On 11/10/2016 04:43 PM, Nathan Sidwell wrote: > 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?
My initial motivation was to automatically selected -fprofile-update=atomic if supported by a target and when '-pthread' is present on command line. As it's very problematic to identify (from GCC driver) whether a target supports or not atomic updates, 'maybe' option is the only possible we can guess. > > But as ever, I'm not going to veto it. Other option is to disable selection of -fprofile-update=atomic automatically. Martin > > nathan >
