[Dwarf] Support `__ptrauth` qualifier in metadata nodes (#83862)

Reland #82363 after fixing build failure
https://lab.llvm.org/buildbot/#/builders/5/builds/41428.

Memory sanitizer detects usage of `RawData` union member which is not
filled directly. Instead, the code relies on filling `Data` union
member, which is a struct consisting of signing schema parameters.

According to https://en.cppreference.com/w/cpp/language/union, this is
UB:
"It is undefined behavior to read from the member of the union that
wasn't most recently written".

Instead of relying on compiler allowing us to do dirty things, do not
use union and only store `RawData`. Particular ptrauth parameters are
obtained on demand via bit operations.

Original PR description below.

Emit `__ptrauth`-qualified types as `DIDerivedType` metadata nodes in IR
with tag `DW_TAG_LLVM_ptrauth_type`, baseType referring to the type
which has the qualifier applied, and the following parameters
representing the signing schema:

- `ptrAuthKey` (integer)
- `ptrAuthIsAddressDiscriminated` (boolean)
- `ptrAuthExtraDiscriminator` (integer)
- `ptrAuthIsaPointer` (boolean)
- `ptrAuthAuthenticatesNullValues` (boolean)

Co-authored-by: Ahmed Bougacha <ahmed@bougacha.org>

1 files changed, 37 insertions, 21 deletions

diff --git a/llvm/lib/IR/DIBuilder.cpp b/llvm/lib/IR/DIBuilder.cpp
index c673abd8..f484680 100644
--- a/llvm/lib/IR/DIBuilder.cpp
+++ b/llvm/lib/IR/DIBuilder.cpp
@@ -296,7 +296,20 @@ DIStringType *DIBuilder::createStringType(StringRef Name,
 
 DIDerivedType *DIBuilder::createQualifiedType(unsigned Tag, DIType *FromTy) {
   return DIDerivedType::get(VMContext, Tag, "", nullptr, 0, nullptr, FromTy, 0,
-                            0, 0, std::nullopt, DINode::FlagZero);
+                            0, 0, std::nullopt, std::nullopt, DINode::FlagZero);
+}
+
+DIDerivedType *DIBuilder::createPtrAuthQualifiedType(
+    DIType *FromTy, unsigned Key, bool IsAddressDiscriminated,
+    unsigned ExtraDiscriminator, bool IsaPointer,
+    bool AuthenticatesNullValues) {
+  return DIDerivedType::get(VMContext, dwarf::DW_TAG_LLVM_ptrauth_type, "",
+                            nullptr, 0, nullptr, FromTy, 0, 0, 0, std::nullopt,
+                            std::optional<DIDerivedType::PtrAuthData>(
+                                std::in_place, Key, IsAddressDiscriminated,
+                                ExtraDiscriminator, IsaPointer,
+                                AuthenticatesNullValues),
+                            DINode::FlagZero);
 }
 
 DIDerivedType *
@@ -307,8 +320,8 @@ DIBuilder::createPointerType(DIType *PointeeTy, uint64_t SizeInBits,
   // FIXME: Why is there a name here?
   return DIDerivedType::get(VMContext, dwarf::DW_TAG_pointer_type, Name,
                             nullptr, 0, nullptr, PointeeTy, SizeInBits,
-                            AlignInBits, 0, DWARFAddressSpace, DINode::FlagZero,
-                            nullptr, Annotations);
+                            AlignInBits, 0, DWARFAddressSpace, std::nullopt,
+                            DINode::FlagZero, nullptr, Annotations);
 }
 
 DIDerivedType *DIBuilder::createMemberPointerType(DIType *PointeeTy,
@@ -318,7 +331,8 @@ DIDerivedType *DIBuilder::createMemberPointerType(DIType *PointeeTy,
                                                   DINode::DIFlags Flags) {
   return DIDerivedType::get(VMContext, dwarf::DW_TAG_ptr_to_member_type, "",
                             nullptr, 0, nullptr, PointeeTy, SizeInBits,
-                            AlignInBits, 0, std::nullopt, Flags, Base);
+                            AlignInBits, 0, std::nullopt, std::nullopt, Flags,
+                            Base);
 }
 
 DIDerivedType *
@@ -327,7 +341,7 @@ DIBuilder::createReferenceType(unsigned Tag, DIType *RTy, uint64_t SizeInBits,
                                std::optional<unsigned> DWARFAddressSpace) {
   assert(RTy && "Unable to create reference type");
   return DIDerivedType::get(VMContext, Tag, "", nullptr, 0, nullptr, RTy,
-                            SizeInBits, AlignInBits, 0, DWARFAddressSpace,
+                            SizeInBits, AlignInBits, 0, DWARFAddressSpace, {},
                             DINode::FlagZero);
 }
 
@@ -338,15 +352,16 @@ DIDerivedType *DIBuilder::createTypedef(DIType *Ty, StringRef Name,
                                         DINodeArray Annotations) {
   return DIDerivedType::get(VMContext, dwarf::DW_TAG_typedef, Name, File,
                             LineNo, getNonCompileUnitScope(Context), Ty, 0,
-                            AlignInBits, 0, std::nullopt, Flags, nullptr,
-                            Annotations);
+                            AlignInBits, 0, std::nullopt, std::nullopt, Flags,
+                            nullptr, Annotations);
 }
 
