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List:       gcc-patches
Subject:    RE: Proposal to remove '--with-cuda-driver'
From:       Thomas Schwinge <thomas () codesourcery ! com>
Date:       2022-04-29 13:55:31
Message-ID: 878rrodmek.fsf () euler ! schwinge ! homeip ! net
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Hi Roger!

On 2022-04-05T19:46:08+0100, "Roger Sayle" <roger@nextmovesoftware.com> wrote:
> I apologise that it might complicate things

No worries; that's why I asked.  :-)

> one potential benefit of --with-cuda-driver
> (i.e. linking the compiler against proprietary libraries) is that it would allow \
>                 support for
> -march=native on nvptx (i.e. the gcc driver can figure out what sm_xx is available \
> on the GPU(s) of the current machine, and pass that to cc1.  Like with all the \
> microarchitectures on other platforms (x86_64), figuring this out is not a trivial \
> task for many end-users.

Ah, interesting idea!  (I suppose still not too relevant right now, but
once we've got GCC/nvptx multilibs making better use of modern PTX
features, I certainly do see the point.)

> Of course, ideally I'd love to be able to figure out the PTX hardware \
> specifications and driver versions without using a third-party library, but I've no \
> idea how this could be done (portably across the platforms that support libcuda).  \
> Perhaps dlopen at runtime? Or calling out to (executing) nvptx-tools?

Indeed I suppose I'd do this via 'dlopen', and not directly link GCC
against 'libcuda.so' etc.: so that the GCC build may also be used on a
system where no 'libcuda.so' is available.

So -- sorry ;-) -- that's not a show-stopper for removing the
'--with-cuda-driver' etc. 'configure'-time options.


Grüße
 Thomas
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