Re: optimization/10862: [tree-ssa] Segfault for (essentially) empty function

[Diego Novillo <dnovillo@redhat.com>]

The following reply was made to PR optimization/10862; it has been noted by GNATS.

From: Diego Novillo <dnovillo@redhat.com>
To: bangerth@dealii.org
Cc: gcc-gnats@gcc.gnu.org
Subject: Re: optimization/10862: [tree-ssa] Segfault for (essentially) empty function
Date: Mon, 19 May 2003 11:14:47 -0400

 On Mon, May 19, 2003 at 02:43:41PM -0000, bangerth@dealii.org wrote:
 > 
 > >Number:         10862
 > >Category:       optimization
 > >Synopsis:       [tree-ssa] Segfault for (essentially) empty function
 > >Confidential:   no
 > >Severity:       serious
 > >Priority:       medium
 > >Responsible:    unassigned
 > >State:          open
 > >Class:          sw-bug
 > >Submitter-Id:   net
 > >Arrival-Date:   Mon May 19 14:46:01 UTC 2003
 > >Closed-Date:
 > >Last-Modified:
 > >Originator:     Wolfgang Bangerth
 > >Release:        unknown-1.0
 > >Organization:
 > >Environment:
 > 
 > >Description:
 > This one's rather funny (and was much simpler to reduce).
 > We ICE on a function that's essentially empty:
 > ---------------------------------------template <int N> void foo () {
 >   int i;
 >   switch (i) {
 >     case 1:
 >           switch (N) {}
 >     default: ;
 >   }
 > }
 > 
 > template void foo<1> ();
 > ---------------------------
 > 
 When removing blocks with empty conditionals, we should not
 assume that the block has a post dominator.  I'm testing this
 patch.
 
 
 Diego.
 
 
 
 	* tree-ssa-dce.c (remove_conditional): Don't assume that the block
 	to remove has a post-dominator.
 
 Index: tree-ssa-dce.c
 ===================================================================
 RCS file: /cvs/gcc/gcc/gcc/Attic/tree-ssa-dce.c,v
 retrieving revision 1.1.2.37
 diff -d -u -p -r1.1.2.37 tree-ssa-dce.c
 --- tree-ssa-dce.c	16 May 2003 18:09:19 -0000	1.1.2.37
 +++ tree-ssa-dce.c	19 May 2003 15:11:18 -0000
 @@ -633,15 +633,16 @@ remove_conditional (basic_block bb)
       in DCE.  */
  
  #ifdef ENABLE_CHECKING
 -  {
 -    tree phi;
 -    for (phi = phi_nodes (pdom_bb); phi; phi = TREE_CHAIN (phi))
 -      if (necessary_p (phi))
 -        abort ();
 -  }
 +  if (pdom_bb)
 +    {
 +      tree phi;
 +      for (phi = phi_nodes (pdom_bb); phi; phi = TREE_CHAIN (phi))
 +	if (necessary_p (phi))
 +	  abort ();
 +    }
  #endif
  
    /* Add an edge to BB's post dominator.  */
    if (bb->succ == NULL)
 -    make_edge (bb, pdom_bb,  EDGE_FALLTHRU);
 +    make_edge (bb, pdom_bb ? pdom_bb : EXIT_BLOCK_PTR,  EDGE_FALLTHRU);
  }