[PATCH] Fix possible sanopt compile-time hog

[PATCH] Fix possible sanopt compile-time hog

[Richard Biener]

While working on bitmap operations I figured sanopt.cc uses
a sbitmap worklist, iterating using bitmap_first_set_bit on it.
That's quadratic since bitmap_first_set_bit for sbitmap is O(n).

The fix is to use regular bitmaps for the worklist and the bitmap
feeding it and to avoid a useless copy.

Bootstrap and regtest running on x86_64-unknown-linux-gnu.

OK for trunk?

Thanks,
Richard.

	* sanopt.cc (sanitize_asan_mark_unpoison): Use bitmap
	for with_poison and alias worklist to it.
	(sanitize_asan_mark_poison): Likewise.
---
 gcc/sanopt.cc | 17 ++++++-----------
 1 file changed, 6 insertions(+), 11 deletions(-)

diff --git a/gcc/sanopt.cc b/gcc/sanopt.cc
index aed22850079..b356a21eca3 100644
--- a/gcc/sanopt.cc
+++ b/gcc/sanopt.cc
@@ -987,15 +987,11 @@ static void
 sanitize_asan_mark_unpoison (void)
 {
   /* 1) Find all BBs that contain an ASAN_MARK poison call.  */
-  auto_sbitmap with_poison (last_basic_block_for_fn (cfun) + 1);
-  bitmap_clear (with_poison);
+  auto_bitmap with_poison;
   basic_block bb;
 
   FOR_EACH_BB_FN (bb, cfun)
     {
-      if (bitmap_bit_p (with_poison, bb->index))
-	continue;
-
       gimple_stmt_iterator gsi;
       for (gsi = gsi_last_bb (bb); !gsi_end_p (gsi); gsi_prev (&gsi))
 	{
@@ -1010,8 +1006,8 @@ sanitize_asan_mark_unpoison (void)
 
   auto_sbitmap poisoned (last_basic_block_for_fn (cfun) + 1);
   bitmap_clear (poisoned);
-  auto_sbitmap worklist (last_basic_block_for_fn (cfun) + 1);
-  bitmap_copy (worklist, with_poison);
+  /* We now treat with_poison as worklist.  */
+  bitmap worklist = with_poison;
 
   /* 2) Propagate the information to all reachable blocks.  */
   while (!bitmap_empty_p (worklist))
@@ -1088,8 +1084,7 @@ static void
 sanitize_asan_mark_poison (void)
 {
   /* 1) Find all BBs that possibly contain an ASAN_CHECK.  */
-  auto_sbitmap with_check (last_basic_block_for_fn (cfun) + 1);
-  bitmap_clear (with_check);
+  auto_bitmap with_check;
   basic_block bb;
 
   FOR_EACH_BB_FN (bb, cfun)
@@ -1108,8 +1103,8 @@ sanitize_asan_mark_poison (void)
 
   auto_sbitmap can_reach_check (last_basic_block_for_fn (cfun) + 1);
   bitmap_clear (can_reach_check);
-  auto_sbitmap worklist (last_basic_block_for_fn (cfun) + 1);
-  bitmap_copy (worklist, with_check);
+  /* We now treat with_check as worklist.  */
+  bitmap worklist = with_check;
 
   /* 2) Propagate the information to all definitions blocks.  */
   while (!bitmap_empty_p (worklist))
-- 
2.35.3

Re: [PATCH] Fix possible sanopt compile-time hog

[Jakub Jelinek]

On Tue, Feb 14, 2023 at 04:20:24PM +0100, Richard Biener wrote:
> While working on bitmap operations I figured sanopt.cc uses
> a sbitmap worklist, iterating using bitmap_first_set_bit on it.
> That's quadratic since bitmap_first_set_bit for sbitmap is O(n).
> 
> The fix is to use regular bitmaps for the worklist and the bitmap
> feeding it and to avoid a useless copy.
> 
> Bootstrap and regtest running on x86_64-unknown-linux-gnu.
> 
> OK for trunk?
> 
> Thanks,
> Richard.
> 
> 	* sanopt.cc (sanitize_asan_mark_unpoison): Use bitmap
> 	for with_poison and alias worklist to it.
> 	(sanitize_asan_mark_poison): Likewise.

Ok, thanks.

	Jakub