AW: Wonly-top-basic-asm

David Wohlferd dw@LimeGreenSocks.com
Sun Feb 14 03:57:00 GMT 2016


On 2/12/2016 4:51 AM, Bernd Schmidt wrote:
> On 02/12/2016 08:05 AM, David Wohlferd wrote:
>> Actually, it was my intent that this apply to v6.  It's not like there
>> is a significant change here.  We're documenting long-time behavior, and
>> adding a (disabled) warning.
>
> The doc patch (minus mentioning the warning) could go in now, but for 
> gcc-6 we're at a stage where we're only accepting regression fixes 
> with very few exceptions. If you can convince a RM that this is 
> important enough then it could still go in.

Understood.  While I think the patch is small enough to be safe, whether 
it's important enough for this stage is a different question.

>> 2) There is a significant change to this behavior being proposed for
>> v7.  When this happens, having a way to locate affected statements with
>> features from a stable release seems desirable.
>
> I'm actually not convinced that we'll want to change much in asm 
> behaviour. Clobbering memory, maybe, but I can't see much beyond that 
> - there's just no gain and some risk. So I'm a little more relaxed 
> about the whole thing.

And that's the question.  If you are correct that we won't be changing 
this, then yeah, update the docs for v6, push the code change to v7.  Done.

But Jeff sounded quite serious when he said "the only rational behaviour 
for a traditional asm is that it has to be considered a use/clobber of 
memory and hard registers."  If indeed that is the plan for v7, then 
having this warning available in v6 to allow people to prepare becomes 
important.

Jeff Law: If you are listening, care to share your plans here?

> Let's let Sandra have the last word [about the docs].

Good plan.

dw



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