On 2021/9/9 18:55, Richard Biener wrote:
diff --git a/gcc/tree-ssa-loop-im.c b/gcc/tree-ssa-loop-im.c
index 5d6845478e7..4b187c2cdaf 100644
--- a/gcc/tree-ssa-loop-im.c
+++ b/gcc/tree-ssa-loop-im.c
@@ -3074,15 +3074,13 @@ fill_always_executed_in_1 (class loop *loop, sbitmap
contains_call)
break;
if (bb->loop_father->header == bb)
- {
- if (!dominated_by_p (CDI_DOMINATORS, loop->latch, bb))
- break;
-
- /* In a loop that is always entered we may proceed anyway.
- But record that we entered it and stop once we leave it
- since it might not be finite. */
- inn_loop = bb->loop_father;
- }
+ /* Record that we enter into a subloop since it might not
+ be finite. */
+ /* ??? Entering into a not always executed subloop makes
+ fill_always_executed_in quadratic in loop depth since
+ we walk those loops N times. This is not a problem
+ in practice though, see PR102253 for a worst-case testcase. */
+ inn_loop = bb->loop_father;
Yes your two patches extracted the get_loop_body_in_dom_order out and removed
the inn_loop break logic when it doesn't dominate outer loop. Confirmed the
replacement
could improve for saving ~10% build time due to not full DOM walker and marked
the previously
ignored ALWAYS_EXECUTED bbs.
But if we don't break for inner loop again, why still keep the *inn_loop*
variable?
It seems unnecessary and confusing, could we just remove it and restore the
original
infinte loop check in bb->succs for better understanding?
diff --git a/gcc/tree-ssa-loop-im.c b/gcc/tree-ssa-loop-im.c
index d1e2104233b..82a0509e0c4 100644
--- a/gcc/tree-ssa-loop-im.c
+++ b/gcc/tree-ssa-loop-im.c
@@ -3200,7 +3200,6 @@ fill_always_executed_in_1 (class loop *loop, sbitmap
contains_call)
{
basic_block bb = NULL, last = NULL;
edge e;
- class loop *inn_loop = loop;
if (ALWAYS_EXECUTED_IN (loop->header) == NULL)
{
@@ -3213,17 +3212,6 @@ fill_always_executed_in_1 (class loop *loop, sbitmap
contains_call)
edge_iterator ei;
bb = worklist.pop ();
- if (!flow_bb_inside_loop_p (inn_loop, bb))
- {
- /* When we are leaving a possibly infinite inner loop
- we have to stop processing. */
- if (!finite_loop_p (inn_loop))
- break;
- /* If the loop was finite we can continue with processing
- the loop we exited to. */
- inn_loop = bb->loop_father;
- }
-
if (dominated_by_p (CDI_DOMINATORS, loop->latch, bb))
last = bb;
@@ -3232,8 +3220,15 @@ fill_always_executed_in_1 (class loop *loop, sbitmap
contains_call)
/* If LOOP exits from this BB stop processing. */
FOR_EACH_EDGE (e, ei, bb->succs)
+ {
if (!flow_bb_inside_loop_p (loop, e->dest))
break;
+ /* Or we enter a possibly non-finite loop. */
+ if (flow_loop_nested_p (bb->loop_father,
+ e->dest->loop_father)
+ && ! finite_loop_p (e->dest->loop_father))
+ break;
+ }
if (e)
break;
@@ -3242,15 +3237,6 @@ fill_always_executed_in_1 (class loop *loop, sbitmap
contains_call)
if (bb->flags & BB_IRREDUCIBLE_LOOP)
break;
- if (bb->loop_father->header == bb)
- /* Record that we enter into a subloop since it might not
- be finite. */
- /* ??? Entering into a not always executed subloop makes
- fill_always_executed_in quadratic in loop depth since
- we walk those loops N times. This is not a problem
- in practice though, see PR102253 for a worst-case testcase. */
- inn_loop = bb->loop_father;
-
/* Walk the body of LOOP sorted by dominance relation. Additionally,
if a basic block S dominates the latch, then only blocks dominated
by S are after it.
/* Walk the body of LOOP sorted by dominance relation. Additionally,
if a basic block S dominates the latch, then only blocks dominated
--
Thanks,
Xionghu
