[WIP] OpenMP 4 NVPTX support

Hi!

On Tue, 21 Apr 2015 17:58:39 +0200, Jakub Jelinek <jakub@redhat.com> wrote:
> Attached is a minimal patch to get at least a trivial OpenMP 4.0 testcase
> offloading to NVPTX (the first patch).  The second patch is WIP, just first
> few needed changes to make libgomp to build for NVPTX (several weeks of work
> at least).

We're not in particular working on making nvptx offloading work for
OpenMP, but also for OpenACC offloading a tiny bit of code is required to
be shipped in an offloading device's runtime library -- code that
conceptually belongs into libgomp.  (On gomp-4_0-branch, it currently
lives in libgcc because that was easier to do.)  Actually, as I should
find out, building a "dummy" (empty) libgomp for nvptx is not actually
difficult.  Additionally to your second patch (U2; quoted at the end of
this email), we'll need the following:

commit ea5213c1eb6e525f64aa103312e8e0ac88048122
Author: Thomas Schwinge <thomas@codesourcery.com>
Date:   Wed Jul 22 12:12:41 2015 +0200

    Empty libgomp for nvptx

        $ mkdir libgomp/config/nvptx
        $ cp libgomp/config/{linux,nvptx}/omp-lock.h
        $ for f in libgomp{,/config/linux,/config/posix}/*.c; do touch libgomp/config/nvptx/"$(basename "$f")"; done
---
 libgomp/config/nvptx/affinity.c       |  0
 libgomp/config/nvptx/alloc.c          |  0
 libgomp/config/nvptx/bar.c            |  0
 libgomp/config/nvptx/barrier.c        |  0
 libgomp/config/nvptx/critical.c       |  0
 libgomp/config/nvptx/env.c            |  0
 libgomp/config/nvptx/error.c          |  0
 libgomp/config/nvptx/fortran.c        |  0
 libgomp/config/nvptx/iter.c           |  0
 libgomp/config/nvptx/iter_ull.c       |  0
 libgomp/config/nvptx/libgomp-plugin.c |  0
 libgomp/config/nvptx/lock.c           |  0
 libgomp/config/nvptx/loop.c           |  0
 libgomp/config/nvptx/loop_ull.c       |  0
 libgomp/config/nvptx/mutex.c          |  0
 libgomp/config/nvptx/oacc-async.c     |  0
 libgomp/config/nvptx/oacc-cuda.c      |  0
 libgomp/config/nvptx/oacc-host.c      |  0
 libgomp/config/nvptx/oacc-init.c      |  0
 libgomp/config/nvptx/oacc-mem.c       |  0
 libgomp/config/nvptx/oacc-parallel.c  |  0
 libgomp/config/nvptx/oacc-plugin.c    |  0
 libgomp/config/nvptx/omp-lock.h       | 12 ++++++++++++
 libgomp/config/nvptx/ordered.c        |  0
 libgomp/config/nvptx/parallel.c       |  0
 libgomp/config/nvptx/proc.c           |  0
 libgomp/config/nvptx/ptrlock.c        |  0
 libgomp/config/nvptx/sections.c       |  0
 libgomp/config/nvptx/sem.c            |  0
 libgomp/config/nvptx/single.c         |  0
 libgomp/config/nvptx/splay-tree.c     |  0
 libgomp/config/nvptx/target.c         |  0
 libgomp/config/nvptx/task.c           |  0
 libgomp/config/nvptx/team.c           |  0
 libgomp/config/nvptx/time.c           |  0
 libgomp/config/nvptx/work.c           |  0
 36 files changed, 12 insertions(+)

This, obviously, is still very bare-bones, but it works, and can be
extended later.

> we build libgcc.a, libc.a, libm.a, libgfortran.a (and in the future hopefully libgomp.a),
> nothing attempts to link those in :(.

Together with the changes highlighted above, I'd then work on merging
into trunk the nvptx linking code present on gomp-4_0-branch, OK?

For reference, your second patch (U2):

> --- libgomp/configure.tgt.jj	2015-04-21 08:38:00.000000000 +0200
> +++ libgomp/configure.tgt	2015-04-21 10:59:30.857197475 +0200
> @@ -151,6 +151,10 @@ case "${target}" in
>  	XLDFLAGS="${XLDFLAGS} -lpthread"
>  	;;
>  
> +  nvptx*-*-*)
> +	config_path="nvptx"
> +	;;
> +
>    *)
>  	;;
>  
> --- libgomp/libgomp.h.jj	2015-04-21 08:38:00.000000000 +0200
> +++ libgomp/libgomp.h	2015-04-21 11:15:35.952217394 +0200
> @@ -40,7 +40,9 @@
>  #include "gstdint.h"
>  #include "libgomp-plugin.h"
>  
> +#ifdef HAVE_PTHREAD_H
>  #include <pthread.h>
> +#endif
>  #include <stdbool.h>
>  #include <stdlib.h>
>  #include <stdarg.h>
> --- libgomp/configure.ac.jj	2015-04-21 08:38:00.000000000 +0200
> +++ libgomp/configure.ac	2015-04-21 11:06:38.418117846 +0200
> @@ -179,6 +179,9 @@ case "$host" in
>    *-*-rtems*)
>      # RTEMS supports Pthreads, but the library is not available at GCC build time.
>      ;;
> +  nvptx*-*-*)
> +    # NVPTX does not support Pthreads, has its own code replacement.
> +    ;;
>    *)
>      # Check to see if -pthread or -lpthread is needed.  Prefer the former.
>      # In case the pthread.h system header is not found, this test will fail.
> --- configure.ac.jj	2015-04-21 08:38:09.000000000 +0200
> +++ configure.ac	2015-04-21 09:14:50.107827544 +0200
> @@ -539,6 +539,9 @@ if test x$enable_libgomp = x ; then
>  	;;
>      *-*-darwin* | *-*-aix*)
>  	;;
> +    # And on NVPTX as an offloading target.
> +    nvptx*-*-*)
> +	;;
>      *)
>  	noconfigdirs="$noconfigdirs target-libgomp"
>  	;;

Grüße,
 Thomas

[WIP] OpenMP 4 NVPTX support

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