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//===--- 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.
//
//===----------------------------------------------------------------------===//
#include "CodeGenTBAA.h"
#include "Mangle.h"
#include "clang/AST/ASTContext.h"
#include "llvm/LLVMContext.h"
#include "llvm/Metadata.h"
using namespace clang;
using namespace CodeGen;
CodeGenTBAA::CodeGenTBAA(ASTContext &Ctx, llvm::LLVMContext& VMContext,
const LangOptions &Features, MangleContext &MContext)
: Context(Ctx), VMContext(VMContext), Features(Features), MContext(MContext),
Root(0), Char(0) {
}
CodeGenTBAA::~CodeGenTBAA() {
}
llvm::MDNode *CodeGenTBAA::getTBAAInfoForNamedType(llvm::StringRef NameStr,
llvm::MDNode *Parent) {
llvm::Value *Ops[] = {
llvm::MDString::get(VMContext, NameStr),
Parent
};
return llvm::MDNode::get(VMContext, Ops, llvm::array_lengthof(Ops));
}
llvm::MDNode *
CodeGenTBAA::getTBAAInfo(QualType QTy) {
Type *Ty = Context.getCanonicalType(QTy).getTypePtr();
if (llvm::MDNode *N = MetadataCache[Ty])
return N;
if (!Root) {
Root = getTBAAInfoForNamedType("Experimental TBAA", 0);
Char = getTBAAInfoForNamedType("omnipotent char", Root);
}
// For now, just emit a very minimal tree.
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 Char;
// 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);
// Other builtin types.
default:
return MetadataCache[Ty] =
getTBAAInfoForNamedType(BTy->getName(Features), Char);
}
}
// For now, treat all pointers as equivalent to each other.
if (Ty->isPointerType())
return MetadataCache[Ty] = getTBAAInfoForNamedType("TBAA.pointer", Char);
// 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, two anonymous enums are compatible iff their members
// are the same -- see C99 6.2.7p1. For now, be conservative. We could
// theoretically implement this by combining information about all the
// members into a single identifying MDNode.
if (!Features.CPlusPlus &&
ETy->getDecl()->getTypedefForAnonDecl())
return MetadataCache[Ty] = Char;
// 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()->getLinkage() != ExternalLinkage)
return MetadataCache[Ty] = Char;
// TODO: This is using the RTTI name. Is there a better way to get
// a unique string for a type?
llvm::SmallString<256> OutName;
MContext.mangleCXXRTTIName(QualType(ETy, 0), OutName);
return MetadataCache[Ty] = getTBAAInfoForNamedType(OutName, Char);
}
// For now, handle any other kind of type conservatively.
return MetadataCache[Ty] = Char;
}
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