This was added in commit 1cf9fda4936de54198858b8f54cd9707a3725f4e
"amdgcn: Adjust failure mode for gfx908 USM".
In a GCC configuration with both AMD and NVIDIA GPU code offloading supported,
and the selected AMD GPU code generation not supporting USM, but an USM-capable
NVIDIA GPU available, I see all test cases that require effective-target
'omp_usm' turn UNSUPPORTED, because:
Executing on host: gcc usm_available_2778376.c [...]
[...]
In function 'main._omp_fn.0':
lto1: warning: Unified Shared Memory is required, but XNACK is disabled
lto1: note: Try -foffload-options=-mxnack=any
gcn mkoffload: warning: conflicting settings; XNACK is forced off but
Unified Shared Memory is required
UNSUPPORTED: [...]
That warning is, however, not relevant in the scenario described above: we're
not going to exercise AMD GPU code offloading at run time.
With the effective-target 'omp_usm' check robustified like this, the affected
test cases are then no longer UNSUPPORTED, but of course, there's then the
corollary issue that compilation of the test case itself now emits the very
same warning, which results in the "test for excess errors" FAILing, despite
the execution test PASSing, for example:
FAIL: libgomp.c++/target-std__valarray-concurrent-usm.C (test for excess
errors)
PASS: libgomp.c++/target-std__valarray-concurrent-usm.C execution test
That's clearly not ideal either (but is representative of what real-world usage
would run into), but is certainly better than the whole test case turning
UNSUPPORTED. To be continued, I guess...
libgomp/
* testsuite/lib/libgomp.exp (check_effective_target_omp_usm):
Robustify.
---
libgomp/testsuite/lib/libgomp.exp | 14 +++++++++++---
1 file changed, 11 insertions(+), 3 deletions(-)
diff --git a/libgomp/testsuite/lib/libgomp.exp
b/libgomp/testsuite/lib/libgomp.exp
index cce2e93f857..93e2a681cb4 100644
--- a/libgomp/testsuite/lib/libgomp.exp
+++ b/libgomp/testsuite/lib/libgomp.exp
@@ -728,8 +728,16 @@ int main() {
# return 1 if OpenMP Unified Shared Memory is supported by offload devices
proc check_effective_target_omp_usm { } {
- if { [check_effective_target_offload_device_nvptx]
- || [check_effective_target_offload_target_amdgcn] } {
+ set flags ""
+ if { [check_effective_target_offload_target_amdgcn] } {
+ # Specify '-mxnack=any' to inhibit GCN offloading compilation
+ # 'warning: Unified Shared Memory is required, but XNACK is disabled'.
+ # This run-time effective-target check shouldn't fail in case there's
+ # actually no AMD GPU, but there's an USM-capable NVIDIA GPU.
+ lappend flags "-foffload-options=amdgcn-amdhsa=-mxnack=any"
+ }
+ if { $flags != ""
+ || [check_effective_target_offload_device_nvptx] } {
if [check_runtime usm_available_ {
#include <omp.h>
#pragma omp requires unified_shared_memory
@@ -740,7 +748,7 @@ proc check_effective_target_omp_usm { } {
a = omp_is_initial_device ();
return a;
}
- } ] {
+ } "$flags" ] {
return 1
}
}
--
2.34.1
