[PATCH] rtl-optimization/105559 - avoid quadratic behavior in delete_insn_and_edges

[Richard Biener]

On Wed, 11 May 2022, Richard Biener wrote:

> When the insn to delete is a debug insn there's no point in figuring
> out whether it might be the last real insn and thus we have to purge
> dead edges.
> 
> Bootstrap and regtest running on x86_64-unknown-linux-gnu.

Actually revisiting PR94618 which introduced this the following is better
and is what I'm going to test, making sure to never purge edges for
DEBUG_INSNs.

diff --git a/gcc/cfgrtl.cc b/gcc/cfgrtl.cc
index 74ea14efc61..06be46d75df 100644
--- a/gcc/cfgrtl.cc
+++ b/gcc/cfgrtl.cc
@@ -235,7 +235,7 @@ delete_insn_and_edges (rtx_insn *insn)
 {
   bool purge = false;
 
-  if (INSN_P (insn) && BLOCK_FOR_INSN (insn))
+  if (NONDEBUG_INSN_P (insn) && BLOCK_FOR_INSN (insn))
     {
       basic_block bb = BLOCK_FOR_INSN (insn);
       if (BB_END (bb) == insn)



> 2022-05-11  Richard Biener  <rguenther@suse.de>
> 
> 	PR rtl-optimization/105559
> 	* cfgrtl.cc (delete_insn_and_edges): Only perform search to BB_END
> 	for non-debug insns.
> ---
>  gcc/cfgrtl.cc | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/gcc/cfgrtl.cc b/gcc/cfgrtl.cc
> index 74ea14efc61..8e9fd1266b3 100644
> --- a/gcc/cfgrtl.cc
> +++ b/gcc/cfgrtl.cc
> @@ -240,7 +240,7 @@ delete_insn_and_edges (rtx_insn *insn)
>        basic_block bb = BLOCK_FOR_INSN (insn);
>        if (BB_END (bb) == insn)
>  	purge = true;
> -      else if (DEBUG_INSN_P (BB_END (bb)))
> +      else if (NONDEBUG_INSN_P (insn) && DEBUG_INSN_P (BB_END (bb)))
>  	for (rtx_insn *dinsn = NEXT_INSN (insn);
>  	     DEBUG_INSN_P (dinsn); dinsn = NEXT_INSN (dinsn))
>  	  if (BB_END (bb) == dinsn)
> 

-- 
Richard Biener <rguenther@suse.de>
SUSE Software Solutions Germany GmbH, Maxfeldstrasse 5, 90409 Nuernberg,
Germany; GF: Ivo Totev; HRB 36809 (AG Nuernberg)