[CodeGen] Unify generation of scalar and struct-path TBAA tags

This patch makes it possible to produce access tags in a uniform
manner regardless whether the resulting tag will be a scalar or a
struct-path one. getAccessTagInfo() now takes care of the actual
translation of access descriptors to tags and can handle all
kinds of accesses. Facilities that specific to scalar accesses
are eliminated.

Some more details:
* DecorateInstructionWithTBAA() is not responsible for conversion
  of types to access tags anymore. Instead, it takes an access
  descriptor (TBAAAccessInfo) and generates corresponding access
  tag from it.
* getTBAAInfoForVTablePtr() reworked to
  getTBAAVTablePtrAccessInfo() that now returns the
  virtual-pointer access descriptor and not the virtual-point
  type metadata.
* Added function getTBAAMayAliasAccessInfo() that returns the
  descriptor for may-alias accesses.
* getTBAAStructTagInfo() renamed to getTBAAAccessTagInfo() as now
  it is the only way to generate access tag by a given access
  descriptor. It is capable of producing both scalar and
  struct-path tags, depending on options and availability of the
  base access type. getTBAAScalarTagInfo() and its cache
  ScalarTagMetadataCache are eliminated.
* Now that we do not need to care about whether the resulting
  access tag should be a scalar or struct-path one,
  getTBAAStructTypeInfo() is renamed to getBaseTypeInfo().
* Added function getTBAAAccessInfo() that constructs access
  descriptor by a given QualType access type.

This is part of D37826 reworked to be a separate patch to
simplify review.

Differential Revision: https://reviews.llvm.org/D38503

llvm-svn: 314979

7 files changed, 76 insertions, 102 deletions

diff --git a/clang/lib/CodeGen/CGAtomic.cpp b/clang/lib/CodeGen/CGAtomic.cpp
index c03e06d571e..030c944ffeb 100644
--- a/clang/lib/CodeGen/CGAtomic.cpp
+++ b/clang/lib/CodeGen/CGAtomic.cpp
@@ -1425,8 +1425,8 @@ llvm::Value *AtomicInfo::EmitAtomicLoadOp(llvm::AtomicOrdering AO,
   // Other decoration.
   if (IsVolatile)
     Load->setVolatile(true);
-  if (LVal.getTBAAAccessType())
-    CGF.CGM.DecorateInstructionWithTBAA(Load, LVal.getTBAAAccessType());
+  TBAAAccessInfo TBAAInfo(LVal.getTBAAAccessType());
+  CGF.CGM.DecorateInstructionWithTBAA(Load, TBAAInfo);
   return Load;
 }
 
@@ -1942,8 +1942,8 @@ void CodeGenFunction::EmitAtomicStore(RValue rvalue, LValue dest,
     // Other decoration.
     if (IsVolatile)
       store->setVolatile(true);
-    if (dest.getTBAAAccessType())
-      CGM.DecorateInstructionWithTBAA(store, dest.getTBAAAccessType());
+    TBAAAccessInfo TBAAInfo(dest.getTBAAAccessType());
+    CGM.DecorateInstructionWithTBAA(store, TBAAInfo);
     return;
   }
 
diff --git a/clang/lib/CodeGen/CGClass.cpp b/clang/lib/CodeGen/CGClass.cpp
index 75a0fd43e8b..e86c8dcc8a6 100644
--- a/clang/lib/CodeGen/CGClass.cpp
+++ b/clang/lib/CodeGen/CGClass.cpp
@@ -2383,7 +2383,7 @@ void CodeGenFunction::InitializeVTablePointer(const VPtr &Vptr) {
   VTableAddressPoint = Builder.CreateBitCast(VTableAddressPoint, VTablePtrTy);
 
