On Tue, 6 Oct 2020, Qing Zhao wrote:
> Richard,
>
> On behalf of John Henning, I am sending the following simple documentation
> patch
> for an official approval. Hopefully this patch can get into gcc11.
>
> Per John, the wording of the documentation change was based on the discussion
> between him and you on 25-Aug-2020.
>
> I created a gcc bugzilla bug
> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97309
> to record this issue.
>
> Okay to commit?
OK.
Richard.
> thanks.
>
> Qing
>
> ChangeLog:
>
>
> 2020-10-06 John Henning <john.henn...@oracle.com>
>
> * gcc/doc/invoke.texi: Improve documentation of -fallow-store-data-races
>
> ---
> gcc/doc/invoke.texi | 13 ++++++++++++-
> 1 file changed, 12 insertions(+), 1 deletion(-)
>
> diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
> index 7c81d7f41bd..926ee1ff28e 100644
> --- a/gcc/doc/invoke.texi
> +++ b/gcc/doc/invoke.texi
> @@ -11621,7 +11621,18 @@ Do not remove unused C++ allocations in dead code
> elimination.
>
> @item -fallow-store-data-races
> @opindex fallow-store-data-races
> -Allow the compiler to introduce new data races on stores.
> +Allow the compiler to perform optimizations that may introduce new data races
> +on stores, without proving that the variable cannot be concurrently accessed
> +by other threads. Does not affect optimization of local data. It is safe to
> +use this option if it is known that global data will not be accessed by
> +multiple threads.
> +
> +Examples of optimizations enabled by @option{-fallow-store-data-races}
> include
> +hoisting or if-conversions that may cause a value that was already in memory
> +to be re-written with that same value. Such re-writing is safe in a single
> +threaded context but may be unsafe in a multi-threaded context. Note that on
> +some processors, if-conversions may be required in order to enable
> +vectorization.
>
> Enabled at level @option{-Ofast}.
>
>
--
Richard Biener <rguent...@suse.de>
SUSE Software Solutions Germany GmbH, Maxfeldstrasse 5, 90409 Nuernberg,
Germany; GF: Felix Imend
