Fix typo in 'libgomp.c/target-51.c' (was: [patch] OpenMP: Set default-device-var with OMP_TARGET_OFFLOAD=mandatory)

[Thomas Schwinge <thomas@codesourcery.com>]

[-- Attachment #1: Type: text/plain, Size: 5278 bytes --]

Hi!

On 2023-06-13T20:44:39+0200, Tobias Burnus <tobias@codesourcery.com> wrote:
> I intent to commit this tomorrow, unless there are comments.

I'm sorry I'm late.  ;-P

> It does as it says (see commit log): It initializes default-device-var
> to the value using the algorithm described in OpenMP 5.2, which
> depends on whether OMP_TARGET_OFFLOAD=mandatory was set.
>
> NOTE: With -foffload=disable there is no binary code but still
> devices get found - such that default-device-var == 0 (= first
> nonhost device). Thus, in that case, libgomp runs the code on that
> device but as no binary data is available, host fallback is used.
> (Even if there would be executable code for another device on
> the system.)
> With mandatory, this unintended host fallback is detected and an
> error is diagnosed. One can argue whether keeping the devices
> makes sense (e.g. because in a dynamic library device code will
> be loaded later) or not (don't list if no code is available).

This reminds me of the (unresolved) <https://gcc.gnu.org/PR81886>
"Means to determine at runtime foffload targets specified at compile time".

> Note that TR11 (future OpenMP 6.0) extends OMP_DEFAULT_DEVICE and
> adds OMP_AVAILABLE_DEVICES which permit a finer-grained control about
> the device, including OMP_DEFAULT_DEVICE=initial (and 'invalid') which
> the current scheme does not permit. (Well, there is
> OMP_TARGET_OFFLOAD=disabled, but that's a too big hammer.)

> PS:  DejaGNU testing was done without offloading configured
> and with remote testing on a system having an offload device,
> which which does not support setting environment variables.
> Manual testing was done with offloading enabled and depending
> on the testcase, running on a system with and/or without offloading
> hardware.

> --- a/libgomp/target.c
> +++ b/libgomp/target.c
> @@ -150,7 +150,11 @@ resolve_device (int device_id, bool remapped)
>        if (device_id == (remapped ? GOMP_DEVICE_HOST_FALLBACK
>                                : omp_initial_device))
>       return NULL;
> -      if (device_id == omp_invalid_device)
> +      if (gomp_target_offload_var == GOMP_TARGET_OFFLOAD_MANDATORY
> +       && gomp_get_num_devices () == 0)
> +     gomp_fatal ("OMP_TARGET_OFFLOAD is set to MANDATORY but only the host "
> +                 "device is available");
> +      else if (device_id == omp_invalid_device)
>       gomp_fatal ("omp_invalid_device encountered");
>        else if (gomp_target_offload_var == GOMP_TARGET_OFFLOAD_MANDATORY)
>       gomp_fatal ("OMP_TARGET_OFFLOAD is set to MANDATORY, "
|                   "but device not found");
|
|        return NULL;
|      }
|    else if (device_id >= gomp_get_num_devices ())
|      {
|        if (gomp_target_offload_var == GOMP_TARGET_OFFLOAD_MANDATORY
|         && device_id != num_devices_openmp)
|       gomp_fatal ("OMP_TARGET_OFFLOAD is set to MANDATORY, "
|                   "but device not found");
|
|        return NULL;
|      }
|
|    gomp_mutex_lock (&devices[device_id].lock);
|    if (devices[device_id].state == GOMP_DEVICE_UNINITIALIZED)
|      gomp_init_device (&devices[device_id]);
|    else if (devices[device_id].state == GOMP_DEVICE_FINALIZED)
|      {
|        gomp_mutex_unlock (&devices[device_id].lock);
|
|        if (gomp_target_offload_var == GOMP_TARGET_OFFLOAD_MANDATORY)
|       gomp_fatal ("OMP_TARGET_OFFLOAD is set to MANDATORY, "
|                   "but device is finalized");
|
|        return NULL;
|      }
|    gomp_mutex_unlock (&devices[device_id].lock);
|
|    return &devices[device_id];
|  }

