Re: [PATCH] Fix PR71598, aliasing between enums and compatible types

[Jeff Law <law at redhat dot com>]

On 3/29/19 9:09 AM, Jason Merrill wrote:
> On Fri, Mar 29, 2019 at 4:48 AM Richard Biener <rguenther@suse.de> wrote:
>>
>> On Thu, 28 Mar 2019, Jason Merrill wrote:
>>
>>> On 3/26/19 4:40 AM, Richard Biener wrote:
>>>> On Mon, 18 Mar 2019, Richard Biener wrote:
>>>>
>>>>> On Fri, 15 Mar 2019, Jason Merrill wrote:
>>>>>
>>>>>> On 3/15/19 9:33 AM, Richard Biener wrote:
>>>>>>>
>>>>>>> The following is an attempt to fix PR71598 where C (and C++?) have
>>>>>>> an implementation-defined compatible integer type for each enum
>>>>>>> and the TBAA rules mandate that accesses using a compatible type
>>>>>>> are allowed.
>>>>>>
>>>>>> This does not apply to C++; an enum does not alias its underlying type.
>>>>>
>>>>> Thus the following different patch, introducing c_get_alias_set and
>>>>> only doing the special handling for C family frontends (I assume
>>>>> that at least ObjC is also affected).
>>>>>
>>>>> Bootstrap & regtest running on x86_64-unknown-linux-gnu, OK?
>>>>
>>>> Ping.  Also consider the additional testcase below to be added.
>>>>
>>>> Richard.
>>>>
>>>> 2019-03-18  Richard Biener  <rguenther@suse.de>
>>>>
>>>>          PR c/71598
>>>>          * gimple.c: Include langhooks.h.
>>>>          (gimple_get_alias_set): Treat enumeral types as the underlying
>>>>          integer type.
>>>
>>> Won't this affect all languages?
>>
>> It affects all languages during the LTO optimization phase, yes.
>> There's unfortunately no way around that at the moment.
> 
> Ah, well.  Looks good to me, then.
Likewise.  And with Joseph largely offline right now, that's going to
have to be sufficient :-)

jeff