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Re: libgomp: Make GCC 5 OpenACC offloading executables work

From: Bernd Schmidt <bschmidt at redhat dot com>
To: Thomas Schwinge <thomas at codesourcery dot com>, Nathan Sidwell <nathan at codesourcery dot com>, Jakub Jelinek <jakub at redhat dot com>, gcc-patches at gcc dot gnu dot org
Date: Thu, 12 May 2016 11:20:52 +0200
Subject: Re: libgomp: Make GCC 5 OpenACC offloading executables work
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References: <55DC6DC2 dot 5030600 at acm dot org> <55FA89AF dot 2020403 at t-online dot de> <55FAD0D9 dot 1050205 at acm dot org> <55FBD59F dot 1060700 at redhat dot com> <20150924084034 dot GC1847 at tucnak dot redhat dot com> <56099751 dot 6000208 at acm dot org> <87bn54343j dot fsf at kepler dot schwinge dot homeip dot net> <87d1oswvuq dot fsf at hertz dot schwinge dot homeip dot net> <57334030 dot 2050807 at redhat dot com> <6bc2d58c-063d-347a-3b87-4c94a066d936 at acm dot org> <874ma4wpk7 dot fsf at hertz dot schwinge dot homeip dot net>

On 05/11/2016 06:02 PM, Thomas Schwinge wrote:

I conceptually agree to that.  (If we're serious about that, then we can
remove more code, such as the legacy libgomp entry point itself -- a
"missing symbol: [...]" is still vaguely better than a SIGSEGV.)  Yet,
what I fixed here, is just what Jakub and Nathan agreed upon in
<http://news.gmane.org/find-root.php?message_id=%3C20150924084034.GC1847%40tucnak.redhat.com%3E>:
"GCC 5 compiled offloaded OpenACC/PTX code will always do host fallback".
Currently such code will always result in a SIGSEGV, which the patch
fixes.  (And, given that we now have this patch, it seems "unfair" to
"wait until someone actually reports that in bugzilla".)

I'll defer to Jakub. Don't want to block an existing patch if you reallywant to apply it, I just think we should go in the other direction ofremoving this fallback support eventually.



Bernd

References:
- Re: libgomp: Make GCC 5 OpenACC offloading executables work
  - From: Thomas Schwinge
- Re: libgomp: Make GCC 5 OpenACC offloading executables work
  - From: Bernd Schmidt
- Re: libgomp: Make GCC 5 OpenACC offloading executables work
  - From: Nathan Sidwell
- Re: libgomp: Make GCC 5 OpenACC offloading executables work
  - From: Thomas Schwinge

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