   llvm::StoreInst *Store = Builder.CreateStore(VTableAddressPoint, VTableField);
-  CGM.DecorateInstructionWithTBAA(Store, CGM.getTBAAInfoForVTablePtr());
+  CGM.DecorateInstructionWithTBAA(Store, CGM.getTBAAVTablePtrAccessInfo());
   if (CGM.getCodeGenOpts().OptimizationLevel > 0 &&
       CGM.getCodeGenOpts().StrictVTablePointers)
     CGM.DecorateInstructionWithInvariantGroup(Store, Vptr.VTableClass);
@@ -2477,7 +2477,7 @@ llvm::Value *CodeGenFunction::GetVTablePtr(Address This,
                                            const CXXRecordDecl *RD) {
   Address VTablePtrSrc = Builder.CreateElementBitCast(This, VTableTy);
   llvm::Instruction *VTable = Builder.CreateLoad(VTablePtrSrc, "vtable");
-  CGM.DecorateInstructionWithTBAA(VTable, CGM.getTBAAInfoForVTablePtr());
+  CGM.DecorateInstructionWithTBAA(VTable, CGM.getTBAAVTablePtrAccessInfo());
 
   if (CGM.getCodeGenOpts().OptimizationLevel > 0 &&
       CGM.getCodeGenOpts().StrictVTablePointers)
diff --git a/clang/lib/CodeGen/CGExpr.cpp b/clang/lib/CodeGen/CGExpr.cpp
index 74ad9dcf463..076034ff51c 100644
--- a/clang/lib/CodeGen/CGExpr.cpp
+++ b/clang/lib/CodeGen/CGExpr.cpp
@@ -1526,12 +1526,9 @@ llvm::Value *CodeGenFunction::EmitLoadOfScalar(Address Addr, bool Volatile,
     Load->setMetadata(CGM.getModule().getMDKindID("nontemporal"), Node);
   }
   if (TBAAInfo.AccessType) {
-    bool MayAlias = BaseInfo.getMayAlias();
-    llvm::MDNode *TBAA = MayAlias
-        ? CGM.getTBAAMayAliasTypeInfo()
-        : CGM.getTBAAStructTagInfo(TBAAInfo);
-    if (TBAA)
-      CGM.DecorateInstructionWithTBAA(Load, TBAA, MayAlias);
+    if (BaseInfo.getMayAlias())
+      TBAAInfo = CGM.getTBAAMayAliasAccessInfo();
+    CGM.DecorateInstructionWithTBAA(Load, TBAAInfo);
   }
 
   if (EmitScalarRangeCheck(Load, Ty, Loc)) {
@@ -1614,12 +1611,9 @@ void CodeGenFunction::EmitStoreOfScalar(llvm::Value *Value, Address Addr,
     Store->setMetadata(CGM.getModule().getMDKindID("nontemporal"), Node);
   }
   if (TBAAInfo.AccessType) {
-    bool MayAlias = BaseInfo.getMayAlias();
-    llvm::MDNode *TBAA = MayAlias
-        ? CGM.getTBAAMayAliasTypeInfo()
-        : CGM.getTBAAStructTagInfo(TBAAInfo);
-    if (TBAA)
-      CGM.DecorateInstructionWithTBAA(Store, TBAA, MayAlias);
+    if (BaseInfo.getMayAlias())
+      TBAAInfo = CGM.getTBAAMayAliasAccessInfo();
+    CGM.DecorateInstructionWithTBAA(Store, TBAAInfo);
   }
 }
 
@@ -3727,12 +3721,9 @@ LValue CodeGenFunction::EmitLValueForField(LValue base,
 
       // Loading the reference will disable path-aware TBAA.
       TBAAPath = false;
-      if (CGM.shouldUseTBAA()) {
-        llvm::MDNode *tbaa = mayAlias ? CGM.getTBAAMayAliasTypeInfo() :
-                                        CGM.getTBAATypeInfo(type);
-        if (tbaa)
-          CGM.DecorateInstructionWithTBAA(load, tbaa);
-      }
+      TBAAAccessInfo TBAAInfo = mayAlias ? CGM.getTBAAMayAliasAccessInfo() :
+                                           CGM.getTBAAAccessInfo(type);
+      CGM.DecorateInstructionWithTBAA(load, TBAAInfo);
 
