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  <jakub@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.

diff --git a/libgomp/loop.c b/libgomp/loop.c
index 682df39a4ed46dadb74091f30b87f472c200dd6e..be85162bb1ecec4ab458cbc5d33a68b1505e23cf 100644 (file)
--- a/libgomp/loop.c
+++ b/libgomp/loop.c
@@ -270,8 +270,11 @@ GOMP_loop_start (long start, long end, long incr, long sched,
 #define INLINE_ORDERED_TEAM_IDS_OFF \
   ((offsetof (struct gomp_work_share, inline_ordered_team_ids)         \
     + __alignof__ (long long) - 1) & ~(__alignof__ (long long) - 1))
-         if (size > (sizeof (struct gomp_work_share)
-                     - INLINE_ORDERED_TEAM_IDS_OFF))
+         if (sizeof (struct gomp_work_share)
+             <= INLINE_ORDERED_TEAM_IDS_OFF
+             || __alignof__ (struct gomp_work_share) < __alignof__ (long long)
+             || size > (sizeof (struct gomp_work_share)
+                       - INLINE_ORDERED_TEAM_IDS_OFF))
            *mem
              = (void *) (thr->ts.work_share->ordered_team_ids
                          = gomp_malloc_cleared (size));

diff --git a/libgomp/loop_ull.c b/libgomp/loop_ull.c
index 2aaa34e3bca673766d859022563efb4171d82172..602737296d400b47e614eba75056ddc450ec9366 100644 (file)
--- a/libgomp/loop_ull.c
+++ b/libgomp/loop_ull.c
@@ -269,8 +269,11 @@ GOMP_loop_ull_start (bool up, gomp_ull start, gomp_ull end,
 #define INLINE_ORDERED_TEAM_IDS_OFF \
   ((offsetof (struct gomp_work_share, inline_ordered_team_ids)         \
     + __alignof__ (long long) - 1) & ~(__alignof__ (long long) - 1))
-         if (size > (sizeof (struct gomp_work_share)
-                     - INLINE_ORDERED_TEAM_IDS_OFF))
+         if (sizeof (struct gomp_work_share)
+             <= INLINE_ORDERED_TEAM_IDS_OFF
+             || __alignof__ (struct gomp_work_share) < __alignof__ (long long)
+             || size > (sizeof (struct gomp_work_share)
+                       - INLINE_ORDERED_TEAM_IDS_OFF))
            *mem
              = (void *) (thr->ts.work_share->ordered_team_ids
                          = gomp_malloc_cleared (size));

diff --git a/libgomp/sections.c b/libgomp/sections.c
index e9d99e434ac5afe4a2a2dc3396cea484b54bb806..7751d5aac830b406bfa6c6de5182e21626bd15cb 100644 (file)
--- a/libgomp/sections.c
+++ b/libgomp/sections.c
@@ -121,8 +121,11 @@ GOMP_sections2_start (unsigned count, uintptr_t *reductions, void **mem)
 #define INLINE_ORDERED_TEAM_IDS_OFF \
   ((offsetof (struct gomp_work_share, inline_ordered_team_ids)         \
     + __alignof__ (long long) - 1) & ~(__alignof__ (long long) - 1))
-         if (size > (sizeof (struct gomp_work_share)
-                     - INLINE_ORDERED_TEAM_IDS_OFF))
+         if (sizeof (struct gomp_work_share)
+             <= INLINE_ORDERED_TEAM_IDS_OFF
+             || __alignof__ (struct gomp_work_share) < __alignof__ (long long)
+             || size > (sizeof (struct gomp_work_share)
+                       - INLINE_ORDERED_TEAM_IDS_OFF))
            *mem
              = (void *) (thr->ts.work_share->ordered_team_ids
                          = gomp_malloc_cleared (size));

diff --git a/libgomp/work.c b/libgomp/work.c
index a88409dc78b0e5e595f7939eea7a26331f6e2e43..c53625afe2c6a41884f07d6106efd6145f5b618b 100644 (file)
--- a/libgomp/work.c
+++ b/libgomp/work.c
@@ -113,7 +113,9 @@ gomp_init_work_share (struct gomp_work_share *ws, size_t ordered,
          size_t o = nthreads * sizeof (*ws->ordered_team_ids);
          o += __alignof__ (long long) - 1;
          if ((offsetof (struct gomp_work_share, inline_ordered_team_ids)
-              & (__alignof__ (long long) - 1)) == 0)
+              & (__alignof__ (long long) - 1)) == 0
+             && __alignof__ (struct gomp_work_share)
+                >= __alignof__ (long long))
            o &= ~(__alignof__ (long long) - 1);
          ordered += o - 1;
        }