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Date: Tue, 25 Jun 2002 20:56:00 -0000
Message-ID: <20020626032602.11578.qmail@sources.redhat.com>
To: nobody@gcc.gnu.org
Cc: gcc-prs@gcc.gnu.org,
From: Alan Modra <amodra@bigpond.net.au>
Subject: Re: optimization/7120: Run once loop should *always* be unrolled
Reply-To: Alan Modra <amodra@bigpond.net.au>
X-SW-Source: 2002-06/txt/msg00623.txt.bz2
List-Id: <gcc-prs.sourceware.org>

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

From: Alan Modra <amodra@bigpond.net.au>
To: davem@gcc.gnu.org, gcc-bugs@gcc.gnu.org, gcc-prs@gcc.gnu.org,
  nobody@gcc.gnu.org, rth@twiddle.net, rusty@rustcorp.com.au,
  gcc-gnats@gcc.gnu.org
Cc: gcc-patches@gcc.gnu.org
Subject: Re: optimization/7120: Run once loop should *always* be unrolled
Date: Wed, 26 Jun 2002 12:54:56 +0930

 On Tue, Jun 25, 2002 at 04:21:32PM -0000, davem@gcc.gnu.org wrote:
 > Synopsis: Run once loop should *always* be unrolled
 
 This patch cures the problem.  bootstrap i686-linux in progress.
 
 	* unroll.c (loop_iterations): Handle EQ loops.
 
 Index: gcc/unroll.c
 ===================================================================
 RCS file: /cvs/gcc/gcc/gcc/unroll.c,v
 retrieving revision 1.168
 diff -u -p -r1.168 unroll.c
 --- gcc/unroll.c	15 Jun 2002 01:10:49 -0000	1.168
 +++ gcc/unroll.c	26 Jun 2002 03:19:38 -0000
 @@ -3941,12 +3941,6 @@ loop_iterations (loop)
  	}
        return 0;
      }
 -  else if (comparison_code == EQ)
 -    {
 -      if (loop_dump_stream)
 -	fprintf (loop_dump_stream, "Loop iterations: EQ comparison loop.\n");
 -      return 0;
 -    }
    else if (GET_CODE (final_value) != CONST_INT)
      {
        if (loop_dump_stream)
 @@ -3957,6 +3951,15 @@ loop_iterations (loop)
  	  fprintf (loop_dump_stream, ".\n");
  	}
        return 0;
 +    }
 +  else if (comparison_code == EQ)
 +    {
 +      if (loop_dump_stream)
 +	fprintf (loop_dump_stream, "Loop iterations: EQ comparison loop.\n");
 +      if (INTVAL (increment) == 0)
 +	return 0;
 +      loop_info->n_iterations = 1;
 +      return loop_info->n_iterations;
      }
  
    /* Final_larger is 1 if final larger, 0 if they are equal, otherwise -1.  */
 
 -- 
 Alan Modra
 IBM OzLabs - Linux Technology Centre