[nvptx] Improve gcc.target/nvptx/atomic_fetch-*.c test-cases
Fix a few issues in test-cases gcc.target/nvptx/atomic_fetch-*.c:
- atomic_fetch-1.c uses scan-assembler instead of scan-assembler-times,
which is less accurate
- atomic_fetch-2.c only contains negative testing using
scan-assembler-not
- the test-cases use stack variables to generate generic addresses,
while stack atomics are not natively supported
- the test-cases only test (64-bit) x (generic), instead of
(32-bit, 64-bit) x (generic, global, shared)
- the test-cases use a hardcoded '0' instead of the clearer
MEMMODEL_RELAXED
Tested on nvptx.
gcc/testsuite/ChangeLog:
2022-01-12 Tom de Vries <tdevries@suse.de>
* gcc.target/nvptx/atomic_fetch-1.c: Rewrite.
* gcc.target/nvptx/atomic_fetch-2.c: Rewrite.