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Date: Wed, 26 Jun 2002 12:58:00 -0000
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From: Richard Henderson <rth@twiddle.net>
Subject: Re: optimization/7120: Run once loop should *always* be unrolled
Reply-To: Richard Henderson <rth@twiddle.net>
X-SW-Source: 2002-06/txt/msg00635.txt.bz2
List-Id: <gcc-prs.sourceware.org>

The following reply was made to PR optimization/7120; it has been noted by GNATS.

From: Richard Henderson <rth@twiddle.net>
To: davem@gcc.gnu.org, gcc-bugs@gcc.gnu.org, nobody@gcc.gnu.org,
       rusty@rustcorp.com.au, gcc-gnats@gcc.gnu.org, gcc-patches@gcc.gnu.org
Cc:  
Subject: Re: optimization/7120: Run once loop should *always* be unrolled
Date: Wed, 26 Jun 2002 10:54:53 -0700

 On Wed, Jun 26, 2002 at 06:02:10PM +0930, Alan Modra wrote:
 > +      if (((INTVAL (initial_value) + INTVAL (increment))
 > +	   & (((unsigned HOST_WIDE_INT) 1
 > +	       << (GET_MODE_BITSIZE (GET_MODE (iteration_var)) - 1)
 > +	       << 1) - 1)) == INTVAL (final_value))
 
 Need to use gen_int_mode here and for the final_value calulation.
 Suggest something like
 
   rtx incone = gen_int_mode (INTVAL (initial_value) + INTVAL (increment),
 			     GET_MODE (iteration_var));
 
   if (incone == final_value)
     {
       ...
     }
   else
     {
       loop_info->n_iterations = 1;
       loop_info->final_value = incone;
       loop_info->final_equiv_value = incone;
       return 1;
     }
 
 
 r~