Re: [patch] Removal of dead labels

["Richard Guenther" <richard dot guenther at gmail dot com>]

On 5/1/07, Richard Guenther <richard.guenther@gmail.com> wrote:
> On 5/1/07, Zdenek Dvorak <rakdver@atrey.karlin.mff.cuni.cz> wrote:
> > Hello,
> >
> > with http://gcc.gnu.org/ml/gcc-patches/2007-04/msg01840.html, most of
> > the tree labels are unused once cfg is built.  This patch makes us
> > remove those dead labels (we still keep user labels even if they are not
> > referenced, for debug info).  This saves some peak memory, and the
> > optimization passes that traverse all statements are a bit faster, as
> > they do not need to skip the labels.
> >
> > Additionally, the patch makes cfgexpand avoid creating new tree labels.
> >
> > A few changes to code that did not handle empty blocks
> > (apply_return_prediction) or blocks not starting with a label
> > (rewrite_use_nonlinear_expr, vect_create_epilog_for_reduction)
> > were necessary.
> >
> > The timings for combine.i compilation (-O2, with checking enabled)
> > without and with the patch:
> >
> >  TOTAL                 :  25.42             0.57            26.00 43480 kB
> >  TOTAL                 :  24.48             0.43            25.21 42528 kB
> >
> > Compilation of preprocessed gcc sources (-O2, checking disabled) is
> > faster by about 2-3% with the patch, on all architectures where I tested
> > it.  Bootstrapped & regtested on i686, x86_64, ia64 and ppc64-linux.
>
> This is ok.
>
> Thanks,
> Richard.
>
> > Zdenek
> >
> >         * tree-ssa-loop-ivopts.c (rewrite_use_nonlinear_expr): Use
> >         bsi_after_labels.  Always insert statements before bsi.
> >         * tree-vect-transform.c (vect_create_epilog_for_reduction): Ditto.
> >         * predict.c (apply_return_prediction): Check for empty blocks.
> >         * cfgexpand.c (lab_rtx_for_bb): New variable.
> >         (label_rtx_for_bb): Do not create new tree labels.
> >         (expand_gimple_basic_block): Add labels recorded in lab_rtx_for_bb.
> >         (tree_expand_cfg): Initialize lab_rtx_for_bb.
> >         * tree-cfg.c (build_tree_cfg): Call cleanup_dead_labels after
> >         creating edges.
> >         (label_for_bb): Add field used.
> >         (update_eh_label, main_block_label): Mark the label used.
> >         (cleanup_dead_labels): Remove unused labels.

I'm going to apply

+ 2007-05-01  Richard Guenther  <rguenther@suse.de>
+
+       * tree-ssa-loop-manip.c (ip_normal_pos): Check if last stmt
+       is NULL.

to fix an ICE for  gcc.c-torture/execute/20011008-3.c -Os

Richard.
Index: ChangeLog
===================================================================
*** ChangeLog	(revision 124328)
--- ChangeLog	(working copy)
***************
*** 1,3 ****
--- 1,8 ----
+ 2007-05-01  Richard Guenther  <rguenther@suse.de>
+ 
+ 	* tree-ssa-loop-manip.c (ip_normal_pos): Check if last stmt
+ 	is NULL.
+ 
  2007-05-01  Joseph Myers  <joseph@codesourcery.com>
  
  	* config/rs6000/libgcc-ppc-glibc.ver (__gcc_qgt): Fix typo.
Index: tree-ssa-loop-manip.c
===================================================================
*** tree-ssa-loop-manip.c	(revision 124328)
--- tree-ssa-loop-manip.c	(working copy)
*************** ip_normal_pos (struct loop *loop)
*** 505,511 ****
  
    bb = single_pred (loop->latch);
    last = last_stmt (bb);
!   if (TREE_CODE (last) != COND_EXPR)
      return NULL;
  
    exit = EDGE_SUCC (bb, 0);
--- 505,512 ----
  
    bb = single_pred (loop->latch);
    last = last_stmt (bb);
!   if (!last
!       || TREE_CODE (last) != COND_EXPR)
      return NULL;
  
    exit = EDGE_SUCC (bb, 0);