Re: [lttng-dev] [PATCH 02/11] urcu/uatomic: Use atomic builtins if configured
Mathieu Desnoyers via lttng-dev <[email protected]>
| Newsgroups | org.lttng.lists.lttng-dev |
|---|---|
| Message-ID | <[email protected]> |
On 6/22/23 15:53, Olivier Dion wrote: > On Thu, 22 Jun 2023, "Paul E. McKenney" <[email protected]> wrote: > >> I suggest C11 volatile atomic load/store. Load/store fusing is permitted >> for non-volatile atomic loads and stores, and such fusing can ruin your >> code's entire day. ;-) > > Good catch. Seems like not a problem on GCC (yet), but Clang is extremely > aggressive and seems to do store fusing on some corner cases [0]. I don't think this is an example of store fusing, but rather just that the compiler can eliminate stores to static variables which are otherwise unused, making the entire variable useless. Thanks, Mathieu > > However, I do not find any simple reproducer of load/store fusing. Do > you have example of such fusing, or is this a precaution? In the > meantime, back to reading the standard to be certain :-) > > [0] https://godbolt.org/z/odKG9a75a > -- Mathieu Desnoyers EfficiOS Inc. https://www.efficios.com _______________________________________________ lttng-dev mailing list [email protected] https://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev