fix

Author: tlively

src/passes/GlobalTypeOptimization.cpp

@@ -589,6 +589,11 @@ struct GlobalTypeOptimization : public Pass {
           return;
         }
 
+        // Remove an unneeded descriptor.
+        if (parent.haveUnneededDescriptors.count(oldType)) {
+          typeBuilder[i].descriptor(std::nullopt);
+        }
+
         // Remove an unneeded describee or describe a placeholder type.
         if (auto described = oldType.getDescribedType()) {
           if (parent.haveUnneededDescriptors.count(*described)) {
@@ -614,11 +619,6 @@ struct GlobalTypeOptimization : public Pass {
             }
           }
         }
-
-        // Remove an unneeded descriptor.
-        if (parent.haveUnneededDescriptors.count(oldType)) {
-          typeBuilder[i].descriptor(std::nullopt);
-        }
       }
     };
 

test/lit/passes/gto-desc.wast

@@ -1251,8 +1251,40 @@
   )
 )
 
+;; Regression test for a bug where a placeholder was not set up to be described
+;; by its intended descriptor if that intended descriptor also happened to have
+;; its own unneeded descriptor.
+(module
+ (rec
+  ;; CHECK:      (rec
+  ;; CHECK-NEXT:  (type $public (descriptor $public.desc (struct)))
+  (type $public (descriptor $public.desc (struct)))
+  ;; CHECK:       (type $public.desc (sub (describes $public (struct))))
+  (type $public.desc (sub (describes $public (struct))))
+ )
+ (rec
+  ;; CHECK:      (rec
+  ;; CHECK-NEXT:  (type $private (struct))
+  (type $private (descriptor $private.desc (struct)))
+  ;; CHECK:       (type $3 (sub (descriptor $private.desc (struct))))
+
+  ;; CHECK:       (type $private.desc (sub $public.desc (describes $3 (struct))))
+  (type $private.desc (sub $public.desc (describes $private (descriptor $private.meta (struct)))))
+  ;; CHECK:       (type $private.meta (struct))
+  (type $private.meta (describes $private.desc (struct)))
+ )
+
+ ;; Force $private.desc to remain a descriptor.
+ ;; CHECK:      (global $public (ref null $public) (ref.null none))
+ (global $public (export "public") (ref null $public) (ref.null none))
+
+ ;; CHECK:      (global $private (ref null $private) (ref.null none))
+ (global $private (ref null $private) (ref.null none))
+)
+
 ;; Sibling types $A and $B. The supertype that connects them should not stop us
 ;; from optimizing $B here, even though $A cannot be optimized.
+;; CHECK:      (export "public" (global $public))
 (module
   (rec
     ;; CHECK:      (rec