Re: Fix wrong code in ldist-strlen-1.c

[Richard Biener <richard.guenther@gmail.com>]

On October 16, 2021 2:47:51 PM GMT+02:00, Jan Hubicka via Gcc-patches <gcc-patches@gcc.gnu.org> wrote:
>Hi,
>while updating compute_points_to_sets I missed that the code not only
>sets the nonlocal/escaped flags but also initializes pt.  With my
>previous change if uses_global_memory is false pt is not updated
>correctly which may lead to wrong code.
>
>This is fixed by the following patch I comitted to avoid strange
>misoptimizations.
>
>Bootstrapped/regtested x86_64-linux and also tested with LTO.

OK. 

Richard. 

>Honza
>
>gcc/ChangeLog:
>
>	PR tree-optimization/102720
>	* tree-ssa-structalias.c (compute_points_to_sets): Fix producing
>	of call used and clobbered sets.
>
>diff --git a/gcc/tree-ssa-structalias.c b/gcc/tree-ssa-structalias.c
>index 6f12a66ee0d..2e6513bb72a 100644
>--- a/gcc/tree-ssa-structalias.c
>+++ b/gcc/tree-ssa-structalias.c
>@@ -7541,17 +7541,18 @@ compute_points_to_sets (void)
> 	      determine_global_memory_access (stmt, NULL,
> 					      &reads_global_memory,
> 					      &uses_global_memory);
>-	      if (!uses_global_memory)
>-		;
>-	      else if ((vi = lookup_call_use_vi (stmt)) != NULL)
>+	      if ((vi = lookup_call_use_vi (stmt)) != NULL)
> 		{
> 		  *pt = find_what_var_points_to (cfun->decl, vi);
> 		  /* Escaped (and thus nonlocal) variables are always
> 		     implicitly used by calls.  */
> 		  /* ???  ESCAPED can be empty even though NONLOCAL
> 		     always escaped.  */
>-		  pt->nonlocal = uses_global_memory;
>-		  pt->escaped = uses_global_memory;
>+		  if (uses_global_memory)
>+		    {
>+		      pt->nonlocal = uses_global_memory;
>+		      pt->escaped = uses_global_memory;
>+		    }
> 		}
> 	      else if (uses_global_memory)
> 		{
>@@ -7572,17 +7573,18 @@ compute_points_to_sets (void)
> 	      determine_global_memory_access (stmt, &writes_global_memory,
> 					      NULL, NULL);
> 
>-	      if (!writes_global_memory)
>-		;
>-	      else if ((vi = lookup_call_clobber_vi (stmt)) != NULL)
>+	      if ((vi = lookup_call_clobber_vi (stmt)) != NULL)
> 		{
> 		  *pt = find_what_var_points_to (cfun->decl, vi);
> 		  /* Escaped (and thus nonlocal) variables are always
> 		     implicitly clobbered by calls.  */
> 		  /* ???  ESCAPED can be empty even though NONLOCAL
> 		     always escaped.  */
>-		  pt->nonlocal = writes_global_memory;
>-		  pt->escaped = writes_global_memory;
>+		  if (writes_global_memory)
>+		    {
>+		      pt->nonlocal = writes_global_memory;
>+		      pt->escaped = writes_global_memory;
>+		    }
> 		}
> 	      else if (writes_global_memory)
> 		{