[llvm] [PAC][ELF] Place AUTH constants in .data.rel.ro for position dependent code (PR #150418)

[Anatoly Trosinenko via llvm-commits]

================
@@ -226,6 +227,20 @@ void TargetLoweringObjectFile::emitPseudoProbeDescMetadata(
   }
 }
 
+static bool containsConstantPtrAuth(const Constant *C) {
+  if (isa<ConstantPtrAuth>(C))
+    return true;
+
+  if (isa<BlockAddress>(C) || isa<GlobalValue>(C))
+    return false;
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atrosinenko wrote:

IIUC this would make `containsConstantPtrAuth` return false for global variable like this
```
@global_var = global ptr ptrauth (ptr @f, i32 0)
```
which is still "constant" (as a constant pointer to `global_var`). This doesn't seem to hurt in case of this PR, but possibly a bit unexpected w.r.t. function name vs. its behavior.

https://github.com/llvm/llvm-project/pull/150418