 DIDerivedType *DIBuilder::createFriend(DIType *Ty, DIType *FriendTy) {
   assert(Ty && "Invalid type!");
   assert(FriendTy && "Invalid friend type!");
   return DIDerivedType::get(VMContext, dwarf::DW_TAG_friend, "", nullptr, 0, Ty,
-                            FriendTy, 0, 0, 0, std::nullopt, DINode::FlagZero);
+                            FriendTy, 0, 0, 0, std::nullopt, std::nullopt,
+                            DINode::FlagZero);
 }
 
 DIDerivedType *DIBuilder::createInheritance(DIType *Ty, DIType *BaseTy,
@@ -358,7 +373,7 @@ DIDerivedType *DIBuilder::createInheritance(DIType *Ty, DIType *BaseTy,
       ConstantInt::get(IntegerType::get(VMContext, 32), VBPtrOffset));
   return DIDerivedType::get(VMContext, dwarf::DW_TAG_inheritance, "", nullptr,
                             0, Ty, BaseTy, 0, 0, BaseOffset, std::nullopt,
-                            Flags, ExtraData);
+                            std::nullopt, Flags, ExtraData);
 }
 
 DIDerivedType *DIBuilder::createMemberType(
@@ -368,7 +383,7 @@ DIDerivedType *DIBuilder::createMemberType(
   return DIDerivedType::get(VMContext, dwarf::DW_TAG_member, Name, File,
                             LineNumber, getNonCompileUnitScope(Scope), Ty,
                             SizeInBits, AlignInBits, OffsetInBits, std::nullopt,
-                            Flags, nullptr, Annotations);
+                            std::nullopt, Flags, nullptr, Annotations);
 }
 
 static ConstantAsMetadata *getConstantOrNull(Constant *C) {
@@ -381,10 +396,10 @@ DIDerivedType *DIBuilder::createVariantMemberType(
     DIScope *Scope, StringRef Name, DIFile *File, unsigned LineNumber,
     uint64_t SizeInBits, uint32_t AlignInBits, uint64_t OffsetInBits,
     Constant *Discriminant, DINode::DIFlags Flags, DIType *Ty) {
-  return DIDerivedType::get(VMContext, dwarf::DW_TAG_member, Name, File,
-                            LineNumber, getNonCompileUnitScope(Scope), Ty,
-                            SizeInBits, AlignInBits, OffsetInBits, std::nullopt,
-                            Flags, getConstantOrNull(Discriminant));
+  return DIDerivedType::get(
+      VMContext, dwarf::DW_TAG_member, Name, File, LineNumber,
+      getNonCompileUnitScope(Scope), Ty, SizeInBits, AlignInBits, OffsetInBits,
+      std::nullopt, std::nullopt, Flags, getConstantOrNull(Discriminant));
 }
 
 DIDerivedType *DIBuilder::createBitFieldMemberType(
@@ -395,7 +410,7 @@ DIDerivedType *DIBuilder::createBitFieldMemberType(
   return DIDerivedType::get(
       VMContext, dwarf::DW_TAG_member, Name, File, LineNumber,
       getNonCompileUnitScope(Scope), Ty, SizeInBits, /*AlignInBits=*/0,
-      OffsetInBits, std::nullopt, Flags,
+      OffsetInBits, std::nullopt, std::nullopt, Flags,
       ConstantAsMetadata::get(ConstantInt::get(IntegerType::get(VMContext, 64),
                                                StorageOffsetInBits)),
       Annotations);
@@ -409,7 +424,8 @@ DIBuilder::createStaticMemberType(DIScope *Scope, StringRef Name, DIFile *File,
   Flags |= DINode::FlagStaticMember;
   return DIDerivedType::get(VMContext, Tag, Name, File, LineNumber,
                             getNonCompileUnitScope(Scope), Ty, 0, AlignInBits,
-                            0, std::nullopt, Flags, getConstantOrNull(Val));
+                            0, std::nullopt, std::nullopt, Flags,
+                            getConstantOrNull(Val));
 }
 
 DIDerivedType *
@@ -420,7 +436,7 @@ DIBuilder::createObjCIVar(StringRef Name, DIFile *File, unsigned LineNumber,
   return DIDerivedType::get(VMContext, dwarf::DW_TAG_member, Name, File,
                             LineNumber, getNonCompileUnitScope(File), Ty,
                             SizeInBits, AlignInBits, OffsetInBits, std::nullopt,
-                            Flags, PropertyNode);
+                            std::nullopt, Flags, PropertyNode);
 }
 
 DIObjCProperty *
@@ -555,10 +571,10 @@ DIDerivedType *DIBuilder::createSetType(DIScope *Scope, StringRef Name,
                                         DIFile *File, unsigned LineNo,
                                         uint64_t SizeInBits,
                                         uint32_t AlignInBits, DIType *Ty) {
-  auto *R =
-      DIDerivedType::get(VMContext, dwarf::DW_TAG_set_type, Name, File, LineNo,
-                         getNonCompileUnitScope(Scope), Ty, SizeInBits,
-                         AlignInBits, 0, std::nullopt, DINode::FlagZero);
+  auto *R = DIDerivedType::get(VMContext, dwarf::DW_TAG_set_type, Name, File,
+                               LineNo, getNonCompileUnitScope(Scope), Ty,
+                               SizeInBits, AlignInBits, 0, std::nullopt,
+                               std::nullopt, DINode::FlagZero);
   trackIfUnresolved(R);
   return R;
 }