include "clang/Frontend/CodeGenOptions.h" +#include "llvm/ADT/SmallSet.h" +#include "llvm/IR/Constants.h" +#include "llvm/IR/LLVMContext.h" +#include "llvm/IR/Metadata.h" +#include "llvm/IR/Type.h" +using namespace clang; +using namespace CodeGen; + +CodeGenTBAA::CodeGenTBAA(ASTContext &Ctx, llvm::LLVMContext& VMContext, + const CodeGenOptions &CGO, + const LangOptions &Features, MangleContext &MContext) + : Context(Ctx), CodeGenOpts(CGO), Features(Features), MContext(MContext), + MDHelper(VMContext), Root(0), Char(0) { +} + +CodeGenTBAA::~CodeGenTBAA() { +} + +llvm::MDNode *CodeGenTBAA::getRoot() { + // Define the root of the tree. This identifies the tree, so that + // if our LLVM IR is linked with LLVM IR from a different front-end + // (or a different version of this front-end), their TBAA trees will + // remain distinct, and the optimizer will treat them conservatively. + if (!Root) + Root = MDHelper.createTBAARoot("Simple C/C++ TBAA"); + + return Root; +} + +// For both scalar TBAA and struct-path aware TBAA, the scalar type has the +// same format: name, parent node, and offset. +llvm::MDNode *CodeGenTBAA::createTBAAScalarType(StringRef Name, + llvm::MDNode *Parent) { + return MDHelper.createTBAAScalarTypeNode(Name, Parent); +} + +llvm::MDNode *CodeGenTBAA::getChar() { + // Define the root of the tree for user-accessible memory. C and C++ + // give special powers to char and certain similar types. However, + // these special powers only cover user-accessible memory, and doesn't + // include things like vtables. + if (!Char) + Char = createTBAAScalarType("omnipotent char", getRoot()); + + return Char; +} + +static bool TypeHasMayAlias(QualType QTy) { + // Tagged types have declarations, and therefore may have attributes. + if (const TagType *TTy = dyn_cast<TagType>(QTy)) + return TTy->getDecl()->hasAttr<MayAliasAttr>(); + + // Typedef types have declarations, and therefore may have attributes. + if (const TypedefType *TTy = dyn_cast<TypedefType>(QTy)) { + if (TTy->getDecl()->hasAttr<MayAliasAttr>()) + return true; + // Also, their underlying types may have relevant attributes. + return TypeHasMayAlias(TTy->desugar()); + } + + return false; +} + +llvm::MDNode * +CodeGenTBAA::getTBAAInfo(QualType QTy) { + // At -O0 or relaxed aliasing, TBAA is not emitted for regular types. + if (CodeGenOpts.OptimizationLevel == 0 || CodeGenOpts.RelaxedAliasing) + return NULL; + + // If the type has the may_alias attribute (even on a typedef), it is + // effectively in the general char alias class. + if (TypeHasMayAlias(QTy)) + return getChar(); + + const Type *Ty = Context.getCanonicalType(QTy).getTypePtr(); + + if (llvm::MDNode *N = MetadataCache[Ty]) + return N; + + // Handle builtin types. + if (const BuiltinType *BTy = dyn_cast<BuiltinType>(Ty)) { + switch (BTy->getKind()) { + // Character types are special and can alias anything. + // In C++, this technically only includes "char" and "unsigned char", + // and not "signed char". In C, it includes all three. For now, + // the risk of exploiting this detail in C++ seems likely to outweigh + // the benefit. + case BuiltinType::Char_U: + case BuiltinType::Char_S: + case BuiltinType::UChar: + case BuiltinType::SChar: + return getChar(); + + // Unsigned types can alias their corresponding signed types. + case BuiltinType::UShort: + return getTBAAInfo(Context.ShortTy); + case BuiltinType::UInt: + return getTBAAInfo(Context.IntTy); + case BuiltinType::ULong: + return getTBAAInfo(Context.LongTy); + case BuiltinType::ULongLong: + return getTBAAInfo(Context.LongLongTy); + case BuiltinType::UInt128: + return getTBAAInfo(Context.Int128Ty); + + // Treat all other builtin types as distinct types. This includes + // treating wchar_t, char16_t, and char32_t as distinct from their + // "underlying types". + default: + return MetadataCache[Ty] = + createTBAAScalarType(BTy->getName(Features), getChar()); + } + } + + // Handle pointers. + // TODO: Implement C++'s type "similarity" and consider dis-"similar" + // pointers distinct. + if (Ty->isPointerType()) + return MetadataCache[Ty] = createTBAAScalarType("any pointer", + getChar()); + + // Enum types are distinct types. In C++ they have "underlying types", + // however they aren't related for TBAA. + if (const EnumType *ETy = dyn_cast<EnumType>(Ty)) { + // In C++ mode, types have linkage, so we can rely on the ODR and + // on their mangled names, if they're external. + // TODO: Is there a way to get a program-wide unique name for a + // decl with local linkage or no linkage? + if (!Features.CPlusPlus || !ETy->getDecl()->isExternallyVisible()) + return MetadataCache[Ty] = getChar(); + + SmallString<256> OutName; + llvm::raw_svector_ostream Out(OutName); + MContext.mangleTypeName(QualType(ETy, 0), Out); + Out.flush(); + return MetadataCache[Ty] = createTBAAScalarType(OutName, getChar()); + } + + // For now, handle any other kind of type conservatively. + return MetadataCache[Ty] = getChar(); +} + +llvm::MDNode *CodeGenTBAA::getTBAAInfoForVTablePtr() { + return createTBAAScalarType("vtable pointer", getRoot()); +} + +bool +CodeGenTBAA::CollectFields(uint64_t BaseOffset, + QualType QTy, + SmallVectorImpl<llvm::MDBuilder::TBAAStructField> & + Fields, + bool MayAlias) { + /* Things not handled yet include: C++ base classes, bitfields, */ + + if (const RecordType *TTy = QTy->getAs<RecordType>()) { + const RecordDecl *RD = TTy->getDecl()->getDefinition(); + if (RD->hasFlexibleArrayMember()) + return false; + + // TODO: Handle C++ base classes. + if (const CXXRecordDecl *Decl = dyn_cast<CXXRecordDecl>(RD)) + if (Decl->bases_begin() != Decl->bases_end()) + return false; + + const ASTRecordLayout &Layout = Context.getASTRecordLayout(RD); + + unsigned idx = 0; + for (RecordDecl::field_iterator i = RD->field_begin(), + e = RD->field_end(); i != e; ++i, ++idx) { + uint64_t Offset = BaseOffset + + Layout.getFieldOffset(idx) / Context.getCharWidth(); + QualType FieldQTy = i->getType(); + if (!CollectFields(Offset, FieldQTy, Fields, + MayAlias || TypeHasMayAlias(FieldQTy))) + return false; + } + return true; + } + + /* Otherwise, treat whatever it is as a field. */ + uint64_t Offset = BaseOffset; + uint64_t Size = Context.getTypeSizeInChars(QTy).getQuantity(); + llvm::MDNode *TBAAInfo = MayAlias ? getChar() : getTBAAInfo(QTy); + llvm::MDNode *TBAATag = getTBAAScalarTagInfo(TBAAInfo); + Fields.push_back(llvm::MDBuilder::TBAAStructField(Offset, Size, TBAATag)); + return true; +} + +llvm::MDNode * +CodeGenTBAA::getTBAAStructInfo(QualType QTy) { + const Type *Ty = Context.getCanonicalType(QTy).getTypePtr(); + + if (llvm::MDNode *N = StructMetadataCache[Ty]) + return