[llvm] [PAC][IR][AArch64] Add "ptrauth(...)" Constant to represent signed pointers. (PR #85738)

[Nikita Popov via llvm-commits]

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@@ -1007,6 +1007,73 @@ struct OperandTraits<NoCFIValue> : public FixedNumOperandTraits<NoCFIValue, 1> {
 
 DEFINE_TRANSPARENT_OPERAND_ACCESSORS(NoCFIValue, Value)
 
+/// A signed pointer
+///
+class ConstantPtrAuth final : public Constant {
+  friend struct ConstantPtrAuthKeyType;
+  friend class Constant;
+
+  ConstantPtrAuth(Constant *Ptr, ConstantInt *Key, ConstantInt *Disc,
+                  Constant *AddrDisc);
+
+  void *operator new(size_t s) { return User::operator new(s, 4); }
+
+  void destroyConstantImpl();
+  Value *handleOperandChangeImpl(Value *From, Value *To);
+
+public:
+  /// Return a pointer authenticated with the specified parameters.
+  static ConstantPtrAuth *get(Constant *Ptr, ConstantInt *Key,
+                              ConstantInt *Disc, Constant *AddrDisc);
+
+  /// Produce a new ptrauth expression signing the given value using
+  /// the same schema as is stored in one.
+  ConstantPtrAuth *getWithSameSchema(Constant *Pointer) const;
+
+  /// Transparently provide more efficient getOperand methods.
+  DECLARE_TRANSPARENT_OPERAND_ACCESSORS(Constant);
+
+  /// The pointer that is authenticated in this authenticated global reference.
+  Constant *getPointer() const { return cast<Constant>(Op<0>().get()); }
+
+  /// The Key ID, an i32 constant.
+  ConstantInt *getKey() const { return cast<ConstantInt>(Op<1>().get()); }
+
+  /// The discriminator.
+  ConstantInt *getDiscriminator() const {
+    return cast<ConstantInt>(Op<2>().get());
+  }
+
+  /// The address discriminator if any, or the null constant.
+  /// If present, this must be a value equivalent to the storage location of
+  /// the only user of the authenticated ptrauth global.
+  Constant *getAddrDiscriminator() const {
+    return cast<Constant>(Op<3>().get());
+  }
+
+  /// Whether there is any non-null address discriminator.
+  bool hasAddressDiversity() const {
+    return !getAddrDiscriminator()->isNullValue();
+  }
+
+  /// Check whether an authentication operation with key \p KeyV and (possibly
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nikic wrote:

```suggestion
  /// Check whether an authentication operation with key \p Key and (possibly
```

https://github.com/llvm/llvm-project/pull/85738