Hi! I've used function for omp single expansion also for omp scope. That is mostly ok, but as the testcase shows, there is one important difference. The omp single expansion always has a fallthru body, because it during omp lowering expands the body as if wrapped in an if to simulate that one thread runs the body and others wait (unless nowait) until it completes and continue. omp scope is invoked by all threads and so if the body is non-fallthru, the barrier (unless nowait) at the end will not be reached by any of the threads.
The following patch fixes that by handling the case where cfg pass optimizes away the exit bb of it gracefully. Bootstrapped/regtested on x86_64-linux and i686-linux, committed to trunk. 2021-09-22 Jakub Jelinek <ja...@redhat.com> PR middle-end/102415 * omp-expand.c (expand_omp_single): If region->exit is NULL, assert region->entry is GIMPLE_OMP_SCOPE region and return. * c-c++-common/gomp/scope-3.c: New test. --- gcc/omp-expand.c.jj 2021-09-11 09:33:37.895331824 +0200 +++ gcc/omp-expand.c 2021-09-21 19:08:18.841588400 +0200 @@ -8428,11 +8428,17 @@ expand_omp_single (struct omp_region *re exit_bb = region->exit; si = gsi_last_nondebug_bb (entry_bb); - gcc_assert (gimple_code (gsi_stmt (si)) == GIMPLE_OMP_SINGLE - || gimple_code (gsi_stmt (si)) == GIMPLE_OMP_SCOPE); + enum gimple_code code = gimple_code (gsi_stmt (si)); + gcc_assert (code == GIMPLE_OMP_SINGLE || code == GIMPLE_OMP_SCOPE); gsi_remove (&si, true); single_succ_edge (entry_bb)->flags = EDGE_FALLTHRU; + if (exit_bb == NULL) + { + gcc_assert (code == GIMPLE_OMP_SCOPE); + return; + } + si = gsi_last_nondebug_bb (exit_bb); if (!gimple_omp_return_nowait_p (gsi_stmt (si))) { --- gcc/testsuite/c-c++-common/gomp/scope-3.c.jj 2021-09-21 19:04:19.124972662 +0200 +++ gcc/testsuite/c-c++-common/gomp/scope-3.c 2021-09-21 19:09:39.699446866 +0200 @@ -0,0 +1,21 @@ +/* PR middle-end/102415 */ + +extern +#ifdef __cplusplus +"C" +#endif +void abort (); + +void +foo (void) +{ + #pragma omp scope nowait + abort (); +} + +void +bar (void) +{ + #pragma omp scope + abort (); +} Jakub