Re: [PATCH]middle-end: skip checking loop exits if loop malformed [PR111878]

[Richard Biener <rguenther@suse.de>]

On Wed, 15 Nov 2023, Tamar Christina wrote:

> Hi All,
> 
> Before my refactoring if the loop->latch was incorrect then find_loop_location
> skipped checking the edges and would eventually return a dummy location.
> 
> It turns out that a loop can have
> loops_state_satisfies_p (LOOPS_HAVE_RECORDED_EXITS) but also not have a latch
> in which case get_loop_exit_edges traps.
> 
> This restores the old behavior.
> 
> Bootstrapped Regtested on x86_64-pc-linux-gnu and no issues.
> 
> Ok for master?
> 
> Thanks,
> Tamar
> 
> gcc/ChangeLog:
> 
> 	PR tree-optimization/111878
> 	* tree-vect-loop-manip.cc (find_loop_location): Skip edges check if
> 	latch incorrect.
> 
> gcc/testsuite/ChangeLog:
> 
> 	PR tree-optimization/111878
> 	* gcc.dg/graphite/pr111878.c: New test.
> 
> --- inline copy of patch -- 
> diff --git a/gcc/testsuite/gcc.dg/graphite/pr111878.c b/gcc/testsuite/gcc.dg/graphite/pr111878.c
> new file mode 100644
> index 0000000000000000000000000000000000000000..6722910062e43c827e94c53b43f106af1848852a
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/graphite/pr111878.c
> @@ -0,0 +1,19 @@
> +/* { dg-options "-O3 -fgraphite-identity -fsave-optimization-record" } */
> +
> +int long_c2i_ltmp;
> +int *long_c2i_cont;
> +
> +void
> +long_c2i (long utmp, int i)
> +{
> +  int neg = 1;
> +  switch (long_c2i_cont[0])
> +    case 0:
> +    neg = 0;
> +  for (; i; i++)
> +    if (neg)
> +      utmp |= long_c2i_cont[i] ^ 5;
> +    else
> +      utmp |= long_c2i_cont[i];
> +  long_c2i_ltmp = utmp;
> +}
> diff --git a/gcc/tree-vect-loop-manip.cc b/gcc/tree-vect-loop-manip.cc
> index b9161274ce401a7307f3e61ad23aa036701190d7..ff188840c1762d0b5fb6655cb93b5a8662b31343 100644
> --- a/gcc/tree-vect-loop-manip.cc
> +++ b/gcc/tree-vect-loop-manip.cc
> @@ -1792,7 +1792,8 @@ find_loop_location (class loop *loop)
>    if (!loop)

The testcase asks for the location of the root of the loop tree,
I think it's more sensible to explicitly handle this case adding

  /* For the root of the loop tree return the function location.  */
  if (!loop_outer (loop))
    return dump_user_location_t::from_function_decl (cfun->decl);

OK with that change.

Richard.

>      return dump_user_location_t ();
>  
> -  if (loops_state_satisfies_p (LOOPS_HAVE_RECORDED_EXITS))
> +  if (loops_state_satisfies_p (LOOPS_HAVE_RECORDED_EXITS)
> +      && loop->latch != EXIT_BLOCK_PTR_FOR_FN (cfun))
>      {
>        /* We only care about the loop location, so use any exit with location
>  	 information.  */
> 
> 
> 
> 
> 

-- 
Richard Biener <rguenther@suse.de>
SUSE Software Solutions Germany GmbH,
Frankenstrasse 146, 90461 Nuernberg, Germany;
GF: Ivo Totev, Andrew McDonald, Werner Knoblich; (HRB 36809, AG Nuernberg)