Re: [PATCH 1/7] Add __builtin_speculation_safe_value

["Richard Earnshaw (lists)" <Richard.Earnshaw@arm.com>]

On 27/07/18 01:46, Paul Koning wrote:
> 
> 
>> On Jul 26, 2018, at 7:34 PM, Joseph Myers <joseph@codesourcery.com> wrote:
>>
>> On Wed, 25 Jul 2018, Richard Earnshaw (lists) wrote:
>>
>>>>> Port maintainers DO need to decide what to do about speculation, even if
>>>>> it is explicitly that no mitigation is needed.
>>>>
>>>> Agreed.  But I didn't yet see a request for maintainers to decide that?
>>>>
>>>
>>> consider it made, then :-)
>>
>> I suggest the following as an appropriate process for anything needing 
>> attention from architecture maintainers:
>>
>> * Send a message to the gcc list, starting its own thread, CC:ed to all 
>> target architecture maintainers, stating explicitly in its first sentence 
>> that it is about something needing action from all such maintainers.
> 
> Yes, because it was not clear to me that a patch discussion about a speculation builtin was something that every target maintainer was supposed to look at.  "Speculation" is not a term that shows up in my target...
> 
>> ...
>> * Over the next few months, send occasional reminders, each including a 
>> list of the ports that have not been updated.
> 
> Would the GCC Wiki be a good place to collect all the responses and track what is still open?  If not, what is a good way to do the tracking?
> 
> 	paul
> 

The c-c++-common/spec-barrier-1.c test will fail on any target that has
not been updated (it deliberately doesn't check for
__HAVE_SPECULATION_BARRIER before trying to use the new intrinsic).  The
test contains a comment to that effect.  That should be enough to alert
maintainers if they are tracking testsuite errors.

I'll be posting some examples for how to handle various types of target
shortly.  Target maintainers should then be able to decide which action
they need to take.

R.