[clang] [PAC] Re-sign a pointer to a noexcept member function when it is converted to a pointer to a member function without noexcept (PR #109056)

[Akira Hatanaka via cfe-commits]

================
@@ -2419,8 +2419,13 @@ Value *ScalarExprEmitter::VisitCastExpr(CastExpr *CE) {
     return Visit(const_cast<Expr*>(E));
 
   case CK_NoOp: {
-    return CE->changesVolatileQualification() ? EmitLoadOfLValue(CE)
-                                              : Visit(const_cast<Expr *>(E));
+    if (CE->changesVolatileQualification())
+      return EmitLoadOfLValue(CE);
+    auto V = Visit(const_cast<Expr *>(E));
+    if (CGF.CGM.getCodeGenOpts().PointerAuth.CXXMemberFunctionPointers &&
+        CE->getType()->isMemberFunctionPointerType())
+      V = CGF.CGM.getCXXABI().EmitMemberPointerConversion(CGF, CE, V);
+    return V;
----------------
ahatanak wrote:

Sema does use `CK_NoOp` for those, but we don't need to re-sign function pointers because the presence of `noexcept` on a function type doesn't change the discriminator. The function that encodes the function type (`encodeTypeForFunctionPointerAuth`) encodes the parameter and return types, but ignores `noexcept`.

https://github.com/llvm/llvm-project/pull/109056