       mayAlias = false;
       type = refType->getPointeeType();
@@ -3769,7 +3760,7 @@ LValue CodeGenFunction::EmitLValueForField(LValue base,
     // update offset to be relative to the base type.
     unsigned CharWidth = getContext().getCharWidth();
     TBAAAccessInfo TBAAInfo = mayAlias ?
-      TBAAAccessInfo(CGM.getTBAAMayAliasTypeInfo()) :
+      CGM.getTBAAMayAliasAccessInfo() :
       TBAAAccessInfo(base.getTBAAInfo().BaseType, CGM.getTBAATypeInfo(type),
                      base.getTBAAInfo().Offset + Layout.getFieldOffset(
                          field->getFieldIndex()) / CharWidth);
@@ -3784,7 +3775,7 @@ LValue CodeGenFunction::EmitLValueForField(LValue base,
   // FIXME: this should get propagated down through anonymous structs
   // and unions.
   if (mayAlias && LV.getTBAAAccessType())
-    LV.setTBAAAccessType(CGM.getTBAAMayAliasTypeInfo());
+    LV.setTBAAInfo(CGM.getTBAAMayAliasAccessInfo());
 
   return LV;
 }
diff --git a/clang/lib/CodeGen/CodeGenModule.cpp b/clang/lib/CodeGen/CodeGenModule.cpp
index a16f350f9d5..895bd5d5794 100644
--- a/clang/lib/CodeGen/CodeGenModule.cpp
+++ b/clang/lib/CodeGen/CodeGenModule.cpp
@@ -578,10 +578,14 @@ llvm::MDNode *CodeGenModule::getTBAATypeInfo(QualType QTy) {
   return TBAA->getTypeInfo(QTy);
 }
 
-llvm::MDNode *CodeGenModule::getTBAAInfoForVTablePtr() {
+TBAAAccessInfo CodeGenModule::getTBAAAccessInfo(QualType AccessType) {
+  return TBAAAccessInfo(getTBAATypeInfo(AccessType));
+}
+
+TBAAAccessInfo CodeGenModule::getTBAAVTablePtrAccessInfo() {
   if (!TBAA)
-    return nullptr;
-  return TBAA->getTBAAInfoForVTablePtr();
+    return TBAAAccessInfo();
+  return TBAA->getVTablePtrAccessInfo();
 }
 
 llvm::MDNode *CodeGenModule::getTBAAStructInfo(QualType QTy) {
@@ -590,30 +594,22 @@ llvm::MDNode *CodeGenModule::getTBAAStructInfo(QualType QTy) {
   return TBAA->getTBAAStructInfo(QTy);
 }
 
-llvm::MDNode *CodeGenModule::getTBAAStructTagInfo(TBAAAccessInfo Info) {
+llvm::MDNode *CodeGenModule::getTBAAAccessTagInfo(TBAAAccessInfo Info) {
   if (!TBAA)
     return nullptr;
-  return TBAA->getTBAAStructTagInfo(Info);
+  return TBAA->getAccessTagInfo(Info);
 }
 
-llvm::MDNode *CodeGenModule::getTBAAMayAliasTypeInfo() {
+TBAAAccessInfo CodeGenModule::getTBAAMayAliasAccessInfo() {
   if (!TBAA)
-    return nullptr;
-  return TBAA->getMayAliasTypeInfo();
+    return TBAAAccessInfo();
+  return TBAA->getMayAliasAccessInfo();
 }
 
-/// Decorate the instruction with a TBAA tag. For both scalar TBAA
-/// and struct-path aware TBAA, the tag has the same format:
-/// base type, access type and offset.
-/// When ConvertTypeToTag is true, we create a tag based on the scalar type.
 void CodeGenModule::DecorateInstructionWithTBAA(llvm::Instruction *Inst,
-                                                llvm::MDNode *TBAAInfo,
-                                                bool ConvertTypeToTag) {
-  if (ConvertTypeToTag && TBAA)
-    Inst->setMetadata(llvm::LLVMContext::MD_tbaa,
-                      TBAA->getTBAAScalarTagInfo(TBAAInfo));
-  else
-    Inst->setMetadata(llvm::LLVMContext::MD_tbaa, TBAAInfo);
+                                                TBAAAccessInfo TBAAInfo) {
+  if (llvm::MDNode *Tag = getTBAAAccessTagInfo(TBAAInfo))
+    Inst->setMetadata(llvm::LLVMContext::MD_tbaa, Tag);
 }
 
