[llvm] r281773 - [WebAssembly] Fix function types of CFGStackify tests

[Dan Gohman via llvm-commits]

On Fri, Sep 16, 2016 at 4:41 PM, Dan Gohman <sunfish at mozilla.com> wrote:

>
>
> On Fri, Sep 16, 2016 at 3:04 PM, Derek Schuff <dschuff at google.com> wrote:
>
>>
>> Which you could simplify to
>> (module
>>   (func $minimal_loop (param $0 i32) (result i32)
>>     (block $label$1
>>       (loop $label$0
>>         (br $label$0)
>>       )
>>     )
>>   )
>> )
>>
>> Which is a type check failure because the loop/block structure
>> yields/pushes no value but the function expects an i32 return.
>>
>
> This is actually a valid WebAssembly program :-). One of the main branches
> of the reference interpreter currently issues an error here, but it's a
> bug: the intention is that because the `br` makes code after it
> unreachable, so there doesn't need to be a return value after it.
>

Actually, I misspoke. This is the situation where consumers are not
required to type-check, but they may type-check, so producers have to
follow a complex set of rules just in case. I think what we should do here
is add type signatures to `block` and `loop`, to mirror the 0xc change, and
then make LLVM add an `i32` return type to the `loop` and `block` here.

Dan
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