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[Stack Switching] Unsubtyping: Handle continuation subtyping #8463

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Merged
kripken merged 1 commit into from
Mar 13, 2026
+51 −2
Merged

[Stack Switching] Unsubtyping: Handle continuation subtyping #8463

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6 changes: 4 additions & 2 deletions src/passes/Unsubtyping.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -949,8 +949,10 @@ struct Unsubtyping : Pass, Noter<Unsubtyping> {
noteSubtype(elem.type, super.getArray().element.type);
break;
}
case HeapTypeKind::Cont:
WASM_UNREACHABLE("TODO: cont");
case HeapTypeKind::Cont: {
noteSubtype(sub.getContinuation().type, super.getContinuation().type);
break;
}
case HeapTypeKind::Basic:
WASM_UNREACHABLE("unexpected kind");
}
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47 changes: 47 additions & 0 deletions test/lit/passes/unsubtyping-stack-switching.wast
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Expand Up @@ -591,3 +591,50 @@
)
)

(module
;; CHECK: (rec
;; CHECK-NEXT: (type $super (sub (func)))
(type $super (sub (func)))
;; CHECK: (type $sub (sub $super (func)))
(type $sub (sub $super (func)))
;; CHECK: (type $cont-super (sub (cont $super)))
(type $cont-super (sub (cont $super)))
;; CHECK: (type $cont-sub (sub $cont-super (cont $sub)))
(type $cont-sub (sub $cont-super (cont $sub)))

;; CHECK: (type $4 (func (param (ref $cont-sub)) (result (ref $cont-super))))

;; CHECK: (func $cont-new (type $4) (param $sub (ref $cont-sub)) (result (ref $cont-super))
;; CHECK-NEXT: (local.get $sub)
;; CHECK-NEXT: )
(func $cont-new (param $sub (ref $cont-sub)) (result (ref $cont-super))
;; This requires $cont-sub <: $cont-super and $sub <: $super.
(local.get $sub)
)
)

(module
;; CHECK: (rec
;; CHECK-NEXT: (type $super (sub (func)))
(type $super (sub (func)))
;; CHECK: (type $sub (sub (func)))
(type $sub (sub $super (func)))
;; CHECK: (type $cont-super (sub (cont $super)))
(type $cont-super (sub (cont $super)))
;; CHECK: (type $cont-sub (sub (cont $sub)))
(type $cont-sub (sub $cont-super (cont $sub)))

;; CHECK: (type $4 (func (param (ref $cont-sub)) (result (ref $cont-sub))))

;; CHECK: (func $cont-new (type $4) (param $sub (ref $cont-sub)) (result (ref $cont-sub))
;; CHECK-NEXT: (local $keepalive (ref $cont-super))
;; CHECK-NEXT: (local.get $sub)
;; CHECK-NEXT: )
(func $cont-new (param $sub (ref $cont-sub)) (result (ref $cont-sub))
(local $keepalive (ref $cont-super))
;; As above, but now we return the subtype, so there is no constraint. We
;; can unsubtype both the continuations and the funcs.
(local.get $sub)
)
)

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