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[Stack Switching] wasm-ctor-eval: stop on serializing continuations to globals #8585

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Merged
kripken merged 1 commit into from
Apr 9, 2026
+80 −0
Merged

[Stack Switching] wasm-ctor-eval: stop on serializing continuations to globals #8585

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7 changes: 7 additions & 0 deletions src/tools/wasm-ctor-eval.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -213,6 +213,13 @@ class EvallingModuleRunner : public ModuleRunnerBase<EvallingModuleRunner> {
return ModuleRunnerBase<EvallingModuleRunner>::visitGlobalGet(curr);
}

Flow visitGlobalSet(GlobalSet* curr) {
if (curr->value->type.isContinuation()) {
throw FailToEvalException("cannot serialize continuations to globals");
}
return ModuleRunnerBase<EvallingModuleRunner>::visitGlobalSet(curr);
}

Flow visitTableGet(TableGet* curr) {
// We support tableLoad, below, so that call_indirect works (it calls it
// internally), but we want to disable table.get for now.
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73 changes: 73 additions & 0 deletions test/lit/ctor-eval/cont-noserial.wast
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Expand Up @@ -351,3 +351,76 @@
(func $export (export "export")
)
)

;; Now the problem happens when we write a continuation to a global, which we
;; cannot do. Nothing can be optimized here.
(module
;; CHECK: (type $func (func))
;; NOKEEP: (type $func (func))
(type $func (func))
;; CHECK: (type $cont (cont $func))
;; NOKEEP: (type $cont (cont $func))
(type $cont (cont $func))

;; CHECK: (type $2 (func (result (ref null $cont))))

;; CHECK: (global $global (mut (ref null $cont)) (ref.null nocont))
;; NOKEEP: (type $2 (func (result (ref null $cont))))

;; NOKEEP: (global $global (mut (ref null $cont)) (ref.null nocont))
(global $global (mut (ref null $cont)) (ref.null $cont))

;; CHECK: (elem declare func $func)

;; CHECK: (export "read" (func $read))

;; CHECK: (export "test" (func $test))
;; NOKEEP: (elem declare func $func)

;; NOKEEP: (export "read" (func $read))

;; NOKEEP: (export "test" (func $test))
(export "test" (func $test))

;; CHECK: (func $func (type $func)
;; CHECK-NEXT: (nop)
;; CHECK-NEXT: )
;; NOKEEP: (func $func (type $func)
;; NOKEEP-NEXT: (nop)
;; NOKEEP-NEXT: )
(func $func
)

;; CHECK: (func $test (type $func)
;; CHECK-NEXT: (global.set $global
;; CHECK-NEXT: (cont.new $cont
;; CHECK-NEXT: (ref.func $func)
;; CHECK-NEXT: )
;; CHECK-NEXT: )
;; CHECK-NEXT: )
;; NOKEEP: (func $test (type $func)
;; NOKEEP-NEXT: (global.set $global
;; NOKEEP-NEXT: (cont.new $cont
;; NOKEEP-NEXT: (ref.func $func)
;; NOKEEP-NEXT: )
;; NOKEEP-NEXT: )
;; NOKEEP-NEXT: )
(func $test
(global.set $global
(cont.new $cont
(ref.func $func)
)
)
)

;; CHECK: (func $read (type $2) (result (ref null $cont))
;; CHECK-NEXT: (global.get $global)
;; CHECK-NEXT: )
;; NOKEEP: (func $read (type $2) (result (ref null $cont))
;; NOKEEP-NEXT: (global.get $global)
;; NOKEEP-NEXT: )
(func $read (export "read") (result (ref null $cont))
(global.get $global)
)
)
Comment on lines +416 to +425
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@stevenfontanella stevenfontanella Apr 8, 2026

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nit: I guess this isn't needed?

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@kripken kripken Apr 9, 2026

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The above testcases use this pattern, because without it, the global is only written to and never read, so it can be trivially optimized out. I suspect this case might not need it as it can't optimize, but I think it's better to follow the shape of the above testcases so the diff compared to them is small and clear.

(Note that even if we don't need this now, we might need it later - ctor-eval runs a few opt passes after its work, and while simplify-globals, the pass that would remove the write-only global, is not yet run, we might add it later. Similar passes are already there.)


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