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Subject: Re: [committed][nvptx] Set -misa=sm_35 by default
To: Thomas Schwinge <thomas@codesourcery.com>
Cc: gcc-patches@gcc.gnu.org
References: <20201009115608.GA26608@delia>
 <878s8xqc8d.fsf@euler.schwinge.homeip.net>
 <87k0pyz46d.fsf@euler.schwinge.homeip.net>
From: Tom de Vries <tdevries@suse.de>
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Date: Tue, 4 May 2021 08:30:29 +0200
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On 3/23/21 9:04 AM, Thomas Schwinge wrote:
> What is your opinion about backporting that (plus Tobias' documentation
> update, plus corresponding web 'changes.html' updates?) to release
> branches, so that nvptx offloading users may use GCC 10/9/8 with CUDA
> 11.0+?

Hmm, so you're talking about making -misa=sm_35 the default for gcc 10/9/8?

Let's see, users of the latest nvidia consumer microarchitecture: ampere
are forced to use a cuda11.0+ toolchain, which means that the sm_30
default is wrong for them.

Cuda 5.x supports both sm_30 and sm_35, so users should be fine.

Cuda 4.x supports neither sm_30 nor sm_35, so users also shouldn't
observe a difference.

There might be users of cuda 4.x or older and a specific newer driver
that supports sm_30 but not sm_35, and those will be the only ones
affected.  I think we can explicitly unsupport that scenario.

So, in conclusion, LGTM.

Thanks,
- Tom