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[Wasm GC] Allow tail call subtyping in DeadArgumentElimination #4035

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Merged
kripken merged 3 commits into from
Jul 28, 2021
Merged

[Wasm GC] Allow tail call subtyping in DeadArgumentElimination #4035

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kripken Jul 28, 2021
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kripken Jul 28, 2021
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kripken Jul 28, 2021
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10 changes: 2 additions & 8 deletions src/passes/DeadArgumentElimination.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -327,14 +327,8 @@ struct DAE : public Pass {
// affect whether an argument is used or not, it just refines the type
// where possible.
refineArgumentTypes(func, calls, module);
// Refine return types as well, if we can. We cannot do so if this
// function is tail-called, because then the return type must match that
// of the function doing a tail call of it - we cannot change just one of
// them.
//
// TODO: Try to optimize in a more holistic manner, see the TODO in
// refineReturnTypes() about missing a global optimum.
if (!tailCallees.count(name) && refineReturnTypes(func, calls, module)) {
// Refine return types as well.
if (refineReturnTypes(func, calls, module)) {
refinedReturnTypes = true;
}
// Check if all calls pass the same constant for a particular argument.
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8 changes: 4 additions & 4 deletions test/lit/passes/dae-gc.wast
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Expand Up @@ -579,16 +579,16 @@
)

;; This function does a return call of the one after it. The one after it
;; returns a ref.func of this one. They both begin by returning a funcref; if
;; we refine the return type of the latter (which ref.func allows us to do)
;; then the return type would not match, and we would get a validation error.
;; returns a ref.func of this one. They both begin by returning a funcref;
;; after refining the return type of the second function, it will have a more
;; specific type (which is ok as subtyping is allowed with tail calls).
;; CHECK: (func $do-return-call (result funcref)
;; CHECK-NEXT: (return_call $return-ref-func)
;; CHECK-NEXT: )
(func $do-return-call (result funcref)
(return_call $return-ref-func)
)
;; CHECK: (func $return-ref-func (result funcref)
;; CHECK: (func $return-ref-func (result (ref $none_=>_funcref))
;; CHECK-NEXT: (ref.func $do-return-call)
;; CHECK-NEXT: )
(func $return-ref-func (result funcref)
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