Hi,
I.
In openmp expansion of loops, we do some effort to try to create
matching loops in the loop state of the child function, f.i.in
expand_omp_for_generic:
...
struct loop *outer_loop;
if (seq_loop)
outer_loop = l0_bb->loop_father;
else
{
outer_loop = alloc_loop ();
outer_loop->header = l0_bb;
outer_loop->latch = l2_bb;
add_loop (outer_loop, l0_bb->loop_father);
}
if (!gimple_omp_for_combined_p (fd->for_stmt))
{
struct loop *loop = alloc_loop ();
loop->header = l1_bb;
/* The loop may have multiple latches. */
add_loop (loop, outer_loop);
}
...
And if that doesn't work out, we try to mark the loop state for fixup,
in expand_omp_taskreg and expand_omp_target:
...
/* When the OMP expansion process cannot guarantee an up-to-date
loop tree arrange for the child function to fixup loops. */
if (loops_state_satisfies_p (LOOPS_NEED_FIXUP))
child_cfun->x_current_loops->state |= LOOPS_NEED_FIXUP;
...
and expand_omp_for:
...
else
/* If there isn't a continue then this is a degerate case where
the introduction of abnormal edges during lowering will prevent
original loops from being detected. Fix that up. */
loops_state_set (LOOPS_NEED_FIXUP);
...
However, loops are fixed up anyway, because the first pass we execute
with the new child function is pass_fixup_cfg.
The new child function contains a function call to
__builtin_omp_get_num_threads, which is marked with ECF_CONST, so
execute_fixup_cfg marks the function for TODO_cleanup_cfg, and
subsequently the loops with LOOPS_NEED_FIXUP.
II.
This patch adds a verification that at the end of the omp-expand
processing of the child function, either the loop structure is ok, or
marked for fixup.
This verfication triggered a failure in parloops. When an outer loop is
being parallelized, both the outer and inner loop are cancelled. Then
during omp-expansion, we create a loop in the loop state for the outer
loop (the one that is transformed), but not for the inner, which causes
the verification failure:
...
outer-1.c:11:3: error: loop with header 5 not in loop tree
...
[ I ran into this verification failure with an openacc kernels testcase
on the gomp-4_0-branch, where parloops is called additionally from a
different location, and pass_fixup_cfg is not the first pass that the
child function is processed by. ]
The patch contains a bit that makes sure that the loop state of the
child function is marked for fixup in parloops. The bit is non-trival
since it create a loop state and sets the fixup flag on the loop state,
but postpones the init_loops_structure call till move_sese_region_to_fn,
where it can succeed.
III.
Bootstrapped and reg-tested on x86_64.
OK for trunk?
Thanks,
- Tom
Mark inner loop for fixup in parloops
2015-07-13 Tom de Vries <t...@codesourcery.com>
PR tree-optimization/66846
* omp-low.c (expand_omp_taskreg) [ENABLE_CHECKING]: If
!LOOPS_NEED_FIXUP, verify_loop_structure in child_fn.
(expand_omp_target) [ENABLE_CHECKING]: Same.
* tree-cfg.c (move_sese_region_to_fn): Only allocate struct loops if
necessary. Preserve dest_cfun->x_current_loops->state while calling
init_loops_structure.
* tree-parloops.c (gen_parallel_loop): If inner loop is cancelled,
allocate struct loop and mark child_fn for loop fixup.
---
gcc/omp-low.c | 8 ++++++++
gcc/tree-cfg.c | 26 +++++++++++++++++++++-----
gcc/tree-parloops.c | 10 +++++++++-
3 files changed, 38 insertions(+), 6 deletions(-)
diff --git a/gcc/omp-low.c b/gcc/omp-low.c
index 0e69bc2..64d9742 100644
--- a/gcc/omp-low.c
+++ b/gcc/omp-low.c
@@ -5603,6 +5603,10 @@ expand_omp_taskreg (struct omp_region *region)
}
if (gimple_in_ssa_p (cfun))
update_ssa (TODO_update_ssa);
+#ifdef ENABLE_CHECKING
+ if (!loops_state_satisfies_p (LOOPS_NEED_FIXUP))
+ verify_loop_structure ();
+#endif
pop_cfun ();
}
@@ -8983,6 +8987,10 @@ expand_omp_target (struct omp_region *region)
if (changed)
cleanup_tree_cfg ();
}
+#ifdef ENABLE_CHECKING
+ if (!loops_state_satisfies_p (LOOPS_NEED_FIXUP))
+ verify_loop_structure ();
+#endif
pop_cfun ();
}
diff --git a/gcc/tree-cfg.c b/gcc/tree-cfg.c
index d97b824..6b415fe 100644
--- a/gcc/tree-cfg.c
+++ b/gcc/tree-cfg.c
@@ -7126,11 +7126,27 @@ move_sese_region_to_fn (struct function *dest_cfun, basic_block entry_bb,
}
}
- /* Initialize an empty loop tree. */
- struct loops *loops = ggc_cleared_alloc<struct loops> ();
- init_loops_structure (dest_cfun, loops, 1);
- loops->state = LOOPS_MAY_HAVE_MULTIPLE_LATCHES;
- set_loops_for_fn (dest_cfun, loops);
+ struct loops *loops;
+ int loop_state_flags = 0;
+ if (dest_cfun->x_current_loops == NULL)
+ {
+ /* Initialize an empty loop tree. */
+ loops = ggc_cleared_alloc<struct loops> ();
+ set_loops_for_fn (dest_cfun, loops);
+ }
+ else
+ {
+ loops = dest_cfun->x_current_loops;
+ loop_state_flags = loops->state;
+ }
+
+ if (loops->tree_root == NULL)
+ {
+ init_loops_structure (dest_cfun, loops, 1);
+ loops->state |= loop_state_flags;
+ }
+
+ loops->state |= LOOPS_MAY_HAVE_MULTIPLE_LATCHES;
/* Move the outlined loop tree part. */
num_nodes = bbs.length ();
diff --git a/gcc/tree-parloops.c b/gcc/tree-parloops.c
index 036677b..23b134f 100644
--- a/gcc/tree-parloops.c
+++ b/gcc/tree-parloops.c
@@ -2267,7 +2267,8 @@ gen_parallel_loop (struct loop *loop,
cond_stmt = last_stmt (loop->header);
if (cond_stmt)
loc = gimple_location (cond_stmt);
- create_parallel_loop (loop, create_loop_fn (loc), arg_struct,
+ tree child_fn = create_loop_fn (loc);
+ create_parallel_loop (loop, child_fn, arg_struct,
new_arg_struct, n_threads, loc);
if (reduction_list->elements () > 0)
create_call_for_reduction (loop, reduction_list, &clsn_data);
@@ -2276,6 +2277,13 @@ gen_parallel_loop (struct loop *loop,
/* Cancel the loop (it is simpler to do it here rather than to teach the
expander to do it). */
+ if (loop->inner)
+ {
+ struct function *child_cfun = DECL_STRUCT_FUNCTION (child_fn);
+ struct loops *loops = ggc_cleared_alloc<struct loops> ();
+ set_loops_for_fn (child_cfun, loops);
+ child_cfun->x_current_loops->state = LOOPS_NEED_FIXUP;
+ }
cancel_loop_tree (loop);
/* Free loop bound estimations that could contain references to
--
1.9.1
