Add the clang library to the repo (with some of my changes, too).

1 files changed, 163 insertions, 0 deletions

diff --git a/clang/lib/CodeGen/CodeGenTBAA.cpp b/clang/lib/CodeGen/CodeGenTBAA.cpp
new file mode 100644
index 0000000..a3cadcf
--- /dev/null
+++ b/clang/lib/CodeGen/CodeGenTBAA.cpp
@@ -0,0 +1,163 @@
+//===--- 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/Mangle.h"
+#include "llvm/LLVMContext.h"
+#include "llvm/Metadata.h"
+#include "llvm/Constants.h"
+#include "llvm/Type.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),
+    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;
+}
+
+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 = MDHelper.createTBAANode("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) {
+  // 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] =
+        MDHelper.createTBAANode(BTy->getName(Features), getChar());
+    }
+  }
+
+  // Handle pointers.
+  // TODO: Implement C++'s type "similarity" and consider dis-"similar"
+  // pointers distinct.
+  if (Ty->isPointerType())
+    return MetadataCache[Ty] = MDHelper.createTBAANode("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, 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()->getTypedefNameForAnonDecl())
+      return MetadataCache[Ty] = getChar();
+
+    // 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] = getChar();
+
+    // TODO: This is using the RTTI name. Is there a better way to get
+    // a unique string for a type?
+    SmallString<256> OutName;
+    llvm::raw_svector_ostream Out(OutName);
+    MContext.mangleCXXRTTIName(QualType(ETy, 0), Out);
+    Out.flush();
+    return MetadataCache[Ty] = MDHelper.createTBAANode(OutName, getChar());
+  }
+
+  // For now, handle any other kind of type conservatively.
+  return MetadataCache[Ty] = getChar();
+}
+
+llvm::MDNode *CodeGenTBAA::getTBAAInfoForVTablePtr() {
+  return MDHelper.createTBAANode("vtable pointer", getRoot());
+}