dexonsmith added a comment. I have a couple of suggestions below to add to the mix (but I don't feel strongly about either of them, just adding them for consideration).
In D92808#2552100 <https://reviews.llvm.org/D92808#2552100>, @ahatanak wrote: > define void @test() { > %r = call i8* @foo() [ "clang.arc.rv"(i64 1) ] > call void (...) @llvm.objc.clang.arc.noop.use(i8* %r) > ret void > } Firstly, it feels to me like this IR would clarify that the bundle looks at the return value: define void @test() { %r = call i8* @foo() [ "clang.arc.rv"(i64 1, i8* %r) ] ret void } Notice this passes `%r` to the operand bundle, which the verifier rejects. I wonder if the IR rule could safely be weakened to allow an operand bundle to reference the call/invoke it's attached to? (Not sure what all the implications would be, or if this would be sufficient...) In D92808#2552100 <https://reviews.llvm.org/D92808#2552100>, @ahatanak wrote: > Or we could use a bundle that is more generic than `clang.arc.rv` (for > example, `"implicitly.used.by"(@llvm.objc.retainAutoreleasedReturnValue)`, > which indicates the result is used by an instruction that isn't explicitly > emitted in the IR). Secondly, I agree it might be cleaner to formalize a generic operand bundle that has the semantics ARC needs. It might be nice to have this also model the inlining semantics, maybe something like "returnfilter": %x = call type @f1(...) [ "returnfilter"(type(type)* @f2) ] The semantics could be that `%x` is implicitly passed through `@f2`. Concretely, maybe that's: - `%x` has an implicit use. - `@f1`'s return type cannot be changed. - Inlining `@f1` generates explicit calls to `@f2`. - The backend lowers the bundle as late as possible to calls to `@f2`. Thirdly, you could combine the two previous ideas, generalizing the semantics to an "onreturn" bundle that is allowed to self-reference the callable, that the inliner knows about, etc., something like: %x = call type @f1(...) [ "onreturn"(type(type)* @f2, type %x) ] This `@f2` is implicitly called and its return used in place of `%x`, but it explicitly lists its arguments. Compared to "returnfilter", it has the flexibility to specify argument order and might be more useful for other applications. Repository: rG LLVM Github Monorepo CHANGES SINCE LAST ACTION https://reviews.llvm.org/D92808/new/ https://reviews.llvm.org/D92808 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
