[PATCH] xfail and improve some failing libgomp tests

[Harwath, Frederik]

Hi,
the libgomp testsuite contains some test cases (all in /libgomp/testsuite/libgomp.c/)
which fail with nvptx offloading because of some long standing issues:

* {target-32.c, thread-limit-2.c}:
no "usleep" implemented for nvptx. Cf. https://gcc.gnu.org/PR81690

* target-{33,34}.c:
no "GOMP_OFFLOAD_async_run" implemented in plugin-nvptx.c. Cf. https://gcc.gnu.org/PR81688

* target-link-1.c:
omp "target link" not implemented for nvptx. Cf. https://gcc.gnu.org/PR81689


All these issues have been known, at least, since 2016:

https://gcc.gnu.org/ml/gcc-patches/2016-11/msg00972.html

As suggested in this mail:
 "Short term, it should be possible to implement something like -foffload=^nvptx
to skip PTX (and only PTX) offloading on those tests."

Well, we can now skip/xfail tests for nvptx offloading using the effective target
"offload_target_nvptx" and the present patch uses this to xfail the tests for which
no short-term solution is in sight, i.e. the GOMP_OFFLOAD_async_run and the "target link"
related failures.

Regarding the "usleep" issue, I have decided to follow Jakub's suggestion
(cf. https://gcc.gnu.org/ml/gcc-patches/2016-11/msg01026.html) to
replace usleep by busy waiting. As noted by Tobias
(https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81690#c4), this involves creating separate
test files for the cases with and without usleep. This solution is a bit cumbersome but I
think we can live with it, in particular, since the actual test case implementations do not
get duplicated (they have been moved into auxiliary header files which are shared by both
variants of the corresponding tests).

Since the "usleep" issue also concerns amdgcn, I have introduced an effective target
"offload_target_amdgcn" to add xfails for this offloading target, too. This behaves like
"offload_target_nvptx" but for amdgcn. Note that the existing amdgcn effective targets
cannot be used for our purpose since they are OpenACC-specific.

The new thread-limit-2-nosleep.c should now pass for both nvptx and amdgcn offloading
whereas thread-limit-2.c should xfail. The new target-32-nosleep.c passes with amdgcn
offloading, but xfails with nvptx offloading, because it also needs the unimplemented
GOMP_OFFLOAD_async_run.

With the patch, the detailed test summary now looks as follows for me:

nvptx offloading:

// Expected execution failures due to missing usleep
PASS: libgomp.c/target-32-nosleep.c (test for excess errors)
XFAIL: libgomp.c/target-32-nosleep.c execution test    // missing GOMP_OFFLOAD_async_run
XFAIL: libgomp.c/target-32.c (test for excess errors)
UNRESOLVED: libgomp.c/target-32.c compilation failed to produce executable

PASS: libgomp.c/thread-limit-2-nosleep.c (test for excess errors)
PASS: libgomp.c/thread-limit-2-nosleep.c execution test
XFAIL: libgomp.c/thread-limit-2.c (test for excess errors)
UNRESOLVED: libgomp.c/thread-limit-2.c compilation failed to produce executable

// Expected execution failures due to missing GOMP_OFFLOAD_async_run
PASS: libgomp.c/target-33.c (test for excess errors)
XFAIL: libgomp.c/target-33.c execution test
PASS: libgomp.c/target-34.c (test for excess errors)
XFAIL: libgomp.c/target-34.c execution test

// Expected compilation failures due to missing target link
XFAIL: libgomp.c/target-link-1.c (test for excess errors)
UNRESOLVED: libgomp.c/target-link-1.c compilation failed to produce executable


amdgcn offloading:

// Tests using usleep
PASS: libgomp.c/target-32-nosleep.c (test for excess errors)
PASS: libgomp.c/target-32-nosleep.c execution test
XFAIL: libgomp.c/target-32.c 7 blank line(s) in output
XFAIL: libgomp.c/target-32.c (test for excess errors)
UNRESOLVED: libgomp.c/target-32.c compilation failed to produce executable

PASS: libgomp.c/thread-limit-2-nosleep.c (test for excess errors)
PASS: libgomp.c/thread-limit-2-nosleep.c execution test
XFAIL: libgomp.c/thread-limit-2.c 1 blank line(s) in output
XFAIL: libgomp.c/thread-limit-2.c (test for excess errors)

// No failures since GOMP_OFFLOAD_async_run works on amdgcn
PASS: libgomp.c/target-33.c (test for excess errors)
PASS: libgomp.c/target-33.c execution test
PASS: libgomp.c/target-34.c (test for excess errors)
PASS: libgomp.c/target-34.c execution test

// No xfail here
PASS: libgomp.c/target-link-1.c (test for excess errors)
FAIL: libgomp.c/target-link-1.c execution test

Note that target-link-1.c execution does also fail on amdgcn.
Since - in contrast to nvptx - it seems that the cause of this failure
has not yet been investigated and discussed, I have not added an xfail
for amdgcn to this test.

All testing has been done with a x86_64-linux-gnu host and target.

Ok to commit this patch?

Best regards,
Frederik





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