N; + + SmallVector<llvm::MDBuilder::TBAAStructField, 4> Fields; + if (CollectFields(0, QTy, Fields, TypeHasMayAlias(QTy))) + return MDHelper.createTBAAStructNode(Fields); + + // For now, handle any other kind of type conservatively. + return StructMetadataCache[Ty] = NULL; +} + +/// Check if the given type can be handled by path-aware TBAA. +static bool isTBAAPathStruct(QualType QTy) { + if (const RecordType *TTy = QTy->getAs<RecordType>()) { + const RecordDecl *RD = TTy->getDecl()->getDefinition(); + if (RD->hasFlexibleArrayMember()) + return false; + // RD can be struct, union, class, interface or enum. + // For now, we only handle struct and class. + if (RD->isStruct() || RD->isClass()) + return true; + } + return false; +} + +llvm::MDNode * +CodeGenTBAA::getTBAAStructTypeInfo(QualType QTy) { + const Type *Ty = Context.getCanonicalType(QTy).getTypePtr(); + assert(isTBAAPathStruct(QTy)); + + if (llvm::MDNode *N = StructTypeMetadataCache[Ty]) + return N; + + if (const RecordType *TTy = QTy->getAs<RecordType>()) { + const RecordDecl *RD = TTy->getDecl()->getDefinition(); + + const ASTRecordLayout &Layout = Context.getASTRecordLayout(RD); + SmallVector <std::pair<llvm::MDNode*, uint64_t>, 4> Fields; + unsigned idx = 0; + for (RecordDecl::field_iterator i = RD->field_begin(), + e = RD->field_end(); i != e; ++i, ++idx) { + QualType FieldQTy = i->getType(); + llvm::MDNode *FieldNode; + if (isTBAAPathStruct(FieldQTy)) + FieldNode = getTBAAStructTypeInfo(FieldQTy); + else + FieldNode = getTBAAInfo(FieldQTy); + if (!FieldNode) + return StructTypeMetadataCache[Ty] = NULL; + Fields.push_back(std::make_pair( + FieldNode, Layout.getFieldOffset(idx) / Context.getCharWidth())); + } + + SmallString<256> OutName; + if (Features.CPlusPlus) { + // Don't use the mangler for C code. + llvm::raw_svector_ostream Out(OutName); + MContext.mangleTypeName(QualType(Ty, 0), Out); + Out.flush(); + } else { + OutName = RD->getName(); + } + // Create the struct type node with a vector of pairs (offset, type). + return StructTypeMetadataCache[Ty] = + MDHelper.createTBAAStructTypeNode(OutName, Fields); + } + + return StructMetadataCache[Ty] = NULL; +} + +/// Return a TBAA tag node for both scalar TBAA and struct-path aware TBAA. +llvm::MDNode * +CodeGenTBAA::getTBAAStructTagInfo(QualType BaseQTy, llvm::MDNode *AccessNode, + uint64_t Offset) { + if (!AccessNode) + return NULL; + + if (!CodeGenOpts.StructPathTBAA) + return getTBAAScalarTagInfo(AccessNode); + + const Type *BTy = Context.getCanonicalType(BaseQTy).getTypePtr(); + TBAAPathTag PathTag = TBAAPathTag(BTy, AccessNode, Offset); + if (llvm::MDNode *N = StructTagMetadataCache[PathTag]) + return N; + + llvm::MDNode *BNode = 0; + if (isTBAAPathStruct(BaseQTy)) + BNode = getTBAAStructTypeInfo(BaseQTy); + if (!BNode) + return StructTagMetadataCache[PathTag] = + MDHelper.createTBAAStructTagNode(AccessNode, AccessNode, 0); + + return StructTagMetadataCache[PathTag] = + MDHelper.createTBAAStructTagNode(BNode, AccessNode, Offset); +} + +llvm::MDNode * +CodeGenTBAA::getTBAAScalarTagInfo(llvm::MDNode *AccessNode) { + if (!AccessNode) + return NULL; + if (llvm::MDNode *N = ScalarTagMetadataCache[AccessNode]) + return N; + + return ScalarTagMetadataCache[AccessNode] = + MDHelper.createTBAAStructTagNode(AccessNode, AccessNode, 0); +} |
