RE: [PATCH] Fix PR tree-optimization/77654

[Richard Biener <rguenther at suse dot de>]

On Tue, 20 Sep 2016, Doug Gilmore wrote:

> It looks like the original message was dropped, resending.
> 
> Doug
> ________________________________________
> From: Doug Gilmore
> Sent: Tuesday, September 20, 2016 2:12 PM
> To: gcc-patches@gcc.gnu.org; rguenth@gcc.gnu.org
> Subject: [PATCH] Fix PR tree-optimization/77654
> 
> From:
> 
> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=77654
> 
> Richard Biener wrote:
> > Looks good though addr_base should always be a pointer but it might
> > not be an SSA name so better check that...
> 
> I took a look at other situations where duplicate_ssa_name_ptr_info()
> is called and found that there are no checks for the SSA name since
> that check is done in duplicate_ssa_name_ptr_info().  Do you still
> want the additional check added?

It checks for !ptr_info but it requires NAME to be an SSA name.

>From the attachment in bugzilla (the attachment didn't make it
here)

 	
+
+      if (POINTER_TYPE_P (TREE_TYPE (addr_base)))
+	{
+	  duplicate_ssa_name_ptr_info (addr, SSA_NAME_PTR_INFO 
(addr_base));
+	  /* As this isn't a plain copy we have to reset alignment
+	     information.  */
+	  if (SSA_NAME_PTR_INFO (addr))
+	    mark_ptr_info_alignment_unknown (SSA_NAME_PTR_INFO (addr));
+	}
+

I was talking about changing the if to

    if (TREE_CODE (addr_base) == SSA_NAME
        && TREE_CODE (addr) == SSA_NAME)

because the addresses could be invariant as far as I can see.

> Also does it make sense to make a test case for this?

I'm not sure how to easily test this.

Richard.

> I was thinking of making the following change to:
> 
> diff --git a/gcc/tree-ssa-alias.c b/gcc/tree-ssa-alias.c
> index 8051a66..b799c43 100644
> --- a/gcc/tree-ssa-alias.c
> +++ b/gcc/tree-ssa-alias.c
> @@ -296,7 +296,16 @@ ptr_derefs_may_alias_p (tree ptr1, tree ptr2)
>    pi1 = SSA_NAME_PTR_INFO (ptr1);
>    pi2 = SSA_NAME_PTR_INFO (ptr2);
>    if (!pi1 || !pi2)
> -    return true;
> +    {
> +      if (dump_file)
> +       {
> +         if (! pi1)
> +           fprintf (dump_file, "%s pi1 is NULL\n", __FUNCTION__);
> +         if (! pi2)
> +           fprintf (dump_file, "%s pi2 is NULL\n", __FUNCTION__);
> +       }
> +      return true;
> +    }
> 
> Then when compiling the test case, we could scan for the RE
> "pi. is NULL" in the dump file created by compiling with -fdump-rtl-sched2.
> 
> I attached the original patch.
> 
> Thanks,
> 
> Doug
> 
> gcc/
>         PR tree-optimization/77654
>         * tree-ssa-alias.c (issue_prefetch_ref): Add call
>         to duplicate_ssa_name_ptr_info.
> 
> 

-- 
Richard Biener <rguenther@suse.de>
SUSE LINUX GmbH, GF: Felix Imendoerffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nuernberg)