https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105358
--- Comment #10 from CVS Commits <cvs-commit at gcc dot gnu.org> --- The master branch has been updated by Jakub Jelinek <ja...@gcc.gnu.org>: https://gcc.gnu.org/g:57a957cb71c004de80b0fd30c8db3cc67576e0ce commit r12-8259-g57a957cb71c004de80b0fd30c8db3cc67576e0ce Author: Jakub Jelinek <ja...@redhat.com> Date: Tue Apr 26 08:57:17 2022 +0200 libgomp: Fix up two non-GOMP_USE_ALIGNED_WORK_SHARES related issues [PR105358] Last fall I've changed struct gomp_work_share, so that it doesn't have __attribute__((aligned (64))) lock member in the middle unless the target has non-emulated aligned allocator, otherwise it just makes sure the first and second halves are 64 bytes appart for cache line reasons, but doesn't make the struct 64-byte aligned itself and so we can use normal allocators for it. When the struct isn't 64-byte aligned, the amount of tail padding significantly decreases, to 0 or 4 bytes or so. The library uses that tail padding when the ordered_teams_ids array (array of uints) and/or the memory for lastprivate conditional temporaries (the latter wants to guarantee long long alignment). The problem with it on ia32 darwin9 is that while the struct contains long long members, long long is just 4 byte aligned while __alignof__(long long) is 8. That causes problems in gomp_init_work_share, where we currently rely on if offsetof (struct gomp_work_share, inline_ordered_team_ids) is long long aligned, then that tail array will be aligned at runtime and so no extra memory for dynamic realignment will be needed (that is false when the whole struct doesn't have long long alignment). And also in the remaining hunks causes another problem, where we compute INLINE_ORDERED_TEAM_IDS_OFF as the above offsetof aligned up to long long boundary and subtract sizeof (struct gomp_work_share) and INLINE_ORDERED_TEAM_IDS_OFF. When unlucky, the former isn't multiple of 8 and the latter is 4 bigger than that and as the subtraction is done in size_t, we end up with (size_t) -4, so the comparison doesn't really work. The fixes add additional conditions to make it work properly, but all of them should be evaluated at compile time when optimizing and so shouldn't slow anything. 2022-04-26 Jakub Jelinek <ja...@redhat.com> PR libgomp/105358 * work.c (gomp_init_work_share): Don't mask of adjustment for dynamic long long realignment if struct gomp_work_share has smaller alignof than long long. * loop.c (GOMP_loop_start): Don't use inline_ordered_team_ids if struct gomp_work_share has smaller alignof than long long or if sizeof (struct gomp_work_share) is smaller than INLINE_ORDERED_TEAM_IDS_OFF. * loop_ull.c (GOMP_loop_ull_start): Likewise. * sections.c (GOMP_sections2_start): Likewise.
