This is a follow-up fix for commit 0f5e9bee.
Only write effects to thread-local memory should be considered safe to
parallelize in workshare lowering, not reads. When both reads and writes
were safe, the cascading effect in moveToSingle could cause entire
SingleRegions to become fully parallelized, eliminating the omp.single
and its implicit barrier. This removed synchronization points needed to
keep threads coordinated inside sequential loops containing workshared
operations, causing race conditions in forall-workshare patterns.
This was exposed by the Fujitsu Test Suite and made the following tests
regress:
FAIL: test-suite :: Fujitsu/Fortran/0398/Fujitsu-Fortran-0398_0031.test
FAIL: test-suite :: Fujitsu/Fortran/0398/Fujitsu-Fortran-0398_0013.test
FAIL: test-suite :: Fujitsu/Fortran/0398/Fujitsu-Fortran-0398_0030.test
FAIL: test-suite :: Fujitsu/Fortran/0398/Fujitsu-Fortran-0398_0014.test
Updates #143330
db5cd626b9