https://gcc.gnu.org/g:57dcb27e7a48151ad5f9a6122c6a40fac31843e9
commit r15-6030-g57dcb27e7a48151ad5f9a6122c6a40fac31843e9
Author: Richard Biener <rguent...@suse.de>
Date: Fri Dec 6 16:36:39 2024 +0100
middle-end/117932 - speed up DF solver
The following addresses slow bitmap operations for maintaining the
iteration order of df_worklist_dataflow_doublequeue for large number
of basic-blocks. The main complexity change is switching the
worklist and pending bitmaps to tree view, a secondary change is
avoiding the fully populated initial bitmap for the first iteration
and instead special-casing that plus avoiding all forward worklist
bitmap sets in that iteration. Usually second or later iterations
are sparse, so optimizing the first iteration seems worthwhile.
For PR117932 when isolating from ext-dce and fold-mem-offset issues
this results in a 10% compile-time reduction.
PR middle-end/117932
* df-core.cc (df_worklist_propagate_forward): When WORKLIST
is NULL, do not set bits there.
(df_worklist_propagate_backward): Likewise.
(df_worklist_dataflow_doublequeue): Separate first pass
over all blocks with NULL worklist.
(df_worklist_dataflow): Do not initialize pending and adjust.
Diff:
---
gcc/df-core.cc | 70 ++++++++++++++++++++++++++++++++++++++++------------------
1 file changed, 48 insertions(+), 22 deletions(-)
diff --git a/gcc/df-core.cc b/gcc/df-core.cc
index 0f27bd2524b3..99fe466d053c 100644
--- a/gcc/df-core.cc
+++ b/gcc/df-core.cc
@@ -872,7 +872,8 @@ make_pass_df_finish (gcc::context *ctxt)
Given a BB_INDEX, do the dataflow propagation
and set bits on for successors in PENDING for earlier
and WORKLIST for later in bbindex_to_postorder
- if the out set of the dataflow has changed.
+ if the out set of the dataflow has changed. When WORKLIST
+ is NULL we are processing all later blocks.
AGE specify time when BB was visited last time.
AGE of 0 means we are visiting for first time and need to
@@ -925,7 +926,10 @@ df_worklist_propagate_forward (struct dataflow *dataflow,
{
if (bbindex_to_postorder[bb_index]
< bbindex_to_postorder[ob_index])
- bitmap_set_bit (worklist, bbindex_to_postorder[ob_index]);
+ {
+ if (worklist)
+ bitmap_set_bit (worklist, bbindex_to_postorder[ob_index]);
+ }
else
bitmap_set_bit (pending, bbindex_to_postorder[ob_index]);
}
@@ -979,7 +983,10 @@ df_worklist_propagate_backward (struct dataflow *dataflow,
{
if (bbindex_to_postorder[bb_index]
< bbindex_to_postorder[ob_index])
- bitmap_set_bit (worklist, bbindex_to_postorder[ob_index]);
+ {
+ if (worklist)
+ bitmap_set_bit (worklist, bbindex_to_postorder[ob_index]);
+ }
else
bitmap_set_bit (pending, bbindex_to_postorder[ob_index]);
}
@@ -1010,26 +1017,55 @@ df_worklist_propagate_backward (struct dataflow
*dataflow,
static void
df_worklist_dataflow_doublequeue (struct dataflow *dataflow,
- bitmap pending,
sbitmap considered,
int *blocks_in_postorder,
unsigned *bbindex_to_postorder,
- int n_blocks)
+ unsigned n_blocks)
{
enum df_flow_dir dir = dataflow->problem->dir;
int dcount = 0;
- bitmap worklist = BITMAP_ALLOC (&df_bitmap_obstack);
int age = 0;
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);
- /* Double-queueing. Worklist is for the current iteration,
- and pending is for the next. */
+ /* We start with processing all blocks, populating pending for the
+ next iteration. */
+ bitmap pending = BITMAP_ALLOC (&df_bitmap_obstack);
+ bitmap_tree_view (pending);
+ for (unsigned index = 0; index < n_blocks; ++index)
+ {
+ 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);
+ else
+ changed = df_worklist_propagate_backward (dataflow, bb_index,
+ bbindex_to_postorder,
+ NULL, pending,
+ considered,
+ last_change_age,
+ prev_age);
+ last_visit_age[index] = ++age;
+ if (changed)
+ last_change_age[index] = age;
+ }
+
+ /* Double-queueing. Worklist is for the current iteration,
+ and pending is for the next. */
while (!bitmap_empty_p (pending))
{
std::swap (pending, worklist);
@@ -1037,11 +1073,8 @@ df_worklist_dataflow_doublequeue (struct dataflow
*dataflow,
do
{
unsigned index = bitmap_clear_first_set_bit (worklist);
-
- unsigned bb_index;
+ unsigned bb_index = blocks_in_postorder[index];
dcount++;
-
- bb_index = blocks_in_postorder[index];
prev_age = last_visit_age[index];
if (dir == DF_FORWARD)
changed = df_worklist_propagate_forward (dataflow, bb_index,
@@ -1091,7 +1124,6 @@ df_worklist_dataflow (struct dataflow *dataflow,
int *blocks_in_postorder,
int n_blocks)
{
- bitmap pending = BITMAP_ALLOC (&df_bitmap_obstack);
bitmap_iterator bi;
unsigned int *bbindex_to_postorder;
int i;
@@ -1118,21 +1150,15 @@ df_worklist_dataflow (struct dataflow *dataflow,
/* Initialize the mapping of block index to postorder. */
for (i = 0; i < n_blocks; i++)
- {
- bbindex_to_postorder[blocks_in_postorder[i]] = i;
- /* Add all blocks to the worklist. */
- bitmap_set_bit (pending, i);
- }
+ bbindex_to_postorder[blocks_in_postorder[i]] = i;
/* Initialize the problem. */
if (dataflow->problem->init_fun)
dataflow->problem->init_fun (blocks_to_consider);
/* Solve it. */
- df_worklist_dataflow_doublequeue (dataflow, pending, considered,
- blocks_in_postorder,
- bbindex_to_postorder,
- n_blocks);
+ df_worklist_dataflow_doublequeue (dataflow, considered, blocks_in_postorder,
+ bbindex_to_postorder, n_blocks);
free (bbindex_to_postorder);
}
