Re: gcc -fno-common
On Thu, Feb 06, 2020 at 11:01:56AM +0000, Dave Love wrote:
Jakub Jelinek <jakub(a)redhat.com> writes:
> On Wed, Feb 05, 2020 at 05:13:27PM +0000, Dave Love wrote:
>> GCC doesn't document the targets for which -fno-common produces better
>> code. Can someone say for which of the Fedora ones it makes a
>> difference?
>
> E.g. on any that is capable of vectorization.
Thanks. I'll pass that on to the maintainer of the (x86_64-specific)
performance library, though I guess he'll fix it anyhow.
Note, if for whatever reason one wants the common behavior e.g. on a few
selected variables, one can add __attribute__((__common__)) to those
variables to override the default, it doesn't have to be just -fcommon
that changes the behavior of all non-automatic variables without
initializers.
Jakub