optimization/8599: [3.2 regression] loop unroll bug with -march=k6-3

[Franz Sirl]

On Sunday 01 December 2002 15:19, Franz Sirl wrote:
> On Saturday 30 November 2002 15:08, Eric Botcazou wrote:
> > > Now, the problematic part is the doloop.c hunk as I just verified. So
> > > we have to find out how to fix it or we have to revert the patch on the
> > > branch
> >
> > Try the attached patch.
>
> Neither with my version of the backport nor with yours the regression is
> fixed. But I can confirm that there is no such bug in the mainline.

This one backported fixes the branch regression:

2002-07-21  Richard Henderson  <rth@redhat.com>

        * loop.h (LOOP_AUTO_UNROLL): Rename from LOOP_FIRST_PASS.
        * loop.c (strength_reduce): Update.
        * toplev.c (rest_of_compilation): Do unrolling in the first
        loop pass, not the second.

I'm running a branch bootstrap now on powerpc-linux-gnu and i686-linux-gnu.

Richard, do you think it's safe to move this patch to the branch? Do you 
remember any prerequisites?

Franz.
-------------- next part --------------
Index: gcc/loop.c
===================================================================
RCS file: /cvsroot/gcc/gcc/gcc/loop.c,v
retrieving revision 1.389.2.7.2.5
diff -u -p -r1.389.2.7.2.5 loop.c
--- gcc/loop.c	22 Nov 2002 21:20:04 -0000	1.389.2.7.2.5
+++ gcc/loop.c	1 Dec 2002 18:52:55 -0000
@@ -5251,7 +5251,7 @@ strength_reduce (loop, flags)
      collected.  Always unroll loops that would be as small or smaller
      unrolled than when rolled.  */
   if ((flags & LOOP_UNROLL)
-      || (!(flags & LOOP_FIRST_PASS)
+      || ((flags & LOOP_AUTO_UNROLL)
 	  && loop_info->n_iterations > 0
 	  && unrolled_insn_copies <= insn_count))
     unroll_loop (loop, insn_count, 1);
Index: gcc/loop.h
===================================================================
RCS file: /cvsroot/gcc/gcc/gcc/loop.h,v
retrieving revision 1.58.6.1.4.1
diff -u -p -r1.58.6.1.4.1 loop.h
--- gcc/loop.h	17 Sep 2002 03:25:06 -0000	1.58.6.1.4.1
+++ gcc/loop.h	1 Dec 2002 18:52:55 -0000
@@ -28,7 +28,7 @@ Software Foundation, 59 Temple Place - S
 #define LOOP_UNROLL 1
 #define LOOP_BCT 2
 #define LOOP_PREFETCH 4
-#define LOOP_FIRST_PASS 8
+#define LOOP_AUTO_UNROLL 8
 
 /* Get the loop info pointer of a loop.  */
 #define LOOP_INFO(LOOP) ((struct loop_info *) (LOOP)->aux)
Index: gcc/toplev.c
===================================================================
RCS file: /cvsroot/gcc/gcc/gcc/toplev.c,v
retrieving revision 1.574.2.16.2.3
diff -u -p -r1.574.2.16.2.3 toplev.c
--- gcc/toplev.c	2 Nov 2002 00:57:23 -0000	1.574.2.16.2.3
+++ gcc/toplev.c	1 Dec 2002 18:52:56 -0000
@@ -2890,16 +2890,21 @@ rest_of_compilation (decl)
 
   if (optimize > 0)
     {
+      int do_unroll, do_prefetch;
+
       timevar_push (TV_LOOP);
       open_dump_file (DFI_loop, decl);
       free_bb_for_insn ();
 
+      do_unroll = flag_unroll_loops ? LOOP_UNROLL : LOOP_AUTO_UNROLL;
+      do_prefetch = flag_prefetch_loop_arrays ? LOOP_PREFETCH : 0;
       if (flag_rerun_loop_opt)
 	{
 	  cleanup_barriers ();
 
 	  /* We only want to perform unrolling once.  */
-	  loop_optimize (insns, rtl_dump_file, LOOP_FIRST_PASS);
+	  loop_optimize (insns, rtl_dump_file, do_unroll);
+	  do_unroll = 0;
 
 	  /* The first call to loop_optimize makes some instructions
 	     trivially dead.  We delete those instructions now in the
@@ -2912,9 +2917,7 @@ rest_of_compilation (decl)
 	  reg_scan (insns, max_reg_num (), 1);
 	}
       cleanup_barriers ();
-      loop_optimize (insns, rtl_dump_file,
-		     (flag_unroll_loops ? LOOP_UNROLL : 0) | LOOP_BCT
-		     | (flag_prefetch_loop_arrays ? LOOP_PREFETCH : 0));
+      loop_optimize (insns, rtl_dump_file, do_unroll | LOOP_BCT | do_prefetch);
 
       close_dump_file (DFI_loop, print_rtl, insns);
       timevar_pop (TV_LOOP);