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

[Fangrui Song via llvm-commits]

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@@ -972,6 +972,35 @@ class DIStringType : public DIType {
 ///
 /// TODO: Split out members (inheritance, fields, methods, etc.).
 class DIDerivedType : public DIType {
+public:
+  /// Pointer authentication (__ptrauth) metadata.
+  struct PtrAuthData {
+    // RawData layout:
+    // - Bits 0..3:  Key
+    // - Bit  4:     IsAddressDiscriminated
+    // - Bits 5..20: ExtraDiscriminator
+    // - Bit  21:    IsaPointer
+    // - Bit  22:    AuthenticatesNullValues
+    unsigned RawData;
+
+    PtrAuthData(unsigned FromRawData) : RawData(FromRawData) {}
+    PtrAuthData(unsigned Key, bool IsDiscr, unsigned Discriminator,
+                bool IsaPointer, bool AuthenticatesNullValues) {
+      assert(Key < 16);
+      assert(Discriminator <= 0xffff);
+      RawData = (Key << 0) | (IsDiscr ? (1 << 4) : 0) | (Discriminator << 5) |
+                (IsaPointer ? (1 << 21) : 0) |
+                (AuthenticatesNullValues ? (1 << 22) : 0);
+    }
+
+    unsigned Key() { return (RawData >> 0) & 0b1111; }
+    bool IsAddressDiscriminated() { return (RawData >> 4) & 1; }
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MaskRay wrote:

Nit: `functionName`. The code base is unfortunately inconsistent, but newer functions mostly stick with the recommended convention.

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