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Re: Deprecating basic asm in a function - What now?
- From: Michael Matz <matz at suse dot de>
- To: Andrew Haley <aph at redhat dot com>
- Cc: "gcc at gcc dot gnu dot org" <gcc at gcc dot gnu dot org>
- Date: Tue, 21 Jun 2016 14:08:26 +0200 (CEST)
- Subject: Re: Deprecating basic asm in a function - What now?
- Authentication-results: sourceware.org; auth=none
- References: <dc3ca16c-3521-757f-fcf0-50061f510f75 at LimeGreenSocks dot com> <alpine dot LSU dot 2 dot 20 dot 1606201931460 dot 13156 at wotan dot suse dot de> <57682A85 dot 4060803 at redhat dot com> <alpine dot LSU dot 2 dot 20 dot 1606201941340 dot 13156 at wotan dot suse dot de> <57690227 dot 2050501 at redhat dot com>
On Tue, 21 Jun 2016, Andrew Haley wrote:
> > As said in the various threads about basic asms, all correctness
> > problems can be solved by making GCC more conservative in handling
> > them (or better said: not making it less conservative).
> Well, yes. That's exactly why we've agreed to change basic asms to make
> them clobber memory, i.e. to make GCC more conservative.
Exactly. But this thread is about something else, see subject.
> Well, maybe. It's also fairly likely that many work by accident. IMO
> this is more of a statement of hope than any kind of reasonable
Like yours, of course.
> > Then the compiler better won't change into less conservative handling
> > of basic asms.
> Repeat, repeat: the change being made is to make gcc MORE
This thread is about deprecating basic asms. That's not more
conservative, it's simply breaking backward compatibility for many users.
> > they work fine now. Even if it weren't so it still would be silly if
> > GCC simply could regard the former as the latter internally.
> That's what we're doing.
Currently. But not the proposed patch in this thread, and the general
idea of deprecating the basic syntax.