From: Leon Romanovsky <leon-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
To: Jason Gunthorpe
<jgunthorpe-ePGOBjL8dl3ta4EC/59zMFaTQe2KTcn/@public.gmane.org>
Cc: Doug Ledford <dledford-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>,
linux-rdma-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
Subject: Re: [PATCH rdma-core 1/5] Pull uninitialized_var into util/compiler.h
Date: Tue, 11 Oct 2016 22:46:33 +0300 [thread overview]
Message-ID: <20161011194633.GP9282@leon.nu> (raw)
In-Reply-To: <20161011180517.GA17866-ePGOBjL8dl3ta4EC/59zMFaTQe2KTcn/@public.gmane.org>
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On Tue, Oct 11, 2016 at 12:05:17PM -0600, Jason Gunthorpe wrote:
> On Mon, Oct 10, 2016 at 07:09:30AM +0300, Leon Romanovsky wrote:
>
> > > I think people would complain about the extra stores. gcc 6 will
> > > eliminate them, but older compilers will not.
> >
> > This unintialized_var(x) adds extra store too (... x = x ...).
>
> I have confirmed that the unintialized_var macro does not impact code
> generation on the old gccs while the =0 approach does.
Ohh, thanks.
But I'm still left under impression of this article [1] that using such
macro is a bad thing and we are "punishing" all users of modern compilers.
[1] https://lwn.net/Articles/529954/
>
> So no extra store.
>
> Jason
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next prev parent reply other threads:[~2016-10-11 19:46 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-10-07 22:36 [PATCH rdma-core 0/5] clang support Jason Gunthorpe
[not found] ` <1475879772-29458-1-git-send-email-jgunthorpe-ePGOBjL8dl3ta4EC/59zMFaTQe2KTcn/@public.gmane.org>
2016-10-07 22:36 ` [PATCH rdma-core 1/5] Pull uninitialized_var into util/compiler.h Jason Gunthorpe
[not found] ` <1475879772-29458-2-git-send-email-jgunthorpe-ePGOBjL8dl3ta4EC/59zMFaTQe2KTcn/@public.gmane.org>
2016-10-09 5:46 ` Leon Romanovsky
[not found] ` <20161009054601.GB9282-2ukJVAZIZ/Y@public.gmane.org>
2016-10-09 23:01 ` Jason Gunthorpe
[not found] ` <20161009230150.GB12551-ePGOBjL8dl3ta4EC/59zMFaTQe2KTcn/@public.gmane.org>
2016-10-10 4:09 ` Leon Romanovsky
[not found] ` <20161010040930.GF9282-2ukJVAZIZ/Y@public.gmane.org>
2016-10-11 18:05 ` Jason Gunthorpe
[not found] ` <20161011180517.GA17866-ePGOBjL8dl3ta4EC/59zMFaTQe2KTcn/@public.gmane.org>
2016-10-11 19:46 ` Leon Romanovsky [this message]
[not found] ` <20161011194633.GP9282-2ukJVAZIZ/Y@public.gmane.org>
2016-10-11 20:06 ` Jason Gunthorpe
2016-10-10 15:18 ` Steve Wise
2016-10-07 22:36 ` [PATCH rdma-core 2/5] ibacm: Avoid clang 3.8 warning -Wmissing-field-initializers Jason Gunthorpe
2016-10-07 22:36 ` [PATCH rdma-core 3/5] mthca: Avoid bogus gcc 4.8 warning -Wmaybe-uninitialized Jason Gunthorpe
2016-10-07 22:36 ` [PATCH rdma-core 4/5] Improve linker flag detection to work with clang and -Werror Jason Gunthorpe
2016-10-07 22:36 ` [PATCH rdma-core 5/5] Update TravisCI to use clang 3.9 as well Jason Gunthorpe
2016-10-12 18:07 ` [PATCH rdma-core 0/5] clang support Doug Ledford
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