The triple-indirect memory reference we perform for each incoming
edge age <= last_change_age[bbindex_to_postorder[e->src->index]]
is pretty bad and when there are a lot of small BBs like for the
PR26854 testcase this shows in the profile. The following reduces
this by one level by making last_change_age indexed by BB index
rather than postorder number and realizing that for the first
iteration the age check is always true. We pay for this by
allocating last_change_age for all BBs in the function but we
do it like for sparsesets and avoid initializing given we check
the considerd bitmap anyway. We can also elide initializing
last_visit_age in an obvious way given we separated the initial
iteration in the previous change.
Together this improves compile-time in the PR117932 setting by
another 2%.
Bootstrapped on x86_64-unknown-linux-gnu, testing in progress.
PR middle-end/117932
* df-core.cc (df_worklist_propagate_forward): Elide
age check for the first iteration, adjust for
last_change_age change.
(df_worklist_propagate_backward): Likewise.
(df_worklist_dataflow_doublequeue): Make last_change_age
indexed by BB index, avoid clearing both age arrays.
---
gcc/df-core.cc | 31 ++++++++++++++++---------------
1 file changed, 16 insertions(+), 15 deletions(-)
diff --git a/gcc/df-core.cc b/gcc/df-core.cc
index 99fe466d053..3b5076e2fa6 100644
--- a/gcc/df-core.cc
+++ b/gcc/df-core.cc
@@ -905,8 +905,7 @@ df_worklist_propagate_forward (struct dataflow *dataflow,
if (EDGE_COUNT (bb->preds) > 0)
FOR_EACH_EDGE (e, ei, bb->preds)
{
- if (bbindex_to_postorder[e->src->index] < last_change_age.length ()
- && age <= last_change_age[bbindex_to_postorder[e->src->index]]
+ if ((!age || age <= last_change_age[e->src->index])
&& bitmap_bit_p (considered, e->src->index))
changed |= dataflow->problem->con_fun_n (e);
}
@@ -962,8 +961,7 @@ df_worklist_propagate_backward (struct dataflow *dataflow,
if (EDGE_COUNT (bb->succs) > 0)
FOR_EACH_EDGE (e, ei, bb->succs)
{
- if (bbindex_to_postorder[e->dest->index] < last_change_age.length ()
- && age <= last_change_age[bbindex_to_postorder[e->dest->index]]
+ if ((!age || age <= last_change_age[e->dest->index])
&& bitmap_bit_p (considered, e->dest->index))
changed |= dataflow->problem->con_fun_n (e);
}
@@ -1028,13 +1026,17 @@ df_worklist_dataflow_doublequeue (struct dataflow
*dataflow,
bool changed;
vec<int> last_visit_age = vNULL;
vec<int> last_change_age = vNULL;
- int prev_age;
bitmap worklist = BITMAP_ALLOC (&df_bitmap_obstack);
bitmap_tree_view (worklist);
- last_visit_age.safe_grow_cleared (n_blocks, true);
- last_change_age.safe_grow_cleared (n_blocks, true);
+ last_visit_age.safe_grow (n_blocks, true);
+ last_change_age.safe_grow (last_basic_block_for_fn (cfun) + 1, true);
+ /* Make last_change_age defined - we can access uninit values for not
+ considered blocks but will make sure they are considered as well. */
+ VALGRIND_DISCARD (VALGRIND_MAKE_MEM_DEFINED
+ (last_change_age.address (),
+ sizeof (int) * last_basic_block_for_fn (cfun)));
/* We start with processing all blocks, populating pending for the
next iteration. */
@@ -1044,24 +1046,23 @@ df_worklist_dataflow_doublequeue (struct dataflow
*dataflow,
{
unsigned bb_index = blocks_in_postorder[index];
dcount++;
- prev_age = last_visit_age[index];
if (dir == DF_FORWARD)
changed = df_worklist_propagate_forward (dataflow, bb_index,
bbindex_to_postorder,
NULL, pending,
considered,
- last_change_age,
- prev_age);
+ last_change_age, 0);
else
changed = df_worklist_propagate_backward (dataflow, bb_index,
bbindex_to_postorder,
NULL, pending,
considered,
- last_change_age,
- prev_age);
+ last_change_age, 0);
last_visit_age[index] = ++age;
if (changed)
- last_change_age[index] = age;
+ last_change_age[bb_index] = age;
+ else
+ last_change_age[bb_index] = 0;
}
/* Double-queueing. Worklist is for the current iteration,
@@ -1075,7 +1076,7 @@ df_worklist_dataflow_doublequeue (struct dataflow
*dataflow,
unsigned index = bitmap_clear_first_set_bit (worklist);
unsigned bb_index = blocks_in_postorder[index];
dcount++;
- prev_age = last_visit_age[index];
+ int prev_age = last_visit_age[index];
if (dir == DF_FORWARD)
changed = df_worklist_propagate_forward (dataflow, bb_index,
bbindex_to_postorder,
@@ -1092,7 +1093,7 @@ df_worklist_dataflow_doublequeue (struct dataflow
*dataflow,
prev_age);
last_visit_age[index] = ++age;
if (changed)
- last_change_age[index] = age;
+ last_change_age[bb_index] = age;
}
while (!bitmap_empty_p (worklist));
}
--
2.43.0
