SignatureRefining: Do not refine results of functions used in continuations (#8675)

This can break with `cont.bind`, see testcase.

Author: kripken

src/passes/SignatureRefining.cpp

@@ -168,13 +168,12 @@ struct SignatureRefining : public Pass {
         false;
     }
 
-    // Continuations must not have params refined, because we do not update
-    // their users (e.g. cont.bind, resume) with new types.
-    // TODO: support refining continuations
+    // Continuations must not have params or results refined, because we do not
+    // update their users (e.g. cont.bind, resume) with new types.
     if (module->features.hasStackSwitching()) {
       for (auto type : ModuleUtils::collectHeapTypes(*module)) {
         if (type.isContinuation()) {
-          allInfo[type.getContinuation().type].canModifyParams = false;
+          allInfo[type.getContinuation().type].canModify = false;
         }
       }
     }

test/lit/passes/signature-refining-cont.wast

@@ -0,0 +1,48 @@
+;; NOTE: Assertions have been generated by update_lit_checks.py --all-items and should not be edited.
+;; RUN: wasm-opt %s --signature-refining -all -S -o - | filecheck %s
+
+;; cont.bind places restrictions on signature refining.
+(module
+ (rec
+  ;; CHECK:      (rec
+  ;; CHECK-NEXT:  (type $A (func (result (ref null $cont-A))))
+  (type $A (func (result (ref null $cont-A))))
+
+  ;; CHECK:       (type $B (func (result (ref null $cont-A))))
+  (type $B (func (result (ref null $cont-A))))
+
+  ;; CHECK:       (type $cont-A (cont $A))
+  (type $cont-A (cont $A))
+
+  ;; CHECK:       (type $cont-B (cont $B))
+  (type $cont-B (cont $B))
+ )
+
+ ;; CHECK:      (elem declare func $0)
+
+ ;; CHECK:      (func $1 (type $A) (result (ref null $cont-A))
+ ;; CHECK-NEXT:  (cont.bind $cont-B $cont-A
+ ;; CHECK-NEXT:   (cont.new $cont-B
+ ;; CHECK-NEXT:    (ref.func $0)
+ ;; CHECK-NEXT:   )
+ ;; CHECK-NEXT:  )
+ ;; CHECK-NEXT: )
+ (func $1 (type $A) (result (ref null $cont-A))
+  ;; cont.bind requires that the continuation type's results match, so we
+  ;; cannot refine the type $A: if we make it return an exact result, we would
+  ;; be binding a continuation that returns an inexact result to an exact one.
+  (cont.bind $cont-B $cont-A
+   (cont.new $cont-B
+    (ref.func $0)
+   )
+  )
+ )
+
+ ;; CHECK:      (func $0 (type $B) (result (ref null $cont-A))
+ ;; CHECK-NEXT:  (unreachable)
+ ;; CHECK-NEXT: )
+ (func $0 (type $B) (result (ref null $cont-A))
+  (unreachable)
+ )
+)
+