Re: [PATCH] Introduce -fprofile-update=maybe-atomic

[Nathan Sidwell <nathan at acm dot org>]

On 11/10/2016 05:19 AM, Martin Liška wrote:

> > On 10/13/2016 05:34 PM, Martin Liška wrote:
> > > Hello.
> > >
> > > As it's very hard to guess from GCC driver whether a target supports atomic updates
> > > for GCOV counter or not, I decided to come up with a new option value (maybe-atomic),
> > > that would be transformed in a corresponding value (single or atomic) in tree-profile.c.
> > > The GCC driver selects the option when -pthread is present in the command line.
> > >
> > > That should fix all tests failures seen on AIX target.
> > >
> > > Patch can bootstrap on ppc64le-redhat-linux and survives regression tests.
> > >
> > > Ready to be installed?

I dislike this.  If it's hard for gcc itself to know, how much harder 
for the user must it be?   (does gcc have another instance of an option 
that behaves 'prefer-A-or-B-if-you-can't'?

It's also not clear what problem it's solving for the user?  If the user 
needs atomic update, they should get a hard error if the target doesn't 
support it.  If they don't need atomic, why ask for it?

But as ever, I'm not going to veto it.

nathan

--
Nathan Sidwell