Re: patch for loop bug (fwd)

[Chandra Chavva <cchavva at cygnus dot com>]

Hi Jeff,
 

On Mon, 17 Jul 2000, Jeffrey A Law wrote:

>   In message <Pine.SOL.3.91.1000711122952.2307P-100000@emperor.cygnus.com>you w
> rite:
>   > 
>   > 
>   > 
>   > ---------- Forwarded message ----------
>   > Date: Tue, 11 Jul 2000 12:15:29 -0700 (PDT)
>   > From: Chandra Chavva <cchavva@emperor.cygnus.com>
>   > To: gcc-patches@gcc.gnu.org
>   > Subject: patch for loop bug
>   > 
>   > 
>   > Here is the patch which fixes the following 'C' program. Please let me 
>   > know if it is okay to apply.
>   > 
>   > 
>   > while.c
>   > 
>   > int main()
>   > {
>   >     int i = 1;
>   >     int j = 0;
>   > 
>   >     while (i != 1024 || j <= 0) {
>   >         i *= 2;
>   >         ++ j;
>   >     }
>   > 
>   >     if (j != 10)
>   >      abort ();
>   >  
>   >     exit (0);
>   > }
>   > 
>   > I have added this testcase to gcc testsuite - gcc.c-torture/execute/2000071
>   > 1-1.c 
> The test is fine.  Please install it.
> 
> 
>   > 	* loop.c (check_dbra_loop): Check if more than one condition
>   >  	controls the loop.
>   > 	 
>   > 
>   > Index: loop.c
>   > ===================================================================
>   > RCS file: /cvs/gcc/egcs/gcc/loop.c,v
>   > retrieving revision 1.256
>   > diff -p -r1.256 loop.c
>   > *** loop.c      2000/06/14 07:41:57     1.256
>   > --- loop.c      2000/07/11 19:01:41
>   > *************** check_dbra_loop (loop, insn_count)
>   > *** 7795,7800 ****
>   > --- 7795,7811 ----
>   >     else
>   >       return 0;
>   >   
>   > +   {
>   > +     /* If more than one condition is present to control the loop, then
>   > +        do not procceed as the this function makes decision on the
>   > +        condition (JUMP_INSN) present just before NOTE_INSN_LOOP_END. */
>   > + 
>   > +     rtx jump1;
>   > +     if ((jump1 = prev_nonnote_insn (jump)) != loop_continue)
>   > +       if (GET_CODE (jump1) == JUMP_INSN))
>   > +         return 0;
>   > +   }
>   > + 
> I would slightly change the comment.  Is this version accurate?
> 
> " ... as this function does not know how to rewrite loop tests with more
>   than one condition.  */
> 
> If it's more accurate/readable, then you should install the change with
> the updated comment.  If the comment is not more accurate, then we should
> iterate once more on the patch.
> 
  Yes, it is more clear with your comments.
  
  Thanks
  Chandra