[PATCH Coroutines] Fix issue with unused corutine function parameters

[JunMa]

在 2020/1/20 下午6:07, Iain Sandoe 写道:
> Hi JunMa,
>
> JunMa <JunMa@linux.alibaba.com> wrote:
>
>> Hi
>> Accroding to N4835: When a coroutine is invoked, a copy is created
>> for each coroutine parameter. While in current implementation, we
>> only collect used parameters. This may lost behavior inside constructor
>> and destructor of unused parameters.
>>
>> This patch change the implementation to collect all parameter.
>
> thanks for the patch.
>
> I am not convinced this is the right way to fix this, we do not want 
> to increase
> the size of the coroutine frame unnecessarily.  I would like to check 
> the lifetime
> requirements; such copies might only need to be made local to the ramp 
> function.
>
> Iain
>
For type with trivial destructor, There is no need to copy parameter if 
it is
never referenced after a reachable suspend 
point(return-to-caller/resume) in the
coroutine. Since we are in front end, that should be inital_suspend 
point. so we
can create field for type with non-trivial destructor first, and skip 
unused parameters
in register_param_uses. I'll update the patch

Regards
JunMa
>>
>> Bootstrap and test on X86_64, is it OK?
>>
>> Regards
>> JunMa
>>
>> gcc/cp
>> 2020-01-20Â  Jun Ma <JunMa@linux.alibaba.com>
>>
>> Â Â Â Â Â Â Â  * coroutines.cc (build_actor_fn): Skip rewrite when there is no
>> Â Â Â Â Â Â Â  param references.
>> Â Â Â Â Â Â Â  (register_param_uses): Only collect param references here.
>> Â Â Â Â Â Â Â  (morph_fn_to_coro): Create coroutine frame field for each
>> Â Â Â Â Â Â Â  function params.
>>
>> gcc/testsuite
>> 2020-01-20Â  Jun Ma <JunMa@linux.alibaba.com>
>>
>> Â Â Â Â Â Â Â  * g++.dg/coroutines/torture/func-params-07.C: New test.
>> <0001-Fix-issue-when-copy-function-parameters-into-corouti.patch>
>