> --- /dev/null
> +++ b/libgomp/testsuite/libgomp.c/target-51.c
> @@ -0,0 +1,24 @@
> +/* Check OMP_TARGET_OFFLOAD on systems with no available non-host devices,
> +   which is enforced by using -foffload=disable.  */
> +
> +/* { dg-do run } */
> +/* { dg-additional-options "-foffload=disable" } */
> +/* { dg-set-target-env-var OMP_TARGET_OFFLOAD "mandatory" } */
> +
> +/* { dg-shouldfail "OMP_TARGET_OFFLOAD=mandatory and no available device" } */
> +
> +/* See comment in target-50.c/target-50.c for why the output differs.  */
> +
> +/* { dg-output ".*libgomp: OMP_TARGET_OFFLOAD is set to MANDATORY but only the host device is available.*" { target { ! offload_device } } } */
> +/* { dg-output ".*libgomp: OMP_TARGET_OFFLOAD is set to MANDATORY but device not found.*" { target offload_device } } */

I intend to push the attached "Fix typo in 'libgomp.c/target-51.c'" after
testing.

Let me know if I should also adjust the new 'target { ! offload_device }'
diagnostic "[...] MANDATORY but only the host device is available" to
include a comma before 'but', for consistency with the other existing
diagnostics (cited above)?


Grüße
 Thomas


> +
> +int
> +main ()
> +{
> +  int x;
> +  #pragma omp target map(tofrom:x)
> +    x = 5;
> +  if (x != 5)
> +    __builtin_abort ();
> +  return 0;
> +}


-----------------
Siemens Electronic Design Automation GmbH; Anschrift: Arnulfstraße 201, 80634 München; Gesellschaft mit beschränkter Haftung; Geschäftsführer: Thomas Heurung, Frank Thürauf; Sitz der Gesellschaft: München; Registergericht München, HRB 106955

[-- Warning: decoded text below may be mangled, UTF-8 assumed --]
[-- Attachment #2: 0001-Fix-typo-in-libgomp.c-target-51.c.patch --]
[-- Type: text/x-diff, Size: 1464 bytes --]

From 2464d87db542b87a1d276637f334e9c6eb35be64 Mon Sep 17 00:00:00 2001
From: Thomas Schwinge <thomas@codesourcery.com>
Date: Wed, 14 Jun 2023 09:25:15 +0200
Subject: [PATCH] Fix typo in 'libgomp.c/target-51.c'

..., and therefore, given 'target offload_device':

    PASS: libgomp.c/target-51.c (test for excess errors)
    PASS: libgomp.c/target-51.c execution test
    [-FAIL:-]{+PASS:+} libgomp.c/target-51.c output pattern test

Fix-up for recent commit 18c8b56c7d67a9e37acf28822587786f0fc0efbc
"OpenMP: Set default-device-var with OMP_TARGET_OFFLOAD=mandatory".

	libgomp/
	* testsuite/libgomp.c/target-51.c: Fix typo.
---
 libgomp/testsuite/libgomp.c/target-51.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/libgomp/testsuite/libgomp.c/target-51.c b/libgomp/testsuite/libgomp.c/target-51.c
index 7d09bceacd58..cf9e690263e9 100644
--- a/libgomp/testsuite/libgomp.c/target-51.c
+++ b/libgomp/testsuite/libgomp.c/target-51.c
@@ -10,7 +10,7 @@
 /* See comment in target-50.c/target-50.c for why the output differs.  */
 
 /* { dg-output ".*libgomp: OMP_TARGET_OFFLOAD is set to MANDATORY but only the host device is available.*" { target { ! offload_device } } } */
-/* { dg-output ".*libgomp: OMP_TARGET_OFFLOAD is set to MANDATORY but device not found.*" { target offload_device } } */
+/* { dg-output ".*libgomp: OMP_TARGET_OFFLOAD is set to MANDATORY, but device not found.*" { target offload_device } } */
 
 int
 main ()
-- 
2.39.2