[clang] [PAC] Add support for __ptrauth type qualifier (PR #100830)

[Aaron Ballman via cfe-commits]

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@@ -5708,6 +5732,27 @@ CGCallee CodeGenFunction::EmitCallee(const Expr *E) {
       return EmitCallee(ICE->getSubExpr());
     }
 
+    // Try to remember the original __ptrauth qualifier for loads of
+    // function pointers.
+    if (ICE->getCastKind() == CK_LValueToRValue) {
+      const auto *SubExpr = ICE->getSubExpr();
+      if (const auto *PtrType = SubExpr->getType()->getAs<PointerType>()) {
+        auto Result = EmitOrigPointerRValue(E);
+
+        QualType FunctionType = PtrType->getPointeeType();
+        assert(FunctionType->isFunctionType());
+
+        GlobalDecl GD;
+        if (const auto *VD =
+                dyn_cast_or_null<VarDecl>(E->getReferencedDeclOfCallee())) {
+          GD = GlobalDecl(VD);
+        }
+        CGCalleeInfo CalleeInfo(FunctionType->getAs<FunctionProtoType>(), GD);
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AaronBallman wrote:

I don't see any code which prohibits use on K&R C functions, so this `getAs` can return null. Should we prohibit such a use in Sema or fix the use here and add test coverage?

https://github.com/llvm/llvm-project/pull/100830