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

[Anton Korobeynikov via llvm-commits]

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@@ -975,34 +975,29 @@ class DIDerivedType : public DIType {
 public:
   /// Pointer authentication (__ptrauth) metadata.
   struct PtrAuthData {
-    union {
-      struct {
-        unsigned Key : 4;
-        unsigned IsAddressDiscriminated : 1;
-        unsigned ExtraDiscriminator : 16;
-        unsigned IsaPointer : 1;
-        unsigned AuthenticatesNullValues : 1;
-      } Data;
-      unsigned RawData;
-    } Payload;
-
-    PtrAuthData(unsigned FromRawData) { Payload.RawData = FromRawData; }
+    unsigned RawData;
+
+    PtrAuthData(unsigned FromRawData) : RawData(FromRawData) {}
     PtrAuthData(unsigned Key, bool IsDiscr, unsigned Discriminator,
                 bool IsaPointer, bool AuthenticatesNullValues) {
       assert(Key < 16);
       assert(Discriminator <= 0xffff);
-      Payload.Data.Key = Key;
-      Payload.Data.IsAddressDiscriminated = IsDiscr;
-      Payload.Data.ExtraDiscriminator = Discriminator;
-      Payload.Data.IsaPointer = IsaPointer;
-      Payload.Data.AuthenticatesNullValues = AuthenticatesNullValues;
+      RawData = (Key << 0) | (IsDiscr ? (1 << 4) : 0) | (Discriminator << 5) |
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asl wrote:

Please add comment describing the layout of `RawData`.

https://github.com/llvm/llvm-project/pull/83862