[PATCH] Speedup loop splitting SSA update

[Richard Biener <rguenther@suse.de>]

Since we never process loops with inner loops that have been split
we can delay SSA update until after the pass is done with the whole
loop, avoiding the O(function-size) work associated with it.

Bootstrapped and tested on x86_64-unknown-linux-gnu, pushed.

2022-06-28  Richard Biener  <rguenther@suse.de>

	* tree-ssa-loop-split.cc (fix_loop_bb_probability): Do not
	call update_ssa.
---
 gcc/tree-ssa-loop-split.cc | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/gcc/tree-ssa-loop-split.cc b/gcc/tree-ssa-loop-split.cc
index d61bad5ba47..bccf621493b 100644
--- a/gcc/tree-ssa-loop-split.cc
+++ b/gcc/tree-ssa-loop-split.cc
@@ -491,8 +491,6 @@ static void
 fix_loop_bb_probability (class loop *loop1, class loop *loop2, edge true_edge,
 			 edge false_edge)
 {
-  update_ssa (TODO_update_ssa);
-
   /* Proportion first loop's bb counts except those dominated by true
      branch to avoid drop 1s down.  */
   basic_block *bbs1, *bbs2;
@@ -1668,7 +1666,8 @@ tree_ssa_split_loops (void)
       if (loop->aux)
 	{
 	  /* If any of our inner loops was split, don't split us,
-	     and mark our containing loop as having had splits as well.  */
+	     and mark our containing loop as having had splits as well.
+	     This allows for delaying SSA update.  */
 	  loop_outer (loop)->aux = loop;
 	  continue;
 	}
-- 
2.35.3