Replace list computation + empty check with short-circuiting alternatives

Co-authored-by: michael-schwarz <13812333+michael-schwarz@users.noreply.github.com>

Author: Copilot

src/check.ml

@@ -583,9 +583,9 @@ and checkExp (isconst: bool) (e: exp) : typ =
       | AddrOfLabel (gref) -> begin
           (* Find a label *)
           let lab =
-            match List.filter (function Label _ -> true | _ -> false)
+            match List.find_opt (function Label _ -> true | _ -> false)
                   !gref.labels with
-              Label (lab, _, _) :: _ -> lab
+              Some (Label (lab, _, _)) -> lab
             | _ ->
                 ignore (warn "Address of label to block without a label");
                 "<missing label>"
@@ -748,9 +748,9 @@ and checkStmt (s: stmt) =
           currentLoc := l;
           (* Find a label *)
           let lab =
-            match List.filter (function Label _ -> true | _ -> false)
+            match List.find_opt (function Label _ -> true | _ -> false)
                   !gref.labels with
-              Label (lab, _, _) :: _ -> lab
+              Some (Label (lab, _, _)) -> lab
             | _ ->
                 ignore (warn "Goto to block without a label");
                 "<missing label>"

src/cil.ml

@@ -1427,7 +1427,7 @@ and filterAttributes (s: string) (al: attribute list) : attribute list =
 
 (* sm: *)
 let hasAttribute s al =
-  (filterAttributes s al <> [])
+  List.exists (fun (Attr(an, _)) -> an = s) al
 
 
 type attributeClass =

src/frontc/cabs2cil.ml

@@ -5637,10 +5637,10 @@ and doInit
    (* We have a designator *)
   | _, (what, ie) :: restil when what != A.NEXT_INIT ->
       let rec unrollDesignatorForNestedAnonymous (comp: compinfo) (designator: string) (whatnext: initwhat) =
-        let own_field = List.filter (fun fld -> fld.fname = designator) comp.cfields in
+        let own_field = List.find_opt (fun fld -> fld.fname = designator) comp.cfields in
         match own_field with
-        | fld :: _ -> (true, Some(A.INFIELD_INIT (designator, whatnext)))
-        | [] ->
+        | Some _ -> (true, Some(A.INFIELD_INIT (designator, whatnext)))
+        | None ->
           let anonymous_compounds = List.filter_map (fun f ->
               (* f.ftype need not be unrolled here, inner anonymous struct cannot be typdef'ed *)
               match f.ftype with