 void CodeGenModule::DecorateInstructionWithInvariantGroup(
diff --git a/clang/lib/CodeGen/CodeGenModule.h b/clang/lib/CodeGen/CodeGenModule.h
index 33b622972d9..50e23d55c4a 100644
--- a/clang/lib/CodeGen/CodeGenModule.h
+++ b/clang/lib/CodeGen/CodeGenModule.h
@@ -656,28 +656,31 @@ public:
   /// the given type.
   llvm::MDNode *getTBAATypeInfo(QualType QTy);
 
-  llvm::MDNode *getTBAAInfoForVTablePtr();
+  /// getTBAAAccessInfo - Get TBAA information that describes an access to
+  /// an object of the given type.
+  TBAAAccessInfo getTBAAAccessInfo(QualType AccessType);
+
+  /// getTBAAVTablePtrAccessInfo - Get the TBAA information that describes an
+  /// access to a virtual table pointer.
+  TBAAAccessInfo getTBAAVTablePtrAccessInfo();
+
   llvm::MDNode *getTBAAStructInfo(QualType QTy);
 
-  /// Get path-aware TBAA tag for a given memory access.
-  llvm::MDNode *getTBAAStructTagInfo(TBAAAccessInfo Info);
+  /// getTBAAAccessTagInfo - Get TBAA tag for a given memory access.
+  llvm::MDNode *getTBAAAccessTagInfo(TBAAAccessInfo Info);
 
-  /// getTBAAMayAliasTypeInfo - Get TBAA information that represents
+  /// getTBAAMayAliasAccessInfo - Get TBAA information that represents
   /// may-alias accesses.
-  llvm::MDNode *getTBAAMayAliasTypeInfo();
+  TBAAAccessInfo getTBAAMayAliasAccessInfo();
 
   bool isTypeConstant(QualType QTy, bool ExcludeCtorDtor);
 
   bool isPaddedAtomicType(QualType type);
   bool isPaddedAtomicType(const AtomicType *type);
 
-  /// Decorate the instruction with a TBAA tag. For scalar TBAA, the tag
-  /// is the same as the type. For struct-path aware TBAA, the tag
-  /// is different from the type: base type, access type and offset.
-  /// When ConvertTypeToTag is true, we create a tag based on the scalar type.
+  /// DecorateInstructionWithTBAA - Decorate the instruction with a TBAA tag.
   void DecorateInstructionWithTBAA(llvm::Instruction *Inst,
-                                   llvm::MDNode *TBAAInfo,
-                                   bool ConvertTypeToTag = true);
+                                   TBAAAccessInfo TBAAInfo);
 
   /// Adds !invariant.barrier !tag to instruction
   void DecorateInstructionWithInvariantGroup(llvm::Instruction *I,
diff --git a/clang/lib/CodeGen/CodeGenTBAA.cpp b/clang/lib/CodeGen/CodeGenTBAA.cpp
index 0d40748c456..3f0f942ea99 100644
--- a/clang/lib/CodeGen/CodeGenTBAA.cpp
+++ b/clang/lib/CodeGen/CodeGenTBAA.cpp
@@ -171,8 +171,8 @@ llvm::MDNode *CodeGenTBAA::getTypeInfo(QualType QTy) {
   return MetadataCache[Ty] = getChar();
 }
 
-llvm::MDNode *CodeGenTBAA::getTBAAInfoForVTablePtr() {
-  return createTBAAScalarType("vtable pointer", getRoot());
+TBAAAccessInfo CodeGenTBAA::getVTablePtrAccessInfo() {
+  return TBAAAccessInfo(createTBAAScalarType("vtable pointer", getRoot()));
 }
 
 bool
@@ -211,8 +211,8 @@ CodeGenTBAA::CollectFields(uint64_t BaseOffset,
   /* Otherwise, treat whatever it is as a field. */
   uint64_t Offset = BaseOffset;
   uint64_t Size = Context.getTypeSizeInChars(QTy).getQuantity();
-  llvm::MDNode *TBAAInfo = MayAlias ? getChar() : getTypeInfo(QTy);
-  llvm::MDNode *TBAATag = getTBAAScalarTagInfo(TBAAInfo);
+  llvm::MDNode *TBAAType = MayAlias ? getChar() : getTypeInfo(QTy);
+  llvm::MDNode *TBAATag = getAccessTagInfo(TBAAAccessInfo(TBAAType));
   Fields.push_back(llvm::MDBuilder::TBAAStructField(Offset, Size, TBAATag));
   return true;
 }
@@ -232,8 +232,10 @@ CodeGenTBAA::getTBAAStructInfo(QualType QTy) {
   return StructMetadataCache[Ty] = nullptr;
 }
 
-/// Check if the given type can be handled by path-aware TBAA.
-static bool isTBAAPathStruct(QualType QTy) {
+/// Check if the given type is a valid base type to be used in access tags.
+static bool isValidBaseType(QualType QTy) {
+  if (QTy == QualType())
+    return false;
   if (const RecordType *TTy = QTy->getAs<RecordType>()) {
     const RecordDecl *RD = TTy->getDecl()->getDefinition();
     if (RD->hasFlexibleArrayMember())
@@ -246,10 +248,9 @@ static bool isTBAAPathStruct(QualType QTy) {
   return false;
 }
 
-llvm::MDNode *
-CodeGenTBAA::getTBAAStructTypeInfo(QualType QTy) {
+llvm::MDNode *CodeGenTBAA::getBaseTypeInfo(QualType QTy) {
   const Type *Ty = Context.getCanonicalType(QTy).getTypePtr();
-  assert(isTBAAPathStruct(QTy));
+  assert(isValidBaseType(QTy));
 
   if (llvm::MDNode *N = StructTypeMetadataCache[Ty])
     return N;
@@ -263,11 +264,8 @@ CodeGenTBAA::getTBAAStructTypeInfo(QualType QTy) {
     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 = getTypeInfo(FieldQTy);
+      llvm::MDNode *FieldNode = isValidBaseType(FieldQTy) ?
+          getBaseTypeInfo(FieldQTy) : getTypeInfo(FieldQTy);
       if (!FieldNode)
         return StructTypeMetadataCache[Ty] = nullptr;
       Fields.push_back(std::make_pair(
@@ -290,21 +288,23 @@ CodeGenTBAA::getTBAAStructTypeInfo(QualType QTy) {
   return StructMetadataCache[Ty] = nullptr;
 }
 
-llvm::MDNode *CodeGenTBAA::getTBAAStructTagInfo(TBAAAccessInfo Info) {
+llvm::MDNode *CodeGenTBAA::getAccessTagInfo(TBAAAccessInfo Info) {
   if (!Info.AccessType)
     return nullptr;
 
   if (!CodeGenOpts.StructPathTBAA)
-    return getTBAAScalarTagInfo(Info.AccessType);
+    Info = TBAAAccessInfo(Info.AccessType);
 
-  const Type *BTy = Context.getCanonicalType(Info.BaseType).getTypePtr();
+  const Type *BTy = nullptr;
+  if (Info.BaseType != QualType())
+    BTy = Context.getCanonicalType(Info.BaseType).getTypePtr();
   TBAAPathTag PathTag = TBAAPathTag(BTy, Info.AccessType, Info.Offset);
   if (llvm::MDNode *N = StructTagMetadataCache[PathTag])
     return N;
 
   llvm::MDNode *BNode = nullptr;
-  if (isTBAAPathStruct(Info.BaseType))
-    BNode = getTBAAStructTypeInfo(Info.BaseType);
+  if (isValidBaseType(Info.BaseType))
+    BNode = getBaseTypeInfo(Info.BaseType);
   if (!BNode)
     return StructTagMetadataCache[PathTag] =
        MDHelper.createTBAAStructTagNode(Info.AccessType, Info.AccessType,
@@ -314,17 +314,6 @@ llvm::MDNode *CodeGenTBAA::getTBAAStructTagInfo(TBAAAccessInfo Info) {
     MDHelper.createTBAAStructTagNode(BNode, Info.AccessType, Info.Offset);
 }
 
-llvm::MDNode *
-CodeGenTBAA::getTBAAScalarTagInfo(llvm::MDNode *AccessNode) {
-  if (!AccessNode)
-    return nullptr;
-  if (llvm::MDNode *N = ScalarTagMetadataCache[AccessNode])
-    return N;
-
-  return ScalarTagMetadataCache[AccessNode] =
-    MDHelper.createTBAAStructTagNode(AccessNode, AccessNode, 0);
-}
-
-llvm::MDNode *CodeGenTBAA::getMayAliasTypeInfo() {
-  return getChar();
+TBAAAccessInfo CodeGenTBAA::getMayAliasAccessInfo() {
+  return TBAAAccessInfo(getChar());
 }
diff --git a/clang/lib/CodeGen/CodeGenTBAA.h b/clang/lib/CodeGen/CodeGenTBAA.h
index 2b2c2d4b098..198c2005db9 100644
--- a/clang/lib/CodeGen/CodeGenTBAA.h
+++ b/clang/lib/CodeGen/CodeGenTBAA.h
@@ -86,8 +86,6 @@ class CodeGenTBAA {
   llvm::DenseMap<const Type *, llvm::MDNode *> StructTypeMetadataCache;
   /// This maps TBAAPathTags to a tag node.
   llvm::DenseMap<TBAAPathTag, llvm::MDNode *> StructTagMetadataCache;
-  /// This maps a scalar type to a scalar tag node.
-  llvm::DenseMap<const llvm::MDNode *, llvm::MDNode *> ScalarTagMetadataCache;
 
   /// StructMetadataCache - This maps clang::Types to llvm::MDNodes describing
   /// them for struct assignments.
@@ -127,26 +125,23 @@ public:
   /// given type.
   llvm::MDNode *getTypeInfo(QualType QTy);
 
-  /// getTBAAInfoForVTablePtr - Get the TBAA MDNode to be used for a
-  /// dereference of a vtable pointer.
-  llvm::MDNode *getTBAAInfoForVTablePtr();
+  /// getVTablePtrAccessInfo - Get the TBAA information that describes an
+  /// access to a virtual table pointer.
+  TBAAAccessInfo getVTablePtrAccessInfo();
 
   /// getTBAAStructInfo - Get the TBAAStruct MDNode to be used for a memcpy of
   /// the given type.
   llvm::MDNode *getTBAAStructInfo(QualType QTy);
 
-  /// Get the MDNode in the type DAG for given struct type QType.
-  llvm::MDNode *getTBAAStructTypeInfo(QualType QType);
+  /// getBaseTypeInfo - Get metadata node for a given base access type.
+  llvm::MDNode *getBaseTypeInfo(QualType QType);
 
-  /// Get path-aware TBAA tag for a given memory access.
-  llvm::MDNode *getTBAAStructTagInfo(TBAAAccessInfo Info);
+  /// getAccessTagInfo - Get TBAA tag for a given memory access.
+  llvm::MDNode *getAccessTagInfo(TBAAAccessInfo Info);
 
-  /// Get the scalar tag MDNode for a given scalar type.
-  llvm::MDNode *getTBAAScalarTagInfo(llvm::MDNode *AccessNode);
-
-  /// getMayAliasTypeInfo - Get TBAA information that represents may-alias
+  /// getMayAliasAccessInfo - Get TBAA information that represents may-alias
   /// accesses.
-  llvm::MDNode *getMayAliasTypeInfo();
+  TBAAAccessInfo getMayAliasAccessInfo();
 };
 
 }  // end namespace CodeGen